An escapement mechanism, a fluid delivery actuator and a fluid dispensing apparatus

Abstract

An escapement mechanism including a rotary actuator that moves a pallet fork to release an escape wheel an escape wheel. A rotatable coupling rotatably couples a rotor arm of the rotary actuator to the pallet arm. The mechanism is configured so that as the rotor arm rotates between first and second angular positions the pallet fork is caused to rotate about between first and second positions to alternately engage and release the pallets of the pallet fork with teeth of the escape wheel to allow progressive rotation of the escape wheel. A lost motion mechanism may advantageously be employed in the rotatable coupling. The escapement mechanism can be employed in a fluid delivery actuator used in a fluid dispensing apparatus including a fluid reservoir so that a precise measure of fluid is dispensed from the fluid dispensing apparatus as the rotor rotates between first and second positions.

Description

[0001] AN ESCAPEMENT MECHANISM, A FLUID DELIVERY ACTUATOR AND A FLUID DISPENSING APPARATUS FIELD OF INVENTION

[0002] This invention relates to an escapement mechanism, a fluid delivery actuator for a fluid dispensing apparatus, and a fluid dispensing apparatus comprising the fluid delivery actuator. The fluid delivery actuator may be particularly suitable for controlling the release of fluid over a prolonged period of time, such as for dispensing a metered dosage of fluid over time.

[0003] BACKGROUND

[0004] Insulin pumps commonly come in two forms: a patch pump, and a tubed pump.

[0005] A patch pump typically includes an electronically controlled, powered actuation system, a fluid cartridge comprising insulin and connected or connectable to an infusion set, comprising a fluid channel connected to an outlet of the fluid cartridge and a needle for piercing the patient's skin to administer insulin fluid from the cartridge. An adhesive patch attaches the powered actuation system, cartridge and infusion set to the patient - usually to the upper arm of the patient.

[0006] A tubed insulin pump also typically includes an electronically controlled, powered actuation system, a fluid cartridge comprising insulin and connected or connectable to an infusion set, comprising an elongate tube that provides a fluid channel having one end of the tube connected to an outlet of the fluid cartridge, and a needle located at the other end of the tube for piercing the patient's skin to administer insulin fluid from the cartridge. The tubed pump is typically carried or worn by the patient, such as at the waist, and the needle is typically inserted in the patient's torso.

[0007] The actuation systems for both types of pumps include powered actuators that, by necessity, provide precise control over the volume of fluid (insulin) dispensed. Actuators for apparatus providing a controlled release of fluid over a prolonged period of time, such as an insulin pump and other accurate measurement fluid dispensing pumps, typically require a battery powered actuator to move multiple mechanical parts, such as a gear system and to hold parts in a particular position. This places a heavy current load on the battery and requires the battery to be frequently replaced or recharged, creating increased inconvenience and cost for the user. For example, batteries in a patch pump may be replaced as frequently as every three days, and batteries in a tubed insulin pump may be replaced monthly.

[0008] Another problem with known insulin pumps is the waste generated. For example, many insulin pumps must be discarded in entirety and replaced when the battery loses its charge. Somepumps provide a rechargeable battery, but many require the actuation system, including controller and motor, to be discarded once the battery loses its charge.

[0009] Therefore, a need exists for a fluid delivery actuator that uses less battery power in order to reduce the frequency at which the battery needs to be replaced or recharged.

[0010] It may also be useful to provide a reusable fluid delivery actuator for an infusion pump, where only the consumables of the infusion pump are discarded, such as the fluid cartridge, infusion set, and adhesive patch (where used).

[0011] SUMMARY OF INVENTION

[0012] According to one example there is provided an escapement mechanism comprising:

[0013] a. an escape wheel rotatable about a first axis and having a plurality of teeth, b. a rotary actuator having a rotor that is rotatable with respect to a stator and having a rotor arm extending from the rotor that can be driven between first and second angular positions,

[0014] c. a pallet fork having a pair of pallets and a pallet arm, the pallet fork being rotatable about a second axis, offset from the first axis, and

[0015] d. a rotatable coupling rotatably coupling the rotor arm to the pallet arm,

[0016] the mechanism being configured such that as the rotor arm rotates between the first and second angular positions the pallet fork is caused to rotate about the second axis between first and second positions to alternately engage and release the pallets of the pallet fork with teeth of the escape wheel to allow progressive rotation of the escape wheel.

[0017] According to a further example there is provided a fluid dispensing mechanism comprising:

[0018] a. an escapement mechanism as claimed in any one of the preceding claims;

[0019] b. a gear train coupled to the escape wheel of the escapement mechanism;

[0020] c. an energy storage device driving the gear train; and

[0021] d. a linear actuator driven by the gear train,

[0022] wherein the escape mechanism controls rotation of the gear train so as to regulate the rate of movement of the linear actuator.

[0023] According to a further example there is provided a fluid delivery actuator for a fluid dispensing apparatus, the fluid delivery actuator comprising:

[0024] a stator having at least one electromagnetic coil wound on the stator;a rotor comprising a magnet and a rotor arm, wherein the rotor is rotatable in a first direction to reach a first position and in a second direction to reach a second position;

[0025] a controller configured to supply pulses of electrical current of alternate polarity from a power supply to the at least one electromagnetic coil to rotate the rotor between the first and second positions;

[0026] an escapement that is engageable by the rotor arm; and

[0027] an energy storage device for storing mechanical energy, the energy storage device being configured to drive a gear system including a linearly moveable plunger having a first end and a second end;

[0028] wherein the escapement is engaged with the rotatable gear system to regulate movement of the gear system based on movement of the escapement so as to release sored energy from the energy storage device to move the plunger.

[0029] According to another example there is provided a fluid dispensing apparatus incorporating the fluid delivery actuator. The fluid dispensing apparatus can be a wearable insulin pump

[0030] According to another example there is provided a method of operating an insulin pump, the method comprising the steps of:

[0031] a. locating a fluid receptacle comprising an insulin cartridge within the housing of the insulin pump so that a first end of the insulin cartridge is directly or indirectly contactable by the second end of the plunger;

[0032] b. connecting the insulin cartridge to an infusion set;

[0033] c. removably attaching the housing to a user of the fluid dispensing apparatus; d. inserting a needle of the infusion set beneath the skin of the user; and

[0034] e. powering on the insulin pump.

[0035] According to another example there is provided an escapement mechanism comprising:

[0036] a. an escape wheel rotatable about a first axis and having a plurality of teeth, b. an actuator having an effector that can be driven between first and second positions, c. a pallet fork having a pair of pallets and a pallet arm, the pallet fork being rotatable about a second axis, offset from the first axis, and

[0037] d. a rotatable coupling rotatably coupling the effector to the pallet arm,

[0038] the mechanism being configured such that as the effector moves between the first and second positions the pallet fork is caused to rotate about the second axis between first and secondpositions to alternately engage and release the pallets of the pallet fork with teeth of the escape wheel to allow progressive rotation of the escape wheel.

[0039] Examples may be implemented according to any one of the dependent claims.

[0040] In another example there is provided a fluid delivery actuator for a fluid dispensing apparatus, the fluid delivery actuator comprising: a controller; a power supply; at least one electromagnetic coil operatively connected to the power supply; a stator that is at least partially surrounded by the electromagnetic coil, and a rotor comprising a magnet and a lever. The rotor is rotatable in a first direction to reach a first position and in a second direction to reach a second position. The fluid delivery actuator also comprises an escapement that is engageable by the rotor lever, and a pair of first and second limit stops positioned to limit movement of the escapement between a first, locked position and a second, locked position. The escapement is held in the first, locked position when the rotor is in the first position, and in the second locked position when the rotor is in the second position. The fluid delivery actuator further comprises a rotatable gear system that engages with the escapement when the rotor is in the first position and the second position, and disengages with the escapement when the rotor is between the first and second positions; and an energy storage device for storing mechanical energy, the energy storage device being operatively engaged with the gear system and a linearly moveable plunger comprising a first end and a second end. The rotor rotates between the first and second positions when the electromagnetic coil receives alternating pulses of electrical current from the power supply upon input from the controller. When the rotor is rotating between the first and second positions, the energy storage device releases stored mechanical energy to move the plunger toward a fluid outlet of the fluid dispensing apparatus to dispense a measure of fluid through the outlet.

[0041] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of "including, but not limited to".

[0042] Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world.

[0043] The invention consists in the foregoing and also envisages constructions of which the following gives examples only.BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings which are incorporated in and constitute part of the specification, illustrate embodiments of the invention and, together with the general description of the invention given above, and the detailed description of embodiments given below, serve to explain the principles of the invention, in which:

[0045] Figure 1 is an isometric view of one form of fluid dispensing and dosage system comprising an actuation system;

[0046] Figure 2 is a schematic top view of one form of U core stator, coil, and rotor of one form of rotary actuator in one orientation;

[0047] Figure 2a is a schematic plan view of another form of stator, the stator comprising a cylindrical shape within which are located a pair of opposing stator arms, the end faces of which define a rotor receiving opening within which a rotor is located and that includes a rotor lever for engagement with an escapement mechanism;

[0048] Figure 2b is a schematic plan view of another form of stator, the stator comprising a cylindrical shape within which are located three pairs of opposing stator arms, the end faces of which define a rotor receiving opening within which a rotor is located and that includes a rotor lever for engagement with an escapement mechanism;

[0049] Figure 3 is a side view of one form of rotor for a rotary actuator;

[0050] Figure 4 is an exploded view of one form of rotary actuator and rotary actuator housing; Figure 5 is a schematic side view of one form of rotary actuator and shows the rotor operatively connected to, and engaged with, the escapement of the rotary actuator in the second position, and also shows distal ends of the first and second arms of the stator providing limit stops to limit rotation of the rotor and pallet fork of the escapement, and shows a pallet fork having a pallet arm opening formed in a distal end of the pallet arm body;

[0051] Figure 5a is a schematic side view of another form of rotary actuator and shows an asymmetrical clearance gap between the rotor and each of the first and second arms of the stator, the stator in this example also comprising a coil on each arm;

[0052] Figure 5b is a schematic side view of another form of rotary actuator and shows a pallet fork having a pallet arm opening formed within the pallet arm body;

[0053] Figure 5c is a schematic side view of an example employing a linear actuator with a pallet fork having a pallet arm opening formed within the pallet arm body;

[0054] Figure 6a is a schematic side view of one form of rotor operatively engaged with an escapement in the first position;Figure 6b is a schematic side view of one form of rotor operatively engaged with an escapement in the second position;

[0055] Figure 6c is another schematic side view of one form of rotor that includes a lever located within a pallet arm opening of one form of pallet fork to operatively engage the rotor with the pallet fork, and in which the rotor is in the second position, pressed against a second sidewall of the pallet arm opening to hold the pallet fork in the second, stop position and push the pallet arm, and therefore the pallet fork, against the second limit stop;

[0056] Figure 6d is a schematic side view of the rotor and pallet fork of Figure 6c and in which the pallet fork remains in the second, stop position, but the rotor has started to move sideways toward its first position;

[0057] Figure 6e is a schematic side view of the rotor and pallet fork of Figure 6d and in which the rotor has moved sufficiently toward its first position to contact and press against a first sidewall of the pallet arm opening to move the pallet fork toward the first, stop position;

[0058] Figure 6f is a schematic side view of the rotor and pallet fork of Figure 6e and in which the rotor is in its first position, pressed against the first sidewall of the pallet arm opening to hold the pallet fork in the first, stop position and to push the pallet arm, and therefore the pallet fork, against the first limit stop;

[0059] Figure 6g is a schematic side view of one form of rotary actuator and shows the rotor operatively connected to, and engaged with, the escapement of the rotary actuator in the second position and also shows limit stops in the form of pins connected to the first and second arms of the stator;

[0060] Figure 7 is a cutaway schematic view of one form of fluid dispensing and dosage system comprising an actuation system located within a housing of an insulin pump;

[0061] Figure 8 is a cutaway schematic view of one form of fluid dispensing and dosage system comprising an actuation system connected to a control system and power supply, all located within a housing of an insulin pump, and also showing a winding mechanism for applying torsion to a torsion spring of the actuation system;

[0062] Figure 9 is an exploded isometric view of one form of plunger mechanism for one form of fluid dispensing actuation system, and includes a fluid receptacle at one end of the mechanism;

[0063] Figure 10 is an isometric cutaway view of one form of plunger mounted on a rotatable threaded shaft and located within a housing, the plunger being slidable along opposing channels within the housing;

[0064] Figure 11 is an isometric view of the fluid dispensing and dosage system of Figure 1 within a housing;Figure 12 is another isometric view of the fluid dispensing and dosage system of Figure 11; Figure 13 is a top view of the fluid dispensing and dosage system of Figure 11;

[0065] Figure 14 is a perspective view from above of an insulin pump housing in which an actuation system is housed;

[0066] Figure 15 is a perspective view from below of the insulin pump housing of Figure 14;

[0067] Figure 16 is an exploded perspective view of the insulin pump housing of Figure 14, in which an insulin cartridge has been removed for replacement;

[0068] Figure 17 is a schematic cut-away perspective view of the insulin pump housing of Figure 14, showing the actuation system and particularly the exposed plunger of the actuation system and a space within the housing where the insulin cartridge is located during use;

[0069] Figure 18 is a schematic cut-away perspective view of a fluid dispensing apparatus within a wine barrel and being used to dispense a fluidic substance, such as flavouring, to wine within the barrel;

[0070] Figure 19 is a schematic cut-away perspective view of a fluid dispensing apparatus being used to dispense a fluidic substance (such as conditioning agents, fragrances, balancing fluids, treatment chemicals, or other additives) into water in a pool; and

[0071] Figure 20 is an exploded perspective view of a fluid dispensing apparatus within a housing and in which the housing includes mounting features to allow the device to be secured to a fixed structure.

[0072] DETAILED DESCRIPTION

[0073] Various exemplary embodiments and methods of use will now be described with reference to Figures 1 to 20, by way of example only. It will be appreciated that the invention as claimed is not intended to be limited in any way by these examples.

