U.S. patent number 3,867,008 [Application Number 05/283,790] was granted by the patent office on 1975-02-18 for contact spring.
This patent grant is currently assigned to Harvey Hubbell Incorporated. Invention is credited to Albert J. Gartland, Jr..
United States Patent |
3,867,008 |
Gartland, Jr. |
February 18, 1975 |
CONTACT SPRING
Abstract
A double wiping female contact for engagement with straight male
contacts of varying thickness, particularly where very high contact
pressures must be developed between such contacts. Cooperatively
configured spring members are disposed on the female contact to
achieve a deflection bias which magnifies the contact pressure
developed when the spring members are forced to separate by any
distance. Contact pressures proportional to the magnitude of
separation are attained beyond the elastic limit of the spring
members by incorporating sufficient deflection bias to compensate
for the permanent set incurred.
Inventors: |
Gartland, Jr.; Albert J.
(Trumbull, CT) |
Assignee: |
Harvey Hubbell Incorporated
(Bridgeport, CT)
|
Family
ID: |
26962252 |
Appl.
No.: |
05/283,790 |
Filed: |
August 25, 1972 |
Current U.S.
Class: |
439/857 |
Current CPC
Class: |
H01R
13/113 (20130101) |
Current International
Class: |
H01R
13/115 (20060101); H01r 013/12 () |
Field of
Search: |
;339/258R,258A,258F,260,258P,261,262,47,49,74,259 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
|
163,698 |
|
Aug 1922 |
|
GB |
|
888,893 |
|
Feb 1962 |
|
GB |
|
1,108,074 |
|
Apr 1968 |
|
GB |
|
932,390 |
|
Nov 1947 |
|
FR |
|
Primary Examiner: Frazier; Roy D.
Assistant Examiner: Staab; Lawrence J.
Attorney, Agent or Firm: Wooster, Davis & Cifelli
Claims
1. An electrical female contact comprising; spring members disposed
to deflect in opposite directions away from a central plane as
straight male contacts are slideably engaged therebetween, each
said spring member having a contact surface and presenting an
inclined tip across the full width of engagement, said inclined
tips being complementarily oriented to create a guided entrance for
the male contacts along said central plane, said contact surfaces
being separated across the thickness of the male contacts upon
engagement thereby and bearing against the male contacts under a
contact pressure of proportional magnitude to the deflection
incurred by said spring members, each said spring member including
at least one advanced section and at least one retracted section,
said advanced and retracted sections being juxtaposed on each said
spring member in a direction substantially perpendicular to the
direction of male contact engagement along said central plane, said
advanced section of each spring member meshing across said central
plane into said retracted section of said other spring member, said
contact surfaces being disposed on said advanced sections at an
offset distance from said central plane and deflecting thereacross
through said offset distance during engagement by male contacts,
whereby the total deflection at said contact surfaces of said
spring members away from each other during engagement is the sum of
said offset distances plus the thickness of the male contact and
thereby said contact pressure is magnified proportionally to the
sum of said
2. The female contact of claim 1 wherein said spring members are
deflected beyond the elastic limit of their material, said offset
distance being reduced in magnitude by the permanent set resulting
therefrom, said contact pressure exerted by said contact surfaces
being proportional thereafter to deflection of said spring members
beyond the deflection at
3. The female contact of claim 2 wherein said spring members are
configured to engage with male contacts of a particular thickness
range, said spring members being deflected beyond the elastic limit
of their material on
4. An electrical female contact comprising; cantilevered spring
members having free ends for deflecting in directly opposite
directions from a plane disposed therebetween, said free ends being
mutually opposed with each said free end having an inclined tip
across the full width of each said spring member, said inclined
tips being complementarily oriented to provide a guided entrance
for insertion of the male contact, said spring members each
including at least one first section and at least one second
section, each said first section having a surface portion which
extends a distance through said plane, each said second section
accommodating one said surface portion of said other spring member,
said surface portions on each said spring member deflecting
outwardly of said plane through said distance upon insertion of the
male contact, said first and second sections being juxtaposed on
each said spring member in a direction substantially perpendicular
to the direction of male contact engagement along said plane, the
total deflection at said surface portions of said free ends away
from each other during insertion being substantially equal to the
sum of said distances across said plane plus the thickness of the
male contact, whereby the pressure exerted on the inserted male
contact by
5. The female contact of claim 4 wherein each said spring member is
configured to have an askewed bend, each said askewed bend being
dislocated from and divergent relative to said other askewed bend,
said askewed bends being overlapped across said plane to provide
said first
6. The female contact of claim 4 wherein said spring members are
deflected beyond the elastic limit of their material, said distance
being reduced in magnitude by the permanent set resulting
therefrom, the pressure exerted by said free ends being
proportional thereafter to deflection of said spring members beyond
the deflection at which the elastic limit occurred.
