GB2469271A

GB2469271A - Welding Apparatus

Info

Publication number: GB2469271A
Application number: GB0905923A
Authority: GB
Inventors: Edward John Reed
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-04-06
Filing date: 2009-04-06
Publication date: 2010-10-13
Also published as: GB0905923D0

Abstract

Welding apparatus is disclosed comprising:(a) a supply of pressurised welding gas (1)(b) a welding gun (10) comprising an electrical power supply and a connection to the supply of pressurised gas;(c) a pressure sensor (28) arranged to sense the pressure of the pressurised welding gas and produce a variable control output in dependence of the sensed pressure of the pressurised gas;(d) a flow sensor (not shown) arranged to sense the rate of flow of the pressurised welding gas from the gas supply to the gun; and,(e) a control arrangement for disconnecting the electrical power supply to the welding gun when the rate of flow sensed by the flow sensor is below a threshold value. The gas flow sensor and pressure sensor providing distinct and separate gas supply monitoring means each capable of causing the electrical supply to be disconnected.

Description

Welding Apparatus The present invention relates to welding apparatus and particularly, but not exclusively, to welding apparatus for use in operations in which gas is supplied to a welding zone such as, for example, in gas shielding' or gas purging' operations.

Pressurised inert gas is frequently utilised in welding techniques to produce a preferred welding environment in which oxidization is inhibited in the weld and/or an optimum weld is produced by minimising porosity or other defects in the weld. Gas purging' is a technique in which an inert gas is directed to provide an inert atmosphere on the underside of a weld.

Gas shielded arc welding is also a well known process in which the welding arc and the molten weld metal are protected from ambient air by means of a shielding gas or mixture of gases which may be inert (for example, argon or helium). Two varieties of the process using an inert gas are common, these being known as "Tungsten Inert Gas" (TIG) and Metal Inert Gas (MIG). In TIG welding, the arc is maintained between an electrode and a work piece to be welded, whereas in MIG welding, the arc is maintained between a filler wire and the work piece. When using an oxidising gas, the process is known as metallic active gas (MAG). Combinations of inert gas and oxidising gas are also possible.

Such welding processes rely upon a consistent supply of shielding gas to the welding zone. It has been found that there can be problems if the gas supply is interrupted, or, when a bottle or cylinder of gas reaches exhaustion. This can cause undesirable porosity to be formed in the weld when the gas shield is breached.

This problem is addressed in my US Patent No.6423936, which relates to welding apparatus employing pressurised welding gas, the apparatus including a driver for the welding apparatus and electrical connection to the driver, in conjunction with i) a pressure sensor arranged to sense the pressure of the pressurised welding gas and produce a control output dependent upon the pressure level sensed; and ii) a control arrangement for initiating a control signal to modify the status of the electrical connection (for example by cutting the connection) when pressure of a predetermined level is sensed by the pressure sensor.

The pressure sensor in the welding apparatus of the abovementioned US Patent 6423936 thus prevents welding operations when the pressure of the pressurised gas falls outside a predetermined range. However, the pressure within the various flow ducts of the apparatus may vary as a result of obstructions or the like within the duct system. In addition, when the welding apparatus is in an inoperative state, pockets of gas may exist within the duct system because of valves (which only open on operation) remaining closed. These pockets will provide an erroneous indication of the actual pressure of the welding gas and so it is possible that the welding apparatus may still be operated in a few circumstances with an insufficient supply of gas, which may therefore lead to a disadvantageous porous weld.

I have now devised a welding apparatus which at least alleviates the above-mentioned problem.

According to the present invention, there is provided welding apparatus comprising: (a) a supply of pressurised welding gas; (b) a welding gun comprising an electrical power supply and a connection to the supply of pressurised gas; (c) a pressure sensor arranged to sense the pressure of the pressurised welding gas and produce a variable control output in dependence of the sensed pressure of the pressurised gas; (d) a flow sensor arranged to sense the rate of flow of the pressurised welding gas from the gas supply to the gun; and, (e) a control arrangement for disconnecting the electrical power supply to the welding gun when the rate of flow sensed by the flow sensor is below a threshold value.

The threshold value may be pre-set (predetermined) or it may be permitted to vary depending on other variables, The control arrangement is preferably further arranged to disconnet the power supply when the pressure sensed by the pressure sensor is below a predetermined level.

