Abstract:
A device and a method for widening elongated metal elements which move in the longitudinal direction and are planar at least in certain regions are described. The device comprises at least two clamping sections which are opposite one another and of which one is arranged and designed for clamping a first longitudinal side of the metal element in place and the other is arranged and designed for clamping a second longitudinal side of the metal element in place, said second longitudinal side being opposite the first longitudinal side of the metal element. The clamping sections are each provided on a support unit by means of which the clamping sections, during the forward movement of the metal element, are automatically moved apart essentially perpendicularly to the direction of movement of the metal element.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. national phase application filed under 35 U.S.C. §371 of International Application PCT/EP2007/001734, filed on Feb. 28, 2007, designating the United States, which claims priority from DE 10 2006 010 795.0, filed Mar. 8, 2006, which are hereby incorporated herein by reference in their entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to an apparatus and to a method for the expansion of elongated metal elements which move in the longitudinal direction and are areal at least regionally. In particular areal metal elements such as are described in German patent application 102 59 307.8 should be expanded using the apparatus and the method in accordance with the invention. 
     BACKGROUND OF THE INVENTION 
     The areal metal elements described in this prepublished German patent application are used, for example, for the manufacture of sectional elements, in particular of upright sections or plaster sections. The metal elements in this connection have incisions in their mid regions which are shaped such that, when the metal elements are drawn apart, metal regions present between the incisions are folded over so that ultimately a widening of the metal element takes place. Wider metal elements can thus be produced with a reduced metal consumption by this folding procedure. The cutting patterns required for the folding procedure can be of the most varied type. A plurality of such different cutting patterns are described in German patent application 102 59 307.8 and are in particular shown in  FIGS. 1-22  of this application. For the better understanding of the present application, the disclosure content of German patent application 102 59 307.8, in particular with respect to the specifically described and shown cutting patterns, are explicitly included and incorporated by reference in the content of the present application. The metal elements in the sense of the present invention are made areal or flat at least in the region of the cutting patterns. In other regions, for example also in the region of the longitudinal sides of the metal elements, the metal elements can also deviate from the areal or flat shape. Thickened regions, steps or bent over regions can in particular be formed at the longitudinal sides. The metal elements can thus e.g. already be preshaped as U-shaped sections or C-shaped sections. 
     It is, however, problematic to carry out the expansion of such elongated metal elements which are areal at least regionally with an economically justifiable effort and so to achieve an economically sensible manufacture of the sectional elements. Since the costs of such sectional elements are mainly determined by the material costs, a widening of the metal element is admittedly generally desired with a reduced material requirement, but the gains recorded by the material saving many not be cancelled out again by increased costs in the production of the sectional elements. An economically worthwhile manufacture is the more difficult in this connection since corresponding sectional elements represent a mass produced article of which thousands of kilometers are produced annually and which is produced at a very high speed (for example 100 to 150 m/min). An apparatus for the expansion of corresponding areal or flat metal elements must therefore be capable of ensuring a correspondingly high throughput with a simultaneous high reliability. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide an apparatus and a method for the expansion of elongated metal elements which move in the longitudinal direction, which are areal or flat at least regionally and which ensure a large throughput with a simultaneously simple and reliable design. The apparatus and the method should in particular be usable in continuous operation. 
     This object is satisfied in accordance with the invention by an apparatus of the initially named kind which comprises at least two mutually oppositely disposed clamping portions of which one is arranged and configured for the holding by clamping of a first longitudinal side of the metal element and the other is arranged and configured for the holding by clamping of a second longitudinal side disposed opposite the first longitudinal side of the metal element, with the clamping portions each being provided at a carrier unit by which the clamping portions are moved apart automatically substantially perpendicular to the direction of movement of the metal element during the forward movement of the metal element. In the method in accordance with the invention, a first longitudinal side of the metal element is clamped in a holding manner into a first clamping portion and a second longitudinal side of the metal element is clamped in a holding manner into a second clamping portion disposed opposite the first clamping portion, with the clamping portions each being provided at a support unit by which the clamping portions are moved apart automatically substantially perpendicular to the direction of movement of the metal element during the forward movement of the metal element. 
