| 摘要 |
PURPOSE:To use a sealing plug as a temporary one and to make it unnecessary to remove the plug after use by making the length of a gas filling port different from that of a sealing plug and forming a groove, whose length is greater than that of either the gas filling port or the sealing plug whichever the shorter, at the middle part in the axial direction of the peripheral surface of the longer one of the above two. CONSTITUTION:Length l1 in the axial direction of a gas filling port 14 is made different from length l2 in the axial direction of a sealing plug 15, or l2 is made about 1/4l1. Meanwhile, at the middle part in the axial direction of the inner peripheral surface of the gas filling port 14 are formed grooves 15 and 16 having a length l3 in the axial direction that is greater than the length l2 in the axial direction of the sealing plug 15. When in use, a sealing plug 15 is pushed by pressure into a temporary sealing part 14a of the gas filling port 14 first to close up the gas filling port 14, and then the working oil is supplied. After this, the sealing plug 15 is further pushed by pressure into the port 14 until the plug 15 is situated at a gas sealing part 14b, and then the pressure gas is supplied. Finally, the sealing plug 15 is again pushed by pressure into the port 14 until the plug 15 is situated at the final sealing part 14c in order to conduct complete sealing to the gas filling port 14. |
