U.S. patent number 3,649,743 [Application Number 05/068,688] was granted by the patent office on 1972-03-14 for wrapped wire connection.
This patent grant is currently assigned to Thomas & Betts Corporation. Invention is credited to Francis A. O'Loughlin.
United States Patent |
3,649,743 |
O'Loughlin |
March 14, 1972 |
WRAPPED WIRE CONNECTION
Abstract
A wrapped wire connection in which an elongated post having at
least one sharp edge is wrapped with a standard insulated wire and
an outer sleeve fits over the wrapped turns of the wire to apply,
at least temporarily, mechanical pressure to the wrapped wire,
causing the sharp edge of the post to pierce the wire insulation
and thereby to form a permanent electrical and mechanical
connection.
Inventors: |
O'Loughlin; Francis A. (Scotch
Plains, NJ) |
Assignee: |
Thomas & Betts Corporation
(Elizabeth, NJ)
|
Family
ID: |
22084106 |
Appl.
No.: |
05/068,688 |
Filed: |
September 1, 1970 |
Current U.S.
Class: |
174/84C; 174/94R;
439/423; 439/877 |
Current CPC
Class: |
H01R
4/14 (20130101); H01R 4/2412 (20130101) |
Current International
Class: |
H01R
4/10 (20060101); H01R 4/24 (20060101); H01R
4/14 (20060101); H02g 015/08 () |
Field of
Search: |
;174/84R,84C,94R,87
;339/95R,95D,97R,97C,276A ;29/628 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Clay; Darrell L.
Claims
What is claimed is:
1. A wrapped wire electrical connection for improved mechanical and
electrical interconnection of a terminal and an insulated wire,
comprising:
a conductive post providing a terminal for an electrical
connection, said post having at least one sharp corner extending
lengthwise thereof;
an insulated wire conductor at least partially wrapped around the
post and crossing said sharp corner; and
a sleeve overfitting said wrapped conductor and applying a
mechanical pressure thereto urging said conductor against the post
causing the sharp corner of said post to pierce the insulation and
electrically contact the conductor.
2. A connector according to claim 1, in which:
the sleeve is radially deformed inwardly to surround said wrapped
conductor.
3. A connection according to claim 2 in which:
the sleeve is formed of sintered powdered conductive material
having a low plastic memory.
4. A connection according to claim 1, in which:
the sleeve is radially resilient and resiliently urges the wrapped
conductor against the post.
5. The connection as set forth in claim 1, in which:
the sleeve is comprised of a plastic material.
6. A connection according to claim 1, in which:
the sleeve has a coefficient of expansion in the radial direction
that is approximately the same as the corresponding coefficient of
the post and wire as a unit.
7. A method for making an electrical connection of an insulated
conductor to a conductive terminal post having at least one sharp
corner extending lengthwise thereof for piercing the insulation of
said insulated conductor comprising:
wrapping at least a partial turn of the insulated conductor around
the post to include crossing the sharp corner thereof;
surrounding the wrapped connection with a deformable sleeve;
and
deforming said sleeve in a radially inward direction causing the
sharp corner of the terminal post to pierce the insulation and
electrically contact the conductor.
Description
BACKGROUND OF THE INVENTION
This invention relates to a new and improved mechanical and
electrical connection between an electrical terminal and a
conductor. It relates specifically to an improved solderless
connection in which a wire conductor is wrapped around a terminal
post.
There are several methods by which electrical components are fixed
to printed circuit boards and the like, among those methods being
the use of crimpable electrical connectors which mechanically and
electrically interconnect the pins or terminal electrical points of
circuit components. In many cases, the component, such as an
integrated circuit pack, has pins that are inserted into holes in a
socket or other terminal on the printed circuit board. In some of
the prior art techniques, the printed integrated circuit component
is carried by a special receptacle that is received within the
holes of the circuit board. The present invention provides a new
connection to the terminals of such components by flexible wire
conductors.
