EP0299692A2 - Edelstein-Poliervorrichtung - Google Patents

Edelstein-Poliervorrichtung Download PDF

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Publication number
EP0299692A2
EP0299692A2 EP88306285A EP88306285A EP0299692A2 EP 0299692 A2 EP0299692 A2 EP 0299692A2 EP 88306285 A EP88306285 A EP 88306285A EP 88306285 A EP88306285 A EP 88306285A EP 0299692 A2 EP0299692 A2 EP 0299692A2
Authority
EP
European Patent Office
Prior art keywords
scaife
motor
bearing
radial
axial
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP88306285A
Other languages
English (en)
French (fr)
Other versions
EP0299692B1 (de
EP0299692A3 (en
Inventor
Eric Joseph Blondeel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Gersan Ets
Original Assignee
Gersan Ets
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Filing date
Publication date
Application filed by Gersan Ets filed Critical Gersan Ets
Publication of EP0299692A2 publication Critical patent/EP0299692A2/de
Publication of EP0299692A3 publication Critical patent/EP0299692A3/en
Application granted granted Critical
Publication of EP0299692B1 publication Critical patent/EP0299692B1/de
Expired legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B9/00—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor
    • B24B9/02—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground
    • B24B9/06—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground of non-metallic inorganic material, e.g. stone, ceramics, porcelain
    • B24B9/16—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground of non-metallic inorganic material, e.g. stone, ceramics, porcelain of diamonds; of jewels or the like; Diamond grinders' dops; Dop holders or tongs

