Bearings – Linear bearing – Recirculating
Reexamination Certificate
2000-01-21
2002-08-20
Bucci, David A. (Department: 3682)
Bearings
Linear bearing
Recirculating
C384S049000, C384S051000
Reexamination Certificate
active
06435720
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear guide device using the rolling movements of balls.
2. Description of the Related Art
Conventionally, as a linear guide device of this type, for example, as shown in
FIG. 18
, there is known an apparatus comprising a guide rail
301
elongated in the axial direction thereof and a slider
302
which is movably mounted on the guide rail
301
in such a manner that it straddles over the two side portions of the guide rail
301
. In the two side surfaces of the guide rail
301
, there are formed rolling element rolling grooves
303
respectively extending in the axial direction of the guide rail
301
. In a slider main body
302
A of the slider
302
, there are formed rolling element rolling grooves (not shown) at the respective inner surfaces of the two sleeve portions
304
thereof in such a manner as to be respectively opposed to the rolling element rolling grooves
303
of the guide rail
301
.
And, between the mutually opposing rolling element rolling grooves, there are rollably interposed a large number of steel balls K serving as rolling elements, and the slider
302
is able to move on the guide rail
101
along the axial direction of the guide rail
301
through the rolling movements of the balls K. As the slider
302
moves, the balls K interposed between the guide rail
301
and slider
302
roll and move to the end portion of the slider main body
302
A of the slider
302
. However, in order to be able to move the slider
302
continuously in the axial direction of the guide rail
301
, the balls K must circulate endlessly.
In view of this, not only, within the two sleeve portions
304
of the slider main body
302
A, there are further formed linear-shaped through holes (not shown) respectively extending through their associated sleeve portions in the axial direction of the slider main body
302
A and serving as a rolling element passage, but also two end caps
305
are respectively disposed on the two front and rear end portions of the slider main body
302
A and, in the two end caps
305
, there are formed rolling element circulation passages (not shown) which are respectively curved in a semi-arc shape and allow the above-mentioned two groups of rolling element rolling grooves and the through holes serving as the rolling element passages to communicate with each other, thereby forming a rolling element endless circulation track.
Also, as shown in
FIG. 19
, between the two mutually adjoining ones of the balls K in the rolling element endless circulation track, a separator T including, in its two side surfaces, recessed portions W respectively opposed to the two mutually adjoining balls K is interposed in such a manner that the two balls K are respectively contacted with their associated recessed portions W of the separator T. The separators T are used to eliminate the clearances of the line of the steel balls of the rolling element endless circulation track in the circulating direction thereof to apply compression forces to the line of the steel balls, thereby enhancing the efficiency of the operation of the linear guide device.
In the above-mentioned conventional linear guide device, the rolling element endless circulation track is composed of a plurality of components. To absorb variations in the track length of each product caused by the working errors of the components as well as to forcibly apply the compression forces to the line of the steel balls, there are required specifications for a separator having a highly accurate and complicated shape (for example, a separator including an elastic portion and a movable portion). However, such separator is difficult to manufacture.
Also, in the conventional linear guide device, the separators are set such that they apply the compression force forcibly to the line of steel balls. Therefore, when an excessive compression force is applied to the line of steel balls due to the working errors of the components, the efficiency of the operation of the steel balls is greatly worsened and also there is generated a harsh grating noise.
Further, the separator T is structured in such a manner that its two outer peripheral surfaces Q are respectively formed as spherical surfaces and the two recessed portions W each formed a spherical-shaped surface are disposed in the two end portions of the separator T which are respectively in contact with the two balls K. Also, the separator T is further structured in such a manner that the radius of curvature of each of the recessed portions W to be contacted with the balls K is set larger than the radius of the ball K. Further, the condition of contact between the separator T and ball K is specified so that forces acting between them are allowed to balance well with each other.
However, in the linear guide device shown in
FIG. 18
, the radius of curvature of each recessed portion W of the separator T to be contacted by the ball K is larger than the radius of the ball K. Therefore, in such a curved track as shown in
FIG. 7
, the ball K is contacted with the recessed portion W on the inner side of the curved track to thereby press against the separator T inwardly of the curved track. Thus, the outer peripheral portion Q of the separator T is pressed against a guide member J which forms the inside track surface of the curved track. Due to this, there is generated friction between the separator T and guide member J, which worsens the operation performance of the ball K and causes noises as well as deteriorates the durability of the separator T.
On the other hand, in the rolling element endless circulation track, the balls, which have moved through a linear track (where a load is applied to the balls) formed of the rolling element rolling grooves for the purpose of linear guidance, enter a curved track formed of the rolling element circulation passages, leave this curved track, and then move through another linear track (where the balls are free from any load). And, the curved track portion (where the balls are free from any load) and the linear track portion (where the balls are free from any load) are also referred to as circulation passages.
In the linear guide device, as an apparatus aiming at enhancing the efficiency of the operation of balls, for example, there are known an apparatus which is disclosed in Japanese Utility Model Unexamined Publication No. 59-103928 of Showa (which is hereinafter referred to as the conventional example 1) and an apparatus disclosed in Japanese Patent Examined Publication No. 63-8330 of Showa (which is hereinafter referred to as the conventional example 2).
Of the two conventional examples, the conventional example 1 is structured such that, of outside guide members referred to as end caps forming the outside ball contact surfaces of the curved track in the circulation passages, the leading end portions thereof with which the balls are firstly contacted are set at positions where the outside guide members are contacted with the balls moving through the linear track while receiving a load, thereby reducing the impact of the balls against the leading end portions of the outside guide members when the balls are contacted therewith, so that the efficiency of the operation of the balls can be enhanced.
Also, the conventional example 2 is structured such that there is disposed a retainer in the entrance of each of the circulation passages so that the ball is scooped up with the retainer, to thereby reduce the impact of the ball against the circulation passage or curved track when the ball enters it from the linear track, so that the efficiency of the operation of the balls can be enhanced.
As described above, these conventional examples, in order to enhance the efficiency of the operation of the balls, aim at preventing the possibility that the balls can be arranged not in order but alternately, that is, preventing the so-called reeling movements of the balls; or, aim at achieving the smooth revolutions of the balls through the circulation track. However, these conventi
Kato Soichiro
Mizumura Yoshinori
Sato Ryoichi
Takahashi Nobumitsu
Yabe Shiroji
Bucci David A.
Hansen Colby
NSK Ltd.
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