US2579666A - Diamond cutting machine - Google Patents

Description

Dec. 25, 1951 c, HANS 2,579,666

DIAMOND CUTTING MACHINE Filed March 20, 1948 2 SHEETS- SHEET l "HHEHHHHHI ea H.

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Patented Dec. 25, 1951 DIAMOND CUTTING MACHINE Charles A. Hans, Wood-Ridge, N. J., assignor to Jewel-Smiths, Inc., Boston, Mass., a. corporation of Massachusetts Application March 20, 1948, Serial No. 16,015

This invention relates to machines for grinding facets on precious and semi-precious stones and, more especially, to improvements in a machine for grinding facets peripherally of the girdle between the crown and pavilion of a diamond, as shown in Edward Goldstein Paten Number 2,340,659, of February 3, 1944.

It is customary to cut precious and semiprecious stones, sometimes called brilliants, so that they have a cone-shaped crown and a coneshaped pavilion located base to base with a narrow band or girdle area between them. The crown is truncated and has a surmounting flat surface called the table and its conical surface is faceted. The pavilion has a truncated apex and its conical surface is also faceted. Prior to the aforesaid Patent No. 2,340,659 the girdle was left unpolished, that is, rough and uncut. In that patent, however, there is disclosed a novel diamond in which the girdle is cut by grinding to form a plurality of polished facets. The provision of these polished facets in the area of the girdle improves the brilliance of the diamond, provides for better anchoring surfaces when the diamond is placed in a setting, and permits easier cleaning as well as other advantages which will appear by reference to that patent. The conventional machine for grinding stones has a dop for holding the stone in a position to be operated upon by a lap, but such machines have been designed primarily to cut the facets on the crown and pavilion as distinguished from the girdle, and are not suitable for cutting facets in the girdle area. In most of such prior machines the stone has been cemented to the dop with an adhesive or sealing wax with the consequent requirement that when the succeeding cut was to be made the stone had to be removed, turned through the proper angle and re-fastened to the dop before this next operation could be performed. While this was not particularly disadvantageous when cutting the comparatively large facet areas of the pavilion and crown which require a long time so that the time required to remove and replace the stone was not disproportionately large, considerable delay and added cost are caused by having to detach and reattach the stone for each out along the girdle areas as these cuts can be made fairly rapidly. Some prior machines have employed a dop provided with mechanical means for holding the stone by engagement with the pavilion and/or the crown, but, on the whole, these have not proved entirely satisfactory because they have been too exacting to manipulate because the 2 Claims. (C1. 51-229) parts have not held the stone securely in place and because the parts obscured or concealed the stone so that the lapidary was unable clearly to see the stone during the grinding operation.

Objects of this invention are to improve the prior machines in such aspects as to make them especially suitable for cutting the minute facets at the girdle area of a stone, regardless of its size, to minimize damage to the faceted surfaces, to provide for smoother and easier operation, better visibility of the work during the grinding operation, and greater efiiciency without sacrificing any of the features and advantages of prior machines.

