SUPERFINISHING MACHINE WITH LAPPING FILM

Abstract: This invention relates to a superfinishing machine with a lapping film (25) which is used for superfinishing the surface (30a) to be finished of a work (30) which is either rotated or reciprocated. The rotating direction of a pair of take-up rollers (2, 3) for taking up the lapping film is switched and controlled by driving switching means (23, 24) and at the same time, a follower friction wheel (8, 9) to be driven is braked by braking means (26). Accordingly, the entire abrasive surface of the lapping film (25) can be utilized effectively and excessive pull-out of the lapping film (25) can be prevented effectively. Since the machine is equipped with press means (29) for pressing the lapping film (25) to the surface (30a) to be polished of the work (30), high precision polish faithful to the contour of the surface (30a) to be polished can be attained.

Description: This invention relates to a superfinishing machine using lapping film according to the preamble of claim 1. Background of the Invention As the surface finishing machine for finishing various roller surfaces by using lapping film abrasives, the device disclosed in the January 1987 issue of the monthly publication "Machine Technology" is known. The January 1987 issue of "Machine Technology, on which the preamble of claim 1 is based, discloses a superfinishing machine for polishing a surface of a work using a lapping film having a grain surface, said work surface being rotated or rotationally reciprocated, said superfinishing machine comprising:- first and second rotatable take-up reels for the lapping film, each said take-up reel having an axial shaft; and pressing means for pressing the lapping film against said surface. In this machine, the lapping film which is taken up in the opposite direction of the roller rotating direction, that is, in a specific direction is pressed against the roller surface (the surface to be polished) by the contact roller reciprocatable in the roller axial direction, and the roller surface is uniformly finished. However, in such composition as this conventional machine in which the lapping film taken up in one direction is pressed against the surface to be polished of the work (roller) rotating in the opposite direction to polish, if the surface to be polished of the work is a curved surface having an arc-shaped section with a small radius of curvature, such as the slipper surface of the rocker arm, the ratio of the length of the portion of the lapping film passing through without being used in polishing of this curved surface with respect to the length of the portion of the lapping film used in polishing of the curved surface is extremely large, and the lapping film is spent wastefully. On the other hand, when it is designed so that the work oscillates around the center of oscillation, the lapping film is advantageously stretched taut when the oscillating direction of the work is opposite to the moving direction of the lapping film, but when both moving directions are same and the oscillation speed of the work is high, the lapping film is excessively drawn out from the feed spool side. Accordingly it may be sometimes impossible to polish while keeping the tension of the lapping film on the surface to be polished of the work. Or, in the conventional structure of taking up the lapping film in one direction, when the lapping film once used in polishing is exchanged with a new lapping film on every occasion of use, the polishing work is interrupted by each exchange, and the working efficiency is significantly lowered. Still more, in the structure of pressing the lapping film against the surface to be polished of the work by the contact roll, if there is a slight curvature in the widthwise direction in the work such as polishing of a curved surface of slipper surface of rocker arm as mentioned above, polishing along the surface to be polished curved in the widthwise direction becomes impossible. Disclosure of the Invention According to the present invention there is provided a superfinishing machine for polishing a surface of a work using a lapping film having a grain surface, said work surface being rotated or rotationally reciprocated, said superfinishing machine comprising:- first and second rotatable take-up reels for the lapping film, each said take-up reel having a respective axial shaft; and pressing means for pressing the lapping film against said surface; said superfinishing machine being characterised in that said pressing means comprises an elastic pressing member; and in that said machine further comprises:- first and second follower friction wheels each attached to one end of the axial shaft of a respective one of said first and second take-up reels respectively; an oscillation member, said oscillation member being rotatable about a pivot between a first position and a second position; first and second driving friction wheels provided on said oscillation member, whereby when said oscillation member is in said first position said first driving friction wheel frictionally engages said first follower friction wheel and said second driving friction wheel does not frictionally engage said second follower friction wheel and when said oscillation member is in said