Abstract:
A rolling element retainer chain provides a row of rolling elements smooth running in a recirculation passage and keeps a predetermined spacing distance between two adjacent rolling elements and the rolling elements be separated without contact to each other; the rolling element retainer chain comprises at least one thin flexible metal strip having a row of longitudinal arranged holes; a row of cross arranged latten between holes are formed thereof; and a number of spacers, incorporated on the cross arranged latten; the strength of the flexible metal strip is much higher than that of the resin materials conventionally used and can endure higher tension without broken, and thus a longer operating duration can therefore be achieved; both ends on the flexible metal strip can be overlapped wholly fixed without interference because of thinner thickness thereof, and a close loop rolling element retainer chain is formed thereof.

Description:
[0001]    The present invention is a continuation in part of U.S. patent application Ser. No. 12/243,966 which is assigned to and invented by the inventor and applicant of the present invention. Thus, the content of U.S. patent application Ser. No. 12/243,966 is incorporated into the present invention as a part of the present invention. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to rolling element retainer chains in linear motion mechanism devices, and more particularly to a longitudinally extended and flexible rolling element retainer chain which retains a longitudinally extended row of rolling elements and keeps a predetermined distance between two adjacent rolling elements whereby the rolling element retainer chain and the rolling elements can circulate smoothly in the recirculation passage provided by the linear motion mechanism device such as linear guide, ball spline and the like. 
       BACKGROUND OF THE INVENTION 
       [0003]    The present mechanism of linear motion comprises a moving part and a guiding part which can extend longitudinally. Both of the moving part and the guiding part provide at least a coupled raceway to form a raceway passage. The moving part provides a return passage and a pair of turnaround passages for every coupled raceway. The turnaround passages connect the inlet and outlet of the return passage and the raceway, and a recirculation passage is therefore formed; a row of rolling elements roll on the raceway passage, through the turnaround passage to the return passage and from the return passage through the turnaround passage and back to the raceway passage. Therefore, the rolling elements can circulate in the recirculation passage by means of the rolling of the rolling elements unlimited; the moving part can therefore slide on the guiding part without limit. 
         [0004]    To avoid the collision between two adjacent rolling elements, the design of a rolling element retainer chain is provided in the moving part. A plurality of spacers are interposed between rolling elements and connected by a connecting strip. Therefore, the rolling elements circulate with a predetermined distance between two adjacent rolling elements and the moving part can slide more smoothly. In conventional designs, as disclosed by JP 05-052217, the ball chain is made of resin through an injection molding process. But if the mechanism of linear motion has to be produced smaller or much compact, it will become more difficult to achieve through the injection molding process. Furthermore, because the low tension strength of resin materials, the ball chain will be unexpectedly broken during the recirculation and cause unsmooth sliding. 
         [0005]    To overcome the problems mentioned above, as disclosed by U.S. Pat. No. 6,142,671, the retainers and the connecting strip are made by a flexible metal strip. Because the tension strength of metal materials is much higher than that of resin materials, the flexible metal strip can increase the tension strength of the rolling element retainer chain and make it not easy to be broken, furthermore, the thickness of the connecting strip will be decreased and the rolling element retainer can still keep high tension strength. If the thickness of the flexible metal strip is not less than 0.1 mm, it is easy to achieve small size design by stamping, punching and bending. Assume that the elastic modulus of metal materials is E, the thickness of the flexible metal strip is h, and the bending radius of the flexible metal strip is P, the maximal stress produced is σ R . 
         [0000]    
       
         
           
             
               σ 
               R 
             
             = 
             
               
                 E 
                 · 
                 h 
               
               
                 2 
                 · 
                 ρ 
               
             
           
         
       
