Tapered Conduit Technical Field

THIS INVENTION relates to metal conduits e.g. tubular metal pipe or tube. Conduits to which the invention relates are generally intended for liquid transfer such as downpipes associated with guttering. However, the conduits may be used for other purposes unconnected with liquids or liquid transfer. Accordingly, the term "conduit" is used in this specification to cover hollow metal members for all such purposes.

The invention is particularl concerned with metal conduit having a relatively thin continuous wall be it round or rectangular and having a thickness for example of from 0.3mm to 1.0mm and more specifically from 0.4mm to 0.6mm. Background Art

It is well-known in the field of metal conduits . to prefabricated metal conduit of uniform cross-sectional area and shape in various selected lengths by roll-forming. Where such lengths are intended to be joined, it is common practice to effect the required joint by either expanding or flaring one end of a length to fit over the end of a further length of similar conduit to be joined thereto or to crimp one end of such length to fit within the end of a similar conduit. However, this procedure is time consuming and adds to the expense of installing metal conduit.

In order to overcome installation problems with conduit of a uniform cross-section, it is also well-known to

form lengths of conduit, which are intended to be joined, with a continuous taper so that lengths of similar conduit can be joined without the need for any alteration to the conduit.

The most practical known methods of manufacturing tapered conduit have involved one or two processes. Firstly, such tapered conduit has been formed by roll-forming a flat tapered (generally trapezoidal) sheet around a tapered mandrel. Examples of such method are disclosed in Australian Patent Specifications 38151/89, 273529, 403577 and 412312. Of these specifications 403577 is considered to be the most relevant to the present invention in that it discloses rectangular downpipe formed from sheet metal and tapered so that the smaller end of section will fit into an adjacent larger end of another similar section. The taper is achieved by deformation of a lock seam attaching adjacent ends of the sheet metal so that it is displaced inwardly from one end to the other so that at the larger end the lock seam projects outwardly of the downpipe and at the smaller end the lock seam projects inwardly of the downpipe leaving the outer surface substantially flat at the smaller end.

In relation to this specification it is relevant to note however that while one wall may have undergone deformation to achieve a required taper the other walls would still have substantially uniform- dimensions from one end to the other and as such this would inhibit satisfactory interfitting of one section within another.

However, a further method of manufacturing tapered conduit has involved the production of conduit of uniform

cross-sectional shape and area usually by roll-forming and subsequently grooving or corrugating the perimeter of the conduit with longitudinally tapering grooves to produce a longitudinal taper along the length of the conduit. Examples of such method and conduit are disclosed in Australian Patent Specifications 563694, 244067 and French Patent Specification 1.260.814.

Thus French Specifications 1.260.814 and Australian Specification 563694 describe the formation of conical or part conical tubular members and Australian Specification 244067 described metal conduit wherein the entire wall or face of generally rectangular hollow conduit is deformed to produce the desired taper.

Reference may also be made to United Kingdom Patent Specification 1 462 370 which describes longitudinally grooving a cylindrical metal tube in a number of stages so as to produce a series of fins in the final product. Each fin is formed by tapering an initial precursor groove and thus the final tube is not tapered from one end to the other. The prior disclosures as described above and in particular Australian Specification 563694 and French

Specification 1.260.814 have involved grooved conduit wherein the grooves are substantially equi-spaced around the periphery of the conduit. The manufacturing processes for formation of such conduit is expensive and complex and this also applies to the cost of the final product. Also such tapered conduit is not especially adapted to be used as downpipe particularly in relation to interfitting of adjacent sections. This is

particularly the case when the entire outer surface of the conduit is subjected to deformation. Disclosure of the Invention

Accordingly, the present invention provides an improved tapered conduit over prior tapered conduits, a new method of producing tapered conduit and also a new apparatus for producing tapered conduit.

Therefore in one aspect the invention provides tapered conduit suitable for downpipe having a smaller end in transverse dimension and a larger end in transverse dimension which includes a longitudinal formation characterized in that there is provided a pair of adjacent longitudinal deformations each having a substantially uniform taper from end to end and wherein each longitudinal deformation is located with the longitudinal formation interposed therebetween to facilitate interfitting of adjacent similar sections of the tapered conduit with the smaller end of one section being insertable in the larger end of the other section.

The tapered conduit of the invention may have any suitable cross-sectional shape and thus comprise a circular shape, square shape, rectangular shape or polygonal shape for example. However the invention is particularly concerned with circular shape conduit and rectangular conduit.

