U.S. patent number 3,781,770 [Application Number 05/182,953] was granted by the patent office on 1973-12-25 for circuit board socket.
This patent grant is currently assigned to E. I. du Pont De Nemours and Company. Invention is credited to Lloyd Mancini.
United States Patent |
3,781,770 |
Mancini |
December 25, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
CIRCUIT BOARD SOCKET
Abstract
A circuit board disconnect socket having an elongate hollow body
open at one end, a strap surrounding the open end and a pair of
contact arms extending from the strap and into the body. A
reinforcing spring is wrapped around the strap and includes spring
arms extending along the outside of the contact arms. Insertion of
a lead between the contact arms spreads the arms apart and stresses
the spring.
Inventors: |
Mancini; Lloyd (New Cumberland,
PA) |
Assignee: |
E. I. du Pont De Nemours and
Company (Wilmington, DE)
|
Family
ID: |
22670767 |
Appl.
No.: |
05/182,953 |
Filed: |
September 23, 1971 |
Current U.S.
Class: |
439/839; 439/876;
439/83 |
Current CPC
Class: |
H01R
12/58 (20130101) |
Current International
Class: |
H01R
9/00 (20060101); H01R 13/10 (20060101); H01R
11/22 (20060101); H01R 11/11 (20060101); H01R
9/16 (20060101); H05K 1/00 (20060101); H01r
009/12 (); H01r 011/22 () |
Field of
Search: |
;339/17R,17CF,217S,217R,255R,256R,256S,256SP,258P,258F,258R,258S |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
719,293 |
|
Nov 1931 |
|
FR |
|
1,431,980 |
|
Feb 1966 |
|
FR |
|
803,001 |
|
Oct 1958 |
|
GB |
|
1,140,583 |
|
Mar 1957 |
|
FR |
|
472,945 |
|
Oct 1937 |
|
GB |
|
Primary Examiner: Champion; Marvin A.
Assistant Examiner: Pate, III; William F.
Claims
What I claim as my invention is:
1. A female contact having a longitudinal passage for reception of
a male lead, the contact including a body formed of material having
a high electrical conductivity and a spring formed of high yield
strength material; said body comprising a band surrounding an end
of the passage, a pair of opposed contact arms extending from the
band along the passage with the free ends of the arms normally
positioned in the passage, and means joining the band for forming
an electrical connection with a circuit element; and said spring
comprising mounting means for securing the spring to the band, and
a pair of cantilever spring arms overlying and extending from the
band longitudinally along the outside surfaces of said contact arms
and joining said mounting means on the outer circumference of said
band at the junctions of the contact arms and the band with the
ends of said spring arms engaging the free ends of the contact
arms.
2. A contact as in claim 1 wherein the spring is formed of a single
length of spring metal and includes a band engaging member
extending around the out-side of the band, and each of the spring
arms comprises two portions of the spring metal, each portion
extending from the band along the outside of the spring arm to a
position adjacent the free end of the spring arm.
3. A contact as in claim 2 wherein the spring is formed of a length
of spring wire of uniform cross section, one of the spring arms
includes a U-shaped connection between the ends of the portions and
the other spring arm includes the end portions of the spring
wire.
4. A contact as in claim 2 wherein part of the spring is fitted
within a groove formed in the band and extending generally between
the junctions of the fingers and the band.
5. A female type disconnect socket having a longitudinal passage
for the reception of a male lead comprising an elongate hollow
socket body formed of high electrical conductivity material and
having an opening at one end for reception of the lead and means at
the other end for forming an electrical connection with a circuit
element, a pair of opposed contact arms formed in the medial
portion of the socket body and extending into the body from one end
thereof with the free ends thereof adjacent each other; and a
reinforcing spring formed of high yield strength material including
a portion wrapped around said one end of the body and spring arms
extending from said portion along the outside of the contact arms
to a position adjacent the free ends thereof for providing contact
pressure between the contact arms and the lead when inserted into
the socket.
6. A socket as in claim 5 wherein the portion of the spring is
confined within a groove in the socket body.
7. A socket as in claim 5 wherein said spring arms comprise
cantilever spring members and said spring portion includes at least
a single torsion spring member.
8. A socket as in claim 5 wherein the medial portion of each of
said contact arms includes reinforcing means for preventing
buckling.
9. A socket as in claim 8 wherein the free end of each contact arm
is bent outwardly of the socket body to provide a recess for
receiving the free end of the adjacent spring arm.
