RECTILINEAR GUIDE DEVICE

Abstract: According to the present invention, a rectilinear guide device comprises: a track base (1) formed to provide a substantially U-shape in section and provided on the inner side surfaces thereof with rolling surfaces (12) for rolling elements (2); and a bearing block (B) having loaded rolling surfaces (31a - 31d) for clamping the rolling elements (2) in cooperation with the rolling surfaces (12) and for stroking in a recessed portion of the track base (1) in accordance with the rotating amount of a feed screw shaft (7) threadably coupled therewith; is characterized in that the bearing block (B) consists of a block body (3), rolling hole-forming plates (5) and lid members (4), and only the joining of the above-mentioned members can form a ball circulation course through which non-loaded balls circulate. Accordingly, a long bearing block can be easily produced, and the number of the loaded rolling elements are increased, so that a rectilinear guide device having a large maximum load and being compact in size can be obtained.

Description: The present invention relates to a linear guide device used, for example, in a linear motion component of a machine tool or an industrial robot. A linear guide device of the type described above and in accordance with the preamble of claim 1 is disclosed in Japanese Laid-Open Patent publication No. 62-200016. Specifically, as shown in Figure 17, a bearing block (a) (will be called merely as a "block") is provided at its opposite side surfaces with load ball grooves (c) in which balls (b) roll. A pair of track beds (d) is disposed with the block (a) therebetween. The beds (d) are provided with ball rolling grooves opposed to the load ball grooves (c). The balls (b) held between the load ball grooves (c) and the ball rolling grooves support the block (a) so that the block (a) may be movable along the track beds (d). A screw shaft (f) of a feed screw mechanism is engaged with a central portion of the block (a), so that the screw shaft (f) may be rotated to move the block (a) along the track beds (d). According to this linear guide device, since the bearing block for supporting a movable member such as a table is constructed integrally with the feed screw mechanism for applying a driving force for the linear motion to the movable member, a compact construction of the device can be achieved, and a height of the movable member can be minimized, which enables a stable motion. However, with respect to the bearing block of the linear guide device described above, opposite ends of each load ball groove must be connected by a ball circulation path so as to guide or introduce the balls from a termination end of the load ball groove to a start end of the load ball groove again. In the prior art, the ball circulation path is generally formed of a no-load ball rolling aperture, which is formed in the block to correspond to each load ball groove, and ball return paths, each of which connects an end of the ball load groove and an end of the no-load ball rolling aperture. However, the no-load ball rolling aperture is a very small aperture having a diameter only slightly larger than that of the ball, and thus it is difficult to form a long no-load ball rolling aperture by drilling. Therefore, machining of the no-load rolling aperture restricts increase of a length of the block, and thus restricts the length of the load ball groove. Generally, in a bearing which employs rolling members such as balls for bearing the motion between two objects, a maximum allowable load may be increased by 1 ○ increasing sizes of the rolling members, or 2 ○ increasing numbers of the rolling members which roll on the load rolling groove. However, the latter can be hardly applied to practical products because the lengths of the load ball grooves are restricted due to the above described reason. The present invention is devised in view of the above problems. It is an object of the invention to provide a linear guide device, which allows easy formation of no-load rolling apertures for rolling members and has a large maximum allowable load and small size. The present invention provides a linear guide device comprising: a track bed having a substantially rectangular section, which track bed is opened at one side and is provided at its inner surfaces with rolling surfaces for rolling members; a bearing block having load rolling surfaces cooperating with said rolling surfaces of the track bed to hold the rolling members therebetween and moving in a hollow portion of the track bed in accordance with a degree of rotation of a feed screw shaft engaging the bearing block, said bearing block having a block body, no-load rolling apertures for the rolling members, and covers which are engaged with front and rear end surfaces of the block body, said covers forming return paths for the rolling members which connect the load rolling surfaces and the no-load rolling apertures, respectively; and said block body including a ball-nut portion engaging the feed screw shaft, and a pair of bearing portions projecting from opposite sides of the ball-nut portion; characterised in that the load rolling surfaces are formed at corners of the bearing portions, and said bearing block further includes rolling aperture forming plates which cooperate with upper and lower sides of the bearing portions to form the no-load rolling apertures, and which retain the rolling members rolling on the load rolling surfaces. According to the subject of the invention described above, the load rolling surfaces formed on the bearing block may be appropriately varied with respect to its configurations including a number of the surfaces and a contact angle thereof to the rolling members, provided that the load rolling surfaces can bear the load applied to the block, and that the variation does not apply the load to the screw shaft engaging the block body. In a construction in which the no-load rolling apertures are formed by the bearing portions of the block body and the rolling aperture forming plates engaging them, the apertures may be formed by no-load rolling grooves provided in the block body and closed