US3811229A

US3811229A - Gem faceter

Info

Publication number: US3811229A
Application number: US00338406A
Authority: US
Inventors: E Montgomery
Original assignee: American Standard Inc
Current assignee: Trane US Inc
Priority date: 1973-03-05
Filing date: 1973-03-05
Publication date: 1974-05-21
Anticipated expiration: 1991-05-21

Abstract

A gem faceter comprising a pivot block which is vertically movable to various positions, a pivot arm pivotally mounted at one end to the pivot block, a head mounted to the other end of the pivot arm and adapted for movement to various positions about a pivot pin, a dop mounted in said head and adapted to be rotated about its axis to various positions, an index plate fixedly mounted on said dop and having markings thereon which indicate the number and position of desired facets to be ground on a gem held by the dop, an index plate clamp for locking the index plate successively in said desired marked positions relative to the head for grinding the desired facets, a lapping table adapted to be contacted by the dopped gem, a protractor for continuously indicating the angular position of the dop relative to the vertical, an adjustable stop for limiting the movement of the head toward the lapping table, a sensor mounted on the stop for sensing the degree of movement of the head toward the lapping table, an electronic circuit for translating the degree of movement sensed by the sensor into an electronic signal, and a visual indicator for indicating the value of the electronic signal and the degree of said movement, whereby the faceting angle may be detected and duplicated with great precision.

Description

[451 May 21, 1974 1 1 GEM FACETER [75] Inventor: Earl D. Montgomery, Warrington,

[73] Assignee: The American Standard Corporation, T'revose, Pa.

[22] Filed: Mar. 5, 1973 [21] Appl. No.: 338,406

[52] US. Cl 51/125, 51/216 LD [51] Int. Cl B24b 7/22, B24b 9/16 [58] Field of Search 51/71, 109 R, 125, 125 S,

51/122, 134.5 R, 216 L, 216 D, 216 H, 216

[56] References Cited UNITED STATES'PATENTS 1,214,009 1/1917 Coleman... 51/125 1,520,948 12/1924 Heinz 51/125 1,730,767 10/1929 Havlicek 51/229 2,829,472 4/1958 Salzer 51/125 3,098,327 7/1963 Malin l 51/125 3,110,136 11/1963 Spira 51/125 3,439,456 4/1969 Bailey 51/125 3,520,088 7/1970 Leibowitz 51/122 Primary Examiner-Othell M. Simpson v Attorney, Agent, or FirmSmith, Harding, Earley & Follmer [5 7 ABSTRACT A gem faceter comprising a pivot block which is vertically movable to various positions, a pivot arm pivotally mounted at one end to the pivot block, a head mounted to the other end of the pivot arm and adapted for movement to various positions about a pivot pin, a dop mounted in said head and adapted to be rotated about its axis to various positions, an index plate fixedly mounted on said dop and having markings thereon which indicate the number and position of desired facets to be ground on a gem held by the dop, an index plate clamp for locking the index plate successively in said desired marked positions relative to the head forgrinding the desired facets, a lapping table adapted to be contacted by the dopped gem, a protractor for continuously indicating the angular position of the dop relative to the vertical, an adjustable stop for limiting the movement of the head toward the lapping table, a sensor mounted on the stop for sensing the degree of movement of the head toward the lapping table, an electronic circuit for translating the degree of movement sensed by the sensor into an electronic signal, and a visual indicator for indicating the value of the electronic signal and the degree of said movement, whereby the faceting angle may be detected and duplicated with great precision.

10 Claims, 7 Drawing Figures PATENTED KAY 9 SHEET 3 0F 3 GEM FACETER BACKGROUND OF THE INVENTION This invention relates to grinding and polishing machines, and more particularly is concerned with machines for grinding facets on gem stones.

Conventional gem faceters are large, complicated pieces of machinery which are difficult to operate, especially by an amateur who is grinding facets on semiprecious gems as a hobby. While all such machines mount the gem to be faceted onto a dop, it is difficult for an operator to position the dop for the desired number and position of facets, and it is difficult for the operator to align adjacent facets, such as pavilion, girdle, and crown facets. Some such machines do not provide for positioning the dop vertically in a first head to grind the table of a gem, and require that the dop be removed from the first head and then placed and positioned precisely in an adapter head to grind the table.

