A mechanical digit assembly

Abstract

A mechanical digit assembly (100) is provided. The assembly comprises a mechanical digit (102), a leadscrew (8) configured to rotate about a leadscrew axis, and a leadscrew nut (3) mounted to the leadscrew (8) such that a rotation of the leadscrew actuates the leadscrew nut (3) in the direction of the leadscrew axis. The assembly further comprises a first axis of rotation (20) about which the mechanical digit (102) rotates from an open position to a closed position and vice-versa, and a second axis of rotation (21) about which the mechanical digit (102) rotates from an opposed position to an unopposed position and vice-versa. The leadscrew (8) comprises a first portion (50) along which the leadscrew nut (3) can travel to selectively drive the mechanical digit (102) about the first axis of rotation (20), and a second portion (51) along which the leadscrew nut (3) can travel to selectively drive the mechanical digit (102) about the second axis of rotation (21). The rotation of the mechanical digit (102) about the second axis of rotation (21) is limited by a rotation boss (70) which is configured to move in a track (43).

Description

[0001] A MECHANICAL DIGIT ASSEMBLY

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a mechanical digit assembly and methods for actuating a mechanical digit assembly. In particular, but not exclusively, it relates to a mechanical digit assembly which forms part of a mechanical gripping apparatus, for example a mechanical digit assembly in the form of a mechanical thumb assembly which may form part of a mechanical or prosthetic hand to allow such a mechanical or prosthetic hand to grip objects.

[0004] Aspects of the invention relate to a mechanical digit assembly and a method of actuating a mechanical digit assembly.

[0005] BACKGROUND

[0006] The ability for a prosthetic hand, for example in the form of a mechanical hand, to grip objects is limited by the operation of mechanical digits on the mechanical hand. For example, a mechanical hand may comprise a plurality of mechanical digits operating as fingers and one mechanical digit operating as a thumb, such that the mechanical finger digits may flex and extend, and the mechanical thumb digit may flex and extend and also take opposed and unopposed positions in order to allow a user to grip or manipulate objects or the environment more effectively.

[0007] For a mechanical hand, an opposed grip may be described as a grip where the mechanical thumb digit is facing the palm of the mechanical hand, that is, opposite the mechanical finger digits, to allow the mechanical hand to be configured into 'pinch', 'tripod', 'power', 'hook' and 'trigger' grips. In such an arrangement of the mechanical digits, the mechanical thumb digit is considered to be in an opposed and flexed position. The mechanical digit, in this example a mechanical thumb digit, pushes against the tip of a mechanical finger digit.

[0008] For a mechanical hand, an unopposed grip may be described as a grip where the mechanical thumb digit is in line with the palm of the mechanical hand, that is, facing in a perpendicular direction to the mechanical finger digits, to allow the mechanical hand to be configured into 'key', 'finger point', 'mouse' and 'column' grips. In such an arrangement of the mechanical digits, the mechanical thumb digit is considered to be in an unopposed and flexed position. The mechanical digit, in this example a mechanical thumb digit, pushes against the side of a mechanical finger digit, such as a mechanical index finger digit.

[0009] Conventionally, to achieve flexion and extension of a mechanical digit of a mechanical hand and also position the mechanical digit in opposed and unopposed positions, two actuators are required. A first actuator actuates the mechanical digit about a first axis of rotation and a second actuator actuates the mechanical digit about a second axis of rotation.

[0010] In a conventional mechanical hand, the first actuator, which may be called the flex driver, drives the mechanical thumb digit towards and away from the palm. For conventional mechanical hands this is the primary source of grip. The second actuator, which may be called the thumb rotate driver, rotates the mechanical thumb digit around an axis approximately parallel to an axis of rotation of a prosthetic wrist.

