Method and machine for manufacturing shaped parts from flat sheet metal

Abstract

A method for the manufacture of shaped parts of elongate shape and having a variable cross-section from a strip of flat sheet metal. The method is characterised in that the strip of sheet metal is displaced along a generatrix of a shaping mandrel whose cross-section varies progressively along this generatrix in predetermined manner by decreasing dimensions, and in that the strip of sheet metal, as it is displaced, is progressively bent around the shaping mandrel on either side of said generatrix by appropriate pressure means which constrain it to follow the contour and dimensions at the point where their action is exerted, and in that the point of action of said pressure means is displaced along the spindle according to any appropriate law for producing a desired variation of section on the shaped part thus obtained. Such shaped parts may be the masts of pleasure-boats, or support poles for the installation of external lighting.

Description

This invention relates to the manufacture of shaped parts of elongated shape and whose cross-section varies progressively, such as, in particular, metal masts for pleasure-boats or support poles for carrying external lighting apparatus, panels, banners or like pieces of fabric. Masts of this type which, however, constitute only one of the possible numerous applications of the present invention, are most frequently constituted by tubular shaped parts of light alloy, which are between 6 and 10 meters long and have a diameter which may vary between 50 to 150 mm; their cross-section is sometimes circular, sometimes oval and it may possibly comprise one or more longitudinal grooves serving for anchoring accessories, such for example as bolt-ropes, chain-wales etc.

A first object of the present invention is to provide a method of manufacture by forming such shaped parts from a strip of flat sheet metal.

One of the known methods for forming a metal shaped part from a flat metal sheet consists in cold rolling the strip of sheet metal by passing it between pressure rollers which by successive bending operations, give the shaped part any predetermined section; nevertheless, shaped parts thus obtained may be only cylindrical and it is necessary to carry out a subsequent re-treatment operation on the cylindrical tube thus obtained if it is desired to obtain a shaped part having a section varying progressively, such, for example, as a slightly conical mast or pole. This re-treatment operation may, for example, consist in cutting a longitudinal notch in the shape of a very close V in the tube and thereafter bringing the edges of the notch together and welding them. A re-treatment operation of this type complicates and makes the manufacture of such shaped parts difficult.

To produce shaped parts of progressively variable section from strips of flat sheet metal, it has been proposed to use a stationary shaping mandrel having a variable section determined by the shape of the shaped part that it is desired to obtain and to press the strip of sheet metal against the periphery of this mandrel by means of an arrangement of suitable pressure rollers and associated actuating jacks displaceable with respect to this mandrel.

Nevertheless, such a method does not lend itself to the production of shaped parts having a closed or practically closed section since the shaping mandrel whose length is equal to that of the shaped part that it is desired to obtain, cannot be cantilever supported on a stationary frame owing to the magnitude of the bending stress to which it is subjected. In addition, the shaping mandrel is specific to a single type of shaped part, both as regards length and section, and this constitutes a major industrial drawback, taking into account the cost of such tools especially where a limited manufacture of identical parts is envisaged.

The invention relates essentially to a method for the manufacture of shaped parts of any length and having a closed or open section, varying progressively according to an entire desired range of variations, by shaping a strip of flat sheet metal on a single predetermined shaping mandrel.

To this end, the method of manufacture according to the invention is characterised in that the strip of sheet metal is displaced along a generatrix of a shaping mandrel, whose cross-section varies progressively along this generatrix in a predetermined manner by decreasing dimensions, and in that the strip of sheet metal during is displacement, is progressively bent around the shaping mandrel on both sides of said generatrix by appropriate pressure means which impart thereto the shape and dimensions of the mandrel at the region where their action is exerted, and in that the point of action of said pressure means is displaced along the mandrel according to any appropriate law for producing a desired variation of section on the shaped part thus obtained.

With such an arrangement, it will be seen that it is possible to manufacture with a given shaping mandrel an entire range of shaped parts of different lengths and/or cross-sections according to the law chosen for the displacement of the point of action of the pressure means (pressure rollers) and the speed chosen for the travel of the strip of sheet metal over the mandrel. In particular, it is possible to produce shaped parts of great length with a relatively short shaping mandrel (order of magnitude 2m), which of course makes it possible to decrease the manufacturing cost of the mandrel but above all to allow such a mandrel to be cantilever mounted to the frame, which mounting is indispensable for facilitating the direct production of shaped parts having a closed section (joined edges).

