AP72A

AP72A - A gemstone polishing machine.

Info

Publication number: AP72A
Application number: APAP/P/1988/000103A
Authority: AP
Inventors: David Trevor Herson; Michael Craig Abraham; Moshe Bezalel Lerner
Original assignee: Prodiamatic Cc
Priority date: 1987-10-20
Filing date: 1988-09-16
Publication date: 1990-02-25
Also published as: BE1002402A5; AP8800103A0; IL88018A0; IL88018A; EP0313369A3; EP0313369A2; ZA885545B; AU609199B2; AU2399788A

Abstract

A polishing machine 70 for polishing a

Description

A pC;ish'ng machine 70 for pel isliirg a gemstone includes a support arrangement 75 movably mountable relative to a polishing means. A holding means 102 for holding the gemstone to

b e p o 1 i s b e d	is rotatably mounted cr, the support arrangement 75
ά·'· is men at	' ¹ k? l _ j r u Π j Γ 'λ , v.I. Ί v > p 3 ,m ’’ u. 6 ,¹' Γ j Γ J v.,3 _ 7 O l 3 ; . / 2
t ? rnnoLma	i u o n a'd eve of contact emto the povshong means. A
o - ;v a r e e n s	112 is provided for rota tee' driving the holding
livans rel-ati	• > e to the support arrangement. The machine 70

includes a control means for ccntrolling operation o' the said drive means 112 and thus the rotation of the holding means 102 relative to the support arrangement 75. A m,err tori-g means 25

monitors a p·	wishing rate of the gemstone et each cf a plurality
o' predate.-.;	aired positions -c' a revol uti c- cf the holding means

132 about the support arrangement 76 and sends data representative of the polishing rat? at the said positions of the holding evens 102 to the control means, the control means controlling the

drive means	112 to position tns holding means 132 at that
p v i t i c n at v	,hich too said optimum polishing rate is achieved.

bad ORIGINAL &

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THIS I WENT I ON relates to the polishing of gemstones. Tcularly, tbs i on relates to a polishing macbir.i ishing a gemstone, -and to a method of polishing a g-x?.AP 0 0 0 0 7 2

Λocord’ing to a first aspect of the invention, there is provided a polishing machine for polishing a gemstone which i nclodes a support arrangement movably mountable relative to a polishing moans;

a holding m--503 for holding the gemstone to be polished, the holding means being rotatably mounted on the support arrangement

and	l	eirg	mevabl ·?	4- r, r~. ’-'-•J	eth	c-r *ith the	support	arrangement to	move
the	- -	'Sio.o	3 into	a 0 d	out	of contact	with the	polishing means;
	a		v e m 0 a	r s	for	rotatably	d r i v i n g	fhe holding	means,
rala	: ii	• if LU	the s.;	ppor	t a	r ; c rg 1.-.,1..- ' _v ;
	a	C ϋ ίΊ	‘.••0! ISO	a ns	for	control 1ing	ope rati	on of the said	d r i v 2

means and thus the rotation of the holding means relative to the s u p p ». r l. / _i n g *. m -..- n f; and a monitoring means for monitoring a polishing rate of the gemstone at each of a plurality of predetermined positions of a

BAD ORIGINAL vb ο ο 0 in

	^{J L} ‘ ^j r’ ·- -· - · -? b , .2
_r ' - · ' - ¹	,7 the he; s'-g .arias at 7,h^;oh as bpt; os po’iuhing rite
is aeh_c ,	zed and to operate the drive ns os ns to position the
holding r	noons at that position at which the said optimum
u υ i j , , g	rate is achieved.

f ~ ‘ - ' '' J	^:r ; *. ,?s ^ι_ι;7· i s. 7·~'ο s'-'J'Nc-'J in
?. / L ',l'	Hi appreciate that a cLamast be polished along its
jn.	each facet of the dsamond res a anoae · grain
C L j r i j ; -... -.,. ,-i - · ·* - - ¹ · ,	’otic, and in order to polish the various facets of the the bast position of the diaraod relative to tire
P ' ¹ rr ! π	i ! G i i j L 'j J - > C - .n ·.- c _r' i I· J. . Έ 1 ; i . ¹ J f J o. at 1 ' . b L t d
r . . r,

	The machine nay include a haicht-varying rue-cos for
₍4 H ' Γ . - *- g '' 1 .	^: varying t'-.e height of the sup. .-1 a r r-a n j e-..a n t and
heroe the	h j i u , ί ig i. .'. o 3 * i_- [ τ t„ ’ v a lb u' ? ρ o . r s η ’ o j v. o s .

	The support a rrongesent :y be pi.otaliy r'-UbOfod on a
free end	of a beam vriich extends cantilever-fashion from a
isovabiG hs	•using, the h_- i gh t- va ry i ng roans noting on tine housing
r . -::.,.4 i u; c^-ij ··: .	holy vary iog the height of the support arrange;:' on t.

BAD ORIGINAL $ .-oo.-n7C co-:: - j .-,11/: a pr/j fi housing, Lo p .si·;: -V; ,r’ich the project;

housing being adjustable to adjust Lie degree to -.-/01011 the height-varying means raises and lowers the support arrangement relative to the polising means.

;·..·pdt J n_, « ; ..·-„ > _r : ----- - j hence the hoi dire means.

AD A 0 0 0 7 2 ;my include a reciprocating raeau; for 7 .notion to the suppo-t arrang-emm-nt and ihe reciprocating means may comprise an electric motor

which has	a cam-1	i k e	f or.nati on	on an output	sha	ft the	roof, the
cam.-l i ke	f 0 rmotic	n c	c-cpe rati	ng with a psi	1- of	sp need	f el 1 ewer
Tvi’uJ vK· d>	r ‘ ’	-%	frem the	h c u s i n g w i th	the	cam-1i^;	-.e forma-
t ; - r- ,-. » · r- L i iy 1 t‘ \ LZ - 1		ween	thc- foil	c,./.-r forma tic	n s .

