Abstract:
The present invention discloses chain links are proposed for the circulating transport chain of a machine tool, which comprise: a pair of rollers which determine the direction of circulation of the chain link by way of the direction in which they roll, over the rollers which is or are placed at a distance from the pair of rollers in the direction of circulation of the chain link and draw a plane as they roll against the roller pair; and a transverse guide, guiding the chain link transverse to its direction of circulation and is either free from rollers transverse to the direction of circulation of the chain link between the pair of rollers or has a transverse guide roller.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a chain link for an endlessly circulating workpiece transport chain and to a continuous process machine used in the machining by chip removal of flat workpieces of wood, plastic or comparable materials, for instance a double end tenoner with one or two guide chains made from said chain links as a circulating workpiece support. 
       PRIOR ART 
       [0002]    EP 1 479 944 A2 (Siemens Aktiengesellschaft) discloses a guide for a circulating transport chain built up of individual chain links. In this prior art the problem was identified that, because of the spring preload on the previously known chains, vibrations or oscillations occur which are perceived detrimentally because of the generation of impact, noise and wear on the chains and their return devices. To reduce or avoid these problems it is suggested that means be provided to generate a magnetic field to exert a magnetic force on the transport chain in such a way that the transport chain is either pressed against or drawn towards its guide device. The guide comprises guide lands on which guide wheels or the rollers for the chain links roll, thus making a track. A magnetic circuit is formed by reducing the width of the guide lands on one side to generate the magnetic force. In this way, magnets can be fitted here, i.e. to one side. This preserves the maximum possible amount of the track width. The resulting magnetic force acts parallel to the axes of the guide wheels or rollers, which have only linear contact with the track. The result is a magnetic force direction which is inadequate in respect of its damping of vibrations. Furthermore, it has become clear that the provision of magnets in the area of the slot between the guide wheels and the track leads to increased frictional corrosion in long term operation (also known as fretting corrosion), which makes more frequent replacement of the components concerned necessary. This is unsatisfactory in remedying the disadvantage of wear and the accompanying replacement of the worn components originally addressed. 
         [0003]    The prior art disclosed in DE 10 2004 023 494 A1 (Homag Holzbearbeitungssysteme AG) proposes an improved solution by comparison. It addresses woodworking machines with high speed transport chains and sets itself the problem of creating a chain guide for such machines in which the magnetic forces achieve good levels of vibration damping. To this end, the chain guide should be embodied in such a way that the magnetic forces acting in the air gap act substantially at right angles to the tracks of the guide lands for the guide wheels or rollers for the chain links. This is intended to efficiently prevent the chain links lifting from the track, which is here held to be the cause for the wear previously identified in EP 1 479 944 A2. This direction of force is achieved by not arranging the magnets in the guide lands forming the track, but in the bed of the groove profile they form. Thus the magnets act via a transverse guide roll mounted on an axle pin beneath the track rollers. Even in the solution according to DE 10 2004 023 494 A1, however, the magnetic circuit closes by way of a linear contact, here between the transverse guide roll and the inner sides of the load carrying rails known as guide lands or on the outer circumference of the end face of the axle pin. Furthermore, the solution according to DE 10 2004 023 494 A1 requires that a grooved profile be present. 
       UNDERLYING PROBLEM 
       [0004]    Starting from this prior art, the technical problem underlying the present invention is to provide a solution for the high speed transport chains on woodworking machines with an improved magnetic flux with respect to the magnetic force generated and a reduced risk of fretting corrosion. 
       SUMMARY OF THE INVENTION 
       [0005]    This technical problem is solved by chain links having the features of claim  1  and/or  5 , and by a continuous throughfeed machine, preferably a double end tenoner, with the features of claim  13 . Advantageous developments are described in the dependent claims. 
         [0006]    The chain link according to the invention embraces a pair of rollers which determine the direction of circulation of the chain link by means of their direction of rolling around typically one chain guide on a machine tool. The circulating transport chain which acts as a workpiece support circulates in a plane that is perpendicular to the transport chain of the workpiece. Machine tool here refers to machines for processing materials such as wood, plastic, aluminum or other materials that exert a comparable stress on the tool, notwithstanding whether this relates to stationary working or working in a continuous process. 
