Discrete dose control and overdose prevention mechanism

Abstract

A dose control and over-run protection mechanism is provided for use in fluid delivery devices such as wearable infusion pumps and drug delivery pens. The mechanism includes opposingly rotating spur gears having surface features that guide a pin on a plate to rotate in an alternating direction along a desired arcuate path (e.g., less than 180 degrees) during each delivery cycle of a predetermined dose. The surface features are configured to controllably rotate one of the individual spur gears and output a selected amount of rotation to another component in the drivetrain of the fluid delivery device regardless of the direction of actuator input and regardless of whether the actuator is rotated beyond the arcuate path.

Description

Technical Field

[0001] This disclosure and the technical solutions described herein generally relate to dose control and overdose prevention in fluid delivery devices for drug delivery, and more specifically to a mechanism for converting input energy from an actuator into output energy to the next component in the power system of the fluid delivery device in such a way that the fluid delivery device delivers only a single dose per cycle and stops energy transfer to the power system when the actuator rotates beyond a desired operating point. Background Technology

[0002] Overdosing refers to the administration of a drug in a quantity greater than the intended dose, potentially posing an intolerable risk to the user. Overdosing can occur in drug delivery systems due to malfunctions in any component responsible for dosing delivery. These components are typically actuators, electronics, and software. In fluid delivery systems used for drug delivery, prevention of overdosing is essential. Summary of the Invention

[0003] The exemplary embodiments described herein overcome problems such as over-application and achieve additional advantages.

[0004] An over-limit operation prevention mechanism is provided in a fluid delivery device having a drive mechanism and an actuator. The drive mechanism uses a rotary input to control the fluid delivery component, and the actuator operates the drive mechanism. The over-limit operation prevention mechanism has a first spur gear and a second spur gear, the first and second spur gears comprising gear teeth and arranged adjacent to each other to engage a selected number of their respective gear teeth. The first spur gear is rotatable clockwise, while the second spur gear is rotatable counterclockwise. The over-limit operation prevention mechanism has a plate having a pin actuated by the actuator in the fluid delivery device to rotate by a controlled amount during a cycle, thereby moving the pin relative to the first and second spur gears along an arcuate path. The plate is actuated to rotate in alternating clockwise and counterclockwise directions in alternating cycles. Each of the first and second spur gears has a face facing the plate having the pin. Each face is configured to have at least one surface feature along which the pin can move when the plate rotates. As the pin travels toward the corresponding end of the arc path, the surface feature of each spur gear is contacted by the pin, causing the spur gear to rotate by a selected amount, and the teeth of the spur gear mesh with the teeth of another spur gear to transmit rotation. The surface feature of each spur gear is also configured to lose contact with the pin at the corresponding end of the arc path before the actuator reverses the direction of rotation of the plate to begin another cycle.

[0005] According to one aspect of the illustrative embodiment, during one cycle, the input to the overrun prevention mechanism corresponds to a 126-degree rotation of the plate along an arcuate path, and the spur gear is configured to rotate 90 degrees during this cycle. For example, the output of the overrun prevention mechanism is a 90-degree rotation imparted by one of the spur gears that is rotated 90 degrees during one cycle. As a further example, the fluid delivery device has a gear train assembly configured to receive the output of the overrun prevention mechanism as input and produce a second output of smaller rotation to be applied to the drive mechanism to obtain a predetermined amount of fluid dose. Alternatively, by another example, the fluid delivery device may be a syringe-type pump that moves a plunger in a cylindrical reservoir, and the drive mechanism includes a telescopic nested screw operable to move the plunger, and a second output is provided to the drive mechanism to move the plunger a distance commensurate with the delivery of a predetermined amount of fluid dose.

[0006] According to one aspect of the illustrative embodiment, the at least one surface feature includes two arcuate grooves defining two biconvex lens-shaped protrusions disposed on either side of a central biconcave lens-shaped protrusion. For example, when the pin travels toward a corresponding end of the arcuate path to rotate the spur gear by a selected amount, the convex surfaces on the biconcave lens-shaped protrusions engage with the pin. As another example, the two biconvex lens-shaped protrusions and the central biconcave lens-shaped protrusion are configured to lose engagement with the pin once the pin reaches the end of the arcuate path and cease rotation.