     
         [0006]    For example, for a steel strip, h=0.03 mm, E=210,000 N/mm 2 , ρ=10 mm, so the maximal stress produced is σ R =315 N/mm 2 . Because the elastic modulus of metal materials is much higher than that of resin materials, under the same bending radius, it is necessary that the thickness of the flexible metal strip is much less than the thickness of the resin strip to avoid producing too high stress and to keep the bending resistance lower. But if the thickness of the flexible metal strip is less than 0.06 mm, it is difficult to achieve through the stamping, punching and bending processes, and it is also difficult to extra work on the flexible metal strip to make the claw part for spacing and retaining the rolling element. To make the manufacturing easier by increasing the thickness of the flexible metal strip, the bending resistance of the flexible metal strip will be also increased and it will cause the bending not sufficiently in the desired shape and cause the circulating obstructed when the two ends of the rolling element retainer chain passing through the turnaround passages. This will also cause the material fatigued and broken earlier as expected life time. 
         [0007]    To overcome the problems mentioned above, as disclosed by U.S. Pat. No. 7,329,047, the rolling member connection belt comprises a corrugated-shaped metal belt, and it use the corrugated-shaped parts to increase bending portions and to share the span range of bending. In  FIG. 34 ,  FIG. 35  and  FIG. 36 , the bending span is 90°, the metal belt has N corrugations, the bending radius is ρ, and the depth of the corrugation is T. To simplify the calculation, assume the top of the corrugation to be a sharp point, therefore, the width of the corrugation is 2 W and the length of the corrugation is L. The geometric relationship is shown as below: 
         [0000]    
       
         
           
             V 
             = 
             
               ρ 
               · 
               
                 ( 
                 
                   1 
                   - 
                   
                     cos 
                      
                     
                       ( 
                       
                         
                           90 
                           ° 
                         
                         
                           2 
                            
                           
                               
                           
                            
                           N 
                         
                       
                       ) 
                     
                   
                 
                 ) 
               
             
           
         
       
       
         
           
             H 
             = 
             
               V 
               + 
               T 
             
           
         
       
       
         
           
             W 
             = 
             
               ρ 
               · 
               
                 sin 
                  
                 
                   ( 
                   
                     
                       90 
                       ° 
                     
                     
                       2 
                        
                       
                           
                       
                        
                       N 
                     
                   
                   ) 
                 
               
             
           
         
       
       
         
           
             L 
             = 
             
               
                 
                   W 
                   2 
                 
                 + 
                 
                   H 
                   2 
                 
               
             
           
         
       
       
         
           
             r 
             = 
             
               L 
               
                 2 
                 · 
                 
                   sin 
                    
                   
                     ( 
                     
                       
                         90 
                         ° 
                       
                       
                         4 
                          
                         
                             
                         
                          
                         N 
                       
                     
                     ) 
                   
                 
               
             
           
         
       
     
         [0008]    In  FIG. 36 , S represents the flexible metal strip without bending and S′ represents the flexible metal strip having bending radius ρ with 90° bending span. The bending angle on each corrugation between S and S′ is 90°/4N. To simplify the calculation, assume that the length of each corrugation of the flexible metal strip is L and bends with a uniform radius r. Therefore, if the thickness of the flexible metal strip is h and the maximal stress produced is σ R . 
         [0000]    
       
         
           
             
               σ 
               R 
             
             = 
             
               
                 E 
                 · 
                 h 
               
               
                 2 
                 · 
                 r 
               
             
           
         
       
