A reusable metal clamp for retaining a fused quartz ampoule during temperature cycling in the range of 20 deg C to 1000 deg C is described. A compressible graphite foil having a high radial coefficient of thermal expansion is interposed between the fused quartz ampoule and metal clamp to maintain a snug fit between these components at all temperature levels in the cycle

Crouch, R. K.

Debnam, W. J., Jr.

Fripp, A. L.

English

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United States Patent 1191 [ i l l  Patent Number: 4,491,427 
Debnam, Jr. et al. [45] Date of Patent: Jan. 1, 1985 
REUSABLE THERMAL CYCLING CLAMP 
Inventors: William J. Debnam, Jr., Hampton; 
Archibald L. Fripp, Williamsburg; 
Roger K. Crouch, Newport News, all 
of Va. 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
Assignee: . The United States of America as 
Appl. No.: 322,321 
Filed: Nov. 17, 1981 
Int. (3 .3  ............................................... GOlK 1/00 
U.S. Cl. ..................................... 374/208; 374/210 
Field of Search ................ 374/208, 210; 285/322, 
285/DIG. 12, 45, 47, 53, 55, 238, DIG. 6, 34, 
35; 403/29, 30, 28, 342, 290 
References Cited 
U.S. PATENT DOCUMENTS 
2,461,414 2/1949 Donner ..................... 
2,583,388 VI952 Nelson e 
3,232,648 2/1966 Franck . 
3,858,914 1/1975 Karie et 
4,190,257 2/1980 Schnitzler 
FOREIGN PATENT DOCUMENTS 
926435 5/1973 Canada ......................... 277/DIG. 6 
1576375 8/1969 France ................................ 285/322 
7833293 7/1980 France ................................ 285/322 
Primaly Examiner-Charles Frankfort 
Assistant Examiner-David R. Schuster 
Attorney, Agent, or Firm-Howard J. Osborn; John R. 
Manning 
P71 ABSTRACT 
A reusable metal clamp 10 for retaining a fused quartz 
ampoule 25 during temperature cycling in the range of 
20" C. to looo" C. A compressible graphite foil 27 hav- 
ing a high radial coefficient of thermal expansion is 
interposed between the fused quartz ampoule 25 and 
metal clamp 10 to maintain a snug fit between these 
633,499 9/1899 Bray .................................... 285/322 
1,086,641 2/1914 Blume ................................. 285/322 components at temperature levels in the cyc1e. 
1,324,046 12/1919 Hatfield ...................... 285/DIG. 12 
1,554,703 9/1925 Berry .................................... 403/29 8 Claims, 4 Drawing Figures 
2 
I I 
2 
27 18 
\ 
U.S. Patent Jan. 1,1985 4,491,427 
FIG. 1 
2 
2 
2 5  
27 
im FIG.2  FIG. 3 
27 18 
50 43 
42 
FIG. 4 
4,49 1,427 
1 
REUSABLE THERMAL CYCLING CLAMP 
ORIGIN OF THE INVENTION 
The invention described herein was made by employ- 
ees of the U.S. Government and may be manufactured 
and used by or for the Government for governmental 
purposes without the payment of any royalties thereon 
or therefor. 
BACKGROUND OF THE INVENTION 
In research and development of structural materials 
and, in particular, the National Aeronautics and Space 
Administration, directional solidification experiments 
that are part of the planned materials processing in 
space (MPS) program for the manned Space Shuttle 
during the next few years, are the process steps involv- 
ing insertion into and retrieval from a high temmpera- 
ture furnace of a fused quartz ampoule. These fused 
quartz ampoules are used to house material samples 
subject to thermal cycling from 20" C. to temperatures 
exceeding + 1ooo' C. Presently, high temperature resis- 
tant adhesive cements are utilized to attach the fused 
quartz ampoules to the metal insertion-retrieval mecha- 
nism. Adhesives that can withstand the extreme temper- 
atures contemplated for use with the present technique 
would likely be of a ceramic origin and brittle. Thus, 
failure of the adhesive connection may occur due to the 
different coefficients of thermal expansion between the 
fused quartz and the metal insertion-retrieval rod. Also, 
cemented objects may not be reusable, leading to higher 
costs and creating additional problems after each ther- 
mal cycling test. 
Also, fused quartz to metal seals have been employed 
by fusing various transition materials such as Kovar and 
Pyrex between the metal holder and the fused quartz 
and molybdenum to quartz seals can be made without 
the use of a transition layer. Holders made with a transi- 
tion material, as well as clamps employing O-ring type 
connections have a limited temperature capability and 
are thus not suitable in the temperature cycling> tests 
contemplated by the present invention. The molybde- 
num to fused quartz seals are not temperature limited, 
but their formation involves a highly specialized pro- 