second position said second driving friction wheel frictionally engages said second follower friction wheel and said first driving friction wheel does not frictionally engage said first follower friction wheel; first driving means for rotating the first and second driving friction wheels; driving change-over means adapted to detect the tail end of the lapping film when said lapping film is taken up on one of said take-up wheels and to move the oscillation member from one of said first and second positions to the other of said first and second positions; and first and second braking means for braking the first and second follower friction wheels respectively, said second follower friction wheel being braked when said oscillation member is in said first position and said first follower friction wheel being braked when said oscillation member is in said second position. Since it is designed so that the rotating direction of the pair of take-up reels for lapping film is changed over and driven by the cylinder for changing over the drive, the effective use of the whole grain surface of the lapping film may be realized. Since the portion of the follower friction wheels of take-up reels is provided with brake cylinder for presenting a pressing force when the follower friction wheels comes to the follower side (driven side), if the oscillating work exerts an oscillating force in the same direction as the moving direction on the lapping film, excessive draw-out of lapping film is prevented, and the tension is maintained, so that polishing of oscillating work is realized. Accordingly, even if the work polishing surface is an arc section such as rocker arm, it is possible to polish with the surface to be polished always kept in contact with the polishing surface of the lapping film, so that the entire grain surface of the lapping film may be effectively utilized in the polishing work. Moreover, since the lapping film is pressed against the surface to be polished of the work by the elastic pressing member, if the surface to be polished is slightly curved in the widthwise direction of the lapping film, polishing along the curved surface to be polished is possible. Brief Description of the Drawings FIG. 1 is a plan view showing a superfinishing machine using lapping film in one of the embodiments of the invention; FIG. 2 is a rear view of the same superfinishing machine, showing part of FIG. 1 in a sectional view; FIG. 3 is a sectional plan view of the same superfinishing machine along line III-III in FIG. 2; FIG. 4 is a side view of essential parts of the same superfinishing machine showing part of FIG. 1 in a sectional view; FIG. 5 is a plan view showing a superfinishing machine using lapping film in another embodiment of this invention; FIG. 6 is a rear view of the same superfinishing machine showing part of FIG. 5 in a sectional view; and FIG. 7 is a side view of essential part of the same superfinishing machine showing part of FIG. 5 is a sectional view. Preferred Embodiments of the Invention FIG. 1 through FIG. 4 show a superfinishing machine using lapping film in one embodiment of the invention. In the drawing, numeral 1 is a horizontal top plate disposed in the upper part of the superfinishing machine, and on this top plate 1, rotary shafts 4, 5 for holding two take-up rolls 2, 3 for lapping film within the same horizontal plane are rotatably supported by bearings 6, 7. At the lower ends of these rotary shafts 4, 5, follower friction wheels 8, 9 of the identical diameter having V-grooves disposed on the outer circumference are provided. The top plate 1 is provided with a pivot 10 which projects downward, at a position equally distant from the rotary shafts 4, 5. At both ends of the flat pi-shaped oscillation member (FIG. 3) rotatably held at the lower end of the pivot 10, driving friction wheels 12, 13 of the shape to be engaged with the follower friction wheels 8, 9 are mounted coaxially with follower gears 16, 17 having the same number of teeth. Numeral 19 is an intermediate plate held parallel to the top plate 1 by means of vertical shafts 18, 18, and on this intermediate plate 19, a driving motor 20 is mounted being disposed so that a driving shaft 21 may be directed upward and that its axial line may coincide with the axial line of the pivot 10. A driving gear 22 fitted to the upper end of the driving shaft 21 is engaged with the two follower gears 16, 17 simultaneously, thereby rotating the driving friction wheels 12, 13 coaxially mounted with the follower gears 16, 17 in the same direction and at the same rotating speed. Which one of the take-up reels 2, 3 is driven is determined by changeover of the moving direction of a rod 24 by a twin rod cylinder 23 for changeover of drive disposed within the pi-shaped contour part of the oscillation member 11. This changeover is effected by moving the rod 24 in either right or left direction in FIG. 3, by the working fluid in the cylinder 23 when the reflected light from the reflection tape glued to the final end of the lapping film 25 being taken up by, for example, a photoelectric tube (not shown). For instance, as shown in FIG. 3, when the rod 24 is moved to the right side, and the oscillation member 11 is rotated counterclockwise around the pivot 10, the