The drive means may comprise a stepper motor for rotating the holding means in a stepwise manner relative to the

supp	0 r t 2 r	ran goment to pr	•ovide tne said positions at which the
ii' ./'<’t	Ιο ϊ' I J	m-'ans n/oritors	the polishing rate of the gemstone by
Li 12	poli in	1 C j ίϊι·? π Π S j Lho	holding means being mounted rotatably
fast	wi th ,	but axially si i	dable relative to, an output shaft of
iho	ς i I r - > ' ·' ' ^J t . '	t a r. m nt ex	tending from the - topper motor. For

example, the stepper motor may rotate the holding means through 0

360 , with the polishing rate of the gemstone being sampled at

BAD ORIGINAL

Ο bousing a-'id a holder for holding the yo.iistcne •-•o i'j ·. Ί i-v? iy rast ·ί Ί to t'-o $a'd ei: 3 of the ;3V c;

' e,’ ί.ίϋί-ΟΓ e wc·.-:;; =:j.·· :·,ο i ch , in turn, is eoge yea bl e with a i th the so a ft of the hs'eiog s o’ a sorfjca of t: :- s/.-As η·;··οι··ι?-?·· aouve, th: ο is'ni so m a ecorArise ·,·;: th tho .· J i :: j? = : i : .- .- j t ’· u v ?a”. u: s f a : :· t s of a : i - 'i.·c~ :h: g·'? r ishr

- . * r * ' · r~·. r 1 - ··. _r, » λ .- · - 1 ,- .·> , . A

CO'itb, L.'U it il-JuOi Λ. I rofaU· th- shaft of ?.'··,.· hslALij 0-,--.-2::5 thcc’.jh 22,5 so toot, cnee o·-·: f ·:·-·A has f; :.-(1 (’ϋΊΆ,Α ci, ft: rolls.,i.-g fa-.o-t will L? L-ooght into position to be polished by the polishing means.

BAD original

·, the id;

ms crrnpri si ng a r*

The bolding means may include a bracket which is suspended from the ojtput shaft of the support ar:-argf_t?ont via 2 a

<a in cue rmocdiment or the invention, the ?noni tori r.·: means may comprise an inductive transducer for monitoring the ::.0v .-rent of trie body relative to the support arrangement, the said movement being caused by removal cf material from the gemstone under the action of the polishing means.

Tr	e transducer my	comprise c
excitable by	a signal of a pre	date rani ned
lines of me	gnetic flux which	results in
the body,	the magnitude cf	the losses
position of	the body' relative	to the sue
	e transducer may	include p
processing v	arialiens in imped	once of th

t least one coil which is •eing dependent cn the cssmg circuitry for ice of the coil as a result of the pddy-curront lonsS to provide an output voltage signal which is directly prnp‘>i lienal to t.ie rite at which material is removed from the gemstone by the polishing mans. The said output voltage signal may be an,analog DC voltage signal which is fed to

....-····------ BAD ORIGINAL $

'ho control ί s , the control irouns ϊ Ί J i n j an an a log lo d: j i^! a 1 urn/ertor Γ·ογ 0 .-,-.( ting the si jnal to a digial signal to tie processed by a micro,grocos mor of the control incans.

The transducer may include two coils, a first coil sensing the movement of the body and the resultant losses with a second coil serving as a compensating coil to balance and cancel the effects of temperature change.

In another embediment of the invention, the monitoring means may comprise a capacitive transducer having a first plate mounted fast with the body of the holding means to be rotatable therewith and a second plate mounted on the support arrangement parallel to and spaced from the first plate.

The capacitive transducer may be arranged in a Wheatstone bridge arrangement which is set to provide a null output prior to commencing polishing of the gemstone. The capacitive transducer may be responsive to removal of material from the gemstone by the polishing means, the said removal of material causing a change of capacitance of the transducer which results in the Wheatstone bridge becoming unbalanced to generate an output signal which is inversely proportional to the rate at which material is removed from the gemstone, the generated signal being fed to, and processed by, a microprocessor of the control means. --BAD ORIGINAL fbose skilled in Lhe art will appreciate that any t.hnnje in flu? distance between the body and the support arrange:..πf will c¹··,;? a cbac-je in the ii'prjuaee of the if-ducti'jq transducer or the capacitive transducer, as the case may be. lienee, any material removed from the gemstone as it is polished will cause the impedance to change. Further, when the gemstone is oriented relative to the polishing means so that it is being polished along its grain, material will be removed more rapidly than will be the case when the gemstone is being polished across, or against the grain. Hence, the rate of change of the impedance will be indicative of the polishing rate of the gemstone.

According to a second aspect of the invention, there is provided a method of polishing a gemstone which includes mounting the gemstone in a holding means which is rotatable about a substantially vertical axis;

bringing a portion of a surface of the gemstone into contact with the polishing means;

rotating the holding means through a revolution about the said vertical axis;

monitoring the rate at which material is removed from the said portion of the surface of the gemstone at predetermined positions of the revolution of the holding moans and generating an electrical output signal representative of the rate of removal of material from the said portion of the surface of the gemstone at each position;

« processing the signals so generated to ascertain at which position of the revolution of the holding means the optimum rate

AP000072

BAD ORIGINAL ft ·· 9 Ο ο

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7» , :·ΐ’.li-'iinj The ’ιοί «1 i :'j * cis Ιο the said position at which the up L i mum rate of re wm/al υΓ :m.i!.? r i a 1 fr;-a the gems tone is achieved and commencing polishing of that portion of the surface of the gemstone.

The method may include mounting the gemstone in a holder mounted at an end of a rotatable shaft arranged at an angle relative tc the said vertical axis about which the holding means is rotatable, and adjusting the angle of the shaft relative to the vertical axis to align the gemstone relative to the poli shi ng means .

The method may	thus include, a	f fe r	sampling and
polishing the said portion of the surface	of	the gemstone,
lifting the gemstone off	the polishing me	ans,	rotating the
rotatable shaft through a	predetenni ned arc	to	bring another

portion of the surface into position to be polished, bringing the

said next	portion of the surface	of the gemstone	into contact
with the	polishing means, and	repea ting the	sampling and
poli shi ng	process on the said nc-x	t portion of the	surface of the
gemstone.

The holding means may be suspended from a support arrangement via a body which is axially displaceable along the

bAD ORIGINAL

Sl’d 'o. rticil	•ids relative to the support arrangi.m.-nt,	a'ul the
:.::: thud 'ly t'	h n inclule · > i i tor I ng the rate of r<m	o.'il of
' ' il fv n	: he porti' O of the .or face of i.'-.e u 'm-.	• ?ne by
moiii tor i ag thi	? axial displacement of the holding means	rc-1 a Live
to the support	arrangement, the axial displacement of the	hoi di ng

means being proportional to the rate of removal of t’ne material.

In one embodiment of the invention, the method may include monitoring the axial displacement of the holding means relative to the support arrangement by means of an inductive transducer.

The method may thus include causing lines of magnetic flux to be generated in the body of the holding means to cause eddy-current losses in the body, and monitoring variations in the impedance of the transducer as a result of the losses to produce the electrical output signal, the signal being an analog signal which is directly proportional to the rate of removal of material from the portion of the surface of the gemstone being polished.

The method may include converting the analog signal to a digital signal for processing by a control means which controls the polishing of the gemstone.

In another embodiment of the invention, the method may include monitoring the axial displacement of the holding means relative to the support arrangement by means of a capacitive transducer.

