Linear bearing

Details Linear bearing Linear bearing

1999-02-03

2001-03-20

Marmor, Charles A (Department: 3681)

Bearings

Linear bearing

Roller bearing

C384S051000, C384S057000

Reexamination Certificate

active

06203201

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a linear bearing which can be suitably used in an apparatus which performs rotational and reciprocal motions, such as a polishing apparatus for a semiconductor.
Conventionally, a linear bearing such as shown in
FIG. 2
is used. The linear bearing comprises a sleeve
52
which supports a shaft
51
via balls
56
. Spline grooves
53
and
54
are formed in the shaft
51
and the sleeve
52
, respectively, and the balls
56
are arranged between the spline grooves
53
and
54
. A retainer
55
which retains the balls
56
is urged by coil springs
57
from both the sides in the axial direction.
When a force in the axial direction acts on the shaft
51
to move the shaft
51
, the balls
56
on the spline grooves
53
and
54
roll along the spline grooves
53
and
54
, and the retainer
55
moves in the axial direction together with the balls
56
against the urging force of the coil springs
57
.
However, the linear bearing of the prior art has the following problem. The shaft
51
can reciprocally move in the axial direction. When a force for rotating the shaft
51
in the circumferential direction is applied to the shaft
51
, however, the shaft
51
cannot rotate in the circumferential direction because the balls
56
cannot move in the circumferential direction beyond the spline grooves
53
and
54
.
SUMMARY OF THE INVENTION
Consequently, it is an object of the invention to provide a linear bearing which can allow a shaft to relatively reciprocally move with respect to an outer race in the axial direction, and also to rotate in the circumferential direction.
In order to attain the object, the linear bearing of the invention is characterized in that the linear bearing comprises: an outer race; plural rolling elements for reciprocably supporting a shaft on the outer race; a retainer which retains the rolling elements; a push ring which is reciprocally disposed in the outer race; a lid fixed to the outer race; an elastic member which is disposed between the push ring and the lid and which urges the push ring toward the retainer; and a rotation preventing member which prevents the push ring from rotating.
In the linear bearing of the invention, when a force for relatively moving the shaft with respect to the outer race in the axial direction is applied, the plural rolling elements supported by the outer race roll, so that the shaft moves in the axial direction and also the retainer retaining the rolling elements moves in the axial direction. When the retainer abuts against the push ring, the push ring is pressed against the force of the elastic member and the shaft moves in the axial direction. In this way, the shaft reciprocally moves in the axial direction.
By contrast, when the shaft is relatively rotated with respect to the outer race in the circumferential direction, the plural rolling elements roll in the circumferential direction and also the retainer retaining the rolling elements rotates in the circumferential direction. When the retainer abuts against the push ring, the retainer slides over the abutting face of the push ring so as to rotate in the circumferential direction. At this time, the rotation preventing member prevents the push ring from corotating with the retainer in the circumferential direction. Therefore, the elastic member which is disposed between the push ring and the lid is not twisted in the circumferential direction nor tilted. As a result, the linear bearing allows the shaft to perform both rotational motion in the axial direction and reciprocal motion in the circumferential direction.
The linear bearing of the invention is characterized in that, the outer race is provided with a stopper against which the push ring is to abut.
In the linear bearing of the invention the push ring urged by the elastic member is engaged with the stopper of the outer race. Therefore, the stop position of the push ring is defined.
The linear bearing of the invention is characterized in that, one of the retainer and the push ring is formed by a member which has excellent slidability with respect to the other one of the retainer and the push ring.
In the linear bearing of the invention, since one of the retainer and the push ring is formed by a member which has excellent slidability with respect to the other one, the retainer can smoothly slide with respect to the push ring.
The linear bearing of the invention is characterized in that, the elastic member is one of a coil spring, a corrugated plate spring, and a magnet.
In the linear bearing of the invention, since the elastic member is one of a coil spring, a corrugated plate spring, and a magnet, the push ring can be returned to the stop position by manes of a structure which is simple, economical, and compact.


REFERENCES:
patent: Re. 34736 (1994-09-01), Hanaway
patent: 4648727 (1987-03-01), O'Neil et al.
patent: 5096307 (1992-03-01), Hanaway
patent: 5141337 (1992-08-01), Hanaway
patent: 5350185 (1994-09-01), Robinson
patent: 5375932 (1994-12-01), Hanaway
patent: 5489253 (1996-02-01), Ito et al.
patent: 5494353 (1996-02-01), Diemer
patent: 5622434 (1997-04-01), Takahashi
patent: 5707153 (1998-01-01), Steinberger et al.
patent: 54-137542 (1979-10-01), None

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