WO2010069573A2

WO2010069573A2 - A syringe driver

Info

Publication number: WO2010069573A2
Application number: PCT/EP2009/009075
Authority: WO
Inventors: Andrew Barr
Original assignee: Surgical Systems Ireland Limited
Priority date: 2008-12-17
Filing date: 2009-12-17
Publication date: 2010-06-24
Also published as: WO2010069573A3; GB0822935D0; GB201110961D0; GB2478253A

Abstract

A syringe driver (10) having a motor-operated syringe actuator that is responsive to sensor signals. The signals may emanate from sensors for detecting the presence of a syringe, or the presence of a cover, or the position of the syringe plunger, or the load experienced by the actuator. A rotary encoder motors the motor shaft to allow accurate control of the actuator when dispensing material from the syringe.

Description

A Syringe Driver

Field of the Invention

The present invention is concerned with a syringe driver, and in particular a portable syringe driver, which is user programmable to provide a range of delivery profiles and additional features.

Background to the Invention

Known syringe drivers are considered to be relatively simplistic in that they provide little or no functionality other than to control the advancement of a syringe plunger.

It would be desirable, therefore, to provide an improved syringe driver.

Summary of the Invention

The invention provides a syringe driver as claimed in claim 1. Preferred features are recited in the dependent claims.

The syringe driver comprises a housing for receiving a syringe; an actuator engagable with a plunger of the syringe, the actuator being displaceable relative to the housing; and a motor operable to displace the actuator.

Preferably, the driver comprises load detection means adapted to measure the load being applied to the plunger by the actuator.

Preferably, the driver comprises means to measure the absolute displacement of the actuator relative to the housing. Preferably, the driver comprises a first sensor to sense when the plunger has been fully depressed.

Preferably, the driver comprises a second sensor to sense the presence of a syringe in the housing.

Preferably, the housing comprises a removable cover to facilitate the location of a syringe within the housing.

Preferably, the driver comprises a third sensor to sense the presence of the cover.

Preferably, the driver comprises a fourth sensor to sense when the plunger bas been fully retracted.

Preferably, the actuator comprises a lead screw rotatable by the motor, and a plate threadably mounted on the lead screw.

Preferably, the driver comprises a coupling disposed between the motor and the lead screw, which coupling is adapted to transmit torque to the lead screw while allowing deviation in alignment of a longitudinal axis of the motor and a longitudinal axis of the lead screw.

Preferably, the coupling enables axial displacement of the lead screw relative to the motor.

Preferably, the motor comprises a servomotor or a stepper motor.

Preferably, the load detection means comprises a load cell, or a strain gauge, located adjacent or against the free end of the lead screw.

Preferably, the load detection means comprises means for monitoring the current driving the servomotor. Preferably, the means for measuring the absolute displacement of the actuator comprises an optical encoder associated with the motor and adapted to count the revolutions of the motor.

Preferably, the driver comprises a visual user interface and associated control circuitry.

Brief Description of the Drawings

An embodiment of the invention is now described by way of example and with reference to the accompanying drawings, in which;

Figure 1 is a perspective view of a syringe driver embodying the present invention, and having a cover of a housing removed therefrom;

Figure 2 is a plan view of the driver illustrated in Figure 1 , with a primed syringe located therein;

Figure 3 is a plan view of the driver, with the syringe fully discharged;

Figure 4 is an exploded perspective view of an interior of the driver;

Figure 5 is a perspective view of the driver, having a removable cover detached therefrom; and

Figure 6 is an alternative perspective view of the driver of the present invention.

Detailed Description of the Drawings

Referring now to the accompanying drawings, there is shown a syringe driver, generally indicated as 10, embodying the present invention. The driver 10 is adapted to house a syringe S, and is advantageously programmable to provide a desired delivery profile for a particular substance, for example a medicament, contained within the syringe S. Preferably, the driver 10 is programmable to dispense pre-set dosages of a substance from the syringe S, at pre-determined intervals, for example in line with a particular treatment program being implemented.

