Abstract:
A ball chain comprises a sequence of balls and an longitudinally elongated spacing chain having a sequence of holes thereon for receiving the balls. The spacing chain further includes a sequence of spacers interposed between the balls whereby the balls will be separated to each other, at least two longitudinally extended flexible strip and a plurality of transverse flexible connecting beam whose two ends respectively are connected to the longitudinal flexible strip, whereby the spacers attach to said connecting beam through an elastic member. The spacers can accordingly deflect and twist freely and the transverse flexible connecting beam can keep as long as possible and provide the best flexibility for being bent in various directions. Therefore, the ball chain can run in a three-dimensionally direction-chain recirculation channel smoothly and with low resistance.

Description:
FIELD OF THE INVENTION 
   The present invention relates to ball chains, more particularly to a ball chain comprising a sequence of balls and an axially elongated spacing band that has a sequence of holes thereon for receiving the balls and the spacers that separate the balls whereby the ball chain can re circulate smoothly in a three-dimensional direction-change channel with low noises and resistance. 
   BACKGROUND OF THE INVENTION 
   A mechanism of motion comprises a moving part and a guiding part. The moving part and the guiding part comprise at least a raceway coupled and there exists a row of load-carrying balls rolling along the raceway coupled. For each raceway coupled the moving part further provide a return channel as well as a turn-around channel to form a recirculation passage, so that the ball chain can circulate in the recirculation passage and the moving part can therefore continue its slide motion on the guiding part without limit. To avoid collision between and the wear of the balls during the slide motion, a plurality of separators are provided among the balls so as to isolate adjacent balls from each other for reducing noises and frictional resistance, wherein the adjacent separators is formed to have un-uniform thickness so as to isolate the adjacent balls in an unequally spaced manner as disclosed in U.S. Pat. No. 5,927,858. However, because of the clearance between the balls and their neighboring separators, the separators are easy to get tilted, causing an interference with the passing channel and unsmooth running of the slide motion. 
   Another connecting chain of balls comprises a pair of strip-like connecting member and a multiple spacers, connected to said connecting member and interposed among respective rolling balls; wherein said spacers form a rosary-like shape for receiving the balls. Further, the connecting chain of balls is fabricated by molding flexible resin and able to deflect in the direction perpendicular to a plane defined by the connecting member. However, because of the rigidity of the band-like connecting chain in the transverse direction, the connecting chain cannot be bent effectively in that direction, which forbids effective three-dimensional bending. 
   To overcome the problem of unsmooth recirculation occurring when the ball chain bending is not on a plane perpendicular to the elongated surface of the connecting chain, linear motion mechanisms such as ball screws or linear guides, as disclosed by U.S. Pat. No. 5,593,064. In that patent, a ball connector comprises a number of balls arranged in one row at predetermined interval; and a flexible connector belt includes four belt members formed in a strip-like shape along peripheral faces of the balls and brought into contact with the plurality of balls; wherein the belt members are connected mutually with other ones of the belt members at intermediaries of the balls contiguous to each other and the connector belt is formed in a shape constrict in comparison with an outer diameter of the ball at positions of the intermediaries connecting the balls. The ball connector is accordingly easy to flex compliantly in any direction at the position and easy to absorb twist operated on the ball connector. This design allows more freedom for the ball connector being bent and twisted, and a smooth slide motion of the ball chain when it is bent deviated from the plane perpendicular to the elongated surface of the connecting chain. However, this invention, since the connector belt is formed in a shape constrict in comparison with an outer diameter of the ball at positions of the intermediaries connecting the balls, that only the top side of four belts falls in the guide grove of the recirculation channel and that the recirculation channel is at least composed of two parts, there must be an engagement section between the two parts, where misalignment could happen. Therefore, every time the top fringe of the four belts pass through the engagement section, they have to be realigned, or the ball connector is easy to get jammed. Moreover, to provide enough flexibility the connecting portion of the belt member should have certain longitudinal length and constriction, such will affect the number of the balls receiving the load and the spacer size negatively. Similarly, the rolling-element hold spacer disclosed by the U.S. Pat. No. 6,247,846 B1 comprises a thick hold section having spherical indents formed on both sides thereof, the thick hold sections being adapted to be interposed between rolling elements and thin bent sections for interconnecting only one thick hold section pair in which the rolling element is to be interposed. The thin bent section can be deflected or twisted in a curved portion of a rolling-element circulation path and the hold spacers which are adjacent to each other with a single rolling element interposed therebetween mutually perform pivotal movement around the rolling element, thereby enabling smooth circulation in three-dimensional change of direction of the rolling elements. However, since the hold spacers are moving independently in the recirculation channel, each of the balls will have to realign itself with the channel when passing through the engagement section between the parts of the recirculation channel, where misalignment could happen and may cause a unsmooth slide motion. 
