Elevator – industrial lift truck – or stationary lift for vehicle – Transportable elevator
Patent
1998-02-11
2000-06-06
Olszewski, Robert P.
Elevator, industrial lift truck, or stationary lift for vehicle
Transportable elevator
187211, 187269, 254 10C, B66B 916
Patent
active
060706996
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic platform lift, in particular a motorcycle platform lift, comprising a parallelogram chassis, in which on one of the two parallel lifting arms a hydraulic cylinder, supported on the sub-frame, engages the one lifting arm at an articulation point on a projection directedly downwardly therefrom to beneath the pivot axis of the one lifting arm on the sub-frame, in order to make available a favorable lever arm between the articulation point and the pivot axis of the one lifting arm for the force transmission of the hydraulic cylinder.
A platform lift known from prior art is depicted in FIGS. 2.1 to 2.3. The pressure force of the hydraulic cylinder which, in platform lifts of the above-described type, can be up to approximately 3 t, is here completely shunted into the sub-frame. This sub-frame as well as also the particular lifting arm must be dimensioned correspondingly thick in order to be able to absorb these forces. This leads to an unfavorable intrinsic weight/lifting-force ratio which is the reason why these lifts as a rule are reserved as stationary equipment for workplaces.
Furthermore, a factor affecting the intrinsic weight/lifting-force ratio disadvantageously is that the second lifting arm is pulled by the lifting arm acted upon by the hydraulic cylinder over the top-frame. This construction would by necessity lead to jamming of the parallelogram chassis with large loads to be lifted and for reasons of reduction of the intrinsic weight thinly dimensioned structural components of the platform lift.
From EP 0 047 976 A2 and U.S. Pat. No. 2,920,773 lifting devices are known in which the hydraulic cylinder supported on the sub-frame engages the sub-frame at an articulation point beneath the pivot axis of the one lifting arm on the sub-frame. For this purpose, this lifting arm comprises in this region a projection directed downwardly. Through this projection a very favorable lever arm for the transmission of the lifting force of the hydraulic cylinder onto the lifting arm is given.
Known platform lifts of the type under consideration here therefore for the reasons listed above have an intrinsic weight between approximately 140 to more than 200 kg with the lifting capability being approximately 400 kg.
SUMMARY OF THE INVENTION
It is the task of the present invention to provide a hydraulic platform lift, in particular a motorcycle platform lift, of the above-described type which has a substantially better intrinsic weight/lifting-force ratio than the comparable platform lifts known from prior art.
This task is solved according to the invention by means of a platform lift a tie member connecting the support point of the hydraulic cylinder on the sub-frame with the lifting arm is provided whose articulation point on the lifting arm is coaxial with its pivot axis.
In order to relieve the source-point of the lifting force of the hydraulic cylinder in the sub-frame, and to permit a deflection from horizontal into vertical motion, according to the invention the tie member from the line of the pivot axis of the lifting arm to the source of the lifting force on the cylinder base is provided. The superposition of these points, i.e. the absorption of the cylinder base in the sub-frame and the end point of the tie member cause the lifting force to experience a deflection about the pivot axis through equivalent tension force. In this configuration of the elements the lifting force of the cylinder is neutralized such that the sub-frame which substantially only must absorb the forces of the load to be lifted and can thus be dimensioned correspondingly thin. Therewith an intrinsic weight/lifting-force ratio of up to approximately 1/6 is possible.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following detailed description, reference will be made to the attached drawings in which:
FIG. 1 is a side elevational view of a platform lift of the present invention shown in an extended state.
FIG. 2.1 is a side elevational view of a prior art platform lift
REFERENCES:
patent: 2922533 (1960-01-01), La Barge, Jr.
patent: 3214136 (1965-10-01), Marks
patent: 4447042 (1984-05-01), Masui
patent: 5040637 (1991-08-01), Hawk
Flanagan John K.
Flanagan John R.
Grip GmbH
Olszewski Robert P.
Tran Thuy V.
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