A removable interfacial insulator design concept is described that simplifies electrical connector repairability when damage occurs to male electrical contacts or resilient interfacial seal

Yamamoto, S.

English

NASA Technical Reports Server

CONTRACT NO. NAS9-13955
DRL NO. T-935
LINE ITEM NO. 2
DRD NO. MA-183T
NASA CR
(NASA-CR-141575) MODIFIED ELECTRICALCONNECTOR Final Report (ITT Cannon N75167
Electric, Inc., Santa Ana, Calif.) 23 p HC
CSCL 09A Unclas
G 3/33 08978
MODIFIED ELECTRICAL
CONNECTOR
FINAL REPORT
DECEMBER 1974
Reproduced by
NATIONAL TECHNICAL
INFORMATION SERVICE
US Department of Commerce
Springfield, VA. 22151
ITT CANNON ELECTRIC
666 E. DYER ROAD
SANTA ANA, CALIF. 92702
PRICES SUBJECT TO CH0"
https://ntrs.nasa.gov/search.jsp?R=19750008647 2020-03-23T01:14:24+00:00Z
The citation of trade names and names of manufacturers
in this report is not to be construed as official
government endorsement or approval of commercial
products or services referenced herein.
CONTRACT NO. NAS9-13955
DRL NO. T-935
LINE ITEM NO. 2
DRD NO. MA-183T
MODIFIED ELECTRICAL CONNECTOR
Final Report
December 1974
Approved by: Prepared by:
Bruce Arnold / Ste hen mamoto
Manager - Military/ Senior Design Specialist
Aerospace Products
ITT CANNON ELECTRIC
Santa Ana, Calif. 92702
I
ABSTRACT
This final report covers a removable interfacial insulator design
concept that simplifies electrical connector repairability when
damage occurs to male electrical contacts or resilient interfacial
seal.
P LEEDING pAGE BLANK 
NOT FILMD
TABLE OF CONTENTS
Page Number
Objective ............................. 1
Background ............................. 1
Design General .......................... 2
Design Features .......................... 2
Design Problem Areas ..................... 10
Operation as a Unit ....................... 11
Test Report .............................. 13
Conclusions ............................. 14
Summary ................................ 16
Recommendations ........................ 17
I
OBJECTIVE
To modify existing electrical connectors and eliminate many of the
problems with bent or broken pins and damaged interfacial seals;
to alleviate much of the time, effort and expense associated with
replacing these pins and seals in the event they do become damaged.
BACKGROUND
In the Apollo Command and Service Module and Lunar Module Programs,
85% of the reported problems with electrical connectors involved one
or more of these three anomalies: recessed or improperly sealed pins,
damaged seals, and bent pins.
Damaged Seals
Although there are several seals in a connector, the interfacial seal
appears to be the most fragile. It can be damaged when pins are
inserted or removed from the connector, or be punctured or torn by
the pin in a rear-release connector. In a front-release connector,
the seal may be damaged either by the pin or contact extraction tool.
Also, foreign objects or contamination could render the seal ineffective.
In any of these cases, the entire connector must be replaced.
Recessed Pins
Recessed pin contacts are due primarily to improper seating of the
pin contact in its retaining device. To re-seat the contact, the
rear accessory hardware must be removed from the shell to gain
access to the insert. After properly seating the contact, the accessory
hardware must be reassembled to the connector.
Bent or Broken Pins
Pin contacts are most often bent or broken by coming into contact with
some foreign object, ie, a tool, hardware, or the mating half of a
connector. In the event of pin contact damage, a new pin contact
must be installed by first removing the aft accessory hardware from
the shell to gain access to the insert, extract the wire with the
damaged contact, remove damaged pin contact, re-strip the wire,
crimp a new pin contact, re-insert, and finally, reassembling the
accessory hardware to the connector.
As indicated above, to repair these anomalies is expensive, time con-
suming and in same cases, these repairs will cause delays in critical
program scheduling.
-1-
DESIGN GENERAL
The interfacial insert consists of a rigid dielectric disc with
pins molded in place and protruding from both sides. An inter-
facial seal is bonded to each side of the disc (see Figure 1).
One side of the disc mates to female contacts in a modified
MS3470, MIL-C-0026482 type connector, the other side will
mate to its standard mate, a MS3476 plug connector with female
contacts.
The interfacial insert is retained in the modified shell by a metal
clip with a series of tines running perpendicular to the strip
axis (see Figure 2).
The clip is cut to a prescribed length and fits into an undercut
in the modified shell. This clip is retained in the undercut by
butting the edges together. The clip is oriented in the shell so
that the tines will deflect upward when the interfacial insert is
installed or removed. In the locked position, the tine lodges
against a shoulder on the interfacial insert (see Figure 3).
