Patent Application
20080231016
The present invention relates to transport truck trailers and more particularly to a slidable mounting assembly for the rear wheels thereof.
It is often desirable to tow or transport large objects such as buses, tractors, or other large machinery on a flatbed trailer. However, loading and unloading these objects on and off of the flatbed trailer can be difficult. In order to ease the loading and unloading of these large objects, flatbed trailers have been developed that tilt the entire bed of the trailer thereby providing a ramp with a relatively gradual incline. In order to present an optimum loading angle as well as to evenly distribute the load carried by the trailer, it has been found desirable to mount the wheels for such trailers in a manner permitting selective fore and aft shifting movement of the wheels relative to the trailer's load carrying bed. By this arrangement, the wheels may be shifted forwardly on the bed to permit tilting of the bed to a desired gradual loading angle, while the wheels may be shifted rearwardly after loading of the bed to provide even weight distribution of the load between the trailer wheels and the wheels of the prime mover vehicle.
An example of the type of trailer described in the previous paragraph is disclosed in U.S. Pat. No. 4,231,710 (Landoll). The trailer disclosed in Landoll comprises a single, relatively long, hydraulic cylinder beneath the bed of the trailer for shifting the wheel assembly forwardly from its normally rearmost roading position to a position permitting tilting of the bed, thereby bringing the rear end of the inclined bed close to the ground. One problem with the device disclosed in Landoll is that it cannot move the wheel assembly the entire length of the trailer because the hydraulic cylinder is too short. Lengthening the cylinder is not an option because this would create many unacceptable problems such as cylinder vibration during over-the-road travel, breakage and inadequate power for shifting the undercarriage, especially when considering the heaviness of many kinds of cargo on the bed. Another problem with the device disclosed in Landoll is that it takes a lot of power to actuate the large hydraulic cylinder. Yet another problem with the device disclosed in Landoll is that the cylinder is expensive to manufacture and maintain due to its relatively large size and weight.
Therefore, there is a need for a trailer having a movable wheel assembly that is capable of extending along generally the entire length of the trailer bed. There is further a need for a trailer having a moveable wheel assembly that is simple to maintain and efficient to operate.
The present invention comprises a trailer combined with a movable wheel assembly. The trailer comprises a front portion and a load carrying bed portion. The front portion is adapted to be combined with a prime mover vehicle. The front portion is combined with the load carrying bed portion at a pivot point so that the front portion and load carrying bed portion can pivot relative to each other. The load carrying bed portion of the trailer further comprises a front end and a rear end.
A rack and pinion means allows selective movement of the wheel assembly relative to the trailer. The rack is combined with the load carrying bed portion of the trailer, and the pinion is combined with the movable wheel assembly. A power assist means, such as a hydraulic motor, is combined with the movable wheel assembly and is adapted to rotate the pinion. Activation of the power assist means rotates the pinion and moves the wheel assembly in a first direction along the rack towards the front of the load carrying bed or in a second direction along the rack towards the rear of the load carrying bed.
As the wheel assembly is moved toward the front of the load carrying bed, the rear end of the load carrying bed can be lowered to the ground. This is accomplished by the actuation of a power assist means, such as a hydraulic lift cylinder. The lift cylinder comprises a first end and a second end. The first end of the lift cylinder is combined with the front portion of the trailer and the second end of the lift cylinder is combined with the load carrying bed portion of the trailer. Actuation of the lift cylinder causes the load carrying bed to pivot relative to the front portion of the trailer so that the rear end of the load carrying bed can be raised or lowered relative to the ground.
The invention is beneficial over existing slide axle trailers because the rack and pinion means powered by the hydraulic motor allows the wheel assembly to move generally the entire length of the load carrying bed. Further, the rack and pinion means powered by the hydraulic motor is a simpler and more cost effective design than the large hydraulic cylinders employed to move wheel assemblies on prior art slide axle trailers.
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A power assist means, such as a hydraulic motor 20, is combined with the movable wheel assembly 16 and is adapted to rotate the pinion 24. Activation of the hydraulic motor 20 in a first direction causes the pinion 24 to rotate in a first direction which moves the wheel assembly 16 along the rack 22 towards the front of the load carrying bed 10. Activation of the hydraulic motor 20 in a second direction causes the pinion 24 to rotate in a second direction which moves the wheel assembly 16 along the rack 22 towards the rear of the load carrying bed 10.
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The bumper 18 is located near the rear of the load carrying bed 10 and provides a stop point that prevents the wheel assembly 16 from sliding too far backward off of the end of the rack 22. The main deck transfer rollers 32 aid in supporting the weight of the load carrying bed 10 as the wheel assembly 16 is moved under the load carrying bed 10. The main deck transfer rollers 32 are combined with the wheel assembly 16 and are adapted to pivot about a central axis. The rollers 32 engage the load carrying bed 10 as the wheel assembly 16 is moved along the length of the bed 10 to help support the weight of the bed 10 and to help the wheel assembly 16 move smoothly in relation to the bed 10.
In some embodiments, the trailer comprises a winch 36, as seen in
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Having thus described the invention in connection with the preferred embodiments thereof, it will be evident to those skilled in the art that various revisions can be made to the preferred embodiments described herein with out departing from the spirit and scope of the invention. It is my intention, however, that all such revisions and modifications that are evident to those skilled in the art will be included with in the scope of the following claims.
