Patent Publication Number: US-2021164549-A1

Title: Ball screw assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This non-provisional application claims priority under 35 U.S.C. § 119(a) to Patent Application No. 201911205360.4 filed in China, P.R.C. on Nov. 29, 2019, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND 
     Technical Field 
     The instant disclosure relates to a ball screw assembly, in particular, to a ball screw assembly with an axial opening. 
     Related Art 
     The ball guider device known to the inventor is provided for converting a rotation motion into a linear motion through the cooperation between the screw and the nut. By the cooperation between the ball nut provided with balls rolling in the circulating race and the screw provided with a spiral groove, the friction between the ball nut and the screw can be reduced during the operation. 
     Most of the ball nuts known to the inventor have complete cylinder shapes. When the length of the screw is longer and is provided with a supporting holder for preventing the screw from sagging, a resilient mechanism is provided on the supporting holder. Hence, when the ball nut rotates around the screw and passes the portion of the screw having the supporting holder, the supporting holder is temporally moved away from the screw through the resilient mechanism. Next, after the ball nut passes the portion of the screw having the supporting holder, the resilient mechanism moves the supporting holder back to the supporting position for providing a sufficient supporting force for the screw. 
     SUMMARY 
     However, when taking the aforementioned configurations, additional resilient mechanisms are configured at the supporting holders. Furthermore, when the supporting holder is at a position away from the screw, the portion of the screw corresponding to the supporting holder may sag due to its weight. As a result, when the open nut passes the portion of the screw having the supporting holder at the position away from the screw, the screw may encounter deflection, or the balls may not roll in the spiral groove properly due to the bending of the guider (e.g., the screw). Consequently, during the application of the ball guider device, the manufacturing precision becomes an issue and is to be considered. 
     In view of these, one embodiment of the instant disclosure provided a ball screw assembly. The ball screw assembly comprises a guider, an open nut, an open shield, a first circulator, a second circulator, and a ball circulating assembly. The guider has a central axis and a spiral channel. The spiral channel is annularly disposed around an outer periphery of the guider. The open nut is slidably fitted over the guider. The open nut comprises an axial cylinder, and the axial cylinder has an axial opening. The axial cylinder has a first axial wall and a second axial wall respectively located at two opposite sides of the axial opening. The axial cylinder comprises an inner annular wall and an outer annular wall. The inner annular wall has an inner spiral channel. The inner spiral channel corresponds to the spiral channel of the guider. The inner spiral channel and the spiral channel form an inner ball race. 
     Moreover, the open shield is coaxially fitted over an outer periphery of the axial cylinder. The open shield has an inner peripheral wall. The inner peripheral wall corresponds to the outer annular wall of the axial cylinder. The inner peripheral wall and the outer annular wall form an outer ball race. In a virtual plane projection of the ball screw assembly from a radial direction, the outer ball race is perpendicular to the central axis. The first circulator is disposed on the first axial wall. The first circulator comprises a first curve. Two ends of the first curve are respectively in communication with the inner ball race and the outer ball race. The second circulator is disposed on the second axial wall. The second circulator comprises a second curve. Two ends of the second curve are respectively in communication with the inner ball race and the outer ball race. The ball circulating assembly comprises a plurality of balls. The inner ball race, the first curve, the outer ball race, and the second curve form a ball circulating race. The ball circulating assembly rolls in the ball circulating race. 
     Accordingly, based on one or some embodiments of the instant disclosure, the axial cylinder of the open nut has the axial opening. Hence, when the open nut is disposed on the guider (e.g., a screw or a conversion rod) and moves along the guider, even if a supporting holder is configured below the guider, the open nut can pass the portion of the guider having the supporting holder through the axial opening, so that the open nut and the supporting holder do not interfere with each other. Therefore, the resilient mechanism on the supporting holder can be omitted. Moreover, when the open nut passes the portion of the guider having the supporting holder, the supporting holder is retained in a supporting state for the guider. Therefore, since the supporting holder does not detach from the guider, the guider does not sag or deform, and the manufacturing precision of the ball screw assembly during the application does not seriously affect the performance of the ball screw assembly. Furthermore, the open shield not only can form the outer ball race with the axial cylinder for the balls rolling in the outer channel, but also provides a dustproof function. 
     In one or some embodiments, a surface of the inner peripheral wall and the outer annular wall further form a second outer ball race. The two ends of the first curve are respectively in communication with the inner ball race and the second outer ball race. The two ends of the second curve are respectively in communication with the inner ball race and the second outer ball race. The inner ball race, the first curve, the second outer ball race, and the second curve form a second ball circulating race. The ball circulating assembly selectively rolls in the ball circulating race or the second ball circulating race. 
