GB2291135A - Device for dispensing fluid - Google Patents

Abstract

A device for dispensing fluid includes a delivery chamber (29) for receiving fluid to be dispensed, a reciprocating piston (32) movable in the delivery chamber for causing, during a suction stroke, fluid to be drawn into the delivery chamber from a collapsible bag (18) and, during a delivery stroke causing the pressurising of the fluid for delivery through a nozzle unit (30). A piston actuating means including resilient means (48) drives the piston during its delivery stroke. The piston actuating means includes a cam follower (40) acting on a helical cam (36). Charging means (12, 45, 42) is manually operated to cause mutual rotation between the cam and the cam follower whereby the cam follower follows a rising cam surface of the cam to effect the suction stroke of the piston. Means are provided for arresting the charging means just before the cam follower reaches the end of the rising cam surface whereby release means (14, 62) can be subsequently operated to cause further mutual rotation of the cam follower and the cam with the result that cam follower passes the end of the rising cam surface, whereby the resilient means effects the delivery stroke of the piston. <IMAGE>

Description

DEVICE FOR DISPENSING FLUID This invention relates to a device for dispensing fluid.

Devices for dispensing fluid are known which comprise a delivery chamber for receiving fluid to be dispensed, a reciprocating piston communicating with the delivery chamber for, during a first stroke, causing reduction in pressure in the delivery chamber to draw fluid into the delivery chamber and, during a second stroke, pressurising the fluid for delivery thereof from the delivery chamber, and piston actuating means including resilient means for urging the piston in the direction of the second stroke.

International patent application WO 91/14468 describes such a device for dispensing fluid. In particular, WO 91/14468 describes a device for supplying a metered dose of a drug for inhaling purposes.

The device includes a piston which is mounted in a cavity within a body. The piston is urged by a pre-loaded spring into a pressure chamber. The piston is loaded by means of an actuating rod having a handle which is pulled downwards. A liquid drug (for example a drug in an aqueous solution) is contained in a collapsible bag. The loading of the piston causes low pressure to be created within the pressure chamber which in turn causes a measured quantity of the drug to be withdrawn from the collapsible bag. At the end of loading stroke of the piston, the actuating rod is latched in the loaded position. An actuating button is provided for releasing the actuating rod when it is intended to administer the drug.This causes the piston to move rapidly under the influence of the spring to cause a sudden and large increase in pressure, thereby ejecting the liquid drug through an atomising head to form a fine, atomised spray. Such fluid dispensing devices provide a practical alternative to the previously used aerosol type devices, thereby enabling a measured quantity of a drug to be applied without the use of propellants such as CFCs.

However, in order to provide sufficient pressure to cause reliable dispensing of the fluid with adequate atomization thereof, a high pressure has to be generated within the delivery chamber. The creation of a high pressure is achieved through rapid movement of the piston and a small piston diameter. In order to achieve rapid movement of the piston, it is necessary to use a strong spring, with the result that considerable force is needed to load the spring. This has disadvantages in that, firstly, a large force needs to be applied to the handle for loading the spring and, secondly, a rather large and cumbersome handle is required in order that sufficient force may be applied thereto.

US Patent US 4,260,082 describes an alternative device for dispensing a measured quantity of a fluid. This US patent describes a hand-held rechargeable liquid dispensing device having an upper part and a lower part. The lower part contains a reservoir for the fluid to be dispensed and is rotatable with respect to the upper part. A cylinder within the lower part of the device co-operates with a relatively reciprocating piston to define a pressurizable chamber which can be charged with liquid from the lower part. The piston is formed with a helical cam which interacts with a co-operating surface of the lower part to cause reciprocation of the piston on relative rotation of the upper and lower parts of the device.Thus, as the lower part of the device is rotated with respect to the upper part, the co-operating cam surfaces cause the piston to rise which in turn causes liquid from the lower portion to flow into the pressurizable chamber. At the end of the helical cam surface, the piston then returns to its original position under the action of a spring. This causes pressurisation of the fluid within the pressurizable chamber. On operation of a valve connected to the pressurizable chamber, the pressurised fluid within the chamber can be expelled to dispense the fluid.

