Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
2000-07-24
2001-11-20
Butler, Douglas C. (Department: 3613)
Brakes
Wheel
Axially movable brake element or housing therefor
C188S058000, C188S071500, C188S2640AA, C188S072900, C192S085060, C192S085060, C192S113400, C192S113200
Reexamination Certificate
active
06318511
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a disk friction device for a transmission shaft. The field of application of the invention is retarding or braking a transmission, in particular for heavy road vehicles, for the motor bogies of rail vehicles, or for industrial rotary machines.
BACKGROUND OF THE INVENTION
Known retarders are frequently of the hydraulic or electromagnetic type and they give rise to problems of size and weight.
Disk brakes are also known that make use of disks made of thermostructural composite material, in particular carbon/carbon (C/C) composite material which provides very good friction behavior and also provides a large saving in weight in comparison with traditional metal disk brakes.
The use of C/C material disk friction devices has already been proposed for transmission brakes or retarders of heavy trucks. Reference can be made in particular to document FR-A-2 607 566 and patent application FR 97 06 959.
The use of such devices as axle brakes on rail vehicles has also been envisaged. Reference can be made in particular to documents FR-A-2 626 541, FR-A-2 697 218, and EP-A-0 478 943.
For heavy road vehicles or for rail vehicles, it would be advantageous to provide retarders or transmission brakes with disks of thermostructural composite material but without requiring the use of hydraulic energy.
Nevertheless, account must be taken both of the high temperatures reached by thermostructural composite materials, in particular C/C materials, when subjected to friction, and the need for high levels of force when pressing the disks together in order to obtain the desired effectiveness, and even though the space available is often very restricted.
OBJECT AND SUMMARY OF THE INVENTION
An object of the invention is to provide a disk friction device for braking or retarding an engine shaft or a transmission, the device being very compact and making it possible to use disks made of thermostructural composite material and pneumatic control.
This object is achieved by a device comprising:
a non-rotary casing having at least one end wall provided with a bearing unit for the rotary shaft;
a set of annular disks on a common axis, with at least friction portions thereof being made of a thermostructural composite material, the disks being received inside the casing and comprising at least one rotor disk constrained to rotate with the rotary shaft and at least two stator disks mounted on either side of the rotor disk and prevented from rotating relative to the casing;
a thrust structure situated facing an outside face of a first stator disk at a first end of the set of disks;
actuator means connected to the thrust structure; and
a backing structure supported by the casing and situated facing an end face of a second stator disk at a second end of the set of disks:
in which device:
the casing is in the form of a cage in which there are received the thrust structure, the set of disks, and the backing structure, and comprises a first end wall at the thrust structure end, a second end wall at the backing structure end, and a peripheral wall provided with ventilation openings;
the actuator means are constituted by a pneumatic actuator mechanically connected to a central portion of the thrust structure via a central opening in the first end wall of the casing; and
thermal insulation means are arranged between the set of disks and the outside of the casing beside the end wall fitted with the bearing unit for the rotary shaft, and comprising at least one heat barrier situated at the bearing unit.
In a first embodiment, the pneumatic actuator is fixed to the first end wall of the casing, beside the thrust structure, making the device compact.
In another embodiment, the pneumatic actuator is fixed to the second end wall of the casing and is connected to the thrust structure by at least one lever, thereby amplifying the thrust delivered by the actuator.
The central portion of the thrust structure can be given the shape of a setback housed in an axial passage surrounded by the disks, so that the mechanical connection between the actuator and the thrust structure extends at least in part inside said axial passage, thereby contributing to making the device more compact.
The thrust structure may be constituted by a thrust piece having a central portion connected to the actuator and an annular peripheral portion, and by a set of cups fixed on said annular peripheral portion and bearing against the outside end face of the first stator disk, thereby limiting contact area and thus limiting heat transfer between the disks and the thrust structure.
Similarly, the backing structure can be formed by an annular backing piece and a set of cups fixed to the backing piece and bearing against the outside end face of the second stator disk.
Rotary connection between the rotary shaft and the or each rotor disk can be achieved by means of a piece fixed on the shaft and provided with riders which penetrate into notches formed in the inside periphery of the or each rotor disk, the riders being made of a material that is a poor conductor of heat so as to limit heat transfer between the disks and the rotary shaft.
In addition, it is advantageous to provide at least one heat screen situated inside the casing between the set of disks and the bearing unit for the rotary shaft. The heat screen can be carried by the backing structure.
The heat barrier situated at the bearing unit is constituted, for example, by at least one baffle constraining air to follow a tortuous path along the bearing unit. This heat barrier, which is advantageously combined with a heat screen inside the casing, provides effective opposition to the transfer of the heat generated by friction from the disks to the drive or transmission members coupled to the rotary shaft outside the casing.
REFERENCES:
patent: 4102438 (1978-07-01), Rancourt
patent: 5058712 (1991-10-01), Noah
patent: 5069321 (1991-12-01), Reik et al.
patent: 5407032 (1995-04-01), Gaudefroy et al.
patent: 5538109 (1996-07-01), Swank
patent: 5671827 (1997-09-01), Demetriou et al.
patent: 5992577 (1999-11-01), Souetre
patent: 6006869 (1999-12-01), Rancourt et al.
patent: 6056089 (2000-05-01), Karlsson et al.
patent: 9400821 (1994-03-01), None
patent: 2697218 (1994-04-01), None
patent: WO 9725548 (1997-07-01), None
Borgeaud Olivier
Clement Didier
Garcia Jean-Michel
Butler Douglas C.
King Bradley
Messier-Bugatti
Weingarten, Schurgin Gagnebin & Hayes LLP
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