Expansible chamber devices – Piston – Nonmetallic portion
Patent
1998-05-14
2000-07-11
Lopez, F. Daniel
Expansible chamber devices
Piston
Nonmetallic portion
F16J 101
Patent
active
06085636&
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a plastic brake piston.
German patent application No. 31 19 921 discloses a plastic brake piston having an open end which is thermally reinforced by a coating of heat-resistant material. This avoids a thermal overload of the brake piston which abuts the metallic support plate of a brake lining which can become very hot during braking.
A disadvantage of the prior art arrangement is that the heat of the brake lining is only very poorly dissipated by the brake piston due to the low heat conductivity of the piston. Therefore, the brake lining may become extremely heated in heavy braking operations so that even the lining material will possibly be detached.
An object of the present invention is to provide a plastic brake piston that is improved in terms of heat conductivity.
SUMMARY OF THE INVENTION
The object of the present invention is achieved by a plastic brake piston including a metallic insert member which extends from one end of the brake piston that abuts the brake lining until the second end of the brake piston which is connected to the hydraulic fluid. Part of the heat is carried off from the brake lining via the metallic insert member and conducted to the hydraulic fluid. The solution of the present invention combines the advantage of low manufacturing costs for the plastic brake piston and the good conductivity of a metallic material.
In a simple embodiment of the present invention, the insert member is a metal wire or pin which, most simply, extends precisely from one end of the brake piston to the second end. A pin of this type can be slipped into the brake piston or laminated by the plastic material.
In a second embodiment of the present invention, a cup-shaped insert member is provided and has its base arranged on the second end of the brake piston. The base of the cup-shaped insert member is connected directly to the hydraulic fluid and is acted upon by its hydraulic pressure. In a preferred aspect of the cup-shaped insert member, the base has a thicker design than the side wall to better withstand the hydraulic pressure. The present invention can still be improved by the provision of an inward circumferential bead on the cup-shaped insert member in the area of its side wall, the bead being used for engagement by a holding spring for the brake lining.
In a preferred aspect of the embodiment of the present invention with a cup-shaped insert member, the cup-shaped insert has a stepped configuration. The insert end close to the base has a diameter smaller than the end which is in contact with the brake lining. The so configured cup-shaped insert has a smaller base surface acted upon by the pressure of the hydraulic fluid and, thus, has an improved resistance against the pressure.
In another preferred aspect of the present invention, the insert member is a U-shaped, spray-coated sheet-metal strip or metal wire. The inside of the insert member includes also in this case a projection which can be backgripped by the anti-rattle spring of the brake lining.
Especially in a cup-shaped or U-shaped configuration of the insert member, the contact surfaces of the brake piston and the insert member have grooves and beads on the piston and the insert member which are in engagement. This provides a stronger support of the insert in the brake piston and ensures seal-tightness of the entire piston in relation to the hydraulic fluid.
In still another preferred aspect of the invention, the insert member is a spray-coated helical spring. Any customary standard part can be used in this case.
In another solution of the present invention, the material of the brake piston has metallic additions to increase the heat conductivity.
Embodiments of the present invention will be explained in more detail hereinbelow making reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE INVENTION
In the drawings,
FIG. 1 is a cross-sectional view of a brake piston in a first embodiment with a pin.
FIG. 2 is a cross-sectional view of a second embodiment of the b
REFERENCES:
patent: 2216577 (1940-10-01), Stillwagon
patent: 2663285 (1953-12-01), Johnson
patent: 2791969 (1957-05-01), Berliner
patent: 2887347 (1959-05-01), Losey
patent: 3172341 (1965-03-01), Garrett
patent: 4170926 (1979-10-01), Emmett
patent: 4190108 (1980-02-01), Webber
patent: 4545288 (1985-10-01), Burke
patent: 4605104 (1986-08-01), Thompson
patent: 4928579 (1990-05-01), Emmett
Birkenbach Alfred
Henein Nabil
Ruckert Helmut
ITT Manufacturing Enterprises Inc.
Lopez F. Daniel
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