U.S. patent number 3,708,611 [Application Number 05/226,140] was granted by the patent office on 1973-01-02 for heat shrinkable preinsulated electrical connector and method of fabrication thereof.
This patent grant is currently assigned to AMP Incorporated. Invention is credited to Leon Joel Dinger.
United States Patent |
3,708,611 |
Dinger |
January 2, 1973 |
HEAT SHRINKABLE PREINSULATED ELECTRICAL CONNECTOR AND METHOD OF
FABRICATION THEREOF
Abstract
A wire barrel and a heat pliable inner sleeve of polymeric
material are maintained in fixed tandem relationship by an outer
heat shrinkable polymeric sleeve which is initially only partially
shrunk, radially into gripping relationship over the wire barrel
and inner sleeve. An exposed conductor wire end portion is received
through the inner sleeve for crimped termination to the wire
barrel, the application of crimping forces being selectively
transmitted through said outer sleeve to said wire barrel without
damaging said inner sleeve. Heat is applied to cause the outer
sleeve to shrink radially in tightly encircling relationship over
the crimped connection to result in a low profile termination. The
inner sleeve is heat pliable for radial relaxation upon the
application of radial compression forces supplied by the shrinking
of said outer sleeve. The inner sleeve is thereby radially
collapsed into gripping compression on the insulation of said
conductor wire to provide a seal at the end of the outer sleeve and
to provide a mechanical support for the conductor wire adjacent to
the crimped termination, which support limits and distributes
strain on the crimped termination caused by external bending forces
applied to the conductor wire. The radial shrinkage of the outer
sleeve provides compression forces sufficiently high to displace
the inner sleeve to a slightly protruding position from the end of
the outer sleeve. The inner sleeve thus provides a seal for the end
of the outer sleeve and radially compresses into encircling sealing
engagement over the conductor wire insulation, thereby forming a
strain relief and mechanical support for the conductor wire.
Inventors: |
Dinger; Leon Joel (Harrisburg,
PA) |
Assignee: |
AMP Incorporated (Harrisburg,
PA)
|
Family
ID: |
22847728 |
Appl.
No.: |
05/226,140 |
Filed: |
February 14, 1972 |
Current U.S.
Class: |
174/84C; 439/730;
439/880; 174/90; 439/877 |
Current CPC
Class: |
H02G
15/1806 (20130101); B29C 61/0616 (20130101); H01R
4/72 (20130101) |
Current International
Class: |
B29C
61/06 (20060101); H02G 15/18 (20060101); H01R
4/70 (20060101); H01R 4/72 (20060101); H02g
015/08 () |
Field of
Search: |
;174/DIG.8,84R,84C,90,94R ;339/276R,276T,201,213 ;29/628,63F |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Clay; Darrell L.
Claims
What is claimed is:
1. In a low-profile preinsulated electrical connector covered
sealably with a heat-shrinkable sleeve, the combination comprising:
a compressibly deformable metal sleeve for crimping onto an
electrical wire, a heat pliable and substantially non-fusible
sleeve of polymeric material in serial tandem relationship with
respect to said metal sleeve, said heat-shrinkable sleeve being
initially received over and partially shrunk in radial compression
over said metal sleeve and said heat softenable sleeve, thereby
retaining said metal sleeve and said heat-shrinkable sleeve in
serial tandem relationship and in fixed position with respect to
said heat-shrinkable sleeve, said metal sleeve being entirely
contained within said heat-shrinkable sleeve, said heat pliable
sleeve including an open end portion thereof partially protruding
from the end of said heat-shrinkable sleeve and adapted to receive
therethrough an electrical conductor wire.
2. The structure of claim 1 wherein said heat-shrinkable sleeve is
resistant to extrusion upon the application of radial crimping
forces applied thereof during crimping of said metal sleeve to a
conductor wire received therein.
3. The structure of claim 1 wherein said heat pliable sleeve is in
serial tandem spaced relationship with respect to said metal sleeve
allowing the application of crimping forces selectively to said
metal sleeve without damaging said heat pliable sleeve.
Description
It is therefore an object of the present invention to provide a
low-profile preinsulated electrical connector covered sealably with
a heat shrinkable sleeve, and with a heat pliable inner sleeve
providing a seal and a mechanical support and strain relief for an
electrical wire terminated to the electrical connector.
Another object of the present invention is to provide a method for
fabricating a low-profile preinsulated electrical connector with an
outer heat shrinkable sleeve and an inner heat softenable and
radially collapsible sleeve providing a seal, mechanical support
and strain relief for a conductor wire terminated to the
connector.
Another object of the present invention is to provide a
preinsulated electrical connector with a heat shrinkable outer
sleeve and an inner heat softenable sleeve which, upon heating,
will be displaced slightly to protrude from the end of the heat
shrinkable sleeve and provide a seal therefor.