According to the invention, the machine comprises essentially a driven lap having a substantially horizontal grinding face composed of a suitable abrasive material, a dop into which the stone may be set and secured, and means for effecting movement of the dop to and from the grinding surface so as to bring the portion of the stone being ground into juxtaposition with the grinding surface and to turn it about a vertical axis normal to the grinding surface in order to orient the stone, that is, to bring the grain thereof substantially parallel to the direction of movement of the grinding surface at its point of contact therewith. As illustrated, the dop is rotatably suspended by a spindle approximately midway between the center of rotation of the lap and its peripheral edge near one end of a horizontal arm, the opposite end of which is fixed to a screw by means of which it and hence the dop may be moved vertically. The spindle is free to move vertically a limited amount in the arm, and a knob fixed to the upper end of the spindle affords means for rotating it about its vertical axis. A look screw is arranged in a boss integral with the arm and may be set up to lock the spindle in any given angular position Without interfering with its vertical movement in the arm. The dop itself includes a block fixed to the lower end of the spindle, the block having a slot therein from its lower end upwardly to form spaced, parallel walls joined at their top by a transverse wall, and between the walls there is situated the diamond clamping members. One element of the clamping members is rigidly fastened between the walls, and to this member there are fastened a plurality of guide pins upon which is arranged to slide the other member. These members are in the form of legs, and near the lower end of each leg there is journaled in a bearing sleeve, set into an aperture in the leg, a spindle. On the inner end of each spindle there is a specially shaped surface for engagement with the stone, and a screw is rotatably fixed in one leg and threaded into the other so that upon rotation of the screw the legs may be drawn toward each other to clamp the stone between the specially shaped surfaces. In a preferred form of the invention one of the clamping members is recessed and has a faceted inner surface for engagement with the pavilion, and the other has a fiat surface for engagement with the table of the stone. members is rotatable about axes parallel to the axis of the stone, one of which is coincident with the vertical axis of the stone, and the other of which is offset therefrom. In this form the axes may be parallel to the surface of the lap. but preferably are inclined at an angle thereto, this angle being selected in accordance with the angle at which the facets are to be cut. To this end the legs are inclined to the spindle upon which the block is supported at an angle which is a complement of the angle at which the facets are to be ground. In this form, that is wherein the legs are inclined, the lower ends of the legs are eccentric with respect 'to the axis of the spindle which supports the dop so that rotation of the dop will move the diamond bodily in a circle over the surface of the lap' rather than about a point. The legs are tapered near their lower ends and recessed on their inner surfaces, and the clamping members have annular shoulders for contact therewith. Rotation of the screw tom-draw the legs together therefore frictionally engages the clamping members with the diamond and their shoulders with the legs to immobilize clamping members as a whole. To permit rotation of the diamond about its vertical. axis, the screw is released slightly and the dia-- mcnd may then be rotated by turning a knob attached to one of .the spindles without releasing the diamond.

The invention will now be described with reference to the accompanying drawings in which:

Fig. 1 is a side elevation of apparatus with which the present invention is concerned, showing a driven lap, a dop for holding a precious or semi-precious stone, and means for adjustably supporting the dop in operating relation to the lap;

Figs. 2 and 3 show a vertical elevation and top plan view of a stone in which the facets in the girdle portion are cut at an angle to the vertical axis of the stone;

Figs. e and 5 show corresponding views of a stone in which the facets in the girdle area are cut parallel to the vertical axis of the stone;

Fig. 6 is a diagrammatic section through the.

vertical axis of the stone showing only one-half thereof and illustrating the angle which the girdle facets made with the vertical axis of the stone;

Fig. '7 shows a corresponding section in which the plane of the facets in the girdle is parallel to the axis of the stone;

Fig. 8 is a vertical side elevation of the dop partly insection;

Fig. 9 is a vertical end view of the dop shown in Fig. 8 looking from the right-hand side thereof;

a Fig. 10 is a side elevation of the dop enlarged with a stone clamped therein and resting in engagement with the upper grinding surface of the lap;

Fig. 11 is a slightly modified form of apparatus 'wherein the dop is constructed to hold the stone Each of the clamping with its vertical axis parallel to the grinding surface of the lap; and

Fig. 12 is an end elevation of the clamping member which receives the pavilion showing its inner surface faceted.

Referring to the drawings, there is shown in Fig. 1 an apparatus it for cutting, by grinding, facets around the girdlearea of a brilliant, for example, a diamond. The conventional diamond is cut, as illustrated in Figs. 2 to 7 inclusive, to have a crown portion C surmounted by a flat table portion T and a subjacent pavilion portion P which terminates in a truncated apex called the culet c. The crown and pavilion are ground to provide a large number of facets F, F, and, according to at least one method of cutting, 32 facets are cut in the crown and 24 in the pavilion.

