Brakes – Vehicle – Cart
Reexamination Certificate
2000-10-27
2001-09-11
Schwartz, Christopher P. (Department: 3613)
Brakes
Vehicle
Cart
Reexamination Certificate
active
06286631
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to wheelbarrow brakes and more particularly to an actuating lever for a braking system having a caliper for braking a rotatably supported disc.
BACKGROUND OF THE INVENTION
Braking systems for wheelbarrows are known in the art. U.S. Pat. No. 2,716,031 to Roessler, for example, discloses a hand operated brake for a wheelbarrow having a pivoting hand lever connected by an adjustable length rod assembly to a pivoting arcuate brake shoe. Pivot of the hand lever by a user of the wheelbarrow causes pivot of the shoe into contact with an inner cylindrical surface of the wheel of the brake. This type of braking system in which an arcuate shoe contacts an inner cylindrical surface of a rotating member is typically referred to as a drum brake system.
A wheelbarrow having another type of braking system known as a disc brake system is disclosed in U.S. Pat. No. 5,690,191 to Burbank. The Burbank reference discloses a brake disc supported on fastened spacers by a vertical surface of a tire rim and a U-shaped caliper which positions brake pads on opposing sides of the brake disc. An actuating cable secured to one of the pads extends in a first pass between the brake pads and is returned in a second pass through aligned openings in the pads. Bushings are located in the brake pad openings to facilitate passage of the cable. Actuation by a user of the wheelbarrow forces withdrawal of a portion of the cable in the first and second passes and pulls the pads towards one another.
The cable actuator system of Burbank fails to provide efficient transfer of the force applied to the cable into a braking force applied to the disc. The forced withdrawal of cable through the bend between the cable passes which is necessary for drawing the pads together generates frictional forces between the cable and the bushings. These frictional losses limit the effectiveness of the pulling force which is applied.
Furthermore, the teaching in Burbank of supporting the disc on fastened spacers from a vertical surface of the wheel fails to provide proper support for the disc. Support from the wheel rim in such a manner results in substantial runout wobble of the disc.
What is needed is an actuator for a disc type braking system for a wheelbarrow in which tension applied to a cable is efficiently converted into a braking force applied to the disc. The interacting cam members and cam grooves of the brake actuator of the present invention provides mechanical advantage and highly efficient conversion of the force applied to the cable into braking force applied to the disc. Furthermore, the actuator of the present invention has bidirectional operation providing for alternative application of the actuator in either a manual cable-applied/spring released braking system or an automatic spring applied/cable released system. A benefit of automatic braking is the ability to park the wheelbarrow on a slope without the need for blocking of the wheel. This allows for safe loading of the wheelbarrow with assurance that the wheelbarrow will not move when gravity forces overcome frictional forces acting on the wheelbarrow supports. Such a system also provides a useful safety feature in that the wheelbarrow would automatically brake in the event a user of the wheelbarrow were to unintentionally lose control over the wheelbarrow while operating the wheelbarrow.
SUMMARY OF THE INVENTION
According to the present invention there is provided an actuator for a braking system having a caliper. The actuator includes cam members supported by the caliper and a lever pivotably supported by the caliper for pivot about an axis. The lever includes variable depth cam grooves on opposite sides of the axis and is oriented with respect to the caliper for contact between the cam members and the cam grooves for translation of the lever away from the caliper upon pivot of the lever. The cam grooves preferably include intermediately located maximum depths which provide for a minimum separation lever position and translation of the lever away from the caliper in either of opposing first and second directions of pivot. The cam members are preferably spherical members movably retained in semispherical recesses in the caliper.
According to an embodiment of the present invention, the caliper is supported by a wheelbarrow having a rotatably supported disc. Translation of the lever away from the caliper results in translation of a brake pad into contact with the disc. The caliper is preferably slidably supported on pins in a bracket for translation of a second brake pad into contact with the disc opposite the first brake pad.
According to an embodiment of the present invention, an operator applied braking system includes a cable secured to the lever at a first end and to a cable actuator adjacent a second end for pivot of the lever in the first direction of pivot to effect braking of the disc. A return spring is preferably secured to the lever and to the wheelbarrow to effect a release of the disc upon release of the cable actuator.
According to an embodiment of the present invention, a spring of a spring applied braking system is preferably secured to the lever and to the wheelbarrow to pivot the lever in the second direction of pivot to effect braking of the disc. A cable is preferably secured to the lever for release of the disc upon use of a cable actuator by a user of the wheelbarrow.
REFERENCES:
patent: 5000294 (1991-03-01), Hunicutt et al.
patent: 5038895 (1991-08-01), Evans
patent: 5203434 (1993-04-01), Teeter et al.
patent: 5343984 (1994-09-01), Bieker et al.
patent: 5690191 (1997-11-01), Burbank
patent: 6148964 (2000-11-01), Huang
Drinker Biddle & Reath LLP
Schwartz Christopher P.
The Hilliard Corporation
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