U.S. patent number 3,812,452 [Application Number 05/279,995] was granted by the patent office on 1974-05-21 for contact spring for plug connectors.
This patent grant is currently assigned to Bach & Co.. Invention is credited to Hermann Sturm.
United States Patent |
3,812,452 |
Sturm |
May 21, 1974 |
CONTACT SPRING FOR PLUG CONNECTORS
Abstract
A contact spring for plug connectors stamped out of
non-corroding sheet metal and comprising an approximately
rectangular shank with a U-shaped head piece connected thereto,
which head piece has two arms which face one another and which are
spaced equidistant from a plane of symmetry running between them
and in the longitudinal direction of the shaft. That width of the
arms which is parallel to the plane of symmetry is broadened to a
multiple of the thickness of the sheet metal by applying pressure
to the arms in a direction transverse to the plane of symmetry.
Inventors: |
Sturm; Hermann (Flein,
DT) |
Assignee: |
Bach & Co. (Heilbronn,
DT)
|
Family
ID: |
23071199 |
Appl.
No.: |
05/279,995 |
Filed: |
August 11, 1972 |
Current U.S.
Class: |
439/857; 439/886;
439/873 |
Current CPC
Class: |
H01R
13/112 (20130101) |
Current International
Class: |
H01R
13/115 (20060101); H01r 011/22 () |
Field of
Search: |
;339/221R,221L,221M,256R,258R,258P,176MP,252R,252F,252PS,278C
;29/629,63D,169.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"CONTIP," Specialties Instr. Co. 1-1966..
|
Primary Examiner: McGlynn; Joseph H.
Assistant Examiner: Hafer; Robert A.
Attorney, Agent or Firm: Becker; Walter
Claims
1. A contact spring for plug connectors of non-corroding sheet
metal and which comprises in combination: a shaft having an
approximately rectangular cross section; a U-shaped head piece
connected to said shaft and forming a connecting zone; and two
contact spring arms connected to said connecting zone, each of said
arms having a free end, said arms facing each other and spaced
equidistant from a plane of symmetry running between said arms and
in the longitudinal direction of said shaft, that width of said
contact spring arms which is parallel to said plane of symmetry
having been broadened to increase progressively as a multiple of
the width of shaft thickness of said sheet metal by compression of
said arms in a direction transverse to said plane of symmetry,
thickness of material of said contact spring arm respectively
decreasing respectively
2. A contact spring in combination according to claim 1, in which
said plug
3. A contact spring in combination according to claim 1, in which
said connecting zone has at least one shoulder surface, said
shoulder surface
4. A contact spring in combination according to claim 1, in which
said contact spring arms, in the vicinity of said free ends, have
contact zones
5. A contact spring in combination according to claim 1, in which
projections are provided on the longitudinal edge of said shaft in
the
6. A contact spring in combination according to claim 4, in which
said protruding contact zones are provided with a layer of precious
metal upon
7. A contact spring in combination according to claim 4, in which
said free ends of said contact spring arms are obliquely spread in
a direction away
8. A contact spring in combination according to claim 5, in which
said
9. A contact spring in combination according to claim 6, in which
said layer is introduced upon said contact zones by means of
galvanic
10. A contact spring in combination according to claim 6, in which
said precious metal is gold.
Description
The present invention relates to a contact spring for plug
connectors, chiefly for printed circuits, which is punched or
stamped out from sheet metal of non-corroding metal and which has
two forked contact spring arms facing one another.
It is important above all with the plug connectors provided for the
printed circuits, that the contact spring arms be able to exert a
sufficient contact pressure even if a contact pin or tongue,
insertable between these arms, deviates from the normal state or
condition intended for them as a result of unavoidable
manufacturing tolerances. It is additionally required with such
plug connectors that, in consideration of wire-wrap connection
technology, the junction ends of the contact springs should have a
cross section of at least 0.6 by 0.6 millimeters.