7. The female contact of claim 6 wherein said spring members are
configured and disposed to engage with male contacts of a
particular thickness range, said spring members being deflected
beyond the elastic limit of their material when the male contact of
maximum thickness is inserted.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a double wiping female contact and
especially to such a contact having spring members which amplify
the deflections imposed to magnify the contact pressures developed.
Hitherto, many different types of double wiping female contacts
have been utilized to develop the high contact pressure necessary
for retaining and electrically interfacing with male contacts. Most
such contacts consist of a pair of opposing cantilever springs and
it would appear that the contact pressures developed thereby could
be increased by merely varying the length, width, or thickness of
the spring members. However, variations in length are not practical
because an increase in contact pressure requires a reduction in
length which thereby affects the required length of the male
contact. Variations in width are not practical because an increase
in contact pressure requires an increase in width and where the
female contact is adapted to receive male contacts of either a
parallel or a tandem pair, the width of the spring members is
limited in magnitude. Generally, this limitation is caused on one
side by the center to center distance separating the male contacts
of the parallel pair and on the other side by the overall
dimensions of the connector body. The contact pressure increases as
the thickness of the spring members increases which usually depends
on the thickness of the material utilized to fabricate the female
contact. Although the thickness of the spring members is relatively
unlimited, increases in material thickness are not practical
because they are accompanied by increased expense for both raw
materials and fabrication. Also, the deflectable range of the
spring members below their elastic limit decreases as the material
thickness increases and therefore the thickness range of engaging
male contacts is reduced.
In some instances the contact pressure has been increased through
the use of materials having a very high modulus of elasticity.
However, the electrical resistivity of many materials, such as
copper, increases as the modulus of elasticity increases and
therefore the current carrying capacity of the contact is decreased
by such an approach. Also, materials having a very high modulus of
elasticity are usually more costly and more difficult to
fabricate.
Various codes and specifications require that female contacts be
capable of engagement by male contacts of varying thicknesses and
that a specific contact pressure be exerted upon male contacts of
minimum thickness after male contacts of maximum thickness have
been engaged. These requirements can not be met by many female
contacts because the spring members will be deflected beyond their
elastic limit when the male contact of maximum thickness is
inserted. Such deflections cause a permanent set in the spring
members which reduces the contact pressure developed thereafter
upon male contacts of minimum thickness.
SUMMARY OF THE INVENTION
It is therefore, a general object of the present invention to
provide a double wiping female contact which minimizes and obviates
the disadvantages of the prior art.
It is a specific object of the present invention to provide a
double wiping female contact having spring members which attain
amplified deflections to thereby magnify the contact pressure
developed.
It is a more specific object of the present invention to provide a
double wiping female contact having spring members which are
disposed to compensate for the permanent set incurred on exceeding
the elastic limit to thereby extend the proportional range of the
contact pressure developed by the spring members.
These objects are accomplished in one form according to the present
invention by configuring the opposing spring members of the female
contact to cooperate in overlapping across the central plane along
which the male contact engages. The contact surface on each spring
member is disposed on the overlapping portion and is offset a
distance from the central plane of engagement. On engagement, the
deflection of the spring members is amplified by the magnitude of
the offset distance and therefore the contact pressure developed
thereby is magnified. Proportionality between the deflection and
the contact pressure developed is extended in range beyond the
elastic limit of the material utilized, by incorporating a
sufficient offset distance to compensate for the permanent set
thereby incurred.
