METHOD AND APPARATUS FOR FORMING A DUCT SECTION

Abstract: Method and apparatus for forming a duct section by means of cutting from a strip supply of sheet metal, a length of such metal to define a leading and trailing end thereof and advancing the length of sheet metal in the direction of its length to a forming station; advancing the length by means of an automated handling system; forming on said leading and trailing edges, seam formation means to make said leading and trailing edges complementary for providing a folded and clenched seam in the final duct section, whilst at said forming station, forming the length of sheet metal into a duct section by folding same in a direction transverse to the length direction of the sheet section to bring leading and trailing edges into seam formation engagement, and folding and clenching said leading and trailing edges to form said seam.

Description: Method and apparatus for forming a duct section. This invention relates to the manufacture of ducts, especially but not exclusively those ducts which are used in domestic and commercial and industrial buildings for the transportation of air for air conditioning systems. Traditionally, such ducts are manufactured in sheet metal which is capable of being folded and bent into appropriate configuration, and many manufacturing methods and techniques are well established. Basically, the ducting is manufactured in lengths or sections, and these sections are connected end to end in situ in order to form the duct work of a building. Over the years, the manufacture of the duct sections has been progressively automated in order to speed up and facilitate manufacture, but basically the duct sections are manufactured from lengths of sheet metal folded into polygonal cross section, usually square or rectangular, and the free edges of the folded sheet are connected together by folding and crimping or by other means such as welding to form the finished duct section. The ends of the section are provided with flanges to permit sections to be connected end to end, and the flanges may be either formed integrally with the duct ends by appropriate processing, or the flanges may subsequently be attached thereto, as described for example in British Patent Specification No. 1,275,526. When the free edges of the sheet metal are folded and crimped in order to form the longitudinal seam of the duct section, it is usual for the folded sheet metal to be fed in the direction of its length through folding and sealing means such as a bank of folding and seaming rollers, and the folding and seaming rollers are offset from or separated from the plant which forms the folding of the sheet metal, because such folding is effected on sheet metal fed from a reel of such material and the folding takes place in a direction transverse to the length direction of the sheet metal strip. Thus, starting from the reeled metal strip, the strip is fed in the direction of its length and is folded at its leading end to define the duct section. The duct section is then cropped from the remainder of the strip and is fed in a direction of its length, which is at right angles to the direction of the length of the strip, through the folding and seaming rollers. This method of manufacture is inconvenient, and the plant utilised takes up substantial valuable floor space. The present invention in a first aspect seeks to provide a novel form of processing for the formation of duct sections. In various other more detailed aspects of the invention, means is provided for enabling the formation of integral flanges on the edges of the sheet metal which will form the ends of the duct section; means is also provided for the effective formation on the leading and/or trailing ends of the length of sheet metal to form a duct section of seam sections to permit the ready crimping together of such leading and trailing ends to form the duct section seam; clamping means is also provided for the crimping and clenching of the said leading and trailing ends to form said seam; a means is also provided for the automatic handling of the sheet metal whilst being formed and clamped as aforedescribed. Although reference is made hereinbefore to sheet metal, and only reference hereinafter will be made to such material, it is to be pointed out that the invention can be utilised with materials which exhibit equivalent characteristics to sheet metal. In accordance with a first aspect of the invention, a method of forming a duct section comprises cutting from a strip supply of sheet metal, a length of such metal to define a leading and trailing end thereof and advancing the length of sheet metal in the direction of its length to a forming station, and forming on said leading and/or trailing edges, seam formation means to make said leading and trailing edges complimentary for providing a folded and clenched seam in the final duct section, whilst at said forming station, forming the length of sheet metal into a duct section by folding same in a direction transverse to the length direction of the sheet section to bring leading and trailing edges into seam formation engagement, and folding and clenching said leading and trailing edges to form said seam. Preferably the said length is cut using blades that are driven by a number of evenly spaced parallel drivers, to enhance the closeness of the cut. The folding of the sheet material length into polygonal form may take place at the forming station, and to this end there may be a former around which the sheet metal is