Patent Publication Number: US-2004041137-A1

Title: Self-locking reduction device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     [0001] This application is a Continuation-in-Part of U.S. Serial No. 10/020,806 filed Dec. 12, 2001. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] The present invention relates to a self-locking reduction device in which rotational force from an input shaft is surely transmitted to output means, while rotational force from the output means is prevented from being transmitted to the input shaft.  
       [0003] In a known spur-gear-type reduction device used in a winch, it is impossible to prevent rotational force from being transmitted to an input shaft without additional braking means.  
       [0004] In a worm-gear-type reduction device, by determining a lead angle less than a friction angle of a tooth surface, self-locking can be made at some extent. But, coefficient of friction can be less than expected value owing to sliding speed, vibration, running feature and lubrication to cause slacking accident and unreliable self-locking.  
       [0005] The inventor invented a reliable self-locking reduction device using a micro-tooth-number-difference composite hypocycloid which has two-step internal gear mechanism, and filed it as Japanese Patent Application No. 11-210793 (Pub.No. 2001-41293).  
       [0006] This reduction device was developed to have high reduction ratio of more than 40:1. But it is required to provide a reliable simplified self-locking reduction device having low reduction ratio of 8:1 to 40:1.  
       SUMMARY OF THE INVENTION  
       [0007] It is an object of the invention to provide a reliable self-locking small high-functional reduction device and a winch in which it is used. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0008] The features and advantages of the invention will become more apparent from the following description with respect to embodiments as shown in appended drawings wherein:  
     [0009]FIG. 1 is a central vertical sectional front view of a winch which has a reduction device according to the present invention;  
     [0010]FIG. 2 is a sectional view taken along the line II-II in FIG. 1;  
     [0011]FIG. 3 is a sectional view taken along the line III-III in FIG. 1;  
     [0012]FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1;  
     [0013]FIG. 5 is a view which shows function of the invention;  
     [0014]FIG. 6 is a central vertical sectional front view of another embodiment of a reduction device according to the present invention;  
     [0015]FIG. 7 is a view similar to FIG. 1 showing a second alternative embodiment;  
     [0016]FIG. 8 is a view similar to FIG. 3 showing the second alternative embodiment. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
     [0017] FIGS.  1  to  5  illustrate an embodiment of a winch which has a self-locking reduction device.  
     [0018] A support  2  in the winch  1  comprises a U-shaped support frame  3 , a cylindrical bearing  5  fixed to the upper part of a left side  3   a  thereof by a screw  4 , and a bearing tube  8  fixed to the upper part of a right side  3   b  to have a coaxial horizontal axis “0” with the bearing  5  by engagement of an external thread  7   b  of an outer tube  7  in an internal thread  6   a  of an inner tube  6  provided in the upper portion of the side  3   b  of the support frame  3 , a head  7   a  of the outer tube  7  being placed outside of the side  3   b.    
     [0019] At the right end of the bearing  5 , an outward flange  5   a  is provided, and there is formed a bearing bore  9  having the axis “O” and an enlarged-diameter bore  9   a . On the right end of the outward flange  5   a , three blind bores  10  are formed on the circumference around the axis “O” at regular intervals. At the left end of the inner tube  6 , an outward flange  6   b  is provided.  
     [0020] The horizontal input shaft  11  is borne by the bearing  5  and the bearing tube  8  of the support  2 .  
     [0021] The input shaft  11  comprises a rectangular shaft portion  11   a , a middle diameter shaft portion  11   b , a larger-diameter shaft portion  11   c , an eccentric shaft portion  11   d  and a smaller-diameter shaft portion  11   e . The rectangular shaft portion  11   a  is projected from the outer tube  7 . The middle-diameter shaft portion  11   b  is provided in the outer tube  7 . The larger-diameter shaft portion  11   c  is provided in a metal sleeve  12  pressed in the inner tube  6 . The smaller-diameter shaft portion  11   e  is borne by a needle roller bearing  13  in the bearing bore  9  of the bearing  5 . Thus, the input shaft  11  is rotatably supported around the axis “0” by the support  2 .  
     [0022] On the eccentric shaft portion  11   d  of the input shaft  11 , a metal sleeve  15  pressed in an axial bore of an external gear  14  is rotatably provided. Three pins  16  engaged in three bores  10  respectively are provided at regular intervals on the circumference around an axis of the eccentric shaft portion  11   d  on the left end of the external gear  14  opposing the right end of the bearing  5 .  
     [0023] As shown in FIG. 5, the distance “r1” between the axis “O” and the center  101  of the bore  10  is nearly equal to the distance “r2” between the center  102  of the eccentric shaft portion  1   d  and the center of  103  of the pin  16 . The difference “r3-r4” between radius “r3” of the bore  10  and radius “r4” of the pin  16  is nearly equal to the eccentricity a“r5” between the axis “O” and the center of the eccentric shaft portion  11   d.    
     [0024] Therefore, when the input shaft  11  is rotated, each of the pins  16  slid on the inner surface of the bore  10  and eccentrically moved therein. The external gear  14  is eccentrically moved with respect to the support  2  without rotating around the axis “O”.  
     [0025] An output winding drum  17  is rotatably provided on the outer circumferences of the bearing  5  and the inner tube  6  of the bearing tube  8  via needle roller bearings  18 ,  19 . The winding drum  17  comprises a tube  20  and outward flanges  21 ,  21  at the ends thereof. The tube  20  comprises two tubular portions  22 ,  23  which are engaged with each other by engagement portions  22   a ,  23   a . On the inner surface of the tubular portion  22  in the middle of the tube  20 , internal teeth of an internal gear  24  are engaged with external teeth of the external gear  14  coaxially with each other. The number “N 2 ” of the internal teeth is slightly more than the number “N 1 ” of the external teeth.  
