Expansible chamber devices – Displacement control of plural cylinders arranged in... – Stroke of one working member adjustable relative to another
Patent
1984-05-15
1985-09-03
Maslousky, Paul E.
Expansible chamber devices
Displacement control of plural cylinders arranged in...
Stroke of one working member adjustable relative to another
92 136, 92 62, 92 75, 92108, F15B 1524, F01B 700
Patent
active
045385068
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a cylinder with a two-step movement, especially a welding gun cylinder for use in welding, there being in a housing with a first and a second end-piece, a first piston sliding in contact with the inside of the housing and a second piston arranged coaxially with the first piston and supporting a piston rod which moves sealingly through the first end-piece of the housing, there being mounted in the second end-piece a pressure medium tube passing through the first piston and through which pressure medium can be led into or out of a first chamber between the first and the second pistons, and there being between the first end-piece and the second piston a second chamber, and between the second end-piece and the first piston a third chamber, the second and the third chambers each having a pressure medium connection.
In electrical resistance welding it is often necessary to be able to move the electrodes relatively far apart to be able to change workpieces for example. During the actual welding, however, the electrodes only need to be separated a short distance to permit movement of the workpiece between different welding points. Welding gun cylinders suitable to this purpose are known in a number of different forms, for example according to Swedish Patent No. 7811488-1. In this known cylinder, the first piston slides against the inside of the housing, while the second piston runs inside the first piston. The two pistons thus have different diameters, and the first piston has a complicated shape.
The purpose of the invention is to achieve a cylinder with a simplified piston design.
This is achieved according to the invention which is characterized in that the second piston also slides in contact with the inside of the housing and in that the pressure medium tube protrudes with its end distant from the second end-piece into, and is guided against the inside of, the tubular piston rod. Thus standardized cylinder tubes can be used, at the same time as the diameter of the second piston follows established standard.
The pressure medium tube can suitably guide the movement of the first piston.
The invention will be described in more detail below with the aid of an example shown in the accompanying drawings, where:
FIG. 1 shows the use of a cylinder according to the invention, and
FIG. 2 shows, partially in longitudinal section, a cylinder according to the invention.
FIG. 1 shows schematically how a cylinder 1 according to the invention is used as a welding gun cylinder and is mounted in a welding gun 2 of tong type, where it is used to fix two pieces 3a and 3b which are to be welded together with the aid of two electrodes 4a and 4b. The welding electrode 4a is movable and is supported by an arm 5a pivoted in the welding gun 2 and which is actuated by a piston rod 11 of the cylinder 1. The welding electrode 4b is fixed and is supported by a fixed arm 5b of the welding gun 2.
At rest, for changing workpieces for example, the movable welding electrode 4a assumes an outer position (not shown). When welding is to take place, the welding electrode 4a is swung inwards to an operating position in which the pieces 3a and 3b are placed in the correct position for welding. The welding electrode 4a is then moved still further inwards to the welding position shown in which the pieces 3a and 3b are pressed together and welding takes place. When changing the welding point, the welding electrode 4a is swung back to the operating position so that the pieces 3a and 3b can be moved the required distance. It may be necessary to swing the welding electrode 4a all the way back to the rest position, if required by the shape of the pieces 3a and 3b.
The construction of a cylinder 1 according to the invention is revealed in FIG. 2. A first piston 6 is axially displaceable in a housing 7 which has a first end-piece 8 and a second end-piece 9. Between the first piston 6 and the first end-piece 8 there is a second piston 10, which, as does the first piston 6, slides against the inside of the housing 7. This second
REFERENCES:
patent: 2596471 (1952-05-01), Densmore
patent: 3139004 (1964-06-01), Haumann
patent: 3150563 (1964-09-01), Carrigan et al.
patent: 3168853 (1965-02-01), Prince
patent: 3968735 (1976-07-01), Boisde
patent: 4076465 (1978-02-01), Pauliukonis
AB Volvo
Maslousky Paul E.
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