CLAMPING DEVICE

Description

[0001] The subject of the invention is a clamping device with a spring-loaded clamping cylinder for actuating clamping tools on lathes according to the preamble of patent claim 1.

[0002] Clamping devices for machine tools, in particular for lathes, are provided, for example, with a power chuck for holding a workpiece, the clamping jaws of which can be adjusted by means of the clamping device via an axially adjustable drawbar as an actuating element.

[0003] Such a clamping device is disclosed, for example, in US 3 643 969 A and has a force accumulator for maintaining the clamping force, which is formed from a pre-tensioned spring assembly.

[0004] An axially adjustable draw tube can be actuated by an actuation module, whereby the clamping device has the energy storage device installed in a machine spindle to maintain the clamping force in order to convert the adjustment movements into the axial adjustment movements of the draw tube required to actuate the clamping jaws.

[0005] A similar clamping device is known from JP 2002 046005 A and comprises a power chuck with clamping jaws for holding a small, thin-walled workpiece, an axially adjustable, tubular adjusting member, an actuating module for actuating the clamping jaws via the adjusting member and a machine spindle with a bell-shaped clamping cylinder, wherein the clamping device has a single helical compression spring within the clamping cylinder to maintain the clamping force in order to implement the axial adjusting movements of the adjusting member required to actuate the clamping jaws.

[0006] In a rotating operating state, the clamping cylinder is designed to rotate with the machine spindle, the actuating module is designed to stand still and the actuating module can be separated from the clamping cylinder without contact.

[0007] The adjusting element is formed by a drawbar, the end of which is threadedly connected to a hollow, tubular piston tube. By manually rotating the piston tube relative to the drawbar with a flange of the piston tube, the compression force of the spring can be axially adjusted. The disadvantage of this device is that only a spring assembly acts as a force accumulator surrounding the drawbar and acting directly on it. This makes the spring force difficult to control, and only low clamping forces can be exerted on a clamped workpiece.

[0008] Hydraulic or pneumatic cylinders are known for operating a collet or chuck on a machine tool. The cylinder and the rotating feed section are firmly bolted together as a complete unit and rotate with the machine spindle, providing the necessary oil or air pressure at all times.

[0009] According to the application DE 440 45 47 C2 and DE 197 52 084, the hydraulic piston is firmly connected to the drawbar actuated by the chuck via a piston tube and rotates as a whole with the machine spindle in the operating state, with the stationary supply housing for oil or air being centered on the rotating rotary distributor via bearings.

[0010] The disadvantages of the prior art are that the supply of pressure fluid from a stationary rotary distributor housing to a rotating rotary distributor shaft causes significant leakage. At high speeds, this also results in high energy consumption and significant heat generation due to viscous friction. The mass of the rotating rotary feed section is firmly connected to the entire cylinder and piston mass and rotates as a single unit.

[0011] The vertical supply housing for oil or air must be centered via ball bearings, which are subject to wear and rolling friction.

[0012] The oil or air pressure supply must be maintained throughout operation, which requires the hydraulic unit to run continuously at high energy consumption to compensate for the rotary feed leakage. In the event of a pressure drop, at least two additional safety valves must ensure that the piston chamber pressure of the pressure medium is maintained if the hydraulic pressure in the cylinder housing fails.

[0013] In addition, elastic retensioning is not possible if there is no hydraulic pressure.

[0014] EP 2 384 839 A1 shows a rotating electric clamping cylinder, the springs of which can be changed by turning the nut of a planetary gear to maintain the clamping force in the operating state, whereby the respective spring force can be transferred to the thread of the draw tube via planetary rollers. 1. To prevent a change in the spring force caused by one of the planetary roller spindles during operation, the nut of the planetary roller spindle is connected in a rotationally fixed manner via gear components to a sliding sleeve, which is rotationally fixedly coupled to the cylinder body via face gearing during operation. 2. The actuating device consists of an axially fixed drive wheel mounted on a shaft-like extension of the cylinder body, which is rotationally fixedly connected to the servo motor via belts or gears. The drive wheel with axial gearing is decoupled from the sliding sleeve during operation. If the spring forces need to be changed, the sliding sleeve is coupled to the drive wheel via a cylinder, whereby the spring forces of the energy accumulator can be changed by rotating the cylinder via gear elements on the planetary roller spindle, enabling a defined retensioning.

[0015] The force accumulator, consisting of several spring assemblies, is activated as soon as the drawbar stops moving. This ensures that all components of the clamping device involved in force transmission are firmly connected to the machine spindle during machining, thus preventing any return movements of the power chuck.

[0016] The sliding sleeve is axially adjustable by means of a servo device in the form of an adjusting piston inserted in a cylinder and adjustable by a pressure medium.

[0017] However, the speed of the rotating servo device of the clamping device must be controlled depending on the drive motor of the machine tool.

