GB2367809A - Metering valve with collapsible chamber - Google Patents

Abstract

A metering valve 1 for use in a pressurised container 4 has a valve body 2 and a flexible sleeve 18 overlaying the valve body 2 and defining a collapsible chamber 19. The valve body 2 has an internal chamber 5 and a channel 17 providing a flow path between the internal chamber 5 and the collapsible chamber 19. A valve stem 13 is slidable axially through the internal chamber 5. An outlet valve means consists of an outer seal 7 which allows fluid to flow from the internal chamber 5 in the open condition of the valve. An inner valve means comprises an inner seal 8 which admits fluid from the container to the internal chamber 5 in a closed condition of the valve. The inner and outer seals 7, 8 extend between the valve stem 13 and the valve body 2 and at least one of them is made from a thermoplastic elastomer. The sleeve member 18 further comprises an outer flange 20 which provides a gasket seal between the sleeve and the container body. When the valve is activated pressure from the propellant inside the container acts on the sleeve 18 and causes the chamber 19 to collapse, dispensing a metered amount of fluid.

Description

DISPENSING APPARATUS FOR A PRESSURISED DISPENSING CONTAINER This invention relates to dispensing apparatus for a pressurised dispensing container of the type in which metered quantities of fluid are dispensed at each actuation of a valve. In particular the invention relates to improvements in the seals and flexible components of such valves.

A particular embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings in which:Figure 1 is a schematic sectional elevation of a valve according to the present invention;Figure 2 is a sectional elevation of a pressurised dispensing container incorporating the valve of Figure 1, in a first configuration; andFigure 3 is a sectional elevation of the pressurised dispensing container of Figure 2 in a second configuration.

In Figures 1 and 2 a pressurised dispensing container 1 comprises a valve 2 of generally cylindrical shape which is co-axially mounted in a ferrule 3 forming an end closure to a cylindrical container body 4. The valve 2 defines a cylindrical internal chamber 5 through which a valve stem 6 extends and is journalied within outer and inner annular seals 7 and 8 respectively at axially opposed ends of the chamber so as to be axially slidable through the chamber 5.

A compression spring 9 co-axially mounted on the stem 6 acts within the internal chamber 5 upon a radially expending flange 10 of the stem such that the stem 6 is biassed outwardly with respect to the

container 1.

The valve 2 is shown in its closed condition in which a radially extending bore 11 of the valve stem 6 is positioned external to the outer seal 7. The bore 11 communicates with an axially extending outlet channel 12 within the stem 6 such that upon depression of the stem to change the valve to its open condition the bore 11 is open to the internal chamber 5 and a flow path is established from the chamber 5, through the bore 11 and into the outlet channel 12. The valve stem 6, the bore 11 and the outer seal 10 thereby constitute an outlet valve means of the valve 2.

The stem 6 has an innermost end 13 with respect to the container 1 having an axially extending groove 14 which defines a by-pass channel permitting fluid to pass the inner seal 8 when the valve 2 is in the closed condition as shown in Figure 1. The groove 14 has a limited axial extent such that when the stem 6 is depressed into the open condition of the valve 2 the groove 14 lies external to the inner seal 8 so that no fluid may enter the internal chamber 5. The stem 6, the groove 14 and the inner seal 8 thereby constitute an inlet valve means of the valve 2.

A cylindrical external surface 15 of the valve 2 includes an annular recess 16 and radial ports 17 communicate between the recess and the internal chamber 5. A tubular elastomeric member 18 overlays the external surface 15 so as to cover the recess 16 and define an annular chamber 19. The member 18 includes a radially projecting annular flange 20 at one end which is held between a radial flange 21 of the valve 2 and the rim 22 of the container body 4.

The member IS is thereby clamped at one end only and has a free end 23.

The elastomeric member 18 is a loose fit within the container body 4.

A flexible sac 25 is provided within the

container body 4, as shown in Figure 2, and divides the container body into an inner compartment 26 containing a product fluid to be dispensed and an outer compartment 27 containing a propellant fluid such as HFA 227 or 134a. The valve 2 is located within the inner compartment 26 such that an inlet 28 of the valve is exposed to product fluid and the outer surface 24 of the flexible member 18 is similarly immersed in the product fluid. The flexible sac 25 is sandwiched between an upper rim of the container body 4 and the radial flange 21 of the valve 2. There is also provided a gasket 40 between the flexible sac 25 and container body 4 to form a fluid tight seal.