In some of the prior art faceting machines, the dop is mounted in a quill rotatably mounted in a head which is pivotally mounted about a horizontal shaft so as to permit the gem mounted on the bottom of the dop to be moved in a vertical plane and brought into contact with the lapping table. For facet angles which are small with respect to the gem table, the grinding operation becomes increasingly difficult as the pivot pin of the head is moved upwardly and father away from the lapping table.

Prior art faceters included a large number of structural members, and those members were required to be of large size in order to'maintain the structural rigidity that is necessary if good repeatability of facets is to be achieved, since there was a tendency for the structural members to flex under the strain of lap drag.

It was also difficult in prior machines to maintain the mounting post in vertical alignment because this post was moved back and forth in a mounting groove for various facet angles. Grit and debris could accumulate in this mounting groove to cause small but important deviations in the vertical alignment of the post and facet angles.

Another disadvantage of a number of the prior art machines was that the dop-quill-head assembly tended to become fairly heavy so that the operator had to be very careful when placing the stone onto the lap in order to avoid damaging the stone or breaking it away from the dop. Another disadvantage was that the size and mass of the prior art machines increased their cost.

SUMMARY OF THE INVENTION It is an object of this invention to overcome the disadvantages of the prior art and provide a gem faceter of greater stability, of smaller size, and with fewer components than the prior art machines, and which is simpler,

- position relative to pivot arm 33 by a head clamp knob easier to use, and less costly. Other objects include pro- BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in side elevation of a gem faceter constructed in accordance with this invention;

FIG.2 is a view in top plan of the gem faceter of FIG.

FIG. 3 is a left end view in elevation of the gem faceter of FIG. 1;

FIG. 4 is a view in elevation on an enlarged scale of the micrometer which forms an element of the invention, taken as indicated by the circle indicated by the arrow 4 in FIG. 1;

FIG. 5 is a view in side elevation of the micrometer apparatus of FIG. 4;

FIG. 6 is a view in top plan of the micrometer apparatus of FIG. 5; and

FIG. 7 is a diagrammatic view of the electrical circuit of the micrometer apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the specific embodiment of the invention shown in the drawings, there is shown a gem faceter 11 which comprises a base 13 that rotatably supports a horizontal lapping table 15 positioned in a splash pan 17 made of a flexible rubber material and driven by a motor 19. A vertical post 21 is threaded through base 13, and may be moved vertically relative to base 13 by turning vertical adjustment knob 23 to thread post 21 through lock nut 25 which locks post 21 in desired'vertical position. Nut 25- bears against a mount 27 which rests on the top of base 13.

The top of post 21 is unthreaded and is received by hole 28 in a pivot block 29 which may be moved in a horizontal plane around post 21 as a pivot. Accordingly, pivot block 29 may be positioned at a desired vertical position by turning vertical adjustment knob 23 to move post 21 vertically, and' pivot block 29 may be positioned horizontally by rotating it to a desired position around post 21.

A pivot-block pulley 31 is fixedly mounted on pivot block 29. One end of a pivot arm 33 is pivotally mounted on pivot block, 29 by a shaft or pin 37 having one end threaded into a nut 39 and the other end clamped by a girdle block 41 separated from pivot block 29 by a spacer 43. Screw 45 clamps the girdle block 41 onto shaft 37 by closing slot 47 to bring por- 1 tion 49 of girdle block 41 to bear against shaft 37.

A head 51 is pivotally mounted on the other end of pivot arm 33 by a shaft or pin 53. Head 51 is locked in 55 which screws into a threaded hole in shaft 53.

A head pulley 57 is freely mounted on shaft 53 and is connected to block pulley 31 by an endless cable or timing belt 59. A protractor 61 is fixedly mounted on head pulley 57, and has markings indicating angles from 0 at top vertical marking 63 to at the horizontal marking. An angle indicator or pointer 65 extends from head 51 in alignment with the axis of a dop 67 mounted on head 51. Accordingly, a dop 67 is inserted .into head 51 and clamped therein by turning head clamp handle 69 of head clamp 70, stone 71 mounted on dop 67 is placed on the lap 15, the dop 67 is rotated about shaft 53 until the pointer 65 indicates the desired cutting angle, 42 for example, and the head 51 is clamped in place on shaft 53 by turning head clamp knob 55. The pointer 65 indicates the angular position of the dop axis relative to the vertical.