     In one or some embodiments, the first curve is obliquely configured with respect to a short side of the first circulator, and the second curve is obliquely configured with respect to a short side of the second circulator. 
     In one or some embodiments, the first circulator comprises a plurality of the first curves, and the first curves are arranged parallel to each other. The second circulator comprises a plurality of the second curves, and the second curves are arranged parallel to each other. 
     In one or some embodiments, the ball screw assembly further comprises a ball retainer, and the balls are connected in series by the ball retainer. 
     In one or some embodiments, the outer annular wall of the axial cylinder has an outer channel, and the outer channel and the inner peripheral wall form the outer ball race. Moreover, in one or some embodiments, the inner peripheral wall of the open shield has an inner channel corresponding to the outer channel, and the outer channel and the inner channel form the outer ball race. 
     In one or some embodiments, the inner peripheral wall of the open shield has an inner channel, and the inner channel and the outer peripheral wall of the axial cylinder form the outer ball race. 
     Detailed description of the characteristics and the advantages of the instant disclosure are shown in the following embodiments. The technical content and the implementation of the instant disclosure should be readily apparent to any person skilled in the art from the detailed description, and the purposes and the advantages of the instant disclosure should be readily understood by any person skilled in the art with reference to content, claims, and drawings in the instant disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will become more fully understood from the detailed description given herein below for illustration only, and thus not limitative of the disclosure, wherein: 
         FIG. 1  illustrates a perspective view of a ball screw assembly according to an exemplary embodiment of the instant disclosure; 
         FIG. 2  illustrates an exploded view of the ball screw assembly of the exemplary embodiment; 
         FIG. 3  illustrates an exploded view of the ball screw assembly of the exemplary embodiment from another perspective; 
         FIG. 4  illustrates a top view of an open nut of the ball screw assembly of the exemplary embodiment; and 
         FIG. 5  illustrates a top view of a second circulator of the ball screw assembly of the exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Please refer to  FIGS. 1 to 5 .  FIG. 1  illustrates a perspective view of a ball screw assembly according to an exemplary embodiment of the instant disclosure.  FIG. 2  illustrates an exploded view of the ball screw assembly of the exemplary embodiment.  FIG. 3  illustrates an exploded view of the ball screw assembly of the exemplary embodiment from another perspective.  FIG. 4  illustrates a top view of an open nut of the ball screw assembly of the exemplary embodiment.  FIG. 5  illustrates a top view of a second circulator of the ball screw assembly of the exemplary embodiment. 
     As shown in  FIGS. 1 and 2 , in this embodiment, the ball screw assembly comprises a guider  10 , an open nut  20 , an open shield  30 , a first circulator  40 , a second circulator  50 , and a ball circulating assembly  60 . The guider  10  may be, for example, a screw or a conversion rod. In this embodiment, the guider  10  is a screw for an illustrative example. As shown in  FIG. 1 , the guider  10  has a central axis C and a spiral channel  11 . 
     As shown in  FIGS. 1 and 2 , the open nut  20  comprises an axial cylinder  21 , and the axial cylinder  21  has an axial opening  211 . The axial cylinder  21  has a first axial wall  212  and a second axial wall  213  respectively located at two opposite sides of the axial opening  211 . The axial cylinder  21  comprises an inner annular wall  214  and an outer annular wall  215 . The inner annular wall  214  has an inner spiral channel  2141 . The inner spiral channel  2141  and the spiral channel  11  of the guider  10  correspond to each other and form an inner ball race. Specifically, in this embodiment, the guider  10  has the spiral channel  11  annularly disposed around an outer periphery thereof. The spiral channel  11  is disposed around the outer periphery of the guider  10  to provide a spiral angle. The open nut  20  can be slidably fitted over the guider  10 , so that the inner spiral channel  2141  and the spiral channel  11  of the guider  1  correspond to each other and form the inner ball race. 
     The open shield  30  is axially fitted over an outer periphery of the axial cylinder  21 . The open shield  30  has an inner peripheral wall  31 . The inner peripheral wall  31  and the outer annular wall  215  of the axial cylinder  21  correspond to each other to form an outer ball race. In this embodiment, to allow the ball circulating assembly  60  to roll in the outer ball race in a circulating manner, an outer channel  2151  is formed on the outer annular wall  215  of the axial cylinder  21 . Hence, the outer channel  2151  can correspond to the inner peripheral wall  31  to form the outer ball race. 