[0074] Features described in the context of separate aspects and examples may be used together and / or be interchangeable unless the context clearly indicates otherwise.

[0075] Figures 1 to 20 describe example escapement mechanisms and fluid dispensing that may be used in a fluid dispensing apparatus. The fluid delivery actuator may be configured to operate under low power to incrementally dispense fluid from a fluid dispensing apparatus.. The fluid delivery actuator generally comprises a controller, a power supply, at least one electromagnetic coil operatively connected via the controller to the power supply, a stator having the electromagnetic coil wound thereon, and a rotor comprising a magnet. The controller provides pulses of electrical current of alternating polarity from the power supply to the electromagnetic coil to create a magnetic field that is shaped by the stator and that naturally causes the rotor to rotate back and forth between two angular positions: a first position, and a second position. The direction of rotation of the rotor depends on the direction of magnetic torque applied to the rotor by the magnetic field. The fluid deliveryactuator also comprises an escapement mechanism that engages with the rotor and is locked in position when the rotor is in the first and second angular positions and is rotatable when the rotor is between the first and second positions. The fluid delivery actuator also comprises a gear system, energy storage device, and a plunger. The escapement mechanism engages the gear system, which is operatively connected to the energy storage device. The energy storage device is configured to store mechanical energy and to release the stored energy through the gear system. The energy storage device may take a variety of forms. Where a torsion spring is employed it may be configured to drive a gear of a gear train, as in examples below. Where a compression or expansion spring is employed it may drive a curved rack to drive the gear train or use an alternate drive mechanism. Where the energy storage device utilises compressed air, such as a gas spring, the linear drive force may likewise be converted to a rotary force driving the gear train. Where compressed air is utilised as the driving force a zinc-air battery may be utilised as a gas source. A rotary actuator may be configured so that the rotor rotates between the first and second positions when the electromagnetic coil receives pulses of electrical current of alternating polarity from the power supply via the controller and, when the rotor is rotating between the first and second positions, the energy storage device releases stored mechanical energy to move the plunger toward a fluid outlet of the fluid dispensing apparatus to dispense a measure of fluid through the outlet. As such, the stored mechanical energy may be incrementally released to dispense a measured volume of fluid as the rotor rotates back and forth between the first and second positions.

[0076] The rotary actuator relies on pulses of electric current of alternating polarity to the electromagnetic coil to drive it, and uses naturally occurring reluctance torque of the rotor to hold the rotor in the first and second positions. Movement of the plunger to dispense fluid is caused by the release of mechanical energy stored in the energy storage device. Thus, the actuation system allows for a controlled release or dosage of a fluid from a fluid dispensing apparatus with only a small electrical energy requirement. The low electrical energy requirement allows the fluid delivery actuator to operate using a limited power supply (such as a battery) for a prolonged period of time before it becomes necessary to replace or recharge the power supply. The fluid delivery actuator may therefore be suitable for dispensing a predetermined volume of fluid over a prolonged period of time.

[0077] By programming the controller to suit the purpose of the fluid dispensing apparatus and / or the needs of the user, the fluid delivery actuator may be particularly suitable for accurately dispensing a measured volume of fluid each time the fluid delivery actuator moves the plunger toward the fluid outlet. Preferably, the fluid dispensing apparatus is configured to dispense a volume of fluid each time the rotor is in the first and second positions. In other forms, the fluid dispensing apparatus may be configured to dispense a volume of fluid each time the rotor is in either the first or the second position.The fluid delivery actuator may be particularly suitable for use with a fluid dispensing apparatus for dispensing insulin, such as a wearable insulin pump, which may be a patch pump or a tubed pump. In other forms, the fluid delivery actuator may be used with a fluid dispensing apparatus for dispensing fluid into a fluid vessel for various purposes, such as for treating water, flavouring a beverage, medicating a fluid for animal consumption, or for any other suitable use.

[0078] The rotary actuator 100, escapement mechanism 150 and fluid dispensing apparatus the will be exemplified with reference to the drawings and primarily in relation to a fluid dispensing apparatus comprising a wearable insulin pump, but it should be appreciated that the rotary actuator 100 and actuation system may also be suitable for other uses without departing from the scope of the invention, such as antibiotic dosing of drinking water or food for farmed animals, such as pigs; and the gradual, metered introduction of a flavouring or other fluidic substance to an alcoholic drink, such as to a wine or spirit, during the aging process.

[0079] As shown in Figures 1 to 8, a rotary actuator 100 comprises a controller 105; a power supply 110; at least one electromagnetic coil 120; a stator 130; a rotor 140; an escapement 150, a gear system 160, an energy storage device 180, and a plunger 190.

[0080] The power supply 110 may be any suitable power supply, but is typically a power supply of limited capacity, such as a battery, or a slow-release capacitor, for example.

[0081] In some forms, the power supply 110 comprises a rechargeable battery and the rotary actuator 100 is located within a fluid dispensing apparatus, such as an insulin pump or fluid delivery pump, which comprises a passive energy capture system to recharge the battery. Such a passive energy capture and recharging system may comprise a solar cell, thermal energy harvesting device or a rotating weight that charges the battery automatically as the apparatus moves with the patient, or otherwise moves (the rotating weight and battery may operate in the manner of a non-mechanically wound quartz watch to recharge the battery).

[0082] In other forms, the power supply may be a mains supply.

[0083] The power supply 110 is connected via the controller 105 to the electromagnetic coil 120. The controller is configured to control the supply of electric current from the power supply 110 to the coil 120.

[0084] The at least one electromagnetic coil 120 comprises at least one current input terminal that is electrically connected to the power supply 110. The controller 105 provides pulses of electric current of alternating polarity to the coil 120, via the at least one input terminal, according to one or more signals from the controller 105. The electric current pulses are preferably provided to the coil(s) at a predetermined frequency and optionally also for a predetermined duration. The, or each, coil 120 may be any suitable coil for receiving electric current from the power supply 110 via controller 105 andgenerating an electromagnetic field about the stator 130. In some forms, the, or each, coil 120 comprises a single-phase stator winding that is positioned around a portion of the stator 130. In some forms, the, or each, electromagnetic coil 120 comprises two 'sub-coils' that are wound onto bobbins and positioned around at least a portion of the stator 130 to appear as a single coil. Preferably, the, or each, electromagnetic coil or sub-coil is a copper coil. In some forms, opposing ends of the coil(s) 120 may form input terminals and may be mounted on a printed circuit board 106 to which the power supply, such as a battery, may be connected and on which the controller 105 may also be mounted to operatively connect the controller 105, battery / power supply 110, and the coil (s) 120 in a simple and compact arrangement, as indicated in Figures 4 and 8.

[0085] The controller 105 is preferably configured to supply pulses of electric current of alternating polarity to the coil(s) 120 according to a pre-determined duration. The controller may be programmed or otherwise configured to cause the pulses to be applied to the coil(s) according to the predetermined duration.

[0086] The controller 105 may be any suitable controller for controlling power supplied to the coil (s) 120 by the power supply 110. In some forms, the controller 105 is a programmable controller. In some forms, the programmable controller is pre-programmed during manufacture. In some forms, the controller is pre-programmed during manufacture, and the operation of the controller may be modified by a user by re-programming the controller via a user interface of a fluid dispensing apparatus comprising the fluid delivery actuator. In other forms, the programmable controller may be pre-programmed during manufacture and may be unable to be modified by being re-programmed by a user. Where the controller is programmable, the controller may be configured to cause the power supply 110 to supply pulses of current to the coil 120 at an adjustable or fixed duration. For example, in some forms, the duration of the pulses may be adjustable via a user interface of a fluid dispensing apparatus comprising the fluid delivery actuator. The user interface may be a physical user interface, such as control buttons that provide inputs to modify operation of the programmable controller, or the user interface may be an electronic display screen displayed on a remote device, such as a cellular phone or personal computer or other remote control interface, and that includes inputs to modify operation of the programmable controller. In other forms, the operation of the controller 105 may be set to have predetermined, desired operating parameters that are not adjustable.

[0087] Whether or not the controller 105 is pre-programmed, adjustable, or non-adjustable, the controller 105 causes the power supply 110 to supply pulses of electric current to the coil(s) 120 to energise the coil(s) during current supply, and de-energise the coil (s) in the absence of current supply. As electric current passes through the coil(s) to energise the coil, the current creates an electromagnetic field having magnetic torque. By alternating the direction of the current through thecoil(s), the direction of the magnetic torque alternates. By stopping current supply to the coil (s), the, or each, coil is de-energised and the magnetic field collapses. Therefore, by controlling the duration and direction of electric current through the coil(s) 120, the controller 105 can control the existence of a magnetic field and the direction of its magnetic torque.

[0088] The stator 130 is configured to shape the electromagnetic field of the coil(s) 120 and to provide a rotor receiving space within which at least a magnet of the rotor 140 can be located and exposed to the electromagnetic field.

[0089] The stator 130 comprises a body comprising at least two opposing stator arms that are distanced from each other and that are connected together by a connecting portion of the stator body. Each stator arm comprises an end surface at which the arm terminates. The end surface of each stator arm is distanced from the end surface of the opposing stator arm to define a rotor receiving space within which at least a magnet of the rotor 140 is located. The shape of the stator may be of any suitable form.

[0090] In some forms, the stator comprises a C core stator (comprising a substantially C-shaped stator) or a U core stator (comprising a substantially U-shaped stator). For example, as shown in Figure 2, the stator 130 may comprise a stator body comprising a first arm 131 and a second arm 132 opposing the first arm 131. The first and second arms 131, 132 are distanced from each other. The stator body also comprises a connecting portion 133 that connects the first and second arms together and extends between the first and second arms 131, 132 to connect the arms and to distance the first and second arms from each other. A rotor receiving space 134 is provided between end surfaces of the distanced first and second arms 131, 132 of the stator 130. For example, in some forms and as shown in Figure 2, the stator comprises a substantially U-shaped stator that comprises two opposing substantially parallel arms, 131, 132. The connecting portion 133 of the stator connects the two arms 131, 132 at the bottom of the "U" and a rotor receiving space is defined between the arms 131, 132. In other forms, the stator may be substantially C-shaped and may have substantially the same arrangement as the U-shaped stator, except that the first and second arms of the stator are arcuate to create a curved inwardly facing side surface and the connecting portion connects the two arcuate arms to form the back of the "C". The rotor receiving space is provided between the inwardly curved stator arms, such as between opposing end surfaces of the arms.

[0091] In yet other forms, as shown in Figures 2a and 2b, the stator comprises a body having a cylindrical or disc-like shape with an enclosed curved peripheral region that forms a substantially circular cross-section. The circular peripheral region forms a connection portion of the stator body and connects the stator arms together. For example, at least two radially extending first and second stator arms may extend from the circular connection portion 133 toward a centre of the stator, suchthat the first and second stator arms 131, 132 project radially from a virtual centre of the stator and connect with the substantially cylindrical stator body. The stator arms 131, 132 are in opposing relationship and are distanced from each other. Each of the opposing first and second stator arms 131, 132 comprises a terminal end having an end surface 136 that faces toward the end surface 136 of the terminal end of the opposing stator arm. In some forms, each arm 131, 132 comprises a crossmember at its terminal end, and an inwardly facing surface of the cross-member (i.e. the surface that faces toward the opposing stator arm) forms the end surface 136 of the stator arm. In some forms, the end surface 136 of each arm 131, 132 is substantially concave and is shaped and dimensioned to define a generally circular rotor receiving space 134 between the first and second arms 131, 132 of the stator 130 and to provide a substantially consistent distance between the rotor and the end surface of the stator arms 131, 132. An opening is provided between the end surfaces of the arms and defines the rotor receiving space 134 within which a rotor 140 is located. The virtual centre of the stator is located within the rotor receiving space 134 and defines the rotational axis p of the rotor 140. The rotor 140 comprises a rotor arm 142 for engagement with an escapement mechanism, as disclosed herein. In the embodiment shown in Figure 2a, the stator 130 comprises two stator arms 131, 132 that form a pair, whereas in the embodiment shown in Figure 2b, the stator 130 comprises six radially extending stator arms that form three pairs of first and second stator arms 131, 132, that extend from the circular connection portion 133 of the stator body and are configured in the same manner as the stator arms of the embodiment of Figure 2a.

[0092] In the embodiments of Figures 2a and 2b, the rotary actuator may comprise multiple electromagnetic coils. For example, an electromagnetic coil may surround at least a portion of each stator arm 131, 132.

[0093] Therefore, as shown in Figures 1, 2, 2a, 2b, and 5, each of the first and second arms 131, 132 comprise inwardly facing end surfaces 136 that face toward the other arm and that define a rotor receiving space 134 between the arms. In some forms, each inwardly facing end surface of each arm 131, 132 may comprise a concave region and is shaped and dimensioned to define a generally circular rotor receiving space 134 between the first and second arms 131, 132 of the stator 130, and to provide a substantially consistent distance between the rotor and the end surfaces of the stator arms 131, 132. The concave regions of the arms 131, 132 each comprise a radius extending from a centre point p located between the concave regions. The centre point p defines the rotational axis of the rotor 140.

[0094] The rotor 140 comprises a magnet portion in which a magnet 143 is located. At least a portion of, or the entirety of, the magnet 143 of the rotor 140 is located within the rotor receiving space 134. Typically, the magnet 143 is concentrically located within the rotor receiving space 134. The magnet 143 (and therefore the rotor 140) is spaced from the opposing first and second arms 131, 132 of thestator 130 to provide a clearance gap (for example an air gap) between the rotor 140 and the stator 130.

[0095] In some forms, the rotor receiving space 134 is substantially circular and the magnet portion of the rotor that is located within the space 134 is substantially cylindrical and is concentrically located within the rotor receiving space to provide a symmetrical clearance gap between the rotor 140 and stator 130. In some forms, the clearance gap between the coil 120 and stator 130 may be greater than 1mm to avoid electrical short circuiting.