[0011] Current state of the art multi-grip mechanical hands use one actuator per mechanical finger digit, and two actuators for a mechanical thumb digit. The conventional configuration of this is a first motor in the mechanical thumb digit that drives the mechanical thumb digit closed, or flexing towards the palm, and a second motor in the palm rotating the base of the mechanical thumb digit about an axis approximately parallel to the wrist of the mechanical hand. The actuators contribute significantly the cost and weight of the mechanical hand.

[0012] It is an aim of the present invention to address at least some of the disadvantages associated with the prior art.

[0013] SUMMARY OF THE INVENTION

[0014] Aspects and embodiments of the invention provide a mechanical digit assembly and a method of actuating a mechanical digit assembly, as claimed in the appended claims. According to an aspect of the invention there is provided a mechanical digit assembly, comprising: a mechanical digit; a leadscrew configured to rotate about a leadscrew axis; a leadscrew nut mounted to the leadscrew such that a rotation of the leadscrew actuates the leadscrew nut in the direction of the leadscrew axis; a first axis of rotation about which the mechanical digit rotates from an open position to a closed position and vice-versa; a second axis of rotation about which the mechanical digit rotates from an opposed position to an unopposed position and vice-versa. The leadscrew comprises: a first portion along which the leadscrew nut can travel to selectively drive the mechanical digit about the first axis of rotation; and, a second portion along which the leadscrew nut can travel to selectively drive the mechanical digit about the second axis of rotation, wherein the rotation of the mechanical digit about the second axis of rotation is limited by a rotation boss which is configured to move in a track.

[0015] An advantage of this invention is that a single actuator may be used to cause the mechanical digit to rotate in two axes, thus reducing the number of actuators required for a mechanical hand comprising the mechanical digit assembly leading to reduced part count, reduced weight, and reduced cost, along with increased robustness and durability, and therefore increased usability and affordability for the user. By using a single centrally mounted actuator the mass of the actuator may be positioned closer to the centre of gravity of the mechanical hand. Having the mass of the actuator closer to the centre of gravity increases the maneuverability of the mechanical hand from a user’s perspective. Further, a single actuator may be more easily protected from mechanical impact and water and dirt ingress.

[0016] The track may be shaped according to a predetermined motion path for the mechanical digit. The track may be approximately U-shaped.

[0017] The mechanical digit assembly may comprise: a bias spring urging the mechanical digit towards the open position.

[0018] The track may comprise: a first portion, wherein the mechanical digit can be selectively driven about the first axis of rotation with the mechanical digit in the unopposed position when the rotation boss is located in the first portion of the track; and, a second portion, wherein the mechanical digit can be selectively driven about the first axis of rotation with the mechanical digit in the opposed position when the rotation boss is located in the second portion of the track.

[0019] The first portion of the track may be a first vertical portion and the second portion of the track may be a second vertical portion.

[0020] The track may comprise: a non-vertical portion, wherein the mechanical digit can be selectively driven about the second axis of rotation when the rotation boss is located in the non-vertical portion of the track.

[0021] The mechanical digit assembly may comprise: a two-position latch, wherein the two- position latch is configured to selectively constrain the leadscrew nut to either the unopposed track or the opposed track.

[0022] The rotation of the mechanical digit about the first axis of rotation may be limited by an end-stop slot.

[0023] According to an aspect of the invention there is provided a method of actuating a mechanical digit assembly, the method comprising: rotating a leadscrew about a leadscrew axis to cause movement of a leadscrew nut, which is mounted to the leadscrew, along the leadscrew in the direction of the leadscrew axis; wherein movement of the leadscrew nut along a first portion of the leadscrew selectively drives the mechanical digit about a first axis of rotation about which the mechanical digit rotates from an open position to a closed position and vice-versa, and movement of the leadscrew nut along a second portion of the leadscrew selectively drives the mechanical digit about a second axis of rotation about which the mechanical digit rotates from an opposed position to an unopposed position and vice-versa, wherein the rotation of the mechanical digit about the second axis of rotation is limited by movement of a rotation boss in a track.

