Electrical connector requiring low insertion force

An electrical connector requiring low insertion force includes a connector housing having a terminal accommodating chamber; and a first terminal contained in the terminal accommodating chamber for engaging a second terminal. The first terminal has an elastic contact portion which is deflected towards one side having a slide-contact with the second terminal when the latter is inserted into the first terminal. The connector housing has a partition wall defining a flexure accepting space which allows the elastic contact portion to be deflected and a guide groove communicated with the flexure accepting space. The electrical connector further includes an urging member inserted into the guide groove through the flexure accepting space to urge the elastic contact portion towards the second terminal.

BACKGROUND OF THE INVENTION 
This invention relates to an electrical connector requiring low insertion 
force and, in particular, to an electrical connector terminal that is 
adapted to mate with a mating connector terminal with low force. 
Such an electrical connector requiring low insertion force can be found in 
the publication, Japanese Utility Model Laid Open No. 12563/1980. The 
connector comprises connector housings engaged with each other to position 
an inner pair of contact pieces against an outer pair of contact pieces. 
For this to occur a rotation lever is rotated allowing a cam body to make 
1/4 revolutions. The cam body thus makes contact with the inner pair of 
contact pieces, deforming them outward, forcing a connection with the 
outer contact pieces. Through this connection an electrical path is 
created. 
In the electrical connector described above, the inner pair of contact 
pieces do not slide on the outer pair of contact pieces when creating an 
electrical connection. Accordingly, there is no sliding resistance or 
friction between the contact pieces and thus little insertion force is 
required (low insertion force) to mate the terminals. However, this mating 
operation is useless against oxide films which can form on the back 
surface of the contact pieces. The reason being, it is impossible to strip 
such oxide films during engagement of the contact pieces because the 
contact pieces are not rubbed against each other. The presence of oxide 
films or adhesions such as dust on the surface of the contact pieces would 
thus tend to make electrical connections unreliable. 
To alleviate this problem, some connectors comprise contact pieces which 
slide against each other when making an electrical connection. This type 
of connector has, however, a disadvantage of requiring high insertion 
force. 
SUMMARY OF THE INVENTION 
Taking the above mentioned problems into consideration, an object of the 
present invention is to provide an electrical connector which requires a 
low insertion force and also enables the contact pieces to rub against 
each other, thereby increasing the reliability of the electrical 
connections. 
Another object of the present invention is to provide an electrical 
connector requiring a low insertion force while ensuring a desired contact 
pressure and good insertion performance. 
In order to overcome the above mentioned objects, the present invention 
provides an electrical connector requiring a low insertion force 
comprising a connector housing having a terminal accommodating chamber; 
and a first terminal contained in the terminal accommodating chamber for 
engaging a second terminal, the first terminal having an elastic contact 
portion that is deflected towards one side having a slide-contact with the 
second terminal when the latter is inserted into the first terminal, 
wherein the connector housing has a wall to separate a flexure accepting 
space that allows the elastic contact portion to be bent from a guide 
groove communicated with the flexure accepting space, the electrical 
connector further comprises an urging member inserted into the guide 
groove through the flexure accepting space to urge the elastic contact 
portion towards the second terminal. 
To use the electrical connector having the above mentioned structure, the 
connector housing is first engaged with a mating connector to insert the 
second terminal of the mating connector into the first terminal in the 
terminal accommodating chamber. In this event, the second terminal slides 
on and contacts with the elastic contact portion of the first terminal, 
thereby oxide films and dust on the contact surface are removed therefrom. 
The elastic contact portion is deflected and shifted towards one side when 
the second terminal is inserted into the first terminal. In this event, 
the elastic contact portion is allowed to be freely deflected into the 
flexure accepting space defined beside the elastic contact portion. This 
means that the elastic contact portion shifts into the flexure accepting 
space without causing high insertion force. Accordingly, repulsion caused 
by the elastic contact portion is less affected on insertion operation 
even when the connector has many terminals and thus the second terminals 
are inserted readily into the respective first terminals. 
Subsequently, the urging member is inserted into the guide groove. This 
insertion of the urging member forces the elastic contact portion towards 
the other side, which causes the elastic contact portion to contact 
strongly with the second terminal. As a result, the second terminal 
contacts with the corresponding elastic contact portion at a desired 
contact pressure. 
In the preferred aspect of the present invention, the connector housing 
further comprises a locking arm that is deflected before completion of 
engagement to mate the connector housing with the mating connector and 
that is restored on completion of engagement to provide a locking state, 
the urging member serves to prevent the locking arm from being deflected 
when it is inserted into the guide groove. 