[0096] In other forms, the clearance gap between the rotor 140 and the stator 130 may be asymmetrical, as shown in Figure 5a, such that different portions of each of the first and second arms 131, 132 of the stator are spaced from the rotor 140 at a different distance. For example, each concave region of the first and second arms 131, 132 may comprise adjacent sections having a different radius from the centre point p. In some forms, the different radius may be created by a notch formed in the concave region of each of the first and second arms 131, 132. In other forms, as shown in Figure 5a, the concave region of each arm 131, 132 comprises a first section a and an adjacent second section b, the first and second sections being delineated by a step 139. The first section a has a larger radius than the second section b. The height of the step 139 is the difference in radius between the first and second sections a, b. Therefore, each concave region comprises a stepped section and does not have a consistent radius of curvature. Conversely, in this embodiment, the magnet portion of the rotor has a circular periphery with a consistent radius of curvature. In this arrangement, the clearance gap between the rotor 140 and the first section a of each concave region is larger than the clearance gap between the rotor 140 and the second section b of each concave region. Optionally, the concave regions may be shaped such that the first section a with the larger radius extends further along the respective concave region than the second section b with the smaller radius. For example, the first section a may form two thirds of each concave region and the second section b may form one third of each concave region. The first and second sections of each of the concave regions are located substantially opposite each other.

[0097] In some forms, the stator 130 may comprise laminations of electric steels. For example, the stator may comprise ferromagnetic laminations. Possible materials for the stator 130 include laminations of electric steels comprising a non-grain orientated structure, such as M250-35A and M600-65A, preferably M250-35a.

[0098] The stator may be of any suitable thickness. In some forms, the stator may be at least 0.8mm - 2mm thick.

[0099] At least one electromagnetic coil 120 surrounds a portion of the stator 130. For example, at least one electromagnetic coil 120 may be wound about a portion of, or the whole of, the first arm131, the second arm 132, both the first and second arms 131, 132, or the connection portion of the body of the stator, such as connecting portion 133 where the stator is a U-shaped or C-shaped stator, or the circular portion where the stator is a cylindrical stator having a short length.

[0100] As the, or each, electromagnetic coil 120 receives a current flow from the power supply 110, the coil 120 is energised and creates an electromagnetic field that is shaped by the stator 130 to create a more focussed magnetic field, referred to herein as a 'stator field'.

[0101] The rotor 140 comprises a rotor body that comprises a magnet 143. The magnet 143 may be attached to or integrally formed within the rotor body. The magnet 143 also has a magnetic field, which is referred to herein as a 'rotor field'. The rotor 140 is located so that the magnet 143 is at least partially located in the rotor receiving space 134 between the first and second arms 131, 132 of the stator 130. The location of the magnet 143 between the arms 131, 132 of the stator 130 ensures that the rotor field interacts with the magnetic field of the stator field.

[0102] An interaction force between the stator field and the rotor field at the stator and rotor interface produces a torque on the rotor 140. The torque that arises from the interaction of the two magnetic fields, is referred to herein as 'magnetic torque', Tm. The magnetic torque is applied to the rotor and initiates rotation of the rotor 140 as a pulse of electric current is applied to the coil, or each, 120. The direction of rotation of the rotor 140 is dependent on the direction of the magnetic torque, which is dependent on the direction in which the electric current flows through the coil(s) 120.

[0103] The magnet 143 may be of any suitable form. In some forms, the magnet 143 is a two-pole diametrically magnetised permanent magnet. In some forms, the magnet comprises a circular outer periphery. For example, in some forms, the magnet 143 may be a cylindrical magnet. In other forms, the magnet 143 may be an annular magnet, such as an annular, two-pole diametrically magnetised permanent magnet. In some forms, as shown in Figures 1 and 3, the magnet 143 is located at or near one end of the rotor body 141, such as at or near a first end of the body 141. In other forms, the magnet 143 may extend along the majority of or the whole of the length of the rotor body.

[0104] In some forms, the rotor 140 comprises a substantially cylindrical two-pole diametrically magnetized permanent magnet 143 that may be adhered to, otherwise attached to, or located within an interior of a non-magnetic rod of the rotor body.

[0105] In other forms, as shown in Figure 3, the rotor 140 comprises a non-magnetic rod 145 that passes through the annulus of an annular, two-pole diametrically magnetised permanent magnet 143, and on which the rotor body 141 is coaxially mounted. In some forms, the rotor body 141 is a substantially cylindrical tubular body that is coaxially mounted on the rod 145. The rotor 140 may comprise first and second supporting elements 144 at each end of the rod 145. In some forms, eachsupporting element 144 may comprise a bushing configured to be rotatably mounted on a supporting surface, such as a supporting surface of a housing or an actuator mount.

[0106] In some forms, the rotor magnet 143 comprises a magnetic material selected from the group comprising: hard ferrite; alnico, samarium cobalt, and neodymium-iron-boron. In one example, the rotor 140 may comprise an NdFeB diametrically magnetised annular magnet 143. In some forms, the rotor 140 may comprise an NdFeB diametrically magnetised annular magnet 143 located on a nonmagnetic rod 145, such as a 316 stainless steel rod that passes through the annulus of the magnet 143 and on which the rotor body 141 is coaxially mounted. The NdFeB magnet may be of a magnet grade having any suitable strength to create a sufficiently large magnetic field to rotate the rotor 140. In some forms, the NdFeB magnet may be an N42 grade magnet. In other forms, the NdFeB magnet may be an N56 grade magnet. In yet other forms, the magnet grade may be of any suitable strength between an N42 grade magnet and an N56 grade magnet.

[0107] In some forms, the rotor 140 comprises a substantially cylindrical rotor body 141, but it is envisaged that the rotor body 141 may be of any suitable shape, provided that the magnet portion of the rotor body (i.e. the portion of the rotor body in which the magnet 143 is located) is shaped to allow the rotor 140 to rotate evenly in two opposing directions and a clearance gap is provided between the rotor and the stator. Preferably, the magnet portion of the rotor body is cylindrical with a circular lateral cross-section. In some forms, the magnet portion of the rotor body comprises a diameter that is equal to a diameter of the remaining length of the rotor body such that the rotor body is substantially cylindrical. In other forms, the magnet portion of the rotor body may be of a different shape or of different dimensions to the rest of the rotor body. For example, the magnet portion may have a circular lateral cross-section, and the rest of the rotor body may have an octagonal lateral cross-section. In another example, both the magnet portion and the rest of the rotor body may have a circular lateral cross-section, but the diameter of the magnet portion may be larger or smaller than the diameter of the rest of the rotor body. In some forms, as shown in Figures 1 and 3, the rotor body 141 may comprise a substantially cylindrical shaft 141a of a first diameter. The shaft extends from an enlarged substantially cylindrical magnet portion 141b in which the magnet 143 is located. The magnet portion 141b has a second diameter that is larger than the first diameter of the rotor body 141.

[0108] The rotor 140 may comprise first and second supporting elements 144 that support the rotor within the rotary actuator. The supporting elements 144 suspend the rotor 140 (particularly the magnet 143 of the rotor) within the rotor receiving space 134, and allow the rotor 140 to rotate freely within the space 134. Optionally, each supporting element 144 comprises a bronze bushing configured to provide a low-friction bearing surface.The rotor 140 is configured to alternately rotate between a first angular position and a second angular position as alternating current pulses are supplied to the coil 120 by the controller 105. In effect, the rotation of the rotor 140 between the first and second angular positions synchronises with the electric current frequency supplied from the power supply 110 and therefore the electric current applied to the coil 120, which is controlled by the controller 105. The rotor 140 is rotatable in a first direction, such as a clockwise direction, to reach the first position. The rotor 140 is also rotatable in an opposing second direction, such as an anticlockwise direction, to reach the second position.

[0109] Magnetic reluctance is a term that is used to refer to the resistance of a magnetic circuit. Magnetic reluctance represents the opposition to magnetic flux. The rotary actuator may be configured such that when the controller 105 causes the power supply to stop providing electric current to the coil 120, the naturally occurring reluctance torque causes the rotor 140 to automatically adopt a position, relative to the stator 130, that maximises magnetic reluctance. The rotary actuator is configured such that the first and second angular positions of the rotor are the positions at which the reluctance torque of the rotor is at its maximum. Therefore, when current stops passing through the coil 120, the rotor 140 will automatically move to the closest of the first and second angular positions, at which positions the magnetic reluctance is maximised to stably hold the rotor in that position. The positional alignment torque acting on the rotor 140 is therefore referred to herein as the 'reluctance torque', Tr. By employing naturally occurring reluctance torque to rotate the rotor to the first and second positions (whichever is closer), the rotary actuator only needs sufficient power from the power supply to cause the rotor to rotate just beyond a central point between the first and second positions, after which point, the reluctance torque may be relied on to cause the rotor to rotate the remaining distance to reach the closest of the first and second positions.

[0110] The effect of reluctance torque helps to hold the rotor in the first and second positions, which means that external forces, such as bumps and knocks, are less likely to inadvertently cause the rotor to move from its first or second position. The rotary actuator therefore uses reluctance torque to assist with the stability of the rotary actuator in both the first and second angular positions. However, because the reluctance torque helps to hold the rotor in the first and second angular positions, it is necessary that the magnetic torque applied to the rotor upon coil energization is in the opposite direction to the reluctance torque, and is larger than the reluctance torque, in order to initiate rotation of the rotor out of the first and second angular positions.

[0111] The rotor 140 is engageable with the escapement mechanism 150.

[0112] A fluid dispensing apparatus including the rotary actuator and escapement mechanism may be configured so that the rate and volume of fluid dispensed by the apparatus is controlled by controlling movement of the escapement mechanism 150.The escapement mechanism 150 may comprise a pallet fork 151 that is moveable to a first, locked position when the rotor 140 is in its first position, and to a second, locked position when the rotor 140 is in its second position. The escapement mechanism 150 may also comprise an escape wheel 154 comprising teeth 155 that are engageable by the pallet fork 151 in the first and second locked, stop positions.

[0113] In some forms, the rotor 140 includes a lever 142a that projects from the rotor arm 142b to engage with the escapement mechanism 150, such as with a pallet fork 151 of the escapement mechanism 150.

[0114] The rotor arm 142b may project from the rotor body 141 at any suitable location along the length of the body 141 that does not interfere with the stator 130 as the rotor 140 rotates. For example, the arm 142b may project substantially centrally from the rotor body 141. In another form, the rotor arm 142b projects from a second end of the rotor body (at an opposite end of the rotor body to the magnet 143). In some forms, the rotor arm 142b may project from a shaft 141a that extends through, or from, the rotor body 141, such as from a second end of the rotor body, opposite to the first end. In some forms, the lever 142a projects from a free, distal end of the rotor arm 142b. The lever 142a may engage with the pallet fork of the escapement mechanism 150.

[0115] Thus, in one form, as shown in Figures 1 to 4, the rotary actuator comprises a stator 130 that comprising first and second arms 131, 132 connected by a connecting portion 133 that extends between the first and second arms 131, 132. The inwardly facing surfaces of each of the first and second arms 131, 132 comprise a concave region to form a substantially circular rotor receiving space 134 between the first and second arms 131, 132. A centre point p of the rotor receiving space is located between the concave regions and denotes the axis of rotation of the rotor. The rotor 140 comprises a tubular rotor body 141 coaxially mounted on a non-magnetic rod 145, such as a 316 stainless steel rod. The rotor comprises an NdFeB diametrically magnetised magnet 143 at or near a first end of the rotor body. The magnet 143 may be of any suitable strength. Optionally, the magnet may be an N42 grade magnet, an N56 grade magnet or any magnet having a strength in between that of an N42 grade magnet and an N56 grade magnet. Optionally, the magnet 143 is an annular magnet and the non-magnetic rod passes through an annulus of the magnet 143 to mount the magnet on the rod 145. Optionally, the rotor 140 comprises a substantially cylindrical body 141 comprising an enlarged cylindrical portion 141b at or near the first end of the body 141, and the magnet 143 is located within the enlarged cylindrical portion 141b. A lever 142a (the term "lever" used broadly to refer to a driving element and can simply be the end of the rotor arm) projects from the rotor body 141, and is distanced from the magnet 143. In some forms, the lever 142a projects from a rotor arm 142b that projects from the rotor body 141. Optionally, as shown in Figure 1, the rotor arm 142bprojects from the rotor body 141 at or near a second end of the rotor body 141, opposite to the first end of the body 141. The lever 142a may be mounted on and may project from the rotor arm 142b, such as near a distal end of the arm 142b. The magnet 143 of the rotor 140 is located within the rotor receiving space 134. The axis of rotation of the rotor 140 aligns with the centre point p of the rotor receiving space 134. The magnet 143 is spaced from the stator to provide a clearance gap 135 between the magnet 143 (and therefore the rotor 140) and the stator 130. The rotor rod 145 projects from each end of the rotor body 141. A supporting element 144, comprising a bushing, is located at each end of the rotor rod 145, such that one element 144 is located adjacent the enlarged portion 141b at the first end of the body 141, and one element 144 is located at the second end of the rotor body 141. The supporting elements 144 are configured to be rotatably mounted on a supporting surface, such as a supporting surface of a housing or an actuator mount to suspend the rotor 140 (particularly the magnet 143 of the rotor) within the space 134 and to allow the rotor 140 to rotate freely within the rotor receiving space 134. The rotor 140 is rotatable in a first direction to reach a first position, and in a second direction to reach a second position, the direction of rotation being dependent on the direction of magnetic torque created by the electromagnetic field applied to the stator 130 by the coil 120. The rotor arm 142b or lever 142a may be rotatably coupled to pallet arm 152 via a rotatable coupling. The rotatable coupling can take a variety of forms but in this example it is a pin-slot type rotary coupling where rotor lever 142a is engageable with the escapement mechanism by engaging with a pallet fork 151 of the escapement mechanism 150. Thus, the pallet fork 151 may be caused to move between first and second stop positions by rotation of the rotatable rotor 140 and engagement between the lever 142a and the pallet fork 151.

