Land vehicles – Wheeled – Coasters
Reexamination Certificate
2001-05-10
2002-12-03
Swann, J. J. (Department: 3618)
Land vehicles
Wheeled
Coasters
C280S011270, C280S028110, C280S011204, C280S011211, C280S011215, C188S072900
Reexamination Certificate
active
06488296
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a brake device for small-wheeled vehicles such as skateboards, scooters, small carts and the like. The brake can be actuated by a mechanical or hydraulic system and activated by means of a remote actuator.
DESCRIPTION OF THE PRIOR ART
Over the past 50 years inventors have developed a variety of brake systems for small-wheeled vehicles. They range from the very crude stick into the ground to a finely designed hydraulic system featuring a remote handgrip. Prior art presented has proven adequate for operation by children and adults at relatively slow speeds. However, prior art does not provide a brake mechanism that will withstand self-generated heat forces when operated by an adult rider at speeds exceeding 15 mph for any length greater that ¼ mile with a downhill inclination greater than 4 degrees. The problem lies within frictional heat generated by a brake mechanism when trying to stop an adult rider traveling under the force of gravity over a period of time.
The force required to slow or stop a rider on a wheeled vehicle is dependent upon the weight and velocity of the rider, and the angle of inclination of the run. Increasing any of these heel variables increases the amount of force required to stow the rider. The consequence of using frictional force to slow a vehicle is heat generation. As a rider travels downhill and applies brake pressure in order to control speed, frictional heat continually builds into the brake mechanism. Considering this heat is localized to the surface area of a small wheel, the amount of heat can be substantial
Testing has shown that during normal recreational use a 180 pound rider traveling on a skateboard equipped with a brake at 15-20 mph for a distance of ½ mile with a downhill inclination of 4-6 degrees will generate brake temperatures between 250° F. and 350° F. Larger riders traveling a longer distance, such as a mile, can generate brake temperatures in excess of 500° F. Urethane and rubber wheels are heat sensitive and will soften to a point of deformation at a temperature of 225° F. As temperatures rise to 300° F. wheels lose the resilient integrity required to maintain their form and can no longer support the rider. Given the use of small-wheeled vehicles by adult riders, heat generated by the brake must be given design consideration to provide for safe, reliable operation over prolonged use.
The invention disclosed was developed over a period of several years by testing various methods for braking small wheel vehicles such as skateboards and small carts. Methods that were tested include drag brakes of various designs, and mechanisms that apply frictional pressure to the wheel surface, The drag brake proved ineffective at delivering enough braking force to slow an adult rider at speeds in excess of 15 mph. A variety of mechanisms were devised tat applied frictional pressure directly to the wheel surface. These mechanisms proved to be ineffective due to heat build up at the wheel. During operation, frictional heat would melt wheels leaving the rider in a perilous condition. Therefore, it became apparent that the materials used to resist frictional force were just as important as the application of force itself. For our application, a mechanism needs to provide enough braking force to slow a small wheeled vehicle carrying an adult rider at speeds in excess of 40 mph without melting the wheels or damaging the brake mechanism. The following is a list of desired operational specifications:
1) The brake needs to be readily adaptable to common wheel axles and commercially available small wheels.
2) The brake must operate to a rider's expectations. Specifically, the brake should operate in a smooth and reliable manner over a minimal distance of at least a mile while traveling downhill at w s ranging from 0-40 mph. An adult rider would be defined as a body having a weight of approximately 180 pounds.
3) The mechanism is preferably hand operated to provide a well regulated and smooth slowing of the vehicle. Hand operation leaves riders feet unencumbered to provide for maximum stability and control.
4) The brake has to effectively transfer frictional heat, generated during operation, away from heat sensitive wheel hubs and tires and into an axle support structure that will not be damaged by thermal loading. Heat must then be effectively convected away from this structure to provide cooling for the brake.
5) The brake must provide thermal insulation for wheels for maximum durability.
6) The brake mechanism must be scaleable to accommodate different size wheels, axles, vehicles riders, hills and performance needs.
7) The mechanism would need to be of a reliable, durable, unobtrusive design that is easy to maintain and repair.
The brake mechanism described herein has been extensively tested on a variety of vehicles, under a variety of operational conditions and has achieved all of the above operational specifications.
Prior art has not provided design consideration for frictional heat generated during brake operation. An example of this is found in U.S. Pat. No. 4,076,266 to Krausz (1978). The Krausz art provides a brake mechanism that utilizes a piston that seats a friction member at it's end, which bears against a brake disc fitted to the inside face of a wheel. When activated, the friction member is brought into contact with the spinning brake disc, which is in direct contact with the wheel. She friction member is intrinsically non-conductive and therefore stops frictional heat from entering the axle support structure. Therefore, as a rider travels downhill and frictional force is applied to the wheel, frictional heat loads directly into the brake discs and then into the wheels. When the brake disc and wheel reaches a temperature of 225° F. the wheel begins to soften to a point of deformation and starts to melt. The Krausz art does not provide for a place for heat to move into apart from the brake disc and wheel. Krausz did not recognize heat as being an issue of concern as evidenced by the use of the friction member and lack of mention within the art
In addition, the Krausz art specifies the fiction member to be limited in size to the diameter of the engaging piston. This limitation does not provide adequate frictional surface area to effect braking force necessary to stop an adult rider traveling under the influence of gravity at any speed greater than 10-15 mph.
In addition, the Krausz art specifies the piston to provide frictional force offset from the axle. This provides an unequal force upon the brake disc and wheel, which tends to bend the axle. This design problem leads to excessive wear of the brake disc, moving additional friction heat into the brake disc and wheel. The Krausz art would not be considered safe for operation by anyone other than a small child at a very slow speed. Another example is discussed within U.S. Pat. No. 4,295,547 to Dungan. The Dungan art describes two separate means of braking a small wheel vehicle. In both instances the art provides for a friction member to apply frictional pressure to a disc attached to the wheel face, whereby isolating frictional heat from the axle support structure. Frictional heat generated during brake operation is directed into the brake discs and the wheel face, as does the Krausz art. The Dungan art provides for an annular friction member, which is an improvement over the Krausz art, however, Dungan, like Krausz does not provide design consideration for frictional heat generated during operation. During normal operational use, frictional heat is directed into the wheels until such time as the wheel temperature reaches 225° F., and begins to melt, placing a rider in a dangerous situation. This temperature can be reached within a distance of 100 feet. In addition, proper design of a small wheel brake involves not only making provision to insulate the wheels from frictional heat, but also to provide a location for heat to reside that will not be damaged by thermal loading. This location should be able to withstand temp
Shriver J. Allen
Swann J. J.
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