Elevator – industrial lift truck – or stationary lift for vehicle – Stationary lift for roadway vehicle or required component... – Having position lock for engaging sustaining drive means or...
Reexamination Certificate
1999-09-14
2001-02-13
Kramer, Dean J. (Department: 3652)
Elevator, industrial lift truck, or stationary lift for vehicle
Stationary lift for roadway vehicle or required component...
Having position lock for engaging sustaining drive means or...
C187S209000, C187S390000
Reexamination Certificate
active
06186280
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to lift assemblies for raising and lowering a vehicle, and, more particularly, to a safety system for use with a multi-post lift assembly used to raise and lower a vehicle.
2. Description of the Related Art
Lift assemblies are well known in the art, particularly in the automotive servicing field, where a technician must often raise an automobile to a predetermined height above the ground in order to make appropriate repairs. Automotive lift assemblies can be constructed in a variety of configurations. For example, one type of lift assembly incorporates a centrally disposed hydraulic shaft that includes a plurality of arms. The arms are extendable to support the vehicle at prescribed load bearing positions. Single post systems, however, have a disadvantage of requiring an underground tunnel within which the hydraulic post can be fully retracted to allow the vehicle to be placed in position for lifting. Such an arrangement is complicated to construct and has an additional disadvantage of being permanently fixed the location constructed.
Other vehicle lift assemblies incorporate multiple posts that are positioned at predetermined locations for raising and lowering the vehicle. For example, one such lift arrangement incorporates two posts, one on either side of the vehicle. Each post includes arms that can be extended to support the vehicle at the load bearing positions. Another system incorporates four posts located at predetermined positions that define a rectangular area. A platform assembly is attached to the four posts and functions to support the vehicle during lifting and lowering operations. Lift assemblies that incorporate multiple posts typically include a lifting mechanism coupled to each post. The lifting mechanism can be mechanical, or hydraulic in nature. For example, a screw type or hydraulic piston arrangement can be provided to apply an appropriate force and allow the posts to raise and lower the vehicle in unison. Each post can be provided with a manual lock that prevents inadvertent movement of the vehicle, or the lift assembly, while the technician services the vehicle.
During normal operations, it is imperative that the lifting mechanism of each post operate in a synchronous manner. Any deviation in the operation of one post will result in the vehicle being tilted in an unsafe manner. This situation will often place the vehicle in an unsafe or unstable orientation wherein the vehicle can be damaged and/or the technician can be injured. In general, the greater the number of posts that are used in the vehicle lift assembly, the greater the probability that one of the lifting mechanisms will malfunction, hence causing the lift assembly to tilt to an unsafe orientation.
There are several conditions that can result in a lift assembly being tilted to an unsafe orientation. One of the most common conditions occurs when a technician inadvertently forgets to disengage the manual lock at one of the posts. If the lift platform is either raised or lowered, the post (or posts) that was left locked will be unable to move, while the remaining posts will be free to move in the selected direction. Hence, the lift platform will be tilted such that the vehicle will occupy a dangerous orientation. If the technician does not detect the malfunction, the lift platform will continue to tilt until the vehicle falls off or the maximum travel distance of the posts have been reached. Further, such a condition can result in damage to the lift assembly.
Accordingly, one disadvantage of current multi-post lift assemblies is the inability to detect when the lift platform has tilted to an unsafe orientation. Another disadvantage associated with current multi-post lift assemblies is the inability to automatically suspend operation of the lift mechanism when the lift platform has tilted to an unsafe orientation.
DISCLOSURE OF THE INVENTION
There exists a need for a lift assembly capable of detecting when a lift platform has tilted to an unsafe orientation, and interrupting operation of the lifting mechanism. This and other needs are addressed by the present invention wherein a safety system for a lift assembly detects when a lift platform has tilted to an unsafe orientation and interrupts operation of the lifting mechanism, thereby providing a technician an opportunity to correct the problem.
In accordance with one aspect of the invention, a vehicle lift assembly is provided for preventing accidental slippage of a vehicle therefrom. The vehicle lift assembly comprises a plurality of vertically disposed posts, a runway, a hoist system, and a sensor arrangement. The runway is slidably coupled to the plurality of vertical posts, and configured to receive the vehicle thereon. The hoist system supplies the force necessary for elevating the runway along the plurality of posts. The sensor arrangement is used to detect whether the runway has tilted beyond a predetermined angular displacement. Furthermore, the sensor arrangement provides an indication of the orientation of the runway. A lift control circuit controls the hoist system to selectively elevate the runway in a prescribed direction. The lift control circuit also receives the tilt warning signal from the sensor arrangement. Upon receiving the tilt warning signal, the lift control circuit suspends operation of the hoist system in order to prevent the vehicle from sliding off the runway.
In accordance with another aspect of the present invention, a safety system is provided for use with a vehicle lift assembly having: a plurality of vertically disposed posts, a runway slidably coupled to the plurality of vertical posts for receiving the vehicle thereon, and a hoist system for elevating the runway relative to the plurality of posts. The safety system comprises a sensor arrangement and a lift control circuit. The sensor arrangement is used for detecting whether the runway has tilted beyond a predetermined angular displacement, and providing an indication of the orientation of the runway. The lift control circuit receives the tilt warning signal, and controls the hoist system to selectively elevate the runway in a prescribed direction. Further, upon receiving the tilt warning signal, the lift control circuit interrupts operation of the hoist system to prevent the vehicle from inadvertently sliding off the runway.
The present invention advantageously provides the ability to automatically suspend operation of the lift assembly if the sensor arrangement detects that the runway has tilted to an unsafe orientation. Hence, potential damage to the vehicle, or harm to the technician, as a result of the vehicle sliding off the runway can be minimized. Once operation of the runway has been suspended, the technician can examine the lift assembly to determine the cause of the malfunction. The lift assembly of the present invention can further include an alarm system to alert the technician when the tilt warning signal has been output by the sensor arrangement. The alarm system can be configured to provide visual and audible signals. Additionally, the hoist system can be hydraulically or mechanically driven depending on the specific implementation. Further, the safety system of the present invention can be adapted to work with various types of existing lift assemblies.
Additional advantages and novel features of the present invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
REFERENCES:
patent: 2238573 (1941-04-01), Steedman
patent: 3985207 (1976-10-01), Petit
patent: 4134501 (1979-01-01), Tune
patent: 4225117 (1980-09-01), Suzuki
patent: 4247922 (1981-01-01), Jackson et al.
patent: 4585092 (1986-04-01), Dossier
patent: 4706458 (1987-11-01), Corght
patent: 501
Chin Paul T.
Kramer Dean J.
McDermott & Will & Emery
Snap-on Technologies, Inc.
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