Low insertion force connector

A low insertion force connector has metal conductors disposed in respective openings in an insulating connector body. Each conductor has a bridge portion extending in a square inside its respective body opening and has integral leaf springs extending from respective sides of the square toward a terminal entry end of the body opening. Two pairs of the springs are disposed so that the springs in each pair face each other around a common axis for receiving a terminal therebetween. Each leaf spring has an obliquely disposed surface to intercept and be moved by a terminal as the terminal is inserted and a contact surface for engaging the terminal said surfaces of one pair of springs being relatively closer to the entry end of the body opening than said surfaces of the other pair of springs, thereby requiring lesser terminal insertion forces. An integral gauge strip on each conductor is connected to one pair of the springs at the terminal entry end of the body opening and extends to define the perimeter of a gauge opening or aperture on the conductor for limiting the cross-section of a terminal which can be inserted between the leaf springs through the gauge aperture. Opposite ends of the gauge strip are preferably interconnected by dove-tail means for positively fixing the perimeter of the gauge aperture. Preferably, the other pair of springs extend in cantilever relation from the conductor so that the distal ends thereof are inside the body opening.

BACKGROUND OF THE INVENTION 
The field of this invention is that of sockets or connectors for 
interconnecting printed circuit boards and the like and the invention 
relates more particularly to low insertion force connectors adapted for 
use in avionic applications. 
Where conventional connectors have been previously used in cooperation with 
plug connectors to interconnect circuit boards in avionic applications and 
the like to meet very high performance standards, the connectors have 
sometimes been provided with contacts or conductors which provide 
resilient, four point contact with each i.c. terminal inserted into the 
connector. Such four point contact has typically been achieved by the use 
of carefully controlled spring forces so that the connectors have been 
adapted to receive terminals therein with modest insertion forces to 
provide reasonable terminal retention forces for use under selected shock 
and vibration conditions. Such known avionic connectors have typically 
included shrouds or the like for preventing the insertion of oversize 
terminals into the connectors to avoid damage to the spring 
characteristics of the connector contacts. Frequently, however, it has 
been difficult to provide connector contacts with suitably low insertion 
forces and suitably high terminal retention forces where mating male 
connectors having large numbers of terminals are to be mated with the 
receptacles of the connectors. It has also been difficult to provide 
shrouds or the like for excluding oversize terminals from the connector 
contacts at reasonable cost. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide novel and improved connectors 
for cooperating with plug connectors or the like to interconnect p.c. 
boards and the like; to provide such connectors which are particularly 
adapted to use in avionic applications and the like where high performance 
standards have to be met; to provide such connectors which have very low 
terminal insertion force characteristics while providing suitably high 
terminal retention properties; to provide such connectors which are of 
sturdy and reliable construction; and to provide such connectors which are 
particularly adapted for low cost manufacture and use. 
Briefly described, the novel and improved connector of this invention 
comprises a body of electrically insulating material having a plurality of 
openings extending through the body and having a plurality of electrical 
conductors disposed in the respective body openings. Preferably each body 
opening has a relatively large inlet portion at the top of the body, has 
an intermediate portion relatively smaller than the inlet forming a first 
shoulder between those portions of the opening, and has an outlet portion 
at the bottom of the body relatively larger than the intermediate portion 
of the opening to form a second shoulder between those latter two portions 
of the opening. Each of the conductors is blanked and formed from an 
electrically conductive metal spring material such as beryllium copper or 
phosphor bronze or the like to provide the conductor with a socket or 
receptacle portion and with a post portion. The conductors are disposed in 
the conductor body openings so that the socket portions fit into the 
respective inlet portions of the openings and the post parts extend 
through the openings to extend from the body of the connector body to be 
electrically connected to circuit paths on a p.c. board or the like. 
In accordance with this invention, the socket portion of each conductor has 
an integral strip shaped to extend around the perimeter of a square to 
form a bridge part of the conductor which is disposed inside the inlet 
portion of a body opening to rest on the first body shoulder in that 
opening. Four integral leaf or beam springs extend up from the respective 
four sides of the square conductor bridge part toward the open end of the 
body opening. That is, two pairs of the leaf springs extend up from pairs 
of opposite sides of the square bridge part in spaced relation to each 
other around a common axis which extends into the opening from the top of 
the connector body. In that way, the leaf springs are each adapted to 
resiliently engage a terminal into the body opening along that common 
axis. 