     [0026] As shown by dotted lines in FIG. 1, a wire  25  is wound on the winding drum  17 , and a drive means  26  is connected to the rectangular shaft portion  11   a  of the input shaft  11 . Instead of the wire  25 , a rope etc. may be wound around the winding drum  17 .  
     [0027] For example, the drive means  26  may be an electric tool  26 A, such as an electric drill, an output shaft of which is connected by an attachment  26 A′ which is engaged with the rectangular shaft portion  11   a  of the input shaft  11 ; an electric motor  26 B joined to the input shaft  11 ; or a manually-operated rotary handle  26 C engaged on the rectangular shaft portion  11   a  of the input shaft  11 .  
     [0028] By the drive means  26 , the input shaft  11  is rotated in a desired direction, and the external gear  14  is eccentrically moved around the axis “O” as mentioned above without turning with respect to the support  2 . Then, the internal gear  24  engaged with the external gear  14  and the winding drum  17  connected therewith are rotated in the same direction as that of the input shaft  11  by (N 2 −N 1 )/N 2  that is angular velocity corresponding to the difference between the number N 2  of the internal teeth and the number N 1  of the external teeth per one rotation of the input shaft  11 , so that the wire  25  is wound around the winding drum  17  or unwound therefrom.  
     [0029] When external force is applied to the winding drum  17  to turn in either of rotational directions while the drive means  26  and the input shaft  11  stop, as shown in FIGS. 3 and 5, one of three combinations of the bore  10  and pin  16  is contacted to prevent rightward and leftward rotations of the external gear  14  in FIG. 3, so that rotation of the winding drum  17  is prevented so as to achieve self-locking, and rotational force from the winding drum  17  is not transmitted to the input shaft  11  and the drive means  26 .  
     [0030] As shown in FIGS. 1 and 4, in the bearing  5 , a pair of rods  27 ,  27  or leaf springs made of spring steel grasps the smaller-diameter portion  11   e  of the input shaft  11  elastically in the enlarged-diameter bore  9   a . The ends of the rods  27 ,  27  are engaged in the support bore  28 . The rods  27 ,  27  elastically grasp the smaller-diameter shaft portion  1  le in the elastically deformable middle portion to act as means for braking the input shaft  11 .  
     [0031] The braking means provides self-locking in more reliable manner and suitable resistance to operation of the drive means  26  to increase operative function.  
     [0032] But, if rotation resistance of the input shaft  11  is high at some extent, such brake means may be omitted and known brake means may be employed instead of the brake means which comprises a pair of rods  27 ,  27 .  
     [0033] The bores  19  may be formed at the lower end of the external gear  14 , and the pins  16  may be provided at the right end of the bearing  5 .  
     [0034] In the foregoing embodiment, the support  2 , the input shaft  11 , the external gear  14 , the internal gear  24  and the winding drum  17  as output means constitute a self-locking reduction device according to the present invention.  
     [0035]FIG. 6 illustrates another embodiment of a self-locking reduction device according to the present invention. The main structure of the embodiment is almost similar to that in the former embodiment, and description thereof is omitted. Only differences will be described.  
     [0036] In the embodiment, a cover  32  is mounted on the right end of a cylinder  1  having an end wall  31   a  at the left end to constitute a support  33  of a self-locking reduction device  30 . An output shaft  34  is projected from the end wall  31   a . An input shaft  39  is supported by ball bearings  37 ,  38  put in bearing bores  35 ,  36  respectively. An external gear  40  is engaged on a larger-diameter eccentric shaft portion  39   a  of the input shaft  39  via a needle roller bearing  41  between the ball bearings  37 ,  38 . Three bores  42  are formed at the right end of the external gear  40  and three pins  43  are provided at the left end of the cover  32  so as to have similar relationship with that of the bores  10  and the pins  16  in the former embodiment. An internal gear  45  fixed to the right end of the output shaft  34  via a spring pin  44  is engaged in the external gear  40 . At the right end of the output shaft  34 , there is provided a pair of rods  46 ,  46  or leaf springs similar to the rods  27 ,  27  in the former embodiment to grasp the left end of the input shaft  39  elastically to apply braking force to the input shaft  39 .  
     [0037] According to similar principle and function to the former embodiment, the reduction device  30  rotates the input shaft  39  in a desired direction, thereby rotating the output gear  34  integrally connected to the internal gear  45  in the same direction at reduction ratio of (N 2 −N 1 )/N 2  wherein N 1  stands for the number of external teeth of the external gear  40  and N 2  stands for the number of internal teeth of the internal gear  45 , and preventing rotational force of the output shaft  34  from being transmitted to the input shaft  39  when the input shaft  39  stops, to achieve reliable self-locking function.  
     [0038] In the reduction device in FIG. 6, the input shaft  39  is projected from one end of the support  33 , and the output shaft  34  is projected from the other end of the support  33  to align with the input shaft  39 , so that drive and driven shafts are provided in the same line, whereby it can be assembled in all types of drive mechanisms to provide multi-usable reduction device.  
     [0039] A second alternative embodiment is shown in FIGS. 7 and 8. The embodiment is substantially similar to the embodiment shown in FIGS.  1 - 5  and described above, except that the roller bearing  13  and the rods or leaf springs  27  have been eliminated. In this embodiment, the small diameter portion  11   e  of the input shaft  11  directly contacts the inner circumferential surface of the bore  9 . The frictional force created by the metal-to-metal contact between the surfaces of the shaft portion  11   e  and the wall of bore  9  functions as brake means with a braking force on the input shaft  11 , so as to provide self-locking to operation of the drive means  26 .  
     [0040] The foregoing merely relates to embodiments of the invention. Various changes and modifications may be made by person skilled in the art without departing from the scope of claims wherein: