Apparatus for manufacturing tubes
This application is a continuation-in-part of previously filed application U.S. Ser. No. 630,256, filed Nov. 10, 1975, abandoned. 
    
    
     BACKGROUND OF INVENTION 
     1. Field of Invention 
     The present invention relates to apparatus for manufacturing tubes by helical coiling of a preferably corrugated strip, in particular a sheet metal strip, comprising coiling means equipped with two connecting means arranged at the strip-entering point and acting on a surface of the two strips to mutually join the adjacent convolution of the tube, then means to guide said joined strip in a circle to produce a next convolution. 
     2. Description of the Prior Art 
     A device of the aforedescribed class is already known (cf. German patent application laid open to public inspection DT-OS No. 2,453,876). This document discloses the means geared to move said strip in a circle to produce a convolution, which is composed of supporting rollers arranged at the periphery of the convolution to be produced and serving to guide same; these supporting rollers are paraxially arranged at a support for free rotation. To achieve a compensation for different values of strip thickness the supporting rollers can be geared for radial adjustment at the support, relative to their circular arrangement. 
     It has become apparent that the known devices cannot always produce tubes having exactly the desired tube diameters; this is true particularly for different strip qualities, and above all for different values of strip thickness or bending resistance. Since in one and the same strip deviations in quality cannot be avoided either, the diameters of the convolutions are frequently different, too, in tubes produced in the known devices. 
     SUMMARY OF INVENTION 
     The objective underlying the present invention is to provide the simplest construction possible in apparatus of the type specified by way of introduction, wherein tubes can be produced whose diameter constantly coincides with the desired values. 
     In accordance with the present invention this objective is achieved by connecting rollers driven to have different peripheral speeds. In an expedient embodiment the rotational speed of the connecting roller can be varied, which is arranged at the inner side of the convolution or tube to be produced whilst the connecting roller provided at the outside of this convolution or tube can be driven at a constant rotational speed. 
     By a corresponding change of the peripheral speeds of the connecting rollers it is possible to oppose an increase in convolution diameter, which is entailed by a changing strip quality. Such effect is obtained by giving a higher peripheral speed, for instance, to the connecting roller provided at the side of the strip convolution, so that the strip convolution superimposing the strip entering in coiling direction is given a feed velocity higher than that of the entering strip; this feature entails reduction of the convolution diameter. 
     If, on the other hand, the convolution diameter starts to decrease, the peripheral speed of that connecting roller is reduced which is provided at the side of the convolution diameter at the strip-entering point; in this way the feed velocity of the convolution superimposing the strip convolution is so reduced that the diameter of convolution is increased. 
     To be able to control the peripheral speeds of the connecting rollers in a way that undesired deviations in the respective convolution diameter are opposed, it is possible to provide contact sensors at the periphery of the strip convolution to be produced, such sensors being coupled with means for variation of the rotational speed of one or either connecting roller. Such contact sensors can be arranged at the outside or at the outside and inside of the strip convolution. When the diameter of convolution starts to increase, one, i.e. the one arranged at the outside of the strip convolution, of the contact sensors is pressurized by the strip convolution; the contact sensor in its turn controls the driving means for the connecting rollers in a manner that the beginning increase in diameter is opposed. 
     If, in a known manner, the coiling apparatus is provided with guide rollers for the strip, which are arranged at the convolution periphery, one or several of these guide rollers can be designed as contact sensors, for this purpose. 
     In certain cases it can also be expedient to achieve different or variable peripheral speeds of the connecting rollers not by a change of the rotational speed but by application of different or variable roller diameters. Such different or variable roller diameter may be, but need not be, tied in with a variation of the rotational speed of the connecting rollers. When, for instance, the production of coiled tubes conically tapering in axial direction is intended, a constant ratio of a different rotational speed of either connecting roller can be desired so that hence a constant variation of the peripheral speed is not decisive. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of the preferred embodiment of the apparatus according to the invention. 
     FIG. 2 is a plan view of the apparatus of FIG. 1. 
     FIG. 3 is an elevational section through the apparatus shown in FIGS. 1 and 2, the section taken through the connecting rollers and their drives. 
     FIG. 4 is an elevational section through an alternate configuration of the section taken through the connecting rollers and their drives. 
     FIG. 5 is an elevational section through the axes of the connecting rollers in another embodiment. 