The arrangement provided in US 4,260,082 enables a desired amount of fluid to be drawn from a reservoir into a pressurising chamber and then expelled therefrom without the provision of an external handle as required by WO 91/14468. However, the arrangement shown in the US patent requires the use of two valves: the first for allowing fluid into the pressurizable chamber and the second for enabling the pressure to be maintained within the pressurizable chamber until the desired time of release. The use of two valves results in an expensive arrangement. The need to maintain the liquid under pressure in the pressurizable chamber also results in an expensive construction.

An object of the present invention is, therefore, to overcome the problems of the prior art.

In accordance with the invention there is provided a device for dispensing fluid, the device comprising: - a piston communicating with a delivery chamber for fluid to be dispensed; - a piston actuating mechanism including a cam and a cam follower; - a charging actuator for causing the cam follower to follow a surface of the cam up to an end thereof for a charging stroke of the piston to precharge the delivery chamber with fluid; and - a release actuator causing the cam follower to pass beyond the end of the cam surface to initiate a return stroke of the piston for pressurising the fluid in the delivery chamber.

The cam and cam follower arrangement with a charging actuator causes the cam follower to follow a surface of the cam up to an end thereof for a first, charging, stroke of the piston to precharge the delivery chamber with fluid. A release actuator causes the cam follower to pass beyond the end of the cam surface to initiate a second, return, stroke of the piston for pressurising the fluid in the delivery chamber. Thus a desired quantity of fluid can be drawn into the delivery chamber (e.g. from a reservoir), where it can be stored until it is subsequently pressurised by actuating the release actuator, for example when the fluid is to be delivery from the delivery chamber.

Preferably the charging actuator is separate from the release actuator whereby two separate actions are required for the first and second strokes of the piston.

Preferably the piston causes a reduction in pressure in the delivery chamber during the charging stroke to draw fluid into the delivery chamber from a reservoir and pressurises the fluid for delivery thereof from the delivery chamber during the return stroke.

Preferably the piston actuating mechanism is arranged to cause mutual rotation between the cam and the cam follower in response to actuation of the charging actuator such the cam follower follows a helical cam surface of the cam to effect the charging stroke of the piston.

The use of a helical cam enables a significant mechanical advantage to be achieved whereby the resilient member can be charged without an excessive exertion of force.

Preferably the piston actuating mechanism is arranged positively to arrest the charging actuator before the cam follower passes the end of the helical cam surface. This ensures that the return stroke of the piston cannot inadvertently be initiated at the end of a charging stroke by over-operation of the charging actuator. By ensuring that a separate operation is required for pressurising the fluid, preferably at the time of delivery of the fluid from the delivery chamber, an expensive construction for withstanding high pressures over an extended period can be avoided.

Preferably therefore, the piston actuating mechanism is arranged to respond to actuation of the release actuator to cause further mutual rotation of the cam follower and the cam to cause the cam follower to pass beyond the end of the cam surface to initiate a return stroke of the piston for pressurising the fluid in the delivery chamber.

Preferably the piston actuating mechanism includes resilient means for urging the piston in the direction of the return stroke, whereby the resilient means effects the second stroke of the piston.

Preferably, the charging means comprises a manually operable knob providing initial lost motion travel before engaging a rotary drive mechanism for causing mutual rotation of the cam and the cam follower.

This provides a mechanism whereby mutual rotation of the cam and cam surface only occurs after the lost motion travel such that the cam follower can be left at or near the end of the cam surface.

Preferably, also, the charging means comprises a rotary knob including a protrusion which, after initial lost motion travel of the knob from a rest position, engages a rotatable drive member for causing mutual rotation of the cam and cam follower. Thus rotation of the charging actuator by a predetermined amount causes mutual rotation of the cam and cam follower by that amount minus the lost motion travel.

Preferably a moveable member, which is operationally connected to the piston, is provided with either said cam surface or said cam follower and a fixed member provided with the other of said cam surface or said cam follower, the moveable member being connected to the rotatable drive member for rotation therewith.