10. A socket as in claim 5 wherein said spring comprises a
continuous length of spring metal with the free ends of the length
located at the free ends of one of the spring arms, the other
spring arm comprising a U-shaped portion of the length and the
portion comprising two lengths of spring metal joining the spring
arms.
11. A female contact having a longitudinal passage for reception of
a male lead, the contact including a body formed of material having
a high electrical conductivity and a spring formed of high yield
strength material; said body comprising a band surrounding an end
of the passage, a contact arm extending from the band along the
passage with the free end of the arm normally positioned in the
passage, and means joining the band for forming an electrical
connection with a circuit element; and said spring comprising
mounting means for securing the spring to the band, and a
cantilever spring arm overlying and extending from the band
longitudinally along the outside surface of the contact arm and
joining said mounting means on the outer circumference of said band
at the junction of the contact arm and the band with the end of
said spring arm engaging the free end of the contact arm.
12. A contact socket comprising an elongate socket body open at one
end, means for forming an electrical connection to a conductor, a
longitudinal cantilever contact arm formed from the body and
extending into the interior of the body for engagement with a lead
inserted therein, and a spring member on the outside of the body
including a cantilever spring arm overlying and engaging the
outside surface of the contact arm to bias the contact arm toward
the interior of the body and a clasp member extending at least
partially around the outside circumference of the body and
resiliently engaging the body for securing the spring member to the
body.
13. A contact as in claim 12 including a displacement resistant
connection between the body and the clasp.
14. A contact socket comprising an elongate socket body open at one
end, means for forming an electrical connection to a conductor, a
pair of longitudinal contact arms formed from the body and
extending into the interior of the body for engagement with a lead
inserted therein, and a spring member on the outside of the body
including a pair of springs engaging the outside surfaces of the
contact arms to bias the contact arms toward the interior of the
body and a resilient clasp connection extending at least partially
around the outside circumference of the body to secure the spring
member thereto.
15. A contact body as in claim 14 wherein said clasp connection
includes at least one spring member associated with each of the
springs for biasing the contact arms toward the interior of the
body.
16. A contact socket as in claim 15 wherein said clasp connection
includes a torsion spring member associated with each contact
arm.
17. A female contact having a longitudinal passage for the
reception of a male lead therein, said contact comprising a body
having a band portion disposed at each of opposite ends of such
passage, a pair of side walls extending between said band portions
and integral with each said band portion, said side walls defining
opposite sides of said longitudinal passage, a pair of contact arms
integral with one of the band portions and extending generally
longitudinally from opposite sides thereof, said contact arms and
said side walls cooperating to form a generally enclosed passage
between said band portions, said contact arms being bent inwardly
to approach each other adjacent the free ends thereof for
engagement with said male lead, means extending from said body for
connecting said female contact to an electrical conductor, and
spring means secured on the outside of said body including two
spring members for biasing said contact arms inwardly toward each
other.
18. A female contact as in claim 17 wherein said spring means
includes a mounting portion carried by said body adjacent said open
end thereof and said spring members comprise cantilever springs
extending along the outside surface of said contact arms for
engagement therewith at a point adjacent the free ends thereof.
19. A female contact as in claim 18 wherein said spring means
includes torsion springs cooperable with said cantilever springs
for biasing said contact arms inwardly toward each other.
20. A female contact as in claim 17 wherein each of said contact
arms includes anti-buckling means and a lead contact located
between the junction of such contact arm with said one band and the
contact point between the arm and the spring member.
21. A female socket comprising a body having a longitudinal passage
for reception of a lead, and a longitudinal contact member
engagable with such lead; and a reinforcing spring on said body
having a pair of opposed spring arms, each spring arm including a
pair of closely spaced cantilever spring members, and a pair of
laterally offset bridging portions joining the ends of spring
members of different spring arms, said bridging portions being
spaced further apart than the spacing between the ends of the
spring members of the spring arms and a connection between the
other ends of at least one pair of spring members, the other ends
of one spring arm engaging said longitudinal contact member.
22. A female socket as in claim 21 wherein each said bridging
portion includes a pair of torsion springs and a cantilever
spring.
23. A female socket as in claim 21 formed of a continuous length of
uniform cross-section spring wire with the ends of the spring wire
forming the other pair of spring members.