[0024] An advantage of this invention is that movement of a single actuator may be used to cause the mechanical digit to rotate in two axes, thus reducing the number of actuators required leading to reduced weight and cost for a mechanical hand comprising the mechanical digit assembly. Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner.

[0025] BRIEF DESCRIPTION OF THE DRAWINGS

[0026] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0027] Figure 1 illustrates a mechanical digit assembly, with a mechanical digit in a fully extended and unopposed position, according to an embodiment of the invention;

[0028] Figure 2 illustrates a mechanical digit assembly, with a mechanical digit in a fully extended and unopposed position with the internal mechanism visible, according to an embodiment of the invention;

[0029] Figure 3a illustrates a mechanical digit assembly, with a mechanical digit in a fully flexed or closed position, according to an embodiment of the invention;

[0030] Figure 3b illustrates a mechanical digit assembly, with a mechanical digit in a fully extended or open position, according to an embodiment of the invention;

[0031] Figure 4 illustrates a static thumb mount assembly, comprising an unopposed track and an opposed track, and a two-position latch, according to an embodiment of the invention;

[0032] Figure 5 illustrates an exploded view of a mechanical digit assembly, according to an embodiment of the invention; Figure 6 illustrates a prosthetic limb comprising a prosthetic socket, a prosthetic arm, a prosthetic wrist, and a prosthetic hand, the prosthetic hand comprising a mechanical digit assembly according to an embodiment of the invention;

[0033] Figure 7 illustrates a prosthetic hand with a mechanical digit in an unopposed and extended position according to an embodiment of the invention;

[0034] Figure 8 illustrates a prosthetic hand with a mechanical digit in an unopposed and flexed position according to an embodiment of the invention;

[0035] Figure 9 illustrates a prosthetic hand with a mechanical digit in an opposed and flexed position according to an embodiment of the invention;

[0036] Figure 10 illustrates a prosthetic hand with a mechanical digit in an opposed and extended position according to an embodiment of the invention;

[0037] Figure 11 illustrates a rotation boss of a locking nut engaging with a track in a static thumb mount according to an embodiment of the invention;

[0038] Figure 12 illustrates a locking nut with three protruding bosses, a rotation boss and two flex bosses according to an embodiment of the invention;

[0039] Figure 13 illustrates an example actuator control diagram when a close hand command signal is issued according to an embodiment of the invention;

[0040] Figure 14 illustrates an example actuator control diagram when an open hand command signal is issued according to an embodiment of the invention;

[0041] Figure 15 illustrates an example actuator control diagram when a change grip to opposed grip command signal is issued according to an embodiment of the invention; Figure 16 illustrates an example actuator control diagram when a change grip to unopposed grip command signal is issued according to an embodiment of the invention;

[0042] Figure 17 illustrates an example control system for a leadscrew actuator, comprising a leadscrew actuator, an encoder for actuator, an actuator sensor, a control unit and a two-position latch sensor according to an embodiment of the invention.

[0043] In the drawings, like parts are denoted by like reference numerals.

[0044] DETAILED DESCRIPTION

[0045] Examples of the present disclosure relate to a mechanical digit assembly and a method of actuating a mechanical digit assembly. In particular, examples of the present disclosure relate to a mechanical digit assembly and a method of actuating a mechanical digit assembly, wherein the mechanical digit assembly has a mechanical digit configured to rotate in two axes of rotation such that the mechanical digit may flex and extend and also take opposed and unopposed positions in order to allow a user to grip or manipulate objects or the environment. Non-limiting examples will now be described with reference to the accompanying drawings.

[0046] In general, the figures illustrate a mechanical digit assembly 100 comprising a mechanical digit 102, a leadscrew 8 and a leadscrew nut 3. The mechanical digit assembly 100 provides a first axis of rotation 20 and a second axis of rotation 21 for the mechanical digit 102, allowing the rotation of the mechanical digit 102 in two separate axes in relation to other digits and / or the palm of a mechanical hand to which the mechanical digit assembly 100 is attached.

