Material or article handling – Elevator or hoist and loading or unloading means therefor – Grab
Patent
1990-03-14
1991-10-22
Bucci, David A.
Material or article handling
Elevator or hoist and loading or unloading means therefor
Grab
B65G 4791
Patent
active
050590880
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to a suction lifter for a material handling device for workpieces, comprising suction surfaces and at least one pneumatic cylinder with a suction cup arranged at its end.
2. Description of the Prior Art
Arrangements are known in which workpieces are sucked up and lifted with such suction lifters for subsequent transportation in manufacture. This is common practice, e.g., in sheet metal fabrication, where a cut-out piece of sheet metal is lifted out of the basic sheet metal for further processing using the suction lifter. Subsequently, either the basic sheet metal or the piece cut out is removed. After positioning, the workpiece is again released by the suction lifter for further processing. It is possible, for example, to arrange a series of such suction lifters in parallel in order to pick up pieces punched out from a large sheet metal plate. It is also known that using appropriate controls, it is possible to pick up only some of the pieces punched out or to activate only some of the suction lifters present.
In a prior-art suction lifter of this class, in which the working cylinder is designed as a constant-pressure cylinder, the piston rod passes through both end faces of the cylinder, and the piston rod, which is of hollow design, carries the suction cup at one of its ends. A connection for the vacuum, which connection is controlled via a directional control valve, is provided at the other end of the piston rod. The stroke of the suction cup is also controlled via a directional control valve, which connects the pressure source or the vent hole with the first working chamber or with the second working chamber.
The control system for such a suction lifter is relatively expensive, because there are two directional control valves operating independently of one another for each suction lifter, and the directional control valves must be finely coordinated with one another and with other valves of the suction lifter. This makes the entire control device complicated and requires a number of additional position transducers.
SUMMARY AND OBJECTS OF THE INVENTION
The suction lifter according to the present invention, has the advantage over prior art arrangements in that only one directional control device is required and the control tasks of the second directional control device are integrated as an automatic control by connecting the first working chamber to the suction cup. The use of only one directional control device makes it possible to substantially simplify the control, because various displacement pickups are no longer necessary, so that program control components can also be eliminated.
According to another embodiment of the present invention, a check valve closing in the direction of the working chamber is arranged in the line between the second working chamber and the directional control device, and the check valve is bypassed by a bypass line, in which a pneumatic time function element is present in the direction of the directional control device. It is thus achieved that the lift with the workpiece sucked up takes place in a controlled manner.
According to another advantageous embodiment of the present invention, a 4/2-way valve is controlled pneumatically, and the dynamic pressure is taken from the line provided between the 4/2-way valve and the first working chamber via a pressure valve and a control line. The pressure valve is set so that it opens only when the suction cup lies upon the workpiece, as a result of which the pressure in the corresponding line rises, so that due to this automation, the switching into the lifting direction always takes place only when the suction cup indeed lies on the workpiece.
According to another advantageous embodiment of the present invention, a plurality of working cylinders are provided, and a control block is connected to each of the working cylinders so that additional lines can be dispensed with. One such control block comprises the 4/2-way valve with the entire control d
REFERENCES:
patent: 2247787 (1941-07-01), Schmidt
patent: 2665013 (1954-01-01), Socke
patent: 3076561 (1963-02-01), Rogers
patent: 3107794 (1963-10-01), Bechtold et al.
patent: 3899087 (1975-08-01), Tamble et al.
Bucci David A.
Keenan James
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