Seal for a joint or juncture – Process of static sealing
Reexamination Certificate
2000-01-24
2001-11-13
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Process of static sealing
C277S630000, C277S641000, C277S646000, C249S063000, C249S065000
Reexamination Certificate
active
06315295
ABSTRACT:
This invention relates to inflatable seals and in particular, but not exclusively, to inflatable seals in the field of the manufacture of interior panels for motor vehicles.
Certain types of interior panels for motor vehicles consist of a substrate (of e.g. glass reinforced urethane, fibre board or the like), a layer of foam, and then a skin (of e.g. PVC). In order to fabricate such panels the skin is placed in a cavity formed in the lower part of a tool. In one method, known as an ‘open pour mould’, liquid foam is then poured onto the skin and the substrate, which is supported by the upper part of the tool, is brought down to within a predetermined distance of the skin. An exothermic chemical reaction causes the foam to expand, filling the volume between the substrate and the skin. Alternatively, the foam could be injected between the skin and the substrate after the tool has been closed.
A seal is required between the upper and lower parts of the tool to prevent escape of the foam from around the periphery of the tool. After the foam has expanded, one technique involves lifting the upper tool initially by a small amount to release pressure slowly without fully opening the tool. However, the foam can then undergo further expansion, distorting the shape of the finished panel. It is therefore generally preferred to use an inflatable seal since this can be deflated slightly to allow the built-up pressure to be released without having to open the tool.
Thus in a known tool for producing vehicle interior panels, an inflatable seal is disposed around the periphery of one of the tool parts, usually the lower part. In multiple production runs it is necessary to clean excess dried foam that has been deposited by a previous operation from the edge of the tool part, in the region near the seal. This is done with sharp implements such as knives and scrapers. Whilst doing this the person scraping the tool may inadvertently cut or nick the seal, thereby causing it to leak when inflated. Not only does this cause considerable delay whilst the seal is replaced, but the leak may not be noticed until after the foam has been poured and the tool parts brought together, potentially causing defects in the panel which then has to be discarded.
In an attempt to solve this problem, it is possible to use a seal reinforced by fibres running along the length of the seal. Whilst this does go some way to alleviating the problem, it has the drawback of reducing the flexibility of the seal, thereby restricting its usefulness for applications in vehicle interior panel production where it is often necessary to incorporate relatively tight curves in the path of the seal.
According to one aspect of the present invention, there is provided an inflatable seal system in a tool having opposed parts which are relatively movable together with the inflatable seal system therebetween, the inflatable seal system comprising a longitudinally extending seal cavity and a seal extending longitudinally along the seal cavity, said seal comprising an inflatable portion and an abutment portion for sealingly abutting against an opposing surface, wherein the inflatable portion remains in the seal cavity when the seal is deflated.
With such an arrangement, when the seal is deflated, the inflatable portion of the seal is protected from damage, for example from scraping implements, by virtue of it remaining in the seal cavity.
The abutment portion may be formed so as to be relatively thick in the radial direction when compared to the inflatable portion and also solid so that, even if the abutment portion projects from the seal cavity when the seal is deflated, any damage caused by scraping or cleaning implements will not cause the inflatable seal to leak. The arrangement is preferably such that only the abutment portion is exposed to the outside when the seal is deflated.
Because the inflatable portion of the seal is protected by the seal cavity, the seal can be made to be relatively deformable, so that it can readily follow arcuate portions of the seal cavity, even quite sharply curved portions if required. It is thus not necessary to mould the seal specially to fit the arcuate portions of a particular cavity. Such arcuate portions may be arcuate in the lateral direction, the upward direction (so as to be “convex”) or the downward direction (so as to be “concave”). It will be appreciated that references to “upward” or “downward” herein are used for the purposes of explanation and on the basis that the seal cavity has a “bottom” and a “top”, but should not be understood as limiting the orientation in which the inflatable seal system may be used. Thus the top of the seal cavity may face upwardly, downwardly, sideways etc.
The seal is preferably not reinforced by a second material. Thus the seal may be relatively deformable and easy and inexpensive to manufacture, as compared to e.g. fibre-reinforced rubber.
Preferably the inflatable seal is an extrusion. Again, this allows it to be easy and inexpensive to manufacture.
The seal cavity may be formed of parts which can be opened up to allow location of the seal, but preferably the seal cavity is of fixed shape. For example, the seal cavity may be defined in a body of moulded material e.g. moulded resin.
Although the seal may be axially insertable along the seal cavity, the arrangement is preferably such that the seal is insertable into the seal cavity through the top thereof. This will greatly facilitate location of the seal and is advantageous in situations where the seal has to be periodically replaced. In order to allow for such insertion, the abutment portion preferably has a width narrower than that of the seal cavity.
It is preferred for the inflatable portion of the seal to remain in the seal cavity when the seal is inflated. This provides further protection for the inflatable portion. In a preferred arrangement, the seal cavity has a main portion in which the inflatable portion of the seal is located, and has at its top a longitudinally extending slot which has a width less than that of the main portion and through which the abutment portion projects when the seal is inflated.
Inevitably small air leaks will sometimes occur from the inflatable seal causing it to lose effectiveness. If these are not too serious, it is possible to increase the pressure at which the seal is inflated in order to compensate. If the inflatable portion of the seal is constrained by the seal cavity when the seal is inflated, the seal can withstand higher pressures as its tolerance to high pressure is not limited to the surface strength of the material from which the inflatable seal is fabricated.
The inflatable portion and the abutment portion of the seal may be formed separately of each other. Preferably, however, they are formed integrally with each other. This again allows the seal to be easy and inexpensive to manufacture, e.g. as an extrusion. In addition, when it is necessary to replace the seal, only one member has to be located along the seal cavity. Thus an integral seal is easier to use than a two part seal.
In a preferred embodiment the seal further comprises an inwardly projecting member such as a tongue or the like projecting into the seal to prevent the abutment portion of the seal fully entering the seal cavity when the seal is deflated. Such a projecting member is of particular value when the seal cavity has a concave arcuate portion, i.e. when the path of the cavity is such that the seal must be curved with its abutment portion on the inside of the curve. In many situations a degree of concavity can be accommodated without any problems, but in some circumstances there may be a tendency for the abutment portion to get stuck in the seal cavity, when the seal is deflated, so that it fails to emerge to effect sealing upon inflation of the seal. Thus the inwardly projecting member may be provided in order to alleviate this problem. It can also ensure that the abutment portion remains at the top of the seal cavity when the seal is deflated, so that the inflatable portion is not exposed to the
Bacon & Thomas
Knight Anthony
Magna International Investments (Barbados) Inc.
Pickard Alison K.
LandOfFree
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