Brakes – Internal-resistance motion retarder – Having a thrust member with a variable volume chamber
Reexamination Certificate
1998-06-04
2001-09-11
Oberleitner, Robert J. (Department: 3613)
Brakes
Internal-resistance motion retarder
Having a thrust member with a variable volume chamber
C188S318000, C188S314000
Reexamination Certificate
active
06286641
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention pertains to an oil brake for vehicles such as all-terrain bikes, motor bikes, cars and the like.
From document U.S. Pat. No. 4,958,706 an oil brake is known in which, during compression, the piston expels the oil from a first working volume of the cylinder toward, on the one hand, a second working volume of the cylinder and, on the other, toward a backup chamber to the outside of which a gas is applied. During expansion, the oil moves from the second working volume and from the backup chamber toward the first working volume. The movable rod that holds the piston is tubular and contains a central rod that projects beyond the movable rod into the first working volume. At its end that is integral with the piston, the tubular rod has an inside diameter that is larger than the outside diameter of the central rod so as to form a central passage for the oil. A valve that is essentially shaped like a hat and is equipped with longitudinal slots is located in the opening of the tubular rod. The edge of the hat that is formed by the valve is superimposed on a heat-expanding stop valve and rests on the edge of the end of the tubular valve. The valve and the heat-expanding stop valve are kept resting on the end of the tubular rod in order to block the central passage by means of an open coil spring that is mounted on the central rod and rest on a washer that is integral with the latter. During expansion, the oil passes through an opening that is located in the cylindrical rod at the base of the piston into the second working volume, and then runs via the central passage around the hat-shaped valve and around the heat-expanding stop valve. The oil then moves into the first working volume through lateral openings that are located in the body of the piston and through an opening that is located in the end of a hat that is integral with the piston and surrounds the end of the central rod that projects into the first working volume. Control of the flow during expansion is accomplished by the two regulators that are the hat-shaped valve and the heat-expanding stop valve. Control of expansion at low oil speeds is accomplished by the heat-expanding stop valve, while control at high speeds is ensured by the openings on the hat-shaped valve. The pressure of the open coil spring can be adjusted by screwing down/unscrewing the central rod in the tubular rod, but the attachment end of the brake on the wheel axle must first be disassembled.
This kind of brake does not ensure adequate control of expansion, however. Thus, at high speed and at the end of its stroke, the piston may knock up against the bottom of the cylindrical body of the brake. Moreover, the system consisting of the stop valve and valve does not make it possible to control the start of expansion adequately since the flow of oil is released abruptly. In addition, the double mechanism for controlling the flows of oil during expansion at high and low speeds involves a significant number of complex parts which increase the cost of the brake; this is especially disadvantageous in the case of a brake for a bike, for example.
BRIEF SUMMARY OF THE INVENTION
A first object of the invention is to propose an oil brake that ensures better control of the flow of oil during run-out, thereby remedying the drawbacks of the prior art.
This object is achieved by virtue of the fact that the oil brake includes a piston that is mounted at the free end of a movable tubular rod which at its other end is integral with the stem of the brake, whereby the tubular rod moves in a hollow cylindrical body, thereby delimiting on both sides of the piston a first and a second working volume, whereby a central rod is arranged inside of the tubular rod and the tubular body contains at least one lateral opening that connects the second working volume to the first working volume via at least one central passage that is made between the tubular rod and the central rod and is formed by a relative difference in transverse dimensions between the central rod and the inside diameter of the tubular rod, whereby the opening or openings are formed on the tubular rod at a distance from the piston that is equal to at least half of the thickness of said piston, whereby the hollow cylindrical body is tightly closed with a plug and/or stem guide that is designed in such a way that, before the end of the expansion stroke, the openings that are formed on the tubular rod are tightly sealed by the inside wall of the stem guide before all of the oil is evacuated from the second working volume toward the first working volume, forming a pocket of oil that is thick enough to constitute a hydraulic cushion for the piston.
According to another feature, the tubular rod contains four openings that connect the second working volume to the first working volume and are located at a distance from the adjacent base of the piston that is essentially equal to the thickness of the piston, whereby the central passage is formed by a reduction in the diameter of the central rod at its end that empties into the first working volume.
According to another feature, the end of the hollow cylindrical body is closed by a stem guide whose length is essentially equal to twice the thickness of the piston.
Another object of the invention is to propose an oil brake that makes it possible to ensure easy adjustment of the opening pressure of the expansion valve without disassembling the brake.
This object is achieved by virtue of the fact that the end of the central rod of the brake extends beyond the tubular rod in the first working volume, whereby an expansion non-return check valve is mounted at the end of the central rod that protrudes into the first working volume and is equipped with a head that forms a support for the elastic means that exert a pressure on the non-return valve in such a way as to support the latter on the seat of a perforation that is located at the end of the tubular rod which is integral with the piston in order to block the outlet opening of the central passage toward the first working volume, and whereby remote-control means that are located close to the end of the tubular rod that is integral with the brake stem make it possible for the central rod to translate with respect to the tubular rod in order to adjust the pressure that is exerted by the elastic means on the expansion valve without disassembling the brake.
According to another feature, the expansion stop valve is essentially shaped like a cylindrical tube that is equipped with a radial shoulder that runs from one of its ends to the other, whereby the expansion stop valve is attached to the central rod and can slide in a supplementary cylindrical seat that is formed at the end of the tubular rod that is integral with the piston, whereby the translation of the expansion stop valve toward the inside of the tubular rod is limited by the stop of the radial shoulder of the stop valve on the edge of the end of the tubular rod and seals the outlet opening of the central passage toward the first working volume, whereby the expansion stop valve is equipped with at least one notch that is located in a plane which contains the longitudinal axis of symmetry of the stop valve and has a depth that decreases from the end facing the shoulder toward the shoulder itself, ensuring a gradual enlargement of the outlet opening of the central passage for the first working volume when the translation of the expansion stop valve takes place in the direction of its outlet toward the cylindrical seat of the end of the tubular rod.
According to another feature, the end of the central rod protrudes beyond the tubular rod in the body of the brake stem and includes an additional transverse bore of an adjustment shaft, whereby the adjustment shaft is seated simultaneously in a transverse seat that is formed in the body of the brake stem and in the bore of the central rod, whereby the transverse seat of the body of the brake stem is shaped in such a way as to permit limited translation of the adjustment shaft in the direction of
Donerre Amortisseur
Kramer Devon
Nixon & Vanderhye
Oberleitner Robert J.
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