[0018] The object of the invention is therefore to design a clamping device of the aforementioned type in such a way that the supply of pressure medium during the circulating operating state, which is prone to leakage and associated with high energy consumption, is eliminated.

[0019] This will also completely eliminate the heat generated by the viscous friction of the pressure medium between the stationary feed housing and the rotating feed shaft. The centering ball bearings, which are subject to wear, will also be eliminated.

[0020] The part connected to the chuck via the draw tube should elastically maintain a defined clamping force without medium pressure and, if necessary, elastically retighten.

[0021] The required rotating mass of the cylinder should be minimized.

[0022] The required drive and braking torque, the GD 2< , should be minimized when starting up and stopping the machine.

[0023] The objects underlying the invention are solved by the features of independent patent claim 1, while advantageous embodiments and further developments of the invention can be found in the subclaims.

[0024] A feature of the invention is that the clamping cylinder can be separated from the actuating module during the rotating operating state.

[0025] Another feature is that the clamping force of the cylinder is maintained and secured by a built-in spring.

[0026] The actuation module is designed to remain stationary in the rotating operating state of the clamping device, whereby there is no contact with the cylinder.

[0027] To adjust the spring force in the cylinder, the piston version of the actuation module is briefly subjected to pressure. This force is transmitted to the cylinder and springs via one or more roller bearings, or via pressure rollers or thrust bearings. To change the spring tension, the stationary actuation module can be briefly docked to the clamping cylinder section.

[0028] For this purpose, the actuation module preferably has one or two piston surfaces of a piston, the size of which corresponds to the maximum spring and clamping force when pressure is applied.

[0029] The actuation module can be designed as a single-piston or multi-piston system, wherein in the coupled state at least one piston surface of the actuation module is subjected to air or oil pressure and, due to the pressure, moves the rolling bearing(s), the pressure rollers or the thrust bearings.

[0030] A multi-piston system with its doubled piston area also allows actuation with low air pressure as the medium.

[0031] However, the present invention is not limited to the use of two piston surfaces; one, three or more piston surfaces can also be used.

[0032] Only to adjust the clamping forces in the clamping cylinder, the piston of the actuating module is briefly pressurized with a pressure medium, whereby the force of the piston can be transferred to the energy accumulator and thus to the clamping cylinder via one or more rolling bearings or via pressure rollers or thrust bearings.

[0033] After adjusting the clamping force while the machine is at a standstill or running, the actuation module is depressurized again, meaning no more pressure is exerted on the piston surfaces. Once the pressure is removed, the contact between the rolling bearing(s), the rolling elements, or the thrust bearings and the parts connected to the cylinder is also released, allowing the actuation module to be decoupled from the cylinder.

[0034] In this state, only the spring or springs of the force accumulator of the clamping cylinder act on the power chuck or the collet via tension elements.

[0035] By using the energy storage device, the stress state of a workpiece can be secured elastically.

[0036] Such an energy accumulator can, for example, consist of a plurality of helical compression springs arranged evenly distributed over the circumference, which are inserted in a first housing designed as a pressure piece.

[0037] Such helical compression springs can have a rectangular, preferably square, an elliptical or a circular cross-sectional area.

[0038] In the following, only one spring is described as the force accumulator, although the clamping device in question is not limited to the use of a single spring. Multiple spring assemblies or elastomeric spring bodies can also be used as force accumulators in the clamping device.

[0039] In addition to the effect of the actuation module on the spring, a fine adjustment of the effective spring forces is possible, which can be done manually using an adjustment wheel.

[0040] The parts connected to the cylinder, which are controlled by the roller bearing(s), the pressure rollers, or the thrust bearings of the actuation module, consist of, among other things, the draw tube, which is at least partially screwed into a sliding part with its end facing away from the power chuck

[0041] The sliding part, with the screwed-in draw tube, is connected via its external thread to the internal thread of an axially fixed hollow shaft, which can be manually rotated with an adjusting wheel to finely adjust the force of the spring(s) axially.

[0042] According to one embodiment, the open state of the collet chuck can be determined by a Bero sensor, while in another embodiment, the spring travel can also be monitored or measured by a displacement sensor. The displacement sensor can determine the exact position of the drawbar and thus the clamping jaws. The pressure ring can be equipped with a signal transmitter that interacts with the displacement sensor to determine the current position of the piston tube. This signal transmitter can thus be used to acquire measured variables that enable reliable control of the machine tool.

[0043] A further advantage can be that in the event of a sudden pressure drop due to a hose break on the actuation module, the collet or power chuck is completely closed.

[0044] The invention is explained in more detail below with reference to drawings illustrating several embodiments. Further features and advantages of the invention will become apparent from the drawings and their descriptions, with the invention being defined solely by the wording of the following independent patent claim.

