Abstract:
An end face polishing device has a first revolution shaft mounted for undergoing revolving movement about a first axis, a rotational shaft mounted for undergoing rotation about a second axis eccentric from the first axis, and a second revolution shaft mounted for undergoing revolving movement about a third axis eccentric from the second axis. A polishing disc is connected to the second revolution shaft for revolving movement therewith.

Description:
FIELD OF THE INVENTION 
     BACKGROUND OF THE INVENTION 
     The present invention relates to an end face polishing device polishing end face of bar member such as optical communication fiber. 
     In the end face polishing device of the related art, polishing is performed by pressing a polishing disc moving by a combination of rotation and revolution on an end face of a fixed bar member as described in Japanese Patent Laid-Open No. 296451/2000. A locus of polishing has a shape where plural circles moving on a circumference of radius r to a center P overlap continuously as shown by locus  1  in FIG.  1 . The state of making a circuit of an external circumference  2  of the locus  1  is shown in FIG.  2 . As shown in FIG. 2, an internal circumference  3  of the locus  1  has much overlapping of the locus, the abrasion quantity of a polishing sheet is increased, and the polishing sheet can not be used uniformly. Accordingly, efficient use of the sheet is difficult to accomplish. 
     It is an object of the present invention is to prevent local concentration of the locus overlapping of polishing on the polishing sheet and to improve efficiency of polishing. 
     In the polishing device of the related art, since a locus of the end face on the polishing sheet consists of circles moving along a circumference, it is necessary to increase the rotational speed of rotation or revolution in order to increase the polishing speed. However, an increase in the rotational speed results in scattering of abrasive liquid caused by centrifugal force, thereby making it difficult to perform the polishing operation. 
     SUMMARY OF THE INVENTION 
     In the present invention, an end face polishing device comprises a pressing unit for pressing an end face of a fixed bar member to a polishing sheet and a driving unit for driving the polishing sheet in a roulette-like movement while rotating on a circumference parallel to the end face of the bar member. Here, a roulette shape movement means a curved line where a fixed point on another curved line moves when another curved line rolls along a fixed curved line. 
     In another aspect, the present invention is directed to a method for polishing an end face of a fixed bar member by pressing the end face of the fixed bar member against a polishing sheet, driving the polishing sheet in a roulette shape movement while rotating on a circumference parallel to the end face of the bar member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view showing polishing locus of the polishing device of related art; 
     FIG. 2 is a plan view showing polishing locus of the polishing device of related art; 
     FIG. 3 is a view showing a polishing mechanism according to the invention; 
     FIG. 4 is a sectional view of a polishing device according to the invention; 
     FIG. 5 is a plan view showing polishing locus of the polishing device according to the invention; 
     FIG. 6 is a plan view showing polishing locus of the polishing device according to the invention; 
     FIG. 7 is a plan view showing polishing locus of the polishing device according to the invention; 
     FIG. 8 is a plan view showing polishing locus of the polishing device according to the invention; 
     FIG. 9 is a plan view showing polishing locus of the polishing device according to the invention; and 
     FIG. 10 is a plan view showing polishing locus of the polishing device according to the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The invention is an end face polishing device comprising a pressing unit pressing an end face of a fixed bar member to a polishing sheet and a driving unit driving the polishing sheet in a roulette-like movement while rotating on circumference parallel to the end face of the bar member. By using roulette-like movement relative speed of end face of a bar member to a polishing sheet varies, and polishing speed can be increased at high area in relative speed. Oppositely, in low area in relative speed, time that polishing liquid flows into area where quantity of polishing liquid decreases by contact of the end face on the polishing sheet increases, quantity of the polishing liquid becomes constant even when loci of polishing are overlapped, and high symmetric to axis of the bar member, that is, little eccentric polishing becomes possible. 
     In the invention, the polishing device has a rotating shaft eccentric from revolution center of a first revolution shaft in the revolution shaft, a second revolution shaft eccentric from the rotation center of the rotation shaft in the rotation shaft, and a polishing disc connected to the second revolution shaft. 
     Further, in the end face polishing device, the second revolution shaft has an internal gear fixed at a frame of the end face polishing device, a first transfer gear engaging with the internal gear, a rotation shaft having a second transfer gear at opposite end portion of the end portion of the first transfer gear, and an external gear engaging with the second transfer gear. 
     FIG. 3 is a view showing characteristic part of the driving mechanism of the polishing device according to the invention. In the figure, the whole performs revolution RE 1 . Revolution center of revolution shaft and center position are eccentric R, and inner part of rotation shaft RO rotating by the external gear EG 1  engaging with the gear IG 1  is performed with revolution RE 2  to rotation shaft by revolution of the gear G 2  engaging with the gear G 1  driven by the external gear EG 2  engaging with the internal gear IG 2 . 