[0116] In some forms, as shown in Figures 5, 5b, and 6a to 6g, the escapement mechanism 150 comprises a substantially T-shaped pallet fork 151 comprising a pallet arm 152 at its first end. The pallet arm 152 is connected to a crossbar from which a pair of first and second pal lets / pallet arms 153a, 153b project at an opposing second end of the pallet fork 151, i.e. the forked end. The first and second pallet arms 153a, 153b are distanced from each other. The pallet fork 151 is rotatable about a pivot pin 157 that is located between the first and second ends of the fork 151, and is preferably located between the pallet arms 153a, 153b. In some forms, the pivot pin 157 is located off-centre between the pallet arms so as to be closer to one pallet arm than the other.

[0117] The escapement mechanism 150 also comprises an escape wheel 154 rotatably and coaxially mounted on an axial shaft 158. The axis of axial shaft 158 is offset from the axis of pivot pin 157. The escape wheel 154 comprises a plurality of teeth 155 extending around its circumference. Each pallet arm 153a, 153b is configured to engage with the teeth 155 of the escape wheel 154.In some forms, the rotor lever 142a is engageable with the pallet fork 151 to cause the pallet fork 151 to move between the first stop position and the second stop position as the rotor 140 moves between its first position and second positions respectively.

[0118] In some forms, the pallet arm 152 of the pallet fork 151 engages with the rotor 140 via the lever 142a of the rotor. For example, the pallet arm 152 may comprise an opening 152a for receiving at least a portion of the lever 142a therein. Preferably, the opening 152a is provided at or near a distal end of the pallet arm.

[0119] In some forms, the pallet arm opening 152a is formed within the pallet arm body and may comprise opposing side walls and one or more end walls. At least a portion of the lever 142a may project into or through the opening 152a. In some forms, the lever 142a comprises a substantially cylindrical pin and the pallet arm opening 152a comprises a slot-like elongate opening that is located at or near a distal end of the pallet arm 152 and extends substantially centrally along a longitudinal axis of the pallet arm toward the pallet arms 153a, 153b. However, it is envisaged that the lever 142a may be of any suitable shape to fit within the pallet arm opening 152a.

[0120] In some forms, the pallet arm opening 152a comprises opposing side walls and opposing end walls such that the opening is enclosed on all sides by the pallet arm body, as shown in Figure 5b. At least a portion of the lever 142a may project into or through the opening 152a. In one example, as shown in Figure 5b, the opening 152a may comprise a slot that extends along a longitudinal axis of the pallet arm 152. The opening 152a may form a substantially straight or arcuate slot. However, it is envisaged that the opening 152a may take other suitable shapes, such as a circular, an oblong, a bulbous, square, or rectangular shape, for example. Preferably, opposing side walls of the pallet arm opening are of a consistent profile to enable accurate control of the escapement mechanism as the lever 142a engages with the pallet fork 151 by contacting each side wall of the pallet arm opening, either simultaneously or one at a time. For example, the opposing side walls may each be flat or concave with the same radius of curvature to mirror each other.

[0121] Figure 5c shows a variant of the design in Figure 5b where a linear actuator 146 has been substituted for the rotary actuator 100. Like reference numerals have been used for like elements from Figure 5b. In this example linear actuator 146 has an effector 148 that is driven up and down between first and second positions to drive pallet arm 152 between its first and second positions. The same type of rotatable coupling is employed between effector 148 and opening 152a to provide a lost motion coupling and to also allow for lateral movement of effector 148 within opening 152a during motion between first and second positions. Operation of the escapement mechanism is otherwise as described above.In other forms, the pallet arm opening 152a may be provided at a distal end of the pallet arm 152. For example, as shown in Figures 5 and 6a to 6g, the pallet arm 152 may comprise an opening 152a that extends from the distal end of the pallet arm and into the body of the pallet arm toward the pallet arms 153a, 153b, such that the opening 152a is defined by opposing side walls and a singular end wall (i.e. one end is open). In some forms, the opening 152a may have a slot-like shape having a length extending along the longitudinal axis of the pallet arm 152, as shown in Figures 5 and 6a to 6g. However, it is envisaged that the opening 152a may take other suitable shapes, such as a circular, an oblong, a bulbous, square, or rectangular shape, for example. Again, it is preferred that opposing side walls of the pallet arm opening are of a consistent profile to enable accurate control of the escapement mechanism as the lever 142a engages with the pallet arm 152 of the pallet fork 151 by contacting each side wall of the pallet arm opening, either simultaneously or one at a time. For example, the opposing side walls may be flat or concave with the same radius of curvature to mirror each other.

[0122] Regardless of whether the pallet arm opening 152a is defined on all sides by the body of the pallet arm 152, or formed in a distal end of the pallet arm, the opening 152a may be configured to receive at least a portion of the lever 142a therein, and one or both of the opposing side walls of the opening 152a are contactable by the lever 142a when the rotor 140 is in the first and second positions.

[0123] A distance between the opposing side walls of the pallet arm opening 152a defines the width or diameter of the opening 152a.

[0124] In some forms, the width or diameter of the lever 142a may be less than the width or diameter of the pallet arm opening 152a (in the direction of travel of the lever 142a) to form a gap between the lever 142a and the side walls of the opening 152a when the lever 142a is centrally located within the opening 152a. This arrangement forms a lost motion mechanism allowing the lever 142a to move partially within the opening 152a, when moving from the first and second positions, before contacting with the body of the pallet fork pallet arm 152 by contacting and pressing against the opposite side wall of the opening 152a. The ability of the lever 142a to move within the opening 152a without contacting the pallet arm body allows the rotor 140 to at least partially rotate without resistance from the pallet fork 151 and therefore, from the escapement mechanism 150. Because the arrangement allows the rotor 140 to already be rotating and therefore have momentum when the lever 142a contacts and presses against the pallet arm body to cause the pallet fork 151 to rotate toward a different stop position, the rotor 140 is in a position of greater magnetic torque, when contacting the pallet arm body, than if the lever 142a was in constant contact with side walls of the pallet arm opening 152a (in which case the rotor would require sufficient torque to overcome the resistance ofthe escapement mechanism, at the outset). The momentum of the rotor (and therefore of the lever 142a) also helps to unlock the pallet fork 151 from its first or second stop position.

[0125] In this example the rotor arm 142b moves about half a degree from an end position before lever 142a engages the opposite side of opening 152a. This is 3.33% of the 15 degrees of total travel between end positions. The amount of lost motion can be between 2% to 50% of the total movement between end positions. The amount of lost motion can be between 3% to 25% of the total movement between end positions. It will be appreciated that other "lost motion" type mechanisms may be employed such as:

[0126] • Slotted crank / scotch yoke: A pin rides in a curved or straight slot in a driven plate. The slot has a dwell arc where the pin travels without moving the plate and then engages a driven section. This is essentially a generalised pin-in-fork with programmable lost motion angle via slot geometry. Using this method, the lost motion angle can be tuned precisely by changing slot geometry rather than being limited to fork gap width.

[0127] • Inverted slot: A slot sit is provided on the rotor arm which engages a pin on the pallet fork. This allows adjustment of the slot position from the radius of the rotor and stop position rather than the pallet fork / escapement mechanism.

[0128] • Magnetic striker: The rotor arm carries a permanent magnet. The pallet arm has a ferromagnetic or opposing magnet target. As the rotor sweeps its free arc and the magnets approach, repulsive force accelerates the pallet before contact. Lost motion is now a field interaction zone rather than a geometric gap. The impulse profile is set by magnet geometry and gap distance rather than contact face angles.

[0129] • Cam with dwell arc: A cam profile on the rotor arm face driving a follower pin on the pallet. The cam has a circular dwell arc (no follower movement) through the free arc, then a rising face that strikes and drives the follower at the desired point. This allows design of the velocity profile at contact through the cam face angle. A steep rise gives a short sharp impulse. A gradual rise gives a longer lower-force impulse.

[0130] • Compliant rotor arm: When striking the pallet fork the rotor arm compresses (compressible engagement surface) or bends (flexible arm) and once the arm has moved over equilibrium, it snaps back returning the energy to the escapement mechanism.

[0131] • Toggle / over-centre mechanism with snap action: Lost motion is stored as elastic energy. The stator arm drives a mechanism towards an over-centre point but the output doesn't move until the toggle snaps through.

[0132] The use of a lost motion mechanism reduces the starting force required to move the rotor arm from a stop position, where the magnetic holding force is greatest. It can also reduce the totalenergy required by applying the input energy from the electromagnetic coil in an effective manner across the entire range of motion.

[0133] In other forms, the diameter of the lever 142a may be only slightly smaller than the length or width of the pallet arm opening 152a (in the direction of travel of the lever 142a) to form a snug fit with the pallet arm opening 152a, such that the lever is substantially constantly in contact with both side walls of the opening 152a. Where the lever 142a is dimensioned to fit snugly within the pallet arm opening 152a in the direction of rotation of the lever, rotation of the rotor 140 causes simultaneous rotation of the pallet arm 152, and therefore of the pallet fork 151.

[0134] In some forms, the maximum extent of rotation of the pallet fork 151 about its pivot pin 157 may be limited by a pair of first and second limit stops 156a, 156b, which are distanced from each other and located on each side of the pallet arm 152, as shown in Figures 5, 5a, 5b, and 6a to 6g. The first and second limit stops 156a 156b may be located between the axis of rotation 147 of the rotor 140 and the axis of rotation of the pallet fork 151, which is defined by the pivot pin 157 (i.e. the limit stops can be positioned to limit the movement of either the pallet fork 151 or the rotor arm 142b). The width of the pallet arm 152 is less than the distance between the limit stops so that the pallet arm is moveable between the stops 156a, 156b and presses against a respective one of the limit stops 156a, 156b when the pallet arm 152 is in a first position and a second position. In some forms, the limit stops 156a, 156b are aligned with each other along a first virtual line that is located substantially perpendicular to a second virtual line extending between the axis of rotation 147 of the rotor and the pivot pin 157. In some forms, each limit stop 156a, 156b comprises a projecting element, such as a pin or block, that projects from an adjacent structure, such as from a housing for the rotary actuator or for an apparatus comprising the rotary actuator. In some forms, as shown in Figure 5, distal ends of the first and second arms 131, 132 of the stator may form limit stops 156a, 156b to physically limit the extent of rotation of the rotor 140 and pallet fork 151. For example, the first and second arms 131, 132 of the stator 130 may each comprise inwardly facing substantially concave regions, and the arms 131,132 may project towards each other and form first and second limit stops 156a, 156b at the distal ends of the first and second arms 131, 132 respectively. In a similar arrangement, as shown in Figures 5a and 6g, limit stops 156a, 156b in the form of pins are connected to distal ends of the first and second arms 131, 132 of the stator. In such arrangements, the limit stops 156a, 156b are distanced from each other and at least a portion of the pallet arm 152 is located between the stops 156a, 156b and is moveable between the stops 156a, 156b to reach a first stop position and a second stop position as the rotor 140 moves between a first position and second position respectively.Rotation of the rotor 140 between the first and second positions and movement of the pallet fork 151 between the first and second stop positions will now be described in relation to Figures 6a to 6f.

[0135] In some forms, as shown in Figure 6a, as the rotor 140 rotates toward its first position, the engagement between the rotor and pallet arm 152 (i.e. between the lever 142a and one side wall of the pallet arm opening 152a, or both opposing side walls) causes the pallet fork 151 to rotate about the pivot pin 157 in a first direction (such as a clockwise direction) to reach its first, stop position, at which point the pallet arm 152 abuts the first limit stop 156a to prevent further rotation of the pallet fork 151 and the rotor 140 in the first direction. Similarly, as the rotor 140 rotates toward its second position, the engagement between the rotor 140 and pallet arm 152 (i.e. between the lever 142a and the other side wall of the pallet arm opening 152a, or both opposing side walls) causes the pallet fork 151 to rotate about the pivot pin 157 in an opposing second direction (such as an anti-clockwise direction) to reach its second, stop position, at which point the pallet arm 152 abuts the second limit stop 156b to prevent further rotation of the pallet fork 151 and the rotor 140 in the second direction, as shown in Figure 6b.

[0136] Rotation of the pallet fork 151 and pallet arm 152 between the first and second stop positions, causes the pallet arms 153a, 153b to rotate such that one pallet arm extends closer to the escape wheel 154 than the other pallet arm each time that the pallet fork 151 reaches the first and second stop positions. For example, when the pallet fork 151 is in the first position, the first pallet 153a extends closer to the escape wheel 154 than the second pallet 153b, and the first pallet 153a engages with the escape wheel 154, such as by projecting between adjacent teeth of the escape wheel. Conversely, when the pallet fork 151 is in the second position, the second pallet 153b extends closer to the escape wheel than the first pallet 153a and engages with the escape wheel 154, such as by projecting between adjacent teeth of the escape wheel.

[0137] Figures 6c to 6f show more detailed movement of the lever 142a and the pallet fork 151 as the rotor 140 moves between the first and second positions to cause the pallet fork 151 to move between the first and second stop positions.

[0138] Turning first to Figure 6c, the lever 142a is located within the pallet arm opening 152a and presses against a second side wall of the pallet arm opening, pushing the pallet arm of the pallet fork 151 against the second limit stop 156b and holding the pallet fork 151 in the second, stop position. In this position, the second pallet arm 153b projects between two adjacent teeth of the escape wheel and engages with at least one of those two teeth by pressing against the tooth to lock the escape wheel, such that the escape wheel is prevented from rotating in a first direction.To rotate the rotor 140 to its first position, the controller 105 provides an opposing pulse of electric current to the coil 120 to energise the coil and create an electromagnetic field that is shaped by the stator 130. The electromagnetic field applies a magnetic torque to the rotor 140 in the first direction. The magnetic torque is in the opposite direction to the reluctance torque and must be sufficient to overcome the natural reluctance torque of the rotor to cause the rotor to start rotating in the first direction, toward its first position. In the embodiment shown in Figure 6d the lever 142a comprises a width or diameter smaller than the width of the pallet arm opening. Thus, at the beginning of the rotor rotation, as the rotor 140 rotates toward its first position and as shown in Figure 6d, the lever 142a moves sideways within the pallet arm opening 152a, moving away from the second side wall and toward the opposing first side wall of the pallet arm opening 152a. Because the width or diameter of the lever 142a is less than the width or diameter of the pallet arm opening 152a, the rotor 140 can begin rotating before the lever contacts the facing side wall of the pallet arm opening 152a. Thus, the rotor can begin its rotation without bearing the resistance of the pallet fork 151, and therefore of the escapement mechanism 150. In this arrangement, the rotor 140 has a lower reluctance torque and increased magnetic torque at the time the rotor 140 contacts the facing side wall of the pallet arm opening 152a and meets the resistance of the pallet fork 151, than if the width or diameter of the lever was substantially the same size as the width or diameter of the pallet arm opening 152a, which would cause the lever 142a to press against both side walls of the pallet arm opening, and be resisted by, the pallet arm body at the beginning of rotation of the rotor 140. As such, the magnetic torque required by the rotor at the time of contact with the facing side wall of the pallet arm opening 152a is less than the torque that would be required if the rotor and lever were subject to the resistance of the pallet arm (and the entire escapement mechanism) when the rotor first begins to rotate (such as when the lever is snugly held within the pallet arm opening). Furthermore, because the rotor 140 gains velocity and momentum as it rotates, when the rotor 140 has rotated sufficiently that the lever 142a contacts and presses against the first side wall of the pallet arm opening 152a, the contact pressure of the rotating rotor 140 against the pallet arm 152 is able to unlock the pallet fork 151 from the second, stop position.

[0139] Further rotation of the rotor 140 causes the lever 142a to contact the facing side wall of the pallet arm opening 152a and push against the pallet arm to rotate the pallet arm 152 in the same direction as the rotor. As the lever 142a pushes against the pallet arm 152, the pallet fork 151 rotates about its axis of rotation 157 toward the first, stop position. As the pallet fork 151 moves between the first and second stop positions, the pallet fork 151 reaches a central position, as shown in Figure 6e. In the central position, neither pallet arm 153a, 153b engages with the escape wheel 154 and the escape wheel is able to freely rotate. In the embodiment shown in Figure 6e, which includes limit stops156a, 156b, the pallet arm 152 is located substantially centrally between the limit stops.

[0140] In some forms, the escape wheel 154 may be biased to rotate in a first direction so that as the pallet fork 151 disengages with the escape wheel 154, the escape wheel rotates freely in the first, biased direction.

[0141] The rotor 140 continues to rotate until it reaches its first position, at which point the lever 142a pushes the pallet arm 152 of the pallet fork 151 against the first limit stop 156a, as shown Figure 6f, holding the pallet fork in the first, stop position. In the first, stop position, the first pallet arm 153a engages with the escape wheel 154 to prevent rotation of the wheel 154 in a first direction.

[0142] In some forms, the rotary actuator is configured so that the rotor 140 rotates 15° from its first position to reach its second position and vice versa, and the pallet arm of the pallet fork rotates 11° from its first stop position to reach its second stop position and vice versa.

[0143] Where the lever 142a is snugly received within the pallet arm opening 152a, the rotor 140, lever 142a, pallet fork 151, and escape wheel 154 interact in the same manner as described above in relation to the embodiment of Figures 6a to 6f, but the pallet arm (and therefore the pallet fork) is caused to rotate as soon as the rotor begins to rotate. Thus, rotation of the rotor in the first or second direction causes the lever 142a to simultaneously rotate the pallet arm 152 (and therefore the pallet fork 151) because the lever 142a remains in substantially constant contact with the side walls of the pallet arm opening 152a. Thus, when the rotor is in the first or second position, the pallet fork is also in the first or second position respectively. In such an arrangement, the magnetic torque applied to the rotor needs to be greater than that of the embodiment shown in Figures 6a to 6f because the rotor bears the resistance of the escapement mechanism at the start of the rotor rotation and does not have the opportunity to build up velocity and momentum before meeting that resistance. As such, a larger draw on current from the power supply is needed to initiate rotation of the rotor where the lever is snugly received within the pallet arm opening.

[0144] To exemplify the extent and direction of rotation of the rotor 140, Figure 5 shows a virtual line d that passes through the centre of the rotor 140 and is perpendicular to the first and second arms 131, 132 of the stator 130. Rotor angles of 0 = 0° (or 180°) correspond to the permanent magnetic poles of the rotor being in parallel alignment (or anti-parallel alignment) with the axis denoted by line d. The poles of the stator 130 align with this axis. The angle of rotation of the rotor 140 will be described in relation to line d. Because the stator 130 is formed of a material that has high relative permeability compared to the surrounding air regions, the position of the rotor 140 that maximises reluctance depends on the geometry of the clearance gap between the rotor 140 and stator 130. If the clearance gap was symmetrical on each side of the rotor (i.e. between the rotor 140 and each of the first and second arms 131, 132 of the stator), the rotor would rest at 0 = 0° and at 0 = 180° wherethe reluctance torque would be zero, and where the magnetic poles of the stator and rotor are aligned in parallel or anti-parallel and thus where the magnetic torque, Tm= 0. But a symmetrical clearance gap between the rotor 140 and each of the first and second portions of the stator 130 does not produce a magnetic torque sufficient to start rotating the rotor from the first and second positions because Tm= 0 when the stator and rotor fields are aligned to be parallel. Therefore, for this topology limit stops 156a, 156b may be provided on each side of the rotor to restrict rotation of the rotor to a range smaller than 0° - 180°, such as between an angle greater than 0° and an angle less than 180°, such as to an angle between about 80° - 100°, and preferably to an angle between about 82.5° -97.5°. Therefore, in some forms, the rotary actuator is configured so that the rotor rotates between 0 = 82.5° and 0 = 97.5° relative to virtual line d. In such an arrangement, the reluctance torque, Tris equal and opposite at the two limits of the range of rotor movement.

[0145] The limit stops 156a, 156b therefore limit rotation of both the escapement mechanism 150 and the rotor 140 in each direction, such that: the rotor 140 is rotatable in a first direction until the rotor 140 reaches its first position and the pallet fork 151 reaches its first, stop position; and the rotor 140 is rotatable in a second direction until the rotor 140 reaches its second position and the pallet fork reaches its second, stop position. The first and second positions of the rotor are preferably where the rotor is at 82.5° and 97.5° relative to virtual line d respectively.

[0146] Thus, the rotary actuator may be configured such that the selection of the angular operating range of the rotor maximises magnetic torque, and provides sufficient reluctance torque for stability of the rotor within its first and second positions.

[0147] In some forms, the rotary actuator may be configured to provide an alternative range of nonzero magnetic torque operating limits, such as 0 = 84.5 to 0 = 95.5. However, it should be noted that, as shown in Graph 1 below, the reluctance torque would be near-zero at these limits and, as such, is less able to oppose external forces acting to move the rotor from the first or second position. Consequently, when the rotary actuator is configured to allow the rotor to rotate between 0 = 84.5 to 0 = 95.5, the rotor 140 is less stable in the first and second positions than if the rotary actuator is configured to allow the rotor to rotate between 0 = 82.5 to 0 = 97.5.

[0148] Returning to the description of the escapement mechanism, the escape wheel 154 is rotatable about its axial shaft 158. Each of the teeth 155 of the escape wheel 154 may slope in a first direction and comprise a front face and a rear face. The front face of each tooth may be comparatively blunt compared to the rear face, which has a greater angle of slope than the front face. In such an arrangement, as the escape wheel 154 rotates in a first direction toward the blunt front face of each tooth (i.e. a clockwise direction in the embodiment of Figure 5), and the pallet fork 151 is in the first or second position, a respective one of the first and second pallet arms 153a, 153b may extend towardT1

[0149] the escape wheel 154 and abut the more blunt, front face of an adjacent tooth to stop rotation of the wheel 154 in the first direction. However, if the escape wheel 154 rotates in a second, opposite direction (such as anticlockwise), one or both of the first and second pallet arms 153a, 153b may contact and slide over the rear face of each tooth without engaging with the teeth 155 to stop rotation of the wheel 154. For example, as shown in Figures 5, 6a and 6b, the rotary actuator may be configured so that the first pallet arm 153a abuts a front face of a tooth to engage with the escape wheel 154 when the pallet fork 151 is in the first stop position to hold the wheel 154 stationary, and the second pallet arm 153b abuts a front face of a tooth to engage with the escape wheel 154 when the pallet fork 151 is in the second stop position to hold the wheel 154 stationary. When the pallet fork 151 is between the first and second positions, neither of the first and second pallet arms 153a, 153b engage with and lock the escape wheel 154, so the escape wheel 154 is free to rotate / advance.

[0150] In some forms, the escape wheel 154 is biased to rotate in the first direction by a biasing member, such that the escape wheel automatically begins to rotate in the first direction as soon as the wheel is released from the first or second locked position by the pallet fork 151. As the escape wheel 154 rotates, the wheel 154 engages with the gear system 160, which is operatively connected to the plunger 190, to dispense a discrete volume of fluid during a fluid dispensing moment in time. The duration of the fluid dispensing moment depends on the length of time for the pallet fork 151 to move between the first and second positions and vice versa (i.e. the length of time in which the escape wheel 154 may freely rotate).

[0151] Thus, the pallet fork 151 of the escapement mechanism 150 is moveable between a first, stop position and a second, stop position as the rotor 140 rotates and oscillates between a first position and a second position. The pallet fork 151 is configured such that the first and second pallet arms 153a, 153b engage with teeth 155 of the escape wheel 154 to stop rotation of the wheel in at least one direction. When the pallet fork 151 is in the first position and the first pallet 153a engages with and locks the escape wheel 154, the escapement mechanism 150 may be referred to herein as being in the first, locked position. Similarly, when the pallet fork 151 is in the second position and the second pallet 153b engages with and locks the escape wheel 154, the escapement mechanism 150 may be referred to herein as being in the second, locked position. As such, it is considered that the rotor 140 oscillates the pallet fork 151, and therefore the escapement mechanism 150, between its first and second locking positions as the rotor rotates between the first rotor position and the second rotor position.

[0152] In some forms, the rotary actuator is configured so that the rotor 140 rotates only a small amount to rotate the pallet fork 151 sufficiently to advance the escape wheel 154. In such arrangements, complete revolutions of the rotor 140 are unnecessary. For example, in some forms,the rotary actuator may be configured so that the rotor rotates 15° to oscillate the pallet fork 11° in order to advance the escape wheel 154. In some forms, the escapement mechanism 150 may be configured such that the escape wheel 154 rotates through the pitch of one tooth (or more than one tooth) for each single or double swing of the pallet arm 152 (i.e. for each oscillation of the pallet fork), depending on the volume of fluid to be dispensed at each fluid dispensing moment. Therefore, small volumes of fluid to be dispensed by a fluid dispensing apparatus comprising the fluid delivery actuator.

[0153] In some forms, as shown in Figures 1 and 7, the escapement mechanism 150 of the fluid delivery actuator is operatively connected to the gear system 160 and controls movement of the gear system 160 such that when the escapement mechanism 150 is in the first or second locked position, the gear system is prevented from rotating. In some forms, the gear system 160 includes a plurality of gears, at least one of which is rotatably mounted on the axial shaft 158 of the escape wheel 154. For example, a first gear wheel 161a may be mounted on the axial shaft 158 of the escape wheel and may directly or indirectly engage with one or more other gear wheels 161 of the gear system 160 such that the gear wheels and escape wheel 154 rotate simultaneously.

[0154] The gear system 160 is also operatively connected to the energy storage device, and to a linear element 180 to which the plunger 190 is attached. Preferably, the plunger is slidably attached to the linear element.

[0155] The energy storage device is configured to release stored mechanical energy to move the plunger toward a fluid outlet of the fluid dispensing apparatus.

[0156] In some forms, the energy storage device comprises a biasing member 170 that releases mechanical energy, stored in the biasing member, as a biasing force applied to the linear element 180, and the escape wheel 154, via the gear system 160.

[0157] The linear element 180 is configured to transmit a biasing force from the biasing member 170 to the plunger to move the plunger 190 toward a fluid outlet of the fluid dispensing apparatus. The biasing force may be a linear force or a rotational force, depending on the nature of the biasing member and the mechanical energy stored by the biasing member, for moving the plunger 190 in a first direction, toward the fluid outlet. For example, the biasing force may be a turning moment / torque, a physical push or pull force, or a pressure force.

[0158] In some forms, as shown in Figures 1, 7, and 8, the linear element 180 may comprise a rotatable shaft 180' and the energy storage device may comprise a biasing member 170 comprising a torsion spring 170'. The biasing force may be a turning moment imparted on the rotatable shaft 180' by the torsion spring. The biasing member may be mounted on the rotatable shaft and operatively connected to the gear system. The biasing member stores mechanical energy in the form of a biasingforce that, when released, rotates the shaft 180' in a first direction, which also causes rotation of the gear system and escape wheel.

[0159] For example, a second gear wheel 161b of the gear system may be coaxially and fixedly attached to the rotatable shaft 180' and may mesh with another gear wheel of the gear system 160, such that the gear wheels 161 of the gear system, the escapement mechanism 150, and the shaft 180' are simultaneously rotatable when the escapement mechanism is released from its first or second locked position. Because the second gear wheel 262b is fixedly attached to the shaft 180', the gear wheels rotate as the shaft 180' rotates.

[0160] Also as shown in Figures 1, and 7 to 9, the torsion spring 170' may be coaxially mounted on the rotatable shaft 180'. The torsion spring 170' is fixedly attached to the shaft 180' and is torsioned in a second direction such that the spring 170' is biased to rotate in an opposing first direction, such as a clockwise direction. Thus, under torsion, the torsion spring 170' biases the shaft 180' to rotate in the same first direction. The torsion spring 170' may be operatively connected to the gear system 160 via the second gear wheel 161b that is mounted on the rotatable shaft 180'. Thus, under torsion, the torsion spring 170' applies a biasing force in the form of a torque to the gear system 160 (and the escape wheel 154) via torque applied to the rotatable shaft 180' and the second gear wheel 161b mounted thereon. Therefore, when the pallet fork 151 disengages with the escape wheel 154, the escape wheel is caused to rotate in the direction of the biasing torque created by the biasing member 170, 170'.

