Polishing apparatus

A polishing apparatus includes a polishing device for polishing a baseboard, a feeding device for transporting it to the polishing device and a discharging device for discharging the polished baseboard from the polishing device. The baseboard is clamped in one direction between rollers of the feeding device and is transported upwards while polishing tapes are run and backup members for pressing the polishing tapes to the baseboard undergo reciprocating motions in a perpendicular direction to polish both surfaces of the baseboard. The polished baseboard is transported further upwards, being clamped between rollers of the discharging device.

DETAILED DESCRIPTION OF THE INVENTION The invention is described next by way of an example. FIG. 1 shows a polishing apparatus 10 embodying this invention, comprising a polishing device 30 for polishing a baseboard, a feeding device 20 for feeding the baseboard into the polishing device 30 and a discharge device 70 for discharging a baseboard from the polishing device 30 . These constituent devices are arranged inside a housing 11 . The feeding device 20 comprises, as shown in FIG. 2, a first feeder 21 and a second feeder 21 ′, each including a plurality of rollers (or “feeder rollers”) 22 a - 22 g (or 22 a ′- 22 g ′) for transporting a baseboard, a frame (or “feeder frame”) 23 (or 23 ′) which supports the rollers 22 a - 22 g (or 22 a ′- 22 g ′) rotatably and a driving means (or “feeder driving means” (not shown)) for causing the rollers to rotate. The first and second feeders 21 and 21 ′ are disposed symmetrically in the right-left direction (with reference to the figure) such that corresponding ones of their rollers 22 a - 22 g and 22 a ′- 22 g ′ are opposite each other. The feeding of a baseboard is effected with the baseboard clamped between the mutually oppositely facing pairs of rollers 22 a - 22 g and 22 a ′- 22 g ′ and by rotating the rollers 22 a - 22 g and 22 a ′- 22 g ′ by the driving means. The driving means may comprise, for example, ball screws arranged vertically, each engaging a screw groove provided at an edge portion of a corresponding one of the rollers 22 a - 22 g and 22 a ′- 22 g ′ and means for rotating these ball screws. The feeding device 20 also includes a feeder moving means for moving the first and second feeders 21 and 21 ′ towards or away from each other such that a baseboard can be clamped between the pairs of rollers 22 a - 22 g and 22 a ′- 22 g ′. The moving means includes guides 24 and 24 ′ formed respectively on the frames 23 and 23 ′ and actuators 26 and 26 ′ affixed to the housing 11 . The guides 24 and 24 ′ are respectively engaged with rails 25 and 25 ′ affixed to the housing 11 so as to move along the rails 25 and 25 ′ as the actuators 26 and 26 ′ are activated. The polishing device 30 comprises, as shown in FIG. 3, a first polishing head 31 and a second polishing head 31 ′, each including a tape feeding means for feeding a polishing tape T (or T′), a winding means for winding up the polishing tape T (or T′), a backup member 40 (or 40 ′) for pushing the polishing tape T (or T′) to the baseboard and a reciprocating means for causing the backup member 40 (or 40 ′) to undergo a reciprocating motion in a forward-backward direction (with reference to the figure and perpendicular to the right-left direction). The first and second polishing heads 31 and 31 ′ are disposed symmetrically and opposite to each other. The baseboard is polished thereby as it is clamped between the polishing tapes T and T′ on the surfaces of the polishing heads 31 and 31 ′ and the backup members 40 and 40 ′ are caused to undergo reciprocating motions in the forward-backward direction. The polishing device 30 is also provided with a head-driving means for moving the polishing heads 31 and 31 ′ towards and away from each other such that a baseboard can be clamped between their backup members 40 and 40 ′. Like the moving means for the feeding device 20 , the head-driving means includes guides 35 and 35 ′ on the frames 34 and 34 ′ and actuators (shown at 37 and 37 ′ in FIG. 6 ) affixed to the housing 11 . The guides 35 and 35 ′ engage with rails 36 and 36 ′ such that the polishing heads 31 and 31 ′ travel in the right-left direction along the rails 36 and 36 ′ as the actuators 37 and 37 ′ are activated. The tape feeding means and the winding means respectively include tape rolls 32 and 32 ′ rotatably affixed to top parts of the frames 34 and 34 ′ and windup