Each leaf spring has one surface obliquely disposed relative to the noted 
axis to initially intercept and be moved by a terminal extending into the 
body opening for establishing a selected spring force in the leaf spring. 
That is, the obliquely disposed spring surfaces engage a terminal entering 
the body opening and are cammed or moved laterally in the opening to a 
predetermined extent to establish selected resilient spring forces in the 
leaf springs. The spring leaves also have contact surfaces located 
immediately adjacent to the obliquely disposed spring surfaces. Those 
contact surfaces serve to electrically engage a terminal when the terminal 
has been disposed in the noted body opening. 
In accordance with this invention, the contact surfaces on one pair of the 
leaf springs are located relatively closer to the entry end of the inlet 
portion of the body opening than the contact surfaces on the other pair of 
leaf springs. Preferably, the contact surfaces on the first pair of 
springs are relatively closer to the entry than the obliquely disposed 
surfaces of the second pair of leaf springs. In that way, terminal 
insertion is initially required to deflect only a single pair of the leaf 
springs so that a lesser insertion force is required. The obliquely 
disposed surfaces of the second pair of springs are engaged by the 
terminal to be separated by further movement of the terminal into the body 
opening only after separation of the first pair of springs has been 
completed. 
In accordance with this invention, each conductor also has an integral 
gauge strip portion connected to one of the pairs of leaf springs adjacent 
to the entry portion of the body opening. The gauge strip forms the 
perimeter of a gauge aperture for excluding the entry of oversize 
terminals into the socket portions of the conductors. Preferably, the 
gauge strip extends to define the four sides of a square gauge aperture 
for limiting entry of a round terminal of selected diameter. Preferably 
also, the ends of the gauge strip have dove-tail means interconnected so 
that the strip positively limits the length of the perimeter of the gauge 
aperture. In that way, the connector provides low terminal insertion 
forces and excellent terminal retention forces, positively excludes the 
entry of oversize terminals into the connector contacts, provides the 
desired four point terminal engagement with well controlled spring forces, 
and is adapted to be manufactured at low cost.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings, 10 in FIGS. 1 and 3 indicates the novel and 
improved low insertion force connector of this invention which is shown to 
include a connector body 12 of electrical insulating material having a 
plurality of openings 14 extending through the body and having a plurality 
of electrical conductors 16 disposed in the respective body openings to 
make detachable electrical engagement with terminal pins from male 
connectors inserted into the body openings and to extend from the 
connector body to be electrically connected to circuit paths on a printed 
circuit board. For illustrating purposes, one opening 14a is shown in 
FIGS. 1 and 3 with the conductor omitted. Preferably for example, the body 
opening 14 has a relatively large inlet or entry portion 14.1 located at 
the top 18 of the body, has an intermediate portion 14.2 forming a 
shoulder 14.3 inside the opening, and has an outlet portion 14.4 at the 
bottom 20 of the body relatively larger than the intermediate portion of 
the opening to form a second shoulder 14.5 inside the opening as is shown 
particularly in FIG. 3. In the preferred embodiment, the connector body is 
formed of a rigid, easily moldable material such as glass-filled diallyl 
phthalate or polyphenylene sulfide has locating holes 22 shown in FIG. 1 
in the top of the body for use as pilot holes in assembling the connector 
or for positioning terminal locating hardware on the connector during 
mounting of a mating male connector unit or the like on the connector 10 
in conventional manner. Preferably, a pair of grooves 14.6 are provided on 
the top of the body adjacent respective opposite sides of each body 
opening to extend to respective opposite edges of said opening. The 
electrical conductors 16 are disposed in the respective body openings as 
is shown in FIGS. 1 and 3. 
In accordance with this invention, the electrical conductors 16 have a 
configuration such that they are adapted to be blanked and formed from a 
metal strip material in a continuous process in any conventional manner. 
Preferably for example, the conductors are formed from a strip 24 of an 
electrically conductive metal spring material such as beryllium copper or 
phosphor bronze or the like by blanking as indicated as 16a in FIG. 2 and 
by folding or bending as indicated at 16b and 16c in FIG. 2 in any 
conventional manner. In that way, each of the conductors is provided with 
a socket portion 26 and with a post portion 28 as shown in FIG. 2 in an 
economical manner. 
