EP2517310B1

EP2517310B1 - Power contact

Info

Publication number: EP2517310B1
Application number: EP09807721.7A
Authority: EP
Inventors: Peter Nuetzel; Sylvia Weiss
Original assignee: Delphi International Operations Luxembourg SARL
Current assignee: Delphi International Operations Luxembourg SARL
Priority date: 2009-12-23
Filing date: 2009-12-23
Publication date: 2017-09-06
Anticipated expiration: 2029-12-23
Also published as: CN102714369A; WO2011077190A1; CN102714369B; EP2517310A1

Description

1. Field of the invention

The invention relates to power contacts designed to transmit high electrical powers by conducting electrical currents in the range of tens and up to hundreds of Amperes as they are needed e.g. in the field of electrical or hybrid vehicles.

2. Technical background

The growing field of electrical and hybrid vehicles demands for new solutions for mechanical and electrical components. In particular new power contacts are needed for transmitting large electrical powers in the order of kilowatts which translates into the capability of conducting electrical currents in the range of tens or hundreds of Amperes. However, such power contacts have to be nevertheless cheap and easily manufacturable in mass production.
Power contacts as used e.g. in automotive applications commonly comprise a contact terminal made from a piece of sheet metal (in this application, the sheet metal may be of copper alloy, aluminum, or any other appropriate conductive material), which is stamped and bent into a desired shape. On one end the contact terminal is usually provided with holding or crimping means for the attachment of a cable or a wire. The opposite end of the contact terminal is the actual contact portion and is usually provided with a pin reception member in the case of a female contact or a contact pin in the case of a male contact. The contact portion may also be at least partially covered by an additional and separate spring element to support the contact portion and improve the electrical and mechanical contact. Usually these contact terminals as well as the corresponding spring elements are shaped in essentially rectangular form. This naturally hinders relative rotation of the two members and therefore torsion forces between the contact terminal and the spring element are of minor importance. Additionally, in the common fields of application as for example signal transmission or general electronics the used power contacts are small pieces connected to cables of small diameter typically on the order of one or two millimeters. In electronic applications, of course, forces applied to the power contact e.g. by bending or twisting of the cable are negligible. However, for new applications as for example in the case of electrical or hybrid vehicles power contacts for the transmission of high powers in the range of kilowatts are needed. The therefore needed high voltages require a far higher resistance against electrical breakdown and therefore demand for cylindrically shaped connectors. From the further requirement to conduct large electrical currents, it follows that the connected cables need to be of large cross section, the conducting part without isolation having often a diameter well exceeding a centimeter. As opposed to the typical cables used in electronics or also in daily life, such cables are very inflexible and stiff. Thus, for example during assembly of the vehicle where cables have to be bent in different occasions as for example in the case that parts of the machinery behind the cables have to be accessed, large torsion forces are easily transferred to the power contact which is firmly connected