Implements or apparatus for applying pushing or pulling force – Apparatus for hauling or hoisting load – including driven... – Device includes rotatably driven – cable contacting drum
Reexamination Certificate
2000-02-08
2001-11-27
Matecki, Katherine A. (Department: 3653)
Implements or apparatus for applying pushing or pulling force
Apparatus for hauling or hoisting load, including driven...
Device includes rotatably driven, cable contacting drum
C248S329000, C362S401000, C362S407000
Reexamination Certificate
active
06322053
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates generally to balancing systems of the type used in manufacturing facilities.
II. Description of the Prior Art
There are many manufacturing operations which require a heavy load to be lowered from an elevated position and to a lower position in preparation for a manufacturing and/or assembly operation. For example, in the manufacture of automobiles with hoods or rear hatchback doors, it is conventional to utilize a carrier to move the jig fixture centering the closure from an elevated position and to a predetermined lower position where the closure is secured to the vehicle body.
In order to provide a controlled movement of the jig fixture or other load from an elevated position and to a lower position, it has been previously known to utilize one or more pneumatic balancers. Such pneumatic balancers typically have an elongated cable with a free end secured to the load. As the load is lowered from an elevated and to a predetermined lower position, the pneumatic balancers exert an upward force on the load to thereby control and cushion the downward descent of the load as it is moved into its assembly position.
One disadvantage of these previously known balancing systems, however, is that certain vehicle components, such as vehicle hoods or hatchbacks, require a very heavy jig fixture, e.g. 1700 pounds, such that even a pair of pneumatic balancers is inadequate to provide to the jig fixture the vertical compliance required in its lower position to self-locate it onto the vehicle with a low level of constraint transmit to this vehicle. While it is possible to multiply by 2, 3 or 4 the number of these pneumatic balancers in order to increase the upward force exerted on the load during its descent, such pneumatic balancers are relatively expensive and are also subject to periodic maintenance and repair.
The previously known pneumatic balancers conventionally apply a substantially constant force, e.g. 100-300 pounds each, upwardly on the load, e.g. 1800 pounds during the entire descent of the load from its elevated and to its lower position. With two pneumatic balancers, only 30% of the weight can be compensated and the 70% remaining will be supported by the vehicle shell, causing not only some damage on the contact area, but generating also an inaccurate setting of the closure onto its opening.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a force multiplying device for use in conjunction with a balancing system which overcomes all of the above-mentioned disadvantages of the previously known devices.
In brief, the device of the present invention comprises a base which is secured to the load so that the base moves in unison with the load. A lever is pivotally secured about an intermediate point on the lever to the base about a generally horizontal axis.
A fixed length flexible member, such as a chain, has one end secured to a first end of the lever and a second end fixedly secured to a support position above the load. The fixed length flexible member is dimensioned so that it is in a fully extended position when the load is in the predetermined lower position for the assembly and/or manufacturing operation.
An elongated rocker arm has a first end in abutment with the base while the cable from a balancer, such as a pneumatic balancer, is secured to a second end of the rocker arm. The second end of the lever, in turn, is pivotally secured to an intermediate point of the rocker arm. Consequently, as the load nears the predetermined lower position, the first end of the lever pivots upwardly due to the force exerted by the fixed length flexible member. In doing so, the lever simultaneously pivots the second end of the rocker arm, i.e. the end of the rocker arm connected to the balancer cable, downwardly to thereby exert an increased downward stroke on the cable and the corresponding increased upward force on the load. This increased upward force remains directly proportional to initial counterbalancing effort and can be accurately adjusted to exactly match the weight of the jig fixture as the load nears its final lower position.
REFERENCES:
patent: 1847819 (1932-03-01), Davies
patent: 2514307 (1950-07-01), Boyd
patent: 1439125 (1966-04-01), None
patent: 1114348 (1968-05-01), None
patent: 1017647 (1983-05-01), None
Gifford, Krass, Groh Sprinkle, Anderson & Citkowski, P.C.
Matecki Katherine A.
Valiant Machine & Tool Inc.
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