ΔΡΩ Ω 0 0 7 2 bad original

I ' b ' :, 1 L ' ,:.7,..1- ,- ' j ', , [ _;. .? 1 f Γ f < p 'd apart par-illel p¹ 1 .'.as, a f i i . t pi if.? bring m j-i · t-'d fist with the support arrangr-nent nr,-J a second plate being mosntrd fast with the body of the holding means to be rotatable therewith, and the method may include monitoring variations in the capacitance of the transducer due to variations in the spacing between the plates, the spacing between the plates being variable in response to the removal of material fr-xn the portion of the surface of the gemstone.

The method may include connecting the plates in an arm of a Wheatstone bridge arrangement and initially balancing the Wheatstone bridge arrangement to provide a null output prior to commencing polishing of the portion of the surface of the gemstone, the removal of material from the portion of the gemstone causing the Wheatstone bridge arrangement to become unbalanced to generate the said electrical output signal which is inversely proportional to the rate of removal of material f reel the portion of the surface of the gemstone, the output signal being an analog signal .

The method may include converting the analog signal to a digital signal for processing by a control means which controls tiie polishing of the gemstone.

The invention, is now described by way of example with reference to the accompanying diagraiauatic drawings.

BAD ORIGINAL ft

- 12 figure I ' ,s a _r ti tly t. i -J si,.!.? view of a p el i: u i_: -g odiin.?, in vice·; ida nee with a first aspect of the invention, for polishing gemstones;

Figure 2 shews a plan view of a polishing machine, in accordance with a second aspect of the invention, for polishing gemstones;

Figure 3 shews a side view of the machine of Figure 2 with a portion thereof emitted for the safe of clarity;

Figures 4A to 4D show a circuit diagram of control circuitry of the machine of Figures 2 and 3;

Figure 5 shows a block diagram illustrating the relationship between the circuits illustrated in Figures 4A to 40;

Figure 6 shows a schematic block diagram of a transducer circuit of the machine of Figures 2 and 3; and

Figures 7A and 7B and Figure 8 show flow charts of controlling software of the machine of Figures 2 and 3.

Referring firstly to Figure 1 of the drawings, a polishing machine in accordance with a first aspect of the invention for polishing a gemstone such as a diamond is designated generally by the reference numeral 10. The polishing machine 10 includes a support arrangement 12 which, in use, is mounted above a polishing means 14 comprising a rotatable scaive 16 mounted on a bench 18.

BAD ORIGINAL A

		e ^1:. p^,J r t .'ll ; ·. :		::c i2	IS pr-'.it tl !y m .,	.·' ; on a
t		-0 v :.1 Ί pi .· >t	₍. .‘1	?,	fhe c. s 20 _r. nJ	. ’ S f. n a
’ .-,;,,g	.14	t.nj.’i 11 i n i ·i j a dr i	70 u	, .ns (	not s'e.e/n) for	h iΊ i n g fee
•Ίi ai 20	i n	t.iiC d i i i u e i nil e	f nr	rows 2	6. fro hous’in	g 24 also
centai ns	a	rec ipr'uca ti ng	a ns	(al so	not shown) for i	mparting a
roci proc	a t i:	vj oliun to the	a on	20 and	hence the suppo	rt arrange-
ment 12.	A	holding moans p	8 is	rotat	ably mounted on	the support

ύr'Γ'/i'j ..λ:ηt 12. Τϊϊο holding means 23 c·>',ρci sρs a holder 30 in which a diamond 32 is receivable. The holder 30 is οουηίοό on The end of⁷ a shaft 34 which is rotatably mounted in a housing 36. The machine 10 includes a drive means in the form of an electric motor 37 rotatably driving the shaft 34 as will be discussed in greater detail below. A worm gear 33 is driven by the electric rotor 37. The worn gear 38 co-o,.c-i'ates with a spur guar 40 mounted rotatably fast with the shaft 34.

The housing 36 is pivotally mounted via a pivot pin 41 on a bracket 43.

	The polishing machine 10 further i	ncl odes a dr-	ive in-	sans
42 for	rotatably driving the holding means	28 relative	to	the
support	arrange;;ic-nt 12. The drive mrans 42	comprises a	S t Pi	j per
η. o tor’	14 driving an cutpuc shaft 46. Th.	o b r a c k o t 43	of	the

holding r.'.Ptins 23 is mounted rotatably fast with the output shaft of the drive means 42.

BAD ORIGINAL

^r' · -r J >..	mb me 10 ^r Hit.	Jr· i ·m ?s a .! ,fii	···· ;-j	m. .ms 43
^r ,r ' ' i i j	' he p 4 i .', i i g im	! e the di . 'md	h2 by	the sc live
. S . . ’ · ‘ 1 1 '	·, h'J ms '3 is	.. r c 1.,-1 ! 9 a i	h n ,1	means (met.
·,·.·;)	trolling t'.e Oper	ttija of the mac hi	no 10.
The	monitoring means 48 comprises	a	capaciti ve
transducer 50	which includes a	first plate 52 mounted	fast wi Lh
the support arrangement 12 and	a second' plate 54	mounted on the
bracket 43 of	the holding means	28. Thus, it will be a	pprec i a ted
that the plat	o 54 is relatable	relative to the	pi ate	52. The

AP000072 capaci Li vc transducer 50 is connected in a h'hea l.stone bridge arrangement of the control means. The capacitive transducer 50, also controls the operation of the stepper motor 44 via the control means.

A connection means comprising a slip ring arrangement 56 is mounted on the output shaft 46 of the drive means 42 for enabling electrical signals to be sent to the motor of the holding means 28.

The shaft 34	of	the holding means 23 is arranged at	an
angle relative to the (	.. , A .! ^J -	put shaft 46 of the drive means 42.	The
angle of the shaft	34	relative to the output shaft - 45	i s
adjustable by means	of	an adjustment means in the . form of	a
thimble micrometer 58.	A	lock nut arrangement 60 is provined	for
enabling the shaft 34	to	be locked in position relative to	the

BAD ORIGINAL ft i o i j is -i 1 a ί , . i. . 11,

Vb Οϋ 0 0 i S

In use, ίο set up ’.’·? much I no 10, the 1,'hra Is I. one bridge arrangement of the monitoring means ’.8 is balanced so that there is a zero output fri-it the bridge arrong, - et. The capacitive transducer 50 is also used to level the machine 10 relative to the polisuing means 14.

The support arra·; jc.uent 12 is lowered onto the polishing means 14 in the direction of arrow 62 so that the diamond 32 in the hoi ier 30 is brought into contact with the o

rotating scaive 16. The holding means 28 is rotated through 360 and the polishing rate of the diamond by the scaive 16 is sampled at predetermined intervals by time capacitive transducer 50. It will be appreciated that witii the provision of a stepper motor

44, the hoi ding means 23 is rotated in a stepwise manner. For o example, the polishing rate is sampled every 5 .