     In some embodiments, the inner peripheral wall  31  of the open shield  30  may be formed as the inner channel, and the outer annular wall  215  of the axial cylinder  21  is a curved surface, so that the inner channel and the outer annular wall  215  of the axial cylinder  21  form the outer ball race. Alternatively, in some embodiments, the outer annular wall  215  of the axial cylinder  21  has the outer channel  2151  and the inner peripheral wall  31  of the open shield  30  has the inner channel corresponding to the outer channel  2151 . Hence, when the open shield  30  is assembled with the axial cylinder  21 , the inner channel of the inner peripheral wall  31  and the outer channel  2151  of the outer annular wall  215  form the outer ball race. 
     Furthermore, the open shield  30  not only can form the outer ball race with the axial cylinder  21  for the ball circulating assembly  60  rolling in the outer channel  2151 , but also provides a dustproof function. 
     In this embodiment, as shown in  FIGS. 2 and 3 , the number of the inner spiral channel  2141  and the number of the outer channel  2151  are both plural, but the embodiment is provided as an illustrative example, not a limitation to the instant disclosure. According to practical requirements, the ball screw assembly may include one inner spiral channel  2141  and one outer channel  2151 ; in some embodiments, the ball screw assembly may include two or more inner spiral channels  2141  and two or more outer channels  2151 . For the sake of clarity, in  FIGS. 2 and 3 , one of the inner spiral channels  2141  and one of the outer channels  2151  are labelled. 
     Next, please refer to  FIGS. 2 to 4 . An XYZ triaxial coordinate where the axes are perpendicular to each other is illustrated in  FIG. 2 . In order to clearly present the structure of the ball screw assembly from different viewing angles, the figures are described based on the provided coordinate. As shown in  FIGS. 2 and 4 , the central axis C of the guider  10  extends in the X axis direction. For the sake of convenience, one of the radial directions is defined as a direction extending in a radial direction of the open shield  30  and perpendicular to the central axis C, and the defined direction is called a top viewing direction P, namely, the Z axis direction shown in  FIG. 2 . The top viewing direction P is a direction from the top of the figure to the bottom of the figure (viewing toward the direction of the Z axis having negative values). 
     As shown in  FIG. 4 , in this embodiment, the outer channel  2151  provided as the outer ball race is annularly disposed on the outer annular wall  215  along the radial direction. As shown in  FIG. 4 , the channel direction of each of the outer channels  2151  is the top and bottom direction shown in the figure (in this embodiment, the configuration of the outer channel  2151  is called straight groove). When the outer channel  2151  and the central axis C are projected along the direction shown in  FIG. 4  (i.e., the top viewing direction P), in the virtual plane projection of the open nut  21  from the top viewing direction P, the outer channel  2151  and the central axis C are perpendicular to each other; in other words, the angle A between the outer channel  2151  and the central axis C is a right angle. 
     In this embodiment, the outer channel  2151  is configured parallel to the radial direction of the axial cylinder  21 , the outer channel  2151  has linear configurations (configuration of straight channels). Hence, the outer channel  2151  can be manufactured easily. Moreover, upon the axial cylinder  21  is provided with the outer channel  2151  in linear configuration, due to the axial cylinder  21  having the outer channel  2151  extending to the first axial wall  212  and the second axial wall  213  in a symmetrical manner, the stress force applied to the open nut  20  can be distributed over the two sides of the open nut  20  in a balanced manner, thereby allowing the open nut to operates stably. 
     Furthermore, as shown in  FIGS. 1 to 3  as well as  FIG. 5 , the first circulator  40  is disposed on the first axial wall  212 . The first circulator  40  comprises a first curve  41 . Two ends of the first curve  41  are respectively in communication with the inner spiral channel  2141  (the inner ball race) and the outer channel  2151  (the outer ball race). The second circulator  50  is disposed on the second axial wall  213 . The second circulator  50  comprises a second curve  51 . Two ends of the second curve  51  are respectively in communication with the inner spiral channel  2141  (the inner ball race) and the outer channel  2151  (the outer ball race). Moreover, by configuring the first circulator  40  on the first axial wall  212  and the second circulator  50  on the second axial wall  213 , the circulators at two sides of the open nut  20  are arranged in a same axial position. Hence, the assembly of the open nut  20  and the circulators can have a balanced configuration, allowing the ball screw assembly to operate stably without severe shaking. 
     In this embodiment, as shown in  FIGS. 2 and 5 , the number of the first curve  41  and the number of the second curve  51  are both plural, but the instant disclosure are not limited thereto. According to practical requirements, the ball screw assembly may include one first curve  41  and one second curve  51 ; in some embodiments, the ball screw assembly may include two or more first curves  41  and two or more second curves  51 . For the sake of clarity, in  FIGS. 2 and 3 , one of the first curves  41  and one of the second curves  51  are labelled. 