         [0007]    A workpiece support is provided over the rollers. At least one further roller is located at a distance in the direction of circulation of the chain link, i.e. from the front to the rear, from the pair of rollers. In this way, the rollers ensure stability against tipping around the transverse axis. The, at least one, further roller and the roller pair when rolling together draw a plane that acts as a reference plane for the disposal of one or a plurality of surfaces to create an improved air gap. A guide, guiding the chain link transversely to its direction of circulation, is also provided. It may have a transverse guide roll or be roller-free transverse to the direction of circulation of the chain link between the pair of rollers. 
         [0008]    Observed in the direction of circulation, with roller-free transverse guidance between the pair of rollers and the at least one further roller, a ferromagnetic material is provided forming a surface substantially parallel to the plane formed by the rollers and disposed at a distance from this plane in such a way that a two-dimensional air gap is formed there when the transport chain is in operation. The gap may be downwards, if the chain guide has a guide groove. In the absence of a guide groove of this kind, the surface is a little way above, so that a tight, two-dimensional, parallel air gap is formed with the neighboring surface of the chain guide in the inset in the chain link. This embodiment suggests itself if, rather than a roller, a blade is provided as a transverse guide. 
         [0009]    Alternatively, if a transverse roller is used, a ferromagnetic material is provided between the pairs of rollers observed in the direction of circulation, forming at least one surface at a distance from the end face of the axle pin for the transverse guide roller substantially parallel to the plane formed by the rollers and disposed at a distance from this plane in such a way that a two-dimensional air gap is formed there when the transport chain is in operation. This surface or these surfaces can be at a distance from the axle pin in the direction of circulation, but they can also surround it radially, but at a distance from it so that a two-dimensional parallel air gap is also formed at the end face of the axle pin. However, the air gap is spatially separated from the points where the chain links revolve, which reduces the possibility of fretting corrosion. 
         [0010]    According to the invention, the chain links in the present invention are used in continuous-throughfeed machines because of the predominantly series production involved, the high feed velocity of the workpieces through the machine and the influence of the lower circulating workpiece support on the quality of processing previously considered significant. The circulating transport chain which acts as a workpiece support here also circulates in a plane that is perpendicular to the transport chain of the workpiece. The previous requirement of synchronous running of the support or the right-hand and left-hand supports can be reduced with the help of the invention. With the improved vibration behavior, there is also less significance in the synchronization of the left-hand and right-hand support, as long as the parallelism of the workpiece transport is ensured. This is a noticeable advantage in the processing of workpieces with inkjet printers, for example, such that if the chain links according to the invention are used for the transport of the workpiece in inkjet or other print stations, the matrix spacing of the print is effectively ensured. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows a first embodiment, in which 
           [0012]      FIG. 1.1  shows it in bottom view, and the rollers are omitted to simplify the illustration. 
           [0013]      FIG. 1.2  shows the first embodiment in an end view. 
           [0014]      FIG. 1.3  shows the first embodiment with rollers in a side view, with the chain link according to the invention being partially cut away to show the fastening of a transverse roller on the axle pin and the fastening of the axle pin in the chain link according to the invention. 
           [0015]      FIG. 1.4  shows the chain link according to the invention of the first embodiment along the section line A-A from  FIG. 1.3  interacting with the chain guide of a machine tool and the magnet package mounted there. 
           [0016]      FIG. 2  shows a second embodiment, in which 
           [0017]      FIG. 2.1  shows the second embodiment in bottom view with the rollers omitted to simplify the illustration. 
           [0018]      FIG. 2.2  shows the second-embodiment in an end view. 
           [0019]      FIG. 2.3  shows the second embodiment in a side view, with the rollers illustrated here. 
           [0020]      FIG. 2.4  shows the chain link according to the invention of the second embodiment in the section plane of the transverse roller along the section line A-A from  FIG. 2.3  interacting with the chain guide of a machine tool and the magnet package mounted there. 
           [0021]      FIG. 2.5  shows a section view along the section line B-B in  FIG. 2.3  with permanent magnet attached to the chain link according to the invention. 
           [0022]      FIG. 3  shows a third embodiment, in which 
           [0023]      FIG. 3.1  shows the third embodiment in bottom view and the rollers have been omitted to simplify the illustration. 