Once components are mechanically secured to the circuit board, wire
leads are attached to terminal posts for connection to other
circuit boards or distant components. Where possible, solderless
connections are often used, the most common of which is the wrapped
wire connection whereby the connecting wires and leads from the
circuits are wrapped around upstanding terminal posts. In this
case, of course, the wire conductor leads wrapped around a single
post may originate from one or more electrical components.
The concept of wrapping an electrical conductor around a terminal
post is, of course, an old technique that has been used for several
years. One of the disadvantages of this technique, however, is
that, alone, it cannot be used to connect insulated wire to the
terminal, unless the insulation is first stripped away before
making the connection. In order to connect a stranded insulated
wire to a terminal post, it has been the usual practice first to
strip the insulation from the wire end and then to solder the wire
to the terminal. Wire wrapping methods have not been possible in
such cases, particularly if the wire is at all delicate or of small
gauge, because the individual strands tend to separate and break
during winding. Fine solid wires, of course, also may rupture
during attempted winding, especially if the terminal post has a
small cross section, requiring turns of extremely small diameter.
For these reasons, it has been considered more reliable to solder
such small gauge wires to the post or to use other types of
connections to the post, in any case it being necessary to strip
the insulation prior to connection.
SUMMARY OF THE INVENTION
In accordance with the invention these and other disadvantages of
earlier practices are remedied by the improved wrapped wire
electrical connection described herein, which provides wrapped wire
connection to a terminal post without stripping the insulation from
the wire conductor. In brief, this connection comprises a
conductive terminal post, preferably having at least one sharp
edge, extending in the lengthwise direction of the post, at least a
partial turn of the insulated conductor wrapped about the post, and
an outer sleeve fitting over and partially surrounding the turns of
the wrapped conductor to apply, at least temporarily, a mechanical
pressure to urge the conductor against the post and to cause the
post to pierce the insulation for electrical contact of the post
and the conductor. In a preferred embodiment, the sleeve is
constructed from a powdered metal material having a low plastic
memory such that it can be crimped into close proximity to the
wrapped conductor to force it against the sharp edge of the post,
but which can be broken away from the post to repair the
connection, if necessary, by applying, for example, a moderate
stress to the outside of the sleeve.
Because the insulation remains on the wire conductor during the
wrapping operation, the insulation sleeve, in the case of plastic
or fabric materials, provides strain relief for the conductor. That
is, the insulating sleeve carries and relieves the wire conductor
of tension and other loads that otherwise would be applied directly
to the conductor. Furthermore, by leaving the insulation on the
wire end throughout the connecting operation, stranded wires may be
wrapped as easily as solid conductor wires.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention, reference may be made
to the following detailed description of preferred embodiments and
to the accompanying drawings, in which:
FIG. 1 is a partial perspective view of a circuit board having
terminal posts to which wire conductors are connected in accordance
with the invention;
FIG. 2 is a plan view of a connection according to the
invention;
FIG. 3 is an elevational view in partial cross section of the
connection of FIG. 2;
FIG. 4 is a plan cross-sectional view, showing the connection of
FIGS. 2 and 3 after the outer sleeve has been deformed into close
contact around the conductor turns;
FIG. 5 is yet another form of outer sleeve suitable for use in the
invention; and
FIG. 6 is a plan view of a rectangular terminal post and sleeve
according to the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
FIG. 1 illustrates one manner in which the present invention may be
found in practice. There, an insulated printed circuit board 11 is
shown to include an electronic component, such as an integrated
circuit pack 13 (or socket for such a component) that has terminal
posts or pins 15 as terminals extending through apertures in the
circuit board 11. Wire conductors 17 used for interconnecting the
circuit component 13 with other components are wrapped in a series
of close helical turns around the terminal post 15 and, in
accordance with the invention, sleeves 19 are placed over at least
some of the turns of the wire conductor 17 and (preferably)
crimped.
FIGS. 2 and 3 depict the wrapped wire connection in greater detail.
