Spacer for linear motion apparatus and linear motion apparatus provided with spacer

Abstract: A spacer (5) for a linear motion apparatus (1) is to be interposed alternately between balls (4) arranged in an endless circulation passage of the linear motion apparatus (1). The spacer (5) has a body portion comprising spherical retaining surface (11) portions formed for supporting the balls (4) on both end portions thereof in an advancing direction of the spacer (5) when moving in the endless circulation passage and a circumferential surface portion constituting an outer peripheral portion of the spherical retaining surface portions (11). The spherical retaining surface portion (11) has a radius of curvature smaller than a diameter of the ball (4) and the circumferential surface portion is provided with a groove (13) extending in the circumferential direction thereof so that one of the spherical retaining surface portions (11) is elastically deformable towards another one thereof. The spacer (5) is preferably applicable to various kinds of linear motion apparatus (1). Further, rollers as rolling members may be utilized in place of the balls (4).

Description: The present invention relates to a spacer which is to be interposed between 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 spacer being maintained, to make smooth the operation of the linear 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 case 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 realise 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 of 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 conditions can be maintained. There are known examples utilising 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. Patent 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 coast 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 is 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. Document CH-A-621 608 discloses a spacer for a linear motion apparatus which is to be interposed between rollers arranged in an endless circulation passage of the linear motion apparatus, the spacer having a solid body portion formed of an elastic material and comprising U-shaped recesses formed in both end portions thereof in an advancing direction of the spacer when moving in the endless circulation passage, the U-shaped recesses having a shape smaller than the circumferential shape of the roller such that upper and lower arm portions of the spacer supporting the rollers are elastically deformable away from one another. FR-A-1 104 502 discloses improvements relating to a device for maintaining the spacing of rolling elements in ball bearings and the like. LU-A-61 956 discloses a conical roller bearing and a method of assembling such a bearing. JP-A-06 173946 discloses a direct acting guide device. An object of the present invention is to substantially eleminate 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. According to a first aspect of the invention, there is provided a spacer for a linear motion apparatus which is to be interposed between rollers arranged in an endless circulation passage of the linear motion apparatus, said spacer having a body portion comprising curved retaining surface portions having a shape corresponding to a circumferential shape of the roller for supporting the rollers on both end portions thereof in an advancing direction of the spacer when moving in the endless circulation passage, characterised in that: the body portion further comprises a pair of upper and lower side surface portions connecting both the curved retaining surface portions, and an inner hollow portion is defined in the spacer body portion by the curved retaining surface portions and the pair of upper and lower side surface portions, said inner hollow portion extending in a direction substantially parallel to an axial direction of the roller so that one of the curved retaining surface portions is elastically deformable towards another one thereof in the advancing direction. In a preferred embodiment, the body portion has a length in the axial direction of the roller which is smaller than an axial length of the roller and has a height smaller than a length of the roller in a direction normal to the axial direction thereof. The body portion may be formed of a synthetic resin material through an injection molding process. According to the spacer of the invention, since the spacer is formed as a single member, it is easy to handle or maintain the spacers, contributing to cost reduction. Moreover, since one of the retaining surfaces is elastically deformable towards the other one thereof, the spacer can be sufficiently elastically deformed in its advancing direction. Therefore, such spacers 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 rollers on both sides of the spacer, and hence, the circulation between the loaded area and the non-loaded area in the roller circulation passage can be made smooth. Furthermore, in the arranged state of the spacers in the circulation passage, since the rollers are compressed and contracted, the space between the endless row of the rollers and spacers alternately arranged in the circulation passage is made no space (i.e. minus space) with respect to the wall portion thereof, so that the spacers can be positioned at the predetermined constant