It should also be noted that by acting on the simultaneous displacements, with respect to the shaping mandrel, of the strip of sheet metal and of the shaping head it is also possible to obtain shaped parts having at least partially either a constant cross-section or even a recess. Finally, the method of the invention allows high speed production (of the order of 1 to 2 meters/minute for example) and lends itself to continuous manufacture by imparting an appropriate reciprocating motion to the shaping head.

Another object of the invention is to provide a machine for carrying out the abovedescribed method, which machine comprises a shaping mandrel having a cross-section decreasing progressively from its base and appropriately mounted in a fixed frame, and at least one shaping head which moves parallel to a generatrix of the spindle and supports at least one pair of shaping rollers and associated actuating means for applying a strip of flat sheet metal against the shaping mandrel on both sides of said generatrix, and being characterised in that it also comprises first drive means for moving the strip of sheet metal at a uniform speed along said generatrix and second drive means for the displacement of the shaping head with respect to the mandrel according to any appropriate predetermined law for producing the desired variation of section of the shaped part obtained.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawing, in which:-

FIG. 1 is a diagrammatic elevation of a machine according to the invention and showing only the essential parts;

and,

FIGS. 2, 3, 4, 5 and 6 are detailed sectional views, to a larger scale, on the lines II--II, III--III, IV--IV, V--V and VI--VI of FIG. 1, these sections illustrating the successive stages of the method for forming the shaped part from a strip of flat sheet metal.

The machine comprises a rigid frame comprising longitudinal girders

an end support 2 from which a shaping mandrel 3 is cantilever mounted and another end support 4 on which inclined slides 5 rest.

In this embodiment, the shaping mandrel 3 has an oval cross-section, but, naturally, it could also have other types of cross-section with respect to those of the shaped part to be obtained; for this reason, the mandrel must be mounted on the frame of the machine so that it may be removed and interchanged. For carrying out the method according to the invention, it is only essential that the shaping spindle 3 has a cross-section decreasing progressively and homothetically along its upper generatrix.

As illustrated in FIG. 1, the shaping mandrel 3 is secured to the support 2 with its axis slightly inclined above the horizontal by an angle such that its upper generatrix is substantially contained in the horizontal plane extending the upper plane of the end support 2; this arrangement ensures a virtually horizontal discharge of the shaped part as it is formed.

On the other hand, the machine includes a moveable shaping head 6 comprising a rigid carriage 7 supporting shaping rollers and their actuating mechanisms and movable along the longitudinal girders 1 of the machine frame, and a box 8 connected to the carriage 7 by a pivot 9 which allows it to slide vertically, the box being guided in its movements by the inclined slides 5.

The inclination of the slides 5, which may be advantageously adjustable within certain limits, corresponds substantially to that of the lower generatrix of the shaping spindle 3. It will thus be understood that when the carriage 7 moves along the horizontal longitudinal girders 1, the box 8 moves with it, while it is, in turn, displaced parallel to the lower generatrix of the shaping mandrel 3. The movements of the movable head 6 are controlled by conventional means, such, for example, as a screw control means 7a driven by an electric motor 7b and at a speed which is uniform or variable according to the law of the desired variation of the dimensions of the section on the shaped part to be obtained.

The moveable head 6 supports a succession of rollers or groups of machining rollers staggered along the longitudinal axis of the shaping mandrel 3 and acting, one after the other, on the strip of sheet metal 10 which moves forward in the direction of the arrow and at a uniform speed along the upper generatrix of the mandrel. The respective functions of these various rollers or groups of rollers will become clear on examining FIGS. 3 to 6 of the drawing, assumed to correspond to one and the same position of the movable head 6 on the machine frame.

