Expansible chamber devices – Collapsible chamber wall portion – Wall portion formed of flexible material
Reexamination Certificate
2000-10-16
2002-06-18
Ryznic, John E. (Department: 3745)
Expansible chamber devices
Collapsible chamber wall portion
Wall portion formed of flexible material
Reexamination Certificate
active
06405635
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to spring brake actuators used on heavy duty commercial vehicles, and more particularly to an apparatus for attaching either an emergency brake housing cup, a service brake housing cup, or both, of a spring brake actuator to an adaptor made of the same or a dissimilar metal.
2. Description of the Prior Art
Various forms of pneumatic vehicle spring brake actuators have been introduced over the years primarily for use in the trucking industry. A typical actuator includes a service brake assembly that is used for slowing or stopping a vehicle, and may also include an emergency or parking brake assembly.
The service brake assembly is characterized by a closed housing which contains an elastomeric diaphragm sealingly attached to the sides of the housing, dividing the housing into two chambers. A first chamber is defined on one side of the diaphragm. A centrally located slidable push rod is provided in the first chamber and is operably associated with the diaphragm. The rod extends out of the service brake housing for attachment to the braking mechanism of the vehicle. A second sealed chamber is formed within the housing on the opposite side of the diaphragm. An opening is provided in the second chamber for connection to a pneumatic (air) pressure source usually provided by an on-board air compressor. The brakes of the vehicle can be applied by variably introducing sufficient pneumatic pressure into the sealed chamber to act against the diaphragm to move the push rod out. A small return spring is provided inside the service brake housing around the push rod to urge it to retract when the air pressure behind the diaphragm is reduced.
When employed, the emergency brake assembly is attached in axial alignment with the service brake assembly. The emergency brake is a separate closed housing which also contains a diaphragm sealingly attached to the sides of the housing dividing the housing into two chambers. A heavy compression spring is provided in the first chamber, and a slidable central rod is provided in the second sealed chamber for communication with the push rod of the service brake assembly. As with the service brake, the sealed chamber of the emergency brake is connected to the on-board pressurized air source of the vehicle. As long as sufficient air pressure is provided, the diaphragm in the emergency brake housing holds off the large compression spring. However, should pressure fall, or should there be a leak in the sealed chamber, the diaphragm will be unable to hold the large compression spring in place. When this occurs, either slowly or quickly, the large compression spring expands, causing the central rod to move the push rod out thereby applying the brakes of the vehicle. Under normal conditions, when the vehicle is parked, the air pressure to the emergency brake portion is cut off causing the large compression spring to apply the brakes.
Because the spring brake assembly is a critical safety system, it has to be designed and manufactured for exceptional reliability. Moreover, the compression spring inside the emergency brake actuator can be potentially dangerous. It must be capable of exerting a sufficient force to apply the brakes of the vehicle independent of any external air pressure or assistance from the service brake. This spring in its compressed state stores substantial kinetic energy which may be dangerous if the spring brake housing is opened without first taking adequate precautions to secure the spring in its compressed state or to release the stored energy in a controlled manner.
It is conventional to fabricate the emergency brake housing in two opposing sections: a cup or head for holding the large compression spring, and an adaptor for receiving the cup. The emergency brake cup and the corresponding adaptor each have an open central area and an annular peripheral edge. These peripheral edges are joined to form the emergency brake housing. At this peripheral junction, the peripheral edge of the elastomeric diaphragm is also attached. The two opposing sections are coupled together with sufficient force to maintain an air-tight seal between the diaphragm and the housing, dividing the housing into two chambers. The adaptor includes an inlet that allows for fluid communication between the second sealed chamber and the on-board pressurized air supply.
Similarly, it is also conventional to fabricate the service brake housing in two opposing sections: a cup or head, and an adaptor for receiving the cup. As with the emergency brake, each of these parts has an open central area and an annular peripheral edge joined to form the service brake housing, with the peripheral edge of the diaphragm sealingly attached between. The service brake housing is also divided into two chambers, and the adaptor also includes an inlet which allows for fluid communication between the second sealed chamber and the on-board pressurized air supply.
In a tandem brake actuator which includes both an emergency brake assembly and a service brake assembly (sometimes called a double-diaphragm adaptor), a single adaptor piece is provided which has oppositely facing axially aligned receptacles for attachment to, respectively, the emergency brake housing cup and the service brake housing cup. Normal positioning of the two elastomeric diaphragms results in the adaptor being part of the sealed chambers of both the service brake and the emergency brake. As a result, it is common for a tandem adaptor to have an hourglass shape and to include the openings into each chamber for attachment to the on-board air supply for the brakes.
It will be appreciated that each adaptor (whether emergency brake adaptor, spring brake adaptor, or tandem adaptor) requires numerous critically angled walls together with a specially positioned inlet opening for attachment to the on-board air supply. Because of its hourglass shape, making a tandem adaptor from steel requires the welding together of two halves. There is great expense involved in creating the necessary tooling to make these two halves, providing inlet openings on each of them, and then attaching them together. As a result, it is more common for adaptor parts to be made from cast aluminum. Not only does the price of aluminum make it an attractive alternative to steel, using cast aluminum also makes it possible to easily establish the critical angles and inlet openings of the adaptor in the mold, thereby avoiding the need for expensive fabrication and tooling. Making adaptors from aluminum is also desirable for a brake manufacturer or remanufacturer to be able to use its conventional existing aluminum molds to inexpensively create adaptor pieces that may be attached to existing housing cups. Casting the adaptor pieces from aluminum is also desirable in that, compared to steel, many different molds may be easily and inexpensively created for the various sized pieces.
Because they have a more simple design, it is also common for emergency brake and service brake housing cups to be made of steel. However, for the same reasons described above, it may be equally advantageous to make these housing cups from aluminum. Thus, depending upon the situation, it may be desirable to make either the adaptor or the housing cup from aluminum, and to make the corresponding piece from the other metal. However, it is difficult to join together such parts when made from dissimilar metals, presenting the continuing problems of assuring that the coupling be air tight as well as safe and secure.
Since unauthorized opening of the emergency brake housing is potentially dangerous to the inexperienced mechanic, and since unauthorized re-sealing using defective seals or improper procedures could result in a poor diaphragm seal or other internal defect, it is also conventional to discourage unauthorized access, disassembly, and reassembly of the emergency brake housing by appending a warning label to the housing and using an attachment means which is temper-resistant or at least tamper-evident, so that a ne
Russell Ralph D.
Smith Greg
Smith Teddy D.
Stubblefield Michael D.
Miller Mark D.
Ryznic John E.
TSE Brakes, Inc.
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