Jig and method for clamp-positioning single crystal ingot

Abstract: A jig and a method are provided for accurately and easily positioning a single crystal ingot with respect to the clamp rotary shafts of a device for grinding the peripheral surface of the ingot. The jig includes male positioning fixtures 10L and 10R and female positioning fixtures 32L and 32R. In the male positioning fixtures, negative-pressure suction cups 105 made of an elastic or viscoelastic material and blocks 101 at the backs of the cups are integrally formed with each other. In the female positioning fixtures, holes 325 are formed at the ends of the clamp rotary shafts 30L and 30R of the grinding device. The male positioning fixtures are accommodated in the holes, and the blocks are fitted into the holes so as to be concentric with the clamp rotary shafts.

Description: BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a jig for positioning a single crystal ingot with respect to the clamp rotary shafts of a device for grinding the peripheral surface of this ingot and to a method of employing this jig to clamp-position the single crystal ingot. DESCRIPTION OF THE RELATED ART A single crystal ingot grown by a CZ or FZ method is formed into a cylinder by the following processes: (1) Both ends of the single crystal ingot are cut perpendicularly to the axial direction thereof so as to form a cylinder like body. (2) As shown in Fig. 5, clamp rotary shafts 31L and 31R are pressed against cut surfaces 21L and 21R of the single crystal ingot 20 to clamp it slightly. Gauges 70 and 71 are fixed above both ends of the single crystal ingot 20. Movable pins of the gauges for detecting the shape of the single crystal ingot 20 are brought into elastic contact with the periphery of the ingot 20. Under the above conditions, the single crystal ingot 20 is rotated, and the gauges 70 and 71 measure the peripheral shape of the ingot 20 as displacements of the ends of the movable pins so that the positional deviations between a center of the cut surface 21L and the axis of the clamp rotary shaft 31L and between a center of the cut surface 21R and the axis of the clamp rotary shaft 31R are computed. (3) The rotation of the single crystal ingot 20 is stopped, and the ends of the single crystal ingot 20 are forced with a hammer to minimize such positional deviation. (4) The above processes (2) and (3) are repeated until there is no substantial positional deviation. (5) The single crystal ingot 20 is tightly clamped by the clamp rotary shafts 31L and 31R, and is rotated. A grinding stone is brought into contact with the peripheral surface of the single crystal ingot 20 while it is moving, thus grinding it into a cylinder. However, when the single crystal ingot 20 is clamped in process (1), it is positioned by visual observation; consequently, there is a relatively large amount of positional deviation from ideal. To correct this deviation, the single crystal ingot 20 must be forced with a hammer several times, thus producing an unfavorable effect on the quality of the ingot 20 by the external mechanical shock. Furthermore, it is necessary to repeat process (2) to accurately position the single crystal ingot. Thus, such an operation is complicated and time-consuming. DE-A-30 36 489 discloses a grinding machine for spectacle lenses, in which the lense is clamped between two suction cups. These are attached to clamp rotary shafts by means of a male positioning fixture realized by a block, which is received by an according hole in the clamp rotary shaft. As the lense is only held by the suction cups and no further stabilization is given, it is not possible to work heavy single crystal ingots with a grinding machine of the type of this document. SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a jig for accurately and easily clamp-positioning a single crystal ingot with respect to clamp rotary shafts. Another object of this invention is to provide a method of employing such a jig for positioning the single crystal ingot. In accordance with one aspect of the present invention, there is provided a jig for clamp-positioning a single crystal ingot according to the preamble of claim 1, which jig further comprises the features of the characterizing part of claim 1. Concerning another aspect of the invention characterising part of claim 4 teaches an inventional method of clamp-positioning a single crystal ingot by means of a transparent centering plate. Further details and preferred embodiments of the invention become clear from the subclaims and the following description of the invention. The jig is employed as follows: (1) The suction cups of the male positioning fixtures are pressed against and suctioned under negative pressure to the centers of both end surfaces of the single crystal ingot, which surfaces are cut perpendicularly to the axial direction of the ingot. (2) The blocks of the male positioning fixtures are fitted into the holes of the female positioning fixtures at the ends of the two clamp rotary shafts facing each other. As obvious