Drug delivery device drive mechanism

Abstract

Techniques for managing force application of a drive mechanism in a drug delivery device and devices for implementing the disclosed techniques are disclosed. The one or more drive arms are operable to drive the respective ratchets, and the one or more sensor contacts may be positioned to determine when to control the respective drive arms to no longer drive the respective ratchets, thereby conserving power. The disclosed techniques and devices may be incorporated in drug delivery devices, such as those carried by or secured to a person's skin.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority and benefit of U.S. Provisional Application No. 63 / 476,076, filed on December 19, 2022, the entire content of which is incorporated herein by reference. Technical Field

[0003] The disclosed embodiments generally relate to drug delivery. More specifically, the disclosed embodiments relate to techniques, processes, systems, and devices for delivering pharmaceuticals to a user using a two - wheel drive mechanism. Background Art

[0004] In body - worn drug delivery systems, efforts are made to achieve power - efficiency savings in multiple different areas, with the expectation of saving power to reduce the required size or number of power systems (e.g., multiple batteries). One area where power savings are beneficial is in the drive system of the pump mechanism of a body - worn drug delivery system. For example, as explained in more detail below, significant power savings can be achieved by minimizing the amount of time that the components of the drive system must be powered on. A drive system utilizing shape - memory alloy (SMA) wires would benefit from shortening the time that the SMA wires are powered on.

[0005] Current drive systems utilizing SMA wires and ratchets can include tolerances that allow for over - travel of a non - driving drive arm to ensure that the drive arm has disengaged from the ratchet teeth driven by the drive arm.

[0006] Accordingly, there is a need for a more energy - efficient and compact drive mechanism for a drug delivery device for expelling liquid drugs from a reservoir. Summary of the Invention

[0007] A drive mechanism for a drug delivery device is provided. The drive mechanism for the drug delivery device can include a first ratchet, a second ratchet, a first drive arm, a second drive arm, a first sensor contact, and a second sensor contact. In other embodiments, only a single ratchet may be required. The first ratchet can have a plurality of first drive teeth, and the second ratchet can have a plurality of second drive teeth. The second ratchet and the first ratchet can rotate about a common axis. The first drive arm can be operable to engage a first drive - tooth surface of the plurality of first drive teeth and rotate the first ratchet in a first direction. The second drive arm can be operable to engage a second drive - tooth surface of the plurality of second drive teeth and rotate the second ratchet in the first direction. The first sensor contact can be operable to cause the second drive arm to stop pushing against the second ratchet in response to being contacted by the first drive arm. The second sensor contact can be operable to cause the first drive arm to stop pushing against the first ratchet in response to being contacted by the second drive arm.

[0008] There is also disclosed a drug delivery device drive system, which includes a control circuit, a first ratchet, a second ratchet, a first drive arm, and a second drive arm. The first ratchet may have a plurality of first ratchet teeth, and the second ratchet may have a plurality of second ratchet teeth. The first ratchet and the second ratchet can rotate consistently about a common axis. The first drive arm is operable to contact a corresponding one of the plurality of first ratchet teeth. The second drive arm is operable to contact a corresponding one of the plurality of second ratchet teeth. The control circuit alternates between causing the first drive arm to contact a corresponding one of the plurality of first ratchet teeth and causing the second drive arm to contact a corresponding one of the plurality of first ratchet teeth.

[0009] In another aspect, there is provided another drug delivery device drive system, which includes a control circuit, a drive mechanism, a first ratchet, a second ratchet, a first drive arm, a first sensor contact arm, and a second sensor contact arm. The drive mechanism is coupled to the control circuit. The first ratchet may have a plurality of first ratchet teeth, and the second ratchet may have a plurality of second ratchet teeth. The first ratchet and the second ratchet rotate consistently about a common axis. The first drive arm is coupled to the drive mechanism and is operable to contact a corresponding one of the plurality of first ratchet teeth. The first sensor contact arm is coupled to the drive mechanism and the control circuit. The second drive arm is coupled to the drive mechanism and is operable to contact a corresponding one of the plurality of second ratchet teeth. The second sensor contact arm is coupled to the drive mechanism and the control circuit. The first drive arm and the first sensor contact arm are in contact with each other, and the drive mechanism is operable to push the first drive arm and the first sensor contact arm against the surface of the corresponding first ratchet tooth until the first sensor contact arm no longer contacts the first drive arm.

[0010] In yet another aspect, a drug delivery system includes an actuator, a first ratchet, a second ratchet, a first sensor contact, and a second sensor contact. The actuator includes a pivot point, an actuating protrusion, a first drive arm, and a second drive arm. The first ratchet is operable to be pushed by the first drive arm, and the second ratchet is operable to be pushed by the second drive arm. The first sensor contact is operable to be contacted by the first drive arm; the second sensor contact is operable to be contacted by the second drive arm. The contact between the first drive arm and the first sensor contact causes the actuator to apply a force via the first drive arm to push the first ratchet. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In the drawings, like reference numerals generally refer to like components in different views.

[0012] In the following description, various embodiments of the present disclosure are described in conjunction with the following drawings, in which:

[0013] Figure 1 A schematic diagram showing a drug delivery system according to an embodiment of the present disclosure;

[0014] Figure 2A Perspective view showing a drug delivery system according to an embodiment of the present disclosure;

[0015] Figure 2B Showing an example of a drug delivery system according to an embodiment of the present disclosure Figure 2A Detailed perspective view of a part of the example;

[0016] Figure 2C Showing an example of a drug delivery system according to an embodiment of the present disclosure Figure 2A Top view of an example of the drive mechanism of the drug delivery system;

[0017] Figure 3A Showing an example of a first ratchet and a drive arm in a drive position as part of an example drive system according to an embodiment of the present disclosure;

[0018] Figure 3B Showing an example of a second ratchet in a rest position as another part of an example drive system using a ratchet with a corresponding drive arm and corresponding sensor contacts according to an embodiment of the present disclosure;

[0019] Figure 3C Showing an example of a drug delivery system according to an embodiment of the present disclosure Figure 3A The first ratchet in the rest position in the example;

[0020] Figure 3D Showing an example of a drug delivery system according to an embodiment of the present disclosure Figure 3B The second ratchet in the drive position in the example;

[0021] Figure 4A Perspective view of a ratchet configuration with corresponding drive arms and sensor contacts according to an embodiment of the present disclosure;

[0022] Figure 4B Showing an example drive mechanism system according to an embodiment of the present disclosure;

[0023] Figure 4C Showing an example sensor arrangement that can be used in embodiments of the present disclosure;

[0024] Figure 5A Top view of an example drive mechanism of a liquid drug delivery device incorporating an example sensor arrangement according to an embodiment of the present disclosure;

[0025] Figure 5B Showing Figure 5A Perspective view of the example drive mechanism; and

[0026] Figure 6 Showing an example operation of the drive mechanism of a liquid drug delivery device according to an embodiment of the present disclosure.