24. A female socket as in claim 21 wherein the cross-sectional area
of each of said cantilever spring members decreases along the
length thereof from said bridging portions.
25. A female socket comprising an elongate hollow socket body at
one end, a band at the open end, a pair of contact arms extending
into the interior of the body from the band, a spring wrapped
around the body adjacent said band and including spring arms
extending along the exterior surfaces of the contact arms for
holding the contact arms into engagement with a lead inserted into
the body, and a pivot connection between said spring and band to
permit pivotal movement of the spring about an axis perpendicular
to the longitudinal axis of the body.
26. A female disconnect socket comprising an elongate hollow socket
body open at one end and having a pair of opposed contact arms
formed therein with the free ends thereof extending away from the
open end and into the interior of the body, and a spring including
a pair of spring arms extending along the outside of said contact
arms with the free ends of the spring arms engaging the free ends
of the contact arms, lead contact areas on the inside of said
contact arms, each spring arm comprising a pair of cantilever
spring members with the ends of at least one pair of spring members
being joined, and bridging members surrounding the outside of the
socket body and joining together cantilever spring members of each
spring arm, each of said bridging members including torsion springs
extending laterally from the joined cantilever spring members and a
cantilever spring joining said torsion springs, said torsion
springs and said cantilever springs extending around the
circumference of said body whereby insertion of a lead into the
socket forces the contact arms apart and stresses said cantilever
spring members, said torsion springs and said cantilever
springs.
27. A female disconnect socket as in claim 26 wherein said contact
areas are located between the free ends of the spring arms and the
junction between the spring arms and the socket body.
28. A female disconnect socket as in claim 26 including a pivot
connection between said body and each bridging member whereby the
spring is free to pivot relative to an axis perpendicular to the
longitudinal axis of the body.
29. A female disconnect socket as in claim 28 wherein said pivot
connection comprises a reduced area contact between the body and
each cantilever spring.
Description
The invention relates to an improved disconnect socket having a
socket body with a pair of contact arms and a spring wrapped around
the socket body including spring arms lying on top of contact arms
in the body. The spring arms provide contact pressure for forming a
high pressure electrical connection between the contact arms and a
male lead inserted into the socket. In a socket of this type, the
spring is elastically stressed during deflection for mating with
both thick and thin leads. Because the spring is stressed
elastically the high contact pressure is retained after repeated
insertions of leads into the socket and even when a thin lead is
inserted into the socket subsequent to insertion and withdrawal of
a thick lead.
The bi-metal construction results in a compact socket having a high
contact force. This in part results from the fact that when a lead
is inserted the entirity of the spring is stressed to bias the
contact arms against the lead. The spring arms are stressed as
cantilever springs and the portions of the spring wrapped around
the strap are stressed as both torsion springs and additional
cantilever springs. Thus, the spring pressure exerted against the
contact arms results from stressing of all of the various spring
components. This arrangement is highly efficient since all of the
spring is used to provide the contact pressure. Because all of the
spring is stressed during insertion of the lead, the socket is much
smaller than one using conventional cantilever springs alone to
provide an equivalent pressure on the contact arms. Because the
spring is not part of the electrical circuit high yield strength
material may be used resulting in greater contact pressure. The
reduction in size of the disconnect socket with the improved spring
properties permits use of the socket in circuits where a minimum of
space is available for sockets or where a number of sockets must be
mounted on a circuit board or like member in dense
configuration.
One form of spring used to bias the contact arms into engagement
with the lead inserted into the socket is formed from a continuous
length of spring wire and includes two pairs of cantilever spring
members, torsion springs extending to one side of the ends of the
cantilever spring members and bridging cantilever springs joining
the ends of the torsion springs. One of the pairs of cantilever
spring members is formed from a U-shaped portion of spring wire
while the other cantilever spring members comprise the free ends of
the wire. The ends of the cantilever spring members engage the free
ends of the contact arms to bias the same toward the interior of
the socket. The arms are reinforced to prevent buckling and include
contact points located approximately halfway along the length of
the arms for engaging the lead. Since the contact arms are rigid
and the spring engages the ends of the contact arms, the contact
pressure on the lead is greater than the contact pressure between
the ends of the cantilever spring members and the contact arms,
thus providing an improved connection between the lead and the
socket.
In another embodiment of the invention the spring is formed from a
hollow hourglass-shaped portion of flat metal spring stock. This
spring also includes the two pairs of cantilever spring arms, the
torsion springs and the bridging cantilever springs. The strength
of the individual spring members of either spring may be adjusted
to assure that the desired spring contact pressure is achieved.