Definitions

  • the present invention relates to a gemstone polishing apparatus comprising a scaife, a supporting structure for the scaife, a bearing for the scaife, and a drive for the scaife.
  • a scaife is a wheel which is used to polish gemstones, e.g. polishing facets on a brilliant-cut diamond.
  • the scaife runs at a high speed, e.g. up to 6000 rpm (3000 rpm for standard scaifes), normally about a vertical axis, and a flat face of the scaife is used for the polishing, usually with the application of an abrasive oil to the face.
  • the scaife has a diameter of e.g. 150 to 350 mm and a thickness of 10 to 20 mm and is made of soft steel or cast iron, so that it is heavy, for example weighing 10 to 15 kg.
  • the term "scaife” is also used to include the whole item of equipment or apparatus.
  • the supporting structure is normally a flat table.
  • the gemstones can be applied to the scaife in hand-held dops, but are normally mounted on polishing machines, referred to as tangs, which hold the stones in the correct orientation, and more than one tang can be used at the same time on the same scaife.
  • any vibration of the scaife and table must be avoided.
  • This problem can be reduced by special motor drives, or by using a special motor and bearing design, or by using a normal motor with a radial-axial air bearing combination for the scaife.
  • Such solutions are quite expensive, for example ten to twenty times the cost of a standard drive motor, and they cannot reduce the residual inbalance remaining after assembling the balanced scaife.
  • the present invention provides gemstone polishing apparatus as set forth in Claim 1 and a method as set forth in Claims 17.
  • the remaining Claims set forth optional features of the invention.
  • the system is run over-critically, i.e. between nodes of the critical frequency, so that the scaife is self-balancing - although the scaife (and the motor) should be separately balanced, the radial float of the scaife centres the residual imbalance.
  • the running frequency must be higher than the first radial critical frequency, but the amount depends upon the desired running accuracy and the damping in the system. Higher damping requires a larger difference between the running frequency and the first radial critical frequency.
  • the unbalance vector has to be opposite to the displacement vector, a 180° shift or phase angle. For low damping, the magnitude of unbalance is very high when going through the critical frequency, but above critical frequencies the magnitude soon becomes very small, with a phase angle very close to 180°.
  • the radial float may be free, i.e. not against any elastic force, in ideal conditions, but in general there will be some radial elastic restraint or stiffness (see the equation above for the first radial critical frequency).
  • An axial bearing pre-load can be applied e.g. by direct magnetic action on the scaife or air pressure cells, and/or by the deadweight of the motor, and/or pre-loading an air bearing by use of the motor mounting means.
  • the motor drive shaft may be rigidly fixed to the scaife or there may be a universal or flexible coupling, i.e. a flexible or swivel coupling where rotary motion is permitted between the motor drive shaft and the scaife about transverse axes, or even a coupling which permits radial float.
  • a universal, flexible or floating coupling must be able to transmit torque, and must provide (if necessary in association with other means) a stiffness corresponding to an over-critical drive, and in some cases, depending upon the pre-load system, must be capable of transmitting preload to the axial scaife bearing.
  • Figure 1 shows a gemstone polishing apparatus having a supporting structure including a table 1 carrying a drive motor 2 (such as a high quality AC motor with limited mechanical and magnetic inbalance) by way of flexible couplings in the form of silent blocks 3 which are axially stiff but radially weak.
  • the motor shaft 4 is rigidly fixed to a scaife 5.
  • the scaife has an axial air bearing one part of which is the rear or bottom face of the scaife 5 and the other part of which is indicated at 6.
  • Axial pre-load is provided by the deadweight of the motor 2, shaft 4 and scaife 5, but if desired, further axial pre-load can be provided by the silent blocks 3 or by magnets 7 exerting direct magnetic action on the scaife (which will be ferromagnetic).
  • an anti-friction bearing 8 around the shaft 4.
  • a radial gap can be provided between the bearing 8 and the shaft 4 (when the shaft is central) of about 0.2 to 0.3 mm, for example, i.e. at least the sum of the eccentricities of the scaife 5 and of the shaft 4.
  • the air bearing is shown as extending to the outer periphery of the scaife 5, it can for instance have an outer diameter of 110-285 mm.
  • the air bearing should be effective enough to limit axial movement of the scaife 5 to less than ⁇ 1 micron.
  • One of the advantages of the use of the axial air bearing underneath the scaife 5 is the high stiffness and the fact that bearing errors of the drive have negligible effect on the vertical vibration of the scaife, and hence one can use a traditional, cheap motor drive.
  • the vertical movement of the polishing surface of the scaife is nearly completely determined by the flatness of the lower side of the scaife (and if a multipad air bearing is used, that error is averaged out to about one third of its actual value) and the non-parallelism of the scaife 5, which can be kept very low. Hence the bearing on the back of the scaife 5 provides good vertical running accuracy.
  • the motor 2 is of relatively light weight whereas the scaife 5 is heavy, and the centre of gravity of the rotationally rigid system formed by the motor 2, shaft 4 and scaife 5 is at 9, approximately on the plane of the axial bearing or just slightly below the plane.
  • the motor 2 is run at a frequency higher than this first radial critical frequency.
  • the scaife running speed can be 3,000 rpm, with a scaife mass of 15 kg and a mass of the motor 2 and the remainder of the system of 7 kg.
  • the silent blocks 3 have a damping ratio of 0.3.
  • the phase angle is assumed to be 165° (instead of the theoretical 180°).
  • the axial stiffness is determined by the stiffness of the axial bearing and is preferably from half to one tenth of the radial stiffness of the silent blocks 3, the choice depending upon mounting accuracy and bearing pre-load.
  • the air bearing is an aerostatic bearing
  • an air pressure reservoir is necessary to avoid running the motor 2 without pressurised air.
  • the motor 2 is only energised if a certain minimum air pressure is present.
  • the reservoir should contain at least sufficient air to pressurise the bearing during running out (i.e. as the scaife 5 slows to a stop), and preferably for sufficient time to polish a facet (or even a whole stone) plus the running out time.
  • the electrical resistance of the air gap can be checked to avoid starting the motor 2 before the electrical resistance reaches a threshold, e.g. 100 ohms. Such measures are not necessary when using an aerodynamic (e.g. herringbone) air bearing.
  • Figure 2 shows an arrangment similar to that of Figure 1, but the shaft 4 carries a universal joint 10 which permits rotary motion between the shaft 4 and the scaife 5 about transverse axes, whilst transmitting torque (a splined arrangement can be used).
  • a splined arrangement can be used.
  • the radial movement of the scaife 5 can be blocked using a magnetic clamp 11.
  • the silent blocks 3 can be replaced by rigid blocks to prevent lateral float (as well as axial float) of the motor 2 and the scaife 5 can be run under-critically so that it can bear high tangential loads e.g. for multi-tang polishing.
  • FIG 3 shows a somewhat different arrangement in which the motor shaft 4 is connected to the scaife 5 by a torque transmitter 12 which permits limited movement in any radial direction and limited axial movement.
  • a radial spring system 13 which applies an elastic bias to radial movements of the scaife 5.
  • an axially-movable clutch plate 14 which can be made to bear against the underside of the scaife 5.
  • the motor 2 is carried on the table 1 by means of blocks 15 which allow axial movement as well as radial float, and a controlled preload is applied to the casing of the motor 2 by an arrangement indicated schematically as a pivoted arm 16 having a pre-load applied by a spring 17 which can be reduced by means of a coil 18.
  • the motor 2 is lifted up and keeps the scaife 5 in balance due to the engagement of the clutch plate 14 with the underside of the scaife 5.
  • the air bearing can be pre-loaded by the deadweight of the motor 2 via the torque transmitter 12, possibly additionally using a magnetic pre-load as in Figures 1 and 2.
  • the first radial critical frequency is determined by the mass of the scaife 5 and the spring constant of the spring system 13.
  • Figure 4 shows an arrangement in which, with a heavy scaife 5 and well engineered mounting of the scaife 5 onto the motor drive, the radial bearing is on the housing of the motor 2. Because the motor housing makes only very small oscillatory movements, there is no air bearing and the silent blocks 3 are replaced by axially-stiff rolling balls 21 and the radial stiffness is purely determined by a radial working spring or spring and damper system 22 (shown schematically).
  • the ball bearing system is carried by an annular race 23 hung on pre-stressed bolts 24 and engages a motor housing flange 25.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Magnetic Bearings And Hydrostatic Bearings (AREA)
  • Connection Of Motors, Electrical Generators, Mechanical Devices, And The Like (AREA)
EP19880306285 1987-07-14 1988-07-08 Edelstein-Poliervorrichtung Expired EP0299692B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8716512 1987-07-14
GB8716512A GB2206825B (en) 1987-07-14 1987-07-14 Gemstone polishing apparatus

