Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
1999-11-24
2002-01-22
Oberleitner, Robert J. (Department: 3613)
Brakes
Wheel
Axially movable brake element or housing therefor
C188S071500
Reexamination Certificate
active
06340075
ABSTRACT:
FIELD OF INVENTION
This invention relates to braking systems. In particular, this invention relates to multi-disk brake systems used in vehicles. More particularly, this invention relates to aircraft disk brake systems. The brake disk assembly contains a brake disk stack, which comprises an end plate, a pressure plate and interleaved rotors and stators. The available wear portions of the rotors and stators have different wear thicknesses, so that the thickest disks in the stack are capable of being used for three service runs before being refurbished or replaced. Similarly, the available wear portions of the pressure plate and end plate each may have a different available wear portion thickness, which may be the same as the available wear portions of the stators and rotors. Therefore, with this configuration, the mid-thickness disks are replaced or refurbished after two service runs and the thin disks are replaced or refurbished after one service run. Furthermore, this invention relates to a method of assembly of a disk brake stack having disks of different thicknesses.
BACKGROUND OF THE INVENTION
Aircraft brake systems have brake disk stacks comprised of interleaved rotor and stator disks. The disks are alternatively splined to the rotatable wheel and stationary (non-rotatable) torque tube. An end plate is provided at one end of the stack, while an axially moveable pressure plate is provided at the other end of the stack. Upon application of force to the pressure plate, the disks frictionally engage and provide braking activity to the vehicle.
Generally in the past, brakes have been assembled with the available wear portions of the rotors and stators having the same available wear thickness. These brakes were operated until the wear portions of all of the disks were fully worn. At that time, all of the disks were removed and replaced with new unworn disks or refurbished or reworked disks. The heat sink mass of the brake is reduced by the total wear of all the disks in the brake stack. The heat sink mass must be above a certain level to hold the operating temperature of the brake down. Due to the size and weight limitations on aircraft, the thickness of available wear portions is also limited. The thickness of the available wear portions controls the number of landings between the replacement or refurbishing of the disks. The piston cylinder or other actuator assemblies for actuating the brakes also have a predetermined travel length, which is a function of the total wear of the disks. Where the brake is operated until all disks are fully worn, the actuator travel length is increased and accordingly the total brake envelope is increased as well as weight of the brake assembly. The brake envelope includes a heat sink envelope which is the distance between the end of the piston or thrust member facing the brake stack and the backing plate or reaction member at the opposite end of the brake stack.
Various different brake configurations have been proposed to minimize the turnaround time, maximize the brake cooling, reduce the amount of piston or actuator travel, as well as the size and the weight of the brake, while at the same time retaining a substantial portion of the heat sink mass to a lower operating temperature. For example, U.S. Pat. No. 3,480,115 to Lallemant discloses a brake, which comprises two groups of coaxial disks. The first group of coaxial disks is smooth since the disks are not equipped with a friction lining. The second group of disks has a friction lining. The disks of the first group are disposed alternatively with the disks of the second group. The disks of one group are angularly coupled to a rotatable structure such as an aircraft wheel and the disks of the other group are coupled to a non-rotating structure. Lallemant discloses various embodiments in which the disks of at least one of the two groups have thicknesses that vary from one disk to another depending upon the axial position of the disks. The thicker disks have greater thermal capacities due to their greater mass. According to Lallemant, the purpose of these various embodiments is to provide multiple disk brakes that fulfill the requirements of practice, particularly with respect to their longevity, uniformity of braking efficiency and conditions in which maintenance operations can be carried out. Furthermore, Lallemant contemplates the possibility of re-machining the smooth disks and moving these disks to a new axial position in the brake for which new axial position the reduced thickness that has been given to the smooth disks is adapted to the working conditions corresponding to the new position. Lallement alleges that the overall thermal capacity of the brake is not affected by the re-machining of the smooth disks and therefore, the efficiency of such brakes is constant.
U.S. Pat. No. 4,613,017 to Bok discloses a method of assembling and overhauling a disk brake having a plurality of disks with available wear portions of predetermined different thicknesses. The method comprises positioning first a first group of disks in overlapping relationship with a second group of disks. The first group of disks have an available wear portion of a first thickness and the second group of disks have an available wear portion of a second thickness which is greater than the thickness of the first group of disks. A third group of disks having a third thickness at an intermediate overhaul replace the first group of disks when the available wear portions of the first group of disks are substantially fully worn. The third group of disks have a third thickness which is greater than the thickness of each of the available wear portions of the second group of the disks at intermediate brake overhaul time.
Similarly, U.S. Pat. No. 4,742,895 to Bok discloses a carbon disk brake assembly. The assembly comprises a plurality of disks in which the first group of disks, for example, the stators and end plates, have an available wear portion of a first thickness which is less than and preferably one half of the thickness of the wear portions of the second group of disks, in this example, rotors. After a predetermined number of landings, the stators and end plates will be substantially fully worn. These worn stators and end plates are replaced by a third group of disks, which are new or refurbished stators and end plates. Preferably, the wear thickness of this third group of disks is double the thickness of the available wear portions of the rotors at the intermediate overhaul. The brake assembly is then operated to another intermediate overhaul when the available wear portions of the rotors will be fully worn and replaced by new or refurbished rotors.
U.S. Pat. No. 4,977,985 to Wells, et al. discloses a method of carrying out the maintenance of a multi-disk brake. The disks are made of a carbon-carbon material. The brake comprises a stack of interleaved rotor and stator disks provided between a thrust member and a reaction member. The rotor and stator disks are selected and arranged so that the wear allowance of a set of disks at one end of the stack is less than the wear allowance of a set of disks at the other end of the stack. A fully worn group of disks is removed from one end of the stack during brake service operation following wear. The remaining partially worn disks are axially moved or shifted to a new position towards the one end of the stack. An unworn stack of disks is added at the other end of the stack.
Similarly, U.S. Pat. No. 5,323,880 to Wells, et al. discloses a multi-disk brake system. The brake comprises a stack of interleaved rotor and stator disks disposed in an axially aligned relationship. The disks are made of a carbon-carbon material, which provides the frictional surfaces of the disk as well as their structural integrity. The stack of disks comprises a first group of adjacent rotors and stators and a second group of adjacent rotors and stators in an axially aligned relationship with the first group. Each wear surface of the first group which confronts a wear surface of an adjacent disk of the firs
Bok Lowell D.
Prenger Mark W.
Reed Eric J.
Burch Melody M.
Oberleitner Robert J.
Ronyak, Esq. David M.
The B. F. Goodrich Company
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