Abstract:
A machine tool comprising a machining spindle, a device for inserting an auxiliary unit into the machining spindle, a tool magazine for providing a multitude of tools and a tool changer comprising at least one tool gripper for holding tools for the machining spindle for the transportation of tools between the tool magazine and an exchange position at the machining spindle. To ensure an automatic supply to the machining spindle as well as to the auxiliary unit in a simple and fast way the tool changer has at least one additional tool gripper for holding tools for the auxiliary unit.

Description:
BACKGROUND 
     1. Field of Invention 
     This invention relates generally to machine tools, and more particularly to a machine tool having a machining spindle, a device for inserting an auxiliary unit into the machining spindle, a tool magazine for providing a multitude of tools and a tool changer having at least one tool gripper for holding tools for the machining spindle for the transportation of tools between the tool magazine and the machining spindle. 
     2. Discussion of Related Art 
     In known machine tools of the above mentioned type, for example, a high speed spindle or a polishing head insertable into the machining spindle, if necessary, are used as the auxiliary unit. Thus the speed range for certain machining operations can be increased and the application range of the machine tool can be widened. For high speed spindles or other auxiliary units, however, generally tool holding fixtures different from those used for the machining spindle are required. In conventional machine tools the tool exchange at the auxiliary units is therefore often effected manually or by separate changing devices. This is either time consuming or requires increased expenses with respect to construction and control. 
     SUMMARY OF THE INVENTION 
     It is a primary purpose of the invention to provide a machine tool of the above mentioned type enabling a fully automated supply of the respectively required tools to the machining spindle as well as the auxiliary unit to be inserted into the machining spindle in a simple and fast manner. 
     The most important advantage of the machine tool according to the invention is that not only different tools for the machining spindle but also a plurality of tools for an auxiliary unit inserted into the machining spindle can be provided for machining and may be automatically exchanged by a common tool changer. For the automatic exchange of the tools in the auxiliary unit no expensive additional driving and control elements are required. Thus a fully automated complete machining may be carried out without manual operations. 
     The tool changer comprises a quadruple gripper arrangement including two diametrically opposed tool grippers for holding tools for the machining spindle and two additional tool grippers respectively displaced by 90° with respect to these for holding tools for the auxiliary unit. By simply rotating the quadruple gripper arrangement by 90° the tool changer can thus be used as a double gripper for supplying tools to the machining spindle or as a double gripper for supplying tools to the auxiliary unit. By the respectively opposed pairs of grippers a previously used tool on the machining spindle can be replaced by a new tool taken out of the tool magazine beforehand by turning the gripper arrangement by 180°. Thus a fast tool exchange, including minimal control requirements, is enabled at the machining spindle as well as at the auxiliary unit inserted into the machining spindle. 
     The auxiliary unit may, for example, be a high speed spindle, a polishing head or any other assembly device by which the range of applications of the machine tool may be widened. 
     The tools are generally held in special tool holding fixtures by corresponding clamping cones. Since the tool holding fixtures for the machining spindle are, as a rule, larger than those for the tools of the auxiliary unit, the corresponding tool grippers for the respective tool holding fixtures are also of a different sizes. 
     In a constructively simple embodiment the tool gripper is disposed on a support horizontally movable on a frame of the tool magazine by means of a linear drive and can be rotated about a vertical axis by means of a motor. The horizontal movement of the support and the rotation of the tool gripper may be effected via electrical, hydraulic or pneumatic actuator drives. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The objects, advantages and features of the inventions will be more clearly perceived from the following description, when read in conjunction with the accompanying drawing, in which: 
     FIG. 1 is a perspective illustration of a machine tool constructed according to the invention; 
     FIG. 2 is a side view of a part of the tool magazine including a tool changer on the machine tool of FIG. 1; 
     FIG. 3 is a side view of the tool changer of FIG. 2; and 
     FIG. 4 is a plan view of the tool changer of FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The machine tool shown in FIG. 1 contains a machine bed  1  which has horizontal guide rails  2  on which table sled  3 , which is shiftable in the Y-direction by a motor (not shown), and a workpiece table  4  is disposed on the sled and is rotatable about a vertical axis. On machine bed  1  is disposed main frame  5  which includes vertical guide rails  6  and  7  on which transverse support  8  is guided, vertically shiftable in the Z-direction via threaded spindles  9  and  10  which are driven by a motor (not shown). On the front side of transverse support  8  are horizontal guiding rails  11  and  12  which provide for guiding machining unit  14  horizontally shiftable in the X-direction via threaded spindle  13  driven by a motor (not shown). Guide rails  11  and  12  for the machining unit, guide rails  6  and  7  for the transverse support, and guide rails  2  for the table sled are protected against contamination by different cover sheets  15 ,  16  and  17 , respectively. 
     Horizontally movable machining unit  14 , which is guided on transverse support  8 , comprises support housing  18  including face wall  19  inclined by 45° with respect to the vertical plane and oriented obliquely downwardly on which a pivotable milling head  20 , pivotable about a pivoting axis perpendicular to the face wall  19 , is mounted. In pivotable milling head  20  machining spindle  21  is disposed at less than 45° with respect to the pivoting axis. The milling head may be pivoted between the vertical machining posture shown in FIG. 1 and a horizontal machining posture by a corresponding rotation of pivotable milling head  21 . 
     Tool magazine  23 , formed as a chain hopper and comprising frame  22  and link chain  24 , circulates on the upper side of the frame. The chain is driven by a motor and includes tong shaped tool holders  25 . Tool magazine  23  is laterally disposed on machine bed  1 . 
     Also on the upper side of frame  22  is a device  27  for holding and inserting high speed spindle  28 . Device  27  comprises gripper arm  30  horizontally movable on guide arm  29  in which high speed spindle  28  is held by clamping cone  31  protruding upwardly. By horizontally shifting gripping arm  30  high speed spindle  28  can be moved into a replacement position under machining spindle  21  when the spindle is moved into an exchange position. By a vertical movement of machining unit  14  in the Z-direction high speed spindle  28 , including its clamping cone  31 , can then be inserted into machining spindle  21  and fixed there by corresponding standard or known clamping means. 
     Additionally, tool changing means  32 , including offset support  33  shiftable in the X-direction by a motor (not shown), is laterally disposed on frame  22 . Tool changer  34 , shown in detail in FIGS. 2-4 and turnable about a vertical axis, is mounted on support  33 . 
     As can be seen from FIG. 2 in particular, support  33  is guided on rail  35  attached to accommodation  36  which is laterally disposed on frame  22  in the embodiment shown. The horizontal movement of support  33  is effected by linear drive  37  which may be formed as a hydraulic, electric or pneumatic drive. At the front end of support  33  is disposed the tool changer which is turnable about a vertical axis by a drive (not shown). At the upper side of frame  22  is link chain  24  which includes tong shaped tool holders  25 . These are provided to hold tool holding fixtures  38  of different sizes for the tools of machining spindle  21  and for those of high speed spindle  28 . Tools having the maximum dimensions indicated by broken line  40  can be inserted into tool holding fixtures  38 , each of which is provided with clamping cone  39  protruding vertically upwardly. However, tools provided with a clamping cone formed directly thereon may also be held by tool holding fixtures  25 . Link chain  24  is driven by actuator motor  41  via an appropriate gear arrangement or a sprocket chain, for example. By correspondingly instructing actuator  41  the desired tools corresponding to the respective machining program can be moved into a predetermined exchange position in which tool changer  34 , including its quadruple gripper arrangement  42  shown in detail in FIGS. 3 and 4, can come into engagement with the tool or its tool holding fixture  38  with a corresponding horizontal movement of support  33 . 
     Two operating buttons  43  and  44  for releasing a gripper catch (not shown in detail) are disposed at the upper side of quadruple gripper arrangement  42 . Operating buttons  43  and  44  are operable by a wedge shaped operating element  45  at the bottom side of actuator arm  46  attached to frame  22  when the tool changer  34  is inserted into the tool magazine. 
     As shown in FIG. 3, tool changer  34  comprises support post  47  having a quadratic diameter on the upper side of which quadruple gripper arrangement  42  is arranged. At the bottom side of support post  47  tappet  48  is provided via which support post  47  is rotatably borne in support  33 . According to FIG. 4, quadruple gripper arrangement  42  comprises two diametrically opposed tool grippers  49  and  50  which are provided for removing or holding the tools insertable into machining spindle  21  or their tool holding fixtures. Two additional tool grippers  51  and  52 , which are also diametrically opposed, serve to remove and hold the tools insertable into the high speed spindle or their tool holding fixtures. Tool grippers  51  and  52  are arranged in an offset angle of 90° with respect to tool grippers  49  and  50 . Since high speed spindle  28  is designed to receive smaller tools or tool holding fixtures than the machining spindle, additional tool grippers  51  and  52  are correspondingly dimensioned smaller as well. 
     On the upper side of quadruple gripper arrangement  42  are arranged the two operating buttons  43  and  44 . By depressing the catch of the tool grippers for exchanging the tools preloaded to the inside, for example, by springs, the tools are released. 
     In the machine tool illustrated in FIG. 1, a tool exchange is effected as now described. For exchanging tools in machining spindle  21  tool magazine  23  is moved in correspondence with a predetermined machining program so that the desired tool holding fixture  25  containing the required tool is moved into a predetermined exchange position. Then support  33 , including tool changer  34 , is moved in the direction of tool magazine  23  from the standby posture shown in FIG. 2 until tool gripper  49 , directed to the tool magazine, comes into engagement with tool holding fixture  38 . After that, tool changer  34 , including the tool taken from the tool magazine  23 , is moved under machining spindle  21 , which has been shifted into a take-over position. Support  33  is moved away from the tool magazine so that empty tool gripper  50  can take up the tool positioned in machining spindle  21 . Then machining unit  14  is moved upwardly in a Z-direction after a per se known tool clamp within machining spindle  21  has been released. By a subsequent turn of tool changer  34  by 180° the new tool is then moved under the machining spindle. The machining spindle is then again moved in the Z-direction and the tool clamp is reactivated. By moving support  33  the previous tool can then again be placed in tool magazine  23 , and tool changer  34  is moved back to its standby posture by a corresponding movement of support  33 . 
     The exchange of the tools at high speed spindle  28  previously inserted into machining spindle  21  by device  27  is effected correspondingly. Tool changer  34  is first turned by 90° so that additional tool grippers  51  of  52  are used. 
     The invention is not limited to the embodiment described in detail and illustrated in the drawing. Thus, the tool magazine including the tool changing means may also be used for machine tools having another design. In addition, the different gripper for the tools of the machining spindle and the tools of the auxiliary unit may be disposed in a different orientation corresponding to the design of respective the machine tool. Instead of the complete tool changer only the quadruple gripper arrangement may also be formed in a turnable fashion.