Abstract:
A machining device for material-removing machining of a workpiece includes a stationary frame, a workpiece magazine, a workpiece slide movable relative to the frame and accommodates a workpiece and a housing which encompasses a machining chamber and is located outside the workpiece magazine, wherein the workpiece magazine accommodates a plurality of workpieces, the workpiece magazine moves workpieces to an interchange point, the workpiece slide imparts translational movement to a workpiece along an X axis during workpiece machining and the workpiece slide is movable along the X axis to such an extent that the workpiece located on the workpiece slide is movable to the interchange point disposed outside the machining chamber encompassed by the housing.

Description:
RELATED APPLICATIONS 
     This is a §371 of International Application No. PCT/EP2010/000198, with an international filing date of Jan. 15, 2010 (WO 2010/081711 A1, published Jul. 22, 2010), which is based on German Patent Application Nos. 10 2009 005 945.8, filed Jan. 16, 2009, and 10 2009 011 672.9, filed Feb. 24, 2009, the subject matter of which is incorporated by reference. 
     TECHNICAL FIELD 
     This disclosure relates to a machining device for machining a workpiece, more particularly for machining a workpiece or a blank for the fabrication of a dental prosthetic item or a dentition model. 
     BACKGROUND 
     A generic machining device comprises a stationary frame, a workpiece magazine, and a workpiece slide capable of being moved relatively to the frame and adapted to accommodate one workpiece. The workpiece magazine is configured to accommodate a number of workpieces that can be moved by the workpiece magazine to an interchange point. Furthermore, the workpiece slide is configured to carry out a translational movement of the workpiece along an X axis when the workpiece is being machined, for example, in a milling, drilling, and/or grinding operation. 
     Generic machining devices are known. In such generic machining devices, the workpiece magazine serves to accommodate a plurality of workpieces so that the workpiece can be interchanged automatically without manual intervention when one workpiece has been machined to completion and a new workpiece is to be mounted on the workpiece slide for machining purposes. The known machining devices usually comprise a separate manipulating mechanism that serves to transfer a workpiece from the workpiece magazine to the machining position. For this purpose, the manipulating equipment picks up a workpiece located at the interchange point of the workpiece magazine and keeps it in the machining position for subsequent machining Pallet systems are also known in which pallets, together with workpieces clamped thereon, are moved automatically to a machining position, in which machining then takes place while the pallet remains stationary. 
     The disadvantage of that known design is that the manipulating equipment requires additional space and involves additional costs. Particularly in the case of machining devices configured to produce dental prosthetic items from blanks, the additional space required by the manipulating equipment is a drawback since these devices are intended to have a space-saving design to allow them to be set up in a dental laboratory or a dentist&#39;s premises. 
     It could therefore be helpful to improve a generic machining device, especially to the effect that workpieces can be transferred from the workpiece magazine to the machining position on the workpiece slide without incurring the drawbacks of the prior art. 
     SUMMARY 
     We provide a machining device for material-removing machining of a workpiece including a stationary frame, a workpiece magazine, a workpiece slide movable relative to the frame and accommodates a workpiece, and a housing which encompasses a machining chamber and is located outside the workpiece magazine, wherein the workpiece magazine accommodates a plurality of workpieces, the workpiece magazine moves workpieces to an interchange point, the workpiece slide imparts translational movement to a workpiece along an X axis during workpiece machining, and the workpiece slide is movable along the X axis to such an extent that the workpiece located on the workpiece slide is movable to said interchange point disposed outside the machining chamber encompassed by the housing. The X axis is defined as an imaginary straight line extending between the workpiece maching chamber and the interchange point. 
     Our machining device includes a workpiece slide that can be moved along the X axis to such an extent that the workpiece mounted on the workpiece slide can move to the interchange point. 
     Separate manipulating equipment for manipulating the workpieces is thus completely unnecessary. Instead, the capability of the workpiece slide to move along the X axis for machining purposes is implemented for the purpose of moving the workpiece to the interchange point. For this purpose, the interchange point is arranged to be in alignment with the path of movement of the workpiece along the X axis. Preferably, the capability of the workpiece to move along the X axis provides the only way of displacing the workpiece relatively to the tool along the X axis. 
     With regard to the workpiece magazine, the aforementioned interchange point can be reached by the workpiece to be mounted on the workpiece slide without previously effecting removal of this workpiece from the other workpieces. Preferably, the workpieces are capable of being moved automatically along a common path of movement, the interchange point being located in this path of movement. Collective movement of all of the workpieces accommodated in the workpiece magazine thus makes it possible to move the workpiece intended for the machining operation to the interchange point. When this workpiece has reached the interchange point, the drive for the workpiece magazine is stopped so that the workpiece in question ceases to move at the interchange point. It can be picked up directly by the workpiece slide in that the workpiece slide is moved beyond the boundary of the machining chamber in which the workpiece slide is moved for the purpose of machining the workpiece. The workpiece slide is moved out to such an extent as to make it possible to couple the workpiece to the workpiece slide. Once the workpiece slide has been coupled to the workpiece, the workpiece is moved away from the interchange point by the workpiece slide into the machining chamber. 
     Preferably, a coupling mechanism is provided on the workpiece slide, which coupling mechanism can be activated by a control unit pertaining to the machining device and by which a workpiece located in a coupling position can be securely connected to the workpiece slide. 
     In the case of an interchange of a previously machined workpiece with a workpiece yet to be machined, the previously machined workpiece is first inserted by the machining device into a slot of the workpiece magazine at the interchange point. If this workpiece had previously been securely connected to the workpiece slide by the aforementioned coupling mechanism, the previously machined workpiece is decoupled from the workpiece slide at the interchange point. Then a new workpiece is moved to this interchange point by the drive for the workpiece magazine, which workpiece is then picked up by the workpiece slide or coupled by the coupling mechanism to the workpiece slide. 
     Preferably, the workpieces are each fastened to a workpiece holder, the workpiece magazine and the workpiece slide being configured to manipulate these workpiece holders. Thus, in such an example, it is not merely the workpieces or blanks that are transferred from the workpiece magazine to the workpiece slide, but instead this action is carried out by the workpieces or blanks together with a workpiece holder firmly attached thereto. This facilitates manipulation since coupling means for coupling the workpiece holder to the workpiece magazine and/or the workpiece slide can be readily provided on the workpiece holder. More particularly, separate coupling means can be provided on the workpiece holder for coupling the workpiece holder to the workpiece slide, on the one hand, and for guiding the workpiece holder by means of the workpiece magazine, on the other. 
     It is particularly advantageous when the workpiece magazine is in the form of a separate detachable and removable unit. This results in a modular design of the machining device, by which operation of the device is occasionally possible without the need for a workpiece magazine. In one example of the machining device not including the attachable workpiece magazine, the interchange point is preferably accessible from outside to manually change the workpieces. It is then possible to implement the same motion sequence as is carried out by the workpiece slide when a workpiece magazine is present, and the workpiece to be coupled to the workpiece slide is manually placed by an operator at the interchange point for the purpose of coupling the workpiece to the workpiece slide, instead of the workpieces being moved automatically by the workpiece magazine. 
     In this context, it is particularly advantageous when the machining device comprises a housing that encompasses a machining chamber, while the workpiece magazine is provided outside this housing. In such an example of the machining device, the interchange point is also provided outside the housing. Therefore, in both cases, in which the workpiece magazine is either present or not present, the interchange of workpieces takes place outside the machining chamber. Thus, when the workpiece is changed manually, it is unnecessary to open the machining chamber in its entirety. Instead, it is sufficient to move the workpiece slide along the X axis to a point that is at least partly outside the machining chamber and thus outside the housing, so that a workpiece to be subsequently machined can be coupled to the workpiece slide when outside the housing. 
     The workpiece magazine is configured to move the workpieces along a path of movement. This path of movement can be one that is not closed so that the workpieces in the workpiece magazine can be moved between two end positions. However, an example of the workpiece magazine comprising a closed path of movement is preferred in which each of the workpieces in the workpiece magazine can be moved from two alternative directions to the interchange point. In the case of such a closed path of movement, that is, complete rotational capability of the workpieces, the average distance to be covered by the workpieces mounted in the workpiece magazine is shorter. 
     In the simplest case, the path of movement is linear, as provided, for example, by a workpiece magazine that can move the workpieces in the vertical direction. However, it is preferred that the path of movement be not linear but instead in the form of a circle or an arc of a circle, for example, since this shape makes it possible to provide a comparatively large number of workpieces in a comparatively small space. The direction of movement of the workpieces mounted in the workpiece magazine, particularly in the region of the interchange point, is preferably oriented to extend orthogonally to the X axis. 
     In our machining device of the invention, the workpiece magazine can be of a very simple design. In the simplest case, it is merely configured to automatically and collectively handle all workpieces present therein. Thus, the workpiece magazine need not have any motors or actuators that make it possible for every single workpiece to be manipulated individually. Instead, only one common drive unit is provided, by which all workpieces present in the workpiece magazine can be moved collectively. Thus, for example, this drive unit can be provided for effecting rotational movement of a rotor comprising a number of workpiece slots provided at its periphery. 
     Preferably, the workpieces are secured, along at least part of the path of movement, from removal thereof from the workpiece magazine and can only be removed from, or inserted into, special sections thereof. Preferably, such a section is also provided at the interchange point so that a workpiece located at the interchange point can be removed from the workpiece magazine transversely relatively to the path of movement, more particularly along the X axis, without requiring the workpiece to be decoupled beforehand from the workpiece magazine by a motor. 
     Preferably, the machining device comprises a control unit configured such that it controls the movement of the workpiece slide both for the purpose of moving the workpiece relatively to the tool during the machining operation and for the purpose of carrying out workpiece interchange. Thus, this control unit is adapted activate the workpiece slide in the sense of the double function just described. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Additional aspects and advantages are revealed in the appended claims and in the following description of a preferred example, which is explained below with reference to the figures, in which: 
         FIG. 1  shows a machining device including a workpiece magazine, 
         FIG. 2  shows an open state of the machining device shown in  FIG. 1 , 
         FIG. 3  shows a coupling mechanism provided on a workpiece slide of the machining device shown in  FIGS. 1 and 2 , 
         FIG. 4  shows means for securing the workpieces in the workpiece magazine, and 
         FIGS. 5   a  to  5   f  show various stages of a workpiece interchanging operation. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows our machining device. The machining device comprises a main unit  10 , in which there is provided a machining chamber  12  visible through a pane in the closed state of the machining device shown in that figure. On the main unit  10  there is provided a workpiece magazine unit  50  that is detachably coupled to the main unit  10 . 
       FIG. 2  shows an open state of the machining device shown in  FIG. 1 . Both an access cover  14  for the main unit  10  and an access cover  54  for the workpiece magazine unit  50  are open in this state so that the machining chamber  12  and the workpiece magazine chamber  52  are freely accessible. 
     A spindle  20  with a tool  22  inserted therein is provided in the machining chamber  12 . This spindle  20  can be moved translationally along a Z axis and is pivoted about two axes U and B, which extend orthogonally to each other, by a moving unit  24  not described in detail. 
     In the machining chamber  12  there is also disposed a workpiece slide  30  that can be moved translationally along an X axis. For this purpose, guide rails are provided on the rear wall of the machining chamber, which guide rails are not visible in the view shown in  FIG. 2 . A clamping device  34 , which can pivot about an A axis and to which a workpiece  36   a  can be coupled by a workpiece holder  38   a  firmly attached to the workpiece, is provided on the workpiece slide  30 . The position of the workpiece  36   a  relative to the tool  22  during a machining operation, not described in detail, is controlled by way of the capability of the workpiece slide  30  to move along the X axis to make it possible to carry out three-dimensional machining of the workpiece  36   a  by the tool  22 . 
     A plurality of workpieces  36   b  to  36   z  is disposed in the open workpiece magazine chamber  52 . These workpieces  36   b  to  36   z  are mounted on a transporting wheel  56  that is mounted for rotation about an axis of rotation D by an electric motor. All the workpieces  36   b  to  36   z  mounted on this transporting wheel  56  can be moved by the same collectively along a path of movement  60 . This path of movement  60  is circular in accordance with the shape of the transporting wheel  56 . The workpieces are moved along this path of movement  60  in a plane, the normal vector of which is parallel to the X axis. 
     The path of movement  60 , along which the workpieces  36   b  to  36   z  can be moved by the transporting wheel  56 , is disposed in such a way relative to the workpiece slide  30  and to its capability to move along the X axis that a interchange point  70  is provided on the path of movement  60 , which interchange point  70  aligns with the direction of movement of the slide  30  along the X axis, so that the slide  30  can, together with the clamping device  34 , be moved to the interchange point. In the state shown in  FIG. 2 , the workpiece  36   f  is at said interchange point  70 . 
     The interchange point  70 , which can be reached, on the one hand, by the workpieces attached to the transporting wheel  56  in the workpiece magazine  50  and, on the other hand, by the clamping device  34  or the workpiece  36   a  coupled to the clamping device  34  by virtue of the movement of the slide  30 , allows workpieces  36   a  to  36   z  to be interchanged between the workpiece slide  30  and the transporting wheel  56  in the workpiece magazine  50  without any need for additional manipulating equipment for the purpose of moving the workpiece from the transporting wheel  56  to the slide  30  or from the slide  30  to the transporting wheel  56 . Instead, a new workpiece  36   f  can be coupled to the workpiece slide  30  in that this workpiece  36   f  to be coupled is first moved to the interchange point  70  by the transporting wheel  56 . Then, the workpiece slide  30  travels to the right, with reference to  FIGS. 1 and 2 , until the clamping device  34  on the workpiece slide  30  bears against the workpiece  36   f  to be machined or against its workpiece holder  38   f . In this state, the workpiece holder  38   f  is coupled to the clamping device  34  by a control unit pertaining to the machining device. On completion of this coupling operation, the workpiece slide  30 , together with the workpiece  36   f  now attached thereto, is moved to the left so that the workpiece  36   f  enters the machining chamber  12 . Subsequently, machining of the workpiece  36   f  can begin at this stage, for which purpose the capability of the workpiece slide  30  to move is implemented during the machining operation to move the workpiece  36   f  relatively to the tool  22  along the X axis. Therefore, it is not necessary for, say, the tool  22  to be additionally capable of being moved along the X axis. 
     The coupling device for coupling a workpiece or the workpiece holder to the clamping device  34  and the method of attaching the workpieces disposed in the workpiece magazine to the transporting wheel  56  will now be explained with reference to  FIGS. 3 and 4 . 
     In the machining chamber  12  there is also disposed a workpiece slide  30  that can be moved translationally along an X axis. For this purpose, guide rails are provided on the rear wall of the machining chamber, which guide rails are not visible in the view shown in  FIG. 2 . A clamping device  34 , which can pivot about an A axis, which is an imaginary line that is parallel to the X axis, and to which a workpiece  36   a  can be coupled by a workpiece holder  38   a  firmly attached to the workpiece, is provided on the workpiece slide  30 . The position of the workpiece  36   a  relative to the tool  22  during a machining operation, not described in detail, is controlled by way of the capability of the workpiece slide  30  to move along the X axis to make it possible to carry out three-dimensional machining of the workpiece  36   a  by the tool  22 . 
     In addition to the first plug-in element  39   a , the workpiece holder  38   a  comprises a second plug-in element  39   b , the significance of which will be explained in connection with  FIG. 4 . 
       FIG. 4  shows the interchange point  70  of the workpiece changer  50  on an enlarged scale. It can be seen that the transporting wheel  56  comprises slot-shaped recesses  56   a  provided at the periphery of the transporting wheel for each workpiece holder. The second plug-in elements  39   b  of the workpiece holders shown in  FIG. 3  can be inserted into these recesses  56   a . Thus, the workpiece holders will be held firmly in these recesses  56   a  without any need for any additional securing means to stay immovable in relation to the transporting wheel when trans-ported by the transporting wheel  56  during rotation of the same. In a manner not shown in detail, the recesses  56   a  are provided on both sides with grooves that are oriented toward each other and that positively cooperate with the second plug-in elements  39   b  of the workpiece holders. 
     When inserting a workpiece holder into the transporting wheel, the clamping device  34  is moved together with the workpiece holder far enough to enable the second plug-in element  39   b  pertaining to the workpiece holder  38   a  to slide into the recess  56   a , where the second plug-in element is coupled positively with the transporting wheel  56 , as mentioned above, by engagement of the second plug-in elements in the aforementioned grooves. The securing elements of the clamping device  34  that previously established the positive lock between the first plug-in elements  39   a  and the clamping device  34  then disengage. By reason of the previously established positive lock between the second plug-in element  39   b  and the transporting wheel  56 , the subsequent return movement of the clamping device  34  to the left results in the workpiece holder  38   a  of interest being detached from the clamping device  34  and remaining on the transporting wheel  56 . 
     When a new workpiece is to be coupled to the clamping device, the vacant clamping device  34  approaches the respective workpiece holder held on the transporting wheel  56  such that the first plug-in element  39   a  enters the recess  34   a . When this has taken place, the securing elements engage the workpiece holder, and the clamping device is moved, together with the workpiece holder coupled thereto, back into the machining chamber. The workpiece holder is released from the transporting wheel, with which it is no longer positively connected at this stage. 
       FIGS. 5   a  to  5   f  show various stages of the workpiece interchange operation. 
       FIG. 5   a  shows, on an enlarged scale, a state of the machining device that corresponds to the state shown in  FIG. 2 . In this state, there is already a workpiece  36   a  coupled to the clamping device  34  on the workpiece slide  30 , which workpiece  36   a  is to be inserted into the workpiece magazine, after which another workpiece  36   j  is to be removed from the workpiece changer  50  for machining purposes. 
     For this purpose, the transporting wheel  56  pertaining to the workpiece changer  50  is first activated. Thus, all workpieces present in the workpiece changer are rotated about the axis of rotation D until a vacant slot  58  has reached the interchange point  70 . This state is shown in  FIG. 5   b.    
     At this stage, the slide  30  is moved to the right, together with the workpiece  36   a  coupled to the clamping device  34 . In this way the workpiece holder  38   a  on the workpiece  36   a  engages the transporting wheel  56 . Once this state, shown in  FIG. 5   c , has been achieved, the workpiece holder  38   a  is decoupled from the clamping device  34  by the control unit pertaining to the machining device. 
     After the slide  30  has moved slightly to the left to become detached from the workpiece holder  38   a , the transporting wheel  56  is moved on by the electric motor pertaining to the workpiece changer. The workpiece  36   a , now decoupled from the clamping device  34 , is moved by the transporting wheel away from the clamping device  34 . This state is shown in  FIG. 5   d.    
     The movement of the transporting wheel  56  is continued until the workpiece  36   j  is situated at the interchange point  70 . Once this state, shown in  FIG. 5   e , has been achieved, the slide  30  is again moved slightly to the right so that the clamping device  34  engages the first plug-in element  39   a  of the workpiece holder  38   j . The clamping device  34  is then activated by the control unit pertaining to the machining device such that the clamping device couples the workpiece  36   j , together with the workpiece holder  38   j  situated at the interchange point  70 , to the workpiece slide  30  by means of the securing elements. 
     The workpiece slide is then moved back into the machining chamber  12  together with the workpiece  36   j  coupled to the clamping device  34 . Machining of the workpiece  36   j  can then begin, for which purpose the capability of the slide  30  to move, as utilized previously for changing the workpiece, is now implemented to achieve three-dimensional mobility of the workpiece  36   j  in relation to the tool  22 .