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.
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 composition carriage frame composed of end caps and side walls integral with the end caps. The components making up the slider contributes to a remarkable reduction of the desired parts and members in their numbers, and each of which has any engaging means that may come into mutually interlocking or fitting relation with a complementary engaging means of any counterpart, thus allowing to complete a composite construction with even no use of fasteners such as bolts, screws and so on.
The present invention is concerned with a linear motion guide unit; comprising a track rail having first raceway grooves on lengthwise sides thereof, a slider conforming to the track rail to fit over the track rail for movement relatively to the track rail and also having second raceway grooves confronting the first raceway grooves, and a ball-recirculating circuit allowing rolling elements to run through there, the ball-recirculating circuit including a load raceway defined between the first and second raceway grooves, a turnaround formed in the slider and connected at any one end thereof with the load raceway, and a return passage formed in the slider and connected to another end of the turnaround; wherein the slider is composed of a carriage including an upper major section extending in opposition to and parallel with an upper surface of the carriage and sidewise opposing wings depending downward from widthwise opposing side edges of the upper major section to extend over the lengthwise sides of the track rail, one to each side, and a composite carriage frame including end caps arranged on forward and aft ends of the carriage, one to each end, and side walls integral with the end caps and extending along sidewise outside surfaces of the carriage; and wherein the carriage has on the forward and aft ends thereof first engaging means, while the end caps have second engaging means that will come into fitting engagement with the first engaging means.
In one aspect of the present invention, a linear motion guide unit is disclosed in which the return passage in the slider is constituted with a first channel made lengthwise on the sidewise outside surface of any one of the wings of the carriage, and a second channel made lengthwise on an inside surface of any one of the side walls in opposition to the first channel.
In another aspect of the present invention, a linear motion guide unit is disclosed in which the first channel on the wing of the carriage is made semicircular in cross section and arranged to provide the return passage extending in parallel with the associated second raceway groove.
In another aspect of the present invention, a linear motion guide unit is disclosed in which at a corner where any one of the wings merges into the upper major section of the carriage there is provided a notched mark to indicate which side of the carriage is made with upper and side reference surfaces.
In another aspect of the present invention a linear motion guide unit is disclosed in which the first engaging means on the carriage is any one of first concavity and convexity, while the second engaging means on the end cap is any one of second convexity and concavity, which is complementary to the first engaging means to make fitting engagement between them.
In another aspect of the present invention, a linear motion guide unit is disclosed in which the convexity, whether the first or the second, is a pin circular in cross section and the concavity, whether the first or the second, is a hole circular in cross section.
In another aspect of the present invention, a linear motion guide unit constructed as defined in claim 1 wherein the upper major section of the carriage is made in a configuration that has a traverse cross-section uniform lengthwise throughout overall the length thereof.
In another aspect of the present invention, a linear motion guide unit is disclosed in which the composite carriage frame is made in a frame construction capable of accommodating the carriage.
In a further another aspect of the present invention a linear motion guide unit is disclosed in which the composite carriage frame is made warped elastically to allow the lengthwise opposing end caps to embrace the forward and aft ends of the carriage, whereby the second engaging means of the composite carriage frame come into fitting engagement with the first engaging means of the carriage to unite the composite carriage frame with the carriage.
In another aspect of the present invention, a linear motion guide unit is disclosed in which the composite carriage frame is composed of a first composite component that is made up of first inside end cap parts and first side wall panels integral with the first inside end cap parts, and a second composite component that is made up of second outside end cap up parts and second outside side wall panels integral with the second outside end cap parts.
In another aspect of the present invention, a linear motion guide unit is disclosed in which the first end cap part is composed of a first crossbar section and first legs, which are arranged to directly face the associated end face of the carriage, and the second end cap part is also composed of a second crossbar section and second legs, which are arranged to cover over the outermost face of the first end cap part.
In another aspect of the present invention, a linear motion guide unit is disclosed in which the first side wall panels fit in undercuts made in sidewise outsides of the carriage to provide upper halves of the side walls and further the second side wall panels conform underneath the first side wall panels, with coming into abutment with both undersurfaces of the first side wall panels and outside surfaces of the undercuts thereby providing lower halves of the side walls.
In another aspect of the present invention, a linear motion guide unit is disclosed in which the legs of the first end cap part are provided with third engaging means, while the second legs of the second end cap part are provided with fourth engaging means complementary to the third engaging means, so that fitting engagement between the third and fourth engaging means makes sure of joining together the first end cap part with the second end cap part.
In a further another aspect of the present invention, a linear motion guide unit is disclosed in which the third engaging means is either a pair of convexities rectangular in cross section or a pair of concavities rectangular in cross section, while the fourth engaging means is either a pair of concavities rectangular in cross section or a pair of concavities rectangular in cross section, which are complementary to the third engaging means.
In another aspect of the present invention, a linear motion guide unit is disclosed in which the first end cap parts of the first composite component each have the second engaging means, and an upper turnaround channel to define the turnaround, while the first side wall panels of the first composite component each have an upper second channel to form partly an upper region of the second channel, and further the second end cap parts of the second composite component each have a lower turnaround channel to form the turnaround, while the second side wall panels of the second composite component each have a lower second channel to form partly a lower region of the second channel, so that the return passage is made up of the first channel formed on the carriage, the upper second channel and the lower second channel.
In another aspect of the present invention, a linear motion guide unit is disclosed in which the first channel on the carriage to provide the return passage is made semicircular in cross section while the upper second channel on the first side wall panel and the lower second channel on the second side wall panel are each made a quarter segment in cross section.
In another aspect of the present invention, a linear motion guide unit is disclosed in which there are provided claws at an area where the second raceway groove on the carriage joins with the associated upper turnaround channel in the first end cap part and at another area where the second raceway groove on the carriage joins with the associated lower turnaround channel in the second end cap part, the claws serving to scoop rolling elements, which run through the ball-recirculating circuit, thereby transferring the rolling elements either from the load raceway to the associated turnaround or from turnaround to the load raceway.
In a further another aspect of the present invention, a linear motion guide unit is disclosed in which the first end cap part of the first composite component and the second end cap part of the second composite component have positioning means, respectively, which will come into fitting engagement with each other to help assemble the components with accurate positioning relation.
With the linear motion guide unit constructed as stated earlier, the slider is made up of only the carriage, and the first and second composite components. This construction results in reducing the number of parts or components required. Assembly of the carriage with the composite components is realized with the mutual fitting system, with no need of fasteners such as bolts and screws. This assembling system contributes to making the slider simple in construction and much conformable to a linear motion guide unit for use in very small machines, with even helping ensure the accurate positioning among the components and also the high precision enough to realize smooth sliding motion of the slider.
According to the linear motion guide unit of the present invention, the slider moving along the track rail is constituted with only two parts: the carriage and the composite carriage frame, the latter having the end caps and side walls, and further the two parts are assembled mutually into an unitary composite construction by only mutual engagement of fitting elements with any complementary elements, rather than using any fastener such as screws and so on. Thus, it will be said that the present invention succeeds to provide a linear motion guide unit that realizes reducing the number of components or parts needed and correspondingly making the slider itself as small as possible. The linear motion guide unit of the present invention may be made in a wide range of sizes and used in a variety of types, and therefore most favorable for machines that are very small in construction, with even requiring high precision in operation.