[0027] The accompanying drawings are not necessarily to scale. The drawings are merely schematic representations and are not intended to depict specific parameters of the present disclosure. The drawings are intended to depict exemplary embodiments of the present disclosure and should not be regarded as limiting its scope. In addition, for clarity, some elements in some of the figures may be omitted or not drawn to scale. Further, for clarity, reference numerals may be omitted in some of the drawings. Detailed Description

[0028] The systems, devices, and techniques according to the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which one or more embodiments are shown. The systems, devices, and techniques may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the methods and devices to those skilled in the art. Each system, device, and technique disclosed herein provides one or more advantages over conventional systems, components, and methods.

[0029] In the disclosed drive system, tolerances associated with drive arm overtravel can be removed because the described drive system sensor arrangement waits for a signal indicating that the drive arm has disengaged from the tooth gap of the drive gear. This enables energy savings to be achieved on each ratchet pulse (or cycle) by appropriately timing the travel of the drive arm. If the travel is too long, additional energy will be used and wasted. On the other hand, if the travel is too short, the drive arm will not be able to complete its travel, and the second ratchet drive arm may not be able to rotate the ratchet, resulting in insulin delivery failure. By having two drive arms rotate the respective ratchets, an optimal travel occurs at the precise time / distance required for the non-operating drive arm to disengage from the previous ratchet tooth, thereby preparing the non-operating drive arm to become the operating drive arm and initiate a ratchet pulse or cycle. The above advantages are achieved by adding sensor contacts to the dual drive arm drive mechanism, which allows detection of when the non-driven drive arm is ready to initiate a ratchet pulse or cycle.

[0030] Figure 1 A simplified block diagram of an exemplary drug delivery device is shown. The drug delivery device 100 may include a controller 121, a memory 123, an AP application 129 and a delivery control application 199 stored in the memory 123, a drive mechanism 124, a communication device 126, a user interface 127, and a power supply 128. The memory 123 is operable to store programming code and applications, including the delivery control application 199, the AP application 129, and data. The delivery control application 199 and the AP application 129 may optionally be stored on other devices.

[0031] The AP application 129 is operable to perform various functions related to open-loop operation, such as determining a daily total dose setting of a drug or drug combination, such as a daily total insulin setting, etc. In an example, the AP application 129 is configured to provide automatic delivery of insulin via the delivery control application 199 based on analyte sensor input (e.g., a signal received from an analyte sensor, such as a continuous glucose monitor, etc.). The delivery control application 199 is, for example, operable to interpret or apply signals provided by the AP application 129 to the drive mechanism 124 and / or the user interface 127.

[0032] The controller 121 may be coupled to the drive mechanism 124 and the memory 123. The controller 121 may include logic circuits, a clock, a counter or timer, and other processing circuits, and is operable to execute programming code and applications stored in the memory 123, including the delivery control application 199. The communication device 126 may be communicatively coupled to the controller 121 and is operable to wirelessly communicate with external devices, such as a personal diabetes management device, a smart device (e.g., a smart phone and / or a smart watch), etc.

[0033] The drive mechanism 124 is operable to deliver a drug, such as insulin, at a fixed or variable rate. For example, an AP application or an AID algorithm executed on a personal diabetes management device or a smart phone may determine or be informed that the user's daily total insulin (e.g., bolus and / or basal delivery) is 48 units per 24 hours, which may translate to an exemplary physiological basal dose rate of 1 unit / hour (48 / 24 / 2 (assuming a basal / bolus ratio of 1:1)), which may be determined according to a diabetes treatment plan. Of course, the drive mechanism 124 is operable to deliver insulin at a physiological dose rate different from 1 unit / hour. In an example, the system 100 may be attached to a user (e.g., a patient or a diabetic patient) body, for example, by an adhesive (e.g., directly attached to the user's skin), and may deliver any therapeutic agent to the user, including any drug or medicament, such as insulin, morphine, etc. In an example, the surface of the system 100 may include an adhesive (not shown) to facilitate attachment to the user. The system 100 may, for example, be worn on the user's belt or in a pocket, and the liquid drug may be delivered to the user through a catheter to an infusion site on the user.

[0034] In various examples, the system 100 may be an automatic wearable drug delivery device. For example, the system 100 may include a reservoir 125 configured to hold a liquid drug (e.g., insulin), a needle and / or cannula 133 for delivering the drug into the user's body (which may be achieved by subcutaneous, intraperitoneal, or intravenous means), and a drive mechanism 124 or other drive mechanism for delivering the drug from the reservoir 125 through the needle or cannula 133 into the user's body.

[0035] The drive mechanism 124 can be fluidly coupled to the reservoir 125 and communicatively coupled to the medical device controller 121. The drive mechanism 124 can be coupled to the reservoir 125 and can be operative to output a liquid drug from the reservoir 125 via a fluid delivery path and out of the cannula 133. The drive mechanism 124 can have mechanical parameters and specifications, such as pump resolution, which indicates the mechanical capabilities of the drive mechanism. The drive mechanism 124 can also have an electrical connection to a control circuit (not shown), which can be operative to control the operation of the drive mechanism 124. The pump resolution is the fixed amount of insulin delivered by the drive mechanism 124 in a drive mechanism pulse, which is the actuation of the drive mechanism over a preset time period. The actuation can be the case when power from the power source 128 is applied to the control circuit coupled to the drive mechanism 124 and the drive mechanism 124 operates to pump a fixed amount of insulin from the reservoir 125 over a preset amount of time. Alternatively, the drive mechanism 124 can be substantially mechanical in structure and operation and utilize a mechanical energy storage device, such as a spring or other biasing member, to operate the drive mechanism 124. The (one or more) drive sensors 122 can be coupled to an element of the drive mechanism 124, such as a ratchet, etc. The drive sensors 122 can be circuits having a high potential or a ground potential, which are monitored by the controller 121.

[0036] Figure 1 The cannula 133 can be coupled to the reservoir 125 via the fluid delivery path 134. When the cannula 133 is inserted into a user, the cannula 133 can be operative to output a liquid drug to the user.