The socket may be mounted on a circuit board by means of a contact
pin secured to a collar at the end of the socket body away from the
lead receiving opening. Alternatively, a solder resistant plug may
be crimped within the collar so that solder does not wick into the
socket interior when the socket is mounted in a circuit board hole
and the board is wave soldered.
For low profile mounting, tabs may be struck from the body side
walls between the contact fingers for forming a solder connection
with printed circuitry on the top of the board. In this case the
end of the terminal opposite the lead receiving end may be
positioned within an oversize circuit board hole.
An alternative low profile mounting may be achieved by positioning
the socket end away from the lead receiving end within a solder
resistant cup which in turn is mounted in an oversize circuit board
hole and resoldered to the board.
Circuit board sockets of the type disclosed may be used to receive
leads attached to circuit elements such as relatively delicate
integrated circuit modules. The socket spring may be pivoted
relative to the socket body to permit movement of the cantilever
spring members to either side of the socket axis thereby permitting
insertion of misaligned leads into the socket without subjecting
these leads to un-balanced forces. In this way integrated socket
leads which are somewhat off-center may be inserted into the socket
without subjecting the module itself to forces likely to injure or
break it.
The following patents disclose disconnect sockets of the type
having a pair of opposed cantilever contact arms: Deakin U.S. Pat.
No. 3,120,418, Evans U.S. Pat. No. Re. 26,837 and Gluntz U.S. Pat.
No. 3,363,224. In each of the sockets disclosed in these patents
contact pressure is provided by the resiliency of the spring arm
itself so that the socket is not capable of mating with leads of
different thicknesses while retaining the high contact pressure.
The arms also form part of the electrical circuit through the
socket. For a given size socket the integral contact and spring
arms are unable to provide contact pressures as high as those
achieved in a socket of the type disclosed. Further, insertion of
leads into a conventional socket having integral contact and spring
arms stresses the arms beyond their yield point thus resulting in
reduced contact pressure. The disclosed socket avoids this problem
because deflection of the contact arms stresses the spring without
exceeding the elastic limits of any of the spring components which
contribute to the total contact force. Thus the socket may be
reliably used in situations where leads are plugged and unplugged a
number of times without decrease in the contact pressure. The
integrity of the electrical connections between the socket and the
lead is maintained despite repeated insertions of the lead and
stressing of the spring. The socket body is formed of highly
conductive metal and need not have a high yield strength while the
spring material has a high yield strength and need not have high
electrical conductivity.
Other objects and features of the invention will become apparent as
the description proceeds, especially when taken in conjunction with
the accompanying drawings illustrating the invention, of which
there are four sheets.
IN THE DRAWINGS:
FIG. 1 is a perspective view of a circuit board with components
attached thereto by sockets according to the invention;
FIG. 2 is a partially broken away perspective view illustrating one
of the sockets of FIG. 1;
FIGS. 3 and 4 are sectional views taken along lines 3--3 and 4--4
respectively of FIG. 2;
FIGS. 5, 6, 7 and 8 are sectional views taken through the socket of
FIG. 4 along lines 5--5, 6--6, 7--7 and 8--8 respectively;
FIGS. 9, 10 and 11 illustrate further embodiments of the
invention;
FIG. 12 is a sectional view taken along line 12--12 of FIG. 10;
FIG. 13 is a sectional view taken along line 13--13 of FIG. 11;
FIGS. 14, 15 and 16 illustrate still further embodiments of the
invention;
FIG. 17 is a sectional view taken along line 17--17 of FIG. 15;
FIG. 18 is a sectional view taken along line 18--18 of FIG. 14;
FIG. 19 is a representational view illustrating pivoting of the
spring in a socket in response to the position of the lead within
the socket;
FIG. 20 illustrates engagement between one end of the spring
fingers and the socket contact arm;
FIG. 21 and 22 illustrate the socket body after formation and prior
to mounting of the spring;
FIG. 23 is a sectional view taken along line 23--23 of FIG. 21;
FIG. 24 is a perspective view of a further embodiment of the
invention provided with a stamp-formed spring;
FIGS. 25 and 26 are respective views of the springs used in the
embodiment illustrated in FIGS. 2 and 24 respectively; and
FIGS. 27 and 28 illustrate the formation of the spring of FIG.
