CLAMPING SYSTEM FOR A HOLLOW SHAFT WITH SELF-LOCKING

Description

[0001] Clamping systems with a hollow shaft and a complementarily shaped centering mount, for example according to ISO 12164 or ISO 26623, have proven themselves on the market for many years.

[0002] They are used, among other things, in driven or fixed tool holders. In these cases, the centering mount and clamping system are integrated into the spindle of the driven tool holder or the tool holder housing. The hollow shank is part of an adapter that supports a drill, turning tool, or other tool.

[0003] The known clamping systems for clamping such a hollow shaft comprise a collet consisting of several clamping segments. The clamping segments are arranged around a draw bolt. Through an axial movement of the draw bolt relative to the clamping segments, these are pressed radially outwards. This initially results in a positive connection with the hollow shaft at the front ends of the clamping segments. Further movement of the draw bolt creates an axial clamping force, which the clamping segments exert on the hollow shaft of the adapter, so that the

[0004] The adapter is pulled into the centering mount. An example of such a clamping system is known from EP 2 164 662 and DE 10 2012 108143.

[0005] This clamping system is not self-locking. As a result, a constant actuating force must be applied to the clamping system during tool holder operation to maintain the clamping force. Otherwise, the clamping system would become loose.

[0006] This is particularly difficult to achieve with a hydraulic clamping system in a rotating spindle of a driven tool holder. If the actuating force, and thus the clamping force, is applied by a spring located in the tool holder, this requires more space. Furthermore, the force required to release the clamping system increases, as the force of the clamping spring must also be overcome.

[0007] EP 1 924 379 B1 discloses a clamping device with a self-locking mechanism. The clamping process is carried out by a clamping head 6, which interacts with clamping claws 5 in a manner known per se. A draw bolt 4 is arranged in front of the clamping head 6 and is moved in the axial direction by an actuating device in order to clamp or release the clamping device. A two-part drag grip 7 and a clamping sleeve 11 are provided between the draw bolt 4 and the clamping head 6. During clamping, a shoulder 15 of the draw bolt 4 rests against an inner collar of the drag grip 7, so that the movement of the draw bolt 4 is transmitted directly via the drag grip 7 to the clamping head 6. After the draw bolt has traveled a certain distance, the halves of the drag grip 7 deflect radially outwards. This eliminates the positive connection between the half-shells of the drag grip 7 and the draw bolt.

[0008] As the clamping process continues, the drag tongs 7 are only slightly dragged in the axial direction, but are wedged between a conical head 12 of the draw bolt 4 and a clamping sleeve 11 fixed to the housing until the desired self-locking is achieved.

[0009] This device is complex in design; in addition to the clamping head and the draw bolt, it also requires a two-part drag grip and a clamping sleeve 11. Furthermore, it requires a relatively large travel of the draw bolt, requires a lot of installation space, and is expensive to manufacture.

[0010] DE 196 18 610 A1 describes another clamping device with self-locking from the field of machine tools. In this case, self-locking occurs at the front end of the clamping segments. However, this self-locking is not sufficient. Therefore, an additional locking device is required. This additional locking device comprises a compression spring that presses wedge segments against a conical / tapered part of the draw bolt, so that the spring force of this compression spring creates a frictional connection to the spindle via the wedge segments. This frictional connection prevents the clamping set from being accidentally opened. This solution also requires a lot of installation space and is expensive to manufacture. Furthermore, in addition to the frictional forces, the force of the compression spring must also be overcome to release the clamping system. This results in high forces, which in turn require a large cylinder structure, which is also disadvantageous.

[0011] The invention is based on the object of providing a clamping system that is self-locking and has a very compact, simple, and robust design. This compact design is particularly important when space is limited. This is the case, for example, on turrets in turning centers. Here, the clamping system must be able to be flexibly mounted in various positions and orientations in stationary and driven tool holders. The installation space is severely limited, for example, by permissible swivel diameters, the width of the mounting surface, and the interface to the turning center.