A strip of flat sheet metal 10, which moves in contact substantially along its longitudinal axis with the upper generatrix of the shaping mandrel 3, is firstly turned down through a certain angle on both sides of this generatrix by a pre-shaping roller 11 having a concave profile and preferably made from a resilient material such as, for example, rubber or a thermoplastics material having similar properties. This roller 11, which is supported by a horizontal spindle integral with the carriage 7 rolls with sufficient pressure on the strip of sheet metal 10, which it begins to turn down around the shaping mandrel 3, as illustrated in FIG. 3 of the drawings. If necessary, other pre-shaping rollers may be provided for assisting the action of the roller 11 or for completing it with a view to facilitating the subsequent operation of the shaping rollers proper.

Shaping rollers 12 are at least two in number and may be supported by the carriage 7 or by the box 8 of the movable head 6 with their axes substantially at right angles to the axis of the shaping mandrel 3. These rollers 12, also have a concave profile and are applied transversely and with substantial pressure on either side of the preformed metal sheet 10 with a view to completing the bending around the shaping mandrel 3 (FIG. 4).

In the embodiment illustrated in the drawing, these shaping rollers 12 are made from a material having resilient properties, for example rubber and have a groove profile corresponding substantially to the configuration and to the radius of curvature of the middle section of the shaping mandrel 3; owing to their elasticity as well as to the pressure to which they are subjected in the direction of the mandrel, they may follow the shape of the mandrel at every point of its axis due to elastic deformation of their generatrix of contact.

Owing to the variation of thickness of the shaping mandrel along its axis and likewise to the possibility of employing mandrels of different dimensions on the same machine, the shafts of the shaping rollers 12 must be movable in a horizontal direction transversely to the axis of the mandrel. Thus, as far as possible, the necessary pressure must be provided by actuating means developing a force independent of their travel. Preferably, to this end, the invention envisages employing oleopneumatic jacks of adjustable force depending on the thickness of the metal to be shaped.

According to the invention, it is also possible to make use of the natural adhesion of the rubber of the shaping rollers 12 to the strip of sheet metal 10 so that they may also fulfil the function of means for driving this strip of sheet metal along the shaping mandrel 3. To this end, the rollers 12 may be set in rotation at a uniform speed and in the desired direction by means of electric motors 12a provided with reduction gears or even by means or rotary hydraulc motors. This makes any other means for controlling the forwards movement of the strip of sheet metal 10 superfluous.

The shaping rollers above described seem the most appropriate for the manufacture of shaped parts of light alloys. Nevertheless, the number and shape of the shaping rollers as well as their constituent material may vary depending on the sections of the shaped parts to be obtained and on the nature of the metal used for their manufacture. Thus, for example, in the case where the shaped parts are to be made of steel, it would be suitable to substitute for the pair of rubber shaping rollers above described, a group of rollers constituted by a hard material, for example of polished steel, these rollers thus being distributed in pairs, two by two, on opposed generatrices of the shaping mandrel.

In this embodiment, when it is a question of producing a shaped part having a closed contour, in order to avoid material falling during manufacture, it would clearly be possible to give the strip of flat sheet metal 10 a width corresponding exactly to the length of the developed circumference of the shaped part, this width thus clearly having to vary along the strip of sheet metal in order to take into account the desired variation of dimensions of section on the shaped part. Nevertheless, it is more simple to give the strip of rought sheet metal an excess width and to remove the superfluous parts as the shaped part is produced, which superfluous parts could moreover be readily recovered, in particular in the case of light alloys. This operation may take place by any appropriate means for example, sawing, shearing etc. Preference is given to a shearing operation which may in particular be undertaken by means of steel rollers having an appropriate cutting edge.

In order to obtain a clean cut such as to avoid a subsequent re-treatment operation, the superfluous lateral parts may advantageously be previously folded outwards by means of other steel rollers having a straight profile, the folding line thus imparted to the shaped part serving to guide the shearing rollers. The machine illustrated in the accompanying drawing thus comprises, downstream of the shaping rollers 12, a pair of folding rollers 13 and a pair of shearing rollers 14 both supported by the box 8 of the movable head 6, these steel rollers being provided with the same pressure means and being rotated in the same direction and at the same tangential speed as the shaping rollers 12, but being displaced parallel to the lower generatrix of the shaping cylinder 3. FIG. 5 shows how the rollers 13 finish off the shaping of the contour of the shaped part by bending the superfluous parts 15 of the strip of sheet metal substantially at right angles towards the outside. FIG. 6 shows how the shearing rollers 14, whose cutting edges roll in the folding lines, detach the superfluous parts 15 from the shaped part.