to the stiff cable. As opposed to the case of rectangular power contacts which are composed of rectangular parts, in the case of a cylindrical power contacts the intrinsic barrier against relative rotation of the two members is missing. The large torque applied to the contact e.g. by the mechanic bending of the connected cable can therefore easily deform the additional spring element which is usually fixed in an insulating housing. Therefore new strong locking mechanisms are required which assure the connection of the power contact's members in the case of the occurrence of twisting and bending forces as described above.
Document DE 102 48 809 A1 describes a typical prior art electrical contact to be applied e.g. for signal transmission. It is made from two separate parts each made of sheet metal being stamped and bent into a rectangular shape forming the contact terminal and a hood. The contact terminal comprises a pin reception member on the one end adapted to receive a contact pin. The contact terminal comprises an essentially rectangular shape. In assembled form the essentially rectangular hood is mounted covering most of the contact terminal making use of latching elements.
Documents DE 89 15 087 U1 and EP 1 378 028 B1 disclose two examples of electrical contacts, intended to be used e.g. for signal transmission. They are very similar to the previous one with the main difference of being essentially cylindrical. They comprise two main portions - the actual contact terminal mostly covered by an essentially cylindrical hood. The cylindrical hood is mounted on the contact terminal only using latching elements which are bent following the curvature of the cylindrical hood. The latching elements are bent following the curvature of the parts.
The above described parts are examples of the commonly used contacts e.g. in signal transmission or general electrical applications. They are not suitable to be used for high power applications. As described above, in the case of high power applications cables of large cross section are required which are not very flexible. Therefore bending or twisting of those cables transmits large torques on the order to the power connector, bending and destroying the latching elements as they are described in the prior art documents. The multiple use of similar latching elements as described in the prior art documents to achieve a higher resistance against torques should be avoided in the case of high power applications. Indeed, the power contact would need to comprise additional holes for latching the additional latching elements. These additional holes would be a disadvantage for the conduction of large electrical currents. Additionally, such latching devices would provide more edges which can cause arcing and electrical breakdown and thus prohibit the needed use of high voltages.
WO03032450A1 discloses a power contact according to the preamble of claim 1.
One of the subjects of the invention is to provide a new power contact comprising a contact terminal and a spring element. It is a further object of the invention to provide a power contact to be used to conduct currents in the range of hundreds of Amperes and which allows the use of voltages in the Kilovolt range. Further it is an object of the invention to achieve all the above advantages with an inexpensive product, which preferably can be made from only two pieces of sheet metal mountable without any additional separate holding elements or welding operations to function properly.
These and other objects, which become apparent upon reading the following description, are solved by a power contact according to claim 1.

