Self-locking mating terminal structure

A mating terminal structure includes a generally box-shaped female terminal defining a receptacle with a flexible cantilevered contact beam formed from a bottom wall thereof. The beam includes a radiused contact portion. A male terminal is insertable into the receptacle in a given insertion direction (A) and includes a contact cam for deflecting the cantilevered contact beam and engaging the contact portion thereof. The contact cam has a leading ramp surface extending at a relatively small acute angle relative to the insertion direction for engaging the contact portion and gradually deflecting the cantilevered contact beam. The contact cam also has a trailing locking surface extending at a relatively larger acute angle relative to the insertion direction for providing locking interference between the contact portion of the cantilevered beam and the contact cam of the male terminal to thereby removably lock the male terminal to the female terminal.

FIELD OF THE INVENTION 
This invention generally relates to the art of electrical connectors and, 
particularly, to an electrical connector assembly in which a pair of 
connectors are locked together by interengagement of the mating terminals 
of the connectors. 
BACKGROUND OF THE INVENTION 
In general, an electrical connector assembly conventionally includes a pair 
of electrical connectors such as plug and receptacle or other male and 
female connectors that mate together in a particular configuration. Each 
connector conventionally includes an insulating or dielectric housing 
within which are mounted one or more electrical terminals. The terminals 
may be hard wired to electrical wires or cables, or one or both of the 
connectors may be mounted to a printed circuit board with the terminals 
coupled to circuit traces on the board. In any event, the terminals of the 
two mating connectors also mate or interconnect in a particular 
configuration. For instance, a female or receptacle terminal may be 
adapted for receiving a male or pin terminal. 
In connector assemblies of the character described above, a positive 
connection between the mating connectors typically is ensured by one or 
more of the following systems: (a) positive locking between the connector 
housings; (b) positive locking between the terminals; or (c) frictional 
retention between the housings and/or the terminals. Each of these systems 
heretofore has created various problems. 
In particular, when the locking function is performed by positive locking 
between the connector housings, such as integrally molded or separate 
metallic latches, the housings often involve complicated molds or costly 
secondary components and assembly, and consequently create a larger 
envelope size for the overall connector assembly in order to accommodate 
these locking mechanisms. This is highly undesirable particularly in 
contemporary proposals for greater miniaturization of electrical connector 
assemblies. In the case of secondary metallic latches, the costs of the 
separate dies and secondary assembly procedures can drastically increase 
the costs associated with the connectors. Furthermore, the latches may be 
inadvertently unlocked, broken or removed from the housing and the 
connectors inadvertently uncoupled. 
When positive locking occurs between the terminals themselves, excessive 
mating forces often make unmating of the connectors difficult, if not 
impossible. This is particularly true when one or both of the interlocked 
terminals must be "actuated" in order to release the locking mechanism. In 
other words, locking mechanisms such as depressible cams or wedges must be 
manually released in order to disconnect the terminals. Furthermore, 
latching between the terminals can often lead to damage to one or both of 
the terminals when the connectors are subjected to repeated mating cycles. 
The locking capability of the releaseable latches eventually degrades as 
the number of cycles increase. 
Frictional retention of the terminals and/or the connector housings often 
is adversely affected in environments wherein the connectors are subjected 
to vibrations or thermal expansion which can lead to uncontrolled and 
undesired unmating of the connectors. Furthermore, a strictly frictional 
connection does not provide a sensory feedback to a user as to the 
complete mating of the connectors, thereby increasing the risk of open 
circuits and incomplete or partial mating in such applications. 
The present invention is directed to solving the myriad of problems 
outlined above by providing a positive connection between mating 
connectors by employing a removably latchable mating terminal structure 
that does not compromise the locking capability of the structure over a 
large number of mating cycles, yet still provides a sensory or tactile 
feedback upon complete mating of the component male and female terminals. 
