| 摘要 |
PURPOSE:To improve the durability of an oil seal, by using lubricating oil so that back pressrure almost equal to air pressure is applied to the oil seal. CONSTITUTION:Oil pressure chamber 63, 60 are provided opposite an air passage 45 across oil seals 42, 43. A balancing valve 70 is installed in a halfway part of an oil passage 65 extending from a hydraulic pump 67 to the oil pressure chambers 63, 60, so that the valve acts to approximate the pressure of these oil pressure chambers to that of air at the outlet port of an inching valve 7, namely, to that of the air passage 45. The pressure on the front of the oil seals 42, 43 and that of their rear are thus balanced to each other to heighten the durability of the seals. |