   SUMMARY OF THE INVENTION 
   Accordingly, the primary objective of the present invention is to provide a ball chain that can be bent in three dimensions with a high degree of freedom, whereby it can slide smoothly and quietly along linear motion mechanism such as a ball screw and a linear guide. The ball chain comprises a row of balls and a spacing chain with a multitude of holes for housing the balls. The spacing chain further includes a row of spacers disposed between the balls for preventing the collisions between adjacent balls. The ball chain further comprise a pair of longitudinally extended thin flexible strips and a multitude of transversely extended flexible connecting beam interposed between the balls; both ends of the flexible connecting beam is connected to the longitudinal flexible strips, the spacers attach to the flexible connecting beam through an elastic member, whereby the transversely extended flexible connecting beam can keep as long as possible and provide the best flexibility for being bent in various direction, and whereby the spacers attached to the connecting beam through the elastic member can deflect or twist freely. Further, the spacers, slightly smaller than the diameter of the balls, have a larger contact area with the corresponding balls, whereby the contact pressure between a spacer and a rolling ball will be reduced. Further, each of the spacers has a groove whose clearance is large enough so that the bending of the corresponding transverse connecting beam will not interfere with the spacer. 
   There is at least a guiding groove within the recirculation channel for guiding the longitudinal flexible strips, whereby the ball chain can slide along an elongated guiding plane defined by the guiding grooves within the recirculation channel. When the recirculation channel is turned on a plane perpendicular to the guiding plane, the longitudinal flexible strips will be also curved two dimensionally along the guiding plane, and the flexibility of the longitudinal flexible strips will facilitate the bending of the ball chain, and therefore the balls will move smoothly with low resistance in the channel. 
   When the recirculation channel is turned in a way that the vertical planes to the guiding plane are no more lying on the same plane but displaced or tilted to each other, for example in the ballscrew or some linear guide design, as the ball chain is moving in the recirculation channel and the longitudinal flexible strip is inside and guided by the groove, the trajectory of the moving ball chain is accordingly three dimensional, and there will be relative displacement, bending, and tilting between the longitudinal flexible strips and the transverse flexible connecting beam. In the meanwhile, the spacers still have to be properly aligned to the balls. The different alignment of the strip, connecting beam and spacer require the deformations among them, so that they can be adjust to the curvature of the recirculation channel smoothly. This can be realized by the flexibility of the the strip and connecting beams themselves and the elastic member between the connecting beam and the attached spacer also. Thereby, a full three dimensional curving of the ball chain can be performed with high degree of freedom and the ball chain, having its flexible longitudinal strips inside and guided by the grooves and its spacers properly aligned to the rolling balls, runs smoothly in the recirculation channel. The spacing chain can be made by nylon, TPE resin or rubber . . . etc. fabricated by injection molding to achieve its flexibility. 
   The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a linear guide for applying the present invention, which is a front cross-sectional view thereof wherein the return channel is not on the plane T 1  perpendicular to the spacing chain in the load zone channel. 
       FIG. 2  is the A-A cross sectional view of  FIG. 1 . 