Those skilled in the art will appreciate that each f-.ed. of a diamond has a uriig.je grain characteristic. To achieve Ike <:·,)!.imum polishing rate of the diamond 32 the diamond must be polished along the grain of the facet, ie. the softest portion of the diamond. Cucc Live polishing rate of the diamond 32 has btί:π sampled through a revolution of the bolding means 23 about the shaft 46, the holding means 23 returns to the position at which the optimum polishing rate has been monitored by the

BAD ORIGINAL

Jl

- . :) -

' J - '·> ' '	d ; ; .· ' e -	d ' * ^! i ', h : 1	To
• i ; i i 1. 1 · ·· .’) 1, . i · 1 1 1 ·	5 i j nf H.e dim; md 52, ch	e a.aa 20	a.id the
,. c · 11 η -1 ήg , hi t 12	, i r.C 1 nd i ng Hue holder 30,	is , . ci	p i η' a fed
th e r< “C i ρ roc a t i ng	means, thereby causing the	di amend	32 to
Hate back and	forth radially across the	surf ace	of the

sci i vo 15.

As n.itorial is r. moved from the diem Hid 32, the disdnce between the plates 52 end 54 of the capacitive transducer 50 will change thereby varying the capacitance of the transducer 50, and hence its impedance. This causes the rtheatstone bridge arrangement to become unbalanced thereby generating an output signal. The output signal is an analog signal which is inversely proportional to the polishing rate of the diamond 32. Tin's output signal is fed to a miccoprocessor of the control means. Tire microprocessor controls the stepper motor 44 to orientate the diamond 32 to its correct grain position, and at trie sane time auleiatically adjusts the pressure on the diamond

32.

When polishing of the particular facet of the diamond 32 has been completed, the holder 30 comes into contact with the scaive 16 causing a signal io be sent via the slip ring arrangement 55 to the Microprocessor of the control means.

processor then delivers a command to the drive means 20 thereby raising the \uppoit arrangement 12 so that 32 is dear of the cr.aiye 16. _____________···'

AP 0 0 0 0 7 2 ine microof the arm the di amend

BAD ORIGINAL ft '3

• c*	,·'''· F ·, Pr	,1
r- 1 -ii.	els, the uuF,r 0	of the	held;-
34	thr ;ugh 22,5	so that	the r,e
pel	i.' d. The	w’pOr't	:rr u:g,
dir	ecti.n of acre	w 62 so	I ha t t
32	is or aught into	C J'i tic t	; wi th
Pol	i c. i r g process	is th,:O	r,p'F.

' ¹ /. j ¹. ' i		¹ Cl
e, with a - :,1	V , ; .,J 'W.o	on
g means <3 .-ill rot	i to the sh	a Γ t
xt facet of the die	mund 32 can	be
went 12 is ·g i :n 1c	• ,··. d in	LhC
'no said next f,cet	of the die,)	end
tb.e scaive 16. Th	e se.epl ing	and
ed.

If it is desired to inspect the distend 32 at any stage

of the polishing
the arm 20.	, The
pivot p i n	22
m o u 111 — d c n	top 0

process, the support arra support arrangement 12 is n the direction of arrow the support arrangement _-ment 12 is Phon pivoled using a h ] 2 .

lifted by about the andle 66

Referring

pol i Or	i ng	machine i
i ri . < ί t	„r.	is i11 us 1
re ί c-1\- ·	ce	numeral 70.
/2 of	;p	, e !; a cί i r. e,
be! ow,	i s	cmitied fur

In this t low to Figures 2 and l accordance with a •dic'd and is ecsijra In Figure 3 of the which will be d-asc ri the sate of clarity.

Fed Fee ut of the invc of the drawings, a

second	aspect of	the
f,d gen	,? rally by	the
d-'c.wi ngs	, a control	box
1 o d i n	«greater detail
nt ion,	the machine	70

comprises a bane plate /4 m.iuni.able on a bench top (nut shown) carrying the rotatable scaive (also not shown). Although the bench top and scaive are not illustrated, it will be appreciated

BAD ORIGINAL that they are the same as the scaive 16 and bench 18 illustrated in Figure 1.

The machine 70 includes a support arrangement 76 pivotally mounted at a free end of a cantilevered arm or beam 78. The support arrangement 76 is pivotal on the beam 78 in a substantially vertical plane. An opposed end of the arm 78 is mounted on a housing 80. The housing 80 is substantially vertically displaceable relative to the base plate 74 in the direction of arrows 82.

AP 0 0 0 0 7 2

A drive means comprising a DC motor 84 is mounted on the base plate 74. An eccentric 86 is mounted on an output shaft 88 of the DC motor 84. A projection 90 extends from the housing 80 and abuts against a periphery of the eccentric 86. Thus, by activating the motor 84 the housing 80 can be raised or lowered, as desired. The degree to which the housing 80 can be raised or lowered is adjustable by an adjustment means 92 comprising a threaded rod 94, a free end of the threaded rod 94 abutting against the projection 90. Those skilled in the art will appreciate that the degree to which the housing 80 and therefore the arm 78 and the support arrangement 76 is raised and lowered is dependent on the size of the diamond (not shown) being polished.

To effect reciprocatory motion of the diamond back and forth radially across the scaive, a second drive means in the

BAD ORIGINAL A form of a DC motor 96 is mounted on the base plate 74.

A cam-like formation 98 projects from the output shaft of the motor 96 and is sandwiched between a pair of follower formations 100 extending from the housing 80. As the DC motor 96 rotates, in use, the housing 80 is caused to reciprocate thereby '**·.·**

O causing reciprocatory motion to be imparted to the support

O arrangement 76.

jo >

A holding means 102 is rotatably mounted on the support arrangement 76. The holding means 102 comprises a holder 104 in which a diamond to be polished is receivable. The holder 104 is mounted fast with the end of a shaft 106, the shaft 106 being rotatably mounted in the housing 108. A drive means in the form of a stepper motor 110 is mounted on the housing. The stepper motor 110 drives the shaft 106 in a step-wise manner by means of a worm gear which engages a spur gear mounted rotatably fast with the shaft 106.

A further drive means comprising a stepper motor 112 is also mounted on the support arrangement 76 for rotatably driving the holding means 102 relative to the support arrangement 76. In this regard, the housing 108 together with its associated’output shaft 106 and stepper motor 110 is pivotally mounted via a pivot pin 114 on a bracket 116. The bracket 116 is suspended on a rotatable output shaft 118 of the support arrangement 76, via a body (hereinafter referred to as the target) 120. The target

BAD ORIGINAL

- 20 120 is mounted rotatably fast with the output shaft 118 of the support arrangement 76. The stepper motor 112 drives the output shaft 118 via a worm gear and spur gear assembly located within the support arrangement 76.

The shaft 106 of the holding means 102 is arranged at an angle relative to the shaft 118. The angle of the shaft 106 relative to the shaft 118 is adjustable by means of an adjustment moans in the form of a thimble micrometer 122. A lock nut arrangement 124 is provided for enabling the shaft 106 to be locked in position relative to the output shaft 118. It will be appreciated that, by adjusting the ang*le of the shaft 106 relative to the shaft 118, the angle of the diamond relative to the scaive is also adjusted.

