GB2162701A

GB2162701A - An electrical connector

Info

Publication number: GB2162701A
Application number: GB08512091A
Authority: GB
Inventors: Leslie Trevor Adshead; Fred Torr
Original assignee: TYTAN Ltd
Current assignee: TYTAN Ltd
Priority date: 1984-06-21
Filing date: 1985-05-13
Publication date: 1986-02-05
Also published as: GB8512091D0

Abstract

An electrical connector for use in arc welding comprises a magnet (14) of generally cup-shape configuration secured by a screw (15) to an electrically conductive housing body (11) having a surrounding annular face (12) substantially coplanar with the end face of the rim of the cup-shape magnet. A cable, such as an earthing cable, is connected to the housing. The magnet is made from a material incorporating a high proportion of cobalt having a low temperature coefficient and resistant to both high temperatures and substantially unaffected by the high welding current which flows therethrough in operation. <IMAGE>

Description

SPECIFICATION An electrical connector The present invention relates generally to an electrical connector, and particularly to an electrical connector for making a temporary connection between a cable and an electrically conductive article or component.

There are many circumstances where a temporary electrical connection may be required, and such connections are usually made by means of spring loaded clips which act to retain the electrically connected components by resilient mechanical action. Such clips require there to be available an edge or narrow part of the component or article to which the clip is connected since the jaw has a limited width.

For use on components having extensive flat surfaces such connectors are inconvenient since they require excessively long connecting cables to reach the nearest adjacent edge.

A requirement for such temporary connection arises particularly when using electric arc welding techniques, but other occasions also arise when temporary electrical connections are required and could be effected using the techniques of the present invention. However, the present invention will be described with particular reference to its application to welding technology although no loss of generality is intended to be occasioned thereby.

According to one aspect, therefore, the present invention provides an electrical connector for making a temporary connection between a cable and an electrically conductive ferromagnetic surface, comprises a magnet housed in an electrically conductive body electrically connected to the said cable, the magnet and/or body having an exposed face for contact with the said surface.

Preferably, although not exclusively, the magnet is a permanent magnet which may in some embodiments be reinforced with an electromagnet energised by the current flowing through the cable. The permanent magnet may then be used for effecting a preliminary attachment which provides an electrical path through the cable and the component to which the connector is attached. When the current flows in the electromagnet it reinforces the permanent magnet to generate an attractive force securely holding the connector in place. The force applied by the electromagnet may be sufficient, for example, to resist vibration or manual separation of the components.

In a preferred embodiment of the invention the magnet is generally cup-shaped with a circular rim and secured in a cavity in the housing by fixing through the bottom wall of the magnet leaving the rim thereof exposed, and preferably coplanar with the face of the housing in which the magnet is secured. A circular contact face has been found to be particularly suitable for the purpose.

The housing is preferably an electrically conductive non- magnetic material such as brass or aluminium or an alloy of one or both these metals, and the magnet may be positioned therein such that the exposed face of the magnet is slightly recessed from the contact face of the housing so that secure electrical contact between the housing and the article to which electrical connection to be made is effected and maintained by the magnetic attraction between the magnet and the article, but electrical contact is made between the housing and the article. For such an arrangement to work satisfactorily an extremely powerful magnet is required, but it has the advantage that the magnet is not harnessed by the electric current, nor subject to the direct heating effect thereof.In the preferred embodiment, however, the magnet is made from a material capable of withstanding high temperatures without losing its magnetisation. Such a material preferably includes a composition comprising cobalt and iron. One suitable composition capable of resisting the high temperatures involved comprises the following: Cobalt ...... 29% Nickel ...... 15% Aluminium 7% Copper ...... 4% Titanium ...... 4% Niobium ...... 2% Iron ..... balance It is believed that the temperature resistance of this compound is largely attributable to the cobalt in the composition. Such a magnet may be made by casting, or sintering, or, if other materials such as rare earths are included, the process may comprise sintering and bonding.A typical reversible temperature coefficient of -0.02"C has been noted with a magnet being the composition set out above.

Another suitable composition for the magnet is one with an even higher proportion of cobalt and no niobium. Such a composition may comprise: Cobalt ...... 34% Nickel ...... 15% Aluminium 7% Copper ...... 4% Titanium ...... 5% Iron ...... Balance The force applied by the permanent magnet between itself and a ferromagnetic article, may be sufficiently great to resist direct manual separation. The force applied by a magnet of this type is sometimes referred to as the "pull" of the magnet and such magnets having a "pull" of up to 25 kilogrammes are commercially available.

The dimensions of such magnets having a composition such as that outlined above are such that they can be housed within a casing sufficiently small to be gripped by one hand. Preferably, the casing is shaped so that even so such a high force cannot always easily be applied and, for this reason, a specific embodiment of the invention is provided with a release face inclined at a shallow angle with respect to the contact face in such a way that the line of intersection of the two faces constitutes a fulcrum about which the casing can be rocked in effecting release of the magnet from the component. Moreover, for special purposes, such as attachment of the connector to spherical or cylindrical surfaces, contact faces having correspondingly shaped spherical or cylindrical forms may be provided.