The combined use of a pressure sensor and a flow sensor can thus ensure that the welding apparatus according to the invention cannot be used when there is an insufficient supply of welding gas. The flow sensor measures the flow of gas independently of gas pressure and the pressure sensor measures the pressure of gas independently of the gas flow. Accordingly, each sensor provides a separate test of the presence of a sufficient gas supply before enabling the operation of the welding apparatus.

In a preferred embodiment of the invention, the output produced by the pressure sensor is variable so as to result in a range between a maximum and a minimum.

This enables variation of the gas pressure threshold at which the electrical disconnection of the gun is The maximum and minimum pressure levels defining the range between the minimum and maximum (as described above) are preferably adjustable.

Preferably, the control arrangement is arranged to generate a control signal when the pressure of the pressurised gas reaches the maximum or minimum pressure level.

This enables the welding gun electrical supply to be disconnected if gas at excess pressure or if insufficient pressure is being delivered to the welding zone Preferably, the control arrangement is arranged to generate a control signal when the flow rate of the pressurised gas is below a threshold vale.

The apparatus according to the invention preferably further comprises a display for displaying the pressure range and/or the actual flow rate.

Preferably, the apparatus further comprises a current sensor for sensing the electrical current supply to the welding gun. The current sensor is preferably a non-intrusive current sensor, such as a Hall effect sensor for example.

Preferably, the apparatus further comprises memory means for recording the operating characteristics of the welding apparatus as a function of time. The operating characteristics preferably comprise at least one of gas pressure, gas flow rate and current.

Preferably, the apparatus further comprises a connection for outputting the operating characteristics of the welding apparatus as a function of time, to a network or alternative memory means.

The welding gun preferably comprises a trigger for operating the welding apparatus, such that pressing the trigger and holding the trigger in a pressed configuration activates a welding operation and releasing the trigger de-activates the welding operation. Preferably, pressing the trigger at least twice in quick succession activates the welding apparatus, without having to hold the trigger in the pressed condition.

The welding apparatus preferably further comprises a connector comprising an inlet for receiving welding gas from the pressurised gas supply, and at least one outlet for outputting the gas supply to the welding apparatus. Preferably, the connector further comprises a valve for venting gas between the pressurised gas supply and the connector to the atmosphere.

Preferably, the connector further comprises: i) a first outlet communicating with the inlet and arranged to enable welding gas to be delivered to a first location; and ii) a second outlet communicating with the inlet and arranged to enable welding gas to be delivered to a second location.

A closure is preferably provided within the connector for controlling the flow of gas through at least one of the first and second outlet.

Preferably, gas is arranged to be delivered from the gas supply to the welding apparatus to perform a shielding' welding function when the closure closes one of the outlets. Preferably, gas is arranged to be directed simultaneously through the first and second outlet to perform a simultaneous purging' and shielding' welding function when the closure remains opened.

An embodiment of the present invention will now be described, by way of example only, and with reverence to the accompanying drawings in which: Figure 1 is a perspective view of apparatus according to an embodiment of the present invention; and, Figure 2 is a schematic illustration of the control regulator.

Referring to Figure 1 of the drawings, there is shown a Metal Inert Gas or "MIG" welding apparatus 100 comprising a variable voltage regulator (not shown) to enable connection to range of voltage power supplies.. A gas cylinder 1 is provided for supplying an inert gas, such as helium or argon for example, to the welding apparatus 100 and comprises a conventional regulator 2, for regulating the flow of gas from the gas cylinder 1. A gas line or duct 3 extends from the regulator 2 to a control unit 4 and subsequently to a further conduit 5. The control unit 4 also includes a power unit 8, together with gauges 9 for providing an indication of the power supply to the apparatus 100.

The conduit 5 comprises a filler wire 6 that is fed from a spool 7. The filler wire 6 passes through the control unit 4 and along conduitS to a welding gun 10; the wire 6 further extends along the gun 10 to a nozzle 11 disposed at a distal end thereof. The wire 6 is fed through the nozzle 11 to a welding zone upon a workpiece 13, to which is secured an earth clamp 14. At the same time, the control unit 4 controls the feed of gas through the conduit 5 to the welding zone from the gas cylinder 1. The gas acts to shroud the wire at the welding zone and thus minimise any air pockets developing within the weld upon the workpiece 13.

