| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent the deterioration of a sealing material caused by the humidity increase of a bellows so as to improve durability by firmly fixing the sealing material to the cap of the bellows via a heat insulating material. SOLUTION: When the pressure of hydraulic oil is lower than a cracking pressure, a sealing material 11 is brought into contact with the shell inner wall 10 of a shell 6 like that indicated by a double dotted chain line. When the hydraulic pressure exceeds the cracking pressure, a sealed part between the sealing material 11 and the shell inner wall 10 is open like that indicated by a solid line and after the cap 9 of a bellows 8 is moved away from a port 5a, the pulsation of the hydraulic pressure in an outlet pipe path is absorbed by the elongation/contraction of the bellows 8. During this operation, even if heat is generated by the compression/expansion of injected gas in the bellows 8 and the temperature of the cap 9 is increased, the transmission of heat to the sealing material 11 is reduced by the heat insulating material 15. Thus, the deterioration of the sealing material 11 made of rubber or the like which is caused by its hardening is prevented and its durability is improved.</p> |