       FIGS. 3(A) and 3(B)  are front views of the spacing chain disclosed by the present invention in a recirculation channel having a return channel, turnaround channel and a load zone channel and its G-G perspective view. 
       FIGS. 4(A) and 4(C)  are top views of the spacing chain disclosed by the present invention in a recirculation channel having a return channel, turnaround channel and a load zone channel and its D-D and E-E perspective view. 
       FIGS. 5(A) and 5(F)  show the first preferred embodiment of the present invention. 
       FIGS. 6(A) and 6(E)  show the second preferred embodiment of the present invention. 
       FIGS. 7(A) and 7(F)  show the third preferred embodiment of the present invention. 
       FIGS. 8(A) and 8(F)  show the fourth preferred embodiment of the present invention. 
       FIGS. 9(A) and 9(F)  show the fifth preferred embodiment used in a ball screw design. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIGS. 1 and 2 , a linear guide comprises a moving part  01 , a guiding part  2  and a plurality of ball chains  03 . The moving part  01  has a plurality of longitudinally extended tracks  11 , an about longitudinal arranged return channels  12  nearby each of the track  11 . The tracks  11  and the return channels  12  are respectively connected by turnaround channel  13  on both ends. The guiding part  2  provides a track  21  in the position opposed to each of the tracks  11 , to form a load zone channel  14 . Said return channel  12 , turnaround channel  13  and the load zone channel  14  form a recirculation channel  15  altogether. 
   Each of the ball chains  03  comprises a row of balls  31  and a longitudinally extended spacing chain  30 . Each of the spacing chain  30  has a multitude of hole for receiving the balls  31 . Each of the ball chains  03  moving in a corresponding recirculation channel  15  wherein the balls  31  in the load zone channel  14  roll on the track  11 ,  21  and carry the load, turnaround in the turnaround track  13  and return in the return channel  12 . Thereby, the moving part  01  is sliding along the guiding part  2  indefinitely. As shown in  FIG. 1 , there are guiding grooves  16  elongated in each of the recirculation channels  15 . A guiding plane H 1  is defined by a pair of guiding grooves  16  in the corresponding lead zone channel  14 , and a guiding plane H 2  defined by the pair of guiding grooves  16  in the corresponding return channel  12 . An optimal position of the return channel  12  in the linear guide design is not always on the plane T 1 , having intersecting the center of the load zone channel  14  and perpendicular to the plane H 1 . The plane C 1  defined by the rolling ball centers in the return channel  12  and in the load zone channel  14  inclines to said plane T 1  with an angle φ 1 . Therefore, there is a displacement Δ between the plane T 1  and the plane T 3  intersecting the rolling ball center in the return channel  12  and having perpendicular to the guiding plane H 2  in the return channel  12 . As shown in  FIGS. 3 and 4 , a ball chain  03  runs through the load channel  14 , the turnaround channel  13  and the return channel  12 ;  FIGS. 3 and 4  are a front view and other views from various perspectives. The spacing chain  30  of the ball chain  03  comprises a row of spacers  32  arranged between the balls  31 . The contact faces  35  of a spacer with adjacent balls are respectively aligned with the balls. The thin longitudinal flexible strips  33 , and the multitude of transversely extended flexible connecting beam  34 , the strip  33 , confined and moving in the guiding grooves  16  of the load zone channel and the connecting beams  34  are laying on the plane H. The G-G perspective view in  FIG. 3  shows the orientation of X, Y and Z axes; X is along the moving direction of the ball chain  03 , Y is perpendicular to X and on the plane H, and Z is perpendicular to the plane H and Y. The X, Y and Z axes are curved along with the curvature of the guiding grooves  16  in the recirculation channel  15 . When the spacing chain  30  is either in the load zone channel  14  or the return channel  