It is known to punch out contact springs having forked contact
spring arms from sheet metal, in which connection the arms are
formed together with a connecting zone in a U shape. During the
introduction of a contact pin in the form of a tongue or clip,
difficulties arise with the heretofore known plug connectors in
that the contact spring arms become permanently deformed during
assembly at a bending stress beyond the stress or elastic
deformation limit. On the other side, the cross section of the
contact spring arms can be varied for the realization of an
adequate bending flexibility only to such an extent as will still
assure a sufficient contact surface for the current flowing through
the plug connectors.
It is an object of the present invention to produce a contact
spring for plug connectors which assures on the one hand the
necessary contact surface for the passage of current and assures on
the other hand a sufficient contact pressure of the contact spring
arms.
It is a further object of the present invention that the contact
spring be insertable into an insulating material plate or panel in
a simple manner. The junction ends should be suitable for wire-wrap
connection, and should therefore have a minimum cross section of
0.6 by 0.6 millimeters.
These and other objects and advantages of the invention will appear
more clearly from the following specification in connection with
the accompanying drawing in which:
FIG. 1 shows a view of the breadth of a contact spring according to
the invention after the first machining process, namely a stamping
or punching operation.
FIG. 2 also shows a view of the breadth of the contact spring shaft
according to the invention, this time after the subsequent cold
working process.
FIG. 3 is a view of one of the transverse edges of the contact
spring shank of the invention in a deformed state.
FIG. 4 is a section taken along the line IV -- IV of FIG. 1.
FIG. 5 shows a section taken along the line V -- V of FIG. 2 after
the cold working of the contact spring.
The invention is characterized primarily in that the contact spring
has a rectangular shank and changes or turns into a U-shaped head
piece, the arms of which are spaced equidistantly from a plane of
symmetry running in the longitudinal direction of the shank. These
arms are widened or spread in a direction parallel to the plane of
symmetry to a multiple of the sheet metal thickness by means of
pressure applied transverse to the plane of symmetry. In a further
refinement of the invention, it is especially advantageous if that
width or thickness of the contact spring shank measured parallel to
the plane of symmetry progressively increases from its connecting
zone with the shank up to the free ends of the arms.
In a further development according to the invention, the adhering
strength of the contact spring in an insulating material plate or
panel serving as a carrier or holder may be improved by providing
sawtooth shaped rims or shoulders in the immediate vicinity of the
connecting zone of the shank of the contact spring and its two
contact spring arms. In order to improve the fit or seat of the
contact spring and its strength of adherence in an insulating
material plate or panel, it may be provided according to a further
refinement of the invention, that the connecting zone of the two
contact spring arms be limited or defined in the direction of the
shank by at least one shoulder area, which shoulder area, when
plugging in the contact spring, will abut the plate or panel of
insulating material, thereby limiting the depth of insertion of the
contact spring. In view of the chip-less deformation of the contact
spring arms according to the invention, it is possible without
difficulty to form the press die or stamp in such a way that the
contact spring arms obtain or receive contact zones protruding
towards one another. These contact zones stand facing each other so
closely with regard to each other that during insertion of the
counterparts of the plug pins or tongues, which latter form the
plug connection, the arms are pressed apart under spring elastic
bracing or load. To increase the certainty of the contact, each of
these protruding contact zones, according to a further refinement
of the invention, may be provided with a coating of precious metal,
especially silver or gold, upon the surfaces which face one
another. Coatings of this type may be applied by means of pointed
or aimed galvanic treatment and require only a small consumption of
precious metal. It is especially advantageous according to a
further refinement of the invention, if the end sections of the
arms, which are connected to the just mentioned contact zones, are
obliquely spread or forced away from the plane of symmetry. Due to
this, above all with polyphase plug connectors, the introduction of
the plug pins or tongues is substantially simplified, and beyond
that, the deformation of the contact spring arms beyond their limit
of elasticity during untrue attaching or fastening of these contact
counterparts is eliminated.