The longitudinal formation may comprise for example a corner edge or jointing seam of the ^• conduit which may be part of the conventional structure of the conduit. In the case of conduit of round or circular cross-section a jointing seam such as a lock seam, welded seam or even a seam

interconnected by fasteners (eg rivets) is a suitable example of a longitudinal formation. In the case of rectangular conduit a corner edge is a suitable example of a longitudinal formation. The adjacent longitudinal tapering deformations may comprise longitudinal grooves, ribs, steps or shoulders for example.

The preferred longitudinal tapered deformation are grooves and it is also preferred that such grooves be located closely adjacent to the longitudinal formation which may separate the longitudinal formations from each other.

The invention also includes within its scope a method of construction of the aforementioned tapered conduit and this method may include the step of passing conduit of tubular configuration having a specific orientation through a tapering station for the purpose of causing said conduit to have at least a pair of longitudinal deformations imparted thereto wherein each of said longitudinal deformations taper substantially uniformly from one end to the other wherein a longitudinal formation is interposed between each longitudinal deformation.

To this end suitably the conduit is oriented at the tapering station so that each longitudinal deformation is formed on either side of the longitudinal formation which has already been preformed.

It is also possible in regard of the method of the invention that each longitudinal deformation may have already been partly formed when the conduit reaches the tapering

station so that the only function of the tapering station is to cause the required longitudinal taper in each longitudinal deformation.

Thus for example if each longitudinal deformation is a rib or groove, such rib or groove may have already been preformed in the conduit for example by a preliminary pass of the conduit through a roll forming mill.

However it is preferred that at the tapering station each longitudinal deformation will also be fully formed in the conduit so the tapering station has not only means for imparting each longitudinal deformation to the conduit but also means for causing the required degree of taper in each longitudinal deformation.

While it is also possible to pass preformed conduit of the required tubular shape through the tapering station which may have already been formed at a location separate from the site of the tapering station it is preferred that the tapering station be located on a rear or outfeed end of a rolling mill so that metal plate or strip may be passed through the rolling mill ^' so. as to already have the required shape before passing through the tapering station.

The invention also includes within its scope forming apparatus for forming the longitudinal deformations in the conduit. This apparatus may include a first set of primary and secondary rollers and a second set of primary and secondary rollers to form the at least one pair of longitudinal deformations with one of the pair of primary rollers or the pair of secondary rollers being laterally

movable relative to the other pair of primary or secondary rollers and also to the direction of movement of conduit through the forming apparatus to form the tapered longitudinal deformations. Thus it will be appreciated that one of the primary pair of rollers or secondary pair of rollers is stationary while the other pair of rollers is laterally movable or both pairs of rollers are movable toward and away from each other. The former arrangement is the one that is preferred. In a preferred embodiment of the apparatus of the invention the conduit after passing through a rolling mill may be supported by appropriate support means such as a support mandrel before passing through the forming apparatus of the invention. The support mandrel may also constitute means for orienting the tapered conduit so that it has a required specific orientation as it passed through the forming apparatus. The forming apparatus of the invention may also include means for causing the lateral movement of the primary pair of rollers or the secondary pair of rollers and this means is suitably cam operated.

In a preferred form the forming apparatus may include a support block for each of the primary rollers and the secondary rollers. Suitably the primary rollers and associated primary support block are located within the interior of the conduit and the secondary rollers and associated secondary support block are located externally of the conduit as it passes through the forming apparatus. In this arrangement the secondary support block may be movable

toward and away from the primary support block and this may be accomplished by the cam operated means referred to above.

In one example of cam operated means the secondary support block may also support an idler roller which may engage a support slot located in a cam member located adjacent to the secondary support block. The cam member is preferably circular and is rotatable by appropriate drive means. The support slot in the cam member is suitably offset to the circumference or periphery of the cam member so that upon traversal of the idler roller in the support block a certain distance (eg from one end of the support slot to the other) will cause an inward movement of the secondary block relative to the primary block and thus cause the required taper in the longitudinal deformation being formed in the conduit. There also may be provided guide means to guide the secondary block so that it may move a required fixed path which include toward and away from the primary block. A suitable guide means is thus a pair of guide blocks located on each side of the secondary block. There may be many primary roller and secondary roller combinations as are required so as to produce the required number of longitudinal tapered deformations in the conduit for example in relation to a rectangular conduit having four corner edges there may be a pair of longitudinal deformations located on either side of each corner edge. This will mean the production of eight longitudinal deformations and this may be produced by providing four secondary blocks which may all move along a required path by the provision of

the abovementioned guide means. Each secondary block may mount a pair of secondary rollers which may co-act with a corresponding pair of primary rollers located on a centrally located primary block to produce two longitudinal deformations in each side wall of the rectangular conduit adjacent an associated corner edge.

