Abstract:
Multispindle lathe comprising a machine frame ( 12 ), a spindle drum ( 14 ) which is arranged in the machine frame ( 12 ), is rotatable about a spindle drum axis ( 16 ) and is made up at least partially of segments ( 80 ) which are cut out from flat material in a stacking direction ( 82 ) parallel to the spindle drum axis ( 16 ) and extend in stacking planes ( 88 ) transverse to the stacking direction ( 82 ), these segments having receiving cutouts ( 90 ) and cooling channel cutouts ( 92, 96, 106 ) which overlap with one another such that the spindle drum ( 14 ) has spindle motor receptacles ( 30 ) for spindle motors ( 32 ) and a cooling channel system ( 120, 130, 180 ) separated therefrom by wall webs ( 98 ), characterized in that the cooling channel system has several channel subsystems ( 120, 130, 180 ) for a liquid cooling medium which are fed in parallel.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application is a continuation of International application No. PCT/EP2011/053223 filed on Mar. 3, 2011. 
     This patent application claims the benefit of International application No. PCT/EP2011/053223 of Mar. 3, 2011 and German application number 10 2010 002 804.5 of Mar. 12, 2010, the teachings and disclosure of which are hereby incorporated in their entirety by reference thereto. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a multispindle lathe comprising a machine frame, a spindle drum which is arranged in the machine frame, is rotatable about a spindle drum axis and is made up at least partially of segments which are cut out from flat material in a stacking direction parallel to the spindle drum axis, extend in stacking planes transverse to the stacking direction and have receiving cutouts and cooling channel cutouts which overlap with one another such that the spindle drum has spindle motor receptacles for spindle motors and a cooling channel system separated therefrom by wall webs. 
     Such a multispindle lathe is known from EP 1 414 615. 
     In the case of the known multispindle lathe, it is, in principle, possible to cool the spindle drum but is not, however, possible to cool the spindle drum as uniformly as possible in order to avoid thermal displacements to as great an extent as possible and to discharge the heat generated by the spindle motors as optimally as possible. 
     SUMMARY OF THE INVENTION 
     This object is accomplished in accordance with the invention, in a multispindle lathe of the type described at the outset, in that the cooling channel system has several channel subsystems for a liquid cooling medium which are fed in parallel. 
     The advantage of the solution according to the invention is to be seen in the fact that, on the one hand, an efficient cooling of the spindle drum takes place via the cooling channel system by way of the liquid cooling medium and, on the other hand, the channel subsystems which are fed in parallel offer the possibility of adapting the cooling capacity in various areas of the spindle drum which experience heat input to various different degrees. 
     In this respect, it is particularly favorable when the channel subsystems cool different sections of the spindle motor receptacle which follow one another in the direction of the spindle drum axis. 
     It is possible, as a result of the allocation of the channel subsystems to individual, different sections of the respective spindle motor receptacle, to cool the sections which are each subject to a different heat input in a targeted manner. 
     In principle, it would be conceivable to nevertheless arrange the channel subsystems such that they overlap in sections. 
     For reasons of as simple and, therefore, inexpensive a construction as possible, it has proven to be expedient when the several channel subsystems are arranged to the side of the spindle motor receptacle in areas of the spindle drum which follow one another in the direction of the spindle axis. 
     In this respect, a channel subsystem is preferably provided in each of the respective areas and cools this area while the other channel subsystems are each arranged in a different area of the spindle drum and cool this area. 
     In principle, it would be possible to arrange the channel subsystems such that they each surround the spindle motor receptacle. 
     For reasons of as inexpensive and, at the same time, space-saving a construction as possible, it is, however, of advantage when the channel subsystems are arranged in intermediate spaces between spindle motor receptacles which are arranged so as to follow one another in a circumferential direction around the spindle drum axis and so the radial extension of the spindle drum with respect to its spindle drum axis can be kept as small as possible. 
     In this respect, several channel subsystems are preferably arranged in each intermediate space between two spindle receptacles so as to follow one another in the direction of the spindle drum axis. 
     With respect to the feeding of the channel subsystems, no further details have been given in conjunction with the preceding description of the solution according to the invention. 
     One advantageous solution, for example, provides for the channel subsystems to be fed with liquid cooling medium through a common annular space surrounding the spindle drum. 
     Such an annular space surrounding the spindle drum allows the liquid cooling medium to be supplied to the spindle drum in any rotary position in a simple manner, despite the rotatability of the spindle drum, namely to all the channel subsystems at the same time. 
     In this respect, it is provided, in particular, for a stationary annular space cover to engage over the annular space and to adjoin it sealingly on both sides thereof. 
     Furthermore, it is preferably provided for the channel subsystems to discharge the liquid cooling medium into an annular space for outflowing cooling medium which surrounds the spindle drum. 
     Such an annular space also has the advantage that, as a result, it is possible in a simple manner to drain off the cooling medium flowing into this annular space and collect it again. 
     In principle, the annular space for the outflowing cooling medium could discharge the cooling medium into those channel subsystems which also serve, at the same time, to collect the cooling medium. 
     It is, however, particularly favorable when the annular space for the outflowing cooling medium merges into a collecting receptacle, in which the cooling medium flowing into the annular space and thereby flowing out is collected and used again for cooling the channel subsystems. 
     In order to be able to adapt the cooling capacity provided by the individual channel subsystems to the heat input, it is preferably provided for the flow of cooling medium through the different channel subsystems to be coordinated by throttle elements. 
     In this respect, it is particularly favorable when the throttle elements are associated with exit openings of the channel subsystems. 
     For example, the throttle elements can be adjustable throttle elements or even throttle elements which can be controlled by a control of the multispindle lathe so that regulation of the heat discharged by the channel subsystems would be possible. 
     One particularly simple solution provides, however, for the throttle elements to be statically adjustable throttle elements. 
     With respect to the design of the stator body of the spindle motors, no further details have so far been given. 
     For example, the stator body could, as is normal for spindle motors thus far, be provided with a casing and arranged in the spindle motor receptacle with this casing. 
     One particularly favorable solution provides for the stator body to be designed as a stack of metal sheets and for the stack of metal sheets of the stator to abut directly on an inner wall of a stator receptacle of the spindle motor receptacle so that an optimum transfer of heat from the stator body to the spindle drum and, therefore, an optimum discharge of heat is ensured. 
     Additional features and advantages of the invention are the subject matter of the following description as well as the drawings illustrating several embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a vertical section through a machine frame of a multispindle lathe bearing a spindle drum; 
         FIG. 2  shows a perspective view of the spindle drum of the multispindle lathe according to the invention; 
         FIG. 3  shows a section along line  3 - 3  in  FIG. 2 ; 
         FIG. 4  shows a section along line  4 - 4  in  FIG. 2 ; 
         FIG. 5  shows an exploded illustration of consecutive segments with corresponding cutouts; 
         FIG. 6  shows an illustration of the segments similar to  FIG. 5  in the region of inlet openings of a first channel subsystem; 
         FIG. 7  shows a section along line  7 - 7  in  FIG. 3  and 
         FIG. 8  shows a sectional, enlarged, perspective exploded illustration of throttle elements in the region of outlet openings of the first channel subsystem and the third channel subsystem. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A multispindle lathe  10 , which is illustrated in parts in  FIG. 1 , comprises a machine frame  12 , in which a spindle drum designated as a whole as  14  is mounted for rotation about a spindle drum axis  16 , wherein the rotatable mounting of the spindle drum  14  in a spindle drum receptacle  18  of the machine frame  12  is brought about by means of rotary bearings  20  and  22  arranged on the casing side of the spindle drum  14 . 
     The spindle drum  14  comprises, as illustrated in  FIG. 2 , a plurality of spindle motor receptacles  30  which are arranged in the spindle drum  14  around the spindle drum axis  16  and pass through it over its entire length. 
     A spindle motor, which is designated as a whole as  32  and designed as a hollow shaft motor, is seated in each of the spindle motor receptacles  30  and has a stator  34  which accommodates the stator coils as well as a rotor  36  which is arranged within the stator  34 , is seated directly on a spindle tube  38  and is mounted by this spindle tube  38  so as to be rotatable about a spindle axis  40  relative to the stator  34 . In this respect, the spindle tube  38  has, for example, on a side facing an operating space  42  a workpiece clamping device, which is not illustrated, for clamping a workpiece accommodated in the spindle tube  38  in the known manner. 
     As illustrated, in particular, in  FIG. 3  on an enlarged scale, the spindle motor receptacle  30  passing through the spindle drum  14  comprises a forward section which forms a spindle bearing receptacle  50  and in which a forward spindle bearing  52  is seated which mounts the spindle tube  38  at a forward end area  54  facing the operating space  42 . 
     Furthermore, the spindle motor receptacle  30  comprises a section which forms a stator receptacle  60  and in which the stator  36  is seated with a stator body  62  which accommodates stator coils and is built up of stator metal sheets, wherein a casing surface  64  of the stator body  62  abuts directly on an inner wall  66  of the stator receptacle  60  of the spindle drum  14 , merely, where applicable, coupled to a heat conducting mass, in order to ensure a good transfer of heat between the stator body  62  which accommodates the stator coils of the stator  36  and the spindle drum  14  in the region of the stator receptacle  60 . 
     The spindle tube  38  is, in addition, supported on the spindle drum  14  via a rear bearing receptacle  70 , wherein a bearing ring  72  engages, for example, in the rear bearing receptacle  70  and accommodates a rear spindle mounting  74  which mounts the spindle tube  38  at a rear end area  76  so as to be rotatable. 
     As illustrated in  FIGS. 3 to 7 , the spindle drum  14  is built up, at least in the region of the stator receptacle  60 , from a plurality of segments  80   a ,  80   b  and  80   c  which are cut out from flat material, for example from steel plates, and stacked in a stacking direction  82  parallel to the spindle drum axis  16  and are connected to one another in a materially joined manner, for example by way of soldering, in particular hard soldering, to form a coherent body. The individual segments  80  preferably have plane parallel surfaces  84  and  86  and extend in stacking planes  88  which are at right angles to the stacking direction  82 , as also described, for example, in the European patent application EP 1 414 615. 
     For the purpose of forming the spindle motor receptacle  30 , the segments  80  are provided with receiving cutouts  90  which together form the spindle motor receptacle  30  in the direction of the stacking direction  82 . 
     Furthermore, for the purpose of cooling the spindle motor receptacle  30 , in particular in the region of the stator receptacle  60 , cooling cutouts  92  are provided in segments  80   a  between respective receiving cutouts  90  following one another in a circumferential direction  100  ( FIGS. 4 to 7 ) while cooling cutouts  96  are provided in the segments  80   b  which overlap with areas  94  of the cooling cutouts  92  located radially outwards with respect to the spindle drum axis  60  and these cooling cutouts  96  overlap in the next following segment  80   a  with the areas  94  of the cooling cutouts  92  located radially outwards. 
     Furthermore, cooling cutouts  106  are provided in the segments  80   c  which overlap with areas  104  located radially inwards with respect to the spindle drum  16  and so with a stack sequence of a segment  80   a , a segment  80   b , a segment  80   a  and a segment  80   c  as well as a following segment  80   a  of a next stack sequence, a flow path  110  for a cooling medium results which extends in the segments  80   a  in a direction approximately radial to the spindle drum axis  16  either with a flow path section  110   1  from the inside outwards or with a flow path section  110   3  from the outside inwards, and extends in the segment  80   b  with a flow path section  110   2  and in the segment  80   c  with a flow path section  110   4  approximately parallel to the spindle drum axis  16  each time so that the flow path  110 , during its overall extension in the direction of the spindle drum axis  16 , has sections which extend alternately in an axial direction  110   2  and  110   4  and in a radial direction  110   1  and  110   3  to the spindle drum axis  16  and these sections efficiently cool the adjoining segments  80   b  and  80   c  and the wall sections  98  located in the segments  80   a  between the cutouts  90  and the cooling cutouts  92 . 
