Abstract:
A tool head includes a working slide which can be adjusted relative to a basic body, and an electric adjusting motor which acts on the working slide via gears. The motor includes a stator and a rotor which runs round in the stator, bears an output shaft and is mounted in two pivot bearings arranged at a distance from one another, wherein one of the pivot bearings is arranged with an outer ring in a basic body-mounted stator housing and with an inner ring directly or indirectly on the output shaft.

Description:
FIELD OF THE INVENTION 
     The invention relates to a tool head for use in machine tools comprising a base body, comprising at least one working slide which can be adjusted in relation to the base body, and comprising an adjustment motor which is arranged in the base body and acts on the working slide via gear means, wherein the adjustment motor which is embodied as an electric motor has a stator which is arranged in the base body and a rotor which rotates in the stator, is fitted with an output shaft and is mounted in two rotary bearings which are arranged at a distance from one another, wherein one of the rotary bearings is arranged with an outer ring in a stator housing which is fixed to the base body and with an inner ring directly or indirectly on the output shaft. 
     DESCRIPTION OF THE RELATED ART 
     A tool head of the type mentioned at the beginning is known (EP-1 222 983 B1) in which the essentially cylindrical motor housing of the adjustment motor is arranged axially centrally in the base body, and in which the stator housing has a casing part which engages axially over the outside of the stator and is fixedly connected to the stator in terms of rotation and displacement and an end part which closes off the casing part on the side lying opposite the transmission and is fitted with the outer ring of the second rotary bearing. This design requires a joint between the drive assembly and a transmission assembly, which itself requires a correspondingly large amount of expenditure on mounting. 
     BRIEF SUMMARY OF THE INVENTION 
     Taking this as the basis, the invention is based on the object of improving the known tool head of the type mentioned at the beginning to the effect that the expenditure on mounting is reduced when the tool head is assembled, and a shorter assembly length can be achieved. The feature combination is proposed as a means of solving this problem. 
     The solution according to the invention consists primarily in the fact that the stator housing has a sleeve part which partially engages over the stator axially on the outside and is fixedly connected to the stator in terms of rotation and displacement, and a bearing cover which closes off the sleeve part on the gear side and is fitted with the outer ring of the first rotary bearing. The output shaft is expediently arranged coaxially with respect to the rotational axis of the base body here. 
     A preferred embodiment of the invention provides that the second rotary bearing is arranged in a separate centering ring which is secured to the stator on the inside, on the side facing away from the bearing cover. In contrast to the prior art, the centering ring is not directly associated with the stator housing. Between the sleeve part and the centering ring there is instead a gap in the housing which is spanned by a base body wall. The respective base body wall is adapted in its contour to the outer contour of the stator in the spanned area. The second rotary bearing is advantageously secured by its outer ring to the centering ring and by its inner ring to the rotor. The adjustment motor can be embodied here as an asynchronous motor or as a DC motor. The stator of the adjustment motor expediently has a laminated core which surrounds the rotor and has winding heads which protrude at the ends. A particularly compact design is achieved by virtue of the fact that the stator engages with the associated winding head and/or part of its laminated core in the sleeve part, open at one end, of the stator housing and is secured therein and centered, while the centering ring engages in a free space in the other winding head and/or in the laminated core and is secured therein and/or centered. 
     The sleeve part is advantageously bonded or cast to the laminated core and/or the adjacent winding head, while on the other side the centering ring is connected in a positively locking fashion to the adjacent winding head and/or the laminated core and/or is bonded or cast with it. On one of its front ends, the adjustment motor is fitted with an encoder which is preferably arranged in an annular free space within one of the winding heads. 
     A down step transmission which is embodied as a harmonic drive transmission whose input and output shafts are preferably arranged coaxially in the base body is preferably used as the gear means. The output shaft of the rotor of the adjustment motor preferably engages in a coaxial drive opening of the input shaft of the step down transmission, while the inner ring in the first rotary bearing can be connected in a rotationally fixed fashion to the input shaft of the step down transmission, and the output shaft of the rotor is mounted indirectly in the first rotary bearing by means of the input shaft. 
     A further preferred embodiment of the invention provides that the harmonic drive transmission has an oval drive plate which is preferably coupled to the output shaft of the adjustment motor via the input shaft, an internally toothed ring which is fixedly connected to the base body in terms of rotation and has a flexible, externally toothed sleeve which is coupled to the output shaft. The rotor shaft and the adjoining transmission parts advantageously have an axially central cavity which is embodied as a cooling duct or as a functional feed through. 
     In order to avoid magnetic interactions between the adjustment motor and the bearing parts, according to one preferred embodiment of the invention it is proposed that the centering ring which engages in the stator be composed of a magnetically impermeable material and that at least the second rotary bearing be embodied as a hybrid bearing whose roller body is composed of an electrically insulating material, preferably of ceramic. 
     One of the two rotary bearings, expediently forms a fixed bearing, and the other forms a freely moving bearing which can move axially in relation to the latter. This measure allows stresses within the drive system, which can occur, for example, when there are changes in temperature, to be avoided. The first rotary bearing is expediently embodied as a fixed bearing and the second rotary bearing is embodied as a freely moving bearing. 