A programmed index plate 72 is fixedly mounted on dop 67 and is provided with notches 73 at predetermined and desired positions along its periphery to indicate the position and number of facets to be ground into the stone or gem 71. An index plate clamp 75 is mounted above head 51 and includes a finger 77 which is spring-loaded upwardly and is adapted to seat in the notches 73 to hold index plate 72 and dop 67 from rotation during the grinding of a facet. Finger 77 is locked in notches 73 against the spring force by the downward pressure from a locking screw 79.

in a conventional index plate, the notches are spaced evenly around its periphery and are numbered sequentially, for example, from 1 to 64 fora standard 64 posi-.

tion index plate. To cut a series of facets, the operator must select the notches by number and only these notches which are required for his specific type of cut. Instead of the conventional numbered notches, index plate 72 is programmed with just the notches needed for cutting the desired shape of stone. For example, the illustrated index plate 72 is programmed for cutting ovals. The notches are not numbered and are not spaced apart a uniform distance. Other index plates are programmed for cutting other desired gem shapes, such as oval brilliant, or marqui.

' The degree of angular movement of the pivot arm 33 about pin 37, and also the degree of angular movement about pin 37 of dop 67 and head 51, which are clamped to pivot arm 33 by head clamp knob 55, is limited by V a stop member 91 which extends from pivot block 29 and" supports a bracket 93 having a sensor 95 mounted thereon. A stop adjustment screw 97 is adapted to contact pivoted upper plate 95a of sensor 95 to move it toward fixed lower plate 95b and signal an electrical circuit including anamplifier and a meter indicator which is hereinafter explained. Screw 97 is adjustably mounted by being threaded into a rod 99 extending from pivot arm 33. If desired, sensor 95 may be removed so that stop member 91 forms a positive mechanical stop for screw 95 and arm 33.

One end of a counterweight arm 100 is pivotally mounted on pivot arm 33, and a counterweight 101 is mounted-on the free end of arm 100. A stop 103 projects inwardly from counterweight arm 100 and is adapted to contact pivot arm 33 in the rearward position of arm 100 shown in FIGS. 1 and 2 so as to counterbalance the weight of head 51 to make the dop 67 feel light and easy to handle by the operator.

counterweight 101 may be moved to its forward position by pushing counterweight 101 and counterweight arm 100 forwardly about its pivot until stop 103 again engages pivot arm 33 at a position closer to head 51. ln this forward position, the weight of counterweight the gem 71 is held against lapping table 15 to grind the desired number and position of girdle facets. Block 41 is called a girdle block because the head 51 is inserted into block 41 when the girdle facets are being ground, and pivot block 29 is vertically positioned so that pin 37 is in about the same horizontal plane as lapping table 15. The facets around the sides of a gem are called girdle facets, the facets above the girdle facets are crown facets, the facets below the girdle facets are pavilion facets, and the large flat facet above the crown facets is the table.

After the girdle facets have been ground, head 51 and dop 67 are removed from girdle block 41 as a unit andare mounted on shaft 53 on the forward end of pivot arm 33. Accordingly, since there has been no relative movement between dop 67 and head 51, the pavilion facets may be ground in perfect alignment with the girdle facets. During the grinding operation, the operator may lift a dop and head away from lapping table 15 for visual inspection of the stone or gem 71 by rotating dop 67, head 51, and pivot arm 33 around shaft or pin 37.

Regardless of the position of arm 33 the protractor 61 is always maintained in the same position relative to the vertical and to the plane of the lap table, because rotation of arm 33 around pin 37 causes rotation of block pulley 31 which moves cable 59 to rotate head pulley 57 to hold protractor 61 in the same position relative to lapping table 15.

During the grinding of the facets, pivot arm 33 moves downwardly, as does stop adjustment screw 97 which moves against sensor 95 that provides a signal which is translated by its electrical circuit to actuate a visual indicator with a pointer that moves in response to the progress of the grinding. When the pointer reaches a I certain marking on the visual indicator, the grinding of the facet is finished. This visual indicator makes it easy for the operator to grind all facets of the same course to the same degree so that they are identical.

