Patent ID: 7247005

Claim:
An oil seal arrangement for a pump which contains oil and in which positive and negative oil pressures are alternately produced, said pump comprising a housing, a motor mounted to said housing, a cylinder fixedly mounted in said housing, a rotary shaft inserted in and rotatably supported by said cylinder and coupled to said motor at one axial end of said cylinder, and a pump unit disposed around and coupled to said rotary shaft at another axial end of said cylinder, said oil seal arrangement comprising: a high-pressure seal mounted in said cylinder around said rotary shaft; said high-pressure seal being disposed between said motor and said pump unit; said pump unit being driven by said motor through said rotary shaft to suck and discharge oil into and from said cylinder; a low-pressure seal mounted in said cylinder around said rotary shaft between said high-pressure seal and said motor; and an oil seal chamber defined in said cylinder around said rotary shaft between said high-pressure seal and said low-pressure seal; said oil seal chamber containing oil of the same type as oil in said pump unit, said rotary shaft being completely submerged in the oil in said oil seal chamber; and said oil seal chamber being sealed from outside the housing.