[0012] This object is achieved according to the invention in a clamping device for a hollow shaft, in particular a hollow shaft cone with a circular or polygonal outer contour, comprising one or more clamping segments and a draw bolt cooperating with the clamping segments, wherein each clamping segment has a front clamping claw on its outer side at a front end and a front nose on its inner side cooperating with the draw bolt, wherein each clamping segment has a rear clamping claw on its outer side at a rear end and a rear nose on its inner side cooperating with the draw bolt, wherein in the clamping position the front clamping claw of each clamping segment engages in a clamping groove of the hollow shaft and the rear clamping claw is pressed against a cone, wherein in the open position the front clamping claw(s) are not engaged in the clamping groove of the hollow shaft,wherein the draw bolt moves the clamping segment(s) from the clamped position to the open position and from the open position to the clamped position by axial displacement, wherein the clamping segment(s) execute a first pivoting movement during the transition from the open position to the clamping position, so that the front clamping claws of the clamping segments engage positively in the clamping groove and form a joint for a subsequent second pivoting movement of the clamping segment(s), wherein during the second pivoting movement the rear lugs of the clamping segment(s) slide on a third conical section of the draw bolt and press the rear clamping claws of the clamping segments against the cone of the conversion part or the spindle and axially clamp the clamping segment(s), thereby released,that during a further axial movement of the draw bolt following the second pivoting movement, the rear lugs of the clamping segment(s) slide on a second conical section of the draw bolt, so that a self-locking effect is created between the clamping segments and the draw bolt.

[0013] Through the movement sequences coordinated according to the invention, the positive connection between the front clamping claw of the clamping segments and a clamping groove in the hollow shaft is achieved in a first pivoting movement. From then on, this positive connection at the front end of the clamping segments serves as a pivot point / bearing for the clamping segment(s). Then, in a second pivoting movement, the rear end of the clamping segments is pressed radially outwards against the cone of the accessory part or the spindle, thereby building up an axial clamping force. In a subsequent further movement of the draw bolt, the axial clamping force is further increased. At the same time, a self-locking action occurs between the rear lugs of the clamping segments and the second conical section of the draw bolt. The self-locking action occurs at the rear end of the draw bolt.This has, among other things, the positive effect that the tension bolt is clamped and fixed at the front and rear ends.

[0014] According to the invention, no additional components of the clamping system are required to create reliable self-locking. Rather, the desired self-locking is achieved through an inventive design of the draw bolt and its coordination with the clamping segments and the cone. As a result, the inventive solution is very compact and also very advantageous in terms of manufacturing and cost. A further advantage is that the actuating forces for clamping and releasing are relatively small and do not differ significantly in magnitude. Naturally, the actuating force required for clamping is somewhat greater than the actuating force required for releasing.

[0015] The approximately equal forces for clamping and releasing are particularly advantageous when the clamping system is operated automatically using an actuator, such as a hydraulically actuated cylinder assembly. The dimensions of such an actuator are generally determined by the maximum actuating force.

[0016] A further advantage of the clamping system according to the invention is that after the second pivoting movement, when the rear lugs of the clamping segment(s) slide on a second conical section of the draw bolt, the axial clamping of the clamping segments is increased, so that the hollow shaft is pulled into the component or spindle with greater force (booster function).

[0017] Furthermore, in the clamping system according to the invention, the draw bolt is centered at its front end by the front lugs of the clamping segments in the clamping groove of the hollow shaft, and at its rear end by the rear lugs of the clamping segments in the cone. As a result, the clamping system has no or only very little imbalance. This improves the machining quality of workpieces machined with a tool clamped in the hollow shaft and allows machining at very high spindle speeds with driven tools.

[0018] A further advantage of the clamping system according to the invention is that the shape of the front lugs and the clamping groove can be designed relatively freely. It can be used with the following systems, among others: ISO 12164 (HSK) or ISO 26623 (Coromant Capto).

[0019] In an advantageous embodiment of the invention, a first cylindrical section, a first conical section, a second cylindrical section, the second conical section, the third conical section, and a third cylindrical section are formed successively on the tension bolt, starting at its front end VE. During the first pivoting movement, the front lug slides on the first conical section. During the second pivoting movement, the rear lug slides on the third conical section. During the subsequent pivoting movement, caused by a further axial movement of the tension bolt, the rear lug slides on the second conical section, and the self-locking mechanism is established.

[0020] Self-locking means that after the clamping system has been tightened, no further actuating force needs to be exerted on the draw bolt, the draw bolt remains in its position due to the self-locking and a sufficiently large clamping force continues to be applied.

