Controller for spot welding
First Claim
1. A welding controller for a spot welder having a welding tip for contacting a workpiece and injecting an electric welding current into the workpiece to produce a spot weld and having a control signal input for receiving a signal for controlling the magnitude of the welding current comprising a well located in the interior of said welding tip, a thermographic phosphor disposed in said well in thermal contact with said welding tip so that the intensity of phosphorus radiation emitted by the phosphor when it is illuminated is a measure of the temperature of the phosphor, a multi-filament fiber optic cable having a trunk portion extending into said well in close proximity to said phosphor and a plurality of branches extending outwardly therefrom, a phosphor illumination source disposed adjacent the end of a first one of said branches for supplying radiation for illuminating said phosphor, first radiant-energy sensor means disposed adjacent a second one of said branches responsive to radiant-energy in a first wavelength range for producing an output signal, second radiant energy sensor means disposed adjacent the end of a third one of said branches responsive to radiant energy in a second wavelength range for producing an output signal, memory means adapted to contain data indicative of the desired thermal pattern for a weld and electronic circuit means operatively associated with said first and second sensor means and said memory means for comparing the output signals of said first and second sensor means with the data in said memory means to provide a control signal for controlling the magnitude of the welding current.
1 Assignment
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Accused Products
Abstract
A controller for a spot-welding machine compares the temperature evolution at a site at which a spot weld is being made to a standard thermal history stored in a digital read/write memory in controlling the welding current for the weld. Standard thermal histories can be generated and written into the memory as needed by an operator of the welding machine to take into account changes in operating conditions. The temperature evolution of the spot-welding operation is monitored by detecting radiant energy whose intensity provides a measure of a temperature of the weld. Phosphorescent radiation from a thermographic phosphor located in a welding tip of the welding machine and thermal infrared radiation are preferred for monitoring the temperature evolution of the spot-welding operation.
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Citations
21 Claims
- 1. A welding controller for a spot welder having a welding tip for contacting a workpiece and injecting an electric welding current into the workpiece to produce a spot weld and having a control signal input for receiving a signal for controlling the magnitude of the welding current comprising a well located in the interior of said welding tip, a thermographic phosphor disposed in said well in thermal contact with said welding tip so that the intensity of phosphorus radiation emitted by the phosphor when it is illuminated is a measure of the temperature of the phosphor, a multi-filament fiber optic cable having a trunk portion extending into said well in close proximity to said phosphor and a plurality of branches extending outwardly therefrom, a phosphor illumination source disposed adjacent the end of a first one of said branches for supplying radiation for illuminating said phosphor, first radiant-energy sensor means disposed adjacent a second one of said branches responsive to radiant-energy in a first wavelength range for producing an output signal, second radiant energy sensor means disposed adjacent the end of a third one of said branches responsive to radiant energy in a second wavelength range for producing an output signal, memory means adapted to contain data indicative of the desired thermal pattern for a weld and electronic circuit means operatively associated with said first and second sensor means and said memory means for comparing the output signals of said first and second sensor means with the data in said memory means to provide a control signal for controlling the magnitude of the welding current.
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18. A process for controlling a welding current for a spot welding operation carried out on a workpiece comprising:
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(a) directing ultraviolet radiation through at least one fiber optic filament onto a thermographic phosphor disposed in a well in thermal contact with a welding tip, (b) directing the radiation emitted by the phosphor through at least one fiber optic filament to a first radiant-energy sensor to provide an output signal indicative of a temperature in a low temperature range for the welding tip, (c) directing infrared radiation emitted from the welding tip within said well through at least one fiber optic filament to a second radiant-energy sensor to produce an output signal indicative of a temperature in a higher temperature range for the welding tip, comparing the sequential output signals of said first and second sensors during a spot welding operation to a corresponding sequence of standard thermal history values to obtain a sequence of error values and continually adjusting the magnitude of the welding current in response to the sequence of error values to reduce differences between the temperature at the welding site in the workpiece during the course of a spot welding operation and the standard thermal history.
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19. A welding tip for a spot welding machine having a welding controller for controlling a welding current in response to infrared radiation providing a measure of a temperature of a weld, the welding tip comprising:
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(a) a generally cylindrical shank made of an electrically conductive material, an end surface of the shank defining a contact surface for making mechanical and electrical contact with a workpiece to transmit a welding current to the workpiece, the end of the shank opposite to the contact surface being securable to the spot welding machine in an electrically contacting relationship to receive the welding current from the machine, the shank having a passageway through it, the intersection of the passageway with the contact surface defining a thermal-radiation entrance port; and (b) a window element made of a material which is transparent to infrared radiation and capable of enduring temperatures of up to about 600°
C., the window element being fitted in passageway of the shank. - View Dependent Claims (20, 21)
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Specification