Two embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure t is a perspective view of a releasable electrical connector formed as a first embodiment of the present invention; Figure 2 is a sectional side view of a connector iilustrated in Figure 1; Figure 3 is a view in the direction of the Arrow A of Figure 2; and Figure 4 is a side view of a second embodiment of the invention.

Referring first to Figures 1 to 3 of the drawings, the connector shown comprises a body generally indicated 11 made from brass or cast aluminium or an alloy including one or comprising both of these metals having a flat lower face 12 with a recess 13 housing a shallow so-called pot magnet 14 secured in the housing 11 by a countersunk screw 15. The space 16 within the pot magnet may be left empty or may be filled with a resin or other magnetically permeable filler to prevent the accumulation of dust and dirt.

The casing 11 also has a bore 17 for receiving a cable 18 which can be clamped in place by a clamping screw 19 passing through a threaded opening 20 in the upper face of the casing. The material of the magnet comprises the following constituents: Cobalt ... 29% Nickel ...... 15% Aluminium 7% Copper ...... 4% Titanium ...... 4% Niobium ...... 2% Iron ...... Balance Such magnets are commercially available, for example from Swift Levick Magnets Ltd., of Sheffield, and are sold under the trade name HYCOMAX 2.

The connector described above is particularly suitable for use as an earth connector for electric arc welding because the magnet provides a good electrical connection and can resist the high temperatures involved, and the partial arcing from imperfect face-to-face contact, without demagnetisation or physical degradation of the contact face.

The cable 18 is constituted by the normal earthing cable provided for arc welding purposes, which according to conventional welding techniques would otherwise be provided with a crocodile clip. When gelding flat panels or extensive surfaces, however, crocodile clips have the disadvantage that they can only be attached to an edge and the earth clamp of the present invention offers the significant advantage that it can be positioned easily anywhere over the surface being welded to provide an easily made and secure electrical connection. A large part of the electric current passes through the casing and not the magnet if the rim 12 is accurately coplanar with the end face of the rim 14 of the magnet.

In the alternative embodiment (illustrated in Figure 4) the magnet material is as follows: Cobalt ...... 34% Nickel ...... 15% Aluminium 7% Copper ...... 4% Titanium ...... 5% Iron ...... Balance Such magnets may be obtained commercially from Swift Levick Magnets Ltd., of Sheffield under the trade name HYCOMAX 3. These magnets have a higher energy product than the hycomax 2 magnets and for much the same dimensions can provide a significantly greater attractive force. In this embodiment the flat face 12 of the casing 11 is supplemented by an additional face 21 at a shallow angle a with respect thereto and the casing 11 projects over this face enabling it to be rocked about a fulcrum constituted by the line of intersection of the two planes.

The present invention also comprehends a method of electric arc welding in which the earthing connection is made by magnetically retaining a contact face of a connector to a work piece, the connector and the magnet having electrically conductive properties and a temperature coefficient such as to enable sufficient current to pass for welding, whilst having a low contact resistance with the metal being welded.

Claims

1. An electrical connector for making a temporary electrical connection between a cable and an electrically conductive ferromagnetic surface, comprising a magnet housed in an electrically conductive body which is electrically connected to the said cable, the magnet and/or the body having an exposed face for contact with the said surface, and the magnet having a temperature coefficient to resist demagnetisation and thermal degradation when a welding current is passed therethrough.

2. An electrical connector as claimed in Claim 1, in which the magnet is a permanent magnet.

3. An electrical connector as claimed in Claim 2, in which the magnet is an electromagnet.

4. An electrical connector as claimed in Claim 2 or Claim 3, in which the magnet is a permanent mag net supplemented by an electromagnet.

5. An electrical connector as claimed in any preceding Claim, in which the permanent magnet is a generally cup-shape magnet mounted such that the rim of the cup is exposed for physical contact with a workpiece.

6. An electrical connector as claimed in Claim 5, in which the cup-shape magnet is secured by a me chanical fixing passing through the bottom of the cup and leaving the rim exposed.

7. An electrical connector as claimed in any preceding Claim in which the housing in which the mag net is fixed comprises a non-magnetic or paramagnetic material.

8. An electrical connector as claimed in Claim 7, in which the housing for the magnet is composed of brass or aluminium or an alloy of one or both thereof.

9. An electrical connector as claimed in any preceding Claim, in which the magnet has a percentage of cobalt exceeding 20%.

10. An electrical connector as claimed in Claim 9, in which the permanent magnet has a proportion of cobalt between 25% and 35%.

11. An electrical connector as claimed in any preceding Claim, in which the magnet composition includes the following components by weight: Cobalt - between 25% and 35% Nickel - between 10% and 20% Aluminium; between 5% and 10% Copper - up to 5% Titanium - up to 5% Niobium - between 1% and 3%

12. An electrical connector as claimed in any preceding Claim, in which the housing for the magnet has a face contiguous with the face coplanar with the magnet and intersecting along the rectilinear line with such face.

13. A method of electric arc welding in which electrical connection between the welding apparatus and the workpiece is effected by a magnetic connector incorporating a magnet having a proportion of cobalt in excess of 25% and a composition giving the magnet a temperature co-efficient such that the face of the magnet is not substantially physically degraded by the high temperature and/or parasitic arcing which takes place during welding.

14. An electrical connector substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

15. A method of electric arc welding substantiaily-as hereinbefore described with reference to the accompanying drawings.