Curvilinear motion guide units

Bearings – Linear bearing – Recirculating

Reexamination Certificate

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Details

C384S013000, C384S015000, C384S451000

Reexamination Certificate

active

06547437

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a curvilinear motion guide unit, which is comprised of a track rail extending lengthwise curved with a preselected curvature, and a slider arranged for a curvilinear motion along the track rail by virtue of rolling elements.
2. Description of the Prior Art
Recently various types of bearing guide unit have been used incorporated between components movable relatively of each other in modern advanced machine tools, conveyors, industrial robots, transfer machines, assembling apparatus, semiconductor fabricating apparatus, and so on.
Disclosed in Japanese Patent Laid-Open No. 101914/1987 is bearing means for revolving motion, which comprises a guide rail curved to have a preselected radius of curvature and provided on both radially opposing sides thereof with raceway grooves for load areas through which balls are allowed to run, a slider having two confronting legs that are made on inwardly faced surfaces thereof with raceway grooves for load areas conforming in curvature with the raceway grooves on the guide rail, and turnaround means for non-loaded areas where the balls are allowed to recirculate through there. The prior bearing means has a detachable cover, which can be opened to take the balls in and/or out of the slider. The cover when closed keeps the balls against falling away from the slider. Moreover, the turnaround means for non-loaded areas is provided by a tubular member of J-pattern, which is divided into halves opposing to one another.
Another Japanese Patent Laid-Open No. 186028/1988 discloses a curvilinear sliding-motion bearing system equivalent in construction with the bearing means for revolving motion cited just above, in which a slider containing rolling elements therein can move along a circular guide rail. The known curvilinear sliding-motion bearing system is designed for sliding components in devices and systems as diverse as machine tools, industrial robots, any conveying systems or the like to guide or transfer commodities or parts along any curvilinear line from a home or reference station to any other demand positions. The curvilinear sliding-motion bearing system is comprised of a movable platform provided therein with both raceway grooves for load areas and other raceway grooves for non-loaded areas, which are connected one another through turnarounds in end covers attached to the platform, to form endless raceways allowing rolling elements to recirculate through them, and a track rail made with raceway grooves confronting the raceway grooves in the platform to provide the load areas of the recirculation passages for the ball. The track rail is formed in arc or circle, and the confronting raceway grooves for the load areas in the platform and on the track rail are made so as to describe imaginary circles having centers of curvature, which are common to each other and also in alignment with the center of curvature of an imaginary circle along the track rail. Thus, the rolling elements or balls can run through the load areas defined between the confronting raceway grooves, while continuing to carry loads in all directions. With the curvilinear sliding-motion bearing system stated earlier, the adjustment of pre-loading can be performed by selecting balls somewhat larger in size than the clearance between the confronting raceway grooves for the load areas, or varying the clearance between the confronting raceway grooves by tightening bolts.
Moreover, a recirculating-curvilinear motion bearing system for revolving motion has been known in, for example, Japanese Patent Publication No. 11213/1987, in which bearing blocks movable along a circular track rail are arranged at angular intervals around the circular track rail. The circular track rail is made on only radially outside surface thereof with two rows of raceway grooves while the bearing block is also made on only its inside with two rows of raceway grooves confronting the raceway grooves on the track rail to form between them load areas through which balls run to carry the load. The bearing block has return passages of non-loaded areas for recirculating the balls. The balls in the load areas come in rolling contact with the associated raceway grooves at two radially opposing sectorial portions thereof. With the bearing system for revolving motion described just above, the bearing blocks can revolve around the radially outside of the circular track rail by virtue of balls. An eccentric bolt is arranged between the bearing block and a turntable mounted on the bearing block to urge the bearing block towards the circular track rail, adjusting finely the pre-loading.
Another type of curvilinear motion rolling guide unit has been developed, as unveiled in for example Japanese Patent Laid-Open No. 30638/1998, in which a slider is installed for sliding movement on a curved spline shaft extending lengthwise with a desired curvature. In the prior curvilinear motion rolling guide unit, the slider has a casing that is slashed off diagonally at lengthwise opposing ends thereof, which thus come perpendicular to the centroidal axis of the spline shaft. While the casing is more subjected at its radially outside half to the load than at its radially inside half, the outside half is longer lengthwise than the inside half because the opposing ends are tilted whereby the load may be made balanced between the inside and outside halves. Similar curvilinear motion guide units to that stated earlier are further disclosed in Japanese Patent Laid-Open Nos. 21441/1996 and 21440/1996.
In addition, a recirculating-ball linear motion bearing system has been known as in, for example, Japanese Patent Publication No. 2809/1992, which is comprised of an elongated track rail of rectangular shape in cross section having on its widthwise opposing upright surfaces raceway grooves, each to each upright surface, and a slider casing made with raceway grooves confronting the raceway grooves on the track rail, and rolling elements arranged in load areas defined between the confronting raceway grooves to allow the slider casing to move linearly. For recirculation of the rolling elements, return passages for non-loaded areas are made in the slider casing at locations above any upper shoulders of the track rail and closer to the centroidal axis than the shoulders of the track rail.
To this day, yet a variety of curvilinear motion guide units for moving the slider along the curved guide way have been conventionally proposed as stated earlier, and no commercially viable curvilinear motion guide unit has been developed. In the curvilinear motion guide unit where the track rail extends curved with a preselected curvature, the application of the slider similar in construction to the slider currently available for the prior linear-motion rolling guide units becomes problematic because the raceway grooves on the slider needs extending curved in compliance to the track rail and, therefore, the slider is required to afford to provide the return passages in the widthwise inward/outward areas. This causes a corresponding increase in widthwise dimension of the casing for the slider, thus, resulting in the major problem of failing in making the slider slim or compact with well balance. With the prior curvilinear motion guide units, moreover, it is required to always stock a variety of end caps different in specification depending on the diverse specifications of the curvature of the track rail and the overall length of the slider. This eventually raises disadvantages of increasing the number of parts required and rendering the management of parts and components much complicated.
SUMMARY OF THE INVENTION
The present invention, therefore, has as its primary object to overcome the major problem in the prior curvilinear motion guide units in which a slider can move along a track rail extending curved with a preselected curvature. More particular, it relates to a curvilinear motion guide unit in which the slider has a casing modified in location where return passages are arrange

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