In accordance with this invention, each of the conductors 16 as best shown 
in FIGS. 3-5 has an integral strip portion 30 which is folded to define 
the perimeter of a square bridge part 32 of the conductor. The conductor 
is disposed in a connector body opening 14 (see FIG. 3) so that the bridge 
part of the conductor rests on the shoulder 14.3 inside the opening. In 
the preferred embodiment, barbs or detents 32.1 are formed on the square 
bridge part at the corners of the square for example for use in 
positioning the square bridge part in said body opening 14. Four leaf 
springs 34, 36, 38 and 40 are provided integral with the bridge strip 30 
and extend up from respective opposite sides of the square bridge part 32 
toward the top 18 of the connector body and toward the open end of the 
body opening 14. The pair 34, 36 of the leaf springs are disposed in 
spaced, facing relation to each other on opposite sides of an axis 42 
which extends into the body opening. The pair 38, 40 of the leaf springs 
also extend in spaced, facing relation to each other on opposite sides of 
the same common axis. In that way, the leaf springs define a square space 
between the springs for receiving a terminal of a mating connector or the 
like between the springs and the springs are each adapted to resiliently 
engage such a terminal as it is axially inserted into the body opening 14 
along the axis 42. 
In accordance with this invention, each of the noted leaf springs is 
provided with a surface 34.1, 36.1, 38.1 and 40.1 which is disposed 
obliquely relative to the axis 42 to initially intercept a terminal 
(indicated by the broken lines 44 in FIGS. 4 and 5) as the terminal is 
being inserted into the conductor socket portion 26 and to be moved or 
cammed laterally away from the axis 42 to a predetermined extent by 
movement of the terminal to establish a selected spring force in each of 
the leaf springs. Each of the springs also has a contact surface 34.2, 
36.2, 38.2 and 40.2 which is preferably located immediately adjacent to 
the obliquely disposed surface 34.1, 36.1, 38.1 or 40.1 to make electrical 
engagement with the terminal 44 when the terminal is fully positioned in 
the body opening 14. 
In accordance with this invention, an integral gauge strip portion 46 of 
the conductor is connected to at least one of the leaf springs and is 
folded to define the perimeter of a gauge aperture 48 aligned with the 
common axis 42 of the conductor. Preferably, the ends of the strip portion 
46 are connected together so that they positively fix the length of the 
perimeter of the gauge aperture 48. In a preferred embodiment for example, 
the gauge strip is integrally connected to two of the leaf springs 38, 40 
adjacent to the open end of the body opening 14 at the top of the body, a 
dove-tail 50 is formed at one end of the gauge strip, and a dove-tail 
groove 52 is formed at the opposite end of the strip, the dove-tail being 
fitted into the groove as shown in FIGS. 2 and 3 for securing the strip 
ends together. In that arrangement, the other leaf springs 34, 36 are 
terminated below the gauge strip so that the distal ends 34.3, 36.3 of the 
spring are disposed inside the body opening 14. Tabs 54 provided on the 
gauge part of the conductor are preferably folded into the grooves 14.6 at 
the sides of the openings on top of the connector body for orienting the 
conductors in the body openings as will be understood. In that way, the 
gauge aperture 48 defines the maximum cross-section of the terminal 44 
which can be fitted through the aperture into the socket portion 26 of 
each conductor. Preferably for example, the square gauge aperture is about 
0.032 inches on a side and the aperture is adapted to typically receive a 
round terminal of 0.030 inches diameter and will exclude a terminal of 
greater than 0.032 inches diameter. The gauge aperture thereby avoids risk 
of deforming the socket portion of a conductor such as may result from the 
insertion of an oversize terminal therein. 
In accordance with this invention, the post part 28 of the conductor is 
preferably folded as indicated at 28.1 (See FIG. 2) to provide ribs to 
increase the strength of the post part as will be understood. Tabs 56 are 
also formed on the post and are adapted to be folded out or apart after 
the conductor is inserted into a body opening so that the tabs spread out 
into the outlet portion 14.4 of the opening to engage the shoulder 14.5 as 
shown in FIG. 3, thereby to lock the conductors in the body openings. If 
desired, other conventional post configurations such as solder cup shape 
or the like are alternately provided. 