     
         [0009]    In general designs, the width of the guiding groove provided by the recirculation passage is 0.1 to 0.2 times of the diameter of the rolling element, the depth of the corrugation is less than the width of the guiding groove, and the turnaround radius is about 1.5 to 3.0 times of the diameter of the rolling element. 
         [0010]    For example, for a rolling element with diameter φD=5 mm and a steel belt with elastic modulus E=210,000 N/mm 2  and turnaround radius ρ=10 mm therefore we will have the maximal stress produced σ R  on the corrugated-shaped steel belt under different conditions as following: 
         [0011]    T=0.8 mm, h=0.0685 mm, N=20, 2 W=0.8 mm, σ R =315N/mm 2    
         [0012]    T=1.0 mm, h=0.823 mm, N=20, 2 W=0.8 mm, σ R =314 N/mm 2 ; 
         [0013]    T=0.8 mm, h=0.126 mm, N=60, 2 W=0.4 mm, σ R =315 N/mm 2 . 
         [0014]    From above calculation we understand, under the same stress by larger number of corrugations N or deeper depth of the corrugation T the thickness of the flexible metal strip will be increased. In general design, as the example above, under the same stress, the thickness of the metal belt with corrugations is about 2 to 4 times of the thickness of the metal belt without corrugations, and this design will solve the problem caused by the metal belt without corrugations. But this design will make the both side faces of the corrugated-shape metal belt but not flat. Because the metal belt will run in the guiding groove provided by the recirculation passage of linear motion mechanism and the rolling element retainer chain and the rolling elements will be guided and running smoothly in the recirculation passage. Each corrugation is about perpendicular to the guiding groove, whereby the top point of each corrugation is unfavorable for the smooth running in the guiding groove. Also the guiding groove always comprise more than two portions and when the top point of each corrugation passes through the joint position where misalignment happens, it will cause an unstable vibration and unsmooth recirculation. 
       SUMMARY OF THE INVENTION 
       [0015]    The purpose of the present invention is to provide a rolling element retainer chain with flexible metal strips which can solve the problem of difficult manufacturing by stamping, punching or bending process and the problem of unsmooth recirculation caused by corrugation design mentioned above, the rolling element retainer chain with flexible metal strips can even increase the tensile strength of the connecting belt as the way of the corrugated-shape design can achieve. 
         [0016]    According the purpose mentioned above, the present invention provides a rolling element retainer chain comprising at least a flexible metal strip and a number of spacers; the at least one flexible metal strip has longitudinally arranged holes on it, a row of cross arranged latten between holes are thereof formed, and the spacers are incorporated on the cross arranged latten; two connecting strips at upsides and downsides of the holes are thereof formed and all the cross arranged latten are incorporated on the connecting strips; a row of longitudinally arranged rolling elements are disposed in the holes and a predetermined distance is kept between two adjacent rolling elements by the spacers; the connecting strips run in the guiding groove provided by the recirculation passage to guide the rolling element retainer chain running smoothly in the recirculation passage. The rolling element retainer chain runs about straightly in the raceway passage and the return passage and curvedly with the arc of the turnaround passage in the turnaround passage, the rolling element retainer chain repeats bent and straightened thereby during recirculation. To avoid the plastic deformation caused by repeated stress, the thickness of the flexible metal strip h is restricted as h&lt;h o  and h o =2·R p0.2 ·ρ/E, where E is the elastic modulus of the metal material, R p0.2  is the yielding strength of 0.2% plastic deformation of the metal material and ρ is the minimum turnaround radius of the guiding groove provided by the turnaround passage. Therefore, the rolling element retainer chain will achieve repeating bent without plastic deformation when passing the turnaround passage. 
         [0017]    To achieve expected life or repeat times without fatigued, according to the property of each metal, a suitable coefficient f is chosen to determine the thickness of the flexible metal strip h≦f·h m  and h m ·2·R m ·ρ/E, where R m  is the tensile strength of the metal material. For example, if the metal is steel and the expected repeat times of bending are more than 1 million times, the coefficient f=0.6˜0.7. the guiding groove provided by the recirculation passage is closed and usually comprises more than two portions, and the joint position will form discontinuous surface caused by misalignment or positioning error. Because the both side faces of the metal connecting strip have no corrugations and keep flat, when passing through the joint position in the guiding groove, an unsmooth recirculation will not happen. 
         [0018]    The face of the spacer adjacent to the rolling element forms an envelop shape, the rolling element is thereby retained between two envelop shaped face of spacers in the rolling element retainer chain without freely escaping. The flexible metal strip having longitudinally arranged holes but without claw portion can be made by stamping, punching or etching process in much thinner thickness. 