In a preferred example of the invention, the arresting means arrests the knob after 360 degrees of rotation thereof, 360 degrees of rotation of the rotary knob causing 360- degrees of rotation of the moveable member, where P1 degrees is the angular free travel of the rotatable knob before the protrusion engages the drive member.

Preferably, a pin is provided for connecting the drive member and the moveable member to prevent mutual rotation therebetween, the pin being located in a slot permitting mutual axial movement between the drive member and the moveable member.

The arresting means preferably comprises one or more detent pins for engaging arresting notches in the rotatable knob, the detent pins being urged into engagement with the arresting notches by axial movement of the moveable member.

Preferably the release means comprises a pusher rod for nudging an abutment on the moveable member to cause further rotation thereof.

There are preferably provided a reservoir for the fluid to be dispensed, valve means connecting the reservoir to the delivery chamber, and a delivery means for delivering the fluid from the delivery chamber.

An embodiment of the present invention will be described hereinafter with respect to the accompanying drawings where like reference signs are used to identify like parts and in which: Figures 1A, 1B and 1C are schematic representations of a front view, a side view and a top view, respectively, of an example of a device in accordance with the present invention; Figure 2 is a vertical cross section through the device of Figure 1, along lines X-X of Figure 1B, for illustrating a first operating state; Figure 3 is a similar cross section of the device of Figure 1 for illustrating a second operational state; Figure 4 is a partial cross-sectional view of the device of Figure 1, generally along line Y-Y in Figure 1B, for further illustrating the second operational state of the device; Figure 5 is a schematic plan view of a lower member of the device of Figure 1;; Figure 6 is a schematic plan view of certain parts of the device of Figure 1 for illustrating the first operational state of the device; Figure 7 is a schematic plan view of certain parts of the device of Figure 1 for illustrating an intermediate operational state of the device; Figure 8 is a schematic plan view of certain parts of the device of Figure 1 for illustrating the second operational state of the device; and Figures 9A, 9B and 9C are schematic representations of a front view, a side view and a top view, respectively, of a second example of a device in accordance with the present invention Figure 1A is an external side view of an example of a device in accordance with the invention. The device comprises a main body 10, an upper portion 11 and a lower portion 12. The lower portion is rotatably attached to the main body and forms a lever or knob.The upper portion closes the top of the main body and is shaped at the upper right of the device as seen in Figure 1 to form a housing 13 for a fluid delivery unit (shown in Figures 2 to 4). The fluid delivery housing 13 can be configured to suit an intended application. For example, if the device of Figure 1 is intended for nasal application of a liquid drug in the form, for example, of an atomised spray, the housing 13 can be configured for location at or in the entrance to a patient's nostril. Likewise, if the device of Figure 1 is intended for oral application of a liquid drug in an atomised spray, the housing 13 can be configured for location at or in the entrance to a patient's mouth. At the left-hand side of the device as seen in Figure 1, a firing lever 14 is provided.In one example of the invention, the device has an overall height of about lOOmm and width of about 30mm.

Figure 1B is a front view of the device of Figure 1A viewed in the direction of the arrow A in Figure 1. Figure 1C is a plan view of the device of Figure 1A viewed in the direction of the arrow B shown in Figure 1A. Here, the exit orifice 15 for the fluid to be delivered can be seen in the fluid delivery housing 13.

It will be appreciated from the following description that the drawings show merely a schematic representation of possible embodiments of a device in accordance with the invention. For example, the shape of the device illustrated is not essential to the present invention, and alternative embodiments of the device could look quite different from the exterior views shown in Figure 1.

Figure 2 is a vertical cross-section along the line X-X in Figure 1B. Figure 2 illustrates, in cross-section, the various portions of the device shown in Figure 1. It can be seen that the main body portion 10, the upper portion 11 and the lower portion 12 are hollow.

Also shown in Figure 2 is a dust cover 16 including sealing member 64 for the exit orifice 15.

The main body portion 10 and the lower portion 12 are rotatably connected by a rotary bearing 17. The bearing is illustrated schematically in the drawings and could be implemented in any suitable manner.

Fluid to be delivered by the device of Figure 1 is contained within a collapsible flexible bag 18 defining a fluid reservoir 19.

The collapsible bag 18 is arranged within a tubular sleeve 20 which locates the bag and ensures that it does not interfere with the movable parts of the device. The collapsible bag 18 is exposed to atmospheric pressure via a small aperture or vent 21 (e.g. of 2mm diameter) in the bottom of the sleeve 20 whereby, in use, the bag is caused to collapse as fluid is withdrawn therefrom.

The fluid reservoir 19 is connected to a fluid delivery unit 22 by means of a capillary tube 23. The fluid reservoir 19 is sealed by means of an 'O'-ring 24 which fits between the capillary tube 23, a retaining member 25 and a reservoir cap 26 and by a gasket 27 which fits between the reservoir cap 26 and the sleeve 20.

Fluid which, in use, is drawn up the capillary tube 23 into the fluid delivery unit 22 passes a one-way pressure-operated valve 28 located in the entrance to a delivery chamber 29 of the fluid delivery unit 22. The delivery chamber 29 is configured to contain a measured quantity of fluid to be dispensed defined by differential volume of the delivery chamber on movement of a piston 32, that is by the crosssectional area and stroke of the piston. In one embodiment of the invention the piston is about 1.5mm diameter and has a stroke of about 9.5mm.

The fluid delivery chamber 29 communicates with the exit orifice 15 via a nozzle unit 30. For an application where, for example, a drug is to be administered in the form of an atomised spray, an atomising nozzle assembly 31 can include a filter arrangement and/or one way valve arrangement. It will be appreciated that the representation of the nozzle unit 30 and assembly 31 in Figure 2 is purely schematic as the configuration of the nozzle is not important to the present invention. However, one suitable form of nozzle assembly which incorporates an atomising nozzle and filter arrangement is described in International patent application W094/07607. This nozzle assembly creates a sufficient back-pressure in use in a device according to the invention to avoid the need for a separate one-way valve in the nozzle unit 30.

The piston 32 communicates with the delivery chamber 29. The piston 32 is used to draw fluid from the reservoir 19 into the delivery chamber 29 and then to expel the fluid therefrom, as will be explained later. The fluid delivery unit 22 can be of unitary construction or, for reasons of ease of manufacture can be assembled as desired from separate units, for example from one containing the one-way valve 28, one in the form of a T-piece including the delivery chamber 29 and a bore for the piston, and one forming the nozzle unit 30. Appropriate sealing between the component parts will be necessary as will be apparent to one skilled in the art.

Within the piston bore, which is of small cross-section, the cooperating rod-shaped piston 32 is slidably located. A connecting member 34 connects the rod-shaped piston 32 to a hollow cylindrical and movable member 35. The movable member 35 is provided externally with a helical cam formation 36, the upper surface of which defines a helical cam surface 37. The helical cam surface extends from a lower extremity 38 to an upper extremity 39. A roller 40 is rotatably mounted on an internal wall 41 of the main body portion 10 and forms a cam follower for following the cam surface 37. In this first operating state of the device, the roller 40 is located on the cam surface 37 adjacent its lower extremity 38.

A rotatable drive connector 42 is linked to the movable member 35 by means of a pin 43 which extends through a hole in the drive connector 42 into opposed vertical slots 44 in the movable member 35.

This connection arrangement means that rotation of the drive connector 42 causes rotation of the movable member 35. However, due to the location of the pin 43 in the slots 44, the movable member 35 can slide axially with respect to the drive connector 42. The drive connector 42 is formed with a stem 45 which extends through the rotary bearing 17 between the main body portion 10 of the device and the rotatable knob 12 into the interior of the knob 12. A blade 46 is formed as an integral part of, or is attached by suitable means (e.g, by means of a nut 63 engaging with a screw thread on the stem 45) to the end of the stem 45. The knob 14 is provided with a wall 47 which, in use, cooperates with the blade 46 to cause rotation of the drive connector 42 and the movable member 35 as will be described later.