[0161] The plunger 190 may also be mounted on the rotatable shaft 180' and is moveable along the shaft 180' under a biasingforceof the torsion spring. Preferably, the plunger is concentrically mounted on the rotatable shaft. In some forms, the rotatable shaft 180' is a threaded shaft and the plunger 190 comprises a threaded portion that meshes with the shaft 180'. Thus, the plunger may be movable along the rotatable shaft as the rotatable shaft rotates. Preferably, the plunger 190 comprises a first end and an opposing second end. The first end of the plunger comprises an opening 191 to a threaded hollow to receive a portion of the threaded shaft 180' therein, and to mesh with the shaft 180'. To prevent rotation of the plunger 190 as the shaft 180' rotates, the plunger 190 is configured to engage with and slide relative to a fixed element, such as a portion of a housing or mount for the actuation system. For example, in some forms, the plunger 190 may comprise at least one slider 192, such as a pin, that projects from one side of the plunger 190. Preferably, the plunger 190 comprises a pair of sliders 192 that project from opposing sides of the plunger. The plunger 190 may be located within a mount 200 of the fluid delivery actuator housing 300. The mount 200 may comprise at least one elongate channel 210 that extends parallel to the plunger 190 and is configured to engage with a respective slider 192 of the plunger 190. Where the plunger 190 comprises two sliders 192, the mount200 may comprise two channels 210, each channel being located adjacent to a respective one of the sliders 192. In some forms, each slider 192 comprises a screw that projects from a cap 193 of the plunger and each channel 210 comprises a slot formed in the plunger mount 200, as indicated in Figures 9 and 10. Each slider 192 is held within the respective channel 210 and is slidable along the channel as the plunger 190 slides in a first direction and a second direction. Upper and lower side walls of the channel 210 limit upward and downward movement of the sliders 192 to prevent rotation of the plunger. In other forms (not shown), at least one elongate channel may be provided along one side of the plunger or along opposing sides of the plunger, and at least one corresponding slider may project from the plunger mount to be received within the channel and to slide along the channel as the plunger slides in the first direction and the second direction. Again, upper and lower side walls of the channel limit upward and downward movement of the sliders to prevent rotation of the plunger. The parts 180, 190 and 200 thus form a linear actuator driven by the gear train.

[0162] The plunger 190 is moveable along the shaft 180' and toward a fluid receptacle of the fluid dispensing apparatus, under a biasing force of the biasing member when the escapement mechanism 150 is released from its first or second locked position. Thus, the plunger 190 is configured to move in a first direction, such as a forward direction, as the shaft 180' rotates in a first direction, and to move in a second direction, such as a backward direction, as the shaft 180' rotates in a second direction, but the plunger 190 itself is unable to rotate.

[0163] The fluid receptacle 400 may comprise a fluid reservoir for containing a fluid therein, and a fluid outlet 410. The fluid outlet 410 of the fluid receptacle 400 is in fluid communication with the fluid reservoir to allow fluid to flow from the reservoir and through the outlet. In some forms, the fluid receptacle is an insulin cartridge comprising a fluid reservoir for containing insulin therein.

[0164] As the plunger moves in the first direction toward the fluid receptacle 400, the second end of the plunger 190 may engage with the fluid receptacle 400 to push fluid from the fluid receptacle and through a fluid outlet in the fluid receptacle during a fluid dispensing moment. For example, a first end of the fluid receptacle may be directly or indirectly contactable by the second end of the plunger. In some forms, the fluid receptacle 400 comprises a first end that may be located adjacent the second end of the plunger, and a second end at which the fluid outlet is located. Preferably, the fluid outlet 410 is substantially opposite the first end of the fluid receptacle 400.

[0165] In some forms, the first end of the fluid receptacle comprises a compressible seal, such as a rubber or silicone sleeve that the second end of the plunger directly or indirectly presses against. In some forms, the second end of the plunger comprises a sleeve that presses against the compressible seal. In other forms, the first end of the fluid receptacle 400 may mechanically engage with the plunger 190 by any suitable means, such as by friction fit, a threaded connection, or by one or more clipattachments. For example, the second end of the plunger may comprise a stretchable sleeve, such as a rubber or silicone sleeve, which fits over the first end of the fluid receptacle 400 in a friction fit arrangement.

[0166] Preferably, the fluid receptacle 400 is removable and replaceable once it is empty of fluid, as indicated in Figures 16 and 17. For example, the fluid receptacle 400 may be removably attachable to the plunger 190. In some forms, the fluid receptacle 400 comprises a removable and replaceable insulin cartridge that is attachable to an infusion set at its first end and to the plunger 190 at its second end. Preferably, the infusion set is removably attachable to the insulin cartridge. Typically, the insulin cartridge and infusion set are disposable after use.

[0167] It should therefore be understood that the fluid delivery actuator may be used in a fluid dispensing apparatus, in which the energy storage device of the fluid delivery actuator incrementally releases stored mechanical energy to move the plunger to dispense discrete volumes of fluid from a fluid receptacle, preferably for a predetermined duration. The increments are a function of the selected gearing of the gear system, as would be appreciated by a person skilled in the art.

[0168] Operation of the fluid delivery actuator will now be described with reference to its use within a fluid dispensing apparatus, such as an insulin pump by way of example only. However, it should be appreciated that the fluid delivery actuator may be used with other types of fluid dispensing apparatus.

[0169] In use, the coil 120 of the rotary actuator is connected to the power supply 110, such as to a rechargeable battery, via the controller 105. When the controller 105 provides a pulse of electric current from the power supply to the coil 120, an electromagnetic field is created and is enhanced by the stator 130, creating the stator field. The direction of the magnetic field depends on the direction at which the electric current passes through the coil 120. A second magnetic field (herein referred to as the 'rotor field') is created by the diametrically magnetised permanent magnet 143 of the rotor 140. Ferromagnetic laminations of the stator 130 may guide the stator field lines to stator poles, each of the stator poles being found on a respective one of the first and second arms 131, 132 of the stator 130. For example, the first arm 131 may comprise a first stator pole, and the second arm 132 may comprise a second stator pole. The first and second arms 131, 132 and therefore the first and second stator poles, are separated by a rotor receiving space 134 within which a magnet of the rotor 140 is at least partially located. The controller provides sufficient electric current from the power supply to the coil 120 such that the magnetic torque that arises from the interaction of stator field and rotor field, when the coil 120 is energised, is greater than, and in the opposite direction to, the reluctance torque applied to the rotor. The magnetic torque therefore initiates rotation of the rotor 140 as a pulse of electric current is applied to the coil 120. The direction of rotation of the rotor 140 isdependent on the direction of the magnetic torque, which is dependent on the direction in which the electric current passes through the coil 120.

[0170] The relationship between the rotor angle, the magnetic torque, the reluctance torque, and the total torque is exemplified in Graphs 1 and 2 below (Graph 1 being an enlarged version of Graph 2).

[0171] In some forms, the rotary actuator is configured so that the rotor 140 rotates between an angle of 82.5° to 97.5° relative to a virtual line d passing perpendicular to the arms of the stator 130 and a centre of the rotor 140. The virtual line d defines an axis at which the electromagnetic field of the stator 130 and a magnetic field of the rotor 140 align in parallel. When the rotor is at the angle of 0 = 82.5°, the rotor is in the first position, and when the rotor is at the angle 0 = 97.5°, the rotor is in the second position. When the rotor is in the central position of the range such that the rotor angle 0 = 90°, the reluctance torque applied to the rotor is zero.

[0172] An electrical current pulse from the power supply 110 to the coil 120 creates an electromagnetic field at the stator 130, creating a starting magnetic torque in a first direction that causes the rotor 140 and therefore the lever 142a to rotate in the first direction, such as a clockwise direction, away from its second position and toward the first position. The starting torque is opposite in direction to the reluctance torque and is greater than the reluctance torque to initiate movement of the rotor. As the rotating lever 142a pushes against the facing side wall of the opening 152a, the rotational movement of the rotor 140 begins to rotate the pallet arm (and therefore the pallet fork 151) about pivot pin 157. As the rotor passes the angle of 0 = 90°, (relative to line d), the reluctance torque causes the rotor to rotate to its first position until the pallet arm 152 abuts the first limit stop 156a. The first limit stop 156a prevents further rotation of the pallet fork 151 and rotor 140 in the first direction. The effect of the reluctance torque biases the rotor toward the closest of the first and second positions once the rotor is at an angle 0 * 90°, relative to axis d. Thus, to move the rotor between the first and second positions, the rotary actuator only needs to provide sufficient electrical current to move the rotor just beyond 0 = 90°, because the remaining rotational movement of the rotor is naturally caused by the reluctance torque. The reluctance torque also helps to hold the rotor 140 and escapement mechanism 150 in the first position, in which the rotor angle 0 = 82.5°. Where the rotor angle 0 = 82.5°, the reluctance torque, Tris negative, as indicated in Graph 2 below. The negative reluctance torque acts in the clockwise direction, pushing the pallet fork 151 to the first position and against the first stop 156a, as shown in Figure 6a, and causing the first pallet arm 153a to engage with a tooth of the escape wheel 154 to stop rotation of the escape wheel, i.e. to help hold the rotor 140 in the first position and hold the escape wheel in the first, locked position, thereby stabilising the rotary actuator.The total torque Ttapplied to the rotor is the sum of the magnetic torque Tmand the reluctance torque Tr, i.e. Tt= Tm+ Tr, as shown in Graph 1 below.

[0173]

[0174] Graph 1 - showing Tm, Tr, and Ttmagnitude and direction for 0 = 0° to 0 = 180°

[0175] Bi-directional oscillation of the rotor 140 is achieved by alternating the direction of the current used to energise the coil and stator 130. Thus, the controller 105 may be configured to cause the direction of the electrical current from the power supply 110 to the coil 120 to alternate to change the polarity of the stator field and thereby produce a negative torque or a positive torque on the rotor 140, in order to alternate the direction of rotation of the rotor 140 to oscillate the rotor between the first and second positions.

[0176] Therefore, as the controller reverses the direction of current applied to the coil, the polarity of the stator field is reversed, which reverses the direction of magnetic torque applied to the rotor. The resulting magnetic torque in a second direction causes the rotor 140 to rotate in the second direction, such as an anticlockwise direction, to rotate from the first position to the second position. For example, to rotate the rotor 140 from the first position to the second position, such as from 0 = 82.5° to 0 = 97.5°, the controller 105 provides a pulse of electrical current from power supply 110 to the coil 120, which generates a starting torque, Tmin the second direction. The starting torque, Tm, is in the opposite direction to the reluctance torque currently applied to the rotor and must be sufficientto overcome the reluctance torque Trto cause the rotor 140 and lever 142a to rotate.

[0177]

[0178] Rotor Angle #)

[0179] Graph 2 - Magnitude and direction of Tmand T-between rotor limits of 0 = 82.5° to 0 = 97.5°

[0180] As the rotor rotates and the lever 142a pushes against the facing side wall of the pallet arm opening 152a of the pallet fork, the pallet arm 152 is caused to rotate. The rotational movement of the rotor 140 rotates the pallet arm (and therefore the pallet fork 151) about pivot pin 157. As the rotor rotates past 0 = 90°, the reluctance torque pushes the rotor 140 to the second position and presses the pallet fork 151 against the second limit stop 156b in the second position. The limit stop 156b prevents further rotation of the pallet fork 151 and rotor 140 in the second direction, and the reluctance torque holds the rotor 140 and escapement mechanism 150 in the second position, in which the rotor angle 0 = 97.5°. In this position, the reluctance torque Tris positive, as indicated in Graph 2. The positive torque acts in the anti-clockwise direction, pushing the pallet fork 151 against the second stop 156b, as shown in Figure 6b, and causes the second pallet 153b to engage with a tooth of the escape wheel 154 to stop rotation of the escape wheel, i.e. to help hold the rotor 140 in the second position and hold the escape wheel in the second, locked position.

[0181] To return the rotor 140 to the first position, the controller 105 provides a pulse of electric current of opposite polarity to the coil 120, which generates a negative starting torque, - Tm,preferably of the same magnitude but opposite direction to Tm. Again, once the rotor 140 rotates past 0 = 90°, the reluctance torque Trpushes the rotor 140 to the first position and presses the pallet fork 151 against the first stop 153a in the first position, at which 0 = 82.5°.

[0182] The rotary actuator is therefore configured to use the reluctance torque, Tr, to bias the rotor toward the first and second positions and oppose any external forces acting to toggle the rotor from the first position or the second position to the other of the first and second positions. For example, the resistance provided by the reluctance torque reduces the likelihood of external vibrations accidentally moving the motor from the first and second positions, which would allow the escape wheel 154 to rotate and cause fluid to be dispensed accidentally from the fluid dispensing apparatus. The rotary actuator is therefore configured so that reluctance torque Trhelps to hold the rotor 140 in the first position and in the second position. As such, the rotor 140 is substantially stable in each of the first and second positions such that the rotary actuator 100 operates as a bistable rotary actuator.

[0183] As the rotor 140 rotates between the first position and the second position, the escapement mechanism 150 moves between the first locked position and the second locked position. Between the firstand second locked positions, the pallet arms 153a, 153b of the pallet fork 151 release engagement with the escape wheel 154 and the escape wheel is free to rotate.

[0184] The escape wheel 154 is operatively engaged with the gear system 160 that is operatively engaged with the rotatable shaft 180' that is biased to rotate in a first direction by the energy storage device, which may comprise a biasing member, such as a torsion spring 170'. In the embodiment shown, the first direction of rotation of the rotatable shaft is the clockwise direction, but the actuation system may be reversed so that the first direction of rotation is the anticlockwise direction.

