The crystal slicing method is described as follows. A crystal is sliced in a plane parallel to flat, opposed parallel end faces of the crystal. The end faces of the crystal are gripped by a pair of opposed, perforated platens of a pair of vacuum chambers, one of which is translatable relative to the other. A blade cuts the crystal through the desired plane. A spring biases one of the vacuum chambers away from the other vacuum chamber while both of the faces are gripped by the vacuum chambers and the blade is cleaving the crystal. A sliced portion of the crystal gripped by one of the vacuum chambers is pulled away from the remainder of the crystal gripped by the second vacuum chamber when the crystal was cleaved by the blade through the plane

Benedicto, J. S. J.

Hallberg, F. C.

Woodgate, B. E.

English

NASA Technical Reports Server

United States Patent [191 
Benedicto et al. 
METHOD AND APPARATUS FOR SLICING 
CRYSTALS 
Inventors: John S. J. Benedicto, Falls Church, 
Va.; Bruce E. Woodgate, Crofton; 
Frederick C. Hallberg, Wheaton, 
both of Md. 
The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
Assignee: 
Appl. No.: 906,298 
Filed: May 15, 1978 
Int. CI.2 ............................................... B28D 1/32 
U.S. CI .  .................................... 125/23 R; 51/235; 
83/152; 83/870; 269/21 
Field of Search ........................... 83/870, 152, 27; 
51/235, 283; 125/13 R, 23 R, 269/21 
References Cited 
U.S. PATENT DOCUMENTS 
FOREIGN PATENT DOCUMENTS 
1,387,590 3/1975 United Kingdom ...................... 83/152 
Primary Examiner-Harold D. Whitehead 
Attorney, Agent, or Firm-Robert D. Marchant; John R. 
Manning; John 0. Tresansky 
1571 ABSTRACT 
A crystal is sliced in a plane parallel to fiat, opposed 
parallel end faces of the crystal. The end faces of the 
crystal are gripped by a pair of opposed, perforated 
platens of a pair of vacuum chambers, one of which is 
translatable relative to the other. A blade cuts the crys- 
tal through the desired plane. A spring biases one of the 
vacuum chambers away from the other vacuum cham- 
ber while both of the faces are gripped by the vacuum 
chambers and the blade is cleaving the crystal. Thereby, 
a sliced portion of the crystal gripped by one of the 
vacuum chambers is pulled away from the remainder of 
the crystal gripped by the second vacuum chamber 
when the crystal has been cleaved by the blade through 
1,872,415 SA932 Growley ................................ 51/283 the piane. 
2,597,180 5/1952 Reaser ............................ 51/235 UX 
3,901,423 8/1975 Hillberry ........................... 125/23 R 3 Claims, 4 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=19800010674 2020-03-21T02:26:37+00:00Z
U S .  Patent Jan. 22, 1980 9 1 72 
4,184,472 
1 2 
cutting plane can be adjusted relative to the end faces to 
METHOD AND APPARATUS FOR SLICING enable the crystal to be sliced through each of a plural- 
CRYSTALS ity of desired planes. The blade intersection with the 
side of the crystal is precisely controlled, to within one 
ORIGIN OF THE INVENTION 5 mil, by connecting the blade holder to a pair of orthogo- 
The invention described herein was made by employ- nally mounted lead screws that respectively Control the 
ees of the United States Government and may be manu- cutting plane of the blade and the: blade position relative 
factured and used by or for the Government for govern- to the side of the crystal. 
mental purposes without the payment of any royalties A further feature of the invention is that the perfo- 
thereon or therefor. lo rated area of the translatable plate is bordered by a 
resilient cushion, formed, for example, of neoprene 
rubber. The cushion protects the crystal from damage BRIEF SUMMARY OF THE INVENTION 
The Present invention relates generally to an appara- when the opposed faces of the crystal are simulta- 
tus for slicing a crystal, and more Particularly, to such neously gripped, and enables irregularities on the crys- 
an apparatus wherein flat, opposed Parallel end faces of l5 tal face to be compensated, whereby there is increased 
the crystal are gripped and urged apart while the crystal suction and more uniform pull by the vacuum on the 
is being cut through a plane parallel to the end faces. 
as utilized in connection with X-ray spectrometers, 
When the crystals are cleaved by a wire they have a 
tain crystals having uniform thickness. When the crys- cisely to a thickness Of 
impossible to obtain very thin crystals, ice., crystals tal cutting apparatus wherein crystals of uniform thick- 
having thicknesses on the order of 5 mils, a frequent ness are easily obtained, at relatively high speed and 
requirement of KAP and RAP, soft crystals utilized in with high yield. 
X-ray spectrometers. Both ofthe prior art, manual tech- Another object of the invention is to provide a crystal 
niques were found to be slow and have a poor yield. 30 cutting apparatus wherein the Crystal iS cut without 