folded. Preferably the leading and trailing edges of the length of sheet metal will be provided with said seam formations so that they can be interclipped when the sheet metal is folded into polygonal form. Preferably the leading edge is formed with a seam formation defined by folding said leading edge upwardly and over the remainder of the sheet metal to form a hook edge on the top side of the sheet metal, whilst at the trailing edge there is preferably formed a U-shaped seam formation with the open side of the U facing downwardly so that when the sheet metal is folded to polygonal configuration, the leg of the ϋ section defining the extremity of the sheet material length engages in said hook formation, and in the subsequent clenching, the hook formation and said leg are folded and clenched together into a position lying in the plane of the adjacent side of the duct section. Preferably the length of sheet metal is advanced by means of an automated handling system. Preferably the automatic handling system comprises a carriage means, preferably having at least one attachment means such as a selectively activatable magnetic means or a suction means, adapted to travel along at least one carriage track such that the carriage means advances the length of sheet metal by a predetermined amount. Preferably the carriage means engages the length of sheet metal when at least one magnetic means is activated. Preferably the activated magnetic means or the suction means advances the length of sheet metal in a stepwise fashion. Preferably the automatic handling system comprises a plurality of carriage tracks such that the carriage means can engage the length of sheet metal from a plurality of positions. Preferably further still at least one track is located above the length of sheet metal and said track is provided with a downwardly sloping section which preferably terminates in a U-shaped bend such that the carriage means engages the length of sheet metal at a first position, prior to the downwardly sloping se ion, and thereafter moves the length of sheet metal downwardly, as the carriage means travels along the downwardly sloping section of the track, and then upwardly, as the carriage means travels along the U-shaped bend of the track. Preferably the carriage means when travelling along the track located above the length of sheet metal engages an end of the length of sheet metal at the first position and moves the engaged end downwardly towards a second end of the length of sheet metal in order to effect the engagement of said ends. According to a further aspect of the invention there is provided a method of forming a duct section wherein a length of metal is cut from a supply strip and is fed to a forming station at which it is multi-folded into duct form, and wherein a magnetic means or a suction means is used to feed the length stepwise to the forming station, said magnetic means also being positionable to assist in the final formation of the length into duct shape. A duct section fabricated in accordance with the invention may be provided with integral flanges, but it will be appreciated that the invention can be applied for the fabrication of duct sections for use with the separate "knock-on" flanges. Novel means for the folding of the seam formations are provided, novel means for the clenching and crimping of the inter-engaged seam formations is also provided, and novel means for the handling of a cut blank is further provided. When the sheet material length is provided with integral flanges, said flanges may be formed on the length prior to the arrival of same at the forming station. Appropriate forming rollers may be provided for forming such flanges, and the flanges may be progressively formed as the sheet metal is fed whilst part of the strip and before the cropping of same. In this connection, in order to be able to accommodate strip material of differing widths, it is provided that the forming rollers for forming said integral flanges be mounted for position adjustment towards and away from each other, and in a preferred construction, banks of rollers are inter¬ changeable with other rollers to provide flanges of different heights. Said rollers may be interchangeable in that an assembly is provided carrying two sets of rollers, and the assembly is rotatable in the nature of a turret to enable the different sized rollers to be independently selectable. By such utilisation of rollers of different sizes, and by virtue of the fact that the respective rollers for forming respective sides of the sheet metal can be moved together and apart, considerable flexibility in the handling of the most common sizes of sheet metal strips used for forming said ducts can be accommodated. Each of the various individual aspects of the present invention in itself constitutes a novel and advantageous feature, as does any combination of said features, and the various aspects in their specific embodiments will be described hereinafter in more detail in relation to the accompanying drawings which are partly diagrammatic, and wherein:- Figs. 1, 2 and 3 show in perspective view, various steps in the cropping of sheet metal strip to provide blanks which are formed into duct sections, Figs. 1, 2 and 3 showing the flanging and seam forming steps; Figs. 4 to 8 show in a sequence of steps the formation of the partly formed blank of Fig. 3 into the duct section to be produced; Fig. 9 is a perspective view of the completed duct section; Fig. 10 is a diagrammatic perspective elevation of a plant