[0037] The system 100 can also include a power source 128, such as a battery, a supercapacitor, a piezoelectric device, etc., which can be operative to supply power to the drive mechanism 124 and / or other components of the system 100 (e.g., the controller 121, the memory 123, and the communication device 126).

[0038] The controller 121 can be implemented in hardware, software, or any combination thereof. In various examples, the controller 121 can be implemented as dedicated hardware (e.g., implemented as an application specific integrated circuit (ASIC)). The controller 121 can be an integral part of the system 200, can be implemented as a computational model in software, or can be implemented external to the system 100 (e.g., remotely). The controller 121 can be configured to communicate with one or more sensors (not shown).

[0039] The reservoir 125 may be included in a drug delivery device to store a liquid drug (e.g., insulin). For example, the reservoir 125 may be filled or partially filled with a liquid drug or a liquid drug solution. In one example, the liquid drug solution is a mixture of a liquid drug and an added preservative. The reservoir may store the liquid drug until all of the liquid drug has been dispensed (e.g., via a cannula into a patient's body). Thus, the liquid drug (or solution) may remain in the reservoir for a period of time (e.g., 1 day, 3 days, 1 week, 2 weeks, etc.).

[0040] The medical device 102 may be a wearable drug delivery device worn on a user's body. For example, an adhesive may couple the medical device 102 to the skin of the user's body. The medical device 102 may be a multi-component device. For example, the medical device 102 as a wearable drug delivery device may have a first part and a second part that are coupled or connected together. The first part and / or the second part may be inserted or slid into a tray or holder that adheres to the user's body, and the first part and / or the second part may be removed from the tray. If the first part and the second part are used, the first part may include reusable components (e.g., an electronic circuit, a processor, a memory, a drive mechanism, and a potentially rechargeable battery), and the second part may include disposable components (e.g., a reservoir, a needle and / or a cannula, a disposable battery, and other parts or components that contact the liquid drug or agent). Additionally, the first part and the second part may each include their own housing, or may be combined together to form a single housing. The wearable drug delivery device 102 may be directly coupled to the user (e.g., directly attached to a body part and / or the skin of the user via an adhesive, directly, attached to a body part and / or the skin of the user via a tray, or the like). In an example, the surface of the wearable drug delivery device 102 or the tray to which the wearable drug delivery device 102 is coupled may include an adhesive to facilitate attachment to the user's skin.

[0041] Although the medical device 102 is described with reference to the delivery of insulin and the use of an AID algorithm, the medical device 102 may be operable to implement a drug delivery regimen by using a drug delivery algorithm for a variety of different liquid or therapeutic drugs. The liquid drug may be or include any drug in liquid form that is capable of being administered via a subcutaneous cannula by the drug delivery device, including, for example, insulin, glucagon-like peptide-1 (GLP-1), pramlintide, glucagon, and co-formulations of two or more of, for example, GLP-1, pramlintide, and insulin; and pain medications such as opioids or anesthetics (e.g., morphine, etc.), methadone, arthritis medications, hormones (e.g., estrogen and testosterone), blood pressure medications, chemotherapy medications, fertility medications, etc.

[0042] As Figure 2AAs shown, system 200 may include a plunger 202 positioned within a reservoir 225. An end or stem of the plunger 202 may extend outside of the reservoir 225. A drive mechanism 224, under the control of a controller 221, may be operable to expel a fluid (e.g., a liquid drug (not shown)) from the reservoir 225 and into a fluid component 204 and cannula 233 by advancing the plunger 202 within the reservoir 225. In various examples, a pressure sensor (e.g., as shown at 222) may be integrated anywhere along the entire fluid delivery path of the system 200, the fluid delivery path including the reservoir 225, fluid delivery path components 204, and cannula 233.

[0043] The controller 221 may be implemented in hardware, software, or any combination thereof. In various examples, the controller 221 may be implemented as dedicated hardware (e.g., an application specific integrated circuit (ASIC)). The controller 221 may be an integral part of the system 200, may be implemented as a software-based computational model, or may be implemented external to the system 200 (e.g., remotely). The controller 221 may be configured to communicate with one or more sensors (e.g., Figure 1 sensor 108).

[0044] As described above, a reservoir (e.g., 225) may be included in a drug delivery device to store a liquid drug (e.g., insulin). For example, the reservoir 225 may be filled or partially filled with a liquid drug or a liquid drug solution. In one example, the liquid drug solution is a mixture of a liquid drug and an added preservative. The reservoir may store the liquid drug until all of the liquid drug has been dispensed (e.g., dispensed via a cannula into a patient's body). Thus, the liquid drug (or solution) may remain in the reservoir for a period of time (e.g., 1 day, 3 days, 1 week, 2 weeks, etc.).

[0045] Figure 2B At a greater magnification than Figure 2A views, an example of a reservoir coupled to a drive mechanism 224 is shown. Similarly, Figure 2CA perspective view of the drive mechanism 250 is shown. As disclosed in subsequent embodiments, the drive mechanism 224 (shown in more detail in subsequent embodiments) may include a coaxial ratchet, a drive arm, sensor contacts, and an actuator. The coaxial ratchet may be coupled to the plunger 202 via an elongate shaft 254. Generally speaking, the ratchet of the drive mechanism 224 engages with the drive arm in response to a force applied by the actuator to progressively advance the plunger 202 and the elongate shaft 254 into the reservoir 225. The elongate shaft 245 advances the plunger 202 to dispense the liquid drug from the reservoir 225. In one example, the drive mechanism coupler 251 may be operable to rotate the drive element 252 in response to a force applied to the first ratchet or the second ratchet of the drive mechanism 224. The drive element 252 may include (or otherwise be coupled to) a lead screw 253 that is coupled to the plunger 202 (e.g., via the elongate shaft 254). The drive element 252 may be operable to rotate, causing the lead screw 253 to advance the elongate shaft 254 and the plunger 202 within the reservoir 225 to expel the liquid drug from the reservoir 225.

[0046] In at least one embodiment, the provided drive mechanism may include a pair of coaxial ratchets (i.e., a first and a second ratchet) that are driven by a first drive arm and a second drive arm. In some examples, the sensor contact arrangement coupled to the first and second ratchets allows the drive mechanism to respond to the travel of the respective ratchet arms in various embodiments and configurations. In this context, a coaxial arrangement refers to an arrangement in which the first and second ratchets rotate about the same axis or a common axis.

