US3882641A

US3882641A - Cabochon gem grinder

Info

Publication number: US3882641A
Application number: US429084A
Authority: US
Inventors: Earl D Montgomery; Jan Michael Montgomery
Original assignee: American Standard Inc
Current assignee: Trane US Inc; American Standard Corp
Priority date: 1973-12-28
Filing date: 1973-12-28
Publication date: 1975-05-13
Anticipated expiration: 1992-05-13

Abstract

A cabochon gem grinding machine comprising a drum having a cylindrical wall and a lip extending inwardly from the sides of the wall for retaining a slurry of abrasive grain or grit, a pair of rollers which support and rotate the drum to distribute and maintain the slurry against the inner wall of the drum by centrifugal force, a dop for holding a gem to be ground in contact with the slurry at a desired angle to the vertical to grind a desired area of the gem, a pattern for indicating the desired shape of the gem, and a drive mechanism for rotating the gem and the pattern and for moving them toward a vertical position to grind new areas of the gem. Also, sensing and actuating apparatus is provided for detecting when a gem area has been ground to the desired size and for rotating the gem and pattern and for moving them toward vertical position to grind new areas of the gem. Also, sensing and actuating apparatus is provided for detecting when a gem area has been ground to the desired size and for rotating the gem and pattern and for moving them toward vertical position to grind new areas of the gem. A method of grinding cabochons and the like, comprising maintaining a slurry of abrasive material inside a rotating drum, holding a gem to be ground in contact with the slurry at a desired angle to the vertical to grind a desired area of the gem, rotating the gem and moving it toward the vertical when said gem area has been ground to the desired size, and repeating said steps until the gem has been ground to the desired pattern.

Description

Montgomery et al.

[4 1 May 113, 1975 CABOCHON GEM GRINDER [75] Inventors: Earl D. Montgomery; Jan Michael Montgomery, both of Warrington, Pa.

' [73] Assignee: The American Standard Corporation, Trevose, Pa.

[22] Filed: Dec. 28, 1973 [21] Appl. No.: 429,084

[52] U.S. Cl 51/73 R; 51/283; 51/317 [51] Int. Cl B24b 7/00; B24b 9/00; B24b 1/00 [58] Field of Search 51/73 R, 317, 318,283

[56] References Cited UNITED STATES PATENTS 583,670 6/1897 Chambers et aI. 51/73 R 2,387,138 10/1945 Fruth 51/73 R 2,745,225 5/1956 Vonada t 51/73 R 10/1970 Campbell 51/73 R Primary Examiner-Othell M. Simpson Attorney, Agent, or Firm-Smith, Harding, Earley & Follmer ABSTRACT A cabochon gem grinding machine comprising a drum having a cylindrical wall and a lip extending inwardly from the sides of the wall for retaining a slurry of abrasive grain or grit, a pair of rollers which support and rotate the drum to distribute and maintain the slurry against the inner wall of the drum by centrifugal force, a dop for holding a gem to be ground in contact with the slurry at a desired angle to the vertical to grind a desired area of the gem, a pattern for indicating the desired shape of the gem, and a drive mechanism for rotating the gem and the pattern and for moving them toward a vertical position to grind new areas of the gem. Also, sensing and actuating apparatus is provided for detecting when a gem area has been ground to the desired size and for rotating the gem and pattern and for moving them toward vertical position to grind new areas of the gem. Also, sensing and actuating apparatus is provided for detecting when a gem area has been ground to the desired size and for rotating the gem and pattern and for moving them toward vertical position to grind new areas of the gem. A method of grinding cabochons and the like, comprising maintaining a slurry of abrasive material inside a rotating drum, holding a gem to be ground in contact with the slurry at a desired angle to the vertical to grind a desired area of the gem, rotating the gem and moving it toward the vertical when said gem area has been ground to the desired size, and repeating said steps until the gem has been ground to the desired pattern.

5 Claims, 8 Drawing Figures PATENIEE m a sign; 3, 882.641

SHEET 10F s PATENTED MAY 1 31975 SHEET 2 OF 5 '!llll!!!!!! PAIENIEB MAY 1 3W5 3,882 641 sum 3 0F 5 PATENIEUHAY isms SHEET U BF 5 FIG. 4

Elsi-32am FATENIEB KAY 3 M5 SEEN 5 PF 5 CABOCHON GEM GRINDER BACKGROUND OF THE INVENTION The automatic grinding of gem stones to desired shapes and sizes, such as cabochons, is conventionally performed by a positioning device that places a stone in contact with either a grinding wheel or a flat lap charged with diamond powder. The stone is caused to follow a pattern or template which contacts a wear plate when the stone is ground down to the desired size to stop further grinding. Such prior art templatecontrolled grinding machines for grinding cabochons of semiprecious gems are illustrated by US. Pat. No. 3,568,369 which issued on Mar. 9, 1971.

