A terminal comprises an inner contact and an outer body. The inner contact is U-shaped and has a spring section positioned between a connection section and a contact section for resilient longitudinal movement of the contact section with respect to the connection section for preventing fretting corrosion. The spring section is comprised within side walls and a bottom wall whereby this U-shape is easy to stamp and form thereby increasing the ease of manufacture, which is particularly important from miniature terminals.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an electrical terminal having a longitudinal 
spring for preventing contact fretting corrosion. 
2. Description of the Prior Art 
In some applications, for example in the automobile industry, electrical 
terminals are subject to vibrations that cause small relative 
micro-movements between mating contacts, which in turn causes fretting 
corrosion therebetween thereby increasing the contact resistance. In order 
to overcome fretting corrosion, receptacle terminals have been provided 
with longitudinal springs, as shown in European patent application 492479, 
whereby the spring force is less than the frictional force between mating 
tab and receptacle connector so as to prevent relative movements 
therebetween. 
One of the problems with this design, however, is that it is difficult to 
manufacture due to the completely closed outer box shape, in particular 
for miniature contacts. A further problem with the receptacle of EP 
492479, is that the longitudinal spring action functions essentially by 
bending, in the direction perpendicular to the plane of the sheet metal, 
of a side wall of the box extending between ends of a transverse slot. 
This means that there is a certain rotational movement of the end portion 
of the box from which the contacts extend, thereby causing small 
micro-rotations of the contact arms. For reduced spring forces in the 
longitudinal direction, which is necessary for example when the contact 
forces are reduced for some reason, the rotational movements of the 
contacts will be increased. 
It would therefore be desirable to provide a receptacle terminal with 
improved anti-fretting characteristics. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide a terminal for reducing 
fretting corrosion, that is simple to manufacture, particularly for 
miniature contacts. 
It is another object of this invention to provide a cost-effective terminal 
with longitudinal spring means to avoid fretting corrosion, whereby 
micro-rotational movement of the contacts is reduced. 
The objects of this invention have been achieved by providing a terminal 
for receiving a complementary terminal inserted in that longitudinal 
direction, the terminal comprising an inner contact body having a contact 
section, a longitudinally resilient spring section, and a conductor 
connection section, where the spring section is positioned intermediate 
the connection and contact section, and wherein the inner contact body has 
a U-shape formed by a bottom wall and side walls whereby the 
longitudinally resilient spring section is comprised in the bottom and 
side walls. In an advantageous embodiment, the terminal has a box-shaped 
outer body positioned over the inner contact body and locked there.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring first to FIGS. 5 and 6, a receptacle terminal 2 comprises an 
inner contact body 4 and an outer box-shaped body 6. 
Referring now to FIGS. 1 and 2, the inner contact body 4 comprises a 
connection section 8 extending longitudinally into a U-shaped base section 
10, spring section 12 and contact section 14. The connection section is 
for electrical connection to a conducting wire (not shown) by crimping, 
but could of course be any other suitable connection means. The base, 
spring and contact sections 10, 12, 14 are stamped and formed into a 
general U-shape comprising a bottom wall 16 and a pair of opposed side 
walls 18 extending substantially perpendicular from lateral edges of the 
bottom wall. The base section 10 comprises upper edges 20 for clinching of 
the outer body 6 thereto as seen in FIGS. 5 and 6. 
The spring section 12 comprises two pairs of U-shaped resilient sections 
22, 24 on each side wall and extending into the bottom wall. The sections 
22, 24 each comprise a pair of resilient beams 26, 27 and 28, 29 
respectively, each pair connected at an upper end by U-shaped bridging 
portions 30, 32. Adjacent spring beams 27, 28 of the sections 22, 24 
respectively, are bent into base portions 34, 36 respectively which are 
joined together by a joining portion 38 comprised in the bottom wall 16. 