for forming the duct sections from reeled sheet metal strip; Fig. 10A shows in sectional elevation a proposed flange construction; Fig. 11 is a perspective elevation of the significant elements of the flange roll former station of the machine shown in Fig. 10; Figs. 12, 13 and 14 are respectively a side elevation, an end elevation, and a plan of one section of the flange roll former station of the machine shown in Fig. 10; Fig. 15 is a sectional elevation showing guillotine or cropping equipment for cutting the blank from the strip sheet metal and for simultaneously defining the seam formation at the trailing end of the blank; Fig. 16 is a sectional elevation of the forming station whereat the leading edge of the blank is provided with its seam formation, the blank is folded to duct shape, and the seam is closed; Figs. 16A to 16D show in sectional elevation the steps involved in providing the leading edge seam formation; and Fig. 17 shows in sectional side elevation an alternative mechanism for closing the duct seam. Fig. 18 is an exploded perspective view of a magnetised system for handling a cut blank; Fig. 19 is a side elevation view showing a magnetised handling system in operation; Fig. 20 is a side elevation view showing a magnetised handling system in co-operation with a forming means. Fig. 21 is a perspective view showing the magnetised handling system represented in figures 19 and 20. Referring to the drawings, and firstly to Figs. 1 to 9, in Fig. 1 reference numeral 10 represents a reel of sheet metal, typically sheet steel which is to be used for the formation of duct sections of the configuration shown in Fig. 9. The sheet steel is progressively unwound from the reel 10 and firstly the steel strip passes through a levelling station at which wrinkles and residual stress as a result of the material being in reel form, are removed. Next, the strip edges are notched as indicated at 12 to reduce the width of the strip for a purpose which will be clear from the following description. The notches 12 have an overall length L and the notches are equally spaced to permit the production of a multiplicity of duct sections as shown in Fig. 9 and of identical size. The sheet steel is guillotined, preferably using blades operated by means of a ram arranged in parallel to ensure the reliability of a clean cut at a position intermediate the ends of the notches, which position is accurately ascertained, in order to define the trailing edge 14 and a leading edge 16 which are of widths in a pre-determined ratio. Typically, for reasons which will be clear, the trailing edge 14 is of a width which is twice the width of the leading edge 16. Also, simultaneous with the guillotine as will be explained hereinafter, the trailing edge 14 is deformed from the flat configuration to the U-shaped configuration shown. This deformed configuration forms a seam formation which inter-engages with a corresponding seam formation which is formed on a leading edge 16 at a later stage of the process. By virtue of the cropping of the strip, a blank 20 is defined which has notched corners by virtue of the notching hereinbefore referred to, and the trailing end 14 is deformed as shown in dotted lines in Fig. 1. The blank moves in the direction 22 through the machine which effects further processing of same. In a preferred form of the apparatus movement of blank 20 is effected by means of a magnetised handling system as depicted in Figs. 18, 19, 20 and 21. Referring now to Fig. 18, an apparatus in accordance with the invention shown in Fig. 10 is provided with side panels 2OX. Panels 20X are provided with two spaced tracks 22X and 24X. Track 22X is located above track 24X and has the following profile: track 22X extends parallel with the longitudinal axis of panel 2OX for a short distance, represented by the distance between points N and 0, before extending upwardly at an inclined angle to a point P whereat track 22X extends parallel with the longitudinal axis of panel 2OX to a point Q where track 22X extends downwardly at an inclined angle to a point R where track 22X terminates in a U-shaped bend. Below track 22X is located track 24X which extends parallel with the longitudinal axis of panel 2OX. Neither track 22X nor track 24X extend to the edges of panel 2OX. Tracks 22X and 24X are connected by means of shaft 26X which houses an air cylinder 28X. Panel 2OX is further provided with longitudinal tracks 5OX and 52X on the longitudinal edges of panels 20X. A horizontal carriage 3OX is adapted to travel along panel 2OX in a horizontal direction by means of rollers 32X travelling in tracks 5OX and 52X. Attached to the outermost side of horizontal carriage 30X is a vertical carriage 34X which extends outwardly from carriage 3OX and is bent downwardly into a vertical position at point S and then upwardly into a horizontal position at point T and to so produce a step region whereby vertical carriage 34X extends outwardly from carriage 3OX in a position below same. Carriage 34X is adapted to travel vertically within carriage 3OX by means of rollers 32Y which travel in longitudinal tracks 50Y and 52Y provided on the longitudinal edge of carriage 3OX. Vertical carriage 34X is provided with a series of attachment means such as electromagnets 4OX or suction pads (not shown) which are adapted to engage blank 20. It will be understood that although the attachment means will be described with reference to a magnetic means, the invention encompasses other means of attachments such as suction pads or