driving friction wheel 12 is pressed by the follower friction wheel 8, and the take-up reel 2 is driven, and the take-up reel 2 takes up the lapping film 25 from the other take-up reel 3, which is not driven by the motor 20. The following friction wheels 8, 9 coaxial with the take-up reels 2, 3 are provided with brake cylinders 26, 26 for pressing the periphery of the follower friction wheels 8, 9 with a preset force, in order to apply a tension to the lapping film 25 to be taken up, when they are not driven by the driving friction wheels 12, 13, Numeral 27 is a pressing cylinder disposed between the take-up reels 2, 3, and the lapping film 25 is held to press against the surface to be polished of the work 30 by an elastic pressing member 29 made of, for example, hard urethane rubber attached to the end of the rod 28 of the pressing cylinder 27 through holding member 29a. The polishing operation of the curved surface of rocker arm by the machine of this embodiment is described below. The rocker arm (work) 30 having a curved surface (an arc-shaped section) 30a is fitted to a fixed shaft 32 projecting upward from the jig 31, and the tail end of the rocker arm 30 is pushed to the stopper 34 by the pressing member 33, thereby holding so that the relation to the jig 31 may be specific. This jig 31 is fitted to the oscillation shaft 37 in the vertical direction being oscillated by the servo motor 35 through reduction gear 36, and when the servo motor 35 is driven, the rocker arm 30 oscillates about the center of oscillation 0 together with the jig 31. Operating the pressing cylinder 27, the elastic pressing member 29 attached to the end of the rod 28 is pushed out, and the lapping film 25 taken up on the driving side take-up reel 2 from the driven side take-up reel 3 is pressed against the curved surface 30a of the rocker arm 30 with a specified force. In this state, when the driving motor 20 and servo motor 35 are driven, the follower friction wheel 8 co-axial with the take-up reel 2 rotated by the driving gear 22 does not receive the pressing action of the brake cylinder 26, but the follower friction wheel 9 coaxial with the take-up reel 3 which is not rotated by the driving gear 22 receives the pressing action of the brake cylinder 26. Hence, the lapping film 25 is always kept in the taut state in any direction of the oscillation of the rocker arm 30 by the servo motor 35, thereby polishing the curved surface 30a. Accordingly, the curved surface 30a of the rocker arm 30 oscillated as being held horizontally can be polished to a specified surface finishing degree efficiently in a short time. The rocker arm 30 is oscillated by a set number of times, and when the driving motor 20 stops, the curved surface 30a is stopped at a position not contacting with the elastic pressing member 29. At this stopping position, the pressing action by the pressing member 33 is released, and the rocker arm 30 is drawn out of the fixed shaft 32, and a new rocker arm 30 is mounted on the fixed shaft 32, and the tail end of the rocker arm 30 is pressed against the stopper 34 by the pressing member 33, and the driving motor 20 and servo motor 35 are driven again, and the same polishing operation is repeated. When the lapping film 25 nears its end by the repeated lapping operations, the reflected light from the reflection tape (not shown) glued to the final end of the lapping film 25 is detected by a photoelectric tube (not shown). As a result, by the output from the photoelectric tube, the rod 24 of the cylinder 23 is changed over from the pressing in the right direction shown in FIG. 3 to the pressing in the left direction, and the oscillation member 11 is rotated clockwise about the pivot 10. In consequence, the driving friction wheel 12 which has hitherto been pressing and driving the follower friction wheel 8 is deprived of the driving action of the driving motor 20. Instead, the other driving friction wheel 13 now presses and drives the other follower friction wheel 9, so that the driving side and follower side (driven side) are changed over between the take-up reels 2 and 3. The output from the photoelectric tube changes over the pressing direction of each rod of the two brake cylinders 26, 26 at the same time, and when take-up of the lapping film 25 in one direction is over, the lapping film 25 is automatically rewound in the opposite direction, and the lapping film 25 still having the polishing ability is repetitively used effectively, so that the curved surface 30a of the rocker arm 30 may be polished to a desired degree of surface finishing. In the foregoing embodiment, the curved surface 30a is polished while moving the lapping film 25 continuously, but it is equally possible to stop after feeding the lapping film 25 by a specified amount, and oscillate the rocker arm 30 to polish its curved surface 30a. Or if the degree of surface finishing in the returning stroke of the reciprocal motion of the lapping film 25 is questionable, the number of oscillations of the rocker arm 30 may be set slightly higher in the returning stroke than in the going stroke. FIG. 5 to FIG. 7 relate to other embodiment of the invention. Tubular members 38, 38 disposed downward from the top plate 1 in the foregoing embodiment are respectively held by