[0021] In other words: If the draw bolt is actuated hydraulically, the cylinder assembly that actuates the draw bolt can be depressurized after clamping without affecting the tension of the clamping system according to the invention or of the adapter.

[0022] This is a major advantage, especially when the clamping system is installed in a rotating spindle, and the spindle rotates during machining. Unlike with other systems, there's no need to constantly apply an actuating force to maintain the clamping force; instead, the clamping force is maintained in the clamping system thanks to the self-locking mechanism.

[0023] It's also not necessary to integrate a spring that rotates with the spindle and constantly applies an actuating force. Disadvantages of this solution would be that the spring can cause imbalance, and in addition, the force of the spring must be overcome to release the clamping system, in addition to the frictional forces. This results in high actuating forces, which in turn require a large cylinder structure, which is also disadvantageous.

[0024] The cone is an internal cone and can be machined directly into the housing, an accessory, or a spindle. Alternatively, it is also possible to provide a threaded ring into which the cone is machined. This threaded ring is then screwed into the housing, accessory, or spindle. Of course, the ring and the housing do not have to be threaded. Other connections can also be used that radially center the cone and hold it in position axially in the direction of the clamping force, such as a bore-cylinder pairing with a retaining ring for axial positioning.

[0025] It has proven advantageous if the angle of inclination of the second cone section is less than 5° or less than the arctangent of the friction coefficient µ, which arises from the pairing of the contact surfaces of the clamping segment and the draw bolt. This achieves self-locking in a simple and very reliable manner. Naturally, when determining the coefficient of friction and thus also the angle of inclination of the second cone section, it is also advisable to consider the influences of fluids such as oil or cooling lubricant, the surface quality, the material pairing, any coating, and additional safeguards against loosening due to vibration. By taking these circumstances into account, self-locking can be guaranteed under all operating conditions.

[0026] In many cases, it has proven sufficient or even advantageous if the angle of inclination of the second cone section is in a range between 3° and 5°. 4° has proven to be a very good value.

[0027] The inclination angles of the first cone section and the third cone section, in contrast, are much larger. They range between 30° and 60°; preferably, the inclination angle of both sections is 45°.

[0028] In the tension bolt according to the invention, the second conical section and the third conical section merge into one another without a jump in diameter and without a cylindrical intermediate section. This minimizes the required clamping travel of the tension bolt. The transition between the two conical sections is seamless.

[0029] The front lugs of the clamping segments (starting at the front end) have a first contact surface aligned with the inclination angle of the first conical section of the draw bolt and a second contact surface aligned with the cylindrical section. This optimally controls the first pivoting movement during which the front clamping claws of the clamping segments engage the clamping groove of the hollow shaft.

[0030] "Matched" in this context means that the contact surfaces between the noses of the clamping segments and the draw bolt are as large as possible in the various positions of the draw bolt relative to the clamping segments, and that no highly stressed edge supports occur in order to reduce surface pressure and wear. The inclination angles are therefore usually the same.

[0031] However, it is also possible, for example, for the contact surfaces to be slightly spherical or barrel-shaped to prevent edge wear that can result from the pivoting movements of the clamping segments. Likewise, the cylindrical sections of the tension bolt can be slightly barrel-shaped.

[0032] In order to increase the self-locking of the clamping system according to the invention, it may be advantageous to design the first cylinder section as a cone with a small negative angle of inclination α.

[0033] The inclination angle α of the first cylinder section can be positive or negative. Despite the resulting linguistic "inaccuracy," the term "first cylinder section" is used even if it has a small inclination angle and is therefore, strictly speaking, a fourth conical section.

[0034] The magnitude of the inclination angle α can be equal to or less than 4°. A negative inclination angle α is smaller than the inclination angle of the second conical section on the tension bolt. A positive inclination angle α can increase the clamping travel and, like the second conical section, can have an inclination angle smaller than the arctan of the friction coefficient µ.

[0035] At a negative angle of inclination α, the cone at the front end of the tension bolt (= first cylinder section) is directed in the same direction as the cone in the threaded ring; it is directed opposite to the second cone section and the third cone section of the tension bolt. Figure 8 a negative inclination angle α is illustrated.

[0036] Accordingly, with a negative inclination angle α, the cone at the front end of the draw bolt (= first cylinder section) and the cone in the threaded ring are oppositely directed; a positive inclination angle can be useful, for example, with HSK to increase the clamping travel, since the gripper groove is wedge-shaped there.