the like. The apparatus is further provided with grid bars 6OX that are mounted at a far end (not shown) by convential mounting means. Grid bars 6OX are of rectangular section and positioned such that their longitudinal axis lies in a horizontal plane. Grid bars 6OX lie above lower grid members 60Y and so define gaps 60Z through which blank 20 moves as it travels within the apparatus towards the forming means. Thus grid bars 6OX ensure blank 20 remains relatively flat as it travels through the apparatus. The farthermost end 62X of grid bars 6OX are inclined downwardly and so provide a surface on which the leading end of a blank 20 may rest during movement of a blank 20 about the forming means. Magnets 4OX attached to carriage 34X are positioned to lie in between grid bars 6OX. Thus it can be seen that this arrangement provides for magnets 4OX to be raised between grid bars OX. The magnetised handling system operates as follows:- At a point in the handling cycle air cylinder 28X will occupy a lowermost position in shaft 26X, carriage 30X will be located next to shaft 26X and carriage 34X positioned on carriage 3 X, will be located opposite shaft 26X at a point immediately next to track 24X. At this stage in the cycle electromagnets 4OX are activated and thus engage the trailing end of blank 20. As seen in figure 19 magnets 40X engage blank 20 at a position to the rear of same thus contacting the outermost downwardly extending limb of edge 38. As horizontal carriage 3OX travels along track 24X in the direction indicated by arrow 42X the carrier 34X moves blank 20 through gaps 60Z towards folding searner 84. This action of the automated handling system guides blank 20 towards searner 84. When horizontal carriage 30X reaches the end of panel 20X electromagnets 40X are deactivated and the blank 20 is disengaged from same. Carriage 3OX then carries carriage 34X back along tracks 50X and 52X towards shaft 26X. With this arrangement carriage 34X reaches the end of track 24X and then occupies shaft 26X so resting on top of cylinder 28X which in turn is activated and moves carriage 34X upwardly in tracks 50Y and 52Y towards track 22X. This results in magnets 40X travelling upwardly between grid bars 60X Carriage 3OX is then activated and begins to move towards the furthermost end of panel 2OX in the direction of arrow 42X. As this happens carriage 34X engages track 22X and travels therealong until it reaches point Q at which point electromagnets 40 are energised. It will be understood by reference to Figs. 6 and 7 that at point Q the activated magnets 40X engage the leading edge of blank 20 since blank 20 has been folded about searner 84. As the carriage 30X continues along tracks 5OX and 52X carriage 3OX moves downwardly from Q to R by means of rollers 32Y moving downwardly in tracks 50Y and 52Y as carriage 34X is guided along track 22X and so, along with the movement of blank 20 about the searner 84, carriage 34X moves the leading end of blank 20 towards the lower edge of block 40 at a position where the trailing edge 38 of blank 20 is located. Travel of carriage 34X along the U-bend at the end of track 22X provides for leading edge 36 to be placed below edge 38 and then being pushed into the edge 38 of the resultant seam formation. It will be understood that face 62X of grid bars 6OX provide a support means on which blank 20 can rest as magnets 40X travel downwardly, as directed by carriage 34X traveling along track 22X from position Q to R. Once this action has been completed magnetic means 4OX are de-magnetised and carriage 3OX returns along track 5OX and 52X towards shaft 26X. When carriage 3OX overlies shaft 26X, carriage 34X will rest on the top of extended cylinder 28X. Cylinder 28X is then activated and so retracted. This results in carriage 34X being moved downwards so that it lies next to track 24X and upon activation of carriage 30X, carriage 34X travels there along thus the cyclical operation is repeated. As carriage 34X is moved downwards magnets 4OX move downwards between grid bars 6OX. In this fashion blanks 20 are advanced towards sea er 84 and positioned therearound in interlocking relationship. During passage through the machine the blank is further acted upon to form a duct section as will now be described. As the blank moves through the machine, the sides 24 and 26 of the blank 20 are roll formed by suitable roll forming apparatus so as to define flanges 28 which having regard to Figs. 1 to 3 are downwardly directed. These flanges are at least partly defined before the strip is cropped and they are firstly formed when the end of the blank leaves the forming rollers. The configuration of flanges will be described in greater detail hereinafter. As shown in I g. 3, the flanges are severed from the bottom edge upwards as indicated by reference numerals 30, 32 and 34 at locations which are to provide the corners of the duct section which eventually is produced. The blank processed thus far moves to a forming station whereat the leading edge 16 is provided with a seam formation in that a portion of the leading edge 16 is folded upwardly and back towards the remainder of the blank as shown in Fig. 3. In Fig. 3 the leading edge seam formation is indicated by reference numeral 36 whilst the trailing edge seam formation is indicated by reference numeral 38, although they will be described in greater detail hereinafter. The blank moves in the direction 22 into the forming station and is subjected to a number of processing steps as illustrated in Figs. 4 to 