Bearings – Linear bearing – Recirculating
Reexamination Certificate
2000-04-28
2002-03-05
Hannon, Thomas R. (Department: 3682)
Bearings
Linear bearing
Recirculating
C384S051000, C384S520000, C384S551000
Reexamination Certificate
active
06352367
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a spacer, as a rolling member and as a retaining member, interposed between balls or rollers arranged in an endless circulation passage of a linear motion apparatus and also relates to a linear motion apparatus provided with such spacer.
It is conventionally known to interpose spacers between rolling members such as balls or rollers accommodated and arranged in the endless rolling member circulation passage of linear rolling motion guide apparatus, ball screws, ball splines or like, which will be generally called as “linear motion apparatus” herein. The location of such spacers prevents the rolling members from being directly contacted to each other with a proper space being maintained, to make smooth the operation of the liner motion apparatus and to effectively prevent generation of noise caused by collision of the respective rolling members.
However, in the arrangement in which the spacers are interposed each between the rolling members, it is inevitable to cause a dimensional error between a total length of an endless row of the rolling members and the spacers arranged alternately with the state contacted to each other and a total length of the endless circulation passage in which these rolling members and spacers are accommodated. In order to obviate such defect, at least one spacer having a length different from that of another spacer is incorporated as an error absorbing spacer.
In a case of adopting the structure in which such error absorbing spacer is incorporated, in order to obtain or realize the most suitable arranging conditions of the rolling members for a plurality of apparatus or different kinds of devices, it is necessary to prepare a plurality of error absorbing spacers having different lengths and incorporate them by selecting suitable one for each of the linear motion apparatus or devices. However, it is troublesome and inconvenient for the maintenance of parts or the like to always prepare or reserve a plurality of error absorbing spacers for these different kinds of apparatus or devices. Furthermore, since the spacers are usually formed of resin materials, it is also necessary to prepare or manufacture a plurality kinds of molds to manufacture the spacers, involving much cost, thus being inconvenient.
Still furthermore, there is a possibility of existing a slight gap between the rolling members and the rigid spacers even if the error absorbing spacer is incorporated, and such gap may be increased due to wearing of the spacers through a long time use even if the apparatus or device is assembled with substantially no dimensional error at the assembling time.
In order to eliminate such defect, there is provided a countermeasure of using an elastic spacer having an elasticity. When such elastic spacers are used, the elastic spacers are shrunk in the endless row to thereby obtain substantially complete (tight) contact condition between the rolling members and the spacers, and even if the rolling members and the spacers are worn, the spacers are expanded by their elasticity, so that the tight contact condition can be maintained.
There are known examples utilizing such elastic spacers as disclosed in Japanese Utility Model Laid-open Publication No. SHO 53-90158 showing a structure that a spring is interposed between a pair of disc-shaped ball retainers and also disclosed in U.S. Pat. No. 2,827,345 showing a structure two dish-shaped elastic members having recessed portions adjacent to each other. However, in such structures that the elastic spacer is composed of a plurality of portions or elements, there is a fear that the spacer may be disassembled during the use thereof, thus being inconvenient and troublesome in the maintenance thereof and cost increasing will be inevitable, thus being not practical.
Still furthermore, in order to solve the above problem, the prior art further provides an elastic spacer composed of a single member, as disclosed in Japanese Utility Model Publication No. SHO 51-10285, having a ring-shaped spacer body formed with spherical retaining surfaces at both end surfaces in an advancing direction thereof for holding the ball and formed with a slit connecting an inner periphery and an outer periphery of the ring-shaped spacer body. However, since this elastic spacer is elastically deformed so that the ring is opened at both sides of the slit, it is impossible to make large a deformable (displaceable) amount in the advancing direction of the elastic spacer. Because of this reason, it is not sure that such elastic spacer is properly usable for various kinds of linear motion apparatus or devices to be manufactured, and there may cause a case where relative motion of the balls which are going in and out from loaded area and unloaded area. Thus, the smooth circulation of the rolling members cannot be expected.
Still furthermore, a prior art provides an elastic spacer composed of a single member, as disclosed in Japanese Patent Publication No. HEI 4-27405, having a structure in which the spacer is formed, at its both ends in the advancing direction, with curved retaining surfaces for holding the roller and cutouts are formed on the curved retaining surfaces so as to extend in an axial direction thereof. However, such elastic spacer is also elastically deformed so that both sides of the cutout of the curved retaining surface is opened, so that it is impossible to make large a deformable (displaceable) amount in the advancing direction of the elastic spacer.
SUMMARY OF THE INVENTION
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a spacer, composed of a single member, of a linear motion apparatus capable of having a relatively large elastically deformable amount in its advancing direction and also provide a linear motion apparatus provided with such spacers.
This and other objects can be achieved according to the present invention by providing, in the first aspect, a spacer for a linear motion apparatus which is to be interposed between balls arranged in an endless circulation passage of the linear motion apparatus, the spacer having a body portion comprising spherical retaining surface portions formed for supporting the balls on both end portions thereof in an advancing direction of the spacer when moving in the endless circulation passage and a circumferential surface portion constituting an outer peripheral portion of the spherical retaining surface portions, wherein the spherical retaining surface portion has a radius of curvature smaller than a diameter of the ball and the circumferential surface portion is provided with a groove extending in the circumferential direction thereof so that one of the spherical retaining surface portions is elastically deformable towards another one thereof in the advancing direction.
In a preferred embodiment of this first aspect, the body portion has a length in a direction normal to the advancing direction thereof smaller than the diameter of the ball, and the body portion may be formed of a synthetic resin material through an injection molding process.
According to the spacer of this first aspect, since the spacer is formed as a single member, it is easy to handle or maintain the spacers. Moreover, since the radius of curvature of the spherical retaining surface is made smaller than the diameter of the ball as rolling member, a gap is present therebetween, and since the outer peripheral portion of one of the spherical retaining surfaces is elastically deformable towards the other one thereof, the spacer can be sufficiently elastically deformed in its advancing direction. Therefore, such spacer are applicable to many kinds or types of linear motion apparatus or like, thus being widely practicable.
Much elastically deformable amount of the spacer in its advancing direction makes it possible to ensure sufficient relative movement of the balls on both sides of the spacer, and hence, the circulation between the loaded area and the non-loaded area in the b
Konomoto Masashi
Michioka Hidekazu
Armstrong Westerman & Hattori, LLP
THK Co., LTD
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