Further, the present invention relates to an apparatus for polishing gemstones, which includes two polishing means installed at different levels so that grinding and polishing can be collectively performed in a single apparatus.

Background Art In processing natural gemstones including diamonds or artificial gemstones, a gemstone to be processed is generally fixed to a gemstone holder and then pressed against a rotating polishing surface with a certain force to form facets on the gemstone. To form facets with different inclination angles with respect to a central axis of the gemstone held by the gemstone holder, the gemstone holder requires three types of motion modes with respect to the rotating polishing surface placed at a fixed position. A first mode is an inclining motion mode in which the angle of the central axis of the gemstone holder is adjusted on a plane perpendicular to the polishing surface to adjust an inclination angle of a facet to be formed. A second mode is a vertically feeding motion mode in which the gemstone holder holding the gemstone is precisely fed vertically by a polishing amount with respect to the polishing surface. A third mode is an index motion mode in which the gemstone holder is rotated through a certain angle around the central axis to polish a facet that is close or not close to a completely processed, specific facet.

Conventional apparatuses for polishing gemstones are constructed such that some of the three motion modes are established mechanically and the remainder is established through manual adjustment, or all the three motion modes are established automatically.

Since gemstone processing particularly requires high accuracy, there is a need for an apparatus for polishing gemstones, which has a means capable of correcting processing or assembly errors in the apparatus, mechanical deformation in use or the like, if desired, in a case where the three motion mode are established mechanically.

Further, the conventional apparatuses for polishing gemstones have problems in that processing accuracy for a facet is lowered and a polishing surface should be often exchanged since the polishing surface comes into contact with the gemstone holder at a constant position and thus is unevenly worn. To prevent this, a method of reciprocating a gemstone holder has been known. However, there is a risk that vibration will occur at the gemstone holder upon reciprocation thereof so that a facet cannot be smoothly processed.

Disclosure of Invention An object of the present invention is to provide an apparatus for polishing gemstones, which has a means for easily correcting processing or assembly errors of parts or errors resulting from mechanical deformation in use while automatically performing an inclining motion, a vertically feeding motion and an index motion of a gemstone holder.

Another object of the present invention is to provide an apparatus for polishing gemstones, wherein concentrated wear of a polishing surface is prevented to improve processing accuracy.

A further object of the present invention is to provide an apparatus for polishing gemstones, which has a means capable of adjusting levels of a polishing surface and a housing for supporting a plurality of gemstone holders fixed to a single cartridge.

A still further object of the present invention is to provide an apparatus for polishing gemstones, which has a means capable of reducing errors due to a backlash upon inclining motion of a gemstone holder.

According to the present invention for achieving the objects, there is provided an apparatus for polishing gemstones, comprising a base; a polishing means that is rotatably installed on the base and has a polishing surface parallel with the base; a supporting unit with a vertically feeding member installed to vertically move in a direction of an axis substantially perpendicular to the polishing surface; an inclination-adjusting unit that is

fixed to the vertically feeding member and has a rotational shaft installed rotatably about an axis substantially parallel with the polishing surface; a gemstone holder for holding a gemstone, which is fixed to a first arm radially extending from the rotational shaft and is installed to be rotatable in a plane substantially perpendicular to the polishing surface; a first motor for driving vertical movement of the vertically feeding member; a second motor for driving rotation of the rotational shaft of the inclination-adjusting unit; a third motor for driving rotation of the gemstone holder; a first sensor for sensing a relative position of the vertically feeding member with respect to the polishing surface; a second sensor for sensing an angular position of the rotational shaft; a third sensor for sensing an angular position of the gemstone holder; and a control unit for receiving signals from the respective sensors and controlling the respective driving means.

The control unit causes a gemstone fixed to the gemstone holder to come into contact with the rotating polishing surface so as to form facets on the gemstone. At this time, the control unit receives a signal from the first sensor to place the gemstone holder at an initial position upon driving the first motor, a signal from the second sensor to place the gemstone holder at an initial position upon driving the second motor, or a signal from the third sensor to place the gemstone holder at an initial position upon driving the third motor.

In a case of processing a new facet, the control unit performs control in such a manner that the gemstone holder starts from the predetermined initial position in response to the received signal from one of the sensors and moves by a certain angle or distance, thereby preventing accumulation of errors.

The apparatus of the present invention may further comprise a horizontally feeding means for horizontally moving the supporting unit with respect to the base; and a second polishing means that is rotatably installed on the base and has a polishing surface parallel with the base at a level higher than that of the polishing surface of the polishing means.