BRIEF DESCRIPTION OF THE DRAWINGS
The manner in which these and other objects of the invention are
achieved will be best understood by reference to the following
description, the appended claims, and the attached drawings
wherein:
FIG. 1 is a side elevational view of an unengaged electrical
connector with portions of the connector body cut away to
illustrate the female contacts of this invention;
FIG. 2 is an enlarged sectional view of the engaged connector taken
along line 2--2 of FIG. 1 to illustrate the forced separation
caused to the opposing spring members upon insertion of the male
contacts;
FIG. 3 is an enlarged partial elevational view thereof taken
perpendicularly to plane 3--3 of FIG. 2 but with the male contacts
withdrawn to illustrate the cooperative configuration existing
between the opposing spring members.
FIG. 4 is an enlarged partial elevational view thereof taken
perpendicularly to plane 4--4 of FIG. 2 to illustrate the central
plane along which the male contact engages between the opposing
spring members;
FIG. 5 is a view similar to that of FIG. 4 with the male contact
disengaged to illustrate the overlap existing between the opposing
spring members across the central plane of engagement;
FIG. 6 is an enlarged perspective view of an alternately shaped
female contact incorporating the features of this invention;
FIG. 7 is an enlarged perspective view of another female contact
incorporating the features of this invention; and
FIG. 8 is an enlarged perspective view of still another female
contact incorporating the features of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Turning now to the drawings, and more particularly to FIG. 1, there
is illustrated a cable connector 10 having a cap 12 and a connector
body 14. An electrical cable 16 is connected separately to each of
the cap 12 and the connector body 14. Straight male contacts 18
extend from the cap 12 and engage into double wiping female
contacts 20 within the connector body 14, as shown by the phantom
lines, to electrically interconnect the power conductors (not
shown) of the cable 16. A male ground contact 22 also protrudes
from the cap 12 for engagement into a female ground contact 24
within the connector body 14 to electrically interconnect the
ground conductor (not shown) of the cable 16. All contacts 18, 20,
22, and 24 include suitable terminal means for connecting to the
conductors, such as screw lugs 26 which are shown in FIGS. 2 and 3.
The cable 16 is secured to both the cap 12 and the connector body
14 by a cable clamp 28 which is fastened thereto by any suitable
means, such as screws 30.
Generally, the male contacts 18 and the male ground contact 22 are
arranged on the cap 12 to designate specific electrical parameters,
such as operating voltage or current levels. The character of each
arrangement is determined by the relative orientation of the male
contacts 18 which may be located in parallel, or in tandem, or in
any combination resulting from the parallel and tandem locations.
The female contact 20 is constructed to receive the male contacts
18 in either of two perpendicular directions. Within the connector
body 14, a pair of female contacts 20 are arranged to receive the
male contacts 18 of any relative orientation but may be limited to
particular orientations through the use of slotted entrances in the
connector body 14.
As illustrated in FIGS. 2 and 4, male contacts 18 in tandem
locations are received into the female contacts 20 between
cooperating spring members 32 which separate in opposite directions
to receive the male contacts 18 along a central plane of engagement
A--A. Male contacts 18 in parallel locations are received between a
third spring member 34 and the sides of the cooperating spring
members 32, with the third spring member 34 deflecting as the male
contact 18 enters therebetween. When male contacts 18 are arranged
in a combination of parallel and tandem locations, one male contact
18 is received between the cooperating spring members 32 on one
female contact 20 while the other male contact 18 is received
between the third spring member 34 and the sides of the cooperating
spring members 32 on the other female contact 20.