While numerous machines have been developed to cut scratches. 
crystals and other objects in a precise manner, none An additional object of the invention is to provide a 
apparently has been developed to precisely cut soft crystal cutting apparatus wherein opposite, parallel end 
crystals, such as KAP and RAP crystals to thicknesses faces of the crystal are gripped and urged away from 
of 5 mils. A further problem is dealing with cleavable 35 each other while the crystal is being cleaved by a cut- 
soft crystals, such as the RAP and KAP crystals, is that ting blade. 
they are extremely fragile as they are formed of delicate The above and still further objects, features and ad- 
materials. In consequence, handling these crystals by vantages of the present invention will become apparent 
hand, Particularly to cleave them to 5 mils, is extremely upon consideration of the following detailed description 
difficult and there is a high risk of such handling and 40 of one specific embodiment thereof, especially when 
cleaving leading to irreparable crystal damage. taken in conjunction with the accompanying drawing. 
In accordance with the present invention, a new and 
improved aparatus for cutting crystals, particularly soft BRIEF DESCRIPTION OF THE DRAWINGS 
crysta1s, to thicknesses On the Order FIG. 1 is a perspective, overall1 view of a preferred 
ofl.005 inches, includes bringing a blade into contact 45 embodiment of the apparatus of the invention; 
parallel faces of the crystal, while the opposed faces are 
the crystal as the crystal is being cleaved by the blade 50 larly showing a rubber cushion in contact with the 
through a plane where it is desired to make a slice. In a 
faces are gripped by first and second opposed, perfo- 
' 
faces of the crystal, 
Previously, relatively soft, KAP (potassium acid It is, accordingly, an object of the present invention 
2o to provide a new and improved apparatus for cutting 
Another object of the invention is to provide a crystal 
crysta1s to be cut Pre- 
phthalate) and RAP (rubidium acid phthalate) 
have been crystals in a precise manner, by hand using a wire Or sharp 
tendency to be scratched and it is often difficult to ob- 
tals are cut by sharp blades, such 
cutting apparatus which 
razor blades, it is 25 A further Object of the invention is to provide a crys- 
and 
with an edge Of the 
being gripped and urged apart* 
tion of the 
between a Pair Of opposed FIG. 2 is a perspective view of a crystal adapted to 
the cut by the apparatus of FIG. 1; a POr- 
is pulled away from the remainder of 
FIG. 3 is a top plan view of a plate included in a 
vacuum chamber for holding the crystal in situ, particu- 
crystal; and preferred embodiment, the flat, opposed? parallel end FIG. 4 is a side view in cross FIG. 1 specifi- 
rated plates of a pair of vacuum chambers. The use of a 
vacuum to grip the opposite faces of the crystal is par- 55 Opposed faces Of the crysta1 in situ* and a 
cdlY showing the crysta1, a pair Of plates for 
for 
ticularly advantageous because of the delicate nature of 'leaving the crysta1 in a plane between the faces 
the crystal and the very thin slices which are obtained gripped by the vacuum plates. 
DESCRIPTION OF THE PREFERRED from it. In addition, the vacuum facilitates release of the 
EMBODIMENTS crystal slices and enables the force applied to the oppo- 
site faces of the crystal to be easily controlled, to pre- 60 
vent possible breakage of the crystal at points other than Reference is now made to FIG. 1 of the drawing 
the desired cleavage plane. wherein there is illustrated a station 11 for gripping a 
The first plate is translatable relative to the second relatively Soft mother crystal 12, such as a, KAP, or 
plate, with a spring urging the first plate away from the RAP crystal, having the shape of right parallelepiped, 
second plate while the plates grip the end faces. A 65 as illustrated in FIG. 2. Crystal 12 includes a pair of 
holder for the crystal cutting blade is positioned to opposed, parallel faces 13 and 14 and is to be cleaved in 
enable the crystal to be cut by the blade through each of a plurality of planes 15 parallel to faces 13 and 14. Crys- 
the several planes. The holder position is variable so the tal 12 is cleaved so that a plurality of very thin crystal 
4,184,472 
3 
slices, each typically having a thickness on the order of 
5 mils, are formed. 
The apparatus for cleaving crystal 12 through planes 
15 includes microtome or blade-16 that is carried by a 
blade holder 17. Blade holder 17 is adapted to be verti- 
cally and horizontally translated by vertical and hori- 
zontal lead screws 18 and 19. Lead screw 18 is manually 
controlled by handle 21 so that the positon of the cut- 
ting edge of microtome 16 can be controlled very pre- 
cisely, preferably to within one mil. Blade 16 and holder 
17 are horizontally translated into a side wall of crystal 
12, between faces 13 and 14, by driving the holder with 
lead screw 19, that is driven by motor 22. The entire 