         [0019]    The materials of the spacer may be resin materials, including the resin materials mixed by oil-containing, glass-fiber, carbon-fiber and the like. 
         [0020]    Said resin spacers can be incorporated on the flexible metal strip by injection molding directly. By another incorporating method, the spacer is divided into left and right half-spacers by the flexible metal strip, and there are coupled pins and holes and a recess for receiving the cross arranged latten on the left and right half-spacers, hence a complete spacer is formed by combining the left and right half-spacers through the coupling of the coupled pins and holes on the left and right sides of the cross arranged latten of the flexible metal strip. By another incorporating method, the spacer is divided into front and rear half-spacers by the plane perpendicular to the flexible metal strip, and there are coupled pins and holes and a recess for receiving the cross arranged latten on the front and rear half-spacers, hence a complete spacer is formed by combining the front and rear half-spacers through the coupling of the coupled pins and holes on the front and rear sides of the cross arranged latten of the flexible metal strip. 
         [0021]    The pins of the front and rear half-spacers can protrude out the front and rear half-spacers, and the end faces of the pins form a envelop shape face adjacent to the rolling elements. The rolling elements are enveloped and separated by the end faces of the pins thereof; lubricant can be stored in the recess around the pins and will not be drained when the rolling elements rolling in the recirculation passage and a direct lubrication on the rolling elements can be kept for a long operating time. 
         [0022]    To increase the bending ability of the flexible metal strip, the thickness of the flexible metal strip h shall be decreased; it will cause the tension strength of the rolling element retainer chain with flexible metal strips become low. To solve this problem, the rolling element retainer chain has at least two flexible metal strips overlapped and the spacers are incorporated on the overlapped cross arranged latten of the flexible metal strips to increase the tension strength of the rolling element retainer chain. The thickness of each flexible metal strip is restricted as h 1 , h 2 , . . . &lt;h o  and h o =2·R p0.2 ·ρ/E. Because each flexible metal strip can be bent independently, the rolling element retainer chain comprising a plurality of flexible metal strips can keep the same bending ability as the rolling element retainer chain comprising one single flexible metal strip and the tension strength of the rolling element retainer chain comprising a plurality of flexible metal strips can increase multiply in accordance with the number of the overlapped flexible metal strips increased. 
         [0023]    By the incorporating methods of left and right half-spacers or front and rear half-spacers, the recess for receiving the flexible metal strips on the left and right half-spacers or the front and rear half-spacers can be a little larger than the cross arranged fatten of the flexible metal strips, to provide space for the free opposite movement between the flexible metal strips when being bent. Whereby the bending resistance and the produced maximal stress of the rolling element retainer chain with a plurality of overlapped flexible metal strips remains the same as that with one flexible metal strips. 
         [0024]    To enhance the strength of the spacers of the rolling element retainer chain with at least one flexible metal strip, the cross arranged latten between the longitudinal arranged holes of at least one flexible metal strip are separated as upside and downside portions; the upside and downside half cross arranged latten are firmly connected through the spacers and a rolling element retainer chain is formed thereof. 
         [0025]    To decrease the friction caused by the flexible metal strip having higher friction coefficient running in the recirculation guiding groove, the at least one flexible metal strips cane be covered by resin materials having lower friction coefficient by injection molding process together with spacers. 
         [0026]    The rolling elements can be balls, rollers or the like. 
         [0027]    Because the thickness of the flexible metal strip is much less than the thickness of the rolling element retainer chain made of resin materials, more space exists for overlapping the flexible metal strips; whereby the two ends of the flexible metal strip can be overlapped wholly. There is at least one half-spacer on one end of the flexible metal strip and a corresponding half-spacer on the other end of the flexible metal strip for coupling. At least one complete spacer is formed by combining the at least one half-spacer and its coupled half-spacer through the coupled pins and holes on the half-spacer; the overlap portion on both ends of the flexible metal strips is thereof firmly combined and a closed loop of the rolling element retainer chain with at least one flexible metal strip is achieved. Such design solves the problem of unsmooth recirculation caused by an opened loop of rolling element retainer chain. 
