WO2012073090A1

WO2012073090A1 - Arc welding apparatus

Info

Publication number: WO2012073090A1
Application number: PCT/IB2011/002837
Authority: WO
Inventors: Willem Nicolaas Van Rensburg
Original assignee: Robo-Arc Consulting (Pty) Ltd
Priority date: 2010-11-30
Filing date: 2011-11-28
Publication date: 2012-06-07

Abstract

Welding apparatus (1 ) of the type employing welding rods (2) coated with flux material is provided. A feed mechanism for feeding welding rods individually in a longitudinal direction along a feed path towards a welding site includes a feed carriage (6) having an electrically conductive clamp (7) for transferring electrical energy to a welding rod, in use, and a reversible drive mechanism for moving the feed carriage towards and away from the welding site. An automatic welding rod transfer mechanism generally includes one or more grippers (20) movable in a direction transverse to that of the movement of the feed carriage in order to grip and transfer a welding rod contained in a predetermined position in a magazine (40) supported on the body, in use, to the feed path. A clamp releasing mechanism is preferably associated with the welding rod transfer mechanism for releasing the electrically conductive clamp to disengage any welding rod stub that may be gripped thereby and enable a welding rod stub to be engaged and a fresh welding rod to be moved from the magazine to an operative position in the feed path. An indexing mechanism (30) is provided for presenting a fresh welding rod in a position in which the welding rod transfer mechanism can engage it preparatory to moving it into the feed path of the welding apparatus.

Description

ARC WELDING APPARATUS

FIELD OF THE INVENTION

This invention relates to arc welding apparatus of the type that employs welding rods of a finite length that are typically covered with flux along a major part of their length with the welding rod itself being exposed at one end for connection to an electrical power supply by way of an electrically conductive clamp.

BACKGROUND TO THE INVENTION Arc welding apparatus that uses consumable electrodes generally takes one of two forms, namely the type outlined above, and the so-called metal inert gas (MIG) apparatus in which metal wire is used as the consumable welding medium and the arc is maintained in an inert gas atmosphere. The latter type of apparatus works effectively in many applications that are often of a relatively light duty type. However, the type that employs consumable welding rods, is also widely used for numerous different purposes and especially in heavier duty applications. It is, indeed, the preferred welding method in many applications such as the fabrication of pressure equipment due to the enhanced weld quality and depth.

It is to be mentioned that there is also a different variety of welding that uses non-consumable tungsten electrodes, namely tungsten inert gas (TIG) welding, that may use no consumable filler wire in which instance the metal of the workpiece is welded directly, or it may use a consumable filler metal wire.

CONFIRMATION COPY

P2360PC00(WeWwg Apparatus) The balance of this specification will be directed exclusively at the type of welding that employs consumable welding rods covered with a flux material and that is sometimes referred to as stick welding. It has been proposed that the feed of welding rods of this type to a workpiece during welding operations be automatic with the welding rods being fed in an end on end relationship. The speed of feeding the welding rod to the arc is dependent on ambient conditions, the thickness and composition of the material being welded, and the speed at which the welding head is moved relative to the workpiece. However, applicant is not aware of any commercially available apparatus of this nature.

One of the main drawbacks of apparatus of the type using welding rods is the fact that when a welding rod has been consumed, the stub that remains needs to be released from the electrically conductive clamp and replaced by a full-length rod in order to continue with a single weld. Such replacement is generally carried out manually and is accompanied by the drawback that the procedure usually takes longer than the period of time for which a molten pool of slag at the weld remains hot enough for an arc to be re-struck and the weld to be continued without cleaning away any solidified slag.

As a result, the procedure is generally to manually discard the residual stub, replace it manually with a full-length welding rod, and, because this generally takes an appreciable length of time, chip away solidified slag before continuing with the weld.

This procedure is therefore time-consuming and also opens up the possibility of a weld having deleterious discontinuities along its length.

