Patent Application
20080202299
The invention relates on the one hand to a cutting device for substantially linear workpieces, in particular for substantially continuously fed linear workpieces in which a cutting carriage is moved jointly with the workpiece and a cutting device provided on the cutting carriage cuts the workpiece during its movement. Furthermore, the invention relates to a method of separating substantially linear workpieces, in particularly substantially continuously fed linear workpieces.
Cutting devices for substantially linear workpieces are known from the prior art such as, for example, for tubes made of copper or aluminium which can also be processed in coil form.
Thus, various tubes are cut into tube pieces of predetermined tube lengths, for example, by means of circulating blades which cut the tube over its circumference, whereby the circulating blade is set against the tube at the desired location and is then guided around the tube. Optionally, such cutting is supported by additionally subsequently exposing the tube to tensile or bending stress. In this case, the circulating blades do not need to completely cut through the wall of the tube at the provided cutting point since the actual parting process then takes place due to the bending or pulling. A corresponding example is disclosed in US 4,552,047.
In particular, compared with material-removing cutting processes in which a tube is cut into tube pieces of arbitrary lengths, for example, by means of a cold circular saw, cutting process using circulating blades are characterised in that substantially less or no loss of material is achieved during the cutting.
Cutting processes using circulating blades are described in detail, for example, in the specialist journal Bander, Bleche, Rohre 1-1980 in the article by R. Bardolete, “Burr-free and geometrically true cutting to length”.
In addition, a stationary device is described in U.S. Pat. No. 4,111,346 by means of which tubes can be cut into different lengths, where the tubes are partially cut on their circumference and then broken off so that the tube breaks off at the partial cut.
Furthermore, flying shears are sufficiently known from the prior art, and can also be used for cutting moving workpieces whereby they are moved with the workpiece and then cut through the tube at a specific point with a rapid impact. However, such impact cutting has the disadvantage that the tube ends are subjected to considerable stresses and are usually deformed. U.S. Pat. No. 3,771,393 discloses a cutting device comprising a rotating cutting blade which is moved with the workpiece, whereby this also subjects to the tube ends to considerable stress.
It is the object of the present invention to further develop and effectively configure known methods for cutting tubes, in particular circulating blades.
The object of the invention is achieved by a cutting device for substantially linear workpieces, in particular for substantially continuously fed linear workpieces, in which a cutting carriage is moved together with the workpiece and a cutting device provided on the cutting carriage cuts the workpiece during this movement and in which the cutting device is characterised by at least two successively arranged cutting carriages.
As a result of the two successively arranged cutting carriages, it is possible to cut even short tube pieces without reducing the conveying speed of the workpiece to be cut for this purpose in such a manner that the performance of the entire cutting device must be inefficiently throttled. In the present case, it is rather possible to adapt the tube length of the tube pieces by modulating the relative speed and/or the relative movement of the two cutting carriages with respect to one another and/or the conveying speed of the workpiece. Ideally, even short tube lengths can be cut at the maximum conveying speed of the tube.
The cutting carriages advantageously each run through a cyclic movement sequence where they can in particular execute a linear forward and backward movement. The movements of the cutting carriages are preferably synchronized, where this relates to the synchronization of the cyclic movements and in particular does not necessarily imply a synchronous movement of the cutting carriages. However, the cutting carriages can also be driven asynchronously as long as they are moved at the same speed as the tube during the actual cutting.
Accordingly, the object of the invention is also achieved by a method for cutting substantially linear workpieces, in particular substantially continuously fed linear workpieces, which is characterised in that two successively arranged cutting carriages are moved forwards and backwards with a phase difference.
By means of such a phase difference between the two cutting carriages, the tube lengths to be cut can be modulated in a manner not hitherto known. In this way, in particular variable workpiece lengths can be cut to length for a given distance between the cutting carriages and given workpiece speed.
A cutting device rotating around the workpiece can preferably be provided, this device being moved on a cutting carriage with the workpiece during the cutting and running around this workpiece during the cutting.
It is found to be advantageous if such a rotating parting or cutting devices such as, for example, one or a plurality of cutting blades, cut the workpiece whilst this workpiece is moved at a conveying speed. By this means, the cutting performance can advantageously be increased compared with methods in which the workpiece is not continuously moved forwards.
