| 摘要 |
This invention consists of a combined pneumatic and hydraulic cylinder the purpose of which is to provide a very high pressure, particularly in the process of resistance welding, without the necessity of having a very large cylinder nor a high pressure line. In the invention, the cylinder is comparatively small in size and is equipped with two pistons and piston rods, one above the other. The lower piston is at first activated by compressed hydraulic fluid until it makes contact with the work. The upper piston which is activated by compressed air travels toward the lower piston so that its piston rod entraps the pressurized hydraulic fluid above the lower piston, and proceeds to add its own pressure to the pressure already acting upon the lower piston. The entire action is controlled by a delayed action valve and a four-way valve.
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