A monitoring means 126 for monitoring the polishing rate of the diamond by the scaive is mounted on the support arrangement 76. The monitoring means 126 is connected to a control means located in the control box 72 for controlling the operation of the machine 70. The monitoring means 126 comprises an inductive transducer 128 which will be discussed in greater detail below with reference to Figure 6 of the drawings. The inductive transducer monitors the movement of the target 120 relative to the support arrangement 76. Those skilled in the art will appreciate that as material is removed from a facet of the diamond being polished, the target 120 will move relative to the support arrangement 76 and this movement will be monitored by the

BAD ORIGINAL &

Z L 0 0 0 0 dV

V3

Ci · i : 1 « ο ,	t m 0 C '	•:/ey of the cob;	· 11 . J j · i u c , £·-·£.££ i □
illLstrste	d and	is designated goner	ally ty to? r?^cer?rcG rum?-·:!
130. The	cont	no! circuitry 130	effectively comprises nine
modules,	v iz a	digital processor	module 133, a keyboard and
stepper m	otor i,	nterface module 134,	a digital ram port module

136,	a	timer interrupt control 1er module 1	'' f	an analog
d^; g '	- n?	converter module 1-C^!, a sto-poe’ mo,?;:	n lea	^; a a j d -	'!'/££
m?c.	’ o	i * -, m e i!, o l. ο r i o g i _ a n d r. . — r m O'...	le 1-	i, a con	ί J £ t
S	? circuit module 145 and a host ccmmuric	£ £ j C £	port mo	tule
145.
		Referring firstly to the digital pro	cesso	r module	·. no - - - J
V k ·. . — L ! 1 1 J	me	:dule 132 comprises a microprocessor	1 ££ - · - j	an eras	--1.
Ρ··Ό<	-am,	'otl? read only memory (EPRC”) 153, a	r- ’ ; - c	random ac	£ - S S
memo	u	(3.-.2) 152. The FA2 152 may ccrtver.ien	j b	e a CM IS	3.-.2 .
F urt	her.	, this module 132 comprise an address	decod	er 154.	The
mode	1 e	132 further comprises a crystal c	soil! »	a ter 155	for
p rov	idi r	;g clocking pulses via a hex Schmitt	trig?	er 153 to	t r. o
c i re	Jit	130.
		The module 132 effectively controls	t ii e b	asic funct	i ons
of	the	machine 70 and receives ar.d precesses	data	from exte	rnal
i npu	4- '-b .	It also controls the operation cf tr	e CC	motors 84	and
96	and	the stepper motors 110 and 112. Furth	er,	the module	132

controls and interprets data received from the monitoring means

BAD ORIGINAL : si odes c a the ka.'board 150 ;Ie 145 to a host

P¹ΐ row t: the keyboard and stepper ssntor irterraosr.able peripheral Lerr-2 7-2 bed,sen tr?

eoeer ir.opo·' 1 c-oic and driver i:;c-^!-'jl e 142.

:e mod-T e 134, trie model e c.-gris-s a pr

AP 0 0 0 0 7 2 d'g'^:te.l ram port module 135

-..: J. I j'J;

-1 ve T adores ±>4 eight bit latched memory mapped 1/<

jorts for direct processor interface cf the keyboard 150, the CC :odd.r 1 ooio and d-'ioe.' modole 144 and the contact sense circuit moo to Lee's c n the keyboard 153

The timer interrupt controller module 133 comprises a counter timer controller 163. Tin’s module 138 provides interrupts to the processor module 132 and also provides timing logic for delay routine and abort timers. Is also functions to sense contact of the holder 104 with the scaive to permit immediate reaction cf the contact of the holder 104 with the sealve by terminating polishing of the diamond and also reducing damage to the scaive and the holder 104. The contact of the

BAD ORIGINAL ft hoi car 104 wit:

contact sense ci

The analog to digital convertor module 140 comprises a fast 12 bit analog to digital convertor 172. This module 142 converts a varying analog signal output by the monitoring means 126 into a correspond!ng 12 bit digital word for use by the processor module 132. The module 140 also contain: a sample and ho'd circuit 173 to provide stable analog input signals to the he convertor 172 has direct interface ctosbil ithe processor module 132. The processor medals 132 together with a reading from the analog to digital cor.vertc.' module 140 controls the beam 78 and hence ensures a constant ;rtcr 172.

ties one	3	the
together	wi	th

module 1	40	co
pressure	on	the

The stepper motor logic and driver module 142 comprises two identical circuits 172, one for each stepper motor 110, 112. Each circuit 174 comprises a stepper motor controller 176, the output of which is connected to a quad Darlington array integrated circuit 178. The relevant stepper motor 110 or 112 is connected to its associated circuit 174 via a connector 130.

The DC motor logic and driver module 144 provides bidirectional control for both the motors 84 and 96. The module includes brake stepping capabilities which enables accurate control of the DC motors 84 and 96 and individually variable speed inputs. The module 144 comprises an audio amplifier 182 which is used to generate a saw tooth waveform. An output from

BAu ORIGINAL driver 1 ampli fier 132 is cογ,γ.:-cted to a push-pu 11 four c for driving the DC motors 84, 98. The DC motors ::1

84,96 are connected to the driver 134 via connectors 185.

The contact sense circuit module 145 provides clean response pulses which are fed into the counter timer controller 168 of the timer interrupt controller module 133. These pulses are interpreted via an interrupt from the counter timer control', er 163 by the processor module 132 which activates the DC motor 84 thereby terminating further polishing cf the facet of the diamond being polished. Variable response speed is provided to ensure the correct lifting action of the beam. 78 by the motor 84. The holder 104 of the holding means 1C2 comprises a pot

104.1 and a ring 104.2. Thus, the module 145 comprises two sensors 170, one for sensing contact between the pot 104.1 and the scaive, and the other for sensing contact between the ring

104.2 and the scaive.

Referring finally to the host communication port module 146, this module comprises two D-type latches 188 which are connected to a twenty way connector 130. This module 145 enables the machine 70 to be connected to a host computer for monitoring, inter alia, the performance of the machine to ensure constant operation of the machine, for monitoring operation and fault status of the machine and coupling the machine to a wages and salaries department to aid in wage calculations for an operator of the machine. Further, by means of this module 146

BAD ORIGINAL

ad the connection tc tec ''cost computer, daily, weekly, cr itenthly outputs can be obtained to determine productivity and efficiency of a plurality of the machines 73 a-..1 their cctrators.

(Ο

Ζ3 ο

Referring now to Figure 6 of the drawings, a schematic block diagram of a circuit of the monitoring means 126 is shown. The transducer 128 comprises a dual coil sensor 192 comprising a first coil 194 and a second coil 196. The sensor 192 measures movement of the target 120 relative to the transducer 123.