     As a result of such a construction of the stator receptacle  60  from the segments  80   a ,  80   b  and  80   c  described, which are located one on top of the other in the stacking direction  82 , it is possible to efficiently cool the spindle drum  14  in its wall area adjoining the stator receptacle  60  and, therefore, to efficiently discharge the heat transferred from the stator  34  to the spindle drum  14  in the region of the stator receptacle  60 . 
     Preferably, for the purpose of cooling the stator receptacle  60 , as illustrated in  FIG. 3 , a first channel subsystem  120  and a second channel subsystem  130  are provided which are arranged in intermediate spaces  118  located between the spindle motor receptacles  30  in circumferential direction and in areas  122  and  132  of the intermediate spaces  118  which follow one another in the direction of the spindle drum axis  16 , wherein the first channel subsystem  120  is arranged in an area  122  facing the forward spindle bearing receptacle  50  and adjoining the stator receptacle  60  while the second channel subsystem  130  is provided in an area  132  facing away from the spindle bearing receptacle  50  and bordering on the stator receptacle  60 . 
     The two channel subsystems  120  and  130  are operated in parallel with cooling medium, in particular with liquid cooling medium. 
     For this purpose, as illustrated in  FIGS. 1 to 3 , an annular space  140  is provided which surrounds the spindle drum  14  on its outer side and has an annular space cover  142  engaging over it which is arranged stationarily in the machine frame  12  and adjoins sealingly on cylinder surfaces  144  and  146  of the spindle drum  14  on both sides of the annular space  140  so that liquid cooling medium supplied to the annular space  140  remains in the annular space  140  and from this annular space can enter the first channel subsystem  120  and the second channel subsystem  130 , respectively, via entry openings  124  and  134  ( FIG. 3 ), formed by entry cutouts  150  provided in special segments  80   d  ( FIG. 6 ). 
     Proceeding from the entry cutouts  150  in the segments  80   d , the liquid cooling medium then has the possibility of entering the areas  94  of the cooling cutouts  92  in the next following segments  80   a  which are located radially outwards. 
     Furthermore, the channel subsystems  120  and  130  are also provided at their ends with exit openings  126  and  136  which likewise open into an annular space  170  which surrounds the spindle drum  14  on its casing side and via which the liquid cooling medium entering this annular space  170  can run off the casing side of the spindle drum  14  in line with gravity, namely as far as a collecting receptacle  172 , from which the cooling medium will be taken up by a cooling medium pump. 
     As illustrated in  FIG. 3 , a third channel subsystem  180  is provided in addition for the spindle bearing receptacle  50  and this is located in an area  182  in the intermediate space  118  between the bearing receptacles  50  for separately cooling the spindle drum and has an entry opening  184  for cooling medium supplied to the annular space  140 , which is located between the entry openings  124  and is likewise formed by an entry cutout  152  in the segment  80   d , as well as an outlet  186  which faces the annular space  170  for discharging the cooling medium into the annular space  170 . 
     The third channel subsystem  180  is likewise formed by cooling cutouts  192  and  194  in segments  80   e  and  80   f  which are arranged in the area  182  of the intermediate space  118  and also comprises entry channels  194  which lead from the entry openings  184  to the area  182  as well as exit channels  196  which lead from the area  182  to the exit openings  186 . 
     In order to coordinate the cooling of the spindle drum  14  by the channel subsystems  120 ,  130  and  180  such that the spindle drum  14  has in all the areas  122 ,  132 ,  182  cooled by the channel subsystems  120 ,  130  and  180  an essentially constant temperature which is essentially identical in all the areas  122 ,  132 ,  182  which the channel subsystems  120 ,  130  and  180  pass through, the exit openings  126  of the channel subsystem  120  and the exit openings  186  of the channel subsystem  180  are provided with throttle elements  202  and  204 , respectively, which allow adjustment of the liquid cooling medium flowing out of the channel subsystem  120  and  180 , respectively, into the annular space  170  for adjusting the respective temperature. 
     The throttle elements  202  and  204  are preferably arranged in a receiving block  200  which can be screwed onto a flange  208  of the spindle drum  14  which includes the openings  126  and  186 , namely such that the throttle elements  202  and  204  are seated directly in front of the openings  126  and  186 , respectively, and throttle the flow rate of the exiting cooling medium.