Other objects and many attendant advantages of the present
invention will become apparent upon perusal of the following
detailed description taken in conjunction with the accompanying
drawings, wherein:
FIG. 1 is an enlarged perspective of a preferred embodiment
according to the present invention with the component parts thereof
exploded to illustrate the details of fabrication thereof;
FIG. 2 is an enlarged elevation in section of a fully assembled
preferred embodiment according to the present invention;
FIG. 3 is an enlarged elevation in section illustrating the
preferred embodiment as shown in FIG. 2 crimped to corresponding
ends of two conductor wires and prior to heating a heat shrinkable
outer sleeve;
FIG. 4 is an enlarged elevation in section of the preferred
embodiment illustrated in FIG. 3 with the heat shrinkable outer
sleeve thereof having been heated to shrink radially and to
radially collapse a heat softenable inner sleeve into sealing
compressive engagement over the conductor wire insulation to
provide a sealing, mechanical supporting and strain relieving
function for the conductor wire insulation;
FIG. 5 is a section taken along the line 5--5 of FIG. 3;
FIG. 6 is a section taken along the line 6--6 of FIG. 4;
FIG. 7 is an enlarged perspective with parts shown exploded of a
modification of the preferred embodiment as shown in FIG. 2;
FIG. 8 is an enlarged perspective of the preferred embodiment as
shown in FIG. 7 connected to respective ends of conductor wires;
and
FIG. 9 is a section along the line 9--9 of FIG. 8.
With more particular reference to the drawings, there is shown in
FIG. 1 generally at 1 a low profile preinsulated electrical
connector according to the present invention. The connector
comprises an outer, generally cylindrical sleeve 2 of heat
shrinkable polymeric material which is assembled over a reduced
diameter, generally cylindrical elongated compressibly deformable
metal sleeve, more generally identified as a wire barrel. With the
wire barrel 4 generally assembled entirely internally of the outer
sleeve 2, a reduced diameter cylindrical inner sleeve 6 of heat
softenable polymeric material is inserted with each open end of the
outer sleeve 2. As shown in the figure, the inner sleeves 6 may be
each received initially over a mandrel 8. Each mandrel 8 is
provided with a tapered portion defining a reduced diameter tip 10
to facilitate insertion of the mandrel and corresponding inner
sleeve 6 in a corresponding end of the outer sleeve 2. The tip 10
of the mandrel may be received partially in the end of the wire
barrel 4 with the tapered remainder of the mandrel positively
stopped against the end of the wire barrel to facilitate
positioning of the inner sleeve 6 within the outer sleeve 2. With
the component parts thus assembled, heat is applied in any well
known manner to the outer sleeve 2 causing it initially to
partially shrink radially and conform to the shape of the reduced
diameter wire barrel 4 and the tapered shape of the mandrel 8.
Although the inner sleeves 6 are made pliable upon the application
of heat, the presence of the mandrel therein ensures that the inner
sleeves 6 retain their original diameter. Thus, upon removal of the
mandrels 8 from the assembly, the outer sleeve 2 will be of a shape
wherein the open end portions 3 of the outer sleeve 2 are of
relatively large diameter, and in encircling relationship with and
conforming to the exterior shape of the inner sleeves 6. After
shrinkage, the assembly is cooled to allow the sleeve 2 to take a
"set". The sleeve 2 upon taking a "set" thus tightly encircles and
grips the wire barrel 4 and the sleeves 6, thereby fixedly
retaining them in serial tandem relationship in proper alignment
for the introduction of a conductor wire for termination to the
wire barrel 4, in a manner to be hereinafter explained in detail.
In the typical application, the wire barrel 4 is provided with
generally central opening 12 providing a window. To positively
anchor the sleeve 2 to the wire barrel 4, the sleeve 2 includes a
recessed portion 14 partially received in the window portion 12 of
the wire barrel 4. Often, the described, radial shrinkage alone of
the sleeve 2 upon heating is sufficient to provide the recessed
portion 14. However it is sometimes necessary to physically deform
the sleeve 2 by forcibly depressing the sleeve with a tool (not
shown) to form the recessed portion 14. It is necessary that the
recessed portion 14 is created during heating of the sleeve 2
since, upon cooling, the sleeve 2 will take a "set". However, even
after the sleeve has been initially shrunk and then cooled to a
"set", it may be repeatedly heated and the recessed portion 14
formed while the sleeve is in its heated state. Upon cooling, the
recessed portion 14 will take a "set" recessed within the window
12, thereby physically anchoring the sleeve 2 in position on the
wire barrel 4. As shown, the sleeves 6 can partially protrude from
the open end portion 3 of the sleeve 2 as shown in FIG. 2.
Alternatively, the inner sleeves 6 may be trimmed flush with the
open end portions 3 of the outer sleeve 2 if desired.