slide balls 39, 39 provided between vertical shafts 18, 18, so as to be slidable in the vertical direction along each vertical shaft 18. The tubular members 38, 38 are linked together by a horizontal linkage member 40, and the driving shaft 21 of the driving motor 20 is stopped on the linkage member 40, and its upper end is rotatably held by a bearing 41 which abuts against the lower surface of the boss part 22a of the driving gear 22. Inside the driving motor 20, the majority of the driving shaft 21 is inserted into the tubular member 49 integrally coupled with the motor shaft 20a by means of key and screw so as to be slidable in the vertical direction. The tubular member 49 is rotatably held by bearings 43, 43, and a woodruff key 44 abutting against the inside of a hollow tube 50 mounted between bearings 43, 43 and held in the tubular member 49 is engaged with a key guide groove 42 formed in the lengthwise direction of the driving shaft 21, so that the movement in the lengthwise direction of the driving shaft 21 may be effected smoothly. Numeral 45 is a vertical motion cylinder having a rod 46 set downward in the vertical direction, and the vertical motion cylinders 45, 45 are installed outside of the tubular members 38, 38 by means of L-members 47, 47, and the lower ends of their rods 46 are fixed on an intermediate plate 19. Accordingly, when a downward fluid pressure acts on the rods 46, 46 the vertical motion cylinders 45, 45 are moved upward. Along with this movement, by the tubular members 38, 38 on which the vertical motion cylinders 45, 45 are mounted, the top plate 1 is moved upward and, at the same time, the driving shaft 21 on which the driving gear 22 is mounted is moved upward by the bearing 41 of the linkage member 40 which couples the tubular members 38, 38 together. Therefore, even when the top plate 1 moves in the vertical direction, the engagement between the driving gear 22 and follower gears 16, 17 is kept in normal state. In the machine of this embodiment, the servo motor 35 with reduction gear 36 in the foregoing embodiment is held together on the intermediate plate 19, and the rocker arm 30 fitted on the fixed shaft 32 is oscillated about the center of oscillation 0 together with the jig 31. Numeral 48 is a grinding wheel having a U-section polishing surface, and this grinding wheel 48 is designed to be moved toward the rocker arm 30, and it has a curved surface 30a about the center of oscillation 0 with respect to that rocker arm 30 which is oscillated. The operation of this embodiment is explained below. In the state as shown in FIG. 5, by the rotation of the grinding wheel 48 and the oscillation of the rocker arm 30 indicated by double dot chain line being held by the jig 31, a downward force is applied to each rod 46 of the vertical motion cylinders 45, 45 while the curved surface 30a of specified radius is formed in the rocker arm 30 in order to move so that the lowest surfaces of the holding member 29a and elastic pressing member 29 attached to the front end of the rod 28 of the pressing cylinder 27 may be set slightly higher than the highest surfaces of rocker arm 30 of the jig 31 and pressing member 33. When forming of the curved surface 30a by the grinding wheel 48 is over, the rocker arm 30 is once stopped at a position oscillated in the outward direction (counterclockwise in FIG. 5) so as not to contact between the curved surface 30a and the grinding wheel 48, and then the curved surface 30a is rotated to the position opposite to the elastic pressing member 29 by means of the servo motor 35. Simultaneously with stopping of this rotation, the direction of the fluid pressure acting on each rod 46 of the vertical motion cylinders 45, 45 is changed over, and the top plate 1 is lowered to the original height. In this state, the pressing cylinder 27 is operated, and the lapping film 25 is pressed against the curved surface 30a with a preset force by the elastic pressing member 29 at the end of the rod 28. In succession, by the driving of the driving motor 20, the lapping film 25 is moved in one direction, while the rocker arm 30 is oscillated in a specified angle range around the center of oscillation 0 by the servo motor 35, and by sharing the oscillation means of the device for forming the curved surface 30a of approximately arc section in the rocker arm 30, the curved surface 30a immediately after being formed by the grinding wheel 48 can be superfinished by the lapping film 25. The other effects obtained by the machine of this embodiment are same as in the embodiment shown in FIG. 1 to FIG. 4. In the machine of this embodiment, meanwhile, when the grinding wheel 48 is composed so as to be moved forward and backward with respect to the rocker arm 30 together with its rotation driving means and rotate the jig 31 clockwise around the center of oscillation 0 after moving back the grinding wheel 48, the vertical motion means of the top plate 1 may be omitted. As clear from the description herein, the constitution of this invention brings about the following outstanding effects: (1) Since the rotating direction of a pair of take-up reels for lapping film is designed to be changed over and controlled by the driving changeover cylinder, the whole grain surface of the lapping film