SUMMARY OF THE INVENTION 
An object, therefore, of the invention is to provide a new and improved 
mating terminal structure for removably latching together a pair of 
electrical connecting devices or connectors. 
In the exemplary embodiment of the invention, the terminal structure 
generally includes a planar male blade terminal. A generally box-shaped 
female terminal receives the male blade terminal. The female terminal has 
a flexible cantilevered contact beam with a radiused contact portion 
adapted to be engaged and deflected by the male blade terminal upon 
insertion of the blade terminal into the female terminal in a given 
direction of insertion. 
The invention contemplates that the male blade terminal include an integral 
contact cam for engaging the radiused contact portion of the female 
terminal upon complete insertion of the blade terminal thereinto. The 
contact cam has a leading ramp surface extending at a relatively small 
acute angle relative to the direction of insertion for deflecting the 
cantilevered contact beams and engaging the contact portion thereof. The 
contact cam also has a trailing locking surface extending at a relatively 
larger acute angle relative to the insertion direction for providing 
locking interference between the contact portion of the cantilevered beam 
and the contact cam of the male terminal to thereby removably lock the 
male terminal to the female terminal. 
In the preferred embodiment of the invention, the male blade terminal 
comprises a stamped and formed sheet metal component with the contact cam 
integrally formed from a planar portion of the terminal. 
The cantilevered contact beam of the female terminal is complementarily 
shaped for receiving and interfacing with the male terminal. In 
particular, the cantilevered contact beam extends upwardly and rearwardly 
towards the contact portion of the female terminal from a bottom wall 
thereof at a relatively small acute angle relative to the direction of 
insertion of the male terminal for gradual engagement by the leading ramp 
surface of the contact cam. On the other side of the contact portion, the 
beam extends at a relatively larger acute angle relative to the insertion 
direction for locking engagement with the trailing locking surface of the 
contact cam. 
Lastly, the invention includes a connector assembly in which first and 
second dielectric connector housings respectively mount one or more of the 
disclosed locking male and female terminal structures. 
Other objects, features and advantages of the invention will be apparent 
from the following detailed description taken in connection with the 
accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings in greater detail, and first to FIG. 1, the 
invention is incorporated in a mating terminal structure, generally 
designated 10, which includes a generally planar male blade terminal, 
generally designated 12, and a generally box-shaped female terminal, 
generally designated 14. Male terminal 12 includes a tail portion 16 for 
coupling to a circuit trace on a printed circuit board, as will be 
apparent hereinafter. Female terminal 14 includes a pair of crimp arms 18 
for crimping or otherwise terminating to the conductors 20 of an 
electrical cable 22. 
More particularly, male blade terminal 12 is stamped and formed of 
conductive sheet metal material, with tail portion 16 forming a 
terminating end of the terminal, and a generally planar portion 24 forming 
the mating or blade end of the terminal. The planar portion of male blade 
terminal 12 includes a longitudinally extending reinforcing rib 26 and 
side tangs 28 for skiving into the plastic material of a connector housing 
to secure the terminal therein. The distal end of blade portion 24 is 
chamfered or tapered, as at 30, to facilitate insertion of the male 
terminal into female terminal 14 in a direction of insertion as indicated 
by arrow "A". Lastly, the male blade terminal incudes a contact cam, 
generally designated 32, formed out of planar portion 24 at the mating end 
of the terminal to be discussed in detail hereinafter. It is understood 
that the crimp arms 18 of female terminal 14 and the terminating end of 
the male terminal are exemplary only and that the terminals may include 
any such terminating ends known in the art. 
Female terminal 14 is formed of conductive sheet metal material and 
includes a box-shaped mating end defined by a top wall 34, a bottom wall 
36 and a pair of side walls 38 and function to center and guide male blade 
terminals 12 upon insertion into the female terminal. A flexible 
cantilevered contact beam, generally designated 42, is formed upwardly and 
rearwardly from a forward edge of bottom wall 36 within the box-shaped 
mating end of the terminal and toward the crimp arms 18 for engaging 
contact cam 32 of male terminal 12, as will be described hereinafter. A 
second pair of crimp arms 44 are located at the terminating end of female 
terminal 14 rearward of conductor crimp arms 18 for crimping onto the 
outer insulation or cladding 46 of electrical cable 22 to provide strain 
relief means therefor. 