26.
DETAILED DESCRIPTION OF THE INVENTION
As illustrated in FIG. 1, rows of spaced apart disconnect sockets
10 may be mounted on a circuit board for forming electrical
connections with the leads 12 extending from a circuit element 14
and into the sockets. The circuit element may be an integrated
circuit.
Each socket 10 includes a stamp-formed socket body 16 with a
reinforcing spring 18 wrapped around the strap 20 at the end of the
body adjacent lead receiving opening 17. A pair of like contact
arms 22 formed from the sides of the socket body extend into the
interior of the socket from opposed portions of strap 20. The
spring 18 includes opposed spring fingers 24 and 26 which extend
from the outside of the strap portion along the outside surfaces of
the contact arms and engage the contact arms adjacent their free
ends. The spring fingers are joined by spring portions 28.
As illustrated in FIG. 2, socket 10 may be provided with a collar
30 at the end of the body 16 away from lead receiving opening 17 to
facilitate mounting of the socket within a hole 32 formed through
the thickness of circuit board 34. The collar may be secured to a
pin 35 by a crimp and reflow solder connection. The pin may be used
for making connections between socket 10 and other circuit elements
by either a wire wrap or socket connector mounted on the pin.
The construction of socket 10 will now be described in further
detail. As indicated in FIG. 5, the socket body 16 is generally
square in cross section and includes a pair of opposed flat sides
36 joining sides 38 from which the contact arms 22 are formed. Ths
strap 20 is formed from the ends of the socket side walls adjacent
opening 17 and is flared outwardly to define a funnel-shaped
lead-in for guiding a lead 12 between arms 22. A seam defined by
the edges of the blank from which the socket body is formed extends
along one side 36. Rectangular collar 30 is reduced in cross
section somewhat from that of body 12 so that the connecting
portion 42 joining the body and collar forms a seat for a limiting
insertion of the socket into circuit board hole 32.
The width of contact arms 22 decreases from the strap 20 to the
free ends 44 thereof. The lower half 46 of the contact arms are
bent away through a shallow angle from the upper half of the arms
to define lead contacts 48 located in the medial portions of the
arms. The free ends 44 are bent outwardly around a small radius to
provide recesses for retaining the free ends of the spring arms 24
and 26.
Insertion of lead 12 into the socket body bends the contact arms 48
outwardly of the body. Since the arms are stamped from the body it
is desirable to provide clearance between the arms and the edges of
the finger cut-outs in sides 38. Binding between the free ends 44
and the lower edges 50 may be eliminated by bending the free ends
outwardly to thereby foreshorten the arms. The bend at the medial
portion of the arms also serves to foreshorten the arms. Because
the arms are tapered the foreshortening moves the lower half of the
arms away from the edges 50 to permit flexing of the arm into the
cut-out without binding.
Binding between the upper portions of contact arm 18 and the
cut-outs may be eliminated by bending the upper edges 52 of the
cut-outs 50 outwardly of the socket as indicated in FIG. 2. FIGS.
5, 6 and 7 illustrate that the upper edges 52 are gradually bent
outwardly from the middle of the cut-out to the end of the cut-out
adjacent the strap 20. Thus, in FIG. 5, the portions 54 of side
walls 38 are bent slightly outwardly of the socket; in FIG. 6 the
portions are bent out at an angle of approximately 45.degree.; and
in FIG. 7 the portions are bent out through an angle of nearly
90.degree. so that they form extensions of the adjacent side walls
36. Bending out of the wall portions 54 increases the width of the
cut-out to permit bending of the contact arms within the cut-outs
without engagement or binding between the arms and the edges of the
cut-outs.
It is important that the contact arms are rigid along their length
in order to assure that they do not buckle during insertion of the
lead with a resulting reduction of the pressure at contacts 48. The
arms may be inwardly dished as indicated in FIGS. 4 and 5 to
provide additional beam strength. With this construction it is
possible to locate the contact points 48 at a position nearer the
strap 20 than the engagement between the contact arms and the
spring fingers. The construction results in a contact force between
each arm 22 and the lead 12 greater than the force between the
spring finger and the end of the contact arm.
FIG. 25 illustrates reinforcing spring 18 prior to mounting on
socket body 16. The spring is formed from a single length of spring
wire stock with the end portions of the wire forming the two
straight cantilever springs 56 comprising spring finger 26. The
spring ends 58 of the springs 56 are severed from a continuous
length of spring stock to provide smooth corners 60 for engagement
within the recess at contact arm ends 44 as indicated in FIG. 20.
