Abstract:
A linear roller guide unit comprises an elongated rail and a carrier straddling the rail. A plurality of rollers is installed between the carrier and the rail so that the carrier can slide along the elongated rail. By installing six rows of rollers within the existing standard cross section, the invention can achieve long life, high load capacity and high rigidity.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a design regarding the linear roller guide unit for compressive load, which is applied in the linear transmission device and is capable of substantially improving the performance of the linear roller guide unit in many respects, including the service life, the structural strength, the rigidity, the load capacity and the impact-resistant. 
   2. Description of the Prior Art 
   The existing linear guideway essentially comprises a rail and a slide block. The rail is an elongated structure defined with rolling grooves for allowing the rollers to circulate therein. The slide block is reverse U-shaped and also defined with grooves for cooperating with the rolling grooves. And two end caps are installed at both ends of the slide block to enable the rollers to circulate. Each of the end caps is defined with a return path for enabling the rollers to circulate from the slide block to the rail. 
   The existing technologies for the roller type linear guideway are generally classified into the following categories: 
   Firstly, four-row type linear roller guide unit is one of the conventional technologies, for example, which is disclosed in U.S. Pat. Nos. 4,692,037, 4,715,729, 6,109,789 and JP Pt 60139912.  FIG. 1  shows a conventional four-row linear roller guide unit, wherein the four rows of rollers are arranged at both wing portions of the slide block  22  in a crossed manner. 
   After analyzing the structural strength and the geometric relation, with reference to  FIG. 2 , it is found that the four-row type linear roller guide unit has the following disadvantages: 
   1. When the rail is subjected to a compressive load F, the compressive load will be applied to the lower two rows of rollers  34 , 35  only, and this is likely to cause trumpet deformation of the slide block  32 , and a poor precision of the linear guide unit. 
   2. when only two rows of rollers  35  carry the compressive load, the rollers will produce a comparatively large contact stress, and as a result, the material of rollers are more susceptible to fatigue, substantially reducing the service life of the linear guide unit. 
   Secondly, U.S. Pat. No. 5,672,011 discloses another six-row type linear ball guide unit, as shown in  FIGS. 3 and 4 , wherein the six rows of balls  30  are horizontally arranged at both wing portions of the slide block  10 . This design requires three circulating holes  4  to be formed in each wing portions of the slide block  101  to allow for the circulation of the balls  30 . 
   After analyzing the structural strength and the geometric relation, with reference to  FIG. 4 , it is found that the six-row type linear roller guide unit has the following disadvantages: 
   1. The thickness of the slide block  10  will be substantially reduced under the condition that the cross section is fixed, result in a poor structural strength of the slide block, and this is likely to cause trumpet deformation of the slide block  22  and a poor precision of the linear guide unit. 
   2. As compared to the line-to-line contact relation between the roller and the surface of the rolling path, the balls  30  are in a point-to-point contact with the rolling path  50 . When carrying the compressive load, the balls  30  will produce a comparatively large contact stress, thus accelerating the material fatigue of rollers, substantially reducing the service life of the linear guide unit. 
   The present invention has arisen to mitigate and/or obviate the afore-described disadvantages. 
   SUMMARY OF THE INVENTION 
   The primary objective of the present invention is to provide a design regarding the linear roller guide unit for compressive load, which is applied in the linear transmission device and is capable of substantially improving the performance of the linear roller guide unit in many respects, including the service life, the structural strength, the rigidity, the load capacity and the impact-resistant. 
   To achieve the abovementioned objective, the linear roller guide unit for compressive load in accordance with the present invention comprises: 
   a rail, a slide block, six rows of rollers, a plurality of retaining members for holding the rollers, six turning members, six circulation pipes, two end caps, and a plurality of fasteners. 
   The present invention is characterized in that: 
   the rail is an elongated structure approximately I-shaped in cross section, a flat rolling surface for rollers is formed at each of a top right, a bottom right, a top left, a bottom left of a head portion of the rail, and at a top right and a top left of a bottom of the rail, the slide block has at least six through holes allowing for circulation of the rollers, and at least six flat rolling surfaces on which the rollers roll, the six flat surfaces of the slide block are located correspondingly to the flat rolling surfaces of the rail. The six rows of rollers are arranged in pairs between the flat rolling surfaces, the retaining members serve to hold the rollers and to prevent the rollers from falling off when the slide block is disengaged from the rail. The six turning members includes inner members and outer members, each of the inner and outer turning members is defined with an arc-shaped surface, an arc-shaped surface is formed on an inner side of each of the outer turning members and is located opposite the respective inner turning members, the turning members are set at both ends of the slide block and serve to turn the moving direction of the rollers. Each of the circulation pipes is a hollow structure inserted in the through holes of the slide block for allowing the rollers to circulate. The end caps are installed at both ends of the slide block, and each of the end caps is defined with six arc-shaped surfaces for mating with the turning members. The turning members cooperate with the circulation pipes and the two end caps to form a circulation path for allowing the rollers to circulate endless. 
