| 摘要 |
Constant, smooth forward pressure stroke is maintained during pressure casting operation by the elimination of any erratic, jerky reverse action due to the complex mould shape. This steady stroke action is obtained by maintaining a definite back pressure against the piston movement in the hydraulic cylinder to absorb any irregular motion. This is achieved by means of a throttle valve in the hydraulic circuit- The pressure cylinder containing the piston is filled with hydraulic medium. An intensifier piston applies pressure to the fluid medium to operate the piston. The flow of the hydraulic medium from the cylinder is governed and regulated by a sensitive throttle valve to maintain a back pressure in the cylinder. The back pressure can be set in the range of 0 to 140 bar. The pressurecylinder (12) contains the piston (11) and piston rod (13) connected to the casting chamber. A throttle valve (21) is fitted in the outlet (17). The throttle valve has a cone shaped valve seat containing two drilled ports. The throttle valve can be accurately set to obtain the required back pressure by a precise adjustment of the valve on its seat. When the hydraulic pressure in the cylinder (12) is increased the piston travels against the set back pressure without any erratic movement until the stroke is completed. By means of the return valve (19) the hydraulic medium returns the piston on the reverse stroke.
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