8. The thus formed blank 20 passes into the forming station until that portion between the cut lines 30 and 32 lies under a forming bar or block 40 (this being after the formation 36 has been formed at the block 40) and a first portion 42 of the blank is folded upwardly as shown in Fig. 5 until it lies at right angles to the remainder of the blank. Subsequently, the blank is advanced until the portion lying between the cut lines 32 and 34 underlies the bar 40 and the portion 44 is folded at right angles to the remainder of the blank, which brings the portion 42 back into a horizontal plane but above the bar 40. The blank is again advanced in relation to the block 40 until the last portion 48 lies under the bar 40 and the portion 46 is folded upwardly which brings the seam formation 36 into clipping engagement with the seam formation 38 as shown in Fig. 7. In this connection, it should be noted that the block 40 has a height which is less than the length of each of the portions 42 to 48 so that the block 40 can be moved up and down as indicated by arrow 50 in Fig. 7 to a limited extent within the now formed duct section. The block 40 after the folding of the portion 46 is moved to the upwards position shown in Fig. 7 to permit the formations 36 and 38 to inter-engage. At this stage it is worth noting that the formation 36 is a hook portion, whilst the formation 38 is an inverted U-sectioned portion, and the outer limb thereof engages in the hook of the formation 36. The duct section is eventually closed by folding and clenching the inter-engaged formations 36 and 38 to the position shown in Fig. 8. The finished duct section is shown in Fig. 9 and it will be seen that the portions 42, 44, 46 and 48 form the wall portions of the duct. These portions are of identical length and width so that the resulting duct is of square cross section. The flange 28 by virtue of the saw cuts 30, 32 and 34 fold into individual flange sections and each is in fact of the configuration shown in Fig. 10A. It will be seen that each flange 28 comprises a front wall 52, a rear wall 54, and a top wall 56 defining between them a cavity 58. The inner wall 54 has a rearward extension 60 which lies flush with the adjacent wall 42 to 48, and is connected thereto for example by welding or by means of dimple formations provided during the roll forming, or by other suitable means. The respective cavities 58 are for receiving mounting plates 62 in the manner for example as set forth in our British Patent Application 8826511.1. Essentially the plates 62 are overlapped and connected by means of a bolt after bieng fitted into the cavities 58, and these plates therefore together form corner pieces by which the duct section shown in Fig. 9 can be connected to adjacent duct sections, for example as shown in dotted lines also in Fig. 9 completing the duct work. Reference is now made to Fig. 10 which shows in diagrammatic elevation a machine for forming the duct sections of Fig. 9 from the reeled strip steel sheet 10, and referring to Fig. 10, the machine is constructed so that any one of a plurality of strips 64, 66, 68 and 70 may be fed through the machine for processing, depending upon the size of duct, or the gauge of material required. Reference numeral 72 indicates the levelling station which may be of conventional construction is therefore not described in detail. The emerging strip is indicated at reference 74, and its direction of travel is indicated by arrow 76 which corresponds to arrow 22 as shown in Figs. 1 to 8. Reference numeral 78 indicates the notching station at which the notches 12 are provided, and after the notching, the strip 74 passes through a guillotine station 80 which is of the construction and performs the operation illustrated in Fig. 15 to which reference will shortly be made. After the guillotine station 18 whereat the strip is cropped so as to provide a blank of the sheet steel, the blank in the form shown in Fig. 1 but with the trailing edge seam formation 38 proceeds to a flange roll forming station 82, particulars of which will be given hereinafter when referring to Figs. 11 to 14. The partly-formed blank is thereafter advanced to the folding and seaming station 84 which performs the operations described in relation to Figs. 4 to 8. Reference is now made to Fig. 15 which illustrates the guillotine station 80, in sectional elevation. The guillotine station comprises an upper cutting beam 86 which is provided with a cutting blade 88 having a horizontal cutting edge 90, and a lower cutting beam 92 having a co¬ operating cutting blade 94 which has an inclined cutting edge 96 which co-operates scissor fashion with the cutting edge 90 in order to slice through the strip of sheet metal 74 in the nature of scissors. As shown clearly, the beam 96 has a recess 98 behind the cutting blade 88 which extends to a lower position than the lower surface 100 of the beam 86. Equally, the upper surface of the beam 92 is provided with a projection 102 adjacent a recess 104, the recess 104 being positioned to receive the downwardly projecting portion of the blade 88 when cutting is effected, and the projection 102 serving to deflect the sheet material into the recess 98. Recess 98 is defined by a horizontal surface 106, a trailing vertical surface 108 defined by the blade 88, and a leading inclined surface 110 arranged at a 45° angle so that when cutting takes place, the sheet metal 74 as shown in dotted lines deflects into the recess 98 by virtue of the projection 102 to shape the sheet