It is to be noted that pivot block 29 rotates freely about'vertical post 21 permitting pivot arm 33 and the gem 71 to sweep across the lapping table 15. Post 21- justment of the facet-to-girdle angle.

101 bears downwardly against dop 67 and helps to hold the gem 71 against lapping table 15. This forward position of counterweight 101 is useful in polishing the gem 71 automatically without requiring the hand or attention of the operator.

In operation, a preformed stone or g'em 71, preformed in that it has been ground to its approximate final shape, is adhesively attached to the dop 67 with wax in the usual fashion. Head shaft 53 is inserted into hole 105 in girdle block 41 and is held in place by tightening set screw 107.1ndex plate 72 is rotated to various notches and held in place by index plate clamp 75 and Head 51- may be locked in a position with dop 67 vertical with respect to lapping table 15 so that the table may be cut on gem 71 without using an adaptor block and without removing the dop 67 from head 51. The electical circuit for the faceting micrometer is as shown in FIG. 7 and provides a nonlinear output so that the meter reading gives a highly accurate indication of when the facet has been ground to the proper depth. lnput lines 111, 112 receive 1 15 volts AC which are impressed across the primary of a transformer l 13. A switch 115 is provided in line 111. The output of transformer 1 13 is 12 volts AC, and this voltage is rectifiedby diode 133, limited by Zener diode 135, and filtered by capacitor 1 17. Unijunction transistor 1 19 and

resistors

139, 143 and 145 and capacitor 141 constitute an oscillator the output of which is in the audio range and is amplified by a direct-coupled transistor 121. The collector output is applied to the sensor 95, a variable capacitor having a fixed plate 95b and a pivoted plate 95a which transmit a signal proportional to capacity to a receiver transistor 123. The output from transistor 123 is clamped by a germanium diode 125, thus producing a direct current through meter 127 which is proportional to the output from sensor 95. Meter 127 is zeroed by a small off-set voltage through the resistor network that includes 3.3 k ohm resistor 129 and 470 ohm resistor 131.

The capacitor sensor 95 comprises pivoted plate 95a and fixed plate 95b, and pivoted plate 95a is driven toward plate 95b as the grinding action on the stone 71 proceeds, producing a non-linear output approximately according to the square root law. Accordingly, sensitivity of the meter reading increases as the cutting or grinding proceeds. This high sensitivity permits great accuracy as to repeatability of facet depth, since the cutting is stopped when the needle of the meter indicates a certain meter reading.

In practice, satisfactory results have been obtained where transformer 113 is a 115/12 volt transformer, rectifier 133 is a 12 volt transistor diode, Zener diode 135 has a reverse breakdown voltage of 12 volts, resistor 137 is 47 ohms, capacitor 117 is a 250 microfarad volt capacitor, resistor 139 is 3.9 k ohms, capacitor 141 is 0.1 microfarads, resistor 143 is 500 ohms, resistor 145 is 47 ohms, capacitor 147 is 0.02 microfarads, resistor 149 is 500 ohms, capacitor 151 is a 1 microfarad 6 volt capacitor, resistor 153 is 100 ohms, capacitor 155 is a 5 microfarad 6 volt capacitor, resistor 157 is a 1 megohm resistor, resistor 159 is 1 k ohms, resistor 161 is 100 ohms, capacitor 163 is a 5 microfarad 6 volt capacitor, and capacitor 165 is a l microfarad 50 volt capacitor.