3. Summary of the invention

According to the invention a new power contact is provided comprising a contact terminal and an essentially cylindrical spring element. The contact terminal comprises a connection portion and a contact portion, where the connection portion serves for power connection, i.e. it is for example equipped with holding or preferably crimping means for the attachment of a power cable. In the preferred realization of the power contact as a female member, the contact portion is adapted for the reception of a preferably round contact pin. When the contact pin is correctly inserted, the electrical contact between a pin surface and the contact portion is preferably established by means of a circular assembly of contact spring arms (see below for explanation). The essentially cylindrical spring element is mountable on the contact terminal in an essentially coaxial fashion and preferably surrounds most part of the contact portion. In other words, the two members should share essentially the same longitudinal axis. When the two parts are assembled fastening mechanisms are required to hinder relative motions of the two members with respect to each other. According to the invention the spring element comprises at least one locking tongue which in the preferred embodiment is an essentially rectangular part bent inwards into a plane approximately perpendicular to the cylinder's longitudinal axis. The contact terminal comprises at least one stop edge which together with the the spring element's locking tongue blocks the relative rotation of the contact terminal and the spring element with respect to each other at least in one direction around their common axis. Of course the special shape of the locking tongue is of minor importance; its main purpose is to fit to the stop edge so that the relative rotation is blocked. In the preferred embodiment the contact terminal's stop edge is part of a stopping clearance which can be a rectangular clearance cut out for example of one end of the contact portion, in which the locking tongue fits to block the relative rotation of the two members in both directions.
The stronger locking mechanism according to the invention hinders the relative rotation of the two members of the power contact against torsion forces.
It is of importance to mention that above as well as in the following the meaning of cylindrical is not in the strict mathematical sense, but refers to the more or less round shape which results from bending a stamped piece of sheet metal. In the preferred embodiment the two halves of a piece of sheet metal are bent forming an essentially cylindrical tube with two open ends. It follows that "coaxial mounting" or "sharing the same axis" again, cannot refer to a mathematical definition but is meant in the sense of the definition of main directions.
In a preferred embodiment the electrical contact between the power contact and the correctly inserted contact pin is established by means of a preferably circular arrangement of contact spring arms. These contact spring arms are preferably oriented essentially parallel to the power contact's longitudinal axis and preferably comprise an inwardly extending bulge to provide a well-defined contact point improving the electrical and mechanical connection with the contact pin's surface. This arrangement preferably extends for example from a cylindrical support portion. In the preferred embodiment the spring element further comprises a stopping latch which in assembled condition is situated between two of the contact spring arms further hampering the relative rotation of the contact terminal and the spring element with respect to each other around their common longitudinal axis. Preferably the support portion further comprises a locking corner between neighboring contact spring arms which together with the stopping latch of the spring element blocks the relative linear motion of the two members at least in one direction parallel to the longitudinal axis of the power contact.
In a preferred embodiment the contact terminal further comprises an essentially half-cylindrical or half-conical intermediate portion between the connection portion and the contact portion and the spring element preferably comprises further at least one stopping lug which for example can be cut out of the spring element following its curvature. In mounted condition this stopping lug is adapted to be bent around one of the edges of the intermediate portion of the contact terminal.
The power contact is preferably adapted to be mounted in a connector housing. Therefore the spring element comprises a locking means to fix the position of the assembled power contact when it is inserted in the connector housing. Therefore, in the preferred embodiment the spring element comprises at least one latching wing adapted to snap behind a ledge of the housing when the power contact is mounted, blocking a movement of the power contact with respect to the housing preferably in the direction opposed to the insertion direction. The latching wing can for example be cut out of the spring element applying essentially a u-shaped cut, the two ends of the u facing in the insertion direction. Thus, the latching wing is bent outwards, and its free end faces the direction opposing the insertion direction. The spring element preferably comprises at least one second stop member adapted to interact with a stop shoulder inside of the housing limiting the linear movement of the power contact in the insertion direction; the stop member is also cut from the spring element and bent outwards but such that at least one of its edges opposes the insertion direction. Thereby these two stop members form an arrestor fixing the position of the power contact when it is mounted inside the housing.
The end of the spring element which is adapted to receive the contact pin comprises a plurality of tongues extending essentially parallel to the power contact's longitudinal axis and arranged essentially circular around this axis. These tongues comprise at least one portion which is bent inwards. In a preferred embodiment the relative rotation of the contact terminal and the spring element essentially around their common longitudinal axis is hindered for a torque up to 6 Nm, and a strength of up to 860 N at 1 meter, and the power contact allows to conduct a current of 250 A, with a voltage of up to 600V.
Further according to the invention the spring element's locking tongue is produced in a simple and inexpensive way: The features of the spring element are stamped into a piece of sheet metal and then bent forming the spring element tube. Hereby a tongue of metal inevitably is left connecting the spring element to a guiding portion which is a part of the sheet metal used for guiding the spring elements through the assembly line (for more details on the production process of contact terminals it is referred exemplarily to EP 1 128 476 B1 ). Instead of cutting the spring element leaving this tongue with the guiding portion, the tongue is kept part of the spring element. Bent essentially into a plane perpendicular to the spring element's axis it is used for the mechanism to block the relative rotation of the two members of the assembled power contact.