[0047] Figure 3A and 3B The various ratchets of the disclosed subject matter are shown, which may be operable to work individually or in concert to drive a drive element that results in the delivery of a liquid drug. The following discussion covers an example in which the first ratchet drive wheel and the second ratchet operate in concert, but for ease of illustration and discussion, the respective ratchets are shown individually to better show the positions of the corresponding drive arms and sensor contacts.

[0048] Each ratchet may be configured with a plurality of teeth. For example, the first ratchet 310 may have a plurality of first drive teeth, such as Figure 3A the drive teeth 312 shown. Each drive tooth 312 may have a drive tooth surface 315 and a drive tooth flank 316. Figure 3B The second ratchet 340 is shown, which may also have a plurality of second drive teeth, such as the drive teeth 342. Each drive tooth 342 may have a drive tooth surface 345 and a drive tooth flank 346. The second ratchet 340 and the first ratchet 310 may rotate about Figure 3A the common axis A shown.

[0049] Thus, by applying Figure 3AAt least one or both of the first ratchet 310 or the second ratchet 340 are coupled to a pumping mechanism (e.g., drive mechanism 224), and the progressive rotational movement of the ratchets 310 and 340 can be used to actuate the pump and deliver a liquid medicament to a patient. For example, a drive mechanism coupler can be operable to connect the first ratchet 310 or the second ratchet 340 to a drive element (e.g., Figure 2C the drive mechanism 224). The drive element can include a lead screw (and / or a pipe nut that can be threadedly engaged with the lead screw) coupled to a plunger (e.g., Figure 2B the plunger 202). In some examples, the size (e.g., diameter) of the ratchets 310, 340 controls the dose provided by the drive mechanism. For example, a larger diameter ratchet can enable the drive mechanism 300 to operate with a higher dose resolution (e.g., smaller dose size).

[0050] Figure 3A An example of a first ratchet drive cycle is shown. In Figure 3A , the first drive arm 321 can be operable to engage a first drive tooth surface (e.g., 315) of one of a plurality of first drive teeth and rotate the first ratchet 310 in a first direction 311. At the end of the drive cycle, the first drive arm 321 is shown being pushed against the drive tooth surface (e.g., 315) of the drive tooth, and the first sensor contact 331 is positioned at the next drive tooth 317. As Figure 3B shown, when the first drive arm 321 is pushed against the drive tooth surface, the second ratchet 340 can be in a non-drive (or rest) cycle. At the end of the non-drive or rest cycle, the second drive arm 361 contacts the second sensor contact 351 and is not pushed against the drive tooth surface of the drive teeth of the second ratchet 340. In Figure 3B , the second drive arm 361 is shown positioned in front of the second sensor contact 351 (e.g., more to the left or offset from the end of the second sensor contact 351). Both the first drive arm 321 and the second drive arm 361 can be slightly bent to provide a spring force that allows the first drive arm 321 and the second drive arm 361 to spring up (or bend) to contact the respective sensor contacts 331 and 351. A controller (e.g., Figure 1 the controller 121) can be enabled to generate a first tooth gap signal to cause the first drive arm 321 to stop driving.

[0051] The second sensor contact 351 can be operable to be contacted by the second drive arm 361. In this example, the contact of the second sensor contact 351 with the second drive arm 361 can communicate to the controller ( Figure 3A and 3B(not shown) indicates (i) that the second drive arm 361 is in place relative to the tooth surface, or (ii) that the first drive arm 321 has completed its full stroke of pushing against its corresponding drive tooth surface, or both (i) and (ii). As the first ratchet 310 and the second ratchet 340 rotate in response to the force applied by the first drive arm 321, the second drive arm 361 can slide along its corresponding drive tooth surface towards the second sensor contact 351 and the next drive tooth.

[0052] The purpose of the example shown is to allow the controller to determine as precisely as possible when the corresponding drive arm (i.e., the first drive arm 321 or the second drive arm 351) disengages from the drive tooth, so that the controller is informed when contact is made with the sensor contact and when the controller should optimally stop driving the first drive arm because the second drive arm is ready to start driving, and vice versa.

[0053] Figure 3B shows the second ratchet 340 in a reset position (e.g., a rest or non-driving position), while Figure 3C shows the second ratchet 340 at the end of its drive cycle. Eventually, as the second drive arm 361 continues to rotate the second ratchet 340 as Figure 3B shown, the second sensor contact 351 loses contact with the second drive arm 361 as the second sensor contact 351 lands on the next drive tooth of the second ratchet 340, as Figure 3C shown. In this example, when the second sensor contact 351 loses contact with the second drive arm 361, a second tooth clearance signal can be enabled (e.g., caused to start). For example, in response to the loss of contact, the controller (e.g., Figure 1 controller 121) can enable the generation of a second tooth clearance signal, which can be used in combination with the first tooth clearance signal to stop driving the second drive arm 361. The confirmation of the first and second tooth clearance signals warns (i) that the first drive arm 321 is in place to start pushing against the drive tooth surface to start rotating the first and second ratchets in direction 311, and (ii) that the second drive arm 361 and the sensor contact 351 are correctly positioned for the next cycle. The near-instantaneous response to the second drive arm being in place enables the controller to conserve the energy stored in the power supply (i.e., Figure 1 power supply 128).

[0054] Similarly, when the first drive arm 321 contacts the first sensor contact 331, the controller can be operated to stop the second drive arm 361 from pushing against the second ratchet 340, as Figure 3C and Figure 3DAs shown. For example, the controller can be operated to enable a first tooth clearance signal when the first drive arm 321 contacts the first sensor contact 331. The first tooth clearance signal indicates that the second drive arm 361 is in a position to apply a force against the next second drive tooth 342 among the plurality of second drive teeth. Note that the use of terms such as "first tooth clearance signal" and "second tooth clearance signal" is not intended to indicate any timing requirement or sequential limitation of the corresponding tooth clearance signals. When one of the first or second drive arms drives the corresponding ratchet, the controller 121 is monitoring the drive sensor contacts of the non-driving arm. In one example, the controller 121 can monitor the drive sensor 122 for the contact of the drive arm with the corresponding drive sensor contact. In some examples, the controller 121 can monitor the contact or loss of contact of the drive arm with the drive sensor contact to generate a corresponding ratchet signal (e.g., a first tooth clearance signal or a second tooth clearance signal). This change in contact (i.e., making contact or losing contact) enables the generation of a signal indicating that the drive arm has disengaged from the ratchet tooth and is ready to drive the ratchet in the next pulse of the drive mechanism. A pulse of the drive mechanism can be considered, for example, a cycle of applying a force against the drive tooth surface and stopping the application of the force when generating the tooth clearance signal.

[0055] In an example of the drive mechanism pulse, Figure 3A shows the first drive arm 321 at the end of its drive stroke and, Figure 3B in which, the second drive arm 361 is shown after it has disengaged from the ratchet tooth and contacted the second sensor contact 351. In Figures 3A - 3D the example, the two independent sensor contacts, the first sensor contact 331 and the second sensor contact 351, can be fixed cantilever beams (i.e., not moved leftward by the drive mechanism), while the corresponding drive arms 321 and 361 are operable to linearly move from right to left by the force applied by the drive mechanism to drive the corresponding ratchet / gear. In response to the force applied by the drive mechanism, the corresponding ratchet is operable to rotate clockwise (i.e., in the direction 311) while pivoting about its center (e.g., the common axis A).

[0056] Figure 3C and 3DShows the next cycle of the drive mechanism. In response to the first ratchet 310 (which may be coupled to the second ratchet 340 in the exemplary embodiment) being pushed in direction 311 and the second ratchet being offset by half a drive tooth and also rotating, once the second drive arm 361 lands on the next drive tooth and contacts the second sensor contact 351, the controller may allow the second drive arm 361 to start driving the second ratchet 340, which causes the second ratchet 340 to rotate in direction 311. When the second drive arm 361 drives the second ratchet, the first drive arm 321 rests on or contacts the tooth surface 316, which indicates to the controller to continue driving the second drive arm 361 because the first drive arm 321 is not ready to be driven.

[0057] As Figures 3A - 3D shown in the example of, an improved drive system is provided by adding at least one additional overhanging arm in the drive mechanism. The two additional overhanging arms (i.e., sensor contacts) shown in the figure that engage the ratchet can be non-driving arms located on the ratchet teeth either before or after the drive arm. The sensor contacts can be part of respective circuits (described in more detail below with reference to Figure 4B and 4C ), and depending on the arrangement of the drive arm and the sensor contacts, the circuit can be open or closed when in contact with the drive arm.

[0058] For example, if the sensor contact is located before the non-driving arm, the circuit will be open and look for a closed circuit to warn the drive arm to stop pushing. Since the drive arm is turning the wheel, the non-driving arm will eventually fall off the next tooth onto the sensor contact, closing the circuit. The movement of the arm falling off the tooth is the non-driving arm moving into a position where it can continue to drive the ratchet.

[0059] Figure 4A Shows another example configuration of the first and second ratchets about a common axis. In Figure 4A this, the first ratchet 410 and the second ratchet 440 are arranged such that the corresponding drive teeth of each ratchet are offset from each other by approximately half a drive tooth. By this offset, when driven, the corresponding drive arms 421, 461 will substantially determine to push the ratchet a distance such that the adjacent non-driving sensor contacts fall off the respective tooth surfaces of the adjacent ratchets. In the example of Figure 4A this, the first drive arm 421 drives the first ratchet 410 by applying a force to the drive tooth surface 415. The second drive arm 461 has just fallen off the tooth surface it was resting on onto the second sensor contact 451, thereby allowing the controller to stop driving the first drive arm 421.

[0060] Note that although the ratchets are shown as being substantially in contact with each other in Figure 4A and 4B this, the ratchets do not have to be in contact with each other. The description in connection with Figure 4AMore details of an example of a drive mechanism system of an example of a ratchet configuration may be beneficial.

[0061] Figure 4B An example of a drive mechanism system is shown. The drive mechanism system 400 may include a first ratchet 410 and a second ratchet 440, a first drive arm 421, a first sensor contact 431, a second drive arm 461, a second sensor contact 451, a ratchet force transfer coupler 470, a drive engine 480, and a controller 405. The ratchet force transfer coupler 470 may be configured to apply a force to the respective first drive arm 421 and second drive arm 461. The force applied by the ratchet force transfer coupler 470 may be configured to alternate between applying a force to the first drive arm 421 and subsequently applying a force to the second drive arm 461.

[0062] In an example, the ratchet force transfer coupler 470 may be configured to have two independent force transfer couplers, a first ratchet force transfer coupler 471 and a second ratchet force transfer coupler 473. The first ratchet force transfer coupler 471 may be operable to apply a force to the first drive arm 421, and the second ratchet force transfer coupler 473 may be operable to apply a force to the second drive arm 461. The sensor contacts 431 and 451 may be configured as fixed cantilever beams that are offset from the respective drive arms 421, 461 to reduce the likelihood of forming a capacitive circuit between the respective drive arms and the respective sensor contacts (e.g., 461 and 451). In this example, the first ratchet force transfer coupler 471 and the second ratchet force transfer coupler 473 may be operable to alternately apply a force to the respective first drive arm 421 and second drive arm 461 based on contact with or loss of contact with the respective sensor contacts 431, 451 as described herein Figures 3A - 4A and the loss of contact with the respective sensor contacts 431, 451.

[0063] In another example, in addition to only monitoring whether the resting drive arm has lost contact with its respective sensing contact, the controller 405 may be operable to implement a two-step check. The controller 405 may perform the two-step check by verifying that the resting arm has contacted its respective sensing contact and that the drive arm being driven has lost contact with its respective sensing contact.

[0064] The drive engine 480 may be mechanically coupled to the ratchet force transmission coupler 470 or corresponding separate ratchet force transmission couplers 471 and 473, and may be any of a variety of different mechanisms configurable to apply alternating forces to the corresponding drive arms 421, 461. Examples of drive engine mechanisms may include linear actuators, electromagnetic coil arrangements, shape memory alloys, biasing elements (e.g., springs or elastic members), flexed plastic members (which have spring-like forces), combinations of the foregoing, and the like. The drive engine 480 may be electrically coupled to a controller 405 that is operable to actuate the drive engine 480 in response to sensor signals (e.g., those described with reference to the previous examples).

[0065] Reference Figures 3A - 4B The example described describes signal examples where the controller monitors the closed circuit between the corresponding drive arm and the corresponding sensor contact. However, in alternative examples, it is also contemplated that the controller may be operable to monitor the open circuit between the corresponding drive arm and the corresponding sensor contact. In Figures 3A - 4B the example, the corresponding drive arm is shown outside (or above) the sensor contact, and in operation, the drive arm falls onto its corresponding sensor contact.

[0066] In an alternative example, the positions of the sensor contact and the drive arm are reversed. For example, if the sensor contact is located "above" the non-drive arm (which is opposite to what is shown in Figures 3A - 3D ), the circuit may be closed, and an open circuit is looked for to warn the drive arm to stop pushing. Since the drive arm is turning the wheel, the non-drive arm will eventually fall off the next tooth, thereby opening the circuit. The movement of the arm falling off the tooth is the non-drive arm moving to a position where it will be able to continue driving the ratchet. In this configuration, the drive arm is below the sensor contact, and when the drive arm pushes against the corresponding ratchet tooth surface, the other drive arm of the other ratchet does not contact the other sensor contact until the other ratchet has traveled far enough such that the sensor contact falls off the ratchet tooth on which it was resting. In this configuration, the controller may monitor multiple signals or signals having a predetermined duration and then start driving the other drive arm.

[0067] Figure 4C shown for use as Figure 4BAn example sensor configuration of a ratchet in the system shown in the example. System 408 may include examples of a ratchet 469, a controller 405, a drive arm 466, and sensor contacts 467. The sensor contacts 467 may include one or more contacts, such as contact pads 468. The contact pads 468 may be connected to the controller 405. The drive arm 466 may include a conductive surface 463. In the example, the contact pads 468 on the sensor contacts 467 may be embedded in the first surface of the sensor contacts 467 facing the drive arm, and through-holes extend through the sensor contacts 467 to the second surface, where a signal path 499 couples the contact pads 468 to the controller 405. By establishing contact across two contact pads 468 by the conductive surface 463 of the drive arm 466, the circuit between two wires of the signal path 499 is closed, and when the conductive surface 463 does not establish contact across two contact pads 468, the circuit is open. The controller 405 may be configured to detect when the circuit is open or closed and take appropriate actions, such as signaling the drive arm to stop rotating the ratchet or similar operations.

[0068] Alternative configurations of the ratchet can also be designed, such as separating the ratchet in an alternative drive mechanism system. Figure 5A and 5B Examples of alternative drive mechanism systems are provided. The drive mechanism 500 may include an actuator 540 and a drive mechanism 510. The drive mechanism 510 may include a first ratchet 534, a second ratchet 535, a drive member 520, drive sensor contact arms 526 and 527. The drive member 520 includes a first drive arm 514, a second drive arm 515, a pivot point 512, and an actuator coupler 518. The actuator 540 is configured to be coupled to the actuator coupler 518 and move the drive member 520 in the direction shown by arrow 588. The actuator 540 may be at least one shape memory alloy wire, an elastic structure, a spring, a yoke, or a combination of one or more of a shape memory alloy wire, an elastic structure, a spring, or a yoke. In this example, the actuator coupler 518 may be operable to engage the yoke of the actuator 540 and be fixed to (e.g., by crimping, adhesive, Velcro, or a clamp) a shape memory alloy wire, an elastic structure, a spring, or the like.

[0069] Similar to Figures 3A - 4B the example, the first and second drive arms 514 and 515 may be operable to alternately push against the drive tooth surfaces of the corresponding first ratchet 534 and second ratchet 535. In this example, the first drive arm 514 and the first sensor contact arm 526 are configured to be substantially offset such that only a portion of the first drive arm 514 and the first sensor contact arm 526 overlap. Similarly, the second drive arm 515 and the second sensor contact arm 527 are configured to be substantially offset such that only a portion of the second drive arm 514 and the second sensor contact arm 527 overlap.

[0070] The first sensor contact arm 526 and the second sensor contact arm 527 are also coupled to a controller (shown in another example), and so are portions of the first drive arm 514 and the second drive arm 515, to complete or break a circuit, thereby indicating a change from a drive cycle to a rest cycle and vice versa.

[0071] Figure 5B An isometric view of the drive mechanism system 500 is shown. In this view, a portion 528 of the offset first sensor contact 526 is shown below the first drive arm 514 and rests on the face of a drive tooth (e.g., 536). In Figure 5A and 5B the example shown, the first drive arm 514 is in a drive cycle and the second drive arm 515 is shown resting on a portion of the offset second sensor contact 527.

[0072] Figure 5A and 5B The example drive mechanism of and is only one example of a drive mechanism operable to provide the functions described herein.

[0073] Figure 6 An example ratchet configuration utilizing an alternative sensor contact arrangement is shown. In Figure 6 the ratchet configuration 600 shown, the first drive arm 621 and the second drive arm 661 are used to rotate corresponding first ratchet 610 and second ratchet 640. In this example, the sensor contacts of the previous example are replaced by drive face contacts 631, which are coupled to a ring circuit 630 and a slip ring coupler 635. More specifically, the face of each tooth (the entire face of each tooth or only a portion of the face) may have an electrical contact (e.g., 631) thereon such that when the drive arm (e.g., 621 or 661) engages the particular tooth face, the electrical contacts on the drive arm and the tooth face form a circuit. The slip ring coupler 635 may be electrically coupled to a controller that detects when the second drive arm 661 contacts the drive tooth contact 631, then loses contact with the drive tooth contact 631 when the second drive arm 661 begins to fall onto the next drive tooth, or when it loses contact with the drive tooth contact 631 and then re - establishes contact with a subsequent drive tooth contact 632 on the next drive tooth (e.g., a driven tooth). For purposes of illustration in Figure 6 only the ring circuit 630, the slip ring coupler 635, and the drive tooth contacts 631 and 632 are shown. However, the same arrangement of the ring circuit, the slip ring coupler, and the drive tooth face contacts may also (or alternatively) be present on the first ratchet 610.

[0074] In an alternative embodiment similar to that shown in Figure 6 only one ratchet and one drive arm may be used. For example, referring to Figure 6The ratchet 640 and the drive arm 661 therein. When the distal end of the drive arm 661 advances the ratchet 640 to cause the ratchet 640 to rotate clockwise, the driven (or "following") teeth of the ratchet 640 will eventually contact the proximal portion of the drive arm 661. If each tooth surface has an electrical contact formed thereon (e.g., 631), and at least the proximal portion of the drive arm 661 (where the driven tooth contacts the drive arm 661) also includes an electrical contact (e.g., 632), then when the drive arm 661 advances the ratchet 640 far enough such that the driven tooth of the ratchet 640 contacts the proximal portion of the drive arm 661, the driven tooth and the drive arm 661 will form an electrical circuit. When this circuit is closed or completed, the controller will then know that the drive arm 661 has advanced the ratchet 640 far enough, and then the drive arm can be pulled back (e.g., Figure 6 to the right in ) far enough such that the drive arm 661 falls onto the next tooth (i.e., the driven tooth). The size of the teeth will be known such that the controller knows how far to pull back the drive arm 661 to cause it to fall onto the next tooth. Then the process can be repeated: the controller can cause the drive mechanism to advance the drive arm 661 to the left to force the ratchet 640 to rotate further clockwise until the next driven tooth contacts the proximal portion of the drive arm 661.

[0075] Certain examples of the subject matter of the present disclosure have been described above. However, it is expressly noted that the subject matter of the present disclosure is not limited to these examples, but is intended to include additions and modifications to what is expressly described herein within the scope of the disclosed subject matter. Additionally, it should be understood that the features of the various examples described herein are not mutually exclusive, but can exist in various combinations and permutations, even if these combinations or permutations are not expressly stated herein, without departing from the spirit and scope of the disclosed subject matter. In fact, those of ordinary skill in the art will envision variations, modifications, and other implementations of what is described herein without departing from the spirit and scope of the disclosed subject matter. Accordingly, the disclosed subject matter should not be limited solely by the foregoing illustrative description.

[0076] The foregoing description of the example embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Given the disclosure, many modifications and variations are possible. It is intended that the scope of the disclosure not be limited by this detailed description, but rather by the appended claims. Future applications claiming priority to this application may claim the disclosed subject matter in a different manner and may generally include any set of one or more limitations disclosed herein in various ways or otherwise shown.

[0077] In particular, although the drug delivery device drive mechanism has been described above and is defined in the appended claims, it should be understood that the drug delivery device drive mechanism according to the present disclosure may alternatively be defined according to the following embodiments:

[0078] 1. A drug delivery device drive system, comprising: a control circuit; a drive mechanism coupled to the control circuit; a first ratchet having a plurality of first ratchet teeth; a second ratchet having a plurality of second ratchet teeth, wherein the first ratchet and the second ratchet rotate in unison about a common axis; a first drive arm coupled to the drive mechanism and operable to contact a corresponding one of the plurality of first ratchet teeth; a first sensor contact arm coupled to the drive mechanism and the control circuit; a second drive arm coupled to the drive mechanism and operable to contact a corresponding one of the plurality of second ratchet teeth; and a second sensor contact arm coupled to the drive mechanism and the control circuit, wherein when the first drive arm and the first sensor contact arm contact each other, the drive mechanism is operable to push the first drive arm against the surface of a corresponding first ratchet tooth until the first sensor contact arm no longer contacts the first drive arm.

[0079] 2. The drug delivery device drive system according to embodiment 1, wherein the first ratchet and the second ratchet are operable to rotate in response to the first drive arm and the first sensor contact being pushed against the surface of a corresponding first ratchet tooth.

[0080] 3. The drug delivery device drive system according to embodiment 1 or 2, wherein the first sensor contact arm is configured to move to the surface of the next tooth of the plurality of first ratchet teeth when the first sensor contact arm no longer contacts the first drive arm.

[0081] 4. The drug delivery device drive system according to any one of embodiments 1 to 3, wherein in response to the first sensor contact arm no longer contacting the first drive arm and the second drive arm and the second sensor contact arm contacting each other, the control circuit is operable to cause the drive mechanism to push the second drive arm and the second sensor contact arm against the surface of a corresponding second ratchet tooth until the second sensor contact arm no longer contacts the second drive arm.

[0082] 5. The drug delivery device drive system according to any one of embodiments 1 to 4, wherein the first ratchet and the second ratchet are operable to rotate in response to the second drive arm and the second sensor contact being pushed against the surface of the corresponding second ratchet tooth.

[0083] 6. The drug delivery device drive system according to any one of embodiments 1 to 5, wherein the second sensor contact arm is configured to move to the surface of the next tooth of the plurality of second ratchet teeth when the second sensor contact arm no longer contacts the second drive arm.

[0084] 7. A drug delivery device drive system, comprising: an actuator including a pivot point, an actuating protrusion, and a first drive arm; a first ratchet operable to be pushed by the first drive arm; a first sensor contact operable to be contacted by the first drive arm; wherein contact between the first drive arm and the first sensor contact causes the actuator to apply a force via the first drive arm to push the first ratchet.

[0085] 8. The drug delivery device drive system according to embodiment 7, wherein when the first drive arm no longer contacts the first sensor contact, the actuator stops applying a force via the first drive arm to push the first ratchet.

[0086] 9. The drug delivery device drive system according to embodiment 7 or 8, comprising: a second drive arm; a second ratchet operable to be pushed by the second drive arm; and a second sensor contact operable to be contacted by the second drive arm, wherein contact between the second drive arm and the second sensor contact causes the actuator to apply a force via the second drive arm to push the second ratchet.

[0087] 10. The drug delivery device drive system according to embodiment 9, wherein when the second drive arm no longer contacts the second sensor contact, the actuator stops applying a force to the second drive arm and stops applying a force to the second ratchet via the second drive arm.

[0088] 11. The drug delivery device drive system according to any one of embodiments 7 to 10, comprising: an actuator coupled to the actuating protrusion, wherein the drive actuator force transmission means is a shape memory alloy wire, an elastic structure, a spring, a yoke, or a combination of one or more of the shape memory alloy wire, the elastic structure, the spring, or the yoke.

[0089] 12. The drug delivery device drive system according to any one of embodiments 9 to 11, wherein the first ratchet and the second ratchet rotate in the same direction about a common axis.

[0090] 13. A drug delivery device drive system, comprising: a first ratchet having a plurality of drive teeth, wherein each drive tooth of the plurality of drive teeth includes an electrical contact; a drive arm operable to contact the electrical contact of the first drive tooth of the plurality of drive teeth and rotate the first ratchet in a first direction; and a controller operable to detect when the drive arm contacts the electrical contact of the first drive tooth.

[0091] 14. The drug delivery device drive system according to embodiment 13, wherein the controller is further operable to detect an electrical contact of the drive arm with a second drive tooth of the plurality of drive teeth after the first drive tooth.

[0092] 15. The drug delivery device drive system according to embodiment 13 or 14, wherein the controller is further operable to: in response to detecting that the drive arm has contacted an electrical contact of a second drive tooth of the plurality of drive teeth, move the drive arm away from the face of the first drive tooth, wherein the drive arm is positioned to engage a tooth face of the second drive tooth.