     FIG. 6 is a view of a fastening (pressure) disk used in the connecting rollers as shown in FIG. 5. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An apparatus according to the invention as shown in the drawings includes a strip 1, which is to be coiled into a tube 13, guided in a straight line between a series of rollers 2, 3 and 4 arranged in pairs one after another in the direction of strip movement. As the strip 1 passes through the rollers 2, 3 and 4, it is longitudinally corrugated. After leaving rollers 4, the strip 1 enters between two connecting rollers 5 and 6. The axes of the rollers 5 and 6 are positioned parallel to those of the rollers 2, 3 and 4 and have the purpose of connecting an adjacent convolution 10 to the strip 1. 
     The connecting rollers 5 and 6 may be so formed that the interengaging corrugations of the incoming strip 1 and of the convolution 10 which is superposed onto the strip 1 are compressed in such a way that these corrugations assume a proximate dovetailed shape in cross section, i.e. the corrugations are wider at their top than at their bottom as is explained in our co-pending British Patent Application No. 30263/73. The strip 1 and the corrugation form therefore together a compression joint. 
     A coiling means 7 includes a support plate 8 on which a number of guide rollers 9 are arranged in a circle. The connecting rollers 5 and 6 are positioned such that the peripheral surface of the connecting rollers 5 and 6 is substantially tangential to the circle formed by guide rollers 9. The one connecting roller 5 is located inside the circle and the other connecting roller 6 at its outside. After passing between the rollers 5 and 6, the strip 1 travels past the guide rollers 9 and at the same time is deflected by them into a circular convolution. The deflection of the strip 1 is initiated immediately after the strip 1 leaves the rollers 5 and 6 by a deflecting roller 11 arranged on the support plate 8 so that the axis of that roller 11 is parallel to those of the guide rollers 9. 
     Since the strip 1 has to be coiled helically to produce the tube 13 as desired, the support plate 8 is capable of being pivoted about a shaft 12 which is positioned perpendicular to the plane of the incoming strip 1. In this way the support plate 8 can be set in an oblique position relative to the longitudinal axis of the incoming strip 1 as required by the pitch of the helical convolutions of the tube to be produced. Since the deflecting roller 11 and the guide rollers 9 are secured to the plate 8 and the plate 8 is freely rotatable about the shaft 12, rotation of the plate 8 causes a change in the oblique position of the guide rollers 9 and the deflecting roller 11 as shown in FIG. 2. The guide rollers 9 and the deflecting roller 11 are thus able to adapt to the pitch of the convolutions 10 of the tube 13 being produced. 
     After a complete convolution has been formed, this convolution 10 is again passed between the connecting rollers 5 and 6. A portion of the outer surface of the corrugations in the convolution 10 interface with a portion of the inner surface of the incoming strip 1 so that the convolution 10 is offset axially relative to the strip 1 by the amount called for by the pitch of coiling. These offsets between successive convolutions gradually build to create the tube 13. 
     In order to cause the convolution 10 to be offset in the manner required after it has passed through the coiling means 7, the convolution 10 is directed axially by the guide roller 9 in addition to being radially supported on the outer peripheral surface of each. The axial guiding may be obtained in a positive manner by means of an annular flange or a lip extending around the periphery of a guide roller 9, the flange engaging the unconnected edges of the convolution 10. Axial guiding of the strip 1 to produce convolution 10 also may be obtained by providing like corrugations in the guide rollers 9 which engage the corrugations in the strip 1. 
     As can be seen from FIG. 3 of the drawings, the connecting rollers 5 and 6 are divided in their axial direction into two parts 22, 23 and 14, 15, respectively. As the tube 13 is built up in a direction parallel to the axes of the rollers 5 and 6, each of these two rollers has a part which trails and another part which leads with respect to the direction of tube build-up. 
     The parts 22, 23 as well as the parts 14, 15 are of different diameters and are fixedly mounted on drive shafts 16 and 16&#39;, respectively, the trailing part 22 of connecting roller 5 being of smaller diameter than the leading part 23, while conversely the trailing part 14 of connecting roller 6 is of corresponding greater diameter than the leading part 15. The incoming strip 1 is so guided between the rollers 5 and 6 that it is engaged across its width by both parts of each of the rollers 5 and 6. Depending on its desired pitch, a convolution 10 is, after passing the deflecting roller 11, guided back between the connecting rollers 5 and 6 in such a manner that it passes between the parts 22 and 14 of those rollers it can also be expedient that the part 15 or the part 23 may be freely mounted and undriven as shown for part 33 in FIG. 4. 