The interfacial insert, insert retaining clip is accommodated in
a modified female shell. The engaging portion is unchanged and
will mate to its standard mating connector (see Figure 4).
DESIGN FEATURES
Interfacial Insert
a. Insert to Shell Polarizing Key - This key assures correct
alignment when mated to symmetrical layouts. The key will
also preclude incorrect installation into the insertion tool
because the key height is greater than the tool I.D. (see Figure 5).
b. Keyways - A normal and three alternate position keyways are
provided on the peripheral should&r. These keyways engage a
key on the insertion tool to further assure correct installation.
The normal keyway will also always be in line with the insert
to shell polarizing key to provide a visual inspection that the
interfacial insert is correctly aligned for normal position
installation (see Figure 5).
-2-
MOLDED-IN PIN
S E A L
DIELELECT IC
FIG 1 BASIC
INSERT CONSTRUCTION
-3-
Z TINE
FIG 2
METAL INSERT RETENTION CLIP
., .
SHELL CLIP
SEALS SOCKET
I-S-Li LAT OR
PIN/PIN
INSERT ASSY
FIG 3
INSTALLED INSERT ASSY
-5-
RETENTION DEVICE
PERIPHERAL SEAL
INTERFACIAL INSERT
0
FEMALE SHELL MS 3470
MALE SHELL MODIFIED
MS 34 76
COUPLING RING & LOCK
MODIFIED MIL-C-83723 MATING ELECTRICAL CONNECTOR
WITH INTERFACIAL INSERT
FIGURE 4
EXTRACTION TOOL
INSERT TO SHELL
POLARIZING KEY
KEYWAY-NORMAL AND
A \ LTERNA TE POSITIONS
SHELL MASTER KEYW Y
iNDIICATO R
KEY
INSERTION TOOL-
DESIGN FEATURES
FIG 5
-7-
DESIGN FEATURES , Continued
Interfacial Insert
c. Raised Shoulder - The raised shoulder on the interfacial
insert performs two functions. First it precludes over
insertion by stopping against a shoulder in the shell:
second, it is the holding surface for the metal clip
tines (see Figure 6).
d. Seals - Seal compression in the area indicated in Figure 6
will provide a constant preload on the interfacial insert.
This preload is transfered to the metal clip tines so that
the interfacial insert is rigidly affixed to the modified
shell (see Figure 6).
e. Insertion Tool - The insertion tool has a key on the engaging
end which engages the applicable keyway on the interfacial
insert. In line with the key on the tool is an indicator which
is aligned with the master keyway of the shell. The com-
bination of the indicator, key and keyway on the interfacial
insert are features to assure correct installation. The chamfer
on the leading O.D. edge allows the tine to drop down and
retain the interfacial insert when the tool is extracted. To
further assure correct installation, the tool body diameter is
the same as the mating male plug connector. This feature
eliminates excessive tool side play in the receptacle engaging
I.D. (see Figure 6).
f. Extraction Tool - This tool has the same basic features of the
insertion tool except it has no key and no chamfer. The O.D.
of this tool deflects the metal clip tines away from the shoulder
when inserted in the engaging I.D. of the shell. On the assumption
that the extraction tool is only used to remove a damaged inter-
facial insert, a needle nosed pliers or any other similar tool is
used to pull the damaged insert and tool from the connector.
-8-
SEAL COMPRESSION-
SHELL
CLIP TSOCKET
INSERT
INTERFACIAL INSERT
/ /
LSHELL STOP
SHOULDER
-I NSER T S TO P SHOULDER
DESIGN FEATURES
FIG 6
-9-
DESIGN PROBLEM AREAS
In anticipation of implementing the interfacial insert in production
type MIL-Spec connectors, the problem areas listed below must be
considered.
1. A 66% increase in receptacle connector weight.
2. A 57% increase in receptacle connector length.
3. Increased equipment penetration or front of panel extension
depending on where the receptacle mounting flange is located.
4. Increased connector costs, due to special non-MIL-type shell.
5. New socket insulator is required for contact arrangements which
are not symmetrical about the vertical axis. This non-symmetry
only occurs in a few contact arrangements covered by MIL-C-5015.
Both MIL-C-38999 and MIL-C-0026482 contact arrangements are
all symmetrical about the vertical axis.
-10-
OPERATION AS A UNIT
(See Figure 7)
The top figure depicts a connector with a damaged seal and
contact. To replace the interfacial insert, simply insert the
extraction tool and remove the damaged insert, gripping the
pin contacts with a needle nose plier.
Place the new interfacial insert into the insertion tool, install
as shown in the lower figure, remove the tool and connector
is now repaired and ready for service.
