Electrical connector

An electrical connector is composed of a socket and a plug. The socket is made of fiat configuration which is capable of reducing the height or thickness along a direction of inserting the plug into the socket. The socket has a socket base (10) mounting contacts (20) with a slot (22). The plug having a plug base (30) which carries posts (40) extending perpendicular to the plug base. The post is adapted to have its end engaged into the slot (22) with the plug base (30) held in parallel with the socket base (10) for electrical interconnection between the post (40) and the contact (20). The contact (20) is made flat to have the slot extending generally in parallel with the planar socket base, thereby reducing the dimension of the socket along the inserting direction of the post.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is directed to an electrical connector, and more 
particularly to a plug-in type socket utilized in the connector. 
2. Description of the Prior Art 
A plug-in type socket generally comprises a socket base and contacts 
carried thereon for connection with associated conductors, i.e., pins or 
posts of a plug. Such socket and plug are known in prior electrical 
connector as disclosed. for example, in Japanese Utility Model Early 
Publication (KOKAI) Nos. 3-8885, 4-14382, and 4-129484. As illustrated 
generally in FIG. 17 of the attached drawings, the contacts 20A in the 
conventional socket 10A are generally designed to have slots 22A which are 
elongated in the direction of inserting the post 40A of the plug 30A with 
a correspondingly increased height dimension for the contacts and 
therefore the socket. With this result, the connector occupies a great 
height H between the socket and plug. Where only a limited height is 
permitted at electrical connection, for example, between connection of 
closely stacked printed boards, the above prior connector fails to satisfy 
such requirement. Therefore, a socket of reduced height is desired to 
enable the electrical connection within a space of limited thickness or 
height. 
SUMMARY OF THE INVENTION 
To satisfy the above requirement, the present invention has been achieved 
to provide an electrical connector having a socket of flat configuration 
which is capable of reducing the height or thickness along a direction of 
inserting a plug into the socket. The electrical connector in accordance 
with the present invention comprises a socket having a socket base (10) 
mounting contacts (20) with a slot (22), and a plug having a plug base 
(30) carrying posts (40) extending perpendicular to the plug base. The 
post is adapted to have its end engaged into the slot (22) with the plug 
base (30) held in parallel with the socket base (10) for electrical 
interconnection between the post (40) and the contact (20). The contact 
(20) is made flat to have the slot extending generally in parallel with 
the planar socket base, thereby reducing the dimension of the socket along 
the inserting direction of the post. 
In a preferred embodiment, the contact (20) is configured to have a pair of 
elongated legs (21) which defines therebetween the slot (22). The 
elongated legs (21) are formed at their free ends respectively with bulges 
(23) projecting to give a constriction at one end of the slot (22) between 
the legs so that the slot has a varying width along the length of the 
slot. The post (40) is configured to have a trunk (41) and a pilot (42) at 
an end of the trunk. The trunk and pilot are dimensioned to have a length 
extending along the length of the slot, a thickness along the width of the 
slot, and a height in the projecting direction of the post. The slot (22) 
has a wider section of which width W1 is greater than the thickness T1 of 
the trunk (41) and a narrow section at the constriction of which width W2 
is less than the thickness T1 of the trunk (41). The pilot (42) is tapered 
to have opposed inclined side faces (43) and have a reduced tip thickness 
T2 which is less than the width W2 at the narrower section. The pilot (42) 
is cut off at one longitudinal end portion thereof to define thereat a 
beveled edge (44) which is angled with a remaining square edge (45) at the 
tip of the pilot. The pilot (42) is in use adapted to be inserted into the 
slot (22) with the square edge (45) leading into the wider section and 
with the beveled edge (44) leading into the narrow section so that the 
post (40) is engaged at a portion adjacent the opposed inclined side faces 
(43) with the bulges (23). Thus, the pilot can be easily guided into an 
exact contacting position where the post is engaged at the portion 
corresponding to the beveled edge with the bulges at the narrow section of 
the contact after the square edge is smoothly led into the slot of wide 
section. This facilities the insertion of the post into the slot of the 
contact and lessens a force required to insert the pilot into the slot, 
which prevents buckling of the post and therefore assures reliable 
electrical connection over repeated connections and disconnections. The 
beveled edge is preferred to be inclined at an angle .alpha. of 30.degree. 
to 80.degree. with respect to the square edge (45) along the length of the 
pilot (42). The inclined side faces (43) are preferred to be inclined at 
an angle .beta. of 15.degree. to 45.degree. with respect to a vertical 
line extending along the height of the post (40). 
Further, each of the bulges (23) has a vertex which is continuous with a 
remaining inner edge (25) of said leg (21) through a slope (24) which is 
inclined at an angle .gamma. of 5.degree. to 45.degree. with respect to 
the inner edge (25) along the length of the slot. It is this slope that is 
cooperative with the inclined side face to smoothly guide the inclined 
side face into engagement with the bulge of the contact to further 
facilitate the insertion of the post into engagement with the contact. 
The electrical connector is best utilized for connection between closely 
stacked printed board without requiring additional height or thickness for 
connection between the printed boards. In this application, the socket and 
plug are surface-mounted respectively on first and second printed boards. 