     The mutually oppositely disposed clamping portions thus form an expansion region for the metal element between them in which the spacing between the mutually oppositely disposed clamping portions increases. The expansion of the metal element takes place in the expansion region by enlarging the lateral spacing between the mutually oppositely disposed clamping portions which each draw the mutually oppositely disposed longitudinal sides of the metal element apart. 
     The apparatus in accordance with the invention is very robust thanks to its simple design and thereby also suitable for a high throughput. It is furthermore achieved by the clamping portions that the expansion of the moving metal element can take place in continuous operation so that the required throughput is ensured. It is generally, however, also possible for the expansion to take place in intermittent operation, for example also in a progressive tool. It is thus not absolutely necessary in the sense of the present application for the metal element to move forward simultaneously with the expansion. The forward movement of the metal element in intermittent operation, for example, includes repeating stationary phases in which the expansion can take place. The expansion during a stationary phase in intermittent operation is thus also to be understood as an expansion during the forward movement in the sense of the present invention since the individual stationary phases also represent parts of the total forward movement of the metal element. With a correspondingly short length of the metal element, it can also be expanded simultaneously over its total length, i.e. in plate production. In this case, the forward movement includes the infeed, the stationary phase during which the metal element is expanded and the outfeed of the metal element. 
     A preworking of the longitudinal sides of the metal element is not necessary due to the use of clamping portions. The longitudinal sides of the metal element do not need to have any folds or other engagement elements into which, for example, drawing elements engage for the drawing apart of the metal element. The longitudinal sides can be made completely smooth due to the clamping in accordance with the invention of the longitudinal sides of the metal element, whereby the application possibilities of the expanded metal elements are very wide and complex pre-treatments of the metal element associated with additional costs for the production of engagement points can be dispensed with. The clamping portions can be made such that a free longitudinal strip of 0.5 to 5 mm (for example approximately 1, 1.5, 2 or 3 mm) is already sufficient at both longitudinal sides of the metal element to clamp them in each case into the clamping portions and to draw the metal element apart. 
     In accordance with an advantageous embodiment of the invention, the clamping portions each comprise a contact region and a clamping region, with the longitudinal sides of the metal element being able to be clamped between the contact region and the clamping region. The clamping region can advantageously be formed by an eccentric member. The formation of the clamping region by an eccentric member also makes the whole apparatus very robust and simultaneously simple since the eccentric member can be supported at a supporting section of the clamping portion such that the clamping force generated by the eccentric member automatically increases on the moving apart of the clamping portions. The higher the force acting on the metal element thus is on the moving apart, the more firmly the metal element is clamped in the clamping portion. 
     It is generally also possible for the clamping portion to be pre-tensioned with respect to the contact region by spring bias. Any possible suitable type of spring can be used, for example helical springs, gas compression springs or other springs. A hydraulic, pneumatic, electric, magnetic or other mechanical pre-tensioning of the clamping portion with respect to the contact region and any other suitable type of pre-tensioning are also generally conceivable. Such a pre-tensioning is also sensible in connection with an eccentric design of the clamping region when the eccentric member does not yet unfold the full clamping force by the pre-tensioning, for example on the gripping of the metal element. Due to the pre-tensioning, the eccentric member can automatically be brought so far into the clamping position that ultimately the holding of the metal element is achieved only on the basis of the clamping force. 
     In accordance with a further preferred embodiment of the invention, the clamping portions each comprise a plurality of clamping elements. The development of the expansion of the metal element can be set in a simple manner by the division of the clamping portions into a plurality of clamping elements. 
