Abstract:
A separable ball screw comprises a screw shaft having a helical groove; a transfer ring, a plurality of balls and a separable nut being sequentially engaged to the screw shaft; the balls being distributed in the holes in the annular surface of the transfer ring; the transfer ring being hollowed, the retaining ring enclosing around the screw shaft; the plurality of holes being formed in the annular surface; the balls being received in the holes; the balls being received in the holes of the transfer ring as power transfer medium between the transfer ring and the screw shaft; and a separable nut having a hollow center; the separable nut enclosing around the transfer ring; an inner annular surface of the separable nut having at least one grooves; the inner annular surface and the groove serving for limiting positions of the balls.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to ball screws, and particularly to a separable ball screw, which has both functions of helical movement and linear movement so as to match different movement mechanism. A separable nut is used to control the positions of the balls. By the indirect contact of the screw shaft and the separable nut, the application of the ball screw is promoted, which is especially suitable for rapid reciprocal and traveling limited ball screw. 
       BACKGROUND OF THE INVENTION 
       [0002]    The ball screw has the advantages of low friction coefficient, high efficiency, and high precision. In industry, a predetermined number of balls are arranged in the helical groove between the screw shaft and the sleeve of the screw shaft. By rotating the screw shaft, the sleeve will move reciprocally along the screw shaft. However for a long time, the balls will wear so that a great error generates, even the wearing of the groove will make the screw shaft shift, bend or break. 
         [0003]    In Taiwan Patent No. TW266376Y, “Improved structure of nut circulation structure for ball screw”, at least one ball circling groove is formed at an outer side of a screw shaft. A plurality of balls roll between the helical grooves of the screw shaft and the nut unit. The balls are guided to a tube inlet and then to a helical groove between the screw shaft and the helical groove of the nut so as to form a cyclic path. 
         [0004]    Furthermore, in another Taiwan Patent No. TW259875B, “Ball screw for high load and with limited travel”, in that a ball screw has a screw shaft, an outer seat, a ball sleeve, and a limit element. A shaft body of the screw shaft is formed with a helical groove. The feature is that the sleeve is installed between the screw shaft and the seat and then the limiting element is positioned by a fixing cover. A post of the limiting element passes through a positioning hole of the sleeve so that the limiting element will control the positioning and interface of the sleeve and the helical groove so as to calibrate the errors in the reciprocal movement of the sleeve and thus the lifetime of the ball screw is prolonged. 
         [0005]    However the prior art features have some defects, such as the structure is more complicated and the reciprocal movement speed is low. Moreover, the ball screw is not economic to a small size electronic device. Therefore, it is desired to have a structure which can move helically or linearly by the coupling between a separable nut and a screw shaft so as to promote the application of the ball screw, which is especially suitable for a rapidly reciprocal ball screw. 
       SUMMARY OF THE INVENTION 
       [0006]    Accordingly, the primary object of the present invention is to provide a separable ball screw, which has both functions of helical movement and linear movement so as to match different movement mechanism. A separable nut is used to control the positions of the balls. By the indirect contact of the screw shaft and the separable nut, the application of the ball screw is promoted, which is especially suitable for rapid reciprocal and traveling 
         [0007]    To achieve above objects, the present invention provides a separable ball screw, comprising: 
         [0008]    a screw shaft having a helical groove; a transfer ring, a plurality of balls and a separable nut being sequentially engaged to the screw shaft; the balls being distributed in the holes in the annular surface of the transfer ring; 
         [0009]    the transfer ring being hollowed, the retaining ring enclosing around the screw shaft; the plurality of holes being formed in the annular surface; the balls being received in the holes; 
         [0010]    the balls being received in the holes of the transfer ring as power transfer medium between the transfer ring and the screw shaft; and 
         [0011]    a separable nut having a hollow center; the separable nut enclosing around the transfer ring; an inner annular surface of the separable nut having at least one grooves; the inner annular surface and the groove serving for limiting positions of the balls; when the balls in the grooves, the screw shaft being not engaged to the transfer ring; the screw shaft moves linearly, when the balls being limited by the inner annular surface, it is driven as the ball screw. 
         [0012]    By above components, the separable nut serves to limit the positions of the balls so as to control the coupling between the transfer ring and the screw shaft to promote the application of the ball screw, and particularly to a rapid reciprocal and traveling limit ball screws. 
         [0013]    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 drawing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of the ball screw of the present invention. 
           [0015]      FIG. 2  is an explosive schematic view showing the components of the ball screw of the present invention. 
           [0016]      FIG. 3  is a schematic view showing the separation state of the ball screw and the balls of the present invention. 