[0047] Figure 1 illustrates a mechanical digit assembly 100 in the form of a mechanical thumb assembly 100, having a mechanical digit 102 in the form of a mechanical thumb 102. The mechanical thumb assembly 100 may be mechanically mounted to, be comprised in, or form part of, a mechanical gripper, which may be in the form of a prosthetic hand or mechanical hand 61, as illustrated in Figures 6 to 10. The mechanical digit assembly 100 enables the mechanical digit 102 to be rotated in two axes as illustrated in Figure 2, a first axis of rotation 20, which may be called the flex axis or thumb flex axis, and a second axis of rotation 21 , which may be called the rotate axis or thumb rotate axis, such that the mechanical digit 102 may be actuated in two planes, a first plane or flex plane perpendicular to the first axis 20, and a second plane or rotate plane perpendicular to the second axis 21.

[0048] Rotation of the mechanical digit 102 about the first axis of rotation 20 enables the mechanical digit 102 to move from a flexed or closed position to an extended or open position and vice versa. Rotation of the mechanical digit 102 about the second axis of rotation 21 enables the mechanical digit 102 to move from an opposed position to an unopposed position and vice versa.

[0049] The first axis of rotation 20 intersects with the second axis of rotation 21. In particular, the first axis of rotation 20 and the second axis of rotation 21 intersect at a single point such that the mechanical digit 102 can rotate about that single point, which may be called the central rotation point 26.

[0050] In some embodiments the rotation of the mechanical digit 102 about that central rotation point 26 is effected using, or provided by, a ball joint 28, where the ball joint 28 is centralized on and configured to rotate about the central rotation point 26. As illustrated in Figure 1, and more clearly seen in the exploded view of Figure 5, the ball joint 28 comprises a chassis 5, which may be called a thumb chassis 5, a proximal phalange 15, which may be called a thumb proximal phalange 15, and proximal bolts 4, which may be called thumb proximal bolts 4, which together make up a spherical surface which bear again an external spherical bush 10 to strengthen and stabilise the mechanical digit 102.

[0051] By using a ball joint 28 for the chassis 5 or base of the mechanical digit assembly 100 allows for a large external bearing or external spherical bush 10 to seal the mechanical digit 102 against dirt and water ingress. The large external spherical bush 10 has a larger surface area meaning the mechanical digit assembly 100 is stronger when compared with four small bearings on two conventional axes which would otherwise be required. The ball joint 28 also negates the need for a gaiter or rubber glove, which are a common location for mechanical failure. Another common issue with using a gaiter or rubber glove is that the power consumption of the actuators is greater as they are required to overcome the stiffness that the gaiter or rubber glove provides.

[0052] As illustrated in Figure 5, the mechanical digit assembly 102 m ay include various gears, including include an idler gear 6 and a leadscrew gear 7 for driving the leadscrew 8. The mechanical digit 102 may comprise a lower cross link 11 , an upper cross link 12, a mid-phalange 13, a distal phalange 14, and a proximal phalange (15) forming the sections of the mechanical digit 102.

[0053] The mechanical digit assembly 100 uses a single actuator to achieve both flex and rotation of a mechanical digit 102. When the mechanical digit assembly 100 operates as a mechanical thumb assembly 100, a single actuator is used to achieve both flex and rotation of a mechanical thumb digit 102.

[0054] The mechanical digit assembly 100 comprises a leadscrew 8. The leadscrew 8 will be mounted approximately parallel to a mechanical wrist 63, as shown in Figure 6, when the mechanical digit assembly 100 is formed as part of a mechanical hand 61 to be attached to the mechanical wrist 63. Figure 6 also illustrates the location of the mechanical hand (61) relative to a prosthetic arm 64 having a prosthetic socket 66.

