IES70920B2 - Improvements in and relating to welding jigs - Google Patents

Abstract

A welding jig (1) comprises a main chassis (10) on which jig member (20) for locating and clamping components (2) to be welded is rotatably mounted for movement into a plurality of different orientations to facilitate accessing joints (7) to be welded. A spring loaded engagement pin (55) slidable in a housing (56) is mounted on a braking disc (46) fast on one of the shaft (34) is selectively engagable with eight engagement openings (58) in a fixed disc (45) mounted on the main chassis (10) for selectively securing the jig member (20) in eight respective desired orientations. A brake is provided to control rotation and the workpiece may be cleaned while still mounted on the jig.

Description

Improvements in and relating to welding jigs Introduction The present invention relates to a welding jig for supporting and locating a plurality of components of a workpiece to be welded.

Welding jigs for locating and supporting components of a workpiece during welding are known. In general, such jigs comprise a platform or framework on which locating means for locating the components relative to each other are provided, and clamping means, in general, are also provided for clamping the components in position when located. Depending on the size of such jigs, they may be placed on a work bench, or on the floor. However, where jigs are relatively large, in general, they must be left in the one orientation, either placed on the ground or placed on the work bench. Thus, all welds which are required to weld the components together must be carried out with the jig in this orientation. In many cases, this presents major problems, particularly, where the workpiece comprises a number of components, and some of the joints to be welded are difficult to access. In such cases, after welding some of the joints and tacking others of the joints together, it is necessary to remove the components from the jig for welding of the remainder of the joints which are difficult to access from the jig. This, it will be appreciated has many disadvantages, in that it is inefficient, and can seriously affect the dimensional accuracy of the fully welded workpiece.

There is therefore a need for a welding jig for supporting, and locating components of a workpiece to be welded which overcomes these problems. $7092» J - 2 The present invention is directed towards providing such a welding jig. .

Statements of Invention According to the invention there is provided a welding jig for supporting and locating components of a workpiece to be welded, the welding jig comprising a main chassis, a jig means for supporting and locating the components of the workpiece, a mounting means formed from an elongated shaft extending outwardly from respective opposite ends of the jig means, and defining a rotational axis, and bearing means on the main chassis for rotatably carrying the shaft, a securing means for selectively securing the jig means in a plurality of orientations relative to the main chassis for presenting the workpiece to an operator at different orientations and an adjustable brake means for varying the rotational speed of the jig means on the shaft. * The advantage of an adjustable brake means is hard to over-emphasise. It is easy to appreciate the advantage of a brake, however, to have one that can be adjustable so that the operator can ensure that the correct resistance to rotation of the jig is achieved is all important. It ensures that when the jig is to be moved from one orientation to another orientation that on release of the securing means, the jig will not, under the weight of itself alone or of itself and the workpiece, move rapidly or sharply causing possible injury. It will also ensure that the operator will be able to relatively easily move the workpiece from one orientation to another. Safety is a primary requirement and indeed should a securing means become disengaged for some reason, it is vital that injury to a tradesman will not occur.

Additionally a particularly suitable embodiment of the invention is one in which the brake means comprises a braking disc rigidly mounted on the shaft, the braking disc being located adjacent a fixed disc and co-axially aligned therewith, and having a first radial surface which faces a second radial surface of the fixed disc, a disc of friction material being provided between the first and second surfaces for co-operating with the first and second surfaces for controlling the speed of the jig means. This is particularly advantageous in that it is a relatively simple construction, can be easily adjusted and the use of friction material has been found to be particularly advantageous.

Again such an open work construction in an environment such as will be the case with welding is one that provides additional advantages. It can be relatively easily cleaned, it will not clog up with dirt, thus, operating erratically and in general is a most efficient way of performing the invention.

In this context it is preferable that the disc of friction material is rotatable relative to the fixed and braking discs. This ensures that clogging will not occur and provides a relatively simple and easily manufactured device of welding jig. petajjed pescyjptipn pf......the-laygntiop The invention will be more clearly understood from the following description of a preferred embodiment thereof given by way of example only, with reference to the accompanying drawings in which:30 Fig. 1 is a perspective view of a welding jig according to the invention; Fig. 2 is an end elevational view of the welding jig in one orientation; Fig. 3 is a view similar to Fig. 2 illustrating the welding jig in another orientation; Fig. 4 is a view similar to Fig. 2 illustrating the welding jig in a further different orientation; Fig. 5 is a cross-sectional view of a detail of the -welding jig of Fig. 1 on the line V-V of Fig. 2; Fig. 6 is a view similar to Fig. 5 of the detail of Fig. 5 illustrating portion of the detail of Fig. 5 in a different position; Fig. 7 is a cross-sectional end elevational view of portion of the detail of Fig. 5 on the line VII-VII of Fig. 5; and Fig. 8 is a perspective view of a workpiece also according to the invention which was welded together on the welding jig of Fig. 1.