The horizontally feeding means is fixed to the base. After facets of the gemstone have been completely polished by the polishing means with the polishing surface at a lower level, the gemstone is horizontally fed to and continuously processed by the second polishing means with the polishing surface at a higher level to obtain smoother facets. At this time, since the polishing surface of the second polishing means for finer polishing is at

the higher level, it is possible to somewhat prevent chips produced during coarse polishing from being introduced into the finer polishing surface.

In the apparatus of the present invention, the polishing means may be installed to rotate while revolving around an axis offset by a predetermined distance from a rotation center thereof. Since the polishing surface of the polishing means rotates and revolves at the same time, a wide contact surface is established between the gemstone fixed to the gemstone holder and the polishing surface, thereby preventing uneven wear of the polishing surface and improving accuracy of resultant facets.

In the apparatus of the present invention, the polishing means may further comprise a driving means for causing the polishing surface to rotate and revolve, and a rotation speed sensor for measuring a rotation speed of the polishing surface, and the control unit may control the output of the first motor in response to a signal from the rotation speed sensor. That is, if the rotation speed of the polishing surface decreases due to high contact pressure between the polishing surface and the gemstone, the control unit stops the feeding of the gemstone holder by detecting the decrease of the speed based on the signal from the rotation speed sensor, or reduces the contact pressure by decreasing the feeding speed, thereby maintaining the rotation speed to be constant.

For simultaneous polishing of a plurality of gemstones, the apparatus of the present invention may further comprise a housing for supporting a plurality of gemstone holders such that ends of the holders are exposed to the outside toward the polishing surface; a clamping means that has one end fixed to the first arm and clamps the housing to be placed above the polishing surface; a second arm fixed to the other end of the clamping means; a supporting shaft that rotatably supports the second arm and is installed coaxially with the rotational shaft of the inclination-adjusting unit; and a first supporting bracket having one end fixed to the vertically feeding member and the other end installed to support the supporting shaft. The housing may include worm gears connected to a rotational shaft of the third motor installed on the second arm, and worm wheels fixed to the respective gemstone holders and engaged with the worm gears.

Further, in order to cause mechanisms for the inclining and index motions of the gemstone holders to adjust horizontality of the holders with respect to the polishing surface

without being restricted by the vertically feeding member and to cause the plurality of gemstones to be simultaneously polished in the apparatus of the present invention, the inclination-adjusting unit may comprise a housing for supporting the rotational shaft, a worm wheel fixed to the rotational shaft, and a worm gear coupled to the rotational shaft of the second motor and supported by the housing to be rotatable by being engaged with the worm wheel, and further comprise a second supporting bracket having one end fixed to the vertically feeding member and the other end fixed to an upper surface of the housing by means of a plurality of bolts, and a steel ball interposed between the upper surface of the housing and the second supporting bracket so that they can be spaced by a predetermined distance away from each other.

Moreover, in the apparatus of the present invention, the supporting shaft may comprise an arm shaft portion supported via a supporting bearing by the second arm and a supporting shaft portion supported by the first supporting bracket to horizontally adjust the polishing surface and the housing for supporting the plurality of gemstone holders, and the arm shaft portion and the supporting shaft portion may be placed such that their central axes are spaced by a predetermined interval away from each other. Therefore, the horizontality of the polishing surface and the housing for supporting the gemstone holders can be adjusted by rotating the supporting shaft about the supporting shaft.

In addition, in the apparatus of the present invention, the worm gear rotatably supported by the housing of the inclination-adjusting unit may be supported by a pair of backlash-adjusting disks with offset centers of inner and outer diameters thereof to adjust backslashes of the worm wheel and the worm gear of the inclination-adjusting unit, and the pair of backlash-adjusting disks may be installed on the housing such that installation angles of outer peripheries thereof can be adjusted. Therefore, since a relative distance of a worm gear shaft to the worm wheel can be changed by rotating the backlash-adjusting disks, the backlashes of the worm gear and the worm wheel can be adjusted to precisely maintain the adjustment of an inclination angle of the gemstone holders.

Brief Description of Drawings Fig. 1 is a perspective view schematically showing an apparatus for polishing

gemstones according to an embodiment of the present invention.

Fig. 2 is a front view of Fig. 1.

Fig. 3 is a detailed partial perspective view illustrating an operating relationship of the apparatus for polishing gemstones according to the embodiment of the present invention shown in Fig. 1.

Fig. 4 is an explanatory view schematically illustrating revolution and rotation of a polishing means in the apparatus for polishing gemstones according to the embodiment of the present invention shown in Fig. 1.