As illustrated, the post 15 extending through the circuit board 11
has a square cross-sectional configuration and is wrapped with
several closely spaced turns of the wire 17. The method of wrapping
terminal posts in this manner is well known in the art and may be
accomplished by hand, by special tool or by machine. As already
mentioned, one of the problems with merely wrapped connections is
that they could not be readily applied to stranded wire and,
moreover, if the conductor was an insulated conductor having, for
example, an insulating varnish or plastic coating, the insulation
must be stripped from the conductor prior to wrapping. In
accordance with the invention, however, the sleeve 19 fits closely
around the wrapped turns of the conductor 17, as is best seen in
FIG. 2. When the sleeve is inserted over the turns, they are
pressed against one or more of the sharp corners 15a of the post.
Generally, the sleeve must be deformed radially, as by squeezing,
to apply sufficient pressure to the wire to cause the post to
pierce the insulation on the conductor 17. On the other hand,
varnish coating insulation can sometimes be pierced if the sleeve
alone fits tightly about the turns. In either case, the post thus
makes electrical contact and intimate physical contact with the
conductor.
After the sleeve 19 has been placed over the conductor wrapped
post, it is preferable to crimp it. FIG. 4 is a cross-sectional
view through the connection following crimping. As shown there, the
sleeve 19 has been deformed to squeeze the wrapped turns of the
conductor 17 around the post 15 and thereby obtain a very secure
electrical and mechanical connection.
As summarized above, the sleeve can be constructed of various
materials, both dielectric and conductive. Sintered powdered metal
sleeves are adaptable to crimping, if required, and can be broken
away easily thereafter if the connection is to be repaired or
replaced merely by applying lateral pressure to the sleeve. Plastic
sleeves are also suitable, as are sleeves constructed from yet
other materials that can be made to contract or deform radially
into tighter contact about the wire turns.
It is preferred in any case that the sleeves possess a coefficient
of thermal expansion in the radial direction that is not
appreciably different than the corresponding coefficient of the
post and/or turns so that the sleeve tends to stay in close contact
to the wrapped wire. When temperatures only higher than the
assembly temperature are expected, this coefficient may be selected
to be smaller.
FIG. 5 indicates an alternate form of sleeve 21, which is
cylindrical in shape and is formed with a slot 23 cut at an angle
to the axis through the wall of the sleeve. The sleeve in this case
is constructed from a resilient material and may be dimensioned
slightly undersize so that it fits extremely tightly over the
wrapped turns of the conductor. The slot 23 enables the sleeve 21
to expand to accommodate the wrapped turns and yet continue to
apply force urging the turns against the post. As in the case of
the continuous sleeve, the slotted sleeve 21 may be crimped, or
deformed, by any suitable tool to form a permanent mechanical and
electrical connection.
An electrical connection according to the invention, can, of
course, be used with any post geometry. FIG. 6 shows a thin
rectangular post 25 and an associated oval-shaped sleeve 27. In
some cases it may be desirable to make the clearance gap 28 between
the corner of the post 25 and the sleeve 27 of a slightly smaller
dimension than the diameter of the wire surrounding the post. If
the insulation of the wire is of the varnish type, for example,
this can ensure the application of enough radial force to cause the
insulation to be pierced by the post merely by placing the sleeve
over the post. On the other hand, where the sleeve is positioned by
hand or where it must be placed over the wrapped conductor without
moving any of the turns, it is preferable to have the clearance gap
28 slightly larger than the wire diameter. In such cases, of
course, the sleeve must be crimped following its placement over the
wrapped turns.
Although the invention has been described with reference to
particular embodiments, yet other variations, embodiments and
modifications may occur to those skilled in the art. For example,
several types of materials may be used in the construction of the
sleeve and the post may take on any geometry operable to effect the
electrical connection through insulated wire. Thus, all such
embodiments, variations and modifications are intended to be
included within the scope of the appended claims.
* * * * *