The smooth corners 60 and recesses prevent binding between the
spring finger and arm during insertion of a lead into the socket
10.
Spring arm 24 comprises a flat U-shaped medial portion of the
spring wire including a pair of straight cantilever springs 62 and
a connecting U bend 64. The interconnecting spring portions 28 each
include short torsion springs 66 extending outwardly from the
cantilever springs 56 and 62 to bridging cantilever springs 68.
The socket body 16 may be rolled from portions of sheet metal stock
on a carrier strip 70 as illustrated in FIG. 21. The seam 40 at
collar 30 is left open to permit insertion of the end of pin 35
prior to closing the collar about the pin and forming a reflow
solder connection therebetween. A groove or recess 72 is formed in
each body side wall 36 extending along the strap 20 slightly above
the juncture between the contact arms and the strap. Spring 18 is
fitted or wrapped around the socket body 16 with the bridging
portions 68 of the spring positioned in the recesses 72 so that the
spring arms 24 and 26 extend along the outside of the contact arms
22 with the free ends thereof 64 and 58 seated in the recesses at
arm ends 44. Contacts 48 may be provided with a precious metal
coating to reduce contact resistance.
The bridging portions 68 are spaced apart a distance slightly less
than the spacing between recesses 72 so that when the springs are
mounted on the bodies spring arms 62 are held apart slightly and
the bridging portions 68 are biased against the recesses 72, thus
holding the spring in proper position on the body. The connection
between the ends of the spring fingers and the contact arm also
serve to hold the spring in proper position.
In spring 18, as illustrated in FIG. 25, the free ends of the
spring arms are normally positioned adjacent each other. When the
spring is fitted on the socket body, the spring tension normally
holds the contact portion 48 of arms 22 against each other. By
prestressing the spring it is possible to preload the contacts and
achieve a high contact pressure. Insertion of lead 12 through
opening 17 and into the socket body forces apart contact arms 22
and stresses the spring 18.
It is important to note that spreading of the contact arm stresses
each portion of the spring 18. The springs 56 and 62 are bent
outwardly and stressed as cantilever springs, the four torsion
springs 66 are stressed by rotation and the bridging portions 68
are stressed as cantilever springs. With this construction the
entirity of the spring is stressed with the result that a high
spring force is applied to the contact arms. As mentioned
previously, this force is multiplied because of the location of the
contacts 48 with relation to the connection between the spring
fingers and contact arms.
Because of the nature of spring 18, the pressure between the
contact arms and the lead 12 is directly proportional to the
deflection of the contact arms for leads of varying thickness. Thus
it is possible to use the socket for forming reliable electrical
connections with relatively thin leads as shown in FIGS. 2 and 5
and with leads having a greater thickness. This flexibility permits
the use of the same socket for forming electrical connections with
any of a variety of leads thereby reducing inventory requirements
while assuring that a high pressure electrical connection is formed
with all leads. Insertion of leads into the socket elastically
deforms the springs 18 so that the contact pressure does not
decrease with repeated insertions of the lead into the socket. This
is important where the socket is used for forming connections with
leads of integrated circuit elements or other elements where it is
contemplated that the leads may be withdrawn from the elements and
reinserted during the useful life of the socket.
The width of fingers 22 and their dished configuration assures that
all leads inserted within the socket are forced between the fingers
with the result that an electrical connection is formed. As
illustrated in FIG. 9, the socket may be used to form an electrical
connection with round leads 80. Even if round leads are not
inserted along the longitudinal axis of the socket and contact a
side wall 36, the contact fingers 22 engage the lead to form the
desired electrical connection.
As illustrated in FIGS. 1, 3 and 4, the socket 20 may be positioned
in a circuit board hole 32 with a printed circuit pad 74
surrounding the end of the hole adjacent the socket body to permit
formation of a solder connection 76 between the socket and the pad.
If hole 32 is plated, the bottom of circuit board 34 may be wave
soldered so that solder flows up through the passages 78 defined by
the edges of collar 30 and the interior surfaces of the plated hole
to provide solder for the connection 76.
