This claims the benefit of U.S. Provisional Patent Application No. 60/743,820 filed Mar. 27, 2006.
Not applicable.
This relates to hydraulic pumps, and in particular to air powered hydraulic pumps.
Air powered hydraulic pumps such as the Enerpac PA-133 available from Enerpac, an Actuant company, having a place of business in Glendale, Wis., are well-known. In such pumps, air pressure drives the hydraulic pump. The air pressure input to the hydraulic pump is typically line pressure, which is normally about 60-120 psi, and the pump intensifies the pressure so that the hydraulic fluid pressure output of the pump is considerably higher than the air pressure, for example up to 10,000 psi. Typically, the air pressure cyclically drives a piston linearly, which drives a smaller diameter piston that pressurizes the hydraulic fluid in these types of pumps.
These pumps are typically used to power single-acting hydraulic cylinders, for example to lift a load. In some applications, the cylinder may have to extend for a distance before any significant resistance to further extension is encountered. In these applications, the initial extension of insignificant load can be time-consuming, since the hydraulic flow rate from the pump results in a relatively slow advance.
Also, typically, in these pumps the reservoir is at or near atmospheric pressure. If the pump motor is operated too fast, cavitation occurs and the pump chamber is not completely filled.