from the above method of using the jig, it becomes accurate and easy to position the single crystal ingot with respect to the clamp rotary shafts. Step (1) will be described in detail for only one end of the single crystal ingot. (1a) A centering hole having a diameter which is slightly larger than the diameter of one end of the suction cup is formed in a transparent plate, a centering plate. A centering circle is drawn on the centering plate, which circle is concentric with the centering hole and has a diameter substantially equal to that of the single crystal ingot. The centering plate is pressed against the cut surfaces of the single crystal ingot. (1b) The centering hole is positioned on the basis of the relative positions of the centering hole of the centering plate and the outer periphery of the single crystal ingot. (1c) The suction cup is pressed against the cut surface of the single crystal ingot so that the center of the cup agrees with that of the centering hole in the centering plate. It is possible to accurately and easily suction the male positioning fixtures to the centers of the cut surfaces of the single crystal ingot. The suction cups and the blocks, for example, are originally separate components, which can be formed integrally with each other in the following way. Screws penetrate the shaft centers of the suction cups. Ends of the screws are mated with the blocks, and the heads of the screws are inserted into the recesses. Screw holes are formed at the shaft centers of the heads of the screws. After the peripheral surface of the single crystal ingot has been ground, if it is difficult to disengage the male positioning fixtures from the female positioning fixtures, a screw provided separately from the above screw is inserted into the screw hole, and is pulled in the axial direction thereof, thus making disengagement easy. The blocks of the male positioning fixtures have the shape of, for example, a truncated conical portion. The degree to which the holes formed in the female positioning fixtures is the same as the degree to which the tapered peripheral surfaces of the truncated cone portions taper. This tapering makes it easier to mate the male positioning fixtures with the female positioning fixtures. The female positioning fixtures are linked to, for example, ends of the clamp rotary shafts. Because of such linkage, the present invention may readily be applied to an existing device for grinding the peripheral surface of a single crystal ingot. BRIEF DESCRIPTION OF THE DWARINGS Fig. 1 is a side view illustrating the clamping of a single crystal ingot to clamp rotary shafts; Fig. 2 is a sectional view of a jig for clamp-positioning the single crystal ingot; Fig. 3 is a perspective view showing a male positioning fixture of the jig; Fig. 4 is a view illustrating how a female positioning fixture is positioned with respect to a cut surface of the single crystal ingot; and Fig. 5 is a perspective view illustrating problems with the conventional method. DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings. As shown in Fig. 1, male positioning fixtures 10L and 10R are respectively suctioned to the centers of cut surfaces 21L and 21R of a single crystal ingot 20. These surfaces 21L and 21R are formed by cutting both ends of the single crystal ingot 20 perpendicularly to the axial direction thereof. The male positioning fixtures 10L and 10R have the same structure, which will be shown in Figs. 2 and 3. The following description will be for only the left side of the single crystal ingot 20. A tapered block 101 has the shape of a substantially truncated cone. A screw hole 102 is formed at the center of the end of the tapered block 101 which has a larger diameter. The inside diameter of the screw hole 102 is the same as those of a collar 103 and a washer 104, both fixed to the tapered block 101. A hole is formed penetrating the shaft center of a cup 105 and has the same inside diameter as those of the screw hole 102, the collar 103 and the washer 104. The cup 105 is formed of rubber or synthetic resin with elasticity or viscoelasticity. A setscrew 106 is inserted into the hole penetrating the cup 105, the washer 104 and the collar 103. Thus, the ends of the setscrew 106 are mated with the screw hole 102 in the tapered block 101. The tapered block 101, the collar 103, the washer 104 and the cup 105 are integrally formed with each other. Another screw hole 107 is formed at the shaft center of the head of the setscrew 107. A withdrawing screw 108 is provided which is separated from the setscrew 106 and can be mated with the screw hole 107 for removing the male positioning fixture 10L when it is difficult to disengage it from a female positioning fixture 32L. As shown in Fig. 1, a device for grinding the peripheral surface of the single crystal ingot 20 is disposed so that a clamp rotary shaft 30L coaxially faces another clamp rotary shaft 30R capable of moving in the axial direction thereof. The clamp shaft 30L is a rotary driving shaft, the clamp shaft 30R is a rotary driven