The object is likewise achieved by a method for cutting substantially linear workpieces, in particular substantially continuously fed linear workpieces, by means of a cutting device which is preferably moved with the workpiece during the cutting, wherein the workpiece is gripped on both sides of a parting surface and is cut under tension with the cutting device at the parting surface.
In this context, the term “parting surface” means a plane along which a workpiece is to be cut and ultimately is cut within the framework of the accuracy of the selected cutting method.
If a tube for cutting is cut under tensile stress, a cutting process can be executed more rapidly than during cutting without tensile stressing.
The fact that a workpiece is gripped on both sides of a parting surface and cut under tension with a cutting device at the parting surface is hitherto not yet known from the prior art. Although it is known from the article by B. Bardolette “Burr-free and geometrically true cutting to length” in the technical journal Bander, Bleche, Rohre 1-1980 and from U.S. Pat. No. 4,111,346 or U.S. Pat. No. 4,552,047 that workpieces can be partially cut and then separated by subsequently pulling or breaking, these documents do not, however, provide instructions to process a workpiece simultaneously under tension with a cutting device. By suitably matching the tensile forces to the cutting process which is taking place simultaneously, the cutting edge can advantageously be modulated as well as the cutting speed. This makes it possible to dispense with any further after-treatment of the parting surface, for example, any deburring, since a tear-off edge can be produced by the tension which, for example, does not project radially inwards or radially outwards over a tube wall. In particular, a cutting process under tension is not known in connection with a cutting carriage moved together with the workpiece.
One variant of the method provides that the cutting process and the pulling are matched to one another in such a manner that the parting edge thus produced comprises an expanded tube wall and/or a tear or break edge. This ensures that a tube is already separated before a cutting device has completely cut through the tube wall.
The object of the invention is also achieved independently of the preceding by a method for cutting substantially linear workpieces, in particular substantially continuously fed linear workpieces by means of a cutting device, which is moved with the workpiece during cutting, which is characterised in that the workpiece is gripped on both sides of a parting surface and is cut under tension and/or break. This solution certainly has the disadvantage that the movement sequences between the workpiece and the cutting carriage on the one hand and between the holder exerting the tension and a cutting device on the cutting carriage on the other hand are relatively complex. However, this can be countered in particular by arranging the holder and the cutting device on a cutting carriage. On the other hand, the solution has the surprising advantage that after cutting, the two workpiece parts are at a short distance from one another although they are still moving together with the cutting carriage so that subsequent workpiece guides or intermediate workpiece guides can convey the workpieces more simply separately from one another so that they can also be separated more easily. This problem does not occur with a stationary cutting device and stationary workpiece so that at this point the cutting under tension or breaking with a cutting carriage moving with the workpiece has surprising advantages.
In order that cutting carriages can be moved independently of one another, it is advantageous if at least one cutting carriage is driven independently of the other cutting carriage for its movement with the workpiece. By means of drives operating independently of one another, the speed of the cutting carriages can be varied with respect to one another in a structurally particularly simple fashion and thus the length of the separated workpiece sections can be modulated over the phase of the carriages.
For the adjustment of particularly short tube lengths, it is furthermore advantageous if the movement paths of the cutting carriages overlap. The cutting carriages each describe a movement path during their to and fro movement. If the movement paths of two cutting carriages overlap, a further variation in tube length is available. In this case, however, care must be taken to ensure that the cutting carriages run with overlapping movement paths phase-shifted with respect to one another to prevent any collision of the cutting carriages in the overlap region. In addition, as a result of the overlap, intermediate guides for the tube can be dispensed with since the transfer path from a first workpiece guide of a first cutting carriage to a second workpiece guide of a second cutting carriage can be reduced substantially by this means. This is particularly advantageous in connection with short tube lengths which have been cut by the first or front cutting carriage and must be transported further.
In some circumstances, the cutting carriages can run on separate guides. In this way, an overlap of the movement paths [can be achieved] which ultimately is not critical for the respective carriages per se but is merely important in relation to the assemblies of each cutting carriage which lie on the path of the workpiece or which embrace the workpieces. In this way, the distance between the cutting means or between the assemblies embracing the workpiece can be further reduced, such a configuration being advantageous in particular for cutting carriages in which the guide devices and the drives are substantially larger than any cutting means such as, for example, an arrangement of tensile-acting retaining devices and rotating cutting blades.