The operation of the electronic micrometer is as follows. A dop stone 71 rests on the lap 15. The head 51 is locked on the pivot arm 33 so that the stone 71 is addressed to the lap or lapping table 15 at a desired angle, for example 45, as indicated by the protractor 61. Stop adjustment screw 97 is mounted on rod 99 extending from pivot arm 33 and as the pivot arm 33 moves downwardly as the cutting of the stone 71 progresses, the stop adjustment screw 97 contacts the upper plate 95a of sensor 95 which is lightly spring loaded and may be compressed about one-tenth of an inch before it stops the downward movement of pivot arm 33. As the pivot arm 33 moves downwardly, upper plate 95a moves downwardly proportionately and sends a signal to the amplifier. Although the movement of sensor plate 95a is linear with respect to movement of the pivot arm 33, the output from sensor 95 is non-linear, increasing approximately according to the square of the distance travelled by upper plate 95a. Thus as the cutting or grinding of the facet proceeds, the sensor 95 becomes increasingly sensitive to the movement of the stone as the stone material is ground away. At the high end of the meter scale, movement of the stone 71 is about one-thousandth of an inch per meter division. This high sensitivity enables the cutter to cut or grind a series of facets, as required in a round brilliant, for example, by advancing the index plate '9'5a and observing the meter. It is not necessary to examine the stone 71 after each facet is cut, you simply out each facet to the same meter reading.

The pivot block 51 is important to the easy use of the electronic micrometer because stop screw 97 may be adjusted to contact sensor 95 regardless of the faceting angle or the size of the stone 71.

Gem faceter 11 is adapted for automatic operation in that an operator can set the faceter to grind with the dop stone 72 on lapping table 15 and walk away and the faceter grinds until pivot arm 33 brings stop adjustment screw 97 into contact with a mechanical or electrical stop mechanism. The head and arm mechanism of gem faceter 11 are balanced so as to grind facets automatically, which is something that cannot be done with a conventional high-post gem faceter. An operator can handle a number of gem faceters 11 at the same time.

An angle compensator 167 is provided for adjusting or rotating index plate 72 and dop 67 relative to head 51 for an angle less than the angle between notches 73 on index plate 72 without moving head 51 or loosening head clamp knob 55. For example, the operator may wish to rotate index plate 72 a quarter degree or a half degree when it is ascertained by visual inspection that facets on stone 71 are not exactly aligned after transfer dopping, an operation wherein the stone 71 is transferred to another dop. The table of stone 71 is adhesively attached to dop 67 during the grinding of the girdle and pavilion facets. Then stone 71 is transferred to another dop and the pavilion is adhesively adhered to the dop so that the table facet of stone 71 may be ground. During this transfer of the stone 71 from one dop to another, a small misalignment may occur between the position of stone 71 with the'first dop and the second dop.

Angle compensator 167 includes an adjustment block 169 which is pivotally mounted on head 51 so as to be rotatable about the center axis of the dop 67, a rotary adjustment screw 171 which is threaded through block 169 and is adapted to abut against the broadened base of pointer 65 fixedly mounted on head 51, and a spring 173 with one end mounted on head 51 and its free end bearing against the upper portion of adjustment block 169, above its pivot, to urge block 169 toward the head of rotary adjustment screw 171 Finger 77 is pivotally mounted at one end in the top of block 169, and the other end of finger 77 is positioned in a vertical notch in a front plate 177 having a rearwardly extending flange 179 through which is threaded locking screw 79 having a shoulder which bears down on finger 77 to hold it in notches 73.

In operation of angle compensator 167, block 169, finger 77, locking screw 79, front plate 1 l7 and flange 179, index plate 72, dop 67, and stone 71, all move as a unit and rotate about the longitudinal axis of dop 67,

moving relative to head 51. While this rotary adjust- .a head pivotally mounted on the other end of the.

pivot arm, a dop rotatably mounted in said head,

index plate means fixedly mounted on said dop for rotatively positioning said dop to grind desired facets on a gem held by said dop, index plate locking means for holding the index plate means and dop indesired positions relative to said head for grinding the desired facets, a lapping table adapted to be contacted by the gem mounted on said dop, and means forindicatingthe angular position of the dop relative to the vertical. 2. The gem faceter of claim '1 including adjustable stop means for limiting the movement of said head around a horizontally positioned pivot.

' 3. The gem faceter of claim 2 including micrometer sensing means mounted on said stop means for sensing the degree of movement of a gem mounted on said dop.

4. The gem faceter of claim.3 including means for translating said degree of movement sensed by the sensing means into an electronic signal, and visual means adapted to receive the electronic signal andvisually indicate its value,

whereby the depth of the facet may be detected and duplicated with great precision.

S. The gem faceter of claim '1,

said index plate means including an indicator plate in the form of a disk attached to the dop,

and a number of notches formed in the perimeter of the index plate,

said notches being programmed so as to grind facetsof desired number and position.

v 6. The faceter of claim I,

including protractor means which indicates the angle of the dop relative to the vertical.