The preferred driver 10 comprises a housing 12 that defines an interior cavity 14, or seat, for receiving the syringe S. The cavity 14 comprises a first section 16 for receiving the main body of the syringe S and a second section 18 for receiving a plunger P of the syringe S. The first section 16 is preferably provided with a number of clips 20, or other retaining means, that are adapted to retain the syringe S within the cavity 14. Located within the second section 18, and displaceable therealong, is a plunger actuating member, which forms part of means for actuating the plunger P, in the convenient form of a plate 22, which is arranged to engage with the free end of the plunger P, and so to drive the plunger P into the chamber of the syringe S, as will be described in greater detail hereinafter. Conveniently, the plate 22 does not grip or is not otherwise connected to the plunger - it only abuts against the plunger when engaging therewith. Alternatively, the plate 22 may be adapted to releasably grip the plunger. This allows the driver 10 to retract the plunger as well as depress it.

Thus the driver 10 provides means for automating the dispensing of a substance from the syringe S. The driver 10 is preferably battery powered, in order to be portable, although any other suitable power source may be used. For example, the driver may be provided with lead or socket for connection to a mains electrical supply.

Referring in particular to Figure 4, the preferred housing 12 contains a number of components that co-operate to provide the desired functionality of the driver 10. In the preferred embodiment, the housing contains a motor 24, preferably a servomotor, but alternatively a stepper motor or any other suitable motor, especially electric motors. The motor 24 is coupled to drive means in the preferred form of a lead screw 26, although any other means for translating rotation into linear motion may be used. Typically, the motor 24 is a rotational motor, i.e. having a rotatable output shaft, and so a lead screw or equivalent devices is required to achieve linear movement of the plunger. In alternative embodiments, a liner motor may be employed in which case the lead screw is not required.

In the illustrated embodiment, the lead screw 26 forms part of the actuator along with the plate 22. The lead screw 26 is coupled to the plate 22 by any suitable means, conveniently a threaded coupling 23. The arrangement is such that rotation of the motor 24 causes a corresponding rotation of the lead screw 26, which in turn effects a corresponding linear translation of the plate 22 within the second section 18. Preferably, the coupling 23 comprises a non-releasable, full surround threaded coupling such that a unitary annular threaded element surrounds and engages with the lead screw 26. This is in contrast to a releasable clamping threaded element and offers the advantage of a better transmission of force to the plate 22. However, since the coupling is not releasable, the motor 24 must be reversible to allow the plate 22 to be retracted.

A coupling 28 is preferably provided between the motor 24 and the lead screw 26. The coupling 28 is adapted to accommodate alignment deviations between the longitudinal axis of the motor 24 and the longitudinal axis of the lead screw 26. This is ensures ease of assembly of the driver 10, and avoids the risk of jamming caused by misalignment of these components. In addition, the coupling 28 is preferably resiliently deformable (at least axially) to allow axial movement of the lead screw 26 relative to the motor 24, for reasons that will be described hereinafter in detail. The coupling 28 may take any suitable form and may, for example, comprise a conventional spring coupling. The motor 24, lead screw 26, and couplings 23, 28 are conveniently housed within a compartment provided in the housing 10 beneath the cavity 14. The preferred driver 10 includes a controller (not shown), typically in the form of a programmable microprocessor, microcontroller, PLC or other convenient control circuitry. The controller is cooperable with at least one, but preferably a plurality of sensors, conveniently in the form of micro switches, although any other suitable switch or sensor, e.g. reed switches, optical sensors or electromagnetic filed sensors, may be alternatively used as appropriate. Advantageously, on or more of the sensors may be used by the controller to determine whether or not all or part of the driver 10 should be disabled, for example to prevent delivery, or further delivery, of the contents of the syringe.

A first sensor 30 is provided in or adjacent the cavity 14 and arranged to detect the presence of the syringe S within the housing 12. The controller maybe arranged to disable the driver 10 (or at least disable operation of the motor) when the first sensor 30 indicates that the syringe is not present. Alternatively, or in addition, the controller may operate the motor 24 to cause the plate 22 to retract when it is detected that a syringe is not present in readiness for a new syringe. Advantageously, the plate 22 is retracted to a known start position to facilitate measurement of the delivery of the contents of the syringe, as is described in more detail below.

A second sensor 32 is positioned to detect when the plunger P has been fully depressed by the plate 22, or has reached another depressed position, and can therefore be used by the controller to turn off the motor 24, or inhibit further motor activity, once the plunger P has reached this position. When the plunger is fully depressed, the plate 22 may be said to be in its fully extended state.

A third sensor 34 is positioned to detect the presence of a cover 38 which is releasably connectable to the housing 12 in order to enclose the syringe S, as can be seen in particular from Figure 5. The controller maybe arranged to disable the driver 10 (or at least disable operation of the motor) when the third sensor 34 indicates that the syringe is not present. Alternatively, or in addition, when the cover 38 is fitted to the housing 12 to enclose the syringe S, it maybe locked in place on the housing 12 via a lock 44. The controller may control operation of the lock 44 using the output of the third sensor 34. This prevents tampering with the syringe S during use, and also prevents the ingress of any contaminants or other matter which might adversely affect the operation of the driver 10.

A fourth sensor (not shown) is positioned to detect when the plate 22 has been fully retracted (i.e. retracted to the start position in the preferred embodiment). The output of the further sensor can therefore be used by the controller to turn off the motor 24, inhibit further motor activity, or otherwise fully or partially disable the driver 10 once the plate 22 has reached this retracted position. This facilitates the preferred feature whereby the controller causes the plate 22 to retract when it is detected that the syringe has been removed in readiness for a replacement syringe.

Conveniently, the controller and sensors are provided on, or connected to (as appropriate), a printed circuit board 36 (PCB) in conventional fashion.

In one embodiment, located at the end of the lead screw 26 opposite that of the motor 24 is load detecting means, for example in the form of a spring, especially a leaf spring 40. The leaf spring 40 serves as a resilient end stop for the lead screw 26. The lead screw 26 is positioned such that its free end (lightly) abuts against the leaf spring 40. In this way the lead screw 26 is supported at either end in a manner that tolerates minor axial displacements of the lead screw 26. The leaf spring 40 (or other load detector) is connected to an electronic strain gauge 42 in order to measure the load imparted to the leaf spring 40 by the lead screw 26. In particular, the strain gauge 42 enables electronic measurement of the deflection of the leaf spring 40 corresponding to axial displacement of the lead screw 26. All of these components may be housed internally of the housing 12 and are not visible during normal use of the driver 10.

During normal operation of the driver 10, the motor 24 effects rotation of the lead screw 26, which drives the plate 22, and therefore depresses the plunger P. The motor 24, preferably a servomotor, may be electronically controlled to displace the plunger P in predefined steps or continuously. A servomotor is preferred over, for example, a stepper motor, as it consumes less current, and has a high reversing speed which is beneficial when resetting the device 10. As the plate 22 is displaced along the lead screw 26 to depress the plunger P, the plate 22 will experience resistance as it depresses the plunger P, which resistance will cause a relatively small axial displacement of the lead screw 26 with respect to the leaf spring 40. If the plate 22 encounters an excessive resistive force, further rotation of the motor 24 will cause the lead screw 26 to be translated further axially with respect to the leaf spring 40, which will therefore experience an increased deflection which is quantified electronically by the strain gauge 42. Thus the output of the strain gauge 42 is a measure of the resistive force encountered by the lead screw 26. Excessive resistive force may be experienced as a result of, for example, a kink in tubing (not shown) leading from the syringe S, or a blockage in the needle, or because the plunger P has reached the end of its travel. The driver 10, via the controller, may calibrate the electronic signal from the strain gauge 42 and interpret the measured resistive force according to a programmed course of action. Thus when such excessive resistive force is experienced, the driver 10 can, for example, halt the motor 24, and/or effect a reversal of the motor 24 to withdraw the plate 22 by, say a predetermined amount, in order to remove pressure from the plunger P.

As an alternative or additional safety feature, the motor 24, when provided as a servomotor (or other motor that allows load detection from the operating characteristics, such as current drawn, of the motor), may itself provide the load detection means. In particular, the load on the servomotor can be measured by monitoring the current drawn by the motor 24. Thus if the current were to increase beyond a normal operating value, or normal operating range, the controller may be programmed to halt the motor 24, and/or effect a reversal of the motor 24. Monitoring the load on the motor 24 by the electrical operating characteristics of the motor may also be used to determine when the plunger P has been fully depressed by the plate 22 (an increased load is experienced by the plate when the plunger engages with the end of its chamber), and/or to determine when the plate 22 has been retracted to the start position, or other retracted position, (the plate 22 maybe arranged to engage with a portion of the housing 12 when in the retracted position thereby increasing the load on the motor 24). The load sensing capabilities of the motor 24 may be used as well as or instead of the second and/or fourth sensors described above.

The preferred driver 10 is arranged to monitor the absolute position of the plunger P, or more specifically the plate 22, and/or relative movement of the plunger/plate. Thus the driver 10 comprises measuring means capable of accurately measuring the number of revolutions of the spindle of the motor 24. Conveniently, the measuring means comprises a rotary encoder, preferably a relative rotary encoder, for example an optical encoder (not shown). The encoder is positioned with respect to the shaft of the motor 24 in order that it may detect rotation of the shaft. Conveniently, the encoder may be incorporated into the motor 24. The controller may use the output of the encoder to determine the number of revolutions and/or partial revolutions, of the shaft. This allows the extent of the travel of the plate 22 to be determined and so indicates the quantity of substance dispensed from the syringe, hi one mode of use, the rotation of the motor shaft is measured starting from when the plate 22 adopts its start position. Measurement may stop in response to any desired event, for example the plate 22 reaching the other end of its travel and/or detection of the syringe being removed. This allows the controller to monitor each dose delivered to a patient during the period that a given syringe is installed and removed. The driver 10 may include a clock for allowing the controller to record the time and/or date, as applicable, of the delivery of the substance. The clock may be used by the controller to determine when to deliver a given quantity of the substance in accordance with a regimen. The quantity of substance delivered may also be measured and recorded across the installation and removal of a plurality of syringes in order to monitor the administration of the substance over a predetermined period of time and/or a prescribed regimen.

Advantageously, monitoring the rotation of the motor shaft, in combination with one or more other advantageous features including enabling delivery only when a syringe is present, enabling delivery only when the cover is fitted, enabling delivery only when the lock is on, allows the delivered to be verified with a reasonably high degree of certainty.

Hence, by monitoring each dose of drug delivered from the syringe S by the driver 10, the driver 10 is capable of continuous self-verification of the delivery of said doses, in additional to enabling intelligent services to a user, such as a continuous indication, for example in millilitres, of the dosage delivered. The driver 10 can also provide an estimation of "near end of travel", optionally with an audible alert, and a recorded profile of the delivery rate, etc. This information is preferably displayable on a visual user interface in the form of an LCD screen 46 mounted on an exterior of the housing 12, as illustrated in Figure 6.

The preferred driver 10 further comprises a number of keys 48 which are operable to program the driver 10, or to retrieve information therefrom, preferably via a menu system displayed on the LCD 46 and supported by the controller. The controller may be set up, preferably via a software based interface, to provide a large number of additional functions. For example, the driver 10 may be programmed to require entry of a security code in order to prevent the unauthorised operation and/or programming of the device. This could then give the option of enabling a complete shutdown of the driver 10 in the event of any tampering therewith, for example by means of excessive attempts to guess the security code.

The controller may also be adapted to prevent operation of the driver 10 unless certain conditions are met. For example, if no syringe S is present in the cavity 14, the first sensor 30 will register this, and the control circuitry can be programmed to prevent operation of the driver 10 (or at least to prevent operation of the motor). If the plunger P has been fully depressed, the second sensor 32 will detect this, and prevent the further operation of the driver 10 (or at least to prevent operation of the motor), or alternatively the control circuitry may be programmed to reverse the motor 24 until the plate 22 has been fully reversed away from the plunger P. Optionally, if the cover 38 is not secured to the housing 12, the third sensor 34 will register this, and prevent operation of the driver 10 (or at least to prevent operation of the motor).

In a preferred embodiment, the second sensor 32, or another sensor, is positioned to detect when the plate 22 has reached a position that is close to, but not at, the fully extended position (where the plunger P is fully depressed). In response to determining that the plate 22 is at this position, the controller is arranged to cause the plunger P to be further depressed by a pre-determined distance. The dispensing of the contents of the syringe is deemed to be complete once said further depression is completed and so the controller may deactivate the motor. The appropriate pre-determined distance may be determined empirically by a suitably skilled person during a calibration process and may depend on, for example, the size of the syringe. An advantage of this arrangement is that the device 10 can fully empty a syringe while still being able to detect an occlusion in the line in, say, the last few millimetres of the plate's 22 travel. Another advantage is that the device 10 may accommodate syringes of different sizes by appropriate calibration of the pre-determined distance.

The housing defines a port 50 from which tubing (not shown) connected to the syringe S can exit the driver 10. The housing 12 also incorporates a battery cover 52 providing access to the interior of the housing 12, in order to enable replacement of the battery.

The present invention is not limited to the embodiment described herein, which may be amended or modified without parting from the scope of the present invention.

Claims

CLAIMS:

1. A syringe driver comprising a housing for receiving a syringe; an actuator engagable with a plunger of the syringe, the actuator being displaceable relative to the housing between a retracted state and an extended state; a motor coupled to the actuator and operable to displace the actuator relative to the housing, means for sensing at least one physical characteristic of said syringe driver, and means for controlling the operation of said motor in response to signals received from said sensing means.

2. A syringe driver as claimed in claim 1, wherein said sensing means comprises means for measuring displacement of said actuator at least in a first direction corresponding to movement of said actuator from said retracted state to said extended state.

3. A syringe driver as claimed in claim 2, wherein said measuring means comprises a rotary encoder arranged to measure rotation of a drive shaft of said motor.

4. A syringe driver as claimed in claim 2 or 3, wherein said sensing means includes at least one sensor arranged to detect when said actuator reaches, from said retracted state, a priming position, said controller being arranged to cause said actuator to be actuated further in said first direction by a pre-determined distance in response to detection of said actuator reaching said priming position, and subsequently to terminate actuation of said actuator in said first direction.

5. A syringe driver as claimed in any preceding claim, wherein said sensing means includes at least one sensor arranged to detect when said actuator reaches said extended state, said controller being arranged to terminate actuation of said actuator in said first direction in response to detection that said actuator has reached said extended state.

6. A syringe driver as claimed in any preceding claim, wherein said sensing means includes at least one sensor arranged to detect when said actuator reaches said retracted state, said controller being arranged to terminate actuation of said actuator in a second direction opposite said first direction in response to detection that said actuator has reached said retracted state.

7. A syringe driver as claimed in any preceding claim, wherein said sensing means further includes at least one senor arranged to detect the presence or absence of said syringe, said controller being arranged to at least partially disable the operation of the syringe driver in response to detection that said syringe is absent.

8. A syringe driver as claimed in claim 7, wherein, in response to detection that said syringe is absent, said controller is arranged to cause said actuator to be actuated to said retracted state.

9. A syringe driver as claimed in any preceding claim, wherein the housing comprises a removable cover for enclosing said syringe when present, said sensing means including at least one sensor arranged to detect the presence or absence of said cover, said controller being arranged to at least partially disable the operation of the syringe driver in response to detection that said cover is absent.

10. A syringe driver as claimed in claim 9, further including a lock for locking said cover in place, said controller being arranged to at least partially disable the operation of the syringe driver in response to detection that said cover is not locked.

11. A syringe driver as claimed in any preceding claim, further including load detection means arranged to measure the load exerted on said actuator said controller being arranged to terminate actuation of said actuator in response to detecting that said load exceeds a threshold level.

12. A syringe driver as claimed in any preceding claim, wherein the actuator comprises a lead screw coupled to and rotatable by the motor, and an actuating member coupled to the lead screw and arranged for engagement with said plunger when present.

13. A syringe driver as claimed in claim 13, wherein said actuating member is coupled to said lead screw by means of a non-releasable annular threaded coupling.

14. A syringe driver as claimed in claim 12 or 13, further including a coupling between the motor and the lead screw, which coupling is adapted to transmit torque to the lead screw while allowing deviation in alignment of a longitudinal axis of the motor and a longitudinal axis of the lead screw.

15. A syringe driver as claimed in claim 14, wherein the coupling is adapted to accommodate axial displacement of the lead screw relative to the motor.

16. A syringe driver as claimed in any of claims 11 to 15, wherein said load detection means comprises a load cell, or a strain gauge, coupled to a free end of the lead screw.

17. A syringe driver as claimed in claim 16, wherein said load cell or strain gauge is arranged to measure said load in response to axial movements of said lead screw.

18. A syringe driver as claimed in any preceding claim, wherein said motor comprises a reversible motor.

19. A syringe driver as claimed in any preceding claim, wherein said motor comprises a servomotor.

20. A syringe driver as claimed in any preceding claim, wherein said load detection means comprises means for monitoring at least one electrical characteristic of said motor, preferably the current drawn by the motor during use.

21. A syringe driver as claimed in claim 20, wherein said housing includes a portion for engaging with said actuator when said actuator reaches said extended state, said controller being arranged to terminate actuation of said actuator in said first direction in response to detection of an increased load corresponding to engagement of said actuator with said portion of the housing.

22. A syringe driver as claimed in claim 20 or 21 , wherein said housing includes a portion for engaging with said actuator when said actuator reaches said retracted state, said controller being arranged to terminate actuation of said actuator in said second direction in response to detection of an increased load corresponding to engagement of said actuator with said portion of the housing.