.To avoid too sharp and hence too fragile corners where the plane surfaces of the facets on the crown meet those on the pavilion what is known in the trade as the girdle portion G is left unground between the crown and pavilion portions. The unground girdle is rough, non-reflective and a place for catching and retaining dirt, thus reducing the brilliance of the stone and making it difficult to keep it clean. In accordance with the aforesaid patent, however, this girdle area is ground to provide a plurality of facets f to afford among other advantages increased brilliance of the stone, a better anchoring area for the setting, and to facilitate keeping it clean. In one form,,as shown in that patent, the planes or fiat faces of the facets, illustrated by the line a/a of Fig. 6, are inclined at a small angle which may vary as desired from approximately 10 to 30] from the vertical axis ra: of the stone toward the crown so that, as shown in Fig. 3, the surfaces of the facets are seen when looking down upon the top of the brilliant. This increases the sparkle and brilliance of the-diamond. However, in another form of the invention illustrated by the line 17-?) of Fig. 7, the planes of the facets are made parallel to its vertical axis :c-.r.

Heretofore there have been numerous grinding, polishing and lapping machines, for cutting the facets on the crown and pavilion portions of stones, and it has been customary to mount the work which is to be ground in a carrier commonly known as a dop and to hold the work by means 7 ting the facets on the crown and pavilion, and

in most instances the stone has been fastened to the dop by means of cement, sealing wax or some other adhesive compound. Since the operation of forming, by cutting, the facets on the crown or pavilion is a slow one, it made little difference that it was necessary to remove the work after In the grinding of the facets around the girdle area, however, the area involved during. any given operation is so small that a given facet may be ground in a very short time, and hence the time required to dismount and re-mount the work between the grinding of each successive facet becomes a disproportionately large part of the entire operation, with the result that time is lost and the cost is increased. The invention is primarily concerned, with the provision of an improved dop for holding a stone in a position to grind the facets in the girdle area at the required angle and which will permit indexing of the work for grinding the successive facets circumferentially of the girdle without dismounting and re-mounting the work for each successive grinding operation. Further objects are to reduce chattering, eliminate scratching, and to provide means for holding any size stone.

The apparatus as shown, Fig. 1, comprises es sentially a grinding lap I2 which is motor driven, a dop M for supporting the work in operative position with respect to the lap, an adjustable overhanging arm l6 from which the dop is susl pended, and a supporting structure or frame It for the arm.

The frame or supporting structure It is com prised of an upright hollow post 22, stiffened by a web 23, fixed at its lower end to a horizonal base which extends laterally from one side thereof. A bracket 24 is fastened to the post 22 substantially midway betweenits upper and lower ends in a position to project horizontally over the base, and is constructed to hold a motor M with its shaft 26 in a substantially vertical position. To the upper end of the shaft 23 there is fixed a horizontal circular table 28 which is adapted to be rotated by the motor, and fastened to the upper surface of the table is a flat grinding disk 3!], made of an abrasive material, suitable for cutting diamonds, the table 28 and disk 30 constituting what is known in the trade as a lap or skeif. The dop I4 is supported above the lap and at a distance from the center of rotation thereof, that is, substantially midway of its axis of rotation and its periphery by a spindle 32, to the lower end of which it is fastened, which is mounted near the free end of the arm I6 for rotation about its vertical axis and for vertical movement therein. As illustrated, the spindle 32 passes through and is splined in a sleeve 34 set into a vertical aperture 36 formed in the arm [6 and free to rotate therein. A collar 40, fixed to the upper end of the spindle, engages the top of the arm and prevents the spindle and sleeve from slipping downwardly through the aperture 35. A knob 42is also fixed to the spindle and serves to facilitate rotation thereof about its vertical axis with respect to. the lap to change the position of the dop, for example, to permit orienting the stone so. that it may be ground in the direction of its grain structure. In order that the dop may be fixed at any given angular position about its vertical axis, but without inhibiting free vertical movement, a lock screw 31 is threaded into an aperture 39 formed in a boss 4! on the underside of the arm against the sleeve, and a knob 43 is provided for setting it up or backing it off. The arm I6 is in turn fastened to the upper end of a long screw 44 which projects downwardly therefrom into the hollow post 22. The threaded portion of the screw passes through a threaded aperture in a worm gear 46 set into a recess in the hollow post 22 so that it will not have vertical movement but may be rotated, with which there meshes a worm 48 mounted on a horizontal shaft 49, journaled in the web 23. The shaft projects laterally from the post and may be provided with a handle, not shown, for effecting rotation thereof. By rota tion of the handle, the screw 44 may be raised or lowered in the pest, and by way of the arm Hi the dop l4 may be raised and lowered a corresponding amount to bring the dop close to the tween the walls 52 by means of pins 58.

surface of the lap. With this construction it is the weight of the dop which holds the stone against the top of the skeif during the grinding operation.