FIG. 9 illustrates a modification of terminal 10 in which a pair of
tabs 82 are lanced out of side walls 36 to permit positioning of
the lower portion of the socket within oversize circuit board hole
84 extending through the thickness of board 86. The tabs 82 may be
soldered directly to a printed circuit pad 88 surrounding the top
of hole 84. By mounting the sockets 10 on the circuit board in this
manner, it is possible to locate the circuit components carried by
the sockets closer to the circuit board thus resulting in a lower
profile and in a saving of space. The saving of space is important
in computers and other apparatus containing a large number of
circuits when limited space is available or where components are
required to be located close together to achieve high speed
operation.
FIGS. 10 and 12 illustrate a modification of the invention in which
the collar 30 at the bottom of the socket body is crimped around a
solder flow plug 90, in this case a cylindrical plug of Teflon. As
indicated in FIG. 12, the walls of the collar 30 are deformed
inwardly so that the collar tightly grips the plug. The collar and
plug may be fitted within a plated circuit board hole 92 extending
through the thickness of board 94 so that upon wave soldering
molten solder wicks up through the four channels 96 defined by the
walls of the collar and the plating at the sides of the hole to
provide a solder connection between 98 with printed circuitry 100
on the top of the board. The plug 90 serves to prevent the molten
solder from flowing into the interior of the socket.
FIGS. 11 and 13 illustrate a further embodiment of the invention in
which socket body 16 is formed without a collar 30 on the lower end
thereof, and the lower half of the socket body is fitted within
solder impervious cup 102. The cup is generally square in cross
section having side walls 104 closely fitted against the socket
body side walls 36 and 38. The bottom of the cup forms a projection
106 which is useful in seating the socket and cup within a circuit
board hole 108 formed through the thickness of board 110. Lip 105
at the edge of the cup limits insertion into hole 108. The circuit
board 110 may then be wave soldered to provide a solder connection
112 between the cup and printed circuitry 114 on the bottom of the
board. A reflow solder connection or other suitable electrical
connection is formed between the cup and the body of the socket 10
so that an electrical connection is formed between circuitry 114
and a lead positioned within the socket. This type of low profile
mounting permits wave soldering of the socket to form the
electrical connection while also assuring that the molten solder is
prevented from entering the socket body.
FIG. 16 illustrates a modification of the socket shown in FIG. 2 in
which locking barbs or lances 118 are formed in the corners 120 of
collar 30. When the collar is tightly fitted into circuit board
hole 122, formed through the thickness of board 124, the barbs 118
engage the interior of the hole and prevent movement of the socket
10 with respect to the circuit board prior to and during formation
of the solder connection 126 between the socket and printed
circuitry 128 on the top of the circuit board. The barbs may be
formed prior to or subsequent to rolling of the sheet metal stock
to form the socket body 16.
FIGS. 14 and 15 illustrate two embodiments of the invention in
which the bridging portions of reinforcing spring 18 pivot on the
socket body side walls 36 thereby permitting insertion of axially
offset leads into the socket. Leads 12 are connected to the body of
circuit element 14 at a point 130 located above the lead receiving
opening 17 of the socket. As indicated schematically in FIG. 19,
the axial alignment 132 of the leads may not coincide exactly with
the axis 133 of the socket. Thus the leads may extend from point
130 within the socket to one side or the other side of the axis of
the socket. It is important that the socket receive and form
electrical connection with the offset leads without stressing the
leads unduly and thus risking injury to circuit element 14. To this
end, means are provided to permit the spring 18 to pivot slightly
on axis 140 with regard to the socket body 16 thereby allowing the
contact arms 22 to swing together to one side or the other side of
the axis of the socket for reception of offset leads. Pivoting of
the spring assures maintenance of an electrical contact with the
lead despite vibration or shock loading of the circuit board.
In the embodiment illustrated in FIGS. 14 and 18 the centers of the
bridging portions 138 of spring 18 are bowed inwardly so that they
are held against the recesses 72 at the center of socket body side
walls 36 thus permitting slightly pivoting of the entire spring
about axis 140 as indicated. Freedom to pivot permits the socket to
receive and form a high pressure electrical connection with each
side of leads offset somewhat from the axis of the socket without
subjecting the lead to unbalanced forces which could injure the
circuit element from which the lead extends.
FIGS. 15 and 17 illustrate an alternative pivot connection to that
illustrated in FIGS. 14 and 18 in which pivot projections 144 are
provided within the recesses 72 at the middle of sides 36. Spring
bridging portions 146 rest upon projections 144 to permit the
desired pivotal movement of the spring upon insertion of axially
offset leads.
