Patent Publication Number: US-2023148187-A1

Title: Turret unit with b-axis and machine tool, in particular lathe

Description:
The present application relates to a compact turret unit for a machine tool, in particular lathe. 
     Conventional turret units as in DE 42 35 095 C2 have a tool turret having a turret body and a turret disk and tool holders for fixed and rotating tools, wherein a turret disk is supported by a hollow shaft. To drive the turret and the tools, gears are provided between the respective drive and the turret or the shaft. This requires a relatively large amount of space and increases the susceptibility to interference with each additional transmission component. Furthermore, resulting from the use of gearboxes inevitably asymmetries in the design that lead to the operation of the tool turret unit and the associated mechanical stresses to disadvantages due to the vibrations of the system and the uneven and thus less effective cooling. 
     In order to provide the tools for machining, tool carriers are supplied which are usually made available on movable tool carrier slides, in particular compound slides, which are arranged at the machine frame and can be moved by means of one or more linear axes relative to the work spindles (e.g. can be moved in three direction such as e.g. the X, Y or Z directions). Such machine tools of this type are known, for example, from EP 2 714 307 B1, EP 2 714 308 B1, EP 2 714 309 B1 or EP 2 714 310 B1. 
     For performing particular workpiece machining operations, it is frequently required that the overall turret be controllably revolved and, simultaneously, the machining tool must also perform a rotary movement. 
     It is an object of the present invention to provide an optimized turret unit which overcomes the problems of conventional turret structures. A further object is to provide a turret unit which requires reduced space and which at the same time has an increased rigidity and which allows to improve the machining accuracy of the machine tool. Moreover, it is an object to provide an optimized machine tool, in particular lathe. 
     To solve the problems the features of the independent claims are suggested. Preferred developments are in the dependent claims. 
     A turret unit according to an embodiment of the present application may comprise a turret main body configured to be mounted to a carrier support of the machine tool (and or a tool carrier support or assembly), and a turret head mounted to the turret main body and including a turret disk. The turret disk may be configured to be rotatable, by a first driving means, around a disk axis which is an axis of rotation of the turret disk. Said axis may preferably be the axis of symmetry of the preferably symmetric turret disk. The turret unit may include a second driving means for pivoting the turret head around a turret axis. The second driving means is a motor such as a direct drive motor, having a rotor arranged radially outside of the stator and the second driving means may be integrated in the turret main body. By providing this specific structure a compact and cost-effective assembly with increased rigidity can be achieved. Moreover by providing the turret unit according to the present invention, the unit can be placed at different carrier supports of the machine tool due to the symmetric design. 
     The second driving means may be integrated in the turret main body such that a cylindrical inner part (preferably most inner cylindrical part) of the turret main body forms the stator of the second driving means and/or a cylindrical outer part of the turret main body forms the rotor of the second driving means. Moreover the turret main body may have a cylindrical shape wherein the ratio of the length of the cylinder to the outer diameter thereof may preferably be in the range of 0.5 to 1.7 and more preferably about 1.2 for which significant vibration reduction can been achieved. Moreover, a compact and efficient turret unit can be provided. 
     The turret main body may include an inner cylinder part and an outer cylinder part wherein the outer cylinder part is provided to at least partially enclose the inner cylindrical part. The inner cylindrical part may include mounting surfaces for mounting the turret unit to the tool carrier assembly wherein on the inner surface of the outer cylinder part magnets of the rotor of the second driving means are attached. 
     The second driving means may be configured to directly (gearless) drive the turret head to pivot around the turret axis. Moreover the second driving means and a base of the turret head may provide a synchronized driving assembly. Accordingly a compact and efficient turret unit can be provided. 
     The turret head may be mounted directly to the rotor of the second driving means. Moreover, the turret main body may have a symmetric structure so that the turret unit can be used for left and right sides of the lathe or machine tool. In other words, the turret main body may be symmetric in view of the longitudinal axis thereof. A compact and efficient turret unit can be provided with increased rigidity. 