           [0017]      FIG. 4  is a schematic view showing the power transfer in the combination state of the screw shaft and the ball screw according to the present invention. 
           [0018]      FIG. 5  is a schematic view showing the application of the present invention, where the present invention is combined to a silica gel tube of a silica gel gun. 
           [0019]      FIG. 6  is a schematic perspective view about another embodiment of the ball screw according to the present invention. 
           [0020]      FIG. 7  is an explosive schematic view about another embodiment of the present invention. 
           [0021]      FIG. 8  is a schematic view showing the separation state of the screw shaft and the balls according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    In order that those skilled in the art can further understand the present invention, a description will be provided in the following in details. However, these descriptions and the appended drawings are only used to cause those skilled in the art to understand the objects, features, and characteristics of the present invention, but not to be used to confine the scope and spirit of the present invention defined in the appended claims. 
         [0023]    Referring to  FIGS. 1 and 2 , the separable ball screw  1  of the present invention is illustrated. The present invention has the following elements. 
         [0024]    A screw shaft  10  has a helical groove  100  around a shaft body of the screw shaft  10 . A transfer ring  13 , a plurality of balls  14  and a separable nut  12  are sequentially engaged around the screw shaft  10 . One end of the transfer ring  13  is retained with a retaining ring  11  for sealing and limiting the transfer ring  13 . The balls  14  are densely distributed upon holes  131  in the annular surface  13 A of the transfer ring  13 . The balls  14  are moveable longitudinally in the hole  131  and is contactable with the inner annular surface  12 B of the separable nut  12 . The ball  14  is embedded in the hole  131 , while a part of the ball  14  is helical groove  100  of the screw shaft  10 . 
         [0025]    The transfer ring  13  is hollowed. The plurality of holes  131  are arranged in the annular surface  13 A. Each hole  131  is received with a ball  14 . The arrangement of the holes  131  are corresponding to the helical groove  100  of the screw shaft  10 . 
         [0026]    A separable nut  12  has a hollow central portion. An inner annular surface  12 B of the separable nut  12  has a plurality of axial grooves  12 B′. Each axial groove  12 B′ is recessed into the inner annular surface  12 B. The inner annular surface  12 B is suitable for receiving the annular surface  13 A of the transfer ring  13 . The ball  14  is embedded in the holes  131  in the annular surface  13 A of the transfer ring  13 , while two opposite parts of the ball  14  are located between the inner annular surface  12 B of the separable nut  12  and the helical groove  100 . One end of the separable nut  12  is extended with an annular rib  12 C. In assembly, the axial groove  12 B resists against an annular stop  13 C of the transfer ring  13 . By the respective position of the axial groove  12 B′ to the annular stop  13 C, the respective portion of an axial groove  12 B′ in the inner annular surface  12 B of the separable nut  12  and the balls  14  are controllable. 
         [0027]    When the ball  14  and the axial groove  12 B′ are collinear, the ball  14  is movable outwards to contact with the axial groove  12 B′ so that the ball  14  separates from the helical groove  100  of the screw shaft  10 . At this moment, the transfer ring  13  is parallel to the screw shaft  10 . When the when the ball  14  and the inner annular surface  12 B of the separable nut  12  are collinear, the ball  14  is limited in the holes  131  of the transfer ring  13  so that the ball  14  is embedded into the helical groove  100  of the screw shaft  10 . At this situation, the transfer ring  13  is only rotatable with respect to the screw shaft  10 . 
         [0028]    In detail, by the annular rib  12 C of separable nut  12  to resist against the annular stop  13 C of the transfer ring  13 , the rolling operation between the screw shaft  10  and the balls  14  can be transferred into the sliding displacement. 
         [0029]    Referring to  FIG. 3 , when the annular rib  12 C of the separable nut  12  rotates counterclockwise and is in contact to the annular stop  13 C at one end of the transfer ring  13 , through the connection of the annular rib  12 C and the annular stop  13 C, the balls  14  are at the axial groove  12 B′ in the inner annular surface  12 B of the separable nut  12 , the balls  14  do not separate from the helical groove  100 . When the screw shaft  10  rotates counterclockwise (clockwise), the dynamic force is not transferred to the transfer ring  13  through the balls  14 . Thus, the transfer ring  13  and the separable nut  12  are not rotated with respect to the screw shaft  10 , while it moves along the X axis. The screw shaft  10  is slidable along the transfer ring  13 . 