In the preferred aspect having the above mentioned structure, the locking 
arm is deflected when the engagement is not completed, thus preventing the 
urging member from being inserted into the guide groove. This indicates 
that the connector housing is not completely mated with a mating 
connector. 
These and other objects and features of the present invention will become 
more fully apparent from the following description and appended claims 
taken in conjunction with the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A embodiment of the present invention is now described with reference to 
the drawing. Throughout the following detailed description, numerals refer 
to the corresponding elements in all figures of the drawing. 
In FIGS. 1 through 3, an electrical connector 10 comprises a connector 
housing 11 having multiple terminal accommodating chambers 12. The 
terminal accommodating chambers 12 are banked up, i.e., arranged into an 
upper bank of sockets and a lower bank of sockets. These socket banks are 
separated by a partition 13 composed of two walls 13a and 13b. A guide 
groove 14 is defined between the walls 13a and 13b. The central portion of 
the partition 13 along the longitudinal direction has a gap to form a 
flexure accepting space 15 described below. 
A locking arm 16 is provided on an external surface of an upper wall 11a of 
the connector housing 11. The locking arm 16 has a front portion 
cantilevered by the connector housing 11 and extends backward and parallel 
along the upper wall 11a, and is freely deflected downward. When the 
connector 10 according to the present invention is engaging with the 
mating connector, the locking arm 16 deflects downward and is restored on 
completion of engagement to provide a locking state. A flexure accepting 
space 17 is defined between the locking arm 16 and the upper wall 11a of 
the connector housing 11 to enable sufficient bending of the locking arm 
16. 
Female terminals 20 are inserted from the rear of the respective terminal 
accommodating chambers 12 and secured. Each female terminal 20 is provided 
with an elastic contact piece 21 that slides against a corresponding 
contact piece from a mating male terminal 30 when the latter is inserted 
into a female terminal 20. The elastic contact piece 21 has, as best shown 
in FIG. 2, a cantilevered front end which extends backwards. It is bent 
entirely and formed into an approximate U-shape or C-shape. The elastic 
contact piece 21 comprises a first curved portion 21c, a U-shaped turning 
portion 21d, a second curved portion 21e and an up-turned edge portion 
21f. The first curved portion 21c is extended backward from a supporting 
portion 21a such that it is shaped into a convex shape in the direction 
towards a male terminal 80. The U-shaped turning portion 21d flows from 
first curved portion 21c. The second curved portion 21e is extended 
forward from the turning portion 21d such that it is bent into a convex 
shape towards the partition 13. The up-turned edge portion 21f flows from 
the second curved portion 21e. In addition, an opening 20a is formed in 
the bottom of the female terminal 20 from which the second curved portion 
21e and the up-turned edge portion 21f of the elastic contact piece 21 is 
projected outward. 
The partition 13 has a gap at the sides of the elastic contact pieces 21 to 
provide the flexure accepting space 15 adjacent to the opening 20a. The 
female terminals 20 are inserted into the upper and the lower banks of the 
terminal accommodating chambers 12 with the flexible portions opposing 
each other. When this is done, the female terminals 20 are so arranged 
that the second curved portion 21e is positioned into the flexure 
accepting space 15. 
An urging member (slider) 40 is inserted into the guide groove 14 defined 
between two walls 13a and 13b composing the partition 13. The slider 40 
can move in the forward and backward directions. The slider 40 is formed 
into a plate as shown in FIGS. 4 and 5 and is provided with an operation 
portion 41 at the rear end. To move this operational portion 41 into 
receiving slits 18 and 19 (see FIG. 1) are formed in the connector housing 
11. 
Operation is now described below. 
To use the electrical connector 10, first, the male terminals 30 are 
inserted into their respective female terminal 20 by connecting the mating 
connector to the electrical connector 10. During insertion, each of the 
male terminals 30 slides against and makes electrical contact with the 
first curved portion 21c of the elastic contact piece 21. During this 
operation, male terminal 30 applies a force on the elastic contact piece 
21, deflecting it with the supporting point 21a as a fulcrum. This slide 
contact contributes to the removal of the oxide films on the contact 
surface. The deforming elastic contact piece 21 is located in the flexure 
accepting space 15, so that the deformation can proceed uninhibited. In 
other words, the elastic contact piece 21 bends freely into the space 15 
(towards the one side). As a result, a low insertion resistance is 
generated and it is possible to easily insert the male terminals 30 into 
the respective female terminals 20 without a large amount of opposition 
from the elastic contact piece 21 even when the connector has many 
terminals. 