or covered with the rolling aperture forming plates, or conversely, may be formed by the no-load rolling grooves provided in the rolling aperture forming plates engaging the block body. Further, the rolling members used in the invention may be appropriately selected from balls, rollers and others. According to the above subject, since the no-load rolling apertures in the bearing block are formed by attaching the rolling aperture forming plates to the block body, the no-load rolling apertures can be easily manufactured by forming grooves for receiving the rolling members in one or both of the members, which facilitates manufacturing of a long bearing. Since the bearing block is formed by attaching the rolling aperture forming plates and the covers to the block body, the block body may have a vertically and laterally symmetrical configuration which allows manufacturing of the long body by drawing. Further, since the rolling aperture forming plate forms one side of the no-load rolling aperture, collision noises of the rolling members during rolling thereof in the no-load rolling apertures can be sufficiently prevented by employing such plates made from resin. An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is a cross section illustrating an embodiment of a linear guide device according to the invention; Figure 2 is a perspective view with a certain part cut away; Figure 3 is an exploded view illustrating components of a linear guide device according to the embodiment of figures 1 and 2; Figures 4-7 are an elevation, a side view, a top view and a bottom view illustrating a block body, respectively; Figure 8 is a longitudinally sectional view illustrating a ball-nut portion of the block body; Figures 9 and 10 are a front view and a rear view of a cover; Figure 11 is a view taken along an arrow A in Figure 9; Figures 12 and 13 are a rear view and a side view illustrating a rolling aperture forming plate; Figure 14 is a cross section taken along line XIV-XIV in Figure 13; Figures 15 and 16 are a side view and an elevation of a ball retainer; and Figure 17 is a cross section illustrating a linear guide device of the prior art. A linear guide device according to an embodiment of the invention will be described in greater detail with reference to the accompanying drawings. Figures 1 and 2 illustrate an embodiment of the linear guide device of the invention, which is basically formed of a track base or bed 1 having a substantially rectangular section and an opening at one side, the track base or bed 1 being fixed to, e.g., a bed, a substantially rectangular bearing block B (will be also called as a "block") engaging a screw shaft 7 of a feed screw mechanism for moving in a concave portion of the track bed 1, and a plurality of balls 2 or rolling members which bear loads between the block B and the track bed 1 during rolling therebetween. The block B is formed of, as shown in Figure 3, a block body 3 engaging the feed screw shaft 7, covers 4 attached to front and rear end surfaces of the block body 3, rolling aperture forming plates 5 engaging four corners of the block body 3, and a pair of ball retainers 6 engaging side surfaces of the block body 3. The block body 3 includes, as shown in Figures 4-7, a ball-nut portion 3a engaging the screw shaft 7 and a pair of bearing portions 3b, and thus has a section similar to a cross. Each bearing portion 3a is provided at corners or edges with a pair of load ball grooves 31a and 31b, or 31c and 31d, in which the balls 2 roll. No-load ball grooves 32a-32d for circulating the balls which roll from ends of the load ball grooves 31a-31d are formed at corners between the bearing portions 3b and the ball-nut portion 3a. Each bearing portion 3b is provided with tapped bolt apertures 37 into which attaching bolts 55 are screwed for attaching the rolling aperture forming plates 5. The ball-nut portion 3a engaging the screw shaft 7 is provided with, as shown in Figure 8, a through aperture 33 having a diameter slightly larger than the screw shaft 7 and a rolling groove 34 which is formed at a portion of the through aperture 33 and corresponds to a spiral ball rolling groove on the screw shaft 7. Further, a return tube 36 is fixed to the ball-nut portion 3a by a holder member 35 to form a circulation path. Preloads are applied to balls (not shown) disposed between the screw shaft 7 and the block body 3 for increasing accuracy of motion of the block B. Since the block body 3 thus constructed has a vertically and laterally symmetrical configuration, it can be manufactured by drawing without utilizing conventional machining such as cutting. Specifically, the block body 3 can be manufactured in such a manner that drawing is applied to a steel member to form the above sectional shape and then polishing for the load ball grooves 31a-31d and drilling for the through apertures 33 are applied to it. According to this manufacturing method, block bodies 3 having intended lengths can be easily manufactured by appropriately cutting the drawn steel member into pieces. The cover 4 has a sectional shape similar to a cross, as shown in Figures 9 and 10, and includes a base 4a and a pair of arms 4b projected therefrom. The cover 4 is formed by injection molding of synthetic resin. The base 4a is provided with a through aperture 41 into which the screw shaft 7 is inserted. Each projected arm 4b is provided at its opposite side surfaces with ball return grooves 42a-42d for connecting the load ball grooves 31a-31d on the block body 3 and the corresponding no-load ball grooves 32a-32d to each other (see Figure 11). In Figure 11, numeral 43 indicates one of the projections for scooping and guiding the balls 2, which roll from the load ball grooves 31a-31d, into the ball return grooves 42a-42d. Numeral 44 indicates one of the positioning seats for bearing the guide projections 53 which will be described later and are provided in the rolling aperture forming plates 5. The rolling aperture forming plates 5 are manufactured by injection molding of synthetic resin, similarly to the covers 4. As shown in Figures 12-14, the plates 5 each are provided at one surface with ball