Title of Invention

POWER SAVING DEVICE FOR DC ARC WELDING MACHINE

Abstract

Power saving device for DC arc welding machine comprising a voltage sensor whose input terminals are connected to the welding electrode and welding fixture of the DC arc welding machine, a timer whose input is connected to the output of the voltage sensor, a voltage comparator whose input is connected to the output of the timer and whose output is connected to a contactor through a relay, the primary winding of the voltage step down transformer of the welding machine being cormectable to a power supply through the contactor and the voltage sensor, timer and voltage comparator being connected to the power supply.

Full Text

FORM 2 THE PATENTS ACT 1970 (39 of 1970) COMPLETE SPECIFICATION (See Section 10; rule 13) TITLE Power saving device for DC arc welding machine APPLICANTS Tata Motors Limited, Bombay House, 24 Homi Mody Street, Hutatma Chowk, Mumbai 400001, Maharashtra, India, an Indian Company INVENTOR Under Section 28(2) Pathak Jay Vinayak, Tata Motors Limited, Manufacturing Division CVBU, Pimpri, Pune - 411018, Maharashtra, India, an Indian National The following specification particularly describes the nature of this invention and the manner in which it is to be performed : ORIGINAL 986/MUM/2003 19-9-03 FIELD OF INVENTION This invention relates to a power saving device for DC arc welding machine, PRIOR ART DC arc welding machine comprises a voltage step down transformer whose primary is connectable to a power supply and whose secondary is connected to the input terminals of a bridge rectifier. The positive output terminal of the bridge rectifier is connected to a welding electrode provided with a welding rod and the negative output terminal of the bridge rectifier is connected to a welding fixture. A cooling blower is connected across the primary of the transformer. During operation of the welding machine, it always remains connected to the power supply. Therefore, during idling time of the machine i.e. non-arcing or non-welding time power continues to flow to the transformer because of which iron and copper losses occur in the transformer resulting in wastage of power. The blower also remains on during non-arcing resulting in further wastage of power. Life of both the transformer and blower is also reduced as they remain on during idling of the machine. ■* OBJECTS OF INVENTION An object of the invention is to provide a power saving device for DC arcing welding machine which reduces or minimises wastage of power during icgno; time of the welding machine. Another object of the invention is to provide a power saving device for DC arcing welding machine which increases the life of both the transformer and blower. Another object of the invention is to provide a power saving device for DC arc welding machine which is simple in construction and easy to operate. Another object of the invention is to provide a power saving device for DC arc welding machine which is economicai. DETAILED DESCRIPTION OF THE INVENTION According to the invention there is provided a power saving device for DC arc welding machine comprising a voltage sensor whose input terminals are connected to the welding electrode and welding fixture of the DC arc welding machine, a timer whose input is connected to the output of the voltage sensor, a voltage comparator whose input is connected to the output of the timer and whose output is connected to a contactor through a relay, the primary winding of the voltage step down transformer of the welding machine being connectabie to a power supply through the contactor and the voltage sensor, timer and voltage comparator being connected to the power supply. The following is a detailed description of the invention with reference to the accompanying sole Figure 1 which is block diagram of a DC arc welding machine comprising the power saving device according to an embodiment of the invention. As illustrated in Fig 1 of the accompanying drawings, the DC arc welding machine comprises a voltage step down transformer 1 whose primary and secondary windings are marked 2 and 3 respectively. The secondary winding of the transformer is connected to the input terminals of a bridge rectifier 4 of the machine. The positive output terminal of the bridge rectifier is connected to a welding electrode 5 provided with a welding rod 6. The negative output terminal of the bridge rectifier is connected to a welding fixture 7. 8 is a cooling blower of the welding machine connected across the primary winding of the transformer. The device 9 of the invention comprises a voltage sensor 10 whose input terminals are connected to the welding electrode and welding fixture. 11 is a timer whose input is connected to the output of the voltage sensor. 