Handling: hand and hoist-line implements – Utilizing fluid pressure – Venturi effect
Patent
1997-01-24
1998-10-06
Kramer, Dean
Handling: hand and hoist-line implements
Utilizing fluid pressure
Venturi effect
414627, B66C 102
Patent
active
058166351
DESCRIPTION:
BRIEF SUMMARY
The present invention refers to a shock or speed variation valve for vacuum lifting devices.
For moving and transporting different types of objects short distances in modern goods handling it is frequently used vacuum lifting devices, of the type equipped with a flexible vacuum hose, which at one of its ends is connected to a vacuum source, preferably in the form of a pump, and which at the opposite end is provided with one or more suction nozzles, or alternatively some other type of coupling member, e.g. a hook. When the suction nozzle is placed against a surface of an object which shall be raised, and the vacuum pump is started, the suction nozzle due to the vacuum generated in the hose and in the nozzle will attach sealingly to the object. When thereupon the operation of the pump causes an increase of the sub-pressure the flexible hose will be "sucked in" thereby being shortened, whereby the load is raised. A lifting hose equipped with another type of coupling means e.g. a hook, will be shortened in a corresponding manner and thereby raise the load suspended from the other type of coupling means. In the vicinity of the suction nozzle or the alternative coupling means there is provided a vacuum valve, by means of which it is possible, in dependency of the degree to which it is opened, to alter the pressure ratio in the conduit, from a maximum negative pressure when the valve is closed, to a pressure substantially corresponding to the pressure of the surrounding atmosphere, when the valve is completely open. In this manner it is possible to set the desired lifting speed, to balance the sub-pressure thus that the load is maintained in an arbitrarily raised position and by further opening eventually to achieve that the vacuum becomes insufficient for lifting the weight of the load, whereby the load is lowered again. When the valve is completely opened and/or when the vacuum pump is turned off, the suction nozzle will come loose from the load, or the hose will be so mobile, that other types of coupling means easily may be unhooked. Lifting devices of this type are often used frequently in different material handling connections, whereby much heavy lifting work can be eliminated.
However, due to the big dynamical forces to which the hose and suction head are subjected during lift, there is a risk, which has not been sufficiently observed earlier, for damages to equipment and particularly injuries to personnel, attending to the lifting device, if the load for any reason should come loose in an uncontrolled manner during a lift or during balanced retention of the load in raised position, e.g. in that the load during the lift should hit some fixed object at the place of the lift, e.g. a railing, a wall or the like. Hereby the hose, due to the fact, that the load suddenly ceases to act in a direction opposed to that of the vacuum force, will be thrown upwards at a very high velocity and due to the flexibility of the hose it will be flinged about in an uncontrolled manner, whereby there is a risk that the comparatively heavy suction head/coupling means and the operating valve may hit other objects and cause damage to those or to itself and/or hit personnel dwelling thereabout, meaning an apparent risk for personnel injuries. Also in the case with suction heads, which are exposed at a possible coming loose of the load, a very rapid speed increase will arise as the openings of the suction head have an insufficient area for momentarily compensating the intense negative pressure in the hose.
The purpose of the present invention is to provide a shock or speed variation valve for a vacuum lifting device of the type described in the introduction, which in a simple and efficient manner and at rather low manufacturing costs, to a very high extent eliminates the problem described, and in order to achieve this the shock valve is designed in accordance with the characterizing part of claim 1.
Hereinafter the invention will be further described with reference to embodiments illustrated in the accompanying drawings.
FIG. 1 show
REFERENCES:
patent: 3322454 (1967-05-01), Mindrum
patent: 4561687 (1985-12-01), Bostrom
patent: 5035456 (1991-07-01), Messinger
patent: 5330314 (1994-07-01), Bennison
Kramer Dean
Ljungblad-Petre Maskin AB
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