An object of the present invention is to provide a two dimensional drive system driven by fluid pressure. The drive system of the present invention comprises: a pair of X-guides; a pair of Y-guides; an X-rod whose each end is slidably attached to each Y-guide; a Y-rod whose each end is slidably attached to each X-guide; an X-piston section being provided at the midway of the X-rod; a Y-piston section being provided at the midway of the Y-rod; and a moving body having an X-chamber through which the X-rod is pierced and a Y-chamber through which the Y-rod is pierced, the X-chamber being divided into two subchambers by the X-piston section, the Y-chamber being divided into two subchambers by the Y-piston section. With this structure, the moving body is capable of moving in a plane by selectively supplying fluid to each subchamber.

The actuator of the present invention comprises a cylinder with a circular cylindrical cavity slidably engaged by a stationary piston secured to the frame of the actuator by at least one rod extending through one end wall of the circular cylindrical cavity in a leak-proof manner, wherein the stationary piston divides the circular cylindrical cavity into two compartments in a leak-proof manner. Pressurizing one and venting the other of the two compartments moves the cylinder relative to the stationary piston. The outer cylindrical surface of the cylinder includes fastening device for securing an object to be linearly actuated thereto or rack engaging a pinion gear that converts the linear motion of the cylinder to a linear motion of a sliding member with another rack or to a rotary motion of the pinion gear shaft.

A pipe gripping device is taught which is useful for moving pipe into and/or out of a well. The pipe gripping device includes a first set of slips for holding a pipe in a pipe light condition and a second set of slips for holding a pipe in a pipe heavy condition. The second set of slips are actuatable independently from the first set of slips. The pipe gripping device can include a slip moving system which prevents the slip carrier blocks from being driven outwardly against the housing, to thereby prevent the carrier blocks from locking, by being driven against the housing.

Disclosed herein is a slide cylinder basically consisting of a cylinder block internally defining a plural number of intercommunicating cylinder bores in parallel relation with each other, a piston and a piston rod fitted in each cylinder bore, and plate-like cross members integrally connecting the respective piston rods at the opposite ends thereof. The drive chambers defined by the pistons are communicated with fluid supply/discharge ports at the opposite ends of one of the piston rods and one of fluid supply/discharge ports provided in the cylinder block, permitting a diversity of piping modes by selective use of these ports. When installed upside down, it is possible to move either the cylinder block or cross plates whichever is desired. The slide cylinder can transfer loads accurately without involving rotational motion. Fixing of a piston against a piston rod is by means of caulking the ends of cylindrical portion of a piston at fixing grooves of a piston rod. This fixing work is simple and no backlash is permitted. A position sensor that permits applications for various purposes is easily installed.

A hydraulic circuit comprises first and second cylinders, and a piston disposed in each of the cylinders. A pump communicates with one side of one of the pistons, and a pressure relief valve has a position wherein the pump communicates with another side of the one piston and with the other piston.