Patent Publication Number: US-2007110346-A1

Title: Linear slide assembly method and apparatus

Description:
This application claims priority from International Patent Application No. PCT/US04/22925, international filing date 16 Jul. 2004, entitled LINEAR SLIDE ASSEMBLY METHOD AND APPARATUS.  
    
    
     BACKGROUND OF THE INVENTION  
      This invention relates generally to linear slides, and more particularly to low friction slides.  
      Low friction linear slides generally include a bifurcated member straddling another. Either member can be fixed and the other slides with respect to it on two linear bearings sandwiched between the bifurcations of the one member and the sides of the straddled member. According to one known low friction linear slide structure, four longitudinally extending rods form a raceway with two of the rods retained by each member. Carried by the rods are either ball bearings or cylindrical bearings that roll along the rods during relative movement between the slide members. Various types of such linear slide devices include those with cylindrical rods and ball bearings, flattened rods and crossed roller bearings and grooved rods and ball bearings.  
      Previous ball slides typically use set screws pressing on a gib to provide optimum adjustment. The gib pushes on both rods constrained in a channel. By design, the centers of the two rod diameters do not change in the vertical direction as both rods can move and provide adjustment in the horizontal direction pressing on the bearing balls contained between the rods in the base of the slide and the top of the slide. Examples of those types of slide devices are disclosed in U.S. Pat. Nos. 2,672,378; 3,113,807; 3,790,233; 3,897,119; 4,696,586; 4,797,008; 4,923,311; and 5,672,010. During assembly of previous ball slides, bearing members typically consisting of rods, balls and ball retainers, are slid into ends of raceways formed between base and slide members of the device. In some ball slide devices a gib and compliant elastomer strip are inserted into an end of one raceway and then engaged by an adjusting screw to provide a preload on the bearing members. These procedures rendered assembly of the ball slides quite difficult.  
      The object of this invention is to provide an improved linear slide mechanism that exhibits extreme smoothness and ease of assembly.  
     SUMMARY OF THE INVENTION  
      The invention is a linear slide apparatus including a bifurcated base member having spaced apart first and second upright portions; a slide member spaced from the base member and disposed between the first and second upright portions; a first raceway formed between the slide member and the first upright portion; and a second raceway formed between the slide member and the second upright portion and extending parallel to the first raceway with the raceways having substantially square cross sections and open tops. Also included are a support assembly retained by each raceway and arranged to support the slide member on the base member with each support assembly having four elongated rods each disposed in a different corner of the retaining raceway, a plurality of balls engaged between the four elongated rods and a carriage member maintaining separation between the balls. A first base top cover is secured to the first upright portion, partially covering the open top of the first raceway, and engaging the rod disposed in an upper outer corner thereof, a second base top cover secured to the second upright portion, partially covering the open top of the second raceway, and engaging the rod disposed in an upper outer corner of the second raceway; and a slide top cover is secured to the slide member, partially covering the open tops of the raceways and engaging the rods disposed in upper inner corners thereof. The support members can be inserted through the open tops of the raceways to simplify assembly of the slide device.  
      According to certain features of the invention, the first and second base top covers are secured to the upright portions by a plurality of removable fasteners, and the slide top cover is a unitary plate secured to the slide member by a plurality of removable fasteners. These features further simplify assembly and adjustment.  
      According to other features of the invention, the raceways have at least one open end and the device includes a base end cover secured to the base member and partially covering the open ends thereof, and a slide end cover secured to the slide member and partially covering the open ends of the raceways. Further assembly simplification is provided by these features.  
      According to yet other features, the raceways include one longitudinal bottom corner formed by perpendicularly intersecting surfaces of, respectively, the first and second upright portions, and another longitudinal bottom corner formed by perpendicularly intersecting surfaces of the slide member, and each pair of the intersecting surfaces retains one of the rods. These features provide accurate alignment of the support bearing components.  
    