[0185] The escapement mechanism 150 is held in the first and second locked positions by the engagement between the pallet fork 151 and the escape wheel 154, which prevents the escape wheel 154 from rotating. The escape wheel 154 is operatively connected to the gear system 160 such that when the escape wheel is prevented from rotating, the gear system 160 is unable to rotate and the shaft 180' is also unable to rotate under the biasing force of the torsion spring 170'. Thus, the components of the actuation system are locked and stationary when the rotor 140 and escapement mechanism 150 are in the first and second positions.

[0186] When the rotor 140 and pallet fork 151 move between the first and second positions, the escape wheel 154 is released from engagement with the pallet arms 153a, 153b and is free to rotate, thereby releasing the operatively connected components of the actuation system.

[0187] Thus, the escapement mechanism 150 engages with and prevents movement of the gear system 160 in the first and second locked positions and allows movement of the gear system when the escapement mechanism is released from engagement with the pallet fork 151.When the escapement mechanism 150 is unlocked / released, the torsion spring 170' is able to release mechanical energy as a result of the tension within the spring and automatically begins to rotate the rotatable shaft 180' in a first direction, such as a clockwise direction. As the shaft 180' rotates, the second gear wheel 161b rotates in the same direction, which causes the other gear wheels of the gear system 160 to rotate, including the first gear wheel 161a mounted on the axial shaft 158 of the escape wheel 154. Thus, the escape wheel 154 is also caused to rotate with rotation of the axial shaft 158. In the embodiment shown, the gear system 161 is configured to rotate the escape wheel 154 clockwise. Rotation of the torsion spring 170' in the first direction causes rotation of the shaft 180' in the first direction and movement of the plunger 190 in a first direction, toward the fluid receptacle 400 and fluid outlet 410.

[0188] The engagement between the plunger slider(s) and the plunger channel(s) allows the plunger 190 to slide toward the fluid receptacle 400 without rotating. The second end of the plunger 190 presses against a slidable first end of the fluid receptacle 400 that slides within the fluid reservoir under the force of the plunger 190. The first end of the fluid receptacle 400 slides toward the fluid outlet 410 and pushes fluid from the fluid reservoir through the fluid outlet to discharge a discrete volume of fluid from the fluid dispensing apparatus.

[0189] Once the rotor 140 reaches the other first or second position and the escapement mechanism 150 is locked, the fluid delivery actuator is also locked such that the plunger 190 is unable to slide toward the fluid receptacle 400 and fluid remains within the fluid reservoir until the next instance at which the escapement mechanism 150 is released. Thus, when unlocked / released, the escapement mechanism 150 allows the fluid delivery actuator to dispense fluid from a fluid receptacle. However, when the escapement mechanism 150 is in each of the first and second locked positions, the escapement mechanism prevents the fluid delivery actuator from dispensing fluid.

[0190] Therefore, by configuring the controller 105 to oscillate power to the rotary actuator, and by configuring the rotary actuator to release the escapement mechanism 150 for a particular duration (i.e. for the fluid dispensing moment of time), it is possible to control the volume / dose of the fluid discharged each time that the escapement mechanism 150 is released. In this way, the fluid delivery actuator can be used to provide a metered discharge of fluid from a fluid dispensing apparatus.

[0191] In some forms, the torsion spring 170' can be re-torsioned to restore the mechanical energy stored within the torsion spring.

[0192] For example, in some forms, the rotatable shaft 180' may be rotatable in a second direction to rotate the torsion spring 170' in the second direction to apply torsion to the spring. The gear system 160 may be engageable with a ratchet 162 to prevent rotation of the torsion spring 170' in the first direction as the spring 170' is being tensioned. For example, as shown in Figure 1, the second gearwheel 161b may engage with a ratchet to prevent rotation of the gear wheel in the first direction as the torsion spring is rotated in the second direction to re-torsion the spring 170'.

[0193] The torsion spring 170' may be re-torsioned in any suitable manner. For example, the fluid delivery actuator may comprise a removable torsion key that engages with the rotatable shaft and that is manually rotatable to rotate the rotatable shaft to torsion the torsion spring, such as by rotating the shaft in the second direction. In one form, a torsion key 171 may be removably attachable to one end of the rotatable shaft 180'. When attached to the shaft 180', the torsion key may be manually rotated in the second direction to apply torsion to the spring 170'. In other forms, the fluid delivery actuator may be located within a housing of a fluid dispensing apparatus and the torsion spring may be re-torsioned by pushing a fluid receptacle into a housing of the apparatus to engage the fluid receptacle with the rotatable shaft, and then rotating the fluid receptacle in a second direction, causing the torsion spring to rotate in the second direction. In some forms, the step of pushing a fluid receptacle, such as an insulin cartridge into a housing of the fluid dispensing apparatus, such as into a cartridge housing for an insulin cartridge, may cause the torsion spring to rotate in the second direction and be re-torsioned. For example, the act of pushing the cartridge into the housing may cause the plunger or the cartridge to back-drive the rotatable shaft, translating linear movement of the fluid receptacle to rotational movement of the rotatable shaft. The rotation in the second direction of the rotatable shaft may wind the torsion spring through the gearbox. Optionally, a one-directional rotational bearing connects the gearbox to the escapement wheel to allow the gearbox to rotate in the reverse direction, while the escapement wheel and pallet fork remain still.

[0194] In some forms, a portion of the fluid delivery actuator is located in a first housing 500, as shown in Figures 4, 7 and 11 to 13, and a portion of the fluid delivery actuator (such as the plunger, energy storage device, rotatable shaft) and the fluid receptacle may be located in a second housing 600 that includes a mount for the plunger and fluid receptacle, as shown in Figures 7 and 10 to 13. Both the first and second housings 500, 600 may be located within an apparatus housing / pump housing 700, such as a housing for a fluid delivery pump, such as an insulin pump, as shown in Figures 14 to 17. The insulin pump may be a patch pump or a tubed pump.

[0195] The fluid delivery actuator, and a fluid dispensing apparatus comprising the fluid delivery actuator, offers several advantages.

[0196] For example, the fluid delivery actuator may be reusable by replacing or recharging the battery / power supply once the energy levels of the battery / power supply are depleted. The fluid delivery actuator may also use less battery power than known infusion pump actuators in order to reduce the frequency at which the battery needs to be replaced or recharged.Where the fluid delivery actuator is used for an infusion pump, the reusability of the fluid delivery actuator and actuation system means that only the consumables of the infusion pump are discarded, such as the fluid cartridge, infusion set, and adhesive patch (where used).

[0197] Furthermore, broken or worn components of an actuation system (such as a gear system and plunger mechanism) may be replaced, if necessary, without needing to replace the entire actuation system.

[0198] The fluid delivery actuator may be removably attachable to disposable elements of a fluid dispensing apparatus, such as an insulin cartridge and infusion set of an insulin pump, and may comprise a sealed interface between the plunger and the fluid within the fluid receptacle. Thus, the disposable elements may be disposed of, as shown in Figures 16 and 17, but the fluid delivery actuator, including the plunger, may be re-used, thereby minimising waste and cost. An insulin pump comprising an fluid delivery actuator is therefore more environmentally friendly and sustainable than at least some existing insulin pumps.

[0199] The rotary actuator may be configured to substantially balance the emittance of magnetic torque with reluctance torque applied to the rotor to help move the rotor between the first and second positions and to hold the rotor stably within each of the first and second positions. For example, by aligning each of the first and second angular positions of the rotor with positions that maximise the reluctance torque applied to the rotor, it is possible to use the reluctance torque to provide positional stability of the rotor 140 in each of the first and second positions when the coil 120 is in the non-energised state (i.e. to provide passive stability when electric current is not being supplied to the coil).

[0200] Furthermore, because the reluctance torque pushes the rotor 140 to the first and second positions once the rotor rotates past the central position at which 0 = 90°, the power supply 110 of the rotary actuator only needs to provide sufficient energy to move the rotor from its first or second position to just beyond 0 = 90°. The remaining rotational motion of the rotor is driven by the reluctance torque without draining the power supply. The reluctance torque then holds the rotor in the first and second positions, thereby locking movement of the escapement mechanism and gear system, without requiring the power supply to hold the escapement mechanism and gear system in the locked position against the constant force of the biasing member. As such, only small quantities of electric current are needed to operate the rotary actuator. Where the power supply is a battery, the low power requirements of the rotary actuator can prolong the life of the battery.

[0201] And, where the interface between the rotor and pallet fork is created by providing a lever with a smaller width or diameter than the width or diameter of the pallet arm opening of the pallet fork, the rotor and pallet fork are able to rotate at different angles, so that the rotor can rotate within arange of angles that generate sufficient reluctance torque to provide positional stability to the rotor in the first and second positions and therefore controlled operation of the escapement mechanism.

[0202] Furthermore, where the lever comprises a smaller width or diameter than the width or diameter of the pallet arm opening of the pallet fork, the rotor is able to rotate before contacting the pallet arm body (when the rotor is moving between its first and second positions), therefore increasing the magnetic torque of the rotor and lowering the reluctance torque of the rotor by the time the rotor contacts the pallet arm body. This lost motion interface between the pallet arm opening and lever also allows the lever to contact the pallet arm body with velocity to help push the pallet fork from its first or second stop position.

[0203] Regardless of whether the lever is smaller in width or diameter than that of the pallet arm opening of the pallet fork, or the width or diameter of the lever is substantially equal to the width or diameter of the pallet arm opening, because the reluctance torque continuously acts to pull the rotor toward one of its first and second positions, the rotor is generally only moveable between the two first and second positions if a current is passed through the coil 120 to generate a magnetic torque that is induced on the rotor 140 and which is in the opposite direction to, and is greater than, the reluctance torque. The result is that the energy required to move the rotor between the first and second positions is in part provided by the power supply (to initially move the rotor) and is in part free energy that naturally occurs as a result of the reluctance torque after the rotor passes the central point between its range of angular movement. As such, the power requirements of the rotary actuator are reduced.

[0204] The rotary actuator, fluid delivery actuator, and fluid dispensing apparatus may be employed for many different uses, not just for the delivery of a medicinal fluid. For example, the fluid dispensing apparatus may be used to dispense controlled amounts of fluid into a fluid vessel for various purposes.

[0205] Figure 18 shows a fluid dispensing apparatus being used to dose a beverage contained within a fluid vessel 800 (such as wine within a wine barrel), with a fluidic substance that is a non-medicinal fluid. In this example, the apparatus / pump housing 700 is mounted to a structural element associated with the vessel / barrel, such as a lid or internal support. A fluid outlet 410 of the apparatus connects to a flexible tube 420 that extends into the liquid beverage inside the vessel / barrel 800. The tube 420 comprises a tube outlet 420a that is positioned below the liquid level so that the dispensed fluid is released directly into the beverage. The fluid reservoir within the fluid receptacle 400 of the apparatus may contain a beverage additive. Examples include flavourings, aroma compounds, tannins, acids, or other conditioning additives used during beverage processing or ageing. The rotary actuator 100 operates to dispense small, controlled volumes of the additive over time, allowing gradual adjustment of the beverage without manual intervention. Thus, the rotary actuator, fluid delivery actuator, andfluid dispensing apparatus can also be used in a non-medical context where accurate, repeatable dosing into a bulk liquid is required.

[0206] Figure 19 shows one form of fluid dispensing apparatus 700 being used to dispense a fluidic substance into a pool. The fluid dispensing apparatus 700 may use a fluid delivery applicator according to one of the examples above. For example, the fluid delivery apparatus may be used to dose water in a fluid vessel 800, such as a pool, a spa pool, or similar fluid vessel. In this configuration, the apparatus 700 is positioned outside the water, while the fluid outlet 410 of the apparatus is connected to a tube 420 that extends into the volume of water such that the tube outlet 420a is positioned within the water. As shown in Figure 20 fluid dispensing apparatus 700 dispenses controlled amounts of fluid from fluid receptacle 400 through the fluid outlet 410, the tube 420 and the tube outlet 420a and into the water at a predetermined dosage rate. The fluidic substance being dispensed in this example may include conditioning agents, fragrances, balancing fluids, treatment chemicals, or other additives used to maintain or modify the properties of the water within the pool. The actuator allows these fluids to be delivered automatically and in measured quantities over time.

[0207] Thus, the fluid dispensing apparatus may be used for general liquid dosing applications that do not involve delivery of a therapeutic substance to a person or animal.

[0208] Figure 20 shows an example in which the fluid dispensing apparatus 700 includes mounting features 710 to allow the apparatus to be secured to a fixed structure. In this example, the mounting features 710 comprise flanges on opposing sides of the housing 700. Each flange comprises an aperture 720 for receiving a fastener therein, to allow the fluid dispensing apparatus to be mounted to a surface, bracket, or support structure. The mounting features 710 are positioned so that it does not interfere with the fluid outlet or the connection of downstream tubing. This configuration allows the fluid delivery actuator and fluid dispensing apparatus to be installed in a stable, fixed position for use in a range of applications when delivering controlled amounts of fluid to a fluid vessel, such as for use in beverage processing, liquid conditioning systems, and other non-medical dosing scenarios. The mounting features are shown as one example of how the pump may be attached, rather than as a dedicated or specialised mounting system.

[0209] Various methods of using a fluid dispensing apparatus utilising the fluid delivery actuator are envisaged. For example, where the fluid delivery actuator is used with a fluid dispensing apparatus comprising an insulin pump, a method of operating an insulin pump may include the steps of: locating a fluid receptacle comprising an insulin cartridge within the housing of the insulin pump so that a first end of the insulin cartridge is directly or indirectly contactable by a second end of the plunger; connecting the insulin cartridge to an infusion set; removably attaching the housing to a user of the fluid dispensing apparatus; inserting a needle of the infusion set beneath the skin of the user; andpowering on the insulin pump. Where the fluid delivery actuator is used with a fluid dispensing apparatus for delivering a fluid to a fluid vessel, the method of using the apparatus may comprise attaching the apparatus housing to a support structure by any suitable attachment system, such as via fasteners and / or adhesive, and then locating the tube outlet 420a within liquid contained within the fluid vessel 800 before initiating the fluid dispensing apparatus to start the fluid delivery actuator and fluid pump to dispense fluid within the liquid of the fluid vessel 800.