In order that sufficient tube guidance is provided along the workpiece axis in the case of two successively arranged cutting carriages, one embodiment provides that a workpiece guide is provided on at least one cutting carriage.
Advantageously such a movable workpiece guide can bridge partial sections between two workpiece guides which are provided, for example in a fixed position on the cutting device, in particular for tube pieces which have already been cut by means of the first cutting carriage and must be conveyed further to the second cutting carriage. This is particularly advantageous for two overlapping movement paths since a workpiece guide disposed between the cutting carriages would be in the way of the cutting carriage.
However, if the partial sections to be bridged exceed a critical length, it is advantageous to provide an intermediate workpiece guide which is disposed between two cutting carriages independently of their movement sequence. By means of such an intermediate workpiece guide, a workpiece which has already been cut can be moved in particular from a first cutting carriage to a second cutting carriage in a sufficiently guided manner without one of the two cutting means needing to be in engagement with the workpiece which has already been cut and needs to be conveyed further.
It is understood that the intermediate workpiece guide which has been described can be attached arbitrarily to the cutting device. In particular, the intermediate workpiece guide can be fixed in a displaceable manner. Thus, the intermediate workpiece guide can also be moved together with a workpiece, in particular to ensure the safest possible guidance and optionally to be able to pass the cutting carriage. However, it is structurally particularly simple if the intermediate workpiece guide is disposed in a fixed position.
A further embodiment provides that at least one intermediate workpiece guide is disposed so that it can move jointly with the workpiece. In this case, the intermediate workpiece guide can firmly grip the workpiece, at least in sections in order to optionally exert tensile or bending forces on the workpiece in cooperation with another device. However, it is also feasible that the intermediate workpiece guide has its own conveying means for the workpiece to ensure, for example, an advance or a braking of the workpiece. Alternatively, however, the intermediate workpiece guide can be configured passively so that it merely permits the workpiece to slide further in a guided manner.
In this context, it should be noted that optionally more than two cutting carriages can be provided. The number of cutting carriages depends in particular on the workpiece speed and the minimum cycle duration for the movement of the cutting carriages or the desired workpiece lengths to be cut to length. If these two characteristics cannot be matched to one another, a further cutting carriage is advantageous. Higher workpiece lengths can then be achieved by the previously described phase difference, whereas for a given workpiece speed and given minimum cycle time for the movement of the cutting carriages, the minimum workpiece length should be achieved with cutting carriages running round in phase.
A cutting device can comprise rotating means for chipless cutting of the workpiece.
Compared with the prior art, the present cutting device has the advantage that it operates substantially more rapidly than has hitherto been possible with fixed rotating cutting devices and in addition can operate with a clocked feed. In addition, compared with revolving impact shears, the present cutting device has the advantage that it leaves behind a substantially better cut and thus a substantially higher-quality parting-cutting point on the workpieces.
It is advantageous if the cutting means comprises a rotating cutting device. This ensures that a clean cut is formed running around the workpiece and an exact cut edge can be formed requiring no further after-treatment.
A particularly clean cut is formed if the cutting device comprises a cutting blade. In addition, cutting blades are very wear-resistant.
It is advantageous if the cutting blade is a rotating cutting blade circulating externally around the outside diameter. Particularly high cutting performance can be achieved by means of such an externally circulating cutting blade, where circulating rotating cutting blades are also technically well known per se and thus can be suitably controlled.
A particularly exact cutting of the linear workpiece is achieved if the cutting blade is a circulating blade having an inner cutting edge. This can reduce the risk of material compression particularly on the outside of the tube.
In addition, it is advantageous if the cutting device comprises a rotating chuck for a cutting tool. In particular, cutting blades can advantageously be mounted and guided by means of the rotating chuck.
In order to advantageously adjust a required change in diameter with regard to a tube to be cut on the cutting device, it is advantageous if the circulating chuck has radially displaceable cutting blade holders for at least one cutting tool and means for radial displacement of the cutting blade holder for a cutting process. The cutting blade holder can ensure secure guidance of the cutting tool or the cutting tools.
In order that the cutting device in particular has an especially radially compact structure, it is advantageous if the displacement means comprises a toggle lever wherein one arm of the toggle lever is preferably disposed on the cutting blade holder and the other arm of the toggle lever is disposed on a retaining part such as, for example, on retaining jaws for the cutting tool and the displacement means act on the elbow. By means of this toggle lever construction, axial input forces can be deflected particularly advantageously into radial retaining forces. In particular co-rotating assemblies are suitable as retaining parts, where these can be configured as radially displaceable, for example, for adjustment purposes so that different workpiece diameters can be processed simply.
In addition, it is advantageous if the displacement means comprise a thrust plate, preferably a thrust plate circulating with the cutting device. By this means, a plurality of blades and/or cutting tools can be synchronized particularly easily.
A particularly cost-effective embodiment provides that the separating device is opened by centrifugal forces. Opening the cutting device by means of centrifugal forces makes a restoring mechanism for radial displacement of the separating tools away from the workpiece superfluous.
In this case, it is particularly advantageous if the cutting tools circulate constantly or rotate continuously over at least two cutting processes. Starting and braking processes for the cutting tools which merely cost time and energy can be minimised in this way. In particular, larger masses whose acceleration processes accordingly cost more time and energy, such as adjusting motors or other drives, can then co-rotate. The centrifugal forces as described previously can then optionally be used particularly reliably and simply. For cutting, only the cutting device or cutting devices are accordingly adjusted and then opened again preferably without varying the rotational speed.
In order that the cutting device can be adjusted flexibly and particularly rapidly to different workpiece diameters, it is advantageous if the cutting device or the cutting apparatus has means for radial adjustment of the cutting means with respect to different workpiece diameters. The cutting means can then be radially adjusted by the radial adjusting means with respect to the workpiece axis in such a manner that the present cutting device can be adjusted even to large differences in workpiece diameters in a rapid and uncomplicated manner.
A particularly advantageous embodiment in this connection provides that the adjusting means comprise retaining jaws on which the cutting means or cutting-means holders are mounted.
In the present case, the term “retaining jaws” describes means for radial adjustment which are arranged radially around the workpiece axis and are mounted so that they are radially adjustable with respect to this workpiece axis. The retaining jaws are preferably only adjusted radially when the cutting device is to be adapted to a different workpiece diameter. In particular, the retaining jaws are not usually adjusted during the actual delivery of the cutting means for cutting, during cutting or after cutting. For the delivery process as well as for the opening, the cutting means themselves are arranged radially displaceably on the cutting carriage, preferably radially displaceably on the retaining jaws.
It has proved to be advantageous if a toggle lever, in particular an arm of a toggle lever, is mounted on the retaining jaws. Then the adjusting mechanism for the cutting means is thus mounted on the retaining jaws so that it can advantageously be adjusted with respect to the workpiece axis together with the retaining jaws.
If the retaining jaws are mounted radially adjustably on the cutting carriage with respect to a workpiece axis, the cutting carriage can easily be matched even to a range of different workpiece diameters.
Furthermore, the object of the invention is achieved by a cutting device for substantially linear workpieces, in particular for substantially continuously fed linear workpieces, in which a cutting carriage is moved together with the workpiece and a cutting device provided on the cutting carriage cuts the workpiece during this movement, which is characterised in that at least two retaining devices are provided on the carriage which, when viewed along the workpiece axis, are disposed on both sides of a cutting device, wherein at least one of the two retaining devices can be moved along the workpiece axis relative to the other retaining device and/or relative to the cutting carriage or relative to the cutting device.
By this means a workpiece can be cut under tension in a particularly simple manner whereby this then tears substantially earlier and in particular reliably under predefined conditions compared with when a cut is first made and a tensile stress is then applied to the linear workpiece.
By means of the retaining devices disposed on both sides of the cutting device, on the one hand a particularly exact retention and guidance of cut tube pieces can advantageously be ensured in some circumstances. In particular, additional forces such as, for example, tensile forces can be applied to the workpiece by means of the bilateral retaining devices and these substantially promote cutting processes on the workpiece as has already been described.
In this case, it has been found that as a result of cutting under simultaneous tensile stress, the tensile stress appears to influence the cutting process as a critical parameter. In this respect, for a predefined tensile stress which ultimately accordingly leads to a predefined deformation of the workpiece in the area of the parting point, the parting point can always be reliably executed as the same. For a predefined tensile stress, the cutting means such as, for example, a cutting blade can then circulate and cut until the cut is sufficiently deep so that the tensile stress ruptures the workpiece at the corresponding point.