Referring to the drawings there is illustrated a welding jig according to the invention indicated generally by the reference numeral 1 for locating and supporting a plurality of components 2 which are to be welded together to form a workpiece 3. Briefly, the workpiece 3 is a framework comprising a plurality of the components 2 which are struts 5 of box-section material which are all seam welded together by seam welds 6 which extend continuously around each joint 7, see Fig. 8. The workpiece 3 is a particularly high precision framework, and accordingly, it is essential that when the component struts 2 are welded together that the framework is dimensionally accurate.

The welding jig 1 comprises a main chassis 10 which comprises a ground engaging base frame 11, and a pair of uprights 12 extending upwardly from opposite ends of the base frame 11. The base frame 11 comprises a pair of spaced apart longitudinally extending side members 15 of channel section steel joined by end members 16, also of channel section steel. The uprights are of box steel and extend upwardly from the end members 16 and are located and strengthened by pairs of inclined struts 17 of boxsection steel extending from the end members 16. The base frame 11, uprights 12 and struts 17 are welded together.

A jig means for locating and supporting the components 2 during welding comprises a double sided jig member 20 which is rotatably mounted about a horizontal rotational axis 21 through a plurality of orientations relative to the main chassis 10, as will be described below.

A plurality of locating means, namely, locating members 30 of steel are secured to the jig member 20 for locating the components 2 in position as are a plurality of clamps 32.

Mounting means comprising an elongated shaft 34 of steel extends through the sub-frame 23 and outwardly from the jig member 20 at opposite ends thereof and is rotatably carried on the main chassis 10 by a pair of bearings 35 mounted on the uprights 12 of the main chassis 10 for rotatably mounting the jig member 20 about the rotational axis 21. The shaft 34 extends through mounting plates 37 of steel which are secured by welding to the end members 27 of the sub-frame 23, and the shaft 34 defines the rotational axis 21 of the jig member 20. Side edges 38 of the platforms 24 extend parallel to the rotational axis 21, and the rotational axis 21 lies halfway between the side edges 38, and halfway between the platforms 24. The bearings 35 are plummer block bearings which are secured by screws (not shown) to horizontal support plates 40 of steel supported on and welded to the tops of the uprights 12. A sleeve 41 rotatably mounted in a housing 42 of each bearing 35 engages and locates the shaft 34 relative to the main chassis 10. Grub screws 43 in the sleeves 41 locate and secure the shaft 34 in the sleeves 41 for locating the jig member 20 relative to the main chassis 10.

Brake means for controlling the rotational speed of the jig member 20 relative to the main chassis 10 comprises a fixed annular disc 45 of steel which is welded to one of the support plates 40, and a braking disc 46 also of steel which is welded to the shaft 34 and is co-operable with the fixed disc 45. The fixed disc 45 and braking disc 46 are co-axial with the shaft 34. The braking disc 46 and the fixed disc 45 are provided with respective first and second radial faces 48 and 49 which face each other. A friction means comprising a friction disc 50 is located between the fixed disc 45 and the braking disc 46 and is rotatable on the shaft 34 and is co-operable with the first and second faces 48 and 49, respectively, for controlling the rotational speed of the jig member 20 relative to the main chassis 10. Adjusting means for adjusting the braking force between the discs 45 and 46 and the friction disc 50 for varying the rotational speed of the jig member 20 in the main chassis 10 is provided by axially sliding the shaft 34 in the respective sleeves 41 of the bearings 35 for varying the pressure between the first and second faces 48 and 49, respectively and the friction disc 50. Thus, the grub screws 43 effectively act as adjusting means for adjusting the braking force. By loosening the grub screws 43 the shaft 34 may be axially slid in the sleeves 41 until the desired braking pressure between the discs 45, 46 and 50 is achieved, at which stage the grub screws 43 are secured to hold the shaft 34 captive in the sleeves 41.

Securing means comprising complementary inter-engagable first and second engagement means are provided for selectively securing the jig member 20 in each of the plurality of orientations, which in this case, are eight orientations so that the receiving surfaces 25a and 25b of the platforms 24a and 24b may be presented in any of the various orientations relative to the main chassis 10 to an operator to facilitate welding of the components 2 of the workpiece 3. The first engagement means comprises an engagement pin 55 of circular cross-section slidably carried in a cylindrical housing 56 of steel welded to the braking disc 46. A plurality of second engagement means formed by eight engagement openings 58 are provided at circumferentially equi-spaced intervals around the fixed disc 45 for releasably receiving the engagement pin 55.