7. The gem faceter of claim 6,

said protractor means including a pulley fixedly mounted onsaid pivot block, a head pulley freely mounted on a shaft extending between the head and the pivot 'arm,

a protractor with angle indicating markings fixedly mounted on the head pulley,

a pointer fixedly mounted onthe head and adapted to point to the protractor markings to indicate the angle between the dop andthe vertical,

and a .cable trained around said pulleys whereby movement of the dop and pivot arm about the pivot block pivot pin causes relative movement of the protractor to maintain its attitude in space,

whereby the position of the pointer against the protractor markings continuously indicates the angle between the dop and the vertical. I

8. The gem faceterv of claim 1 including counterweight means mounted on the pivot arm and having a first positionfor making the head and dop lighter and easier to handle,

stop means for holding the pivot arm in said first position, a

a second position wherein its weight bears against the gem to hold it in contact with the lapping table to assist in polishing the gem automatically,

Y and stop means for holding the pivot arm in said second position. I

9. The gem faceter of claim 1 including angle compensator means for adjusting the rotative position of said index plate means without unlocking said index plate locking means.

10. The gem faceter of claim 1 wherein said angle compensator means includes an adjustment block pivotally mounted on said head and connected to said index plate means,

adjustment screw means threaded through said adjustment block for rotating said adjustment block and index plate means in one direction,

and spring means pressing against said adjustment block and urging rotation thereof in the opposite direction.

Claims

1. A gem faceter comprising a base, a vertical post mounted in said base, means for moving said post to various vertical positions and locking it in place, a pivot block mounted on said post and movable vertically therewith, a pivot arm having one end pivotally mounted to the pivot block, a head pivotally mounted on the other end of the pivot arm, a dop rotatably mounted in said head, index plate means fixedly mounted on said dop for rotatively positioning said dop to grind desired facets on a gem held by said dop, index plate locking means for holding the index plate means and dop in desired positions relative to said head for grinding the desired facets, a lapping table adapted to be contacted by the gem mounted on said dop, and means for indicating the angular position of the dop relative to the vertical.

2. The gem faceter of claim 1 including adjustable stop means for limiting the movement of said head around a horizontally positioned pivot.

3. The gem faceter of claim 2 including micrometer sensing means mounted on said stop means for sensing the degree of movement of a gem mounted on said dop.

4. The gem faceter of claim 3 including means for translating said degree of movement sensed by the sensing means into an electronic signal, and visual means adapted to receive the electronic signal and visually indicate its value, whereby the depth of the facet may be detected and duplicated with great precision.

5. The gem faceter of claim 1, said index plate means including an indicator plate in the form of a disk attached to the dop, and a number of notches formed in the perimeter of the index plate, said notches being programmed so as to grind facets of desired number and position.

6. The faceter of claim 1, including protractor means which indicates the angle of the dop relative to the vertical.

7. The gem faceter of claim 6, said protractor means including a pulley fixedly mounted on said pivot block, a head pulley freely mounted on a shaft extending between the head and the pivot arm, a protractor with angle indicating markings fixedly mounted on the head pulley, a pointer fixedly mounted on the head and adapted to point to the protractor markings to indicate the angle between the dop and the vertical, and a cable trained around said pulleys whereby movement of the dop and pivot arm about the pivot block pivot pin causes relative movement of the protractor to maintain its attitude in space, whereby the position of the pointer against the protractor markings continuously indicates the angle between the dop and the vertical.

8. The gem faceter of claim 1 including counterweight means mounted on the pivot arm and having a first position for making the head and dop lighter and easier to handle, stop means for holding the pivot arm in said first position, a second position wherein its weight bears against the gem to hold it in contact with the lapping table to assist in polishing the gem automatically, and stop means for holding the pivot arm in said second position.

10. The gem faceter of claim 1 wherein said angle compensator means includes an adjustment block pivotally mounted on said head and connected to said index plate means, adjustment screw means threaded through said adjustment block for rotating said adjustment block and index plate means in one direction, and spring means pressing against said adjustment block and urging rotation thereof in the opposite direction.