It is understood that an intermediate workpiece guide disposed between two cutting carriages in particular independently of the movement sequence of the cutting carriages is advantageous for a cutting device regardless of the remaining features of the present invention. The same applies to the displacement means if this comprises a toggle lever and/or a thrust plate as well as for a cutting head to be opened by centrifugal forces and the means for radial adjustment of the cutting means.
Further advantages, aims and properties of the present invention are explained by reference to the description of the appended drawings which show the present cutting device as an example, its movement and cutting sequences as well as components of the cutting device.
In the figures
The tandem cutter 1 shown in
In the present exemplary embodiment, between the inlet region 3 and the outlet region 4 there is provided an inlet region guide 12, a middle region guide 13 and an outlet region guide 14 which, in a suitable configuration, serve as workpiece holders or intermediate workpiece holders to guide the tube 9 or an already-cut tube piece (not shown here) of the tube 9 additionally to or independently of the rollers 5, 6, 7, 8 and/or additionally to or independently of the cutting carriages 15 or 16 along the tandem cutter 1. In this case, these guides can be configured actively or passively, that is drivingly or merely guidingly. Optionally, the guides 12, 13 and/or 14 can also serve to receive sensors (not explicitly shown here) such as, for example, an inductively operating sensor. In principle, all sensors suitable for determining the speed and/or the position of the workpiece or the position of a workpiece region are suitable as sensors. In this respect, particular mention may be made of the aforesaid inductively operating sensors. However, optical sensors or ultrasound sensors can also be used. Speed-sensitive sensors such as, for example, optical sensors or ultrasound sensors using the Doppler effect appear to be particularly suitable.
In addition, the first cutting carriage 15 and the second cutting carriage 16 move forwards and backwards independently of one another between the inlet region 3 and the outlet region 4 along the workpiece axis 10 in relation to the conveying direction 11.
The tube length of a tube piece to be produced can be varied depending on how the first cutting carriage 15 and the second cutting carriage 16 move with respect to one another in their respective reciprocating regions 17, 18, for example, with an in-phase forward and backward movement or phase-shifted with respect to one another. The reciprocating region 17 of the first cutting carriage 15 extends substantially between the inlet region guide 12 and the middle region guide 13 whereas the reciprocating region 18 of the second cutting carriage 16 extends substantially between the outlet region guide 14 and the middle region guide 13.
The tandem cutter 101 shown in
In contrast to the tandem cutter 101 from
The two optical sensors 225 and 226 are displaceable along the workpiece axis 210. In order to achieve this in a structurally particularly simple manner, the first mobile optical sensor 225 is secured to a first cutting carriage 215 and the second mobile optical sensor 226 is secured to a second cutting carriage 216. The two optical sensors 225, 226 can in this case substantially detect the position and in particular also the exact speed of a tube 209 which is conveyed in accordance with the conveying direction 211 along the workpiece axis 210 through the tandem cutter 201 from an inlet region 203 to an outlet region 204. In the present case, the two optical sensors 225, 226 can easily follow the movement of the tube 209 via the cutting carriages 215 and 216.
The cutting carriages 215, 216, guided on a frame 202, move forwards and backwards in the manner already described for the preceding exemplary embodiments between the inlet region 203 and the outlet region 204 with respect to the conveying direction 211 and in this exemplary embodiment, the inlet region 203 also comprises two inlet region rollers 205 and 206 and the outlet region 204 comprises two outlet region rollers 207 and 208.
The known single cutter 330 shown in
The movement sequence of the cutting carriage 315 is illustrated in detail in a coordinate system 335 in which the respectively current position of the cutting carriage 315 is plotted on the abscissa 336 and the speed of the cutting carriage 315 present at the respective location is plotted on the ordinate 337. In this case, an upper curve 338 (positive) shows the speed profile of the cutting carriage 315 in its forward movement, that is in the conveying direction 311. A lower curve 339 (negative) shows the speed profile of the cutting carriage in its backward movement, that is opposite to the conveying direction 311. The current position of the cutting carriage 315 in the speed/position coordinate system 335 is characterised by a position marker 340.
In the exemplary embodiment shown in
The location of the starting position 341 and the location of the starting position* 341* are identical but the additional marker * indicates that the starting position* 341* is adopted after the starting position 341 in time.