positions between the rollers due to the restoring force, thus preventing the rollers from biting the spacers during the rolling motion thereof. According to a preferred feature of the invention, the spacer comprises a projection piece formed on one of the upper and lower side surface portions of the body portion so as to extend in a direction perpendicular to an axial direction of the roller. According to a further preferred feature of the invention, the projection piece comprises a projected end having a round shape. The projection piece may be a plate member formed at substantially the central portion of one side surface portion of the spacer in the advancing direction. Specifically, the spacers may be formed with projection plates which are inserted into a guide groove formed on the roller circulation passage, so that the rollers can be smoothly moved and guided along the predetermined track in the circulation passage without meandering therein. According to a preferred feature of the invention, the spacer body is formed of a single elastic material. Preferably, the body portion has a length in the axial direction of the roller which is smaller than an axial length of the roller and has a height smaller than a length of the roller in a direction normal to the axial direction thereof. Preferably, the spacer is formed as a single member, such that it is easy to handle or maintain the spacers, contributing to cost reduction. Moreover, since one of the curved retaining surfaces is elastically deformable towards the other one thereof, the spacer can be sufficiently elastically deformed in its advancing direction. Therefore, such spacers are applicable to many kinds or types of linear motion apparatus or like, thus being widely practicable. According to a second aspect of the invention, there is also provided a linear motion apparatus comprising: a track member formed with a roller rolling surface; a slide member mounted to be relatively moveable to the track member formed with a roller circulation passage including a loaded roller rolling groove opposing to the roller rolling surface of the track member when mounted, the slide member being provided with guide groove formed along the roller circulation passage; a number of rollers arranged in the roller circulation passage so as to circulate therein in conformity with the relative motion of the slide member with respect to the track member; and a number of spacers arranged between the rollers in an alternate manner, each of the spacers being in accordance with the first aspect of the invention. In the accompanying drawings: Fig. 1 is a perspective view showing a linear rolling motion guide apparatus incorporated with a spacer according to a first embodiment of the present invention; Fig. 2 is a sectional view of a linear rolling motion guide apparatus incorporated with a spacer according to the first embodiment; Fig. 3 is a sectional view of a ball circulation passage along an axial direction of a rail of the linear motion rolling apparatus of Fig. 1; Fig. 4 is a perspective view of the spacer and rollers according to the first embodiment; Fig. 5 is a sectional view showing the spacer and the rollers according to the first embodiment; Fig. 6 is a sectional view of a linear rolling motion guide apparatus incorporated with a spacer according to a second embodiment of the present invention; Fig. 7 is a partial sectional view of Fig. 6 in an enlarged scale; Fig. 8 is a sectional view of a roller circulation passage along an axial direction of a rail of the linear motion apparatus of Fig. 6; Fig. 9 is a perspective view of the spacer and rollers according to the second embodiment; and Fig. 10 is a sectional view showing the spacer and rollers according to the second embodiment. With reference to Figs. 1 and 2, a linear rolling motion guide apparatus 21 provided with spacers 20 according to the first embodiment of the present invention is adapted to linearly guide a moveable member such as table or like on a fixed (fixing) member such as bed, saddle or like. The linear rolling motion guide apparatus 21 comprises a guide rail (track shaft) 22 disposed on the fixed member and formed with roller (rolling member) rolling surfaces 22a and ball rolling grooves 22b extending along a longitudinal direction thereof, a slide member 33 formed with a roller circulation passage including a loaded roller rolling groove 34a corresponding to the roller rolling surface 22a of the guide rail 22 and assembled with the guide rail 22 to be relatively moveable along the guide rail 22, a number of rollers (rolling members) 24, 24, ―, 24 arranged in the roller circulation passage and circulating therein in conformity with the relative motion of the moveable block 33 with respect to the guide rail 22, and a plurality of spacers 20, 20, ―, 20 interposed alternately between a plurality of rollers 24. Each roller 24 has a cylindrical shape having a circular cross section when cut along the rolling direction thereof. The roller rolling surface 22a provides a horizontally flat surface, and the ball rolling groove 22b has a circular sectional shape. The guide rail 22 has a long scale member having substantially a rectangular cross section. Two rows of the roller rolling surfaces 22a as tracks for rolling the rollers 24 are formed