     A further advantageous or alternative embodiment of the invention provides for the adjustment motor, the gear means and the adjustable working slide to form an enclosed assembly which is detachably connected via a joint to a connecting assembly which has a connecting stem. The connecting assembly has, in this case, an axially open receptacle for an axially protruding part of the combined drive/gear/slide assembly which is embodied in the shape of a cup and can be equipped with the respective parts of the open side. 
     The invention is explained below in more detail with reference to an exemplary embodiment which is illustrated in a schematic fashion in the drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The single FIGURE shows a longitudinal section through a tool head which is embodied, for example, as a facing head and which is intended for use in machine tools. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The tool head is essentially composed of a base body  10  which can rotate about a rotational axis  12 , a working slide  16  which can be displaced transversely with respect to the rotational axis  12  in the base body  10  and is fitted with a cutting tool (not illustrated), an electric adjustment motor  24  which acts on the working slide  16  with the intermediate connection of a step down transmission  22 , and a tool stem  28  which protrudes axially over the base body  10  and which can be coupled to a machine spindle (not illustrated) of a machine tool. 
     The tool head is composed of three assemblies which are detachably connected to one another at joints  30 ,  32 , a slide assembly  34  which holds the working slide  16 , a drive assembly  36  which contains the adjustment motor  24  and the step down transmission  22 , and a connecting assembly  38  which is fitted with the tool stem  28  and has a cup-shaped receptacle  33  in the region of the joint  32 . The components of the drive assembly  36  and of the slide assembly  34  are premounted, forming a standard enclosed assembly, and are then inserted into the cup-shaped receptacle  33  of the connecting assembly  38 . The connection between the assemblies is made by means of screws  40 ,  42  which run axis-parallel. 
     The adjustment motor  24  is arranged axially centrally in the base body  10 . The exemplary embodiments shown are an electric motor which is embodied, for example, as an asynchronous motor and is composed of an annular laminated core  44  located on the outside, and stator  45  having two axially protruding winding heads  46 ,  48 , and a rotor  56  which rotates in the stator, is fitted with an output shaft  50  and is mounted in two rotary bearings  52 ,  54  which are arranged at a distance from one another. One of the rotary bearings  54  is arranged with an outer ring  58  in a stator housing  60  which is fixed to the base body and with an inner ring  62  which is arranged on the output shaft  50  of the adjustment motor  24 , indirectly via a drive shaft  64  of the step down transmission  22 . 
     A particular feature of the invention is that the stator housing  60  has a sleeve part  66  which partially engages over the stator  45  axially on the outside and is fixedly connected to the laminated core  44  of the stator in terms of rotation and displacement, and a bearing cover  68  which closes off the sleeve part on the gear side and is fitted with the outer ring  58  of the rotary bearing  54 . The bearing cover  68  and the sleeve part  66  may be constructed from one or more parts. 
     The other rotary bearing  52  is arranged in a separate centering ring  70  which is secured, on the side facing away from the bearing cover  68  of the stator housing  60 , on the rear winding head  46  on the inside or in the laminated core  44 . Between the free end  72  of the sleeve part  66  and the centering ring  70  there is a gap in the housing which is spanned by the inner face of the base body  10  in the region of the cup-shaped receptacle  33 . It has proven particularly advantageous if the centering ring  70  is bonded or cast in the interior of the stator  45  directly with the winding head  46  and/or the laminated core  44 . The connection between the sleeve part  66  and the stator  45  can also be made in a materially joined fashion by means of an adhesive or a sealing compound. 
     Within the front winding head  48  there is an annular free space  74  which can be used to accommodate an encoder  76  which is arranged between the stator and rotor. 
     The step down transmission  22  is expediently a harmonic drive transmission whose oval drive plate  82  is coupled by means of the engine-end output shaft  50  and the gear-end drive shaft  64 , whose internally toothed ring  86  is connected fixedly in terms of rotation to the base body  10  in the region of the drive assembly  36  using the screws  40 , and whose flexible, externally toothed sleeve  90  is coupled to the output shaft  92 . In the rotor  56  of the adjustment motor  24  and in the step down transmission  22  there is a central functional duct  94  to which a cooling lubricant can be applied, for example from the machine side. On the slide assembly side, the duct  94  is made to extend as far as the blade of the cutting tool (not illustrated). 
     To summarize, the following is to be noted: the invention relates to a tool head for use in machine tools. The tool head has at least one working slide  16  which can be adjusted in relation to a base body  10 , and has an adjustment motor  24  which is arranged in the base body  10  and acts on the working slide  16  via gear means  22 . The adjustment motor which is embodied as an electric motor has a stator  45  which is arranged in the base body and a rotor  56  which rotates in the stator, is fitted with an output shaft  50  and is mounted in two rotary bearings  52 ,  54  which are arranged at a distance from one another, wherein one of the rotary bearings  54  is arranged with an outer ring  58  in a stator housing  60  which is fixed to the base body and with an inner ring  62  directly or indirectly on the output shaft  50 . According to the invention, the stator housing  60  has a sleeve part  66  which partially engages over the stator axially on the outside and is fixedly connected to the stator  45  in terms of rotation and displacement, and a bearing cover  68  which closes off the sleeve part on the gear side and is fitted with the outer ring  58  of the first rotary bearing  54 . The second rotary bearing  52  is arranged in a separate centering ring  70  which is secured to the stator  45  on the inside on the side facing away from the bearing cover of the stator housing.