A strong coil spring 48 is provided in the interior of the movable member 35 and extends between the drive connector 42 and the underside of the connecting member 34. The coil spring 48 acts to urge the movable member 35 and the piston 32 in the upward direction represented by the arrow 49 in Figure 2.

A piston tube 50 is attached to internal walls 51 of the main body portion. Located within the piston tube 50 and acting between the bottom surface 52 of the fluid delivery unit 22 and the upper surface 53 of a relatively weak coil spring 54. This coil spring 54 forms a piston return spring which tends to urge the piston in the downwards direction against the direction of the arrow 49. In this first state of the device, the piston return spring is in a compressed condition.

Also shown in Figure 2 are detent pins 56 which, in use, cooperate with arresting notches 57 in the upper surface of the knob 14 as will be described with reference to Figures 3 and 5. The detent pins 56 are urged in the upward direction (that is away from contact with the arresting notches 57) by means of a plate spring 59. The detent pins 56 are prevented from falling out of the holes in which they are located by engagement with the lower side of the drive connector 42.

The lever 14 is pivotally mounted to the main body portion 10 at a pivot 60. The pivotal movement of the lever is controlled, at least in part by means of a cam follower 61 and firing blade 62 arrangement, as will be described below with reference to Figure 4.

The first operational state illustrated in Figure 2 will be further described later with reference to Figure 6.

Figure 3 represents the device in a second operational state.

The cap 16 has been omitted from Figure 3. In this second operational state the device is in its cocked state. To reach the cocked state of the device, the knob 12 is rotated through 3600 in a clockwise direction as viewed from the underside of the device. The first few degrees of motion of the knob (e.g., the first 200) form lost motion travel after which the wall 47 engages the blade 46. Further rotation of the knob 12 then causes the wall 47 to act on the blade 46 to rotate the drive connector 42 and, consequentially, the movable member 35. During rotation of the movable member 35, the roller 40 is caused to follow the upper cam surface 37 of the helical cam 36 from the lower extremity 38 towards the upper extremity 39. As the roller 40 follows the cam surface 36 this forces the moveable member 35 downwards in the direction of the arrow 65 in Figure 3.At the same time the pin 43 moves relatively upwards within the slot 44 (which in Figure 3 is hidden by the drive connector 62). The downward movement of the moveable member 35 causes the connecting member 34 and the piston 32 to be drawn downwards in the direction of the arrow 65 causing the coil spring 48 to compress. The piston is aided to follow the downward movement of the moveable member by the force exerted by the coiled spring 54.

The downward movement of the moveable member 35 also causes the movement of the detent pins 56 downwards against the force of the spring 59 as a result of the lower edge of the moveable member 35 acting on the top of the detent pins 56. The detent pins 56 are thus moved into engagement with the arresting notches 57 in the upper surface of the knob 14. This causes the knob 14 to stop in the same position which it occupied in the first operating state illustrated in Figure 2. However, as a result of the initial lost motion travel, the complete 3600 rotation of the knob does not cause a complete 360 rotation of the moveable member.Consequently, the cam follower roller 40 remains located adjacent the upper extremity 39 of the cam surface 37 (e.g., within 3-50 of the end of the cam surface 37), whereby the piston is maintained in its cocked or loaded, but unpressurized position.

During downward movement of the piston 32 (that is between the state illustrated in Figure 2 and that illustrated in Figure 3) low pressure is created in the delivery chamber 29 which causes the one-way valve 28 to open drawing a predetermined amount of fluid from the reservoir 19 under the influence of atmospheric pressure to the exterior of the bag 18. The length of the piston stroke is controlled by the slots 44 in the moveable member.

Figure 4 is a partial cross-sectional view of the device of Figure 1 taken generally along the line Y-Y in Figure 1B in the second state described with reference to Figure 3. In Figure 4, therefore, the exterior of the fluid delivery unit 22, the sleeve 20 for the reservoir 19, the moveable member 35 and the stem portion 45 of the drive connector 42 can be seen. The helical cam formation 36 can be seen as well as the portion of the pin 43 which protrudes from the opposed slots 44 in the moveable member 35.