The welding operation is controlled via a trigger type switch 12 arranged upon the gun 10, whereby pulling the trigger 12 and holding the trigger 12 in a pressed configuration activates the control unit 4 to feed wire 6 to the gun 10 from the spool 7, and to supply a flow of gas from the gas cylinder 1 to the welding zone upon the work piece 13. Pressing the trigger 12 further enables an electrical connection to be made between the electrical power supply and the gun 10. Upon releasing the trigger 12, the welding operation is terminated.

Pressing the trigger 12 twice in quick succession is arranged to hold the apparatus in an operative state, so that the user (not shown) need not continuously hold the trigger 12. When it is desired to cease welding, the user can press the trigger 12 to release it from the pressed configuration and thus stop the supply of wire 6 and gas to the gun 10 and to further disconnect the electrical supply to the gun 10.

The gas supply duct 3, arranged upstream of the control unit 4, includes a control regulator 20, which is arranged regulate the operation of the welding apparatus 100 in dependence upon the gas pressure in supply line 3. The control regulator 20 comprises a venting valve (not shown) to release gas overpressure upstream of the regulator, in the flow duct 3.

The control regulator 20 is arranged to shut off the welding apparatus 100 by disabling the control unit 4, components feeding the wire 6 and/or disconnecting the electrical power supply to the gun 10. Disconnecting the power supply ensures that the arc at the tip of the wire 6 is extinguished.

Referring to Figures 2 of the drawings, the control regulator 20 comprises a housing 21 having a gas line connector 22 with an upstream gas inlet 23, a downstream gas outlet 24 and a purging gas outlet 25, which is selectively closable by a closure or threaded plug 26 which is arranged to engage therewith. With plug 26 removed, a purging' gas line may be connected to outlet 25, to enable a simultaneous purging' welding operation via outlet 25 and a shielding' welding operation via outlet 24 to be provided from a common pressurised gas source.

Connector 22 includes a passage 27 communicating with a diaphragm (not shown) of an electronic thick film pressure sensor 28 within the housing 21. The gas pressure in gas line 3 is thus sensed by sensor 28 which produces an output signal proportional to the gas pressure sensed. A flow sensor (not shown) is also provided within the housing 21 for sensing the rate of flow of gas along the passage 27 and is arranged to generate an output signal indicative of the flow rate of the gas. The pressure sensor signal and flow rate signal are outputted to an electronic circuit 30 provided internally of housing 21.

The electronic circuit 30 to which the pressure sensor 28 and flow sensor (not shown) output is directed includes, in sequence, a rectifier (not shown), an amplifier (not shown), and a comparator integrated circuit (not shown) which compares the pressure sensor output with upper and lower threshold settings. If the level is above the upper threshold setting, or below the lower threshold setting, a relay (not shown) is de-activated to open a switch 32 bridging connections 33, 34 to the welding apparatus driver circuitry (loop 35 including control unit 4 and welding gun trigger 12).

The comparator circuit (not shown) is further arranged to compare the signal from the flow rate sensor with a threshold value. If the signal is below a minimum threshold setting, a relay (not shown) is similarly de-activated to open a switch 32 bridging connections 33, 34 to the welding apparatus driver circuitry (loop 35 including control unit 4 and welding gun trigger 12).

The pressure sensor 28 is capable of producing a continuously variable output between a maximum and a minimum and does not simply act as an on/off gauge.

The comparator circuitry is adjustable to alter the upper and lower threshold levels at which the welding apparatus cut out is initiated. This is typically achieved by means of a manually operable potentiometer 38. The adjustability of the apparatus enables versatility of use with variety of different welding apparatus with convenient adjustment of the threshold pressure settings as and when required. Typically, the pressure settings vary from 50 millibars up to 500 millibars.

The regulator 20 is therefore suitable for retro-fitting to existing welding apparatus, or incorporation into an integrated control unit of welding apparatus. The adjustable threshold pressure levels and regulated voltage can be set at manufacture or be

adjustable in the field by the end user.

The control unit 4 further comprises a display for displaying the upper and lower pressure thresholds and also the actual measured flow rate of gas, so that a user can accurately control the welding operation. The unit 4 further comprises a memory (not shown) for recording the operating characteristics of the apparatus 100, such as gas pressure, gas flow rate and current supply to the gun 10 as a function of time. In this respect, the control unit further comprise a non-intrusive current sensor, such as a Hall-Effect sensor, for sensing the current in the power line to the gun 10. The control unit 4 further comprises means (not shown) for sensing the operative state of the welding apparatus 100 and is arranged to power down the apparatus 100 from an operative mode to a stand-by mode, whereby only the essential components of the apparatus 100 remain powered, when the apparatus 100 remains idle for greater than a predetermined time threshold. The standby function serves to reduce energy wastage associated with leaving the apparatus 100 fully powered when not in use.

