Connector internal force gage for measuring strength of electrical connectio

Bond, W. W.

English

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NATIONAL 
(ACCESSIOR NUMBER) 
“z 
8 
REPLY TO 
ATTN OF. 
LL 
$ (NASA CW OR TMX OR AD NUMBER) 
AERONAUTICS AND SPACE ADMINISTRATION 
/f March 29, 1971 
(CATEG RY) 
LL 
. 
TO : USI/Scientific & Technical Information Division 
Attention: Miss Winnie M. Morgan 
FROM: GP/Office of Assistant General 
Counsel for Patent Matters 
SUBJECT: Announcement of NASA-Owned 
U.S. Patents in STAR 
In accordance with the procedures contained in the Code GP 
to Code US1 memorandum on this subject, dated June 8, 1970, 
the attached NASA-owned U.S. patent is being forwarded for 
abstracting and announcement in NASA STAR. 
The following information is provided: 
U.S. Patent No. : 3,388,590 
Corporate Source : California I n s t i t u t e  of Technology 
Supplementary 
Corporate Source jet Propulsion Laboratory 
NASA Patent Case No.: XNP-0393-8 
Please note that this patent covers an invention made by an 
employee of a NASA contractor. Pursuant to Section 305(a) of 
the National Aeronautics and Space Act, the name of the 
Administrator of NASA appears on the first page of the patent; 
however, the name of the actual inventor (author) appears at 
the heading of Column No. 1 of the Specification, following the 
words ‘I. . . with respect to an invention of. . . .It 
Enclosure: 
Copy of Patent 
https://ntrs.nasa.gov/search.jsp?R=19710013611 2020-03-17T03:00:24+00:00Z
June 18, 1968 HUGH L. DRYDEN, DEPUTY 3,388,590 
ADMINISTRATOR OF THE NATIONAL 
AERONAUTICS A N D  SPACE ADMINISTRATION 
CONNECTOR INTERNAL FORCE GAUGE 
Filed Nov. 29, 1965 
FIG. 2 
F/6. 3 +, 
INVENTOR 
WILLIAM w. BONO s"17s, 
United States Patent Office patented June 18, 1968 
1 
3,388,590 
CONNECTOR INTERNAL FORCE GAUGE 
Hugh L. Dryden, Deputy Administrator of the National 
Aeronautics and Space Administration, with respect to 
an invention of William W. Bond, Alhambra, Calif. 
Filed Nov. 29, 1965, Ser. No. 510,475 
6 Claims. (Ci. 73-88.5) 
ABSTRACT OF THE DISCLOSURE 10 
A strain sensing transducer is attached to  a connector 
pin positioned within a female connector receptacle. The 
strain produced in the pin by biasing means in the wall of 
the receptacle is sensed by the transducer and the result- 15 
ing electrical signal produced is a measure of the quality 
of the electrical connection between the pin and the 
receptacle. 
Origin of the invention 20 
The invention described herein was made in the per- 
formance of work under a NASA contract and is subject 
to the provisions of Section 305 of the National Aero- 
nautics and Space Act of 1958, Public Law 84-568 (72 25 
Stat. 435; U s e  2457). 
This invention relates to an electrical connection. 
More particularly this invention relates to an electrica: 
connection wherein means are provided to instantaneously 
and accurately determine the strength of the electrical 3o 
connection. 
The common electrical connectors such as found in the 
home consist of a prong which is inserted into a recepta- 
cle and is considered or is referred to as a male and 
female conneciton. Other types of connections include 35 
soldered connections and clamps. The prior art is replete 
with many examples of these connections. 
This invention is directed to the plug-in socket or male 
and female connections in which the jack or male mem- 
ber is inserted into a receptacle or female member. Prior 4o 
art examples have included a spring action in the female 
connector whereby a force is imparted on the male mem- 
ber thus ensuring a strong electrical connection. By strong 
electrical connection is meant that force between the 
metallic male and female members such that adequate 45 
conduction of electricity is assured. In other words, the 
voltage drop across the members should be at a minimum. 
There have been problems with these types of con- 
nectors in the past and with the advent of modern space 
technology this problem is even more pronounced. This is 50 
particularly the case with low voltages where any sub- 
stantial voltage drop at the connectors is undesirable. 
Since high reliability is demanded of space components 
and other electronic modules, it is mandatory that either 
completely reliable connectors be provided or that some 55 
means be utilized to determine which of the connections 
in an electronic module assembly are not strong enough 
so that they may be replaced prior to use. It is also a nec- 
essity that some means be provided in modern electronic 
circuits to immediately determine which connections are 6o 
inadequate as between a male and female connector in a 
circuit so that the (components can either be replaced or 
repaired. 
This invention in its briefest aspect comprises a male 
and female electrical connection in which the female 65 
member has a bias means therein so as to provide a 
strong electrical connection as it is exerted against the 