     In accordance with a further advantageous embodiment of the invention, a control section, in particular in the form of a cam track guide, is provided with which the clamping elements can be brought automatically from a release position into a clamping position on the movement of the metal element. In a similar manner, a further control section can be provided with which the clamping elements can automatically be brought back from the clamping position into the release position on the further movement of the metal element after the expansion of the metal element. After the release of the metal element, the clamping elements can remain in their release position or can again be brought into the clamping position, but without a metal element clamped in. It must only be ensured that the clamping elements are in the release position shortly before the clamping elements again come into contact with the metal element. Said release position can be achieved again by corresponding control sections. 
     In particular the control sections made for the movement of the clamping elements into the clamping position can be made so movable that different positions of the clamping elements can be compensated which are produced, for example, by different thicknesses of the metal elements or by a penetration of the metal elements into the clamping elements of different amounts. The control sections can, for example, be movably supported hydraulically or against a spring force. 
     The carrier unit is preferably made as a circulating carrier unit, in particular as an endless circulating carrier unit. It is ensured by the configuration of the carrier unit as a circulating carrier unit that a metal element of any desired length can be expanded using the apparatus in accordance with the invention. 
     In accordance with a further advantageous embodiment of the invention, at least two circulating carrier units are arranged at each longitudinal side of the metal element, with each longitudinal side of the metal element being respectively clamped between at least two carrier units. With a horizontally arranged metal element, each longitudinal side of the metal element can thus be clamped, for example, between a carrier unit arranged above the metal element and a carrier unit arranged beneath the metal element. The clamping portions can thus preferably be made integrally with the carrier unit in this case. Generally, however, a separate configuration of the clamping portions is also possible. 
     In accordance with a further preferred embodiment of the invention, at least one circulating carrier unit is arranged at each longitudinal side of the metal element, with each longitudinal side of the metal element being respectively clamped in the clamping portions provided at the circulating carrier units. In this case, the longitudinal sides of the metal element are thus not clamped between two different carrier units, but each longitudinal side is rather respectively clamped in clamping portions which are, for example, arranged extending at carrier units to the side of the metal elements along its longitudinal sides. 
     The carrier units are preferably made as a track conveyor. It can, for example, be made as a steel tread. Generally, a design as a band, as a belt or as another peripheral unit, in particular suitable for clamping, is also conceivable. 
     In accordance with a further advantageous embodiment, a run-in region is provided for the metal element in which the mutually oppositely disposed clamping portions have substantially a constant spacing from one another, with an expansion region adjoining the run-in region in which the spacing between the mutually oppositely disposed clamping portions increases. It is ensured by the constant spacing of the clamping portions in the run-in region that the metal element can first be securely gripped by the clamping portions without any other forces acting on the metal element, in particular in the lateral expansion direction. Only after the metal element has been securely gripped by the clamping portions after running through the run-in region does the expansion of the metal element take place in the expansion region by enlarging the lateral spacing between the mutually oppositely disposed clamping portions which each draw apart the oppositely disposed longitudinal sides of the metal element. The spacing of the mutually oppositely disposed clamping portions preferably increases substantially continuously in the expansion region so that a continuous strain on the metal element is ensured which results in a uniform expansion of the metal element. 
     In accordance with a further preferred embodiment of the invention, the carrier units are configured as rotating disks, tires or wheels inclined with respect to one another. The clamping portions can each be formed in the outer marginal region of the rotating disks, tires or wheels. With this embodiment, in particular the contact regions of the clamping portions can be formed by the peripheral surfaces of the rotating disks, tires or wheels. 
     In this embodiment, the expansion of the metal element takes place by the angular position of the rotating disks, tires or wheels in that the metal element is clamped tight by the clamping portions in the region of the marginal regions of the carrier units inclined toward one another, is drawn apart by the peripheral surfaces of the rotating carrier units running apart and is released by the clamping portions again before the maximum spacing between the mutually inclined rotating carrier units is exceeded. 
