Zero insertion socket with normally closed contacts

A zero insertion force socket using normally closed contacts and three adjacently overlying plates. Upon lifting the activating arm, a cammed cylinder is rotated which pushes the middle plate and pulls the top plate to thereby open the prongs of the contact for component lead insertion therebetween. Upon the activating arm being moved back into its original position the cammed cylinder rotates and the middle plate shifts back to its original position under the influence of a contact prong closing about the component lead as the top plate shifts back to its original position under the influence of the cammed cylinder.

SUMMARY OF THE INVENTION 
This invention relates to a zero insertion force (ZIF) socket for 
connecting electrical components to a circuit board and will have 
application to a ZIF socket having normally closed contacts. 
Heretofore, ZIF sockets used to connect electrical components, such as 
integrated circuits, to a circuit board have used a normally open contact 
arrangement. Such a socket is described in U.S. Pat. No. 3,763,459. One 
problem associated with the use of normally open contacts is due to the 
constant force required to maintain the contacts in a closed position. 
This force requirement creates excessive stress upon the plastic socket 
parts which may eventually break, or worse, weaken so as to cryptically 
disconnect the contact from the component lead. 
The ZIF socket of this invention eliminates the above problems by using a 
one piece normally closed contact. The contact is designed such that the 
only time force is exerted by the plastic socket parts is during the brief 
time required to open the contacts and insert the component leads. The 
elimination of force required to secure the component leads reduces socket 
wear or breakage. Further, the use of normally closed contacts insures a 
stable electrical and mechanical connection to a component lead. 
Accordingly, it is an object of this invention to provide for a novel and 
unique ZIF socket. 
Another object of this invention is to provide for a ZIF socket having 
normally closed contacts. 
Another object of this invention is to provide for a ZIF socket which 
places less stress on the plastic socket parts. 
A further object of this invention is to provide for a ZIF socket that can 
be produced economically. 
Further objects of this invention will become apparent upon a reading of 
the following description taken along with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The preferred embodiment herein described is not intended to be exhaustive 
or to limit the invention to the precise form disclosed. Rather, it is 
chosen and described to enable others skilled in the art to utilize its 
teachings. 
Referring now to the drawings, the zero insertion force (ZIF) socket 10 
depicted in FIGS. 1-14 includes base member 12, middle plate 14, top 16 
and actuator 18 all preferably formed of a molded plastic. 
Base member 12, as shown in FIG. 3 includes a support housing 34. Housing 
34 defines a through bore 82 which accommodates a camming cylinder 58 of 
actuator 18. Base member 12 also includes a pair of spaced end flanges 78 
which define a notch therebetween to accommodate cam 64 of actuator 18. A 
second pair of flanges (one flange 79 shown in FIG. 12) also defining a 
notch (not shown) are positioned at the opposite end of housing 34 (and 
are similar to flanges 78 and notch 80) to accommodate cam 68 of actuator 
18. A straight faced guide rail 30 is formed on plate 12 as shown. Base 
member 12 also defines a plurality of openings 86 which, as best shown in 
FIG. 6, includes a narrow lower portion 90 in communication with a widened 
upper portion defined by ledge 88. Corner located standoffs 91 extend from 
the bottom of base member 12 to maintain a constant distance between plate 
12 and a supporting surface. Base 12 further includes L-shaped notches 26 
and 28 (only one fully shown). 
Middle plate 14 includes flanges 92 and 93 which define notch 94 and 
flanges 95 and 97 which define notch 96. Flanges 93 and 95 are spaced to 
define a center notch 98 which accommodates housing 34 of base member 12. 
A groove 100 is defined in the plate 14 and complementally fits rail 30 to 
prevent side to side movement between plates 12 and 14. An upright stop 
102 is formed at end 104 of plate 14. Plate 14 defines a plurality of 
openings 106 which are aligned with openings 86 of base member 12 and are 
shaped as shown in FIGS. 6 and 19-12. Each opening 106 is defined by wall 
108, (FIGS. 6 and 12) and downturned radial wall portion 109. Wall 108 
includes at spaced intervals protrusions 105 having an edge 103 being 
substantially perpendicular to side wall 108 (FIG. 10). 
Top 16 includes formed integral supports 32 and 33 which define bores 116 
and 118 respectively. Top 16 also includes L-shaped protrusions 110 and 
112 which mate with notches 26 and 28 of base member 12 to slidably secure 
the top to the base member with plate 14 slidably positioned therebetween. 
A notch or squared opening 120 is defined in support 32 and communicates 
with bore 116. Likewise, support 33 defines a notch or squared opening 122 
which communicates with bore 118. Top 16 further defines openings 14 which 
are aligned with openings 106 of plate 14 and are shaped as shown in FIG. 