rollers 33 and 33 ′ rotatably affixed to bottom parts of the frames 34 and 34 ′. There are also included motors (shown at 38 ′ in FIGS. 5 and 7 ) for rotating the tape rolls 32 and 32 ′ and the windup rollers 33 and 33 ′. The speed of travel of the polishing tapes T and T′ can be varied by adjusting the speeds of rotation of the tape rolls 32 and 32 ′ and the windup rollers 33 and 33 ′. The tape rolls 32 and 32 ′ and the windup rollers 33 and 33 ′ are each removably attached to the frame 34 or 34 ′. As soon as the polishing tape T or T′ is completely wound up by the windup roller 33 or 33 ′, a new tape roll in a cartridge form can be installed and the windup roller 33 or 33 ′ which has wound up the completed polishing tape T or T′ is replaced by a new windup roller. The polishing tapes T and T′ may be of any hitherto known types such as a tape having a polishing layer with abrading particles affixed with a resin binder formed on the surface of a plastic film, a tape with a layer of a foamed material formed on the surface of a plastic film, a tape with hairs of plastic fibers planted on the surface of a plastic film, a woven tape or an unwoven tape. As shown in FIGS. 6 and 8 , the reciprocating means for causing the backup members 40 and 40 ′ to undergo a reciprocating motion is attached to the frames 34 and 34 ′ so as to be rotatable therethrough, comprising shafts 41 , 41 ′, 43 and 43 ′ and a shaft driving means (shown at 50 in FIG. 8 ) for causing these shafts 41 , 41 ′, 43 and 43 ′ to rotate. These shafts 41 , 41 ′, 43 and 43 ′ each have an eccentric part 42 , 42 ′, 44 or 44 ′ which is displaced from the central axis of the corresponding one of the shafts 41 , 41 ′, 43 and 43 ′. Each of these eccentric parts 42 , 42 ′, 44 or 44 ′ is inserted into an opening provided at one end part of one of the backup members 40 and 40 ′ such that the backup members 40 and 40 ′ will undergo a reciprocating motion in the forward-backward direction as the shafts 41 , 41 ′, 43 and 43 ′ are caused to rotate. As shown in FIG. 8 , the shaft driving means 50 for rotating the shafts 41 , 41 ′, 43 and 43 ′ connected to the eccentric parts 42 , 42 ′, 44 or 44 ′ comprises a motor 51 which is affixed to a shelf 12 of the housing 11 , a cross-sectionally polygonal shaft 52 rotatably supported on the shelf 12 through brackets 53 and pulleys 54 , 55 and 55 ′ each having an opening with a shape matching the cross-sectional shape of the shaft 52 and being penetrated by the shaft 52 therethrough. As the motor 51 is activated, the shaft 52 begins to rotate through a belt 56 . As a result, shafts 43 and 43 ′ rotate through the pulleys 55 10 and 55 ′, belts 57 and 57 ′ and pulleys 47 and 47 ′ affixed to end parts of the shafts 43 and 43 ′, thereby causing the backup members 40 and 40 ′ to undergo a reciprocating motion, as described above and shown in FIGS. 6 - 8 . The shaft 52 is disposed parallel to the rails 36 and 36 ′ such that each of the polishing heads 31 and 31 ′ moves in the right-left direction along the shaft 52 as the actuators 37 and 37 ′ are activated. As shown in FIG. 3 , the polishing device 30 is further provided with a distortion preventing means 60 for preventing the polishing tapes T and T′ from becoming distorted by the reciprocating motion of the backup members 40 and 40 ′. The distortion preventing means 60 includes rollers 61 a - 61 d and 61 a ′- 61 d ′ which are rotatably arranged on both the upper and lower sides of the backup members 40 and 40 ′ so as to undergo the same reciprocating motion with the backup members 40 and 40 ′. As shown in FIGS. 3, 7 and 8 , these rollers 61 a - 61 d and 61 a ′- 61 d ′ are supported rotatably by cross-sectionally U-shaped frames 62 and 62 ′ provided with openings 63 and 63 ′ on both sides. Eccentric parts at the tips of shafts 64 a - 64 d and 64 a ′- 64 d ′ having the same cross-sectional shape as aforementioned shafts 41 , 41 ′, 43 and 43 ′ are inserted into these openings 63 and 63 ′ such that, as the motor 51 is activated, the rollers 61 a - 61 d and 61 a ′- 61 d ′ undergo a reciprocating motion in the forward-backward direction through the belts 57 and 57 ′ and the pulleys 65 and 65 ′ together with the backup members 40 and 40 ′. Each of the backup members 40 and 40 ′ (only the member 40 being shown in FIG. 9 ( a )) is provided with a plurality of indentations 48 on its surface, each of the indentations 48 containing therein a nozzle 49 for emitting pressurized air. The amount of pressurized