Material or article handling – Self-loading or unloading vehicles – Loading or unloading by other carrier or mover means – and...
Reexamination Certificate
1999-10-23
2001-02-06
Olszewski, Robert P. (Department: 3652)
Material or article handling
Self-loading or unloading vehicles
Loading or unloading by other carrier or mover means, and...
C414S917000, C296S057100, C280S495000, C187S272000
Reexamination Certificate
active
06183187
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to lift gates used to bring loads to and from ground level and the level of a vehicle's payload area. Specifically, the invention relates to lift gates that also provide a tow hitch for pulling additional loads.
2. Description of the Related Art
Lift gates are typically mounted at the rear of trucks and the like to bring payloads from ground level up to the bed of the truck. A difficulty associated with conventional lift gates is that they often prevent the use of tow hitches.
One prior art solution has been to recess the tow hitch under the vehicle body so that raising and lowering the lift gate does not interfere with the hitch. However, such a location greatly reduces the usability of the hitch. The recessed hitch complicates access, increases the risk of jack-knifing the pulled load and reduces the effective turning radius of the vehicle-trailer combination.
Other prior art attempts include the inventions disclosed in U.S. Pat. No. 3,545,791 to Lugash and U.S. Pat. No. 3,638,811 to Robinson, both of which are incorporated by reference for their teaching of conventional hydraulic lift gate technology, that use a hitch secured to the lift gate mechanism. These systems suffer from reliability and wear problems due to the stress placed on the lift gate mechanism by the towing forces of the hitch.
Further attempts to address these shortcomings have not been satisfactory. For example, U.S. Pat. No. 3,474,921 to Rossoni discloses a lift tailgate that offers an attachment point for a removable hitch. Although this allows the operation of the lift gate without interference from the hitch, it requires the additional effort of installing the hitch before it can be used. Furthermore, this attachment point presents another potential area for failure due to mechanical stress or operator error. Another attempt is disclosed in U.S. Pat. No. 3,666,121 to Denner et al. A movable hitch ball can be swung and locked into position. Again, this requires additional effort and is subject to mechanical failure or operator error. Finally, U.S. Pat. No. 3,112,833 to Novotney discloses a pintle hook for towing that is secured to the lift gate mechanism. To help reinforce the lift gate mechanism, Novotney locks the lift gate mechanism to the vehicle chassis thus offloading the towing forces from the mechanism. However, as with the other systems discussed above, the locking means represents another failure point and an additional complication in using the hitch.
Accordingly, what has been needed is a lift gate and tow hitch system where the hitch is easily accessible and does not interfere with the operation of the lift gate. What has also been needed is a lift gate and tow hitch system that presents the tow hitch in a position designed to minimize the risk of jack-knifing a towed trailer and maximize the turning radius of the vehicle and towed trailer. Additionally, there is a need for lift gate and tow hitch systems that have a lift gate that stores compactly when not in use to allow easy access to the vehicle payload area. There is also a need for a lift gate and tow hitch system that permits the use of a loading ramp. This invention meets these and other needs.
SUMMARY OF THE INVENTION
Generally, the invention comprises an integrated lift gate and hitch assembly configured to be secured to a vehicle chassis having opposing support brackets secured to the vehicle chassis, a cross brace carrying a hitch secured to the support brackets, opposing parallelogram linkages each having upper and lower arms and proximal and distal pivot members, wherein the proximal pivot members are secured to the support brackets, a lift gate rotatably attached to the distal pivot members, having a stop configured to prevent rotation of the lift gate away from the upper and lower arms past a generally horizontal position parallel with the vehicle chassis and configured to allow rotation of the lift gate toward the upper and lower arms to a generally vertical position perpendicular with the vehicle chassis, a torque member secured to the lower arms; and an hydraulic cylinder pivotally secured at one end to the support brackets and at the other end to the torque member; wherein when the lift gate is rotated to the horizontal position, extension of the hydraulic cylinder raises the lift gate from a lowered position to a raised position while maintaining the horizontal position and when the lift gate is rotated to the vertical position, extension of the hydraulic cylinder raises and inverts the lift gate into a stowed position above the hitch and below the vehicle chassis. Preferably, the lift gate further comprises a hinged extension that can unfold from the lift gate to the horizontal plane, but no further. The upper and lower arms carry support members to receive the hinged extension when the lift gate is inverted into the stowed position. The hitch is placed sufficiently aft to provide easy access, while maximizing the turning radius of the vehicle trailer combination; minimizing the risk of jack-knifing the trailer when reversing. Preferably, the hitch ball is recessed no more than about
6
inches. The system is configured to allow the use of a convention sliding loading ramp when the lift gate is lowered.
REFERENCES:
patent: 2989196 (1961-06-01), Lugash
patent: 3112833 (1963-12-01), Novotney
patent: 3113684 (1963-12-01), Novotney
patent: 3138270 (1964-06-01), McCarty
patent: 3258140 (1966-06-01), Appleman
patent: 3369678 (1968-02-01), Robinson
patent: 3429464 (1969-02-01), Robinson
patent: 3474921 (1969-10-01), Rossoni
patent: 3498481 (1970-03-01), Size
patent: 3528573 (1970-09-01), Denner
patent: 3545791 (1970-12-01), Lugash
patent: 3638811 (1972-02-01), Robinson
patent: 3666121 (1972-05-01), Denner et al.
patent: 3737055 (1973-06-01), Pettit
patent: 4078676 (1978-03-01), Mortenson
patent: 4395187 (1983-07-01), Corley
patent: 4722651 (1988-02-01), Antal
patent: 4763487 (1988-08-01), Wicks
patent: 4836736 (1989-06-01), Neagu
patent: 4930973 (1990-06-01), Robinson
patent: 5277275 (1994-01-01), Ablabutyan
patent: 5449267 (1995-09-01), Ablabutyan
patent: 3307857 (1984-09-01), None
patent: 3737651 (1989-05-01), None
patent: 49193 (1982-04-01), None
Maxon Lift Corporation
O'Connor Gerald J.
Olszewski Robert P.
Wittenberg Malcolm B.
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