Displacement-measuring apparatus, and static-pressure bearing device for use in the displacement-measuring apparatus

A displacement-measuring apparatus, comprising:

• a cylindrical housing;
• a static-pressure bearing located in said housing, wherein said static-pressure bearing comprises:
• a hollow cylindrical bush having a plurality of restriction holes formed in said bush, said holes being equidistantly spaced along the circumference of said bush, said holes for supplying air to a gap between said bush and a probe shaft supported by said bearing in non-contact fashion and movable in an axial direction;
• a first set of grooves formed in an inner surface of said bush, said grooves extending along an axis of said bush, each groove of said first set opposing at least one restriction hole;
• and
• a second set of grooves formed in the circumferential surface of said probe shaft, the grooves in said second set being disposed in paris having two grooves symmetrical with respect to a corresponding groove of said first set;
• a stylus connected to one end of said probe shaft, for applying a contact pressure to an object;
• and
• contact pressure-adjusting section partly connected to said housing and partly connected to said probe shaft.

A displacement-measuring apparatus comprising:

• a cylindrical housing;
• a static-pressure bearing located in said housing, wherein said static-pressure bearing comprises:
• a hollow cylindrical bush having a plurality of restriction holes formed in said bush, said holes being equidistantly spaced along the circumference of said bush, said holes for supplying air to a gap between said bush and a probe shaft having a large-diameter portion and a small-diameter portion, said large diameter portion being supported by said bearing in non-contact fashion and being movable in an axial direction;
• a first set of grooves formed in an inner surface of said bush, said grooves extending along an axis of said bush, each groove of said first set opposing at least one restriction hole;
• and
• a second set of grooves formed in the circumferential surface of said probe shaft, the grooves in said second set being disposed in pairs having two grooves symmetrical with respect to a corresponding groove of said first set;
• a stylus connected to one end of said probe shaft, for applying a contact pressure to an object;
• and
• a contact pressure-adjusting section partly connected to said housing and partly connected to said probe shaft, for adjusting the contact pressure said stylus is applying to the object;
• wherein said contact pressure adjusting section includes an exhaustion adjusting plate loosely holding said probe shaft, a step portion defined by the large-diameter portion and small-diameter portion of said probe shaft and located in the vicinity of said exhaustion adjusting plate, a plurality of restriction holes for supplying compressed air into a space defined by said exhaustion adjusting plate and said step portion, and air-supplying means for supplying compressed air under a variable pressure into said restriction holes.

A static-pressure bearing device comprising:

• a shaft having a circular cross section;
• a bush loosely holding said shaft including:
• a plurality of restriction holes formed in said bush and equidistantly spaced along the circumference of said bush, for supplying air into a gap between said shaft and said bush;
• a first set of grooves formed in an inner surface of said bush, extending along an axis of said bush, and each opposing at least one restriction holes;
• and
• a second set of grooves formed in a circumferential surface of said shaft, extending along an axis of said shaft, and disposed in pairs, each pair consisting of two grooves symmetrical with respect to a corresponding groove of the first set.

A displacement-measuring apparatus comprising:

• a cylindrical housing;
• a static-pressure bearing located in said housing;
• a probe shaft supported by said bearing in non-contact fashion and movable in an axial direction;
• and
• a stylus connected to one end of said probe shaft, for applying a contact pressure to an object,
• wherein part of said static-pressure bearing comprises a hollow cylindrical bush, a plurality of restriction holes formed in said bush and equidistantly spaced apart along the circumference of said bush, for supplying air into the gap between said probe shaft and said bush, a first set of grooves formed in the inner surface of said bush, extending along the axis of said bush, and each opposing at least one restriction hole, and a second set of grooves formed in the circumferential surface of said probe shaft, extending along the axis of said probe shaft, and arranged in pairs, each pair consisting of two grooves symmetrical with respect to the corresponding groove of the first set.