Referring now to the drawing in detail, the contact spring is first
produced as a stamped metal part, in the form shown in FIG. 1, out
of a sheet metal strip of uniform thickness, which metal strip may
be of a relatively soft spring brass or of bronze. In this
condition, a U-shaped forked head piece is connected to a slender
rectangular or square shaft 1. The inner axial edges 4 of the arms
2, 3 of the forked head piece run parallel to each other and are
equidistant from a common plane of symmetry AA. The two inner axial
edges 4 turn or change into one another at the connecting zone 5
with a rounding out 6. The breadth of the arms 2, 3 shown in FIG. 1
is insignificantly narrowed or tapered from the connecting zone 5
out to its end edges 7 and, in the processing state shown in FIG.
1, has the same thickness as the shaft 1.
Saw-tooth shaped projections 8 are provided in pairs on both
longitudinal or axial edges of the shaft 1 in the immediate
vicinity of the connecting zone 5. The projections 8 assure a
secure seating of the shaft 1 and consequently of the entire
contact spring when the shaft 1 is inserted into an appropriate
recess in a not illustrated insulating material plate or panel. The
shaft 1 has the square or rectangular cross section of sufficient
thickness necessary for the wire-wrap connection technology. Two
shoulder surfaces 11, 12, which run at right angles to the shaft 1,
are provided on the connecting zone 5 for limiting the depth of the
insertion of the shaft 1 and for increasing the stability of the
thus arrived at seating of the contact spring in the printed
circuit board. The connecting zone 5 is set off from the shaft 1
with the shoulder surfaces 11, 12.
The punched or stamped out contact spring according to FIG. 1 is
then subject to a cold working process indicated in FIG. 2. In this
connection a core part 14 is first interposed between the arms 2,
3. This core part 14 almost completely fills the available or
existing space between the arms 2, 3. Then each of the two arms 2,
3 are deformed with two instrument jaws or dies 15, 16, attached or
fastened from the transverse or section edges of the arms, by means
of pressure exerted transverse to the plane of symmetry AA. The
arms 2, 3 are so deformed that each of them, in a manner more
clearly visible from FIG. 3, are spread or broadened to a multiple
of the sheet metal thickness, the latter being indicated in FIG. 3
with a D. This spreading or broadening begins from the connecting
zone 5 and progresses toward the end edge 7. The two instrument
jaws or dies 15, 16 have protruding prominences or heads 17, 18,
with which they press the contact spring arms 2, 3 into appropriate
recesses 19 of the core 14. In so doing, the two arms 2, 3, in the
vicinity of their end segments, receive contact zones 21, 22 which
protrude toward one another. The mutual interval or spacing of the
contact zones 21, 22 is substantially smaller than that spacing at
the section of the arms extending up to the rounding out 6. After
the pressing and stamping process, these protruding contact zones
21, 22 are provided with a coating, for example out of gold, on
those of their surfaces which face one another by means of pointed
or aimed galvanic treatment. The end sections of the arms, which
are connected to the contact zones 21, 22, are so deformed during
stamping that they are obliquely spread apart or forced away from
the plane of symmetry AA; this considerably simplifies the
introduction of plug or connector pins or tongues.
The particular advantage of the contact spring according to the
invention is characterized primarily in that, by means of the cold
working process, the material in the area of the connector tongues
is strengthened and thereby the spring or elastic quality is
considerably improved. At the same time, the thickness of the
material of the connector tongues is narrowed in line with the
contact imparting heads 17, 18, so that a uniform bending stress of
the material results over the entire elastic length. This allows
attainment of a high contact pressure with high mechanical
stability and thereby a reliable contact dose. Complicated and
accuracy influencing or affecting bending processes are eliminated
with contact springs according to the invention.
It is, of course, to be understood that the present invention is by
no means limited to the specific showing in the drawing but also
comprises any modifications within the scope of the appended
claims.
* * * * *