[0210] The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

[0211] Although the invention has been described by way of example, it should be appreciated that variations and modifications may be made without departing from the scope of the invention as defined in the claims. Furthermore, where known equivalents exist to specific features, such equivalents are incorporated as if specifically referred in this specification.

[0212] For example, an alternative form of energy storage device may be provided as a means of storing and releasing mechanical energy. For example, as shown in Figure 7, the energy storage device may comprise a biasing member that comprises a that comprises a pressure member adapted to release pressure to move the plunger in a first direction toward the fluid outlet when the escapement mechanism is disengaged from the gear system. In some forms, the pressure member may comprise a compressed air or zinc-air battery that generates consistent pressure against the plunger to move the plunger in a first direction. The pressure may be generally proportional to current load. The escapement mechanism and gear system operationally connected to the plunger prevents the plunger from moving in the first direction under the biasing force, except when the escapement mechanism is unlocked to allow the gear system to release its lock on the plunger and allow the plunger to move in the first direction until the escapement mechanism is locked again in one of the first and second locked positions. In this arrangement, the pressure generating biasing means controls the linear movement of the plunger 190 being pushed toward the fluid outlet 410 of the fluid receptacle 400 by the increased air-pressure within a pressure cavity pressing against the first end of the plunger, such that the second end of the plunger pushes against the fluid receptacle.

[0213] In other forms, the rotatable shaft and second gear wheel of the actuation system may be replaced with a rack and pinion arrangement in which the pinion engages with the gear system and the rack, and also engages with the plunger to move the plunger linearly back or forth along the longitudinal direction of the rack. In such forms, the rack forms a linear element of the actuation system and the pinion forms part of the gear system.

Claims

CLAIMS1. An escapement mechanism comprising:a. an escape wheel rotatable about a first axis and having a plurality of teeth,b. a rotary actuator having a rotor that is rotatable with respect to a stator and having a rotor arm extending from the rotor that can be driven between first and second angular positions, c. a pallet fork having a pair of pallets and a pallet arm, the pallet fork being rotatable about a second axis, offset from the first axis, andd. a rotatable coupling rotatably coupling the rotor arm to the pallet arm,the mechanism being configured such that as the rotor arm rotates between the first and second angular positions the pallet fork is caused to rotate about the second axis between first and second positions to alternately engage and release the pallets of the pallet fork with teeth of the escape wheel to allow progressive rotation of the escape wheel.

2. An escapement mechanism as claimed in claim 1 wherein the rotatable coupling includes a lost motion mechanism.

3. An escapement mechanism as claimed in claim 2 wherein the lost motion mechanism is configured to lose motion during initial movement of the rotor away from the first and second angular positions.

4. An escapement mechanism as claimed in claim 2 or claim 3 wherein the lost motion mechanism is configured to lose between 2% to 50% of the motion between the first and second angular positions.

5. An escapement mechanism as claimed in claim 2 or claim 3 wherein the lost motion mechanism is configured to lose between 3% to 25% of the motion between the first and second angular positions.

6. An escapement mechanism as claimed in any one of claims 2 to 5 wherein the rotatable coupling is a pin-slot type rotary coupling and the lost motion mechanism is formed by a gap between the pin and walls of the aperture, dimensioned to provide the desired degree of lost motion.

7. An escapement mechanism as claimed in any one of the preceding claims wherein the rotary actuator is a bistable rotary actuator.

8. An escapement mechanism as claimed in any one of the preceding claims wherein the rotor is held in the first and second angular positions by reluctance torque.

9. An escapement mechanism as claimed in any one of the preceding claims wherein the stator has a C type core having one or more electromagnetic coil wound about the core.

10. An escapement mechanism as claimed in any one of the preceding claims wherein an asymmetrical clearance gap is provided between the rotor and the stator.

11. An escapement mechanism as claimed in any one of the preceding claims including first and second limit stops positioned to limit the range of movement of the pallet fork between a first, locked position and a second, locked position, wherein the pallet fork is held in the first, locked position when the rotor is in the first angular position, and in the second locked position when the rotor is in the second angular position.

12. An escapement mechanism as claimed in claim 11 wherein the limit stops limit the range of movement of the pallet arm.

13. A fluid dispensing mechanism comprising:a. an escapement mechanism as claimed in any one of the preceding claims;b. a gear train coupled to the escape wheel of the escapement mechanism;c. an energy storage device driving the gear train; andd. a linear actuator driven by the gear train,wherein the escapement mechanism controls rotation of the gear train so as to regulate the rate of movement of the linear actuator.

14. A fluid dispensing mechanism as claimed in claim 13 configured to receive a replaceable fluid cartridge, the contents of which may be dispensed by movement of the linear actuator.

15. A fluid dispensing mechanism as claimed in claim 13 wherein the linear actuator includes a threaded shaft driven by the gear train engaged with a plunger which moves axially along the threaded shaft as it rotates.

16. A fluid dispensing mechanism as claimed in claim 13 wherein the energy storage device is a spring which when tensioned drives the gear train.

17. A Fluid delivery actuator for a fluid dispensing apparatus, the fluid delivery actuator comprising:a stator having at least one electromagnetic coil wound on the stator;a rotor comprising a magnet and a rotor arm, wherein the rotor is rotatable in a first direction to reach a first position and in a second direction to reach a second position;a controller configured to supply pulses of electrical current of alternate polarity from a power supply to the at least one electromagnetic coil to rotate the rotor between the first and second positions;an escapement that is engageable by the rotor arm; andan energy storage device for storing mechanical energy, the energy storage device being configured to drive a gear system including a linearly moveable plunger having a first end and a second end;wherein the escapement is engaged with the rotatable gear system to regulate movement of the gear system based on movement of the escapement so as to release stored energy from the energy storage device to move the plunger.

18. The fluid delivery actuator of claim 17, wherein reluctance torque holds the rotor in the first position and in the second position.

19. The fluid delivery actuator of claim 17 or claim 18, wherein the stator comprises first and second arms connected by a connecting portion, wherein at least one of the first and second arms or the connection portion has the electromagnetic coil wound thereon, and wherein the first and second arms are distanced from each other and define a rotor receiving space between the first and second arms in which the rotor magnet is located.

20. The fluid delivery actuator of claim 19, wherein inwardly facing surfaces of each of the first and second arms of the stator comprise concave regions to define a generally circular rotor receiving space within which the magnet of the rotor is located.

21. The fluid delivery actuator of claim 19 or 20, wherein the rotor magnet is located between the opposing first and second arms of the stator and is spaced from the stator to define a clearance gap between the rotor and the first and second arms of the stator.

22. The fluid delivery actuator of claim 21, wherein an asymmetrical clearance gap is provided between the rotor magnet and the stator.

23. The fluid delivery actuator of any one of claims 17 to 22 including first and second limit stops positioned to limit movement of the escapement between a first, locked position and a second, locked position, wherein the escapement is held in the first, locked position when the rotor is in the first position, and in the second locked position when the rotor is in the second position.

24. The fluid delivery actuator of any one of claims 17 to 23, wherein the limit stops limit rotation of the rotor between an angle of 82.5° to 97.5° relative to a virtual line d passing perpendicular to the arms of the stator and through a centre of the rotor, the virtual line d defining the axis at which an electromagnetic field of the stator and a magnetic field of the rotor align in parallel.

25. The fluid delivery actuator of any one of claims 17 to 24, wherein the stator comprises a U-core or C-core stator.

26. The fluid delivery actuator of any one of claims 17 to 25, wherein the escapement includes a pallet fork and an escape wheel, and wherein the rotor arm rotatably engages with the pallet fork to oscillate the pallet fork between different configurations of engagement with the escape wheel.

27. The fluid delivery actuator of claim 26, wherein the rotor rotates 15° between the first and second positions and the pallet fork rotates 11° between the first and second locked positions.

28. The fluid delivery actuator of claim 26 or 27, wherein the pallet fork comprises a pallet arm and a pair of opposing pallets, the pallet arm comprising a pallet arm opening formed within a body of the pallet arm for receiving a lever of the rotor arm therein.

29. The fluid delivery actuator of claim 28, wherein at least one of the pallets engages with the escape wheel to prevent rotation of the escape wheel when the rotor is in the first position and when in the second position, and wherein the at least one pallet releases engagement with the escape wheel to allow free rotation of the escape wheel when the rotor is between the first and second locked positions.

30. The fluid delivery actuator of claim 28 or 29, wherein the lever is substantially cylindrical and the pallet arm opening comprises an elongate slot-like opening at a distal end of the pallet arm and wherein the pallet arm opening extends substantially centrally along a longitudinal axis of the pallet arm toward the pallets.

31. The fluid delivery actuator of any one of claims 28 to 30, wherein the lever comprises a width or diameter less than a width or diameter of the pallet arm opening to enable the rotor to move partially toward the other of the first and second positions without contacting the pallet arm body.

32. The fluid delivery actuator of any one of claims 28 to 31, wherein a respective one of the limit stop abuts the pallet arm when the escapement is in the first and second locked positions to prevent further rotation of the escapement and the rotor in the first and second directions respectively.

33. The fluid delivery actuator of any one of claims 17 to 32, wherein the rotor magnet comprises a diametrically magnetised permanent magnet.

34. The fluid delivery actuator of any one of claims 17 to 33, wherein the rotor comprises a material selected from the group comprising: hard ferrite; alnico, samarium cobalt, and neodymium-iron- boron.

35. The fluid delivery actuator of any one of claims 17 to 34, wherein the stator comprises laminations of electric steels comprising a non-grain orientated structure.

36. The fluid delivery actuator of any one of claims 17 to 35, wherein the at least one electromagnetic coil comprises a single-phase stator winding.

37. The fluid delivery actuator of any one of claims 17 to 36, wherein the energy storage device comprises a biasing member mounted on a rotatable shaft and being operatively connected to the gear system, and wherein the biasing member stores mechanical energy in the form of a biasing force that, when released, rotates the shaft in a first direction.

38. The fluid delivery actuator of claim 37, wherein the plunger is also mounted on the rotatable shaft and wherein the rotatable shaft is a threaded shaft that meshes with a threaded portion of the plunger such that the plunger is movable along the rotatable shaft as the rotatable shaft rotates.

39. The fluid delivery actuator of claim 37 or 38, wherein the gear system comprises a gear wheel concentrically mounted on the rotatable shaft and operatively connected to another gear wheel mounted on a rotational axis of the escape wheel such that the escape wheel and the gear system rotate simultaneously.

40. The fluid delivery actuator of any one of claims 37 to 39, wherein the biasing member comprises a spring.

41. The fluid delivery actuator of any one of claims 37 to 39, wherein the biasing member comprises a pressurised gas element.

42. The fluid delivery actuator of claim 40, wherein the biasing member comprises a torsion spring and the rotatable shaft is rotatable in a second direction to rotate the torsion spring in the second direction to apply torsion to the spring.

43. The fluid delivery actuator of claim 42, wherein the fluid delivery actuator is located in a housing of a fluid dispensing apparatus, and wherein the torsion spring is torsioned by pushing a fluid receptacle into the housing to engage with and rotate the rotatable shaft in a second direction.

44. The fluid delivery actuator of claim 42 or 43, and further comprising a ratchet that is engageable with the gear system to prevent rotation of the torsion spring in the first direction as the torsion spring is being torsioned.

45. The fluid delivery actuator of any one of claim 42 to 44, and further comprising a removable torsion key that engages with the rotatable shaft and is manually rotatable to rotate the rotatable shaft in the second direction to torsion the torsion spring.

46. The fluid delivery actuator of any one of claims 17 to 45, wherein the power supply comprises a rechargeable battery and the apparatus comprises a passive energy capture system to recharge the battery.

47. The fluid delivery actuator of any one of claims 17 to 46, wherein the controller is programmed to cause the power supply to provide a series of alternating electric pulses to the electromagnetic coil for a desired duration.

48. A fluid dispensing apparatus comprising:a. a housing;b. the fluid delivery actuator of any one of claims 17 to 47; andc. a fluid dispenser comprising a fluid receptacle;wherein at least a portion of the fluid delivery actuator and the fluid receptacle are located within the housing, wherein a first end of the fluid receptacle is directly or indirectly contactable by a second end of the plunger, and wherein the fluid receptacle comprises a fluid reservoir comprising a fluid outlet at a second end of the fluid receptacle, and through which fluid is dispensed by the fluid delivery actuator.

49. The fluid dispensing apparatus of claim 48, wherein the fluid receptacle is removably attachable to the plunger or to a housing of the apparatus.

50. The fluid dispensing apparatus of claim 48 or 49, wherein the second end of the plunger presses against a first end of the fluid receptacle and is moveable toward the fluid outlet to push fluid from the fluid receptacle and through the fluid outlet when the rotor rotates between the first and second positions and the escapement is unlocked.

51. The fluid dispensing apparatus of any one of claims 48 to 50, wherein the fluid receptacle comprises a removable and replaceable fluid cartridge that is attachable to an infusion set.

52. The fluid dispensing apparatus of any one of claims 48 to 51, wherein the apparatus comprises a wearable insulin pump.

53. A method of operating an insulin pump according to claim 50, the method comprising the steps of:a. locating a fluid receptacle comprising an insulin cartridge within the housing of the insulin pump so that a first end of the insulin cartridge is directly or indirectly contactable by the second end of the plunger;b. connecting the insulin cartridge to an infusion set;c. removably attaching the housing to a user of the fluid dispensing apparatus; d. inserting a needle of the infusion set beneath the skin of the user; ande. powering on the insulin pump.

54. An escapement mechanism comprising:a. an escape wheel rotatable about a first axis and having a plurality of teeth, b. an actuator having an effector that can be driven between first and second positions, c. a pallet fork having a pair of pallets and a pallet arm, the pallet fork being rotatable about a second axis, offset from the first axis, andd. a rotatable coupling rotatably coupling the effector to the pallet arm,e. the mechanism being configured such that as the effector moves between the first and second positions the pallet fork is caused to rotate about the second axis between first and second positions to alternately engage and release the pallets of the pallet fork with teeth of the escape wheel to allow progressive rotation of the escape wheel.

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