     The first circulator  40  and the second circulator  50  may be respectively disposed on the first axial wall  212  and the second axial wall  213  using threading, adhering, or engaging techniques. In the case that the threading technique is applied to disposed the circulators on the open nut  20 , when the first circulator  40  and the second circulator  50  are worn due to long-term use, a user can simply replace the first circulator  40  and the second circulator  50  with new ones for continued use of the ball screw assembly. 
     Furthermore, as shown in the embodiment, the first circulator  40  and the second circulator  50  may have the same structure. Hence, during the manufacturing process, one element is manufactured and served as both the first circulator  40  and the second circulator  50 . It is understood that, according to practical requirements, the first circulator  40  and the second circulator  50  with different structures may be applied in the ball screw assembly. For instance, the first circulator  40  and the second circulator  50  with different numbers of curves may be applied, or the first circulator  40  and the second circulator  50  with different curve arrangement or different curve spacing may be applied. 
     Moreover, in this embodiment, the number of the first curve  41  of the first circulator  40  and the number of the second curve  51  of the second circulator  50  are eight as an example, but the instant disclosure is not limited thereto. In some embodiments, the first circulator  40  and the second circulator  50  may respectively have two curves and reduced size. Hence, when the axial cylinder  21  has a small size or when the number of the inner spiral channel  2141  and the number of the outer channel  2151  of the axial cylinder  21  are not too many (e.g., one), the first circulator  40  and the second circulator  50  with fewer curves can be used to match with the axial cylinder  21 . When the axial cylinder  21  is to be mated with the first circulator  40  and the second circulator  50  with more curves, several first circulators  40  with two curves and several second circulators  50  with two curves can be locked on the axial cylinder  21  for different practical requirements. Hence, in this embodiment, the manufacturer does not need to manufacture the first circulators  40  and the second circulators  50  in different lengths corresponding to the axial cylinder  21  in different lengths. 
     As shown in  FIG. 2 , the ball circulating assembly  60  comprises a plurality of balls  61 . As shown in  FIG. 1 , when the first circulator  40  and the second circulator  50  are assembled on the axial cylinder  21 , the first curve  41  of the first circulator  40  on the first axial wall  212  of the axial cylinder  21  is in communication with the inner ball race and the outer ball race, and the second curve  51  of the second circulator  50  on the second axial wall  213  of the axial cylinder  21  is also in communication with the inner ball race and the outer ball race. The inner ball race, the first curve  41 , the outer ball race, and the second curve  51  together form a ball circulating race. Accordingly, all of the balls  61  of the ball circulating assembly  60  can roll in the ball circulating race in a circulating manner. 
     As above, the first circulator  40  and the second circulator  50  are disposed on the axial cylinder  21 . Hence, the first circulator  40  is adapted to be in communication with the inner spiral channel  2141  on the inner annular wall  214  of the axial cylinder  21 , and the second circulator  50  is adapted to be in communication with the outer channel  2151  on the outer annular wall  215  of the axial cylinder  21 . Moreover, under this configuration, the ball circulating assembly  60  can roll from the inner spiral channel  2141  to the outer channel  2151  in a smooth manner. 
     Moreover, in the foregoing embodiment, the ball screw assembly is described to have a single ball circulating race, but as shown in  FIGS. 2 and 3 , the number of the ball circulating race can be adjusted according to practical requirements; the ball screw assembly may be provided with one ball circulating race, or two or more ball circulating races. According to different loading requirements, for instance, the ball screw assembly may be provided with two ball circulating race or several ball circulating race; alternatively, the ball circulating races may completely cover the entire open nut  20  and the entire open shield  30 . Hence, the ball screw assembly can be applied for light and heavy loading requirements. 
     Further, as shown in  FIGS. 2 and 3 , in this embodiment, one ball circulating assembly  60  is disassembled and for illustrative purpose and also for showing the configuration of the balls  61  of the ball circulating assembly  60  in the ball circulating race. The ball circulating assembly  60  surrounds the inner ball race, the first curve  41 , the outer ball race, and the second curve  51  to form a loop, and the ball circulating assembly  60  rolls in a circulating manner in an individual ball circulating race. In practice, as shown in  FIGS. 2 and 3 , the ball screw assembly may be provided with several ball circulating assemblies  60 , and each of the ball circulating assemblies  60  individually rolls in the corresponding ball circulating race in a circulating manner. 