6 and FIGS. 9-12. Openings 114 are defined by three converging walls 123 
and one vertical wall 124. Protrusions 122 extend into openings 114 and 
are shaped substantially like protrusions 105 of plate 14. FIG. 12 has 
been included to more clearly depict the shape of the overlying openings 
in plates 12, 14, and 16. 
As is shown in the figures, contact 20 is preferably formed from a single 
piece of electrically conductive metal and includes a lead leg 36 and a 
head 38. Head 38 is offset horizontally from leg 36 and includes spaced 
resilient prongs 40, 42 which terminate in oppositely extending ears 44, 
46 respectively. Prongs 40 and 42 are preferably formed so as to press 
against one another in their at rest or closed position. Prongs 40 and 42 
abut one another at lead contacting surfaces 50 and 54. 
Actuator 18 as shown in FIG. 3 includes arm 56 and integral camming rod 58 
which is positioned substantially perpendicular to arm 56. Arm 56 includes 
handle portion 60 which is elevated for easier access to the user. Camming 
rod 58 includes a central cylinder body 62 and peripheral circular cam 
members 64, 66 and 68 which are of like periphery and eccentric to main 
cylinder body 62 as can be seen in FIGS. 7 and 8. Camming rod 58 also 
includes recessed cam surfaces 70 and 72 which are adjacent each side of 
cam 64 and recessed cam surfaces 74 and 76 which are adjacent each side of 
cam 66. Recessed cam surfaces 70, 72, 74, 76 are of like periphery, and as 
is shown in FIG. 7, both recessed cam surfaces 70 and 72 terminate in like 
positioned end walls. Referring to FIG. 8, it can be seen that cam surface 
76 gradually tapers to its outer circumference as does can surface 74. 
FIG. 9 illustrates that in the closed position extension 93 of plate 14 
abuts recessed cam surface 72. In a like manner, extension 92 abuts 
surface 70, extension 85 abuts surface 74 and extension 97 abuts surface 
76. In this position, prongs 40, 42 are biased against one another due to 
their spring-like quality and, therefore, no force is exerted on members 
12, 14 or 16. Thus the likelihood of stress related breakage or distortion 
of socket parts is minimized. FIG. 13 illustrates the orientation of cam 
64 relative to top plate 16 while actuator 18 is in the closed position. 
To open prongs 40 and 42 for component lead insertion therebetween, the 
user lifts and rotates actuator 18 into the position shown in FIG. 2 by 
broken lines. Lifting actuator 18 causes camming rod 58 to rotate into the 
position shown in FIGS. 10 and 11. The recessed cam surfaces 70, 72, 74 
and 76 press against their respective adjacent extensions 92, 93, 95, and 
97 to urge plate 14 in the direction of arrow 125 in FIG. 11. 
Simultaneously, cams 64 and 66 are rotated and catch in squared openings 
120 and 122 of supports 32 and 33 to urge plate 16 in the opposite 
direction as indicated by arrow 126. FIG. 14 illustrates the orientation 
of cam 64 relative to top plate 16 while actuator 18 is in the open 
position. As plate 14 and top 16 are so disposed, ledge 108 of plate 14 
urges ear 44 of prong 42 in the direction of arrow 125 and ledge 122 of 
top 16 urges ear 46 of prong 42 in the direction of arrow 126. Thus, with 
prongs 40 and 42 urged in opposite directions, a component lead (not 
shown) may be inserted between lead contacting surfaces 50 and 54 of the 
prongs. Therefore, in the manner of component lead insertion described 
above, a component may be inserted downward into socket 10 without force 
and held in place without stress on members 12, 14 or 16. 
To close prongs 40 and 42 subsequent to a component lead being inserted 
therebetween, actuator 18 is moved into its original position shown in 
FIG. 2 in solid lines. Due to the spring quality of prongs 40, 42, the 
flexed prongs 40 and 42 close around and grasp the component lead for a 
secure mechanical and electrical connection. As each prong 40 springs 
toward its closed position, plate 14 is urged into its original position 
as shown in FIG. 5. Plate 16 is moved into its original position by cams 
64 and 66 abutting the edges of squared openings 120 and 122. Therefore, 
the movement of plate 16 follows or is dependent upon cams 64 and 66 of 
camming rod 58. 
It is understood that, although socket 10 is of a ten opening by ten 
opening pin grid array, the basic principles of this invention are 
applicable to any size or shape of socket, having any number or variety of 
holes to accommodate various leaded IC components. 
It should be further understood that the invention is not limited to the 
precise form disclosed by the details above but may be modified within the 
scope of the appended claims.