The engagement pin 55 is of steel of circular crosssection and is slidable in a bore 60 extending through the cylindrical housing 56 parallel to the rotational axis 21 of the jig member 20. The engagement pin 55 is slidable from an engaged position illustrated in Fig. 5 engaging one of the engagement openings 58 for securing the jig member 20 in one of the orientations relative to the main chassis 10 to a disengaged position illustrated in Fig. 6 disengaged from the engagement openings 58 to permit rotation of the jig member 20 relative to the main chassis . A compression spring 62 located in the bore 60 in the cylindrical housing 56 acts between a shoulder 63 in the bore 60 and a flange 64 on the engagement pin 55 for spring, urging the engagement pin 55 into the engaged position. An opening 65 which is axially aligned with the bore 60 in the braking disc 46 accommodates the engagement pin 55 into the engagement openings 58. The engagement openings 58 are of circular cross-section and of diameter substantially similar to the diameter of the engagement pin 55 to facilitate sliding engagement between the engagement pin 55 and the respective engagement openings 58, and also to facilitate securing the jig member 20 to the main chassis 10 relatively securely without angular play between the jig member 20 and the main chassis 10 when secured by the engagement pin 55. A knob 67 is provided on the engagement pin 55 to facilitate sliding the engagement pin between the engaged and disengaged positions. The outer diameter of the friction disc 50 is such as to provide clearance for the engagement pin 55.

With the engagement pin 55 held in the disengaged position the jig member 20 is rotated relative to the main chassis 10 until it is in the horizontal position with the locating members 30 exposed. The engagement pin 55 is moved into the engaged position engaging the appropriate engagement opening 58 for securing the jig member 20 in the horizontal orientation. The components 2 of the workpiece 3 are then placed on the jig member 20 and are located in their correct positions by the locating members 30. The clamps 32 are operated to clamp the located components relative to each other. While the jig member 20 is horizontal, the parts of the joints 7 between the components 2 which can readily easily be seam welded are seam welded. Once the part of all the joints 7 between the components have been partly seam welded, or at least tacked, the engagement pin 55 is moved into and held in the disengaged position, and the jig member 20 is rotated until the receiving surface 25 with the workpiece 3 thereon is in a desired orientation so that other parts of the joints 7 becomes more easily accessible. The engagement pin 55 is moved into the engaged position engaging the appropriate engagement opening 58 for securing the jig member 20 in the selected orientation. These parts of the joints 7 are then welded. The engagement pin 55 is again moved into the disengaged position and the jig member 20 is rotated into another orientation where further parts of the joints 7 between the components 2 become more easily accessible. The engagement pin 55 is moved into the engaged position engaging the appropriate engagement opening 58 for securing the jig member 20 in the selected orientation. These parts of the joints are then welded, and if necessary, the jig member 20 is again rotated into a further orientation, and so on, until all the parts of the joints 7 which can be accessed with the workpiece 3 secured on the jig member 20 have been welded. The clamps 32 are then released and the workpiece 3 is removed from the receiving surface 25. Any remaining parts of the joints 7 which have not been seam welded are now seam welded.

The advantages of the invention are many. The main advantage of the invention is that by virtue of the fact that the jig member 20 is rotatable and may be secured in a number, in this case, eight different orientations, parts of joints between the components 2 forming the workpiece 3, which would otherwise be inaccessible while the components are clamped on the jig member 20 in the horizontal or in one fixed orientation, can readily easily be accessed by merely changing the orientation of the jig member 20. Thus, by using the welding jig 1 according to the invention considerably greater lengths of seam 6 between joints 7 of the workpiece 3 can be seam welded prior to the workpiece 3 being removed from the jig member 20. This thus, provides a considerably more dimensionally accurate workpiece.

While the welding jig has been described as comprising a main chassis of particular shape and construction, other suitable forms of main chassis may be provided. Needless to say, other suitable jig means may be provided. It will of course be appreciated that other suitable locating means and clamp means for locating and clamping the components of the workpiece to the jig means may be provided, and of course it will be readily apparent to those skilled in the art that the location and orientation of the locating members and clamps may be rearranged for receiving components of other workpieces.

While a particular construction of securing means has been provided, other suitable securing means may be provided, and while it is preferable, it is not essential to provide brake means. Where brake means are provided, any other suitable brake means may be used.

Claims (5)

1. A welding jig for supporting and locating components of a workpiece to be welded, the welding jig comprising a main chassis, a jig means for supporting 5 and locating the components of the workpiece, a mounting means formed from an elongated shaft extending outwardly from respective opposite ends of the jig means, and defining a rotational axis, and bearing means on the main chassis for rotatably 10 carrying the shaft, a securing means for selectively securing the jig means in a plurality of orientations relative to the main chassis for presenting the workpiece to an operator at different orientations and an adjustable brake means for varying the 15 rotational speed of the jig means on the shaft.

2. A welding jig as claimed in Claim 1 in which the brake means comprises a braking disc rigidly mounted on the shaft, the braking disc being located adjacent a fixed disc and co-axially aligned therewith, and 20 having a first radial surface which faces a second radial surface of the fixed disc, a disc of friction material being provided between the first and second surfaces for co-operating with the first and second surfaces for controlling the speed of the jig means. 25

3. A welding jig as claimed in Claim 2 in which the disc of friction material is rotatable relative to the fixed and braking discs.

4. A welding jig substantially as described herein with reference to and as illustrated in the accompanying 30 drawings.

5. A workpiece comprising a plurality of components welded together on the welding jig of any of Claims 1 to 4.