           [0024]      FIG. 3.2  shows the third embodiment in an end view. 
           [0025]      FIG. 3.3  shows the third embodiment in a side view, with the rollers illustrated here. 
           [0026]      FIG. 3.4  shows the third embodiment of the chain link according to the invention in cross-section, along the section line A-A in  FIG. 3.3 , and in particular the options for closing a magnetic circuit. 
           [0027]      FIG. 3.5  shows the third embodiment of the chain link according to the invention in the section along the line B-B in  FIG. 3.3 , with the land from  FIG. 3.3  being omitted for clarity. 
           [0028]      FIG. 3.6  shows the same section line as  FIG. 3.5 , but with the land. The lines for the magnetic flow across the air gap have been drawn in for the purposes of clarity. 
           [0029]      FIG. 4  shows a fourth embodiment, in which 
           [0030]      FIG. 4.1  shows the fourth embodiment in bottom view and the rollers have been omitted to simplify the illustration. 
           [0031]      FIG. 4.2  shows the fourth embodiment in an end view. 
           [0032]      FIG. 4.3  shows the fourth embodiment in a side view with rollers. 
           [0033]      FIG. 4.4  shows the chain link according to the invention in the fourth embodiment along the section line A-A from  FIG. 4.3  interacting with the chain guide of a machine tool and the magnet mounted there. 
           [0034]      FIG. 5  shows a fifth embodiment, in which 
           [0035]      FIG. 5.1  shows the fifth embodiment in a bottom view with rollers. 
           [0036]      FIG. 5.2  shows the fifth embodiment in an end view. 
           [0037]      FIG. 5.3  shows the fifth embodiment in a side view. 
           [0038]      FIG. 5.4  shows the chain link according to the invention in the fifth embodiment along the section line A-A from  FIG. 5.3  interacting with the chain guide of a machine tool and the magnet mounted there. 
           [0039]      FIG. 6  shows a sixth embodiment, in which 
           [0040]      FIG. 6.1  shows the sixth embodiment in bottom view and the rollers have been omitted to simplify the illustration. 
           [0041]      FIG. 6.2  shows the sixth embodiment in an end view. 
           [0042]      FIG. 6.3  shows the sixth embodiment in a side view, with the rollers illustrated here. 
           [0043]      FIG. 6.4  shows the chain link according to the invention in the sixth embodiment along the section line A-A from  FIG. 6.3  interacting with the chain guide of a machine tool and the magnet mounted there. 
           [0044]      FIG. 6.5  shows a schematic plan view of a partial area of the chain guide from  FIG. 6.4 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0045]    Preferred embodiments of the present invention are described below in detail with reference to the accompanying drawings. The same or similar reference signs will be used for identical or similar components throughout all the embodiments. A description of identical or similar components will be given only once and is intended to apply for all embodiments unless otherwise described. 
         [0046]      FIG. 1  shows the first embodiment.  FIG. 1.1  shows a bottom view, in which the chain link can be seen-in general at  10 . Roller axes  12  and  14  extend transverse to the longitudinal extent of chain link  10  and are only shown schematically here. In order to provide a connection to the neighboring chain links and thus to form a chain, chain link  10  has in the generally known manner at one end a bearing bush  16  and at the other end, two axle journals  18 ,  20 . The axle journals  18 ,  20  grip around the bearing bush  16  of an adjacent chain link, and so the adjacent chain links are fastened together by way of an axle or shaft for the rollers  24 ,  26  ( FIG. 1.3 ). 
         [0047]      FIG. 1.2  shows a front view of chain link  10 , in which it is also possible to identify axle journals  18 ,  20 . The rollers  24 ,  26  and the workpiece support  22  are clear from  FIG. 1.3  which shows a side view of the chain link illustrated in  FIG. 1.1 . The workpiece support  22  lies above the roller axes  12 ,  14 , here in accordance with the preferred embodiment over the complete rollers  24 ,  26 . In  FIG. 1.3 , therefore, the workpiece support  22  is located at a distance ‘upwards’ relative to rollers  24 ,  26 . The location illustrated in  FIG. 1.3  corresponds to the location of the chain link in the upper chain strand, during the transportation of the workpiece on a number of workpiece supports  22  of adjacent chain links  10 . This orientation and location of the chain link is used here to make referencing the directions easier, so that ‘upwards’, for instance, means orientation in the direction of the workpiece support. Directional statements such as ‘up’ or ‘down’, ‘front’ or ‘back’ are not intended to specify an absolute orientation, however. 