P2360PC00(WeWwg Apparatus) SUMMARY OF THE INVENTION

In accordance with this invention there is provided welding apparatus of the type employing welding rods coated with flux material to effect welding operations, the welding apparatus comprising a body having a feed mechanism for feeding welding rods individually in a longitudinal direction along a feed path towards a welding site that is external of the body, the feed mechanism including a feed carriage having an electrically conductive clamp for transferring electrical energy to a welding rod, in use, and a reversible drive mechanism for moving the feed carriage towards and away from the welding site; the welding apparatus being characterised in that it includes a welding rod transfer mechanism including one or more rod transfer elements movable in a direction transverse to that of the movement of the feed carriage in order to transfer a welding rod contained in a predetermined position in a magazine supported in a position fixed relative to the body, in use, to the feed path; a clamp releasing mechanism for releasing the electrically conductive clamp to disengage any welding rod stub that may be gripped thereby and enable such welding rod stub to be removed from the clamp and a replacement welding rod to be moved from the magazine to an operative position in the feed path and thereafter releasing the electrically conductive clamp to engage an electrically conductive end of the welding rod once it is in its operative position, and an indexing mechanism for presenting a replacement welding rod in a position in which the one or more rod transfer elements can engage it to moving it into the feed path of the welding apparatus.

Further features of the welding apparatus of the invention provide for the reversible drive mechanism to include an endless drive belt or chain; for the feed carriage to be longitudinally movable on a rail therefor; for the reversible drive mechanism to include a main drive servo motor; for the body to be configured to be supported by a transport carriage for moving the welding apparatus over the surface of a workpiece, especially in relation to a track

P2360PC00(We«i/jg Apparatus) iCMB20 1 1 / 0 0 2 8 3 7

4 provided on the surface of the workpiece and that may be removable therefrom in which instance the workpiece may be a large diameter pipe with the track encircling the outer surface of the pipe adjacent and end thereof. Still further features of the welding apparatus of the invention provide for the indexing mechanism to include a magazine drive for moving a holder, typically in the form of a carousel, in a magazine to a predetermined position in which a particular welding rod is presented for engagement by the one or more grippers; for the indexing mechanism to include a rotatable driving coupling for co-operation with a coupling on the magazine; for the magazine drive to be coupled to the clamp releasing mechanism such that the clamp is released ahead of any movement of the holder or carousel to a position in which a particular welding rod is presented for engagement by the one or more grippers in order to release any welding rod stub that may be clamped thereby; and for a separate magazine drive servo motor to be arranged to operate the clamp releasing mechanism and holder or carousel.

Yet further features of the welding apparatus of the invention provide for the one or more rod transfer elements to be one or more grippers and wherein a gripper is optionally configured to grip any residual stub of a welding rod and eject it or return it to the magazine; for there to be at least two grippers spaced longitudinally along the feed path; for the two grippers to be carried by a gripper carrier that is movable transversely to the feed path; for the gripper carrier to be movable by means of a gripper carrier servo motor and gear assembly; and for the individual grippers to be movable between open and closed positions by means of separate actuators, especially solenoids having their axes extending transverse to the feed path.

The invention also provides a magazine for housing and dispensing welding rods in association with welding apparatus as defined above wherein the magazine has a movable holder having multiple parallel docking positions spaced apart relative to a magazine housing in which the holder is housed

P2360PC00(Welding Apparatus) wherein parallel welding rods can be releasably accommodated in a predetermined array with a spring catch arrangement for retaining each of multiple welding rods and any welding rod stubs that may be installed therein releasably in position in the magazine, and a coupling member rotatable in unison with the holder and engageable with a driving cooperant coupling provided on the welding apparatus.

The features of the magazine provide for the holder to be a rotatable carousel having multiple docking positions angularly spaced about an axis of rotation of the carousel relative to the magazine housing in which the carousel is located; for the holder to have recesses extending along the length of the docking positions over a major part of the length of a welding rod with portions of the recesses being open to allow access to a welding rod accommodated in a recess by the one or more grippers of the welding apparatus; and for at least one channel shaped retaining spring plate to be provided for retaining an end region of a welding rod or welding rods in association with the holder in a manner in which release thereof by means of a gripper of welding apparatus as defined above is permitted. The invention also provides welding apparatus as defined above in combination with a magazine as defined above.

The welding apparatus may form part of dedicated welding apparatus designed for specific purposes, especially, but not exclusively, welding apparatus for butt welding ends of relatively large diameter pipes together.

