The present invention relates to a position-sensitive shock absorber with a one-piece cast body construction.
Suspension systems are essential to provide a smooth ride over rough surfaces and therefore just about all vehicles today are equipped with some type of suspension system. A number of different types of suspension systems have been used in the past. A simple shock absorber is a cylinder, or tube, containing oil and a piston. The piston has a number of small holes in it, called valves, that allow oil to flow from one side to the other of the piston. Whether the piston is moving in the compression stroke or rebound stroke, the oil must pass through the valves in the piston. The resistance of the oil in passing through the small holes eliminates much of the energy that is directed to the suspension system from, for example, the motion of a vehicle over an uneven surface.
Another type of shock absorber is the bypass shock absorber. Bypass shock absorbers are position-sensitive shock absorbers that use external passages that allow fluid to bypass the shock piston. Conventional bypass shock absorbers use a twin tube design. That is, the shock absorber has an inner tube and an outer tube. The inner tube contains a piston and when the piston moves through the inner tube it displaces oil, or some other fluid. On the compression stroke, the piston displaces oil and the displaced oil is transferred from the inner tube to the outer tube via a transfer port. On the rebound stroke, oil is drawn back into the inner tube. U.S. Pat. No. 6,296,092, incorporated herein by reference, is one example of a twin tube shock absorber with position-sensitive damping.
The twin tube design, however, has several drawbacks. For example, the twin tube design requires the manufacture of two separate tubes. In addition, since the twin tubes are separately manufactured, the twin tubes have to be assembled into a single unit. Obviously, this increases both the time that it takes to assemble a shock absorber and increases the cost of the final product. Moreover, additional assembly steps also increase the likelihood that the shock absorber will be incorrectly or defectively assembled.