   A contact angle of upper rows of the rollers with respect to the flat rolling surface is a, a contact angle of mid rows of rollers with respect to the flat rolling surface is β, and a contact angle of lower rows of the rollers with respect to the flat rolling surface is γ. The mid rows of rollers cross the lower rows of the rollers, for ensuring that the rollers can roll smoothly, the circulating direction Y i  of the respective rows of rollers is approximately vertical to the long axis direction X i  of the rollers, and the β and γ is approximately 45 degrees. When the contact angle a of the upper rows of rollers is 90 degrees, the linear guide unit will have an optimum load capacity and impact-resistant performance when it is subjected to a compressive load, when the contact angle a is 45 degrees, the upper rows and lower rows of rollers will share the load equally, thus prolonging the service life of the linear roller guide unit, therefore, 45°≦a≦90 degrees. 
   The present invention will be more clear from the following description when viewed together with the accompanying drawings, which show, for purpose of illustrations only, the preferred embodiment in accordance with the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a conventional four-row linear roller guide unit; 
       FIG. 2  is an illustrative view of showing a slide block of a conventional four-row linear roller guide unit; 
       FIG. 3  is a cross section assembly view of a conventional six-row linear roller guide unit; 
       FIG. 4  shows a conventional end cap; 
       FIG. 5  is an illustrative view of showing a slide block of the conventional six-row linear roller guide unit; 
       FIG. 6  is an exploded view of showing a linear roller guide unit in accordance with the present invention; 
       FIG. 7  is a cross sectional assembly view of the slide block and the rail in accordance with the present invention; 
       FIG. 8  is a perspective assembly view of showing the liner guide unit in accordance with the present invention; 
       FIG. 9  is a cross sectional view taken along the line F-F of  FIG. 9 ; 
       FIG. 10  is a cross sectional view taking along the line A-A of  FIG. 9 ; 
       FIG. 11  is a cross sectional view taking along the line B-B of  FIG. 9 ; 
       FIG. 12  is a cross sectional view taking along the line C-C of  FIG. 9 ; 
       FIG. 13  is an assembly cross section view of showing the slide block and the rail in accordance with the present invention; 
       FIG. 14  is an illustrative view of showing a slide block of the conventional six-row linear roller guide unit of  FIG. 13 ; 
       FIG. 15  is an exploded view of showing the inner and outer turning members; 
       FIG. 16  is an assembly view of showing the inner and outer turning members; 
       FIG. 17  is an exploded view of the circulation pipe in accordance with the present invention; and 
       FIG. 18  is an assembly view of the circulation pipe in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The foregoing, and additional objects, features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments thereof, taken in conjunction with the accompanying drawings. 
     FIG. 6  is an exploded view of showing a linear roller guide unit in accordance with the present invention, the linear roller guide unit comprises a rail  1 , a slide block  2 , six rows of rollers  4 , a plurality of retaining members  51 ,  52  and  53  for holding the rollers  41 ,  42 ,  43 ,  44 ,  45 , and  46 , six inner turning members  61 , six outer turning members  62 , six circulation pipes  7 , two end caps  3 , and a plurality of fasteners  8  for fixing the two ends caps  3  to the slide block  2 . 
     FIG. 7  is a cross sectional assembly view of the slide block and the rail, wherein the rail is an elongated structure approximately I-shaped in cross section. A flat rolling surface for rollers is formed at the top right  11 , the bottom right  12 , the top left  13 , the bottom left  14  of the head portion (in cross section) of the rail  1 , and at the top right  15  and the top left  16  of the bottom of the rail  1 . The slide block has at least six through holes  20  allowing for circulation of the rollers, and six flat rolling surfaces  21 ,  22 ,  23 ,  24 ,  25  and  26  on which the rollers  41 ,  42 ,  43 ,  44 ,  45 , and  46  roll. 
     FIG. 8  is a perspective assembly view of showing the liner guide unit in accordance with the present invention, and  FIG. 9  is a cross sectional view taken along the line F-F of  FIG. 8 , the six flat surfaces of the slide block are located correspondingly to the six flat rolling surfaces of the rail  1 , the six rows of rollers are arranged in pairs between the flat rolling surfaces. The retaining members  51 ,  52 , and  53  serve to hold the rollers and to prevent the rollers from falling off when the slide block is disengaged from the rail. 
     FIG. 10  is a cross sectional view taking along the line A-A of  FIG. 9 ,  FIG. 11  is a cross sectional view taking along the line B-B of  FIG. 9 , and  FIG. 12  is a cross sectional view taking along the line C-C of  FIG. 9 . Each of the circulation pipes  7  is a hollow structure inserted in the through holes of the slide block  2  for allowing the rollers to circulate. The end caps  3  are installed at both ends of the slide block  2 , and each of the end caps  3  is defined with six arc-shaped surfaces for mating with the turning members. 