Also seen is a rib 65 which is formed on the exterior of the moveable member 35. Not shown to the rear of the moveable member is a lobe which engages with a cam follower 61 connected to the firing lever 14. The cam follower engages the lobe after about 2850 of rotation of the moveable member 35 and causes the firing lever 14 to rotate anticlockwise into the cocked position of the firing lever shown in Figures 3 and 4. The movement of this cam follower 61 also causes a firing blade 62, equally connected to the firing lever 14, to move to the left from the position shown in Figure 2 to the position shown in Figures 3 and 4. The firing blade 62, which is arranged substantially tangentially to the body of the moveable member 35 now engages behind the rib 65. The mechanism is now cocked with the firing lever 14 presented ready for firing.

The position illustrated in Figure 4 corresponds to that of Figure 3, with the measured quantity of fluid having been drawn into the fluid delivery chamber 29. Firing the device, pressuring and ejecting the measured quantity of fluid from the delivery chamber 29, is achieved by squeezing the firing lever 14.

Squeezing the firing lever 14 causes the firing blade 62 to engage the rib 65. This in turn nudges the moveable member 35 into further rotation. After about a further 40 of rotation the roller 40 reaches the upper extremity 39 of the cam surface 37. As the roller passes the end of the cam surface the moveable member is free to move upwards as shown in the Figures under the action of the strong spring 48 shown in Figures 2 and 3. The counter force exerted by the piston return spring 54 is chosen to be such as not significantly to hinder the upward movement of the moveable member 35. As the moveable member moves upwards, the connecting member 34 urges the piston upwards to pressurise the fluid in the delivery chamber 29. This causes the oneway valve 28 to close and the fluid to be ejected via the atomizer nozzle assembly 31.In operation of one embodiment of the invention a pressure of about 380 bar is reached, although other embodiments could use other pressures depending on the application. The pressure is dictated by the piston stroke and the spring pressures. For example, in one embodiment of the invention, the main spring 48 provides lOON in the cocked state and 88 N installed, and the piston return spring provides 8 N cocked and 14 N in the installed state, leaving a net spring force of about 60 N in the installed state.

The atomizer nozzle assembly 31 can be provided with a valve means such that, during downward movement of the piston 32, air is prevented from being drawn from the exterior of the device into the delivery chamber 29, and is then opened by the increase of pressure within that chamber during upward movement of the piston.

Alternatively, it can be designed to provide sufficient back-pressure during downward movement of the piston such that the course of least resistance is for fluid to be drawn from the reservoir 19 via the oneway valve 28.

Upward movement of the moveable member 35 enables the detent pins 56 to be driven in the upward direction by the spring plate 59 to release the detent pins 56 from the arresting notches 57. As a result of the firing sequence, the remaining 200 or so of the rotation of the moveable member 35 is achieved and the knob 12 is released so that a further operation to charge the delivery chamber 29 can be carried out.

Figure 5 is a plan view of the knob 12 illustrating the formation of the arresting notches 57 in the upper surface thereof. It will be noted that the arresting notches have a sloping leading edge 57S whereby, on gradual depression of the moveable member 35, the detent pins 56 can be gradually moved downwards into the notches 57. The notches are provided with a vertical surface 57V at their trailing edges whereby the engagement of the detent pins against the rearward edge of the arresting notches prevents further rotation of the knob 12.

The operation of the device will be further described with reference to Figures 6 to 8 which further illustrate the first operating position of Figure 2, an intermediate operating position and the second operating position of Figures 3/4, respectively.

Figure 6 is a schematic representation of the relationship of the wall 47 within the knob 12 and the blade 46 attached to the stem 45 of the drive member 42. In this initial position, the knob 12 is aligned with the main body portion 10 so that the main body portion 10 overlies the knob 12. Hence the dual reference to the outline shown in Figure 6. In this position, there is a gap between the wall 47 formed within the knob 14 and the blade 46 attached to the stem 45. Thus, on initial movement of the knob 12, which is rotated in an anti-clockwise direction as illustrated in Figure 6, no rotation of the stem 45, and consequently of the drive member 42 and the moveable member 35 occurs.