The monitoring means 126 comprises a dual track voltage regulator 193. Tne regulator 193 has a -^37 and a -8V output serving as a voltage supply to all the components of the circuit of the monitoring means 126.

The monitoring means circuit comprises an oscillator 200 connected in series with an automatic gain control circuit 202 and a buffer driver 204. The oscillator oscillates at a predetermined frequency which is in the region of one MHz. The output signal from the oscillator 200 is fed via a differential phase detector 205 to the coils 194 and 195 of the sensor 192. An output signal from the sensor 192 is fed back via the differential phase detector 206 through a buffer driver 208, to a logarithmic amplifier 210 where a log signal is converted to a linear signal and is amplified, through a final buffer amplifier 212 and a sample and hold voltage follower 214 to an analog output terminal 216. The analog output terminal 216 is connected . I to an input terminal 218 of the analog to digital convertor

BAD ORIGINAL hT e 14j (,-i ί·¹,;

of tr

C on r J i Ci r; >

try 130

The monitoring moans 126 operates on the eddy-current loss principle. The coils 134 and 195 of the sensor 192 are activated by the 1 MHz signal from the oscillator 200. Magnetic

flux lines	emanating frcm	the coils 194 and 195 at a 1 MHz rate
pass into	the target 120	and produce eddy-currents. As the
target 120	moves closer to	the sensor- 192, more eddy-current are
g-.-n: rated	and the Tosses	within the sensor 192 become greater.
Conversely,	as the target	120 moves away frown the sensor 192 tne
losses become less.

AP 0 0 0 0 7 2 tage via v ariacio

152.

These impedance variations are converted to a DC volthe phase detector 205 which is directly proportional to s in the distance between the target 120 and the sensor

The first coil 194 is an active element which senses the movement of the target 120 and the second coil 195 serves as a compensating coil to balance and cancel the effects of temperature change.

Referring once again to Figure 2 reference is made to the control box 72 of the machine 70. All the electronic circuitry including the circuit 130 is housed within the control box 72.

BAD ORIGINAL &

STOOOOAA

		f ” a k	?ycctrd 160 comprises	,Ί	C. ’ 5 ~ ,	ay el overt in f'9
f: '*n	cf	c ·- ί .'Z	.mar c i s ρ i ay e. c e see a^;	’ 1	in	to a pi oral it.- c '
		-,-?	I ma seven Ls L a i r c rec	;* Ί	* -. - w -.-	i me cf facets c“ 2

r* 4 - _:Li . Cl i ¹	,-. η ;j	In t:	ne embodiment of the i	ny	en ti on	illustrated, the
CISC	i □ '/ --	220 is	divided into sixteen		secmen	ts 222. A light
emi t	ti ng	di ode	(LED) 224 is arranged	in	each	segment 222. The
I r 3 ¹ LLU	s 224 are	connected to connectors	166.1	and 166.2 of the
digi	tai	ram port	module 136 of the cir	cuit 130

facets cf facets is energised energised,

rus,	the LED's 224	w. I I b	V. Q »' tl ’	- -------		v a r	i C ·.» o
the di	amend are pol	1 S hi 0 d .	If a	d I am. j r	c havi	ng e	¹ '3 ‘ -
bei nc	i poli shed ,	two adj	acerb	LEC s	224	wi 11	be
si mu I	tanecusly in	re spec	*- r· ^c L O .	each	facet	•	Cnee
tee	LED's 224 re	main on	so that the	oper	d lO Γ	can

monitor the progress of the polishing of the facets. The LEO's 224 will ba de-energised when the polishing process has been completed O;^- w.’ien tee maemr.e is reset.

The keyboard 150 comprises a plurality cf buttons and may be in the form of a membrane-type keyboard. Thus, the keyboard 153 includes a start button 225 with its associated LED

223, and an auto button 250 with its associated LED 232. A button 234 is provided for raising and lowering the housing 80 via the DC motor 84.

A set of buttons 245, 233 and 243 each with an associated LED 242 is provided and the button 236, 233 or 240 are operable in dependence on the number of facets of the diamond to

BAL) ORIGINAL

- 23 be polished. Thus, for exnmpl?, for a sixteen facet diarn;-; butte.-. 225 will be epe.-ated, and for an eight facet diamonc, button 240 will be operated. If the lift circuit is to be a;fvated or: the pot 104.1 of the holder 104 making contact with t-e scaive, either buttons 236 or 240 as described above will be operated, depending on whether a diamond having sixteen facets or eight facets respectively is to be polished. However, if the lift circuit is to be activated on contact of the ring 104.2 of the holder 104 with the scaive, and for a diamond having eight facets, button 233 will be operated.

AP000072

Tne keyboard 160 further comprises a seek on button 244, a seek off button 246 and a level button 243. Each button 244, 246 and 248 has an LED 250 associated therewith. The LED's 223, 232, 242 and 250 are connected to the connectors 166.3 cf the chgital ram port module 136.

The keyboard 160 further comprises a pair of buttons 252 for rotating the shaft 106 to bring a predetermi ned facet into contact with the scaive. A further pair of buttons 254 is provided for rotating the holding means about the shaft 118 for varying the orientation of the grain of a predetermined facet of the diamond relative to the scaive.

Yet a further pair of buttons, the wass buttons 256, is provided for rotating the shaft 106 through fractions of a degree for bringing various portions of a predetermined facet of

BAD ORIGINAL the ,i ph toe si ϋ! s;

zoo r pro 7 n;

display 253 is electrically connected

	nioni tori ng	means	ci rcui t	The display
>-«
	provi des	vi sual	indication of the rate
Ό	from the	facet of	the diamond being pol
μ***	operator	of the	mac hi ne	70 to moni tor

Ar ·.	material	v i s u a 11 y	and to	take apprepria

	eg. by a	uj u s ti ng	the o;	rientaticn of t
	reia t i ve	to tine	scaive	to improve t

material.

o terminal 216 cf the is a digital display and of removal of material shed. This enables an he rate of removal of e action when necessary, e facet o' the diamond e rate cf r-mo-.a! of

The display 258 can also be used to calibrate the transducer 12S when the machine 70 is initially installed. Further, the display 253 aids in levelling Ge machine 70 relative to the scaive, in use.