In use, the container 1 as shown in Figure 1 is supplied with the valve 2 in a closed condition in which the inner compartment 26, the inlet 28, the groove 14, the internal chamber 5, the radial port 17 and the annular recess 16 are filled with product fluid. (This assumes that priming strokes of the valve 2 have been completed so as to displace any trapped air).

Upon depression of the valve stem 6 the bore 11 moves beyond the outer seal 7 to communicate with the internal chamber 5 and simultaneously the groove 14 is moved clear of the inner seal 8 so as to seal the inlet 28. The internal chamber 5 is then vented to atmospheric pressure and a pressure differential is established across the elastomeric member 18 which deforms to infill the recess 16. A quantity of product filled equal to the volume of the recess 16 is displaced from the valve to be dispensed through the outlet channel 12. A metered dose of the product fluid corresponding to the initial volume of the now collapsed chamber 19 is thereby dispensed.

Upon release of depression pressure upon the valve stem 6 the valve 2 is restored to its closed condition by action of the spring 9 which moves the

bore 11 out of communication with the internal chamber 5. Simultaneously, a flowpath is re-established through the inlet 28 and the groove 14 by which means product fluid enters the internal chamber 5 to refill and reflate the chamber 19 as the elastomeric member 18 relaxes to its tubular shape.

With each action of the valve 2 resulting from the dispensing of a metered dose, the flexible sac 25 is inwardly deformed within the container body 4, as shown in Figure 3, so as to equalise pressure on opposing faces of the flexible sac 25.

An advantage offered by such apparatus is that accurately metered doses of product fluid are dispensed throughout the life of the dispenser since the quantity dispensed is independent of the available propellant pressure. Moreover, the dispensing container can be operated in any orientation so that for example it may be used with the stem 6 in a downwardly directed orientation or at an inclined attitude suitable for nasal or oral delivery of medicinal products. The stem 6 may be connected to a conventional actuator incorporating an aerosol nozzle or may for example be connected to a hypodermic needle in order to deliver an infusion of the product fluid.

The invention has particular application to dispensing metered doses of medical products which are solvent sensitive such as water based peptide formulations as the solvent and propellant never contact the valve 2.

According to the present invention one or more of the outer seal 7, inner seal 8, elastomeric member 18, annular flange 20 and gasket 40 are formed from a thermoplastic elastomer, examples of which includeSantoprene, Pebax, Vitaprene and Hydre'-.

The use of thermoplastic elastomers for these components is advantageous as it has seen found that the characteristics of the material provide for good sealing properties between the flexible member 18 and the valve 2. In addition, thermoplastic elastomers are relatively inert and less susceptible to extraction than previous seal and gasket materials.

This makes them advantageous for use with product formulations and propellants which may be susceptible to extraction known seal and gasket materials.

Further, thermoplastic elastomers may be more easily recycled compared to known seal and gasket materials.

Claims (8)

1. Claims : 1. A metering valve for use in a pressurised dispensing container comprising a valve body, a sleeve member coaxially overlaying the valve body and defining a collapsible chamber therebetween, the valve body defining an internal chamber, channel means providing a fluid flowpath between the internal chamber and the collapsible chamber, an axially slidable valve actuating stem extending coaxially through the internal chamber, outlet valve means to dispense fluid from the internal chamber in an open condition of the valve and inlet valve means to admit fluid into he internal chamber in a closed condition of the valve, the outlet valve means comprising an outer seal and inlet valve means comprising an inner seal, both seals extending between the stem and the valve body, wherein at least one of the outer seal, inner seal and sleeve member is made from a thermoplastic elastomer.
2. 2. A metering valve as claimed in claim 1 wherein the sleeve member further comprises a radially outwardly extending flange at its outer extremity, which flange provides sealing gasket means in use between the valve body and a pressurised dispensing container, wherein the flange is made from a thermoplastic elastomer.
3. 3. A metering valve as claimed in claim 1 or claim 2 wherein each of the outer seal, inner seal and sleeve' member are made from a thermoplastic elastomer.
4. 4. A metering valve as claimed in any preceding claim wherein the thermoplastic elastomer is one ofSantoprene, ? ebax, Vitaprene, Hytrel or the like.
5. 5. A pressurised dispensing container incorporating a metering valve as claimed in any preceding claim.
6. 6. A pressurised dispensing container as claimed in claim 5 further comprising a thermoplastic elastomer gasket between a container body and the valve body.
7. 7. A pressurised dispensing container as claimed in claim 5 or claim 6 adapted for nasal use.
8. 8. A metering valve substantially as hereinbefore described with reference to and as shown in the accompanying drawings.