Still referring to the case of manufacture of a shaped part having a closed contour, the movable head 6 of the machine may also comprise, downstream of the shearing rollers 14, a spot or continuous welding apparatus 18 which may be used to connect the lips of the joint of the shaped part at the end of the shaping operations.

The shaped part formed by the abovedescribed machine progresses continuously along the shaping mandrel 3 and its shape as well as its sectional dimensions correspond, apart from the differences due to the thickness of the constituent metal, to those of the section of the shaping mandrel 3 in the vicinity of which the action of the folding rollers 13 is exerted. Naturally, under these conditions, if the movable head 6 does not move during the shaping operation, the shaped part obtained will be of uniform section determined as a function of the adjustment of the shaping head 6. Nevertheless, in the most general case when it is proposed to produce a shaped part having a variable section, this result is obtained by an appropriate displacement of the shaping head 6 along the longitudinal girders 1 during the passage of the strip of sheet metal 10 along the shaping mandrel 3. This displacement of the shaping head generally takes place at a speed less than that imparted to the strip of sheet metal; by way of example, these speeds may be respectively 0.3 m/min and 1.8 m/min.

Assuming that the passage of the strip of sheetmetal over the shaping mandrel takes place at a constant speed, the law of displacement of the shaping head itself depends on the law of desired variation of the sectional dimensions on the shaped part to be produced. While a uniform speed of movement of the head is translated in the case of a frusto-conical shaping mandrel by a linear variation of the sectional dimensions along the axis of the shaped part, an appropriate control of this speed as a function of times may facilitate, in this particular case, other laws of variation of the sectional dimensions, for example, parabolic, exponential etc., a possibility which is particularly advantageous when it is proposed to obtain a solid member of equal resistance to bending forces or compression (in the case of ships masts, for example). Such a control of the speed of displacement of the head may be obtained automatically by any known means acting, for example, on the speed of rotation of the drive screw of the movable head 6 on the machine frame.

It may even be advantageous to vary the thickness of the wall of the shaped part at the same time and in the same direction as the dimensions of its section. Such a result may be obtained easily with the method according to the invention, since, for this purpose, it is sufficient to combine with the aforedescribed shaping machine, a rolling-mill between the rolls of which the strip of rough sheet metal must pass before reaching the shaping mandrel. The spacing of the rolls of this rolling-mill may be modified during the operation, either manually or preferably by means of a control mechanism itself controlled by the displacement of the shaping head along the mandrel. Here also, the variation of thickness of the wall along the shaped part obtained may obey a linearlaw or any other appropriate law, the regulation of the mechanism controlling the spacing of the rolls being designed accordingly; it is also possible to modify this spacing of the rolls discontinuously in order to obtain, if need be, sudden changes in the wall thickness of the shaped part.

The cycle of operation for forming the shaped part may be preceded and/or followed by any appropriate heat treatment. In particular, the strip of rough sheet metal may be subjected to a continuous or discontinuous heat softening treatment by an apparatus 16, before it passes to the shaping machine, the observation being made in this case that by means of the method according to the invention it is possible to produce shaped parts of hard metals or alloys which are not suited or ill-suited to drawing. Likewise, the shaped part may be subjected at the same time as the shaping operations to a continuous or discontinuous head treatment by an apparatus 17 for restoring its characteristics, such as, for example, a hardening treatment able to impart thereto certain desired mechanical properties.