[0045] They show: Figure 1 : Sectional view of clamping device with pressurized actuation module Figure 2 : Sectional view of clamping device pressureless actuation module Figure 3 : Sectional view of clamping device 2. Variant pressureless actuation module (not part of the invention) Figure 4 : Sectional view of clamping device with fine adjustment (not part of the invention) Figure 5 : Sectional view of clamping device with fine adjustment 2nd variant (not part of the invention) Figure 6 : Top view of tool (not part of the invention) Figure 7 : Sectional view of adjustment wheel bushing Figure 8 . Sectional view of the actuation module with a pressure chamber Figure 9 : Sectional view of clamping device with ball screw Figure 10 : Sectional view of clamping device with eccentric drive

[0046] The Figures 1 to 10 The clamping device shown and designated 1 serves to actuate a power chuck 6 arranged on a machine tool, by means of whose radially adjustable clamping jaws 134 of a collet 5 a workpiece 4 to be machined can be clamped in the power chuck 6. The power chuck 6 is accommodated in a bell 131 on the front side of the clamping device 1.

[0047] The collet 5 is supported in the axial direction on the inner circumference of the bell 131 and has a conical area 132 on its outer circumference of the clamping jaws 134 facing away from the workpiece 4, which in the sectional view according to Figure 1 is shown as an inclined surface.

[0048] The clamping jaws 134 are at least partially received with their conical region 132 inside the hollow draw tube 18, which at its end facing the workpiece 4 also has a conical region 133 on the inner circumference, which cooperates with the conical region 132 on the outer circumference of the collet 5. This conical region is also shown in the sectional view according to Figure 1 shown as an inclined surface.

[0049] Due to the conical regions 132, 133 rising in the same direction (opposite to the direction of arrow 16), the power chuck 6 is moved radially inward during an axial feed movement of the draw tube 18. The bell 131 is connected in a rotationally fixed manner to the machine spindle 135, with the spring clamping cylinder 2 being connected to the flange 136 of the machine spindle 135 by means of screws 137.

[0050] The machine spindle 135 is acted upon by a spindle motor 7 which is designed as an electric motor by which the machine tool can be driven.

[0051] On the side facing away from the machine spindle 135, a pressure piece 77 is attached to the spring clamping cylinder 2. The pressure piece 77 has a hollow shaft 140 formed thereon, which extends in the axial direction and encloses the piston tube 29.

[0052] Inside the bell-shaped spring tensioning cylinder 2 is the energy accumulator 138, which has a plurality of helical compression springs 9.

[0053] A movement bushing 43 is arranged in the spring tensioning cylinder, which is held in a rotationally fixed manner with the spring tensioning cylinder 2 via an anti-rotation device 45. A receiving space 83 is provided in the movement bushing 43, in which the helical compression springs 9 are mounted, the left end of which is partially received in the movement bushing 43 and there abuts the stop 76.

[0054] The right end of the helical compression springs rests against a stop 33 located at the end of an axially directed receiving space 75 inside the bell-shaped pressure piece 77. For this purpose, a plurality of bores arranged evenly around the circumference are machined into the pressure piece 77 as receiving spaces 75, in which helical compression springs 9 with a square cross-section are inserted.

[0055] Thus, the helical compression spring 9 is accommodated between the stop 76 inside the receiving space 83 of the movement bush 43 and between the stop 33 inside the receiving space 75 of the pressure piece 77. Preferably, the helical compression spring is subjected to a preload before it is compressed due to the pressure application.

[0056] This compression of the helical compression spring is caused by a movement of the movement bushing 43 in the direction of arrow 16, whereby the stop 76 moves in the direction of the stop 33.

[0057] In the example shown after Figure 1 the helical compression spring 9 in the spring clamping cylinder 2 is maximally tensioned, and the collet 5 or the jaw chuck is open so that the workpiece 4 can be inserted.

[0058] In order to move the movement bush 43 for a compression of the helical compression spring 9, the actuation module 3 is stressed, which has in its interior an adjusting piston 34 actuated by a pressure medium.

[0059] Starting from connection 11, the medium, for example, compressed air or compressed oil, is supplied via pressure channels 21a,b to the pressure chambers 19, 20 of the actuation module 3. The pressure chambers 19, 20 extend in the radial direction and are each bounded on their right-hand side by the piston surfaces 39, 40 of the radially extending piston ribs 69, 70 of the axially displaceable piston 34.

[0060] On their left side, the pressure chambers 19 are delimited by the plate-shaped piston housing 89 and the pressure chamber 20 by the plate-shaped housing 90, which in the areas parallel to the piston surfaces 39, 40 have approximately the same size counter surface to the piston surfaces 39, 40 and delimit the pressure chambers 19, 20 laterally with the piston surfaces.

[0061] A spring 46 is arranged between the pressure chambers 19, 20, which is received on the left side in the piston rib 69 and is mounted on its right side in the housing 90.

[0062] When pressure medium is supplied, the pressure in the pressure chambers 19, 20 increases and thus also the pressure forces on the piston surfaces 39, 40 of the movable piston ribs 69, 70, whereby the adjusting piston 34 formed thereon moves in the direction of arrow 16.

[0063] A pressure ring 13 is connected to the adjusting piston 34 via the screw 47. The pressure ring 13 surrounds the piston tube 29 but is arranged at a radial distance from it. In the example shown according to Figure 1 the pressure ring 13 is connected to the right piston rib 70 of the adjusting piston 34 via the screw 47.

[0064] The movement of the piston 34 also moves the pressure ring 13 in the direction of arrow 16.

[0065] A bearing pin 35 is accommodated in the pressure ring 13 and extends radially in the direction of the piston tube 29.

[0066] A roller bearing 36 is rotatably mounted at the end of the bearing pin 35. This roller bearing 36 is also moved in the direction of arrow 16 by the movement of the piston 34, rests against the flat surface 71 of the adjusting wheel 14, and also moves it in the direction of arrow 16.

[0067] The adjusting wheel 14 is connected in a rotationally fixed manner to the piston tube 29 and also moves this in the direction of arrow 16 due to the movement of the rolling bearing 36.

[0068] A tubular sliding part 10 is partially accommodated in the hollow piston tube 29. This sliding part 10 is in the example shown here according to Figure 1 with its right side screwed to the piston tube 29 via a threaded connection 37 and protrudes with its left side from the piston tube 29.

[0069] Due to the loads occurring in the clamping device 1, the threaded connection 37 is designed to be wear-resistant.

[0070] At the left end of the sliding part 10, this has a radially outwardly projecting projection 38 which is integrally connected to the sliding part 10.

[0071] The projection 38 is connected to the rotating spring tensioning cylinder 2 via an anti-twist device consisting of a stud bolt 72 that is firmly received in the spring tensioning cylinder 2 and slidably mounted in a recess 73 of the sliding part 10. The anti-twist device connects the sliding part 10 to the spring tensioning cylinder 2 in a force-locking manner.

[0072] The piston tube 29 has, in the area of overlap with the inner sliding part 10, a radially outwardly projecting shoulder 31 at its left end. This shoulder 31 rests against the shoulder 42 of the movement bushing 43, which surrounds the shoulder 31 in a ring. The shoulder 42 of the movement bushing 43 is directed radially inward, with the shoulder 31 of the piston tube 29 engaging its left-side contact surface 82 and thus being moved in the direction of arrow 16 when the piston tube 29 moves in the direction of arrow 16.

[0073] The bell-shaped pressure piece 77 surrounds the piston tube 29 in its longitudinal extension and has an anti-rotation device 15 on its right-hand end face 78. This anti-rotation device 15 consists of a spring-loaded bolt, the end 79 of which protrudes from a bore on the end face 78 of the pressure piece 77 and engages positively in a recess 80 in the adjusting wheel 14.

[0074] Figure 1 shows the state in which the adjusting wheel 14 is moved into the disengaged position by contact with the rolling bearing.

[0075] A sensor 12 is arranged on the actuation module 3 and signals that the collet 5 is fully open.

[0076] The clamping force position can also be queried using an optional position measuring sensor.

[0077] Figure 2shows that there is no longer any pressure in the pressure chambers. The return of the piston ribs 69, 70 is accomplished by the return spring 46, which is supported on the plate-shaped housing 90. If a pressure drop occurs in the pressure chambers 19, 20, which is the case as soon as no more pressure medium is supplied from the outside via the connection 11, the spring 46 between the piston rib 69 and the housing 90 relaxes and presses the piston rib 69 in the direction of arrow 86. Since the piston rib 69, like the piston rib 70, is an integral part of the piston 34, the piston 34 is also moved in the direction of arrow 86 due to the spring action. Figure 2 the workpiece 4 is clamped in the collet 5 by the previously adjusted spring force of the helical compression spring 9.

[0078] The actuation module is enclosed by a piston housing 89 on the side facing the machine spindle 135, with a shoulder 103 formed axially on the piston housing 89 and screwed to the headstock 85 via screws 64. Thus, the actuation module 3 is attached to the headstock 85, with the spindle motor 48 mounted in the headstock.

[0079] The headstock 85 rests on the machine spindle 135 via the rolling bearings 130.

[0080] Due to the movement of the piston 34 in the direction of arrow 86, the left-hand piston rib 69 approaches the piston housing 89 and the right-hand piston rib 70 approaches the housing 90 and the respective pressure chambers 19, 20 located between these components become smaller.

[0081] As the spring 46 relaxes and the piston 34 moves in the direction of arrow 86, the thrust ring 13 connected to the piston 34 also moves in the direction of arrow 86. As a result, the roller bearing 46 lifts off the flat surface 71 of the adjustment wheel 14, and there is no longer any contact between these two components. Thus, the actuation module 3 is no longer in contact with the rotating clamping cylinder, since the thrust ring 13 with the roller bearing 46 has no axial connection with the flat surface 71 of the adjustment wheel.

[0082] Sensor 12 is not damped and reports that workpiece 4 is clamped.

[0083] Figure 3 shows a further embodiment, not according to the invention, in which a central compression spring 49 is used between the projections 42' and 31', which is installed depending on the required clamping force. However, the function and reference numerals are the same as in the previously described embodiment.

[0084] Such a spring body can, for example, be made of an elastomeric material.

[0085] In a further embodiment, also not covered by the invention, according to Figure 4 A disc spring can also be used, or a disc spring package, which represents an equivalent embodiment to the spring bodies shown previously.

[0086] For fine adjustment of the disc spring, or another spring body of the previous examples, the adjustment wheel 14, which is non-rotatably mounted on the piston tube 29, is rotated clockwise around the axis 44, for example in the direction of arrow 81. Due to the non-rotatable connection to the piston tube 29, the latter is also rotated clockwise around the axis 44, stressing the threaded connection 37, whereby the internal thread of the piston tube 29 moves clockwise along the thread pitch of the external thread of the sliding part 10.

[0087] Due to this stress, the sliding part 10 remains stationary and only the piston tube 29 is moved clockwise and moves in the direction of arrow 16. As a result, due to the lugs 31" and 42", the tension spring 29 is also further compressed in the direction of arrow 16 and a fine adjustment takes place.

[0088] In the adjusting wheel 14 there are several recesses 84 on a circular path, into which an anti-rotation device 15 can engage when the adjusting wheel 14 is rotated and can hold it in a rotationally secure manner.

[0089] By turning the adjustment wheel 14, more or less compression force can be adjusted, which acts on the helical compression spring. When the adjustment wheel 14 is turned, the anti-rotation device 15 is pushed out of the recesses 84 until the desired tensioning force is reached, e.g., as shown in the table, and then re-engaged. The adjustment causes only the piston tube 29, which is connected to the adjustment wheel 14 via keys or pins, to rotate, thus tensioning or relaxing the spring body, which is designed as a disc spring, spiral spring, or elastomer spring body.

[0090] Figure 5 shows in a two-part sectional view, a further embodiment of a draw-in collet, this embodiment not being covered by the invention.

[0091] In the upper view, pressure is applied to the actuation module 3' and the collet is fully open, with no workpiece clamped. Sensor 12 indicates that no workpiece is clamped. The helical compression spring 9' is pressed into the position with the highest clamping force. The helical compression spring 9' is mounted with its right side in a bushing 50, with a shoulder 93 acting in the axial direction on the right end face of the bushing 50.

[0092] The left side of the helical compression spring 9' is held in a receiving part 101, which is slidably supported on the bushing 50 via a leg 100. The receiving part 101 is connected, with its left end face, via a screw 102, in a rotationally fixed manner to the bell 97. At its end facing the workpiece, the bell 97 has a conical region 98 on the inner circumference, which interacts with a conical region 99 on the outer circumference of the draw-back collet 88.

[0093] Due to the conical areas 98, 99 rising in the same direction (arrow direction 86), when the bell 97 moves in the axial direction, the draw-back collet 88 is displaced radially inwards, so that the clamping jaws of the draw-back collet 88 are pressed against the workpiece 4 and thus clamp it in the power chuck 6'.

[0094] The helical compression spring 9', which is accommodated between the receiving part 101 and the bushing 50, is compressed by a movement of the bushing in the direction of arrow 86 relative to the receiving part 101.

[0095] Such a movement of the bushing 50 is caused by the projection 93 on the bushing, which projection is in turn pressed by a rolling bearing 36 in the direction of arrow 86.

[0096] The rolling bearing, which in the upper view rests on the shoulder 93, is connected to a thrust ring 95.

[0097] The pressure ring 95 has a piston surface 92 in the upper area, which together with the counter surface of the fixed part 94 defines a pressure chamber 91 in the interior of the actuating module 3'.

[0098] The introduction of a pressure medium into the pressure chamber 91 leads to a displacement of the piston surface with increasing pressure and thus to a displacement of the pressure ring 95 in the direction of arrow 86. Due to the displacement of the pressure ring, the roller bearing 36 connected to it presses on the shoulder 93 and the helical compression spring 9' is compressed in the direction of arrow 86.

[0099] The lower view of the Figure 5 shows a pressureless actuation module 3', with the pressure medium escaping from the actuation module in the direction of arrow 105. Since no pressure force acts on the piston surface 92, the pressure ring 95 is moved in the direction of arrow 16 due to a relaxation of the spring 46, and the associated rolling bearing 36 lifts off the contact surface 106 of the projection 93.

[0100] The spring 46 is supported on the extension 103' and, when released, pushes the piston in the direction of arrow 16.

[0101] In this situation, the helical compression spring 9' is relaxed to such an extent that the clamping force is sufficient to hold the workpiece 4.

[0102] For a fine adjustment of the spring tension of the helical compression spring 9', a Figure 7 The adjustment wheel bushing 51 shown is inserted into the actuation module 3' in the direction of arrow 86. The adjustment wheel bushing 51 has positioning surfaces 54 on its circumference, which interact with circularly arranged lugs 55 in the interior of the adjustment part 56 and, upon a rotational movement of the adjustment wheel bushing 51, can transmit this rotational movement to the adjustment part 56 in a force-fitting manner.

[0103] The rotation of the adjustment wheel bushing 51 causes the adjustment part 56, which is rotatably mounted in a sliding bushing 52, to rotate below the spring tension cylinder 2'. The sliding bushing 52 is mounted in the bushing 50.

[0104] The adjustment part 56 is connected to the pull rod 57 via a threaded connection 53. For this purpose, the adjustment part 56 has an internal thread and the pull rod 57 has an external thread.

[0105] Due to the threaded engagement, the rotational movement of the adjusting part 56 causes a translational movement of the pull rod 57.

[0106] By moving the draw rod 57, the draw-in collet 88 connected to the draw rod is moved axially and thus the cutting force is adjusted.

[0107] In the example shown here, the draw-back collet 88 is pulled in the direction of arrow 16, whereby the draw-back collet 88 moves with its conical area 99 along the conical area 98 of the bell 97 and the draw-back collet 88 is thus pressed in the direction of the workpiece 4.

[0108] After the fine adjustment has been made, the adjustment wheel bushing 51 is removed from the actuation module 3'.

[0109] A stationary sensor 12 detects the position of the pressure ring 95, which is movable relative to it, and can therefore determine whether a workpiece is clamped or not.

[0110] Figure 6 , which is not covered by the invention, shows an adjusting wheel 14 or which can also form the front side of the adjusting wheel bushing 51 for adjusting the spring tension force, wherein both parts have the same attack options for a tool.

[0111] Thus, a hook wrench (e.g. DIN1810) with its hook 108 can be inserted into the grooves arranged in a circle on the outer circumference of the adjustment wheel or the adjustment wheel bushing 51 and rotates the adjustment wheel or the bushing around the axis 44.

[0112] Figure 7 shows a cross-sectional view of the adjustment wheel bushing 51, which can be turned with the hook wrench. After adjustment, the adjustment wheel bushing 51 is removed from the actuation module.

[0113] Figure 8 shows a pressureless actuation module 3" with a simple adjusting piston 34' with a piston rib 70' of an embodiment in which only one piston is used. The adjusting piston 34' is pressed against the fixed part 90' by the built-in spring 46'.

[0114] Figure 9 shows an electrical adjustment system in the rest position, with a ball screw 63 for adjusting the dead-collet chuck, with no workpiece inserted.

[0115] The 9" helical compression spring on the clamping cylinder 112 is minimally tensioned with a preload acting in the direction of arrow 16'. The dead-collet chuck (not shown) or the jaw chuck are closed.

[0116] In this embodiment, the pressure ring of the actuating module 3‴ is formed by the ball roller nut 61, on the right side of which a rolling bearing 65 is attached.

[0117] Actuating module 3‴ is not connected to the clamping cylinder 112, since the rolling bearing 65 has no axial connection with the flat surface 71' of the adjusting wheel 14'.

[0118] To generate a voltage, energy is supplied to the motor 62 so that it sets the belt 110 in motion via a belt drive 60, which drives the ball screw 63 and thus the ball nut 61.

[0119] The ball screw nut 61 would then press the adjusting wheel 14' via the roller bearing 65 against the flat surface 71' of the adjusting wheel 14', which is non-rotatably connected to the piston tube 29'. The piston tube 29' rests with a radially outwardly projecting shoulder 31' against the radially inwardly directed shoulder 42' of the movement bushing 43'.

[0120] By moving the piston tube 29' against the direction of arrow 16', the movement bush 43' would now compress the helical compression spring 9" against the direction of arrow 16'.

[0121] All axial movements of the adjustment wheel 14' can be detected by an analogue distance measuring sensor 66, which determines the clamping force based on the detected distance.

[0122] If a workpiece is now inserted, the motor 62 drives the belt 110 in the opposite direction and the ball nut 61 runs in the direction of arrow 116 and lifts the rolling bearing 65 from the flat surface 71'.

[0123] A workpiece is thus only clamped by the clamping force of the 9" helical compression spring.

[0124] Figure 10 shows an electrical adjustment system using an eccentric drive 68, which drives an eccentric shaft 67. This is a 180° eccentric adjustment for a dead-end collet (not shown) in the rest position.

[0125] The eccentric shaft 67 points perpendicularly to the piston tube 29" and carries a rolling bearing 104 on its circumference. Depending on the position of the eccentric shaft 67, the rolling bearing 104 is moved towards or away from the adjusting wheel 14".

[0126] The helical compression spring 9‴ on the spring tensioning cylinder 2" is minimally tensioned and has a preload force in the direction of arrow 86'.

[0127] To compress the helical compression springs, the eccentric shaft 67 moves the roller bearing 104 toward the adjusting wheel 14" and pushes it axially backward in the direction opposite to the arrow 86'. The movement of the adjusting wheel 14" also pulls the piston tube 29" connected to it in a rotationally fixed manner in this direction.

[0128] The piston tube 29" has a radially outwardly projecting shoulder 31" which interacts with a shoulder 42" of a movement bushing 43" and thus also moves the bushing in the opposite direction to the arrow 86'. This compresses the helical compression spring 9‴ applied to the movement bushing 43". After inserting a workpiece (not shown), the eccentric drive 68 moves the roller bearing 104 away from the adjustment wheel 14‴ until there is no longer any connection. The workpiece is now held only by the clamping force of the helical compression springs 9‴.

[0129] All movements of the adjustment wheel can be recorded with the travel measuring sensor 129, which determines the clamping force from the recorded travel distance. Drawing legend

[0130] 1.Clamping cylinder 2.Spring clamping cylinder 2', 2" 3.Actuating module 3', 3", 3‴ 4.Workpiece 5.Collet 6.Power chuck 6' 7.Spindle motor 9.Compression spring 9', 9" 10.Sliding part 11.Connection (Pneumatic / Hydraulic) 11‴ 12.Sensor 13.Pressure ring 13' 14.Adjusting wheel 14', 14", 14‴ 15.Anti-twist device 16.Arrow direction 16' 18.Draw tube 19.Pressure chamber 20.Pressure chamber 21.Pressure channels 21a, 21b, 21' 29.Piston tube 29', 29" 31.Attachment 31', 31" 33.Stop 34.Adjusting piston 34' 35.Bearing bolt 35' 36.Rolling bearing 36' 37.Threaded connection 38.Shoulder 39.Piston surface (of 19) 40.Piston surfaces (of 20) 42.Shoulder (of 29) 42', 42" 43.Motion bushing 43', 43" 44.Shaft 45.Anti-rotation device 46.Return spring 46' 47.Screw connection 48.Spindle motor 49.Compression spring 50.Bushing 51.Adjusting wheel bushing 52.Sliding bushing 53.Threaded connection 54.Positioning surface 55.Nose 56.Adjustment part 57.Pull rod 58.Tool 59.Groove 60.Belt drive 61.Ball rolling nut 62.Motor 63.Ball screw 64.Screw 65.Rolling bearing 66.Position sensor 67. Eccentric shaft 68. Eccentric drive 69. Piston rib (of 19) 70. Piston rib (of 20) 71 Flat surface 71' 72. Stud bolt 73. Recess 75. Mounting space 76. Stop 77. Thrust piece 77' 78. End face (of 77) 79. Bolt end 80. Recess 81. Arrow direction 82. Contact surface (of 32) 83. Mounting space (of 43) 84. Recess 85. Headstock 86. Arrow direction 89 88. Draw-back collet piston housing 89' 90. Housing (plate-shaped) 91. Pressure chamber 92. Piston surface 93. Extension 94. Fixed part 95. Thrust ring 96. Actuating nose 97. Bell 98. Conical area (of 97) 99. Conical area (of 104) 100. Leg 101. Receptacle 102. Screw 103. Extension 103' 104. Roller bearing 105. Arrow direction 106. Contact surface 108. Hook 109. Helical compression spring 110. Belt drive 112. Clamping cylinder 129. Position sensor 130. Bearing 131. Bell 132. Conical area (of 134) 133. Conical area (of 18) 134. Clamping jaws 135. Machine spindle 136. Flange 137. Screw 138. Energy storage device 139. Bore (of 77) 140.Hollow shaft.

