Material or article handling – Elevator or hoist and loading or unloading means therefor – Comprising means enabling additional movement of carrier or...
Patent
1994-08-06
1996-11-12
Bucci, David A.
Material or article handling
Elevator or hoist and loading or unloading means therefor
Comprising means enabling additional movement of carrier or...
60591, 10026906, 414785, F15B 1122
Patent
active
055733662
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to a hydraulic device incorporating a cylinder-piston assembly, and more particularly a double acting hydraulic device having at least two cylinder-piston assemblies which operate synchronously.
2. Description of the Prior Art
A device having a double acting cylinder-piston assembly is known from FR-A-2 380 218.
Because the effective piston surfaces are the same in the chambers mutually connected by the direct connection, the quantity of oil displaced from the one chamber will provide in the other chamber an equal displacement of the relevant piston. The valve means bring about a synchronous adjustment of the pistons at the end of each stroke. Any leakage of oil from the two chambers mutually connected by the direct connection would normally result in a nonsynchronous position of the pistons, although the movements continue to proceed at exactly the same speed. Use of the said valve means results in the oil that may be lost through leakage being supplemented via the bypass at the end of each stroke.
Due to the non-return valves oil under pressure can only be fed in one direction, in the shown embodiment in the direction in which the piston rod extend. The ingoing stroke occurs due to external force.
SUMMARY OF THE INVENTION
The invention has for its object to provide a device of the kind set forth above in which the cylinder-piston assemblies can be fed with oil under pressure in two directions, such that the piston rods can be extended as well as retracted by oil under pressure.
In a hydraulic device according to the invention this object is achieved with the characterizing measures described herein In a specific embodiment of the invention easily available identical cylinder-piston assemblies can be used. The effective piston surfaces are the same in all chambers of these assemblies so that in a random series connection the desired synchronous operation is automatically obtained.
In applications wherein it is not possible to work with cylinder-piston assemblies with a continuous piston rod a preferred embodiment of the invention described subsequently can be applied. Also in this case the same effective piston surface of the mutually communicating chambers is obtained, which ensures the desired synchronous operation.
With the measure as characterized in that a further valve is formed by the piston in association with openings of the bypass in the cylinder wall a simple, and reliable construction is achieved.
A further favorable development is characterized in that the relevant end position both valve means are opened so that hydraulic oil fed from a pressure conduit can flow through the chambers connected in series of the cylinder-piston assemblies. Venting of the cylinders hereby takes place automatically and after a possible disassembly the system can in this manner be filled with oil very rapidly, wherein any air that may be present is simply displaced.
With a further embodiment is achieved that the valve means are simple to maintain. By removing the pistons from the cylinders the valve means become directly accessible.
According to a further development of the invention the device can comprise a number of pairs of cylinder-piston assemblies each connected in series, wherein the hydraulic control circuit comprises valve means for connecting the pairs of assemblies at choice in parallel or in series. when the pairs are connected in series an absolutely precise synchronous operation of each of the cylinder-piston assemblies is achieved, wherein each of the assemblies produces force corresponding to its load, while in the case of the parallel connection of the pairs a greater force can be generated at a lower speed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows schematically a fork-lift truck according to the invention.
FIG. 2B shows a cross section according to line IIA--IIA of FIG. 2.
FIG. 2B shows a cross section according to line IIB--IIB of FIG. 2.
FIG. 2 shows a diagram elucidating the invention.
FIG. 3
REFERENCES:
patent: 855266 (1907-05-01), Thorschmidt
patent: 2536068 (1951-01-01), Lehmann
patent: 3393635 (1968-07-01), Richardson
patent: 3590581 (1971-07-01), Biarchi
patent: 3998312 (1976-12-01), Ragigade
patent: 4157066 (1979-06-01), Pretty
patent: 4641894 (1987-02-01), Belart
patent: 4908522 (1990-03-01), Crumb et al.
patent: 5011363 (1991-04-01), Conley, III et al.
Bucci David A.
Zovko Mark
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