         [0048]    The linear contact of all four rollers  24 ,  26  downwards, i.e. in the typical use of the chain links, line contact on chain guides  52 , creates a plane which is used as a reference plane for the formation of the air gap. Additionally, rollers  24 ,  26  rolling together specifies the direction of circulation of the chain link. 
         [0049]    The side view of chain link  10  in  FIG. 1.3  is partially cut away. It is clear from the cutaway that an axle pin  30  is inserted into chain link  10  as a transverse guide roller. The axle pin may be fitted from above before the workpiece support  22  is fitted or alternatively from below. In the embodiment illustrated, a snapring  32  is used to secure the axle pin, but other means of fastening are possible. Axle pin  30  has an upper axle pin expansion  34  and a lower axle pin expansion  38 . Depending on how the axle pin  30  is fastened in chain link  10 , either the lower axle pin expansion  38  or the upper axle pin expansion  34  may also be formed in a single piece with the axle pin  30 . It is also possible to provide the two expansions  34 ,  38  as separate components that are then to be non-rotatably fastened to the axle pin  30 . 
         [0050]    Although this is not expressly illustrated, it is also preferred if axle pin  30  is non-rotatably located in chain link  10 , for example by means of a positive joint using a wedge or a non-round cross-section in its upper end. Non-rotable location of axle pin  30  in conjunction with a non-rotatable fastening of the expansions  34 ,  38  prevents the axle pin expansions rotating relative to the chain link. 
         [0051]    The axle pin expansions  34 ,  38  provide areas on which an air gap forms during operation of the chain. The faces of the upper axle pin expansion  34 , on which the air gap forms, are identified as  36 , those for the lower axle pin expansion  38  as  40 . For simpler reference, the present faces on which an air gap forms during the operation of the chain links are referred to as air gap faces. The axle pin expansions  34 ,  38  are made in a ferromagnetic material to guide and bundle the lines of the field and thus to increase the magnetic force exercised on the chain link. Tool steel C45Pb complying with EN ISO 4957 is preferred as the ferromagnetic material, although other materials with iron, nickel or cobalt constituents are also conceivable. 
         [0052]    It can be seen from the figures, in particular from  FIG. 1.1 , that the transverse guidance roller  42  carried on the axle pin  30  projects slightly beyond the axle pin expansions  34 ,  38 . This ensures that the transverse guide roller  42  rolls inside the chain guide and thus can exercise its transverse guidance function without the axle pin expansions  34 ,  38  non-rotatably fastened in the chain link colliding with the chain guide. However, the projection on the transverse guide roller is so slight that only a small gap forms at the air gap faces  36 ,  40  across which a magnetic circuit is able to close itself without problem. The projection and hence the air gap is between 0.5 and 2 mm, preferably approximately 1.5 mm and more preferably 1.4 mm, which results in an attraction force of around 100 N with conventional magnets. 
         [0053]    The location of the chain link in chain guide  50  is illustrated in  FIG. 1.4 , which shows a section through the central axis of the axle pin  30  following the course of section line A-A in  FIG. 1.3 . 
         [0054]      FIG. 1.4  shows the chain guide  50  which here comprises two guide tracks  52 . Between the guide tracks there is a guide groove  54  in the bed of which magnet packages  56  are disposed. In the present embodiment, the magnet packages are bolted down into the bed of the groove, but lateral screws or a screw fitting through the guide tracks  52  or another means of fastening is conceivable, in which a slight distance can be specified between the magnet packages  56  and the groove bed. 
         [0055]      FIG. 1  shows that the air gap face  40  is some distance from the axle pin  30 , specifically from its end face. It surrounds the axle pin and its end face radially. At the same time, it lies parallel to the plane drawn by the contacts of the roller pairs with their chain guides. At  36  there are further air gap faces running perpendicular to face  40  and parallel to the direction of circulation of the chain link. All three faces  36 ,  40  form a narrow, two-dimensional and plane-parallel air gap in the typical configuration of the chain guide. 