In order that the above and other features of the invention may be more fully understood one embodiment of both the welding apparatus and the magazine will now be described with reference to the accompanying drawings.

P2360PC00(WeW;ng Apparatus) BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:-

Figure 1 is a perspective view of one embodiment of welding apparatus according to the invention in exploded relationship relative to one embodiment of cooperating magazine according to the invention from a first side thereof;

Figure 2 is an elevation of the welding apparatus according to the invention from a second side thereof with the magazine removed and with its cover plate also removed in order to reveal certain aspects of the interior thereof;

Figure 3 is a side view of the welding apparatus with the magazine installed thereon and part of the covers removed to reveal the magazine drive servo motor and associated mechanism; Figure 4 is an enlarged view of the magazine drive servo motor and associated mechanism;

Figure 5 is a perspective view of a magazine with the door open and a portion of the side wall cut away to show a part of the carousel therein;

Figure 6 is a perspective side view of the welding apparatus from a raised position on the second side thereof with the cover plates and some components removed to reveal much of the operating mechanism;

P2360PC00(WeWing Apparatus) Figure 7 is a similar side view to that shown in Figure 6 but taken from a lower position to reveal more clearly some components not clearly shown in Figure 6;

Figure 8 is an enlarged perspective view of the upper gripper assembly;

Figure 9 is a block diagram of the control circuit arrangement;

Figure 10 is a perspective view illustrating one application of the welding apparatus to the welding of large diameter pipe ends from one side thereof; and,

Figure 11 is a perspective view of the welding apparatus illustrated in

Figure 10 from the other side thereof.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

In the embodiment of the invention illustrated in the drawings, the welding apparatus, generally indicated by numeral (1), is of the type employing welding rods (2) coated with flux material along a major part of their length to effect welding operations wherein a short length of the metallic rod is exposed at one end for engagement by an electrically conductive clamp as described below.

The welding apparatus comprises a body having a feed mechanism for feeding welding rods individually in a longitudinal direction along a feed path towards a welding site that is external of the body at a working end (3) of the apparatus and that is outside of a footplate (4) having an aperture (5) through which the welding rod is moved, during use.

P2360PC00(WeW/ng Apparatus) The feed mechanism includes a feed carriage (6) having an electrically conductive clamp (7) for transferring electrical energy to a welding rod, in use. The feed carriage is longitudinally slidable in forward and reverse directions on a rail (8) therefor so as to move the feed carriage towards and away from the welding site. A reversible drive mechanism for the feed carriage includes an endless drive belt or chain (9) that is driven by a reversible drive mechanism including a main drive servo motor (10).

A flexible braided electrical conductor enclosed within a series of juxtaposed electrically insulating sheath elements, the entire assembly being collectively indicated by numeral (1 1 ), extends in a lateral direction so that the electrically conductive clamp remains always positively connected to the electrical supply by means of fixed conductors (12), as shown in Figure 2. The flexible electrical conductor is biased to a retracted position by a long compression spring (13). It will be understood that as the feed carriage is moved towards the welding site with a welding rod in position, the welding rod will be fed towards the relevant workpiece and become consumed as arc welding progresses. As provided by this invention, the welding apparatus includes a welding rod transfer mechanism including, in this instance, two longitudinally spaced welding rod transfer elements in the form of grippers (20) each of which is composed of two channel shaped jaws adapted to accommodate and grip the outer surface of the flux coating of a welding rod in the operative position. The grippers are carried by a common gripper carrier (21 ) that is movable at generally right angles to the feed path with the gripper carrier being movable outwards and inwards by means of a gripper carrier servo motor (22) and gear assembly (23). The individual grippers are movable between open and closed positions by means of separate solenoids (24) (see Figure 6) mounted to the gripper carrier and having their axes also extending at generally right angles to the

P2360PCOOfWeWing Apparatus) feed path. The grippers and gripper carrier are thus movable in unison in a direction transverse to that of the movement of the feed carriage, and thus the feed path. Opening and closing of the grippers in order to grip and transfer a welding rod stub from the feed carrier to the magazine, and subsequently engage a fresh welding rod contained in a predetermined position in a magazine (40) when it is supported on the body, in use, to move it into the feed path, is achieved by operation of the solenoids and a suitable mechanical linkage. The arrangement is such that the gripper more remote from the working end of the welding apparatus is configured to grip any residual stub of a welding rod held by the retracted carriage and electrically conductive clamp, and return it to the magazine prior to engaging a fresh full-length welding rod in the magazine as will be more fully explained below.