         [0028]    In another embodiment of the present invention, a half rolling element retainer chain with at least one flexible metal strip comprises at least one flexible metal strip and half-spacers disposed on one side of the at least one flexible metal strip, coupled pins and holes on the half-spacers. At least one flexible metal strip and half-spacers can be incorporated together by injection molding process. A complete rolling element retainer chain is formed by combining two half flexible metal strip rolling element retainer chains with at least one flexible metal strip through the coupling of the coupled pins and holes on the half-spacers. The embodiment of half flexible metal strip rolling element retainer chain spilt the spacers having envelop shape into two halves, such half spacers simplify and solve the difficulty of a complete rolling element retainer chain having spacers with envelop shape while withdrawing directly from the molding die by injection molding process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  is the side view of the flexible metal strip rolling element retainer chain disclosed by the present invention. 
           [0030]      FIG. 2  is a cross sectional view along line I-I of  FIG. 1 . 
           [0031]      FIG. 3  is a cross sectional view along line II-II of  FIG. 1 . 
           [0032]      FIG. 4  is a part view of the flexible metal strip of the rolling element retainer chain disclosed in the present invention. 
           [0033]      FIG. 5  is an illustrated section view of the flexible metal strip rolling element retainer chain disclosed in the present invention circulating in the moving part. 
           [0034]      FIG. 6  is a side view showing the design of the cross arranged latten of the rolling element retainer chain disclosed in the present invention. 
           [0035]      FIG. 7  is the perspective view of the second embodiment of the spacers of the rolling element retainer chain disclosed in the present invention. 
           [0036]      FIG. 8  is a view of the focus A of  FIG. 7 . 
           [0037]      FIG. 9  is a side view of the third embodiment of the spacers of the rolling element retainer chain disclosed in the present invention. 
           [0038]      FIG. 10  is a view focusing on part B of  FIG. 9 . 
           [0039]      FIG. 11  is a perspective view of the front half-spacer of the third embodiment of the spacers disclosed in the present invention. 
           [0040]      FIG. 12  is a top view of the front half-spacer of the third embodiment of the spacers disclosed in the present invention. 
           [0041]      FIG. 13  is a cross sectional view along line III-III of  FIG. 12 . 
           [0042]      FIG. 14  is a top view of the rolling element retainer chain with a plurality of flexible metal strips disclosed in the present invention. 
           [0043]      FIG. 15  is a view focusing one part C of  FIG. 14 . 
           [0044]      FIG. 16  is the diagram showing plurality of flexible metal strips according to the present invention. 
           [0045]      FIG. 17  is a side view of the left half-spacers having wider recesses incorporated on a plurality of flexible metal strips according to the present invention. 
           [0046]      FIG. 18  is a section view of the front and rear half-spacers having wider recesses incorporated on a plurality of flexible metal strips of the present invention. 
           [0047]      FIG. 19  is atop view showing another embodiment of the rolling element retainer chain with at least one flexible metal strip disclosed in the present invention. 
           [0048]      FIG. 20  is a side view of the rolling element retainer chain with resin material covering on it disclosed in the present invention. 
           [0049]      FIG. 21  is a cross sectional view along line VI-VI of  FIG. 20 . 
           [0050]      FIG. 22  is a cross sectional view along line V-V of  FIG. 20 . 
           [0051]      FIG. 23  is a perspective view of the rolling element retainer chain with rollers according to the present invention. 
           [0052]      FIG. 24  is a top view of the rolling element retainer chain with rollers in present invention. 
           [0053]      FIG. 25  is a cross sectional view along line VII-VII of  FIG. 24 . 
           [0054]      FIG. 26  is the side view of the embodiment of the rolling element retainer chain with a plurality of flexible metal strips with ends connecting embodiment disclosed by the present invention. 
           [0055]      FIG. 27  is a top view of the embodiment of the rolling element retainer chain with a plurality of flexible metal strips with ends connecting embodiment disclosed in the present invention. 
           [0056]      FIG. 28  is a top view of the connecting of both ends of the rolling element retainer chain with a plurality of flexible metal strips disclosed in the present invention. 
           [0057]      FIG. 29  is the illustrated perspective view of the connection on both ends of the rolling element retainer chain with a plurality of flexible metal strips disclosed in the present invention. 
           [0058]      FIG. 30  is the side view of the embodiment with half flexible metal strip rolling element retainer chain disclosed in he present invention. 