Referring to FIG. 2 in conjunction with FIG. 1, flexible cantilevered 
contact beam 42 of female terminal 14 is generally U-shaped and includes a 
bottom leg 48 having a free end 50 for engaging the inside of bottom wall 
32, as at 52. A top leg 54 is cantilevered upwardly and rearwardly within 
the box-shaped female terminal from the front edge of bottom wall 36. 
Bottom and top legs 48 and 54 of the contact beam are joined by a curved 
or radiused contact portion 56. It can be seen clearly in FIG. 2 that this 
particular shape of contact beam 42 includes an angled surface 54a on top 
leg 54 which extends at a relatively shallow acute angle relative to the 
insertion direction of arrow "A" from one side of contact portion 56. On 
the opposite side of contact portion 56, the shape of the beam includes 
locking surface 56a which extends at a relatively larger acute angle 
relative to insertion direction "A". 
Still referring to FIG. 2, as stated above, male blade terminal 12 has an 
integral radiused contact cam, generally designated 32 protruding from 
planar portion 24. This contact cam is operatively associated with 
flexible cantilevered contact beam 42. More particularly, contact cam 32 
has a leading ramp surface 60 extending at a relatively small acute angle 
relative to insertion direction "A" for gradually deflecting contact beam 
42 and riding over angled surface 54a and contact portion 56 as the male 
blade terminal is inserted into the female terminal. Because of the 
relatively small acute angle of leading ramp surface 60 and the 
correspondingly small acute angle of surface 54a of the contact beam, 
relatively low insertion forces are required to insert the male terminal 
into the female terminal. The contact portion 56a of the contact beam may 
include an area of higher normal force for improved contact between the 
terminals in their mated condition. 
Contact cam 32 further includes a trailing locking surface 62 which extends 
at a relatively larger acute angle relative to the direction of insertion 
"A". The angled locking surface 62 is adapted for providing locking 
interference between contact portion 56 of cantilevered contact beam 42 
and contact cam 32 to thereby removably lock male terminal 12 to female 
terminal 14. 
The functional operation of contact cam 32 and the configuration of 
cantilevered contact beam 42 can be understood in FIG. 2 by noting that 
phantom line 66 represents a plane tangent to the mating interface between 
trailing locking surface 62 of the contact cam and locking surface 56a of 
contact portion 56 of the cantilevered contact beam. Arrow 68 represents 
an axis normal to tangent plane 66, i.e. the axis of the normal force 
between the mating terminals in response to a pulling force on male 
terminal 12 opposite insertion direction "A". Arrow 70 represents the 
component of normal force 68 extending parallel to insertion direction "A" 
which represents the locking force between the terminals. This 
configuration provides a reliable high contact force connection and allows 
unmating of the terminal structure at a relatively high threshold force 
but without risk of damage to the terminals because the terminals 
interengage on two radiuses (i.e. at angles other than zero degrees to 
axis 66). This radiused configuration actually facilitates mating of the 
connectors. In other words, the radiused configuration creates a "pull-in 
effect" due to the spring-back forces of cantilevered contact beam 42. 
Furthermore, due to the abrupt angles of trailing surface 62 of contact 
cam 32 and of locking surface 56a of contact beam 42, a sudden reduction 
of insertion forces is created during insertion of the male terminal, also 
due to the spring-back of the contact beam, to provide sensory feedback to 
a user that the terminals are fully mated. 