shaft. The female positioning fixture 32L is linked to one end of the clamp rotary shaft 30L, and another female positioning fixture 32R is linked to one end of the clamp rotary shaft 30R. The ends of the clamp rotary shafts 30L and 30R have the same structure. As illustrated in Fig. 2, a cylindrical connecting projection 311, which is formed by grinding the peripheral surface thereof, is provided at one end of a shaft 31L. A pin hole 312 runs in the diametrical direction of the connecting projection 311. A cylindrical connecting recess 322 is formed in a short shaft 321 of the female positioning fixture 32L so as to correspond to the connecting projection 311. Another pin hole 323 is formed corresponding to the pin hole 312. The connecting projection 311 is mated with the connecting recess 322, and a retaining pin 324 is inserted into the pin holes 312 and 323. The shaft 31L is linked to the female positioning fixture 32L. A tapered hole 325 is formed at the shaft center of the short shaft 321 so that one end of the short shaft 321 communicates with the connecting recess 322. The tapered hole 325 has the shape of a truncated cone with a smaller diameter at the side of the connecting recess 322. The degree to which the hole 325 tapers is equal to the degree to which block 101 of the male positioning fixture 10L tapers. As shown in Fig. 4, a centering plate 40 is used to suction the male positioning fixture 10L to the cut surface 21L. The centering plate 40 is a transparent plate, such as a rectangular acrylic-made plate 41, with a centering hole 42 formed at the center thereof. The inside diameter of the centering hole 42 is larger by several mm than the diameter of the cup 105 fully suctioned. A centering circle 43 which is concentric with the centering hole 42 is drawn on the surface of the transparent plate 41. The centering circle 43 can be accurately and easily scribed, for example, by a lathe. The diameter of the centering circle 43 is equal to the outside diameter of a cylinder formed by grinding the peripheral surface of the single crystal ingot 20. It is smaller by several mm than the average diameter of the cut surface 21L of the single crystal ingot 20. A description will be given of a method of employing the thus-constructed jig to clamp-position a single crystal ingot. (1) Apply the centering plate 40 to the cut surface 21L on one end of the single crystal ingot 20. (2) As shown in Fig. 4, the centering hole 42 is positioned on the basis of the relationship between the centering circle 43 and the cut surface 21L of the single crystal ingot 20. For instance, the centering hole 42 is positioned so that the centering circle 43 becomes concentric with the imaginary inscribed circle of the cut surface 21L. (3) Under the above conditions, the cup 105 of the male positioning fixture 10L is pressed against the cut surface 21L so that the cup 105 is concentric with the centering hole 42. The male positioning fixture 10L is suctioned to the cut surface 21L. (4) The steps (1) to (3) are repeated for the cut surface 21R on the other end of the single crystal ingot 20. (5) As shown in Fig. 1, the single crystal ingot 20 is interposed between the clamp rotary shafts 30L and 30R. The tapered block 101 of the male positioning fixture 10L is mated with the tapered hole 325 of the female positioning fixture 32L. (6) Under such conditions, the clamp rotary shaft 30R is brought at a high speed near the cut surface 21R of the single crystal ingot 20. The other tapered block 101 of the male positioning fixture 10R is mated with the other tapered hole 325 of the female positioning fixture 32R while slowly bringing the shaft 30R near the cut surface 21R. One end of the female positioning fixture 32R is pressed against the cut surface 21R, and at the same time one end of the female positioning fixture 32L is pressed against the cut surface 21L. In this way, it is possible to accurately and easily position the single crystal ingot 20 with respect to the clamp rotary shafts 30L and 30R. Under the conditions mentioned above, the clamp shaft 30L is rotatively driven, thereby rotating the single crystal ingot 20. An unillustrated grinding stone is pressed against the peripheral surface of the single crystal ingot 20 to grind it into a cylindrical form. After grinding has been completed, the clamp rotary shafts 30L and 30R are moved away from each other to remove the single crystal ingot 20 from the grinding device. When it is difficult to disengage the male positioning fixtures 10L and 10R from the female positioning fixtures 32L and 32R, respectively, the drawing screw 108 is inserted into the screw hole 107 and is pulled in the axial direction thereof to disengage the male positioning fixtures 10L and 10R. The present invention includes various modifications other than the embodiment described above. For example, it may be applied where the male positioning fixtures 10L and 10R are integrally formed of synthetic resin, or may be applied where the clamp rotary shafts 30L and 30R are also integrally formed.