metal to define the trailing end formation 38 of the inverted U-shape shown. The trailing limb 112 of the formation 38 eventually will be folded into the interior of the formation 38 during the final seaming operation as will be described. The beams 86 and 92 are operated in synchronism with the operation of the machine, for example by means of hydraulic rams or the like embodied in housings 114 as shown in Fig. 10. The thus formed blank i.e. of the configuration shown in Fig. 1 now progresses to the flange roll forming station 82 which is shown in its principle elements in Fig. 11, and in slightly more detail in Figs. 12 to 14, to which figures reference is now made. The roll forming section 82 comprises a base frame 120 of rectangular configuration arranged with its length direction in the direction of feed of the strip steel through the machine. The frame 120 comprises longitudinal members 122, 124 connected by channels 126. One of the channels 126 is provided on its upper surface and opposite ends with toothed racks 128 which are engaged by pinions 130 (only one rack and pinion is shown in Fig. 11). Pinions 130 are carried by drive shafts 132 and each pinion and rack is associated with a movable and elongated sub assembly 132 made up of frame members 134 and 136 extending longitudinally of the frame 120, and supported by cross members 138. Each sub-assembly 132 carries rollers 140 at the ends thereof, so that the sub-assembly can move laterally of the main frame 120 when the shafts 132 are driven to cause the pinions 130 to run on racks 128. Stop members 142 and 144 limit the extent to which the sub- assemblies 132 can move in the lateral direction as indicated by arrow 146. The sub-assemblies can therefore be moved closer together or further apart, and as the sub assemblies carry the forming rolls as will be explained for forming the flanges 28 on the sheet metal blanks, so the machine is equipped to handle strip material of differing widths. In practise, there are two main width sizes of strip material which account for 90% of the ducting produced at least for the United Kingdom. The sub-assemblies have vertical legs 148 for carrying there¬ between forming roller housings 150, and a drive shaft 152 extends transversely of the frame 120 and couples the respective sub-assemblies 132, the shaft having a central and telescopic coupling 154 for this purpose. When the shaft 152 is driven, power is transmitted to the respective sub- assemblies 132 for the purposes to be explained with reference to Figs. 12 to 14. Referring to these figures, in Fig. 12 a single forming roller housing 150 is shown, and it will be seen that a common drive shaft 156 carries chain wheels 158 located in the legs 140. Around chain wheels 158 are trained endless chains 160 which engage sprocket wheels 162 at the top ends of the posts 148, and carried by stub shafts 164. Each stub shaft 164 is supported by roller bearings 166 in the post, and the shaft 162 projects into the housing 150 and the projecting portion supports a bevel gear 168. Bevel gear 168 metres with a bevel gear 170 whose axis is horizontal and transverse to the length direction of the frame 120. Bevel gear 170 drives pinion 172 which in its turn drives pinions 174 and 176 supported on shafts 178 and 180. The bevel gear 170 is carried by a shaft 182, and as shown in Fig. 13, the shafts 178, 180 and 182 project laterally of the housing 150 and are arranged in pairs so as to carry pairs of forming rolls 184, 186 to one side of the head and 188 and 190 to the opposite side of the housing 150. As shown in Fig. 14, there are five pairs of rolls 184, 186 and 188, 190 to opposite sides of the housing 150 and these pairs of rolls are driven in synchronism by virtue of a gear train 192, 194, 196, 198, 200, 202, 204 and 206 which are inter-engaged spur gears, and the spur gears 194, 198, 202 and 206 driving gear pairs 174 and 176 as already described. The respective pairs of forming rollers 184, 186 are shown as cylindrical surface rollers, but in fact they will be appropriately profiled in order to perform the necessary roll forming of the flanges 28 to provide same with the configuration shown in Fig. 10A. By virtue of the construction, it will be seen that by appropriately driving the shaft 156 by suitable drive means (not shown) the bevel gears 168 will be driven, which in turn drives bevel gears 172, which will cause the housings 150 to rotate as indicated by arrows 208 in Fig. 11 whereby the rollers 184 and 186 if they are in a position for forming the blank edges, will be replaced by rollers 188 and 190 to give a flange of a different profile or depth. The sub-assemblies 132 can be moved closer together or further apart as required. Reference is now made to Fig. 16 which serves to illustrate the steps involved in providing the leading edge formation 36. In Fig. 16A, the forming bar 40 is illustrated, and the blank is indicated by reference 210. It has arrived at a position where the leading edge 16 projects beyond a lip or step 212, best seen in Fig. 16 which extends beyond the downstream vertical face 214 of the beam 40. An L-shaped frame made up of sections 214 and 216 is located adjacent to support beam 218 such that the leading edge 16 as shown most clearly in Fig. 16 projects beyond a horizontal surface defined by the section 216. The L-shaped frame is then pivoted about pivot axis so as to move to the position shown in Fig. 16B which is at right angles to the position shown in Fig. 16A, the section 216 being moved to