mechanism including gripper 11, lead screws 18 and 19, 
holder 17, and motor 22, is stably mounted on a base 
plate 23. 
Gripping station 11 includes lower and upper vacuum 
chambers 25 and 26 respectively having perforated, 
flat-faced platens 27 and 28 that respectively mate with 
and grip lower and upper faces 13 and 14 of crystal 12. 
Vacuum chamber 25 is fixedly mounted on base 23, 
while vacuum chamber 26 is vertically translatable 
relative to chamber 25, by virtue of the connection 
between chamber 26 and vertically extending rod 29. 
Rod 29 is biased upwardly by tension spring 31, so that 
chamber 26 and platen 28 have a tendency to be biased 
away from chamber 25 and platen 27. Opposite ends of 
tension spring 31 are connected to bracket 32, through 
which shaft 29 extends, and collar 33, the vertical posi- 
tion of which can be adjusted by set screw 34. Adjust- 
ing the vertical position of collar 33 changes the tension 
on spring 31 and therefore the force with which platen 
28 has a tendency to pull face 14 of crystal 12 away 
from the remainder of the crystal when the crystal is 
cleaved by microtome 16. 
As illustrated in FIGS. 3 and 4, platens 27 and 28 
respectively include a matrix of relatively small diame- 
ter, vertical bores 35 and 36 that draw a vacuum on 
faces 13 and 14 of crystal 12. In one preferred embodi- 
ment, bores 35 and 36 are formed on &inch centers by 
using a number 65 drill bit on platens 27 and 28. Sur- 
rounding the matrix of bores 36 is a border formed of a 
resilient, air impervious strip 37, preferably formed of 
neoprene rubber. The bottom face of strip 37 engages 
the top face 14 of crystal 12 so that the crystal does not 
bear directly against platen 28. The resilient, air confin- 
ing strip 37 enables crystals having non-uniform top 
faces to be handled by the machine of the present inven- 
tion without scratching the top surface, and enables any 
non-uniformity introduced on the top surface, during 
the cutting operations, to be compensated. Cushioning 
strip 37 also prevents chipping or cracking of crystal 12 
because face 14 cannot contact platen 28, while en- 
abling an increased force to be applied against face 14, 
resulting in a uniform pull on the face. The areas of the 
matrices in platens 27 and 28, as well as border 37, 
relative to the areas of faces 13 and 14, are such that all 
5 
10 
15 
20 
25 
30 
35 
40 
45 
50 
55 
of the bores 35 are covered by bottom face 13 and all of 
bores 36 are in a chamber formed by the inner edge of 
strip 37 and top face 14 of crystal 12. A suitable vacuum, 60 
of a few pounds per square inch, is applied to faces 13 
and 14 through bores 35 and 36, by virtue of chambers 
25 and 26 being evacuated by vacuum pump 40. Cham- 
bers 25 and 26 are selectively connected to vacuum 
pump 40 and the atmosphere through valves 38 and 39, 65 
respectively. To enable microtome 16 to easily cleave 
crystal 12 in planes 15 and to reach the side of the crys- 
tal without any problems, chambers 25 and 26 include 
4 
beveled faces 41 in proximity to the opposing faces of 
platens 27 and 28. 
Crystal 12 is cut or cleved along planes 15 by the 
following procedures. Initially, valves 38 and 39 are 
adjusted so chambers 25 and 26 are connected to the 
atmosphere and crystal 12 is placed so that bottom face 
13 thereof lies on platen 27, with one side wall of the 
crystal even with beveled edge 41 of chamber 25. If any 
bores 35 are not covered by face 13, it is necessary to 
cover the ends of the bores so that vacuum integrity is 
maintained. Similarly, if there are any bores 36 in platen 
28 which are not within a vacuum chamber between 
upper face 14 of crystal 12 and the lower face of platen 
28, these bores must be covered. When crystal 12 has 
been placed in the desired position on platen 27, valve 
38 is adjusted so chamber 25 is evacuated by pump 40 
and the crystal is held firmly in situ. 
Holder 17 is horizontally translated by motor 22 and 
lead screw 19 so blade 16 is almost in contact with a side 
of crystal 12. The height of microtome 16 is then ad- 
justed, by turning handle 21 so that lead screw 18 drives 
holder 17 vertically until the microtome edge is at the 
top face 14 of crystal 12. Of course, blade 16 was previ- 
ously placed in holder 17 so that the edge of the blade 
is parallel to crystal cleaveage planes 15. A reading 
from a micrometer (not shown), associated with the 
lead screw 18 is recorded to indicate the starting height 
of microtome blade 16. After the height of blade 16 has 
been adjusted so that the blade edge is aligned with face 
14, holder 17 is horizontally translated away from crys- 
tal 12 in response to motor 22 driving lead screw 19. 
Then, handle 21 is rotated so that the edge of blade 16 
is lowered to the plane where the desired cleavage is to 
be made; typically, this is a distance of 5 mils. 
Then, upper vacuum chamber 26 is lowered so that 
cushioned strip 37 abuts against top face 14 of crystal 