Claims

1. A clamping device (1) for machine tools, wherein the clamping device comprises a power chuck (6) with clamping jaws (134) for holding a workpiece (4), an axially adjustable, tubular adjusting member (10, 18, 29, 29'), an actuation module (3, 3'', 3‴) for actuating the clamping jaws (134) via the adjusting member (10, 18, 29, 29'), and a machine spindle (135) with a bell-shaped clamping cylinder (22', 2", 112), wherein the adjusting member (10, 18, 29, 29') has a radially outwardly projecting protrusion (31, 31', 31''), wherein, for implementing the axial adjustment movements of the adjusting member (10, 18, 29) required to actuate the clamping jaws (134), the clamping device (1) has a force accumulator (138) within the clamping cylinder (2, 2', 2", 112) of the machine spindle (135) for maintaining the clamping force, which consists of at least one preloaded spring (9, 9', 9", 49) that is supported on the protrusion (31, 31', 31") of the adjusting member (10, 18, 29, 29'), and wherein in a rotating operating state: the clamping cylinder (2, 2', 2", 112) is designed to rotate with the machine spindle, the actuation module (3, 3'', 37‴) is designed to remain stationary, and the actuation module (3, 3", 3‴) can be separated from the clamping cylinder (2, 2', 2", 112) without contact, characterised in that the adjusting member is formed by a drawbar (18) that is fixedly received at least partially in a tubular displacement member (10) with its end facing away from the power chuck (6), and in that the displacement element (10) is connected via a threaded connection (37) to a hollow, likewise tubular piston tube (29, 29', 29'') and is partially received in the hollow piston tube (29, 29', 29"), and the piston tube (29, 29', 29'') has, in a region of overlap with the inner displacement element (10), the protrusion (31, 31', 31'') that abuts against a radially inwardly directed protrusion (42, 42', 42") of a movement bushing (43, 43', 43") of the clamping device (1), which surrounds the protrusion (31, 31', 31") of the piston tube (29, 29', 29'') in an annular manner and in which the at least one spring (9, 9', 9", 49) is mounted, and in that, when the piston tube (29, 29', 29'') is manually turned relative to the displacement part (10), the compression force of the force accumulator (138) can be axially adjusted by means of an adjusting wheel (14, 14', 14'', 14‴) connected to the piston tube (29, 29', 29") in a rotationally fixed manner, and in that, for changing the clamping forces of the force accumulator (138), the actuation module (3, 3'', 3‴) can be briefly docked to the adjusting wheel (14, 14', 14", 14‴) via one or more roller bearings or via pressure rollers or pressure bearings (36, 65, 104) of the actuation module (3, 3', 3'', 3‴).

2. The clamping device (1) according to claim 1, characterised in that the actuation module (3, 3", 3‴) can be docked to a flat surface (71) of the adjusting wheel (14) by means of a roller bearing (36).

3. The clamping device (1) according to claim 1 or 2, characterised in that the force accumulator (138) consists of a plurality of helical compression springs (9, 9', 9") or spring assemblies or elastomeric spring bodies, which are evenly distributed around the circumference and mounted in a receiving space (83) of the bushing (43, 43', 43'') inside the clamping cylinder (2, 2', 2", 112).

4. The clamping device (1) according to any one of claims 1 to 3, characterised in that the clamping cylinder (2, 2', 2", 112) is screwed to the rotatable machine spindle (135) and the actuation module (3, 3'', 3‴) can be screwed to a fixed spindle block (85).

5. The clamping device (1) according to any one of claims 1 to 4, characterised in that the tension or compression force on the power chuck (6) can be determined via the spring or springs (9, 9', 9", 49) built into the clamping cylinder (2, 2', 2", 112).

6. The clamping device (1) according to any one of claims 1 to 5, characterised in that the actuation module (3, 3", 3‴) has a movable adjustment piston (34, 34'), the piston surfaces (39, 40, 92) of which can be acted upon by air or oil pressure when coupled.

7. The clamping device (1) according to any one of claims 1 to 6, characterised in that, after the spring tension in the clamping cylinder (2, 2', 2", 112) has been changed, the actuation module (3, 3'', 3‴) can be switched to unpressurised and can be decoupled from the clamping cylinder (2, 2', 2", 112) without contact.

8. The clamping device (1) according to any one of claims 1 to 7, characterised in that the spring or springs (9, 9', 9", 49) act within the clamping cylinder (2, 2', 2", 112) via the drawbar (18) on the power chuck (6), wherein the clamping state of a workpiece (4) can be secured elastically.

9. The clamping device (1) according to any one of claims 1 to 8, characterised in that the actuation module (3, 3'', 3‴) has one or two piston surfaces (39, 40, 92), the size of which corresponds to the maximum spring and clamping force when pressure is applied.

10. The clamping device (1) according to any one of claims 1 to 9, characterised in that the displacement part (10) is connected to an internal thread of the piston tube (29, 29', 29") via an external thread.

11. The clamping device (1) according to any one of claims 1 to 10, characterised in that the open state of the power chuck (6) can be monitored by a BERO proximity switch of the clamping device (1).

12. The clamping device (1) according to any one of claims 1 to 11, characterised in that a spring travel of the spring or springs (9, 9', 9", 49) can be monitored or measured by a travel measurement sensor (129) of the clamping device (1).