     The difference in diameter between parts 22 and 23 of connecting roller 5 and parts 14 and 15 of connecting roller 6 causes a convolution on passing again through the connecting rollers 5 and 6 to be driven at a faster rate than the incoming strip 1 by part 14 of the lower connecting roller 6 as a consequence of the greater diameter of that part. Because of this, the incoming strip 1 is thrust firmly against the guide rollers 9 and the deflecting roller 11 in the radial direction of the convolution 10 which is with one half in contact with the rollers 5 and 6. The frictional grip between the connecting rollers 5 and 6 or more precisely between their parts 22, 23 and 14, 15 of one part and the strip 1 of another part is, however, sufficiently slack to allow a certain amount of slip. 
     Because of the difference in diameter between the parts 22, 23 and 14, 15 respectively the strip 1 is further formed by the connecting rollers 5 and 6 with a longitudinal shoulder or step and this, together with the elasticity and flexibility of the strip 1, assists in preventing the diameter of the tube from increasing as coiling progresses and this notwithstanding the interengagement between adjacent convolutions 10 of the tube 13. 
     If a tube 13 is to be produced in which the pitch of the convolution 10 amounts to only a third of the width of the strip instead of a half, it is advantageous for the connecting rollers 5 and 6 to be each divided axially into three parts, the diameters of these parts becoming greater from part to part in the direction of tube formation in the case of the outer roller 6 and smaller in the case of the inner roller 5. The part 22 of the connecting roller 5 is fixedly mounted on a drive shaft 16 and revolves synchronously with the other part. The part 15 of the connecting roller 6 is freely mounted and undriven on a shaft 16&#39;. 
     FIG. 4 shows an alternative configuration of connecting rollers 5, 6. In this embodiment the inner connecting roller 5 is carried by an inner shaft 26 and the outer connecting roller 6 is carried by an outer shaft 28. The outer and inner connecting rollers are divided into two parts 29, 30, 32 and 33. Thus roller parts 29 and 30 of the outer connecting roller 6 and the roller part 32 of the inner connecting roller 5 are connected with the respective shafts 28 or 26 by a wedge or key 27 or 31, respectively, this connection not permitting any rotation between the respective shaft and roller part. On the other hand, the other roller part 33 of the inner connecting roller 5 is arranged for free rotation on shaft 26. The diameter of each roller part 29, 30, 32 and 33 and of both connecting rollers 5 and 6 is the same. 
     In the embodiment shown in FIG. 4, the supporting roller 9a, which is arranged vertically above the two connecting rollers 5, 6, can be designed to be pressure sensitive. If the diameter of convolution starts to increase for reasons of the characteristics of strip material 1 in coiling the strip 1, this increase being produced in the coiling means, the convolution 10 exerts an increased pressure onto the pressure sensitive roller 9a. Such increased pressure is utilized in the embodiment shown in FIG. 4 to increase the rotational speed of the connecting roller 5 provided at the inner side of the convolution. To this end the two connecting rollers 5, 6 are each associated with an independent drive 24, 25, respectively. At least the drive 24 for connecting roller 5 is so designed that it can serve to change the peripheral speed of this roller, since roller 9a is operatively connected, by control means (not shown), to drive 24. 
     The higher peripheral speed of inner connecting roller 5, which is caused by the roller 9a, entails an increase of the advancing speed of the convolution 10 superposed on the strip 1 entering the coiling means, such that the convolution advancing speed is higher than the advancing speed of the strip 1. Such provision entails a reduction of the diameter of the convolution passing through the two connecting rollers 5, 6. When, however, the convolution 10 starts to become smaller, the pressure exerted by the convolution onto the roller 9a decreases. When the roller 9a senses such a decrease in pressure, it actuates said control means which emits a stepping contact pulse to the drive 24 of connecting roller 5 in a way that this drive 24 decreases the peripheral speed of the associated connecting roller 5. Hence, the advancing speed of the convolution 10, which is coiled onto the strip 1 in the coiling means 7, is reduced relative to the advancing speed of the entering strip 1. Such speed decrease entails an increase of the diameter of the convolution passing through the two connecting rollers 5, 6. 
     It is also possible to provide an independent pressure sensitive roller at the inner side of convolution 10 for this sensing operation. This pressure sensitive roller can, for instance, be arranged opposite to the aforementioned roller 9a arranged at the outer side of the convolution 10. 