Of course, each female contact 20 could be arranged within the
connector body 14 to receive male contacts 18 in parallel locations
between the cooperating spring members 32, while receiving male
contacts 18 in tandem locations between the third spring member 34
and the sides of the cooperating spring members 32. However,
throughout this specification the previously described arrangement
will be utilized. In this arrangement the cooperating spring
members 32 are relatively more restricted in cross section than the
third spring member 34 and therefore, to increase the contact
pressure exerted by the cooperating spring members 32 against the
male contacts 18 presents a greater problem. Because of this, the
invention will be disclosed in regard to the cooperating spring
members 32, however, no reason exists to preclude the application
of this invention to the third spring member 34.
An electrical connection results between the male contact 18 and
the female contact 20 when the male contact 18 is engaged between
the cooperating spring members 32. Each spring member 32 includes a
contact surface 36 which is forced to bear against the engaging
male contact 18 and, as illustrated in FIG. 4, the contact surfaces
36 are separated across the thickness of the male contact 18 as a
result of engagement. Therefore, the contact pressure exerted on
the male contact 18 by the contact surfaces 36 is proportional to
the combined deflection caused to the spring members 32 during
engagement.
The spring members 32 are specially constructed to magnify the
contact pressure developed on engaging male contacts 18 by
deflecting through a distance of greater magnitude than the
thickness of the male contact 18. This special construction is
illustrated in FIGS. 3 - 5 and consists essentially of a
cooperative configuration between the opposing spring members 32 to
permit the contact surfaces 36 to overlap across the central plane
of engagement A--A. To achieve this cooperative configuration, the
portion of each spring member 32 in closest proximity to the
central plane of engagement A--A is segmented into bi-level
sections, an advanced section 38 and a retracted section 40, as
illustrated in FIG. 3. The bi-level sections on opposing spring
members 32 are arranged to mesh into each other across the central
plane of engagement A--A, as illustrated in FIG. 5, with the
advanced section 38 on each spring member 32 disposed into the
retracted section 40 on the other spring member 32. The high point
of each advanced section 38 is offset across the central plane of
engagement A--A by a distance "X" and comprises the contact surface
36 on each spring member 32. The sum of the offset distances X at
which both contact surfaces 36 are disposed is equal to an overall
offset distance "Y". Each spring member 32 is configured to have an
inclined tip 42 and the complementary orientation of the tips 42
creates a guided entrance 44 into the female contact 20 along the
central plane of engagement A--A.
When the cap 12 is mated into the connector body 14, the male
contacts 18 enter into the female contacts 20 along the central
plane of engagement A--A, as illustrated in FIG. 4. Initially, the
male contacts 18 enter the guided entrance 44 and come to bear
against the inclined tips 42 of the spring members 32. Then a force
is applied to move the male contacts 18 along the central plane of
engagement A--A, which thereby causes the opposing spring members
32 to deflect in opposite directions and to carry the contact
surfaces 36 across the central plane of engagement A--A. Only after
the spring members 32 have been deflected through a combined
distance equal to the thickness of the male contact 18 plus the
overall offset distance Y, will the male contacts 18 move between
the contact surfaces 36. Therefore, the deflection resulting in the
spring members 32 is amplified beyond the thickness magnitude of
the male contact 18. Since the contact pressure exerted against the
male contact 18 by the contact surfaces 36 is proportional to the
deflection of the spring members 32, the contact pressure is
thereby magnified. Furthermore, the contact pressure to be exerted
on a male contact 18 of any particular thickness can be magnified
to any desired magnitude by merely increasing the overall offset
distance Y of the contact surfaces 36 from the central plane of
engagement A-A.
As illustrated in FIGS. 6 - 8, I have devised several cooperative
configurations by which an overlap of contact surfaces across the
central plane of engagement is accomplished for female contacts
having opposing spring members. Due to the similarities existing
between the configuration shown in FIG. 5 and the configurations
shown in FIGS. 6 - 8, similar parts in FIGS. 6 - 8 are identified
by the same reference numerals as those used in FIG. 5 but with a
prime added thereto in FIG. 6, a double prime added thereto in FIG.
