Linear motion guide unit

Bearings – Linear bearing – Recirculating

Reexamination Certificate

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Details

C384S044000

Reexamination Certificate

active

06685355

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear motion guide unit adapted for use in various types of machinery such as diverse industrial robots, semiconductor manufacturing machines, precision machines, machine tools, and so on.
2. Description of the Prior Art
Most linear motion guide units have been used extensively between relatively movable parts to meet desired functional demands; for example, high precision, high speed, miniaturization, and so on in diverse fields of machinery such as various industrial robots, semiconductor manufacturing apparatus, testing instruments, machine tools, and so on. In recent years the linear motion guide unit, besides ensuring the improved performance such as high precision, high speed, and so on, needs refining on maintenance-free property and also to be miniaturized or made very small in construction. To do this, members and parts making up the linear motion guide unit are made as small as possible in construction, and reduced in their number to lessen the manufacturing steps and any inaccuracy resulting from assembly thereof. This industrial tendency eventually needs to make the members and parts integral in modular construction that all of elements will go together without any processing operation such as boring of small hole, drilling of tiny screwed hole, joining with mechanical fasteners, and so on. While the linear motion guide unit comes to play an indispensable element in modern industrial machines, and therefore is made in a wide range of sizes and used in a variety of types, diverse machines including semiconductor fabricating equipment and assembly machines are in need of a miniature linear motion guide unit in which a slider is allowed to move smoothly along a guide track.
Bearing means for linear sliding motion have been conventionally known, for example disclosed in Japanese Patent No. 2846050, in which a ball-recirculating passage is designed in a way lessening joints or discontinuities therein in number to allow the balls to run smoothly through there, and tiny parts are reduced in number to refine on the efficiency in assembling steps, thereby making it possible to complete the bearing means with an inexpensive cost and a very short time. The prior bearing means recited just above includes a track rail, a sliding platform movable on the track rail and more than one rolling element. The sliding platform has a metallic block of a thick plate integral with a pair of legs that is arranged underneath the thick plate and made with inside raceway grooves, each to each leg, for providing load raceways where the rolling elements run through there, an annular frame formed in a tetragonal configuration in top plan view so as to fit over the legs of the metallic block, the tetragonal frame being made on the underneath thereof with raceway grooves for providing non-loaded raceways that communicate with the load raceways to allow the rolling elements to recirculate through there and recesses that are formed forward and aft to fit over and conform to the track rail, and a pair of sidewise opposing elongated plates made on the upper surfaces thereof with raceway grooves that will form the non-loaded raceways where the rolling elements are allowed to run through there when the plates are joined together with the underneath of the tetragonal frame. The tetragonal frame has projections that will come into fitting engagement with grooves outside the legs to hold the tetragonal frame in assembled relation with the legs. Moreover, the tetragonal frame is made at the four corners thereof with holes in which pins fit to join the elongated plates with the tetragonal frame.
Disclosed in Japanese Patent No. 2775129 is a linear motion guide unit that a sliding block is comprised of a first component made therein with a non-loaded area of a ball-recirculating passage where rolling elements are allowed to run through there, a second metallic component made with a groove to define a load area of the ball-recirculating passage, and a pair of third components that fit between the first and second components at forward and aft ends of the sliding block.
Another prior linear motion guide arrangement is disclosed in Japanese Patent No. 2936166 in which there is shown a snap fastener that does not require any fastening screw to join together the components. With the prior linear motion guide arrangement recited just above, reversing bodies are secured on forward and aft ends of a carriage member by engaging lugs projecting out of the end faces of the reversing bodies on the upper surface of the carriage member. The combination of the carriage member with the forward and aft reversing bodies is accommodated in a guide carriage enclosure and secured to the enclosure by the action of the snap fasteners.
Nevertheless, the bearing means for linear sliding motion recited first, despite being envisaged to render it suitable for use in the miniature linear motion guide units, is so constructed as becoming adversely bulky in size because of the legs jutting out from the underneath of the thick plate of the block. Moreover, the construction that the non-loaded raceways or return passages are defined between the confronting annular frame and elongated plates results in rendering the sliding platform large in widthwise dimension. Any attempt to reduce the sliding platform in width will result in rendering the legs slim in their breadth, thus raising a major disadvantage of reducing the legs in rigidity or stiffness. On assembly to complete the sliding platform, the tetragonal frame is secured to the legs in a way the projections of the tetragonal frame click into the associated recesses formed on the outside surfaces of the legs. This construction will plague the workers with a troublesome exertion of bending forcibly the projections on the tetragonal frame to bring them into interlocking engagement with the inner recesses on the legs.
With the second linear motion guide unit recited earlier, the metallic second component, as being made lengthwise uniform in traverse cross-section, may be produced easily. Nevertheless, both the return passages and the turnarounds making up the non-loaded areas in the ball-recirculating circuits are mainly formed in the third component. Thus, the ball-recirculating circuits, which is provided in a composition of three components: the first, second and third components, will fail to make a tunnel round in traverse cross-section, especially at the turnarounds will become a passage U-shaped in cross section. This ball-recirculating circuit might cause any rattling sound or vibration especially when the small rolling elements run through there, thus interfering with a smooth running of the rolling elements. Besides, drilling operation of screwed holes is needed because of the construction in which fasteners are driven in the holes on the forward and aft ends of the second component to join together all components into an unit.
With the last linear motion guide arrangement recited earlier, the turnarounds and return passages making up the ball-recirculating circuits are formed in distinct components, independently: the reversing bodies made therein with the turnarounds, and the guide carriage enclosure made with the return passages. Such construction is tough of making the ball-recirculating circuits smooth, and also makes the guide carriage an intricate composition.
SUMMARY OF THE INVENTION
The present invention, therefore, has as its primary object to overcome the problems as stated earlier and particularly to provide a linear motion guide arrangement adapted for use in machinery that is legion in uses, industrial fields and made in a wade range of size. The present invention is more particular envisaged to provide a linear motion guide unit that is most preferable for use in very small machines. To this end, the linear motion guide unit of the present invention includes a slider movable on a track rail in a sliding manner, which is constituted with two components: a carriage and a compositi

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