     Such control of the peripheral speed of the inner connecting roller 5 allows coiling of a tube having a precisely controlled diameter with exactly the desired tube caliber even in case of irregularities or different characteristics in the material of strip 1. The aforementioned construction also allows production of coiled tubes having the same diameter even if strips of different quality and thickness are employed for such tubes. 
     It is, of course, possible on principle to achieve a constant diameter of convolutions 10 also by control of the peripheral speed of the outer connecting roller 6 when such control can contribute to control the advancing speed of the entire strip entering the coiling means 7. 
     A corresponding control of the peripheral speed of connecting rollers 5, 6 in the apparatus according to the present invention also permits production of conical tubes whose diameter decreases or increases in the direction of the tube axis. In such a case it is only necessary to set the pressure sensitive rollers correspondingly. 
     It is also possible to provide other pressure sensitive contacts instead of the roller freely rotating along with the convolution 10. 
     In the case of a coiled tube, it is normally required to make provisions for interconnection of successive strip convolutions in their area of overlap. 
     To this end connecting rollers 5 and 6 may be so formed that the interengaging corrugations of the incoming strip 1 and of the convolution 10, which is superposed onto strip 1, are compressed in such a way that these corrugations assume an approximate dovetailed shape in cross section, i.e. the corrugations are wider at their top than their bottom, as is explained in our co-pending British Patent Application No. 30263/73. 
     It is also possible to press the interengaging corrugations of two adjacent convolutions to achieve flat folded edges (cf. U.S. Pat. No. 3,858,421). 
     In both these cases an interengagement or hooking of the mutually enclosing corrugations in achieved which prevents a sliding separation and hence a separation of the overlapping areas of the strip convolutions. 
     As best seen in FIGS. 5 and 6, such hooking can be achieved by the inner connecting roller 5 supported on an inner drive shaft 26 including freely rotatable first inner roller part 33 and a second outer roller part 32 joined to the shaft 26 in a fixed manner. The first and second roller parts 33 and 32 are formed having a series of circumferent grooves 34 having a bottom 36 and apex 42. The second outer roller part 32 has an annular space 37 in which is disposed a disk 35 made freely rotatable by a bearing 38 positioned within the space 37. 
     The disk 35 has an outer peripheral surface 43 which includes a series of cam projections 39 spaced at fixed intervals about the surface 43. 
     A diameter of the surface 43 of the disk 35 is proximate a diameter of the connecting roller 5 as measured between opposing groove bottoms 36 while a diameter of the disk 35 as measured between the camming projections 43 proximates a diameter of the connecting roller 5 as measured between opposing apexes 42. 
     The outer connecting roller 6 is supported on the outer drive shaft 28 in a fixed manner and includes a first inner roller part 30 and a second outer roller part 29. Each roller part 30 and 29 also is formed having a series of circumferent grooves 34 having an apex 42 and a groove bottom 36. The grooves 34 of the inner and outer connecting rollers 5 and 6 are offset so that the apexes 42 of the grooves 34 of the outer connecting roller 6 align with the groove bottom 36 of the groove 34 of the inner connecting roller 5. 
     The groove 34 in the outer connecting roller 6 opposite the disk 35 has a flattened apex 40 to provide a support surface for the projections 43 of the disk 35. 
     In such movement, the apexes of the conformingly enclosing corrugations are broadened in such a way that an approximate dovetailed corrugation cross section is obtained. Such cross section entails hooking of the conformingly enclosing corrugations so that undesired separation of the two convolutions is definitely prevented. 
     Since the conformingly superposed corrugations of two adjacent convolutions can be mutually hooked or joined only on completion of a full coil of convolution 10, in order to still allow for the inventive correction of the convolution diameter the disk serving to hook the corrugations must be arranged for free rotation independent of the connecting roller 5. 
     The freely rotatable disk 35 can be provided also with acute teeth or thorn-shaped projections instead of cams 39. Such acute hooking elements perforate the superposed convolutions so that the latter are also connected with each other by clamping or stapling. In such a case the outer connecting roller 6 must be provided with deep indentations or recesses to match the acute teeth of the inner connecting roller 5 in the corresponding area, which indentations are suited for accommodation of the teeth of the thorned disk. Such construction enables one convolution to be fixedly attached to the adjacent convolution which partly is superposed to the first convolution, even in a case where the strip is not corrugated. 
     While various modifications may be suggested by those versed in the art, it should be appreciated that I wish to embody within the scope of the patent warranted hereon, all such modifications as reasonably and properly come within the scope of my contribution to the art.