Such machines have certain draw-backs. As a stone is abraded by a grinding wheel, the wheel also wears, requiring frequent dressing of the wheel. This dressing causes the surface of the grinding wheel to be positioned at a greater distance from the stone, so the wear plate must be repositioned accordingly to maintain the calibration accuracy of the pattern. Further, diamond laps cut well when new, but become less and less efficient as diamond particles break away from the surface or are driven into the lap material by the impact of cut- .ting or grinding. Moreover, lap replacement cost is high.

SUMMARY or THE INVENTION Accordingly, it is an object of this invention to provide an automatic cabochon gem grinding machine which overcomes the problems of the prior art machines by eliminating the grinding wheel and the flat lap.

This object is accomplished by providing a gem grinder which utilizes a slurry of abrasive grains to grind stones automatically. The abrasive grains are dispersed and maintained in a lipped drum and maintained against the inner wall of the drum by centrifugal force. The stone is held against the slurry by a dop which is rotated about its axis in unison with a pattern and is also progressively moved along the wall of the drum from an initial angle of about 75 from the vertical to the vertical as the stone is ground in accordance with the pattern.

As the grinding proceeds, material is removed from the abraded area of the stone, allowing the pattern to contact a wear or contact plate which causes a motor and gearing to turn a worm shaft to rotate both stone and pattern about their axes and about the worm shaft at right angles thereto to present an uncut area of the stone to the lap. For example, the initial grinding of a stone may start with the dop and pattern axes at 75 from the vertical. As grinding proceeds the dop and pattern axes rotate and also move toward the vertical. When the dop and pattern axis reach the vertical, the gem grinding is complete.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded view in perspective of a cabochon gem grinding machine constructed in accordance with this invention;

FIG. 2 is a view in top plan of the cabochon gem grinder of FIG. 1;

FIG. 3 is a view in elevation, partly in section, and partly cut-away taken as indicated by the lines and arrows 3-3 which appear in FIG. 2;

FIG. 4 is a view in elevation taken as indicated by the lines and arrows 4-4 which appear in FIG. 2;

FIG. 5 is a partial view in perspective of the template and gem holding mechanism;

FIG. 6 is a partial view of the gem holding mechanism at about the beginning of the grinding operation;

FIG. 7 is a partial view in elevation of the template mechanism taken as indicated by the lines and arrows 77 which appear in FIG. 2; and

FIG. 8 is a partial view in elevation of the gem grinding mechanism taken as indicated by the lines and arrows 8-8 which appear in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the specific embodiment of the invention shown in the drawings, there is illustrated a gem grinder 11 which includes a support frame 13, brackets 15 mounted on frame 13 and supporting a pivot pin 17, an assembly plate 19 mounted on pivot pin 17, a mounting plate 21 connected to plate 19 by spacers 23, and a mounting plate 25 connected to plate 21 by spacers 27.

An electric motor 29 has a shaft 31 and a gear 33 that meshes with gear 35 on shaft 37. A spur gear 39 is mounted on the other end of shaft 37 and meshes with a gear 41 mounted on worm gear shaft 43.

A worm 45 (FIGS. 2, 5 and 7) on shaft 43 meshes with gear 47 of shaft 49 which is provided with a chuck or quill 51 that receives shaft 53 of a template 55 having a pattern 57 at the end of the shaft.

A worm 59 (FIGS. 2, 6 and 7) is also mounted on shaft 43 and meshes with a gear 61 on shaft 63 which is at right angles to shaft 43. Shaft 63 has a quill or chuck 65 at one end which receives a dop or dop stick 67. A gem or stone 69 is glued to the end of the dop stick in position to be ground to a smooth finish in a desired configuration which conforms to the configuration of the pattern 57.

Motor 29 also drives another gear train which includes shaft 31, gear 33, gear 35 and shaft 37. A worm 71 is mounted on shaft 37 and meshes with a gear 73 on shaft 75 on which is mounted a worm gear 77 that meshes with a gear 79 on a shaft 81. A crank arm 83 I on shaft 81 drives a connecting rod 85 that tilts rocker arm 87 which is mounted on a hollow shaft 89 that is rigidly connected to a housing 91 having mounting plates 92 which support worm gear shaft 43. Housing 91 moves from its initial position, for example, 75 from the vertical, to the vertical, zero degree position, by means of the rotation of hollow shaft 89.

Another motor 93 with a belt 94 drives a roller 95 mounted on support bracket 97 on frame 13. A freely mounted roller 99 is also mounted on bracket 97, and the two rollers are adapted to support and rotate a drum 101 having a cylindrical wall 103, a sidewall 105 that completely encloses one side of the cylindrical wall 103, and an inner lip 107 that projects inwardly from the other side of wall 103.