cess and is of limited availability. Each of these prior art 
systems require construction of a new holding mecha- 
nism for each test operation. 
It is therefore an object of the present invention to 
provide a reusable novel connection or clamp mecha- 
nism between objects adapted to be subjected to ther- 
mal cycling. 
Another object of the present invention is a novel 
reusable clamp for connecting two objects. 
A further object of the present invention is to provide 
a clamp connection for two objects that will maintain a 
snug connection therebetween throughout the tempera- 
ture cycle of 20" C. to looo" C. and without danger of 
rupturing fragile test objects. 
An additional object of the present invention is a 
method for releasably connecting a fused quartz object 
to a thermal cycling resistance insertion tool. 
A further object of the present invention is a clamp 
mechanism for a thermal cycling test object that will 
maintain constant pressure on the test object during a 
temperature cycle. 
Another object of the present invention is to provide 
a reusable retention mechanism for insertion and with- 
drawal of a fused quartz object relative to a high tem- 
perature environment. 
According to the present invention the foiegoing and 
additional objects are attained by providing a reusable 
5 clamp device integrally attached to or formed with a 
temperature resistant metal insertionhetrieval rod or 
sting device and adapted to releasably retain a test fused 
quartz ampoule. The reusable clamp device is in the 
form of a sleeve having a first end portion integral with 
10 the metal rod and a second end portion being a plurality 
of circumferentially disposed spaced fingers extending 
from and along the longitudinal axis of the first end 
portion. At least a portion of the spaced fingers are 
provided with circumferentional exterior threads to 
15 receive a threaded lock aut or collar thereon. As the 
lock nut is tightened, a squeezing or inwardly biasing 
force is exerted on the fingers to cause a clamping force 
to be exerted on the portion of the fused quartz ampoule 
positioned within the fingers. A compressible seal or 
20 packing is provided between the quartz ampoule and 
the fingers. This compressible seal. is selected from a 
material which has an anisotropic thermal expansion 
coefficient with negligible expansion in the plane of the 
quartz rod walls but a relatively large coefficient of 
25 expansion in the radial direction to thereby maintain a 
snug fit between the fused quartz material and the 
clamp when temperature cycled between 20' C. and 
looo" c. 
BRIEF DESCRIPTION OF THE DRAWINGS 
A more complete appreciation of the invention and 
many of the attendant advantages thereof will be better 
understood as the same becomes more readily apparent 
by reference to the following detailed description when 
35 considered in connection with the accompanying draw- 
ings, wherein: 
FIG. 1 is a sectional view of a portion of a reusable 
clamp device according to the present invention and a 
portion of the elongated insertionhetrieval extension 
FIG. 2 is a part sectional view of the clamp shown in 
FIG. 1 in a operative position retaining two objects 
together; 
FIG. 3 is a sectional view of the device shown in 
FIG. 4 is a view similar to FIG. 2 showing an alter- 
3o 
# sting therefor; 
45 FIG. 2 and taken along line 111-111 of FIG. 2; and 
nate embodiment of the present invention. 
DETAILED DESCRIPTION OF THE 
INVENTION 
Referring now more particularly to the drawings, 
there is shown (FIG. 1) a reusable clamp device gener- 
ally designated by reference numeral 10. Clamp 10 is 
machined from stainless steel, tantalum, Inconel (trade- 
55 name for an alloy consisting essentially of 80% Ni, 14% 
Cr and 6% Fe) or other equivalent heat resistant materi- 
als and is essentially in the form of a sleeve having a first 
portion 12 thereof being integral with an elongated tube 
or rod sting 14. Sting 14 is securely attached via sleeve 
60 16 to an automated furnace insertionhetrieval mecha- 
nism (not shown). 
A plurality of spaced fingers 18 form the other end of 
clamp 10 and extend from end 12 thereof. Fingers 18 
(six shown in the preferred embodiment) are tapered 
65 w e r  the length thereof and are disposed in spaced cir- 
. cumferential relationship about the longitudinal axis of 
clamp 10. A threaded segment 19 (FIGS. 1 and 2) is 
provided on the exterior surface over a portion of the 
50 
4,49 1,427 
3 4 
length of fingers 18. Threaded segment 19 serves to 
receive lock nut or collar 20 to circumferentially en- 
