Apparatus for forming wire grids for electric strain gage

Bonn, J. L.

Gardner, D. E.

English

NASA Technical Reports Server

July 11, 1961 J. L. BONN I X A L  
WIRE GRID FORMING APPARATUS 
Filed May 31, 1955 
2,991,671 
FIG. 2 
F l 6  3 
26 
FIG. 5 
FIG. 4 
BY 
e4 0 rg (ACCESSION N? -S333(-! NUMBER) (THJU) 
E // 
INVENTORS 
JOHN L. BONN 
WMEL E GARDMR 
- 
I \ !  (NASA CR OR TMX OR AD NUMBER) (CATEGORY) 
U 
https://ntrs.nasa.gov/search.jsp?R=19700024019 2020-03-17T01:33:41+00:00Z
Ututed atates patent 
1 
2,991,671 
WIRE GRID FORMING APPARATUS 
John L. Bmn, Westlake, and Daniel E. Gardner, Cleva 
Band, Ohio, asdgnmi, by mesne asdgnments, to &e 
United States of America rn represented by L e  Ad- 
mlnistrntor of the Na@onal Aeronautics and Space 
Admhbat ion  
Hed May 31,1955, Ser. No. 512,352 
.lClaim. (C1.7U) 
(Gmted m e r  Title 35, US. Code (1952), sec. 266) 
The invention described herein may be manufactured 
and used by or for the Government of the United States 
of America for governmental purposes without the pay- 
ment of any royalties thereon or therefor. 
This invention relates to apparatus for making wire 
grids and more particularly to production apparatus for 
forming wire grids which are especially adaptable for 
use in electric strain gages. 
In the types of apparatus in current use, the gage man- 
ufacture involves use of a jig to prduce the desired gage 
grid configuration. To attach the formed gage, the en- 
tire jig, holding the grid, may be placed on the test struc- 
ture while the grid is being partially cemented to the sur- 
face, the jig being then removed. Or, alternatively, the 
jig holding the grid is placed on a special surface and 
cement is then applied. After the cement has hardened 
and the jig removed, the cement film containing the grid 
is peeled from the special surface and stored for later ap- 
plication to a test structure. 
Both of the described techniques and associated equip- 
ment have important disadvantages. In  the first, the jig 
is usually too bulky for easy handling on the test surface 
and impractical for application to C U N ~  surfaces. Fur- 
ther, the apparatus used requires application of a partial 
cement coat which must be dried before further steps are 
taken. The jig is then removed and the final coat of ce- 
ment added, steps that require considerable skill and are 
time consuming. 
The utilization of the jig in the second technique pre- 
sents difficulties in that the cement used is not pliable 
and it is very difficult to secure a firm bond between the 
gage film and the test structure. Moreover, it is not ordi- 
narily possible to apply the gage to a contoured surface. 
An object of the present invention is to provide an 
apparatus for forming wire grids, which grids are readily 
applicable to any test structure. An object also is to 
provide a wire grid forming apparatus which can be op- 
erated without unusual skill on the part of the user. 
An object of importance is that of providing a wire 
grid forming apparatus which lends itself to volume pro- 
duction. 
Other objects and many of the attendant advantages of 
this invention will be readily appreciated as the same 
becomes better understood by reference to the following 
detailed description when considered in connection with 
the accompanying drawings wherein: 
FIG. 1 is a view in elevation of the grid forming a p  
paratus with the grid in position for compression; 
FIG. 2 is an end view of the apparatus for FIG. 1; 
FIG. 3 is a plan view of the grid and supporting equip- 
ment prior to compression; 
FIG. 4 is a plan view of the compressed grid; and 
FIG. 5 is an elevational section of the grid cemented 
on the test structure, 
The grid forming apparatus of the invention is disclosed 
in FIGS. 1, 2 and 3 and includes a hardened steel block 
or plate 10 of greater length than breadth, provided with 
alined holes 11 transversely placed adjacent the block ends 
in which a series of pins 12 are press-fitted to protrude 
above the plate, giving the desired form structure. The 
grid wire 13 is then woven back and forth over these 
, 
/ 2 
pins, beginning with the pins on one side 14 of the plate 
and moving to the opposite side 15, as shown in mG. 3. 
The formed grid with its supporting structure is then 
placed on a flat metal relief block 20, provided with holes 
6 21 which register with holes 11 in plate 10. A hardened 
flat steel block 22 is then placed on the pins 12 and the 
unit transferred to a press between jaws 25 and 26 where 
it is subjected to a pressure of such value as to flatten the 
wire 12, as shown in FIG. 4. At the same time the pins 
10 12 are driven downwardly, entering holes 21 of block 
20, to produce a form for another grid. It is apparent 
that, in sequence, grids may be rapidly constructed, re- 
versing the form block for such successive grid. 