FIGS. 24, 26, 27 and 28 relate to a further embodiment of the
invention utilizing a reinforcing spring 148 which is stamp formed
from flat spring metal stock. The spring may be used with sockets
identical to those previously described.
Spring 148 is stamp formed from sheet metal spring stock as
illustrated in FIG. 27. Generally hourglass shaped hollow spring
preform 152 may be formed from the flat spring stock by a stamping
operation as an integral part of a continuous carrier strip 154.
The preform 152 comprises a continuous strip of spring metal in the
general shape of an hourglass having four tapered spring arms 156.
The two spring arms on each edge of the spring preform are
connected together by a sinuous portion 158 having a pair of curved
contacts 160 facing the interior of the preform. The other ends of
the spring arms 156 are connected by parallel bridging members 162.
The flat stamped preform 152 is symmetrical to either side of axis
164. Preforms 152 are secured to strip 154 by severable connections
165.
Following stamping of the preform, the next step in the formation
of the spring 148 illustrated in FIG. 26 is to bend the ends of the
spring fingers 156 adjacent bridging members 162 to form offsetting
steps 166 which lower the spring fingers below the bridging
members. Following formation of steps 166, manufacture of spring
148 is completed by bending the preform nearly 180.degree. about
axis 164 so that the bridging members 162 are opposite each other
and spaced outwardly of the spring by offsets 166. The
manufacturing operations are carried out with the preform secured
to a carrier strip, as illustrated in FIG. 22. Following completion
of the spring 148, connections 165 may be severed to permit
mounting of the spring on the body 168 of socket 150.
As indicated in FIG. 24, spring 148 is fitted on a socket body 168
by positioning the bridging members 162 in the recess 170 on strap
172 located adjacent the lead receiving end of the body. The
bridging portions rest flat against the strap. The spring arms 156
extend along the outer surface of the socket body contact arms 174
with the rounded contacts 160 seated in the recesses defined by the
curved ends of the contact arms to reduce binding. The remainder of
the spring arms 156 are free of the contact arms.
Insertion of a lead 176 into socket 150 forces apart contact arms
174 and stresses the spring 148. Spring arms 156 act as cantilever
springs. Because the arms decrease in width from the offsets 166 to
the contacts 160 they are uniformly stressed when deflected
resulting in maximum spring force. Offsets 166 are stressed as
torsion springs and bridging members 162 are stressed as cantilever
springs. Thus, as with spring member 18, each portion of the spring
148 is stressed to bias the lead contacts of socket 150 into high
pressure connection with the lead 176. The result is a highly
efficient socket capable of receiving a variety of leads of
different thicknesses and cross sections without stressing the
spring beyond the elastic limits of the component spring parts.
Contact pressure thus is retained despite repeated insertions and
withdrawals of leads within the socket.
In both sockets 10 and 150, it is possible to vary the contact
characteristics of the socket by varying the parameters of the
spring used to urge the contact arms into engagement with the lead.
Thus, in each case, the characteristic of the spring arms which
engage the contact arms of the torsion springs and of the bridging
cantilever springs, may be adjusted to achieve the desired socket
parameters. Adjustment of the spring characteristics is
particularly easy in the case of spring 148 since the width of the
various spring members is easily controlled in the stamping
operation. For instance, for a weaker spring, the tapered width of
the spring arms 156 and of the remaining springs could be reduced.
In each case it is desirable to balance the characteristics of the
three types of springs within each of the socket springs 18 and 148
so that the contemplated use of the socket does not stress any
individual spring beyond it's elastic limit.
The socket 150, as previously described sockets, may be provided
with a wire wrap pin, solder plug, solder cap or other means for
forming an electrical connection with a circuit element. Obviously
the sockets described herein may be provided with a crimp barrel
for forming a crimp connection between the socket and a wire. While
the disclosed embodiments all show formation of an electrical
connection with the socket adjacent the collar, it is not intended
that the invention be limited to such a connection. Obviously a
wire crimp barrelor other contact means could extend from the lead
receiving opening or from other portions of the socket.
Accordingly, while I have illustrated and described preferred
embodiments of my invention, it is understood that these are
capable of modification, and I therefore do not wish to be limited
to the precise details set forth, but desire to avail myself of
such changes and alterations as fall within the purview of the
following claims.
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