12 , the longitudinal flexible strips  33  and the transverse flexible connecting beams  34  are mutually perpendicular, whereas the spacers  32  and the transverse flexible connecting beams  34  are parallel to each other. When the spacing chain  30  is turned into the turnaround channel  13 , the transverse flexible connecting beam  34  will tilt to the flexible strip  33  form a deflection angle φ 3  around the Z axis as shown in  FIGS. 3(A) and 3(B) . At the same time, the spacers shall always keep aligned with the adjacent rolling balls; accordingly the spacers  32  and the transverse flexible connecting beams  34  shall twist each other about the Z axis to form an angle φ 4 , as shown in the E-E perspective view in  FIGS. 4(A) to 4(C) . Further, the spacers  32  and the transverse flexible connecting beam  34  shall twist each other about the Y axis to form an angle φ 5 , also shown in  FIGS. 4(A) and 4(B) . Further, the spacers  32  and the transverse flexible connecting beam  34  shall twist each other about the X axis to form an angle φ 6 , as shown in the D-D perspective view in  FIG. 4 . Since the balls  31  and the longitudinal flexible strips  33  are moving in the recirculation channel  15  and parallel to the recirculation channel  15 , the angle φ 3  will be the same as another angle φ 1  defined by the intersection of the plane C 1  and the plane T 1 , when the transverse flexible connecting beam  34  is parallel to the guiding plane of the spacing chain H. Further, since the spacers  32  are aligned with the balls  31 , the angles φ 3  and φ 4  are the same. Therefore, the larger the displacement Δ defined by the plane T 1  and the plane T 3  is, the more necessary the degree of freedom for the spacing chain  30  to tilt to angles φ 3  and φ 4  is. 
   To facilitate the deformation of the spacing chain  30  when it goes into a turnaround channel  13  with low resistance, the first preferred embodiment of the present invention shown in  FIGS. 5(A) and 5(F)  is a spacing chain  30  comprising a pair of thin longitudinally extended flexible strips  33  and a multitude of transversely extended flexible connecting beams  34 , wherein both ends of said connecting beams  34  are connected on the said flexible strip  33 , and a corresponding one of the spacers  32 . Each of the spacers  32  is interposed between two adjacent balls  31  and has inwardly curved contact faces  35  to accommodate the shape of the balls; the arc of the contact faces  35  is similar to the diameter of the balls  31 . The elastic member for the joint of said spacers and said connecting beam  34  is formed by the constriction of the joint area  36  between the spacers  32  and the transverse flexible connecting beam  34  where the joint area is at least smaller than the diameter of the spacers  32 , whereby the flexible deflection between the spacers  32  and the transverse flexible connecting beam  34  will be increased. Therefore, the spacers  32  and the transverse flexible connecting beam  34  can undergo a flexible deformation with low resistance as shown in  FIGS. 3(A) and 3(B) . Such deformation will achieve a tilt angle φ 4  about the Z axis, another tilt angle φ 5  about the Y axis and a further tilt angle φ 6  about the X axis as required. At the same time, the constriction of the joint areas  36  of the present invention enhance the flexibility and preserve the length of the transverse flexible connecting beam  34 . On the other hand, the connecting areas  37  between the longitudinal flexible strips  33  and the transverse flexible connecting beam  34  is roughly the same as the cross section area of the longitudinal flexible strips  33 , whereby the longitudinal flexible strips  33  and the transverse flexible connecting beam  34  can help achieving flexible deformation and twist about the Z axis to form a tilt angle φ 3 , whereby the spacing chains  30  of the ball chains  03  can slide smoothly with low resistance along the guiding planes defined by respective guiding grooves in the recirculation channel  15 . The size of the joint area  36  depends on the necessary elasticity to form the tilt angle φ 3  required. 