     The turret disk may be arranged such that the disk axis intersects with rotor magnets of the second driving means, preferably perpendicular. Accordingly a compact and efficient turret unit can be provided since the disk is arranged very close to the motor. The turret disk may comprise a controllably driven movable disk including a plurality of turret disk tool holder recesses, arranged in the circumferential direction of the disk, and so designed as to receive, for driving purposes, corresponding contoured end portions of the automatic machining tools. Moreover, the point of intersection of the disk axis with the turret axis may be within the axial range of the magnets of the rotor or inside the axial length of the rotor. 
     The turret unit may be an tool turret, and the form of such a tool turret may implement a disk turret which, to enable each tool to be moved into an operating position, can be turned in a controlled manner about a turret axis extending parallel to the workpiece spindle axis, at least in a lathe without a B-axis or in a lathe with a B-axis in the starting position of the tool turret. 
     The turret head can be rotated by at least 100 degrees, more preferably 110 degrees around the turret axis. Accordingly a compact and flexible turret unit can be provided. 
     The turret main body has a through hole located in the center and extending along the turret axis for allowing wires and hydraulic pipes to pass through. Accordingly a compact and efficient turret unit can be provided with increased rigidity. 
     The turret main body may have a flange part for attaching the turret unit to the carrier support of the machine tool and an inner shaft extending along the turret axis. Accordingly a compact and efficient turret unit can be provided. 
     The inner shaft may be attached to the flange part on one side and on the opposite side the inner shaft may be attached to the stator core of the stator. In a further development the flange part is integrated to the inner shaft (formed integrally). 
     The stator core of the second drive means may extend, in the axial direction, over half the inner shaft to thereby cover the center of the inner shaft. Accordingly, the length of the stator core may be more than 0.5 of the length of the inner shaft. 
     In an alternative embodiment the second drive means can be omitted and the structure of the turret main body includes instead, fixed shafts wherein on the outer circumferential surface of the shaft of the main body, the turret head is mounted. 
     The second driving means may be configured to directly pivot the turret head without a transmission in-between. Accordingly a direct drive can be implemented for the first and/or second and/or third driving means. 
     The turret head may be arranged on the circumference of the cylindrical outer part of the turret main body. For a particular compact structure and improved vibration characteristics the turret head mounting surface attached to the rotor may be arranged to coincide with the outer surface of the rotor of the second driving means. 
     The outer rotor surface may therefore be covered at least partially by the turret head. Preferably the disk axis and the turret axis may be arranged on separate, non-interfering planes. 
     The turret head may be arranged excentric to the turret main body and the turret disk may have a plurality of tool stations for carrying tools and at least one of said tool stations is equipable with a tool rotatively driven by a third driving means around a tool axis oriented preferably at a right angle to the axis of rotation of the turret disk. The axis of rotation of the third driving means may be coaxially to the center axis of a tool slot of the turret disk. 
     The third driving means may be arranged parallel and spaced apart and/or concentric to the disk axis and a coolant guide piston may be arranged to be parallel to the third driving means. Moreover, preferably a disk brake (extending in a radial direction) may be arranged between the rotor and stator of the second driving means. Accordingly, a disk brake may be provided between the outer cylinder part of the turret main body and the inner cylinder part of the turret main body. 
     The first driving means may be attached to a base of the turret head and the rotation axis of the first driving means may preferably be parallel and/or spaced apart from the disk axis. The hydraulic and/or electric lines of the third and first drive means may be connected in parallel to a main support part which extends through the through hole of the turret main body. 
     The turret main body may include an inner turret shaft which is the stator of the second driving means. 
     The first driving means may be arranged to extend away from the turret disk along the rotating axis of the first driving means and preferably orthogonal to the turret axis. Accordingly, improved movement space can be achieved with a compact structure. 
     The rotor of the second driving means may be supported via at least two bearings wherein at least one of the bearings includes a build-in encoder. Preferably, the bearing arranged closer to the mounting surface of the turret unit includes the build-in encoder. 
     Machine tool, in particular lathe, comprising a turret unit according to any of the preceding aspects. 
     The machine tool, in particular a lathe, may further comprise a machine frame having an upper tool carrier support portion, a lower tool carrier support portion and a spindle carrier portion arranged between the upper and lower tool carrier support portions, a spindle carrier, being arranged on or at a height of the spindle carrier portion of the machine frame, supporting a main spindle configured to receive a workpiece, the main spindle having a horizontally arranged spindle axis, one or more tool carriers, each tool carrier being supported on a tool carrier assembly being arranged on either the upper tool carrier support portion or the lower tool carrier support portion of the machine frame, wherein a lower side-surface of the lower tool carrier support portion, to which the one or more tool carriers are mountable, is arranged to have an overhanging inclination. Each carrier support portion and carrier portion is configured to preferably receive a turret unit. 
     Moreover, the lower side-surface of the lower tool carrier support portion may be inclined at an overhanging inclination angle in the range between 300 and 330 degrees, in particular at substantially 315 degrees. 
     The machine tool may be configured such that one or more or each tool carrier assembly is configured to independently move the respective tool carrier in one or more linear directions, including at least one of a Z-axis movement direction for moving the tool carrier horizontally in a direction in parallel to the spindle axis of the main spindle, an X-axis movement direction for moving the tool carrier radially with respect to the spindle axis of the main spindle, and a Y-axis movement direction for moving the tool carrier in a direction perpendicular to the spindle axis of the main spindle and perpendicular to the X-axis movement of the main spindle. 
     Method for machining workpieces using a machine tool with a turret unit of any preceding aspects comprising the step of pivoting the turret head around the turret main body axis to achieve a b-axis movement. 
     According to the aspects of the structure of the turret unit, a compact and cost-effective structure with increased rigidity can be achieved. Moreover by providing the turret unit according to the present invention, the unit can be placed at different carrier supports of the machine tool due to the symmetric design. 
     The disclosure of EP application with the application number EP 18191544.8 (EP 3616832) is herewith incorporated by reference. 
     Those skilled in the art will appreciate that various adaptations, modifications, and/or combination of the just described aspects can be configured. Therefore, it is to be understood that, further aspects may be practiced other than as specifically described herein. Those skilled in the art will also appreciate, in view of this disclosure, that different aspects described herein may be combined to form other aspects of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    exemplarily illustrates a schematic perspective view of a multi-spindle lathe having turret units and details of the turret unit; 
         FIG.  2    exemplary illustrates a schematic perspective view of the tool carrier assembly; 
         FIG.  3    exemplary illustrates a detailed view of the turret unit; 
         FIG.  4    exemplary illustrates a detailed overview of the turret unit; 
         FIG.  5    exemplary illustrates a sectional view of the turret main body; 
         FIG.  6    exemplary illustrates a sectional view of the turret head and different pivoting positions thereof; 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS AND DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In the following, preferred aspects and embodiments will be described in more detail with reference to the accompanying figures. Same or similar features in different drawings and embodiments are referred to by similar reference numerals. It is to be understood that the detailed description below relating to various preferred aspects and preferred embodiments are not to be meant as limiting the scope of the present invention. 
       FIG.  1    exemplarily shows a schematic perspective view of a lathe L according to an exemplary embodiment of the present invention. The lathe L is exemplarily realized as a turret lathe which comprises a machine frame for preferably supporting four tool carrier assemblies  150 , a work piece carrying main spindle supported by a main spindle carrier and a work piece carrying counter spindle supported by a counter spindle carrier in order to provide more efficient work piece processing. The lathe L according to the present invention includes an auxiliary spindle carrier  130  arranged to be between the main spindle carrier and the counter spindle carrier. 
     Moreover, a turret unit T is mounted to the tool carrier assembly  150  and/or the main spindle carrier or counter spindle carrier. 
     In order to provide efficient and cost effective work piece machining, the present invention suggests a superior turret unit T which, on the one hand, requires a reduced mounting space on the machine tool and at the same time has a significantly improved vibration characteristic and mechanical stiffness. Other than for conventional systems an inverted motor concept is combined with a gearless design while at the same time omitting the torque transfer shaft, in one embodiment. 
     As shown in the left side of  FIG.  1   , the turret unit T has a compact design due to the inverted motor configuration and the gearless torque transmission. The turret unit T includes the turret main body M which can be attached via the attachment section M 1  of the turret main body to the tool carrier assembly  150 . The attachment section M 1  is arranged at the rear side of the turret main body M and the opposing side thereof, which may be referred to as the front side of the main body M is a free end of the turret main body M. While conventional turret units include a separated turret main body from a driving means for controlling the pivot of the turret head H around the B axis or Y axis, the present invention suggests an integrated driving means which is referred to as the second driving means D 2 . Said second driving means B 2  is integrally formed in the turret main body M as a structural part thereof. As such, the outer cylindrical part of the turret main body M and the inner cylindrical part of the turret main body are respectively designed as the actual rotor and stator of the second driving means D 2 . As shown in  FIG.  1    in the left side, the outer cylindrical part of the turret main body M is rotatable around the Y axis. This movement is commonly referred to as B axis movement. 
     In the example shown in  FIG.  1   , the Y axis which is the rotation axis of the turret main body (or turret rotation axis) extends orthogonally to the spindle axis of the main spindle. In order to change the turret head position, the B axis movement is integrated into the lathe such that the turret head H and the turret disk H 2  can be rotated around the Y axis such that different tools or work pieces which are attached to the turret disk H 2  can be flexibly arranged in relation to the main or auxiliary spindle allowing flexible and efficient machining of work pieces. The lathe according to the present invention is also superior to conventional lathes since the tool carrier assembly allows movement in vertical and horizontal direction of the turret unit T, as clear from e.g.  FIG.  2    wherein in combination with the turret unit T which allows a B axis movement very efficient processing of the work pieces can be achieved. 
     As clear from  FIG.  1   , the turret head H includes a base of the turret head H 1  and a turret disk H 2 . The turret disk H 2  has a rotation axis X. The turret disk H 2  is configured to rotate around said turret disk rotating axis X. The revolving turret disk H 2  has slots for machine tools and/or work pieces. Moreover, the turret disk H 2  has an integrated third driving means D 3  which allows to drive the tools attached or inserted into the slots of the turret disk H 2 . Preferably, the third driving means is a direct drive motor. 
     The arrangement of the turret disk H 2  extends in a radial direction of the Y axis of the turret main body M. Accordingly, the turret disk H 2  is arranged outside of the turret main body M in the radial direction. With regard to the axial direction of the Y axis of the turret main body M, the turret head H does not extend further than the free end of the turret main body M. The turret head H extends in the axial direction of the Y axis of the turret main body M, approximately to the end surface of the free end of the turret main body M. Accordingly, a very efficient and compact design can be achieved and the distance between the turret disk H 2  and the attachment section M 1  of the turret main body can be minimized. Inventors have realized such a specific design can significantly increase the mechanical stability and accuracy of the turret unit and the entire lathe L. 
     The turret head H has a flat turret design such that a base H 1  of the turret head H is flat. Attached onto said base H 1  the turret disk H 2  is rotatably provided. The turret disk H 2  is rotatable around the X axis. Preferably the X axis is approximately perpendicular to the Y axis of the turret main body M. For further flattening the turret head H, the additional driving means necessary for rotating the turret disk H 2  is arranged as a first driving means D 1  on top of the base H 1  of the turret head and covering the part of the outer cylindrical shaft of the turret main body M. The first driving means D 1  extends away from the turret disk H 2  along the X axis. The base of the turret head H 1  with the attached first driving means D 1  form an L shape which is arranged to enclose the turret main body M to thereby achieve a vibration-resistant and compact turret unit T which can be flexibly attached to each of different tool carrier assembly positions of the lathe L or a machine tool. The radially outer circumferential surface of the turret main body M therefore is the mounting surface of the turret head H so that said turret head H can be attached radially spaced from the turret rotating axis Y. 
     In  FIG.  2    a schematic perspective view of the tool carrier assembly  150  is shown. Exemplary all 1, 2, 3 or 4 tool carrier assemblies  150  raised on the machine frame of the machine tool may be realized similarly. Accordingly, due to the symmetric design of the tool carrier assembly as well as the turret unit T, flexible and interchangeable turret positioning can be achieved for the machine tool. More specifically, due to the specific design of the turret unit, said turret unit can be placed on each of the four positions of the tool carrier assembly of the lathe as shown in e.g.  FIG.  1   . Depending on the respective position on the lathe, the turret head H position can be rotated around the Y axis of the turret main body M. Accordingly, for equipping the lathe L with four turret units T, only a single type of turret unit T is necessary and four identical turret units T can be mounted on the respective mounting positions of the lathe L. Accordingly, with the turret unit T of the present application, a flexible and cost efficient machine tool and lathe can be provided. 
     The tool carrier assembly  150  in  FIG.  2    includes a carrier support slide  151  which is configured to be slidably mounted to the guides of the upper and lower support portions of the machine frame of the lathe or machine tool. Accordingly, when mounted on top of the upper support portion on the guides, the carrier support slide  151  is configured to be moved horizontally on and along the guides in the Z axis in the horizontal direction in parallel to the horizontally and coaxially arranged spindle axis of the spindles. On the other hand, when mounted in a hanging state at the overhanging lower support position at the guides, the carrier support slide  151  is configured to be moved horizontally along the guides in the Z axis in the horizontal direction in parallel to the horizontally and coaxially arranged spindle axis of the spindles. 
     On the front side of the carrier support slide  151  of the tool carrier assembly  150  facing the machining area of the machine tool or lathe in between the spindles, a tool carrier support slide  152  is slidably mounted to the carrier support slide  151 . The tool carrier support slide  152  is configured to be moved vertically on and along vertical guides arranged on a front face of the carrier support slide  151 . Moreover, on the front side of the tool carrier support slide  152  of the tool carrier assembly  150 , facing the machining area of the machine tool between the spindles, a horizontally arranged tool carrier quill or turret  153  extending from the front side of the tool carrier support slide  152  vertically into the machining area of the machine tool is exemplarily provided to mount a tool carrier. Accordingly, the turret  153  as shown in  FIG.  2    may also be a turret unit T in accordance with e.g.  FIG.  1    including the turret head H. Please note that in an alternative embodiment the turret main body M may also be fixed and therefore no rotation around the B axis may be possible for specific applications. Remaining features, however, are the same as in the embodiment shown in  FIG.  1   . 
       FIG.  3    shows a detailed view of the turret unit T and specifically the turret head H. Moreover, in  FIG.  3    the piping and wiring for the hydraulic and electric systems of the turret unit T are indicated. To allow and efficient and optimized wiring and piping, the turret main body M includes a hollow shaft as the innermost cylindrical part. Accordingly, a through hole  24  exists which extends through the turret main body M in the axial direction along the Y axis to provide an opening for the piping and wiring in order to connect the turret head H with the hydraulic system and electric system in an improved manner. 
     As already shown in  FIG.  1   , the attachment section M 1  of the turret main body M is arranged opposite to the free end side of the turret main body M. The turret main body M includes the integrated second driving means D 2 . Said driving means D 2  includes the rotor D 2 R of the second driving means D 2  which is arranged outside of the stator D 2 S of the second driving means. On the outermost surface on the circumference of the rotor of the second driving means D 2 R the base of the turret head H 1  is attached to the turret main body M. 
     The central hydraulic L 1  includes a plurality of hydraulic and/or electric coupling portions for connecting with hydraulic lines. More specifically, bending hydraulic lines L 2  are connected to the respective connection sections of the central hydraulic lines L 1 . These bending sections are configured to be bent depending on the pivoting angle of the turret head H around the Y axis and therefore independent of the axis movement. 
     Preferably, the bending sections can be bent by 90 degrees and more preferably 120 degrees such that a safe hydraulic connection between the central hydraulic line L 1  and the turret head H can be assured, even if the turret head H is pivoted around the Y axis. The bending movement of the bending sections of the hydraulic lines L 2  is configured such that twisting of the pipes and wires along the longitudinal axis can be avoided. Accordingly, with a specific B axis movement of the turret unit also a very reliable, compact and comprehensive connection with the pipes and wires of the electric and hydraulic system can be achieved since bending in the longitudinal direction or the twisting around the longitudinal axis can be avoided and instead only bending around the lateral axis of the pipes is necessary, as also derivable from  FIG.  3   . 
     The central hydraulic line L 1  is connected to the stator of the second driving means D 2 S which forms the innermost cylindrical hollow section of the turret main body M. Via the bending sections of the hydraulic and electric wires a connection of the central hydraulic lines L 1  to the hydraulic attachment side on the rotor of the turret main body M and specifically the rotor of the second driving means D 2 R can be achieved. Accordingly, the outer hydraulic connecting section L 3  is provided which is preferably fixed to the rotor of the second driving means D 2 R. Further, the hydraulic pipes are connected to the base of the turret head H 1  and to hydraulic means attached to the rotor D 2 R. Also electric wires may preferably be included be connected, accordingly. 
     The turret head H has a flat design by having a plate-shaped base of the turret head H 1  which is attached preferably directly to the rotor D 2 R of the turret main body M. The plate-shaped base of the turret head H 1  may include guides for accurately positioning the turret head on the rotor D 2 R. For fixing the base of the turret head H 1  to the rotor D 2 R preferably a plurality of bolts and screws are provided. 
     Moreover, the base of the turret head H 1  provides a support for the turret disk H 2 . Accordingly, the turret disk H 2  can be rotated in relation to the base of the turret head H 1 . The rotation of the turret disk H 2  is preferably around the X axis of the turret disk H 2 . The turret disk H 2  has a plurality of tool receiving slots  35  with disk surfaces  34 . The tool receiving slots  35  extend in a radial direction of the turret disk H 2  towards the X axis of the turret disk H 2 . Preferably, the turret disk H 2  has at least 12 or 16 tool receiving slots  35  for receiving the respective tools. The hydraulic and electric connection of the turret disk H 2  is preferably achieved via the base of the turret head H 1 . Accordingly, the base of the turret head H 1  includes the connection portions of the pipes and wiring to the rotor connection part L 3 . 
     In order to achieve the rotary movement of the turret disk H 2  around the X axis of the turret disk H 2 , the first driving means D 1  is provided. Preferably, the first driving means D 1  is attached via the gear D 10  directly to the base of the turret head H 1 . The first driving means D 1  extends away from the turret disk H 2  over the turret main body M so that the base of the turret head H 1  and the first driving means D 1  have an L shape which encloses at least partially the outer circumference of the turret main body M to achieve a very compact and vibration resistant structure. In the axial direction of the turret disk H 2 , the cover  33  is provided which can be removed for maintenance. 
       FIG.  4    shows another sectional view of the turret unit T with the mounted turret head H. The plane A and B are indicative of the respective sectional views of the turret unit. 
     In  FIG.  5    a sectional view corresponding to the plane extending along the axial direction of the turret main body M, as shown in  FIG.  4   , is displayed. On the left side of the turret main body M the attachment section M 1  of the turret main body is indicated. Said attachment section M 1  is provided for attaching the turret unit T to the tool carrier of the machine tool. Preferably, the left side or the attachment section M 1  of the turret main body M is therefore fixed to the tool carrier of the machine tool or lathe. A compact design can be achieved by integrating the stator of the second driving means D 2  with the fixed part of the turret main body M as shown in  FIG.  5   . Accordingly, the actual stator of the second driving means D 2 S may be regarded as the shaft assembly including the attachment section M 1  with the flange part  32  to which the inner shaft  28  is fixedly connected. Onto said inner shaft  28  the stator core  22  can be fixedly attached. For achieving a specific efficient and compact design and increased machining accuracy, the disk break B is provided on the circumferential outer side of the stator D 2 S adjacent to the flange part  32  and the attachment section M 1 . The length of the disk break B may extend in the radial direction of the stator core  22 . 
     The support of the rotor D 2 R of the second driving means D 2  is achieved by providing the front bearing  25  and the bearing  26  (preferably a roller bearing). In a development, the roller bearing  26  includes the built in encoder for allowing highly accurate control while at the same time achieving compact design by using the integrated encoder. Accordingly, the turret unit T can be designed even more compact. 