Fig. 5 is an explanatory view schematically illustrating the structure of a supporting shaft for adjusting the level of a gemstone holder housing in the apparatus for polishing gemstones according to the embodiment of the present invention shown in Fig. 1.

Fig. 6 is an explanatory view schematically illustrating a supporting structure of a worm shaft for adjusting a backlash of an inclination-adjusting unit in the apparatus for polishing gemstones according to the embodiment of the present invention shown in Fig. 1.

Fig. 7 is a perspective view of an apparatus for polishing gemstones according to another embodiment of the present invention.

<Explanation of reference numerals for designating main components in the drawings> 10: Base 20: Polishing means 30: Supporting unit 31: Vertically feeding member 40: Inclination-adjusting unit 41: Rotational shaft 50: First arm 60: Gemstone holder 61: Gemstone holder housing 65: Clamping means 71,72, 73: Motor 74,75, 76: Sensor 100: Apparatus for polishing gemstones Best Mode for Carrying out the Invention Hereinafter, preferred embodiments of the present invention will be described in detail with reference to accompanying drawings.

Fig. 1 is a perspective view schematically showing an apparatus for polishing gemstones according to an embodiment of the present invention, Fig. 2 is a front view of Fig. 1, Fig. 3 is a detailed partial perspective view illustrating an operating relationship of the apparatus for polishing gemstones according to the embodiment of the present invention shown in Fig. 1, Fig. 4 is an explanatory view schematically illustrating revolution and rotation of a polishing means in the apparatus for polishing gemstones according to the embodiment of the present invention shown in Fig. 1, Fig. 5 is an explanatory view schematically illustrating the structure of a supporting shaft for adjusting the level of a gemstone holder housing in the apparatus for polishing gemstones according to the embodiment of the present invention shown in Fig. 1, and Fig. 6 is an explanatory view schematically illustrating a supporting structure of a worm shaft for adjusting a backlash of an inclination-adjusting unit in the apparatus for polishing gemstones according to the embodiment of the present invention shown in Fig. 1.

As shown in Fig. 1, the apparatus for polishing gemstones 100 according to this embodiment of the present invention includes a polishing means 20 that is rotatably installed and has a polishing surface 21 parallel with a flat base 10. Further, a supporting unit 30 with a vertically feeding member 31 that is installed vertically movably is fixed to the base 10. The vertically feeding member 31 is installed vertically movably in the direction of an axis substantially perpendicular to the polishing surface 21. The vertically feeding member 31 is installed on a ball screw device 32 as shown in the figures. The ball screw device 32 is coupled to a rotational shaft of a first motor (shown in Fig. 3) installed at a lower portion thereof to feed the vertically feeding member 31.

An inclination-adjusting unit 40 for adjusting an inclination angle of a gemstone holder 60 is fixed to the vertically feeding member 31 and has a rotational shaft 41 installed rotatably about an axis substantially parallel with the polishing surface 21.

Further, the gemstone holder 60 to which a gemstone to be processed will be fixed (held) is secured on a first arm 50 radially extending from the rotational shaft 41. The gemstone holder 60 is installed on the first arm 50 such that it can rotate about its central axis in a plane substantially perpendicular to the polishing surface 21.

The apparatus 100 of this embodiment has a plurality of gemstone holders 60 as

shown in Fig. 1. The plurality of gemstone holders 60 are installed on a housing 61 for supporting the gemstone holders such that distal ends of the holders are exposed to the outside toward the polishing surface. Further, a clamping means 65 to which the housing 61 is detachably fixed is provided above the polishing surface 21. The clamping means 65 has one end fixed to the first arm 50 and the other end fixed to a second arm 66. One side of the second arm 66 is rotatably supported by a supporting shaft 67 installed coaxially with the rotational shaft 41 of the inclination-adjusting unit 40. Further, the supporting shaft 67 is fixed to a first supporting bracket 68 secured on the vertically feeding member 31. Therefore, the housing 61 for the gemstone holders 60 are fixed to the clamping means 65, and the plurality of gemstone holders are adjusted by means of the rotational shaft 41 of the inclination-adjusting unit 40 so that they can have an identical angle with respect to the polishing surface 21.

Although not shown in the figures, the gemstone holder housing 61 is constructed such that an index angle of the gemstone holders is adjusted through rotation of a third motor 73 by means of worm gears connected via a belt to a rotational shaft of the third motor 73 fixedly installed on the second arm 66, and worm wheels fixed to the respective gemstone holders and engaged with the worm gears.

Further, the apparatus 100 of this embodiment includes the first motor 71 (see Fig.