     Further advantageous embodiments of the invention are recited in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in more detail in the following with reference to embodiments and to the drawings: 
         FIG. 1  shows a part of an areal or flat metal element with a cutting pattern; 
         FIG. 2  shows further cutting patterns suitable for the expansion of metal elements; 
         FIGS. 3 to 5  show three different states in the expansion of a metal element with the 
         FIG. 6  shows an edge protector section manufactured using an apparatus in accordance with the invention; 
         FIG. 7  shows U-shaped or C-shaped upright sections manufactured using an apparatus in accordance with the invention; 
         FIG. 8  shows a plan view of a first embodiment of an apparatus in accordance with the invention; cutting pattern of  FIG. 1 ; 
         FIG. 9  shows a detailed view of the apparatus in accordance with  FIG. 8  from the front; 
         FIG. 10  shows a detailed view from  FIG. 9 ; 
         FIG. 11  shows a plan view of a second embodiment in accordance with the invention; 
         FIG. 12  shows a side view of the apparatus of  FIG. 11 ; 
         FIG. 13  shows a front view of a further apparatus in accordance with the invention; 
         FIG. 14  shows a side view of the apparatus of  FIG. 13 ; 
         FIG. 15  shows a clamping element of the apparatus in accordance with  FIG. 13 ; 
         FIG. 16  shows the clamping element in accordance with  FIG. 15  in the release position; 
         FIG. 17  shows a further detailed representation of a clamping element; 
         FIG. 18  shows a sectional representation through the clamping element in accordance with  FIG. 17 ; 
         FIG. 19  shows a modification of the embodiment of the invention shown in  FIGS. 13 and 14 ; 
         FIG. 20  shows a part of a further areal metal element with a cutting pattern; 
         FIG. 21  shows the metal element in accordance with  FIG. 20  after the expansion; 
         FIG. 22  shows a further apparatus in accordance with the invention; 
         FIG. 23  shows a schematic detailed view of an apparatus in accordance with the invention; and 
         FIG. 24  shows a further embodiment of a clamping element made in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a section of an areal metal element  1  which is provided along its longitudinal axis  2  with a plurality of U-shaped sections  3  engaging into one another. The section shown in  FIG. 1  is considerably shortened with respect to the actual length of the metal element  1 . In actual fact, the metal element  1  forms a long metal strip which can have a length, for example, of several 100 m. 
     The metal element  1  is already described in the German patent application 102 59 307.8 to which reference is explicitly made. 
     The sections  3  are arranged such that the halves  4 ,  5  of the metal element  1  shown above or beneath the sections  3  in  FIG. 1  can be drawn apart perpendicular to the longitudinal axis  2  so that a resulting metal element with enlarged width is produced. A corresponding folding procedure is shown in detail in  FIGS. 3 to 5 . Further possible cutting patterns are shown by way of example in  FIG. 2 . 
     Correspondingly expanded metal elements can be used, for example, for the manufacture of sections such as are used e.g. as edge protection ( FIG. 6 ) or as upright sections for dry walls ( FIG. 7 ), e.g. in the form of U-sections and C-sections. 
     To be able to expand metal elements  1  known per se at high speed, as shown in  FIGS. 3 to 5 , an apparatus in accordance with  FIG. 8  is, for example, used in accordance with the invention. 
       FIG. 8  shows an elongated areal or flat metal element  11  schematically which is moving along its longitudinal axis  14  in accordance with an arrow  12 . 
     The metal element  11  is provided with cuts in accordance with  FIG. 1  or  FIG. 2  or with other suitable cutting patterns which are, however, not shown in  FIG. 8  or in the further Figures for reasons of clarity. In the upper region of  FIG. 8 , the metal element  11  has its original width as is present before the expansion. 
     The apparatus  13  shown in  FIG. 8  for the expansion of the metal element  11  comprises two substantially identically made track conveyors  15  arranged symmetrically to the longitudinal axis  14  of the metal element  11 . Each track conveyor  15  comprises a plurality of conveyor members  16  which are, for example, connected to one another via a chain not shown in  FIG. 8 . 