The σoaσtion between a set of primary roller and secondary roller will produce the require longitudinal deformation desired. For example if a tapered longitudinal groove is required the primary roller may incorporate a groove which may mate with a corresponding rib on the secondary roller. If a tapered longitudinal rib is required the reverse configuration may be adopted. Brief Description of the Drawings Reference may now be made to a preferred embodiment of the invention as illustrated in the attached drawings wherein

FIG 1 is a plan view of an assembly line including forming apparatus constructed in accordance with the invention in conjunction with a roll forming mill;

FIG 2 is a side view of the assembly line shown in FIG 1;

FIG 3 is a perspective view of forming apparatus constructed in accordance with the invention; FIG 4 is a .perspective view of some components of the forming apparatus of FIG 3 not shown in FIG 3;

FIG 4A is an end view of the forming apparatus shown in FIG 3;

FIG 5 is a side view of the forming apparatus shown in FIG 5;

FIG 6 is a view similar to FIG 4A but with one end plate removed; FIG 7 is a sectional view showing the engagement between a primary roller and a secondary roller and conduit interposed;

FIG 8 shows a side view of tapered conduit constructed in accordance with the invention; FIG 9 is a view of a corner region of the conduit along the line A-A of FIG 8;

FIG 10 is a view of a corner region of the conduit along the line B-B of FIG 8;

FIG 11 is a perspective view of the tapered conduit shown in FIG 8; and

FIGS 12, 13, 14 and 15 illustrate alternative forms of tapered conduit to that shown in FIG 8 which may be made in accordance with the present invention. Description of Preferred Embodiments of the Invention In the drawings and in particular in FIGS 1-2 there is shown an assembly line 10 including a sheet metal or strip coil holder 11 for feeding continuous sheet metal strip 9 to roll forming machine 13 having forming rolls 14 forming the required shape of the conduit from strip 9. There is also shown support stand 15 having support legs 16. After the required shape of the conduit 12 is formed on assembly line 10 the conduit is then supported by a mandrel 17 after passing through forming rolls 18. There is also provided chains 19

driven by drive motor 20 through chain and sprocket transmission 21. The mandrel 17 allows for lock seaming of overlapping parts of the conduit and to this end has sizing rollers 22 and final crimping rollers 23. Also shown is 5 forming apparatus 24 which includes tapering mechanism as hereinafter described and end table 26 having idler rollers 27 for shearing of conduit to the required length.

In FIG 3 there is shown part of the forming apparatus of the invention which includes secondary support 10 blocks 28 having opposed recesses 29 and further recess 30. Each recess 29 mounts a secondary roller 31 having a forming rib 32. Each secondary roller is separated by mounting part 33. There is also shown idler roller 34 located in recess 30. There is shown one side secondary block 28A and a top 15 secondary block 28B. There is also shown primary support block 35 to which is mounted primary rollers 36 having forming grooves 37. Primary block 35 also has recesses 39 and 40 for supporting primary rollers 36. Conduit 12 is also illustrated having an appropriate orientation to rollers 31 and 36 and 20 also to support mandrel 17 which is integral with primary block 35. Conduit 12 also has lock seam 38.

In FIG 4 there is shown a .more detailed view of the forming apparatus of the •invention which includes opposed end plates 41 and 42. End plate 41 includes mounting holes 43 for 25 guide blocks 45 which also have corresponding mounting holes ' 49. The four guide blocks 45 function to maintain each secondary block 28 in a fixed path by abutment surfaces 46. End plate 42 is also provided with central cavity 47 and plate

41 is provided with central cavity 48. Also shown is cam plate 51 having central aperture 52 and internal surface 52A which bears against curved surfaces 45A of guide blocks 45. There is also shown support slots 53 which may mount on associated idler roller 34 of secondary blocks 28.

In FIGS 4A-6 the operation of the forming apparatus of the invention is clearly shown. In FIG 4A each secondary block 28A, 28B, 28C and 28D is at an initial stage of movement with idler roller 34 engaged in an associated support slot 53 at a start point 57. Thus there is a fairly pronounced gap 55 between conduit 12 and secondary blocks 28. Upon rotation of cam plate 52 by appropriate means (not shown) each support block 28A, 28B, 28C and 28D is then caused to move inwardly to primary block 35 and constrained to move in a fixed path by guide blocks 45. A side view of this arrangement is shown in FIG 5.

