Dispensing – With discharge assistant – Fluid pressure
Patent
1999-02-22
2000-09-05
Derakshani, Philippe
Dispensing
With discharge assistant
Fluid pressure
B65D 8300
Patent
active
06112950&
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an improved dispenser valve, and more particularly to a plunger of a metering valve.
Dispenser valves are well known in the state of the art. Their main application lies with aerosol receptacles for dispensing liquid substances that are charged with a propellant (gas dissolved under pressure). For a metering valve, the valve generally comprises a valve body containing a metering chamber defined axially by two annular gaskets, a valve gasket and a chamber gasket, and a valve plunger that is movable between a rest position and an actuation position. The valve plunger is urged by a spring towards its rest position, in which a shoulder on said plunger bears against the bottom surface of said valve gasket. To actuate a metering valve, the valve plunger is pressed so that it slides inside the valve body through annular gaskets to its actuation position, in which a measured quantity of the substance is expelled. The spring then returns the valve plunger to its rest position.
A problem that arises with the plungers of valves, in particular of metering valves, specifically concerns sealing at the valve gasket. Firstly it is necessary for the valve plunger to be able to slide between its actuation position and its rest position under drive from the spring, while preventing any leaks from taking place. Secondly, when the valve plunger is in its rest position, sealing must be complete in spite of the pressure that obtains inside the metering chamber and the receptacle.
To solve those problems, known valves include a cylindrical plunger having as an extension from said shoulder at least on that portion of the valve plunger which slides through the valve gasket, a constant outside diameter approximately equal to (and generally very slightly greater than) the diameter of the central opening in the valve gasket. To guarantee sealing in the rest position, a frustoconical portion is generally provided adjacent to said shoulder extending axially over a portion of the thickness of said valve gasket. In this way, the valve plunger slides with friction through the valve gasket, the force exerted by the spring being greater than said friction, and in its rest position, the frustoconical portion adjacent to said shoulder contributes to providing sealing at the valve gasket.
A drawback of that implementation lies in the fact that the friction which appears during sliding of the valve plunger can be relatively large, which can cause said valve plunger to become jammed.
That phenomenon is further amplified when, particularly for ecological reasons, it is desired to replace propellant gases that are harmful for the environment, such as CFCs, with propellant gases that are not harmful or that are less harmful for the environment, for example HFA gases. Unfortunately, the use of such gases presenting little or no threat to the environment requires the pressure inside the body of the valve to increased considerably, and this increase may be as much as 50%. It is therefore necessary to achieve even greater sealing at the valve gasket, which means a large amount of friction between the plunger and said gasket.
One possible solution for overcoming that drawback is to provide a spring of stiffness that is sufficiently great. However, that requires a large force to actuate the metering valve, which is undesirable.
Another solution consists in coating valve plungers in a layer of silicone in order to improve their friction qualities. That solution is fairly satisfactory with propellant gases such as CFCs, however it is insufficient when HFA gases are used. Such HFA gases remove the silicone progressively, such that after some number of uses, the problem of the valve plunger jamming reappears.
An object of the invention is to provide a valve, in particular a metering valve, having a valve plunger made in such a manner as to avoid untimely jamming thereof by friction against the valve gasket when said valve plunger moves from its actuation position towards its rest position under drive from the spring, while nev
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Di Giovanni Patrick
Williams Geralt
Derakshani Philippe
Glaxo Group Limited
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