    
     DESCRIPTION OF THE DRAWINGS  
      These and other objects and features of the invention will become more apparent upon a perusal of the following description taken in conjunction with the accompanying drawings wherein:  
       FIG. 1  is a front perspective view of a linear slide according to the invention;  
       FIG. 2  is a cross sectional view taken along lines  2 - 2  of  FIG. 1 ;  
       FIG. 3  is a perspective view illustrating relative movement between slide and base members of the device shown in  FIGS. 1-2 ;  
       FIG. 4  is a detailed view illustrating one step in the assembly of the device shown in  FIGS. 1-3 ; and  
       FIG. 5  is a detailed view illustrating another step in the assembly of the device shown in  FIGS. 1-3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
      A linear slide  11  includes a slide member  12  supported on a base member  13  by a pair of elongated support assemblies  14 ,  15  as shown in  FIGS. 1 and 2 . The base member  13  is bifurcated with a pair of spaced apart first and second upright portions  16 ,  17  projecting upwardly from a base portion  18 . Disposed between the first and second upright portions  16 ,  17  and maintained spaced apart therefrom by the first and second support assemblies  14 ,  15  is the slide member  12 .  
      Retaining the first and second support assemblies  14 ,  15  are, respectively, first and second parallel elongated raceways  21 ,  22 . The raceways  21 ,  22  are identical as shown in  FIG. 2 , with each having a square cross-section and an open top  10 . Side and bottom surfaces of the raceway  21  are formed by the upright portion  16 , and the slide member  12  while the raceway  22  is formed by the upright portion  17 , the slide member  12  and a gib  19  separated from the upright portion  17  by a shim  24  and a resilient elastomer strip  20  as shown in  FIG. 2 . The raceway  21  has a longitudinally extending bottom outer corner  25  formed by perpendicularly intersecting surfaces  26 ,  27  of the upright portion  16 , and an inner bottom corner  31  formed by perpendicularly intersecting surfaces  32 ,  33  of the slide member  12 . Similarly, the raceway  22  has a longitudinally extending bottom outer corner  23  formed by the intersection of the gib  20  and a surface  28  of the upright portion  17 , and a longitudinally extending inner bottom corner  29  formed by perpendicularly intersecting surfaces  30 ,  34  of the slide member  12 .  
      The first and second support assemblies  14 ,  15  also are identical and each includes a plurality of longitudinally distributed balls  36  engaged between inner and outer longitudinally extending upper cylindrical rods  37 ,  38  disposed in upper corners of the raceways  21 ,  22  and longitudinally extending lower cylindrical rods  41 ,  42  disposed in, respectively, the inner and outer bottom corners  31 ,  25  of the raceway  21  and the inner and outer bottom corners  29 ,  23  of the raceway  22 . Separation between the balls  36  is maintained by apertured carriage members  44 .  
      Secured to an upper surface of the slide member  12  by machine screw fasteners  51  is a slide top cover  52  as shown in  FIGS. 1 and 2 . The slide top cover  52  covers the entire upper surface of the slide member  12  and extends laterally therefrom to partially cover the open tops  10  of the raceways  21 ,  22  and engage upper surfaces of the upper inner rods  37 . A first base top cover  54  is secured by machine screw fasteners  55  to the upper surface of the first upright portion  16  and extends laterally over the first raceway  21  to partially cover its open top  10  and engage the upper outer rod  38 . Similarly, a second base top cover  56  is secured by fasteners  57  to an upper surface of the second upright portion  17  and extends laterally over the second raceway  22  to partially cover its open top  10  and engage the upper outer rod  38 .  
      A slide end cover  61  is secured to each end surface of the slide member  25  by machine screw fasteners  62  as shown in  FIG. 1 . The end covers  61  extend laterally over the raceways  21 ,  22  to partially cover the open ends thereof and engage the outer ends of, respectively, the upper inner and lower inner rods  37 ,  41 . Similarly secured to end surfaces of the base member  13  by machine screw fasteners  65  are base end covers  66 . The base end covers  66  project laterally from the upright portions  16 ,  17  and over the raceways  21 ,  22  to partially cover the open ends  10  thereof, and engage ends of, respectively, the upper outer and lower outer rods  38 ,  42 .  
      During use of the bearing slide  11 , the slide member  12  moves rectilinearly relative to the base member  13  in a direction defined by the raceways  21 ,  22  as shown in  FIG. 3 . Such movement is facilitated by rolling movement of balls  36  on the rods  37 ,  38 ,  41  and  42  of the support assemblies  14 ,  15 . The accurate alignment of the rods as described below results in highly smooth operation.  
      During assembly of the linear slide  11 , the slide member  12  is positioned between the first and second upright portions  16 ,  17  of the base member  13  mounted on a fixture  71  ( FIG. 5 ). The gib  19  elastomer strip  20  and shim  24  then are positioned in the raceway  22  with ends of the strip  20  secured to clamp blocks  72  to maintain the strip tension and thereby reduce the size of its normal cross section. Next, the assemblies  14 ,  15  with their carriage  44 , ball  36  and rods  37 ,  38 ,  41  and components previously assembled in suitable fixtures (not shown) are inserted into the raceways  21 ,  22  through the open tops  24 . After insertion of the assemblies  14 ,  15  into the raceways  21 ,  22 , the ends of the elastomer strip  20  are released from the blocks  72  allowing the strip to contract and provide a lateral preload on the balls  36 . The slide and base end covers  61 ,  66  then are attached with the screws  62 ,  65  to partially cover the open ends of the raceways  21 ,  22 . Finally, after the slide top cover  52  and the base top cover  56  have been secured, respectively, to the slide member  12  and the base member  13 , the remaining base top cover  54  is secured to the upper surface of the upright portion  16  as shown in  FIG. 4 . As the base top cover  54  is tightened with the fasteners  55  it engages the upper surface of the upper outer rod  38  forcing it downwardly and exerting a compression force on the ball  36  directed at approximately 45 degrees to the ball&#39;s center. The compression force is transmitted to all other balls and rods of both support assemblies  14 ,  15 . Further adjustment can be obtained by selective tightening of the slide top cover  52  and second base top covers  56  to adjust the positions of the upper rods  37 ,  38  and thereby establish precise alignment of the support assemblies  14 ,  15  within, respectively, the raceways  21 ,  22 .  
      Obviously, many modifications and variations of the present invention are possible in light of the above teaching. It is to be understood, therefore, that the invention can be practiced otherwise than as specifically described.