To this end, the socket includes socket terminals which extend 
respectively from the contacts outwardly of the socket base and are 
adapted to be bonded to conductors on the first printed board. Likewise, 
the plug includes plug terminals which extend respectively from the posts 
outwardly of said plug base and are adapted to be bonded to conductors on 
the second printed board. Thus surface-mounted socket and plug allow the 
interconnection between the closely stacked printed boards. 
These and still other objects and advantageous features of the present 
invention will become more apparent from the following detailed 
description of the preferred embodiment when taken in conjunction with the 
attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIGS. 1 and 2, there is shown an electrical connector in 
accordance with a preferred embodiment of the present invention which is 
configured for electrical interconnection between a pair of stacked 
printed boards 1 and 2, although the present invention is not limited 
thereto. The connector is composed of a socket and a plug which are 
surface-mounted on the first printed board 1 and the second printed board 
2, respectively. The socket comprises a socket base 10 of electrically 
insulative plastic material into which plural sets of contacts 20 are 
press-fitted. The plug comprises a plug base 30 of electrically insulative 
plastic material into which plural sets of posts 40 are press-fitted. The 
socket base 10 is of a flat configuration which is formed, as shown in 
FIGS. 3 and 5, in its flat top surface with openings 11 through which the 
posts 40 project for connection with the associated contacts 20. 
Projecting on the bottom of the socket base 10 are studs 12 which are 
fitted into corresponding holes in the printed board 1. Each of contacts 
20 has a socket terminal 28 projecting horizontally outwardly of the 
socket base 10 for welding to a corresponding conductor on the first 
printed board 1, as best shown in FIG. 5. The plug base 30 is also of a 
flat configuration having a flat bottom which mates upon the top surface 
of the socket base 10. Like studs 32 project on top of the plug base 30 
for engagement into corresponding holes in the second printed board 2. 
Each post 40 of the plug has a plug terminal 48 projecting horizontally 
outwardly of the plug base 30 for welding to a corresponding conductor on 
the second printed board 2, as best shown in FIG. 8. The plug base 30 is 
formed at its opposite ends with hooks 33 which are in registration with 
corresponding notches 13 in the socket base 10 for latching engagement 
with shoulders 14 formed adjacent the notches 13, as shown in FIG. 6. 
As shown in FIG. 10, each contact 20 is stamped from a metal stock to have 
a pair of elongated legs 21 which defines therebetween a slot 22 to 
receive the post 40 of the plug and to have the socket terminal 28. The 
legs 21 are permitted to resiliently flex outwardly to some extent when 
engaging the post 40. The legs 21 are formed at their free ends with 
bulges 23 projecting toward each other to give a constriction at an outer 
end of the slot 22. The bulge 23 has its vertex continuous with a 
remaining straight inner edge 215 of the leg 21 through a slope 24 which 
is inclined at an angle .gamma. of 5.degree. to 45.degree. with respect to 
the straight edge 211 along the length of the slot 22. With thus 
configured legs 21, the slot 22 has a wider section of a width W.sub.1 
adjacent the root of the legs, a narrow section of a width W.sub.2 at the 
constriction, and an intermediate section of a width narrower towards the 
constriction along the slope 24. 
The post 40 of the plug is in the form of a blade having a length along the 
length of the slot 22, a thickness along the width of the slot 22, and a 
height along the inserting direction of the post. The post 40 comprises a 
trunk 41 of a uniform thickness of T.sub.1 less than width W.sub.1 at the 
wider section of the slot 22, and a pilot 42 formed at the end of the 
post. The pilot 42 is tapered to have opposed inclined side faces 43 and 
have a reduced tip thickness T.sub.2 which is greater than the width 
W.sub.2 at the narrower section. The inclined side face has an angle 
.alpha. of 15.degree. to 45.degree. with respect to a vertical plane, or 
the side face of the trunk 41. The pilot 42 is further configured to have 
a beveled edge 44 at one longitudinal end thereof in correspondence to the 
constriction of the slot 22. The beveled edge 44 is inclined at an angle 
.beta. of 30.degree. to 80.degree. and merges in a square edge 45 at the 
extremity of the pilot 42. 
When inserting the posts 40 into the slots 22 of the contacts 20, the 
square tip 45 is first led into the wider section of the slot 22 prior to 
the beveled edge 44 reaching the constriction at the narrower section of 
the slot 22. Subsequently, as the post 40 further advances, the inclined 
side faces 43 adjacent the beveled edge 44 are first to come into 
engagement with the slopes 24 of the bulges 23, at points S1 and S2 (as 
indicated in FIG. 15), thereby resiliently deforming the legs 21 outwardly 
to permit the pilot 42 to proceed into between the vertices (point F1) of 
the bulges 23, as shown in FIG. 14. Thereafter, the bulges 23 (point F1) 
are allowed to move past the inclined side faces of the pilot 42 along 
line S.sub.2 to F.sub.2 (as indicated in FIG. 15) to come into firm 
engagement with the trunk 41. In this manner, the posts 40 are firmly 
gripped with the corresponding contacts 20, as shown in FIG. 16.