GB2245936A

GB2245936A - Dispencing device

Info

Publication number: GB2245936A
Application number: GB9009714A
Authority: GB
Inventors: Geoffrey Brace; Richard John Warby
Original assignee: Bespak PLC
Current assignee: Consort Medical PLC
Priority date: 1990-05-01
Filing date: 1990-05-01
Publication date: 1992-01-15
Also published as: AU7752091A; GB9009714D0; WO1991016992A1

Abstract

A dispensing device is described in the form of a pump (10) for dispensing fluids in spray form. The device has a first piston (11) sliding in a first cylinder (15) and a second piston (12) of smaller cross-sectional area sliding in a second cylinder (16), the cylinders being in fluid communication. An inlet (31, 47) to the cylinders is provided and fluid is dispensed through an outlet (24, 25) extending through the first piston and to an outlet nozzle. A valve (28) normally closes the outlet. Springs (22, 29, 45) are provided urging the components of the device into their rest position. A metering chamber of fixed volume is formed by the second piston and cylinder, the second piston moving between limit positions defined by an abutment at the upper end of cylinder (16) and a discontinuity in the wall of the cylinder.

Description

DISPENSING DEVICE The invention relates to dispensing devices and more particularly to pump dispensing devices for dispensing fluids. The invention is particularly, though not exclusively, suitable for dispensing liquid medicaments.

In dispensing liquid medicaments, it is a requirement that the dispensing device is capable of dispensing an accurately metered dose of the medicament at each use of the device.

The invention provides a pump dispensing device comprising a first piston sliding in a first cylinder, a second piston of smaller cross-section than the first piston sliding in the second cylinder, the first and second cylinders being in fluid communication, a fluid inlet to the cylinders and a fluid outlet through the first piston, valve means normally closing the fluid outlet and being opened in operation of the device, in which the second piston and cylinder define a metering chamber for the device, the second piston moving between first and second limit positions which define the volume of the metering chamber.

Preferably the first limit position of the second piston is defined by a physical abutment, the piston being spring urged into contact with the abutment.

The second limit position may be defined by a discontinuity in the bore of the second cylinder which allows fluid flow past the second piston. The discontinuity preferably comprises a step in the bore, the step extending between the second cylinder and an extension of larger diameter.

A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal section through a pump dispensing device according to the invention, and showing the device in a first rest position; Figure 2 is a view similar to Figure 1 showing the device in a second position; Figure 3 is a yiew similar to Figure 1 and showing the device in a third position, and Figure 4 is another view similar to Figure 1 and showing the device in a fourth position.

Referring first to Figure 1, there is shown a pump dispensing device 10. The device is designed to provide accurately metered doses of a product contained in a product container 20. The product is provided to fill the dispensing device by known means. The device is particularly suitable for dispensing liquid medicaments where it is important that accurately metered doses of the medicament are dispensed consistently.

The dispensing device comprises a first piston 11 and a second piston 12. Both pistons are slidable in a piston housing 14 defining a first cylinder 15 in which the first piston 11 is a sliding fit and a second cylinder 16 of smaller bore than the first cylinder in which the second piston 12 is a sliding fit. The first piston 11 is a hollow generally cylindrical member having a tubular extension 18 which extends into a nozzle 21 of the dispensing device. A first spring 22 is located between an internal shoulder of the nozzle 21 and a shoulder formed at the junction between the piston 11 and its tubular extension 18. The nozzle 21 includes an insert 23 which defines with the nozzle an outlet passage 24 for product dispensed by the device.The passage 24 terminates in a swirl chamber 25 formed between the nozzle and the insert so that product forced under pressure through the outlet passage 24 is dispensed in the form of a spray. The upper end of the tubular extension 18 (as viewed in Figure 1) is spaced from the main portion of insert 23 and a cylindrical extension 27 of insert 23 extends axially through the tubular extension 18 of piston 11.

A valve member 28 normally closes off a flow path throught the interior of piston 11 and is spring urged into its closed position by a second spring 29 located between the valve member and a resilient washer 30 at the lower part of cylinder 15. The washer 30 overlies and normally closes inlet passages 31 formed in the piston housing 14 and extending through the wall of the housing at the junction between the first and second cylinders 15, 16. A tubular projection 33 extends upwardly through resilient washer 30 and provides a location pin for the spring 29.

The piston housing 14 includes an annular flange portion 35 at its upper end which serves to locate the piston housing in a cup 36. A first seal 38 is located between the upper surface of annular flange 35 and an upper end of assembly cup 36. The first piston 11 extends slidingly through seal 38. A second seal 40 is located between the lower surface of flange 35 and an upper end of a body member 41 to which the container 20 is fixed. The cup 36 which is normally made of metallic material is crimped around body member 41 and flange 35 to maintain the components in assembled relation.

The piston housing 14 defines below the second cylinder 16 (as viewed in Figure 1) a tubular extension 43 of larger diameter than the second cylinder. The second piston 12 includes an annular flange 44 which is a loose fit within the tubular extension 43. A third spring 45 is located between annular flange 44 and an end plug 46 which fits in the tubular extension 43. Orifices 47 for flow of product are provided in the end plug 46 and the side walls of the tubular extension 43.

A tubular casing 50 for the dispensing device is fixed to an outwardly extending flange 51 of the nozzle 21.

The pump dispensing device 10 is shown in Figure 1 at its rest position. In use, the device is actuated by relative movements of the casing 50 and the product container 20 together with the components fixed thereto. This relative moment may be achieved by upward movement of the product container 20 as viewed in Figure 1 or by depression of the nozzle assembly 21 downwardly as viewed in Figure 1.