The memory provides a data log of the operating characteristics of the welding apparatus 100, which can be output to a network, or a further memory device (not shown) via a connection (not shown) arranged upon the unit 4, such as a universal serial bus (USB) connection.

The gas flow rate sensor and pressure sensor thus provide distinct and separate tests as to whether there is present a sufficient gas supply before enabling the operation of the welding apparatus. From the foregoing therefore, it will be evident that the welding apparatus of the present invention provides an improved control over gas supply to enhance the quality of welds.

Claims

Claims 1. Welding apparatus comprising: (a) a supply of pressurised welding gas; (b) a welding gun comprising an electrical power supply and a connection to the supply of pressurised gas; (c) a pressure sensor arranged to sense the pressure of the pressurised welding gas and produce a variable control output in dependence of the sensed pressure of the pressurised gas; (d) a flow sensor arranged to sense the rate of flow of the pressurised welding gas from the gas supply to the gun; and, (e) a control arrangement for disconnecting the electrical power supply to the welding gun when the rate of flow sensed by the flow sensor is below a threshold value. * **� * * **** * 15

* ***** *
2. Welding apparatus according to claim 1, wherein the control arrangement is further arranged to disconnect the power supply when the pressure sensed by the pressure sensor is below a predetermined level.
3. Welding apparatus according to claim I or 2, wherein the output produced by the pressure sensor is variable so as to result in a range between a maximum and a minimum. S. * . * .5*
4. Welding apparatus according to claim 3, wherein the maximum and minimum pressure levels defining the range between the minimum and maximum areadjustable.
5. Welding apparatus according to claim 3 or 4, wherein the control arrangement is arranged to generate a control signal when the pressure of the pressurised gas reaches the maximum or minimum pressure level.
6. Welding apparatus according to any preceding claim, wherein the control arrangement is arranged to generate a control signal when the flow rate of the pressurised gas is below a threshold vale.
7. Welding apparatus according to any preceding claim, further comprising a display for displaying the pressure range and/or the actual flow rate.
8. Welding apparatus according to any preceding claim further comprising a current sensor for sensing the electrical current supply to the welding gun.
9. Welding apparatus according to claim 8, wherein the current sensor is a non-intrusive current sensor.
10. Welding apparatus according to any preceding claim, further comprising memory means for recording the operating characteristics of the welding apparatus as a function of time.
11. Welding apparatus according to claim 10, wherein the operating characteristics comprise at least one of gas pressure, gas flow rate and current.S..... * .
12. Welding apparatus according to any preceding claim, further comprising a connection for outputting the operating characteristics of the welding apparatus as a * function of time, to a network or alternative memory means.

:** 20 5% * p555
13. Welding apparatus according to any preceding claim, wherein the welding gun comprises a trigger for operating the welding apparatus, such that pressing the trigger and holding the trigger in a pressed configuration activates a welding operation and releasing the trigger de-activates the welding operation.
14. Welding apparatus according to claim 13, wherein pressing the trigger at least twice in quick succession activates the welding apparatus, without having to hold the trigger in the pressed condition.
15. Welding apparatus according to any preceding claim further comprising a connector comprising an inlet for receiving welding gas from the pressurised gas supply, and at least one outlet for outputting the gas supply to the welding apparatus.
16. Welding apparatus according to claim 15, wherein the connector further comprises a valve for venting gas between the pressurised gas supply and the connector to the atmosphere.
17. Welding apparatus according to claim 15 or 16, wherein the connector further corn prises: ii) a first outlet communicating with the inlet and arranged to enable welding gas to be delivered to a first location; and ii) a second outlet communicating with the inlet and arranged to enable welding gas to be delivered to a second location.
18. Welding apparatus according to claim 17, further comprising a closure within the connector for controlling the flow of gas through at least one of the first and ** second outlet. * * ***.

****** *
19. Welding apparatus according to claim 18, wherein the gas is arranged to be delivered from the gas supply to the welding apparatus to perform a shielding' * welding function when the closure closes one of the outlets. * * * **
20. Welding apparatus according to claim 19, wherein the gas is arranged to be directed simultaneously through the first and second outlet to perform a simultaneous purging' and shielding' welding function when the closure remains opened.I