Finally, a reset button 253 is provided for resetting the machine 70. All the buttons referred to above are connected to a connector 261 (Figure 4D) . of the peripheral interface adaptor 162 of the keyboard and stepper motor interface module 134 of the control circuitry 130.

o

In use, the support arrangement is pivoted through 180 in the vertical plane relative to the beam 73 so that a diamond can be placed in the holder 104 of the shaft 105 in the holding means 102. The support arrangement 75 is again pivoted through

BAD ORIGINAL

ΚΊ

152 in sea said vc Wi c al plane so tint the hoi dz r

Assuming a diamond having sixteen facets is t: te polished, button 236 is operated and the start button 225 is operated. If the machine 73 is to polish all facets of the diamond automatically, the button 230 is also operated. The DC motor 84 is activated to lower t'ne diamond into engagement with the rotating scaive and the diamond is' caused to reciprocate radial! v back and forth across the scaive bv activation f-.e DC

AP000072

In auto'^: operation, the holding means 102 is rotated o through 360 and the polishing rate of the diamond in the holder

104 is sampled at predetermined intervals by the inductive transducer 123. The stepper motor 112 rotates the holding means

102 in a stepwiss manner, for example, the polishing rate is o sampled at 5 intervals. The facet of the diamond being polished is indicated by the LED 224 of the relevant segment 222 of the display 220. Once the polishing rate has been sampled through a complete revolution of the holding means 1C2 by the inductive transducer 128 and processed by the circuit 130, the stepper motor 112, under the control of the circuit 150 returns the holding means 102 to the position at which the optimum polishing rate of that particular facet is achieved and polishing of the facet of the diamond commences.

BAD ORIGINAL

As material is removed from the diamond under the action of the scaive, the target 120 moves relative to the inductive transducer 123. Ao the target 120 moves away from the transducer 123 the eddy-current losses are reduced and these impedance variations are sensed by the coils 194 and 195 of the sensor 192 and are converted to a DC voltage by the phase detector 206. The DC voltage is processed and is output at the terminal 216. The DC voltage signal is then fed to the analog to digital convertor module 140 whereafter'it is processed by the digital processor module 132. As previously described, the DC voltage signal output at the terminal 215 is directly proportional to the distance between the target 120 and the inductive transducer 128.

The analog to digital convertor module 140 at the same time controls the pressure on the diamond via the beam 78 and ensures constant pressure on the diamond being polished.

When the polishing of the particular facet has been completed, the pot 104.1 or the ring 104.2, as the case may be, will come into contact with the scaive and this contact will be sensed by the relevant contact sensor 170 of the contact sense circuit module 145 and an appropriate signal is sent by the processor module 132 to the DC motor 84 thereby causing the housing 80 and tnus the beam 78 and the support arrangement 76 to lift the holding means 102 clear of the scaive under the action of the eccentric 86.

APO00072

Bad original

The digital prccessor module 82 tnen ci.z-s a s5ς'a 1 tobe soot to tno stepper :m.‘.ar 110 ~ng pn₃ shaft 103 is rotated through a predetermined amount to orientate the next facet of the diamond 104 for polishing. In the case of a diamond having o sixteen facets the shaft 106 will be rotated through 22.5 . A signal is then sent by the processor module to the DC motor 84 thereby causing the housing 80 and therefore the beam 78 and the support arrangement 76 to bo lowered to bring the said next facet of the diamond into contact with the scaive. The sampling and polishing process is then repeated.

Once all the facets of the diamond have been polished, a final signal is sent to the DC motor 84 to lift the housing 80 and thereby the holding means 102 clear of the scaive and the diamond can then be removed from the holder 104.

It will be appreciated that the machine 70 could also be manually operated and the facet to be polished would then be selected using the buttons 252 and the orientation of that facet relative to the scaive would be selected by the buttons 254. By using the wass buttons 256, the facet being polished can be more accurately aligned relative to the scaive.

It is an advantage of the invention that the entire polishing process is conducted automatically without the need for skilled operatives. Further, the machine 10, 70 can be levelled and set for use rapidly using the capacitive transducer 50 or the inductive transducer 128, as the case may be.________________

BAD ORIGINAL d

Claims

1.

A polishing machine for polishing a gemstone which i ncl udes a support arrangement movably mountable relative to a polishing means;

a holding means for holding the gemstone to be polished, the holding means being rotatably mounted on the support arrangement and being movable together with the support arrangement to move the gemstone into and out of contact with the polishing means;

a drive means for rotatably driving the holding means relative to the support arrangement;

a control means for controlling operation of the said drive means and thus the rotation of the holding means relative to the support arrangement; and a monitoring means for monitoring a polishing rate of the gemstone at each of a plurality of predetenni ned positions of a revolution of the holding means about the support arrangement and for sending data representative of the polishing rate at the said positions of the holding means to the control means, the control means being operable to process the data to determine the position of the holding means at which an optimum polishing rate is achieved and to operate the drive means to position the holding means at that position at which the said optimum polishing rate is achieved.

2. The machine as claimed in Claim 1 which includes a height-varying means for adjustably varying the height of the support arrangement and hence the holding means relative to the ’

AP 0 0 0 0 7 2

BAD ORIGINAL — Ati — pci i shi -,-: means.

3. The machine as claimed in Claim 2 in which the support arrangement is pivotally mounted on a free end of a bean which extends cantilever-fashion from a movable housing, the heightvarying means acting on the housing for adjustably varying the height of the support arrangement.

4. Tne machine as claimed in Claim 3 in which the heightvarying means comprises an electric mote-' having an eccentric mounted on an output shaft thereof, the eccentric co-operating with a projection extending from the housing, the position at which the projection extends from the housing being adjustable to adjust the degree to which the height-varying means raises and lowers the support arrangement relative to the polising means.

5. The machine as claimed in Claim 3 or Claim 4 which includes a reciprocating means for imparting a reciprocatory motion to the support arrangement and hence the holding means.

6. The machine as claimed in Claim 5 in which the reciprocating means comprises an electric motor which has a cam-like formation on an output shaft thereof, the cam-like formation cooperating with a pair of spaced follower formations projecting from the housing with the cam-like formation extending between the follower formations.

BAD ORIGINAL

7. The π ’·. c h i ne as claimed in ar.y erne cf too preceding claims ic which the drive means comprises a stepper motor for rotating the holding means in a stepwise manner relative to the support arrangement to provide the said positions at which the monitoring means monitors the polishing rate of the gemstone by the polishing means, the holding means being mounted rotatably fast with, but axially slidable relative to, an output shaft of the support arrangement extending from the stepper motor.

8. The machine as claimed in any one of the preceding claims in which the holding means comprises a housing within which a shaft is rotatably mounted, at least one end of the shaft projecting from the housing and a holder for holding the gemstone being mounted rotatably fast with the said end of the shaft.

9. The machine as claimed in Claim 8 which includes a second drive means for rotatably driving the shaft of the holding means, the second drive means being controllable by the control means.

10. The machine as claimed in Claim 9 in which the second drive means comprises a stepper motor wfiich drives a worm gear which, in turn, is engageable with a spur gear mounted rotatably fast with the shaft of the holding means, the stepper motor, in use, rotating the shaft in predetermined steps to polish various portions of a surface of the gemstone in a predetermined manner.

AP ο η ο o 7 2

BAD ORIGINAL

Η «* ©

yjr

11. ί η m a ci, 12 as c 1 a ή a d ι π a · irzlusive in which the shaft is arrive· the support arrangement.