   Referring to  FIGS. 6(A) and 6(E) , the second preferred embodiment of the present invention is a spacing chain  40  of a ball chain comprising a pair of longitudinal flexible strips  43 , a multitude of transverse flexible connecting beam  44  and a row of spacers  42  interposed between balls  41 . The elastic member  46  for the joint of the spacers  42  and the transverse flexible connecting beam  44  are formed by a flexible transverse stick  47 , which pierces the plane H defined by said longitudinal flexible strips  43  and the transverse flexible connecting beam  44 . The flexible stick  47  has a joint in the middle connecting with the connecting beam  44 . The spacers  42  are divided by the plane H to form a pair of spacer components  42   a  and  42   b , which are connected on both ends of said flexible stick  47 . The contact faces  45  between pairs of spacer components  42   a  and  42   b  and the balls  41  are arced to fit the shape of the balls  41 , whereby the flexible stick  47  can further enhance the flexibility of deformation between the spacers  42  and the transverse flexible connecting beam  44 . Therefore, when the spacing chain  40 , having its longitudinal flexible strip  43  confined in said guiding groove  16 , enters into the turnaround channel  13 , the spacers  42  can easily deflect and align to the balls, the resistance is reduced, and the movement of the spacing chain  40  in the recirculation channel  15  can be smooth. 
   The terminal spacers at two ends of a spacing chain  40  each comprises a pair of spacer pieces  142   a ,  142   b  and a connecting piece  48  on which the spacer pieces  142   a ,  142   b  are integrated. The holes for receiving the balls  49  between the spacers  42  are each near the size of the balls  41 . Therefore, when the receiving holes  49  are all filled with the balls  41 , all of the pairs of spacer components  42   a  and  42   b  will be confined by the balls  41  and the integrated terminal spacers  142   a ,  124   b , whereby they will not be able to do any unnecessary deflection causing interference with the surrounding of the recirculation channel  15 . The terminals of a pair of longitudinal flexible strips  43  are curved toward the balls  41 , and therefore the connecting pieces  48  will become the guide pieces for the two ends of the spacing chain  40 . 
   Referring to  FIGS. 7(A) and 7(F) , the third preferred embodiment of the present invention is a spacing chain  50  of a ball chain comprising a pair of longitudinal flexible strips  53 , a multitude of transverse connecting beam  54  and a row of spacers  52  interposed between balls  51 ; the spacers  52  are connected to the transverse connecting beam  54 . Each of the spacers  52  is divided by a plane S, intersecting said transverse connecting beam  54 , and perpendicular to the longitudinal flexible strip  50 , into a pair of spacer components  52   a  and  52   b  which are arranged in tandem longitudinally. The front spacer component  52   a  is adjacent to a front one of the balls  51 , and the rear spacer component  52   b  is adjacent to a rear one of the balls  51 . The contact faces  45  between pairs of spacer components  52   a  and  52   b  and the balls  51  are arced to fit the shape of the balls  51 . The flexible connection between the spacer components  52   a  and  52   b  and the transverse connecting beam  54  are achieved by a flexible transverse stick  57 , which pierces the plane H, defined by the longitudinal flexible strips  53  and the transverse connecting beam  54 , and connect the pair of spacer components  52   a  and  52   b  on both ends. The center of the flexible transverse stick  57  is connected to a corresponding one of the transverse connecting beam  54 . The clearance between the transverse flexible connecting beam  54  and the spacer components  52   a  and  52   b  are sufficiently large so that the tilting from the spacer components  52   a  and  52   b  will not interfere with the transverse flexible connecting beam  54 . The transverse stick  57  can further enhance the flexibility of deflection between the spacers  52  and the transverse flexible connecting beam  54 . Therefore, when the spacing chain  50 , having its longitudinal flexible strip  53  confined in the guiding groove  16 , enters into the turnaround channel  13 , the spacers  52  can easily deflect and align to the balls, the resistance is reduced, and the movement of the spacing chain  40  in the recirculation channel  15  can be smoothed as shown in  FIG. 1 . 