compass fingers 18. As lock nut 20 is tightened by the 
threaded connection, the trailing area thereof provides 
thermal expamion for the specific examples described 
herein were: 
an increasingly inwardly biasing force along the cir- 5 ~ ~ ~ ~ " ~ t "  E 0.55 x 10-6/"c. 
= 21 x IO-b/*C.. 
E -0.4 % 10 6/"C (20' C.-1090" C )  
0.5 x 10 -('/"C. (1090' c.-2200" C. )  and ( 14x IO 6/oCc, 
cumference of fingers 18 due to the tapered construc- tantalum ctamps = 6.5 x 10-6/"C., 
tion thereof. This squeezing force is transmitted as a graphite foil radial 
(Grafoil) 
graphrte fad* 
uniform grip to the fused quartz ampoule 25 (FIG. 2) 
disposed within fmgers 18. A compressible graphite 
type foil seal layer 27 having a relatively high radial 10 I ) ~ ~ ~ ~ ~  to quartz 
coefficient of thermal expansion is disposed between the 
fused quartz and the metal fingers 18 to thereby assure 
a snug fit for a m w l e  25 during the thermal cycling Various changes and modifications in the specific 
tests. rn the preferred embodiment, foil 27 was Con- examples are considered within the scope Of the inven- 
structed of multiple layers of graphite foil tape of 0.005 15 tion. For example, Sting 14 may be a solid rod Or tubular 
inch thickness. Foil tapes of this type are available, for and may be constructed of any material having the 
example, from the Union Carbide Corporation under thermal resistant properties necessary to be utilized in 
the tradename Grafoil and are available in the thickness the temperature range disclosed herein- Also, this tern- 
range of 0.005 to 0.020 inch. Any thickness within this P r t w e  range may be expanded as SO required for sPe- 
range would be suitable for use in practice of the pres- 20-CifiC tests. A% clamp 10 may be n~&~ined irectly 
ent invention and in the illustrated embodiments Grafoil from sting element 14 Or it may be formed separately 
0.005 inch thickness was employed in multiple layer. In and integrally secured to sting 14 in a Conventional 
addition to providing a snug fit for the quartz ampoules minner. 
Over the wide thermal cycling range. The foil layer 27 It is thus seen that the present invention as described 
permits a tight grip to be applied to ampoules 25 with- 25 herein is directed to specific embodiments thereof 
Out endangering rupture or breakage thereof due to the which are given merely to illustrate the invention and 
compressible shock absorbing physical property char- are not intended to serve as exhaustive examples 
acteristics of the foil. thereof. The materials employed in these specific em- 
In FIG. 4 an alternate embodiment of the invention is bodiments are also given to comply with the statutory 
shown and designated generally by reference numeral 30 requirements of preferred embodiment description and 
40. As shown therein, the entire length of fingers 48 are are not intended to serve as limitations on applicants' 
provided with fine tapered threads for receiving lock broad inventive concept as defined in the appended 
collar nut 50. This tapered threaded arrangement serves claims. Also, although the specific clamps described 
to provide adequate squeezing force on fingers 48 to herein show six fingers as the holding mechanism, the 
retain the quartz test ampoule 55 therein and without 35 increase or decrease of this number is considered within 
danger of rupturing the ampoule during thermal cycling the scope of the invention as claimed. Also, although 
tests. When desired, threads 48 may be formed on the the graphite foil was used in this embodiment, any ani- 
same radius (or non-tapered) and the cam surface 43 of sotropic material with a high radial thermal expansion 
nut 50 engages cam shoulder 44 to provide adequate coefficient is considered within the scope of this inven- 
squeezing force on fingers 48 to retain ampoule 55 in 40 tion. 
position. Again, a compressible graphite foil seal 47 is It is therefore to be understood that various niodifica- 
provided between fingers 48 and test ampoule 55 to tions and variations of the present invention will be 
compensate for the different coefficients of thermal apparent :o those skilled in the art without departing 
expansion between the quartz and metal clamp struc- from the spirit and scope of the appended claims. 
tures. What is claimed as new and desired to be secured by 
During temperature cycling of the metal clamped Letters Patent of the United States is: 
quartz ampoules, both the ampoule and lock collar will 1. A reusable clamp apparatus for connecting first 
be expected to increase in diameter as the temperature and second objects comprising: 