on side end portions of the upper surface of the guide rail 22 so as to extend along the entire longitudinal direction thereof, and two rows of the ball rolling grooves 22b as track for rolling the balls 25 is also formed on an upper portion of each of side surfaces of the guide rail 22 so as to extend along the entire longitudinal direction thereof. A plurality of bolt holes for fixing the guide rail 22 to the fixed member are formed in the longitudinal direction of the guide rail 22. Further, it is to be noted that a curved guide rail may be utilised in place of the linear guide rail shown in Fig. 1 and, in the illustrated example, as mentioned above, although the upper two rows of roller rolling surfaces 22a and side four rows of ball rolling grooves 22b (six rows in total) are formed on the guide rail 22, the number of rows may be changed in accordance with design, usage, objects of the linear rolling motion guide apparatus 21. The movable block 33 comprises a body portion 34 and end covers (plates) 35 disposed on both longitudinal end sides of the body portion 34, the body portion 34 and the end covers 35 being secured together by means of bolts. As shown in Fig. 2, the body portion 34 is composed of a body block 36a and mold products 36b and 36c. The body block 36a has high rigid structure formed of a rigid material such as steel so as to withstand a load applied to the moveable block 33 and is formed, on its upper surface as viewed, with a screw holes (see Fig. 1) for fixing an object to be guided by the guide apparatus. The mold products 36b and 36c are integrally formed with body block 36a by injecting a fused resin into a mold in which the body block 36a is placed, i.e: through a so-called insert molding method. Further, a metal such as aluminium may be utilised in place of the resin, and in such case, the body portion 34 is formed through a die-casting method. On the other hand, in place of the above method, the mold products 36b and 36c may be manufactured independently from the body block 36a, which will be thereafter assembled, or may be formed integrally through an MIM (metal-injection-mold) method. The body portion 34 comprises, to provide an inverted, substantially U-shaped cross section as viewed in Fig. 2, a horizontal portion 36 opposing (facing) to the upper surface of the guide rail 22 and bilateral skirt (leg) portions 37 extending downward from both end portions of the horizontal portion 36 and opposing to side surfaces of the guide rail 22 when the moveable block 33 is assembled with the guide rail 22. The horizontal portion 36 is formed with two rows of loaded roller rolling grooves 34a respectively opposing to the two roller rolling surfaces 22a formed on the upper surface of the guide rail 22 and the skirt portions 37 each is formed with two rows of the loaded ball rolling grooves 34b opposing the two rows of ball rolling grooves 22b formed on each side portion of the guide rail 22. The roller rolling groove 34a has a rectangular sectional shape, and the rollers 24 roll on the upper bottom surfaces of the roller rolling grooves 34a. The bilateral inside surfaces of the roller rolling grooves 34a are parallel to each other and a small gap is formed between the end faces of the roller 24 and the inside surfaces of the roller rolling groove 34a. According to such structure, the roller 24 is guided by the bilateral inside surfaces of the roller rolling groove 34a. The depth of the roller rolling groove 34a is formed to be smaller than the radial length of the roller 24 and, for example, is of about half length of the radius of the roller 24. Loaded roller rolling passages A and loaded ball rolling passages A' are formed in combination of the roller rolling surfaces 22a and the loaded roller rolling grooves 34a and the ball rolling grooves 22b and the loaded ball rolling grooves 34b, respectively. The horizontal portion 36 is formed with two through holes extending in parallel to the loaded roller rolling grooves 34a and tubular portions of the mold products 36c are integrally formed with these through holes. Return passages B are formed in the tubular portions of the mold products 36c formed with the through holes for returning the rollers 24, 24, ―, 24. The skirt portions 37 are also formed with through holes each extending in parallel to the loaded ball rolling grooves 34b, and tubular portions of the mold products 36c are integrally formed with these through holes. Return passages B' are formed in the tubular portions of the mold products 36c formed with the through holes for returning the balls 25, 25, ―, 25. The mold product 36b is formed integrally with the lower surface of the horizontal portion 36 and entire inner side surfaces of the skirt portions 37 of the body block 36a. Roller retaining portions (retainers) 39 are formed on the mold product 36b for preventing the block rollers 24 from coming off from the loaded roller rolling passages A at a time when the moveable block 33 is removed from the guide rail 22. With reference to Fig. 3, the mold product 36c is formed with arch-shaped inner periphery guide portions 36d which project at both the end portions of the body block 36a for forming rolling member (roller) rolling direction changing passage C, and the end covers 35 are formed with outer periphery guide