         [0056]    It can be seen from the section view in  FIG. 1.4  that the transverse guide roller  42  rolls against the inner side faces of guide track  52 . A transverse movement of chain link  10  relative to the chain guide  50  is thus prevented, which ensures a precise and repeatable transport of the workpiece in a generally known manner.  FIG. 1.4  also shows in its dashed-dotted line how the magnetic circuit closes via air gap faces  36 ,  40 . Thus the magnetic circuits are closed via the magnets and the lower axle pin expansion on the one hand, and the magnets and the upper axle pin expansion  34  and the guide tracks  52  on the other. By contrast with the prior art, it is no longer necessary to close the magnetic circle via a linear contact as the transverse guide roller  42  rolls against the guide tracks  52 . A two-dimensional extension of the magnetic field lines is further effected in a tight parallel gap, which increases the efficiency. This makes it possible to achieve a qualitatively equivalent guidance function with less magnetic force from the magnets. The manufacturing costs can be lowered and handling of the magnets during assembly is made easier. The build-up of frictional corrosion can be reduced by the decoupling of the magnetic circuit from the points of high mechanical loading. 
         [0057]      FIG. 2  shows a second embodiment, in which the views of  FIGS. 2.1 ,  2 . 2 ,  2 . 3  correspond to those of  FIGS. 1.1 ,  1 . 2  and  1 . 3 .  FIG. 2.4  shows a section line running through the centre axis of the axle pin  230  for the transverse guide roller  242 , along the course of the section line A-A from  FIG. 2.3 .  FIG. 2.5  shows an additional cross-section, corresponding to the course of the section line B-B in  FIG. 2.3 . 
         [0058]      FIG. 2  shows that lands  234 ,  238  are provided at a distance in front of and behind the transverse guide roller  242  in the direction of the circulation of the chain link. In the embodiment according to  FIG. 2 , the lands are formed from angle iron pieces  232  and permanent magnets. The permanent magnets also have a surface on which in conjunction with the chain guide  250 , specifically with the bed of the guide groove  254 , an air gap is formed. The air gap faces of the lands are identified as  236  and  240  accordingly. In the embodiment according to  FIG. 2 , because the permanent magnets are fitted in the chain links, it is no longer necessary to provide magnet packages in the chain guide. However, a controlled air gap forms between the lands  234 ,  238  on the one hand and the bed of the guide groove  254  on the other over a considerable length of the chain link. The air gap faces, run parallel to the plane drawn by the guide rollers and are located at a distance from this plane downwards, i.e. away from the workpiece support  22 . The distance between the air gap faces  236 ,  240  to the bed of the guide groove  254  creates the air gap, preferably approximately 1.5 mm and more preferably 1.4 mm. 
         [0059]    Similar lands are implemented in the third embodiment in accordance with  FIG. 3 , with the views as  FIGS. 3.1 ,  3 . 2  and  3 . 3  corresponding to the numbered views in  FIGS. 1 and 2 .  FIG. 3.4  shows a cross-section through the centre axis of the axle pin stub  330  for a transverse guide roller in accordance with the course of the section line A-A as shown in  FIG. 3.3 .  FIGS. 3.5  and  3 . 6  show a comparison of the cross-section along the section line B-B from cut-outs  3 . 3  once with and once without the lands  334  and  338 . 
         [0060]    From the comparison of  FIGS. 3.4 ,  3 . 5  and  3 . 6  described below, it is clear how the provision of the lands  234 ,  238  positively influence the formation of the magnetic circuit. The comparison is made on the basis of the embodiment in accordance with  FIG. 3 , but is also correct for the other embodiments. 
         [0061]    As  FIG. 3.4  shows, without the lands  234 ,  238  it is impossible to clearly forecast whether the magnetic circuit will close itself through the linear contact between transverse guide roller  342  and guide tracks  352 , and/or via the end face of axle pin  330 , which here only takes the form of a projection on the chain link. The two possible magnetic circuit lines are illustrated in  FIG. 3.4 . Their common feature is that the magnetic circuit has to close itself over a diverging air gap, which is narrowest at the linear contact between roller and its bearing surface or at the outer circumference of the axle pin end face. This form of air gap results in saturation losses. 