a vertical position. The means for displacing the frame 214, 216 may suitably be a fluid pressure operated ram which is not shown in the drawings. The result of this operation is to turn half of the leading ends 60 to a vertical position as shown by reference 218 in Fig. 60, and also as illustrated in Fig. 16B. In the next stage of operation, the frame 214, 216 is returned to the initial position, and then, as shown in Fig. 16C, the frame 216, 214 is vertically raised as indicated by arrow 220 by an amount indicated by reference 222. Referring in detail to Fig. 16, it will be noticed that the edge of the portion 216 adjacent the beam 218 i.e. under the lip 212 is recessed as indicated by reference 222, and this recess in the Fig. 16C position comes into horizontal alignment with the lip 212. In this elevated position, the frame 214, 216 is again pivoted about the same axis of pivoting and this causes the vertical portion of the leading end 216 by virtue of the notch 212 to be folded over onto the upper surface of the lip 212 as shown by reference 224 in Fig. 16. The frame 214, 216 is eventually returned to the Fig. 16A position, completing the leading edge of a seam formation 36. When such operation has been completed, the blank is moved forward until it reaches the position shown in Fig. 4 so that it is ready for the folding operation, and the folding operation is performed by moving the frame 214, 216 sequentially between the Figs. 16A and 16B positions to perform the folding steps illustrated in Figs. 5, 6 and 7. After the folding stage of Fig. 7 has been completed, the beam 40 is raised to enable the leading and trailing edge formations to be interclipped as shown in Fig. 16. Fig. 16 also shows that the trailing end of the beam 40 is provided with a recess 226 for receiving the trailing edge formation 38. The leg 112 of formation 38, and formation 36 project downwardly as shown in Fig. 16. Fig. 16 also shows a means for folding the formation 36 and the inter-engaged leg 112 to complete the seaming operation, and such means comprises a rotatable former 228 which is mounted in the embodiment shown in Fig. 16 on bearing rollers 230 so as to have a virtual centre of rotation indicated by reference 232. Former 228 has a circular outer surface 234 which rides on the rollers 230, but is cut away at 236 and 238 to provide a right-angled cut-out which in the rest position shown in Fig. 16 lies slightly inclined to the horizontal so that the edge 236 is sloped downwardly. A former 238 is carried by a plunger 240 which can be moved as indicated by arrow 242 towards the rear lower corner of the bar 40 and into engagement with the bar 40 so that the surfaces 236 and 238 fit neatly to the lower surface and rear surface of the bar 40. As the former 238 is advanced to the bar 40, initially the surface 236 engages the formation 36 as indicated by reference 244 and a cut-away portion of surface 238 contacts the wall 42 of the ducting which is formed around the bar 40. Continued thrusting of the former 228 towards the beam 40 causes the former to turn about its centre 232 which brings the surface 238 into face to face contact with the duct wall 42, and the surface 236 into pressure engagement with the underside of beam 40. This action has the effect of turning the formation 36 and the entrapped leg 112 into the recess 236 in order effectively to form the seam of the duct section to complete the formation of the duct section as shown in ringed detail by reference 246 in Fig. 10. Referring now to Fig. 17, which shows an alternative construction for the closing of the seam compared to that shown in Fig. 16, the alternative construction retains the former 228 which is also rotateable about the virtual centre 232 defined by a pair of support rollers 300 and 302 arranged in the position shown. The former acts in the same manner as described in relation to Fig. 16, to close the seam, and in each of the embodiments of the former 228 i.e. Figs. 16 and 17, as the plunger 240 is retracted, so that former 288 is moved to the position shown in Fig. 16 in which the edges 236 and 232 are inclined slightly to the horizontal and vertical respectively. Any suitable means may be provided for returning the formers 228 to this position. With the formers in this position as they engage the seam portions 36 and 112, effective folding and clenching of the seam takes place. The only assembly not shown in Fig. 10, which requires to be provided is an assembly to form the cuts 30, 32 and 34. It is envisaged that a suitable assembly for performing this function will comprise a circular saw on each side of the machine, which can be raised and lowered in sequence in order to effect the cutting of the flanges. In order that the saw can cut through flanges of different width, it is preferred that not only is the saw capable of being raised and lowered, but also performs an orbital movement whilst the raising and lowering is taking place so that the saw can cut over a greater width of flange and can arrange to be tangential to adjacent wall of the ducting over a length rather than simply at a point which is the case where the circular saw simply moves vertically. It will be seen that the invention provides in a plurality of aspects, an effective means and method for the production of duct sections and the invention extends to any one of these aspects on its own or in combination with any one or more of the others. The invention also extends to method aspects as well as apparatus aspects of the invention.

