WO1989006580A1

WO1989006580A1 - Device for producing a clamping force for operating a power clamping device for rotating working spindles

Info

Publication number: WO1989006580A1
Application number: PCT/EP1989/000046
Authority: WO
Inventors: Hubert Bald
Original assignee: GEDIB Ingenieurbüro und Innovationsberatung GmbH
Priority date: 1988-01-19
Filing date: 1989-01-17
Publication date: 1989-07-27
Also published as: DE3823141A1

Abstract

A hydraulically driven clamping device for machine-tools can operate at high pressures of at least 80 bar. To permit adjustment during rotation of the spindle, a displacement-reducing gear/force-increasing gear is arranged between a stationary adjusting element and the clamping aggregate.

Description

Device for generating a clamping force for the actuation of a force clamping device for rotating work spindles.

The invention relates to cutting devices, in particular for machine tools.

Modern materials for cutting tools allow extremely high cutting speeds, which can be achieved by correspondingly high working machine spindle speeds. The clamping devices used for clamping the workpieces (e.g. in lathes) or tools (e.g. in drilling and milling machines) are generally power-operated, electrical, pneumatic and hydraulic drives being known.

The invention relates to devices for generating clamping movements and clamping forces on rotating work spindles, in particular on hollow work spindles, such as are used in rod turning machines.

The state of the art is characterized by hydraulically operated clamping devices and is evidenced, for example, by the company publication of Paul Forkardt "Circulating pressure oil hollow cylinders OZREJ" No. 422.01.30. These known devices include a revolving tensioning piston with associated cylinder spaces, and the hydraulic fluid is supplied and discharged from a stationary hydraulic unit during the circulation via a so-called rotary feedthrough with gap seals. These seals represent a weak point, since the inevitable leakage limits the maximum working pressure, with the result that clamping pistons with correspondingly large effective cross sections have to be used for a given clamping force; this in turn leads to large rotating masses and thus to a limitation of the permissible speed. This is further limited by the fact that the energy losses in the sealing gaps of the rotating union are speed-dependent and that with increasing speed, more and more heat loss is transferred to the spindle and its bearings. Extremely high speeds are particularly desirable for bar lathes because the machining diameters are small.

Another disadvantage of the known hydraulic clamping drives also results from the large mass of the rotating parts and the rotating union connected to them: This assembly can only be attached to the rear (i.e. the machining side) end of the lathe spindle, cantilevered axially and radially and leads Vibration problems. In the case of bar lathes, the bar feed is also impeded.

The considerable disadvantages of the described prior art result - if the technical problem is formulated in an abstract form - from the principle used to transfer the energy required for the movement and clamping process from stationary parts to the parts rotating with the spindle.

The object of the invention is to improve this transmission principle so that, provided that the rotating drive elements are to be actuated hydraulically, a tensioning device can be created which manages with high pressures and therefore correspondingly small tensioning pistons, so that the overall size and the rotating mass are reduced with the advantageous consequences that higher speeds are permissible --- desirable especially for bar lathes, in which collets are used instead of jaw chucks at risk of centrifugal force - so that other equipment to be arranged on the spindle head can also be advantageously operated hydraulically and thus new, advantageous machine types are made possible, for example those in which the spindle drive motor is arranged coaxially with respect to the spindle axis, the clamping cylinder being accommodated in the interior of the rotor or the spindle box.

The solution provided according to the invention is defined in the independent claims. It is based on the following considerations: The process of clamping a workpiece (or tool) involves several phases:

(a) The clamping device is to be brought up to the diameter of the workpiece / tool with an idle stroke requiring little force.

(b) when the clamping jaws rest on the workpiece, the clamping stroke takes place with elastic deformation of all parts lying in the force flow until the desired clamping force is reached.

(c) during spindle rotation, e.g. Because of the cold flow of the workpiece, a "follow-up" of the clamping device may be necessary.

In the case of bar lathes, it is desirable to also carry out phase (b) during the spindle revolution, that is to say to release, advance and re-tension the bar.

The principle of the invention is to "fill" the revolving hydraulic network, which in addition to the tensioning cylinder and its cylinder spaces also includes supply and discharge channels, auxiliary and control pistons and possibly control valves, by means of a stationary hydraulic unit when the spindle is at a standstill, and to decouple the pressure fluid source during the spindle revolution . A separate unit is provided which can be used to act on the clamping force during the spindle rotation.

This initially allows working with much higher pressures than previously customary, so that the rotating parts of the clamping device can be made correspondingly small. In addition to "filling" the network, phase (a) or even phases (a) and (b) of the tensioning process can also be carried out when the spindle is at a standstill, the separate unit then being designed as a tensioning force store. However, all phases (a), (b) and (c) can also be carried out by means of the separate unit, in particular when turning the rods; the separate unit includes means for controlled displacement of the tensioning piston. In this case, a step-down / force converter is advantageously connected between the (stationary) means and the tensioning piston, so that only small forces have to be transmitted at the first interface between stationary and rotating parts. - The principle of action thus applied is most clearly recognizable when phase (b) is carried out: the (clamping) energy to be transmitted by the clamping piston as a product of high (clamping) force and a small (clamping) path becomes less at the first interface as a product (Adjust) power and large (adjust) way fed. In addition to the hydraulic version of a path reducer / force booster, a mechanical version (according to FIG. 6) is also possible within the scope of the invention.

The second interface between the stationary pressure fluid source and the circulating hydraulic network can be designed for operation during the spindle standstill in the manner of a hydraulic quick coupling with a hermetic seal or with a gap seal coupling point; however, it would also be possible to work with a rotating union, since this only needs to carry out a fluid exchange when the spindle is at a standstill. The above-mentioned principle of displacement-force conversion would even make it possible to use a permanently acted upon or actable rotary lead-through with low pressure. It should be noted that pneumatic clamping means power drives are known in which the compressed air source is only coupled when the spindle is at a standstill. The compressible compressed air then takes over the role of the clamping force accumulator during the circulation (company publication Paul Forkardt "Power operated chucks"# 200.01.9D). Check valves serve as shut-off devices for the rotating clamping cylinder. However, it is known to the person skilled in the art that such tensioning drives can only be used with so-called front end chucks which rotate relatively slowly, since they have large diameters. The principle of revolving tension accumulator is also provided for the electric tension drives according to DE-PS 33 14 629 and EP-OS 86 11 7350.2.

In the electrical tensioners according to DE-PS 32 18084 or DE-OS 36 42 309 mechanical means are provided in order to change, control or even regulate the clamping force during the spindle rotation; the mechanical means include gear elements such as belts, gears, screw drives, etc., factors such as manufacturing costs, noise, energy losses, operational safety, manageable maximum speeds and others being taken into account for the practical use of such devices.

In the context of the present invention, it is preferred to use special roller bearings, namely so-called spindle bearings (angular contact ball bearings), at the first interface between stationary and rotating adjusting members. In the older patent application DE-37 27 445, a tensioning unit with revolving tensioning force storage device is disclosed, in which tensioning forces are transferred from a stationary adjustment unit to the revolving assembly during the spindle revolution via axial roller bearings; however, the full clamping force must be guided through these bearings, which must be dimensioned accordingly and, in order to be able to guarantee a reasonably reasonable service life, should only be loaded for a short time. A displacement force converter according to the present invention would allow this construction to be improved.

Embodiments of the subject of the invention are explained below with reference to the accompanying drawings. Fig. 1 shows an axial longitudinal section through the headstock of a lathe, equipped with a hydraulically operated clamping device according to the invention.

2 shows in partial section the hydraulic interface between the stationary fluid pressure source and the circulating network in two working positions,

3 shows a partial section of a clamping force feeder, as can be provided in the machine according to FIGS. 1 and 2,

4 is a partial side view, partially in section, of a lathe according to the invention with the rotor of the spindle drive motor seated on the work spindle,

5 shows, analogously to FIG. 4, an embodiment of a lathe which is modified compared to this.

Fig. 6 shows an axial longitudinal section through the headstock of a lathe, equipped with a mechanically operated clamping device according to the invention.

Fig. 7 is an axial longitudinal section through the front part of a lathe headstock with hydraulically operated clamping devices on the spindle head for clamping a clamping device.

Figure 8 shows the axial section through the front of a lathe headstock with hydraulically operated operating means located on the spindle head.

1 shows in axial section the headstock 102 of a lathe with a work spindle 104. The spindle is mounted in the headstock by means of a first bearing assembly 106, consisting of three angular contact ball bearings as a fixed bearing, and a loose bearing in the form of a further angular contact ball bearing 105. The loose bearing is axially preloaded by the collar 108 of a flange 118 resting on its outer ring; on the Flange 118 is acted upon by the forces of three hydraulic working cylinders 110 with pistons 114 distributed uniformly over the circumference, the piston rods 112 of which are connected to the flange. Compression springs 116 act in addition to the pressure of the fluid fed in and provide a basic preload.

At its end facing away from the chuck side, the spindle has a pulley 120 outside the headstock, on the outer end of which a cover 122 is fixed by means of screws 124-. The spindle 104-, the pulley 120 and the cover 122 delimit a stepped hollow cylinder which receives a hollow piston 126 of complementary shape.

Fig. 1 shows the piston 126 in its outer (left) end position, from which it can execute a maximum clamping stroke H 1. The piston is shown in the lower part after passing through a partial stroke H 2.

In the hollow spindle 104, the usual pull-push tube 128 is axially displaceable, but non-rotatably connected to the spindle. The connection of the tube 128 with one provided on the spindle head 130

Clamping means is not shown because these constructions are familiar to the person skilled in the art. The transmission of the clamping forces from the hollow piston 126 to the pull-pressure tube 128 takes place via four thrust blocks 132 guided in grooves 134 of the spindle 104 with cylindrical inner and outer lateral surfaces, which are seated in corresponding annular grooves of the piston 126 or the tube 128; the assembly is carried out in the manner of a bayonet lock by means of insertion grooves 136 of the tube 128.

The pulley 120 is secured axially and non-rotatably on the spindle by a plurality of conical pins 140 distributed over the circumference.

The cylinder chambers 144, 146 of the hollow piston 126 can be pressurized with pressurized fluid via assigned channel bores 152 and 154; the cylinder spaces 148 of two auxiliary pistons 142 which can be axially displaced in the cover 122 can also be controlled via the channel bore 150; The lower auxiliary piston in FIG. 1 is shown in its position displaced to the right up to a stop.

The control takes place from a hydraulic movement conversion system or converter 160 via a pressure body 158 with a connection system 156. The converter 160 further comprises, as input members, control pistons 162 which increase the pressure in associated cylinder spaces 164 when shifted to the left, as well as step pistons 166 which when shifting to the right, increase the fluid pressure in assigned cylinder spaces 168. The control and step pistons 162, 166 are axially displaced relative to the pressure body 158 by means of the transmission member 170, which is firmly connected to the inner ring of the angular contact ball bearing 172. Accordingly, the parts of the converter 160 described so far rotate synchronously with the work spindle 104, and the actuation of the cylinder spaces can be changed while the spindle rotates; The piston 126 and the auxiliary piston 142 represent the output organs of the converter, the distances traveled being inversely proportional to the effective piston areas of the input and output organs, for example if the hollow piston 126 is also shifted to the left by moving the control piston 162 to the left. The inner ring of the angular contact ball bearing 172 and a further angular contact ball bearing 172 'arranged next to it in mirror image are axially braced against one another and axially displaceable on the work spindle 104. The pretensioning takes place via the outer rings by means of a flange sleeve 174 and a clamping ring 176 which is screwed to an annular disk 178, which in turn is connected to pistons 180, 180 'via bolts 182. These are assigned to cylinder chambers 184 and 186, which, when appropriately actuated with pressurized fluid, enable the pistons to be displaced to the right or left, taking components 170 to 182 with them. In the event of displacement to the left, the control pistons 162 are pressed into their cylinder chambers while when shifting to the right, the transmission element 170, which engages behind a lug 188 on the stepped piston 166, shifts it into the cylinder space 168. These two positions are drawn in the upper and lower part of FIG. 1. It should be noted that four control and stepped pistons are alternately distributed uniformly in the circumferential direction. The sum of the effective piston areas of each set of four control or stepped pistons is approximately 1/20 of the effective piston area of hollow pistons 126 in the cylinder space 146. Thus, if the cylinder spaces 164 are connected to the cylinder space 146 via channel bores, an axial force acting on the transmission element 170 is sufficient of 300 daN to generate an axial force of 6000 daN through the piston 126 at a hydraulic pressure of 160 bar. An axial load of approximately 300 daN can also be safely transmitted from bearings 105 and 172, 172 'even at extremely high spindle speeds and with diameters corresponding to a spindle passage of, for example, 85 mm. The sum of the effective piston areas of the pistons 114 is designed to be somewhat larger than that of the pistons 180 and 180 ', and a hydraulic connection (not shown) of the cylinders 186 and cylinders 110 ensures that the reaction forces are introduced into the headstock.

The effective piston area of hollow pistons 126 is somewhat larger in the cylinder chamber 146 than in the cylinder chamber 144. If both cylinder chambers are pressurized with the same pressure, the piston works as a differential piston with a large displacement and low force development while feeding in a small volume of hydraulic fluid. The pressure fluid is supplied by a stationary hydraulic unit (not shown), the pressure output of which can be coupled to the rotating hydraulic network when the work spindle 104 is at a standstill. Fig. 2 shows the decoupling position in the upper part, the coupled position in the lower part. The pressure body 158 has, as a coupling part, an unlockable ball check valve 202, while a non-rotating second coupling part is arranged in the headstock 102 and can be connected to the hydraulic unit, for example, via a pressure hose. If the cylinder space 216 is supplied with pressure fluid, the clutch piston 210 moves in the direction of the pressure body until a sealing ring 214 hermetically seals and a mandrel 212 presses the shut-off ball 206 back from the seat 234. Of course, this is only possible if the two coupling parts are aligned; the angle of the spindle would be detected for this purpose, by means of an inductive sensor 198 which interacts with a ring gear 196 (Fig. 1). The connecting bore 230 then opens, for example, into one of the cylinder spaces 164. A flattening 232 of the pressure element 158 is provided in the sealing area of the sealing ring 214. The inlets and outlets of the cylinder space 216 and their control are not shown for the sake of simplicity.

According to FIG. 3, the pressure body also contains a hydraulic fluid reservoir in the form of a cylinder space 306 with a piston 308 that can be displaced against the force of a spring 310. This arrangement can also serve as a tension force reservoir.

The function of the embodiment of the invention according to FIGS. 1 to 3 will be explained below, assuming for simplicity that the tension-compression tube for tensioning is to be shifted to the left in FIG. 1.

Different operating modes are possible:

First operating mode. When the spindle is at a standstill, the hydraulic unit is coupled and the cylinder space 146 is acted upon by a pressure which determines the clamping force and which is stored by the revolving accumulator according to FIG. 3. After uncoupling, the shooting can be done. By reconnecting the hydraulic unit, now depressurized, the workpiece becomes free again and the clamping force accumulator is depressurized. When the recirculating hydraulic circuit is pressurized, the control pistons 162 tend to run to the right and the stepped pistons tend to run to the left; however, both are in engagement with the transmission element 170. A possible difference in force due to unequal effective piston surfaces leads to a displacement of the latter into one of its end positions. From then on, these components of the system are no longer involved in the tensioning and relaxation processes.

Second operating mode. The effective piston surfaces are deliberately designed so that in the first mode of operation the control pistons 162 are always shifted to the right when tensioning takes place. A compression spring can then be accommodated in the cylinder chamber 186, which acts as an (additional) tension force accumulator; Of course, the cylinder space 184 can also contain such a spring, and the design of the piston surfaces would then be irrelevant.

Third mode of operation. As before, however, during the turning work, each of the cylinder spaces 184, 186 can be subjected to hydraulic pressure with a corresponding displacement of the transmission element 170 and the pistons 162 and 166 mechanically / hydraulically coupled to it. In this way, it is possible to increase the clamping forces during the spindle rotation change.

Fourth mode of operation. This mode of operation is particularly intended for bar turning machines, in which not only the clamping force is to be varied or at least kept constant during the spindle revolution, but also a feed of the workpiece is to be possible, which therefore requires loosening and reclamping of the pliers. For this purpose, a change is provided to the device according to FIG. 1, in that a pressure-controllable valve (not shown) is installed in the pressure body 158, which connects this to the cylinder space 144 up to a predetermined pressure in the cylinder space 146, but shuts off above this pressure and therefore Connects cylinder space 144 with channel 168 or cylinder 306.

In the starting position, the pistons 180, 180 'are on their right End position, with the control piston 162 with its left piston head in position "A". The remaining pistons 166, 126 and auxiliary pistons 142 assume the position shown in the lower half of FIG. 1.

The circulating hydraulic network is controlled by the stationary hydraulic unit with a pre-pressure which is below the closing pressure for the pressure-controlled valve mentioned. After uncoupling the stationary pressure source from the circulating network, pressure is applied to cylinder space 186. The pistons 180, 180 'migrate to the left and push the control pistons to the left in position "B". Since the pressure controllable valve is still open, piston 126 operates as a differential piston, and the volume of fluid fed is sufficient to let it pass through stroke H2 so that it reaches the position shown in the upper half of FIG. 1. The jaws of the collet which are operatively connected to the push-pull tube 128 are closed to such an extent that they come to rest on the rod to be machined. Further pressure increase in cylinder 186 leads to an increase in pressure in cylinder 164 above the critical value at which the pressure-controlled valve mentioned switches, and the connection between cylinder spaces 144 and 146 is now blocked while the connection between space 144 and space 168 is established becomes. The piston 126 is thus relieved on one side, and the pressure transmission between the pistons 162 and the piston 126 comes into effect. Accordingly, the tension-compression tube is displaced by the elastic lengthening of the intermediate components by the distance still required for clamping the workpiece rod (maximum one millimeter). The control pistons 162 reach the position "C".

In order to release the collet during the spindle rotation, the pistons 180, 180 'are moved into their right-hand end position, the transmission member dragging the stepped piston 166 after the elastic elongation has relaxed again (piston 162 move back to "B"). As a result, the auxiliary pistons 142 are shifted into their right end position, the hollow piston 126 also being shifted to the right by the stroke H2; that is enough to loosen the collet. The control pistons 162 return to position "A".

It can be seen that the coupling of the stationary hydraulic unit to the circulating system is only necessary to compensate for leaks. Numerous modifications can be made to the exemplary embodiment according to FIGS. 1 to 3. For example, the hollow piston, which is relatively small due to high-pressure operation, could be integrated in a so-called front end chuck or could also be accommodated in the space between the two spindle bearings 105 and 106 - for example integrated in the pressure body 158. This would be advantageous insofar as a spindle drive motor arranged concentrically to the spindle axis, as will be explained further below with reference to FIGS. 4 and 5, whose rotor could be designed with a smaller diameter and / or a rotating support for the workpiece rods or whose feed rod could be provided.

Furthermore, the converter 160 could only be used to carry out the actual clamping movement and the adjusting movement to adapt to other nominal clamping diameters by means of a sliding screw drive, for example according to DE-PS 3727445.

Fig. 4 shows that thanks to the inventive design of the clamping drive, the spindle drive motor can be arranged coaxially with respect to the spindle axis, directly on the rear end of the headstock 102, which sits on the machine base 402. The parts of the spindle between the spindle bearings are designed according to Fig. 1; the rear spindle end, as far as it differs from the illustration in FIG. 1, is explained below.

This rear spindle end carries the rotor carrier consisting of two parts 426, 428, which is fixed axially and rotationally fixed on the spindle 104. In it, the hollow piston 432, which is screwed to the pull-pressure pipe, is installed so as to be axially displaceable, and the piston, with the rotor carrier, delimits the cylinder spaces 434, 436, which can be controlled via channel bores 438. An outer jacket 440 of the rotor carrier is heat-insulating; the cylindrical rotor core 424 sits on it.

The stator of the motor includes the stator carrier 412, the stator core 418 and the stator winding 442. The stator carrier can be screwed onto the headstock by means of the centering flange 414 (shown in the upper one) Half of Fig. 4) or by means of a rib 408 on the machine base 402, the alignment being carried out by means of a large feather key 406 which engages in a groove of the rib 408 and is inserted in a groove 404 of the base 402, so that the stator is positioned axially and radially. The headstock cover 416 then only serves as a stop, and the headstock is protected against thermal heat from the motor by a thermal insulation layer 410.

A synchronous or asynchronous three-phase motor, which is fed by a frequency converter (not shown), is expediently used as the drive motor. At the desired extremely high speeds of rotation of the spindle, the short-circuit rings and rotor bars of the rotor are particularly at risk from centrifugal forces and are therefore wrapped in 430, light, but high-strength fiber material, e.g. Carbon fibers, secured, which are stretched with pretension.

It can be advantageous to use motors with pole changing.

A sleeve 420 surrounding the stator defines a flow path for

Coolant circulating through a nozzle 422 ..

4 while the rotor is flying on the spindle, in the embodiment according to FIG. 5 it is supported by two bearings 536, 538, of which the bearing 536 also represents the rear spindle bearing. Although bending moments acting on the spindle, which can deform the spindle according to FIG. 4, are avoided, there is a risk of misalignment of the three bearings, which constantly causes bending forces on the free end of the spindle, embodied by the cylinder jacket 528 and the hollow piston 530, arise. Therefore, the intention to bend the rotor arrangement is increased by a deliberately provided gap between the cylinder jacket 528 and the rotor support 526. 1 and 4, the person skilled in the art understands the function of the other components without detailed explanation, so that a summary is sufficient: the cylinder spaces 532 and 534 cooperate with the hollow piston in order to axially displace the pull-pressure tube 128 ; Machine base 502, centering ring 512, rib 508, feather key 506, groove 504, thermal shields 510 and 524 are found analogously in FIG. 4, as are rotor core 522, stator carrier 514, stator core 518, stator winding 520 and end flange 516. FIG. 6 shows a further construction variant based on the invention, in which the displacement-force converter converts an actuating stroke H on the input side, which is carried out with a low actuating force, into a small clamping stroke h, which is associated with a large clamping force. In this case, the entire travel-force converter 662 is accommodated between the two spindle bearings 106 and 678 of the work spindle 104 in a headstock 102, which is constructed similarly to the headstock in FIG. 1. For this reason, the headstock needs no further explanation. The drive of the work spindle is similar to that in FIG. 1 via a V-belt pulley 120, which is only indicated, since its construction, including the attachment on the spindle end, is well known to the person skilled in the art.

In contrast to FIG. 1, the pull-pressure pipe 128, to which one has to imagine a clamping device connected on its right side, is only formed in the front part of the work spindle 104. The transmission of the tensioning movement and the tensioning force from the organs attached around the spindle to the tension-pressure pipe 128 takes place via several (e.g. three) wedges 604 which are passed through axially parallel slots 680 in the cylinder jacket of the work spindle and with their lugs 660 in recesses 602 of the push-pull pipe. Outside the spindle, the wedges 604 are fastened in a manner not shown in the thrust ring 606, which is axially displaceable on the outer cylinder of the spindle. An adjusting sleeve 61o is rotatably mounted relative to the spindle via two ball rings 616, the corresponding bearing also being able to transmit high axial forces. An internal thread 612 of the adjusting sleeve is in engagement with an external thread 608 of the thrust ring 606.

The rotationally fixed but longitudinally displaceable thrust ring, together with the rotatable but axially fixed adjusting sleeve, constitutes a sliding screw drive with which, due to a rotational movement of the adjusting sleeve 610, the tension-pressure tube 128 is displaced relative to the sliding sleeve 614 formed on its right side 682 as a roller bearing inner ring can be made. With this movement, the idle stroke is carried out when the spindle is at a standstill, with which, for example, a chuck is adapted to the workpiece diameter. The motor drive for carrying out the idle stroke takes place in the example of FIG. 6 by a drive motor, not shown, which communicates its rotational movement to a gear 620 which is in engagement with a ring gear 618 provided on the adjusting sleeve 610. This gear engagement is only at a standstill and is caused by the fact that the drive shaft 624, with which the gear 620 is firmly connected (symbolized by the line 628), is moved towards the ring gear 618 by a pivoting movement of a mechanism, not shown, in the direction of arrow 626 .

The sliding sleeve 614 is axially displaceable on the outer cylinder of the spindle, but non-rotatably arranged relative to the spindle 104 due to the engagement of a parallel key 640 in a longitudinal groove 674. The left part 684 of the sliding sleeve 614 is designed as a spindle of a ball rolling screw drive with the balls 630 and the nut 632, which on the left side also serves as the outer ring of an axial ball bearing. The inner ring 636 of the axial bearing is fixedly connected to the spindle by means of several special taper pins 638 in order to introduce the axial clamping force transmitted via the balls 634 into the spindle.

When the nut 632 is rotated relative to the spindle, the sliding sleeve 614 is displaced, which corresponds to carrying out a clamping stroke. Since the maximum clamping stroke only has to be of the order of a few millimeters (e.g. three), this displacement stroke (for example with a spindle pitch of 10 mm) corresponds to only a fraction of a turn of the nut 632. The necessary small rotary movement of the nut is achieved in that a plurality of grooving rollers 644 which are non-rotatable but axially displaceable relative to the spindle 104 roll during their longitudinal displacement in steep thread grooves provided on the outer circumference of the nut632. The grooved rollers 644 are accommodated via balls 646 and roller bearing outer parts 648 in the cylinder wall of a sleeve 650, which is arranged axially displaceably on the spindle and is prevented from rotating relative to the spindle by the engagement of a feather key 654 in a longitudinal groove 652.

The longitudinal displacement of the sleeve 650 is derived from the movement of an adjusting device 180, 180 ', 184, 186 (which was already explained in FIG. 1) with the participation of the components 672, 666, 664, 668 and the two angular contact ball bearings 670 and 670'.

The upper and the lower half of the picture show the organs of the displacement force converter 662 in two end positions before and after the path distribution H on the input side and the path distribution on the output side. Displacement h.

With the adjustment movement of the displacement force converter 662, the clamping stroke is carried out with the generation of a large clamping force. In the case of small necessary empty strokes, e.g. when clamping rod material with collets, both the empty stroke and the clamping stroke can be carried out with the displacement force converter - even when the spindle rotates. In order to only have to use a small part of the displacement adjustment H on the input side for this idle stroke, in which only a small force is to be generated on the pull-pressure tube 128, it can advantageously be provided that the steep-thread grooves are divided into two sections with different pitches, whereby the section intended for the idle stroke receives a lower slope. If the tensioning device is used only for those applications in which both the tensioning stroke and a small idle stroke are carried out with the displacement-force converter, an additional device 676 can of course be dispensed with entirely.

The same applies analogously to hydraulically operated displacement-force converters such as for that shown in Fig. 1.

In FIGS. 7 and 8, embodiment variants of the invention are explained in which, above all, the advantages of a hydraulic version of a displacement-force converter are exploited, namely to be able to generate very high hydraulic pressures and also to drive the rotating organs with stationary drive means to be able to drive predeterminable movement sequences, the size of the drive path and / or drive force also being able to be controlled or regulated as a function of parameters, such as distance, time or speed.

FIG. 7 shows the front part of a headstock 702, as shown in FIG. 1, the work spindle 706 being supported only by two front spindle bearings 704. Above and below the line 708 defining the spindle axis, two different design variants for the mechanized clamping of clamping devices are shown. In the present case, the clamping device is a jaw chuck 710 with clamping jaws 712.

The upper part of the figure shows a clamping method in which an adapter flange I 714 connected to the jaw chuck is clamped against the spindle flange 718 by several hydraulically driven clamping bolts 716 arranged on the circumference (only one is shown). Depending on the loading of the feed channels 720 or 722, the clamping bolt can be moved in both axial directions for clamping or releasing the adapter flange I. The transmission of the clamping force from the clamping bolt to the adapter flange I takes place via a nut 724, which is firmly screwed to the clamping bolt, the recesses 726 and 728 are designed as elongated holes or grooves symmetrical to a pitch circle suffocating over a certain angle (e.g. 30 °) and, at the end of the angle, due to an enlargement of the recess 726, enable the nut 724 (not shown) to be introduced axially ). It is a so-called bayonet attachment. The chuck piston 730 is also coupled to the draw tube 732 according to the bayonet principle. The twist angles provided for both bayonet fastenings are of the same size, so that the coupling or decoupling can be carried out at both points with a single corresponding twisting movement of the jaw chuck 710 relative to the spindle 706. A poor way of fastening and coupling is described in more detail, for example, in DE-OS 3615672.

The feed channels 720 and 722 are connected to the corresponding channels 720 'and 722' of the spindle 706, the latter of which is connected to a stationary hydraulic pressure source or to a stationary tank in a manner not shown here by actuating corresponding shut-off elements when the spindle is at a standstill can be, for example, in a manner as shown in Figure 2. Depending on the selected connection of the channels, there is a tensioning or releasing movement on the tensioning bolt 716. A displacement-force converter is provided as the hydraulic motion conversion system 760, which works in a similar way to the motion conversion system 160 in FIG. 1.

In analogy to the described FIG. 1, 758 is the pressure body, 762. the control piston, 770 the transmission element, 772 is an angular contact ball bearing, 778 is the annular disc and 780 is the piston. In FIG. 7, however, the piston 780 is not driven by a pressurized fluid, but by a spring 736, which serves here as a stationary clamping force accumulator. The cylinder space 764 is connected via a channel 766 to the feed channel 720 or 720 '.

After completion of a clamping movement caused by the stationary pressure source of the clamping bolt 716 builds up in Cylinder space 764 a pressure, which ultimately also causes compression of the spring 736 by displacement of the control piston 762. After reaching the maximum pressure that can be predetermined by the stationary fluid pressure source (combined with corresponding maximum spring compression), the shut-off devices (not shown) rotating with the spindle are closed and the tensioning force of the clamping bolt 716 is - regardless of the spindle rotation - saved by the springs 736 Maintain strength. Any loss of tension force caused by leaks is compensated for by expanding the springs736. If the leakage is too great or the voltage falls below a clamping force limit, this can be signaled by a 738 sensor.

In the lower part of the figure, an arrangement is shown with which the adapter flange II 714 'which is firmly connected to the jaw chuck 710 is clamped in a different way against the spindle flange 718'. An overlock nut 744, which is attached to the adapter flange II 714 'in a rotationally fixed manner and is intended to take over tensile forces, is provided with bayonet teeth 746 which, after an axial insertion beforehand after a twisting movement, can be brought into positive engagement with the bayonet teeth 748 of a stepped piston 742. The clamping force on the stepped piston 742 is generated by the application of pressure to a pressure fluid in the cylinder chamber 750 via the feed channel 740. The stepped piston can be actuated when the spindle is at a standstill, as described for the arrangement of the upper part of the figure. Since there is only one feed channel to the stepped piston, provision is made for the stepped piston to be retrieved when it is released using the power-operated pull tube 732. For this purpose, the draw tube can be moved out of the position shown in the direction of arrow 752, this movement being finally communicated to the stepped piston 748 via the chuck piston 730 and the jaw chuck 710.

In the front position reached, then the Decoupling the chuck piston from the draw tube by rotating the jaw chuck. The necessary relative rotation of the jaw chuck relative to the spindle can also be carried out by rotating the spindle. The jaw chuck is secured against rotation during this process in that a stationary bolt 754 is inserted into a groove 756 of the union nut 744.

The displacement force converter 760 'is designed differently in the lower part of the figure than in the upper part of the figure. The pressure body 758 'is of similar design and the control piston 762' 'is driven in a similar manner to that shown in FIG. 1. The fluid pressure generated in the train guide channel 759 serves to drive the (not shown) tensioning piston for the pull pipe 732. In the same pressure element 758 'in the present example the control piston 762' is also accommodated, which was shown broken off because it is in the pressure element 758 'in on a different plane than the ^ oak plane. Similar to the control piston 762 in the upper part of the figure, the control piston 762 'is driven by a stationary mounted piston 774, the pressure force of which, however, in this case is generated by a fluid pressure acting in the cylinder space 773 (and can be controlled in any way). The fluid pressure generated in a cylinder space (not shown) in the pressure body 758 'by the control piston 762' is supplied to the cylinder space 750 via the supply channels 740 'and 740 and is intended to maintain the clamping force of the stepped piston 742 during the spindle rotation.

It should be noted that the clamping force generating elements shown in the upper and lower half of the figure, instead of in the spindle flange 718/718 ', could also be accommodated in a removable additional intermediate flange which would have to be arranged between the adapter flange 714 and the spindle flange 718.

FIG. 8 shows, similar to FIG. 7, a headstock 802 with a work spindle 806 mounted therein. In the upper and lower part of the picture, two different variants of another possible application of the invention are shown. The displacement-force converter 860 is constructed similarly to that in FIG. 1, but with the difference that control pistons 862 are provided in pressure element 858, which are designed as stepped pistons and generate a fluid pressure in both directions of movement.

No special displacement-force converter is shown for the design variant in the lower half of the figure. One of the ones shown in FIG. 1 or FIG. 7 could be considered, or else the one shown in the upper half of FIG. 8.

In the upper half of the figure, a stepped piston 804, which can be driven in two directions, is accommodated in a clamping means 810 connected to an adapter flange 808. The respective drive direction is determined by the optional application of pressure to the train guide channels 812 and 814. The feed channels 812 and 814 are connected to feed channels 820 and 822 in the pressure body 858, as well as to the channels 816 and 818 leading to the rear spindle part. Via the channels 816 and 818, the stepped piston 804 can reach a stationary one when the spindle is at a standstill Be connected to the hydraulic network, similar to how it was described for the arrangement of Figure 7. This process should at least be done so that any leakage losses that may have occurred are replenished. After decoupling from the stationary hydraulic network by closing the channels 816 and 818 with shut-off elements (not shown), the stepped piston 804 is driven exclusively by the pressure conditions generated in the pressure element 858. Provided that the effective areas of the full cylinder space and the ring cylinder space in both stepped pistons 862 and 804 are in the same ratio, actuating the stationary drive piston 824 in both axial directions can also achieve a corresponding proportional displacement of the stepped piston 804 in both directions become. This also applies in the event that there is a case where several stepped pistons 804 are distributed over the circumference.

Different tasks can be performed by the drive device described so far.

The stepped piston 804 could bring about an additional clamping function in a special clamping device, for example in that a clamping element 826, which in this case is radially displaceable, would be driven via a wedge gear 828.

In the case of stepped pistons 804, which are provided several times on the circumference, the driven element 825 could also be axially displaceable and represent the central drive of a collet chuck or pelvic chuck.

In the event that the clamping means 810 is a jaw chuck, in which all jaws are driven synchronously in a known manner by the axial displacement of a chuck piston 830, and that the chuck piston is known in a known manner by a pull-pressure tube 832 (the actuating member of which is not shown) ) can be driven in both axial directions, the stepped piston 804, which is arranged several times on the circumference, could also be used to additionally influence the jaw clamping forces. The axial displacement of the stepped piston 804 could be converted into a radial displacement of an element 826 via a wedge gear 828. The organ 826 could act directly or in another way indirectly on the clamping jaw by fastening to a clamping jaw. In this way, one could, for example, compensate for the centrifugal forces acting on the jaws, or carry out a process-dependent clamping force control. With such an influence of the clamping force by the stepped piston 804, the clamping force generation by the chuck piston could be reduced to a minimum such that the chuck piston only has to synchronize the jaw movements. The combined and / or reciprocal use of chuck pistons and stepped pistons also allows the self-locking effect, which is known to be disruptive, to be eliminated or overcome in a controlled manner while reducing the clamping force.

In another application, part 810 could also be the body of a rotating tool with an adjustable cutting edge. In the upper half of the figure in FIG. 8, the organ 826 could be radially displaceable and thereby cause the radial displacement of a tool cutting edge, which is predetermined depending on the process.

To perform the tasks described above, the stepped piston 804 could, however, also be accommodated directly in the spindle flange 834 or in an adapter which is firmly connected to the spindle flange. The step piston 804 could also be designed as a simple plunger, its resetting otherwise, e.g. by the action of a spring.

In the arrangement in the lower half of FIG. 8, an annular piston 836, which can be actuated in two axial directions, is accommodated on the circumference of the spindle flange 834 ', the drive of which can be accomplished in the same way as described for the stepped piston 804. The ring piston is provided with bayonet teeth 840 on its circumference, which is to be brought into engagement with the bayonet teeth 838 of a union nut 842. The nut 842 is mounted for longitudinal displacement and rotation on the circumference of an adapter ring 846 which is fixedly connected to the equipment body 844 and is able to communicate its axial displacement in both directions to a sleeve 848 which is arranged on the circumference of the equipment body 844. This sleeve 848 is provided for transferring the movement to other organs. As an example of such an organ, a bolt 852 is shown which is arranged radially with an axis 850 but is axially displaceable and which is positively connected to the sleeve 848 by means of a pin 854 is. With such an arrangement, the same tasks should be performed as described for the arrangement according to the upper half of the picture. A special feature of the arrangement according to the lower half of the figure is that the transmission of the drive movement to the rotating equipment body 844 (e.g. a chuck) takes place by means of a single central element, namely in this case the sleeve 848, and that with an annular piston 836 at the same time small dimensions large effective piston areas, ie large operating forces can be generated.

Common to all arrangements according to FIGS. 7 and 8 is that their functions can be implemented with their own displacement-force converter (760, 760 ', 860) and that at the same time a second displacement-force converter for driving one Tensioning cylinders for the actuation of a push-pull pipe can be present, such as is described in Figure 1 or Figure 6. However, two hydraulic displacement-force converters that can be actuated separately from stationary parts can also be accommodated in a common pressure body, as is described in the lower part of FIG. 7. (Pressure body 758 ').

If a hydraulically operated displacement-force converter is already provided for the actuation of a push-pull pipe, this can also take over the pressure supply of the drive elements described in FIGS. 7 and 8, but in the case of the clamping device attachment according to FIG. 7 a switchable shut-off device is to be provided, which prevents the pressure drop in the feed channels 720 and 740 when the correspondingly connected channels are depressurized in the rest of the circulating hydraulic network.

Claims

1. Device for generating a clamping force for actuating a power clamping device on a work spindle (104) that can be driven to rotate, comprising

a circumferential tensioning piston (126, 432, 530) interacting with cylinder spaces (144/146, 434/436, 532/534) and axially displaceable by fluid pressure, which is in motion transmission connection with the tensioning device,

a stationary fluid pressure source that can be coupled to at least one of the cylinder spaces, at least when the spindle is at a standstill,

- co-rotating fluid shut-off devices (202) between the source and the at least one cylinder space, and

- rotating means (306-310) for maintaining the clamping force during the spindle rotation,

characterized in that an essentially incompressible medium, in particular hydraulic fluid, is provided as the pressure fluid, which can be placed under high pressure (at least 80 bar) in the cylinder chambers, and in that the means for maintaining the clamping force comprise a hook-type clamping force accumulator (310), which is pressurized with the pressure fluid.

2. Device according to claim 1, characterized in that the rotating fluid shut-off device is assigned a non-rotating source-side coupling part (208) which can be aligned with a rotating coupling member (206) when the spindle is at a standstill.

3. Apparatus according to claim 2, characterized in that the rotating coupling part (206) is structurally combined with the shut-off element in such a way that the non-rotating coupling part (208) can be displaced in coupling connection with the rotating parts while unlocking the shut-off element.

4. The device according to claim 2 or 3, characterized by a second coupling arrangement of rotating and non-rotating coupling part for the pressure fluid discharge.

5. Device for generating a clamping force for the actuation of a power clamping device on a work-driven spindle (104), comprising

a circumferential tensioning piston (126, 432, 530) which interacts with cylinder spaces (144/146, 434/436, 532/534) and is axially displaceable by hydraulic fluid pressure and which is in motion transmission connection with the tensioning device,

a stationary fluid pressure source that can be coupled to at least one of the cylinder spaces, at least when the spindle is at a standstill, and

Means for influencing the clamping force during the spindle rotation,

characterized in that the latter means comprise: a stationary drive unit (180, 180 ', 184, 186) for the axial displacement of a transmission member (170) rotating with the spindle (104), axial roller bearings (172, 172 ') are interposed, and

- A rotating motion conversion system (160) for converting changes in position of the transmission element into corresponding changes in pressure in the cylinder rooms.

6. The device according to claim 5, characterized in that the movement conversion system comprises at least one control piston (162) which can be displaced parallel to the spindle, which can be coupled to transmit with the transmission member (170) and cooperates with a control cylinder chamber (164) which is in fluid communication with the circulating hydraulic network .

7. The device according to claim 5 or 6, characterized in that the drive unit, the transmission member is designed to be displaceable by predeterminable distances.

8. Apparatus according to claim 5 or 6, characterized in that the drive unit is designed to relocate the transmission element with predeterminable forces.

9. The device according to claim 5 or 6, characterized in that the drive unit as hook 'shear force storage is in operative connection with the transmission member.

10. Device for generating a clamping force for actuating a power clamping device on a work spindle (104) which can be driven to rotate, comprising

- A with cylinder spaces (144/146, 434/436, 532/534) cooperating, rotating, axially displaceable by hydraulic fluid pressure clamping piston (126, 432, 530), which is in motion transmission connection with the tensioning device in such a way that

(a) an idle stroke is carried out to adapt to different nominal diameters,

(b) a clamping stroke is run through with elastic prestressing of the components in the power flow,

(c) the clamping force built up in this way is maintained during the spindle revolution or can be changed in a predeterminable manner, which device furthermore has a stationary fluid pressure source that can be coupled to the rotating hydraulic network at least when the spindle is at a standstill,

characterized in that the pressure transmission between the fluid pressure source and the pressurized circulating hydraulic network is interrupted during the spindle revolution, that the circulating network is sealed by means of controllable shut-off devices (202), and that for the implementation of phase (c), preferably phases ( b) and (c), a separate unit (180, 180 ', 184, 186) is provided.

11. The device according to claim 10, but modified such that there is fluid communication between the source and the rotating hydraulic network during the spindle rotation, but at least the interface between the stationary and the rotating parts is under a hydraulic pressure that is far below the clamping pressure according to (b ) lies.

12. Device according to one of claims 9 to 11, characterized in that the clamping phase (a) takes place in the spindle standstill by fluid exchange between the source and the rotating hydraulic network.

13. Device according to one of claims 9 to 12, characterized in that the clamping phases (a) and (b) take place in the spindle standstill by fluid exchange between the source and the circulating hydraulic network.

14. Device according to one of claims 9 to 13, characterized in that the additional unit comprises:

- A stationary drive unit (180, 180 ', 184, 186) for the axial displacement of a transmission element (170) rotating with the spindle (104), axial roller bearings (172, 172') being interposed between the drive unit and the transmission element, and

- A movement conversion system (160) for converting changes in position of the transmission element into corresponding changes in pressure in the cylinder spaces.

15. The apparatus according to claim 14, characterized in that the movement conversion system comprises at least one control piston (162) which can be displaced parallel to the spindle, which can be coupled to transmit with the transmission member (170) and cooperates with a control cylinder chamber (164) which is in fluid communication with the circulating hydraulic network .

16. The apparatus of claim 5 or 15, characterized by a plurality of control pistons (162) connected in parallel.

17. Device according to one of claims 5, 15 or 16, characterized in that each cylinder chamber (144, 146) of the tensioning piston (126) is assigned at least one separate control piston (162 or 166).

18. The apparatus according to claim 17, characterized in that the control pistons of the two cylinder spaces are alternately coupled to the transmission member.

19. Device according to one of the preceding claims, characterized in that the cylinder spaces (144, 146) of the tensioning piston (126) have different cross sections and can be connected in parallel in order to operate the tensioning piston as a differential piston.

20. The apparatus according to claim 19, characterized by a rotating switching element for blocking the parallel connection and depressurization of one of the cylinder rooms.

21. The apparatus according to claim 6 or one of claims 15 to 19, characterized in that the effective piston surfaces on the input side are a fraction of the effective piston surfaces on the output side of the tensioning piston.

22. The device according to one of claims 9 to 21, characterized by an additional rotating clamping force accumulator (306-310).

23. The device according to claims 19 and 21, characterized in that the power transmission ratio of the movement conversion system when the cylinder spaces of the tensioning piston are connected in parallel differs from that when the parallel connection is canceled.

24. The device according to one of claims 9 to 23, characterized by an at least 80 bar clamping pressure in one of the cylinder spaces of the clamping piston.

25. The device according to claim 9, characterized in that the tensioning phase (a) can be carried out by means of the separate unit.

26. Device according to one of the preceding claims, characterized in that the tensioning piston can be driven for adjustment and tensioning movements in both axial directions.

27. Device according to one of the preceding claims, characterized in that an AC motor is provided for the spindle drive, the rotor of which is arranged concentrically to the spindle axis and is hollow, for example for accommodating the tensioning piston in its cavity.

28. The apparatus according to claim 27, characterized by a rotor of a three-phase motor, which is overhung at the rear spindle end.

29. The device according to claim 27, characterized by a motor rotor with roller bearings on both ends, one of the bearings simultaneously forming a spindle bearing.

30. Device according to one of claims 27 to 29, characterized by prestressed bands made of high-strength fibers for securing rotating parts of the motor against centrifugal damage.

31. Device according to one of the preceding claims, characterized by a measuring and correction device for the clamping force applied by the tensioning piston.

32. Device according to one of the preceding claims, characterized in that the tensioning piston (126) on the one hand, the coupling point between the circulating hydraulic network and the stationary source on the other hand are provided on both sides of a spindle bearing (105) and channels are connected through the spindle.

33. With a work spindle revolving power-operated clamping device for a clamping device, characterized by a revolving path-force converter (160/662), the displacement adjustments made on the input side (BC / H) into small displacement adjustments on the output side, transferred to the clamping device (h ) implemented by a stationary adjusting device (180, 180 ', 184, 186) which can be coupled to the input side of the converter via roller bearings (172, 172' / 670, 670 ') and by additional device (676) for generating an idle stroke for the purpose of adaptation different nominal diameters.

34. Clamping device according to claim 33, characterized by a hydraulic converter operating on the principle of communicating tubes.

35. Apparatus according to claim 33, characterized by a mechanical lever converter.

36. Apparatus according to claim 33, characterized in that the displacement-force converter (160/662) operates purely mechanically and has the following components:

- a first movement converter (650, 646, 644, 642) for converting the axial displacement on the input side into a rotary movement and (632,630,614)

- A second motion converter for converting the rotary motion into an output-side displacement adjustment to be transmitted to the clamping device.

37. Apparatus according to claim 36, characterized in that the second movement transducer (632, 630, 614) is a hob screw drive.

38. Apparatus according to claim 36 and claim 37, characterized in that the first movement transducer has a component (632) with at least one steep thread groove (642) with at least one grooving roller (644) rolling in this groove.

39. Apparatus according to claim 38, characterized in that the steep thread groove (642) has at least 2 sections with different pitches.

40. Device according to one of claims 33 to 39, characterized in that the additional device (676) for generating an idle stroke comprises a rotating sliding screw drive (606, 610).

41. Apparatus according to claim 40, characterized in that the sliding screw drive can be coupled to a stationary drive unit (620, 624) when the spindle is at a standstill.

42. Device according to one of claims 33 to 41, characterized in that the additional device (676) for generating an idle stroke also causes the generation of the clamping stroke and that the adjustment of the adjusting device is carried out by the rebound movement of a stationary tension energy accumulator, the deflection energy (loading of the clamping force accumulator) is derived from the clamping energy of the additional device.

43. Device according to one of the preceding claims

14 to 42, characterized in that the transmission of the clamping force to the tension / compression tube (128) arranged in the machine spindle takes place through recesses (680) made in the cylinder jacket of the machine spindle (104) in the area between two spindle bearings (106, 678) .

44. Device according to one of the preceding claims on a lathe for clamping workpieces.

45. Device according to one of claims 1 to 43 on a drilling or milling machine for clamping tools.

46. With a work spindle revolving power-operated tensioning device for a clamping device, characterized by a revolving travel-force converter (662), which converts large travel adjustments (H) on the input side into small travel adjustments (h) on the output side, transmitted to the tensioning device, by a stationary one , The rolling bearing (670, 670 ') can be coupled to the input side of the converter adjusting device (184, 186) and the transmission ratio of the input-side displacement adjustment (H) to the output-side displacement adjustment (h) also has a finite value at the end of the tensioning path.

47. Apparatus according to claim 46, characterized by a hydraulically operating converter.

46. Apparatus according to claim 46, characterized by a combination with the characterizing features of claim 36.