           [0059]      FIG. 31  is a cross sectional view along line VIII-VIII of  FIG. 30  and the cross sectional view of the other coupled half flexible metal strip rolling element retainer chain. 
           [0060]      FIG. 32  is a perspective view of the combining of two half flexible metal strips rolling element retainer chains disclosed in the present invention. 
           [0061]      FIG. 33  is a view focusing in part D of  FIG. 32 . 
           [0062]      FIG. 34  is a section view of the corrugated-shaped metal belt in the turnaround passage. 
           [0063]      FIG. 35  shows the geometric relationship of the corrugation of bent corrugated-shaped metal belt. 
           [0064]      FIG. 36  is a geometric relationship diagram of the straight and bent corrugated-shaped metal belt. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0065]    As shown in  FIG. 1  and  FIG. 2 , a rolling element retainer chain  01  comprises a flexible metal strip  02  and a plurality of spacers  03 , wherein the flexible metal strip has a row of longitudinally arranged holes  21  on it. As shown in  FIG. 4 , a row of cross arranged latten  22  is formed between the holes  21 . Two connecting strips  23  are formed at both upside and downside of the holes  21  and all of the cross arranged latten  22  are connected to the connecting strips  23 ; the spacers  03  are incorporated on the cross arranged latten  22 . A row of rolling elements  05  are located in the holes  21  in a predetermined distance and separated by the spacers  03 . As shown in  FIG. 3 , the face of the spacer  03  opposite to the rolling element  05  forms an envelop shape  36 , and the rolling elements  05  are retained by two adjacent envelop shaped faces  36  of the spacers  03  in the rolling element retainer chain  01  without freely escaping. As shown in  FIG. 5 , the rolling element retainer chain  01  and the row of rolling elements  05  circulate in the recirculation passage  61  provided by the moving part  06 . A groove  62  extended along the direction of recirculation is provided by the recirculation passage  61  and the connecting strip  23  of the rolling element retainer chain  01  is guided in the groove  62 . the rolling element retainer chain  01  runs about straightly in the raceway passage  64  and the return passage  63  and curvedly with the turnaround passage  65  having the minimum arc ρ, therefore, the rolling element retainer chain  01  bent and straightened repeatedly during recirculation. To avoid the plastic deformation caused by repeated stress, the thickness of the flexible metal strip  02   h , as shown in  FIG. 2 , is restricted as h&lt;h o  and h o =2·R 0.2p ·ρ/E, where E is the elastic modulus of the metal material, R 0.2p  is the yielding strength of 0.2% plastic deformation of the metal material and ρ is the minimum radius of the turnaround passage. Therefore, the rolling element retainer chain  01  will achieve the object of bending repeatedly without plastic deformation when passing the turnaround passage  65 . 
         [0066]    To achieve an expected life or recirculation times without broken caused by material fatigue and according to the property of material, a suitable coefficient f is introduced for the selection of the thickness h of the flexible metal strip  02 , h≦f·h m  and h m =2·R m ·ρ/E, where R m  is the tensile strength of the metal material. For example, if the material of the flexible metal strip  02  is steel and the expected repetition times of straight-bending are more than 1 million times, then the coefficient f=0.6˜0.7. Both side faces of the connecting strips  23  of the flexible metal strip  02  are flat without corrugations. 
         [0067]    As shown in  FIG. 6 , the cross arranged latten  22  can be incorporated with the spacers  03 , and the cross arranged latten  22  provide protrusions  24 , indentations  25  or small holes  26  on the cross arranged latten  22  to prevent the displacement of the spacers  03  along the cross arranged latten  22  longitudinally. It is preferred that the protrusions  24 , the indentations  25  or the small holes  26  locate near the both end sides of the cross arranged latten  22  to decrease the width in the middle portion of the cross arranged latten  22  and the distance between two adjacent the rolling elements  05  can thereof be minimized. 
         [0068]    The flexible metal strip  02  can be made by stamping, punching, etching or laser cutting. As shown in  FIG. 1 , the spacers can be directly incorporated on the flexible metal strip  02  by injection molding process. As shown in  FIG. 7  and  FIG. 8 , the second embodiment of the incorporation method is to divide the spacer  03  into left and right half-spacers  31  and  32  by the flexible metal strip  02 , and there are coupled pins  33 , holes  34  and a recess  35  for receiving the cross arranged latten  22  on the left and right half-spacers  31  and  32 . Hence a complete spacer  03  is formed by combining the left and right half-spacers  31  and  32  on the cross arranged latten  22  through the coupling of the coupled pins  33  and holes  34 . As shown in  FIG. 9  and  FIG. 10 , the third embodiment of incorporation method is to divide the spacers  03  into front and rear half-spacers  41  and  42  by the perpendicular plane to the flexible metal strip  02 . As shown in  FIG. 11 ,  FIG. 12  and  FIG. 13 , there are coupled pins  43 , holes  44  and a recess  45  for receiving the flexible metal strip  02  on the front and rear half-spacers  41  and  42 . Hence a complete spacer  03  is formed by combining the front and rear half-spacers  41  and  42  on the cross arranged latten  22  through the coupling of the coupled pins  43  and holes  44 . As shown in  FIG. 10 , the pins  43  can protrude out of the front and rear half-spacers  41  and  42 , and the end faces  46  of the pins  43  form an envelop surface for receiving the rolling elements  05 . the rolling elements  05  are thereof retained and separated by the end faces  46  of two adjacent spacers, and lubricant can be stored in the recess between the pins  43  and keep direct lubrication on the rolling elements  05 . 