The flattening of the grid wire is, obviously, a cold 
16 working process step, and a result of this operation is to 
produce a stabilized grid which can be readily handled 
with reasonable care, for direct use or for storage or 
In the compressed form the grid is ready for d e d i -  
20 ate application to test structure for electric gage us=. 
While variable methods of application may be used, it is 
preferred to pre-coat the test structure surface with ce- 
ment, as indicated at 30 in FIG. 5, place the grid on this 
cement surface, and then add a cement cover mat 31. 
26 This simple procedure does not require film cementation, 
or use of grid forms or jigs which, in application, may 
easily cause mal-function. The grid is simply placed on 
the test structure and cemented. 
The step of cold forming the grid by the pin-block 
SO method is by way of example, other methods of produc- 
ing the wire deformation being usable. The degree of 
pressing of the gage wire is not necessarily critical, but it 
should be adequate to fix the grid form to a point where 
the grid may be handled without permanent distortion of 
S I  shape. Further, the grid form is merely illustrative, dif- 
ferent configuration being usable dependent on the direc- 
tions of strain measurement. No particular limitation 0s 
to grid wire is required since the material will vary with 
use, wires of tungsten, platinum, nickel and nickel alloys 
40 such is nickel-chromium and iridium-platinum all being 
usable. As to dimensions, the grid wire is generally of 
the order of 0.001 to 0.002 inch diameter and of sufficient 
length to provide B gage resistance of from 50 to 500 
ohms. The cement; which should be electrically non-con- 
45 ducting, will vary in composition depending on whether 
use is with low or high temperature gages, various ceramic 
or other cements being available for high and low tem- 
perature uses. 
Obviously many modifications and variations of the 
60 present invention are possible in the light of the above 
teachings. It is therefore to be understood that within 
the scope of the appended claim the invention may be 
practiced otherwise than as specifically described. 
What is claimed is: 
An apparatus for use in forming wire grids from wire 
stock comprising a plate having a plurality of apertures 
therethrough between the top and bottom flat faces there- 
of, said apertures being positioned along and adjacent to 
the sides of at least one pair of opposite sides of said plate, 
60 pin members having a length greater than the sum of the 
plate thickness and the wire stock thickness, said pin mem- 
bers tight-fittedly disposed in said apertures and being 
slidable therein under pressure, said pin members having 
one end thereof protruding beyond the top face of said 
65 plate for retaining the wire stock to be formed, a relief 
block positioned beneath the bottom face of said plate and 
having a plurality of holes therein in registry with said 
apertures for reception of said pin menbers, a flat sur- 
faced pressure applying block for simultaneously fonn- 
70 ing the retained wire stock and depressing said protruding 
ends of said pin members, said pin members when in de- 
pressed position projecting beyond the bottom face of 
shipment. 6 
65 
a,eo 1,a7 1 
3 
said plate to provide a grid wire forming element thereon 2,455,355 
whereby wire grids may be formed alternately on the 2,487,681 
face9 of said plate. 2,493,029 
2.59 1,123 
Refecencea Cited in the file of this patent 6 2,602,263 
LIETEED STATES PATENTS 2,677,172 
2,853,764 555,895 Carpenter __-___________ Mar. 3, 1896 
1,513,644 Sindelar _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  Oct. 28, 1924 2*878s841 
1,920,258 Hardenbrook _ _ _ _ _ _ _ _ _ _ _  Aug. 1, 1933 10 2,885324 
2,101,195 Randall _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  Dec. 7, 1937 
2,154,009 Priest _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  Apr. 11, 1939 
911,143 2,169,020 Brace _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  Aug. 8, 1939 
2,331,294 Bank et al. _ _ _ _ _ _ _ _ _ _ _ _ _  Oct. 12, 1943 420,288 
2,401,049 Campbell et al. _ _ _ _ _ _ _ _ _  May 28, 1946 16 
4 
Combs __________---___ Dec. 7, 1948 
Weisselberg _ _ _ _ _ _ _ _ _ _ _ _ _  Nov. 8, 1949 
Ramberg _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  Jan. 3, 1950 
Blumensaadt _ _ _ _ _ _ _ _ _ _ _ _  Apr. 1, 1952 
Swirkal __________-______ July 8, 1952 
Oakley -________________ May 4, 1954 
De Michele _ _ _ _ _ _ _ _ _ _ _ _  Sept. 30, 1958 
Peterson et al. ____-____ Mar. 24, 1959 
Eisler _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  May 5, 1959 
FOREIGN PATENTS 
France _________________June  28,1946 
Italy ___________--_-___ Apr. 21, 1947 


Wire grid forming apparatus Patent

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