The welding apparatus includes an indexing mechanism (30) for enabling the magazine to receive any residual welding rod stub and to present a fresh welding rod in a position in which the grippers can engage it preparatory to moving it into the feed path of the welding apparatus. The indexing mechanism includes a rotatable driving coupling (31 ) (see especially Figure 7) in operative cooperation with a coupling (41 ) (see especially Figure 5) on the magazine for moving a carousel (42) in the magazine to a predetermined angular position in which a particular welding rod is presented for engagement by the grippers.

The magazine drive includes a separate magazine drive servo motor (32) arranged to drive the indexing mechanism and also to operate a clamp releasing mechanism once the gripper remote from the welding site has been operated to grip any welding rod or welding rod stub held by the clamp with the feed carriage in the fully retracted position. The arrangement is such that the clamp is released only after any such welding rod or stub has been gripped by the gripper. Immediately thereafter the electrically conductive

P23₆0PC00(W¾M;^'wg Apparatus) clamp is released and the welding rod or stub may be returned to the vacant position in the magazine from which it was extracted prior to being used.

The return of the welding rod stub to the magazine is followed by a retraction of the grippers; and operation of the indexing movement of the carousel to a position in which a fresh welding rod is presented for engagement by the grippers. With the electrically conductive clamp still in the released condition, the fresh welding rod is then moved from the magazine to an operative position in the feed path of the welding apparatus and the electrically conductive clamp is engaged with the electrically conductive end of the welding rod once it is in its operative position in the feed path.

Turning now more particularly to the magazine (40) for housing and dispensing welding rods in association with the welding apparatus as described above, the rotatable carousel (42) has multiple parallel docking positions in the form of longitudinal recesses indicated by numeral (43) angularly spaced apart relative to the axis of rotation of the carousel such that multiple parallel welding rods may be releasably accommodated in a cylindrical array. The recesses extend along the length of the docking positions over a major part of the length of a welding rod with portions of the recesses being open, as indicated by numeral (44), to allow access to a welding rod accommodated in a recess by the grippers of the welding apparatus A channel shaped retaining spring plate arrangement (45) is provided at the end region remote from the working end of the welding apparatus for retaining each of multiple welding rods and any welding rod stubs that may be installed therein releasably in position in the carousel. The spring catch arrangement holds a welding rod or welding rod stub in a manner in which release thereof by means of a gripper of the welding apparatus may be carried out.

P236OPC00(WeWmg Apparatus) ^, .

C UI 2O 1 1 / u y 8 3 7-

11

The coupling member (41 ) of the carousel is rotatable in unison with it and operatively inter-engages with the rotatable driving coupling (31 ) of the welding apparatus when the magazine is it in its installed position. The magazine has a generally rectangular housing (47) and a door (48) for closing an access opening to the magazine when it is not in use. In the installed position on the welding apparatus, the door is held open, as will be quite clear from a reference to Figure 1. For use, the welding apparatus is associated with means for moving it over the surface of a workpiece at a speed that is commensurate with the specifications of the relevant welding rods and the nature of the workpiece as well as ambient conditions. Alternatively, the workpiece could be moved relative to the welding apparatus, such as, for example, on a conveyor of some description. Of course, moving of the welding apparatus relative to a workpiece may involve any known techniques such as moving it such that the welding rod has a zig-zag or orbital motion.

Whilst numerous possibilities exist, in this embodiment of the invention, and as illustrated in Figures 10 and 1 1 , the welding apparatus is configured to be supported by a transport carriage (50) for moving the welding apparatus over the surface of a workpiece, especially in relation to a track (51 ) provided, either temporarily or permanently, on the surface of the workpiece. A mechanism associated with the transport carriage can engage and hold the welding apparatus relative to the track and thus the workpiece, as the welding apparatus is moved along the track by a suitable mechanism at a speed commensurate with the applicable conditions.

