Bearings – Linear bearing – Recirculating
Reexamination Certificate
2000-01-21
2001-06-19
Hannon, Thomas R. (Department: 3682)
Bearings
Linear bearing
Recirculating
C074S424880, C384S051000
Reexamination Certificate
active
06247846
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rolling-element hold spacer for retaining, in a rotatable and slidable manner, rolling elements used in a rectilinearly-movable apparatus, such as a rectilinearly-rolling guide apparatus, a ball screw, and a ball spline, as well as a rectilinearly-movable apparatus using the rolling element hold spacer.
2. Description of the Related Art
As shown in
FIG. 15
, a single-element retainer
2
for individually holding a ball
1
has already been known as a rolling-element hold spacer for a holding ball (corresponding to a rolling element) used in a rectilinearly-movable apparatus (see, for example, Japanese Patent Publication No. 33774/1993). The ball
1
is held, in a rotatable and slidable manner, within a housing hole
2
a
formed in the single-element retainer
2
while the upper and lower portions of the ball
1
are partially exposed. The single-element retainer
2
is incorporated in the rectilinearly-movable apparatus. A fittingly-insert section
2
b
is bulgily formed in the single-element retainer,
2
on either side of the ball
1
and is to be inserted into a guide channel formed in a slide member. The single-element retainers
2
, each housing the ball
1
, are inserted in a circulation path of the slide member. The single-element retainers
2
travel in the direction designated by A shown in the drawing. The opposite ends of the single-element retainer
2
, which come into contact with the corresponding ends of the adjoining single-element retainers
2
while the single-element retainers
2
are traveling along the circulation path, are formed so as to assume a circular-arc shape
2
c
. The distance between the centers of the adjacent balls
1
is maintained constantly. Since the balls
1
are arranged and held in a circulation path while being held by the respective single-element retainers
2
, the balls
1
are prevented from rubbing against each other during circulation, thus preventing generation of a collision sound or abrasion, which would otherwise be caused by rubbing action.
Such a known single-element retainer
2
is suitable for being arranged and housed in the circulation path of the rectilinearly-rolling guide apparatus, as well as for effecting two-dimensional change between linear travel direction A and U-shaped travel direction B, as shown in FIG.
15
. However, there may be a case where a ball screw requires three-dimensional change of direction and torsional movement with respect to a travel direction, as well as two-dimensional change of direction. The single-element retainer
2
is difficult to effect such complicated movements. Further, the circumference of the ball
1
exclusive the upper and lower portions thereof is covered with the single-element retainer
2
. It is difficult for a lubricant to enter the space between the single-element retainer
2
and the ball,thus insufficiently lubricating the ball
1
. Further, since one single-element retainer
2
is used for holding a single ball
1
, space for the circular-arc portions
2
c
of the adjacent single-element retainers
2
must be ensured between the adjacent balls
1
. For this reason, the single-element retainers
2
occupy space within the circulation path, thus imposing a limitation on the number of balls
1
to be inserted into the circulation path. Therefore, the rectilinearly-rolling guide apparatus cannot assume a large load-carrying capacity. The portion of the single-element retainer
2
which comes into contact with the corresponding portion of the adjacent single-element retainer
2
assumes a circular-arc protrudent shape
2
c
, and hence the adjacent single-element retainers
2
come into substantial line contact with each other, thus increasing a contact pressure. Consequently, there is a case where the single-element retainers
2
repeatedly come into collision with each other during the course of circulating operation, thus causing a collision sound. Further, the single-element retainer
2
has the bulgily-formed fittingly-insert sections
2
b
and hence has an irregular thickness with respect to the circulating direction of the single-element retainer
2
(i.e., direction A). Therefore, the single-element retainers
2
may cause pitching during a circulating operation.
SUMMARY OF THE INVENTION
Accordingly, the present invention is aimed at providing a rolling-element hold spacer which ensures smooth Circulating operation even in the case of a complicated movement mode such as that effected in a three-dimensional change-of-direction path and which can increase the load-carrying capacity of a rectilinearly-movable apparatus by means of increasing the number of rolling elements inserted in a circulation path.
Also, the present invention is aimed at providing a rectilinearly-movable apparatus equipped with the rolling element hold spacer.
To achieve the above objects, according to a first aspect of the invention, there is provided a rolling-element hold spacer comprising:
a thick hold section having spherical indents formed on both sides thereof, said thick hold sections being adapted to be interposed between rolling elements so that the spherical indents match the curved surface of the rolling elements; and
thin bent sections for interconnecting only one thick hold section pair in which the rolling element is to be interposed.
In the first aspect of the present invention, the thin bent section is deflected or twisted in a curved portion of a rolling-element circulation path. Further, the rolling-element hold spacers which are adjacent to each other with a single rolling element interposed therebetween mutually perform pivotal movement around the rolling element, thereby enabling smooth circulation of the rolling elements. Clearance arises between the rolling element and the thick hold sections as a result of bent of the thin bent section. Lubricant enters the clearance, to thereby sufficiently lubricate the rolling elements. So long as the rolling-element hold spacer is placed every other the rolling elements, all the rolling elements are eventually held by the rolling-element hold spacers. Consequently, the number of rolling-element hold spacers can be reduced to one-half the number of the rolling elements.
More specifically, the number of rolling-element hold spacers to be inserted into the rolling-element circulation path is reduced, and the number of rolling element can be increased correspondingly. As a result, the load-carrying capacity of a rectilinearly-movable apparatus employing the rolling-element hold spacers can be increased. Further, the thick hold sections of the rolling-element hold spacer hold the rolling element by way of the spherical indents, and hence a contact pressure developing between the rolling-element hold spacer and the rolling element can be diminished. Accordingly, there can be prevented generation of a collision sound, which would arise during the circulation of the rolling elements, thus enabling smooth circulation of the rolling elements. The thin bent section interconnecting the thick hold sections has a strip shape and a uniform thickness in the traveling direction of the rolling-element hold spacer. So long as the width of a guide groove formed in the slide member for the purpose of guiding the thin bent section is set to be slightly greater than the thickness of the thin bent section, the rolling-element hold spacer is stably guided without involvement of a pitching problem, thus ensuring smooth circulation of the rolling elements.
Preferably, the thin bent section is provided on either side of the rolling element.
By means of such a configuration of the present invention, the thin bent section provided on either side of the rolling element stably holds the rolling element, thus prolonging the life of the rolling-element hold spacer.
Preferably, the thin bent section is provided only on one side of the rolling element.
By means of such a configuration of the present invention, even when the rolling elements are circulated through a warped circulatio
Hannon Thomas R.
Morgan & Lewis & Bockius, LLP
THK Co. Ltd.
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