male member. This provides a strong metal to metal con- 
tact to obviate high voltage drops. To determine this con- 
tact, a strain gauge or other transducer is placed on the 
male member with leads emanating therefrom which 
forms a part of a Wheatstone bridge arrangement with a 
2 
voltage readout sent to an indicating means so that the 
strain of the male member is measured. The more the 
male member is biased by the biasing means in the 
female member, the stronger the electrical contact be- 
tween the two. Therefore, this voltage readout is a direct 
indication of the strength of the electrical connection. 
It is therefore an object of this invention to provide a 
means for immediately and accurately indicating the 
strength of an electrical connection. 
It is another object of this invention to provide an im- 
proved method for testing the electrical contact between 
male and female members of an electrical connection. 
Other and more particular objects of this invention will 
become apparent as this description proceeds taken in 
conjunction with the drawings in which: 
FIGURE 1 is a view partially in cross section of an 
electrical connection according to thlis invention; 
FIGURE 2 is a top view partially in cross section of 
the male member constructed according to this invention; 
FIGURE 3 is a schematic of the Wheatstone bridge ar- 
rangement utilized in this invention; and 
FIGURE 4 is a block diagram of an indicating means 
for determining the strength of a plurality of electrical 
connectors. 
Referring to  FIGURE 1 there is shown a male and 
female electrical connection according to this invention. 
This connection is indicated generally at 2 and includes 
a female member 4. This female member leads from a 
cable not shown which is connected to the rear 6. A 
hollow base or receptacle is formed at 8 for reception 
of the male member. This receptacle can be cylindrical 
or of other configurations including a plurality of prongs. 
The male member indicated generally at 10 includes a 
cylindrical member 12 to which is welded or securely 
attached a male pin member 14. As thus far described, 
the combination shown is conventional. Attached within 
space 8 as by welding or the like is a biasing means 16 
which in the form shown comprises a curved spring. 
Other bias means can be employed such as a “napkin 
ring” or retainer. When the male pin member 14 is in- 
serted into the space 8, spring 16 will be contacted which 
due to its inherent bias will tend to “bend” or otherwise 
strain pin member 14. Spring member 16 is placed in 
receptacle 8 so as to ensure a strong electrical connection 
either through the spring itself or through direct contact 
with female member 6.  The greater the bias applied to 
pin member 14 the stronger the electrioal connection. It 
is to determine the strength of this bias and therefore the 
soundness of the electrical connection to which this in- 
vention is directed. 
Referring to FIGURE 2 there is shown the male mem- 
ber as viewed from the top. Pin 14 has a flattened area 
18. A transducer 20 which may comprise a silicon crystal 
strain gauge or other means is mounted on flat area 18. 
This strain gauge can be of the piezo-electric type or it 
can be a simple elastic strain gauge known in the art. In 
any event, this type of gauge changes its electrical char- 
acteristic as strain is imparted thereto. Thus, should strain 
gauge 20 be shortened or lengthened the resistive proper- 
ties thereof change which when utilized in a Wheatstone 
bridge arrangement known in the art can be utilized to 
measure strain. Strain gauge 20 can be mounted on flat 
area 18 by any conventional means such as an epoxy 
resin. In any event, strain gauge 20 is insulated from flat 
area 18 while structurally movable therewith as strain 
is imparted thereto. 
At one end of strain gauge 20 is an electrical lead 22 
and at  the other end an electrical lead 24 is attached. 
These leads emanate through an aperture 26 (see FIG- 
URE 1)  and through cylinder 12 to the voltage readout 
device. 
3,388,590 
3 4 
Referring to FIGURE 3, strain gauge 20 is shown 
schematically as it is placed in a Wheatstone bridge ar- 
rangement. Thus, resistors 26, 28 and 30 which have been 
previously calibrated along with strain gauge 20 are means; 
located in the Wheatstone bridge circuit. When a voltage 5 
such as indicated by battery 32 is applied across the leads 
of electrical connections comprising a male member and 
a female member, that improvement which comprises: 
at least one of said female members having biasing 
a male member received in said female member where- 
by said male member is biased by said biasing means 
as shown, and no strain is imparted to the strain gauge 
element 20, the voltage readout as received by indicating 
means 34 will be zero. When a strain is imparted to strain 
gauge element 20, there will be a voltage readout which 
