GB2031530A - Bellows seals - Google Patents

Abstract

The invention provides a cylindrical pleated gaiter in which the block height is reduced as compared to known gaiters. Such reduction is obtained by forming adjacent pleats or folds (4) with different inner and/or outer diameters. The diameters of adjacent pleats or folds preferably deviate from each other by amounts corresponding to the radial length of an unshortened pleat or fold. <IMAGE>

Description

SPECIFICATION Pleated gaiter The present invention relates to cylindrical pleated gaiters formed of rubber or rubber-like materials.

Pleated gaiters are used in many areas of technology to protect longitudinally or transversely displaceable machine components, for example, piston rods, linkage rods and the like, from contamination whilst at the same time sealing off the associated apertures in housings, cylinders and other cavities or working chambers. Similarly to the rectangular bellows of an accordian, the cylindrical gaiter pleats formed by a succession of circular pleat surfaces are not only limited to axial displacement, i.e. to rectilinear expansion and reduction, but they are capable of manifold possibilities of displacement and are most frequently used as compared to differently shaped bellows, gaiters and the like protecting means.One special feature of gaiters, particularly of gaiters produced by widening an originally smooth cylindrical blank, is their outwardly diminishing wall thickness in the region of the pleats which may vary from case to case depending upon the manufacturing method, the diameter ratio from base of fold to tip of fold and the flow behaviour of the elastomeric or plastomeric gaiter material.Although it does not substantially impair the usefulness and functional capacity of the gaiter, it does, however, prevent compressing to the minimum theoretical block height of a gaiter having pleats of a constant wall thickness and thereby, in turn, limits the overail stroke; since the actual attainable block height is determined by the abutment of the thickest parts of the folds of the pleats, and the summation of many of such points of contact, especially in connection with fold gaiters of substantial length, such may lead to substantial stroke reductions.

It is an object of the present invention to reduce the block height of a cylindrical pleated gaiter beyond the extent predetermined by wall thickness.

This object is attained for cylindrical gaiters formed of rubber or rubber-like elastomeric or plastomeric materials according to the invention in that pleats or folds adjacent to each other are formed with different inner andior outer diameters, whereby the diameters of adjacent pleats or folds may deviate from each other by amounts of an order of magnitude corresponding to the radial length of an unshortened pleat or fold.

The novel configuration of the pleats or folds results in that the regions of greater wall thickness in the compressed state of the gaiter are not coincidental equidistantly spaced from the central axis of the gaiter on a circular plane, but are progressively mutually offset from one pleat or fold to the next.

Thus, only zones of thicker wall thickness will directly abut with zones of thinner wall thickness and the compensation caused thereby permits the gaiter to be compressed to a block height hitherto not attainable.

The present invention will be further illustrated, by way of example, with reference to the accompanying drawings, in which Figure 1 is a portion, in longitudinal section, through a known gaiter design; and Figure 2 and 3 show an identical portion of two different arrangements of a gaiter in accordance with the invention.

The pleated gaiter shown in Figure 1, for example, is made of polyurethane or any otherthermoplastics material by widening an originally smooth cylindrical hose blank in a mould. It is comprised of a sequence of pleats or folds 4 merging into one another, said pleats or folds having an equal shank length, and hose connecting ends 5 provided on both sides. The term "shank length" according to general usage denotes the radial length of the pleats or folds 4 which are to be regarded geometrically as angles with equally long shanks. As a known consequence of the manufacturing method used, the folds all have a wall thickness diminishing from the inner apices 14 in the direction of the outer apices 24.

Therefore, in the completely compressed block state of the pleated gaiter, all inner apices 14 corresponding to the regions of maximum wall thickness are in direct abutment with each other, whilst the outer apices 24 which, on the other hand, are substantially thinner no longer have a usable axial space in which to move.

In the pleated gaiter in accordance with the invention shown in Figure 2, each second pleat or fold is drawn in over a smaller inner diameter substantially corresponding to half the shank length.

Adjacent inner apices 14 in the block state consequently no longer are in direct abutment, but abut again against zones of lesser wall thickness. The pleated gaiter may therefore be compressed to a relatively shorter block height.

In Figure 3 an alternative embodiment of the invention is shown, whereby the outer apices 24 of the reduced pleats or folds are drawn in to a smaller diameter. Since the direct abutment of adjacent pleats or folds is also avoided, there are obtained fundamentally the same effects as with the embodiment of Figure 2.

1. A cylindrical pleated gaiter formed of rubber or rubber-like elastomeric or plastomeric materials, in which adjacent pleats are formed with different inner and/or outer diameters.

2. A pleated gaiter as claimed in claim 1, in which the diameters of adjacent pleats deviate from each other by amounts of an order of magnitude corresponding to the radial length of an unshortened pleat.