In the preferred embodiment of this invention, the contact surfaces 34.2, 
36.2 on one of the pairs of leaf springs are spaced relatively closer to 
the top of the connector body than the contact surfaces 38.2, 40.2 of the 
second pair of leaf springs. Preferably, the contact surfaces 34.2, 36.2 
are relatively closer to the top of the body than the obliquely disposed 
surfaces 38.1, 40.1 of the second pair of springs as is shown in FIGS. 4 
and 5. Preferably also the obliquely disposed surfaces 34.1, 36.1 of the 
first pair of leaf springs are spaced relatively closer to each other and 
to common axis 42. Conversely, the obliquely disposed surfaces 38.1, 40.1 
of the second pair of springs are arranged so they intercept a terminal 
inserted along the axis 42 at a shallow or more oblique angle than the 
surfaces 34.1, 36.1. 
In that arrangement, the obliquely disposed surfaces 34.1, 36.1 of one of 
the two pairs of leaf springs initially intercepts a terminal 44 being 
inserted into the conductor socket 26 as is best shown in FIG. 4. 
Therefore, the terminal insertion force needed to move that one pair of 
leaf springs apart is relatively low and the terminal is adapted to be 
inserted with relatively low force. As the first pair of springs 34, 36 
are fully spaced apart and the terminal engages the contact surfaces 34.2, 
36.2 of that pair of springs, the terminal insertion force needed to 
further insert the terminal into the body opening need only overcome 
sliding frictional forces between the terminal and the contact surfaces of 
that pair of springs. That is, no further force is required for spreading 
of the leaf springs 34, 36 and relatively small terminal insertion forces 
are adequate for sliding the terminal along the contact surfaces 34.2, 
36.2. Then, when the terminal engages the intercepting surfaces 38.1, 40.1 
of the second pair of leaf springs as shown in FIG. 5, the force inserting 
the terminal is again only required to be sufficient to separate a single 
pair of springs and to overcome the sliding friction with the contact 
surfaces 34.2, 36.2. Thus, only limited terminal insertion force is again 
required. Subsequently, when the leaf springs 38, 40 are fully separated 
and the terminal engages contact surfaces 38.2, 40.2, the required 
terminal insertion force is again relatively low and need be only 
sufficient to overcome sliding friction with the noted four contact 
surfaces. The initial spacing of the leaf springs 34, 36 is preferably 
less than that of the springs 38, 40 because, where they are not attached 
to the gauge part 46, they move more freely and require greater movement 
to establish a desired spring force therein. However, that smaller spacing 
provides additional assurance that a terminal inserted between the pair of 
springs will be contacted by at least that one pair of springs. 
Conversely, where the pair of leaf springs 38, 40 are attached to the 
gauge strip 46, they provide a greater column strength, require less 
lateral movement to establish a desired spring force, and are therefore 
disposed with slightly greater initial spacing than the leaf springs 34, 
36 and have intercepting surfaces 38.1, 40.1 disposed at a more oblique 
angle to the terminal 44 being inserted into the body opening. In that 
arrangement, sliding of the terminal 44 along the intercepting surfaces of 
the second pair of leaf springs moves the leaf springs in smaller 
increments using the greater length of the surfaces 38.1, 40.1. 
In that way, the conductors 16 are adapted to be made at low cost. However, 
they have a sturdy and rugged construction. They require relatively low 
insertion forces. Yet, they provide a desired four point contact and 
achieve desirably high terminal retention forces. The leaf springs of the 
conductors assure contact with an inserted terminal, hold the termial with 
desired spring forces under appropriate levels of shock, gravity and 
vibration forces, and the conductor gauge aperture is positively foxed so 
that oversize terminals which might damage the spring characteristics of 
the connector contacts are positively excluded. Further, the manner in 
which the gauge part of the conductor is joined to two of the leafs of 
springs assures that the conductors have substantial column strength. 
It should be understood that although particular embodiments of the 
invention have been described by way of illustrating this invention, the 
invention includes all modifications and equivalents of the disclosed 
embodiments falling within the scope of the appended claims.