         [0062]      FIG. 3.5  reveals that there is also clearance between the chain link and the magnet package  356  that is too great to close the magnetic circuit over a considerable length of the chain link in the direction of circulation of the chain link, that is, where there are no lands. This area remains unused for closing the magnetic circuit, while the chain link runs past the magnet packages in operation. 
         [0063]      FIG. 3.6  shows that filling up these sections with lands  334 ,  336  causes the magnetic circuits to be closed over the air gap faces  336 ,  340  and thus increases the effective length over which the magnetic packages  56  of each individual chain link can be guided. The air gap can also take a two-dimensional, narrow and parallel form, which reduces saturation losses. The materials provided to make the lands  334 ,  336  and the dimensions of the air gap correspond to those of the first embodiment. 
         [0064]    In the fourth embodiment, too, the views of  FIGS. 4.1 ,  4 . 2  and  4 . 3  correspond to those of the correspondingly numbered drawings for the previous embodiments. The fourth embodiment makes particularly clear that the magnetic guidance function for the chain links can also be realized if the magnet packages  456  are built into the guide tracks  452  of the chain guide  450  (see  FIG. 4.4 ).  FIG. 4.4  indicates the polarity, with the poles being identified as “N” for north and “S” for south. 
         [0065]    Lands  434 ,  438  are provided to the side of the transverse guide roller  442  above the axle pin  430  to achieve a controllable air gap in this embodiment. To create a tight air gap with magnet packages  456  closing flush with the guide tracks  452 , the lands  434 ,  438  preferably also close practically flush with the outer circumference of the rollers  424 ,  426 . The concrete disposal and embodiment of the lands will depend, however, on the embodiment of the chain guide  450 . This means that as long as the magnet packages  456  are disposed offset relative to the guide tracks  452  upwards or downwards, the lands  434 ,  438  are also embodied correspondingly offset upwards or downwards. Whatever the precise location of these lands  434 ,  438  relative to the upper surface of the magnet packages  456 , air gap faces  436 ,  440  are formed on them, as can be seen from the drawing. In the embodiment in accordance with  FIG. 4  the lands  434 ,  438  take the form of side projections from the body of the chain link  410  in the area of the transverse guide roller  442 , however, a longer extension of the length of the lands or their attachment to a different section of the chain links is possible. 
         [0066]    The embodiment in accordance with  FIG. 5 , in particular  FIG. 5.4 , shows variants on the principle of the embodiment in accordance with  FIG. 4 .  FIGS. 5.1 ,  5 . 2  and  5 . 3  correspond in their views to the views of the correspondingly numbered drawings for the previous embodiments so that no detailed description is necessary. 
         [0067]      FIG. 5.4  shows a sectional view following section line A-A from  FIG. 5.3 , with the line of the section being offset unlike in the previous embodiments. 
         [0068]      FIG. 5.4  shows two different variant embodiments, one to the left of the centre vertical, one to the right of the centre vertical. Both embodiments have in common with the fourth embodiment in accordance with  FIG. 4  and with one another that lands  534 ,  538  are formed. In the fifth embodiment in accordance with  FIG. 5 , the lands are however, not disposed adjacent to the transverse guide roller  542 , but at a distance from this in the direction of travel of the chain link. In the fifth embodiment, the axes for the rollers  524 ,  526  are used to provide either an expansion of the axle pin  534  or a shoulder on the axle pin  538 . Air gap faces  536 ,  540  are provided at both the axle pin expansion  534  and the axle pin shoulder  538  that are comparable in their technical effect with the air gap faces in the embodiment in accordance with  FIG. 4 . 
         [0069]    The axle pin expansion  534  is formed from a single piece with the roller carrier on the side of axle pin expansion  534 . The axle pin shoulder  538  on the other hand, takes the form of a separate component and is fastened non-rotatably to the carrier for the roller on one side by means of a keyed joint, for instance. The provision of an axle pin expansion  534  and an axle pin shoulder  538  on the same axis makes it possible to fit the axis. In this way the axis can be inserted with the axle pin expansion  534  on one end so that the axle pin shoulder  538  can then be mounted on the protruding end. It is however, also conceivable that an axle pin shoulder  538  or an axle pin expansion  534  be fitted on both sides, if it is not a floating axle. 