     The track conveyors  15  are made as endless track conveyors and are guided rotatably around deflection rollers  18  in accordance with arrows  17 . Two or more deflection rollers can be provided in dependence on the design. 
     Generally, the deflection rollers  18  can be driven or only rotate freely around their respective axes. 
     Clamping elements  19  are in each case arranged at the outwardly facing sides of the conveyor members  16  and move in the arrow direction  17  together with the conveyor members  16 . The track conveyors  15  thus form carrier units for the clamping elements  19 , whereas the clamping elements  19  respectively provided at a track conveyor form a clamping portion of this track conveyor. 
     The two track conveyors  15  are arranged such that a run-in region  20  and an expansion region  21  adjoining it are formed. In the run-in region  20 , respectively mutually oppositely disposed clamping elements  19  facing toward the longitudinal axis  14  of the metal element  11  have the same spacing from one another which corresponds approximately to the width of the metal elements  11  not yet expanded. In the expansion region  21 , the spacing of mutually oppositely disposed clamping elements  19  enlarges continuously, as can be recognized from  FIG. 8 . The run-in region  20  is not necessarily required in this connection so that, for example, the middle deflection rollers  18  can each be dispensed with and the expansion region  21  extends over the total length of the track conveyors  15 . 
     The metal element  11  shown in  FIG. 8  is arranged between the two track conveyors  15  in the run-in region  20  such that the two longitudinal sides  22 ,  23  of the metal element  11  engage into the clamping elements  19  and are held by them. 
     In the expansion region  21 , the metal element  11  is expanded by the clamping elements  19  moving apart in accordance with arrows  24  in a direction substantially perpendicular to the longitudinal axis  14  until it has the desired width at the discharge end of the expansion region  21 . After the expansion has taken place, the metal element can, for example, be rolled or pressed flat in a rolling process, whereby it receives its final width and the folding points produced in the metal element on the expansion are leveled. Generally, this can also take place by an otherwise suitable pressing process (e.g. in a stroke press). 
     Both the holding tight of the longitudinal sides  22 ,  23  of the metal element at the start of the run-in region  20  and the release of the widened metal element at the end of the expansion region  21  is effected by control sections, not shown, which cause an automatic closing and opening of the clamping elements  19 . Corresponding control sections, which bring the possibly closed clamping elements  19  into the release position so that the metal element can penetrate securely into the clamping elements  19  in the run-in region  20  and can be gripped by them, can also be provided before the start of the run-in region  20 . For example, the corresponding control sections can be formed by cam track guides which are provided before and at the start of the run-in region  20  or at the end of the expansion region  21  and cooperate with the clamping elements  19  in a corresponding manner. Generally, the control could also take place, for example, by limit switches or in another suitable manner. If the run-in region  20  is omitted, the control sections at the inlet side can accordingly be provided at the inlet of the expansion region  21 . 
     The track conveyors  15  form carrier units for the clamping elements  19  and effect a movement apart of the clamping elements  19  in the expansion region  21  due to their shape shown in  FIG. 8 , said movement apart in turn resulting in an expansion of the metal element  11 . Possibly present conveyor chains or conveyor belts, to which the individual conveyor members are connected, preferably extend in the region above and/or beneath the clamping elements  19  (perpendicular with respect to the surface of the metal element  11 ). It is avoided in this manner that the metal element  11  is stretched in the longitudinal direction in the curved sections of the track conveyors  15 . 
     A special embodiment of the clamping elements  19  is shown in more detail in  FIG. 9 . A clamping element  19  in accordance with  FIG. 9  is shown again in detail in  FIG. 10 . 
     The clamping element  19  comprises a base element  25  which is fastened to the outer side of the conveyor member  16 , as can be recognized from  FIG. 9 . The base element  25  has a U-shaped structure, with the inner side of the limb shown at the bottom in  FIGS. 9 and 10  forming a contact region  26  for the metal element  11 . 
