Container with pressure control device for dispensing fluid

Details Container with pressure control device for dispensing fluid Container with pressure control device for dispensing fluid

2001-09-06

2002-07-02

Doerrler, William C. (Department: 3754)

Dispensing

With discharge assistant

Fluid pressure

Reexamination Certificate

active

06412668

ABSTRACT:

The invention relates to a container of the type described in the preamble of the main claim. Such container is known from EP-0 349 053.
This known container comprises a pressure capsule having a first, second and third chamber, the first chamber being filled with a pressurised gas to be discharged into the inner space of said container. On top of said first chamber the second and third chamber are positioned, said third chamber being positioned between the first and second chamber. An outlet opening is provided between said first and third chamber, provided with a closing member biased in a closed position by a spring. The second chamber is separated from the third chamber by a membrane. During operation an operating pressure prevails in the second chamber, moving said membrane depending on the pressure in the third chamber, which during use can freely communicate with the inner space of the container. When the pressure drops in the third chamber, the membrane is moved against the closing member, thereby forcing the closing member to an opening position, such that pressurised gas can be discharged from the first chamber through the third chamber into the inner space. Consequently, the pressure rises in the third chamber, thereby forcing the membrane into the direction of the second chamber, once again closing the closing member.
In this known container, before use, a meltable means is provided for keeping the closing member from being operated by said membrane. In a first embodiment this is achieved by providing said meltable member in the opening between the third chamber and the environment, after pressurising the third chamber to a pressure above the operating pressure prevailing in the second chamber during use. In a second embodiment a ring-shaped meltable element is provided around part of the closing member, thereby preventing movement of said closing member before melting said meltable member.
This known container has the disadvantage that said container has to be heated prior to use, for melting said meltabel member, thereby contaminating the fluid to be dispensed and heating said fluid, which may be undesirable. Furthermore, such container is difficult to assemble and cannot be stored easily over relatively long periods.
A further container having pressurising means is known from FR-A-2 690 142.
This known container comprises an inner space in which a fluid to be dispensed is included, which inner space accommodates a pressure vessel with pressure control means. In the pressure vessel, a first chamber is formed into which a gas is introduced under relatively high pressure, while an outlet opening is provided which is closed by a closing member. This closing member is slightly rod-shaped and is surrounded in the outlet opening by an O-ring which tightly seals thereagainst. Provided in the rod-shaped element is a circumferential groove. In the pressure vessel, a second chamber is formed opposite the first chamber, which second chamber, on she side proximal to the first chamber, is closed by a membrane to which the rod-shaped element is attached by one end thereof. In the second chamber, a control pressure is created by means of a gas. Included between the first and the second chamber is a third chamber through which the rod-shaped element extends and which is provided with an opening forming a fluid connection between the third chamber and the inner space of the container.
When in this known apparatus a desired pressure prevails in the third chamber, for instance a pressure equal to the control pressure, the groove is located in the third chamber and the outlet opening is closed by the rod-shaped element. When fluid is dispensed from the inner space, the pressure therein will fall, resulting in the same pressure fall in the third chamber. Consequently, the membrane-shaped wall part of the second chamber will deform in the direction of the first chamber, while moving the rod-shaped element axially, further into the first chamber. When the groove has been moved to the level of the O-ring, gas under pressure will be able to escape via the groove and along the O-ring from the first chamber to the third chamber, and from there to the inner space of the container. This causes the pressure in the third chamber to rise such that the membrane-shaped wall part is deformed back, against the control pressure, while it moves the rod-shaped element along from the first chamber. When the rod-shaped element is again sealingly clasped by the O-ring, no gas will be able to escape from the first chamber anymore, in which condition the pressure in the third chamber and the inner space is again approximately equal to the desired pressure, in this case the control pressure.
This known container has the drawback that already before the gas is introduced under pressure into the first chamber, the closing member and the control means therefor, in this case the second chamber, the membrane-shaped wall part and the rod-shaped element, must have been fitted. The first chamber is filled by pressing gas under particularly high pressure into the third chamber via the opening, such that the membrane-shaped element is deformed in the direction away from the first chamber. This involves the rod-shaped element being pulled from the first chamber so far that a slightly tapering end thereof is located in the outlet opening. The gas can then pass this end under high pressure and be introduced into the first chamber. Upon removal of the high gas pressure, the rod-shaped element will be moved into the outlet opening again under the influence of the control pressure and close said outlet opening. This has the drawback that the introduction of the gas under pressure is relatively complicated and should be effected through relatively small openings. Moreover, there is the danger that in the case of unduly high filling pressure, the rod-shaped element is pulled from the first chamber entirely and will not return into the outlet opening when the gas pressure is removed, for instance in that the rod-shaped element swivels slightly while the closing O-ring can be pressed from the opening. Moreover, during filling, relatively large deformations of the membrane-shaped wall part will occur. When, after the gas has been introduced into the first chamber, this known apparatus is stored for some time, the control pressure will act on the membrane-shaped element continuously without a desired counterpressure prevailing in the third chamber. After all, the pressure in the third chamber will then be substantially atmospheric. As a consequence, the membrane will be held in a relatively highly deformed state for a relatively long time, which is disadvantageous to the elastic properties thereof. Moreover, this entails the risk of a change of the control pressure caused by gas leaking away from the second chamber along or through the highly deformed membrane.
Moreover, in the case of leakage of the membrane, the control pressure may fall out, so that the closure will be lost and the gas from the first chamber will flow freely to the container, as a result of which the container will be subjected to an unduly high pressure.
A further drawback of this known apparatus is that the rod-shaped body closes the outlet opening of the second chamber by means of an O-ring. This O-ring will continuously be subjected to the high gas pressure in the second chamber. This means that when the O-ring and/or the rod-shaped element are not positioned and/or dimensioned exactly properly, gas can simply flow away between the rod-shaped element and the O-ring. This, too, will eventually cause the gas to flow away from the first chamber to the container and build up an unduly high pressure therein. This is undesirable, both because of the unduly high pressure build-up and because of the poor functioning of the fluid dispensing operation.
The object of the invention is to provide a container of the type described in the preamble, in which the drawbacks of the known container are avoided while the advantages thereof are maintained. In particular, the

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