Claims: A jig clamp-positioning a single crystal ingot having an uneven peripheral surface and two flat parallel ends each having an approximate center, comprising: a pair of male positioning futures (10L, 10R), each having an elastic or viscoelastic suction cup (105) for suction attachment to the approximate center of one of the flat ends of the single crystal ingot (20) by pressing an open end of said suction cup (105) against said flat end of the single crystal ingot (20) so as to make the interior of said suction cup (105) airtight and attach to the flat end by under-pressure, each said male positioning fixture (10L, 10R) having a block (101) feed to said suction cup (105) at an opposite end to said open end; and a pair of female positioning futures (32L, 32R), each formed at an end of one of a pair of clamp rotary shafts (30L, 30R) of a device for grinding the peripheral surface of the single crystal ingot (20), each said female positioning fixture (32L, 32R) having a hole (325) for accommodating said male positioning fixture (10L, 10R) by removably fitting said block (101) into said hole (325), characterized in that each said block (101) is tapered concentric with said suction cup (105) and said hole (325) has a tapered wall with a degree of taper substantially the same as said block (101), said hole (325) being concentric with said clamp rotary shaft (30L, 30R), wherein at least one of said female positioning fixtures (32L, 32R) is linked with a respective said end of said clamp rotary shaft (30L, 30R) by a pin (324) arranged perpendicular to the axis of said clamp rotary shaft (30L, 30R), said open end of said suction cup (105) and said end of said clamp rotary shaft (30L, 30R) contacting the flat end of the ingot (20) and each male positioning fixture (10L, 10R) being within said each hole (325) when the single crystal ingot (20) is clamped by said clamp rotary shafts (30L, 30R). A jig according to claim 1, characterized in that said suction cup (105) is fixed at said opposite end of said suction cup (105) to said block (101) by engaging a screw (106) through a central axis of said suction cup (105) and said block (101), a head of said screw (106) being disposed at a bottom of said open end of said suction cup (105), a screw hole (107) being formed at a center of said head of said screw (106), said screw hole (107) constituting means for detaching said male positioning fixture (10L, 10R) from said hole (325) of said female positioning fixture (32L, 32R) by engaging a detaching screw (108) into said screw hole (107) and pulling said detaching screw (108). A jig according to claim 1, characterized by a transparent centering plate (40) for locating an approximate center area on each of said two flat parallel ends of the ingot (20), said transparent centering plate (40) having a center circular hole (42) and a centering circle (43) inscribed concentric with said circular hole (42) such that said centering circle (43) can be approximately aligned in a concentric fashion with the flat end of said single crystal ingot (20). A method of clamp-positioning a single crystal ingot having an uneven peripheral surface and two flat parallel ends each having a center, characterized by the steps of: positioning a transparent centering plate (40) on the flat end (21L, 21R) of the single crystal ingot (20), said transparent centering plate (40) having a circular hole (42) and a centering circle (43) inscribed concentric with said circular hole (42), such that said centering circle (43) is aligned approximately concentric with the flat end of said single crystal ingot (20); positioning a pair of male positioning fixtures (10L, 10R) each having an elastic or viscoelastic suction cup (105) with a diameter at an open end thereof which is slightly smaller than the diameter of said circular hole (42) and a block (101) fixed at an opposite end to said open end of each said suction cup (105), said block (101) being concentric with said suction cup (105), and contacting said open end of said suction cup (105) on the flat end of the single crystal ingot (20) in said centering hole (42) such that said suction cup (105) becomes concentric with said centering hole (42); attaching each said suction cup (105) to said flat end of the single crystal ingot (20) by pressing said male positioning fixture against the flat end of the single crystal ingot (20) so as to make the interior of said cup (105) airtight and attach to the end of the single crystal ingot (20) by under-pressure, removing said centering plate (40) off from the flat end of the single crystal ingot (20); accommodating each said male positioning fixture in a hole (325) with fitting said block (101) into said hole (325) which is formed at an end of clamp rotary shaft (30L, 30R) of a device for grinding the peripheral surface of the single crystal ingot (20), said hole (325) being concentric with said clamp rotary shaft (30L, 30R); and clamping the single crystal ingot (20) by said clamp rotary shafts (30L, 30R).

Inventors: IBE HIROYUKI, NAKATA TOSIHISA, IBE, HIROYUKI, NAKATA, TOSIHISA
Applicants: SHINETSU HANDOTAI KK, SHIN-ETSU HANDOTAI COMPANY, LIMITED
Application year: 1992
Main classification: B24B47
IPC codes: B23Q3, B23B23, B24B47, B24B5, B24B41, C30B33