can be effectively utilized, and the portion of the lapping film passing through without being used in polishing of the surface is completely eliminated. Still more, one lapping film can be used repeatedly by reciprocating, and the life of the lapping film itself is extremely long as compared with that of the conventional film, and the cost may be saved remarkably. (2) Since the pressing force by brake cylinder can be applied to the follower friction wheel of the take-up reel at the follower side, superfinishing can be processed efficiently by the lapping film moved while keeping a taut state with respect to the surface to be polished of the work which is oscillated. (3) Since the surface of the work being oscillated can be superfinished, the waste of the grain surface of the lapping film being fed without use not contacting with the surface is eliminated, and, in this respect too, the whole grain surface of the lapping film can be utilized effectively. (4) When the winding end or terminal end of the lapping film is detected, the oscillating member is rotated about the pivot, and the driving side of the take-up reel is changed over, so that the lapping film still having a sufficient polishing capacity depending on the finishing condition can be repeatedly used in polishing when rewinding. (5) Since the lapping film is pressed against the surface to be polished of the work by the elastic pressing member, if the surface to be polished is slightly curved in the widthwise direction, the entire surface can be polished.

Claims: A superfinishing machine for polishing a surface (30a) of a work (30) using a lapping film (25) having a grain surface, said work surface (30a) being rotated or rotationally reciprocated, said superfinishing machine comprising:- first and second rotatable take-up reels (2, 3) for the lapping film (25), each said take-up reel (2, 3) having a respective axial shaft (4, 5); and pressing means for pressing the lapping film (25) against said surface (30a); said superfinishing machine being characterised in that said pressing means comprises an elastic pressing member (29); and in that said machine further comprises:- first and second follower friction wheels (8, 9) each attached to one end of the axial shaft (4, 5) of a respective one of said first and second take-up reels (2, 3); an oscillation member (11), said oscillation member (11) being rotatable about a pivot (10) between a first position and a second position; first and second driving friction wheels (12, 13) provided on said oscillation member (11), whereby when said oscillation member (11) is in said first position said first driving friction wheel (12) frictionally engages said first follower friction wheel (8) and said second driving friction wheel (13) does not frictionally engage said second follower friction wheel (9) and when said oscillation member is in said second position said second driving friction wheel (13) frictionally engages said second follower friction wheel (9) and said first driving friction wheel (12) does not frictionally engage said first follower friction wheel (8); first driving means (20) for rotating the first and second driving friction wheels (12, 13); driving change-over means adapted to detect the tail end of the lapping film (25) when said lapping film is taken up on one of said take-up wheels (2, 3) and to move the oscillation member from one of said first and second positions to the other of said first and second positions; and first and second braking means (26, 26) for braking the first and second follower friction wheels (8, 9) respectively, said second follower friction wheel (9) being braked when said oscillation member is in said first position and said first follower friction wheel (8) being braked when said oscillation member is in said second position. A superfinishing machine according to claim 1 and further comprising:- holding means (31, 32) for holding said work (30); and second driving means (35, 36) for rotationally reciprocating said holding means (31, 32). A superfinishing machine according to claim 2, wherein said holding means (31, 32) are movable in a vertical direction relative to said first driving means (20), to said driving change-over means and to said pressing means. A superfinishing machine according to claim 1, 2 or 3 wherein first and second follower gears (16, 17) are mounted co-axially with said first and second driving friction wheels (12, 13) respectively, and wherein said first and second follower gears (16, 17) engage with a driving gear (22), said driving gear being driven by said driving means (20). A superfinishing machine according to any preceding claim, wherein said driving change-over means comprises a driving change-over cylinder (23) and a rod (24). A superfinishing machine according to any preceding claim and further comprising grinding means (48), said second driving means (35, 36) being adapted to move said work (30) from a position where said surface (30a) can be ground by said grinding means (48) to another position where said surface (30a) can be polished by said lapping film (25).

Inventors: INOUE, RYOJI, KINUGAWA, MICHIO
Applicants: KABUSHIKI KAISHA NISSHIN SEISAKUSHO
Application year: 1988
Main classification: B24B21
IPC codes: B24B21, B24B33