A wear or a contact plate 109, which conforms to the shape and contours of the inside of drum circumferential wall 103, is mounted on frame 13 just below template 55.

In operation, the drum 101 is rotated by

rollers

95 and 99 so as to maintain a slurry of grinding grits or grains against the inside surface of cylindrical wall 103 by centrifugal force. The gem 69 to be ground to cabochon shape is positioned inside the drumlOl at an angle of about 75 to the vertical'and grinding begins on an area of stone 69 which is located at about 75 from the bottom of the stone. After this area is ground to the desired shape, it touches the inner surface of the drum wall 103, and simultaneously the corresponding area on pattern 57 makes contact with wear or contact plate 109. Pattern 57 and contact plate 109 are both made of electrically conductive material and are connected in an electrical circuit with a source of power and motor 29. The contact between pattern 57 and contact plate 109 acts as an electrical switch to close the electrical circuit and energize motor 29. In other words, the pattern 57 and contact plate 109 sense that the stone area has been ground to the desired size and actuate motor 29 to rotate worms 4S and 59 to rotate pattern 57 and stone 69. The stone is thereby rotated to another high area which the grit slurry starts grinding to size, and the high area moves the pattern 57 away from contact plate 109, breaking electrical contact, and stopping motor 29.

Also, the actuation of motor 29, in addition to rotating the pattern and gem, also actuates the gear train that moves housing 91 and shaft 49 to dop stick 67 incrementally toward vertical position.

As the successive areas of stone 69 are ground to size, the rotation of the stone and the incremental movement toward the vertical cause each successive stone area to be ground to size in a substantially spiral path on the stone, with ever decreasing spiral circumference.

It is to be noted that the stone 69 and pattern 57 are synchronized by means of identical worm and gear drives so as to move in identical fashion. The shape of the pattern constitutes and provides a program which the stone follows in the course of the grinding.

The drum 101 is easily removable for the purpose of changing the compound or for cleaning. Two drums are provided: the first drum is used for grinding the stone and washing, and the second drum may be used for polishing, and may advantageously be made from a transparent synthetic plastic.

Cabochons made from grinding with the inventive machine may have an oval, rounded top with a flat bottorn for use in fingerrings. I 5

One of the important features of the invention is the internal lap of the stone within the drum 101 which permits grinding at less expense than grinding with] the conventional diamond lap. The inventive machine is low in initial cost, and the grinding cost is lowdThe inventive machine is especially suitable forhobbyists be- 7 highly polished, but not faceted. It comes from the;

French word meaning cabbage or rounded head.

41 We claim: 1. A cabochon gemgrinding machinecomp'rising a drum having a cylindrical wall and a lipsextending inwardly from the sides of the wall for retaining a slurry of abrasivematerial, means mounting the drum ,so that its axis is horizontal and for rotating the drumtodistribute and maintain the slurry against the inner wallof the drum, dop means for holding a gem to be ground in contact with the slurry ata desired angle to the vertical to grind a desired area of the gem, and pattern means connected to the dop means for indicating the desired shape of the gem..

2. The gem grinder of claim 1 including means for ro-, tating the gem and the pattern means and for. moving' them toward a vertical position to grind new areas of the gem.

3. The gem grinder of claim 1, wherein said means for rotating the drum includes a drive roller and an idler roller which support the drum and'rotate it,

whereby said drum is easily removed for cleaning and easily replaced by other similar drums;

4. The gem grinder of claim 1, including sensing means for detecting when the gem area being ground has been ground to the desired pattern. 3

5. The gem grinder of claim 4 including actuatin means responsive to thesensing means for rotating the" axes of the pattern means andgem and for moving said axis towardthe vertical to present another gem area to:

Claims

1. A cabochon gem grinding machine comprising a drum having a cylindrical wall and a lip extending inwardly from the sides of the wall for retaining a slurry of abrasive material, means mounting the drum so that its axis is horizontal and for rotating the drum to distribute and maintain the slurry against the inner wall of the drum, dop means for holding a gem to be ground in contact with the slurry at a desired angle to the vertical to grind a desired area of the gem, and pattern means connected to the dop means for indicating the desired shape of the gem.

2. The gem grinder of claim 1 including means for rotating the gem and the pattern means and for moving them toward a vertical position to grind new areas of the gem.

3. The gem grinder of claim 1, wherein said means for rotating the drum includes a drive roller and an idler roller which support the drum and rotate it, whereby said drum is easily removed for cleaning and easily replaced by other similar drums.

4. The gem grinder of claim 1, including sensing means for detecting when the gem area being ground has been ground to the desired pattern.

5. The gem grinder of claim 4 including actuating means responsive to the sensing means for rotating the axes of the pattern means and gem and for moving said axis toward the vertical to present another gem area to be ground.