Wire cleaning apparatus

A newly proposed wire cleaning apparatus used for removing slurry from a wire, which reciprocatively travels between a slicing chamber and a wiring chamber. The wire cleaning apparatus has a couple of multigrooved guide rollers 41, 42 rotatably provided at a cover 30. A slurry receiver 20 is detachably attached to the cover 30. A centrifugal force is generated during repeated reciprocative movement of the wire 5 between the multigrooved guide rollers 41 and 42. Slurry is shaken off from the wire 5 by the centrifugal force and gathered in the slurry receiver 20. Removal of the slurry is accelerated by spraying a cleaning liquid W at the same time. Introduction of the cleaning liquid W into the slicing chamber is inhibited by on-off control of the cleaning nozzles 41, 42 in response to a travelling direction of the wire 5.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to an apparatus for cleaning a wire of a wire
 saw useful for slicing ingots or the like to thin wafers.
 2. Brief Description of the Prior Art
 After top and tail parts are cut off an ingot produced by a pulling method
 or the like, the ingot is ground at its periphery, subjected to
 orientation flat processing and then sliced to wafers of predetermined
 thickness. Although an inner blade slicer has been used so far for slicing
 the ingot, it does not well cope with a tendency of enlargement of wafers
 in diameter. Therefore, a wire saw machine using a piano wire has been
 recently adopted in response to enlargement of wafers.
 A conventional wire saw has three grooved rollers 1-3, one of which (the
 roller 3) is coupled to a drive motor 4, as shown in FIG. 1. A wire 5 is
 pulled out from a reel 6, passed around the grooved rollers 1 to 3
 multiple times and then wound on another reel 7. A tensioner 8 applies a
 tension to the wire 8. Thus, the wire 5 travels in a stretched state along
 a travel path around the grooved rollers 1 to 3.
 An ingot 9 to be sliced is fixed to a holder 10 using a proper adhesion jig
 and located at a position between the grooved rollers 1 and 2. The ingot 9
 is sliced to a plurality of wafers by cutting motion of the wire 5. During
 slicing, slurry 11 is supplied from a slurry tank 11 through a supply tube
 13 to a nozzle 14, sprayed onto the wire 5, collected in a pan 15 and then
 returned to the slurry tank 12, in order to promote the cutting motion.
 The slurry 11 is cooled by circulation between the slurry tank 12 and a
 heat exchanger 16.
 The slurry 11 still adheres onto the wire 5 due to its stickiness, even
 when the wire 5 after being used for slicing the ingot 9 travels toward
 the reel 6 or 7. If the wire 5 together with the slurry 11 is wound as
 such on the reel 6 or 7, the slurry 11 scatters in the circumference
 during winding and causes contamination of a wiring chamber wherein the
 reels 6, 7 are located.
 There are various members and tools except the reels 6, 7 in the wiring
 chamber. For instance, a dancer roller 17 and a traverser 18 for adjusting
 a winding number of the wire 5 on the reels 6, 7 and for controlling a
 tension applied to the wire 5. Scattering and accumulation of the slurry
 11 in such wiring chamber likely induces occurrence of mechanical
 troubles. In this sense, the wiring chamber shall be kept in a dean state
 free from scattering and accumulation of the slurry 11. Unfavorable
 introduction of the slurry of 11 into the wiring chamber also accelerates
 abrasion of various rollers located in the wiring chamber.
 The slurry 11 can be washed off from the wire 5 by a washer provided at a
 travelling path of the wire 5 between the slicing chamber and the wiring
 chamber so as to spray a cleaning liquid to the wire 5. However, such a
 washer shall have enough length along the travel path of the wire 5, in
 order to sufficiently wash off the slurry 11 by spraying the cleaning
 liquid to the running wire 5. As a result, a huge washer is necessitated.
 In addition, removal of the slurry 11 is insufficient only by spraying the
 cleaning liquid, so that some residual slurry is involved together with
 the wire 5 in the reels 6, 7.
 SUMMARY OF THE INVENTION
 The present invention aims at provision of a new wire cleaning apparatus
 without the above-mentioned problems. The newly proposed wire cleaning
 apparatus uses a centrifugal force for shaking off slurry from the wire.
 The centrifugal force is generated by repeated reciprocative movement of
 the wire between multigrooved guide rollers located at a travel path of
 the wire. Removal of the slurry is well performed due to the effect of the
 centrifugal force on separation of the slurry from the wire.
 The newly proposed wire cleaning apparatus has a couple of multigrooved
 guide rollers on which the wire is wound several times, a cover to which
 the multigrooved guide rollers are rotatably attached, and a slurry
 receiver detachably attached to the cover. A centrifugal force is
 generated during repeated reciprocative movement of the wire between the
 multigrooved guide rollers.