12. The position of collar 33 is adjusted so that tension 
spring 31 exerts a desired force on chamber 26. Typi- 
cally, for a crystal having a top face with rectangular 
dimensions of 1 inch by 2 inches, 600 to 800 grams of 
force are exerted by tension spring 31 on shaft 29 and 
chamber 26. Smaller crystals require a smaller lifting 
force while larger ones require a greater force. Exces- 
sive force exerted by spring 31 on shaft 29 and chamber 
26 causes crystal 12 to be improperly cleaved along a 
cleavage plane that is not necessarily parallel to faces 13 
and 14. After the force applied by spring 31 to chamber 
26 has been properly adjusted, valve 39 is adjusted to 
connect pump 40 to the chamber 26 while the top face 
14 of crystal 12 is being engaged by cushioned border 
37. Top and bottom faces 13 and 14 of crystal 12 are at 
this time respectively gripped by vacuum platens 27 and 
28. With crystal 12 gripped by vacuum platens 27 and 
28 and the edge of microtome blade 16 vertically posi- 
tioned for the desired thickness of the crystal to be 
cleaved, motor 22 is activated so that lead screw 19 
advances holder 17 and microtome 16 toward crystal 12 
at a slow speed that is regulated with conventional 
velocity feedback control apparatus. 
In response to the edge of blade 16 contacting the 
wall of crystal 12 between faces 13 and 14, cleavage of 
the crystal occurs through a cleavage plane 15 that is 
parallel to faces 13 and 14. When cleavage occurs, the 
force exerted by spring 31 on rod 29 and chamber 26 
causes the cleaved slice to be suddenly pulled away 
from the remainder of crystal 12, which remains in situ 
on platen 27. The cleaved crystal attached to platen 28 
remains attached to platen 28 until the vacuum on 
5 
4,184,472 
6 
chamber 26 is removed by adjusting valve 39 so that the therein for gripping said first flat end face of said soft 
chamber is connected to the atomosphere. When the crystal with vacuum, a moveable platen having perfora- 
vacuum on chamber 26 is released, the cleved crystal tions therein for gripping said second flat end face of 
drops from platen 28 and is collected either manually or said soft crystal with vacuum, said moveable platen 
automatically. 5 being moveable substantially perpendicular to said 
The next wafer from crystal 12 is obtained in a similar plane, and spring means coupled to said moveable 
way, by lowering chamber 26 so that platen 28 engages platen and applying a continuous force thereto substan- 
the newly formed planar top face of crystal 12. The tially perpendicular to said plane and away from said 
newly formed top face of crystal 12 is again gripped by stationary platen for applying stress forces to said soft 
platen 28 by activating valve 39 so that vacuum pump 10 crystal; a cleaving blade selectively moveable substan- 
40 is connected to chamber 26. Then, blade 16 is low- tially perpendicular to and parallel to said plane; means 
ered to the next desired cleavage plane, by turning for holding said cleaving blade at a position to enable 
handle 21 and reading the micrometer for lead screw 18. said soft crystal to be cut by said cleaving blade through 
Microtome blade 16 and blade holder 17 are then ad- said plane; means for adjusting the position of said hold- 
vanced again by activating motor 22 so that it drives 15 ing means so the cutting plane of said cleaving blade can 
lead screw 19 and the crystal holder. The operation is be adjusted relative to the end faces; and means for 
continued as desired until the mother crystal has been driving said holding means so said cleaving blade is 
sliced into the desired number of cleaved crystal slices driven into contact with a side of said soft crystal in said 
having the desired thickness. cutting plane where said cleaving blade has been ad- 
specific embodiment of the invention, it will be clear 2. The apparatus of claim 1 wherein said moveable 
that variations in the details of the embodiment specifi- platen includes a resilient, air impervious strip border- 
cally illustrated and described may be made without ing said perforations against which said first end face 
departing from the true spirit and scope of the invention bears. 
as defined in the appended claims. 3. The apparatus of claim 1 wherein said stationary 
and moveable platens include beveled faces adjacent 
said perforations in proximity to said first and second 
end faces of said soft crystal for ease in moving said 
cleaving blade into contact with said soft crystal. 
While there has been described and illustrated one 20 justed. 
25 
What is claimed is: 
1. Apparatus for slicing a soft crystal in a plane paral- 
le1 to first and second flat opposed parallel end faces of 
said soft crystal comprising vacuum chamber means 
including a stationary platen having perforations 30 * * * * *  
35 
40 
45 
50 
55 
60 
65 


Method and apparatus for slicing crystals

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