     Furthermore, the clamping element  19  comprises an eccentric member  27  which is rotatably supported around an axis  28  at the limb of the U-shaped base element  25  shown at the top in  FIGS. 9 and 10 . The eccentric member forms a clamping region  29  for the metal element  11  which is clamped between the contact region  26  and the clamping region  29 , as can in particular be clearly recognized by two arrows  30 ,  31  from  FIG. 10 . 
     The eccentric member  27  is rotatably supported off-center around the axis  28  such that, on a rotation of the eccentric member counter-clockwise in accordance with  FIG. 10 , the clamping effect is canceled, whereas it is amplified on a rotation clockwise. On a tensile load of the metal element  11  in the direction of an arrow  32 , the clamping effect is thus increased due to the friction in the clamping gap which is present so that the metal element  11  is automatically clamped more firmly on the tensile strain occurring in the expansion region  21 . Generally, the clamping element  19  can also include a plurality of eccentric members  27  which are in particular arranged next to one another and which can, for example, be supported on the same axis. 
     As can be recognized from  FIG. 9 , a cam spigot  33  is provided at the upper side of the eccentric member  27  and is screwed, for example, into a threaded bore  34  (see  FIG. 10 ). The control spigot  33  can, for example, cooperate with the track guidance described above such that the eccentric member  27  located at the start of the run-in region  20  in its non-clamping release position is automatically moved into the clamping position after one of the longitudinal sides  22 ,  23  of the metal element  11  is moved into the clamping region of the clamping element  19 . In an analogous manner, the eccentric member  27  can be moved from its clamping position into the release position by a further cam track guide at the outlet of the expansion region  21  by a corresponding contact of the cam track guide with the control spigot  33  such that the clamped metal element  11  is released again. 
     By the use of an endless carrier unit with automatic clamping elements, the expansion apparatus in accordance with the invention is very simple and robust in design and can in particular expand metal elements moving at high speed from a first width to an enlarged second width. 
     A modified embodiment of the invention is described in  FIGS. 11 and 12 . Elements already described are shown with the same reference numerals which were already used in the description of the first embodiment in accordance with  FIGS. 8 to 10 . 
     In the embodiment in accordance with  FIGS. 11 and 12 , two track conveyors  35 ,  36 , of which only the upper track conveyor  35  can be seen in each case in  FIG. 11 , are each arranged above one another at both longitudinal sides  22 ,  23  of the metal element  11 . The track conveyors  35 ,  36  in turn have a plurality of conveying members  16  which are each connected to one another, for example via a conveyor chain which is not shown. 
     The conveyor members  16  are guided around horizontally arranged deflection rollers  37  which are either drivable or freely rotatable. 
     The longitudinal sides  22 ,  23  of the areal metal element  11  are each arranged between the upper and lower track conveyors  35 ,  36  which are arranged at both sides and which are arranged so close to one another that the longitudinal sides  22 ,  23  of the metal element  11  are clamped between the upper and lower track conveyors  35 ,  36 . In this embodiment, the outer sides of the conveyor members  16  thus directly form clamping portions  38  for the metal element  11 . 
     As can in particular be recognized from  FIG. 11 , the track conveyors  35 ,  36  arranged at both sides of the metal element  11  are arranged obliquely with respect to the longitudinal axis  14  so that an expansion region  21  is in turn formed. The spacing of respectively mutually oppositely disposed clamping portions  38  enlarges continuously within the expansion region  21  in the movement of direction of the metal element  11  shown by the arrow  12 . 
     As in the embodiment in accordance with  FIGS. 8 to 10 , an expansion and widening of the metal  11  thus likewise takes place in the expansion region  21 , as can be seen from  FIG. 11 . 
     The embodiment in accordance with  FIGS. 13 and 14  in particular differs from the previously described embodiments in that the carrier units are not formed by track conveyors, but rather by two obliquely positioned disks  39 ,  40  symmetrical to one another. The disks  39 ,  40  are rotatably around axes of rotation  41 ,  42  correspondingly inclined with respect to one another and, in the representation shown in  FIG. 13  have minimal spacing from one another at the upper region and maximal spacing from one another at the lower region. 