   Referring to  FIGS. 8(A) and 8(F) , the fourth preferred embodiment of the present invention is a spacing chain  60  of a ball chain comprising a pair of longitudinal flexible strips  63 , a multitude of transverse flexible connecting beam  64  and a row of spacers  62  interposed between balls  61 . The elastic member for the connection between the pair of the spacers  62  and the transverse flexible connecting beam  64  is realized by a flexible transverse stick  67 , which pierces a plane H, defined by the longitudinal flexible strips  63  and the transverse flexible connecting beam  64 . The flexible transverse stick  67  connects the pair of spacer components  62   a  and  62   b  at its two ends and the flexible transverse connecting beam  64  in its middle position. The contact faces  65  of pairs of spacer components  62   a  and  62   b  facing the balls  61  are arced so as to fit the shape of the balls  61 . To prevent the excessive opening of the spacer components  62   a  and  62   b  so that the fringe of them become larger than the cross section area of the balls  61  and they will interfere with the surrounding of the recirculation channel  15 , the pair of spacer components  62   a  and  62   b  are connected by at least a connecting strip  68 . The transverse stick  67  can further enhance the flexibility of deflection between the spacers  62  and the transverse flexible connecting beam  64 . Therefore, when the spacing chain  60 , having its longitudinal flexible strip  63  confined in said guiding groove  16 , enters into the turnaround channel  13 , the spacers  52  can easily deflect and align to the balls, the resistance is reduced, and the movement of the spacing chain  40  in the recirculation channel  15  can be smoothed, as shown in  FIG. 1 . 
   Referring to  FIGS. 9(A) and 9(F) , a ball screw comprises a moving part  110  being a hollow cylindrical nut, a guide rod  120  and at least one balls chain  130  helically wound about the guide rod  120 . The inner wall of the moving part  110  is provided with a least a helically extended track  111 , and the outer wall of the guide rod  120  is provided with at least a corresponding helical track  121 , whereby the coupling between the tracks  111 ,  121  forms a load zone channel  140  helically extended along the axis of the guide rod  120 . The balls chain  130  comprises a row of balls  71  and the associated spacing chain  70 , which is basically the first preferred embodiment of the present invention. The spacing chain  70  is provided with a row of holes for receiving a corresponding one of the balls  71 , whereby they are separated and properly retained. When the moving part  110  is being rotated, the balls chain  130  will move along the helical track  121 , and therefore the moving part  110  will proceed in the axial direction of the guide rod  120 . The spacing chain  70  is in a straight line shape, wherein the transverse flexible connecting beams  74  are perpendicular to the longitudinal flexible strip  73 , when it is free. The spacing chain  70  is wound into a helical shape when it is in a load zone channel  140  and the longitudinal flexible strips  73  are confined between the moving part  110  and the outer surface of the guide rod  120  and together with the balls  71  move along the helically extended track  111 ,  121 . This situation is the same as a ball chain  30  entering into a turnaround channel  13  shown in  FIG. 3 , the plane perpendicular to the guiding plane of the helical load zone channel  140 , defined by the pair of longitudinal flexible strip  73  or the outer surface of the guide rod, is thereof not on the same plane. Therefore the transverse flexible connecting beams  74  will tilt with respect to the longitudinal flexible strip  73  at an angle φ 3 ; in the meanwhile the spacers  72 , aligned with the balls  51  are parallel to the longitudinal flexible strips  73 , the pair of the spacer components  72   a ,  72   b , shall tilt with respect to the transverse flexible connecting beam  74  at angles φ 4 , which two angles φ 3 , φ 4  will increase in accordance with the increase in lead pitch of the helical extended track  111 ,  121 . The spacing chain  70  the same as the spacing chain  40  shown in  FIG. 6 , having the flexible stick  77  as elastic member, has the flexibility of deformation between the spacers  72  and the transverse flexible connecting beam  74 . Therefore, the spacers  72  and the corresponding transverse flexible connecting beam  74  may form a tilt angle φ 4 . Further, since the connecting areas  76  are much smaller than the cross section areas of the spacers  72 , the length of the transverse flexible connecting beam  74  is effectively increased. Further, the flexibility of the longitudinal flexible strips  73  and the transverse flexible connecting beam  74  enable the tilt to form a tilt angle φ 3  between the longitudinal flexible strips  73  and the transverse flexible connecting beam  74 . Therefore the spacing chain  70  together with the balls  71  can move in the helical extended load zone channel  140  smoothly under low resistance. 
   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.