In FIG 6 each idler roller 34 has now moved the length of each slot 53 to approach a finish point 58. This has resulted in inward movement of each secondary block 28A, 28B, 28C and 28D as shown by the arrows in full outline to be proximal to primary block 35. Thus only a relatively narrow gap 56 now exists between the secondary blocks 28 and primary block 35 and thus rollers 31 and 36 may now coact as shown in FIG 7 wherein a forming rib 32 of each roller 31 may mate with a corresponding forming groove 37 of each roller 36 to form a tapered groove 60 in conduit 12. Rollers 31 and 32 may have stubs axles 61 engagable in sockets 62 in blocks 28 and 35.

In operation of the forming apparatus of the

invention as shown in FIGS 3-7 cam plate 52 may be rotated at a predetermined angular speed to achieve movement of secondary rollers 31 into co-action with primary rollers 36. The required co-action or engagement of rollers 31 and 36 may be suitably achieved by an appropriate drive means to rotate cam plate 52 at an angular velocity determined by the speed of the conduit through the tapering mechanism and the length of conduit required to be tapered.

It will also be appreciated that the abovementioned embodiment illustrates location of the tapering mechanism before the cutting of the conduit on table 26. However if desired the conduit may be cut to a desired length prior to passage through the tapering mechanism.

In FIGS 8-11 there is shown conduit 12 which has now been produced in accordance with the invention. This conduit includes two pairs of opposed side walls 63 and 64 and corner edges 65 with tapered grooves 60 each located on either side of an associated corner edge 65. Also shown is lock seam 38. The taper of each groove 60 is shown progressively increasing in depth from point A to point B in both FIG 8 and FIGS 9-10.

The production of tapered grooves 60 in conduit 12 will facilitate interfitting of adjacent sections of conduit 12 because as shown in FIGS 12-15 this will also cause a shrinkage or tapering of corner edges 65 while at the same time maintain structural integrity of webs 66 between grooves 60.

In FIG 12 this is clearly shown with the arrows in full outline showing the shrinkage of corner edges 65 from

point A to point B. Thus the full outline of conduit 12A is shown at point A and conduit 12B is shown in phantom at point B. Thus by the provision of tapered grooves 60 in accordance with the invention adjacent corner edges 65 this means that a uniform degree of taper of the conduit may be achieved without causing undue stresses or deformation in side walls 63 or 64 or indeed in webs 66. Thus interfitting of adjacent sections of conduit 12 is readily accomplished.

In FIG 13 instead of grooves 60 there may be produced tapered ribs 67 in conduit in a variation of conduit produced in accordance with the invention adjacent corner edges 65. Again the view shown in full outline corresponds to point A in FIG 8 and the view in phantom corresponds to point B in FIG 8. In FIG 14 there is illustrated round tapered conduit

12 constructed in accordance with the invention by the use of forming rollers 70 on each side of conduit 12. In this regard there is also shown lock seam 38 and by the provision of tapered grooves 60 on each side of lock seam 38 tapered conduit may be produced having a uniform degree of shrinkage from point A to point B as indicated by conduit 12A in full outline and conduit 12B in phantom. It will be appreciated that lock seam 38 may .be internally formed as well as being externally formed as shown. In FIG 15 there is illustrated another form of conduit constructed in accordance with the invention wherein there is provided tapered shoulders 71 from point A to point B wherein each shoulder is located on either side of a corner

edge 65. This also produces webs 66A located between each shoulder 71 and having a lesser depth than corner edges 65 as shown. Again the amount of shrinkage is indicated from point A to point B by comparison of web 12A with web 12B. Although not wishing to be bound by any particularly theory it is believed that by providing longitudinal deformations having a substantial uniform degree of taper on each side of a corner edge of a rectangular conduit that "oil- canning" or undesired deformations in the planar walls of the conduit will be substantially minimised when a tapering operation is carried out subsequent to a roll forming operation. In this regard when the roll forming operation is effected this may cause potential stresses to the conduit which may well be exhibited after the tapering operation in the form of undesired deformation, ripples or "oil-canning". This potential problem may well be minimised by the location of the longitudinal deformations closely adjacent to each corner edge.

In relation to round tubular conduit the "oil- canning" problem discussed above is of course not relevant to such conduit but location of each tapered longitudinal deformation closely adjacent each side of a lock seam may also minimise any potential stresses being exhibited in the final tapered conduit after the tapering operation. This may also ensure structural integrity of the remainder of the conduit and ensure uniform shrinkage of the round conduit after the tapering operation including the area occupied by the lock seam.

In specific relation to downpipe it will also be appreciated from the foregoing that the forming apparatus of the invention may be modified to .make varying lengths of downpipe to comply with -the requirements of the customer or market place. Thus current standard lengths or modules of 1.8m, 2.4m and 3.0m may be made longer if required eg of the order of 5.0m to 10.0m.