To make a completed electrical connection, a wire end portion
having a conductor wire 18 exposed from its outer insulation
covering 20 is received through a corresponding inner sleeve 6. As
shown with reference to FIGS. 2 and 3, the exposed conductor wire
18 is received internally of a corresponding open end of the wire
barrel 4 in stopped relationship against a wire stop 19 in the form
of a tang struck from a medial portion of the wire barrel 4 and
projecting internally of the wire barrel 4. The insulation 20 of
the conductor wire will then be disposed within a corresponding
inner sleeve 6, such sleeve completely encircling the insulation
20. As shown in FIG. 3, the wire barrel 4 is compressibly deformed
into crimped engagement with a corresponding conductor wire 18 by
the application in any well-known manner of crimping forces
transmitted directly through the outer sleeve 2. With the wire
barrel 4 and the inner sleeves 6 in tandem relationship, the
crimping forces may be applied to the wire barrel without
disturbing or damaging the sleeves 6.
To ensure proper location of the conductor wire 18 in stopped
position against the stop 19, the outer sleeve 2 may be
manufactured from a heat shrinkable transparent polymeric material
such as Kynar, a trademark of Pennwalt Chemical Corporation. By
visual observation through the transparent recessed portion 14 and
window 12, the position of the conductor wires 18 may be
observed.
With reference to FIG. 4, the resulting electrical connection may
be sealed, and a mechanical support and strain relief for the
terminated conductor wires 18 may be provided upon again applying
heat to the heat shrinkable outer sleeve 2 especially at its end
portions 3 thereof. Such application of heat causes the end
portions 3 to shrink radially in even tighter compression over the
inner sleeves 6. Such inner sleeves 6 are fabricated from
non-irradiated and thereby substantially non-cross-linked Kynar
such that it does not have heat shrinking properties similar to
that of the outer sleeve 2. Instead, the sleeves 6 became pliable
upon the application of heat sufficient to cause shrinking of the
outer sleeve 2. Thus application of heat which shrinks the end
portions 3 of the outer sleeve 2 also causes the sleeves 6 to
become limp and less resistant to the radial compression forces
supplied by radial shrinkage of the outer sleeve end portions 3.
Thus upon radial shrinkage of the end portions 3, the heated inner
sleeves 6 readily relax or collapse radially into encircling
relationship compressibly over the insulation 20. Since the inner
sleeves 6 are only made pliable and do not become fluid or fusible,
they do not become bonded to the insulation 20 but only tightly
encircle and grip the insulation with a gripping force provided by
the shrunk outer sleeve end portions 3. The sleeves 6 accordingly
provide a compression, moisture resistant seal for the end portions
3 of the outer sleeve 2 and also mechanically support the conductor
wire and provide strain relief to prevent concentration of bending
forces at the wire barrel which would tend to break the conductor
wire which is crimped within the wire barrel 4. Thus provision of
the sleeves 6 eliminates the need for crimping the wire barrel 4 to
the insulation, a practice heretofore regarded in the prior art as
necessary to provide such strain relief. As a further feature,
since the inner sleeves 6 are not fusible, and are thereby not
reduced to a fluid state, no additional seals are required in the
connector which would ordinarily be required to prevent escape of
fluid or fusible adhesives should such be used to seal the outer
sleeve end portions 3.
As the outer sleeve end portions 3 are shrunk the resultant
compressive forces on the inner sleeves 6 has a tendency to cause
the sleeves to partially protrude from the open ends of the outer
sleeve end portions 3 as shown at 22 in FIG. 4. Such protruding
condition is produced upon a slight displacement of the inner
sleeve mass occasioned by the progressive application of
compression forces produced by the progressive shrinking of the
outer end portions 3 of the sleeve 2. The protruding condition of
the inner sleeves 6 serves as a visual inspection aid indicating,
that sufficient shrinkage of the end portions 3 has occurred to
cause the inner sleeves 6 to be compressed into sealing engagement
over the insulation 20, and that sufficient additional compression
forces have occurred to produce, not only a seal, but the
protruding condition as shown at 22. Thus, even if some relaxation
of the end portions 3 occurs upon cooling, sufficient additional
compression forces have been initially provided to prevent such
relaxation from dissipating entirely the compression forces
required for the sealing effects of the inner sleeves 6. Upon
cooling, the inner sleeves become less pliable and provide
creep-free polymeric seals.
In accordance with accepted chemical principles, the heat shrinking
properties of the outer sleeve 2 are provided, by extruding Kynar
into tube form, irradiating the the tube form with electron energy
to cross-link the Kynar, then physically expanding the tube to an
enlarged cylindrical configuration, followed by cooling the tube to
retain it in a "set" condition in its expanded form. The inner
sleeves 6 are fabricated from tubes of non-irradiated Kynar. By
experimentation it was found that the application of a flame of
about 450.degree.F. to the irradiated Kynar in its expanded form,
causes it to radially shrink back to its original extruded form,
without noticeable limpness or pliability being observed. However,
upon the application of a flame of that temperature to the
non-irradiated Kynar, two significant observations were made.