     The respective outer marginal regions of the disks  39 ,  40  are configured as clamping portions  43 ,  44 , with the peripheral surfaces of the disks  39 ,  40  forming contact regions  45 ,  46  for the areal metal element  11 . 
     The longitudinal sides  22 ,  23  of the metal element  11  contact the contact regions  45 ,  46  of the disks  39 ,  40  and said metal element is guided around the disks  39 ,  40  in accordance with arrows  47 ,  48 . 
     The metal element  11  is pressed toward the contact regions  45 ,  46  via clamping elements  49 ,  50  provided at the marginal regions of the rotating disks  39 ,  40  and is thereby clamped tight between the clamping elements  49 ,  50  and the contact regions  45 ,  46 . 
     Due to the mutually inclined arrangement of the rotating disks  39 ,  40  and to the expanding spacing of the edges of the rotating disks  39 ,  40  shown at the top in  FIG. 13  to their lower edges which results therefrom, the clamped in metal element  11  is expanded on the rotation of the disks  39 ,  40 , as can be seen from  FIG. 13 . 
     In a similar manner as with the previously described embodiments, the clamping elements  49 ,  50  can be adjusted automatically via cam track guides from their release position into the clamping position and back. Corresponding cam track guides can, for example, be provided between the metal element  11  and the rotating disks  39 ,  40  in the region of the starting contact points and end contact points disposed at the top and at the bottom respectively in  FIGS. 13 and 14 . 
       FIGS. 15 and 16  show a special aspect of the clamping elements  49 ,  50  schematically in a detailed view. 
     The clamping element  49  (as well as the clamping element  50  not described any further in the following) has a base part  51  which is fastened to the outer side of the rotating disk  39 . A displaceably and pivotably supported clamping lever  52  is provided at the radially outwardly disposed side of the base part  51  and is located in the clamping position in  FIG. 15  and in the release position in  FIG. 16 . In the clamping position shown in  FIG. 15 , the end of the clamping lever  52  disposed toward the disk  39  presses onto the metal element  11  guided around the disk  39  and clamps it between the disk  39  and the clamping lever  52 . 
     The clamping lever  52  is pressed upwardly in accordance with an arrow  54  in  FIG. 15  at its end remote from the disk  39  so that its oppositely disposed end is pivoted downwardly in accordance with an arrow  53 , whereby the described clamping effect is achieved. The action on the clamping lever  52  at its end remote from the disk  39  can take place, for example, via a gas compression spring  55 . 
     The clamping lever  52  is furthermore displaceably supported in accordance with two arrows  56 ,  57 , with the displacement being able to take place, for example, by a cam track guide which engages into a groove  76  provided at the upper side of the clamping lever  52 . On a displacement of the clamping lever  52  into the release position in accordance with  FIG. 16 , the gas compression spring  55  can also be downwardly displaced by a corresponding cam track guide so that the clamping lever  52  is freely displaceable. 
     A specific aspect of the clamping element  49  is shown again in detail in  FIGS. 17 and 18 . It can be seen from these Figures that the clamping lever  52  can be tilted, for example via an intermediate lever  58 , which is pivotable around an axis  59 . On a pivoting of the intermediate lever  58  by the gas compression spring  55  upwardly around the axis  59 , the clamping lever  52  is likewise pivoted upwardly via a bolt  60  provided at the intermediate lever  58 . 
     If, in contrast, the intermediate lever  58  is pivoted downwardly against the gas compression spring  55  via a cam track guide engaging at its free end  61 , the clamping lever  52  is released for a horizontal displacement which can be controlled via a cam track guide engaging into the groove  76 . 
