Automatic adjusting apparatus for a disc brake

Brakes – Wheel – Axially movable brake element or housing therefor

Patent

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Details

188 726, 188196D, F16D 6556

Patent

active

053500423

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to an automatic adjusting apparatus for a disc brake.


BACKGROUND OF THE INVENTION

An adjusting apparatus for a disc brake of the type under consideration is known from the German patent application published without examination, No. 3,802,014. Two lip seals are positioned at a front end of an adjusting nut. The lip seals result in an increase in length of the adjusting nut in the axial direction, so that a larger mounting space for the adjusting apparatus as a whole is required.


SUMMARY OF THE INVENTION

It is an object of the present invention to reduce the axial mounting space of an adjusting apparatus for a disc brake. It is another object of the present invention to simplify the prior art adjusting apparatus and to render it cheaper.
According to the present invention, a cylinder, directed into the inner space of a brake piston, projects out of the bottom of the brake piston and is surrounded by an adjusting nut. One external surface of the cylinder interacts with a ring-shaped circumferential sealing element. As a result, in the presence of the full thickness of the brake linings, the spindle of the adjusting apparatus and the cylinder projecting into the brake piston toward the spindle are disposed near to each other and present a roughly equal diameter. A simple design, thus, results for the adjusting nut, since it need project beyond the end of the spindle, in axial direction, over the cylinder only by an amount sufficient to result in a firm fitting of a sealing element between the nut and the cylinder. In the event of pressurization, the sealing element prevents rotation of the adjusting nut relative to the brake piston. As a result, an adjustment is prevented during the pressure build-up, but slight axial movement is possible.
In one advantageous embodiment of the present invention, a second sealing element is provided which is retained through a spacer relative to the first sealing element, so that a hydraulically free space exists between the two sealing elements, and the seals can expand toward the hydraulically free space in the event of pressurization.
If, and when, an aeration duct is provided, atmospheric pressure can be maintained within the hydraulically free space even in the event of pressurization.
If, and when, both seals are fitted between the cylinder projecting into the brake piston and the internal cylinder surface of the nut, then, according to a simple design in accordance with the present invention, the bore can advantageously be drilled into the annular chamber from the point of intersection of the axis of symmetry of the piston and the front side of the piston. In this way, the bore will be disposed where there is available sufficient mounting space and where it is protected from dirt and mud by the brake shoe.
In another simple design in accordance with the present invention, one of the two seals is disposed on the inside cylindrical surface of the nut and the second seal is disposed on the outside cylindrical surface of the nut. In this way, the bore can end in the annular chamber at the front side of the piston. Again, the bore is positioned in a range in which sufficient mounting space is available.
In one simple design in accordance with the present invention, the adjusting nut is furnished with a friction cone at its front side facing the bottom of the piston. This friction cone at the front side of the nut is easy to fabricate.
When the external diameter of the adjusting nut increases toward the bottom of the piston, then, due to the large diameter, the surface of the friction cone also will increase. As a result, the piston and the adjusting nut will come into abutment in the event of a mechanical actuation and rotation of the nut will be prevented.
In one simple and cost-effective design in accordance with the present invention, the internal bore of the adjusting nut is configured in the shape of a stepped bore.
If, and when, a ball bearing is disposed on the outer surface of the adjusting nut, then this outer sur

REFERENCES:
patent: 3402791 (1968-09-01), Hoenick
patent: 3991859 (1976-11-01), Coulter et al.
patent: 4014415 (1977-03-01), Pickel
patent: 4637498 (1987-01-01), Thompson et al.
patent: 4681194 (1987-07-01), Tsuruta
patent: 4809822 (1989-03-01), Margetts
patent: 4981197 (1991-01-01), Antony et al.
patent: 5249646 (1993-10-01), Thiel

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