AN ELECTRICALLY OPEKATED HYDRAULIC CONTROL VALVE 715 



identical to each other and somewhat similar to the roll system described 

 above. Each of the three systems employs identical valves. 



GENERAL DESCRIPTION 



Basically, the J-7 valve is a conventional four-way type. Fig. 2 illus- 

 trates the porting arrangement. The parts in sections A, B and C are 

 inserts that are shrunk-fit into the valve body. The plunger accurately 

 fits the holes in the inserts, so that oil cannot flow between the plunger 

 and inserts except where the diameter of the plunger is reduced. The 

 annular space around the outside of the center insert is connected to the 

 high pressure oil supply. The radial passages in this insert (part A) carry 

 the oil to its internal cusps. With the plunger centrally located its center 

 land completely covers the port formed by the cusps and no oil flows. 

 With the plunger moved to the right the oil is carried to the cylinder and 

 back to the exhaust in the manner illustrated by the small sketch in the 

 upper right corner. If the motion of the plunger is to the left, a similar 

 performance occurs but the piston and fin are driven in the opposite 

 direction. To illustrate the construction of the inserts, detail sketches 

 are also shown at the top of Fig. 2. 



The inserts and the plunger are made of hardened steel. Fig. 3 show- 

 their location in the complete valve. The thickness of the inserts, hence 

 the longitudinal location of the ports, is held to an extremely close 

 tolerance by lapping their parallel faces. Their outside diameter is ac- 

 curately ground so that a tight seal will occur between the various pas- 

 sages when they are shrunk fit into the internal bore of the body. After 

 assembly, the internal bore formed by the holes in the various inserts is 

 lapped to a straight and accurate cylindrical shape. This process is con- 

 trolled to provide a diametral clearance of 0.0002 inch on an inter- 

 changeable basis. The plunger must slide freely in the bore in spite of 

 the small clearances involved. The longitudinal location of the lands 

 on the plunger must be controlled to a high degree for reasons that will 

 become apparent. 



Those parts shown in Fig. 2 are not sectioned in Fig. 3. The valve 

 proper is clamped between two manifolds (O and P) ; these are moved 

 apart in the picture to better illustrate the internal construction. The 

 brazed laminated manifolds provide the mounting means for the valve 

 and also serve to connect the multiple outlets of the valve body to stand- 

 ard hydraulic fittings for external connections. The manifolds are 

 designed to adapt the valve to a specific application. In this Avay, 

 different plumljing arrangements can be utilized without changes in the 

 valve proper. The manifold, O, has fittings to connect to the cylinder, 