Although it has not been expressly mentioned, the preceding description implicitly envisages the assumption of discontinuous production, the strip of rough sheet metal being previously cut to the desired length and the width of the strip being able to be cut in a flat condition, thus avoiding subsequent machining on the shaped part; the shaping head is thus operational only in one direction of displacement and at the end of each machining pass, it is restored to its initial position ready for the next pass. Nevertheless, the machine described is quite suitable for continuous production, in which the strip of sheet metal would unwind from a roll, the shaping head being in this case operational in both directions of displacement between its end positions. In this case, it would be advisable to give the speed of displacement of the movable head 6 and/or the speed of rotation of the shaping rollers 12 different values in either of the two displacement directions of the head along the machine frame, and this would take into account the fact that in one direction the speed of travel of the strip of sheet metal over the shaping mandrel 3 is equal to the sum of the tangential drive speed of the rollers 12 and the speed of movement of the head 6 with respect to the shaping mandrel 3, whereas in the other direction, on the contrary, this same speed is equal to their difference. Thus, the machine delivers successive lengths of shaped part having sections increasing and decreasing alternately and it is an advantage to provide on the machine itself, an additional cutting apparatus designed for detaching these successive lengths of shaped part from each other, this apparatus moving in translation on the machine frame at the same speed as the strip of sheet metal and thus as the shaped part throughout the duration of a cutting operation and then returning automatically to its initial position ready for the next operation.

Naturally, the preceding description is given only as an example and it in no way limits the possibilities for carrying out the method of forming tubular shaped parts according to the claimed invention, which may comprise numerous variations. Thus, in particular, the shaping rollers could have no driving action on the strip of sheet metal, the latter being drawn externally as on a drawing bench.

Finally, as a new industrial product, the invention includes tubular shaped parts obtained by applying the method described and/or by means of a shaping machine such as that described above.

Claims

What is claimed is:

1. A method of manufacturing from a strip of flat sheet metal a shaped elongated part having a progressively varying cross section, comprising: displacing said strip along a generatrix of a fixed shaping mandrel the cross section of which decreases progressively along said generatrix in a predetermined manner, and progressively bending said strip as it is displaced around said mandrel on either side of said generatrix so as to follow the shape and dimensions of said mandrel, by pressure means the point of action of which is variable along said mandrel to produce a desired variation in the cross section of the part to be shaped.

2. A method according to claim 1, which includes the step of cutting the edges of said strip after having been bent around said mandrel as the shaped part progresses along said mandrel by cutting means associated with said pressure means.

3. A method according to claim 2, which includes the step of folding said edges outwardly by folding means associated with said pressure means.

4. A method according to claim 3, wherein said cutting means are guided along said mandrel by the fold line of the lateral edges produced by folding means.

5. A method according to claim 1, which includes subjecting said strip prior to said shaping step to a softening heat treatment.

6. A method according to claim 1, which includes the step of subjecting said shaped part to a hardening heat treatment.

7. A method according to claim 1, which includes the step of reciprocating said pressure means along said mandrel and cutting the thus obtained shaped part intermittentaly.

8. A machine for manufacturing from a strip of flat sheet metal a shaped elongated part, comprising: a frame, a shaping mandrel mounted on said frame and having a cross section decreasing progressively in one direction at least one shaping head movable parallel to a generatrix of said mandrel, at least one pair of shaping rollers and associated actuating means supported by said head for urging said strip against said shaping mandrel on either side of said generatrix, first drive means for displacing said strip at a uniform speed along said generatrix, and second drive means for displacing said shaping head with respect to said mandrel for producing the desired variation in cross section of said part.

9. A machine according to claim 8, wherein said first drive means drives at least one of said pair of shaping rollers on said movable head.

10. A machine according to claim 8, which includes a box mounted to slide on said movable head in a direction transverse to the direction of displacement of said head, said shaping rollers being located on said box, and a stationary slide associated with said mandrel for guiding said box in said transverse direction.

11. A machine according to claim 8, comprising at least one resilient pre-shaping roller supported by said movable head upstream of said shaping rollers, said pre-shaping roller being adapted to initiate bending of said strip around said mandrel, and actuating means for exerting pressure on said roller for rolling said strip along said generatrix.

12. A machine according to claim 8, comprising a pair of shearing rollers mounted on said movable head downstream of said shaping rollers, and actuating means for applying pressure on said shearing rollers to detach from said strip portions along the lateral edges thereof.

13. A machine according to claim 12, which comprises a pair of folding rollers located upstream of said shearing rollers for folding said portions outwardly, said shearing rollers being guided along the creases formed in the strip by said folding rollers.

14. A method according to claim 2 which includes the step of welding the shaped part together where the edges of said strip have been cut off.

15. A machine according to claim 12, comprising a welding apparatus supported by said movable head downstream of said rollers for connecting opposite adjacent edges on said shaped part where said portions have been cut off.