From the foregoing, it can be understood that the reliability of mating 
terminal structure 10 is assured by the mating profile described above, 
and the connection is robust against such conditions as vibrations and 
other inadvertent disconnections. The low mating force of the terminal 
structure combined with the larger unmating force avoids unintentional 
disconnections during use yet allows disconnection of the terminals 
without employing an actuating means such as a depressible cam, wedge or 
other releasing mechanism. 
FIGS. 3-5 show the sequence of insertion of male terminal 12 into female 
terminal 14 of terminal structure 10. Specifically, FIG. 3 shows male 
terminal 12 prior to insertion into the box-shaped mating end of female 
terminal 14. It can be seen that flexible cantilevered contact beam 42 of 
the female terminal is in an unstressed, non-deflected condition. 
FIG. 4 shows male terminal 12 partially inserted into female terminal 14, 
with contact cam 32 of the male terminal deflecting cantilevered contact 
beam 42. During this action, the contact cam rides over the contact beam, 
i.e. leading ramp surface 60 of the contact cam gradually deflects and 
rides over contact surface 54a of the contact beam with minimum insertion 
forces. The blade terminal is centered and guided into the female terminal 
by detents 40 in top wall 34 thereof. 
FIG. 5 shows male terminal 12 fully inserted into female terminal 14. This 
fully inserted position corresponds to the relative positions of the 
terminals shown in FIG. 2 and described in detail above. Whereas the male 
terminal was inserted into the female terminal in the direction of arrow 
"A" with minimum forces due to the smaller angles of surface leading range 
surface 60 and contact surface 54a of the male and female terminals 
respectively, in order to withdraw the terminal in the direction of arrow 
"B" (FIG. 5), significantly greater forces must be applied to overcome the 
locking forces created by the larger angles of surface 62 on the male 
terminal and locking surface 56a on the female terminal as described above 
in relation to FIG. 2. 
FIG. 6 shows an electrical connector, generally designated 70, typical of 
connectors found in the prior art. Very generally, the connector assembly 
includes a first connector 72 mounting a plurality of male terminals 74 
which have male terminal pins or blades 76 at mating ends of the terminals 
and tail portions 78 at terminating ends of the terminals. The tail 
portions are adapted for insertion into holes 80 in a printed circuit 
board 82 for coupling to circuit traces on the board and/or in the holes. 
Terminal pins 76 are adapted for insertion into mating ends 84 of female 
terminals 86 of a complementary mating second connector 88. The female 
terminals are connected to discrete electrical cables 90, similar to 
female terminal 14 described above. First and second connectors 72 and 88, 
respectively, of connector assembly 70 are positively locked together 
through the connector housings and by means of a latch arm 92 on connector 
72 having a hooked portion 94 for snapping locking engagement with a 
locking boss 96 on a latch arm 98 of connector 88. 
FIG. 7 shows a connector assembly, generally designated 100, wherein a 
receptacle connector 102 includes a dielectric housing 103 which mounts a 
plurality of the male blade terminals 12 described above in relation to 
FIGS. 1-4. A plug connector 104 includes a dielectric housing 105 which is 
adapted for insertion into a cavity 106 of receptacle connector 102. The 
plug connector mounts a plurality of the female terminals 14 described 
above in relation to FIGS. 104. According to the invention, connectors 102 
and 104 of connector assembly 100 are positively locked by the 
interengagement between male terminals 12 and female terminals 14, as is 
shown and described above and in FIGS. 1-5. 
Now, by comparing the connector assembly of FIG. 7 to the prior art 
connector assembly 71 of FIG. 6, it can be seen how the overall envelope 
size or profile of connector assembly 100 is reduced in comparison to 
connector assembly 70 which uses a locking system between the connector 
housings rather than directly between the terminals as is contemplated by 
the invention. 
It will be understood that the invention may be embodied in other specific 
forms without departing from the spirit or central characteristics 
thereof. The present examples and embodiments, therefore, are to be 
considered in all respects as illustrative and not restrictive, and the 
invention is not to be limited to the details given herein.