increases. Since any metal that can be considered useful means integrally secured to a first object and having 
for practice of the present invention, Le., those having 50 a plurality of fingers extending therefrom and 
relatively high coefficients of thermal expansion com- adapted to receive a second object, 
pared to that of fused quartz, a temperature increase means circumferentially engaging said plurality of 
will be detrimental to maintaining a snug fit. The annu- fingers so as to exert a force thereon to produce a 
lar lock nut (20 or 50) will expand to a larger internal frictional force onto the second object and thermal 
diameter and even though the clamp fingers (18 and 48) 55 expansion means disposed along at least a portion 
will expand as slabs, the expansion of the fingers will of the length of said fingers and between said fin- 
not match the void left by the expanding nut. However, gers and said second object to facilitate securing of 
by using the graphite foil tape with a large radial ther- said second object by said fingers by maintaining 
mal expansion coeftieient as intervening layers, em- frictional force over a wide range of operating 
ployed in the present invention, the greater expansion of 60 temperatures, 
the foil will help maintain the snug fit between the fin- said thermal expansion means comprising a graphite 
gers and test ampoule at all temperatures in the cycle. foil having a relatively high radial coefficient of 
Calculations for the minimum graphite foil thickness thermal expansion to  thereby compensate for any 
required to compensate for the differing coefficients of differences in the coefficient of thermal expansion 
thermal expansion between the quartz ampoules and the 65 between said first and second objects. 
specific clamp embodiments of the present invention 2. A reusable clamp apparatus as in claim 1 wherein 
have been made and are readily reproducible for spe- said first object is a metal rod and said means integrally 
cific clamp ampoule dimensions. The coefficients of secured to said first object includes a sleeve portion, 
45 
4,49 1,427 
5 6 
said plurality of fingers being in the form of a tubular 
extension of said sleeve uortion. 
providing a sleeve secured to a holder device and 
having a plurality of spaced extensions leading 
therefrom; 
positioning the fused quartz device within the plural- 
ity of spaced extensions; 
providing a compressible thermal resistant graphite 
taue spacer between the fused quartz device and 
3. A reusable clamp apparatus as in claim 2 wherein 
external threads are provided on said plurality of fingers s 
over at least a portion of the length thereof and said 
means circumferentially engaging said plurality of fin- 
gers being received by said external threads. the spaced extension and the graphite tape spacer 
4. A reusable clamp apparatus as in claim 2 wherein being selected from a thickness ratio of 0.005 and 
external threads are provided on said plurality of fingers 10 0.020 inch thick graphite tapes and having a rela- 
over the entire length thereof and said means circumfer- tively high radial coefficient of thermal expansion 
to thereby compensate for any differences in the entially engaging said plurality of fingers being a lock coefficient of thermal expansion between the 
hoIder device and the fused quartz device; nut threadingiy received by said external fingers. 
J- A apparatus as in wherein 15 positioning an adjustable retainer around the sleeve 
said first object and said clamp are formed of thermal extension so as to provide a selective compressive 
resistant metal and. said second object is a fused quartz force thereon to force the sleeve extension against 
ampoule. the compressibk graphite tape spacer, and thereby 
6. A reusable clamp as in claim 1 wherein said graph- frictionally retain the fused quartz object in fixed 
ite foil is selected from the thickness range OF foils of '' position adjacent to the 
8. The method of claim 7 including integrally machin- 
from the end of the holder device so as to provide a layers. 
7. A method of releasably retaining a fused quartz decreasing tapered exterior surface leading away from 
object to a holder while subjecting the fused quartz 23 the sleeve toward the end of the extensions. 
device* 
O*Oo5 to 0'020 inch thickness and is used in ~ n g  the sleeve and the plurality of spaced extensions 
object to thermal cycling comprising: * * * * *  
30 
35 
45 
50 
55 
65 


Reusable thermal cycling clamp

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