Only after the knob has turned through a predetermined angle does the wall 47 contact the blade 46. Figure 7 represents the position of the main body portion 10 of the device by a dashed line and the position of the knob 12 by a solid line. It will be seen that the knob 12 rotates about an eccentric axis. This increases the mechanical advantage available, reducing the force needed to turn the knob to charge the spring 48. During further rotation of the knob 12, the wall 47 then causes rotation of the stem 45 by pushing on the blade 46.

Figure 7 illustrates the point at which contact is made between the wall 47 and the blade 46. It can be seen that this occurs after (preferably of the order of 5-300, more preferably of the order of 200) of rotation of the knob 12.

Figure 8 represents the position when the knob 12 has been rotated through 3600 so that it once more lines up with the upper portion 10 of the device. However, due to the lost motion travel between the positions in Figure 6 and Figure 7, when the knob has been rotated through 3600, the blade 46 and the stem 45 have only been rotated through (360-0)0. The arrangement of the cam follower roller 40 and the cam surface 37 of the helical cam formation 36 is such that at the angular rotation of 360- , the cam follower roller 40 is located adjacent the upper extremity 39 of the cam surface 37. The knob 12 is prevented from further rotation due to the engagement of the detent pins 56 in the arresting notches 57 illustrated in Figure 6.

Accordingly, after 3600 of rotation of the knob, the moveable member is retained in the charged or descended position. In this position fluid has been drawn into the delivery chamber 29 but it has not been pressurised.

Only on subsequent operation of the firing lever 14, is further rotation of the moveable member 35 performed through the action of the pusher blade 62 on the rib 65. The further rotation of the moveable member caused by the activation of the firing lever 14 causes rotation of the stem 45 through the remaining angle of from the position shown in Figure 8 to the original position shown in Figure 6. As explained above, on further rotation of the moveable member, the cam follower roller 40 falls off the upper extremity 39 of the cam surface 37 so that the moveable member 35 is able to move upwards under the action of the compressed spring 48. This in turn releases the detent pins 56 from the arresting notches 57 under the action of the spring 59.

From the above description it can be seen that the charging of the delivery chamber with fluid and the subsequent pressurising thereof to cause the fluid to be dispensed is possible with only simple operations to be performed by the user. Charging of the device is performed using the knob 12 and release of the fluid is performed using the activation of the firing lever 14. This can be achieved without the use of a separate manually operated valve for releasing the pressurised fluid. Indeed, pressurisation of the fluid only occurs at the moment of release, relieving the need for materials to be chosen that can withstand pressure over a significant period of time. A device in accordance with the invention enables a measured quantity of a fluid, for example a liquid drug, to be dispensed.The fluid can be dispensed as a fine mist through the use of an atomizer head 31 as illustrated in Figures 2 and 3.

An embodiment of a device for dispensing fluid in accordance with the invention has been described, which embodiment comprises: - a delivery chamber for receiving fluid to be dispensed; - a reciprocating piston communicating with the delivery chamber for, during a first stroke, causing reduction in pressure in the delivery chamber to draw fluid into the delivery chamber and, during a second stroke, pressurising the fluid for delivery thereof from the delivery chamber; and - piston actuating means including resilient means for urging the piston in the direction of the second stroke, wherein the piston actuating means comprises: - a cam follower acting on a helical profile cam; - charging means for causing mutual rotation between the cam and the cam follower whereby the cam follower follows a rising cam surface of the cam to effect the first stroke of the piston; - means for arresting the charging means before the cam follower passes the end of the rising cam surface; and - release means causing further mutual rotation of the cam follower and the cam to cause the cam follower to pass the end of the rising cam surface, whereby the resilient means effects the second stroke of the piston.

While a particular example of the present invention has been described, it will be appreciated that many modifications and/or additions are possible within the scope of the invention.

For example, although in the present embodiment, the knob is rotated through 3600 to charge the spring 48, it could be rotated by another angular range, for example 1800.

For locating the knob 12 in the initial position, even after withdrawal of the detent pins 56, cooperating means could be provided between the knob and the upper part of the housing. For example, a resilient protrusion in one part could be arranged to engage with a cooperating recess in the other.