air to be emitted through each nozzle 49 is electronically controlled individually such that the pressure with which the polishing tapes T and T′ are pressed against the baseboard can be varied locally. The discharging device 70 comprises, as shown in FIG. 7, a first discharger 71 and a second discharger 71 ′, each including a plurality of rollers (or “discharger rollers”) 72 a - 72 h (or 72 a ′- 72 h ′) for transporting a baseboard, a frame (or “discharger frame”) 73 (or 73 ′) which supports the discharger rollers 72 a - 72 h (or 72 a ′- 72 h ′) rotatably and a driving means (or “discharger driving means” (not shown)) for causing the discharger rollers to rotate. The first and second feeders 71 and 71 ′ are disposed symmetrically in the right-left direction such that corresponding ones of their rollers 72 a - 72 h and 72 a ′- 72 h ′ are opposite each other. The discharge of a baseboard is effected with the baseboard clamped between the mutually oppositely facing pairs of rollers 72 a - 72 h and 72 a ′- 72 h ′ and by rotating the rollers 72 a - 72 h and 72 a ′- 72 h ′ by the driving means. The driving means may comprise, similar to the driving means for the aforementioned feeding device 20 , ball screws arranged vertically, each engaging a screw groove provided at an edge portion of a corresponding one of the rollers 72 a - 72 h and 72 a ′- 72 h ′ and means for rotating these ball screws. The discharging device 70 also includes a discharger moving means for moving the first and second dischargers 71 and 71 ′ towards or away from each other such that a baseboard can be clamped between the pairs of rollers 72 a - 72 h and 72 a ′- 72 h ′. The discharger moving means includes guides 74 and 74 ′ formed respectively on the frames 73 and 73 ′ and actuators 76 and 76 ′ affixed to the housing 11 . The guides 74 and 74 ′ are respectively engaged with rails 75 and 75 ′ affixed to the housing 11 so as to move along the rails 75 and 75 ′ in the right-left direction as the actuators 76 and 76 ′ are activated. When a baseboard is to be polished, both methods with fixed abrading particles and free abrading particles may be used. The former method is carried out by using polishing tapes each with abrading particles affixed to a surface. The latter method is carried out by providing a polishing slurry with abrading particles dispersed inside water or a water-based aqueous solution and supplying it to the boundary surfaces between polishing tapes and the surfaces of the baseboard. The baseboard to be polished is initially placed on a plurality of guide rollers 13 (shown in FIG. 1 ) arranged on the bottom surface of the housing 11 in the forward backward direction and the actuators 26 , 26 ′, 37 , 37 ′, 76 and 76 ′ are activated so as to move the first and second feeders 21 and 21 ′, the first and second polishing heads 31 and 31 ′ and the first and second dischargers 71 and 71 ′ towards each other in the right-left direction such that the feeder rollers 22 a - 22 g and 22 a ′- 22 g ′ of the first and second feeders 21 and 21 ′, the discharger rollers 72 a - 72 h and 72 a ′- 72 h ′ of the first and second dischargers 71 and 72 ′, and the backup members 40 and 40 ′ of the first and second polishing heads 31 and 31 ′ will approach each other onto the vertical plane above the guide rollers 13 . Next, the feeder rollers 22 a - 22 g and 22 a ′- 22 g ′ of the feeding device 20 are rotated to transport the baseboard upward. While the polishing tapes T and T′ are run, the backup members 40 and 40 ′ are moved reciprocatingly in the forward-backward direction such that both surfaces of the baseboard are polished. The polished baseboard has its upper end clamped between the discharger rollers 72 a - 72 h and 72 a ′- 72 h ′ of the discharging device 70 and is transported further upward by the rotation of the discharger rollers 72 a - 72 h and 72 a ′- 72 h ′. Thus completes the polishing operation by the polishing apparatus 10 of this invention. With a polishing apparatus thus structured, unused portions of polishing tapes are continuously supplied to the target surfaces to be polished. Thus, overall or local degradation of the tape surface while the tape is being used or the aforementioned problem of clogging can be obviated. Moreover, since the pressure on the tape surface can be locally varied, target surfaces can be polished extremely uniformly. The reproducibility of the target surfaces is thus improved, and the throughput can be increased.