Implements or apparatus for applying pushing or pulling force – Hoisting truck – Single throw lever
Reexamination Certificate
2000-03-27
2001-09-11
Hail, III, Joseph J. (Department: 3723)
Implements or apparatus for applying pushing or pulling force
Hoisting truck
Single throw lever
C254S122000, C254S126000, C254S0930HP, C254S00800R
Reexamination Certificate
active
06286812
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a lifting apparatus and, more particularly, to a portable lifting apparatus including a base frame, a support platform or table disposed above the base frame, a linkage assembly for connecting the support platform to the base frame while maintaining the support platform and base frame in generally parallel relation relative to each other, and a pneumatic actuator for elevationally moving the support platform relative to the base frame.
FIELD OF THE INVENTION
Lifting devices including a support platform connected to a base as through a scissor linkage assembly and which elevationally moves under the influence of a fluid operated system are known in the art. Many conventional lifting devices include a base comprised of a series of members arranged in a rectangular pattern and a floor plate which rigidly interconnects the members of the base. During their operation, the floor plate of such lifting devices is typically secured to a floor or ground surface as through lag bolts or the like to add strength and rigidity to the base and, thus, the lifting device. As will be readily appreciated, requiring such lifting devices to be secured in position severely limits their versatility and use.
Considerable weight may have to be supported by the platform of such lifting devices. Moreover, the elevational position of the support platform relative to the base may frequently change during operation of the lifting device. Accordingly, the fluid operated system of the lifting device is usually subject to the control of an operator. In many lifting devices, the fluid operated system includes an air spring or pneumatic actuator connected to a source of fluid pressure as through an operator controlled valve. Such an air spring typically includes an expandable/contractible bellows defining a variable volume chamber.
Because the bellows of such an air spring is continually expanded and retracted during operation, the walls of the bellows sometimes fail as a result of the stresses placed thereon. Besides the continuous expansion and retraction of the bellows, air springs have been known to fail for several other reasons and generally without any indication of their impending failure. Of course, failure of the air spring or bellows renders the lifting device inoperable. The bellows is typically carried between and sealed to a top plate and a bottom plate which are releasably secured as through fasteners to the scissor linkage assembly and the base frame, respectively.
As is well known in the art, replacement of the air spring has heretofore frequently involved a time consuming and tedious task. Access to the fasteners used to secure the top plate to the scissor linkage assembly are usually readily available and, thus, cause minimum problems. The fasteners used to releasably secure the bottom plate to the base frame, however, are considerably more troublesome. That is, access to the fasteners used to secure the lower plate of the air spring to the base frame is severely limited. Thus, the lifting device is often inverted or turned upside down from its normal operational position to gain access to such fasteners. Of course, having to locate suitable equipment capable of raising and inverting the lifting device exacerbates the problem of replacing/repairing the air spring, thus, adding to the downtime for the lifting device during its repair.
To permit the support platform to remain generally parallel to the base frame during operation of the lifting device, one end of the linkage assembly is required to slide along a predetermined linear path of travel relative to the base frame in response to elevational movements of the lifting device. Of course, there is a degree of friction involved as a result of the relative movement and metal to metal contact between sliding link ends of the linkage assembly and the base frame. Besides the gravitational weight of the support platform and fluid operated system, this friction engagement problem is exacerbated by the weight of any articles supported by the platform.
To significantly reduce the frictional engagement between the sliding link ends of the linkage assembly and the base frame, some lifting devices provide free turning rollers at the link ends. To allow the linkage assembly to upwardly move the table in response to expansion of the bellows of the air spring, each free turning roller at the end of the link is typically positioned or movably entrapped within gib structure. As will be appreciated by those skilled in the art, such gib structure limits movement of the roller along a predetermined path of travel and between set limits.
As a result of their substantially continuous movements, the rollers operably associated with such linkage assembly require regular maintenance and, occasionally, are required to be replaced. Heretofore known gib structures on the base frame, however, significantly hinder access to the rollers to provide regular maintenance thereon and/or replacement of such rollers. As with the fasteners used to releasably secure the air spring assembly to the base frame, the inability to gain access to the rollers provided to enhance operation of the linkage assembly presents a significant and well known problem with heretofore known lifting devices.
Thus, there remains a need and a desire for a lifting apparatus which is readily portable between locations and whose design allows for ready replacement and/or repair of the air spring assembly and access to the rollers used in combination with the linkage assembly thereby enhancing serviceability and maintenance.
SUMMARY OF THE INVENTION
In view of the above, and in accordance with the present invention, there is provided a lifting apparatus which is readily portable between locations and whose design allows for ready replacement and/or repair of component parts thereof to enhance both serviceability and maintenance of the lifting apparatus. In general, the lifting apparatus of the present invention includes a support table, a base frame disposed beneath the support table, a linkage assembly for maintaining the table and the base frame in generally parallel relation relative to each other as the table moves between raised and lowered positions, and a pneumatically operated actuator for moving the table between the raised and lowered positions.
One of the salient features of the present invention relates to the structural rigidity of the lifting apparatus. As will be appreciated from an understanding thereof, the structural rigidity of the lifting apparatus of the present invention allows the lifting apparatus to be moved between locations thereby promoting the versatility and usefulness of the lifting apparatus. In a preferred form of the invention, the rigid base frame is configured to accommodate laterally spaced tines of a moving device, such as a fork lift or pallet jack. As such, the lifting apparatus of the present invention can be readily and easily moved between location as required by the user thereof.
In a most preferred form, the rigid base frame includes a pair of rigid elongated and spaced end members disposed in generally parallel relation relative to each other and a pair of rigid elongated and spaced side members disposed in generally parallel relation relative to each other. The end members and side members are rigidly interconnected in vertically spaced relation relative to each other. One pair of the members for the base frame defines a surface for engaging that surface on which the lifting apparatus is to be disposed. As will be appreciated, the vertical spacing between the pairs of members defines an opening for accommodating the laterally spaced tines of the mobile device. To add further strength and structural rigidity thereto, the base frame can further include an elongated support member. Such elongated support member is preferably disposed between and rigidly connected toward opposite ends of that pair of members which are elevated from that pair of members defining the surface for engaging the support s
Autoquip Corporation
Hail III Joseph J.
Harbst John W.
Wilson Lee
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