DE3620047A1 - Grinding wheel-changing system for grinding machines - Google Patents

Abstract

A grinding wheel-changing system for grinding machines, in particular for cylindrical surface grinders with large grinding wheels, is described. This system has means for moving the grinding spindle head (7) with the grinding spindle (7a) into a changing position, a grinding wheel changer (14) and a movable grinding wheel deposit (18). The grinding wheel changer consists of a changing console (16) and a changer head (17) which is swivellably arranged on the latter, takes up the grinding wheels (11a, 11b) in horizontal axial alignment from the grinding spindle (7a) and delivers them in vertical axial alignment to the grinding wheel deposit (18a), and which has at least one gripping arm (22, 23) with gripping means (24) for taking up and holding grinding discs. The grinding wheel deposit (18) is equipped with grinding wheel receptacles (28, 29) with substantially vertically extending axes for the horizontal reception of the grinding wheels. <IMAGE>

Description

The invention relates to a grinding wheel changing system for grinding machines, especially for external cylindrical grinding machines with large grinding wheels.

In modern automatic production grinding machines there is an increasing reduction in non-productive times where production is interrupted. This affects in addition to the processes when changing workpieces and the dressing of the grinding wheel, especially the Grinding wheel change, which in the automatic produc tion process of such machines is included. A grinding wheel change takes place when worn Grinding wheels to be replaced with new ones or if on the same workpiece or another with another to carry out further grinding work are. In this case, the grinding just used after removal from the grinding spindle for later uses kept in stock, while another grinding wheel is being used.

There are different grinding wheel changers for Known grinding machines. According to DE-AS 20 24 212 the grinding wheels for changing from a horizontal one Grinding spindle of an exchange unit with a horizon passed taler spindle and from this while maintaining orientation in a magazine. The DE-OS 32 46 168 describes an arrangement in which the grinding wheels to be replaced directly on a grinding disc magazine are handed over, also the horizontal axial orientation of the grinding wheels will hold.  

The well-known grinding wheel changers have in common that the grinding wheels are upright, i.e. with horizontal Grinding wheel axis are kept in stock. Grinding discs that are already in use on the grinding machine goods are filled with grinding water. The ready keep such grinding wheels in an upright position, so with horizontal grinding wheel axis, as per the State of the art is provided, leads to the fact that forms a water bag in the grinding wheels below. At a new use of such a grinding wheel in the grinding machine is so unbalanced that a very slow start-up of the grinding wheel rotation Number is required to get the water soaked up again distribute evenly in the grinding wheel. That ver slows down the production process of the machine considerably Dimensions.

The invention is based on the object, a grinding to specify a disc changing system of the type mentioned at the beginning, which significantly reduces the grinding wheels change times allowed and with the grinding used discs in an optimal position for reuse filed and kept ready.

This object is achieved in that the grinding wheel change system for grinding machines Means for moving the grinding headstock with the Grinding spindle in a changing position, a grinding disc changer and a movable grinding disc holder has that the grinding wheel changer from a Changer console and one pivotally arranged on this ten, the grinding wheels in a horizontal axis alignment from the grinding spindle and in vertical Transfer the axis alignment to the grinding wheel holder  Changer head, which has at least one gripper arm with clamping devices for picking up and holding grinding has discs that the grinding wheel rest grinding disc recordings with essentially vertical the axes for the horizontal mounting of the grinding wheels has and that means for each other otherwise moving the clamping means of the gripping arms on the one hand and the grinding spindle or grinding wheel mounts the grinding wheel rest are provided on the other hand. When changing the grinding wheel, the axis of the reoriented to changing grinding wheels, so that the Horizontal grinding wheels ready for the next use being held. This prevents the formation of water bags casually excluded, which to the next grinding could lead to delaying unbalance. The Changer head preferably consists of a cross frame with two roughly crossed gripping arms, which both clamping devices for receiving and holding Have grinding wheels and he is on the changer con sole at an angle of approximately 45 ° to the vertical and axis inclined to the axes of the gripping arms. It is a very space-saving con structure of the grinding wheel changer, which allows the grinding wheel changer directly in the area of Machine. To take over the grinding wheels from the grinding spindle or for storing a grinding Each gripper has a disc on the grinding wheel holder arm a gripper head, and each gripper arm is with Guide and drive means for extending and retracting the Gripper head in the longitudinal direction of the gripper in question arms equipped. This way, additional over Giving agents are not required on the grinding machine.  

A particularly preferred constructive design of the Gripping arms of the cross frame is that everyone Gripper head on one in the longitudinal direction of the concerned Low-grip, movably guided running track attached is which by means of a drive in the longitudinal direction of the The gripper arm can be extended and retracted.

Around the lid of the grinding spindle and the grinding wheel surrounding protective hood for changing the grinding wheel swing out or move sideways what would require additional space on the grinder it is envisaged that each gripper arm means for receiving and holding a protective cover. Every griffin arm also has locking agents and indexie means for securely holding a protection hood cover on. The protective cover are with Fixing means for attaching the protective cover provided on the protective hood. Are on the protective hood with the fixative interacting, controlled actuation bare locking means for locking the protective hood provided on the cover. The Protective hood in a further embodiment of the invention the periphery of its end face in the circumferential direction controlled adjustable clamping ring segment and protection the hood cover is like a bayonet lock Adjustment of the clamping ring segment on the protective hood designed to be lockable. By designing protection hood and the protective hood cover is a quick off Take the protective cover by the gripper in question poor when changing grinding wheels and a safe and problem-free attachment of the protective cover after Grinding wheel change guaranteed.  

To further accelerate the change process enable, the invention further provides that two interchangeable protective cover are provided that each gripper arm the protective cover and the grinding wheel when changing the grinding wheel together from the grinding spindle is designed to take over and that when dropping a grinding wheel on the grinding wheel holder of the respective protective cover on the relevant gripper arm is held.

According to a preferred embodiment of the invention is the grinding wheel shelf as transverse to the axis of the ver tical gripping arms designed movable disc carriage, the loop on its side facing the gripper arm carries recordings. Around the disc carriage for grinding to be able to drive disc changes into defined positions, is provided according to the invention that on the changer console a guide running in the horizontal direction is appropriate that a transport organ along the guide is movable that the disc carriage with coupling means to dock the disc carriage on the transport organ is equipped and that drive means for the process of trans portorgans are provided along the guide. To this Is an automatically controlled process of the Disc carriage for changing grinding wheels possible. A Another embodiment of the invention is that each grinding wheel holder of the grinding wheel holder Sensor means for monitoring the presence of a Grinding wheel are assigned.

To the movement of the disc carriage of bumps of the The disc wagon is used to make the ground independent Docking on the transport element lifted off the floor. The Disc car or the transport organ and the changer  consoles have interacting indexing devices for posi precise provision of the disc carriage. Thereby can the disc trolley exactly in the for Disc change required position be brought.

For the provision of a larger number of grinding has the grinding wheel change system according to the Invention a grinding wheel magazine, which from the movable grinding wheel rest grinding wheels takes over or surrenders to them.

In another embodiment of the grinding wheels change system according to the invention, there is the changer head from a swivel body, which on a frame by one vertical axis rotatable and about a horizontal axis is tiltable. The swivel body is on under different, preferably on opposite sides with gripping means for picking up and holding grinding discs equipped. By rotating around the vertical The grinding wheel to be removed is first removed from the axis pivoted out of the grinding machine area and then by tilting around the horizontal axis to the grinding hand over disc storage. The grinding wheel holder can above or below the horizontal grinding spindle level. Accordingly, the tilting of the Swivel body up or down.

Within the scope of the present invention, which relates to a Grinding wheel change system for grinding machines, independent protection is claimed for a grinding disc change, which is characterized in that he from a changer console and one swiveling on it arranged, the grinding wheels in a horizontal axis alignment of the grinding spindle and in vertical axis alignment on a grinding wheel holder  issuing changer head, which is at least one Gripping device with clamping devices for picking up and holding of grinding wheels, and that he with means for Moving the clamping means towards and away from each other the gripping means on the one hand and the grinding spindle or the grinding wheel holder of the grinding wheel holder on the other hand is equipped.

While it is known grinding wheels in a magazine one above the other in a horizontal position, i.e. with vertical out to store the aligned disc axis (see EP-A 58 913). To remove the grinding wheels from the magazine too lighten them with the support arms on which they are are held in the magazine, pivoted out of the magazine and placed in a vertical position in which it Operators are easier to handle. A grinding disc changer or a grinding wheel change system for an automatic, inte Free grinding wheel changes are this revelation not to be removed.

An advantage of the invention is that the pre struck grinding wheel change system a very fast Grinding wheel change allowed. The grinding wheel changer is located right next to the grinding machine and does not require a long time to change the grinding wheel Displacement routes. For the handover of the grinding wheel from Grinding headstock for grinding wheel changer are the Movements in those already present in the machine Machine axes sufficient. The transfer of the grinding disc from the grinding spindle to the tray and vice versa requires only a short swivel movement of the changer head around the axis inclined at 45 ° to the vertical and is therefore carried out with the shortest possible time.  

The lying grinding wheel rest on the wheel carriage ensures that there are none even in used windows Form water bags, which are used in the next grinding process would lead to imbalance phenomena. That saves the slow run-up of the newly used grinding disc before the next machining process, so that the Grinding process is accelerated overall. The stake of disc trolleys as a grinding disc holder extremely flexible operation of the grinding machine new or replaceable grinding wheels.  

The invention will now be explained in more detail with reference to the drawing. Show it:

Fig. 1 is a plan view of a cylindrical grinding machine with a grinding wheel-change system according to the invention,

Fig. 2 is a front view of a grinding wheels change system according to the invention,

Fig. 3 is a partially sectioned view of the head changer with gripping arms,

Fig. 4 shows a section along IV-IV of Fig. 3,

Fig. 5 is a section along the line VV of Fig. 3,

Fig. 6 is a side view of the grinding spindle head with hood,

FIG. 6a is a developed view taken along AA of Fig. 6,

Fig. 7 is a section along VII-VII of Fig. 6,

Fig. 8 is a plan view of an embodiment of a disc carriage with a guide and drive and

Fig. 9 shows another embodiment of a grinding wheel changer.

In Fig. 1 a plan view is shown on a cylindrical grinding machine with a grinding wheel changing system according to the invention. The grinding machine is designated 1 . It comprises a machine bed 2, on which in the Z direction extending parallel guides 3 are arranged, one on the machine bed 3 along the guides in the Z direction movable carriage 4, a movable on the carriage 4 in the X direction and about a verti Kale axis 6 swiveling grinding headstock 7 and a workpiece clamping device in the form of a workpiece headstock 8 and a tailstock 9th The extending between the driver 8 a of the workpiece headstock and the centering tip 9 a of the tailstock workpiece axis is denoted by W.

The grinding headstock 7 carries a grinding spindle 7 a with a grinding wheel 11 , which is surrounded by a protective hood 12 recognizable in FIGS . 2 and 6 with a removable protective hood door 12 a .

The grinding wheel changing system 13 , which is arranged to the right of the grinding machine 1 in the exemplary embodiment shown, includes, in addition to the guides 3 , which make it possible to bring the grinding headstock 7 into a changing position, a grinding wheel changer 14 , consisting of a console 16 and a changer head 17 , A grinding wheel rest, which is designed in the exemplary embodiment shown as a wheel carriage 18 which can be moved back and forth in the direction of an arrow 19 and, if required, a grinding wheel magazine 21 which is indicated in FIG. 1 by dashed lines.

Fig. 2 shows the grinding wheel changing system in a front view. The same parts are provided with the same reference characters as in Fig. 1, which also applies to the following figures.

As 2 shown in Fig., The carriage 4 carries the grinding machine 1 is a cross carriage 4 a for the movement in the X direction, on which, in turn, a turn table 4 b for the rotation of the grinding spindle head 7 about the vertical axis 6 is mounted.

The changer head 17 of the grinding wheel changer is designed as a cross frame with two gripping arms 22 and 23 crossed at right angles. Each gripper arm is equipped with clamping means 24 for receiving and holding grinding wheels 11 a and 11 b . The structure of the gripping arms 22 and 23 and the clamping means 24 will be described later in connection with FIGS. 3 to 5.

The console 16 of the grinding wheel changer is firmly connected to the machine bed of the grinding machine. It carries a bearing socket 26 , the axis 27 of which is inclined at an angle of approximately 45 ° to the vertical. On the bearing clip 26 , the changer head 17 is mounted and rotatable about the axis 27 . The gripping arms 22 and 23 run approximately at an angle of 45 ° on both sides of the axis of rotation 27 . The rotation of the changer head 17 about the axis of rotation 27 brings the grinding wheel 11 a into the position of the grinding wheel 11 b and vice versa.

The grinding wheel rest in the form of the wheel carriage 18 is assigned to the storage position of the gripping arms. In FIG. 2, the gripping arm 23 is in the storage position. The disc carriage 18 is equipped on its top with grinding disc receptacles 28 , each having a centering cone 29 . The grinding wheels are placed by the respective gripper arm 22 or 23 in the storage position on the grinding wheel holder 28 in question so that the centering cone 29 engages in the grinding wheel flange centering. A gripping or holding means for the grinding wheels is not required on the wheel carriage 18 since the grinding wheels rest firmly on the grinding wheel holders because of their weight. To move the disc carriage 18 in the direction of the double arrow 19 (see FIG. 1), a transport member 31 is provided, which is guided on a fixed to the console guide rail 32 and to which the disc carriage 18 can be docked. A more detailed description of the drive system of the disk carriage 18 will be given later in connection with FIG. 8.

The structure of the changer head 17 and in particular the gripping arms 22 and 23 and the clamping means 24 can be seen in FIGS. 3 to 5. The structure of the gripping arms 22 and 23 is identical, so that it is sufficient to describe the gripping arm 22 .

Each gripper arm consists of two hollow profiles 33 running parallel in a common plane, which are connected to one another via stable cross connectors 34 . The hollow profiles 33 of the gripper arm 22 are connected in the intersection area 36 with the hollow profiles 33 of the gripper arm 23 , where a stable cross frame is formed. This cross frame is supported by a bearing plate 38 on the bearing clip 26 of the bracket 16 rotatably about the axis of rotation 27 around.

Guide rollers 37 are rotatably mounted on the hollow profiles 33 , between which a running rail 39 is guided to and fro parallel to the hollow profiles 33 in the direction of an arrow 41 . Between the hollow profiles 33 , a hydraulic cylinder 42 is attached to the cross connectors 34 , the piston rod 43 engages a gripper head 44 fixed to the running rail 39 . By actuating the hydraulic cylinder 42 , the gripper head 44 with the running rail 39 between the guide rollers 37 can be moved back and forth parallel to the hollow profiles 33 . The gripper head 44 is fastened to the running rail 39 by means of screws 44 a ( FIG. 4).

Each gripper head 44 has clamping means for receiving a protective cover 12 a and 12 b and a grinding wheel 11 a and 11 b . To hold the grinding wheel, claws 46 are provided as clamping means which, by pulling back a push rod 47, engage around a clamping knob 48 of the grinding wheel flange. In Fig. 3, the claws are shown in the tensioned state above the axis and below in the released state. The push rod 47 is actuated by means of a hydraulically actuated piston 51 which is firmly connected to the push rod 47 . The necessary hydraulic connections are designated in Fig. 4 with 52 .

Each protective cover 12 a and 12 b carries a central flange 53 with an inner annular groove 54th The gripper head 44, which is cylindrical in its front part 56, is provided with a ring of radially spring-preloaded tensioning elements, preferably balls 57 , which engage in the annular groove 54 when the gripper head 44 is inserted into the flange 53 . When tensioning the claws 46 by withdrawing the push rod 47 , a bolt 58 is additionally pressed into the ring groove 54 by a curve 59 provided on the push rod, so that the protective cover 12 a or 12 b is locked on the gripper head. An engaging in an end-side bore of the flange 53 index bolt 61 ensures that the protective cover 12 a is held against rotation on the gripper head. A proximity initiator 62 monitors the proper acquisition of the protective cover 12 a on the gripper head.

As shown in FIG. 4, which contains a section along the line IV-IV of FIG. 3, a protective cover 64 is attached to the upper hollow profile via fastening means 63 , which largely completely surrounds the gripping arm. Fig. 5, which shows a section along the line VV of Fig. 3, the arrangement of Magnetven valves 66 and 66 a for the actuation of the hydraulic drives 42 and 51 can be seen. They are attached to a bracket 66 b connecting the hollow profiles 33 .

The running rail 39 is provided with tabs 67 , which cooperate with control initiators 67 a to control the position of the running rail 39 .

The dome Fig. 6, 6a and 7 show the formation of the protective hood and allows the protective cover, which cover a rapid decline and a secure fastening of the protective hoods of the protective hood. FIG. 6a 7 is a development taken along the line AA of Fig. 6 and Fig. Is a sectional view taken along the line VII-VII of Fig. 6.

The protective cover 12 a has on its periphery evenly spaced teeth 68 , the cross-sectional profile, as shown in Fig. 6a, is wedge-shaped. With the protective hood 12 , a guide ring 69 is connected, which guides a clamping ring segment 71 in the circumferential direction of the protective hood cover (see FIG. 7). The clamping ring segment 71 has teeth 72 on its inner periphery, the spacing of which exceeds the width of the teeth 68 by at least a small amount. From stood the teeth 68 of the protective cover 12 a is slightly larger than the width of the teeth 72 of the clamping ring segment 71st The clamping ring segment 71 is seen with a projection 73 , on which an actuating element in the form of a piston 74 a of a hydraulic cylinder 74 engages. The hydraulic cylinder 74 is pivotally attached to a support part 76 connected to the grinding headstock 7 . After changing the grinding wheel 11 , the protective hood cover 12 a is fitted into the protective hood, as shown in FIG. 6. The teeth 68 of the protective hood cover lie between the teeth of the clamping ring segment 71 . By actuating the hydraulic cylinder 74 , the shoulder 73 is moved into the position 77 indicated by the broken line, whereby the clamping ring segment is rotated counterclockwise in the circumferential direction. Since both the teeth 68 and the teeth 72 are wedge-shaped in their cross-sectional profile, as shown in FIG. 6 a, the teeth 68 of the protective cover are pressed against the front of the protective cover 12 during this rotation of the clamping ring segment. In this way, a secure fixation of the protective cover 12 a on the protective cover 12 is guaranteed.

With reference to FIG. 8, which shows a plan view of a grinding wheel serving as a storage disc carriage 18 and its drive means, in connection with FIG. 2, the construction and operation are the grinding ticket benablage explained in more detail. On the console 16 of the grinding wheel changer, the horizontal guide rail 32 is attached. On the guide rail 32 , the transport organ 31 is guided in a longitudinally movable manner by means of guide rollers 78 . This transport member 31 is driven by a hydraulic drive 79 , the cylinder 79 a of which is attached to the guide rail 32 and the piston rod 79 b of which is attached to an angular shoulder of the transport member 31 . Initiators 81 , which monitor the end positions of the disk carriage 18 , are assigned to the two ends of the guide rail 32 . For both possible positions of the discs 18, the carriage transport member 31 carries index members 82, the bolt having a stationary on the console mounted Index cooperate 82 a. The index bolt is actuated by means of a hydraulic drive 82 b .

For docking a disc carriage to the transport member 31 , receiving cones 83 are provided, in which corresponding cones, which are attached to screw drives of the disc carriage, engage. By means of a threaded rod 84 , the thread of which engages in a corresponding counterpart in the transport organ 31 and which can be actuated by means of a handwheel 86 , the disk carriage is docked on the transport organ 31 and centered over the receiving cones. The disc carriage is raised slightly from the ground so that its movement is independent of unevenness in the ground. The arrangement thus allows a safe and positionally precise movement of the wheel carriage 18 , so that the process of depositing the grinding wheel can always take place without problems. In FIG. 8, the forward position of the disc carriage 18 is indicated with dot-dash lines.

Fig. 9 shows another embodiment of the grinding wheel changer. It again consists of a bracket 87 which carries a changer head 88 in the form of a swivel body 90 with gripping arms 89 , which can be designed in the same way as those described in connection with FIGS. 3 to 5. The arrangement of the gripping arms 89 is not perpendicular, however, but parallel to one another. A description of the gripper arms is not necessary at this point. The swivel body 90 is different from the changer head in the embodiment described above game rotatable about a vertical axis 91 and pivotable about a horizontal axis 92 in the direction of an arrow 92 a . After applying a grinding wheel 93 of the spindle 7a of the in Fig. 9 is only indicated wheelhead 7 of the pivot body 90 is rotated about the vertical axis 91 by about 180 °, wherein the acquired grinding wheel now benablage of one of the gripping arms 89 of the grinding ticket 93 a reaches the change position to the grinding headstock. Then the grinding wheel 93 a is transferred to the grinding spindle. Then the swivel body 90 is pivoted about the horizontal axis 92 in the direction of arrow 92 a by 90 °, so that the grinding wheel 93 held on the second gripping arm 89 is brought into a horizontal position and can be placed on the grinding wheel rest. In the case of FIG. 9, the grinding wheel rest is not a wheel carriage, but a wheel carousel 94 with a plurality of grinding wheel holders 28 , 29 , of which only one is shown for the sake of simplicity.

In the above description of the exemplary embodiment of the invention, it was essentially spoken of a wheel carriage 18 as a grinding wheel rest. Instead of such a disc carriage, other receiving units for the grinding discs can of course also be provided as the grinding disc holder. Such receiving units are, for example, the grinding wheel carousel already mentioned in connection with FIG. 9 or a fit of the pallet system.

The grinding wheel benmagazin 21 mentioned in connection with FIG. 1 can be any arrangement of grinding wheel receptacles for stored grinding wheels, which allows space-saving storage of grinding wheels and quick access to these grinding wheels. An arrangement is preferably used here in which the grinding wheels are placed horizontally one above the other.

In connection with FIGS . 6 and 7, a bajo nice locking of the protective cover on the protective cover has been described. In addition to this preferred embodiment, other interlocks are of course also possible. Thus, FIG. 2, according to around the Schutzhau benperipherie hydraulically, pneumatically or electromag netic operable Klemmorgange 96 be mounted which engage around Clamping levers 97 the guard cover and fix on the protective hood. The control of these clamping levers is preferably carried out by the machine control 98 , which also controls all other changes of the grinding wheel changing system.

Claims (16)

1. Abrasive disc changing system for grinding machines, in particular for external cylindrical grinding machines with large grinding wheels, characterized in that it comprises means (3) for moving the grinding spindle head (7) with the grinding spindle (7 a) into a change position, a grinding ticket benwechsler (14) and a movable Grinding wheel location ( 18 ) has that the grinding wheel changer from a changer bracket ( 16 ) and a swivel bar arranged on this, the grinding wheels ( 11 a , 11 b ) in a horizontal axis alignment of the grinding spindle ( 7 a) on receiving and in vertical axis alignment to the grinding wheel rest ( 18 ) giving changer head ( 17 ), which has at least one gripper arm ( 22 , 23 ) with clamping means ( 24 ) for receiving and holding grinding wheels, that the grinding wheel rest ( 18 ) grinding wheel holders ( 28 , 29 ) with in essential vertical axes for horizontal inclusion of the grinding wheels au and that means for moving one another and away from one another the clamping means ( 24 ) of the gripping arms ( 22 , 23 ) on the one hand and the grinding spindle ( 7 a) or the grinding wheel receptacles ( 28 , 29 ) of the grinding wheel holder ( 18 ) on the other hand are provided. 2. Grinding wheel change system according to claim 1, characterized in that the changer head ( 17 ) consists of a cross frame with two roughly crossed gripping arms ( 22 , 23 ), both of which each have clamping means ( 24 ) for receiving and holding grinding wheels ( 11 a , 11 b ) and that the changer head on the changer console ( 16 ) can be pivoted about an axis ( 27 ) inclined at an angle of approximately 45 ° to the vertical and to the axes of the gripping arms. 3. Grinding wheel changing system according to claim 1 or 2, characterized in that each gripper arm ( 22 , 23 ) has a gripper head ( 44 ) and that each gripper arm with guide ( 37 , 39 ) and drive means ( 42 ) for extending and retracting the gripper head is equipped in the longitudinal direction of the gripping arm concerned. 4. System according to claim 3, characterized in that each gripper head ( 44 ) on a in the longitudinal direction of the relevant gripper arm ( 22 , 23 ) movably guided rail ( 39 ) is attached, which by means of a drive ( 42 ) in the longitudinal direction of the gripper arm - and retractable. 5. System according to one of claims 1 to 4, characterized in that each gripper arm ( 22, 23 ) has means ( 56 , 57 , 58 ) for receiving and holding a protective cover ( 12 a , 12 b ). 6. System according to claim 5, characterized in that each gripping arm ( 22 , 23 ) locking means ( 57 , 58 ) and indexing means ( 61 ) for securely holding a protective cover ( 12 a , 12 b ) that each protective cover with fixing means ( 68 ) is provided for attaching the protective cover to the protective cover ( 12 ) and that interlocking means ( 71 , 72 , 96 ) cooperating with the fixing means ( 68 ) are provided for locking the protective cover on the protective cover. 7. System according to one of claims 1 to 6, characterized in that two interchangeable protective cover ( 12 a , 12 b ) are provided that each gripper arm ( 22 , 23 ), the protective cover and the grinding wheel ( 11 a , 11 b ) when changing the grinding wheel is designed to take over together from the grinding spindle ( 7 a) and that when a grinding wheel is placed on the grinding wheel holder ( 18 ), the respective protective cover ( 12 b) is held on the relevant gripping arm. 8. System according to one of claims 5 to 7, characterized in that the protective hood ( 12 ) on the periphery of its end face carries a circumferentially controlled adjustable clamping ring segment ( 71 ) and in that the protective hood cover ( 12 a) in the manner of a bayonet lock through Adjustment of the clamping ring segment ( 71 ) in the circumferential direction on the protective hood ( 12 ) is lockable. 9. System according to one of claims 1 to 8, characterized in that the grinding wheel holder ( 18 ) is designed as a transverse to the axis of the vertical gripper arm ( 22 or 23 ) movable wheel carriage ( 18 ) which benauftake the grinding wheel on its side facing the gripper arm ( 28 , 29 ). 10. System according to claim 9, characterized in that on the changer bracket ( 16 ) a horizontally extending guide ( 32 ) is attached, that a transport member ( 31 ) can be moved along the guide that the disc carriage ( 18 ) with coupling means ( 83 , 84 , 86 ) for docking the disc carriage on the transport member and that drive means ( 79 ) for moving the trans port member are provided along the guide. 11. System according to any one of claims 1 to 10, characterized in that each grinding wheel holder ( 28 , 29 ) of the grinding wheel holder ( 18 ) sensor means ( 99 ) for monitoring the presence of a grinding wheel are assigned. 12. System according to any one of claims 9 to 11, characterized in that the disc carriage ( 18 ) is lifted off the floor when docked to the transport member ( 31 ). 13. System according to one of claims 9 to 12, characterized in that the disc carriage ( 18 ) or the trans port organ ( 31 ) and the changer bracket ( 16 ) cooperate de indexing means ( 82 , 82 a , 82 b ) for providing the positionally accurate Have disc car. 14. System according to one of claims 1 to 13, characterized in that a grinding wheel magazine ( 21 ) is provided for receiving grinding wheels from the grinding wheel holder ( 18 ). 15. System according to one of claims 1 or 3 to 14, characterized in that the changer head ( 88 ) consists of a swivel body ( 90 ) which is rotatable on a frame ( 95 ) about a vertical axis ( 91 ) and about a horizontal axis ( 92 ) is tiltably mounted, and that the swivel body ( 90 ) is equipped on different sides with gripping means ( 89 ) for receiving and holding grinding wheels ( 93 , 93 a ). 16. Grinding wheel changer, in particular for use in a grinding wheel changing system according to one of claims 1 to 14, characterized in that it consists of a changer bracket ( 16 , 95 ) and a pivotably arranged on this, the grinding wheels ( 11 a , 11 b , 93 , 93 a ) there is a changer head ( 17 , 88 ) in the horizontal axis alignment of the grinding spindle ( 7 a) and in the vertical axis alignment to a grinding wheel support ( 18 ) which has at least one gripping means ( 22 , 23 , 89 ) with clamping means ( 44 ) for receiving and holding grinding wheels, and that he with means ( 39 , 42 ) for moving towards and away from each other move the clamping means ( 44 ) of the gripping means on the one hand and the grinding spindle ( 7 a) or the grinding wheel receptacles ( 28 , 29 ) of the grinding wheel storage ( 18 ) is equipped on the other hand.