EP0694991A1

EP0694991A1 - Dual material electrical contact

Info

Publication number: EP0694991A1
Application number: EP95111774A
Authority: EP
Inventors: Bernhard Egenolf; Jochen Horn
Original assignee: Whitaker LLC
Current assignee: Whitaker LLC
Priority date: 1994-07-27
Filing date: 1995-07-26
Publication date: 1996-01-31
Also published as: KR960006150A; GB9415160D0; JPH0864286A

Abstract

An electrical receptacle terminal (2) comprises a wire connection section (6) and a contact section (4). The wire connection section (6) is for crimping to a conducting wire by way of a crimp barrel (8) and strain relief crimp arms (10). The connection section (6) further comprises an attachment portion (14) for interference fit or laser weld connection to the contact section (4). The connection section material is chosen for optimal crimping to conducting wires, and the contact section (4) can be chosen as a resilient material for high contact pressure against a mating terminal and high strength of the locking lances (22). The two part terminal thus allows optimal choice of materials for the required functions of high contact pressure or good crimping qualities in a very compact, cost-effective design.

Description

This invention relates to an electrical terminal comprising a spring beam contact portion and a wire connection portion that are separate parts assembled together, each part having a different material or material that is differently processed.
It is common to find electrical terminals with inner contact bodies of a first material suitable for crimping to a conducting wire, and an outer back-up spring for assisting in providing contact pressure of the inner body contact arms against a mating terminal. The outer back-up spring typically also provides the function of locking the terminal within a connector housing by providing resilient locking lances. The inner contact body must be suited to good electrical contact with a wire to be crimped to, most metals for this function being relatively ductile and having insufficient spring properties, in particular when subject to heat and mechanical solicitation over time. The outer back-up spring ensures that a certain contact force is provided over the life of the contact, whereby this spring material (e.g. stainless steel) cannot be used for crimping due to it's high resiliency. The inner contact body material cannot be chosen optimally for crimping, but rather is a compromise between spring and crimping properties, as the inner contact body must also have sufficient spring force for contacting a mating terminal the back-up Spring only providing spring assistance.
The cost of manufacturing such a contact is relatively high, and the outer back-up spring reduces the compactness of the design. It is however desirable to provide a compact and cost-effective terminal that has excellent crimping properties but also good spring contact properties such that contact pressure against the mating terminal is high and maintained over the lifetime of the terminal subject to thermal and mechanical solicitation.
It is therefore an object of this invention to provide a cost-effective, compact and reliable electrical terminal for optimal connection to a conducting wire and optimal connection to a mating contact.
It is an object of this invention to provide an electrical terminal with a resilient contact section with good spring properties and a wire connection section with good wire connection properties in a simple and reliable manner.
The objects of this invention have been achieved by providing an electrical terminal having a resilient contact section for resiliently contacting a complementary mating terminal, and a wire connection portion for electrical connection to a conducting wire, characterized in that the contact portion is made out of a first resilient material, and the connection section is made of a second material adapted for connection to a conducting wire.
The connection and contact sections may be mechanically and electrically held together by welding or by interference fit as described in certain embodiments of this invention. The contact and connection sections can, in a first embodiment, be made from different metals having the required spring and crimping properties respectively, or in a second embodiment the metal could be the same but having a different temper such that the spring properties of the contact and connection sections are different.
The preferred embodiment of this invention will now be described with reference to the figures, whereby:

Fig. 1: is a side view of an electrical terminal according to this invention;
Fig. 2: is a view through lines 2-2 of Fig. 1;
Fig. 3: is a cross-sectional view through lines 3-3 of Fig. 1;
Fig. 4: is a cross-sectional view through another embodiment of this invention.