[0055] As illustrated in Figure 11 , the leadscrew 8 is mounted to the chassis 5. The chassis 5 has a proximal phalange 15 pivotably mounted on it, as illustrated in Figure 1 , and the chassis 5 is, in turn, pivotally mounted to a static digit mount 1, as illustrated in Figure 11 , which may be called a static thumb mount 1. The static digit mount 1 may then be embedded within the palm of a mechanical hand 61.

[0056] The mechanical digit assembly 100 comprises a leadscrew nut 3, illustrated in Figure 12, which engages with the leadscrew 8, as illustrated in Figure 11 , and as shown in the cutaway illustrations of Figure 3a and Figure 3b.

[0057] As shown more clearly in Figure 12, the leadscrew nut 3 has three orthogonal bosses 70, 71 , 72, protruding from the side of the leadscrew nut 3. These orthogonal bosses 70, 71, 72 are perpendicular to the to the leadscrew 8. The function of the three orthogonal bosses 70, 71, 72, will be described further below. The first orthogonal boss is the rotation boss 70. The second and third orthogonal bosses are the flex bosses 71, 72. The flex bosses 71, 72 are on opposing sides of the leadscrew nut 3, and therefore opposing sides of the leadscrew 8 when the leadscrew nut 3 is affixed to the leadscrew 8, and are parallel to the first axis of rotation 20, that is the flex axis. During operation of the mechanical digit assembly 100, the orthogonal bosses are configured to engage, mate with, or travel within, a path or track 43 in the static digit mount 1 and also to engage with the proximal phalange 15 controlling the position of the mechanical digit 102 along the first plane, or flex plane, or about the first axis of rotation 20, or flex axis.

[0058] The travel of the leadscrew nut 3 along the leadscrew 8 may be defined in terms of two distinct portions of the leadscrew 8 along which the leadscrew nut 3 travels, a first portion 50 of the leadscrew 8, which may be called the flexing portion 50 and a second portion 51 of the leadscrew 8, which may be called the rotating portion 51.

[0059] The first portion 50 of the leadscrew 8, providing a first portion of travel 30 of the leadscrew nut 3 on the leadscrew 8, is used for the flex and extend motions of the mechanical digit 102, that is, to move the mechanical digit 102 from an extended or open position, as shown in Figure 7, to a flexed or closed position, as shown in Figure 8, or vice versa, or from a flexed or closed position, as shown in Figure 9, to an extended or open position, as shown in Figure 10, or vice versa.

[0060] The second portion 51 of the leadscrew 8, providing a second portion of travel 31 of the leadscrew nut 3 on the leadscrew 8, is used for transitioning the mechanical digit 102 from an unopposed position, as illustrated in Figure 7 and Figure 8, to an opposed position, as illustrated in Figure 9 and Figure 10, and vice versa.

[0061] The static digit mount 1 is illustrated more clearly in Figure 4. The static digit mount 1 comprises a slot or track 43 having a number of distinct sections, 40, 41, 42. The rotation boss 70 is configured to travel in the track 43 within the static digit mount 1.

[0062] The shape of the track 43 is such that it enables the mechanical digit 102 to mimic the organic movement of a human digit, such as a human thumb. In some embodiments the shape of the track 43 may be an inverted u-shaped slot, though in other embodiments it may be an inverted v-shaped slot.

[0063] The track 43 has two portions 41 , 42, which are approximately 90 degrees apart in a plane around the second axis 21, which may be defined as a wrist plane. The two portions 41 , 42, may be vertical portions. This enables the rotation boss 70 to travel upwards and downwards along the track 43 without causing the mechanical digit 102 to rotate from an unopposed position to an opposed position or vice versa. The first vertical portion 41 may be known as an unopposed track and the second vertical portion 42 may be known as an opposed track, since they provide for flex and extension of the mechanical digit 102 whilst in the unopposed position and the opposed position respectively. The non-vertical portion 40 of the track 43, which may take a v-shape for example, allows the mechanical digit 102 to move from an unopposed position to an opposed position and vice versa. The non-vertical portion 40 of the track 43 may be called the rotation track.