[0037] Self-locking means that the draw bolt is prevented by design measures from moving from the clamped position to the open position due to imbalance, vibrations, pressure surges from the coolant, or other external forces that may act on it during operation. This would be a movement in the direction of the centering mount.

[0038] Due to the optional negative inclination angle α, radial forces acting from the front noses of the clamping segments on the first cylinder section cause an axial force on the draw bolt in the direction of the clamping position.

[0039] In a further advantageous embodiment, the rear noses of the clamping segments have a third contact surface adapted to the angle of inclination of the third cone section and a fourth contact surface at their rear end adapted to the second cone section.

[0040] This means that initially the second pivoting movement is controlled by the third conical section of the tension bolt.

[0041] Subsequently, after a large portion of the radial stroke and a certain (usually still insufficient) clamping force has been achieved, further clamping occurs between the draw bolt and the rear lugs of the clamping segments, as well as between the rear clamping claws of the clamping segments and the cone in the threaded ring or the spindle housing. The rear lugs of the clamping segments slide on the second cone section. The inclination angle of the second cone section is significantly smaller than the inclination angle of the third cone section. This reduces the reduction ratio between the axial movement of the draw bolt and the pivoting movement of the clamping segments at their rear end. In other words, for the same axial movement of the draw bolt, the radial movement of the clamping segments is smaller.As a result, the axial clamping forces of the clamping segments increase (assuming a constant axial force of the draw bolt), and thus also the axial or clamping force acting on the hollow shaft (booster function). In other words: Despite relatively small displacement forces acting on the draw bolt, the required clamping force is achieved, so that the clamping segments pull the adapter into the centering mount with great force.

[0042] Due to the small angle of inclination of the second conical section, relatively large radial forces occur, which are transmitted safely and without overloading the components via a large contact surface between the second conical section of the tension bolt and the fourth contact surfaces on the rear noses of the clamping segments.

[0043] This, among other things, makes the solution according to the invention very durable, it wears little or not at all, and the surface pressure between the lugs and the second conical section of the tension bolt remains within the permissible values.

[0044] The angle of inclination of the cone in the threaded ring or the housing and the correspondingly coordinated fifth contact surface on the rear clamping jaws of the clamping segments is preferably in a range of 20° to 45°. An angle of inclination in a range of 25° to 40°, particularly 30° or 35°, has proven to be very suitable.

[0045] In a further advantageous embodiment, the clamping segments are supported with their rear end against a spring-loaded intermediate disc or directly against a compression spring, so that the clamping segments can deflect in the axial direction during the clamping process.

[0046] In the case of incorrect clamping, when the front lugs of the clamping segments slide on the first conical section and the front clamping jaws cannot move into the clamping groove of the hollow shaft due to incorrect positioning of the hollow shaft, the clamping segments, when they are in contact with the hollow shaft, can move backwards together with the tension bolt against the force of a spring (see Figures 9 and 10 ) and are also decoupled from the forces on the tension bolts.

[0047] This prevents damage to the clamping system if, of course, the adapter is not in the correct position relative to the centering fixture or the draw bolt at the beginning of the clamping process—which is undesirable. Therefore, the clamping system according to the invention is also fault-tolerant, and a malfunction does not lead to total failure of the clamping system.

[0048] Further advantages and advantageous embodiments of the invention can be found in the following drawings, their descriptions and the patent claims. Figures

[0049] They show: Figures 1 to 5 a first embodiment of the invention in a longitudinal section in different positions; Figure 6 another embodiment of the invention; Figure 7 a longitudinal section of a tension bolt according to the invention; Figure 8 a longitudinal section of a clamping segment according to the invention; Figures 9 and 10 incorrect tension of an adapter in different positions; Figure 11 another embodiment of the invention and Figure 12 another embodiment of the front part of a clamping segment according to the invention in longitudinal section Description of the embodiments

[0050] The adapter 1 to be clamped is inserted manually or automatically into a centering holder 3.

[0051] In the context of the invention, the term "adapter" is used as a generic term for all components or assemblies that can be clamped in a centering fixture 3 using the clamping system according to the invention. This can be a tool, a tool holder (drill chuck), a device or a pallet for clamping workpieces, and more.

[0052] In the Figure 1 the first embodiment of a clamping system according to the invention with self-locking in the open position or the released position is shown.

[0053] In the Figure 5 The same clamping system is shown in the clamping position with self-locking.

[0054] The Figures 2 to 4 show intermediate positions of the clamping system, which explain the functionality of the clamping system. When releasing the clamping system, starting from the Figure 5shown clamping position with self-locking, pass through the positions shown in Figures 4 to 1, ie in the reverse order to clamping.

[0055] The same reference symbols are used for the same components in all figures. For reasons of clarity, not all reference symbols are shown in every figure.

[0056] In the Figure 1 An adapter 1 to be clamped is shown. It is not part of the clamping system according to the invention, but is clamped by it in a centering holder 3.

[0057] In the Figures 1 to 5 In the embodiment shown, the centering holder 3 is a separate component that is inserted into the spindle 37.

[0058] The adapter 1 comprises a hollow shaft 5, which interacts with the clamping device according to the invention. For this purpose, the hollow shaft 5 has a clamping groove 7 and a front face 9.

[0059] The hollow shaft 5 generally engages a centering mount 3, since in machine tools the hollow shaft 5 of the adapter 1 and the centering mount 3 interact axially and radially without play. The requirements for the concentricity and axial runout of the adapter 1, as well as the torques that can be transmitted between the centering mount 3 and the hollow shaft 5, are becoming increasingly stringent. The hollow shaft 5 and the centering mount 3 can, for example, be designed according to ISO 12164 or ISO 26623. However, other designs without a centering effect are also possible. A centering mount is not necessary, for example, if several clamping systems according to the invention are used in a workpiece clamping device to clamp a workpiece in the device.

[0060] In the figures, a "polygonal hollow shank taper with flat contact" according to ISO 26623 (Capto) is used as the centering fixture 3. As shown in the figures, the centering fixture 3 can be an additional or separate component that is accommodated by or in accessories (housings, rotating spindles, stationary workpiece clamping devices, etc.).

[0061] The centering mount 3 can also be integrated into one of the "conversion parts"; in this case, the conversion part and the centering mount are designed as a single piece. A corresponding embodiment is shown in the Figure 6 This design requires less radial space; therefore, it is often used for rotating or driven spindles. In the corresponding figure description for Figure 6 the constructive effects are also described.

[0062] The following is based on the Figures 1 to 5 the tensioning process is presented and explained in different stages.

[0063] First, in the Figure 7 A tension bolt 13 according to the invention is shown. In this embodiment, a piston 15, which is part of a cylinder structure, is connected to the tension bolt 13. In this figure, the functional surfaces according to the invention are clearly visible and provided with reference numerals.

[0064] These are: 101: a first cylindrical portion; 103: a first conical portion; 105: a second cylindrical portion; 107: a second conical portion; 109: a third conical portion; and 111: a third cylindrical portion.

[0065] There may be a diameter jump between the second cylindrical portion 105 and the second conical portion 107.

[0066] A front end VE and a rear end HE are also marked. "Front" is the area of ​​the centering mount 3 (see Figure 1 ); the third cylindrical section 111 (see Figures 7 and1 ) is located in the terminology of the figure description at the rear end HE of the tension bolt 13; it is "rear".

[0067] The Figure 7 The functional surfaces 101 to 111 of the tension bolt 13 shown in the figure interact with the corresponding contact surfaces on the "inside" of the clamping segments. They are shown in the Figure 8 and are designated as follows: A first contact surface 121 and a second contact surface 123 form the front nose 27.

[0068] A third contact surface 129 and a fourth contact surface 131 form the rear nose 29.

[0069] A transition section 125 (here two-part) is not a functional surface in this sense. It creates the clearance required for the second conical section 107 of the tension bolt 13.

[0070] A front claw 31 and a rear claw 41 are formed on the outside of the clamping segments 25. The rear claw 41 is essentially designed as a truncated or conical fifth contact surface 133 and can also be concave. The shape of the front claw 31 is matched to the shape of the clamping groove 7 in the hollow shaft 5. Radius- and chamfer-shaped designs, for example, are known from the ISO standards already mentioned. In particular, a good form fit and the lowest possible surface pressure between the front claws 31 and the clamping groove 7 should be achieved when the clamping system is clamped.

[0071] Back to Figure 1 : For reasons of clarity, the reference numbers 101 to 133 in the Figures 1 to 5 not shown. Nevertheless, these reference symbols are used in the description of the figures.

[0072] When inserting the adapter 1 into the centering seat 3, the hollow shaft 5 is moved towards a stop disc 11 into a defined position. The stop disc 11 is attached to a tension bolt 13 or integrated into the tension bolt 13 (one-piece design). Figure 6 or Figure 11 An example of a one-piece design is shown.

[0073] The stop disk 11 essentially represents a depth stop for the adapter 1 or the hollow shaft 5 and ensures that the adapter 1 assumes a defined position in the axial direction before the clamping process begins. This occurs when the base 19 of the hollow shaft 5 comes into contact with the stop disk 11. For automatic clamping, the relationship between the clamping groove 7 of the hollow shaft 5 and the front clamping jaws 31 of the clamping segment(s) 25 is important; only when this relationship is correct can the front clamping jaws 31 move into the clamping groove 7 of the hollow shaft 5. For this purpose, it may be useful to set the stop disk to the defined position by using the thread for adjustment or by machining the front side of the stop disk to the desired dimension to achieve the position.

[0074] For centering holders with hollow shank taper and flat contact, the defined position is at approximately 1.5 to 0.5 mm, typically at approximately 1 mm flat contact distance between the front side of the centering holder 3 and the flat surface 9 of the adapter 1. The size of the distance depends on the type of adapter.

[0075] The stop disc 11 at the end of the draw bolt 13 has a large outer diameter. A "base" 19 of the hollow shaft rests against the stop disc 11. This improves the flatness of the adapter 1 and reduces the risk of the adapter 1 tilting relative to the centering mount 3.

[0076] At this point (i.e., before the start of the cutting process), the draw bolt 13 must be precisely positioned in its axial position. Only then will the stop disc 11 have a precise axial position, and only then can the aforementioned defined position of the adapter 1 be guaranteed.

[0077] In this embodiment, the axial position of the tension bolt 13 is determined by its actuating means. In the figures, the actuating means is, for example, a piston-cylinder combination (also referred to as a "cylinder assembly"), whose piston 15 is connected to the tension bolt 13 and the stop plate 11.

[0078] When the piston 15, as in Figure 1 shown, rests against its front end stop 23, then the tension bolt 13 and the stop disc 11 have a defined axial position.

[0079] The double-acting piston 15, which actuates the tension bolt 13, is guided in a fluid-tight manner in a cylinder 21. Depending on which cylinder chamber 21.1 or 21.2 is filled with a pressurized fluid, the piston 15 moves in the cylinder 21 in one direction or the other. Figure 1In the axial position of the piston 15 shown at a front end stop 23, the cylinder chamber 21.2 has its maximum volume; the volume of the cylinder chamber 21.1 is minimal.

[0080] The clamping system according to the invention comprises a collet consisting of one or more clamping segments 25. The clamping segments 25 are arranged around the draw bolt 13 in a conventional manner. The clamping segments 25 can be interconnected or can be present as individual clamping segments 25.

[0081] At the front end VE, the first contact surface 121 and the second contact surface 123 form a front nose 27. At the rear end HE, the third contact surface 129 and the fourth contact surface 131 form a rear nose 29.

[0082] The nose 27 on the inside of the clamping segments 25 is designed in such a way that it Figure 1shown position of the tension bolt 13 rests on the second cylindrical section 105 (diameter d1) of the tension bolt 13.

[0083] The nose 29 on the inside of the clamping segments 25 is designed in such a way that it Figure 1 shown position of the tension bolt 13 rests on the third cylindrical section 111 (diameter d 2 ) of the tension bolt 13.

[0084] In the cylindrical sections 101, 105 and 111, the tension bolt 13 is cylindrical; however, a slightly conical, concave or convex design is also possible.

[0085] In this embodiment and in this position of the draw bolt 13, the outer diameter of the collet or the clamping segments 25 in the area of ​​the front clamping jaws 31 is so small that the hollow shaft 5 can be pushed over the front stop disc 11 and the enveloping circle diameter of the following front clamping jaws 31.

