Implements or apparatus for applying pushing or pulling force – Fluid pressure – Vehicle attached
Reexamination Certificate
2000-05-01
2001-10-23
Watson, Robert C. (Department: 3723)
Implements or apparatus for applying pushing or pulling force
Fluid pressure
Vehicle attached
Reexamination Certificate
active
06305668
ABSTRACT:
TECHNICAL FIELD
This invention relates to a compact lifter, and more particularly to a compact lifter with two guide posts or shafts and first and second linear slide bearings on each of the posts so as to provide improved bearing configurations to substantially prevent deviation from the desired lifting path.
BACKGROUND OF THE INVENTION
Conventional lifter assemblies have included a top mounting plate by two pair of shafts located thereunder in order to extend and retract the mounting plate so as to lift a workpiece into a desired location. These lifter assemblies are used extensively in manufacturing operations, and find special utility in automotive manufacturing operations for lifting automotive workpiece components to facilitate the placement of the workpiece during the manufacturing operation.
In the prior art lifter assemblies, the top mounting plate has a linear actuator cylinder centrally located for lifting the mounting plate, and the pairs of shafts have generally supported base and intermediate plates, where the base plate is slidably attached to a first pair of shafts by a first pair of housings having bearings to slidingly support the shafts, while the intermediate plate is slidably attached to the second pair of shafts by a second set of housings and their respective bearings. This has created three distinct problems for modern manufacturing plants.
First, the prior art lifter assemblies required sufficient physical space for both the upward stroke and the bottom stroke of the lifter plate and rods for the lifter assembly. Although attempts have been made to solve this space problem, see for example U.S. Pat. No. 5,690,315, in which two pair of substantially parallel shafts are provided wherein one pair of shafts has the top mounting plate connected to the top of the shafts, while the bottom of the shafts are connected to a separate cross support member, which is, in turn, connected to yet another set of shafts, bearings and all the other necessary parts. This meant that the '315 compact lifter assembly did not require the shafts connected to the top mounting plate to extend beyond the bottom of the lifter assembly, thereby solving the problem of the required sufficient physical space for both the upward and bottom strokes. However, the '315 patent does not address the second and third problems that were presented by the prior art devices.
The second problem presented is that these lifter assemblies are used in very dirty environments, and any shavings, weld flash, or the like which are the by-products of the manufacturing operation, can become embedded directly in the bearings, scratching the cylindrical surface of the shaft, or the particles can become embedded in the lubricant used around the shafts and then be dragged into the bearings, causing great harm to the overall system. Traditionally, the lifter assemblies have taken up such a large “footprint” in the plants, that an enclosure to alleviate this problem has been impractical. The reason that the enclosure was not possible is that a constant ratio is needed for direct and constant contact between the actuating cylinder and the moving mounting plate in order to keep the closed dimension of the lifter kept at a constant, in addition to the necessity for keeping the stroke plus bearing ratio constantly engaged. Once these ratios are kept constant, the total workings of the lifter may be enclosed within a tolerably sized sheet metal guard to prevent outside contaminants from entering the enclosed space, thereby preventing harm to the inner workings. As one can imagine, it would be a real advantage to provide an enclosure over the entire unit, both in the retracted as well as the extended positions, such that the working mechanisms are protected from the working environment atmospheric impurities.
Moreover, a third problem arose in the prior art assemblies in that the conventional two post lifters actually included four posts, rather than two, to allow for the size of the lifter in an attempt to provide a sure and direct path for the shafts to permit reliable lifting and positioning of the workpiece. It would be a great advantage to the art to be able to actually only have two posts in a “two post” lifter as additional costs to the customer would be alleviated. The prior art four post “two post” lifters needed all four posts in order to have the two additional guide posts or shafts to allow for the size of the lifter in a closed state to be contained in the least amount of space. Furthermore, the additional posts or shafts were necessary to prevent deflection in position and path because the first set of shafts did not support the cylinder in the extended position. The additional number of shafts merely added to the problem of environment dirt contamination because there were twice as many shafts that could have problems.
Therefore, it would be a great advantage to the compact lifter if a new compact lifter could be discovered that would alleviate the space problem, prevent contaminants from entering the machinery, and merely utilize two posts, rather than four or six, for a “two post” lifter.
SUMMARY OF THE INVENTION
The present invention seeks to address these three problems while providing additional reliability of the lifting operation itself, and substantially eliminating any deviation from the position from time to time. This is achieved by a double set of bearings on each of two guide shafts, or posts, in the event of a two post compact lifter, and four guide shafts or posts in the event of a four post compact lifter. Furthermore, this linear configuration allows for exterior plates to be placed around the working mechanisms such that they can be shielded from outside contaminants, including, e.g. Weld flash, dirt, dust, and other by-products of the manufacturing operation. A compact lifter made in accordance with the present invention can include a two post lifter, a four post lifter, or any number of appropriate posts for a lifter, all using these same principles. These compact lifters will produce reliable, predictable and accurate results while minimizing the cost to manufacturer, house and maintain, as well as providing the manufacturing industry with a true two post compact lifter that will extend the life of the actuating cylinder rod bearing and its seal, being protected from atmospheric impurities.
Furthermore, compact lifters of the present invention maintain a compact size relative to the stroke of the unit, and the linear relationship of the “stacking” of the bearings provide much greater repeatability than the prior art.
Moreover, due to the exterior plates promoted in the present invention, a pneumatic lock-out pin and electrically shut-off mechanism and arrangement is now possible in a new way. During maintenance of the compact lifter, a safe means is necessary to protect the maintenance workers. Prior art inventions did not have the configuration which made possible a pneumatic lock-out device, although the present invention does. The actual lock-out device and pin are the subject of my concurrently filed patent application entitled “ELECTRICAL AND PNEUMATIC LOCK-OUT DEVICE”.
Other objects, advantages and applications of the present invention will become apparent to those skilled in the art. For instance, individual lifting devices may require more or fewer posts for lifting, and the advantages of the present is invention can be realized by merely including more or fewer guide posts or shafts and bearing configurations. This extension of my invention can be made by a person of ordinary skill in the art without having to perform undue experimentation. Additional embodiments of the present invention will become apparent when the following description of the best mode contemplated for practicing my invention is read in conjunction with the appendant drawings.
REFERENCES:
patent: 3946988 (1976-03-01), Kehren
patent: 4323141 (1982-04-01), Ragan et al.
patent: 5690315 (1997-11-01), Thomas
Cargill Lynn E.
Watson Robert C.
LandOfFree
Compact lifter does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Compact lifter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Compact lifter will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2552886