Welding equipment

Claim 2

A welding apparatus having welding electrodes energizable from an alternating potential source for welding fine wire screen with a controlled current pulse, comprising in combination: means for generating periodic clock signals in synchronized relation with said alternating potential source; switch means actuable in response to positioning of said electrodes enabling weld current flow from said source to said electrodes; means responsive to said clock signals and actuating of said switch means for producing the preselected number of pulses in synchronism with respective ones of said clock signals; means actuable for suppressing preselected ones of said pulses; means responsive to a sufficient pressure of said electrodes against said screen for allowing said pulses to pass therethrough; said means actuable for suppressing pulses comprising a conductor connected between said means responsive to said clock signals and said means responsive to pressure and a switch connecting between said conductor and source of constant potential of a level corresponding to the absence of a pulse on said conductor whereby closure of said switch shunts said pulse to said potential source; trigger means responsive to said pulses for producing corresponding trigger pulses; a firing circuit responsive to each said trigger pulse for producing a portion of a half cycle of weld current flow from said source through said electrodes and screen; whereby actuation of said switch means causes a quantity of electrical energy to be applied to said screen for welding same, said quantity being determined by the time of occurrence of corresponding ones of said clock signals with respect to the alternating potential wave form of said source.

Claim 3

A welding apparatus having welding electrodes energizable from an alternating potential source for welding fine wire screen with a controlled current pulse, comprised in combination: means for generating periodic clock signals in synchronized relation with said alternating potential source; switch means actuable in response to positioning of said electrodes enabling weld current flow from said source to said electrodes; means responsive to said clock signals and actuation of said switch means for producing a preselected number of pulses in synchronism with respective ones of said clock signals; means actuable for suppressing preselected ones of said pulses; means responsive to a sufficient pressure of said electrodes against said screen for allowing said pulses to pass therethrough; trigger means responsive to said pulses for producing corresponding trigger pulses; sAid trigger means comprising a unijunction transistor, a storage capacitor and means for charging same, said capacitor being connected through unidirectional means to the emitter of said unijunction transistor and means coupling the pulse output of said pressure responsive means to said emitter in a manner for increasing potential thereon to fire said unijunction transistor and discharge said capacitor therethrough for producing a trigger pulse; a firing circuit responsive to each said trigger pulse for producing a portion of a half cycle of weld current flow from said source through said electrodes and screen; whereby actuation of said switch means causes a quantity of electrical energy to be applied to said screen for welding same, said quantity being determined by the time of occurrence of corresponding ones of said clock signals with respect to the alternating potential wave form of said source.

Claim 4

A welding apparatus having welding electrodes energizable from an alternating potential source for welding fine wire screen with a controlled current pulse, comprised in combination: means for generating periodic clock signals in synchronized relation with said alternating potential source; switch means actuable in response to positioning of said electrodes enabling weld current flow from said source to said electrodes; means responsive to said clock signals and actuation of said switch means for producing a preselected number of pulses in synchronism with respective ones of said clock signals; means actuable for suppressing preselected ones of said pulses; means responsive to a sufficient pressure of said electrodes against said screen for allowing said pulses to pass therethrough; trigger means responsive to said pulses for producing corresponding trigger pulses; sAid trigger means comprising a unijunction transistor, a storage capacitor and means for charging same, said capacitor being connected through unidirectional means to the emitter of said unijunction transistor and means coupling the pulse output of said pressure responsive means to said emitter in a manner for increasing potential thereon to fire said unijunction transistor and discharge said capacitor therethrough for producing a trigger pulse; a firing circuit responsive to each said trigger pulse for producing a portion of a half cycle of weld current flow from said source through said electrodes and screen; whereby actuation of said switch means causes a quantity of electrical energy to be applied to said screen for welding same, said quantity being determined by the time of occurrence of corresponding ones of said clock signals with respect to the alternating potential wave form of said source.

Claim 5

A welding apparatus having welding electrodes energizable from an alternating potential source for welding fine wire screen with a controlled current pulse, comprising in combination: means for generating periodic clock signals in synchronized relation with said alternating potential source; switch means actuable in response to positioning of said electrodes enabling weld current flow from said source to said electrodes; means responsive to said clock signals and actuation of said switch means for producing a preselected number of pulses in synchronism with respective ones of said clock signals; means actuable for suppressing preselected ones of said pulses; means responsive to a sufficient pressure of said electrodes against said screen for allowing said pulses to pass therethrough; trigger means responsive to said pulses for producing corresponding trigger pulses; a welding transformer for supplying weld current to said welding electrodes and in which said pressure responsive means includes sensing means connected across said welding transformer and energizable to an extent related to the impedence of said weld transformer for producing an output condition indicative of whether the impedence of said weld transformer lies below a threshold value indicating proper contact between said electrodes; gate means interposed between said means for producing said pulses and said trigger means, said gate means being responsive to said output condition of said sensing means for determining whether said pulses will pass form said pulse producing means to said trigger means; a firing circuit responsive to each said trigger pulse for producing a portion of a half cycle of weld current flow from said source through said electrodes and screen; whereby actuation of said switch means causes a quantity of electrical energy to be applied to said screen for welding same, said quantity being determined by the time of occurrence of corresponding ones of said clock signals with respect to the alternating potential wave form of said source.

Claim 6

A welding apparatus having welding electrodes energizable from an alternating potential source for welding fine wire screen with a controlled current pulse, comprising in combination: means for generating periodic clock signals in synchronized relation with said alternating potential source; switch means actuable in response to positioning of said electrodes enabling weld current flow from said source to said electrodes; means responsive to said clock signals and actuation of said switch means for producing a preselected number of pulses in synchronism with respective ones of said clock signals; means actuable for suppressing preselected ones of said pulses; means responsive to a sufficient pressure of said electrodes against said screen for allowing said pulses to pass therethrough; trigger means responsive to said pulses for producing corresponding trigger pulses; a welding transformer for supplying weld current to said welding electrodes and in which said pressure responsive means includes sensing means connected across said welding transformer and energizable to an extent related to the impedence of said weld transformer for producing an output condition indicative of whether the impedence of said weld transformer lies below a threshold value indicating proper contact between said electrodes; gate means interposed between said means for producing said pulses and said trigger means, said gate means being responsive to said output condition of said sensing means for determining whether said pulses will pass form said pulse producing means to said trigger means; a firing circuit responsive to each said trigger pulse for producing a portion of a half cycle of weld current flow from said source through said electrodes and screen; whereby actuation of said switch means causes a quantity of electrical energy to be applied to said screen for welding same, said quantity being determined by the time of occurrence of corresponding ones of said clock signals with respect to the alternating potential wave form of said source.

Claim 7

The apparatus defined in claim 3, including bleed means for providing a low amplitude current path through said welding transformer which is conductive through said welding transformer in the absence of weld current flow therethrough and wherein said sensing means includes a sensing transformer connected across said welding transformer and responsive to a high impedence condition of said welding transformer for conducting more of said bleed current therethrough and means in circuit with said welding transformer and responsive to current flow therethrough of an amount exceeding the threshold value for changing the output condition of said sensing circuit.

Claim 8

The apparatus defined in claim 3, in which said gate means comprises an OR function gate and an AND function gate, the output of said OR function gate being connected to one function gate being connected to one input of said AND function gate, said OR function gate having inputs connected to said pulse producing means, said AND functiOn gate having a further input connected to said sensing means, said OR function gate passing said pulses therethrough, said AND function gate passing said pulses therethrough upon occurrence of an output condition of said sensing means indicating a low impedence condition in said welding transformer, the output of said AND function gate being connected to said trigger means.