Stock material or miscellaneous articles – Hollow or container type article
Reexamination Certificate
2000-11-14
2002-10-08
Bell, Mark L. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
C156S192000, C165S009100, C256S013000, C256S013000, C256S013000
Reexamination Certificate
active
06461695
ABSTRACT:
The present invention relates to articles made in the form of bellows.
More particularly, the invention provides such an article using a fiber reinforced plastic. The invention is not concerned with light duty applications such as are found for example in noise-making toys.
A bellows article, usually of round cross-section, is a hollow cylinder or cone having corrugated walls which allow the length of the article to be changed in response to the application of a moderate axial force. Bellows articles have a small wall thickness to diameter ratio to allow wall bending without causing high material strain.
Known materials used for the construction of bellows are leather, plastics, particularly neoprene-coated nylon fabric, elastomers and metals. Each material has an appropriate field of application and each has its limitations. Leather cracks at low temperatures. Plastics which are flexible enough for use in bellows often have low strength. Elastomers are a very varied group of materials which each have their own characteristics and limitations. Fatigue resistant steel is expensive.
It is one of the objects of the present invention to obviate the disadvantages of prior art bellows-like articles and to provide such an article having improved strength to weight ratio and fatigue life, thus permitting use of bellows for existing and novel products.
The present invention achieves the above object by providing a bellows-shaped article made of fiber reinforced plastics, commonly designated composite materials or composites in short.
In a preferred embodiment of the present invention there is provided a bellows-shaped article having continuous corrugations arranged along helical lines.
In a specially preferred embodiment, helical lines of the corrugations are selected from the group consisting of a single helical line, double helical lines and triple helical lines.
In a most preferred embodiment of the present invention there is provided a bellows-shaped article wherein the reinforcing fibers consist of S-glass fibers, E-glass fibers, carbon fibers, graphite fibers, aramid fibers, or mixtures thereof and the plastic is an epoxide resin, a phenolic resin, a polyester resin or a mixture thereof.
As is known, bellows can have discrete parallel corrugations, these being parallel to the transversal plane, i.e. to a plane perpendicular to the axis.
In the prior art there are known light duty bellows wherein the corrugations follow a helical line.
A first example of such a helical bellows is found in hoses of vacuum cleaners made of homogeneous thermoplastic material, wherein the special helical bellows properties are used to make the hoses flexible in bending. They are considered here as light duty, due to the insignificant pressure differential, when in use, between inside and outside the hose.
Another example of helical bellows is an evacuation air duct of a laundry dryer. These have a composite structure of a helical steel wire, maintaining the ducts' circular cross section, with a very thin sheet wall made of plastic or similar material, ensuring air tightness. Such air ducts, beyond their flexibility in bending, are collapsible in the axial direction so that their transportation and storage demand relatively small volume.
Both of said applications are considered as light duty bellows and said bellows do not possess a wall strength suitable for medium or heavy duty use.
Medium duty bellows are, for example, metallic exhaust gas ducts of gas boilers, where the walls have to withstand relatively high temperatures, beyond the endurance of plastic materials.
Heavy duty, prior art, steel bellows are used to accommodate length differential due to heating of two proximate components, which have significantly different thermal expansion coefficients.
The novel material composition of the present invention is intended to provide the invented articles with medium and heavy duty properties.
High strength is derived from the fibers while the resin provides stability of form.
The present invention is intended to provide new applications for bellows-like articles. Such applications have not hitherto employed bellows-like components, either due to inadequate physical properties of the materials, or due to prohibitive cost.
An example of such novel application is the use of bellows-like articles as a heavy duty elastic spring.
Another example is employing a bellows-like article as a component of a heavy duty pump.
In one embodiment of the present invention the crest line of a corrugation of the bellows is parallel to a transversal plane (in case of composite bellows only, see
FIG. 1.
)
In another embodiment the crest line is disposed along an endless helical line (irrespective of material) so that the bellows obtains a shape of a twist drill, in the case of a double helix, or, the shape of a screw thread, in the case of a single helix. See
FIG. 2
for a double helix.
Throughout this specification the terms “Groove” will indicate the concavity between two adjacent crests of corrugations as seen from the outside. The term “Groove Line” will indicate the deepest line of the groove. For helical bellows, the term “Helix Line” will be taken as including any line on the helical surface that is parallel to the crest line (including the crest line itself and including the groove line).
In discrete parallel corrugations and in helical corrugations, a crest line is longer than any other line parallel to it. A groove line is the shortest of all lines parallel to a crest line and any line parallel to the crest and groove lines located between the two is of intermediate length.
Any line of intersection between the surface of a helix shaped body and a transversal plane, as defined above, is a closed line, where all such lines, irrespective of the particular transversal plane in which they are contained are identical in shape and in length. The only difference is that the said closed lines are rotated relative to one another about the axis of the cylinder enveloping the bellows.
Throughout this specification the term “Transversal Surface Line” will be taken as including any line on the helical surface that is formed by the intersection of that helical surface and a transversal plane.
It is obvious that all lines formed by an intersection of a longitudinal plane through the axis of a helix shaped body and the surface of that same body are identical in developed length, provided that the body is at least as long as one pitch of the helix. This is correct irrespective of the helix being a simple helix, a double helix, or a triple helix. It is also correct for discrete parallel corrugations.
Throughout this specification the term “Longitudinal Surface Line” will be taken as including any line on the bellows surface that is formed by the intersection of that surface and such a longitudinal plane.
As for bellows with discrete parallel corrugations, also for a helical body (the length of which is sufficiently large relative to the pitch of the helix) it is always possible to find a family of mutually parallel spatial lines on its surface, disposed at a non-zero angle to a longitudinal surface line where all the lines of that family are identical in length.
Throughout this specification the term “Surface Line” will be taken as including any line on the bellows surface pertaining to such a family of lines. Obviously, the helix lines as defined above, (and for parallel corrugations, any intersections of the surface with transversal planes) do not make a part of a surface line family, as defined above, since they vary in length between a minimum for the groove line and a maximum for the crest line.
On the other hand, for helical bellows, a transversal surface line is a particular case of a surface line family, disposed at right angles to the longitudinal surface lines. As already mentioned, a transversal surface line, unlike other surface lines, is a closed line.
In a composite material bellows according to the present invention, assume two families of surface lines as defined above are formed by two layers (or plies) of
Bell Mark L.
Manlove Shalie
Townsend and Townsend / and Crew LLP
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