Such a track, as illustrated in Figures 10 and 1 1 , may encircle the outer surface of a large diameter pipe adjacent one end thereof so that the welding apparatus can join two butted ends of two lengths of pipe (55) in collinear relationship, an operation that is somewhat common in the field of welding.

P2360PC₀₀(T elding Apparatus) _

12

With particular reference to the Figure 9, control of the welding apparatus and magazine as described above takes place by way of a microprocessor or any other suitable electronic controller (60) together with, in this instance, input from an ammeter (61) that provides a measure of current being consumed and a voltmeter (62). Together with the ammeter and voltmeter provide a measure of the electrical energy being consumed. It is possible that other sensors could be used either in addition, or as an alternative, such as, for example, an infrared temperature sensor (63) for sensing the temperature of molten slag at the weld site. Of course, any single sensor or combination of sensors may be employed for control purposes.

The controller is programmed to conduct the welding routine of energising the gripper carrier motor to move the carrier and grippers laterally outwards with the feed carriage in a retracted position. This action has the effect of activating the solenoids to grip any welding rod or welding rod stub engaged by the electrically conductive clamp of the feed carriage followed by release of the electrically conductive clamp. The solenoids are then activated to grip any welding rod or welding rod stub gripped by the grippers into a vacant docking recess in the carousel (typically the docking recess from which it was extracted previously) and clipping it in position in the relevant spring catch arrangement. The grippers are then withdrawn momentarily to enable the indexing mechanism to move a fresh welding rod into registration with the grippers whereupon the grippers are moved forward to engage the fresh welding rod. The fresh welding rod is then moved into the feed path by withdrawing the grippers followed by engaging the electrically conductive clamp with the exposed conductive end of the fresh welding rod. The grippers are then disengaged from the fresh welding rod and the grippers and gripper carrier are withdrawn laterally into their inoperative positions. At this stage, the main drive servo motor is operated to move the tip of the fresh welding rod through the aperture in the footplate of the welding apparatus until it touches on the welding site, a condition that is sensed and

P2360PC00(WeW;ng Apparatus) upon which the fresh welding rod is automatically withdrawn an appropriately short distance so as to strike an arc between it and the workpiece.

It has been calculated that the exchange of a welding rod stub for a fresh welding rod in the manner described above can be achieved within a rather short time period and, in particular, a short enough time period to ensure that in at least most instances, slag associated with the last part of a weld that was created does not solidify and therefore an arc can be struck and welding continued without the necessity for removing solidified slag from that part of the weld. It has been estimated that a time period of about 1 second will be needed for a change of welding rods to be carried out in the manner described. Of course, the time period for which the weld remains sufficiently hot to avoid solidification of the slag at the most recent weld position will depend, at least to some extent, on ambient conditions.

It will be understood that numerous variations may be made to the embodiments of the invention described above without departing from the scope hereof. Simply by way of example, the magazine could be incorporated as a permanent part of the welding apparatus in which instance welding would have to be discontinued from time to time in order to recharge the magazine. Also, the one or more rod transfer elements need not be grippers but could be a different mechanism that pushes any residual stub of a welding rod and eject it or return it to the magazine and pushes a replacement welding rod from the magazine into the feed path. Numerous other variations are possible within the scope hereof.

P2360PC00(WeW/ng Apparatus)

Claims

14

CLAIMS:

1. Welding apparatus of the type employing welding rods coated with flux material to effect welding operations, the welding apparatus comprising a body having a feed mechanism for feeding welding rods individually in a longitudinal direction along a feed path towards a welding site that is external of the body, the feed mechanism including a feed carriage having an electrically conductive clamp for transferring electrical energy to a welding rod, in use, and a reversible drive mechanism for moving the feed carriage towards and away from the welding site; the welding apparatus being characterised in that it includes a welding rod transfer mechanism including one or more rod transfer elements movable in a direction transverse to that of the movement of the feed carriage in order to transfer a welding rod contained in a predetermined position in a magazine supported in a position fixed relative to the body, in use, to the feed path; a clamp releasing mechanism for releasing the electrically conductive clamp to disengage any welding rod stub that may be gripped thereby and enable such welding rod stub to be removed from the clamp and a replacement welding rod to be moved from the magazine to an operative position in the feed path and thereafter releasing the electrically conductive clamp to engage an electrically conductive end of the welding rod once it is in its operative position, and an indexing mechanism for presenting a replacement welding rod in a position in which the one or more rod transfer elements can engage it to moving it into the feed path of the welding apparatus.