 Although the slurry is shaken off from the wire by the centrifugal force,
 removal of the slurry is accelerated by spraying a cleaning liquid at the
 same time. In order to spray a cleaning liquid, a nozzle or nozzles
 directed to surfaces of the multigrooved guide rollers are provided at the
 cover. In such a case, the nozzle or nozzles are preferably on-off
 controlled in response to a travelling direction of the wire, so as to
 inhibit introduction of the sprayed cleaning liquid into the slicing
 chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 According to the present invention, two wire cleaning apparatuses A are
 located at two positions near entrances of wiring chambers C, which are
 provided adjacent to a slicing chamber B, corresponding to reels 6, 7,
 respectively, as shown in FIG. 2. One wire cleaning apparatus A may be
 also used for cleaning the wire 5 at both sides of the reels 6, 7. In such
 a case, a travelling path of the wire 5 toward the reel 6 is set close to
 the other travelling path of the wire 5 toward the reel 7. After the wire
 5 is sent from the slicing chamber B to the cleaning apparatus A, the
 slurry 11 is washed off from a surface of the wire 5. Thereafter, the wire
 5 is forwarded through a dancer roller 17 and a traverser 18 and then
 wound on the reel 6 or 7.
 The wire cleaning apparatus A has a drawable slurry receiver 20 provided at
 a cover 30, as shown in FIGS. 3A-B. The slurry receiver 20 is a vessel
 having a side wall 22. A flange 21, which is inserted into a gap 31 of the
 cover 30, is formed at an upper part of the side wall 22. A handle 23 is
 provided at a position below the flange 21, so as to facilitate drawing
 motion of the slurry receiver 20. The slurry receiver 20 is drawn along a
 direction perpendicular to the sheet in FIG. 3A. Of course, the slurry
 receiver 20 may be attached to the cover 30 in other manners.
 The cover 30 has a side wall 33. A slit 32 is formed in the side wall 33
 along a widthwise direction. The wire 5, which reciprocatively travels
 between the slicing chamber B and the wiring chamber C, is sent through
 the slit 32 into the wire cleaning apparatus A. A protection metal fitting
 34 made of a hard material excellent in abrasion-resistance is fixed to an
 edge of the slit 32, in order to inhibit abrasion of the side wall 33 by
 friction with the wire 5.
 A couple of multigrooved guide rollers 41, 42 are located in the wire
 cleaning apparatus A Each multigrooved guide rollers 41, 42 has a rotating
 shaft 41a, 42a rotatably supported with the side wall 33 inside the wire
 cleaning apparatus A The multigrooved guide rollers 41, 42 can be reversed
 in response to both-way travel of the wires 5. Rotation of multigrooved
 guide rollers 41, 42 may be either of motor drive rotation or following
 rotation by friction with the wires 5.
 A plurality of grooves (for instance 10 or so) are engraved on peripheries
 of the multigrooved guide rollers 41, 42. The wire 5 sent from the slicing
 chamber B reciprocatively travels between the multigrooved guide rollers
 41 and 42 at times corresponding to the number of the grooves on the
 multigrooved guide rollers 41, 42, and then forwarded to the reel 6, 7 or
 the slicing chamber B. The number of the grooves on the guide rollers 41,
 42 is properly determined according to the kind of slurry 11 to be used.
 For instance, a large number of grooves are engraved on the guide rollers
 41, 42 in the case where slurry based on an oily coolant is used for
 slicing the ingot 9, since the oily coolant exhibits stronger adhesives
 than an aqueous coolant.
 Cleaning nozzles 45, 46 are attached to an upper wall 35 of the cover 30 at
 positions facing the multigrooved guide rollers 41, 42, respectively. Each
 cleaning nozzle 45, 46 is led through a water supply tube 45a, 46a to a
 water source (not shown). Either one of the cleaning nozzles 45 or 46 may
 be omitted, since the sprayed cleaning liquid W is circulated between the
 multigrooved guide rollers 41 and 42.
 A cleaning liquid W is sprayed from the cleaning nozzles 45, 46 to the wire
 5 travelling around the multigrooved guide rollers 41, 42, as shown in
 FIG. 4. The travel paths of the wire 5 at the position where the cleaning
 liquid W is sprayed are curved along the peripheries of the multigrooved
 guide rollers 41, 42. Due to such curved travel paths, a centrifugal force
 is generated during repeated reciprocative movement of the wire 5 between
 the multigrooved guide rollers 41, 42 and applied to the wire 5. The
 centrifugal force together with an injection pressure of the cleaning
 liquid W promotes scattering of the slurry 11 as splashes D from the wire
 5. The slurry splashes D bump against an inner surface of the cover 40 and
 flow downwards. The used slurry S is collected in the slurry receiver 20
 in this way. When a predetermined amount of the slurry S is accumulated in
 the slurry receiver 20, the slurry receiver 20 is periodically drawn out
 for sending the recovered slurry S to post-treatment such as disposal or
 reprocessing. The recovered slurry S may be continuously discharged from
 the slurry receiver 20 outside the cleaning apparatus A through a conduit
 connected to a slurry tank (not shown), as occasion demands.
 The cleaning nozzles 45, 46 are preferably on-off controlled with
 synchronization with a travelling direction of the wire 5. Concretely, the
 cleaning nozzles 45, 46 are opened to spray the cleaning liquid W to the
 wire 5, when the wire 5 travels from the slicing chamber B to the wiring
 chamber C. When the wire 5 travels from the wiring chamber C to the
 slicing chamber B on the contrary, spray of the cleaning liquid W is
 stopped by shutting the cleaning nozzles 45, 46. The on-off control
 suppresses inflow of the cleaning liquid W into the slicing chamber B and
 inhibits contamination of the slurry 11 with the cleaning liquid W during
 slicing of the ingot 9.