portions 35a forming the direction changing passage C in combination of the inner periphery guide portions 36d. That is, when the end covers 35 are mounted to the body portion 34, the inner and outer periphery guide portions 36d and 35a are assembled to thereby constitute the U-shaped roller rolling direction changing passages C at both the end portions. The endless circulation passage is constituted by the loaded roller rolling passage A, the return passage B and the U-shaped direction changing passages C when assembled. According to the movement of the movable block 33 along the guide rail 22, the rollers 24, 24, ―, 24 are moved (rolled) from one end to the other end of the loaded roller rolling passage Awhile being applied with the load from the movable block 33, scooped by one of the direction changing passages C, guided to the return passage B and then returned to the one end of the loaded roller rolling passage A through the other one of the direction changing passages C. In this circulation motion, the rollers 24 roll, with the load being applied, in the loaded ball rolling passage A and circulate in the non-loaded direction changing passages C and the non-loaded return passage B. Generally, the rollers 24 move at a relatively high speed in the loaded area and at a relatively slow speed in the non-loaded area. According to the present invention, the spacers 20 are sufficiently elastically deformed in their advancing direction and one of the rollers 24, 24, disposed on both sides of the spacer 20 can be moved relatively to the other one thereof, the rollers 24 can smoothly pass the boundary portions between the loaded area and the non-loaded area in the endless circulation passage and, hence, smoothly circulated therein. Figs 4 and 5 show a spacer 20 to be assembled with the linear rolling motion guide device 21 shown in Fig. 1, for example. The spacer 20 is preferably made of a synthetic resin material through an injection molding process, for example. Each of the spacers 20 is disposed between the rollers 24 and is formed with curved retaining surfaces 28 at both end portions in an advancing direction (direction 1 ○, in Fig. 5) of the spacer 20. The curved retaining surface has a shape corresponding to a circumferential shape of the roller 24. When the curved retaining surfaces 28 of the spacer 20 abut against the rollers 24 on both end sides, the central line of the spacer 20 accords with the line connecting the central portions of the rollers 24 disposed on both sides thereof. The spacer 20 has a length, normal to the advancing direction corresponding to the axial direction of the roller 24, slightly smaller than the axial length of the roller so as not to contact the wall portion of the endless roller circulation passage, and the spacer 20 also has a height slightly smaller than a diameter of the roller 24. The spacer 20 has an inner hollow structure having a cavity 29 so that one of the curved retaining surfaces 28 is deformable towards the other one thereof, the cavity 29 extending in the direction parallel to the axial direction of the roller 24. That is, the spacer 20 comprises a pair of retaining portions 20a, each having the curved retaining surface 28, opposing to each other in the advancing direction and a pair of upper and lower connection portions 20b connecting the paired retaining portions 20a with the cavity 29 therebetween. Since the connection portions 20b are formed to be thin so as to be easily flexed, one of the curved retaining surfaces 28 is elastically deformed towards the other one thereof. The spacers 20 of the structure mentioned above and the rollers 24 are accommodated in the endless roller circulation passage in an alternate arrangement to each other. When the spacers 20 and the rollers 24 are assembled therein, since the spacers 20 are arranged in the state tightly compressed in the advancing direction, there is substantially no space or gap between the row of the rollers 24 and the spacers 20 and the wall portion of the endless circulation passage. Accordingly, each of the spacers 20 is firmly clamped between the adjacent rollers 24, 24 to a constant predetermined position by the restoring force of the spacer 20 itself, and hence, there is no fear that the rollers 24 bite the spacers 20 during the circulation thereof. With reference to Fig. 1 as the body block 36a moves along the guide rail 22 the rollers 24, 24, ----, 24 roll, while being applied with the load from the movable block 36a, in the loaded roller rolling passage A from one end to the other end thereof. Thereafter, the rollers 24 are scooped by one of the rolling direction changing passages C, then guided to return passage B, and thereafter, returned to the one end of the loaded roller rolling passage A by way of the other one of the rolling direction changing passage C. In this circulation motion, the rollers 24 roll with the loaded state in the loaded area of the loaded roller rolling passage A and roll with the non-loaded state in the non-loaded area of the direction changing passages C and the return passage B. In general, the rollers 24 roll fast in the loaded area and slow in the non-loaded area. According to this first embodiment, since the spacers 20 are sufficiently elastically deformed in the advancing direction and one of the rollers 