     The front bearing  25  of the turret main body M for supporting the rotor D 2 R of the second driving means D 2  is preferably arranged at the free end of the turret main body M. Opposite to said side, the roller bearing  26  is provided adjacent to the flange part  32 . Between said bearings, the rotor D 2 R provides an attachment section onto which the turret head H is mounted. Preferably, the attachment section does not extend in the axial direction along the Y axis of the turret main body beyond the front bearing  25  or the roller bearing  26 . In other words, preferably the fixing and attachment parts of the attachment section for fixing the turret head H onto the rotor D 2 R are provided between the front bearing  25  and the roller bearing  26 . More preferably, the attachment sections including the attachment holes and guides for attaching the turret head H onto the rotor D 2 R are provided radially above the stator core  22  and the magnets  21  of the rotor D 2 R such that the distance between the attachment section and the base of the turret head H 1  and the magnets  21  of the rotor D 2 R can be minimized. As shown in  FIG.  5   , the first driving means D 1  is provided directly above the magnets  21  of the rotor D 2 R and directly above the stator core  22  so that preferably the first driving means D 1  does not extend in the axial direction along the Y axis, beyond the axial length of the magnets  21  and/or the axial length of the stator core  22 . 
     The second driving means D 2  is configured to be a gearless drive for allowing gearless driving (direct drive) of the turret head H to pivot around the turret axis Y. More specifically, an inverted motor is provided, integrated into the structure of the turret main body M. Said inverted motor has a stator which at the same time is also used as the inner shaft of the turret main body M. The outer shaft of the turret main body M is configured as the rotor D 2 R of the second driving mean D 2 . Due to this design, mainly providing the rotor with the magnets  21  of the rotor on the outside and the stator core  22  on the inside in a radial direction the size of the magnets  21  of the rotor can be significantly reduced. Accordingly, the diameter of the turret main body M in the radial direction thereof can be significantly reduced so that the mechanical load can be reduced. 
     The specific design as described with the inverted motor concept implemented as a structure of the turret main body M synergistically lead to the effect of a compact turret unit design with increased accuracy resulting from reduced mechanical stress. In other words, the compact design with inverted motor concept and the reduced thickness of the magnets  21  can reduce the distances and mechanical forces and therefore the resulting moment applied to the turret unit during movement and during the working process as well as the forces applied during static use cases. 
     In order to further reduce the size of the turret unit T and, at the same time, assure efficient connection of the hydraulic and/or electric means of the turret unit T a main body through hole  24  is provided which extends preferably through the entire turret main body M. Accordingly, wiring and pipes and hydraulic lines  23  can extend along the Y axis of the turret main body M. In order to connect the inner shaft  28  with the flange part  32 , fixing means  30  and  31  are provided which are, for example, bolts or screws for tightly attaching the related parts. Accordingly, the stator core  22  can also be safely attached to the inner shaft  28 . 
     The rotor D 2 R of the second driving means D 2  includes the magnets  21  which are arranged on the circumferential inner side of the rotor D 2 R. Preferably, the rotor D 2 R also includes an outer shaft which has the mounting surface for attaching the base of the base H 1  of the turret head H. Accordingly, the turret head H can be attached directly to the rotor D 2 R of the second driving means D 2 . For achieving an improved support of the rotor D 2 R the front bearing  25  is attached to the rotor D 2 R via the rotor fixing cover  29  attached at the free end of the turret main body M. For further reducing the mechanical stress, the front bearing  25  is arranged in a radial direction inside of the magnets  21  of the rotor D 2 R. At the same time, the roller bearing  26  is arranged radially more distant from the X axis than the front bearing  25 . Accordingly, the roller bearing  26  which is closer to the attachment section M 1  has a larger diameter than the front bearing  25 . 
     One aspect of the present application is that the turret head H is attached closely to the second driving means D 2 . For example, the rotating axis of the turret disk H 2  which is referred to as the X axis in e.g.  FIG.  1    is arranged such as to intersect with the magnets  21  of the rotor so that as a result the turret head H is arranged in close proximity to the driving means D 2  which may also be a direct drive motor. More preferably, the rotating axis of the turret disk H 2  has an intersection preferably perpendicularly, with the outer circumferential side of the magnets  21  of the rotor. Accordingly, in order to transmit the torque of the second driving means D 2  for rotating or pivoting the turret head H no extra transmissions shaft is necessary since the turret head is fixed directly on the outer surface of the rotor D 2 R. Accordingly, the axial distance between the center of the second driving means D 2  and the rotating axis X of the turret disk H 2  is reduced to a minimum and can preferably be held close to 0. Accordingly, in one preferable application the rotating axis X of the turret disk H 2  is placed congruent to the axial center of the second driving means D 2  and specifically the center of the stator core  22  and/or the center of the rotor D 2 R in the axial direction with regard to the Y axis of the turret main body M. 