can be measured at 34 due to the change in resistance of 
strain gauge element 20. 
To test a plurality of connectors at the same time, it 
is within the scope of this invention to provide a sequen- 
tial switching programmer which would immediately 
indicate which of a plurality of connectors are at fault 
in an electronic circuit. Thus, where there are a plurality 
of female receptacles in a single member such as indicated 
by female connection 40, a plurality of male members 
indicated at  42 can be inserted therein to provide a 
plurality of electrical connections. Each of these male 
members 42 would lead t o  different portions of the cir- 
cuit as desired. The common pin collector 44 then would 
have a plurality of leads indicated at 46 which can be 
led to a single sequencing switch system 48. This can 
comprise a dial with a switching system to individually 
test each connection. Thus at a glance at readout console 
50, it can be determined immediately whether any of 
and which one of the male and female connections are 
weak. 
In operation, male pin member 14 is inserted into space 
8 against the bias of spring 15. By proper connection in 
the Wheatstone bridge as shown in FIGURE 3, the strain 
of pip member 14 and hence the electrical connection be- 
tween member 14 and female member 4 can be measured 
by determining the strain of pin member 14. This is im- 
mediately apparent by reading the readout 34 or in the 
case of a plurality of connections by switching means 48 
and readout 50. 
Thus it can be seen that by this invention, an immedi- 
ate determination of electrical characteristics of connec- 
tions can be made. 
Having described this invention, it is to be understbod 
that it is to be limited only by the scope of the claims 
appended hereto. 
What is claimed is: 
1. In an electrical connector having a male member 
and a female member wherein said female member has 
means associated therewith adapted to apply a bias to 
said male member whereby to strain said male member, 
that improvement which comprises: 
a strain sensing transducer on said male member, said 
transducer being adapted to produce signals in re- 
sponse to strain induced in said male member by 
said bias; 
indicator means adapted to receive said signals and to 
produce a readout thereof, said readout being a 
measure of the electrical connection between said 
male and female member. 
2. In an electrical circuit wherein there are a plurality 
10 
15 
20 
26 
80 
35 
40 
45 
50 
to produce a strain in said male member; 
a transducer mounted on said male member and 
adapted to produce a signal in response to strain in- 
duced in said male member; and 
whereby the force exerted between said members can 
be measured to indicate the strength of said electrical 
connection. 
3. In an electrical circuit according to claim 2 wherein 
switching means adapted to selectively obtain the sig- 
whereby the strength of each electrical connection can 
4. In an electrical connector having a first conductor 
member contacting a second conductor member and 
means biasing the conductor members into engagement 
with each other to thereby strain said members, that im- 
provement comprising: 
a strain sensing transducer mounted on one of said 
members adapted to produce signals in response to 
strain induced in said one member by said biasing 
means; 
electrical leads connected to said transducer for trans- 
mitting said signals to means for producing from the 
signals a measure of the quality of the electrical 
connection between said members. 
5, In an electrical connector according to claim 4 
Wherein said first conductor member is a male pin and 
said second conductor member is a female receptacle 
which receives the pin, said transducer is mounted on 
said pin, and said biasing means is associated with the 
inner wall of the receptacle. 
6. In an electrical connector according to  claim 5 
wherein said pin is formed with a flat area on one side 
surface and said transducer is bonded in insulated rela- 
tion to the flat area of the pin; 
said electrical leads are connected to opposite ends of 
the transducer and extend through an aperture in 
the rear of said pin; and 
said biasing means is located on the side of the pin 
opposite from the transducer so that the transducer 
side of the pin is biased against the adjacent wall of 
the receptacle. 
there is a plurality of said male and female members: 
nals produced by each of said transducers; and 
be determined. 
References Cited 
UNITED STATES PATENTS 
3,120,989 211964 Solorow et al. _ _ _ _ _ _ _  339-256 
55 3,188,860 611965 Roberts _ _ _ _ _ _ _ _ _ _ _ _  73-88.5 
3,197,697 711965 McCauley _ _ _ _ _ _ _  73-8.85 XR 
3,201,977 811965 Kutsay _ _ _ _ _ _ _ _ _ _ _ _ _  73-88.5 
3,327,270 611967 Garrison __-_____ 73-88.5 XR 
RICHARD C. QUEISSER, Primmy Examiner. 
CHARLES A. RUEHL, Examiner. 
BO 


Connector internal force gauge Patent

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