The dop, as shown in Figs. 8, 9 and 10, comprises essentially a supporting block 59 fastened to the lower end of the spindle 32, with which there are associated movable members designed to engage and hold the work in a securely clamped position during the grinding operation but capable of manipulation to index, that is, to turn the work from position to position to permit grinding successive facets thereon or to release the work. The form of the dop illustrated in the aforesaid figures is designed to cut the facets circumscribing the girdle at an angle to the vertical axis, that is, inclined toward the crown, and to this end a slot is formed in the block from its bottom side upwardly so as to provide a pair of spaced, depending walls 52 separated by a sloping surface 54 (Fig. 8) inclined to the axis of the spindle 32 at an angle which is the complement of the angle at which the facets are to be cut. A leg 55 is rigidly fastened within the slot be- The leg 56 is inclined with respect to the axis of the spindle 32, that is, it is substantially normal to the surface 54 so that its lower end 60 is eccentric with respect to the axis of the spindle and is tapered as shown in Fig. 9. In the lower tapered end of the leg 56 there isa transverse aperture 62 which is parallel to the surface 54 in which there is disposed a bearing sleeve 64. Within the bearing sleeve there is rotatably positioned a shaft 56 upon the inner end of which there is fastened a circular disk 68 having a fiat, smooth inner face I0 and a fiat, annular shoulder H which bears against the leg bordering the aperture 62. The inner surface of the leg is recessed at 13 so as to accommodate the disk 68 with its,

end face 10 substantiall below the plane of the im'ier surface of the leg and to provide a bearing surface for the annular shoulder H. The terminal end of the leg 56 is cut off at an angle so as to be substantially parallel to the surface of the lap, and the dimensions of the table are such that its periphery does not project beyond the end of this leg. Since the spindle is not fast the disk may be dismounted at any time and replaced by a different size disk.

There are fixed in the upper portion of the leg 56 a plurality of spaced parallel pins 12 (Figs. 8, 10 and 11), these pins being so located that one of them is situated on the center line of the leg near the upper end thereof, while the other is situatedon the center line of the leg near the lower (Fig. 9). The pins 12 are fixed in the leg so that they project from the inner surface thereof substantially parallel to the surface 54, and there is slidably mounted on their free ends a leg 74 corresponding to the leg 56. To this end the leg 14 is provided with a plurality of apertures 16 for receiving the ends of the aforesaid pins 12. The lower end of the a transverse aperture I8 in which there is posi leg 14 is tapered as is the leg 56, and has in it tioned a sleeve for the accommodation of a shaft 82 for rotation therein, the shaft having at its inner end a head 84 and at its outer end a knob 86. The head 84, as shown in Figs. 8 and 10, has at its under side an annular shoulder 88 for engagement with the inner surface of the leg 14, the latter being recessed at 89 in a manner corresponding to the recess 13 in the leg 55. The inner end face of the head 84 is recessed 7 at '90 (Fig. 13) and is cut to have a plurality internal facets. 92 which correspond in number anddimensions to the facets in the pavilion portion of the work which is being operated upon. As'thus constructed, the work, that is a stone, is mounted between the disk 88 and thehead 84, with the table T of the stone in engagement With the inner, flat surface is of the disk 33,

and with the pavilion P seated in the recess 99, as shown in Fig. 10. It is to be observed that the bearing apertures 62 and 863 in the legs 56 and M are not in axial alignment so that-the axes of rotation of the disk and head .do. not coincide. This axis of the head is coincident with the vertical axis of the stone, and is inclined to the surface of the lap at the angle at which the facet is to be cut. The axis of the desk, however, while being correspondingly inclined to the lap, is offset and parallel to the axis of the head so that it lies outside of the vertical axis of the stone, hence the surface of the disk is eccentric with respect to the table of the work. It is also to be observed that since the lower end of the arm 56 is eccentric with respect to the axis of the spindle 32 the disk 6% is eccentric thereto and will move in a circle above the surface of the lap rather than a single point when the spindle is rotated; hence making use of a considerable area of the grinding surface of the lap and reducing the wear thereof;