 The on-off control of the cleaning nozzles 45, 46 is performed by a control
 system 49, whereby a traveling direction of the wire 5 is detected by a
 sensor 47 so as to output a command signal for shutting a check valve 48
 when the travelling direction is from the wiring chamber C to the slicing
 chamber B or another command signal for releasing the check valve 48 when
 the travelling direction is from the slicing chamber B to the wiring
 chamber C. The on-off control may be performed in a different way, wherein
 a rotating direction of the reels 6, 7 or the multigrooved guide rollers
 41, 42 is detected and the detection result is converted to a command
 signal for opening or shutting the cleaning nozzles 45, 46.
 A travelling speed of the wire 5 is ordinarily determined within a range of
 8-13 ml/second under actual operational conditions of the wire-sawing
 machine. When such high-speed travelling wire 5 passes along the curved
 paths on the peripheries of the multigrooved guide rollers 41, 42 having
 great curvatures, a centrifugal force big enough to shake off the slurry
 11 from the wire 5 is generated. Consequently, the slurry 11 is shaken off
 from the wire 5 only by the centrifugal force without spray of the
 cleaning liquid W. Of course, removal of the slurry 11 is accelerated by
 spraying only a slight amount of the cleaning liquid W. Omission or saving
 of the cleaning liquid W means that there is not big fluctuation in the
 properties of the slurry S gathered in slurry receiver 20, and reuse of
 the recovered slurry S is also expected.
 The centrifugal force is bigger, as diameters of the multigrooved guide
 rollers 41, 42 are smaller. However, if the multigrooved guide rollers 41,
 42 are too small in diameter, the wire 5 is apt to be plastically deformed
 due to bending moment which is generated when the wire 5 travels around
 the multigrooved guide rollers 41, 42. In this regard, the multigrooved
 guide rollers 41, 42 preferably have diameters of 70-90 mm for a wire of
 0.18 mm in diameter for instance, taking into account actual operational
 conditions.
 The multigrooved guide rollers 41, 42 shown in the drawings are arranged on
 a horizontal plane. But, the multigrooved guide rollers 41, 42 may be
 arranged on a vertical plane instead. Locations of the cleaning nozzles
 45, 46 are changed in response to such an arrangement. For instance, the
 cleaning nozzles 45, 46 are attached to the side wall 33 of the cover 30
 at positions corresponding to the multigrooved guide rollers 41, 42 or
 hung from the upper wall 35 so as to direct to peripheries of the
 multigrooved guide rollers 41, 42, respectively.
 The slurry 11, which adheres to the wire 5, is sufficiently separated from
 the wire 5 during repeated reciprocative movement of the wire 5 between
 the multigrooved guide rollers 41 and 42. Since the slurry 11 does not
 adhere to the wire 5 sent out of the wire cleaning apparatus A, various
 tools and members arranged along the travel path of the wire 5 through the
 dancer roller 17 and the traverser 18 to the reel 6 or 7 are not
 contaminated with the slurry 11. Consequently, the travelling condition of
 the wire 5 is stabilized without mechanical troubles caused by adhesion of
 the slurry.
 Removal of the slurry 11 from the wire 5 is finished during repeated
 reciprocative movement of the wire 5 between the multigrooved guide
 rollers 41 and 42. Due to such slurry removing action, a space necessary
 for removal of the slurry 11 is ensured enough by positioning the
 multigrooved guide rollers 41, 42 apart from each other in a distance of
 about 100.about.150 mm between their roll centers. Such small space
 enables installation of the wire cleaning apparatus A without necessity of
 either fundamental design change of the wire-sawing machine itself or a
 washing apparatus much elongated along the travel path of the wire 5. In
 addition, the slurry S removed from the wire 5 is gathered in the slurry
 receiver 20 without scattering outside the wire cleaning apparatus A, so
 that a working environment is kept clean.
 According to the present invention as above-mentioned, removal of slurry
 from a wire is well performed by a centrifugal force which is generated
 during repeated reciprocative movement of the wire between a couple of
 multigrooved guide rollers. The slurry is effectively shaken off from the
 wire by the centrifugal force, so as to inhibit introduction of the slurry
 together with the wire to various members and tools such as a dancer roll,
 a traverser and reels. Consequently, various members and tools arranged in
 a wiring chamber are protected from mechanical troubles caused by transfer
 and adhesion of the slurry, and travelling condition of the wire is
 stabilized. A space for removal of the slurry is very small, since removal
 of the slurry is finished during repeated reciprocative movement of the
 wire between the multigrooved guide rollers. Such a small space allows
 design of the wire-sawing machine with a high freedom without necessity of
 fundamental design change of the wire-sawing machine itself. In addition,
 a working environment is kept clean, since the slurry shaken off from the
 wire does not scatter outside the wire cleaning apparatus.