As the nozzle 21 moves downwardly relative to the container 20 from the position shown in Figure 1, the first piston 11 slides downwardly in its cylinder 15. At this stage, the space defined in the first cylinder between the first and second pistons is filled with product and the downward movement of the first piston 11 causes the second piston 12 also to move downwardly in its cylinder 16. It will be appreciated that the second piston moves downwardly more quickly than the first piston because of its relative smaller cross-sectional area. The second piston defines with its cylinder a metering chamber 53 for the dispensing device 10. As its rest position, the upper end of the stroke of the piston 12 is accurately controlled by contact between the piston 12 and the upper wall of cylinder 16. As the second piston 12 moves downwardly, it reaches the position shown in Figure 2.It will be noted that at this position the sealing lip 54 of the piston 12 has moved out of sealing contact with cylinder 16 and into the tubular extension 43 of the piston housing.

At this point, product may flow around the lip 54 and past the flange 44 out through ports 47. Thus, as the first piston 11 continues to move downwardly, the second piston 12 will remain in the position shown in Figure 2 and the metering chamber 53 will remain filled with product. It will be appreciated that the movement of the second piston 12 is very accurately controlled. As described above, the upper limit of its movement is determined by a fixed abutment in the form of the upper wall of cylinder 16 and the lower limit of its movement is determined, as described above, by a discontinuity in the wall of cylinder 16 formed by the step in the piston housing wall between the cylinder 16 and the tubular extension 43. It will also be appreciated that as the second piston moves downwardly, the third spring 45 is compressed.

When the dispensing device has reached the position shown in Figure 2, the pump is primed.

Continued downward movement of the nozzle 21 relative to the container 20 will first of all bringing the first piston 11 into abutment with a shoulder at the lower end of cylinder 15 thus limiting the movement of the upper piston 11. Still further continued movement of the nozzle assembly will compress the first spring 22 as the nozzle 21 now starts to move downwardly relative to the piston 11 and its tubular extension 18. As the spring 22 is compressed, the cylindrical extension 27 of the nozzle insert 23 will move downwardly as viewed in Figure 3 bringing that extension into contact with valve member 28 and moving the valve member 28 downwardly against the action of second spring 29. As the valve member 28 is moved downwardly, the outlet passage around valve member 28, around cylindrical extension 27 and through passage 24 is opened.As shown in Figure 3, the third spring 45 then causes the second cylinder 12 to move upwardly forcing product through the outlet passage described above and through the swirl chamber 25 and thence out in a spray from the device. This discharge movement continues until the second cylinder 12 again reaches the upper limit of its movement controlled by contact between its sealing lip 54 and the upper wall of cylinder 16.

The dose of product stored in the metering chamber 53 will then have been dispensed.

Once dispensing of the product dose has been completed, the user allows the dispensing device to return to its rest position by releasing the nozzle 21 and container 20 so that the nozzle 21 can move upwardly relative to the container 20 as viewed in the drawings. During this movement, the main product chamber defined by the first piston 11 and first cylinder 15 is recharged as shown in Figure 4.

Upward movement of the first piston 11 causes the resilient washer 30 to flex upwardly at its periphery thereby opening inlet 31 and allowing product to flow into the main chamber. The first, second and third springs cause the remaining components to return to the position shown in Figure 1 and the dispensing device is then again ready for use.

It will be appreciated that the components of the pump dispensing device 10 are the same in all the drawings and reference numerals for various parts are not repeated in Figures 2, 3 and 4, except where such reference numerals are useful because they refer to parts particularly described with reference to each of those figures.

The materials from which the various components of the dispensing device are made have not been described in general. It will be appreciated that most of the components of the dispensing device may be plastics mouldings. As described above, the retaining cup 36 is generally of metal and it will be appreciated that the sealing washers 38, 40 and resilient washer 30 will be a suitable resilient sealing material. As described above, it is an important feature of the dispensing device described that the metering chamber which controls the volume of products dispensing by the device is very accurately defined. As described, this is achieved by movement of the second piston 12 being accurately controlled beween two limit positions defined by the second cylinder 16.It will be appreciated that the two features which control the movement of the second piston (i.e. the upper wall of cylinder 16 and the step in diameter at its lower end) will be created in the piston housing 14 by a single mould pin in the manufacturing process. This allows very accurate contol of the size of the metering chamber and therefore accurate control of the dose of product dispensed by the device.

The invention is not limited to the preferred embodiment described above. It will be appreciate that various modifications may be made. For example, the limit of lower movement of the second piston 12 may be controlled by means other than the step in the bore of the piston housing 14. Rather than the increased bore of the tubular extension 43, a side hole in the cylinder wall might be provided to limit the movement of the piston or a physical stop for the piston may also be provided.

Claims

CLAIMS:

1. A pump dispensing device comprising a first piston sliding in a first cylinder, a second piston of smaller cross-section than the first piston sliding in a second cylinder, the first and second cylinders being in fluid communication, a fluid inlet to the cylinder and a fluid outlet through the first piston, valve means normally closing the fluid outlet and being opened in operation of the device, in which the second piston and cylinder define a metering chamber for the device, the second piston moving between first and second limit positions which define the volume of the metering chamber.

2. A device as claimed in claim 1 in which the first limit position of the second piston is defined by a physical abutment, the piston being spring urged into contact with the abutment.

3. A device as claimed in claim 1 or claim 2 in which the second limit position is defined by a discontinuity in the bore of the second cylinder which allows fluid flow past the second piston.

4. A device as claimed in claim 3 in which the distontinuity comprises a step in the bore, the step extending between the second cylinder and an extnsion of larger diameter.