, In order to clamp the stone securely so that it will not rotate about its vertical axis, that is, the axis which passes through the culet c and is normal to' the table T during the grinding operation, the leg l4 must be drawn toward the leg 55 so as to hold the work under suificient pressure, as frictionally to engage its table T with the surface ill of the disk 68, and the shoulders 88 and H of the head 8 and the disk 68, respectively, with the legs i4 and 56 to lock them by friction against any rotational movement. The head lit and disk 58 may for conveniencebe referred to as adapters. To this end an aperture 94 is provided in the mid-portion of the leg 56 in which there is rotatably placed a spindle 95 (Figs. 8 and 19) having a threaded end portion 98 which passes through a threaded aperture I535 formed in the leg M so that by rotation of thespindleiitthe leg it may be moved to or from the leg 56. As illustrated, the spindle 96 is fixed so that'it does. not move with'respect to the leg 56 by a locking ring 62 seated in a groove Mi l cut into the peripheral surface of the spindle and a groove 55 cut into the inner surface of the aperture at. A knurled knob m8 at the outer end of the spindle provides for ease of rotation of the spindle.

Theuse of'the clamping disk 68 is advantageous in that its flat surface may easily be kept clean, and will accommodate the table of any size stone without damage thereto by burning, scratching-0r otherwise damaging the same. It has the further advantage that since it does not positively grip the crown of the diamond when the stone is turned about its vertical axis by rotation of the member 34, the surface of the table will be unconstrained and will turn freely on the surface of the disk. Still another important advantage is that since the crown and table of the diamond arenot fixed either as to rotational movement or movement at right angles to its vertical axis whenthe clamping surface is horizontal, that is, normal to the spindle 32 instead of inclined thereto. The leg 58 is fixed between the Walls 52 in a vertical position, that is, parallel to the axis of the spindle 32. The leg 'i l, the means for moving it to and from the leg 5%, and the work-engaging members correspond exactly to the construction described above with the exception that they in position and render the parts fixed.

worm s9 is then rotated to bring the dop vcrmembers .64 and Stare brought together, a litthereto.

will now be located in planes parallel and normal to the surface of the lap rather than inclined The spindle 82 in this case is parallel to the surface of the lap and coincides with the vertical axis of the stone. The spindle 5% of the disk 52 is also parallel to the surface of the lap but is not coincident with the vertical axis of the work beingspaced upwardly therefrom.

As a result the surface or table T of the stone is not concentric with the axis of rotation of the disk 58 but is eccentric with respect thereto, that is, engages it in an ofi-center relationship.

In whichever form the apparatus takes, that is, whether the work is held with its vertical axis inclined to the surface of the lap or parallel to the surface of the lap, it is apparent anysize stone may be mounted in the dop, that the stone may rigidly be held at one end but free to align'itself at the other end during the grinding operation, chattering is eliminated, that the flat surface of the disc will eliminate scratching, that the work may be indexed to turn it about its vertical axis from one position to the next position for grinding the successive facet very readily and easily without touching the Work with the fingers and accurately so as to insure the correct location of the successive facets, and that the work may be positioned by proper rotation of the dop as a whole around the vertical axis of the spindle 32 so that the grinding will be performed ina direction which is substantially parallel to the grain of the stone at its point of contact with the lap. The freedom of vertical movement of the spindle 3'2 permits the stone to rest on the surface of the lap solely by gravity. A dop provided with the foregoing adjustments greatly facilitates and improves the accuracy of grinding, particularly with small stones which are difiicult to handle with the fingers and which, if attached by cement to the dop, require considerable manipulation and a chance of error in forming the minute facets at the proper spacings and angles with respect to each other.

