AU2005100632A4

AU2005100632A4 - Improvements to Magnetic Earthing Clamps

Info

Publication number: AU2005100632A4
Application number: AU2005100632A
Authority: AU
Inventors: Ian Heard
Original assignee: SERPENT AND DOVE Pty Ltd
Current assignee: Heard Ian Godfrey; SERPENT AND DOVE Pty Ltd
Priority date: 2005-08-08
Filing date: 2005-08-08
Publication date: 2005-09-01
Anticipated expiration: 2013-08-08

Description

SDescription Field of the Invention 00 The invention relates to grounding (or earthing) clamps used to magnetically secure an electrical ground (or earth) connection to workpieces during welding operations.

(NO

Background of the Invention Typically magnetic grounding (or earthing) clamps of the type that employ a copper, brass or other suitably conductive metal electrode that passes through a magnetic device used to secure the electrode to the workpiece, have been found to be subject to electric arcing at the point where the electrode passes through the magnet housing and also at the point where the magnet casing clamps to the steel workpiece. If the copper or brass electrode is not in good electrical contact with the workpiece and the electrode touches the magnet housing the electric current finds a preferential path to ground via the magnet housing. This may cause electric arcing and consequent arcerosion in the metals at the junction of the electrode with the housing, or of the housing with the workpiece. Further, arcing between the magnet housing and the workpiece may deface the workpiece.

Brief Description of the Drawings FIG. 1 illustrates a typical magnetic ground (or earth) clamp. A ferrite, neodymium or other magnetizing element is housed within a ferromagnetic (typically steel) cup or housing, item A. Item B is a copper, brass or other good conductive metal electrode passing through the magnetic device. Item C is a typical cable lug at the end of cable, Item D, shown only for understanding. Frequently nuts, Items E, secure the cable lug and retain a handle, Item F, which handle assists removal of the clamp from a workpiece.

t FIG.2 is a section through the centre of the device to illustrate component parts. The housing, Item A, typically soft iron, conducts one magnetic pole to its edge, Item G, creating an air-gap, Item H, between the edge and the opposite pole face of the magnetizing element, Item I. The magnetic flux across this air-gap provides the 00 device's clamping strength. Electrode Item J passes through the clamping device and is provided with a contact surface, K at its end and is typically spring-loaded by a coil spring device L to provide contact tension between the contact surface of the O electrode and the surface of the workpiece. Typically also, an electrically insulating washer, item M, is placed between the inner face of the housing and the spring device.

t The upper end of the electrode is illustrated without nuts or attachments for clarity.

Items N and O show the typical points at which arcing can occur when the electric current takes a preferential path via the magnet housing to the workpiece.

FIG.3 is the same section as FIG.2, showing the subject of the present invention, insulating sleeve Item P, in position to prevent electrical contact between the electrode Item J and any of its attachments, with housing, Item A.

FIG.4 shows alternative style of electrode insulating sleeve, Item R (not shown as sectioned) and additional or alternative insulating element, Item Q (not shown as sectioned) fitted to the entire contact surface of the magnetic grounding device.

1

Claims

1. In a welding ground (earth or grounding) clamp of the magnetic type where the current-carrying electrode passes through the magnet housing and element, a 00 cylindrical sleeve of electrical insulating material surrounding the portion of the electrode passing through the metal housing to prevent the electrode coming into electrical contact with the metal housing of the clamp.

2. In a welding ground (earth or grounding) clamp of the magnetic type where the in current-carrying electrode passes through the magnet housing and element, a Scylindrical sleeve of electrical insulating material surrounding the portion of the electrode passing through the metal housing, said sleeve having at one end an integral flat portion perpendicular to the cylinder arranged so as to prevent the electrode or nuts or any other fitments on or around the electrode from coming into electrical contact with the metal housing of the clamp.

3. In a welding ground (earth or grounding) clamp of the magnetic type where the current-carrying electrode passes through the magnet housing and element, a cylindrical sleeve of electrical insulating material around the portion of the electrode passing through the metal housing, said sleeve having integral flat portions perpendicular to the cylinder and at each end of the cylinder so as to prevent the electrode or nuts or any other fitments on or around the electrode from coming into electrical contact with the metal housing of the clamp.

4. In a welding ground (earth or grounding) clamp of the magnetic type where the current-carrying electrode passes through the magnet housing and element, a cylindrical sleeve of electrical insulating material around the portion of the electrode passing through the metal housing, said sleeve having flat portions fitted by thread, bonding or sliding means, perpendicular to the cylinder and at each end of the cylinder so as to prevent the electrode or nuts or any other fitments on or around the electrode from coming into electrical contact with the metal housing of the clamp. ti

5. A welding ground (earth or grounding) clamp of the magnetic type with the O O current-carrying electrode passing through a cylindrical sleeve of electrical insulating material such as described in Claims 1, 2 and 3 above. O

6. A welding earth or ground clamp of the magnetic type with the current-carrying 0 electrode passing through a cylindrical sleeve of electrical insulating material such as described in Claims 1, 2 and 3 above and having an electrically insulating disc or plate through which the electrode protrudes, fitted by any means to the clamping osurface of the clamp so as to insulate the entire clamping surface from any other in surface with which it connects.

7. A welding earth or ground clamp of the magnetic type with the current-carrying electrode not passing through a cylindrical sleeve of electrical insulating material such as described in Claims 1, 2 and 3 above but having an electrically insulating disc or plate through which the electrode protrudes, fitted by any means to the clamping surface of the clamp so as to insulate the entire clamping surface from any other surface with which it connects.