Publications (3)

Publication Number Publication Date
EP0299692A2 true EP0299692A2 (de) 1989-01-18
EP0299692A3 EP0299692A3 (en) 1989-11-23
EP0299692B1 EP0299692B1 (de) 1992-05-13

Family

ID=10620601

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19880306285 Expired EP0299692B1 (de) 1987-07-14 1988-07-08 Edelstein-Poliervorrichtung

Country Status (4)

Country Link
EP (1) EP0299692B1 (de)
DE (1) DE3871002D1 (de)
GB (1) GB2206825B (de)
IE (1) IE60355B1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1755825A4 (de) * 2004-06-14 2007-09-26 Sarin Polishing Technologies L Verfahren zur bearbeitung von edelsteinen
CN105364661A (zh) * 2015-12-02 2016-03-02 无锡康伟工程陶瓷有限公司 陶瓷管壳轨迹倒角装置

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IL168588A (en) * 2005-05-15 2010-06-30 Sarin Polishing Technologies L Apparatus and article for polishing gemstones
WO2009066312A1 (en) * 2007-07-17 2009-05-28 Janak Mistry A polishing mill for polishing gemstones
CN107520699B (zh) * 2017-07-28 2019-02-05 义乌市台荣超硬制品有限公司 一种连续平磨机系统

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE400215A (de) *
FR1235975A (fr) * 1959-05-06 1960-07-15 Saint Gobain Procédé et dispositif pour l'équilibrage d'un corps en rotation
US4180946A (en) * 1975-10-02 1980-01-01 Maurice Brunet Tool holding spindle assembly particularly for a grinding machine
DE3227924A1 (de) * 1982-07-27 1984-02-02 Maschinenfabrik Gehring Gmbh & Co Kg, 7302 Ostfildern Vorrichtung zum honen von werkstuecken

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1755825A4 (de) * 2004-06-14 2007-09-26 Sarin Polishing Technologies L Verfahren zur bearbeitung von edelsteinen
CN105364661A (zh) * 2015-12-02 2016-03-02 无锡康伟工程陶瓷有限公司 陶瓷管壳轨迹倒角装置

Also Published As

Publication number Publication date
IE60355B1 (en) 1994-06-29
GB2206825B (en) 1991-11-06
EP0299692B1 (de) 1992-05-13
GB2206825A (en) 1989-01-18
EP0299692A3 (en) 1989-11-23
GB8716512D0 (en) 1987-08-19
DE3871002D1 (de) 1992-06-17
IE882141L (en) 1989-01-14

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