Source: {"pile_set_name": "USPTO Backgrounds"}

The present invention relates generally to wheeled vehicles and more particularly to a three-wheeled vehicle having a pair of spaced wheels mounted on a parallelogram frame for leaning movement with the frame to positions of equilibrium.
Three-wheeled pedalled vehicles having a pair of spaced wheels mounted on a parallelogram frame are known in the art although they are rarely encountered. Such vehicles generally depend on the strength of the operator to control the configuration of the parallelogram frame by means of the handlebars. Whereas manual control of the parallelogram configuration is satisfactory for light-weight pedalled vehicles, problems arise when it is desired to provide power for driving certain of the vehicle wheels. Weight is necessarily added by the engine and drive train, thereby substantially increasing the load to be controlled by the operator. One solution in the prior art was to have the operator's legs control the vehicle inclination since the legs can generate greater force than the operator's arms. Nevertheless, with the increasing speed capabilities of powered vehicles, manual control systems for the vehicle inclination are believed to be unreasonably dangerous.
Other known three-wheeled vehicles have utilized small spaced-apart wheels which remain substantially vertically inclined so that only the vehicle frame leans into turns. But such a construction does not include a parallelogram frame and is somewhat self-defeating in that it lacks a primary advantage of the parallelogram frame, namely that the resultant of all forces is at all times directed through the center of gravity of the vehicle and point of contact of the vehicle wheels with the ground. Hydraulic cylinder load-leveling systems have been devised for four-wheeled automotive vehicles but these are believed to be unsuitable for three-wheeled vehicles including a parallelogram frame because the vehicle frame response to centrifugal force and inclined road surfaces is only indirectly sensed by separate pendulum, plumb bob, or mercury capsule. Such indirect sensing means are not believed to be sufficiently reliable or responsive for maintaining the balance of a three-wheeled vehicle having a parallelogram frame.
Accordingly, a primary object of the invention is to provide an improved three-wheeled vehicle having a pair of spaced wheels mounted on a hinged parallelogram frame.
Another object is to provide an improved three-wheeled vehicle including an automatic sensing device which controls an actuator to effect the lateral inclination of the vehicle to a position of equilibrium.
Another object is to provide an improved three-wheeled vehicle including a sensor directly responsive to the balance of the vehicle itself relative to a state of equilibrium and a power unit responsive to the sensor for keeping the vehicle in balance.
Another object is to provide an improved three-wheeled vehicle including hydraulic circuitry responsive to vehicle imbalance of automatically tilting the vehicle back to a position of equilibrium without over-correcting past the equilibrium position.
Another object is to provide an improved self-balancing three-wheeled vehicle which is simple in construction and efficient and reliable in operation.
These and other objects of the invention will be apparent to those skilled in the art from the summary and description of the invention which follows.