Next, the slider 40 is inserted into the connector 10. The slider 40 moves 
across the flexure accepting space 15 as indicated by the broken line in 
FIG. 1. The slider 40 then slides against the second curved portion 21e of 
the elastic contact piece 21 that has already been shifted into the 
flexure accepting space 15. As the slider 40 is inserted into the slide 
groove 14, the elastic contact piece 21 is forced back towards the male 
terminal 30 (away from the slider 40). The elastic contact piece 21 is 
pressed firmly against the male terminal 30. As a result, the male 
terminals 30 and the elastic contact pieces 21 contact with each other at 
a desired contact pressure. 
On inserting the slider 40 into the slide groove 14, the upper end of the 
operational portion 41 of the slider 40 moves into the flexure accepting 
space 17 located under the locking arm 16. If the connector 10 is 
"half-engaged" with the mating connector housing, the locking arm; being 
deflected into the flexure accepting space 17; will prevent the 
operational portion 41 of the slider 40 from full insertion. This 
indicates that the connector is not completely mated with the mating 
connector. 
The following is a description of the contact pressure between the male and 
female terminals 30 and 20 caused when the male terminal 30 is inserted 
into the female terminal 20. 
FIG. 6 and 7 show an elastic contact piece 50 and the elastic contact piece 
21, respectively, according to the present embodiment. The elastic contact 
piece 50 is approximately equal in structure and in configuration to the 
elastic contact piece 21 as illustrated. The only difference between the 
two configuration is that the elastic contact piece 50 has a wall 51 which 
resists movement in the vertical direction. 
FIGS. 7A and 7B show the elastic contact portion according to the present 
embodiment. This elastic contact portion has no flexure restriction wall 
and the flexure accepting space 15 is provided adjacent with the side of 
the second curved portion 21e. 
For the purpose of comparison, the male terminals are inserted into the 
respective female terminals each of which has either one of these two 
kinds of elastic contact pieces 50 and 21. FIG. 8A shows contact loading 
as a function of displacement (insertion amount of the slider) when a male 
terminal is inserted into a female terminal and FIG. 8B shows displacement 
(insertion amount of the slider) as a function of contact loading when the 
slider 40 acts on the elastic contact piece 21 according to the present 
embodiment. 
Using the elastic contact piece 50 as a comparative example, the contact 
loading indicated by "a" in FIG. 8, over a displacement "C", is caused 
when the male terminal is inserted into the female terminal. High 
insertion force is necessary due to this high loading vs. displacement 
relationship. This is because a cantilever spring as shown in FIG. 6A acts 
as if it is a center-spring, because of the restricting wall 51. 
On the contrary, the elastic contact piece 21 of the present embodiment as 
shown in FIGS. 7A and 7B has no flexure restriction wall. Thus, it is left 
to be operated as the cantilever spring to yield the contact loading as 
indicated by "b", over a displacement "C". Accordingly, the difference 
between a and b corresponds to the difference between the loading of the 
cantilever spring and the center-spring. After completion of engagement of 
the male and female contacts, insertion of the slider into the slide 
groove causes a different loading as indicated by "d" in FIG. 8B, over a 
displacement "e". The value of d is equal to the value obtained by 
subtracting b from a, i.e., a-b, so that the resultant total loading is 
b+d or b+(a-b) which equals "a". The total loading obtained in the 
comparative example, as illustrated in FIG. 6, is equivalent to the 
loading "a". This means that the contact performance of this new connector 
design is equal to that of the comparative connector. However, the load 
vs. displacement relationship for the new design has a smaller value than 
that of the comparative connector, so there is a lower insertion force 
required. It is noted that the slider 40 is made of a resin having a small 
friction coefficient so that the force required to insert the slider is 
significantly low. 
The elastic contact piece 50 with a restrictive wall 51 present (shown in 
FIG. 6) exhibits the characteristic curve of loading said indicated by 
"A"; while curves "B" and "C" show the loading of the elastic contact 
piece 21, where there is no restrictive wall 51, is an example of the 
performance of flexure accepting space 15. As apparent from the figure, 
only the contact loading of B is required for inserting the male terminal 
into the female terminal. In other words, the insertion force is 
relatively low addition, the contact loading applied is equivalent to the 
sum of B and C over a distance c and e, respectively, when the slider 40 
is inserted into the slide groove 14 after mating the male and female 
terminals. Accordingly, it is possible to maintain a sufficient amount of 
contact pressure. 
It should be understood that the present invention is not limited to the 
particular embodiment shown and described above, and various changes and 
modifications may be made without departing from the spirit and scope of 
the appended claims.