Expansible chamber devices – With support or frame
Reexamination Certificate
1999-01-11
2001-11-20
Look, Edward K. (Department: 3745)
Expansible chamber devices
With support or frame
C092S062000, C092S064000, C092S169100
Reexamination Certificate
active
06318240
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to brake actuator service chambers having an improved seal of the pushrod opening in the end wall of the housing and an improved end wall which reduces vibration damage of the service chamber when mounted on a supporting bracket.
BACKGROUND OF TEE INVENTION
Brake actuator service chambers of the type disclosed herein are used on trucks, semitrailers, buses and other large vehicles to actuate the braking system of the vehicle. The service chamber includes a metal housing defining a chamber therein having an end wall which is mounted on a bracket on the vehicle having an opening therethrough which receives a reciprocal pushrod supported in the service chamber. The pushrod has an end portion extending through the opening in the end wall of the housing. The service chamber generally includes a cup-shaped flexible diaphragm secured at is periphery in the service chamber and one end of the pushrod includes a generally flat piston which is received against the flexible diaphragm. Upon actuation of the braking system of the vehicle, pneumatic pressure acts against the side of the flexible diaphragm opposite the pushrod piston, driving the piston through the housing end wall and actuating the vehicle brakes. The brake actuator service chamber may be mounted in tandem with a spring or an emergency chamber or the service chamber may be used alone or in combination with a separate spring chamber.
The service chamber alone or in tandem with a spring chamber is mounted on a bracket attached to the vehicle. The end wall of the service chamber generally includes a pair of holes on opposed sides of the central opening which receives the reciprocal pushrod and bolts are mounted in the holes which attach the service chamber to the vehicle bracket. The mounting bolts may, however, be welded or otherwise attached to the end wall of the service chamber.
As will be understood by those skilled in the art, brake actuator service chambers are exposed to dirt, debris, mud, ice, sleet, etc. which may interfere with the operation of the service chamber or result in wear or deterioration of the components of the service chamber. The service chamber, for example, includes a return spring which is generally biased between the end wall of the service chamber and the piston head of the pushrod. Thus, for example, dirt or ice may interfere with operation of the return spring, which returns the pushrod to its ready position, or cause deterioration of the flexible diaphragm, which is generally formed of synthetic rubber or Neoprene®. The prior art does include annular stone shields mounted in the service chamber surrounding the reciprocal pushrod and tubular flexible dust boots mounted on the pushrod. However, the prior art does not disclose an adequate and practical seal which seals the pushrod opening in the end wall of the service chamber. This is due in part to the fact that the pushrod does not always move directly in a straight line. Instead, the movement of the pushrod is sometimes skewed from the central axis of the brake rod. Thus, the prior seals have had difficulty in maintaining a seal under the extreme conditions of a brake actuator service chamber. Thus, it would be desirable to have a seal for the pushrod opening in the end wall of a brake actuator which can survive in the actual environment in which the brake actuator is used and which will provide a good seal under the operative conditions faced by the brake actuator.
Finally, it would be most desirable to more firmly mount a service chamber on the vehicle mounting bracket to reduce damage from the vibration encountered by such vehicles. Most brake actuator manufacturers subject their brake actuators to vibration testing; however, such testing is done under ideal conditions. In actual practice, the brake actuator is subject to vibration under severe conditions which may result in damage to the housing or components of the brake actuator. This is particularly true with “piggyback” brake actuators wherein the spring chamber is mounted in tandem with the service chamber because of the additional loads.
SUMMARY OF THE INVENTION
The improved sealed brake actuator service chamber of this invention includes a housing defining a service chamber therein and having an opening therethrough, a reciprocal pushrod is supported in the housing chamber having an end portion extending through the housing opening and a flexible tubular seal surrounds the pushrod within the housing chamber having a first end portion secured within the housing opening, preferably in sealed relation. The tubular seal further includes a sealing portion spaced from the first end portion which tightly circumscribes the pushrod in sealed relation. The preferred embodiments of the tubular flexible seal is generally hourglass-shaped including a reduced diameter midportion, which tightly circumscribes the reciprocal pushrod in sealed relation, and a free end portion preferably having a reinforcing rib or more preferably an internal seal which closely receives the reciprocal pushrod. The internal surface of the midportion of the seal preferably includes at least one or a plurality of radial sealing lips which engage the reciprocal pushrod. Grease may be applied to the internal surface of the tubular sealing member, preferably between the sealing lips and between the midportion and the free end portion to improve sealing and reduce friction with the reciprocal pushrod. The internal diameter of the opening through the service chamber housing preferably has a diameter substantially greater than the diameter of the pushrod to accommodate skewing of the pushrod, as described above, and the first end of the tubular seal preferably has a radial groove or channel which receives the end wall of the service chamber adjacent the opening. Thus, the tubular seal in the brake actuator of this invention fully seals the pushrod opening in the end wall of the chamber while accommodating skewed reciprocal motion of the pushrod.
The most preferred embodiments of the sealed brake actuator service chamber of this invention includes a disk-shaped relatively rigid or inflexible washer having an opening therethrough surrounding the midportion of the flexible tubular seal to improve sealing and maintain the concentricity of the seal on the pushrod. The washer is thus preferably fixed on the midportion of the tubular seal. In the disclosed embodiment, the midportion of the tubular seal includes an outwardly opening groove or channel which receives the washer. The most preferred embodiment of the washer includes a maximum radial dimension which is greater than the internal diameter of the pushrod opening in the end wall of the service chamber housing, such that the tubular seal will not be pushed through the housing opening as the pushrod reciprocates through the opening. That is, the washer is biased against an enlarged portion of the tubular seal as the pushrod reciprocates through the opening in the end wall of the housing, but is prevented from being pushed through the opening. The preferred embodiment of the washer further includes a width measured transverse to the maximum radial dimension which is less than the internal diameter of the pushrod opening which permits the tubular seal and washer assembly to be assembled through the pushrod opening on the pushrod. The ends of the washer are also preferably tapered to further facilitate assembly of the washer and seal assembly through the pushrod opening and the washer ends may be semicircular, such that the radial dimension conforms to the radial dimension of the first enlarged portion of the seal.
As set forth above, the preferred embodiments of the tubular flexible pushrod seal of this invention is generally hourglass-shaped, wherein the lower portion of the seal adjacent the service chamber housing opening has a maximum external diameter greater than the maximum radial dimension or diameter of the washer. In the most preferred embodiment of the tubular seal, the lower portion of the seal includes at least two radial
Demus Duane J.
Plantan Ronald S.
Howard & Howard
Indian Head Industries Inc.
Lazo Thomas E.
Look Edward K.
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