The spring beams 26, 27 and 28, 29 are separated by spring slots 40, 42 
respectively, that extend continuously from the bridging portion 30 in one 
side wall to the bridging portion on the other side wall. Further spring 
slots 44, 46 are provided between the spring arm 26 and the base section 
10 and between the spring arms 27 and 28 such that a long spring path is 
provided between the base section 10 and the contact section 14. A very 
compact yet supple spring in the longitudinal direction can thus be 
provided between the base and contact sections. 
The contact section 14 comprises forward portions 48 of the side walls 18 
from which extend rearwardly, opposed cantilever beam contact arms 50 that 
have free ends 52 proximate the spring section 12. As the cantilever beam 
contact arms 50 converge together, they provide a funnelled lead-in for 
guiding a complementary male tab terminal therebetween. 
The frictional force created by the pressure of the contacts 50 against the 
complementary male tab, must be greater that the longitudinal spring force 
of a spring section 12 to ensure that during relative movements between 
the base section 10 and the complementary male tab, the contact section 14 
remains stationary with respect to the complementary contact. The latter 
ensures that at the contact point there are no micro-movements thereby 
avoiding fretting corrosion. Due to the long spring path provided by the 
resilient beams 26-29 and the spring slots therebetween, the spring is 
very supple and can thus be easily made weaker than the frictional force. 
The longitudinal resilience is primarily a result of resilient bending of 
the beams 26, 27, 28, 29 within the plane of side walls 18, whereby the 
profiles of the beams and bridging portions can be designed such that no 
rotation of the contact section 14 occurs when it is extended or 
compressed in the longitudinal direction of the terminal. Micro-rotations 
of the cantilever beam contacts 50 can thus be reduced, thereby also 
reducing the effect on fretting corrosion. 
A further advantage of providing the spring section in the side walls 18 
and bottom walls 16, is the ease of manufacture, in particular for 
miniature terminals. The spring section can be simply edge stamped and 
then the side walls folded upwards from the base in a simple operation. It 
is far easier to form a U-shape than a closed box-shape as shown in 
European patent application 492479. 
Referring now to FIGS. 4-6, the outer stamped and formed body 6 comprises a 
box-shaped body section 56 having a base wall 58, side walls 60 and top 
walls 62 joined together at a seam 64. Extending rearwardly from a rear 
end of the box-shaped body section, are U-shaped retention tabs 66 that 
are folded over the upper edges 20 of the inner contact base section 10 to 
secure the outer body thereto. Proximate a rear end of the bottom wall 58 
is a retention hole 68 engageable with a protrusion 70 of the inner 
contact to further secure and position the outer body to the base section 
10. 
Resilient locking lances 72 are stamped out of the side walls 60 for 
securely retaining the terminal 4 within a cavity of an electrical 
connector housing. Ideally, the housing cavity and box-shaped body section 
56 would fit snugly together (at least at certain points) such that 
relative movement therebetween is minimal to prevent chattering of the 
terminal 4 within the housing. The spring end contact sections 12, 14 are 
however free to float within the body section 56, preferably with minimal 
contact against the body section such that vibrations to the body section 
56 are not transmitted to the contact section 14. 
A stress-limiting tab 74 is stamped from the base wall 58 of the outer body 
and is positioned in the spring slot 42 of the inner contact so as to 
prevent over-compression of the spring section 12 when inserting the male 
tab between the contacts 50. Without the latter, the spring section 12 may 
be damaged as the spring force is lower than the frictional force for the 
purposes of limiting fretting corrosion. During operation, i.e. after the 
first few cycles of vibration, the stress-limiting tab 74 will eventually 
be positioned in a substantially central portion of the slot 42 such that 
movements to the contact section 14 do not cause abutment with the tab 74. 
Protective flaps 76 are bent from the side walls 60 over lateral ends of 
the tab entry end 78 so as to provide a preliminary guide means for a 
mating male tab and to protect the forward portions 48 of the inner 
contact. 
Advantageously therefore, the terminal described herein is simple to 
manufacture, in particular for miniature contacts and also is particularly 
effective in avoiding relative movements of the contact section when mated 
to a complementary contact for avoiding fretting corrosion therebetween.