| 摘要 |
<p>PURPOSE:To automatically prevent the fluid leak from a shaft seal portion while a pump is at halt by controlling a clearance between a piston and a sleeve fitted to a shaft by means of a pump discharge pressure. CONSTITUTION:During a pump operation, a discharge side pressure higher than that of a suction side flows into the right side opposite to an impeller of a cylinder 5 through a pressure guide pipe 10 by means of the pumping-up action of the impeller 4, thereby a piston 6 is moved to the left against the force of a spring 7, and a clearance 11 with a sleeve 2 is expanded. On the other hand, when the pump is stopped, the impeller 4 ceases its pumping-up action, the suction pressure and discharge pressure of the pump become equal, thus pressures applied to both sides of the piston 6 become equal. Accordingly, the piston 6 is moved to the right by means of the force of the spring 7 and is brought into close contact with the left end face of the sleeve 2 to close the clearance 11. Therefore, the inside of the pump is cut off from the atmosphere, and the fluid in the pump is prevented from leaking into the atmosphere.</p> |