3) installed at the lower portion of the ball screw device 32 to drive the vertical movement of the vertically feeding member, a second motor 72 (see Fig. 3) fixed to a side of the inclination-adjusting unit to drive the rotation of the rotational shaft of the inclination- adjusting unit 40, and the third motor 73 fixedly installed on the second arm to drive the rotation of the gemstone holders. Although this embodiment employs stepping motors as the first to third motors in this embodiment, it is not limited thereto. Further, a first sensor 74 for sensing relative positions of ends of the gemstone holders 60 with respect to the polishing surface 21 is installed on the vertically feeding member 31. A second sensor 74 for sensing an angular position of the rotational shaft 41 is fixed to a second supporting bracket 49. A third sensor 76 for sensing an angular index position of the gemstone holders 61 is installed on the second arm 66.

Although not shown in the figures, a control unit for receiving signals from the

respective sensors 74,75 and 76 and controlling the driving means 71,72 and 73 is provided in a control panel 80.

The inclination-adjusting unit 40 in this embodiment will be described in detail with reference to Figs. 1,2 and 6.

As shown in Fig. 6, the inclination-adjusting unit 40 includes a housing 47 for supporting the rotational shaft 41, a worm wheel 42 fixed to the rotational shaft 41, and a worm gear 43 connected to the rotational shaft of the second motor 72 and supported by the housing to be rotatable by being engaged perpendicularly with the worm wheel 42.

Further, the housing 47 is fixed through a plurality of bolts 49b to a housing fixing plate 49a of the second supporting bracket 49 of which one end is fixed to the vertically feeding member 31. The housing supporting plate 49a is arranged parallel with the polishing surface. Particularly, a steel ball 48 is interposed between an upper surface of the housing 47 and a lower surface of the housing fixing plate 49a of the second supporting bracket 49 so that the relative stationary position of the housing 47 can vary without being confined by the second supporting bracket 49. Further, the upper surface of the housing 47 and the lower surface of the housing fixing plate 49a are formed with recesses for receiving the steel ball 48, respectively. Therefore, it is possible to fix the housing 47 to the housing fixing plate 49a with the steel ball 48 interposed therebetween using the bolts 49b in a state where both planes of the housing and the housing fixing plate are at a certain angle with respect to each other.

As shown in Fig. 6, a worm gear shaft 44 in the apparatus 100 of this embodiment is supported via a plurality of bearings 45a and 45b by a pair of backlash-adjusting disks 46 so as to adjust backlashes of the worm wheel 42 and the worm gear 43 of the inclination-adjusting unit 40. Each of the backlash-adjusting disks 46 is formed with a shaft-supporting hole 46a with a central axis Q offset by a predetermined distance from a central axis P of the outer diameter of the disk, and the worm gear shaft 44 is rotatably supported via the bearing within the shaft-supporting hole 46a. The pair of backlash- adjusting disks 46 are installed on the housing 47 such that installation angles of the outer peripheries thereof can be adjusted. That is, each of the backlash-adjusting disks 46 is formed with a groove 46d as shown in a dotted circle of Fig. 6 so that it can be rotated with

respect to and fixed to the housing using bolts.

A mechanism for adjusting horizontal levels of the housing 61 for the gemstone holders 60 and the polishing surface 21 will be described with reference to Fig. 5.

The supporting shaft 67 that pivotably supports the second arm 66 and is fixed to the first bracket 68 comprises an arm shaft portion 67a supported via a supporting bearing by the second arm 66, and a supporting shaft portion 67b supported by the first supporting bracket 68. Particularly, the supporting shaft 67 is constructed such that a central axis S of the arm shaft portion 67a and a central axis R of the supporting shaft portion 67b are offset by a predetermined interval from each other. Therefore, when the supporting shaft 67 is rotated through a certain angle about the supporting shaft portion 67b, the central axis S of the arm shaft portion 67a revolves around the central axis R of the supporting shaft portion 67b, thereby finely adjusting the level of the housing 61 for supporting the gemstone holders.

A structure for revolving and rotating the polishing surface of the polishing means will be described with reference to Fig. 4.

Although not shown in the figure, a boss 22 for supporting a revolution shaft 23 is fixed to the base 10. The revolution shaft 23 is formed with an inner bore for receiving a rotation shaft therethrough, and has a lower end to which a revolution pulley 24 for receiving power through a revolution belt 24a from a motor 29b for the revolution is fixed.