[0064] The flex bosses 71 , 72 protruding from the leadscrew nut 3, are in contact with two tabs on the proximal phalange 15. As the leadscrew nut 3 and, in turn, the two tabs on the proximal phalange 15 move upwards, away from a connection point for a prosthetic wrist 63, or in other words towards the second portion 51 of the leadscrew 8, it causes the mechanical digit 102 to extend. As the leadscrew nut 3 and the proximal phalange 15 move downward towards the connection point for a prosthetic wrist 63, or in other words away from the second portion 51 of the leadscrew 8, the mechanical digit 102 is flexed, such that when connected to a mechanical hand 61 , the mechanical digit 102 flexes towards a palm of the mechanical hand 102.

[0065] The motion of the proximal phalange 15 about the first axis of rotation 20, and therefore motion of the mechanical digit 102 about the first axis of rotation 20, is further constrained by two opposing control bosses 33 embedded in the proximal phalange 15 travelling along a control slot 32 in the chassis 5. The control bosses 33 may be referred to as end-stop bosses. The control slot 32 may also be referred to as an end-stop slot.

[0066] With the end-stop bosses 33 in the open position along end-stop slot 32, as shown in Figure 3b, the mechanical digit 102 ceases to extend any further. With the mechanical digit 102 constrained about the first axis of rotation 20, and the leadscrew 8 still actuating, the leadscrew nut 3 continues to travel along the leadscrew 8 meaning the rotation boss 70 on the leadscrew nut 3 is free to continue to travel upwards along a first vertical portion 41 of the track 43, which may be called the unopposed track 41 without the mechanical digit 102 flexing further about the first axis of rotation 20.

[0067] When the leadscrew nut 3 continues to be driven by the leadscrew 8, the rotation boss 70 may travel into the non-vertical portion 40 of the track 43, in the example of Figure 4 this being an inverted v-shaped section 40 of the of the track 43, this causes the chassis 5 to rotate in the static digit mount 1. For this reason, the nonvertical portion 40 of the track 43 may be called a rotation track or rotation track portion.

[0068] The rotation of the chassis 5 in the static digit mount 1 causes rotation of the mechanical digit 102 about the second axis of rotation 21.

[0069] It will be understood that other non-vertical arrangements can be provided for the non-vertical portion 40 of the track 43, such as a u-shaped section.

[0070] When the rotation boss 70 reaches the top of the non-vertical portion 40 of the track 43, the rotation of the leadscrew 8 may be reversed. The reversal of the rotation of the leadscrew 8 may be effected by a control unit 1710 of a control system 1700, as illustrated in Figure 17, in particular by following a first leadscrew control process 1500. The rotation boss 70 travels downwards along a second vertical portion 42 of the track 43, which may be called the opposed track 42.

[0071] As illustrated in Figure 15, the first leadscrew control process 1500 begins when the mechanical digit assembly 100 is arranged such that the mechanical digit 102 is in an unopposed grip position and an instruction to change grip type to an opposed grip is received.

[0072] If the leadscrew 8 continues to drive in a reverse direction, the leadscrew nut 3 continues to drive the rotation boss 70 down the opposed track 42. Once the rotation boss 70 travels out of the non-vertical portion 40 the track 43, the flex bosses 71 , 72 engage with the two tabs on the proximal phalange 15. The mechanical digit 102 is now able to flex and extend with the digit in an opposed position.

[0073] In Figure 16, the opposite process is defined, where a second leadscrew control process 1600 begins when the mechanical digit assembly 100 is arranged such that the mechanical digit 102 is in an opposed grip position and an instruction to change grip type to an unopposed grip is received.

[0074] In some embodiments the mechanical digit assembly 100 may additionally comprise a two-position latch 2 at the top of the non-vertical portion 40 the track 43 to stop the rotation boss 70 from reversing down the incorrect track when the leadscrew control processes 1500, 1600 reverse the leadscrew 8 direction. The two-position latch 2 may be held in position by a two-position latch retainer 18 and biased by a two- position latch spring 17, as illustrated in Figure 5.