     Accordingly, based on one or some embodiments of the instant disclosure, the axial cylinder  21  of the open nut  20  has the axial opening  211 . Hence, when the open nut  20  moves along the guider  10 , even if a supporting holder (for example, a supporting base (not shown)) is configured below the guider  10 , the open nut  20  can pass the portion of the guider  10  having the supporting holder through the axial opening  211 , so that the open nut  20  and the supporting holder do not interfere with each other. Therefore, the resilient mechanism of the supporting molder for moving a guider to a position away from the ball screw can be omitted. Moreover, when the open nut  20  passes the portion of the guider  10  having the supporting holder, the supporting holder is retained in a supporting state for the guider  10 . Therefore, since the supporting holder does not detach from the guider  10 , the guider  10  does not sag or deform, and the manufacturing precision of the ball screw assembly during the application does not seriously affect the performance of the ball screw assembly. 
     In this embodiment, one ball circulating race is formed by one inner ball race, one first curve  41 , one outer ball race, and one second curve  51 . All of the balls  61  of one ball circulating assembly  60  can roll in one ball circulating race in a circulating manner. As shown in  FIGS. 2 and 3 , in this embodiment, the ball screw assembly is provided with a plurality of ball circulating races and a plurality of ball circulating assemblies  60 , respectively, and each of the ball circulating assemblies  60  individually rolls in the corresponding ball circulating race. 
     In some other embodiments, the two ends of the first curve  41  are respectively in communication with a first one inner ball race and a second one outer ball race, and the two ends of the second curve  51  are respectively in communication with the first one inner ball race and the second one outer ball race. In detail, in these embodiments, the inner spiral channels  2141  (the inner ball races) aligned in order are taken as a first one channel, a second one channel, and so forth, from an end of the axial cylinder  21 , and the outer channels  2151  (the outer ball races) aligned in order are taken as a first one channel, a second one channel, and so forth, from the end of the axial cylinder  21 . In this configuration, one of two ends of the first curve  41  is connected to the first one channel of the outer channels  2151 , and the other end of the first curve  41  is connected to the second one channel of the inner spiral channels  2141 , rather being connected to the first one channel of the inner spiral channels  2141 . Similarly, one of two ends of the second curve  51  is connected to the first one channel of the outer channels  2151 , and the other end of the second curve  51  is connected to the second one channel of the inner spiral channels  2141 . It is understood that, such configuration may be accomplished by adjusting the inclination of the first curve  41  and the second curve  51 . 
     As above, the second one channel of the inner ball races, one first curve  41 , the first one channel of the outer ball races, and one second curve  51  may together form one ball circulating race. Accordingly, the ball circulating assembly  60  can roll in a circulating manner among the second one channel of the inner ball races, the first curve  41 , the first one channel of the outer ball races, and the second curve  51 . Hence, circulators with different configurations can be applied in the ball screw assembly, so that the inner ball race and the outer ball race at different lines can be mated with each other to form individual ball circulating races in different combinations. Therefore, according to different loading requirements, the inner ball race and the outer ball race at same lines or different lines can be mated with each other to form the ball circulating race. 
     Moreover, in this embodiment, the first curve  41  is obliquely configured with respect to a short side of the first circulator  40 , and the second curve  51  is obliquely configured with respect to a short side of the second circulator  50 . In this embodiment, because the first circulator  40  and the second circulator  50  have the same structure, only the second circulator  50  is illustrated in  FIG. 5  for illustrative purposes. As shown from  FIG. 5 , the top view of the second circulator  50 , when the number of the second curves  51  of the second circulator  50  is plural, the second curves  51  are aligned parallel to each other, and the second curves  51  are aligned along a direction from upper right to lower left. Similarly, the number of the first curves  41  of the first circulator  40  is plural, and the first curves  41  are aligned parallel to each other. Supposed that the first circulator  40  is arranged to an orientation the same as the second circulator  50  (i.e., the first circulator  40  and the second circulator  50  are viewed from the same viewing angle), the first curves  40  are also aligned in an oblique configuration from upper right to lower left. 
     Furthermore, in this embodiment, the balls  61  of the ball screw assembly does not need the ball retainer, and the balls  61  can be limited in the ball circulating race formed by the guider  10 , the open nut  20 , the open shield  30 , the first circulator  40 , and the second circulator  50  and can roll in the individual ball circulating race, without detaching off the ball circulating race. In other embodiments, the ball screw assembly further comprises a ball retainer, so that the balls  61  of the ball circulating assembly  60  are connected in series by the ball retainer. 
     While the instant disclosure has been described by the way of example and in terms of the preferred embodiments, it is to be understood that the invention need not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures.