Abstract:
A movement unit for a machine tool comprises a supporting structure movable in a first direction for supporting a functional unit of the machine tool, with two longitudinal guides extending in the first direction which are offset relative to one another in a transverse second direction. A guide unit is mounted on each longitudinal guide to be relatively movable in the first direction and not the second direction. A bearing structure connects the supporting structure to one of the guide units to be not relatively movable in the first direction and movable in the second direction. The bearing structure comprises a bearing receptacle having a receptacle wall extending in the second direction, and a bearing projection which engages the bearing receptacle. The bearing projection and the receptacle wall are supported against one another to prevent their relative motion in the first direction and are movable in the second direction.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    Under 35 U.S.C. §119(a), this application claims the benefit of a foreign priority application filed in the European Patent Office, Ser. No. 12 169 323.8, filed May 24, 2012, the entire contents of which are hereby incorporated by reference. 
       TECHNICAL FIELD 
       [0002]    The invention relates to a machine tool with a movement unit. 
       BACKGROUND 
       [0003]    A movement unit for a machine tool is disclosed in EP 0 935 511 A1. The prior art relates to a machine tool with a supporting structure in the form of a machine gantry, driven in a direction of travel by two linear motors at the longitudinal ends of the machine gantry. In this case, the machine gantry is supported with each of its longitudinal ends on a feed slide, which is in turn connected with the movable part in the direction of travel of the linear motor in question. To guide the machine gantry in the direction of travel, longitudinal guides extending in the direction of travel are provided for the feed slides, the longitudinal guide for the one feed slide being spaced transversely of the direction of travel from the longitudinal guide of the other feed slide. On the one feed slide the machine gantry is mounted without play transversely of the direction of travel. On the other feed slide the machine gantry is mounted with play transversely of the direction of travel. The bearing which exhibits play, forming a floating bearing for the direction transverse of the direction of travel, comprises on the machine gantry an elongate hole extending with its longitudinal axis transversely of the direction of travel and, on the feed slide in question, a bolt engaging in the elongate hole. The bolt provided on the feed slide is inserted into the elongate hole on the machine gantry without play in the direction of travel. 
       SUMMARY 
       [0004]    Certain devices described herein advantageously ensure durably play-free mounting in the direction of travel of a supporting structure on a floating bearing of the supporting structure. 
         [0005]    In some embodiments, a bearing projection and a receptacle wall of a bearing receptacle of a bearing arrangement acting as a floating bearing in a guide transverse direction are preloaded towards one another in the direction of travel and, through the effect of this preloading, can be readjusted relative to one another in the direction of travel. As a result of the features, the bearing arrangement acting as a fixed bearing in the direction of travel readjusts itself automatically. This ensures durable mutual play-free support of the bearing projection and the receptacle wall of the bearing receptacle in the direction of travel. Play-free mounting in the direction of travel is in particular also not impaired by wear of the bearing projection and/or wear of the receptacle wall of the bearing receptacle. 
         [0006]    In some embodiments, a multipart construction is provided for the bearing projection and/or for the receptacle wall of the bearing receptacle. Mutual play-free support of the bearing projection and the receptacle wall of the bearing receptacle is realized by a loading element, which is supported on an associated base. This multipart nature also opens up the possibility of adapting the machine element which ultimately ensures mutual play-free mounting of the bearing projection and the receptacle wall of the bearing receptacle, namely the loading element, to the requirements of the particular application and if necessary, for instance due to wear, of replacing it with a replacement part. 
         [0007]    In further embodiments, the loading element is supported on the associated base in the manner of a wedge transmission. A wedge face inclined in the direction of travel is provided on the loading element and/or on the associated base. The loading element is acted on by a preloading means. The wedge face(s) make(s) it possible to disperse major loads acting in the direction of travel despite the space-saving construction of the wedge transmission. For mutual readjustment of the bearing projection and the receptacle wall of the bearing receptacle in the direction of travel, the loading element moves under the effect of the preloading means along the wedge face(s) relative to the associated base and perpendicular to the direction of travel. 
         [0008]    In further embodiments, movement of the loading element in the opposite direction and thus undesired loosening of the play-free mutual support of the bearing projection and the receptacle wall of the bearing receptacle in the direction of travel is prevented in that the loading element is supported in a self-locking manner on the associated base against movement effected relative to the base along the wedge face(s). The self-locking support may be realized by appropriate selection of the wedge angle of the wedge face on the loading element and/or the wedge face on the base associated with the loading element. 
         [0009]    Two loading elements supported on an associated base and readjustable in the direction of travel relative to the respective other bearing part can be provided on the bearing projection and/or on the receptacle wall of the bearing receptacle, the loading elements being located opposite one another on the base in question. Mutual readjustment of the bearing projection and the receptacle wall of the bearing receptacle is accordingly divided between two loading elements. Consequently, each of the loading elements has in particular only to provide some of the readjusting travel needed overall. 
         [0010]    So that uniform conditions prevail at both loading elements, in further embodiments, the loading elements, which are provided on mutually opposing sides of the associated base in the direction of travel, are coupled together mechanically. As a result of the mechanical coupling, the loading elements perform movements for readjusting the mutual support of the bearing projection and the receptacle wall of the bearing receptacle jointly and by a matching amount. 
         [0011]    The mounting, play-free in the direction of travel and floating in the guide transverse direction, of the supporting structure on the guide unit allows the supporting structure to effect swiveling movements relative to the guide unit about an axis which extends perpendicular to the plane defined by the direction of travel and the guide transverse direction. Such swiveling movements of the supporting structure are performed for example when offset arises undesirably in the direction of travel at the guide units already offset relative to one another in the guide transverse direction. 
         [0012]    Such mutual offset of the guide units spaced from one another in the guide transverse direction may arise in particular in the case, significant in terms of day-to-day operation in which each of the two guide units is moved in the direction of travel by its own drive motor and the drive motors of the guide units are not connected together mechanically. A machine gantry of the machine tool can be provided as the supporting structure. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  shows the fundamental structure of a laser-cutting machine with a movement unit. 
           [0014]      FIG. 2  shows the movement unit of the laser-cutting machine of  FIG. 1  in a schematic plan view. 
           [0015]      FIG. 3  shows an enlarged representation of detail III of  FIG. 2 . 
           [0016]      FIG. 4  shows a sectional representation of the arrangement of  FIG. 3  in a section plane extending perpendicularly to the plane of the drawing in  FIG. 3  along line IV-IV. 
           [0017]      FIGS. 5 and 6  show alternatives to the arrangement of  FIGS. 3 and 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    As shown in  FIG. 1  a machine tool in the form of a laser cutting machine  1  for sheet metal working has a working area  3  defined by a housing  2 . A work support  4  of conventional design is arranged in the working area  3 , which supports a metal sheet to be worked and also supports the products of sheet metal working. For simplicity&#39;s sake,  FIG. 1  does not show metal sheets to be worked or products produced by sheet metal working. 
         [0019]    For cutting machining, a metal sheet supported on the work support  4  is passed over by laser cutting heads  5 ,  6 . The laser-cutting heads  5 ,  6  form functional units of the laser cutting machine and are moved by a movement unit  7  of the laser-cutting machine  1 . The movement unit  7  includes a supporting structure in the form of a machine gantry  8  spanning the work support  4  and a guide means  9  (shown in detail in  FIG. 2 ). The guide means  9  guides the machine gantry  8  in the direction of travel  10 . 
         [0020]    The laser cutting heads  5 ,  6  are displaceable on the machine gantry  8  by drive motors in a guide transverse direction  11 . The machine gantry  8  is moved jointly in the direction of travel  10  with the laser cutting heads  5 ,  6 . To this end, a linear motor of conventional design is provided at each of the longitudinal ends of the machine gantry  8 . The linear motors of the machine gantry  8  are not shown in  FIGS. 1 to 6  for the sake of simplicity. 
         [0021]    The part of each linear motor of the machine gantry  8  moved in the direction of travel  10  is connected with a guide unit of the guide means  9 . The guide units of the guide means  9  take the form of feed slides  12 ,  13 , shown schematically in  FIG. 2 . In place of the feed slides  12 ,  13 , any feed carriages of conventional construction can be provided. The feed slides  12 ,  13  are guided movably in the direction of travel  10  on stationary longitudinal guides  14 ,  15  of the guide means  9 . The longitudinal guides  14 ,  15  are spaced apart from one another in the guide transverse direction  11  and thereby form a space therebetween, in which the work support  4  of the laser-cutting machine  1  is arranged. The feed slides  12 ,  13  are mounted on the longitudinal guides  14 ,  15  without play in the guide transverse direction  11 . 
         [0022]    The feed slides  12 ,  13  in turn are mounted on the machine gantry  8 . In this respect, a first bearing means  16  provided for mounting the machine gantry  8  on the feed slide  12  solely allows a swiveling movement of the machine gantry  8  relative to the feed slide  12 . An axis  17 , about which the machine gantry  8  may swivel relative to the feed slide  12 , extends perpendicular to the horizontal plane defined by the direction of travel  10  and the guide transverse direction  11 . The swivelability of the machine gantry  8  about the axis  17  is indicated in  FIG. 2  by a curved double-headed arrow. In both the direction of travel  10  and the guide transverse direction  11  the first bearing means  16  forms a fixed bearing, which accordingly supports the feed slide  12  and the machine gantry  8  on one another without play in both the direction of travel  10  and the guide transverse direction  11 . 
         [0023]    A second bearing means  18  at the opposing longitudinal end of the machine gantry  8  differs from the first bearing means  16  in that, unlike the first bearing means  16 , it allows movement of the machine gantry  8  relative to the feed slide  13  in the guide transverse direction  11 . In the guide transverse direction  11  the second bearing means  18  consequently forms a floating bearing for the machine gantry  8 . Beyond that, like the first bearing means  16 , the second bearing means  18  acts as a fixed bearing in the direction of travel  10  and also allows swiveling movement of the machine gantry  8  relative to the associated guide unit of the guide means  9 . An axis  19 , about which the machine gantry  8  may swivel relative to the feed slide  13 , is indicated in  FIG. 2 . The axis  19  also extends perpendicular to the horizontal plane defined by the direction of travel  10  and the guide transverse direction  11 . 
         [0024]      FIGS. 3 to 6  show how the fixed bearing function in the direction of travel  10  and the floating bearing function in the guide transverse direction  11  are combined structurally together in the case of the second bearing means  18 . 
         [0025]    As shown in  FIGS. 3 and 4 , the second bearing means  18  includes as its supporting structure-side bearing part a bearing receptacle provided on the machine gantry  8  in the form of a slide channel  20  with a channel wall  21  forming a receptacle wall. The guide-side bearing part of the second bearing means  18  takes the form of a bearing projection in the form of a driver  22  provided on the feed slide  13 . The driver  22  is fitted without play into the feed slide  13  by a cylindrical bearing pin  23 . The cylindrical bearing pin  23  is mounted rotatably on the feed slide  13 , along the axis  19 . 
         [0026]    The driver  22 , connected with the feed slide  13 , engages with a gantry-side part  24  in the slide channel  20  on the machine gantry  8 . Specifically, the gantry-side part  24  of the driver  22  includes a projection base  25  with projection wedge faces  26 ,  27  on opposing sides, in the direction of travel  10 , of the projection base  25 . Projection clamping elements in the form of loading wedges  28 ,  29  are associated with the projection base  25 . The loading wedge  28  lies with a loading wedge face  30  against the projection wedge face  26 , while the loading wedge  29  lies with a loading wedge face  31  against the projection wedge face  27  of the projection base  25 . Perpendicular to both the direction of travel  10  and the guide transverse direction  11 , the loading wedges  28 ,  29  are acted on by a pressure spring  32  serving as a preloading means. The pressure spring  32  is loaded between a pressure plate  33  resting on the loading wedges  28 ,  29  and the bottom of a bolt head  34  of a fit bolt  35 . The fit bolt  35  is screwed with its thread into an internal thread on the projection base  25 . 
         [0027]    The loading wedges  28 ,  29  and the bilaterally wedge-shaped projection base  25  form a wedge transmission. Through the effect of the action of the pressure spring  32 , the loading wedges  28 ,  29  are urged to move with their loading wedge faces  30 ,  31  along the projection wedge faces  26 ,  27  of the projection base  25 . As a result of the wedge effect, the loading wedges  28 ,  29  are preloaded against the channel wall  21  of the slide channel  20 . On their side facing the channel wall  21  the loading wedges  28 ,  29  are provided with sliding coatings  36 ,  37 . 
         [0028]    The preloading of the loading wedges  28 ,  29  against the channel wall  21  is such that in the direction of travel  10  play-free support of the driver  22  against the channel wall  21  is ensured, and thus play-free mounting in the direction of travel  10  of the machine gantry  8  on the feed slide  13 . At the same time, the preloading of the loading wedges  28 ,  29  against the channel wall  21  in the guide transverse direction  11  allows movement of the channel wall  21  relative to the loading wedges  28 ,  29  and thus movement of the machine gantry  8  relative to the feed slide  13 . The sliding coatings  36 ,  37  of the loading wedges  28 ,  29  make it easier for the machine gantry  8  to move in the guide transverse direction  11  relative to the feed slide  13 . 
         [0029]    The action of the pressure spring  32  on the loading wedges  28 ,  29  ensures that the preloading of the loading wedges  28 ,  29  against the channel wall  21  and consequently also the play-free support of the machine gantry  8  on the feed slide  13  is retained in the direction of travel  10  even in the case of wear of the loading wedges  28 ,  29 , for instance wear of the sliding coatings  36 ,  37 . In such cases, through the effect of the pressure spring  32 , the loading wedges  28 ,  29  with their loading wedge faces  30 ,  31  are moved along the projection wedge faces  26 ,  27  of the projection base  25 , and through the resultant wedge effect, are readjusted in the direction of travel  10  relative to the channel wall  21  of the slide channel  20 . 
         [0030]    The size of the wedge angle at the loading wedges  28 ,  29  and at the projection base  25  is selected such that the loading wedges  28 ,  29  can if necessary be readjusted sufficiently far in the direction of travel  10  and at the same time enable self-locking of the loading wedges  28 ,  29  at the wedge faces  26 ,  30  and  27 ,  31  in contact with one another against movement relative to the projection base  25 , which movement would otherwise be caused by forces acting in the direction of travel  10  between the machine gantry  8  and the feed slide  13  and carried out against the action of the pressure spring  32 . 
         [0031]    Shown in  FIG. 5  is a further embodiment in which the loading wedges  28 ,  29  are coupled together mechanically. The mechanical connection between the loading wedges  28 ,  29  is in this case brought about by a connecting pin  38 , which engages with its ends in a longitudinally mobile manner in bores  39 ,  40  on the loading wedges  28 ,  29  and is guided at the projection base  25  in an elongate hole  41  in the projection base  25  so as to be movable in the direction of the axis  19 . The mechanical connection between the loading wedges  28 ,  29  produced by the connecting pin  38  ensures, in addition to the pressure plate  33  acting on the loading wedges  28 ,  29 , that the loading wedges  28 ,  29  travel matching distances in the event of readjusting movement in the direction of the axis  19 . Centering of the driver  22  inside the slide channel  20  is additionally ensured thereby. 
         [0032]      FIG. 6  shows a further embodiment of the second bearing means  18  in which a projection base  45  of the driver  22  is provided with a wedge face  46  only on one of its sides situated in the direction of travel  10  and which makes use of just one single loading wedge  48  with a wedge face  50 . A readjusting movement is accordingly performed only at one of the sides of the driver  22  situated in the direction of travel  10 . On the opposite side from the loading wedge  48  in the direction of travel  10 , the driver  22  is supported with the projection base  45  against the machine gantry  8  without the interposition of a loading element. By supporting the projection base  45  directly against the channel wall  21  of the slide channel  20 , the position of the driver  22  and thus also of the feed slide  13  relative to the machine gantry  8  is constant and in particular defined independently of any readjusting movement of the loading wedge  48 . The projection base  45  also includes a sliding coating on the machine gantry side. 
         [0033]    A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.