Linear guide device

Details Linear guide device Linear guide device

1999-11-23

2002-04-16

Footland, Lenard A. (Department: 3682)

Bearings

Linear bearing

Recirculating

Reexamination Certificate

active

06371648

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates to a linear guide device used for linear sliding in an industrial machine or the like, and particularly to improvements in ball circulating parts in the device.
2. Related Background Art
The appearances of a linear guide device in the prior art are shown in
FIG. 15
of the accompanying drawings, and a cross-sectional view along the direction of line
16
—
16
of
FIG. 15
showing the internal structure thereof is shown in
FIG. 16
of the accompanying drawings. As shown, the linear guide device is comprised of a guide rail
50
having in the outer surface thereof a groove portion
57
receiving therein rolling members, i.e., balls
51
for rolling and extending axially, and a slider
60
having therein a circulation path
4
for the balls
51
and held for sliding on the guide rail
50
by the balls
51
in a groove portion
7
(see
FIG. 11
of the accompanying drawings) opposed to the groove portion
57
. The balls
51
are held in the circulation path
4
and between the two groove portions
57
and
7
and roll in the circulation path
4
and between the two groove portions
57
and
7
with the sliding movement of the slider
60
. The slider
60
is comprised of a slider body
1
having the circulation path straight portion
5
of the ball circulation path
4
and an end cap
2
having a circulation path curved portion
6
communicated with the straight portion
5
and between the two groove portions
57
and
7
to thereby make the ball circulation path
4
into an endless track.
As the ball circulating parts in the linear guide device heretofore used, i.e., the slide body
1
and the end cap
2
, mention may be made of ones disclosed in Japanese Patent Publication No. 62-11215 shown, for example, in
FIGS. 11 and 12
of the accompanying drawings.
FIG. 11
is a view of the joined surface in the slider body
1
with the end cap
2
as it is seen from the direction of joint, and
FIG. 12
is a view of the joined surface in the end cap
2
with the slider body
1
as it is seen from the direction of joint.
The slider body
1
is formed with the straight portions
5
of the circulation path, and the grooves
7
for the balls
51
to support the slider
60
relative to the guide rail
50
and further, the opening portions of the straight portions
5
of the circulation path are formed with tapered surfaces
20
having their opening diameter enlarged toward the opening portions. In
FIGS. 11 and 12
, the reference numeral
21
designates mounting threaded holes for mounting the end cap
2
on the slider body
1
, and the reference numeral
30
denotes chamfered portions for facilitating the rolling of the balls
51
.
The end cap
2
is formed with the circulation path curved portions
6
which are semicylindrical holes relative to the vertical direction in the plane of the drawing sheet and are concave grooves having a semicircular cross-section along the circumferential surfaces of the semicylindrical holes and which communicate with the straight portions of the circulation path of the slide body and a ball holding portion formed between the groove portions
7
of the slider body and the groove portion
57
of the guide rail
50
. The reference numeral
22
designates through-holes for passing therethrough screws for mounting the end cap
2
on the slider body
1
, and the reference numeral
31
denotes a pickup portion for picking up the balls
51
into the circulation path curved portions
6
.
The communicating portion in the circulation path curved portions
6
with the circulation path straight portions
5
of the slider body
1
, as shown in
FIG. 13
of the accompanying drawings which schematically shows the cross-section of the communicating portion (fitting portion), is formed with a substantially circular-ring-like protruding portion
25
formed with a taper fitted correspondingly to the tapered surfaces
20
in the circulation path straight portions
5
, and the slider body and the end cap are designed to be faucet-fitted to each other in this communicating portion. Further, a tapered portion
26
increasing its opening diameter relative to the communicating portion is formed on the inner surface of the substantially circular-ring-like portion of the protruding portion
25
in the end cap
2
so that the smooth circulation of the balls may be obtained.
However, in the faucet-fitted portion as shown above, the fitted portion is formed by the tapered surfaces
20
of the slider body
1
and the protruding portion
25
of the end cap
2
, and when an error of positional dimensions occurs to the fitted portion, it is difficult to absorb it by the elastic deformation in the fitted portion. That is, when as shown in
FIG. 14
of the accompanying drawings which schematically shows a cross-sectional view of the fitted portion, an error of positional dimensions occurs between the center of the circulation path straight portions
5
and the center of the protruding portion
25
lying in the opening portion of the circulation path curved portion
6
, there has been the undesirable possibility that the slider body
1
and the end cap
2
do not closely contact with each other and a gap or a level difference of unexpected magnitude is created even on the endless track of the balls.
Here, when the diameter of the circulation path is defined as &phgr; and the diameter of the balls is defined as Da, the gap G between the balls located in the circulation path and the inner wall of the circulation path is represented by the following expression (1):
G=&phgr;−Da
  (1)
Further, assuming that A indicates the positional dimension from the center line of the slider body
1
to the center line of the circulation path straight portions
5
and B indicates the positional dimension from the center line of the end cap
2
to the center of the opening in the circulation path curved portion
6
, the diameter of the circulation path substantially coincides with L
0
in the fitted portion when as shown in
FIG. 13
, the positional dimensions coincide with each other (A=B), and assuming that the length of the portion in which the diameter of the circulation path changes to effect fitting is &Dgr;, the gap in the fitted portion, i.e., the gap between the balls and the inner wall of the circulation path, is represented by the following expression (2):
G
=(&phgr;
2
+&Dgr;
2
)
½
−Da
  (2)
Further, when as shown in
FIG. 14
, the error of the positional dimensions is A−B, L
1
and L
2
are conceivable as the substantial diameters in the circulation path, but the diameters in question are great in absolute amount. In this case, L
2
>L
1
and therefore, when the extension of the portion in which the diameter of the circulation path created without the slider body and the end cap closely contacting with each other changes is defined as &dgr;, the gap in question is represented by the following expression (3):
G
={[&phgr;+(
A−B
)]
2
+(&Dgr;+&dgr;)
2
}
½
−Da
  (3)
That is, the gap between the inner wall of the circulation path in the fitted portion and the balls increases in conformity with an increase in the dimensional difference between A and B and the resultant increase in &dgr;.
The increase in the gap between the inner wall of the circulation path and the balls is an increase in the magnitude of the amount of play when the balls pass the fitted portion, and this causes the collision of the balls against the wall surface of the circulation path. This problem particularly remarkably arose outside the orbit of revolution of the balls, and as the result, it increased the noise created during the running of the linear guide device, i.e., when the slider body moved on the guide rail.
SUMMARY OF THE INVENTION
The present invention has as its object to provide a linear guide device which decreases the play of balls relative to the orbit of revolution thereof to thereby decrease the collisi

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