         [0030]    Referring to  FIG. 4 , when the annular rib  12 C extended from the screw shaft  10  rotates clockwise to contact with the annular stop  13 C extended from the transfer ring  13 , by the connection of the annular rib  12 C and the annular stop  13 C, the balls  14  are located in the inner annular surface  12 B of the separable nut  12 . The balls  14  are rollable with friction along the helical groove  100  of the screw shaft  10 . When the screw shaft  10  rotates counterclockwise (or clockwise), the balls  14  in the helical groove  100  of the screw shaft  10  will cause the transfer ring  13  and the separable nut  12  to move along the positive (or negative) X axis through the holes  131  of the transfer ring  13 . At this situation, the screw shaft  10  is rollable in contact with the balls  14  for transferring dynamic power. This is so called power transfer of ball screw. 
         [0031]    By above mentioned mechanism between the screw shaft  10  and transfer ring  13  or the separable nut  12 , the movement between the screw shaft  10  and the transfer ring  13  and separable nut  12  may be formed as helical or linear movement from the contact ways of the screw shaft  10  with the ball  14 . The present invention is suitable for the driving operations of various ball screws. Furthermore, by using the traveling control of quick detaching from linear operation, the separation time and speed of the screw are controllable effectively so as to improve the prior art defects about the non-real time separation between the screw shaft moving parts and the screw shaft. 
         [0032]    Referring to  FIG. 5 , it is illustrated that the ball screw  1  of the present invention is applied to a silica gel gun Gp. The separable ball screw  1  of the present invention is inserted into a tube of a silica gel tube Sp. By a driving device to control the screw shaft  10  as a push element, in using the silica gel gun Gp, according to the traveling speed for extruding the silica gel, when the silica gel in the silica gel tube Sp exhausts, the plunger at a force applied end can be returned to an original position rapidly so that the user can update the silica gel tube Sp rapidly and conveniently with a small force. In that, a force applied end at one end of the screw shaft  10  is combined with the transfer ring  13  and the separable nut  12 . This is ball screw  1  power transfer state. The transfer ring  13  is limited in a retained position to rotate. The screw shaft  10  has a plane matched to the body of the silica gel gun Gp for confining the screw shaft  10  to move along the X axis. When the transfer ring  13  drives the screw shaft  10  to move linearly, by the plunger  15  to extrude the silica gel in the silica gel tube. It is outputted from another end of the silica gel tube Sp until the silica gel in the silica gel tube Sp is exhausted. When it is desired to update a new silica gel tube Sp, by controlling the relative position of the transfer ring  13  and the separable nut  12  to cause the balls  14  to separate from the screw shaft  10 , then the screw shaft  10  can separate from the silica gel tube Sp rapidly. Namely, the plunger  15  will separate from the silica gel tube Sp rapidly. 
         [0033]    From about discussion, it is known that by the relative rotation and movement between the transfer ring  13  and the separable nut  12 , the operation of rotation and linear movement can be switched rapidly. In fact, other than rotation, parallel movement and helical movement as described therebelow is allowable in the present invention. 
         [0034]    Referring to  FIGS. 6 to 8 , another embodiment of the present invention is illustrated. The transfer ring  22  of the separable nut  21  linearly displaces with respect to the separable nut  21 . An inner annular surface  21 A of the separable nut  21  is formed with the annular groove  210  for controlling the position of the balls  24  so as to engage the balls  24  and the screw shaft  20 . Another, the inner annular surface  21 A′ of the separable nut  21 ′ can be formed as helical groove  210 ′ so as to control the movement between the transfer ring  22  and the separable nut  21  as parallel movement or rotation movement. The helical groove  210 ′ serves to control the position of the balls  24  so as to control the engagement of the balls  24  and the screw shaft  20 . 
         [0035]    As a whole, by the various designs of holes  220 ′ in the annular surface  22 A of the transfer ring  22  and the radius of curvatures of the helical groove  210 ′ in the inner annular surface  21 A of the separable nut  21  and the distribution and numbers of the balls  24 , in helical movement, the screw shaft can suffer from a heavy load or it can be converted into linear movement easily. Furthermore, the annular stop  22 C extending from one end of the transfer ring  22  has a gap from one end of the separable nut  21 . The gap causes that the separable nut  21  and the transfer ring  22  move linearly and axially. Furthermore, the positions of the balls  24  are limited by the operations of the annular groove  210  or the helical groove  210 ′ of the separable nut  21  so as to control the initial positions for rotation operation or linear operation between the screw shaft  20  and the transfer ring  22 . 
         [0036]    Advantages of the present invention will be described herein. Firstly, the present invention provides the helical operation and linear operation to the movement between the screw shaft and the transfer ring  22  by controlling the positions of the balls. The present invention has a firm and concrete structure. Further, the speed can be controlled easily and vividly. 
         [0037]    The present invention is thus described, 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.