[0093] 16. The drug delivery device drive system according to any one of embodiments 13 to 15, further comprising: a second ratchet having a plurality of drive teeth, wherein each drive tooth of the plurality of drive teeth on the second ratchet includes an electrical contact; a second drive arm operable to contact a first drive tooth of the plurality of drive teeth on the second ratchet and rotate the second ratchet in the first direction; and the controller is operable to detect when the second drive arm contacts a second electrical contact of a second drive tooth of the plurality of drive teeth on the second ratchet.

[0094] 17. The drug delivery device drive mechanism according to any one of embodiments 13 to 16, wherein the ratchet and the other ratchet rotate in the same direction about a common axis.

Claims

1. A drug delivery device drive mechanism, comprising: A first ratchet having a plurality of first drive teeth; A second ratchet having a plurality of second drive teeth, wherein the second ratchet and the first ratchet rotate about a common axis; A first drive arm operable to engage a first drive tooth surface of the plurality of first drive teeth and cause the first ratchet to rotate in a first direction; A second drive arm operable to engage a second drive tooth surface of the plurality of second drive teeth and cause the second ratchet to rotate in a first direction; A first sensor contact operable to cause the second drive arm to stop pushing against the second ratchet in response to contact with the first drive arm; And A second sensor contact operable to cause the first drive arm to stop pushing against the first ratchet in response to contact with the second drive arm.

2. The drug delivery device drive mechanism according to claim 1, wherein the first sensor contact is further operable, when in contact with the first drive arm: To initiate a first tooth gap signal, wherein the first tooth gap signal indicates that the first drive arm is in a position for applying a force to the next first drive tooth among the plurality of first drive teeth.

3. The drug delivery device drive mechanism according to claim 1 or 2, further comprising: A first ratchet force transmission coupler operable to apply a force to the first drive arm; And A second ratchet force transmission coupler operable to apply a force to the second drive arm, wherein the first ratchet force transmission coupler and the second ratchet force transmission coupler alternately apply their respective applied forces to the corresponding first drive arm and second drive arm, at least in part based on the generated first tooth gap signal.

4. The drug delivery device drive mechanism according to claim 1, wherein: The first sensor contact is further operable to initiate a first tooth gap signal when in contact with the first drive arm, and The second sensor contact is further operable to initiate a second tooth gap signal when in contact with the second drive arm, wherein the first tooth gap signal indicates that the first drive arm is in a position for applying a force to the next first drive tooth among the plurality of first drive teeth, and the second tooth gap signal indicates that the second drive arm is in a position for applying a force to the next second drive tooth among the plurality of second drive teeth.

5. A drug delivery device drive system, comprising: A control circuit; A first ratchet having a plurality of first ratchet teeth; A second ratchet having a plurality of second ratchet teeth, wherein the first ratchet and the second ratchet rotate consistently about a common axis; A first drive arm operable to contact a corresponding tooth among the plurality of first ratchet teeth; And A second drive arm operable to contact a corresponding tooth among the plurality of second ratchet teeth, wherein the control circuit alternates between causing the first drive arm to contact a respective one of the plurality of first ratchet teeth and causing the second drive arm to contact a respective one of the plurality of first ratchet teeth.

6. The drug delivery device drive system according to claim 5, further comprising: a first sensor contact arm coupled to the control circuit; and a second sensor contact arm coupled to the control circuit, wherein the first sensor contact arm is capable of inputting a signal to the control circuit in response to contact between the first sensor contact arm and the first drive arm, and the second sensor contact arm is capable of inputting another signal to the control circuit in response to contact between the second sensor contact arm and the second drive arm.

7. The drug delivery device drive system according to claim 6, wherein the control circuit switches to cause the second drive arm to contact a respective one of the plurality of second ratchet teeth in response to the first drive arm contacting the first sensor contact.

8. The drug delivery device drive system according to claim 6 or 7, wherein the control circuit switches to cause the first drive arm to contact a respective one of the plurality of first ratchet teeth in response to the second drive arm contacting the second sensor contact.

9. The drug delivery device drive system according to any one of claims 6 to 8, wherein the first drive arm and the first sensor contact arm are configured to be substantially offset such that only a portion of the first drive arm and the first sensor contact arm overlap.

10. The drug delivery device drive system according to any one of claims 6 to 9, wherein the second drive arm and the second sensor contact arm are configured to be substantially offset such that only a portion of the second drive arm and the second sensor contact arm overlap.

11. The drug delivery device drive mechanism according to any one of claims 5 to 10, further comprising: a first ratchet force transmission coupler operable to apply a force to the first drive arm; and a second ratchet force transmission coupler operable to apply a force to the second drive arm, wherein the first ratchet force transmission coupler and the second ratchet force transmission coupler alternately apply the respective forces applied to the first drive arm and the second drive arm, at least in part based on the generated first tooth gap signal.

12. A drug delivery device drive system, comprising: a control circuit; a drive mechanism coupled to the control circuit; a first ratchet having a plurality of first ratchet teeth; a second ratchet having a plurality of second ratchet teeth, wherein the first ratchet and the second ratchet rotate in unison about a common axis; a first drive arm coupled to the drive mechanism and operable to contact a respective one of the plurality of first ratchet teeth; a first sensor contact arm coupled to the drive mechanism and the control circuit; A second drive arm coupled to the drive mechanism and operable to engage a respective one of the plurality of second ratchet teeth; and A second sensor contact arm coupled to the drive mechanism and the control circuit, wherein when the first drive arm and the first sensor contact arm are in contact with each other, the drive mechanism is operable to urge the first drive arm against the surface of a respective first ratchet tooth until the first sensor contact arm is no longer in contact with the first drive arm.

13. The drug delivery device drive system according to claim 12, wherein the first ratchet and the second ratchet are operable to rotate in response to the first drive arm and the first sensor contact being urged against the surface of the respective first ratchet tooth.

14. A drug delivery device drive system, comprising: An actuator including a pivot point, an actuation protrusion, and a first drive arm; A first ratchet operable to be urged by the first drive arm; A first sensor contact operable to contact the first drive arm; wherein contact between the first drive arm and the first sensor contact causes the actuator to apply a force via the first drive arm to urge the first ratchet.

15. A drug delivery device drive system, comprising: A first ratchet having a plurality of drive teeth, wherein each of the plurality of drive teeth includes an electrical contact; A drive arm operable to contact the electrical contact of a first drive tooth of the plurality of drive teeth and to rotate the first ratchet in a first direction; and A controller operable to detect when the drive arm contacts the electrical contact of the first drive tooth.

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