circulation grooves 51 corresponding to the no-load ball grooves 32a-32d on the block body 3 and the ball return grooves 42a-42d on the covers 4. Also, the plates 5 each are provided at one side edge with a ball retaining groove 52 which connects to the ball circulation groove 51 and corresponds to the load ball groove 31a-31d of the block body 3. Further, inside return portions 51a of the ball circulation paths 51, the guide pieces 53 are projected for positioning the plates 5 with respect to the block body 3 or the covers 4. In an assembly of the block B, each pair of the guide pieces 53 engage the front and rear end surfaces of the bearing portion 3b for positioning the block body 3, and rest on the positioning seats 44 of the covers 4 for positioning the covers 4. Numerals 54 indicate penetrated apertures through which attaching bolts 55 are inserted for attaching the plates 5 to the block body 3. The ball retainer 6 is a rod-like member having a nearly trapezoid shape, as shown in Figures 15 and 16, and has a width so determined that a gap between the projected end 61 of the retainer 6 attached to the block body 3 and the ball retaining groove 52 on the rolling aperture forming plate 5 may be smaller than the diameter of the ball 2, whereby the balls 2 are prevented from disengaging from the load ball grooves 31a-31d when the block B is removed from the track bed 1. The track bed 1 has a nearly rectangular shape opened at one side and includes a fixing portion 1a fixed to a basic member such as a bed, and a pair of support portions 1b projected from the opposite ends of the fixing portion 1a for supporting the block body 3. Each supporting portion 1b is provided at its inner surface with a groove 11, and the grooves 11 are provided at their upper and lower corners with ball rolling grooves 12a-12d opposed to the load ball grooves 31a-31d of the block body 3, respectively. A numeral 13 indicates one of bolt holes into which fixing bolts for fixing the track bed 1 are inserted. In the construction described above, the bearing block B is assembled by attaching the covers 4 to the front and rear end surfaces of the block body 3 by screws (not shown), attaching the four rolling aperture forming plates 5 to the bearing portions 3b of the block body 3 and attaching the ball retainers 6 to the side surfaces of the bearing portions 3b by screws (not shown). Therefore, in the illustrated embodiment, the no-load ball rolling apertures corresponding to the load ball grooves 31a-31d are formed of the no-load ball grooves 32a-32d on the block body 3 and the ball circulation grooves 51 on the rolling aperture forming plates 5 opposed thereto. Further, the ball return paths which connect the no-load ball rolling apertures and the load ball grooves 31a-31d are formed of the ball return grooves 42a-42d on the covers 4 and the ball circulation grooves 51 on the plates 5 faced thereto. In this construction, the no-load ball grooves 32a-32d are facilely formed by applying milling to the block body 3 and the ball return grooves 42a-42d and the ball circulation grooves 51 are facilely formed by the injection molding of the covers 4 and the rolling aperture forming plates 5, respectively. Therefore, even in the long block B, the no-load ball rolling apertures can be facilely and accurately formed. Since the balls 2 are covered with the plates or covers 4 made from synthetic resin, while they are rolling in the ball circulation paths, noises which may be caused by circulation of the balls can be reduced. According to the illustrated embodiment of a linear guide device of the invention, as described hereinabove, the no-load rolling apertures can be easily formed by machining the grooves for receiving the rolling members in the block body and/or the rolling aperture forming plates, so that the long bearing block can be facilely manufactured, and thus the number of the load rolling members can be increased to obtain a linear guide device having an increased maximum allowable load and a compact configuration. Since the block body having an intended length can be manufactured by cutting a drawn member, the productive efficiency can be increased and the costs can be reduced. Further, owing to the rolling aperture forming plates made from resin, the collision noises of the rolling members during rolling in the no-load apertures can be minimized, and thus a linear guide device having a small operation noise can be obtained.

Claims: A linear guide device comprising: a track bed (1) having a substantially rectangular section, which track bed (1) is opened at one side and is provided at its inner surfaces with rolling surfaces (12) for rolling members (2); a bearing block (B) having load rolling surfaces (31a-31d) cooperating with said rolling surfaces (12) of the track bed (1) to hold the rolling members (2) therebetween and moving in a hollow portion of the track bed (1) in accordance with a degree of rotation of a feed screw shaft (7) engaging the bearing block (B), said bearing block (B) having a block body (3), no-load rolling apertures for the rolling members (2), and covers (4) which are engaged with front and rear end surfaces of the block body (3), said covers (4) forming return paths for the rolling members (2) which connect the load rolling surfaces (31a-31d) and the no-load rolling apertures (32a-32d), respectively; and said block body (3) including a ball-nut portion (3a) engaging the feed screw shaft (7), and a pair of bearing portions (3b) projecting from opposite sides of the ball-nut portion (3a); characterised in that the load rolling surfaces (31a-31d) are formed at corners of the bearing portions (3b), and said bearing block (B) further includes rolling aperture forming plates (5) which cooperate with upper and lower sides of the bearing portions (3b) to form the no-load rolling apertures (32a-32d), and which retain the rolling members (2) rolling on the load rolling surfaces (31a-31d).

Inventors: KAWAGUCHI TAKAHIRO, KAWAGUCHI, TAKAHIRO, KAWAGUCHI, TAKAHIRO, 2-2-2, SAKURASHINMACHI
Applicants: THK CO LTD, THK CO. LTD.
Application year: 1991
Main classification: F16C29
IPC codes: B23Q1, F16C29