Expansible chamber devices – With guide or seal on cylinder end portion for piston or... – Non-metallic seal means between piston or member and end...
Patent
1993-05-17
1994-10-18
Look, Edward K.
Expansible chamber devices
With guide or seal on cylinder end portion for piston or...
Non-metallic seal means between piston or member and end...
92249, F16J 1518, F16J 900
Patent
active
053557751
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a potlike hydraulic cylinder comprising a cylinder pot, a piston, which constitutes a cover for the pot, a rubber-elastic plastic body, which occupies the pressure space between the cylinder pot and the piston and which forms a closed pocket that is provided with a partition, which is substantially parallel to the bottom and constitutes the bottom of the pocket and is connected to at least one bottom extension of the cylinder pot, which extension protrudes axially into the plastic body, at least one pressure line for a hydraulic fluid, which pressure line extends through the bottom extension and the partition and opens into the pocket.
When conventional hydraulic cylinders are employed to apply or take up strong pressure forces by which the hydraulic cylinder is subjected to a tilting moment, it is necessary to insert expensive pressure-transmitting spherical caps into the hydraulic cylinder in order to relieve it from tilting moments. The seal which is required between the cylinder wall and the piston of the hydraulic cylinder precludes the provision of a substantial guiding gap, which would be necessary to permit a tilting of the piston. Besides, a plastic deformation of the cylinder wall is not permissible even in local regions if the sealing element is not to be endangered. For this reason relatively long pistons are used to take up the lateral forces and substantially increase the overall height. Another requirement to be met by such hydraulic cylinders resides in that they should be made from a material which has a relatively small elastic elongation and a low coefficient of expansion so that the guiding gap between the piston and the cylinder wall cannot be expanded to an extent which would endanger the sealing element under a high load.
In order to avoid said disadvantages it is known from pot-shaped bearings, particularly if they are used in bridges (German Patent Specification 3,410,275), to fill the space between the cylinder pot and the piston, which constitutes a cover for the pot, by a rubber-elastic plastic body, which usually consists of an elastomer and which permits the provision between the pot wall and the piston of a guiding gap which is sufficiently large to permit a tilting of the piston relative to the cylinder pot whereas a sealing of said guiding gap against an extrusion of plastic need not be feared. Such a potlike bearing is supplied with a hydraulic fluid, which is forced into a closed pocket provided within the plastic body so that the latter owing to its incompressibility is displaced against the piston to raise the latter and the pocket is expanded. That pocket is closed at its bottom by a partition, which is joined to a bottom extension of the cylinder pot. Adjacent to the inlet for the hydraulic fluid a pressure line extends thorugh the extension. That partition is intended to permit a hydraulic cushion to be formed under a pressure which is uniformly distributed throughout the surface area of the partition so that the plastic body disposed over the partition will uniformly be raised. But it has been found in practice that under high hydraulic pressures the partition will be pulled out of the pocket of the plastic body or the piston seal will be pulled from the piston because the deformation of the rubber-elastic plastic body cannot be controlled. For this reason the field of application of such potlike bearings is restricted although they are desirable as regards the taking up of tilting moments and lateral forces and are insusceptible to an elongation of materials.
For this reason it is an object of the invention to provide a potlike hydraulic cylinder which is of the kind described first hereinbefore and is so improved by the provision of a simple means that the advantages afforded by the use of a rubber-elastic plastic body can fully be utilized but the disadvantages involved in an uncontrolled deformation of the plastic body will be avoided.
The object set forth is accomplished in accordance with the invention that the partition is adjoined b
REFERENCES:
patent: 2829500 (1958-04-01), Butler
patent: 3166991 (1965-01-01), Blenkle
patent: 3440930 (1969-04-01), Olson
patent: 3489099 (1970-01-01), Huffsmith
patent: 3880053 (1975-04-01), Trechsel et al.
Look Edward K.
Nguyen Hoang
Reisner & Wolff Engineering Gesellschaft m.b.H & Co. KG
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