7, and a triple prime added thereto in FIG. 8. Generally, the
choice of cooperative configuration selected depends on both the
nature of the application and the fabrication expense to be
borne.
FIG. 6 illustrates a configuration by which an overall offset
distance of nominal magnitude is achieved with a single spring
member 32' crossing the central plane of engagement. In this
configuration a spherical advanced section 38' is disposed on one
spring member 32' and an aperture 46 is disposed through the other
spring member 32'. The aperture 46 is precisely located to allow
the advanced section 38' to pass across the central plane of
engagement prior to deflection of the spring members 32'. A contact
surface 36' is disposed on the tip of the advanced section 38' and
therefore overlaps the contact surface 36' located on the spring
member 32' through which the aperture 46 is disposed.
Where an overall offset distance of very large magnitude is
necessary, the configuration illustrated in FIG. 7 is utilized. In
this configuration, each spring member 32" has an advanced section
38" disposed immediately adjacent to an open notch 48 which is
precisely located to allow the advanced section 38" on the other
spring member 32" to pass across the central plane of engagement
prior to deflection of the spring members 32". A contact surface
36" is disposed at the tip of each advanced section 38" and
therefore the contact surfaces 36" are overlapping.
When fabrication expense is of primary concern, the configuration
illustrated in FIG. 8 may be utilized. In this configuration, the
advanced section 38'" on each spring member 32'" is established
with an askewed bend 50. On each spring member 32'" the askewed
bend 50 is dislocated from the divergent relative to the askewed
bend 50 on the other spring member 32'" to allow the advanced
sections 38'" to overlap across the central plane of engagement
prior to deflection of the spring members 32'". A contact surface
36'" is disposed at the tip of each advanced section 38'" and
therefore the contact surfaces 36'" are overlapping across the
central plane of engagement.
Female contacts having opposing spring members are commonly used in
applications were engagement by male contacts in a wide range of
thicknesses is anticipated. In such applications, the contact
pressure exerted on the male contact of maximum thickness is of
course much greater than that exerted on the male contact of
minimum thickness. Where conventional female contacts are utilized,
this differential in contact pressure presents a problem in that
the contact pressure exerted on male contacts of minimum thickness
is not sufficient to comply with recently published codes. To
further complicate matters, the maximum contact pressure attainable
with the spring members of conventional female contacts is limited
by the elastic limit of the material from which the female contact
is fabricated. This is so because upon exceeding the elastic limit,
the spring members are work hardened and encounter a permanent set.
Thereafter, the combined deflection achieved by the spring members
for any male contact will be reduced by the total magnitude of
permanent set encountered. Since the contact pressure is directly
proportional to the combined deflection of the spring members, it
is reduced in direct proportion to the magnitude of the permanent
set.
The problems caused due to the differential in contact pressure may
be overcome with the female contact 20 of this invention. First of
all, the deflection of its spring members 32 can be amplified to
magnify the contact pressure developed on the male contact 18 of
minimum thickness. Then where the elastic limit of the material is
exceeded on engagement of the male contact 18 of maximum thickness,
the overall offset distance Y may be increased sufficiently to
compensate for the anticipated permanent set. Since the spring
constant of the spring members 32 will remain the same after
exceeding the elastic limit but the zero deflection point thereof
will be shifted due to the permanent set encountered, this
compensation may be utilized to extend the range of contact
pressure developed proportionally to deflection beyond the elastic
limit of the material.
Those skilled in the art should readily appreciate that the female
contact embodied by this invention includes spring members which
attain amplified deflections and thereby magnify the contact
pressure developed against the male contact. Furthermore, the
spring members can be disposed to compensate for the permanent set
incurred upon exceeding the elastic limit of the material which
thereby extends the range of contact pressure developed
proportionally to the deflection of the spring members.
It should be understood that the present disclosure has been made
only by way of example and that numerous changes in details of
construction and the combinations or arrangements of parts may be
resorted to without departing from the true spirit and scope of the
invention, and therefore, the present disclosure should be
construed as illustrative rather than limiting.
* * * * *