Tube pieces 344 of a first tube length 349 can be cut from a tube 309 by means of the single cutter 330.
The process sequence shown in
The movement sequences of the two cutting carriages 415, 416 are illustrated in a speed/position coordinate system 435. Since in this exemplary embodiment both cutting carriages 415, 416 are operated with an identical movement pattern, two identical movement graphs 450 and 451 are obtained in the speed/position coordinate system 435, where the first movement graph 450 shows the movement sequence of the first cutting carriage 415 and the second movement graph 451 shows the movement sequence of the second cutting carriage 416.
For the sake of clarity, the two identical movement sequences of the two cutting carriages 415, 416 are explained substantially by reference to the first movement graph 450. Furthermore, the two movement graphs 450, 451 each correspond to the representation of the speed/position coordinate system 335 of the single cutter 330.
The cutting carriage 415 is accelerated from a starting position 441 and the cutting carriage 416 is accelerated from a starting position 441A each to a conveying speed 442, whereby the cutting carriage 415 cuts the tube 409 in a cutting position 443 and the cutting carriage 416 cuts the tube 409 in a cutting position 443A, ideally substantially at the same time, into individual tube pieces 444 having the second tube length 449.
When the cutting processes have take place, the two cutting carriages 415, 416 are braked and the forward movement is converted into a backward movement 447 at a reversing position 445, 445A. From a braking position 448 or 448A the backward movement 447 is braked down into a further starting position* 441* or 441A* so that the next cutting cycle can begin.
As can be seen immediately, in this exemplary embodiment under the same boundary conditions, that is at the same speed 446 of the tube 409 and at the same maximum speed of the cutting carriage or the same minimum cycle time, twice as many short tube pieces 444 can be cut to length by this procedure compared to the tube pieces 344 with the single cutter 330 according to
As an example,
In this exemplary embodiment, the two movement sequences of a first cutting carriage 515 and a second cutting carriage 516 overlap at least in an overlap region 556. The movement sequences of the two cutting carriages 516, 515 are otherwise identical and correspond in the present case to a first movement graph 550 and a second movement graph 551 which are superposed in the overlap region 556.
The movement cycle of the first cutting carriage 515 starts in a first starting position 541 whereas the movement cycle of the second cutting carriage 516 begins in a second starting position 541A. The two cutting carriages 515, 516 are accelerated to a conveying speed 542 (
A prerequisite for the shorter tube pieces 544 having the third tube length 549 is, however, either a lower workpiece speed 546 of the tube 509 or a high cycle or maximum speed of the cutting carriages 515, 516. Otherwise tube pieces 544 of nonuniform length are cut to length in this procedure. In particular, as a result of the overlap however, corresponding tube piece lengths can be achieved under restricted spatial conditions such as, for example, a restricted maximum length for the frame 502, if the speed of the cutting carriages 515, 516 can be selected to be sufficiently high.
As shown for example in
According to the diagram according to
The first cutting carriage 615 is now accelerated to a conveying speed 642 (
Both cutting carriages 615, 616 stay there for a moment until sufficient tube 609 has been guided further in the conveying direction 611 (see
The first cutting carriage 651 is then accelerated in the conveying direction 611 to the conveying speed 642 in order to again cut through the tube 609 in the first cutting position* 643* and the second cutting carriage 616 is moved back again into the second reversing position 645A*. When another tube piece 644 having the tube length 649 is cut by means of the first cutting carriage 615 (
Both cutting carriages 615, 616 are now accelerated with the backward movement 647 as far as the respective braking position 648* and 648A* before then again reaching the first starting position* 641* or the starting position 641A (see
As can be immediately seen, the cutting carriages 615, 616 dwell temporarily in their starting positions 641, 641A or reversing positions 645 and 645A. In this respect, the phase profile shown is not essential but can be varied as required. In this exemplary embodiment it is assumed that the cutting carriages 615, 616 are each accelerated at their maximum accelerations, that is they increase or retard their speed. In this respect, waiting times are provided, whereby it is immediately clear that these waiting times determine the tube length 649 which can be cut and in this way longer tube lengths 649 than in the previously described tandem cutters are provided. As can be immediately seen, the shortest tube lengths can be cut with in-phase sequences and maximum cycle speed. The tube length can then be arbitrarily lengthened by means of the phase shift and a lengthening of the cycle time until ultimately only one cutting carriage is sufficient to cut the desired tube length under given boundary conditions such as workpiece speed and maximum carriage speed.