12. The machine as claimed in Ci adjustment means for adjusting t'ne an extends relative to the support arrange·, ccmpris'ng a thimble micrometer.

13. The machine as claimed in / inclusive, in which the holding means in suspended from the output shaft of the n body.

14. The machine as claimed i' monitoring means comprises an inducti/e the movement of the body relative to the said movement being caused by removal o stone under the action of the polishing

15. The machine as claimed in Cl a ducer comprises at least one coil which of a predetermined frequency for gene' flux which results in eddy-current loose tude of the losses being dependent or. relative to the support arrangement.

n 11 which includes an e at which the shaft s, the adjustment means .-- cf or Claims 7 to 12 >des a bracket which is eport arrangement via a

a i m 13 in > ,hich the ' -nsducer f or rr ion i tori ng ·. jpport arrange merit, the material from the gem- vans.

m 14 in which the trans; excitable by a signal mi ng lines of magnetic in the body, the magni•e position of the body

BAD ORIGINAL

-Ί

- J Ζ 15. The machine as cl aimed in Claim 15 in which the transducer includes processing circuitry for precessing variations in iccedence of the coil as a result of the eddy-current losses to provide an output voltage signal which is directly proportional to the rate at which material is removed from the gemstone by the polishing means.

17. The machine as claimed in Claim 16 in which the said output voltage signal is an analog DC voltage signal which is fed to the control means, the control means including an analog to digital convertor for converting the signal to a digital signal to be processed by a microprocessor of the control means.

18. The machine as claimed in any one of Claims 15 to 17 inclusive in which the transducer includes two coils, a first coil sensing the movement of the body and the resultant losses with a second coil serving as a compensating coil to balance and cancel the effects of temperature change.

19. The machine as claimed in any one of Claims 1 to 13 inclusive in which the monitoring means comprises a capacitive transducer having a first plate mounted fast with the body of the holding means to be rotatable therewith and a second plate mounted on the support arrangement parallel to and spaced from the first plate.

APO 0 0 0 7 2

B^D ORIGINAL Cjtl

1C

20. The machine as claimed in Claim, 13 in „hich tsc- capacitive transducer is a merged in a Wheatstone bri dge arrangement which is set to provide a null output prior to commencing polishing cf the gem,stone.

•'3

Vb v u u in

21. The machine as claimed in Claim 20 in which the capacitive transducer is responsive to removal of material frcm the gemstone by the polishing means, the said removal cf material causing a change cf capacitance of the transducer which results in the Wheatstone bridge becoming unbalanced to generate an output signal which is inversely proportional to the rate at which material is removed from the gemstone, the generated signal being fed to, and processed by, a microprocessor of the control means .

22. A method of polishing a gemstone which includes mounting the gemstone in a holding means which is rotatable about a substantially vertical axis;

bringing a portion of a surface of the gemstone into contact with the polisning means;

rotating the holding means through a revolution about the said vertical axis;

monitoring the rate at which material is removed from the said portion of the surface of the gemstone at predetermined positions of the revolution of the holding means and generating an electrical output signal representative of the rate of removal of material from the said portion of the surface of the gemstone

BAD ORIGINAL

3?

a t each pc si t ion;

processing the signals so generated to ascertain at which position cf the revolution of the holding means the optimum rate of removal of material from the portion of tne surface of the geifistone is achieved; and returning the holding means to the said position at which the optimum rate of removal of material from the gemstone is achieved and commencing polishing of that portion of the surface of the gemstone.

23. The method as claimed in Claim 22 which includes mounting the gemstone in a holder mounted at an end of a rotatable shaft arranged at an angle relative to the said vertical axis about which the holding means is rotatable, and adjusting the angle of the shaft relative to the vertical axis to align the gemstone relative to the polishing means.

24. The method as claimed in Claim 23 which includes, after sampling and polishing the said portion of the surface of the gemstone, lifting the gemstone off the polishing means, rotating the rotatable shaft through a predetermined arc to bring another portion of the surface into position to be polished, bringing the said next portion of the surface of the gemstone into contact with the polishing means, and repeating the sampling and polishing process on the said next portion of the surface of the gemstone. ..

AP 0 0 0 0 7 2 bad origin*

25. Th:· method as claimed in ary one of Claims 22 to 24 inclusive in which the holding r.-acs is suspended fr;·-. a surcort arrangement via a body which is axially di solaceable alone the said vertical axis relative to the support arrangement, and in which the method includes monitoring the rate of removal of material frcrn the portion of the surface of the gemstone by monitoring the axial displacement of the holding means relative to the support arrangement, the axial displacement of the holding means being proportional to the rate of removal of the material.

26. The method as claimed in Claim 25 which includes monitoring the axial displacement of the holding means relative to the support arrangement by means of an inductive transducer.

27. The method as claimed in Claim 26 which includes causing lines of magnetic flux to be generated in the body of the holding means to cause eddy-current losses in the body, and monitoring variations in the impedance of the transducer as a result of the losses to produce the electrical output signal, the signal being an analog signal which is directly proportional to the rate of removal of material from the portion of the surface of the gemstone being polished.

28. The method as claimed in Claim 27 which includes converting the analog signal to a digital signal for processing by a control means which controls the polishing of the gemstone.

BAD ORIGINAL

23.

nonito ·* r\ - lO LHC

The method as claimed in Claim 25 which :g the axial displacement of the holding means jpport arrange tent by means cf a capacitive tran i n c 1 u oe s rela ti ve due?,-.

30. The method as claimed in Claim 29 in which the capacitive transducer comprises a pair of spaced apart parallel plates, a first plate being mounted fast with the support arrangement and a second plate being mounted fast with the body of the holding means to be rotatable therewith, and in which the method includes monitoring variations in the capacitance of the transducer due to variations in the spacing between the plates, the spacing between the plates being variable in response to the removal of material from the portion of the surface of the gemstone.

31. The method as claimed in Claim 30 which includes connecting the plates in an arm of a Wheatstone bridge arrangement and initially balancing the Wheatstone bridge arrangement to provide a null output prior to commencing polishing of the portion of the surface of the gemstone, the removal of material from the portion of the gemstone causing the Wheatstone bridge arrangement to become unbalanced to generate the said electrical output signal which is inversely proportional to the rate of removal of material from the portion of the surface of the gemstone, the output signal being an analog signal.

32. The method as claimed in Claim 31 which includes converting the analog signal to a digital signal for processing by a control means which controls the polishing of the gemstone.

AP 0 0 0 0 7 2

BAD ORIGINAL

33. new machine for polishing a gemstone substantially as described and as illustrated herein.

34. A novel method of polishing a gemstone substantially as described and as illustrated herein.

•3> -..3 PAT El) tht.? Pry of September ₍1 933. /, _- J3 *v • r—--j/t~ i i 7 ’