Power plants – Pressure fluid source and motor – Pulsator
Patent
1996-05-07
1997-07-22
Lopez, F. Daniel
Power plants
Pressure fluid source and motor
Pulsator
60567, 60574, 60581, F15B 700
Patent
active
056494246
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a two-stage pressure cylinder of the type in which a low pressure fluid provides an initial degree of movement of a work piston and the low pressure is subsequently intensified to provide a high pressure on the work piston for application to a work piece.
BACKGROUND ART
Two-stage pressure systems have been proposed for many applications. One particular application is the use of pressure systems as welding clamps, for the spot welding of metals.
There are numerous other applications are available for a two-stage type pressure cylinder.
One form of two-stage clamping cylinder has been proposed in U.S. Pat. Nos. 3,875,365, 3,828,652, 4,099,436 and 4,135,076.
In this system the hydraulic fluid is located in a holding tank in a separate location, and is connected by hoses to a work cylinder.
However this system does have certain disadvantages. Each work cylinder must be provided with its own hydraulic fluid tank and system of hoses, and the tank must be capable of receiving a pressure from an air pressure source.
French Patent 2,384,977 shows a two-stage air-hydraulic cylinder. The cylinder has a work piston, an oil piston and an intensifier piston.
However, the operating system for the cylinder is a complex system of air chambers, controlled by needle valve at the top of the cylinder on the left hand side of FIG. 1. The intensifier piston 26 must be all the way to the left in order for these needle valves to operate. So long as the intensifier piston 26 is kept at the left hand end, then oil can flow from the oil cylinder 21 through the chamber 13 into the working cylinder.
However, if there is any malfunction of the needle valves caused by dirt or any other means, so that the intensifier piston 26 does not reach all the way back to the left, then no oil flow can take place since the cylinder rod 15 will close off the passage 13.
There is no disclosure of a first valve allowing oil to flow into the working cylinder on a working stroke and preventing its return flow.
There is no disclosure of a second valve which is normally closed to prevent return flow, and which is operable to permit return flow, for a return stroke of the working piston.
German Patent 3,345,002 discloses a two-stage cylinder. There are only two pistons namely, a work piston and an intensifier piston. Oil is apparently contained in the work cylinder, and is in some way forced upwardly by means of air in the conduit 19 and the spring 13. Apparently, this movement will cause the initial downward movement of the work piston until it touches the workpiece.
There is no disclosure of a first valve normally operable to permit flow of oil from an oil cylinder into the working cylinder, and being closed to prevent reverse flow.
There is no disclosure of a valve which is normally closed to prevent reverse flow, but which is operable to open and permit reverse flow of the oil for a return stroke of the work piston.
DISCLOSURE OF THE INVENTION
The invention seeks to provide an improved two-stage pressure cylinder apparatus having a main cylinder, a work piston, and work piston rod movable within said main cylinder, and said work piston rod being adapted to extend therefrom for contact with a work piece, an oil cylinder adapted to contain hydraulic fluid, an oil piston in said oil cylinder movable therein towards and away from said main cylinder, an air cylinder, an air piston in said air cylinder, and an air piston rod of reduced diameter in relation to said air piston, communicating with said hydraulic fluid, working stroke fluid flow valve means allowing hydraulic fluid to pass from said oil cylinder to said main cylinder, and a reverse flow valve means, operable to permit return flow of fluid from said main cylinder into said oil cylinder.
The invention further provides air pressure conduits connecting with said main cylinder, and, in which the work piston and piston rod incorporate a fluid chamber, the air piston rod being movable into and out of the fluid chamber.
The invention further provides that t
REFERENCES:
patent: 2601761 (1952-07-01), Fouron
patent: 2915878 (1959-12-01), Hramoff
patent: 4011724 (1977-03-01), Landes et al.
patent: 4072013 (1978-02-01), Barbareschi
patent: 4288987 (1981-09-01), Grullmeier
patent: 5381661 (1995-01-01), Malina
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