Brakes – Vehicle – Hub or disk
Reexamination Certificate
1999-03-11
2001-12-11
Butler, Douglas C. (Department: 3613)
Brakes
Vehicle
Hub or disk
C188S071800, C188S072300, C188S072400, C188S1960BA, C188S366000, C188S367000, C188S216000, C188S073310, C188S073430, C188S2640AA
Reexamination Certificate
active
06328137
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to disk brakes and more particularly to improvements in large area contact disk brakes for vehicles.
2. Description of the Prior Art
The disk brake of the present invention is a disk brake of the type described in U.S. Pat. No. 5,330,034 issued Jul. 19, 1994 and U.S. Pat. No. Re. 35055 issued Oct. 10, 1995 referring to full annular disk brakes for larger vehicles such as trucks. The concept of the full annular disk brake is now proposed for automobiles and light trucks and the present invention relates to a structure of a full annular disk brake for such vehicles.
There are obvious advantages in having a complete annular array of friction pads contacting an annular disk on both sides of the disk. The braking or thermal energy distribution is related directly to the thermal resistance associated with both sides of the interface where the heat is generated. In a full annular brake there is a large area to distribute the braking energy more efficiently.
It has also been found that vibrations between the inner and outer pads are the major causes for brake squeal.
The analysis of vibration response is of considerable importance in the design of brakes that may be subjected to dynamic disturbances. Under certain situations, vibrations may cause large displacements and severe stresses in the brake. The velocity of a vibrating system is in general, proportional to its frequency and hence a viscous damping force increases with the frequency of vibration. Forces resisting a motion also arise from dry friction along a non-lubricated surface. It is usually assumed to be a force of constant magnitude but opposed to the direction of motion. In addition to the forces of air resistance and external friction, damping forces also arise because of imperfect elasticity or internal friction, called hysteric damping, within the body. The magnitude of such a force is independent of the frequency but is proportional to the amplitude of vibration or to the displacement.
In a brake system, dynamic loading produces stresses and strains, the magnitude and distribution of which will depend not only on the usual parameters encountered previously but also on the velocity of propagation of the strain waves through the material of which the system is composed. This latter consideration, although very important when loads are applied with high velocities, may often be neglected when the velocity of application of the load is low. Since dynamic loading is conveniently considered to be the transfer of energy from one system to another, the concept of configuration (strain energy) as an index of resistance to failure is important. One of the important concepts is that the energy-absorbing capacity of a member, that is, the resistance to failure is a function of the volume of material available, in contrast to the resistance to failure under static loading, which is a function of cross-sectional area or section modulus.
One of the main problems in adapting the technology of a full annular brake system of the type described in the above mentioned patents is the consideration of weight and cost. It would be unrealistic, no matter what the advantages, to assume that the a new full annular brake system would be accepted on the market at a price substantially higher than present day disk brakes. Furthermore any increase of weight compromises the fuel consumption.
SUMMARY OF THE INVENTION
It is an aim of the present invention to provide a brake system, especially for automobiles, that has improved heat distribution properties, and reduces the occurrence of wear.
It is a further aim of the present invention to provide a brake system that reduces low frequency brake squeal.
It is still a further aim of the present invention to provide an annular disk brake system where the maximum brake performance is obtained.
A construction in accordance with the present invention comprises a disk brake assembly for a vehicle wheel wherein the wheel includes a hub journaled to an axle on the vehicle, the disk brake assembly comprises a housing mounted to the vehicle and at least an annular rotor disk within the housing and means mounting the disk to the wheel. The rotor disk has at least a first radial planar friction surface and the housing includes a first annular brake shoe provided adjacent the first planar friction surface of the disk and movable axially towards and away from the first friction surface. Means are provided for restraining the first brake shoe from rotating with the disk. The housing also includes an annular radial wall parallel to the first brake shoe, and an annular fluid expandable bladder extends between the first annular brake shoe and the radial wall, whereby upon expansion of the bladder the first brake shoe moves axially to frictionally engage the friction surface of the disk, means for disengaging the first brake shoe from frictional contact with the rotor disk upon release of the fluid from the expandable bladder.
In a more specific embodiment of the present invention the radial disk is provided with a second annular friction surface, parallel to the first and on an opposite side of the rotor disk wherein the first and second friction disks have different radii, and a second annular brake shoe adjacent the second annular friction disk wherein brake squeal will be reduced.
In a still more specific embodiment of the present invention, the means for retaining the first brake shoe includes a brake shoe backing plate having an annular periphery and the housing includes a concentric wall having an internal surface radially adjacent the periphery of the first brake shoe while the inner surface of the concentric wall and the periphery of the first brake shoe have mating interdigital elements which allow axial movement of the first brake shoe relative to the concentric wall but prevents peripheral movement of the first brake shoe relative to the concentric wall of the housing.
In a still more specific embodiment of the present invention, the means for disengaging the first brake shoe from the first friction surface of the rotor disk is at least one rolling seal provided between axially generated adjacent surfaces of the annular radial wall of the housing and the first brake shoe.
The features of the present invention can be utilized for large trucks as well.
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Birch & Stewart Kolasch & Birch, LLP
Butler Douglas C.
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