Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
1996-12-13
2001-01-09
Graham, Matthew C. (Department: 3613)
Brakes
Wheel
Axially movable brake element or housing therefor
C029S509000, C029S522100, C188S25000B
Reexamination Certificate
active
06170618
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to (a) a brake shoe for disc brakes having a retaining spring which is fixed to the pad back plate and is locked to prevent rotation thereof, and (b) a process for manufacturing such a brake shoe.
DE-OS 3842428 discloses a brake shoe of the afore-described type which is intended for use with a floating caliper spot-type disc brake. When assembled, the brake shoe, with its pad back plate, is in abutment with a brake piston of a hydraulic actuator. During braking, the brake piston acts directly upon the brake shoe, thereby forcing it against the brake disc. After the braking operation, the brake piston, in known manner, is withdrawn, by means of a roll-back sealing ring, a short distance opposite the actuating direction in order to set a clearance between the friction face of the brake shoe and the brake disc. To insure that the brake shoe follows that movement, it is clamped on the brake piston by means of a retaining spring. The retaining spring comprises three tongues which engage the hollow brake piston. One of the tongues, at the same time, serves to prestress the brake shoe vis-{grave over (a)}-vis the brake housing to prevent the brake shoe from clattering in its guides, with the brake shoe being radially forced toward the brake disc axis. To safeguard this function, the retaining spring is fixed to the pad back plate in a predetermined position and is prevented from rotating during operation.
In the conventional brake pad, the retaining spring, in simple manner, is fixed by a single bolt or pin forced into the pad back plate. To prevent the retainer spring from rotating about the bolt, provision has been made for connecting the retaining spring, in form-locking manner, with a damping sheet which also is fixed to the pad back plate. However, this way of locking against rotation is not suitable for use with brake shoes not provided with a damping sheet.
Another means of fixation for locking against rotation of the retaining spring is disclosed by EP 0112255 B1 in which the pad back plate is provided with a molded, punched-through projection, having a D-shaped cross-section, protruding beyond the plate plane. The retaining spring is provided with a D-shaped hole for passage of the punched-through projection, with the form-locking connection preventing rotation of the retaining spring about the single point of fixation from occurring. The fixation is by riveting of the punched-through projection, for example, by wobble riveting.
However, this type of fixation has the disadvantage that strong forces are required for caulking or wobbling to deform the required material volume. In view of unavoidable manufacturing tolerances, the retaining spring, as such, or the pad back plate are likely to be bent so that the proper function of the brake shoe no longer is safeguarded.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide an improved brake shoe, wherein the retaining spring, in simple manner, is fixed to the pad back plate and is locked against rotation. Moreover, an improved process for fixing a retaining spring to a brake shoe of the type disclosed by the present invention is to be provided which is insensitive to manufacturing tolerances.
Basically, the solution resides in that a projection of the pad back plate, provided for fixing the retaining spring, is made to conform to the shape of a hole of the retaining spring, provided for the passage of the projection, only during riveting of the projection. The hole is of a non-circular (e.g. oval or angular) configuration; in any case, it is designed such that the retaining spring is unable to rotate about the projection which fills the hole in the retaining spring.
When designing the brake shoe, the projection is molded to the pad back plate, protruding from the plate plane and, in cross-section, initially, has a maximum cross-sectional dimension which permits passage of the projection through the hole. After assembly of the retaining spring and the projection, the material of the projection, through caulking or wobbling, is laterally forced against the edges of the hole, with the cross-section of the projection automatically conforming to the shape of the hole, thereby establishing a form-locking, anti-rotation connection between retaining spring and brake pad.
In the brake pad designed in accordance with the present invention, substantially lower forces are required for wobbling the projection than are required by the state-of-the-art systems. This is due to the fact that the projection, initially, is of a relatively small diameter so that a relatively small amount of material is to be deformed during wobbling. Conversely, in a conventional system as disclosed, for example, by EP 0112255 B1, the projection, with its D-shaped cross-section, already prior to wobbling, fills up, in form-locking manner, the D-shaped hole of the retaining spring. Hence, with the given dimensions of the hole, it is relatively thick so that correspondingly strong forces are required for wobbling.
In practice, in a brake shoe of the type as provided by the present invention, the force required for wobbling can be reduced to half the amount required by arrangements of conventional design of comparable dimensions. This, among others, involves the advantage that the likelihood of changes in dimension, such as bulging of the retaining spring or of the pad back plate during manufacturing of the brake shoe, is notably reduced and the yield of high-quality brake shoes increased. Equally, the wobble angle and the time required for wobbling are reduced. A lower cyclical time, during manufacture, also results in the benefit that more economical means of production can be used. A small wobble angle is advantageous in unfavorable space conditions, for example, in cases where retaining springs, having closely spaced spring tongues for engagement with small brake pistons of small inside diameters, are to be fixed. In addition, the process of manufacture according to the present invention, as regards wobbling force and wobbling time, permits high tolerances, thereby insuring a high degree of reliability in the manufacturing process. Another advantage arises from the fact that the shape of the projection is adapted to the shape of the hole of the retaining spring only during wobbling, with dimension tolerances, due to technical manufacturing conditions, being automatically compensated. Finally, experience has shown that the quality of a fixation point according to the present invention, in view of its improved outward appearance, by a simple sight check, can be more reliably assessed and monitored than has hitherto been possible.
In accordance with the present invention, the various shapes of the hole in the retaining spring are easy to manufacture and reliably lock the retaining spring against rotation. A particularly preferred embodiment of the present invention is to form the retaining spring with a square hole.
A projection of circular cross-section, in view of its simple shaping, is easy to manufacture and, during wobbling, readily conforms to the shaping of the hole, in particular, in connection with a square hole. In this context, the combination of a circular projection having a diameter of 5 mm and a square hole in the retaining spring having a side length of 5.2 mm has turned out to be optimum. With these shapes and dimensions, a force of 4500 N for wobbling can be used. The projection, as such, preferably is molded to the pad back plate by means of a plunger.
REFERENCES:
patent: 1491230 (1924-04-01), Gray
patent: 2746142 (1956-05-01), Maxwell
patent: 3769676 (1973-11-01), Feller
patent: 4313527 (1982-02-01), Pickel
patent: 4597365 (1986-07-01), Madaffer
patent: 4609077 (1986-09-01), Nakatsuhara
patent: 9 000 489 (1990-05-01), None
patent: 3 842 428 (1990-06-01), None
patent: 0 112 255 (1984-06-01), None
patent: 0 311 239 (1989-04-01), None
patent: 0 440 041 (1991-08-01), None
patent: 2 147 376 (1985-05-01), None
patent: 61-266838 (1986-11-01), None
patent: 92/
Graham Matthew C.
ITT Automotive Europe GmbH
Ratner & Prestia
LandOfFree
Brake shoe with retaining spring locked against rotation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Brake shoe with retaining spring locked against rotation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Brake shoe with retaining spring locked against rotation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2464730