Electrical connectors – With magnet – To urge mating connectors together
Reexamination Certificate
1999-10-14
2001-09-04
Paumen, Gary F. (Department: 2833)
Electrical connectors
With magnet
To urge mating connectors together
C439S040000, C439S100000
Reexamination Certificate
active
06283767
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention concerns a grounding terminal for temporary connection of a grounding conductor to an object to be welded.
BACKGROUND OF THE INVENTION
By all welding a positive and a negative cable are used where the negative cable is the ground cable which is fastened to the construction to be welded. The welding is preformed by the positive cable to which an electrode holder or a feeding piston is mounted. To fasten the ground cable to the construction a grounding terminal is used.
Known grounding terminals comprise among other things earthing clamps, that grip over the construction, example given a pipe, by using a mechanical force providing electrical contact with the construction. However, earthing clamps can not be Fastened to all geometrical surfaces as they are dependent upon being able to grip around the object. The electrical connection is dependent upon the jaws of the earthing clamps gripping around the construction to give sufficient contact. The mechanical force is often provided by screws or mechanical springs. that after a while can get loose and thereby give poorer contact with the construction. If an earthing clamp is to be fastened on bigger constructions, an ear must first be welded to the construction to which the earthing clamp then can be fastened.
Other known grounding terminals are based on magnetism, and comprise as terminals with permanent magnets and terminals based on the use of electromagnets. Such grounding terminals can be used when the construction to be welded is made of a ferromagnetic material. For example, there are described in the patents U.S. Pat. No. 2,287,112 and U.S. Pat. No. 2,437,833 magnetic grounding terminals based on an electromagnet. When the current is switched on, the terminals are magnetized and the contact surface is drawn towards the workpiece. Electromagnetic grounding terminals must however have their own power supply and their own conductor from the power supply to the coil in the electromagnet of the terminal. Grounding terminals with permanent magnets are disclosed in U.S. Pat. No. 2,429,526 and U.S. Pat. No. 4,676,562. The grounding terminal in
U.S. Pat. No. 4,676,562 is designed to be held and fastened by one hand. The terminal will however be hard to unfasten from the workpiece. James Mortem™ has also put on the market a magnetic grounding terminal based on permanent magnets. Known grounding terminals with permanent magnets have generally the disadvantage that the magnetic force can not be“turned off” in the way the current in an electromagnet can be turned off, or otherwise be moved away from the contact surface with the construction. These magnetic grounding terminals will in a typical industrial environment also attract metal shavings that fasten on the contact surface. This is highly unwanted as it will give poorer contact between the workplace and the grounding terminal.
To obtain a good ground connection between the grounding terminal and the workpiece to be welded, the contact surface on the construction must also be free of paint, rust and oxide scale. This is now done by using a separate scraper in some form. The welder must therefor be equipped with several tools during welding.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a grounding terminal which can be fastened on all magnetic constructions/workpieces to be welded independent of the geometry of the construction.
Another object of the invention is to provide a grounding terminal with only one conductor, the grounding conductor, and which also can activate and deactivate the magnetic force in the contact surface with the workpiece.
A third object of the invention is to provide a grounding terminal which can easily be fastened to and unfastened from the construction to be welded.
A fourth object of the present invention is to eliminate the need for extra equipment such as scrapers for scraping away rust, paint and oxide scale from the contact surface on the workpiece.
SUMMARY OF THE INVENTION
According to the invention the aforementioned objects above are achieved by a magnetic grounding terminal for temporary connection of a grounding conductor to an object to be welded. The grounding terminal is characterized in that it comprises permanent magnets, the permanent magnets having a first state for fastening the grounding
terminal to the object and a second state for unfastening the grounding terminal from the object, the grounding terminal being arranged to be fastened and unfastened by one hand, the grounding terminal is fastened by pressing it towards the object to be welded and unfastened by pulling it away from the object to be welded.
The permanent magnets may be moveable between a first and a second position, representing the first and second state of the permanent magnets respectively.
Further, the grounding terminal may comprise a housing, two upper parallel extended metal plates and two or parallel extended metal plates in the housing, the permanent magnets are arranged between the metal plates and in the first position constitute an open magnetic loop together with the metal plates for fastening the grounding terminal to the object, and in the second position constitute a closed magnetic loop together with the metal plates for unfastening the grounding terminal from the object.
A magnet holder may be arranged between the metal plates, the magnet holder having an upper and a lower compartment for mounting of the permanent magnets, that are being constituted by an upper permanent magnet and a lower permanent magnet respectively. In the first position the lower permanent magnet is arranged between the two lower metal plates and the upper permanent magnet is arranged between the two upper metal plates, and in the second position the two permanent magnets are arranged between the two upper metal plates.
The house may be equipped with a handle, to which the upper part of the magnet holder is fixed, and movement of the handle then causes the alteration of position of the magnet holder and thereby the permanent magnets. The lower metal plates may provide contact surfaces for contact with the object to be welded. The metal plates may have a certain thickness providing defined end faces. The contact surfaces may then be constituted by the lower end faces of the two lower metal plates, and by a groove formed by the insides of the lower ends of the two lower metal plates, the groove facilitating the fastening of the grounding terminal on pipes and pipe constructions. In a preferred embodiment the insides of the lower ends of the lower metal plates have the form of opposite slanting faces, the faces slanting upwards in a direction towards each other. The groove may be milled out on the innermost part of the lower end faces of the metal plates.
It is preferred to use permanent magnets made of Neodymium, Nd—Fe—B-35.
The grounding terminal may also comprise scraping tools for scraping off rust, paint or oxide scale on the object, obtaining a better contact surface with the object. The scraping tool then having scraping knives being arranged protruding perpendicular outwards from the contact surfaces, but in such a way that the scraping tool does not affect the contact surfaces contact with the object. Then, the grounding terminal has a shape so that scraping off rust, paint and oxide scale on the object to be welded, and fastening of the grounding terminal to the object and unfastening the grounding terminal from the object, may be performed in successive operations by using one hand only and without changing the grip on the grounding terminal.
In a preferred embodiment the magnetic grounding terminal is also equipped with a quick release coupling for the grounding conductor so that this easily can be disconnected from the grounding terminal.
Measurements have been performed showing that the grounding terminal satisfies the requirements of sufficient grounding by ordinary welding without power loss in the transition resistor between cargo and earthing magnet causes overheating in the grounding term
Factor Tool AS
Ladas & Parry
Paumen Gary F.
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