         [0070]    The materials provided to make the axle pin expansion  534  and the axle pin shoulder  538  and the dimensions of the air gap correspond to those of the fourth embodiment. 
         [0071]    A further embodiment is illustrated in  FIG. 6 , with the views shown in  FIGS. 6.1 ,  6 . 2  and  6 . 3  again corresponding to the correspondingly numbered views of the previous embodiment. 
         [0072]    It can be seen from the embodiment in accordance with  FIG. 6  that this version is embodied without a transverse guide roller. Instead of the transverse guide roller familiar from the previous embodiments, the transverse guidance function is provided in the embodiment according to  FIG. 6  by a guide blade  630 . This makes it possible to embody the chain guide  650  with guide tracks  652  but without the continuous wide guide groove for the transverse guide roller. This for its part makes it possible to use the central area of the chain guide as a rolling surface for a guide roller, which permits the use of chain links with only three guide rollers, for instance. 
         [0073]    Instead of having a guide groove for a transverse guide roller, chain guide  650  is provided with a guide groove  654  in which the guide blade  630  is engaged in sections only, that is, in the areas of the machining tools and machining assemblies. Although it is also possible in principle to provide the guide groove  654  over the entire length of the chain guide  650 , this is not necessary, as a transverse guide on the chain is principally required at points where a transverse force is applied to the workpiece and hence to the chain by machine tools or machine assemblies, for instance. In order to reduce possible losses through friction of the guide blade on the guide groove, in the present embodiment the blade is fixed upright but the longitudinal extent of the guide groove  654  is restricted to only this area of the working tools or assemblies. It would also be conceivable, however, that the guide blade be formed to be moveable so that it is moved in engagement with a guide groove or similar only in the areas critical for transverse guidance. 
         [0074]    The range critical for transverse guidance is indicated in  FIG. 6.5  by a working tool drawn schematically at  660 . The guide groove  654  is only provided in the area of the working tool  660 . In order to assist in the engagement of the guide blade  630  in the guide groove  654 , the groove narrows  655  before the machining tool  660  for the guide blade  630  infeed. A corresponding broadening for the run-out or for the infeed in the event of the reversal of the direction of movement of the chain can also be seen from  FIG. 6.5 . 
         [0075]    Roller-less transverse guidance permits the base of the chain link to be embodied in such a way that the magnetic circuit can close here where a narrow two-dimensional and flat air gap is formed.  FIG. 6.4  illustrates the magnet packages  656  correspondingly provided.  634  identifies the base of the chain-link at which an air gap surface  636  is formed. The materials for the base  634  and the dimensions of the air gap correspond to those of the fourth or fifth embodiments. 
         [0076]    As before in the previous embodiments, it is also possible in the sixth embodiment to adapt the vertical position of the chain link base  634  to the form of the chain guide. It is preferred that the chain guide  650  is flat on top, i.e. that the upper side of the magnet package  656  is flush with the guide tracks  652 . In this case, the base  634  of the chain link and with it the air gap face  636  can be spaced slightly away from the contact point of the rollers in the direction of the workpiece support  622 . The distance defines the air gap which then forms with the upper side of the magnet packages  656 . If the upper side of the magnetic packages  656  is correspondingly then displaced downwards in relation to the guide tracks  652 , the base  634  can be displaced relatively by the same amount. Adapting the chain links to this embodiment of the chain guide  650  thus guarantees the repeatable recreation of a uniform, two-dimensional and parallel air gap. 
         [0077]    As can be seen from the description of the preferred embodiments, the individual embodiments can also be combined with one another. For instance, it is possible also to construct the embodiments according to  FIGS. 4 and 5  with a roller-less transverse guide. The transverse guide blade described with reference to the embodiment in accordance with  FIG. 6  can also be used in the embodiments according to  FIGS. 4 and 5 , as the lands provided in the embodiments in accordance with  FIGS. 4 and 5  leave sufficient space to use a blade instead of the transverse guide roller. 
         [0078]    Finally, it is also possible to form the infeed alternatively or additionally from bottom to top instead of the infeed narrowing from the sides into the transverse guidance groove in accordance with the sixth embodiment.