Patent Application
20070128011
N/A
N/A
A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyrights rights whatsoever.
1. Field of the Invention
The present invention relates to a load pushing mechanism for use in unloading pallets from pallet jacks and forklift vehicles.
2. Description of Related Art
A wide variety of goods are often transported and warehoused on wooden pallets. The goods are typically moved and handled using specialized vehicles adapted for lifting and moving fully loaded pallets. These vehicles, such as pallet jacks and forklifts, are typically wheeled vehicles having hydraulically actuated load-bearing forks that are capable of lifting the pallets upon insertion between the upper and lower pallet slats.
Oftentimes, however, the lift operator experiences difficulty in removing pallets from the lifting forks. This problem is particularly prevalent with pallet jack vehicles, as those vehicles typically have wheels projecting from the ends of each fork. Accordingly, the bottom of the pallet often catches on the wheels preventing the pallet from sliding off of the forks.
As a result of this problem, the prior art reveals a number of attempts directed to modifying lifting vehicles with mechanisms designed to push pallets off of the lifting forks.
For example, U.S. Pat. No. 2,787,393, issued to Horton, discloses an improved hydraulic load pushing and pulling mechanism for industrial trucks for moving loads onto and off the load platform of the truck. U.S. Pat. No. 3,182,836, issued to Sinclair, discloses a push-off attachment for use in removing a load from the tines of a forklift truck. U.S. Pat. No. 3,059,796, issued to Danserau, discloses a hydraulic system for removing materials from pallets. U.S. Pat. No. 3,640,414, issued to Brudi, discloses lift truck push-pull attachment for pulling loads onto the forks and discharging loads from the forks. U.S. Pat. No. 3,788,507, issued to Voss, discloses a lift truck adapted with a materials handling scoop having a push plate slidably mounted therein. Tongs connected to the back of the scoop and push plate are extended and retracted by a hydraulic cylinder. U.S. Pat. No. 4,268,210, issued to Ferguson, discloses an unloading mechanism for fork lifts in which a plate slides over the pallet on a fork lift and pushes the goods off the pallet. The plate is moved across the pallet by two arms connecting the plate to the forklift and operated by a hydraulic cylinder.
The devices disclosed in the prior art, however, are overly complex and not generally suited for use on smaller pallet jack vehicles. Accordingly, there exists a need for an improved pallet removal mechanism for use with a pallet jack.
The present invention overcomes the limitations and disadvantages present in the art by providing a hydraulically actuated mechanism for pushing loaded pallets from the forks of a forklift vehicle, particularly pallet jacks. In pushing pallet loads off the forks it is most desirable to apply the force directly to the pallet so as not to damage or topple the load. Accordingly, the present invention provides a hydraulically actuated ram comprising a push plate and a pair of hydraulic actuators connected to the vehicle proximal the rear end of the forks. The hydraulic actuators are tied into the vehicles existing hydraulic system by installing a T-fitting and an electrically operated, normally closed hydraulic valve. The hydraulic valve includes an output port in fluid communication with each of the hydraulic actuators. The pallet jack operator controls the hydraulic ram using a switch electrically connected to the hydraulic valve. Upon activation of the switch, the hydraulic valve is opened and high-pressure hydraulic fluid is fed to each of the hydraulic actuators thereby causing the actuators to force the pallet off the forks. The hydraulic actuators may be retracted either by spring force, or by hydraulic pressure. By providing dual hydraulic cylinders configured with output shafts directly coupled to the push plate, the present invention provides a powerful, yet compact, mechanism for pushing fully loaded pallets off of the forks. In an alternate embodiment, the hydraulic ram may include multiple stages to achieve sufficient push plate travel.
Accordingly, it is an object of the present invention to provide an improved hydraulic ram for pushing pallets from fork-type lift vehicles.
Another object of the present invention is to provide a compact, yet powerful, hydraulic ram that is easily installed on forklifts and pallet jacks.
Yet another object of the present invention is to provide a hydraulic ram having a pair of hydraulic actuators configured in parallel connection with a push plate.
In accordance with these and other objects, which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings.
With reference now to the drawings,
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Hydraulic actuators 22 may be returned to the retracted configuration by any suitable retraction force. In a first embodiment depicted in