     FIG. 13  is an assembly cross section view of showing the slide block and the rail, wherein the contact angle of upper rows of the rollers  41 ,  43  is a, the contact angle of the mid rows of rollers  42 ,  44  is β, and the contact angle of the lower rows of the rollers  45 ,  46  is γ. 
   The present invention is developed based on the following theoretical analysis: 
   1, Analysis on the Mechanism Geometric Relation Simulation and Structural strength: 
   By using 2D or 3D graphics software to make a mechanism simulation of the primary design of the present invention, it is understood that the linear guide unit of the present invention can be arranged with six rows of rollers if the cross section of the rail of the present invention is the same as that of the prior art. The shoulder portion and the wing portions of the slide block are formed with two circulating holes for allowing the rollers to circulate. In this way, the circulating holes can be dispersedly distributed in the in the cross section, and the resultant structural strength is stronger than the prior art. 
   2, Mechanical Analysis: 
   the arrangement of the rollers in the direction of the compressive load is: the contact angle of upper rows of the rollers with respect to the flat rolling surface is a, the contact angle of the mid rows of rollers with respect to the flat rolling surface is β, and the contact angle of the lower rows of the rollers with respect to the flat rolling surface is γ. The rollers can roll freely in the radial direction but can&#39;t roll in their long axis direction. For ensuring that the rollers can roll smoothly, the circulating direction Y i  of the respective rows of rollers is approximately vertical to the long axis direction X i  of the rollers. Therefore, the mid rows of rollers cross the lower rows of the rollers, and the β and γ is approximately 45 degrees. The load capacity and impact-resistant performance have to do with the contact angle of the rollers. When the contact angle a of the upper rows of rollers is 90 degrees, the linear guide unit will have an optimum load capacity and impact-resistant performance when it is subjected to a compressive load. When the contact angle a is 45 degrees, the upper rows and lower rows of rollers will share the load equally, thus prolonging the service life of the linear roller guide unit. Therefore, 45°≦a≦90°. 
   3, Theory of Fatigue Breakdown 
   As compared to rollers, the balls are in a point-to-point contact with the surface of the rolling path. When the rail is subjected to a heavy compressive load, the rollers produce a comparatively great contact stress, and this will accelerate the material fatigue of the rollers while reducing the service life of the linear roller guide unit. When a conventional four-row linear roller guide unit is subjected to a heavy compressive load, only two rows of rollers carry the load, the rollers will produce a comparatively large contact stress, and as a result, the material of rollers are more susceptible to fatigue, substantially reducing the service life of the linear guide unit. 
   When the six-row type linear roller guide unit of the present invention is subjected to a heavy compressive load, as shown in  FIG. 14 , the rollers will produce a comparatively small contact stress, thus it can decelerate the material fatigue of the rollers and prolong the service life of the linear roller guide unit. 
     FIG. 15  is an exploded view of showing the inner and outer turning members, and  FIG. 16  is an assembly view of showing the inner and outer turning members. The inner turning and outer turning members are set at both ends of the slide block and serve to turn the moving direction of the rollers. An arc-shaped surface  610  is formed on the outer periphery of the inner turning member  61 , and two positioning pins  612  are formed at two sides of the respective inner turning members  61  neighboring the arc-shaped surface  610 . An arc-shaped surface  620  is formed on the outer periphery of the outer turning member  62 , and two positioning holes  623  and two positioning pins  622  are formed in two sides of the respective outer turning members  62  neighboring the arc-shaped surface  610 , for mating with the positioning pins  612  of the inner turning members  61  and for mating with the end caps  3 , respectively. An arc-shaped surface  621  is formed on the inner side of each of the outer turning members  62  and is located opposite the respective inner turning members  61 . 
     FIG. 17  is an exploded view of the circulation pipe in accordance with the present invention, and  FIG. 18  is an assembly view of the circulation pipe in accordance with the present invention. Each of the circulation pipes  7  is a hollow structure inserted in the through holes of the slide block  2  for allowing the rollers to circulate. And the circulation pipe  7  is made of two half pipes  71  and  72 . 
   To summarize, the present invention has the following advantages, as compared with the prior art:
         1. Substantially increasing the service life of the linear roller guide unit.   2. Substantially improving the structural strength of the slide block and increasing the rigidity of the linear roller guide unit, thus achieve super high precision processing.   3. substantially improving load capacity and impact-resistant performance of the linear roller guide unit.   4. all the parts of the present invention can be made by plastic injection molding, it is suitable for mass production.       

   While we have shown and described various embodiments in accordance with the present invention, it is clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.