Electric heating – Metal heating – For bonding with pressure
Reexamination Certificate
2002-12-03
2004-03-16
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
For bonding with pressure
C219S090000
Reexamination Certificate
active
06706990
ABSTRACT:
FIELD OF THE INVENTION
The disclosed device relates to the field of welding. More particularly this invention relates to the field of resistance or spot welding of two or more pieces of metal to each other using electric current. The device may be attached and used in combination with spot-welding guns both fixed and portable. The device herein disclosed and described features a new and unique multi-purpose attachment for a widely used style of spot welding guns which enables a larger opening or throat and welding of metal inserted through that opening in a direction parallel to the direction of the lateral translation of such welding guns. The device also features easily replaceable electrodes in varying sizes along with making the tool more adaptable to be used in vehicle and machinery repair and manufacturing.
BACKGROUND OF THE INVENTION
Spot welding or resistance welding is a common manufacturing procedure of permanently attaching two or more pieces of material, most often steel, together by the means of placing an electrode on either side of the material and applying a given force and electrical high amperage electric current for a period of time. Resistance from the material creates enough heat to melt and weld the material permanently together with no filler metal or flux required. A great percentage of the assembly of automobiles is accomplished with spot welding guns operated on robotic arms. This same procedure is commonly used in many repair processes where the devices used need to be portable and more adjustable than those used for mass production manufacturing tasks. Conventional spot welders use a gun having two electrode holders, one fixed and the other laterally translatable, extending from a handle adapted to pinch together along a line parallel, called a C-type, or perpendicular, to the handle axis called the X-type. The pinching force may be applied in several ways: manually, electrical solenoid, or by pneumatic or hydraulic cylinders, or any combination thereof. The spot welding guns are connected to a welder power supply either through heavy cables or by means of trans-guns where a transformer is connected directly to the spot welding gun carrying the high amperage current necessary for welding and to a source of air or electricity for applying the pinching force.
A number of different welder and electrode configurations have been developed for special purpose welding. While effective for simply welding metal sheets together along an edge or for a single specific arrangement of metal structures, these devices are not portable or easily adaptable to the wide variety of applications necessary in repair and maintenance work, in particular auto body repair work. The portable welders available are limited in their capabilities.
In many cases, it is necessary to spot weld at locations well away from the distal edges of the metal being welded such as on automobile fenders or other metal structures that tend to have long wall portions extending from a weld at a base to an adjacent piece of sheet metal. Often welds must be made in areas having large or thick cross sections between the edge of the structure and the area to be welded. It is difficult and expensive to construct or assemble a special spot welder for each of these difficult situations for small or independent maintenance and repair shops.
Thus, there is a continuing need for spot welding guns and attachments to conventional welders using electrode holders that are interchangeable and adjustable. Such a device should have capabilities of welding at a variety of locations with a wider throat opening capability. Such a device should also allow for welding at the base of a long wall portion of sheet metal by insertion over the distal end of the sheet metal opposite the weld.
U.S. Pat. No. 1,084,673 (Thomson) relates to a class of electric welding machines known as spot welders. In this class of machines as ordinarily constructed, the spot welding electrodes by which the welding pressure is applied at the point of the work where the weld is to be formed between the plates or sheets of metal are mounted on end of rigid arms extended from the base or pedestal. This 673 patent of Thomson illustrates an example of the conventional stationary spot welding machines.
U.S. Pat. No. 1,728,616 (Kondakjian) describes improvements in electric spot welding machines, and the invention has reference more particularly to a simply constructed and easily actuated spot welding machine provided with electrodes having an initial mechanical clamping action to position and hold the work in combination with a novel means for controlling the flow of electric current therethrough after the work is operatively engaged by the electrodes. This 616 patent of Kondakjian is another example of the large stationary spot welders that have been used for years.
U.S. Pat. No. 2,130,657 (Watkin) teaches of a welding machine capable of welding small gauge material, which requires delicate adjustments of the time during which the welding current is flowing so as to prevent burning of the work. The invention also provides a machine which is readily transportable in a compact form and capable of delicate work. The 657 patent of Watkin is another example of a complete spot welding machine capable of fine adjustments and somewhat portable. It is still designed to be mounted in a stationary position and used for production work not repair work.
U.S. Pat. No. 2,452,009 (Woodward) discloses an invention in one of its forms with the upper electrode of a resistance-welding machine that is secured to an arm which is adjustably clamped to a vertical support secured in an insulated relation to the frame of the machine. The lower electrode is secured to one end of a pivoted support arm which is bifurcated at the other end to provide upper and lower fork portions. A toggle linkage connects the upper fork portion to a pressure applying pedal, and a control switch is mounted on the lower fork portion so as to be actuated in response to relative deformation of the forks to effect energization of the welding electrodes only after a predetermined electrode pressure has been attained. The 009 patent of Woodward is another example of stationary spot welding units commonly used in mass production.
U.S. Pat. No. 4,504,725 (Beneteau) additionally describes a resistance welding apparatus with a compound electrode holder provided. The apparatus is more effective in resistance welding members of U-shaped cross section than apparatus heretofore known. The compound electrode holder enables its electrode to travel in one accurate path throughout most of its travel or stroke and to move in a second accurate path as it approaches the work piece. The compound electrode holder achieves a large path of travel of its electrode and at the same time accurate alignment of the electrodes and reliable welds are attained. The 725 patent of Beneteau is still another stationary welding apparatus designed for mass production with improved electrode travel and increased throat size and pressure, but has not been designed to be used as a portable repair tool.
U.S. Pat. No. 4,879,447 (Umeda) teaches a welding gun with a movable arm to move in a large angle or a long distance, relative to a fixed arm with a slight reciprocal movement of a rod attached to a piston without employing a complicated mechanism such as the guide roller, guide plate, and guide groove employed in prior welding guns. The pressing force applied to a work piece by the movable arm is generated by a forward movement of the rod. The 447 patent of Umeda is an example of the spot welding guns that have been adapted to be used in the field of robotic manufacturing. They have increased the throat opening and added a cam action to the pressure in the closure, but this unit would not be used as a portable device and would not be easily adaptable to many different repair situations.
U.S. Pat. No. 5,164,564 (Umeda) teaches of a means to adapt a spot welding gun to a robotic arm. These systems are primarily used in mass productions and
Harms Donn K.
Shaw Clifford C.
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