         [0069]    As shown in  FIG. 15 , the at least one flexible metal strip  200  is formed by a plurality of flexible metal strips  201 ,  202 ,  203 , . . . , overlapped and the resin spacers  03  are incorporated on the flexible metal strip  200 , hence the tension strength of the rolling element retainer chain  01  increases. The thickness of each of the plurality of flexible metal strips  200 , h 1 , h 2 , h 3 , . . . is restricted as h 1 , h 2 , h 3 , . . . &lt;h o  where ho is defined as above. As shown in  FIG. 16 , because each flexible metal strip  201 ,  202 ,  203 , . . . can be bent independently, the rolling element retainer chain comprising the plurality of flexible metal strips  200  can keep the same bending ability as the rolling element retainer chain comprising single flexible metal strip but the tension strength of the rolling element retainer chain comprising the plurality of flexible metal strips  200  can be increased multiply in accordance with the number of the overlapped flexible metal strips layer. 
         [0070]    By using the method of combining the left and right or the front and rear half-spacers  31 ,  32  and  41 ,  42 , as shown in  FIG. 8  and  FIG. 10 , the recesses  350  and  450 , as shown in  FIG. 17  and  FIG. 18 , for receiving the plurality of flexible metal strips  200  on the left and right or front and rear half-spacers  320 ,  410  and  420  can be a little larger than the cross arranged latten  220  to provide space for the free opposite movement between the flexible metal strips  201 ,  202 ,  203 , . . . when being bent. 
         [0071]    To enhance the strength of the spacers  03 , the cross arranged latten  02  between the longitudinally arranged holes  21  of the at least one flexible metal strip  02  are divided into upside and downside half crossed arranged latten  221  and  222  and connected on the connecting strip  23  respectively, as shown in  FIG. 19 , which are incorporated with upside and downside portions of the spacers  03  to form a complete rolling element retainer chain. 
         [0072]    As shown in  FIG. 20 ,  FIG. 21  and  FIG. 22 , to decrease the friction caused by the sliding of the metal connecting strip  23 ,  204  and  223  on the recirculation guiding groove  62 , the metal connecting strip  23 ,  204  and  223  can be covered by a resin layer  301  having lower friction coefficient by injection molding together with the spacers  03 . 
         [0073]    As shown in  FIG. 23 ,  FIG. 24  and  FIG. 25  the rolling elements  05  can be rollers  07 , the roller spacers  08 , incorporated on the cross arranged latten  22  and having envelop shape faces  81  opposite to the adjacent rollers  07 , can separate the rollers  07  to avoid the collision with each other and retained the rollers  07  in the rolling element retainer chain  01  without freely escaping. 
         [0074]    As shown in  FIG. 26  and  FIG. 27 , two half-spacers  09  are provided on one end of the flexible metal strip  02  and two coupled half-spacers  10  provided on the other end of the flexible metal strip  02 , and there are coupled pins and holes on the half-spacers  09  and  10 . As shown in  FIG. 28  and  FIG. 29 , two complete spacers are formed by combining the half-spacers  09  and  10 ; whereby two end portions  27  and  28  of flexible metal strip  02 , having one hole  21 , are overlapped wholly and fixed and a close loop rolling element retainer chain  01  is formed. 
         [0075]    The length of the overlapped portion  27  and  28  can be increased or decreased by increasing or decrease the number of combined the half-spacers  09  and  10 . 
         [0076]      FIG. 30 ,  FIG. 31 ,  FIG. 32  and  FIG. 33  show another embodiment of the rolling element retainer chain  01 ; a half flexible metal strip rolling element retainer chain  11  comprises at least one flexible metal strip  230  and half-spacers  340 , and there are coupled pins  342  and holes  341  on the half-spacers  340 . Because the diameter of the pins  342  is larger than the diameter of holes  231  on the at least one flexible metal strip  11 , the at least one flexible metal strip  230  and the half-spacers  340  can be incorporated together by injection molding process. A complete rolling element retainer chain  01  is formed by combining two the half flexible metal strip rolling element retainer chain  11  through the coupling of the pins  342  and holes  341 , and two the half flexible metal strips  230  can be incorporated together closely. 
         [0077]    The present invention is thus described, and it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.