The present invention relates to a clamping device for a machine spindle of a machine tool, and in particular to a clamping device intended for the machine spindle of a turning lathe.

In order to be able to respond to the ever more frequent demand for flexible production of components, the changeover to different workpieces within a machine is becoming more and more important. Set-up costs also constitute an essential component of the production costs for the corresponding workpieces. Accordingly, in particular in small production runs for rotating parts, the set-up times are the crucial factor in order to achieve a justifiable production price. In particular, the times required to change a tool, a clamping device or clamping jaws, which substantially influence the set-up times, must be emphasized here.

For the reasons given above the lathe chuck industry has been concerned for many years with rapid jaw change systems in order to facilitate and speed up the changeover to different workpieces. It is a disadvantage of rapid jaw change systems that there is often reduced repetition accuracy in production. Moreover, the rapid jaw change systems only make it possible to reduce a relatively small fraction of the set-up times. One would achieve a

considerably greater cost-saving potential by reducing the changing times for the entire chuck.

For the reasons given above it is the object of the present invention to provide a clamping device wherein the set-up times are reduced to a minimum while keeping the repetition accuracy the same.

According to a first aspect of the present invention there is provided, a clamping device for a machine spindle of a machine tool, in particular a turning lathe, the clamping device having the following: a base flange which is designed to connect the clamping device detachably to the machine spindle of the machine tool; a chuck which has at least two clamping jaws for applying a clamping force to a workpiece clamped in the chuck; an intermediate flange which can be connected detachably to the base flange and the chuck and is designed to connect the chuck detachably to the base flange, the base flange comprising a locking mechanism which has a first state in which the intermediate flange can be detached from the base flange, and a second state in which the intermediate flange is connected rigidly to the base flange.

Accordingly, the clamping device has a base flange which is designed to connect the clamping device detachably to the machine spindle of a machine tool. A chuck which has at least two clamping jaws for applying a clamping force to a workpiece clamped in the chuck is also provided. The chuck and the base flange are detachably connected by an intermediate flange. The base flange further comprises a locking mechanism which has a first state, in which the intermediate flange can be detached from the base flange, and a second state, in which the intermediate flange is connected rigidly to the base flange. The advantages of the clamping device according to the invention are obvious. Set-up times can be considerably reduced, particularly due to the fact that the chuck together with the intermediate flange can be detached particularly quickly and easily from the base flange. This is achieved by the locking mechanism of the base flange which serves to rigidly connect the intermediate flange to the base flange and to detach it with a small number of movements of the hand. In the first state of the locking mechanism it is accordingly easily possible to remove the chuck, together with the

intermediate flange, from the base flange. A new chuck with a substantially identical intermediate flange can then be placed on the base flange and can be connected rigidly to the base flange by the locking mechanism.

Moreover, due to the simple structure of the clamping device one is offered especially easy handling and greatly improved repetition accuracy so that the workpiece to be machined is precisely aligned after changing the chuck. Finally, due to the modular structure of the clamping device it is possible to retrofit the latter to existing machines.

Advantageous further developments of the clamping device according to the invention can be gathered from the sub-claims.

In an embodiment, the locking mechanism has a locking ring which is mounted rotatably within an internal space in the base flange so that the locking ring can be moved by a rotational movement from a first position, which corresponds to the first state of the locking mechanism, into a second position, which corresponds to the second state of the locking mechanism, and back. Due to the design of the locking mechanism as a locking ring in the internal space of the base flange, particularly long service lives are possible. In detail, due to the provision of the locking ring the effort of maintaining the locking mechanism is considerably reduced. The locking ring also means that a short rotational movement is sufficient in order to move the locking mechanism from its first into its second state and back. In this way, connection of the base flange to the intermediate flange, and so to the chuck, is substantially speeded up.

In an embodiment, the intermediate flange can have at least two locking elements which are attached detachably to the intermediate flange. The locking elements are designed so that they can be moved into the internal space of the base flange such that in its second position the locking ring is actively engaged with the at least two locking elements. Preferably this establishes a rigid connection between the base flange and the intermediate flange. It is preferable that the at least two locking elements are aligned perpendicularly to the connection plane of the intermediate flange. In other words, the at least two locking elements run substantially parallel to the longitudinal axis of the machine spindle and can be moved into corresponding openings of the base flange. In this way a precisely specifiable alignment of the chuck can be achieved after changing the chuck, by means of which repetition accuracy is increased. The repetition accuracy can be further increased if the intermediate flange does not have two, but rather three, four or more locking elements which are attached detachably to the intermediate flange.

The aforementioned at least two locking elements are preferably made in the form of locking bolts which each have notches on the side. Furthermore, according to this embodiment provision is made such that the locking ring has first regions with a first diameter and second regions with a second, reduced diameter. The first regions are designed to actively engage with the side notches of the locking bolts in the second position of the locking ring. In contrast, the second regions with the reduced diameter are designed such that in the first position of the locking ring there is no contact with the locking bolt. Expressed simply, in its second position the locking ring engages the notches of the locking bolts and so connects the intermediate flange rigidly to the base flange. This design of the locking mechanism that comprises at least two locking elements in the form of locking bolts and a locking ring with regions having different diameters has particularly low susceptibility to damage. Moreover, the individual components, such as the at least two locking bolts and the locking ring, are particularly easy to produce, by means of which the cost of the clamping device can be reduced.

In an embodiment, the locking mechanism also has an actuation device which is designed to move the locking ring from its first position into its second position and back. The actuation device is attached to the base flange such that it can be operated from outside of the base flange. It is noted at this point that the actuation device can be controlled manually (e.g. by hand) and also automatically (e.g. magnetically, electrically or pneumatically). Irrespective of which principle of operation lies behind the actuation device, one must ensure that the actuation device can be operated from outside of the base flange. It is therefore not necessary to remove the base flange from the machine spindle in order to replace the intermediate flange along with the chuck. The actuation device can be arranged on a peripheral region of the base flange, where it is particularly easily accessible. The actuation device preferably has a gear rack which is actively engaged with toothing attached to a peripheral region of the locking ring so that the locking ring can be moved from its first position into its second position and back by a translatory movement of the gear rack. The gear rack is preferably also located within the base flange. The actuation mechanism thus requires a particularly small amount of maintenance effort. Due to the design of the actuation mechanism as a gear rack, direct and rapid power transmission takes place. In an embodiment, the gear rack has a through hole with an internal thread in which an adjustment screw is accommodated. The adjustment screw is attached to the base flange such that it is possible to rotate the adjustment screw from the outside of the base flange. Accordingly, the gear rack can be controlled by a simple rotational movement of the adjustment screw which is converted into a translatory movement of the gear rack. The actuation device can thus be actuated very easily by hand, for example using a screwdriver.

In an embodiment, the base flange also has a first lubricant connection which is attached to a peripheral region of the base flange and is designed to convey lubricant to the gear rack of the actuation device. This guarantees that the gear rack can be moved, as far as possible, without any friction within the base flange. The lubricant connection makes it possible to top up lubricant without having to remove the clamping device from the machine spindle.

Furthermore, the base flange can have a second lubricant connection which is connected or can be connected to at least one lubricant groove of the locking ring. The second lubricant connection serves in particular, in association with the at least one lubricant groove of the locking ring, to convey lubricant to an inner through hole of the locking ring. This guarantees that the locking ring only shows small amounts of wear, even when the chuck is changed frequently. It is also possible to re-lubricate the locking ring from the outside of the base flange, so that the flange does not have to be dismantled. The lubricant groove can run substantially radially over a side surface of the locking ring, as will be described in more detail below.

In an embodiment, the locking mechanism also has a mechanism for displaying whether it is in the first or the second state. It is thus made possible for the operator of the clamping device to identify the fastening state of the intermediate flange to the base flange. This is particularly necessary since it is only possible to move the intermediate flange into the base flange and to detach it from the latter in the first state of the locking mechanism.

Moreover, the machine tool must of course not be operated if the locking mechanism is in the first state. It is moreover conceivable for the mechanism to be additionally monitored automatically, for example by a sensor element, in order to display whether it is in the first or the second state in order to prevent the machine tool from being switched on in the first state of the locking mechanism.

The mechanism for displaying the first and the second state advantageously has an indicator pin which extends radially inwards from the outside of the base flange towards the locking ring and engages a groove of the locking ring. The indicator pin is therefore integrated into the base flange and forms a simple method for displaying the position of the locking ring externally, for example on the peripheral region of the base flange. By moving the indicator pin within a groove of the locking ring it is particularly easily possible to replace the indicator pin if the latter is faulty.

In an embodiment, the groove of the locking ring is made substantially in a V- shape and is thus engages the indicator pin so that in the second state of the locking mechanism the indicator pin ends substantially flush with the outside of the base flange and, in the first state of the locking mechanism, is pushed radially outwards from the base flange. The words "substantially in a V- shape" are to be understood as meaning any groove which has a part that runs radially inwards and a part that runs radially outwards. As will be explained in more detail below, this substantially V-shaped groove means that the indicator pin serves not only as an indicator for the first and the second state of the locking mechanism, but can also be used to indicate over-rotation of the locking mechanism, in particular of the locking disc, i.e. a third position or a third state. In an embodiment, the clamping device further comprises an adapter device which is designed to connect the chuck to a connecting rod of the machine tool. Due to the intermediate flange it can be difficult to connect the connecting rod to the chuck because the distance between the chuck and the machine spindle is increased. For this reason, there can be provided on the clamping device an adapter device which simplifies the connection between the connecting rod and the chuck. The adapter device can be made up modularly of a number of cylinder elements. It is thus easily possible to adapt the adapter device to the opening diameter of the base flange, the chuck and the intermediate flange.

In the following the clamping device according to the invention will be described in more detail by means of the embodiment shown in the figures.

These show as follows:

Fig. 1 A perspective illustration of an embodiment of the clamping

device;

Fig. 2 a top view of the the embodiment of the clamping device

shown in Fig. 1 ;

Fig. 3 a side view of the embodiment of the clamping device shown in

Fig. 1 , the intermediate flange and the chuck being shown separated from the base flange;

Fig. 4 a cross section through the embodiment of the clamping

device along the centre line of the section A-A shown in Fig. 2;

Fig. 5 an exploded view of the base flange and of the adapter device according to the embodiment of the clamping device ;

Fig. 6 a perspective part-section through an intermediate flange and a base flange according to the embodiment of the clamping device in the first state of the locking mechanism; and

Fig. 7 a perspective part-section of the clamping device of Fig. 6, in the second state of the locking mechanism. In the following detailed description of the figures the same components or components having the same effect are provided with the same reference numbers.

Figures 1 to 7 show different views of an embodiment of the clamping device 1 according to the invention. One can see from Fig. 1 that the clamping device according to the invention has a base flange 30 which is designed to connect the clamping device 1 detachably to the machine spindle 2 of a machine tool (not shown). Attached detachably to the base flange 30 is an intermediate flange 20 which serves to connect the chuck 10 detachably to the base flange 30. For this purpose the intermediate flange 20 is also connected detachably to the chuck 10. The connection between the chuck 10 and the intermediate flange 20 is achieved, in particular, by means of fastening elements 12, as can be seen for example from Fig. 4. The chuck 10 can be a chuck that is essentially known from the prior art. For example, the power-actuated FNC chuck made by Forkardt Deutschland GmbH as can be seen in the "FNC power chuck with rapid jaw change system" product catalogue produced by Forkardt GmbH. The chuck 10 has at least two, here three, clamping jaws (not shown) for applying a clamping force to a workpiece clamped in the chuck. In the clamping device 1 it is

insignificant whether the chuck 10 has two, three or more clamping jaws.

The clamping jaws of the chuck 10 shown are connected to the base jaws 16 by means of which they can be moved in a radial direction. In addition, rapid clamping jaw change systems 14 can be provided on the chuck 10. However, these will not be described in any more detail here.

Fig. 3 shows a side view of the clamping device 1 , the intermediate flange 20 and the chuck 10 being detached from the base flange 30. It can be seen immediately that at least two, here three, locking elements 22 are attached to the intermediate flange 20. The locking elements 22 are designed to be moved into the internal space in the base flange 30. As will be described in more detail below, openings are provided for this purpose on the front side of the base flange 30. The chuck 10 is connected detachably by fastening elements 12 to the intermediate flange 20 which in turn can be connected detachably to the base flange 30 by the locking elements 22.

The connection between the intermediate flange 20 and the base flange 30 can be seen, for example, in Fig. 4. It is shown here how the locking elements 22 are formed as locking bolts which each have side notches 24 (see also Fig. 3). The locking bolts are connected detachably to the intermediate flange 20. For this purpose, as shown, respective fastening nuts 26 can be provided which are secured against turning at the side by threaded pins 27. Correct alignment of the locking elements 22 is guaranteed by cylinder pins 28 attached at the peripheral region of the intermediate flange 20. These cylinder pins 28 extend towards the respective locking elements 22 and engage with second notches 25 provided for this purpose at the upper end region of the locking elements 22. The second notch 25 thus ensures that the side notch 24 of the respective locking element 22 is aligned towards the locking ring 40.

The locking elements 22 in the form of locking bolts can be moved into openings 37 on the front side of the base flange 30, which are provided for this purpose. In other words, the locking elements 22 are accommodated in the internal space in the base flange 30 which is made up of a rear housing part 30-1 and a front housing part 30-2. This gives rise to an internal space of the base flange 30 which is designed to accommodate a locking mechanism which has a first state, in which the intermediate flange 20 can be detached from the base flange 30, and a second state in which the intermediate flange 20 is connected rigidly to the base flange 30. The two housing parts 30-1 , 30- 2 of the base flange 30 can, for example, be connected by the fastening elements 34 shown in Fig. 5 which can be brought into the openings 35 on the front side of the base flange 30.

The locking mechanism preferably has a locking ring 40 which is mounted rotatably in the internal space in the base flange 30. The locking ring 40 is disposed within the base flange 30 such that it can be moved by a rotational movement from a first position, which corresponds to the first, open state of the locking mechanism, into a second position, which corresponds to the second, closed state of the locking mechanism, and back. In the illustration of Fig. 4 the second, closed position of the locking mechanism 40 in particular is shown. In this second position the locking ring 40 engages in the

aforementioned notch 24 of the locking element 22, which is in the form of a locking bolt.

A detailed illustration of the locking ring 40 is shown, for example, by the exploded view in Fig. 5. As can be seen, the locking ring 40 has first regions 41 with a first diameter, and second regions 42 with a second, reduced diameter. Three recesses are created by the second regions 42. These recesses make it possible to move the locking elements 22 into the interior of the base flange 30. The first regions 41 are designed to engage operatively with the side notches 24 of the locking elements 22, which are in the form of locking bolts, in the second position of the locking ring 40. In contrast, the second regions 42 with the second, reduced diameter are designed so that in the first position of the locking ring 40 there is no contact with the locking elements 22.

The first position of the locking ring 40, i.e. the first, open state of the locking mechanism, can be seen in Fig. 6. Here the second regions 42 of the locking ring 40 are respectively aligned with the openings 37, so that the locking elements 22 can be moved into the interior of the flange element 30. At the same time, this means that it is only possible to move the locking elements 22 into the openings 37 of the base flange 30 in the first, open state of the locking mechanism. As soon as the locking elements 22 of the intermediate flange 20 have been moved into the openings 37 of the base flange the locking ring 40 is moved by a rotational movement from its first position, shown in Fig. 6, into its second position, shown in Fig. 7. In the second position of the locking ring 40 the first regions 41 , which have the extended diameter, are actively engaged with the notches 24 in the respective locking bolts 22. It is noted that by rotating the locking ring 40 all three of the first regions 41 shown in Fig. 1 actively engage simultaneously with the respective notches 24 in the locking elements 22. Accordingly, it is only necessary to actuate the locking mechanism once in order to connect all of the locking elements 22 rigidly to the base flange. As an equivalent to this, by rotating the locking ring 40 in the opposite direction, all three of the second regions 42 are aligned with the openings 37

simultaneously.

Referring again to Fig. 5 it is noted that in order to actuate the locking ring the locking mechanism further comprises an actuation device which is designed to move the locking ring from its first into its second position and back.

According to the embodiment shown the actuation device has a gear rack 50 which can be actively engaged with toothing 47 attached to a peripheral region of the locking ring 40 such that the locking ring 40 can be moved from its first position into its second position and back by a translatory movement of the gear rack 50.

The gear rack 50 preferably has a through-hole 52 with an internal thread which serves to accommodate an adjustment screw 54. By rotating the adjustment screw 54 a translatory movement of the gear rack 50 within the base flange 30 can be achieved. The adjustment screw 54 can be actuated from the outside of the base flange 30. For this purpose the adjustment screw 54 can be connected, for example, by means of a fastening element 56 to the peripheral region 32 of the base flange 30. Furthermore, as shown in Fig. 5, the locking ring 50 has two lubricant grooves 49 which are connected to a lubricant connection 36. The lubricant

connection 36 is disposed on the front side of the base flange, i.e. on the front housing part 30-2 (see Fig. 4). The lubricant grooves 49 are designed such that the lubricant (i.e. lubricating oil) introduced via the lubricant connection 36 is conveyed towards the inner through-hole of the locking ring 40. For this purpose the lubricant grooves 49 are disposed substantially radially on a side surface of the locking ring 40 facing towards the front housing part 30-2 of the base flange 30. Alternatively, or in addition to this, the base flange 30 can have a second lubricant connection 38 which is attached to its peripheral edge 32, and in particular is connected to the gear rack 50 via a channel (not shown) which extends within the base flange 30. It is thus easily possible to lubricate the moveable parts within the base flange 30 without having to take it apart.

Finally, as shown in Figures 6 and 7, the clamping device preferably has a mechanism for displaying whether the locking mechanism is in its first or its second state. The mechanism for displaying the first and the second state is part of the locking mechanism, and is in the form of an indicator pin 60. The indicator pin 60 extends from the outside, in particular the peripheral region 32 of the base flange 30, radially inwards towards the locking ring 40. The indicator pin 60 contacts a groove 45 of the locking ring 40 at a first end region 62. The groove 45 is on a thinning region 43 of one of the first regions 41 of the locking ring 40. Accordingly, the first end region 62 can engage in the groove 45 without having to enlarge the internal space in the base flange 30.

A second end region of the indicator pin 60 in the form of a sleeve 66 is mounted within the housing of the base flange 30 such that the latter is visible on the outside of the base flange 30. As best shown in Fig. 5, the indicator pin 60 further comprises a displaceable rod element 64 which engages the groove 45 via the first end region 62. Furthermore, the rod element 64 is accommodated in the sleeve 66 of the indicator pin 60 formed in the second end region and is mounted displaceably within the latter. In the first position of the locking ring 40 (shown in Fig. 6) the first end region 62 of the indicator pin 60 is located on an end region of the V-shaped groove 45 that is on the outside radially, so that the rod element 64 is pushed radially outwards and projects from the sleeve 66. By turning the locking ring 40 in the anticlockwise direction, i.e. into the second position of the locking ring 40 (Fig. 7), the first end region 62 of the indicator pin 60 is moved towards the lower end region of the V-shaped groove 45 which is on the inside radially, so that the rod element 64 is drawn into the sleeve 66. At the turning point, e.g. the apex, of the V-shaped groove 45 the rod element 64 ends flush with the sleeve 66. It is thus clear to the user at any time whether the locking mechanism of the base flange 30 is in its first or in its second state.

If the user actuates the actuation element 50 for too long, and turns the locking ring 40 too far in the anticlockwise direction, the indicator pin 60 is moved further towards the end of the V-shaped groove 45 shown on the right in the figures, so that the rod element 64 is in turn pushed outwards. In this way it is clear to the operator that the ideal locking point for the locking ring 40 has been exceeded and it is no longer necessary to turn the adjustment screw 54 any further. Alternatively, a stop can also be provided within the base flange 30 which prevents further turning of the locking ring 40 beyond the second, closed position.

Finally, coming back to the sectional illustration shown in Fig. 4, clamping device 1 preferably further comprises an adapter device which is designed to connect the chuck 10 to a connecting rod (not shown) of the machine tool. The adapter device preferably has a modular structure consisting of a first, a second and a third cylinder element 80, 82, 84 which can be connected to one another by corresponding threads. The adapter device means that, despite the extended distance between the chuck 10 and the machine spindle, it is possible to connect the connecting rod to the chuck. By means of its modular structure, the adapter device can have different dimensions, which means that it can be used for a plurality of chucks 10. The present invention is not restricted to the embodiments shown in the figures. In fact, the invention results from a combination of all of the features disclosed here.

List of reference numbers

1 clamping device

2 machine spindle

10 chuck

12 fastening element

14 rapid clamping jaw change system

16 base jaw

18 passage opening

20 intermediate flange

22 locking element

24 notch

26 fastening nut

27 threaded pin

28 cylinder pin

30 base flange

30-1 rear housing part

30-2 front housing part

32 peripheral region

34 fastening element

35 first openings

36 first lubricant connection

37 second openings

38 second lubricant connection

40 locking ring

41 first regions

42 second regions

43 thinning region

45 V-shaped groove outer toothing

lubricant groove gear rack

through hole

adjustment screw fastening element indicator pin

first end region rod element

sleeve

first cylinder element second cylinder element third cylinder element