[0007] According to one aspect of the illustrative embodiment, the at least one surface feature includes a teardrop-shaped protrusion, each protrusion having a flat surface and a convex surface. For example, teardrop-shaped protrusions are arranged diagonally opposite each other on the surface of each spur gear, with their respective flat surfaces facing each other.

[0008] According to one aspect of the illustrative embodiment, the overrun prevention mechanism is provided with a sensor for detecting when the pin reaches the end of the arc path. For example, the fluid delivery device is configured to have a processor to receive the output of the sensor and control the actuator to reverse when the output indicates that the pin has reached the end of the arc path.

[0009] Additional and / or other aspects and advantages of the illustrative embodiments will be set forth in the following description, or will be apparent from the description, or may be learned by practicing the illustrative embodiments. Illustrative embodiments may include an apparatus having one or more of the foregoing aspects and / or one or more features and combinations thereof, and a method for operating the apparatus. Exemplary embodiments may include one or more features and / or combinations of the foregoing aspects, such as those described in the appended claims. Attached Figure Description

[0010] The above and / or other aspects and advantages of the illustrative embodiments will be more readily understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0011] Figure 1 This is a perspective top view of an exemplary fluid transport device, in which the top and base plate have been removed for clarity;

[0012] Figure 2 yes Figure 1 A side perspective view of part of the plunger actuator, gear train, and drive mechanism in the syringe barrel reservoir of the device.

[0013] Figure 3A and 3B This is a side view of the gear train and drive mechanism for an exemplary fluid transport device with an exemplary end stop circuit;

[0014] Figure 4A , 4B 4C, 4D, 4E, and 4F are side views of an actuator and gear train constructed according to an illustrative embodiment for operation. Figure 1 The drive mechanism of an exemplary fluid transport device;

[0015] Figure 5A , 5B 5C, 5D, 5E, and 5F are side views of an actuator and gear train constructed according to another illustrative embodiment for operation. Figure 1 An exemplary fluid transport device drive mechanism.

[0016] In all the accompanying drawings, the same reference numerals will be understood to refer to the same elements, features, and structures. Detailed Implementation

[0017] Reference will now be made in detail to the illustrative embodiments described in the accompanying drawings. The embodiments described herein are illustrative by way of example and not limitation.

[0018] By employing various design schemes, user risks associated with overdose can be reduced. These solutions can be mechanical, electrical, algorithmic, or any combination thereof. One mechanical solution is an intermittent working mechanism or intermittent working actuator, which is a mechanical mechanism that uses a drive wheel with a pin and a driven wheel with a slot to convert continuous input motion into discrete output motion. As the drive wheel rotates, the pin enters the slot in the driven wheel, thus rotating the driven wheel until it rotates sufficiently to allow the pin to continue traveling with the rotation of the drive wheel, at which point it leaves the slot. The degree of rotation of the driven wheel depends on the number of slots in the driven wheel, as well as other factors. However, intermittent working mechanisms do not have the ability to stop the output motion in the event of an over-limit input.

[0019] The technical solution described herein provides a novel mechanical approach for dose control and overdose prevention in a drug delivery device, such as a wearable infusion device or drug delivery pen for insulin delivery. The technical solution is an over-limit operation prevention mechanism disposed in the power system of a fluid delivery device. This power system may include, for example, a gear train located between an actuator and a drive mechanism for a plunger in a fluid reservoir for the fluid delivery device. According to the technical solution and exemplary embodiments, the over-limit operation prevention mechanism described herein receives input power (e.g., torque × speed) directly or indirectly from an actuator (e.g., a motor) and transmits output power (e.g., torque × speed) to the next component in the power system. This over-limit operation prevention mechanism is designed to regulate motion by physically saturating the output of the mechanism, such that the output of the mechanism, and the corresponding output of any connected intermediate transmission components, is proportionate to the desired dose, and also stops energy transfer when the actuator rotates beyond the desired operating point.

[0020] An overrun prevention mechanism is a stand-alone operating mechanism that delivers only one dose per cycle. A cycle is understood as a specified amount of movement of the actuator and the overrun prevention mechanism to control the drive mechanism and any intermediate power system components in the fluid delivery device, thereby delivering a predetermined amount of fluid from the fluid reservoir. For example, as described below, a cycle can be a reversible rotation of the actuator input shaft to allow the overrun prevention mechanism component with pin or cam followers to travel along an arc path of less than 180 degrees (e.g., 126 degrees), resulting in a 90-degree output rotation applied to intermediate power system components to reduce their output to a smaller input to the drive mechanism, thereby achieving the desired dose of the predetermined amount of fluid. Depending on aspects of the technical solution and some exemplary embodiments of the overrun prevention mechanism, the actuator needs to stop and rotate in the opposite direction to initiate another dose delivery cycle. Regardless of the input rotation direction of the actuator, the output of the overrun prevention mechanism rotates in a single direction. The input rotation direction needs to be reversed to enter the next delivery cycle until the desired dose is delivered.

[0021] The over-limit operation prevention mechanism operates based on the physical interaction between one or more locating pins on the plate and cam surface features on the two spur gears. The way loads are transferred between these components is highly dependent on their geometry, and the input torque curve can be adjusted by changing the geometry of these features, which will be discussed separately below. Figures 4A-4F and Figures 5A-5F The two exemplary embodiments shown are used to describe this. For illustrative purposes, the exemplary embodiments are described in conjunction with exemplary fluid transport devices, such as... Figure 1The image shows a wearable infusion device with a syringe-type pump.

[0022] refer to Figure 1 For clarity, the exemplary fluid delivery device 10 is shown without a cap and base plate. The fluid delivery device 10 has a syringe-type reservoir 12 with a plunger 14, which is controllable by a drive mechanism 16 to extend into the reservoir 12 in a desired amount to discharge a desired quantity of fluid. The drive mechanism may be, for example, an arrangement of telescopic nested screws with an innermost screw connected to the plunger and controllably extended via a power system. For example, the power system may include a rotary actuator (e.g., a motor) 19 having an input shaft 20 connected to a gear train 18 with corresponding gears, which in turn are connected to the drive mechanism 16. An exemplary embodiment of the overrun prevention mechanism 22 shows that the mechanism 22 is positioned near the actuator, with an intermediate gear arranged between the mechanism 22 and the drive mechanism 16. However, it should be understood that the overrun prevention mechanism 22 can be connected at any point along the drivetrain 19 and the drive mechanism 16. Furthermore, it should be understood that the actuator can be other types of actuators besides a motor (e.g., hydraulic, spring-loaded, manual, and solenoid actuators) capable of providing at least a half-turn and reversible rotary input, and the drive mechanism 16 is not necessarily limited to multiple nested screws for driving a plunger in a cylindrical reservoir. For example, the overrun prevention mechanism 22 can be used in the powertrain of various types of positive displacement pumps.

[0023] In these exemplary embodiments, a 126-degree rotation of the input causes the output to rotate 90° via an overrun prevention mechanism, which can be reduced to a 2.57-degree input level, for example, at the pump level (e.g., the input of a drive mechanism 16 with a nested telescopic screw), using a set of intermediate spur gears 18. A 2.57-degree rotation of the pump (e.g., a syringe-type pump with a barrel and plunger) equals one dose delivery. As described below, the overrun prevention mechanism is designed so that a rotation of the input exceeding 126 degrees does not change the 90-degree rotation of the output. Therefore, actuating the input shaft and the pin-connected plate slightly more than 126 degrees ensures the accuracy of the dosage. Moreover, an electrical switch can be added to the fluid delivery device control system to detect a 126-degree input rotation and send stop and reverse commands to the actuator. It should be understood that different degrees of rotation of the input and output of the overrun prevention mechanism 22 can be adjusted depending on the required dose delivery and the design features of the drive mechanism 16 and other components of the fluid delivery device 10.

[0024] refer to Figure 2The over-limit operation prevention mechanism 22 typically includes two spur gears 28 and 30 and a plate 24 or other components provided with one or more pins 26. The pins 26 engage with features on the front surfaces of the spur gears 28 and 30, as described below, to ensure that the pins complete the desired actuation path 32 while delivering only the predetermined output (e.g., a 90-degree rotation of the spur gears 28 and 30) to maintain a consistent full dose. Even if the actuator 19 or other components fail and cause an over-limit operation, the components of the over-limit operation prevention mechanism 22 are configured to prevent output exceeding the predetermined dose delivered in that cycle.

[0025] See Figure 3A and 3B The multiple components of the over-limit operation prevention mechanism 22 are assembled into a different configuration relative to the gear train component 18, for example... Figure 2 The illustrative embodiments shown and described below are more vertical. Figure 3A and 3B The structure shown helps to save space in the fluid delivery device 10 and minimize its size. Figure 3A and 3B An exemplary detection circuit 40 for determining when the direction of actuator 19 should be reversed is also shown. For example, plate 24 with pin 26 can be configured to be conductive, and circuit 40 can be short-circuited when either of its end stop positions 42a, b reaches the end of arc 32, thereby generating a signal for the controller to detect and command actuator 19 to stop and reverse direction. However, other methods for detecting the end of arc 32 may also be used.

[0026] Now refer to Figures 4A to 4F An exemplary embodiment of the overrun prevention mechanism 22 is described. The front surface 36 of each spur gear 28, 30 has two arcuate grooves or traces 50 defining two biconvex lens-shaped protrusions 52 and a central biconcave lens-shaped protrusion 54. These features 50, 52, and 54 on the surface 36 of the spur gears 28, 30 cooperate to intermittently provide an S-shaped path 34 for the pin 26 and the cam surface, utilizing this path to prevent the pin from traveling further along the arc 32.

[0027] Spur gear 30 rotates counterclockwise (CCW), regardless of the input direction of actuator input shaft 20. Spur gear 28 rotates clockwise (CW), also regardless of the input direction of actuator input shaft 20. Actuator input shaft 20 rotates alternately clockwise and counterclockwise to allow pin 26 to travel through arc 32 (e.g., 126 degrees or some other value less than 180 degrees) before stopping and reversing, and to travel through the arc in the opposite direction. For clarity, Figures 4A-4F The plate 24 with pin 26 is shown as an input shaft 20 without connection.

[0028] Figure 4A Plate 24 is shown, with pin 26 rotating clockwise from its bottom arcuate position. As the input shaft connected to plate 24 continues to rotate the plate clockwise, pin 26 moves along... Figure 4A The concave surface of the concave lens-shaped protrusion 54 on the spur gear 30 is shown, and the spur gear is moved 90 degrees counterclockwise, as... Figure 4B As shown. The cooperating teeth on spur gears 28 and 30 cause spur gear 28 to rotate 90 degrees clockwise. The cam surfaces of the biconvex lens-shaped protrusions 52a and biconcave lens-shaped protrusions 54 on spur gear 30 are configured to stop pushing the pin once pin 26 reaches the apex of arc 32. After actuator 19 stops and the direction of input shaft 20 connected to plate 34 is reversed, another S-shaped path 34 is established through the corresponding grooves 50 on spur gears 28 and 30 for pin 26 to travel along... Figure 4C The counterclockwise motion of arc 32 shown.

[0029] refer to Figure 4D Pin 26 follows the concave surface of the concave lens-shaped protrusion 54 on the spur gear 28, and as Figure 4E The diagram shows that spur gear 28 is moved 90 degrees clockwise. The cooperating teeth on spur gears 28 and 30 cause spur gear 30 to rotate 90 degrees counterclockwise. The cam surfaces of the biconvex lens-shaped protrusions 52a and biconcave lens-shaped protrusions 54 on spur gear 28 are configured to stop pushing the pin once pin 26 reaches the other end of arc 32. After actuator 19 stops and input shaft 20 connected to plate 34 reverses direction, another S-shaped path 34 is established through the respective slots 50 on spur gears 28 and 30 for pin 26 to travel along... Figure 4F The clockwise movement of arc 32 shown. Any of the spur gears 28 and 30 can be used as the output of the over-limit operation prevention mechanism 22.

[0030] Now refer to Figures 5A to 5F Another exemplary embodiment of the overrun prevention mechanism 22 is described. Each spur gear 28, 30 has two semi-teardrop-shaped protrusions 70a, b on its front surface 36, and a plate 24 has two pins 26a, b, shown connected to the input shaft 20 of the actuator. The spur gear 30 rotates counterclockwise, regardless of the input direction of the actuator input shaft 20. The spur gear 28 rotates clockwise, regardless of the input direction of the actuator input shaft 20. The actuator input shaft 20 rotates alternately clockwise and counterclockwise to allow the pins 26 to travel through an arc 32 (e.g., 126 degrees or some other value less than 180 degrees), then stops and reverses direction, traveling the arc in the opposite direction.

[0031] The teardrop-shaped protrusions 70a and b on each spur gear 28 or 30 are arranged to be driven by one of the corresponding pins 26a and b, causing the spur gear 28 or 30 to rotate 90 degrees, and due to the cooperating teeth therebetween, causing the other spur gear to also rotate 90 degrees. The teardrop-shaped protrusions 70a and b on the surfaces of the spur gear 28 or 30 are arranged diagonally opposite each other, with their flat surfaces facing each other. The paired teardrop-shaped protrusions 70a and b on the spur gears 28 and 30 are offset relative to each other, and the pins 26a and b on the plate 24 are spaced apart relative to each other, such that when the plate 24 traverses at least a portion of the arc 32 clockwise, the pin 26b pushes the flat surface of the teardrop-shaped protrusion 70 on the spur gear 30, and when the plate 24 traverses at least a portion of the arc 32 counterclockwise, the pin 26a pushes the flat surface of the teardrop-shaped protrusion 70 on the spur gear 28. In the example shown, the dimensions of the spur gears 28, 30 and their corresponding features 70a, b, and the pin are configured to allow the input shaft 20 and plate 24 to rotate by approximately 126 degrees, resulting in an output of approximately 90 degrees from the spur gears 28, 30.

[0032] For example, Figure 5A The input shaft 20 and plate 24 are shown rotating counterclockwise. Pin 26a travels along the flat surface of the semi-teardrop-shaped protrusion 70 on spur gear 28 to rotate it 90 degrees clockwise. The teeth of spur gear 28 then mesh with the teeth of spur gear 30 to rotate it 90 degrees counterclockwise, as shown. Figure 5B and 5C As shown. After rotating 90 degrees, pin 26a disengages from spur gear 28, and each spur gear stops rotating. Then, the actuator reverses direction and begins as shown. Figure 5D The input shaft 20 and plate 24 are rotated clockwise as shown. Reversing the input rotation direction establishes contact between the teardrop-shaped protrusion 70 on another pin 26b and another spur gear 30. (As shown) Figure 5E and 5F As shown, when plate 24 crosses arc 32 clockwise, pin 26b pushes the flat surface of the teardrop-shaped protrusion 70 to rotate it 90 degrees counterclockwise. The teeth of spur gear 30 then engage with the teeth of spur gear 28 to rotate it 90 degrees clockwise. After rotating 90 degrees, pin 26b disengages from spur gear 30, and each spur gear stops rotating. The actuator then reverses and begins to rotate input shaft 20 and plate 24 counterclockwise again. Either spur gear 28 or 30 can be used as the output of over-limit operation prevention mechanism 22.

[0033] As described above, the overrun prevention mechanism 22 described herein with respect to one technical solution and some exemplary embodiments can be implemented in a wearable infusion pump type fluid delivery device and can also be used as an overdose prevention mechanism in a drug delivery pen. The geometry of the teardrop-shaped features 70 or protrusions 52, 54 on the faces of the spur gears 28, 30 can be modified to adjust the input and output torque profiles of the mechanism 22. The pin 26 shown herein can be replaced with pins with different cross-sections to achieve different load distributions. The overrun prevention mechanism 22 can be manufactured in various sizes while retaining its key features (e.g., teardrop features 70 or protrusions 52, 54) and can be made of different materials. The spur gears 28 and 30 can be replaced with other types of gears, such as helical or bevel gears, while retaining important features, such as their clockwise and counterclockwise rotating and mating teeth, to rotate the same amount after the pin engages with one of the features of the spur gears 28 and 30 (e.g., teardrop features 70 or protrusions 52, 54). In addition to 126 degrees and 90 degrees, the input and output rotations required for a complete cycle can be modified to other angles. The overrun prevention mechanism 22 can be modified to deliver different dose volumes based on the required specifications.

[0034] For the reasons mentioned above, the over-limit operation prevention mechanism 22 not only eliminates the risk of drug overdose but also controls the accuracy of the delivered dosage within each cycle. Moreover, due to the use of gears, the over-limit operation prevention mechanism 22 operates at a noise level similar to the rest of the gear train components.

[0035] Furthermore, the over-limit operation prevention mechanism 22 is advantageous because it can be located at different stages in the powertrain (e.g., before, after, or in the middle of the gearbox). For example, spur gears are readily integrated with gearboxes, which are often used in motors, to transmit motion to the drive mechanism of plungers or pistons in fluid delivery devices, and the over-limit operation prevention mechanism 22 can be located at different stages of the powertrain (e.g., between the motor and the gearbox, between the gearbox and the pump mechanism, or within the gearbox). Moving the over-limit operation prevention mechanism 22 away from the pump (e.g., the plunger 14 in the syringe barrel 12) and closer to the actuator 19 has the additional benefit of reducing the torque applied to it and lowering the risk of failure due to high loads.

[0036] The overrun prevention mechanism 22 has a scalable gear ratio and can be configured to optimize the system's efficiency based on the selection of other components such as actuators, gearboxes, and pump mechanisms. This approach is significantly more energy-efficient than other indexing solutions, such as the dual ratchet system of the Omnipod wearable pump developed by Insulet. Furthermore, the Omnipod operates based on complex interactions between multiple components (arms, shape memory alloy wires, ratchet, hinges, stop pins, etc.), and even small deviations during manufacturing or assembly can lead to malfunctions.

[0037] While it can be combined with electronics to optimize performance, the overrun prevention mechanism 22 is a purely mechanical solution and does not necessarily require electronic equipment to operate, unlike direct-drive indexing systems that do require electronics. Introducing electronics into the indexing system of a fluid delivery device can lead to undesirable additional costs. As an example, a direct-drive indexing system may require an encoder and possibly a second microprocessor to analyze the encoder data, which could significantly increase the final cost of the fluid delivery device 10. In contrast, all components used in the overrun prevention mechanism 22 can be manufactured using inexpensive methods such as injection molding.

[0038] Furthermore, due to the non-discrete output of the direct-drive indexing system, errors occurring in the system due to various reasons are cumulative and may accumulate to a higher value over the lifespan of the fluid delivery device 10. On the other hand, each dose delivery cycle in the over-limit operation prevention mechanism 22 is independent of the previous cycle, and errors are not propagated to the next dose delivery cycle.

[0039] As described above, conventional Geneva mechanisms do not have the feature of preventing output rotation in the event of excessive input. In contrast, the over-limit operation prevention mechanism 22 of the present invention prevents overdose by stopping the output after a certain condition is met. The over-limit operation prevention mechanism 22 requires reversing the direction of the actuator 19 (e.g., the motor direction) as a safety feature to continue the metering process. On the other hand, the Geneva working mechanism operates continuously with a motor rotating in a unidirectional direction, which may lead to patient overdose.

[0040] The exemplary embodiments of this disclosure can solve at least the problems and / or disadvantages described above, as well as other disadvantages not described above. Furthermore, the exemplary embodiments are not necessarily required to overcome the aforementioned disadvantages, and may not overcome any of the aforementioned problems.

[0041] Those skilled in the art will understand that this disclosure is not limited in its application to the details of the construction and arrangement of the components set forth in the above description or shown in the accompanying drawings. The embodiments described herein can evolve into other embodiments and can be practiced or performed in various ways. Moreover, it should be understood that the wording and terminology used herein are for descriptive purposes only and should not be considered limiting. The use of “comprising,” “including,” or “having,” and variations thereof herein is intended to include the items listed thereafter and their equivalents, as well as additional items. Unless otherwise limited, the terms “connection,” “coupling,” and “installation,” and variations thereof are used broadly herein and cover direct and indirect connections, couplings, and installations. Furthermore, the terms “connection” and “coupling,” and variations thereof, are not limited to physical or mechanical connections or couplings. Additionally, terms such as upper, lower, bottom, and top are relative and used for illustrative purposes, not for limitation.

[0042] The above description and accompanying drawings are merely illustrative and not intended to limit the exemplary embodiments in any way, except as set forth in the appended claims. It should be noted in particular that those skilled in the art can readily combine various technical aspects of the various elements of the various illustrative embodiments described above in a variety of other ways, all of which are considered to be within the scope of the claims.

Claims

1. An over-limit operation prevention mechanism, characterized in that, The over-limit operation prevention mechanism is suitable for use in a fluid conveying device having a drive mechanism for controlling fluid conveying components using a rotary input and an actuator for operating the drive mechanism. The over-limit operation prevention mechanism includes: A first spur gear and a second spur gear, the first spur gear and the second spur gear including gear teeth and arranged adjacent to each other to engage a selected number of their corresponding gear teeth, the first spur gear being capable of clockwise rotation and the second spur gear being capable of counterclockwise rotation; and A plate having a pin actuated by an actuator in the fluid delivery device to rotate in a controlled amount during a cycle, thereby moving the pin relative to the first spur gear and the second spur gear along an arcuate path, the plate being actuated to rotate in clockwise and counterclockwise directions in alternating cycles; Each of the first spur gear and the second spur gear has a face facing the plate with the pin. Each face is configured to have at least two surface features that, according to the rotation direction of the plate, alternately define two corresponding arcuate paths for the pin to follow on each face. As the pin travels toward the corresponding end of the arcuate path, each surface feature of each of the first and second spur gears is contacted by the pin to rotate the spur gear by a selected amount, and the teeth of the spur gear engage the teeth of the other spur gear to drive its rotation. Each surface feature of each of the spur gears is also configured to lose contact with the pin at the corresponding end of the arcuate path before the actuator reverses the rotation direction of the plate to begin another cycle.

2. The over-limit operation prevention mechanism as described in claim 1, characterized in that, The input to the overrun prevention mechanism corresponds to the plate rotating 126 degrees along the arc path during one cycle, and the first spur gear and the second spur gear are configured to rotate 90 degrees during that cycle.

3. The over-limit operation prevention mechanism as described in claim 2, characterized in that, The output of the overrun prevention mechanism is a 90-degree rotation driven by one of the first and second spur gears, which are rotated 90 degrees during one cycle.

4. The over-limit operation prevention mechanism as described in claim 3, characterized in that, The over-limit operation prevention mechanism is connected to a fluid delivery device having a drive mechanism, such that the fluid delivery device has a gear train component configured to receive the output of the over-limit operation prevention mechanism as an input and generate a second output with a small rotation to be applied to the drive mechanism, thereby achieving a predetermined amount of fluid dosage.

5. The over-limit operation prevention mechanism as described in claim 4, characterized in that, The fluid delivery device is a syringe pump that moves a plunger within a cylindrical reservoir, and the drive mechanism includes a telescopic nested screw operable to move the plunger. A second output is provided to the drive mechanism to move the plunger a distance proportional to the delivery of a predetermined fluid dose.

6. The over-limit operation prevention mechanism as described in claim 1, characterized in that, The at least two surface features include two arcuate grooves that define two biconvex lens-shaped protrusions arranged on either side of the central biconcave lens-shaped protrusion.

7. The over-limit operation prevention mechanism as described in claim 6, characterized in that, As the pin travels toward the corresponding end of the arc path to rotate the spur gear by a selected amount, the pin contacts the convex surface on the biconcave lens-shaped protrusion.

8. The over-limit operation prevention mechanism as described in claim 6, characterized in that, The two biconvex lens-shaped protrusions and the central biconcave lens-shaped protrusion are configured to lose engagement with the pin and cease rotation once the pin has reached the end of the arcuate path.

9. The over-limit operation prevention mechanism as described in claim 1, characterized in that, The at least two surface features include semi-teardrop-shaped protrusions, each semi-teardrop-shaped protrusion having a flat surface and a convex surface.

10. The over-limit operation prevention mechanism as described in claim 9, characterized in that, The teardrop-shaped protrusions are arranged diagonally opposite each other on the surface of each of the first and second spur gears, with the flat surfaces of the teardrop-shaped protrusions facing each other.

11. The over-limit operation prevention mechanism as described in claim 1, characterized in that, The over-limit operation prevention mechanism also includes a sensor for detecting when the pin reaches the end of the arc path.

12. The over-limit operation prevention mechanism as described in claim 11, characterized in that, The overrun prevention mechanism is connected to a fluid delivery device having a drive mechanism that uses a rotary input to control the fluid delivery component and an actuator for operating the drive mechanism, and the fluid delivery device is further configured to have a processor for receiving the output of the sensor and controlling the actuator to reverse when the output indicates that the pin has reached the end of the arc path.

Images