First, the non-irradiated Kynar tube was found to become limp and
in a pliable condition. It was observed however that the
non-irradiated Kynar did not become fluid or fusible and did not
bond to surfaces of materials at ambient temperatures. Again
testing the non-irradiated Kynar, a length of tubing was supported
only at one end, and a flame of about 450.degree.F. was applied to
the other end, which was unsupported in space. The heated Kynar was
observed to become limp and pliable but was not reduced to a fluid
state. No fluid or semi-fluid catenaries or droplets were observed.
Instead the unsupported end of the tube did not behave as a fluid
but remained in a pliable, solid state. The flame was continued to
be applied until the Kynar began to char. As a result of such
observations, it was concluded that the non-irradiated Kynar upon
the application of heat became limp but not fluid, even when heated
to its charring point. The application of heat to the irradiated
and expanded Kynar caused it to return to its original non-expanded
form but without becoming limp. Accordingly, with the sleeve 2
being fabricated from irradiated and expanded Kynar, upon the
application of heat sufficient to cause radial shrinkage to its
original non-expanded form, substantial radial compression forces
could be created by such shrinkage without the sleeve becoming
limp. By fabricating the inner sleeves 6 of non-irradiated Kynar,
which became limp at elevated temperatures but not reduced to a
fluid state, a desired sealing function was obtainable without a
need for separate seals to prevent escape by fluid flow of the
inner sleeves from the outer sleeve 2.
As shown in FIG. 4, when heat is applied to shrink the end portions
3 of the outer sleeve 2, the entire connection will possess a low
profile, by shrinkage of the end portions 3 and crimping of the
wire barrel 4 to only the conductor wire 18. By eliminating the
need for crimping the wire barrel to the insulation 20 for
mechanical support thereof, a much lower profile connection is
achieved as shown in the figure. As a practical matter, it is not
necessary to apply heat only locally to the end portions 3.
Instead, to complete the low profile connection heat is permitted
to be applied along the entire length of the outer sleeve 2. This
will often cause the recessed portion 14 to become less conforming
to the shape of the window 12. More specifically, as shown in FIG.
3, upon crimping the wire barrel to the conductor wire 18, the
recessed portion 14 is shown conforming to the shape of the window
12. However upon reheating, of the recessed portion 14, as shown in
FIG. 4, the sleeve 2 will tend to shrink an additional amount with
the result that the recessed portion stretches across, and becomes
less conforming to the shape of, the window 12.
With more particular reference to FIGS. 7 and 8, a modification of
the embodiment shown in FIG. 1 will be described in detail. FIG. 7
illustrates an outer sleeve 2' of irradiated, heat shrinkable Kynar
with one enlarged open end portion 3' receiving an inner sleeve 6'
of heat softenable non-irradiated Kynar. A wire barrel 4' is
received internally of the sleeve 2', with the sleeve 2' being
initially shrunk to grip and retain the wire barrel 4' and the
inner sleeve 6' in tandem serial relationship. The other end of the
sleeve 2' is closed off as shown at 24 by radially compressing the
end portion to form tightly associated folds. Such folds can be
readily formed during heating of the sleeve 2' to produce its
initial shrinking. The result is a preinsulated electrical
connector having only one open end adapted to receive a pair of
adjacent conductor wires 18' partially exposed from their
surrounding insulation sheaths 20'. In a manner as heretofore
described, and with reference to FIG. 8, the exposed conductor
wires 18' are terminated to the wire barrel 4' by the application
of crimping forces transmitted directly through the outer sleeve 2'
without damaging the inner sleeve 6'. By the application of heat,
the end portion 3' of the outer sleeve is caused to radially shrink
and compress the inner sleeve 6' into radial tightly gripped
compression on the conductor wire insulation 20'. Although the
sleeve 6' does not bond to the insulation 20', it is heat pliable
to the extent that it will completely encircle each of the
conductor wire insulation sheaths 20', as shown in FIG. 9. Between
the adjacent insulation sheaths 20', a definite seam 26 is observed
in the heat pliable sheath 6'. The seam 26 indicates that no fusion
of the pliable sleeve 6' has occurred. However, the compression
forces resulting from radial shrinkage of the outer sleeve end
portion 3' is sufficient to force the heat pliable sleeve 6' into
tight compression with itself along the seam to provide an
effective compression seal without the need for fusion along the
seam 26.
Although preferred embodiments of the present invention have been
shown and described in detail, other modifications and embodiments
of the present invention are intended to be covered by the spirit
and scope of the appended claims, wherein:
* * * * *