4. Description of the preferred embodiments

In the following, the invention is described exemplarily with reference to the enclosed figures, in which:

Fig. 1A is a schematic illustration of the spring element 10 in accordance with the invention still connected to the spring element guiding portion 30;
Fig. 1B is a schematic illustration of the spring element of Fig. 1 now disconnected from the spring element guiding portion 30;
Fig. 2A is a top view of the contact terminal 20 where the contact terminal 20 is still connected to the contact terminal guiding portion 32;
Fig. 2B is a perspective view of the contact terminal of Fig. 2A;
Fig. 3 shows the assembled power contact 50;
Fig. 4 shows the assembled power connector 50 upon insertion into a connector housing;
Fig. 5 shows a blank of the spring element 10 after stamping; and
Fig. 6 shows a blank of the contact terminal 20 after stamping.

In Figs. 1A and 1B a preferred embodiment of the inventive spring element 10 is shown. Preferably the spring element is made from a piece of sheet metal. In the figure the spring element 10 is still connected to the spring element guiding portion 30. The guiding portion 30 comprises a transport hole 31 to facilitate the transport through the assembly line. The spring element 10 is adapted to be cut off the spring element guiding portion in such a way that a preferably rectangular locking tongue 11 is left connected to the spring element. Fig. 1B shows this locking tongue 11 after it is cut off the guiding portion 30 and bent inwards essentially into a plane perpendicular to the spring element's axis. In the preferred embodiment the end of the spring element which is connected to the guiding portion 30 comprises further two stopping lugs 15 which are cut out of the spring element cylinder following the curvature of the cylinder. In the preferred embodiment the two lugs are bent inwards in a hook like manner and are adapted to be bent around the edges of the half cylindrical intermediate portion 22 of the contact terminal 20 (see Fig. 2A or 2B). In the preferred embodiment the end of the spring element 10 further comprises two latches 16 which are cut out of the spring element 10 similar to the two lugs 15 and which are likewise bent inwards following the curvature of the cylinder. In the preferred embodiment the spring element 10 comprises preferably on each side latching wings 13 which are preferably cut in a u-shaped fashion, the two ends of the u facing towards the end of the spring element which is not connected to the guiding portion 30. The latching wings 13 are bent outwards and adapted to snap behind ledges of a housing in which the power contact is mounted, thereby blocking a linear movement of the power contact 50 opposed to its insertion direction into the housing. Preferably, further on each side of the spring element 10 two pairs of stopping members 14 are adapted to block the linear movement of the assembled power contact 50 in the insertion direction (see Fig.4). Together with the latching wings 13 this constitutes an arrester fixing the position of the power contact 50 inside the housing in the assembled case. Note that due to the perspective, on the drawings the latching wing 13 on the back site is not visible as well as only part of the stopping members 14 can be seen. In the preferred embodiment the spring element comprises a plurality of tongues 18 situated at the end of the spring element which in the figure is facing away from the guiding portion 30. These tongues are oriented first parallel to the spring element's axis and then bent inwards. Figure 2A shows a top view of the contact terminal 20. It comprises a contact portion 23 which is adapted to receive a preferably round contact pin, a preferably half cylindrical or half conical intermediate portion 22 and a connection portion 21 which in the preferred embodiment is adapted to be connected to a power cable by crimping means. In the preferred embodiment the contact portion 23 comprises contact spring arms 27 which extend essentially in a direction parallel to the power contact's longitudinal axis preferably away from the essentially cylindrical support portion 24. Preferably the contact spring arms comprise bulges 28 oriented inwards to establish electrical and mechanical connection with the surface of a contact pin in the case of assembly. Every two pairs of contact spring arms 27 form a locking corner 29. Preferably, the side of the support portion 24 which faces away from the spring arms 27 comprises two stop edges 26, which in the preferred embodiment form a clearance 25. Figs. 2A and 2B further show the contact terminal guiding portion 32 and the corresponding guiding hole 33. Fig. 2B shows a perspective view of the contact terminal 20.
In Fig. 3 a possible embodiment of the assembled inventive power contact 50 is shown. The essentially cylindrical spring element 10 is mounted on the essentially cylindrical contact terminal 20 here covering most part of the contact portion 23. This view shows the blocking mechanisms which hinder a relative movement of the spring element 10 with respect to the contact terminal 20. The spring element 10 is mounted on the contact portion sliding the stopping latch 12 between two contact spring arms 27 until the stopping edge 12 reaches a locking corner 29 and further movement is blocked. In the shown embodiment the locking tongue 11 is bent inwards fitting between the two stop edges 26 and two stopping lugs 15 are bent around the edges of the essentially half cylindrical intermediate portion 22 of the preferred embodiment.
Figure 4 shows the assembled power contact 50. Here the connection portion 21 is crimped receiving a schematic connection cable 34. The power contact 50 can be mounted in a housing 40 which is only schematically shown in the figure to facilitate understanding. An arrow on the top of the figure points in the direction of inserting a possible contact pin inside the housing 40 when the power contact 50 is mounted.
Figure 5 shows the spring element 10 after being stamped out of the sheet metal before being bent into its final, essentially cylindrical shape. The features are described above.
Figure 6 similarly shows the contact terminal 20 after being stamped out of the sheet metal before being bent into its final, essentially cylindrical shape. The features are described above.
From Figs. 5 and 6 the skilled person will recognize how the members of the power contact can be produced from blanks of sheet metal in mass production.