Further, a rotation shaft 25 is inserted into and supported within the inner bore of the revolution shaft 23 via a bearing. A grindstone 28 with the polishing surface 21 is fixed to an upper end of the rotation shaft 25, and a rotation pulley 25 for receiving power for receiving power through a rotation belt 25a from a motor 29a for the rotation is fixed to a lower end of the rotation shaft. Particularly, the bore of the revolution shaft 23 is formed such that a central axis V thereof is offset by a predetermined distance from a central axis U of the outer diameter of the revolution shaft. Therefore, when both the motors for the revolution and rotation are operated, the rotation shaft revolves around the central axis U of the revolution shaft so that the grindstone 28 fixed to the rotation shaft can rotate and simultaneously revolve.

Reference numerals 81 and 82 that have not yet been described designate flexible

supply tubes for supplying cooling water and cutting oil to the polishing surface 21 upon polishing a gemstone, respectively.

Next, an operating relationship in the apparatus of this embodiment will be described with reference to Fig. 3.

When the gemstone holder housing 61 for the gemstone holders to which gemstones to be processed have been fixed is clamped by the clamping means 65, and inclination angles, index angles and processing amounts for facets of the gemstones to be processed are determined, the control unit first operates the first motor until it receives a signal from the first sensor so as to place the gemstone holders at an initial feeding position, operates the second motor until it receives a signal from the second sensor so as to place the gemstone holders at an initial inclining position, and operates the third motor until it receives a signal from the third sensor so as to place the gemstone holders at an initial feeding position. Then, the control unit operates the second and third motors by outputting pulses corresponding to determined inclination and index angles so that the gemstone holders can have the determined inclination and index angles. Thereafter, the control unit outputs a command, which causes feeding to be made at a predetermined rate by a feeding distance corresponding to a processing amount determined in consideration of the material of gemstones to be processed, to the first motor.

Particularly, the control unit receives a signal from a rotation speed sensor 25c for measuring the rotation speed of the rotation shaft 25 shown in Fig. 3 and maintains the rotation speed to be constant by reducing the feeding speed if the rotation speed is low or increasing the feeding speed if the rotation speed is high.

When a travel of a feeding distance corresponding to a desired polishing amount is completed, the control unit stops the feeding and repeats the aforementioned procedure to process the next facet.

Reference numeral 25b designates a belt tension adjusting means for tightening the rotation belt 25a to prevent the rotation belt 25a from being loosened and coming off from the pulley 25 as the rotation pulley 25 rotates. Those skilled in the art can simply construct the belt tension adjusting means using a roller for supporting the belt and a hinge shaft and spring for supporting the roller, as shown in the figure.

Fig. 7 is a perspective view of an apparatus for polishing gemstones according to another embodiment of the present invention.

The embodiment shown in Fig. 7 is different from the embodiment shown in Fig. 1 in that it has a single gemstone holder and further includes a horizontally feeding means 110 capable of moving a vertically feeding device 130 corresponding to the supporting unit 30 of the embodiment of the Fig. 1, and a second polishing means 120 rotatably installed on the base 10 and having a polishing surface parallel with the base at a level higher than that of the polishing means 20. Further, the second polishing means 120 is constructed to rotate only without revolution.

Therefore, the apparatus of this embodiment cannot simultaneously polish a plurality of gemstones. However, the apparatus has an advantage in that after facets of a gemstone have been completely polished by the polishing means 20 with the polishing surface at a lower level, the gemstone is horizontally fed to and continuously processed by the second polishing means 120 with the polishing surface at a higher level to obtain smoother facets.

Industrial Applicability According to the present invention, there is provided an apparatus for polishing gemstones, which has a means for easily correcting processing or assembly errors of parts or errors resulting from mechanical deformation in use while automatically performing an inclining motion, a vertically feeding motion and an index motion of a gemstone holder, thereby obtaining a jewel with high-quality facets.

Further, according to the present invention, there is provided an apparatus for polishing gemstones, wherein a polishing surface can be caused to simultaneously rotate and revolve, thereby preventing concentrated wear of the polishing surface and improving processing accuracy of facets of a resultant jewel.

Moreover, according to the present invention, there is provided an apparatus for polishing gemstones, which has a means capable of finely adjusting levels of a polishing surface and a housing for supporting a plurality of gemstone holders fixed to a single cartridge. This apparatus has an advantage in that it can be used while deformation

occurring in the apparatus due to the use thereof is corrected.

It is intended that the embodiments of the present invention described above and illustrated in the drawings should not be construed as limiting the technical spirit of the present invention. The scope of the present invention is defined only by the appended claims. Those skilled in the art can make various changes and modifications thereto without departing from its true spirit. Therefore, various changes and modifications obvious to those skilled in the art will fall within the scope of the present invention.