Brakes – Wheel – Axially movable brake element or housing therefor
Patent
1998-02-23
2000-04-25
Dickson, Paul N.
Brakes
Wheel
Axially movable brake element or housing therefor
188196C, 188196D, F16D 5502
Patent
active
060532890
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a disc brake with automatic adjusting device.
European patent No. 0 403 635 discloses an adjusting device of this type. In the prior art device, a nut screwed to a spindle is integrally formed as a combination unit along with a coupling element having a conical friction surface and an auxiliary piston, slidable in a bore of the brake piston. A device of this type necessitates exact coaxial positioning of the spindle, the combination unit and the bore of the brake piston. This, in turn, entails most accurate manufacturing tolerances and increased manufacturing costs. In addition, it is absolutely necessary that the portion of the combination unit used as the auxiliary piston can be rotated together with the nut. On the other hand, hydraulic sealing of the auxiliary piston is necessary which must be easily rotatable in the known device. This provision is also disadvantageous with respect to manufacturing costs.
An object of the present invention is to improve a prior art disc brake with automatic adjusting device so that greater manufacturing tolerances are allowed and manufacturing costs are reduced.
SUMMARY OF THE INVENTION
This object is achieved by providing the auxiliary piston and the coupling element on two component parts being separately manufactured, and by connecting the component parts. In the coupling zone, a compensation of coaxialities is possible by means of a play which is to be predetermined between the two component parts. A snap-in connection, as claimed in claim 2, permits a sealing arrangement of the auxiliary piston which need not be easily rotatable because the nut may be arranged on the snap-in connection so as to be rotatable relative to the auxiliary piston. When required, different materials for the nut and the auxiliary piston may even be used.
In a preferred aspect of the present invention, the coupling element is integrally designed with the nut. This ensures a simple manufacture of the thread of the nut and the conical friction surface of the coupling element. The auxiliary piston may have a particularly simple shape in this case.
In a first advantageous embodiment of the snap-in connection, the auxiliary piston is accommodated in a bore of the nut and has on its outside a circumferential annular groove which is in alignment with an internal circumferential annular groove in the bore of the nut. As a coupling element, an open metal ring is inserted into the annular grooves which clicks in elastically.
The metal ring may be bent from a piece of wire, and it may have a circular cross-section or a rectangular cross-sectional shape.
In a preferred aspect of the present invention, the snap-in connection can be disengaged, for example, when the auxiliary piston is urged in the one axial direction by a high hydraulic pressure and, on the other hand, the nut is retained in an opposite axial direction. Such a situation may occur when the nut cannot be rotated due to malfunction, or in adjusting devices which permit rotation of the nut only after hydraulic actuation. When, in such situations, a particularly long actuating travel of the brake piston occurs, an axially fixed auxiliary piston would slip out of its bore in the brake piston and cause complete failure of the hydraulic actuating devices. When, however, the snap-in connection is disengageable, the auxiliary piston will always remain in its bore in the brake piston. A disturbance as described above will cause only disengagement of the snap-in connection, but hydraulic leakage will be prevented.
Disengagement of the snap-in connection is simply possible by at least one annular groove having a ramp-like chamfered groove wall, along which the metal ring slips out also in a radial direction when subjected to axial load.
To fill hydraulic fluid into the brake cylinder, the air contained therein must be bled. Such a bleeding action is normally effected by removing the air prior to the fluid replenishment (`vacuum bleeding`) . Problems are involved with niches in the inte
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patent: 4637498 (1987-01-01), Thompson et al.
patent: 4819768 (1989-04-01), Czich et al.
patent: 5086884 (1992-02-01), Gordon et al.
patent: 5219047 (1993-06-01), Fouilleux et al.
patent: 5607033 (1997-03-01), Naedler et al.
Bauer Jurgen
Doll Andreas
Keferstein Hans-Georg
Thiel Rudolf
Dickson Paul N.
ITT Manufacturing Enterprises Inc.
Siconolfi Robert A.
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