     BACKGROUND INFORMATION 
     In the end face polishing device, the first revolution shaft is connected to a motor through a timing belt. 
     In the end face polishing device, the rotation shaft is connected to a motor through another timing belt. 
     Further, the end face polishing device has an ultra sonic actuator contacting outer circumference portion of the first revolution shaft and revolving the revolution shaft. By using the ultra sonic actuator, a polishing device of high torque and small size can be obtained. 
     The invention has steps of pressing an end face of a fixed bar member to a polishing sheet, driving the polishing sheet with roulette-like movement while rotating on circumference parallel to the end face of the bar member, and making the end face for polishing disc. 
     Here, the roulette-like movement may be a cycloid. Further, the roulette-like movement may be an internal cycloid. Moreover, the roulette-like movement may be an external cycloid. 
     Further, the roulette-like movement may be a relative trochoid inscribed to a first circle and drawn by a point fixed at a second circle smaller in diameter than the first circle. The roulette-like movement may be a relative external trochoid inscribed to the first circle and drawn by a point fixed at out of the second circle smaller in diameter than the first circle. 
     Especially, the roulette-like movement may be a relative internal trochoid inscribed to a first circle and drawn by a point fixed in the second circle smaller in diameter than the first circle. 
     Here, an XY table can be used for driving the polishing sheet. By using the XY table, a polishing device can be designed without using complex driving mechanism of rotation system such as an epicyclic gear for usual rotation and revolution. Further, by using large XY table in a moving distance, the polishing sheet is kept away far from the bar member, the state of the end face of the bar member in the middle of polishing, a polishing sheet different in roughness is arranged at another area of the XY table, the same polishing device can be used from coarse polishing to finishing polishing. 
     By varying the driving speed using a single sheet or plural sheets, polishing speed can be decreased at initial coarse polishing so as to reduce load to driving system large in frictional resistance. Because frictional resistance is small at finishing polishing, driving speed is increased, and polishing speed is increased so as to reduce whole polishing time. 
     An embodiment according to the invention will be described in detail with reference to FIGS. 4-9 FIG. 4 is a sectional view showing a driving mechanism of the end face polishing device according to the invention. An elastic body  30  is arranged on a top portion of a polishing disc  10  through a frame  20  of an external circumference, a polishing sheet  40  is arranged on the elastic body  30 , an end face of a bar member is pressed against the sheet  40  during a polishing operation. 
     A lower face side of the polishing disc  10  and a flange  60  on a revolution shaft  50  are connected through plural fixed pins  70   a  and  70   b , and the polishing disc  10  is supported by the revolution shaft  50 . The revolution shaft  50  is connected to a rotation shaft  80  at eccentric position in designated quantity to the rotation shaft  80  through a transfer gear  100  is connected to a transfer gear  101  coaxially. The transfer gear  101  engages with an internal gear in the frame of main body of the polishing device. 
     The lower part of the revolution shaft  50  is connected to a rotation portion  230  through a timing belt  220  arranged at outer side of a pulley  210  connected to a driving shaft of a motor  200  and engages with an internal gear of the rotation portion  230 . 
     A revolution shaft  300  is connected to the driving shaft of the motor  200  though a pulley  310  and a timing belt  320 . The rotation shaft  80  is arranged in the revolution shaft  300 . 
     A polishing locus of the polishing device according to the invention will be described below. FIG. 5 is a view showing the instance when the revolution radius in the rotation shaft is large, and the locus is a continued locus  1  where a shape  4  is given a roulette-like movement in the form of a cycloid shape and has sharp points  5  and revolves in the external circumference  2  where circumference of radius r is center through center P of external circumference  2 . By this polishing locus, overlapping of locus of the internal circumference portion  3  is removed. 
     FIG. 6 is a view where the locus  1  goes around in the external circumference  2 . 
     FIG. 7 is a view when revolution radius in the rotation shaft is small, a shape  6  of locus becomes a shape of three leaves. By driving the shape continuously, the locus becomes like locus  1 . Further, by going around in the external circumference  2 , the density of locus of the internal circumference  3  becomes low as shown in the locus  1  of FIG.  8 . 
     FIG. 9 is a view of the case when the ratio of revolution diameter is further varied. The locus becomes a shape  7  of locus having five times of symmetric axis in the external circumference  2 . FIG. 10 is a view where similarly the shape of the locus  1  goes around driving continuously, and in which a high density locus  1  is obtained in the external circumference  2  so that the polishing sheet can be used efficiently. 
     According to the invention, since a locus of the end face is given a roulette-like motion while rotating on the circumference, life of the polishing sheet can be made long and the polishing time can be decreased to provide a polishing device having a high polishing speed.