Also, although in the present embodiment a single cam surface with a single cam roller is shown, in an alternative embodiment a plurality of cam surfaces with a respective roller or rollers could be provided.

In alternative embodiments the piston return spring could be omitted where the materials and/or pressures used result in reliable operation without the use of the piston return spring.

As mentioned above, various overall configurations of the device are possible. Thus Figures 9A, 9B and 9C, which correspond generally to Figures 1A, 1B and 1C, represent an embodiment where the fluid delivery housing 13 and the exit orifice 15 have been rotated through 900 with respect to Figures 1A, 1B and 1C.

Claims (17)

1. A device for dispensing fluid, the device comprising: - a piston communicating with a delivery chamber for fluid to be dispensed; - a piston actuating mechanism including a cam and a cam follower; - a charging actuator for causing the cam follower to follow a surface of the cam up to an end thereof for a charging stroke of the piston to precharge the delivery chamber with fluid; and - a release actuator causing the cam follower to pass beyond the end of the cam surface to initiate a return stroke of the piston for pressurising the fluid in the delivery chamber.

2. A device as claimed in claim 1 wherein the charging actuator is separate from the release actuator.

3. A device according to claim 1 or claim 2, wherein the piston causes a reduction in pressure in the delivery chamber during the charging stroke to draw fluid into the delivery chamber from a reservoir and pressurises the fluid for delivery thereof from the delivery chamber during the return stroke.

4. A device according to any one of the preceding claims, wherein the piston actuating mechanism is arranged to cause mutual rotation between the cam and the cam follower in response to actuation of the charging actuator such the cam follower follows a rising cam surface of the cam to effect the charging stroke of the piston.

5. A device according to claim 4, wherein the piston actuating mechanism is arranged to arrest the charging actuator before the cam follower passes the end of the rising cam surface.

6. A device according to claim 5, wherein the piston actuating mechanism is arranged to respond to actuation of the release actuator to cause further mutual rotation of the cam follower and the cam to cause the cam follower to pass beyond the end of the cam surface to initiate a return stroke of the piston for pressurising the fluid in the delivery chamber.

7. A device according to any one of the preceding claims, wherein the piston actuating mechanism includes resilient means for urging the piston in the direction of the return stroke, whereby the resilient means effects the second stroke of the piston.

8. A device according to claim any one of the preceding claims wherein the charging actuator comprises a manually operable knob providing initial lost motion travel before engaging a rotary drive mechanism for causing mutual rotation of the cam and the cam follower.

9. A device according to claim 8 wherein the charging means comprises a rotary knob including a protrusion which, after initial lost motion travel of the knob from a rest position, engages a rotatable drive member for causing mutual rotation of the cam and cam follower.

10. A device according to claim 9 comprising a moveable member provided with either said cam surface or said cam follower and a fixed member provided with the other of said cam surface or said cam follower, the moveable member being connected to the rotatable drive member for rotation therewith.

11. A device according to claim 10, wherein the arresting means arrests the knob after 360 degrees of rotation thereof, 360 degrees of rotation of the rotary knob causing 360- degrees of rotation of the moveable member. where PI degrees is the angular free travel of the rotatable knob before the protrusion engages the drive member.

12. A device according to claim 11 or claim 12 comprising a pin for connecting the drive member and the moveable member to prevent mutual rotation therebetween, the pin being located in a slot permitting mutual axial movement between the drive member and the moveable member.

13. A device according to claim 6 comprising one or more detent pins for engaging arresting notches in the rotatable knob, the detent pins being urged into engagement with the arresting notches by axial movement of the moveable member.

14. A device according to any one of claims 10 to 13 wherein the release actuator comprises a pusher rod for acting on an abutment on the moveable member to cause further rotation thereof.

15. A device according to any one of the preceding claims wherein the charging actuator comprises a knob rotatably mounted about an eccentric axis.

16. A device as claimed in any one of the preceding claims comprising a reservoir for the fluid to be dispensed, valve means connecting the reservoir to the delivery chamber.

17. A device for dispensing fluid substantially as hereinbefore described with reference to the accompanying drawings.