2. Welding apparatus as claimed in claim 1 in which the reversible drive mechanism includes an endless drive belt or chain with the feed carriage being longitudinally slidable on a rail therefor.

P2360PC00(WeWi«g Apparatus) Welding apparatus as claimed in either one of claims 1 or 2 in which the reversible drive mechanism include a main drive servo motor.

Welding apparatus as claimed in any one of the preceding claims in which the indexing mechanism includes a magazine drive for moving a holder in a magazine to a predetermined position in which a welding rod is presented for engagement by the one or more rod transfer elements.

Welding apparatus as claimed in claim 4 in which the indexing mechanism includes a rotatable driving coupling for co-operation with a coupling on the magazine.

Welding apparatus as claimed in either one of claims 4 or 5 in which the magazine drive is coupled to the clamp releasing mechanism such that the clamp is released ahead of any movement of the holder to a position in which a particular welding rod is presented for engagement by the one or more rod transfer elements in order to release any welding rod stub that may be clamped thereby.

Welding apparatus as claimed in any one of claims 4 to 6 in which a separate magazine drive servo motor is arranged to operate the clamp releasing mechanism and the holder.

Welding apparatus as claimed in any one of the preceding claims in which the one or more rod transfer elements are one or more grippers and wherein a gripper is optionally configured to grip any residual stub of a welding rod and eject it or return it to the magazine.

Welding apparatus as claimed in claim 8 in which at least two grippers are spaced longitudinally along the feed path and are carried by a gripper carrier that is movable transversely to the feed path. 0(WeW/wg Apparatus) 12/073090 Ρ0Τ/ΙΒ ( Τ/ΙΒ2011/002837 ■ " v <L u :

16

10. Welding apparatus as claimed in either one of claims 8 or 9 in which the gripper carrier is movable by means of a gripper carrier servo motor and gear assembly. 11. Welding apparatus as claimed in any one of claims 8 to 10 in which the individual grippers are movable between open and closed positions by means of separate solenoids having their axes extending transverse to the feed path. 12. Welding apparatus as claimed in any one of the preceding claims in which a magazine is attached to the welding apparatus in cooperating relationship therewith.

13. Welding apparatus as claimed in any one of the preceding claims in which the apparatus is configured to be supported by a transport carriage for moving the welding apparatus over the surface of a workpiece in relation to a track provided, either temporarily or permanently, on the surface of the workpiece wherein a mechanism associated with the transport carriage can engage and hold the welding apparatus relative to the track and thus the workpiece as the welding apparatus is moved along the track by a suitable mechanism at a speed commensurate with the applicable conditions.

14. A magazine for housing and dispensing welding rods in association with welding apparatus as defined in any one of claims 1 to 13 in which the magazine has a movable holder having multiple parallel docking positions spaced apart relative to a magazine housing in which the holder is housed and wherein parallel welding rods can be releasably accommodated in a predetermined array with a channel shaped retaining spring plate arrangement for retaining each of multiple welding rods and any welding rod stubs that may be installed therein releasably in position in the magazine, and a coupling member

P2360PC00(Welding Apparatus) movable in unison with the holder and engageable with a driving cooperant coupling provided on the welding apparatus.

A magazine as claimed in claim 14 in which the holder is a rotatable carousel having multiple docking positions angularly spaced about an axis of rotation of the carousel relative to a magazine housing in which the carousel is located.

16. A magazine as claimed in either one of claims 14 or 15 in which the holder has recesses extending along the length of the docking positions over a major part of the length of a welding rod with portions of the recesses being open to allow access to a welding rod accommodated in a recess by the one or more grippers of the welding apparatus and at least one retaining spring is provided for retaining an end region of a welding rod or welding rods in association with the holder in a manner in which release thereof by means of a gripper of welding apparatus is permitted.

?2360PC00(Welding Apparatus)