Referring First to Figs. 1-3, an electrical terminal 2 is shown comprising a resilient contact section 4 and a wire connection section 6. The wire connection section 6 comprise- a crimping barrel 8 for crimping to bared conducting strands of a conducting wire, and strain relief crimp arms 10 for wrapping around the outer insulation of the conducting wire for retention thereto. The wire connection section 6 further comprises a base portion 12 extending from the crimping barrel 8 towards the contact section 4 into an attachment portion 14 for mechanical and electrical connection to the contact section 4. The contact section 4 comprises a complementary attachment portion 16 for mechanical and electrical interconnection to the crimp barrel attachment portion 14, the attachment portion 16 extending through a U-bend 18 to side walls 28 of a contact body section 20. The contact body section 20 has resilient locking lances 22 stamped therefrom, and a resilient contact section 24 extending axially therefrom. The contact portion 24 comprises a pair of resilient opposed cantilever beams 26 for resiliently receiving a mating tab contact therebetween.
The contact section attachment portion 16 extends from side walls 28 of the contact body 20, and are folded into the contact body and formed into opposing arcuate profiles as best seen in Fig. 3. The connection section attachment portion 14 is formed into a cylinder with a seam 30 resulting from the folding together of the sheet metal into the cylindrical shape. The attachment portion 14 cooperates with the resiliency of the attachment portion 16, whilst nevertheless being relatively stiff such that the attachment portion 14 can be inserted between arcuate walls 29 of the attachment portion 16 in a resilient interference fit. The strength of the interference fit can be increased by extending the walls 29 of the attachment portion 16 within the contact body such that they are supported against an inner face 32 of the contact body side walls 28, as shown by the extension 31. The contact section and connection sections can thus be assembled together in a simple manner by merely inserting the connection section attachment portion 14 into the contact section attachment portion 16.
The terminal as described above thus allows the connection section 6 to be made of a different material from the contact section 4 whilst nevertheless avoiding positioning of an outer back-up spring around the contact section 4 for increasing the contact pressure of the contact spring arms 26. The contact section 4 can be chosen from a spring material that is resistant to thermal and mechanical solicitation of the contact. The resiliency of the contact section material is also beneficial for the locking lances 22 as it will thus have higher strength than if made from the connection section material. The connection section 6 material is chosen to have a relatively high ductility such that the crimping barrel 8 can be easily plastically deformed around conducting strands of the conducting wire, this plastic deformation allowing not only good electrical connection with the strands, but also reducing wear of the crimping tool. The material of the contact and connection sections can either be different materials with possibly different thicknesses, or they could be of the same metal but having been processed differently: for example the contact section material could have a different temper giving it a higher resiliency than the connection section material.
Referring now to Fig. 4, another embodiment of this invention is shown whereby the attachment portion 14' of the connection section 6' is inserted directly contiguous the inner surface 32' of the contact body 20' of the contact section 4'. In this embodiment, the attachment section 14' has a box-shaped cross-sectional profile complementary to the box-shaped inner periphery 32' of the contact body 20'. The contact and connection sections 4', 6' are welded together with laser welds 40 therebetween, for a very rigid mechanical interconnection, but also electrical interconnection between the contact and connection sections.
Advantageously therefore, use of an outer steel backup spring is unnecessary, thus allowing the contact to be very compact and cost-effective. Furthermore, in the typical contact with a steel back-up spring, the back-up spring only provides an added 30 % contact force, and therefore the inner contact material must nevertheless have sufficient resiliency. There is therefore a compromise between the ductility required by the crimping barrel and the resiliency required by the contact spring arms. In the- contact as describe d hereinabove, the crimping barrel material can be chosen more optimally than in the case of conventional contacts, whereby the contact section material can be chosen to have optimal spring qualities such that an outer back-up spring is not required thus producing a terminal with very high contact force whilst nevertheless very good crimping properties. Additionally, the latter causes reduced wear of the crimping tools. This invention is also more compact than conventional terminals.

Claims

A stamped and formed electrical terminal comprising a connection section (6) having a crimping barrel (8) for crimping to a conducting wire, and a contact section (4) having an axially extending contact body (20) and resilient contacts (24) extending therefrom for electrical connection to a mating terminal, characterized in that the contact section (4) is made of a first conducting material and comprises an attachment portion (16, 16') and the connection section is made of a second conducting material and has an attachment portion (14, 14') complementary to the contact section attachment portion (16, 16') for mechanically and electrically interconnecting the contact and connection sections, the contact and connection section being separate parts wherein the material of the contact section has good resilient properties for providing high spring force to the contacts (24), and the material of the connection section has good crimping qualities for plastic deformation thereof around the conductor.
The terminal of any preceding claim characterized in that the contact body (20, 20') is box shaped and the contacts are opposed cantilever beam arms (26) extending therefrom in the axial direction, the contact body (20, 20') substantially fully receiving the connection section attachment portion (14, 14') therein for electrical and mechanical connection thereto.
The terminal of claim 1 or 2 characterized in that the attachment portions (14, 16, 14', 16') are disposed substantially within the contact body (20, 20').
The terminal of claims 1, 2 or 3 characterized in that the contact section attachment portion (16) comprises arcuate profiled walls (29) extending in the axial direction of the contact body (20).
The terminal of claim 4 characterized in that the attachment portion walls (29) are bent through U-shaped portions (18) into the contact body (20) and extend from opposed side walls (28) thereof.
The terminal of any preceding claim characterized in that the connection section attachment portion (14) has a cylindrical shape extending in the axial direction of the contact body (20).
The terminal of any preceding claim characterized in that the attachment portions (14, 16) are interference fit together.
The terminal of any of claims 1-3 characterized in that the attachment portions (14', 16') are welded together.
The terminal of claim 8 characterized in that the inner contact body is box-shaped and contiguous a substantial part of an inner surface (32') of the contact body (20').