Communications: electrical – Land vehicle alarms or indicators – External signal light system
Reexamination Certificate
2001-09-14
2002-11-12
Pope, Daryl (Department: 2632)
Communications: electrical
Land vehicle alarms or indicators
External signal light system
C340S453000, C340S454000, C188S00111E, C188S00111E
Reexamination Certificate
active
06480107
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus for assembly of a brake monitor on a brake actuator of the type used for heavy vehicles, including tractor and trailer combinations, buses and the like, having a brake actuator.
BACKGROUND OF THE INVENTION
Heavy-duty trucks, buses and other large vehicles are typically equipped with a pneumatic brake actuating system. The brake actuating system typically applies air under pressure to a service chamber of a brake actuator to move a diaphragm in a first direction. A piston having a push rod typically moves with the diaphragm and the push rod is connected to a linkage which actuates the vehicle brakes. An emergency chamber having a power spring and a second diaphragm is typically mounted on the service chamber and is operable to move the push rod and actuate the brakes in the event that the pneumatic vehicle system fails or when the vehicle is turned off when the vehicle is parked. Thus, the emergency chamber serves as an emergency braking system for the vehicle and a parking brake.
A brake actuator has a predetermined amount of available movement of the push rod or stroke of the push rod. The amount of movement of the push rod required to fully actuate the braking system of the vehicle should be carefully monitored, such that it is within the stroke of the push rod of the brake actuator. Excessive movement of the push rod can be created by one of several factors. Typically, excessive movement of the push rod is due to brake lining wear. As the brakes wear, more movement of the push rod is required to actuate the brakes. Further, if the linkages and connections between the push rod and the linkages, et cetera, bend or become loose or excessively worn, additional push rod movement is required to actuate the brakes. A combination of these several factors may sometimes cause the amount of push rod movement required to actuate the brakes approach the available push rod movement or stroke available from the brake actuator. As will be understood, this is an undesirable situation.
The prior art has proposed various methods and apparatus to monitor the push rod movement during actuation of the brake and provide some indication to operator or service personnel as to when there is excessive push rod movement, which is referred to as “overstroke.” As will be understood by those skilled in this art, a determination of when there is excessive push rod movement or overstroke is dependent upon the designed or rated stroke of the brake actuator. For example, the push rod of a typical brake actuator may include a brightly colored ring, which may also be painted on the push rod, which indicates an overstroke condition when the ring extends out of the brake actuator during actuation of the brakes. The ring may, however, be difficult to see because of the location of the brake actuators beneath the truck or trailer and accumulated road debris. Automatic slack adjusters located between the push rod and the foundation brake are also conventionally used, wherein the slack adjuster incrementally adjusts to compensate for slack in the braking system and to decrease the required push rod movement.
The prior art has also proposed various electronic monitoring systems which generally monitor either the stroke of the push rod or the movement of the linkages between the push rod and the foundation brake including the slack adjuster. However, there are several obstacles to be overcome. First, powering and monitoring electronic indicators on each brake actuator of an 18-wheel vehicle is costly. Further, the hostile environment in which the brake actuators are mounted beneath the vehicle can damage the monitoring system, particularly where there are exposed pistons, sleeves, sensors, et cetera. Finally, where the stroke of the push rod is monitored by the brake monitoring system, it is essential that the push rod stroke monitoring system be accurately assembled on the brake actuator and be able to withstand the hostile environment of the brake actuator. Finally, it is desirable that the components of the brake monitoring system be accurately assembled on the brake actuator.
The vehicle brake monitoring system disclosed herein and in the above-referenced co-pending patent application solves many of these problems by providing a reliable and relatively inexpensive brake monitor which is incorporated into and becomes part of the vehicle brake actuator. By incorporating the brake monitoring system in the brake actuator, the components are protected, providing greater reliability and reduced cost. The brake monitoring system includes a push rod sleeve which incorporates a first sensor element and a second sensor element is fixed relative to the housing to provide accurate location of the push rod to sense an overstroke condition and may be utilized to sense other brake conditions including a worn brake, a dragging brake condition and a normally functioning braking system. In the preferred embodiment, the first sensor element incorporated in the push rod sleeve is an elongated magnet, most preferably a magnet having north and south poles, and a “null” point spaced between the north and south poles, and the second sensor element is a Hall-effect sensor which is most preferably located in a sensor sleeve which surrounds the push rod sleeve. The sensor sleeve may be located within the brake actuator housing and most preferably also serves as a stone shield preventing entry of foreign material into the brake actuator housing.
As will be understood by those skilled in this art, the accurate location of the magnet in the push rod sleeve on the push rod is critical to accurate monitoring of the push rod stroke. Because of the normal tolerances of vehicle brake actuators, it is critical to adjust the push rod sleeve on the push rod relative to the second sensor element on each brake actuator for reliable performance of the brake monitoring system. Another problem associated with brake monitoring systems for brake actuators is that there are at least three standard strokes for brake actuators which must be taken in to account when assembling the brake monitoring system on the brake actuator. The apparatus for assembling a brake monitor on a brake actuator of this invention assures accurate location of the push rod sleeve and first sensor element on the push rod relative to the second sensor element and may be utilized to assemble a brake monitor on brake actuators having different push rod strokes. The apparatus of this invention thereby assures accurate and reliable operation of the brake monitoring system.
SUMMARY OF THE INVENTION
The apparatus for assembling a brake monitor on a brake actuator of this invention may be used with any conventional brake actuator, wherein the brake actuator includes a housing having an end wall, an opening through the end wall and a reciprocating piston within the housing having a push rod extending through the opening in the housing end wall for actuation of a vehicle brake, particularly pneumatic brake actuating systems for heavy duty trucks, buses, trailers and other large vehicles. As set forth above, a typical brake actuator for heavy duty vehicles includes an enclosed housing, a flexible diaphragm generally having a peripheral edge secured between the housing members, a piston having a piston plate biased against the flexible diaphragm by a return spring and the piston includes a push rod which reciprocates through an opening in the end wall of the brake actuator housing to actuate the vehicle braking system. The brake actuator housing is connected to the pneumatic braking system of the vehicle whereby, upon actuation of the vehicle pneumatic braking system, the diaphragm is driven against the piston plate, which reciprocates the push rod to actuate the vehicle foundation brake. As will be understood by those skilled in this art, the brake actuator may also include an emergency or power spring chamber which actuates the vehicle braking system when the vehicle pneumatic pressure falls below a predetermined pressure or wh
Heron Walter E.
Moore R. Ryan
Osterman Paul S.
Stonehocker Terry L.
Howard & Howard
Indian Head Industries Inc.
Pope Daryl
LandOfFree
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