Brakes – Plastic deformation or breakage of retarder element – Frangible element
Reexamination Certificate
2000-04-28
2002-08-13
Lavinder, Jack (Department: 3683)
Brakes
Plastic deformation or breakage of retarder element
Frangible element
C188S286000
Reexamination Certificate
active
06431332
ABSTRACT:
The present invention relates to a compressible-fluid device of the type including a compression chamber designed to be filled with a compressible fluid, and a piston that is movable in said chamber so as to compress the fluid contained therein.
The fluid which is compressed by the piston exerts a return force on said piston, and when the fluid used is a gas, such a device is also referred to as a gas spring.
The piston includes a rod which slides in a bore of a guide member also referred to as a cartridge, and the rod is provided, at its end situated in the compression chamber, with a collar which at rest comes into abutment against the guide member.
In the event of an accidental stroke of the piston beyond its nominal stroke, the collar is capable of striking the bottom of the compression chamber and of breaking, in which event it no longer performs its function of retaining the rod, and said rod is thus violently projected out of the spring by the pressure of the gas present in the compression chamber, with the risk of causing material and/or bodily damage.
The invention seeks to remedy that problem.
This is achieved by the fact that the compressible-fluid device includes a safety member disposed so as to be struck by the piston in the event of the stroke of said piston being greater than a predetermined nominal stroke, and by the fact that said safety member is arranged so as to cause the compression chamber to be drained when said safety member is struck by the piston.
As a result of the invention, the rod is not violently expelled from the device in the event of the piston impacting against the bottom of the compression chamber with consequent damage to the piston.
In a particular embodiment of the invention, the safety member has a portion with a predetermined breaking force.
Still in a particular embodiment, the safety member projects into the bottom of the compression chamber, preferably by at least 3 mm.
It can be advantageous to secure the safety member to a plug screwed into the body of the spring, said plug serving to test the resistance of the spring to the pressure, and serving to empty the compression chamber at the end of spring use.
When the piston includes a rod having a bottom end provided with a collar, the safety member is advantageously disposed so as to be struck by the collar in a location that is closer to the axis of the rod than to its periphery.
The piston stroke from which said piston strikes the safety member and causes the compression chamber to be drained is preferably at least 2 mm greater than its nominal stroke.
REFERENCES:
patent: 5735371 (1998-04-01), Jobelius et al.
patent: A1 0 427 468 (1991-06-01), None
patent: A2 0 490 386 (1992-06-01), None
Quiri 500 80 verins tous usages . . . de 6 a 500 tonnes.
Commande et Asservissement Hydrauliques verins hydrauliques, Robert Affouard.
Patent Abstracts of Japan, vol. 8, No. 170, Aug. 7, 1984 (JP 59-065609).
Lavinder Jack
Oliff & Berridg,e PLC
Orflam Industries
Torres Melanie
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