The movement sequences of the first cutting carriage 715 are plotted in the first movement graph 750 and the movement sequences of the second cutting carriage 716 are plotted in the second movement graph 751. According to the representation of the speed/position coordinate system 735 from
In this exemplary embodiment, the second cutting carriage 716 as the first of the two cutting carriages 715, 716 executes a forward movement and is hereby accelerated to the conveying speed 742 (see
The second cutting carriage 716 is then moved further into a second reversing position 745A (see
The two cutting carriages 715, 716 each move further by themselves but synchronously and phase-shifted (see
The second cutting carriage 716 again reaches a starting position 741A* whilst the first cutting carriage 715 is still in its backward movement 747 in a braking position 748. When the first cutting carriage 715 also reaches a starting position (not shown here), the entire movement cycle of the tandem cutter 701 begins anew.
It is understood that the movement sequences shown in
The tandem cutter 801 shown in detail in
The structure of the first cutting carriage 815 is shown schematically in detail by reference to the diagrams in
The cutting carriage 815 comprises a drive 871 which drives a rotary chuck 872 with a cutting head 873 disposed thereon as a circulating cutting device. At the end of the drive 871 opposite to the rotary chuck 872, a tube clamping mechanism 874 is provided as a first retaining device by which means the tube 809 or a part of the tube 809 can be clamped and in particular fixed in relation to the cutting carriage 815.
Furthermore, in the area of the cutting head 873 a tube stroke clamping mechanism 875 is provided as a further retaining device by which means the tube 809 or a part of the tube 809 can be clamped and in particular fixed in relation to the cutting carriage 815. In addition, a tube 809 clamped by means of the tube clamping mechanism 874 can be stressed by means of the tube stroke clamping mechanism 875 since the tube stroke clamping mechanism 875 can be displaced with respect to the tube clamping mechanism 874.
When the tube 809 is subjected to tensile stress in such a manner, cutting means in the form of cutting blades 876 (see
The advantage with such a construction can be seen, inter alia, in that the cutting carriages 815 and 816 can be adapted rapidly and structurally simply to different-sized workpiece diameters by means of the retaining jaws 873A which can be adjusted radially to the workpiece axis 810 (see
The cutting head 873 comprises a toggle lever mechanism 879 by which means a force 882 running axially to a workpiece axis 810 or to the tube 809 (see
The toggle lever mechanism 879 comprises a first toggle lever 879A which is fixed in an articulated manner to a retaining jaw 873A. Another toggle lever 879B is connected to the cutting blade holder 878 in an articulated manner. Both toggle levers 879A, 879B of the present toggle lever mechanism 879 are connected to one another in an articulated manner in a toggle lever joint 879C. Since such toggle lever mechanisms are sufficiently known from the prior art, the present toggle lever mechanism 879 is not explained further.
The axially running force 882 is generated by means of a cylinder 880 and transferred by means of a cylinder rod 880A and a thrust plate 881 to the toggle lever mechanism 879. In this case, the thrust plate 881 is displaceable parallel to the workpiece axis 810.
By means of the radially acting force 883, the cutting blades 876 are pressed against the tube 809 and cut into the tube 809 on its circumferential surface 877 until the tube 809, which is additionally under tensile stress, ruptures at the cutting point 884 (see
The diagrams in
In preparation for a cutting process, the tube 809 is clamped on a first side of the cutting carriage 815 by means of the tube clamping mechanism 874. On the opposite side the tube 809 is correspondingly clamped by means of the tube stroke clamping mechanism 875. In this case, the tube stroke clamping mechanism 875 is displaced with respect to the other components, in particular with respect to the tube clamping mechanism 874 so that the tube 809 is under tensile stress 886. At the same time, an axial force 882 is exerted on the cylinder rod 880A with the result that the thrust plate 881 is moved towards the toggle lever mechanism 879. The toggle lever mechanism 879 is hereby brought into a more stretched position (see
The centrifugal forces move the cutting blades 876 back into the initial position as a result of the cylinder rod 880A being unloaded.
In order that different tube diameters of a tube 809 or 809A (see
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 007 061.8 | Feb 2007 | DE | national |
