Machine element or mechanism – Mechanical movements – Reciprocating or oscillating to or from alternating rotary
Reexamination Certificate
2001-02-20
2003-05-13
Joyce, William C (Department: 3682)
Machine element or mechanism
Mechanical movements
Reciprocating or oscillating to or from alternating rotary
C384S007000, C384S008000, C384S049000, C188S043000
Reexamination Certificate
active
06561049
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear guide apparatus which is used in a machine tool and an industrial machine.
2. Description of the Related Art
To guide a table of a machine tool or an industrial machine which can be moved at a relatively high speed by a ball screw or a linear motor, there is used such a linear guide apparatus
51
as shown in FIG.
8
.
The linear guide apparatus
51
shown in
FIG. 8
, which is generally called a linear guide, comprises guide rails
53
serving as guide members respectively extending in one direction, and sliders
54
movably assembled to their associated guide rails
53
. In the outer surface of each guide rail
53
, there is formed a rolling body rolling groove
58
which serves as a guide surface; in each slider
54
, there is formed a load rolling body rolling groove serving as a load guide surface in such a manner that it faces the rolling body rolling groove
58
of the guide rail
53
; between the rolling body rolling groove
58
and load rolling body rolling groove, there are interposed a large number of balls serving as rolling bodies; and, the slider
54
can be moved along the guide rail through these rolling bodies.
As the guide rails
53
, there are used a pair of guide rails
53
which are arranged parallel to each other, and they are respectively mounted on a bed
59
which is generally placed on a floor. In the case of the sliders
54
, a pair of sliders
54
are assembled to each guide rail
53
in such a manner that they are spaced from each other and can be moved along the longitudinal direction of the associated guide rail
53
. The sliders
54
are respectively mounted on a table
52
.
A drive mechanism
55
, which is used to drive the table
52
, includes a screw shaft
60
and a ball nut
61
. The screw shaft
60
includes a screw groove formed on the outer surface thereof and is mounted on the bed
59
along the guide rails
53
in such a manner that it can be rotated about its own axis. The ball nut
61
is threadedly engaged with the screw shaft
60
through a large number of balls serving as the rolling bodies and is mounted on the table
52
. The drive mechanism
55
is structured such that it can rotate the screw shaft
60
to thereby move the table
52
along the guide rails
53
through the ball nut
61
.
Also, the linear guide apparatus
51
includes a friction apply unit (not shown) which is used to stop the slider
54
at a given position of the guide rail
53
. The friction apply unit includes a brake member disposed so as to be opposed to the upper surface or side surface of the guide rail
53
or to the rolling body rolling groove
58
, and a drive device which is capable of pressing the brake member toward the guide rail
53
. The brake member is structured such that, in case where it is pressed toward the guide rail
53
by the drive means and is thereby contacted with the guide rail
53
, it can generate a frictional force.
The friction apply unit pushes the brake member using the drive device to apply a frictional force to the slider
54
and table
52
to thereby set them at their given positions of the guide rail
53
. By driving the friction apply unit, the damping characteristic of the vibrations of the slider
54
and table
52
can be enhanced and thus the rigidity of the slider
54
and table
52
can be enhanced.
However, in the thus structured linear guide apparatus
51
, when the brake member is pressed against the upper surface of the guide rail
53
to thereby generate a frictional force, the slider
54
and table
52
are pushed up as the brake member is pressed against the guide rail
53
, which degrades the positioning accuracy of the slider
54
and table
52
.
In view of this problem, in Japanese Patent Unexamined Publication No. Hei. 7-54845 (JP-A-7-54845), there is disclosed a linear guide apparatus in which the brake member is fitted into the rolling body rolling groove
58
of the side surface of the guide rail
53
and the brake member is pressed by an oil pressure cylinder. In this case, since the brake member is fitted into the rolling body rolling groove
58
, there is no possibility that the slider
54
and table
52
are pushed up when braking. However, because the brake member is pressed against the rolling body rolling groove
58
to thereby a frictional force, there is a tendency that the rolling body rolling groove
58
is worn to such a degree that cannot be ignored, which results in the degraded positioning accuracy of the slider
54
and table
52
.
Also, in the above-cited publication JP-A-7-54845, when removing the braked condition, the oil pressure of the oil pressure cylinder is removed to thereby produce a non-load condition and thus the brake member and the piston of the oil pressure cylinder are retreated due to the elastic force of a coiled spring.
Here, in such structure where the brake member and the piston of the oil pressure cylinder are retreated due to the elastic force of a coiled spring, in case where the response characteristic (speed) of removal of the braked condition is enhanced to thereby control the frictional force with high accuracy, the elastic force of the coiled spring must be set fairly large.
However, in case where the elastic force of the coiled spring is set large, there increases the load that is produced when the brake member is pressed by the oil cylinder against the elastic force of the coiled spring, which degrades the response characteristic of the brake member when it is pressed.
Further, as in the above-cited publication JP-A-7-54845, in the case of a structure in which a brake member (brake shoe) is slidably fitted into a sliding groove formed in a damping block, there exists a clearance between the sliding groove and brake member and this clearance causes the slider
54
to play in the advancing direction thereof. This invites the delayed generation of the frictional force, which makes it difficult to control the frictional force with high accuracy.
SUMMARY OF THE INVENTION
The present invention aims at eliminating the above drawbacks found in the conventional linear guide apparatus. Accordingly, it is an object of the invention to provide a linear guide apparatus which not only can keep the positioning precision at a high level but also can enhance the response characteristic of a brake member to thereby control a frictional force generated by the brake member with high accuracy.
In attaining the above object, according to the invention, there is provided a linear guide apparatus, comprising: a guide member including a guide surface formed on the outer surface thereof; a slider disposed on the guide member so as to be movable along the longitudinal direction of the guide member and including a load guide surface formed so as to face the guide surface of the guide member; a brake member disposed so as to face the side surface of the guide member and contactable with the other portions of the side surface of the guide member than the guide surface thereof; a drive device including an advance and retreat member movable in a direction to be contacted with and separated from the side surface of the guide member, the drive device being capable of driving the advance and retreat member in a direction to approach the side surface of the guide member to thereby press the brake member against the side surface of the guide member and also capable of driving the advance and retreat member in a direction to part away from the side surface of the guide member to thereby remove the pressure thereof; and, a support member for supporting the brake member with high rigidity in other directions thereof than the direction to be contacted with and separated from the side surface of the guide member.
In the thus structured linear guide apparatus, since the brake member is contacted with the other portions of the side surface of the guide member than the guide surface thereof, not only the slider can be prevented from being pushed up but also the guide surface can be prevented against wear
Akiyama Masaru
Kato Soichiro
Nakamura Shinya
Yabe Shiroji
Joyce William C
NSK Ltd.
Sughrue & Mion, PLLC
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