12 is a voltage comparator whose input is connected to the output of the timer and whose output is connected to a contactor 13 through a relay 14. The primary winding of the transformer is connected to a power supply 15 through the contactor. The voltage sensor, timer and voltage comparator are also connected to the power supply 15 for deriving power for their operation. The power supply may be single phase, two phase or three phase and the contactor may be single pole, two pole or three pole respectively. The timer is set for a predetermined interval of time. Jobs (not shown) to be welded together are placed on the welding fixture and the power supply is turned on. Simultaneously both timer and blower are also turned on. The voltage appearing across the transformer through the contactor is stepped down and fed to the bridge rectifier which rectifies the current and feeds it to the welding electrode and a current flows through the welding rod. On contacting the welding rod on to the jobs arcing takes place and the jobs are fused or welded together. During arcing there is a drop in the potential difference between the welding electrode and the welding fixture which is sensed by the voltage sensor. The voltage sensor gives a corresponding voltage signal to the timer. This resets the timer. Since there is no output from the timer to the voltage comparator, the voltage comparator does not give any output to the relay and the relay remains non-operational. The contactor continues to remain closed and power continues to flow to the transformer and blower. During idling time of Ihe DC arc welding machine i.e. the time when the welding rod is not in contact with the jobs and arcing is not taking place, there is no drop in the potential difference between the welding electrode and fixture. The voltage sensor senses this potential difference and gives a corresponding voltage signal to the timer. As a result the timer does not get reset and at the end of the predetermined time interval, it gives a voltage signal to the voltage comparator. The voltage comparator compares the incoming voltage signal with a reference voltage set therein and gives an output to the relay because of which the relay gets energised and opens the contactor thereby cutting off the power supply to the transformer and blower. During idling time the input terminals of the voltage sensor are connected to the welding electrode and welding fixture. Therefore, a potential difference is maintained between the welding electrode and welding fixture. When the welding rod is made to touch the jobs after the idling time, a drop in the potential difference between the welding electrode and welding fixture occurs which is sensed by the voltage sensor. The voltage sensor gives a corresponding voltage signal to the timer. This resets the timer. Since there is no output from the timer to the voltage comparator, the voltage comparator does not give any output to the relay and the relay becomes non-operational and the contactor closes and power flows to the transformer and blower and welding is continued. Since no power flows to the transformer during idling time of the machine, iron and copper losses do not occur in the transformer thereby reducing wastage of power. Since the blower is not on during idling time power consumption is further reduced. Life of both the transformer and blower is also increased as the remain off during idling time of the machine. The device of the invention is simple in construction and easy to operate. The device comprises few components which are inexpensive. Therefore, it is economical. WE CLAIM 1. Power saving device for DC arc welding machine comprising a voltage sensor whose input terminals are connected to the welding electrode and welding fixture of the DC arc welding machine; a timer whose input is connected to the output of the said voltage sensor, a voltage comparator whose input is connected to the output of the said timer and the output is connected to a contactor through a relay; the primary winding of the voltage step down transformer of the welding machine being connectable to a power supply through the said contactor and the said voltage sensor, the said timer and voltage comparator. 2. Power saving device as claimed in claim 1, wherein the power supply is single phase, two phase or three phase and the contactor is single pole, two pole or three pole respectively. 3. Power saving device for DC arc welding machine substantially as herein described particularly with reference to Fig 1 of the accompanying drawings. Dated this 18th day of September 2003 (Karuna Goleria) of DePENNING & DePENNING Agent for the Applicants

Documents:

986-mum-2003-abstract(10-09-2004).doc

986-mum-2003-abstract(10-09-2004).pdf

986-mum-2003-cancelled pages(10-09-2004).pdf

986-mum-2003-claim(granted)-(10-09-2004).doc

986-mum-2003-claim(granted)-(10-09-2004).pdf

986-mum-2003-correspondence(19-10-2005).pdf

986-mum-2003-correspondence(ipo)-(07-01-2004).pdf

986-mum-2003-drawing(10-09-2004).pdf

986-mum-2003-form 1(19-09-2003).pdf

986-mum-2003-form 19(03-11-2003).pdf

986-mum-2003-form 2(granted)-(10-09-2004).doc

986-mum-2003-form 2(granted)-(10-09-2004).pdf

986-mum-2003-form 3(18-09-2003).pdf

986-mum-2003-form 8(03-11-2003).pdf

986-mum-2003-power of attorney(01-10-2003).pdf

986-mum-2003-power of attorney(17-09-2001).pdf

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