Implements or apparatus for applying pushing or pulling force – Hoisting truck – Single throw lever
Patent
1986-12-08
1988-05-03
Watson, Robert C.
Implements or apparatus for applying pushing or pulling force
Hoisting truck
Single throw lever
254122, 248421, B66F 322
Patent
active
047415126
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a load-supporting apparatus.
More particularly, the load-supporting apparatus according to the invention is concerned with an apparatus which is connected to a stand arranged on the floor by means of scissor-like connecting rods; at least two of the connecting rods are each coupled to an axle borne by the stand, and the height of which is adjustable via at least two spring units, each of which has different characteristics and each of which has a starting position in which it is completely relaxed ro relaxed to a maximum extent, and a bearing is assigned to one end of each spring unit and an abutment to the other end of each spring unit.
Load-supporting apparatuses of this type are frequently used in workshops and especially in garages and automobile repair shops. A typical example of such a load-supporting apparatus is described in German Offenlegungsschrift No. 3,240,952, in which the lifting unit has at least one hydraulic cylinder. Since the connecting rods, which have a scissor-like arrangement, necessarily lead to non-linear characteristics for the loading of the lifting unit during the movement of the load-supporting apparatus - formed in this case by two rails - and, this publication proposes operating the lifting unit under different pressures. This is possible without problems in the case of fluid motors of this type. However, for handling relatively small loads, for example in automobile workshops for lifting apparatuses for a mechanic lying underneath a chassis, a fluid (i.e. hydraulic or pneumatic) lifting apparatus with a fluid reservoir and pump is a relatively expensive matter.
This also applies to a design according to German Pat. No. 2,941,454, in which, in order to avoid relatively high loading of the lifting unit at the beginning of the lifting movement, i.e. at the lower end of the path travelled by the load-supporting apparatus, the vertical piston rod of the hydraulic cylinder unit acts on the hinge point of the scissors in the middle of two connecting arms connected to one another by a hinged joint. Although this makes it possible to avoid increased loading of the lifting unit at the lower end, a load peak occurs at the upper end. In this case too, the hydraulic system would be relatively expensive.
U.S. Pat. No. 3,096,059 and EP-A No. 0 142 919, which has not previously been published, have disclosed load-supporting apparatuses of the type stated at the outset, these designs on the one hand making it possible to avoid an expensive driving hydraulic system and on the other hand providing a certain degree of compensation for the load differences arising from the connecting rod geometry, by means of an additional spring which comes into contact, only toward the end of the downward movement of the load-supporting apparatus, with its abutment on the said apparatus (U.S. Pat. No. 3,096,059) or on the stand (EP-A No. 142,919). The locking apparatus is in the form of a brake in the case of the design according to the U.S. proposal, but it is completely missing in the case of EP-A No. 142,919, because here the load-supporting apparatus need only be adjusted between a fully collapsed and a fully extended position; in fact, it is only intended to serve as a support for a television or the like. A similar application is intended in the case of the US-A too, so that in both cases the forces acting on the springs will be fairly constant.
lt is the object of the invention to design a load-supporting apparatus for relatively small loads in an economical manner and in such a way that it can be adjusted for different loads. This is achieved, according to the invention, by connecting the spring units, (15,16) to a bearing and an abutment over the entire lifting height of the load-supporting apparatus (5); and locking apparatus (17) is in the form of an adjusting means which permits the starting position of at least one spring unit (15 or 16) to be fixed at different lifting heights of the load-supporting apparatus (5).
Spring units having locking devices in the form of pneuma
REFERENCES:
patent: 1327103 (1920-01-01), Knowles
patent: 3096059 (1963-07-01), Johnson
patent: 3116910 (1964-01-01), Moore
patent: 3645488 (1972-02-01), Sturhan
patent: 4558648 (1985-12-01), Franklin et al.
patent: 4659052 (1987-04-01), Nagata
Elkuch Harald
Elkuch Sigmund
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