24 disposed on both advancing sides of the spacer 20 can be relatively moved with respect to the other one of the rollers 24, the rollers 24 can be smoothly moved between the loaded area and the non-loaded area in the endless roller circulation passage. Figures 6 to 8 show a linear rolling motion guide apparatus 31 incorporated with a spacer according to a second embodiment of the present invention. With reference to Figs 6 to 8, the linear rolling motion guide apparatus 31 comprises, as like as the apparatus 21 of the former embodiment, a guide rail 22, a movable body block 33 assembled with the guide rail 22 to be relatively movable along the guide rail 22, a number of rollers 24, 24, ---, 24 and a number of balls 25, 25, ---, 25, and accordingly, like reference numerals are added to the features corresponding to those of the guide apparatus 21 and the detailed explanations thereof may be omitted herein. The movable block 33 is composed of a body portion 34 and a pair of end covers 35 which are fastened to each other by means of bolts or like. The body portion 34 comprises a body block 36a and mold products 36b and 36c, and the mold products 36b and 36c are formed integrally with the body block 36a by injecting a fused resin in a mold in which the body block 36a is preliminarily set, by means of a so-called insertion molding process. Furthermore, the body portion 34 has a horizontal portion 36 opposing to the upper surface of the guide rail 22 in an assembled state and a pair of bilateral skirt (leg) portions 37 extending downward from both side ends of the horizontal portion 36 so as to oppose to the side surfaces of the guide rail 22 in the assembled state. The horizontal portion 36 is formed with two roller rolling grooves 34a, 34a as loaded roller rolling surfaces opposing to the roller rolling surfaces 22a of the upper surface of the guide rail 22. The skirt portions 37 are formed with upper and lower loaded ball rolling grooves 34b, 34b corresponding to the ball rolling grooves 22b, 22b formed on the side surfaces of the guide rail 22. The roller rolling surfaces 22a and the roller rolling grooves 34a constitute the loaded roller rolling passages A in combination, and on the other hand, the ball rolling grooves 22b, 22b and the loaded ball rolling grooves 34b, 34b constitute the loaded ball rolling passage A'. The horizontal portion 36 is also formed with two through holes extending in parallel to the roller rolling surfaces 22a of the guide rail 22 in the longitudinal direction of the movable block 33. Tubular portions of the mold products 36c, 36c are inserted into these through holes integrally, and the tubular portions have inner hollow portions formed as roller return passages B. Each of the skirt portions 37 is also formed with two (four in total) through holes in each side extending in parallel to the loaded ball rolling grooves 34b, 34b. The tubular portions of the mold product 36c are inserted into these through holes integrally, and the tubular portions have inner hollow portions formed as ball return passages B'. With reference to Fig. 7, the mold product 36b is formed integrally with the entire inner surface of the body block 36a including the lower surface of the horizontal portion 36 and the inside surfaces of the skirt portions 37. To the mold product 36b, there are provided roller retaining portions (retainers) 39 for preventing the rollers 24 from coming off from the loaded roller rolling passages A at the time of drawing out the movable block 33 from the guide rail 22, and there are also provided ball retaining portions (retainers) 40 for preventing the balls 25 from coming off from the loaded ball rolling passage A' at the movable block draw-out time. Referring to Fig. 8, arch-shaped inner periphery guide portions 36d, 36d are formed on both end portions of the body block 36a so as to project outward to thereby form rolling direction changing passages C to the mold product 36c, and to the end covers 35, there are formed outer periphery guide portions 35a, 35a for forming the rolling direction changing passages C in combination with the inner periphery guide portions 36d, 36d when the end covers 35, 35 are mounted to the body block 36a. As mentioned above, the endless roller circulation passage is thus formed by the combination (assembling) of the loaded rolling passage A, the U-shaped rolling direction changing passages C and the return passage B. According to the linear rolling motion guide apparatus 31 of the present embodiment having the structure mentioned above, when the rollers 24 are circulated, spacers 45 are two-dimensionally changed in their directions. That is, the rollers 24 roll and are changed in the rolling directions from the linear loaded rolling passage A, U-shaped one direction changing passage C, return passage B and U-shaped other direction changing passage C. There is formed a guide groove 43 (see Figs 6-8) to an inner periphery side of the endless roller circulation passage for receiving projection plates 41 of the spacers 45, and in this purpose, the guide groove 43 has a width slightly larger than a thickness of the projection plate 41. When the rollers 24, i.e. spacers 45, are moved in the endless roller circulation passage, the projection plates 41 of the spacers 45 move along the guide