Claims

Power contact (50) comprising a contact terminal (20) and an essentially cylindrical spring element (10), the spring element (10) being mountable essentially coaxially with a contact portion (23) of the contact terminal, the contact terminal (20) comprising at least one stop edge (26) while the spring element (10) comprises at least one locking tongue (11), providing a locking edge which together with at least one of the said contact terminal stop edges (26) blocks a relative rotation of the contact terminal (20) and the spring element (10) with respect to each other at least in one direction around their common axis,
characterized in that
- the contact terminal (20) comprises a connection portion (21) for power connection and said contact portion (23) adapted for the reception of a contact pin, this contact portion (23) being adapted for establishing an electrical connection with a surface of a contact pin when assembled; in that

- the spring element (10) covers most part of the contact portion (23) and the locking tongue is bent inward essentially into a plane perpendicular to the spring element's longitudinal axis; and in that

- the spring element (10) comprises latching wings (13) which are bent outwards and adapted to snap behind ledges of a housing in which the power contact is intended to be mounted.
Power contact according to claim 1, wherein the contact terminal (20) is adapted to receive a round contact pin.
Power contact according to any one of the preceding claims, wherein no welding points are intended for the assembled form of the contact terminal and its spring element.
Power contact according to any one of the preceding claims, wherein the stop edge (26) of the contact terminal is part of a stopping clearance (25) which together with at least one of the locking tongues (11) of the spring element (10) blocks a relative rotation of the contact terminal (20) and the spring element (10) with respect to each other around their common axis.
Power contact according to any one of the preceding claims, wherein the contact portion (23) comprises at least one, preferably multiple contact spring arms (27) oriented essentially parallel to the power contact's longitudinal axis, the contact spring arms (27) arranged essentially circularly around the longitudinal axis of the contact terminal (20).
Power contact according to claim 5, wherein the spring element (10) further comprises a stopping latch (12) which in assembled condition is situated between two of the said contact spring arms (27) of the contact terminal (20) further hampering the relative rotation of the contact terminal (20) and the spring element (10) with respect to each other around their common axis.
Power contact according to claim 5, wherein the contact terminal (20) comprises a support portion (24) from which the contact spring arms (27) extend such that this support portion (24) comprises at least one locking corner (29) between neighboring contact spring arms (27) and together with the said stopping latch (12) further blocks relative linear movement of the spring element (10) and the contact terminal (20) with respect to each other at least in one direction parallel to the longitudinal axis of the power contact.
Power contact according to any one of the preceding claims, wherein the contact terminal (20) comprises an intermediate portion (22) between the contact portion (23) and the connection portion (21), the intermediate portion (22) being shaped essentially in a half cylindrical form while the spring element (10) comprises at least one stopping lug (15) which is cut out of the spring element (10) following the spring element's curvature, adapted to be bendable around the edge of the intermediate portion (22) when the spring element (10) is mounted on the contact terminal (20).
Power contact according to any one of the preceding claims, wherein the spring element (10) comprises at least one latching wing (13) adapted to snap behind a ledge of a housing when the power contact is mounted inside a housing, the latching wing (13) being cut out of the spring element (10) applying essentially a u-shaped cut, the two ends of the u in insertion direction of the power contact when mounting in a housing; the latching wing (13) being bent outwards, and its free end facing the opposite direction.
Power contact according to any one of the preceding claims, wherein the spring element (10) comprises further at least one stop member (14) adapted to interact with a stop shoulder inside of the housing limiting the linear movement of the power contact in insertion direction, the stop member (14) is cut from the spring element (10) and bent outwards such that at least one of its edges opposes the insertion direction.
Power contact according to claims 9 and 10, wherein at least one latching wing (13) and at least one stop member (14) of the spring element (10) are used together forming an arrestor of the power contact inside a housing.
Power contact according to any one of the preceding claims, wherein relative rotations of the contact terminal (20) and the spring element (10) essentially around their common longitudinal axis are blocked for a torque up to 6 Nm.
Method for manufacturing a power contact in accordance with claim 1 comprising the following steps:
a) providing a first band of metal for production of the contact terminal (20), providing a second band of metal for production of the spring element (10);

b) stamping the features into the two sheets as needed to produce the two elements, while in both cases guiding portions (30,32) of each metal band are left unchanged to serve for continuation and guidance of the parts during production.

c) bending the parts into the desired shape;

d) cutting the spring elements (10) and contact terminals (20) off the guiding portions (30,32)
wherein
in the case of cutting the spring element (10) the spring element (10) is not cut at its edge but cut such that a metal tongue is left connected with the spring element (10) as locking tongue (11).