Patent Publication Number: US-2006013675-A1

Title: Workpiece changer for machining machines

Description:
BACKGROUND OF THE INVENTION  
      The invention relates to a workpiece changer for the transfer of workpieces or workpiece palettes between a set-up station in front of a machining machine and a workpiece table of such machining machine, comprising a gripper means for taking up and putting down workpieces or workpiece palettes, a rotary drive for swiveling the gripper means about a vertical axis, and a lifting means for lifting and lowering the gripper means.  
     THE PRIOR ART  
      In the case of such a workpiece changer as disclosed in the European patent publication 1 321 224 B1 the gripper means is arranged pivotally on the free end of a pivotal lever. The combination of the two necessary pivotal movements requires a relatively complex kinematic control and the set-up station that must be arranged relatively close to the workpiece table, since it must be arranged within the range of pivoting of the pivotal arm.  
      A known workpiece changer disclosed in the German patent publication 19,853,945 A1 possesses a double gripper pivotal about a vertical axis having a vertically acting lifting means and. This workpiece changer requires at least one workpiece table able to travel in at least on a linear horizontal axis, of the machining machine and must therefore also be arranged directly on the machine frame of the machining machine. Since not all machining machines possess a workpiece table able to be shifted in this manner, this known workpiece changer has only an extremely limited range of application. It must be arranged directly on the machine frame of the machining center so that the work table of the machining machine is only accessible with substantial difficulty.  
      A workpiece changer disclosed in the European patent publication 1 201 354 A2 also possesses a double gripper able to pivot about a vertical axis, a set-up station being possibly arranged spaced apart from the machining machine. For this purpose an additional linear shifting arrangement is necessary, the transfer of workpieces or workpiece carriers between the double gripper and the linear shifting arrangement being however technically complex and slow. For the complete arrangement there is also a relatively large space requirement. Since the double gripper can not be spatially decoupled from the set-up station, its functionality is also limited.  
     SHORT SUMMARY OF THE INVENTION  
      One object of the invention is to provide a workpiece changer of the type initially mentioned, which is decoupled from the machining machine renders possible the transfer of workpieces or workpiece palettes between a set-up station relatively far from the workpiece table and such workpiece table and provides for satisfactory accessibility to the machining machine or, respectively, its workpiece table.  
      In order to achieve these and/or other objects appearing from the present specification, claims and drawings, the present invention provides a linear drive for shifting the gripper means between a first position at the set-up station and a second position at the workpiece table.  
      The workpiece changer in accordance with the invention renders possible very good accessibility to the machining machine, since during machining it can be shifted into a parked position, in which it is not in the way, by means of the linear drive. Accordingly the zone in front of the machining machine is kept clear for access by the operator. A linear movement of the workpiece table is not necessary so that the workpiece changer may be employed for the most various different types of machines. The gripper means may be decoupled both from the set-up station and also from the machining table that is to say from the machining machine. The gripper means performs all necessary movements so that only one shifting system is necessary and transfer operations for workpieces or palettes between the workpiece table and the set-up station are unnecessary.  
      The measures recited in the dependent claims constitute advantageous further developments and improvements in the workpiece changer defined in claim  1 .  
      The gripper means is arranged in a horizontally moving slide or carriage, which is provided with the lifting means and the rotary drive. This slide accordingly participates in all movements. It is advantageous for it to be guided on a lateral guide means, which is accordingly arranged with an offset in relation to the workpiece table and ensures even better accessibility.  
      The gripper means possesses a simple gripper or a double gripper having two grippers pointing in opposite directions. More particularly in the case of the design as a double gripper the changing operations may be implemented even more rationally, since simultaneously for example a workpiece being worked on the one side and an unworked workpiece on the other side (or workpiece palettes) may be shifted or transferred.  
      The gripper or grippers are designed to be placed underneath a workpiece or a workpiece palette and preferably possess two gripping and/or lifting arms. They may in principle be designed in accordance with the prior art initially referred t (for example the European patent publication 1 321 224 B1).  