       FIG. 19  shows a modification of the apparatus in accordance with  FIGS. 13 and 14 , wherein the metal element  11  runs in on one side of the obliquely positioned disks  39 ,  40  in accordance with arrows  63   64  and runs out again in substantially the same direction of movement on the oppositely disposed side. The disks  39 ,  40  are tilted toward one another in this case such that the spacing between the disks  39 ,  40  is minimal on the run-in side shown on the left in  FIG. 19  and is maximal on the run-out side shown on the right to achieve the desired expansion. 
     To prevent a kinking of the metal element  11 , it is guided in each case in a loop-like manner via guide pulleys  62  in the run-in and run-out regions so that the metal element  11  comes into contact with the peripheral surfaces of the disks  39 ,  40  forming the contact regions  45 ,  46  and also leaves them again substantially tangentially. 
       FIG. 20  shows a section from an areal metal element  65  which is provided with a plurality of parallel cuts  66  arranged alternatingly offset to one another. The longitudinal sides  67 ,  68  of the metal element  65  forming the marginal regions can be clamped using the apparatus in accordance with the invention and the metal element  65  can be drawn apart such that the elongated metal element  65 ′ shown in  FIG. 21  is produced. With a correspondingly tight arrangement of the clamping elements, expanded metal with expanded mesh  69 , for example diamond-shaped mesh, can be manufactured, with the longitudinal sides  67 ,  68 , however, forming straight outer edges, i.e. a closed structure. The stability of a correspondingly manufactured metal element  65 ′ expanded in accordance with the invention is considerably improved with respect to conventional expanded metal due to the straight outer edges. The metal element  65 ′ shown in  FIG. 21  can be used, for example, for the manufacture of sections such as described with respect to  FIGS. 6 and 7 , or for other purposes as replacement for normal expanded metal. 
       FIG. 22  shows a track conveyor  70  which only differs from the track conveyor  14  of  FIG. 8  in that no run-in region  20  is provided, but that rather the metal element  11  runs directly into the expansion region  21 . 
       FIG. 23  shows in a highly schematic manner three control sections  71 ,  72 ,  73  made as cam track guides by which the clamping elements  19  in accordance with the invention can be switched automatically between the release position and the clamping position. In this connection, instead of the clamping elements  19 , only their cam spigots  33  are indicated in  FIG. 23  which cooperate with the control sections  71 ,  72 ,  73 . At the inlet at the top in  FIG. 23 , the cam spigots  33  are tilted radially outwardly (to the left in  FIG. 23 ) by the control section  71 , whereby the clamping elements  19  are automatically brought into their release position so that the metal element  11  running into the expansion region  21  can enter between the contact regions  26  and the clamping regions  29  of the clamping elements  19 . After leaving the control section  71 , the cam spigots  33  run toward the radially inwardly disposed cam surface of the second control section  72 , whereby they are titled radially inwardly. The clamping elements  19  are automatically moved into the clamping position in this manner in which they clamp the longitudinal sides of the metal element  11 . To compensate for irregularities in the thickness of the metal element  11  as well as tolerances in the clamping elements  19 , the second control section  72  is supported movably along a double arrow  74  against pre-tensioning. 
     After the clamping elements  19  defined by the second control section  72  have been brought into their clamping position, the metal element  11  is drawn apart during the running through of the expansion region  21 . At the end of the expansion region  21 , the cam spigots  33  run toward the radially outwardly disposed cam surface of the third control section  73  by which they are again tilted radially outwardly so that the clamping elements  19  are moved into their release position and the metal element  11  is automatically released by the clamping elements  19 . On the return to the start of the expansion region  21 , the clamping elements  19  can be either in their release position or in the clamping position. 
       FIG. 24  shows a further embodiment of a clamping element  19 ′ in accordance with the invention which substantially only differs from the clamping element  19  in accordance with  FIG. 10  in that the eccentric member  27 ′ has a circular shape only partly at its outer surface by which the clamping region  29  is formed. Furthermore, the U-shaped base element  25  is, unlike the clamping element  19 , in each case fastened via an intermediate element  75  to the conveying member  16  (see  FIG. 9 ) which can in particular be made in one piece with the base element  25 .