초록 ▼

A D.C. welder includes an engine-driven D.C. generator, a polarity-reversing switch which can change the direction of current flow through the field winding of that generator to provide a positive or negative polarity at the welder output terminals, a circuit that automatically permits only uni-dire

A D.C. welder includes an engine-driven D.C. generator, a polarity-reversing switch which can change the direction of current flow through the field winding of that generator to provide a positive or negative polarity at the welder output terminals, a circuit that automatically permits only uni-directional current flow through that field winding during the starting of the engine, and a further circuit that energizes a solenoid to close contacts which enable that generator to operate as the starting motor for that engine but which thereafter de-energizes that solenoid and then keeps it de-energized until the engine is at, or close to, rest.

대표청구항 ▼

An electric welder which comprises output terminals, a D.C. generator that can selectively develop a positive voltage or a negative voltage at one of said output terminals, an energizing circuit for the field winding of said D.C. generator, a polarity-controlling switch that can be set in one positi

An electric welder which comprises output terminals, a D.C. generator that can selectively develop a positive voltage or a negative voltage at one of said output terminals, an energizing circuit for the field winding of said D.C. generator, a polarity-controlling switch that can be set in one position to enable said energizing circuit to cause current to flow through said field winding in a direction which will enable said D.C. generator to develop said positive voltage at said one output terminal, said polarity-controlling switch being adapted to be set in a second position to enable said energizing circuit to cause current to flow through said field winding in the opposite direction and thereby enable said D.C. generator to develop said negative voltage at said one output terminal, a sensing circuit which senses a condition that is representative of the operating level of the D.C. generator and which can develop a first signal when the D.C. generator is operating below a predetermined level and which can develop a second and different signal when said generator is operating above said predetermined level, means to establish and maintain different selected levels of current flow through said field winding, and a control circuit which automatically responds to the development of said first signal by said sensing circuit to force all current flow through said field winding to be in the first said direction irrespective of the position in which said polarity-controlling switch is set, said control circuit subsequently and automatically responding to the development of said second signal by said sensing circuit to permit the current flow through said field winding to be in the direction called for by the setting of said polarity-controlling switch, whereby said D.C. generator will automatically develop said positive voltage at said one output terminal whenever said D.C. generator is operating below said predetermined level but will subsequently and automatically permit said D.C. generator to respond to the setting of said polarity-controlling switch to develop either said positive voltage or said negative voltage at said one output terminal whenever said D.C. generator is operating above said level.