      The gripper or grippers may also have two gripping and/or lifting arms, which are able to be shifted toward each other like gripping jaws. Accordingly different types of workpieces and/or workpiece palettes may be transferred.  
      The workpiece changer in accordance with the invention is best made in the form of a self-contained unit able to be positioned in front of the machining machine so that use is possible independently of the type of machining machine and simple upgrading of existing equipment is possible.  
      The arrangement in accordance with the invention provides a simple way of arranging storage for workpieces and/or workpiece palettes (between the storage, reloading station) to the side of the linear path of travel. This and/or at least a portion of the storage arrangement is in this case provided with a shifting drive perpendicular to the linear path of movement of the gripper means between the workpiece table and the set-up station. This storage arrangement may be operated with the same shifting mechanisms, in any case present, for the transfer of workpieces or workpiece palettes between the set-up station and the workpiece table. It is only necessary to have an additional shifting drive acting athwart the direction of movement of the linear drive.  
      The storage arrangement preferably possesses at least one change station for the transfer and receiving of workpieces or workpiece palettes by the gripper means, a conveyor means being provided for the supply and removal of palettes and/or workpiece receiving means to and from the working station. This conveyor means may be designed in the form of an endless conveyor means, more particularly a chain or a turntable or as a linear conveyor.  
      The conveyor means as a whole or its palettes and/or workpiece receiving means may in an advantageous design be provided with the shifting drive to the change station. In this case such a shifting drive for the gripper means is no longer necessary. Furthermore, it is also possible for the conveyor means as a whole or its palettes and/or workpiece receiving means may be provided with a reciprocating or lifting drive.  
      Further advantageous developments and convenient forms of the invention will be understood from the following detailed descriptive disclosure of embodiments thereof in conjunction with the accompanying drawings. 
    
    
     LIST OF THE SEVERAL VIEWS OF THE FIGURES.  
       FIG. 1  is a perspective representation in detail of a workpiece changer with a set-up station and a storage arrangement for workpieces and/or workpiece palettes as a first embodiment of the invention.  
       FIG. 2  shows a second embodiment of the invention in a view looking downward, with a modified shifting drive arrangement.  
       FIG. 3  shows a third embodiment of the invention in a view looking downward with a differently designed storage arrangement and an altered arrangement of the set-up station. 
    
    
     DETAILED ACCOUNT OF WORKING EMBODIMENTS OF THE INVENTION.  
      The workpiece changer represented in  FIG. 1  serves to transfer workpieces and/or workpiece palettes  10  between a workpiece table  11  of a machining machine  12  only depicted diagrammatically and a set-up station  13  and furthermore between a storage arrangement  14  for workpiece palettes  10  or workpieces and the workpiece table  11  and/or the set-up station  13 . In the case of the machining machine  12  it may be for example be a milling machine or a multiple machining machine such as a machining center that can perform further machining operations.  
      A slide arrangement  15  runs on two horizontal guide rails  16  of a guide means  17  which is located in the intermediate space between the workpiece table  11  and the set-up station  13 . A linear drive or linearly moving drive, not illustrated as for example a toothed belt, a linear motor drive, a lead screw drive or a fluid power drive, moves a first slide  18  horizontally along the guide rails  16 . On this first  18  a second slide  19  is vertically guided and driven and serves as a lifting means for a gripper means  20  arranged on its top side. This gripper means  20  is able to be pivoted by means of a rotary drive, not illustrated, about a vertical axis on the second slide  19 .  
      The gripper means  20  is designed in the form of a double gripper means and possesses two grippers  21  and  22  pointing in opposite direction which respectively possess two U-like gripper arms  23 . Such gripper arms serve to fit underneath and lift or lower workpiece palettes  10  or workpieces.  
      The set-up station  13  may be fixedly mounted on the entire workpiece changer means or may be designed in the form of a separate set-up table. A positioning means for workpiece palettes comprising three positioning elements  25  is arranged on a set-up plate  24 , the workpiece palettes  10  possessing bottom side recesses corresponding to this purpose. It is naturally possible for other known positioning means for workpiece palettes  10  or workpieces to be provided, which may also be interchangeable.  
      The storage arrangement  14  that for example is designed as an intermediate storage means for workpiece palettes  10  or workpieces and frequently is also termed a palette reloading station, is designed in the form of a rotary stepper means with a rotary drive, not illustrated in detail. A holding means  27  having four a palette receiving means  26  is able to be moved in steps about a vertical axis so that a palette receiving means  26  or a workpiece palette  10  on it is arranged at a change station  28 , which is positioned for the gripper means  20 . The entire storage arrangement  14  is arranged to the side of the guide means  17 , the change station  28  overlapping the guide means  17 .  
      In the view in accordance with  FIG. 1  the gripper means is positioned for receiving a workpiece palette  10  from the storage arrangement  14 . By lifting the second slide  19  the two gripper arms  23  of the one gripper  21  are fitted underneath the workpiece palette  10  on the change station  28  and start lifting it. After a pivoting movement through 90 degrees in the pivoting direction S and a following linear movement of the first slide  18  the workpiece palette  10  may be put down on the set-up station  13  and fitted with a tool in accordance with the operation to be performed or prepared for the machining operation in some other way. The lowering of the set-up station  13  is again performed using the second slide  19 . The workpiece palette  10  may however be directly supplied to the workpiece table  11 . For this purpose the gripper means  20  and the slide arrangement  15  perform a pivotal movement through 90 degrees in the opposite direction to the pivoting direction S and then the workpiece palette  10  may be supplied by means of a linear movement of the first slide  18  and following lowering to the workpiece table  11 .  
      During the transfer of a workpiece palette  11  between the set-up station  13  and the workpiece table  11  the gripper means  20  performs a pivotal motion through 180 degrees. This is for example the case, when a workpiece palette  10  prepared at the set-up station is supplied to the workpiece table  11  or when a workpiece palette  10  machined on the workpiece table  11  is then again supplied to the set-up station  13  in order to either clean or dismount the workpieces located thereon.  
      Since the gripper means  20  is designed in the form of a double gripper a workpiece palette  10  prepared for machining may for example supplied to the workpiece table  11 , the so far unengaged gripper firstly lifting a workpiece palette  10  (which has been handled) and after a pivoting operation through 180 degrees lowers the so far not handled workpiece palette  10  on to the workpiece table  10 . If the gripper means  20  in accordance with a simpler design has only one gripper, this multiple operation is naturally not possible, i. e. firstly a processed workpiece palette  10  must be taken from the workpiece table  11  and either handed over to the set-up station  13  or the storage arrangement  14  before a so far unprocessed workpiece palette  10  is collected from it and supplied to the workpiece table  11 .  
      The four palette receiving means  26  of the holding means  27  are also provided with corresponding positioning elements  25  in order to position the workpiece palette  10 . Since the storage means  14  in the illustrated working example is fitted with three workpiece palettes  10 , only one of the four palette receiving means  26  is visible.  
      If the gripper arms  23  should not extend as far as the change station  28 , the slide arrangement  15  or the individual palette receiving means  26  may be fitted with a shifting drive not illustrated in detail, which provides for horizontal shifting in the direction C normal to the direction A of motion of the linear drive of the first slide  18 .  
      The guide means  17  is laterally offset from the workpiece table  11  and the first slide  18  runs on this guide means  17 . Accordingly it is possible for the first slide  18  and with it naturally the second slide  19  and the gripper means  20  to be shifted away from the workpiece table  11  during machining so that satisfactory accessibility to same is ensured during machining. In an alternative design the guide rails may in principle also be arranged on the floor of the workpiece changer arrangement, it also being possible for the first slide  18  to be in the form of a carriage or the like.  
      In the working embodiment illustrated the gripper arms  23  of the grippers  21  and  22  are in the form of rigid arm and designed to fit underneath workpiece palettes  10 . Alternatively or in a complementary manner it is possible for the gripper arms  23  also to be moved toward one another like gripping jaws in order to engage different workpiece palettes  10  or differently shaped workpieces.  
      The arrangement of the set-up station  13  and of the storage arrangement  14  may also be reversed so that the storage arrangement  14  is then at the end of the guide means  17  and the set-up station  13  is arranged to the side of the guide means  17 . Moreover, in a simpler design it is possible to have only one set-up station  13  or only one storage arrangement  14 . More particularly in a case in which only one storage arrangement  14  is provided, in lieu of having the vertical stroke in the direction B performed by the second slide  19 , such slide may be dispensed with and the storage arrangement  14  or the holding means  27  or, respectively, the individual palette receiving means  26  may be provided with reciprocating means for motion in the vertical direction B. This as well makes it possible to lower palettes onto the gripper means  20  or to lift them therefrom. For depositing on the workpiece table  11  the latter must be then also provided with a vertical drive.  
      The overall workpiece changer arrangement may be permanently mounted on a machining machine  12  or as a complete workpiece changer arrangement only be placed in front of same.  
      The working example illustrated in  FIG. 2  is substantially similar to the example depicted in  FIG. 1 , identical or functionally equivalent components or subassemblies is being provided with the same reference numerals and not being described twice over. Unlike the first working example the storage arrangement  14  or its palette receiving means  26  lack a shifting drive acting in the shift direction C. Such a drive is accordingly integrated on the slide arrangement  15  for the gripper means  20 . This means that a third slide, not illustrated, of the second slide  19  is able to be moved in the shifting direction C by a motor. It is naturally also possible for such shifting drives to be provided in the storage arrangement  14  too.  
      In the second working embodiment the set-up station  13  is provided with a screen  29  extending vertically upward from the floor or from the plane of the set-up plate  24 . It comprises a fixed wall portion  30  and a pivoting wall portion  31 , which may be pivoted into the fixed wall portion  30  and beyond it in order to be able to prepare or fettle workpieces individually or held on a palette  11 .  
      It is also to be mentioned that the storage arrangement  14  is naturally not limited to having only four palette receiving means  26  and the number thereof may be smaller or more particularly larger.  
      In the case of the third working example illustrated in  FIG. 3  identical or functionally equivalent components or subassembly are again provided with the same reference numerals and not described twice over. Instead of the storage arrangement  14  having one rotary table or turntable there is now a storage arrangement  32  having two linear guides  33  and  34  along which the palette receiving means  26  are able to be shifted by means of linear drives, not illustrated, to and from change stations  35  and  36  in order to be accepted by the gripper means  20  or to be released by same. In the simplest case it is possible for there to be only one linear guide  33  or, respectively,  34  or a larger number of linear guides may be provided. After the removal or acceptance of a workpiece palette  10  or of a workpiece the respective palette receiving means  26  is shifted away from the respective associated change station  35  or, respectively,  36  in order to be removed or loaded at a transfer station leading to a principal storage means.  
      In this working example a set-up station  37  is provided having a set-up plate  38 , which for its part may be arranged at the end of the guide means  17  in a fixed or detachable manner. The set-up station  37  is here designed in the form of a set-up chamber having side walls  39 , sliding doors  40  being able to open the set-up station  37  toward the guide means  17  and shut it off therefrom. A door  41  for a set-up operator is also provided.  
      The guide means  17  as well is arranged in a guide chamber  42 , which has sliding doors  42  for entry. This guide chamber  42  adjoins a chamber-like surrounding wall  44  of the machining machine  12 , there again being sliding doors  45  opening for access to the workpiece table  11  or shutting it off.  
      The working examples in accordance with  FIGS. 2 and 3  as well may, in simpler designs, possess only one set-up station or only one storage arrangement, which may be positioned to the side or at the end of the guide means  17 .