[0075] Optionally, there may be a two-position latch sensor 1720, as illustrated in Figure 17, that communicates to the control unit 1710 the state of the two-position latch 2 via an electrical signal.

[0076] Figure 13 illustrates an actuator control process 1300 for when a close hand command signal is issued. In this actuator control process 1300 a close hand control signal is received, which may be part of a user input command 1760, the leadscrew 8 is actuated in a clockwise direction and a feedback signal is received from an actuator sensor 1750 to detect the condition of the mechanical digit 102. When it is determined that the hand is closed, the rotation of the leadscrew 8 is stopped.

[0077] Figure 14 illustrates an actuator control process 1400 for when an open hand command signal is issued. In this actuator control process 1400 an open hand control signal is received, which may be part of a user input command 1760, the leadscrew 8 is actuated in an anti-clockwise or counter-clockwise direction and a feedback signal is received from an actuator sensor 1750 to detect the condition of the mechanical digit 102. When it is determined that the hand is open, the rotation of the leadscrew 8 is stopped. It is envisaged that the mainly vertical portions 41, 42 of the track 43 may have a slight curvature, or a non-vertical alignment. This could cause the mechanical digit 102 to rotate slightly as it moves from the unopposed, or open, condition or position, to the opposed, or closed, condition or position, enabling more natural movement, that is, movement which is similar to the movement of a human thumb.

[0078] In some embodiments of this invention the mechanical digit 102 is allowed to be passively flexed by pushing the mechanical digit 102 closed from the back of the mechanical digit 102, that is, to push the mechanical digit 102 towards the palm of a mechanical hand 61 to which the mechanical digit 102 may be fixed. In this condition the flex bosses 71, 72 of the leadscrew nut 3 disengage with the two tabs of the proximal phalange 15. This action compresses an open bias spring 9 connected between the proximal phalange 15 and a mid-phalange 13 of the mechanical digit 102.

[0079] When the mechanical digit 102 is released, the open bias spring 9, urges the proximal phalange 15 causing the mechanical digit 102 to open and the flex bosses 71 , 72 on the leadscrew nut 3 to re-engage with the two tabs of the proximal phalange 15.

[0080] In some embodiments, the static digit mount 1 is mounted to a frame of the mechanical hand 61 via a high stiffness spring or mount, converting it to a movable digit mount 1. The movable digit mount 1 may be spring loaded, biased to a central position. A microswitch may be placed on each side of the movable digit mount. A small input force applied by a user to the movable digit mount activates one of the microswitches. The direction of the small input force can be determined by the activation of a particular microswitch. The triggering of a microswitch may enable a control system to actuate the mechanical digit 102 about the second axis of rotation 21 , that is the rotation axis, in the approximate direction of the small input force applied by the user. A strain gauge sensor may be provided on the movable digit mount 1 to determine the direction of the small input force.

[0081] As illustrated in Figure 17, in some embodiments of this invention, the leadscrew 8 is controlled by a leadscrew actuator 1740. The direction of the leadscrew actuator 8 may be controlled by a control unit 1710. The rotation of the leadscrew actuator 1740 may be determined by an electronic sensing element, a potentiometer, or an encoder 1730.

[0082] In some embodiments, the current drawn by the leadscrew actuator 1740 is determined by an actuator sensor 1750 which may be a current sensor.

[0083] In some embodiments, the portion of the track 43, in particular the rotation track 40, the unopposed track 41 or the opposed track 42, that the rotation boss 70 is located upon is determined by an electronic sensor placed on the two-position latch 2. Alternatively, the portion of the track 43, in particular the rotation track 40, the unopposed track 41 or the opposed track 42, that the rotation boss 70 is located upon is determined by an electronic sensor placed on the track 43 or on the rotation boss 70.