groove 43. Figs 9 and 10 show the spacers 45 of the second embodiment to be assembled in the linear motion rolling guide apparatus 31. The spacer 45 is also formed through the molding process of a resin as in the first embodiment mentioned hereinbefore. The spacer 45 is formed with curved retaining surfaces 42 to its both ends in the advancing direction thereof, the retaining surfaces 42 having a shape corresponding to the outer circumferential shape of the roller 24. The spacer 45 is formed with an inner hollow portion (cavity) 46 extending in a direction parallel to the axial direction of the roller 24 so that one of the curved retaining surfaces 42 is elastically deformable towards the other one thereof when compression is applied. Furthermore, as briefly mentioned above, the spacer 45 is formed with the projection plate 41, different from the spacer 20 in the former embodiment, extending outward (upward) in a direction normal to the axial direction of the roller 24. The projection plate 41 is formed at substantially the central portion of one of connection plates 45a connecting both the curved retaining surfaces 42. The projected end portion of the projection plate 41 is inserted into the guide groove 43 formed on the inner periphery surface of the endless roller circulation passage. Further, it is preferred that the projected end portion of the projection plate 41 has a circular outer shape for easy insertion and smooth circulation in the guide groove 43. The spacer 45 of this second embodiment can attain substantially the same functions as those of the first embodiment, and in addition, according to the spacer 45 of the second embodiment, since the projection plates 41 of the spacers 45 can be guided along the predetermined path in the guide groove 43, the rollers 24 supported by the spacers 45 can be moved and circulated smoothly and stably in the endless roller circulation passage without rolling in a meandering manner, for example. Particularly, since the spacers 45 are not moved in the meandering manner in the roller axial direction, the collision of the axial end surfaces of the spacers 45 against the wall portion of the endless roller circulation passage can be effectively prevented. The spacers 20 and 45 according the present invention may be applicable, other than the linear rolling motion guide apparatus 21 and 31 respectively mentioned hereinabove, to a roller screw apparatus or a roller spline apparatus, the latter comprising a spline shaft as a track member and a slide member as an outer cylindrical member mounted to be movable to the spline shaft through a number of rollers.

Claims: A spacer (45) for a linear motion apparatus (31) which is to be interposed between rollers (24) arranged in an endless circulation passage of the linear motion apparatus, said spacer having a body portion comprising curved retaining surface portions (20a, 42) having a shape corresponding to a circumferential shape of the roller (24) for supporting the rollers on both end portions thereof in an advancing direction of the spacer when moving in the endless circulation passage, the body portion further comprising a pair of upper and lower side surface portion (20b, 45a) connecting both the curved retaining surface portions, and an inner hollow portion (46) is defined in the spacer body portion by the curved retaining surface portions and a pair of upper and lower side surface portions (20b, 45a), said inner hollow portion extending in a direction substantially parallel to an axial direction of the roller so that one of the curved retaining surface portions is elastically deformable towards another one thereof in the advancing direction. The spacer (45) for a linear motion apparatus (31) according to claim 1, further comprising a projection piece (41) formed on one of the upper and lower side surface portions (20b, 45a) of the body portion so as to extend in a direction perpendicular to an axial direction of the roller (24). The spacer (45) for a linear motion apparatus (31) according to claim 2, wherein said projection piece has a projected end having a round shape. The spacer (45) for a linear motion apparatus (31) according to any one of claims 1 to 3, wherein said spacer body portion is formed of a single elastic material. A linear motion apparatus (31) comprising: a track member (2) formed with a roller surface; a slide member (3) mounted to be relatively movable to the track member formed with a roller circulation passage including a loaded roller rolling groove (A) opposing to the roller rolling surface of the track member when mounted, said slide member being provided with a guide groove (43) formed along the roller circulation passage; a number of rollers (24) arranged in the roller circulation passage so as to circulate therein in conformity with the relative motion of the slide member with respect to the track member; and a number of spacers (45) arranged between the rollers in an alternate manner, each of the spacers according to any one of the preceding claims.

Inventors: KONOMOTO MASASHI, MICHIOKA HIDEKAZU, KONOMOTO, MASASHI, MICHIOKA, HIDEKAZU, Konomoto, Masashi, c/o THK Co. Ltd, Michioka, Hidekazu, c/o THK Co. Ltd
Applicants: THK CO LTD, THK CO., LTD.
Application year: 2000
Main classification: F16C19
IPC codes: F16C33, F16C29, F16C19