-ll-
SOCKET INSERT DAMAGED PIN ANDASSE MBLY TO RN SEAL
IN TERFACIAL INSERT
DEFLECTED
REMOVE
INSERT
INSERTION TOOL
NEW INTERFACIAL INSERTOPE RATION
FIG. 7 -12-
I tbI AU I MU ILA I IUI I Yamamot -
NEEDED ON OR BY SUPERVISORY AUTHORITY t REPORT ISSED
uI t. ON $25. OVER T1HAT 
A OU O nDAY YR. DIV
DEPARTMENT AU 10 TEST AUTH. NO.ITT CANNON ELECTRIC. 2031 /
0 HUMBOLDT ST. LOS ANGELES CALIF DISION IGINATOS PROJi ESTIMATED COM R R
Ao DVISON OF ..N .TfNAt&.L T LI.ONE AND TI .RAPN CoP..." Central Eng. 0187-501 o. DAY VR
PURPOSE (TO DETERMINE WHAT AND WHY)
To determine the design feasibility of NASA's Interfacial Insert
System as a connector saver.
TEST SAMPLES
I DRAWING NUMBER LINE HO ADL SCCE.ATLS
QUAN. ITEM WITH CHANGE LETTER CODE PART NUMBER / DESCRIPTION HOW MADE. 5C.RCE. MATERIALS CO
1 1 HQ0187-500-110 Shell, Test Aid Eng. Model Shop
1 2 HQ0187-500-113 Tool, Insert Removal Eng. Model Shop
1 3 HQ0187-500-115 Tool, Insert Insertion Eng. Model Shop
1 4 HQ0187-500-107 Interfacial Ins. Assy. Production
1 5 HQ0187-500-112 Clip, Interfacial Ins. Ret. Production
1 6 029-0000-002 Clip, Ins. Ret. PV 16 Production
2 7 144-1842-000 Insulator Assy PV 16 -26S Production
51"M A ST I I RETURN TO ORIGINATOR: 2 SCRAP ' OTHER (SPECTFY
CANNO JO NO A CUSTOMER P 0 Po MILITARY CONTACT NO quorE No
316820 A LBJ SC oPuston, NAS -9-13935 N/A
TESTS REQUIRED AND/OR SPECIAL INSTRUCTJONS (LIST EACn TEST AND APPLICABLE SPECIFICATION)
1. Interfacial Insert Retention. 32 Lbs. Max.
2. Interfacial Insert Insertion Force
3. Socket Contact Insertion Force
4. Pin Contact Retention @20 lbs.
5. Contact Resistance - Set up: REF. MIL-C-39029
6. Durability - 500 cycles.
7. Interfacial Insert Removal Force.
NOTE: Will the test lab please make comments on the operation of the design concept.
GOVT INSPECTION REQUIRED 0 YES [,
REPORT/ABSTRACT OUANTITY OF REPORTS REQUIRED_ FORMAL PRODUCT EVALUATION 
REPORT REQUIRED YES O N
Test Resul ts
Interfacial Insert Retention No dislodgement @ 32 Lbf.-Max deflection
.014 inch.
Interfacial Insertion Force Max. measured force for five insertions was
24.0 lbs.
Socket Contact Insertion Force Max. measured force for 26 socket was 7.3 lb
Pin Contact Retention No dislodgement @ 20 Lbf.-Max.deflection
.015 inch.
Contact Resistance(Set up per MIL-C-39029) Max.measured voltage drop was 38.8mV 0 7.5Ad
Durability (500 cycles). No damage to insert assembly.
Interfacial Insert Removal Force. Max. measured force for five removals was
13.0 lbs.
Abstract: The interfacial insert met all requirements listdabo d exhibited no
perational problems.
-" eaver R.'J. therrard
Sr. Lab Technician -13- Supvr.-Test Laboratory
CONCLUSIONS
As indicated on the enclosed test report, the interfacial insert
met all the requirements and exhibited no operational problems.
Listed below are the conclusions made based on the test results.
1. Test - Interfacial Insert Retention.
Reason - To determine the capability of the metal clip retention.
Criteria - MIL-C-0026482, Paragraph 3.6.30, 32 lbs. max. for
shell size #16.
Results - Passed 32 lbs. max. with .014 inch deflection.
Conclusion - Metal clip retention meets insert retention
requirements as applicable.
2. Test - Interfacial Insert Insertion Force
Reason - To determine axial force required to install interfacial
insert as in service.
Criteria - None
Conclusion - The insertion force of 24 pounds is including the
engaging force of 26 #20 socket contacts, the compression of
the inner interfacial seal and the metal clip tine deflection.
This force of 24 pounds will have to be considered when higher
density contact arrangements and larger shell sizes are evaluated.
3. Test - Socket Contact Insertion Force
Reason - To determine if socket contact insertion force is affected
when a male pin contact must be engaged during the insertion
process.