[0084] In an embodiment of this invention, the control unit 1710 receives a user input command 1760. The user input command 1760 may be, but is not limited to, a close hand control signal, an open and control signal, a change grip type to opposed grip control signal, or a change grip type to unopposed grip control signal.

[0085] Features described in the preceding description may be used in combinations other than the combinations explicitly described.

[0086] Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

[0087] Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

[0088] Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

CLAIMS1. A mechanical digit assembly (100), comprising: a mechanical digit (102); a leadscrew (8) configured to rotate about a leadscrew axis; a leadscrew nut (3) mounted to the leadscrew (8) such that a rotation of the leadscrew actuates the leadscrew nut (3) in the direction of the leadscrew axis; a first axis of rotation (20) about which the mechanical digit (102) rotates from an open position to a closed position and vice-versa; a second axis of rotation (21) about which the mechanical digit (102) rotates from an opposed position to an unopposed position and vice-versa; the leadscrew (8) comprising: a first portion (50) along which the leadscrew nut (3) can travel to selectively drive the mechanical digit (102) about the first axis of rotation (20); and, a second portion (51) along which the leadscrew nut (3) can travel to selectively drive the mechanical digit (102) about the second axis of rotation (21), wherein the rotation of the mechanical digit (102) about the second axis of rotation (21) is limited by a rotation boss (70) which is configured to move in a track (43).

2. A mechanical digit assembly (100) according to claim 1, wherein the track (43) is shaped according to a predetermined motion path for the mechanical digit (102).

3. A mechanical digit assembly (100) according to claim 1 or claim 2, wherein the track (43) is approximately U-shaped.

4. A mechanical digit assembly (100) according to any preceding claim, comprising: a bias spring (9) urging the mechanical digit (102) towards the open position.

5. A mechanical digit assembly (100) according to any preceding claim, wherein the track (43) comprises:a first portion (41), wherein the mechanical digit (102) can be selectively driven about the first axis of rotation (20) with the mechanical digit (102) in the unopposed position when the rotation boss (70) is located in the first portion (41) of the track (43); and, a second portion (42), wherein the mechanical digit (102) can be selectively driven about the first axis of rotation (20) with the mechanical digit (102) in the opposed position when the rotation boss (70) is located in the second portion (42) of the track (43).

6. A mechanical digit assembly (100) according to claim 5, wherein the first portion (41) of the track (43) is a first vertical portion and the second portion (42) of the track (43) is a second vertical portion.

7. A mechanical digit assembly (100) according to any preceding claim, wherein the track (43) comprises: a non-vertical portion (40), wherein the mechanical digit (102) can be selectively driven about the second axis of rotation (21) when the rotation boss (70) is located in the non-vertical portion (40) of the track (43).

8. A mechanical digit assembly (100) according to claim 7, comprising: a two-position latch (43), wherein the two-position latch (43) is configured to selectively constrain the leadscrew nut (3) to either the unopposed track (41) or the opposed track (42).

9. A mechanical digit assembly (100) according to any preceding claim, wherein the rotation of the mechanical digit (102) about the first axis of rotation (20) is limited by an end-stop slot (32).

10. A method of actuating a mechanical digit assembly (102), the method comprising: rotating a leadscrew (8) about a leadscrew axis to cause movement of a leadscrew nut (3), which is mounted to the leadscrew (8), along the leadscrew (8) in the direction of the leadscrew axis; wherein movement of the leadscrew nut (3) along a first portion (50) of the leadscrew (8) selectively drives the mechanical digit (102) about a first axis of rotation (20)about which the mechanical digit (102) rotates from an open position to a closed position and vice-versa, and movement of the leadscrew nut (3) along a second portion (51) of the leadscrew (8) selectively drives the mechanical digit (102) about a second axis of rotation (21) about which the mechanical digit (102) rotates from an opposed position to an unopposed position and vice-versa, wherein the rotation of the mechanical digit (102) about the second axis of rotation (21) is limited by movement of a rotation boss (70) in a track (43).

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