     In other words, with regard to the attachment section M 1  of the turret main body M, the turret unit T of the present application allows that the second driving means D 2  is arranged on the same side of the turret main body M as the turret head H (in view of the flange) so that a transmission shaft for transmitting the torque from a distant driving means to the actual turret head can be avoided. At the same time, the pipes and wiring  23  are provided at the Y axis which is the rotating axis of the turret main body M allowing the B axis movement. Moreover, it may also be clear that with regard to the section shown in  FIG.  5    the design of the turret main body M can be regarded as symmetrical which allows a flexible use of the turret unit for the machine tool and different positions on the machine tool respectively. Accordingly, the turret main body M is configured to be symmetrical with regard to a plane extending along the rotating axis of the turret body and specifically the rotating axis Y. In other words, the turret unit T uses a symmetric turret main body M. 
       FIG.  6    shows a view along the Y axis with sectional view of the turret head H. The turret disk H 2  is provided with several tool receiving slots  35  regularly arranged around the outer circumference of the turret disk H 2 . The respective slots extend in the radial direction of the turret disk H 2 . A coolant guide piston  36  is provided parallel to a driving means arranged in the center of the turret disk H 2 . More specifically, the third driving means D 3  is a motor provided at the inside of the turret disk H 2 . Parallel to said third driving means D 3 , the coolant guide pistons  36  is provided in close proximity to the tool receiving slots  35 . Due to the close arrangement of the coolant guide piston  36  the distance for the coolant to be provided to the tool receiving slots  35  and respectively to the tools applied into the tool receiving slots can be reduced significantly. Accordingly, the compact design of the turret unit can be further improved and be made even more compact while at the same time assuring coolant to be provided the respective tools. In other words, the coolant guide piston  36  is provided spaced apart in the direction along the X axis and parallel to the symmetry axis of the turret disk H 2 . The driving axis of the third driving means D 3  can be provided parallel to the center line of the tool receiving slots  35  and the respective tools to be inserted into the tool receiving slots. 
     The first driving means D 1  is applied to extend over the outer circumferential surface of the turret main body M. The first driving means D 1  is connected via the outer gear part D 10  and the inner gear part D 11  with the base H 1  of the turret head H. The base H 1  of the turret head H combined with the first driving means D 1  form an L shape which at least partially encloses the outer circumferential surface of the turret main body M (preferably in a vertical and horizontal direction). Moreover, as shown in  FIG.  6   , the entire turret head (H) having the x-axis as a center axis may be pivoted, as clear from the two positions for the x-axis shown in the figure. 
     As can be seen in  FIG.  6   , the stator core  22  of the stator body D 2 S and the magnets  21  of the rotor D 2 R are arranged in a radial direction very closely to the attachment surfaces and attachment means of the turret head H and specifically the base of the turret head H 1 . The center of the turret head is arranged outside of the rotating axis of the turret main body M and more specifically the turret head H and the center of the turret disk H 2  are arranged radially spaced apart from the rotating axis of the turret main body and the stator core  22  of the second driving means D 2 . 
     The turret head H 1  has a base through hole  38  provided for the wiring. Accordingly, by providing this additional through hole  38 , it is possible to include wiring through the base of the turret head for attaching hydraulic and/or electric lines of the turret head. 
     By exemplary embodiments as described above, there are proposed beneficial aspects and features to enhance the machining options of the turret unit and machine tool, specifically lathe, to provide a compact machine concept, allowing for more flexible, accurate, efficient and reliable machining operations, and/or to improve accuracy and/or stability of the machine tool. 
     While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and are not restrictive on the broad invention, and that the embodiments of invention are not limited to the specific constructions and arrangements shown and described, since various other changes, combinations, omissions, modifications and substitutions, in addition to those set forth in the above sections, are possible. 
     Those skilled in the art will appreciate that various adaptations, modifications, and/or combination of the just described embodiments can be configured without departing from the scope of disclosure of the present invention. Those skilled in the art will also appreciate, in view of this disclosure, that different embodiments of the invention described herein may be combined to form other embodiments of the invention. Therefore, it is to be understood that, the invention may be practiced other than as specifically described herein.