Abstract:
A storage arrangement ( 1 ) for machine tools is proposed, comprising at least two storage shelves ( 12 ) arranged vertically one above the other and in each case having a multiplicity of tool or workpiece retainers ( 14 ), the tool or workpiece retainers ( 14 ) being arranged in a circle, and a movable gripping arm ( 16 ) which is rotatably arranged about an axis through the center of the circle formed by the storage retainers ( 14 ) and which furthermore is arranged so as to be movable in the vertical direction with respect to the storage shelves ( 12 ) and which furthermore is arranged so as to be movable horizontally and radially from the circle center, the gripping arm ( 16 ), during its horizontal movement, covering at most a distance which corresponds to the radius of the circle formed by the storage retainers ( 14 ).

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The invention relates to a storage arrangement for machine tools, comprising at least two storage shelves arranged vertically one above the other and in each case having a multiplicity of tool and/or workpiece retainers, the tool or workpiece retainers being arranged in a circle, and a movable gripping arm which is rotatably arranged about an axis through the center of the circle formed by the retainers and which furthermore is arranged so as to be movable in the vertical direction with respect to the storage shelves and which furthermore is arranged so as to be movable horizontally and radially from the circle center.  
         [0002]     For the machining of workpieces made of metal, plastic or other materials, programmable “machining centers” monitored by the computer are being increasingly used. A machining center essentially comprises a table on which a workpiece can be held in a defined position during the machining. “Pallets” or work carriers serve for the defined fastening of the workpieces. For the machining of the workpiece, a wide variety of tools are used, for example for drilling, milling, broaching, sawing, cutting or planing. Depending on the form of the initial material and depending on the form of the desired finished product, the workpiece can be machined from several sides. The workpieces and tools can be moved linearly and/or rotationally with respect to one another. Three to six axes are defined for the movement: X, Y and Z for the linear movements and A, B and C for the rotary movements. In order to achieve efficient series production, a multiplicity of machining steps with various tools on a number of workpieces are programmed in advance for a relatively long time segment. The tools also become worn due to the machining. A multiplicity of tool changes are therefore necessary. For the neat grouping of the tools and of the unmachined and machined workpieces, storage arrangements are provided which are operated by program-controlled manipulators or industrial robots. The “chip-to-chip” tool change time, i.e. the time which the machine requires for the changing of the tool, is to be as short as possible for a high efficiency. The preparation time, i.e. the time during which the machine is continuously in readiness for the further tools, likewise contributes decisively to the increase in efficiency. The energy consumption during the tool or workpiece change is to be kept as low as possible.  
         [0003]     WO 2003072300 A1 discloses an arrangement for changing and storing tools for a machining center. A multiplicity of tool retainers are formed on the inner circumference of a ring-segment-shaped frame. A rotatable arm has two gripping devices, the first gripping device serving to store the tools and the second gripping device serving to withdraw the tools from storage. The gripping devices have an embossment or a bevel which interacts with a finger on the tool retainer. This achieves the effect that the tool is stored and withdrawn from storage with a defined orientation.  
         [0004]     The object of the invention is to specify a storage arrangement for machine tools which permits machining which is as efficient as possible and is as favorable as possible in terms of energy.  
       SUMMARY OF THE INVENTION  
       [0005]     The object is achieved by a storage arrangement for machine tools, comprising at least two storage shelves arranged vertically one above the other and in each case having a multiplicity of tool and/or workpiece retainers, the tool or workpiece retainers being arranged in a circle, and a movable gripping arm which is rotatably arranged about an axis through the center of the circle formed by the retainers and which furthermore is arranged so as to be movable in the vertical direction with respect to the storage shelves and which furthermore is arranged so as to be movable horizontally and radially from the circle center, the gripping arm, during its horizontal movement, covering at most a distance which corresponds to the radius of the circle formed by the retainers. The radial movement of the gripping arm is limited to the absolute minimum.  
         [0006]     It is advantageous that the storage arrangement can be attached to the machine tool in any desired manner. This is achieved by a transfer opening being formed in an outer wall, running vertically, of the storage arrangement. This is also achieved by the storage shelves being composed of storage modules in a modular manner.  
         [0007]     It is also advantageous that the storage arrangement has minimum energy consumption. This is achieved by the gripping arm having a single gripping retainer for the workpieces or tools.  
         [0008]     Furthermore, it is also advantageous that the preparation time for the tools and/or workpieces is minimal. This is achieved by the fact that the working steps “withdrawal or storing” of the tool and “removing or installing” of the tool are carried out by two spatially separate manipulators working simultaneously. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     An exemplary embodiment of the invention is described with reference to the figures. In the drawing:  
         [0010]      FIG. 1  shows a perspective view of a storage arrangement according to the invention for machine tools,  
         [0011]      FIG. 2  shows a side view of the arrangement in  FIG. 1 ,  
         [0012]      FIG. 3  shows a further side view of the arrangement in  FIG. 1 ,  
         [0013]      FIG. 4  shows a view from above of a part of the arrangement in  FIG. 1 ,  
         [0014]      FIG. 5  shows a perspective view of a detail of the arrangement in  FIG. 1 ,  
         [0015]      FIG. 6  shows a perspective view of a part of the storage arrangement, and  
         [0016]      FIG. 7  shows a perspective view of a further detail of the storage arrangement in  FIG. 1 .  
     
    
     DETAILED DESCRIPTION  
       [0017]     A storage arrangement  1  for a machine tool is shown in a perspective view in  FIG. 1 . Of the machine tool, only a tool spindle  2 , a tool holder  3 , a spindle drive motor  4  and a spindle guide slide  5  are shown. A transfer station  6  having a change arm  7  is arranged between the machine tool and the actual storage arrangement  1 . The transfer station  6  is fastened in a free-standing manner on the machine base. The change arm  7  is driven by a computer-controlled servomotor  9  and performs merely a circular movement about the drive axis of the servomotor  9 . At its free end, the change arm  7  has two transfer retainers  10 ,  11  for tools and/or workpieces and is therefore also designated as double change arm.  
         [0018]     The actual storage arrangement  1  is designed like a tower rack and, in the present exemplary embodiment, contains nine storage shelves  12  arranged one above the other. Each storage shelf  12  is composed of five circle-segment-shaped storage modules  13 . A storage shelf  12  comprises at least five eighths of a circle, but may also be composed of six or seven eighths. Five storage retainers  14  for tools and/or workpieces are formed in each module  13 . The storage retainers  14  in the storage shelves  12  have the same functions and the same dimensions as the transfer retainers  10 ,  11  on the double change arm  7 . Depending on the size of the tools and/or workpieces, more or fewer storage retainers  14  may be formed per storage module  13 . The distance from one storage shelf to the next is determined by the maximum size of the tool.  
         [0019]     The modular construction of the tower rack permits subsequent expansion of the storage capacity of the storage arrangement  1 . In the present example, space for more than 200 storage retainers  14  is provided. The tower rack is a simple modular construction which can be closed off with wall plates and thus forms a robustly composed storage unit. A plurality of tool storage arrangements  1  for a plurality of machines can be connected to one another via crane systems (not shown here) placed above them. The tools can then be fed and discharged via the top part at the respective tool store.  
         [0020]     The storage retainers  14  are arranged in a circle. A guide  15  is arranged at the center of this circle. The guide  15  carries a gripping arm  16  and is itself arranged so as to be rotatable about the axis C through the center of the circle, which is formed by the retainers  14 . The gripping arm  16  is designed as a guide slide in the horizontal direction and has a single gripping retainer  17  at its free end. The gripping retainer  17  is arranged on the gripping arm  16  in a linearly movable manner. The gripping arm  16  together with the gripping retainer  17  can therefore perform a vertical, a horizontal and a radial movement. The radial movement of the gripping arm  16  is not larger than necessary for the movement of the tools and/or workpieces into and from the storage retainers  14  of the storage shelf  12 . Since the gripping arm  16  does not need to perform any relatively large movements, the gripping arm  16  also does not exert any relatively large torque on the guide  15  in the loaded state. The gripping arm  16  moves only one tool or workpiece in each case. The remaining tools are mounted in a stationary position in the storage retainers  14 . No unnecessary masses need to be moved, which leads to a type of construction of the storage arrangement  1  which is as light as possible and is as favorable as possible in terms of energy.  
         [0021]      FIG. 2  shows the storage arrangement  1  in a front view. The same reference numbers relate to the same features as in  FIG. 1 . It can be seen in  FIG. 2  how the transfer station  6  is fastened to the side wall  8  of the storage arrangement  1  halfway between two storage shelves  12 . However, the level can be adapted to the respective machine tool. A tool  19  is located in the transfer retainer  11  of the change arm  7 , a further tool or workpiece  20  is located in the transfer retainer  10 , a further tool  21  is located in the gripping retainer  17  of the gripping arm  16 , and a further tool or workpiece  22  is located in the storage shelf  12  arranged right at the top. A free space, in which a transfer opening  23  for the transfer station  6  has been formed, has been left between two storage shelves  12 .  
         [0022]      FIG. 3  shows the storage arrangement  1  as viewed toward the side wall  8 . The storage modules  13 , which together form the storage shelf  12 , are covered with a sheet-metal plate bent at right angles. The cover protects the storage retainers  14  from contamination from the outside and prevents cooling and lubricating fluid from dripping onto the tools from the storage shelves lying at the top. A drive motor  24 , which serves for the rotatable drive of the guide  15  about the axis C, can be seen at the top on the storage arrangement  1 .  
         [0023]      FIG. 4  shows the storage arrangement  1  in a view from above toward a storage shelf  12 . The storage arrangement  1  is shown sectioned in the region of the free space between two storage shelves  12 . Here, it can readily be seen how the transfer retainers  10 ,  11  of the change arm  7  are arranged so as to be movable in a circle, which is tangent to the circle formed by the storage retainers  14 . Broken lines show how the change arm  7  changes from a first transfer position in the storage arrangement  1  to a second transfer position in the machine tool. The gripping retainer  17  of the gripping arm  16  is located in the radially retracted position. In this position, the gripping arm  16  can be moved from the transfer station  6  to one of the numerous storage retainers  14  by a rotary movement of the gripping arm  16  in the horizontal plane and/or by a vertical movement along the guide  15 .  
         [0024]     The change arm  7  and the gripping arm  16  are driven and controlled independently of one another and can be moved simultaneously. Due to this independence and by means of a suitable control, the tool  21  can be stored or withdrawn from storage, while the other tool  19  is transferred to the machine tool and exchanged. The maximum turning circle of the gripping arm  16  and the turning circle of the change arm  7  touch one another only at one point, namely during the changing of the tool from the gripping arm  16  to the change arm  7  or vice versa. Due to the separation of the tool storage and the tool change, the downtime of the machine tool can be considerably reduced. The short machining times which are thus achieved result in an unparalleled efficiency for the machining center.  
         [0025]     The transfer of a tool from the gripping arm  16  to the change arm  7  is shown schematically in  FIG. 5 . The change arm  7  has two transfer retainers  10 ,  11 , whereas the gripping arm  16  has merely one gripping retainer  17 . In each case one of the transfer retainers  10 ,  11  is actuated on the side of the storage arrangement  1  and another is actuated on the side of the machine tool.  
         [0026]     An individual storage module  13  having five storage retainers  14  is shown in a perspective view in  FIG. 6 . Here, it can readily be seen how the tools and/or workpieces can be protected against contamination and from liquid dripping down.  
         [0027]     An access door  25  with an operating console  26  and an insertion station  27  for inserting individual tools or workpieces is shown schematically in  FIG. 7 . The insertion station  27  is located at an ergonomically favorable level, but on another side of the storage arrangement  1 , opposite or next to the transfer station  6 . Depending on the space conditions, the access door  25  may be arranged on the side wall opposite the side wall  8  or on the front wall, lying in between, of the storage arrangement  1 .  
         [0028]     Since the storage arrangement  1  is of modular construction, it can be attached to a machine tool in any desired manner. The tower rack can be extended vertically in any desired manner. It is also conceivable to attach two storage arrangements  1  designed in mirror image to a single machine tool. The tower rack is designed as a simple but nonetheless robust sheet-metal structure. Since only one tool is moved in each case in the tower rack by the gripping arm  16  over as short a distance as possible, the expenditure of energy for the storing and withdrawal from storage is restricted to the absolute minimum. The gripping arm  16  is designed as a simple three-axis manipulator with servomotors. The change arm  7  is a simple rotatable arm which can be stopped in at least four different angular positions by a computer-controlled servomotor.