Claims: CLAIMS 1. A method of forming a duct section comprising: cutting from a strip supply of sheet metal, a length of such metal to define a leading and trailing end thereof and advancing the length of sheet metal in the direction of its length to a forming station; advancing the length by means of an automated handling system; forming on said leading and trailing edges, seam formation means to make said leading and trailing edges complimentary for providing a folded and clenched seam in the final duct section, whilst at said forming station, forming the length of sheet metal into a duct section by folding same in a direction transverse to the length direction of the sheet section to bring leading and trailing edges into seam formation engagement, and folding and clenching said leading and trailing edges to form said seam. 2. A method of forming a duct section in accordance with Claim 1 wherein the sheet material is folded into polygonal form at the forming station. 3. A method of forming a duct section in accordance with Claim 2 wherein the polygonal form is produced by folding the sheet metal around a former. 4. A method of forming a duct section in accordance with any preceding claim wherein the seam formation on the leading edge and trailing edge of the length of sheet metal are interclipped when the sheet metal is folded into polygonal form. 5. A method of forming a duct section in accordance with any preceding claim wherein the leading edge is formed with a seam formation defined by folding said leading edge upwardly and over the remainder of the sheet metal to form a hook edge on the top side of the sheet metal. 6. A method of forming a duct section in accordance with any preceding claim wherein the trailing edge is formed by folding said trailing edge into a U-shaped seam with the open side of the U facing downwardly. 7. A method of forming a duct section according to Claims 5 and 6 wherein the said hook formation and U-shaped seam are clenched by engaging the leg of the U-section defining the extremity of the length of sheet material with the hook formation and then folding and clenching same together into a position lying in the plane of the ajacent side of the duct section. 8. A method of forming a duct section according to any preceding claim wherein a length of sheet metal is provided with integral flanges by the shaping and folding of same. 9. A method according to Claim 1 where the length of sheet material is advanced using an automated handling system. 10. A method of forming a duct section according to Claim 9 wherein the automated handling system comprises an attachment means adapted to advance the length of sheet metal by a predetermined amount. 11. A method of forming a duct section according to Claim 10 wherein the automated handling system comprises a magnetised carriage means adapted to advance the length of sheet metal by predetermined amounts. 12. A method of forming a duct section according to Claim 10 wherein the automated handling system comprises a suction means adapted to advance the length of sheet metal by a predetermined amount. 13. A method of forming a duct section according to Claim 11 wherein the carriage means engages the length of sheet metal when the magnetised means is activated. 14. A method of forming a duct section according to claim 13+ wherein the carriage means advances the length of sheet metal in a stepwise manner. 15. A method of forming a duct section according to Claims 11+ or 13 wherein the carriage means travels along at least one carriage track. 16. A method of forming a duct section according to Claim 13 wherein a plurality of carriage tracks are provided such that the carriage means engages the length from a plurality of positions. 17. A method of forming a duct section according to Claim 16 wherein the carriage means when travelling in at least one of the tracks is positioned to engage the leading edge of the length of sheet metal and advances same towards the trailing edge of the length. 18. A method of forming a duct section according to Claim 16 wherein the carriage means when travelling in at least one of the tracks is positioned to engage the trailing edge of the length and advances same towards a forming means. 19. A method of forming a duct section according to claim 16 wherein a plurality of said tracks are operationally connected. 20. A method of forming a duct section according to claim 19 wherein in one of said connected tracks the carriage means is positioned to engage the leading edge of the said length and advances same towards the trailing edge of said length and in a further of said connected tracks is positioned to engage the trailing edge of the length and advances same towards a forming means. 21. A method of forming a duct section wherein a length of metal is cut from a strip supply of sheet metal and is fed to a forming station at which it is multi folded into duct form, and wherein a magnetic means is used to feed the length stepwise to the forming station, said magnetic means also being positionable to assist in the final formation of the length into duct form. 22. A method of forming a duct section according to claim 20 wherein said magnetic means engage said length when activated. 23. A method of forming a duct section according to claim 20 wherein said magnetic means assists in the final formation of the length by bringing a first and second edge of the length into interlocking engagement. 24. An apparatus for forming a duct section comprising a cutting means for cutting a length from a strip supply of sheet metal; an automated handling system for advancing the length of sheet metal in the direction of a forming station; means for forming seam formation means on said leading and trailing edges of said length to make said leading and trailing edges complimentary for providing a folded and clenched seam in the final duct section; a formation means for forming the length of sheet metal into a duct section by folding same in a direction transverse to the length direction of the sheet section to bring the leading and trailing edges into seam formation engagement; and a folding and clenching means for folding and clenching said leading and trailing edges to form said seam. 25. An apparatus according to Claim 24 wherein the folding means is adapted to provide a polygonal shape when the sheet metal is folded at same. 26. An apparatus according to claim 24 wherein the folding means comprises a former around which the sheet is folded. 27. An apparatus according to Claim 24 wherein the automatic handling system comprises a carriage means having a selectively activatable magnetic means. 28. An apparatus according to Claim 27 wherein the carriage means engages the length of sheet material when the magnetic means is activated. 29. An apparatus according to claims 27 or 28 wherein the magnetic means advance said length in a stepwise manner. 30. An apparatus according to Claim 24 wherein the handling system comprises a plurality of carriage tracks. 31. An apparatus according to claim 30 wherein said carriage means is adapted to travel along said tracks. 32. An apparatus according to Claim 30 wherein at least one of said tracks is provided with a downwardly sloping section. 33. An apparatus according to Claim 32 wherein said downwardly sloping section terminates in a U-shaped bend. 34. An apparatus according to claim 30 wherein said tracks are operationally connected. 35. An apparatus according to claim 24 wherein the cutting means comprises blades driven by a plurality of drivers, said drivers being arranged in parallel. 36. An apparatus as substantially herein described. 37. A method as substantially herein described.

Inventors: FIRTH COLIN, FIRTH, COLIN
Applicants: FIRMAC LTD, FIRMAC LIMITED
Application year: 1990
Main classification: B21D51
IPC codes: B21C37