3. A cylindrical pleated gaiter, substantially as hereinbefore described with reference to and as illustrated in Figures 2 and 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Pleated gaiter The present invention relates to cylindrical pleated gaiters formed of rubber or rubber-like materials. Pleated gaiters are used in many areas of technology to protect longitudinally or transversely displaceable machine components, for example, piston rods, linkage rods and the like, from contamination whilst at the same time sealing off the associated apertures in housings, cylinders and other cavities or working chambers. Similarly to the rectangular bellows of an accordian, the cylindrical gaiter pleats formed by a succession of circular pleat surfaces are not only limited to axial displacement, i.e. to rectilinear expansion and reduction, but they are capable of manifold possibilities of displacement and are most frequently used as compared to differently shaped bellows, gaiters and the like protecting means.One special feature of gaiters, particularly of gaiters produced by widening an originally smooth cylindrical blank, is their outwardly diminishing wall thickness in the region of the pleats which may vary from case to case depending upon the manufacturing method, the diameter ratio from base of fold to tip of fold and the flow behaviour of the elastomeric or plastomeric gaiter material.Although it does not substantially impair the usefulness and functional capacity of the gaiter, it does, however, prevent compressing to the minimum theoretical block height of a gaiter having pleats of a constant wall thickness and thereby, in turn, limits the overail stroke; since the actual attainable block height is determined by the abutment of the thickest parts of the folds of the pleats, and the summation of many of such points of contact, especially in connection with fold gaiters of substantial length, such may lead to substantial stroke reductions. It is an object of the present invention to reduce the block height of a cylindrical pleated gaiter beyond the extent predetermined by wall thickness. This object is attained for cylindrical gaiters formed of rubber or rubber-like elastomeric or plastomeric materials according to the invention in that pleats or folds adjacent to each other are formed with different inner andior outer diameters, whereby the diameters of adjacent pleats or folds may deviate from each other by amounts of an order of magnitude corresponding to the radial length of an unshortened pleat or fold. The novel configuration of the pleats or folds results in that the regions of greater wall thickness in the compressed state of the gaiter are not coincidental equidistantly spaced from the central axis of the gaiter on a circular plane, but are progressively mutually offset from one pleat or fold to the next. Thus, only zones of thicker wall thickness will directly abut with zones of thinner wall thickness and the compensation caused thereby permits the gaiter to be compressed to a block height hitherto not attainable. The present invention will be further illustrated, by way of example, with reference to the accompanying drawings, in which Figure 1 is a portion, in longitudinal section, through a known gaiter design; and Figure 2 and 3 show an identical portion of two different arrangements of a gaiter in accordance with the invention. The pleated gaiter shown in Figure 1, for example, is made of polyurethane or any otherthermoplastics material by widening an originally smooth cylindrical hose blank in a mould. It is comprised of a sequence of pleats or folds 4 merging into one another, said pleats or folds having an equal shank length, and hose connecting ends 5 provided on both sides. The term "shank length" according to general usage denotes the radial length of the pleats or folds 4 which are to be regarded geometrically as angles with equally long shanks. As a known consequence of the manufacturing method used, the folds all have a wall thickness diminishing from the inner apices 14 in the direction of the outer apices 24. Therefore, in the completely compressed block state of the pleated gaiter, all inner apices 14 corresponding to the regions of maximum wall thickness are in direct abutment with each other, whilst the outer apices 24 which, on the other hand, are substantially thinner no longer have a usable axial space in which to move. In the pleated gaiter in accordance with the invention shown in Figure 2, each second pleat or fold is drawn in over a smaller inner diameter substantially corresponding to half the shank length. Adjacent inner apices 14 in the block state consequently no longer are in direct abutment, but abut again against zones of lesser wall thickness. The pleated gaiter may therefore be compressed to a relatively shorter block height. In Figure 3 an alternative embodiment of the invention is shown, whereby the outer apices 24 of the reduced pleats or folds are drawn in to a smaller diameter. Since the direct abutment of adjacent pleats or folds is also avoided, there are obtained fundamentally the same effects as with the embodiment of Figure 2. CLAIMS

1. A cylindrical pleated gaiter formed of rubber or rubber-like elastomeric or plastomeric materials, in which adjacent pleats are formed with different inner and/or outer diameters.

2. A pleated gaiter as claimed in claim 1, in which the diameters of adjacent pleats deviate from each other by amounts of an order of magnitude corresponding to the radial length of an unshortened pleat.

3. A cylindrical pleated gaiter, substantially as hereinbefore described with reference to and as illustrated in Figures 2 and 3 of the accompanying drawings.