Criteria - MIL-C-0026482, paragraph 3.6.10, 20 lbs. max. for
size #20 contacts.
Conclusion - Engaging a male pin contact does not affect the
contact insertion process.
-14-
CONCLUSIONS, Continued
4. Test - Pin Contact Retention
Reason - To determine the effects of interfacial seal compression
during the contact retention test.
Criteria - MIL-C-0026482, Paragraph 3.6.32, 20 lbs. load with
.012 max. deflection.
Conclusion - With a 20 lb. load, the interfacial seal is adding
.003 to the .012 max. requirement. This .003 additional
deflection should be considered if this test becomes a require-
ment for the modified connector. Also, during the test, it was
discovered that the mating half of the connector would also
serve as a good insertion device.
5. Test - Contact Resistance
Reason - To determine if contact resistance is affected by the
interfacial insert pin/pin contacts.
Criteria - MIL-C-0026482, Paragraph 3.6.5.1, Size #20
contacts = 55 millivolts max.
Conclusion - The additional pin length does not affect the
electrical performance.
6. Test - Durability
Reason - To determine if repeated mating/unmating would affect
the interfacial insert molded in pin contacts.
Criteria - MIL-C-0026482, Paragraph 3.6.18, 500 cycles of
mating/unmating.
Conclusion - Repeated mating/unmating does not affect the function
of the interfacial insert. If base metal exposure on the pin contacts
is objectionable in service, this design concept provides a simple
solution where many cycles of durability are anticipated.
7. Test - Interfacial Removal Force
Reason - To determine the amount of force required to remove the
interfacial insert.
Criteria - None
Conclusion - The removal force of 13 lbs. includes the separation
force of 26 #20 socket contacts, again the contact arrangement
density and the shell size will influence this force.
-15-
SUMMARY
As evidenced by the test report, the objective of simplified connector
repairability was successfully met with the interfacial insert design
concept.
The design concept of the metal clip method of insert retention and
the molded in pin/pin insulator system functioned as intended.
The separate metal clip insert retention design selection over the
molded integral plastic tine on the periphery of the insert is necessary
so that a functional peripheral seal in the receptacle can be designed
in as required by all high performance electrical connectors.
The metal interfacial insert insertion/extraction tools, a set for each
shell size, could be made from a thermal plastic material to reduce
cost of the tools. To further reduce cost, the tool could be a double
ended tool similar to the conventional contact insertion/extraction
tools.
The interfacial insert did not present problems in any areas of
manufacture and assembly: subsequently, no new technology is
required to produce or assemble the insert.
-16-
RECOMMENDATIONS
Based on the success of the design evaluation study, ITTCE
highly recommends that the follow-on contract to modify a
MIL-type male shell, be considered.
Ref: NASA RFP #9-BC721-4-4-164P
ITTCE Proposal G-19580
The design study concluded under this contract was limited to
insert assemblies without shell hardware. Without hardware,
only a limited number of mechanical and electrical tests are
feasible, also no hardware precluded any environmental testing.
Environmental testing, ie, Vibration, Shock, Thermal Shock,
Humidity, etc, would confirm the interfacial inserts design
capabilities in a MIL-type connector configuration. Subsequently,
it behooves NASA to issue the follow-up contract for further
development immediately so that no lead time will be lost when
an interfacial insert system becomes a real connector requirement.
-17-
APPENDIX A
To comply with Item 3.2.1 of the Statement of Work
as modified by the Amendment IS, dated 12-9-74, toContract No. NAS 9-13955, the following ReliabilityAssessment is submitted as an Appendix to the Final
Report entitled "Modified Electrical Connector" which
was submitted on December 13, 1974.
Submitted by:
Bruce Arnold, Manager
Military/Aerospace Products
Ste hen mamoto
Senior D sign Specialist
-1
RELIABILITY ASSESSMENT
The introduction of the interfacial insert will add the equivalent ofan additional connector into the system when determining reliability.That is, a pin and socket insulator and interfacial seal are added bythe use of the interfacial insert and these elements approach a totalconnector.
The numerical reliability of the series addition can be determined bythe following equation:
RT = R1 x R 2
Where RT = Total Modified Connector Reliability
R & R2 = Standard Connector Reliability
Using this equation, the reliability at specified levels can be determinedas shown in the table below:
Standard Modified
Connector Reliability Connector Reliability % Change
.99 
.98 
- 2
.999 
.998 
- 0.2
.9999 
.9998 
- 0.02
At a very low reliability level of .99, the reduction in reliability is 2%by the use of the interfacial insert. However, the interfacial inserthas the potential of eliminating 85% of connector problems (which cancause failure) and will therefore increase connector reliability by oneorder of magnitude.
mu4


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