In operation the stone is mounted with its table '1 in engagement with the surface it of the 8d and with its pavilion P seated in the recess 953 of the head 86, and then the leg is is drawn toward the leg 56 by rotation of the knurled knob l so as firmly to clamp the stone The tically downward toward the surface of the lap 52 to engage the girdle portion G of the stone with the surface. "The play afforded by the slid ing frictional engagement of the table T with the fiat surface'of the disk 68 allows the. stone to align itself with the parts without damage thereto. The play afforded by the splined connection between the spindle and the sleeve perunits the stone to rest on the lap solely by the gravitational pull on the dop. Since the lower ends of the legs 56 and it are tapered, the girdle portion of the work will project downwardly from their lower ends and be exposed for grinding to a maximum extent without being obscured or hidden by portions of the dop, and hence examining and checking of the grinding operation will be greatly facilitated. After the stone has been fixed in position, the dop is turned about the vertical axis of the spindle 32 to bring the grain thereof substantially parallel to the direction of rotation of the grinding surface at its point of contact therewith, the lay of the grain having been determined prior to mounting it in position. The motor is then started so as to rotate the lap and hence to grind the facet, and, as soon as a given facet is completely ground, the stone may be indexed by rotating the knob I93 just sufficiently to relieve the frictional engagement of the head 84 and the disk 68, whereupon by rotation of the knob 96 fastened to the spindle 82 the stone itself may be rotated about its vertical axis to bring the succeeding portion of the girdle into a position to be ground without completely releasing the stone. By suc cessively indexing the stone about its vertical axis, facets may be ground throughout the peripheral area of the girdle accurately and rapidly.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. A dop for holding a diamond in juxtaposition to the grinding surface of a rotating skeif comprising a body portion secured to one end of a dop positioning spindle, and a diamond holding assembly mounted on said body portion, said assembly including a pair of relatively movable work holding jaws provided with work engaging elements, one of said jaws being fixed to the body portion, a pair of spaced parallel guides fixed at one end to the fixed jaw so as to be substantially perpendicular thereto, said other jaw having spaced openings therein to receive the spaced parallel guides to permit the movable jaw to slide freely to and from the fixed jaw, said work engaging elements being mounted on the jaws close to their free ends for rotation about eccentrically arranged parallel axes parallel to the guides, one of said elements having non-rotatable engagement with the pavilion of the diamond the axis of said one element being concentric with the pavilion engaging portion thereof and the other having a continuous fiat surface for engagement with the table of the diamond, the center of said surface being eccentric to the center of rotation of said one element, and a stud journaled in one of the jaws and having threaded ing a channel in its lower end, said channel being open at the bottom and being defined by spaced parallel side walls and an upper wall which is inclined to the axis of the spindle, and

a diamond holding assembly mounted on said body, said assembly including a pair of relatively movable work holding jaws provided with work engaging elements, one of said jaws being fixed at its upper end to the body portion within the channel so as to be substantially normal to the inclined wall, a pair of spaced parallel guides fixed at one end to the fixed jaw so as to be substantially parallel to said inclined upper wall, said other jaw having spaced openings therein to receive the spaced parallel guides for sliding movement between the parallel walls to and from the fixed jaw, and in parallel relation thereto, said jaws having lower tapering ends and said work engaging elements being mounted at the tapering ends of the jaws for rotation about spaced parallel axes parallel to the inclined wall, one of said elements having non-rotatable engagement with the pavilion of the diamond, and the other having a continuous flat surface for engagement with the table of the diamond, the center of rotation of said continuous fiat surface being eccentric to the center of rotation of said one element and the lowermost peripheral por-- tion of said continuous fiat surface being tangent to the lowermost extremity of the jaw on which it is mounted and a stud journaled in one of the jaws and having threaded engagement with a threaded opening in the other jaw, said stud being rotatable to move the jaws to and from each other to clamp work between the work holding elements and to immobilize the elements from rotation about their axes.

CHARLES A. HANS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 753,992 Marcher Mar. 8, 1904 802,368 Coleman Oct; 24, 1905 969,871 Hornig Sept. 13, 1910 1,094,913 Loesser Apr. 28, 1914 1,373,835 Ryon Apr. 5, 1921 1,646,375 Augenstein Oct. 18, 1927 1,838,423 Loesser et al Dec. 29, 1931 2,383,619 Rosner Aug. 28, 1945 2,435,971 Ludel Feb, 17, 1948

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