[0086] In the rear part of the clamping system according to the invention, a threaded ring 33 is screwed into the surrounding housing / configuration part or a spindle housing 37. A cone 43 is formed on the threaded ring 33, which cooperates with the rear clamping claw 41 or the fifth contact surface 133 of the draw bolt 13. When the rear lugs 29 of the clamping segment(s) 25 are moved radially outward by the third or fourth contact surface 129, 131 of the draw bolt 13, the cone 43 deflects this movement at the rear end HE of the clamping segment(s) 25 into an axial movement of the clamping segment(s) 25. In other words: The clamping segment(s) 25 move in Figure 1 to the right, ie, toward the rear end HE, when the draw bolt 13 is moved to the right. Due to the positive engagement between the front claws 31 and the clamping groove 7 of the hollow shaft 5, the adapter 1 is drawn into the centering receptacle 3. The clamping system is clamped.

[0087] The inner diameter of the threaded ring 33 or the cone 43 is advantageously selected so that the threaded ring 33 can also be pushed over the outer diameter of the front clamping jaws. This must be at least in the Figure 1 The position of the draw bolt 13 shown in the figure should be possible. This simplifies assembly and disassembly of the clamping system in a housing or spindle 37.

[0088] The enveloping circle diameter of the rear clamping claw 41, or the enveloping circle diameter of the fifth contact surface 133, is larger than the inner diameter of the cone 43 in every position.

[0089] If a threaded ring 33 cannot be used, for example due to space constraints, the cone 43 is integrated directly into the component (e.g., the spindle housing 37). The clamping segments 25 are then mounted from the rear.

[0090] In order for the collet or its clamping segments 25 to always form the smallest enveloping circle diameter in this position, the clamping segments 25 must be pre-tensioned. This can be achieved by a tension spring 39 at the rear end HE of the collet or the clamping segments 25 or as shown in the Figures 1 to 6 shown in an approximately central arrangement for the longitudinal expansion of the clamping segments 25. It is also possible to connect the clamping segments 25 to one another in a spring-elastic manner to form a one-piece collet (without a separate spring element) (not shown).

[0091] The aim of these embodiments is to compress the clamping segments 25 centrally around the tension bolt 13 via preload. It is advantageous to arrange the tension spring 39 approximately centrally to the longitudinal extent of the clamping segments 25 so that the clamping segments 25 cannot tilt and come into contact with the tension bolt 13 evenly at the front and rear against the lugs 27 and 29.

[0092] A compression spring 45 in the rear area rests on one end face of the compression spring sleeve 49 and, in the state shown in the figure, presses against an optional intermediate disk 47. The intermediate disk 47, in turn, rests positively against a shoulder of the threaded ring 33. It is also possible to omit the intermediate disk 47, so that the compression spring 45 rests directly against the shoulder of the threaded ring 33.

[0093] The intermediate disc 47 or the compression spring 45 can also rest on a shoulder of the accessory part or the spindle housing 37. Due to this contact, the compression spring 45 cannot move the clamping segments 25 further towards the front end VE than in the Figure 1 shown and may still be biased.

[0094] As already described, the clamping segments 25 are pressed inwards by the tension spring 39 and rest with the front nose 27 and the rear nose 29 on the tension bolt 13.

[0095] In the axial direction, the position of the clamping segments 25 is determined by the (inner) cone 43 of the threaded ring 33, the intermediate disk 47 preloaded by the compression spring 45, or the compression spring 45 and the tension bolt 13.

[0096] In order to generate a slight preload in the axial direction and to prevent free vibrations, it may be advantageous to allow the clamping segments 25 to rest with at least one of the lugs 27, 29 on the first conical section 103 or the third conical section 109 and to achieve a slight tension relative to the preloaded intermediate disk 47.

[0097] If the collet consists of several separate clamping segments 25, it is advisable to manufacture them in such a way that the distance between the individual clamping segments 25, in the position in which they form the smallest diameter, is almost zero. When they move apart, the clamping segments 25 are distributed almost evenly around the circumference by the tension spring 39. This ensures that no or only very small imbalances arise when clamping the clamping system; an additional separation unit, which distributes the clamping segments 25 evenly around the circumference, is not required. If this is nevertheless required (e.g. for machine tool spindles driven at maximum speed), the separation can be created, for example, as a component of the intermediate disk 47 using additional webs or grooves with the corresponding counter-guides on or between the clamping segments.

[0098] In the special training of the Figures 1 to 5The compression spring 45 is accommodated in a compression spring sleeve 49. The compression spring sleeve 49 is accommodated in a shoulder 51 of a stepped bore 53 in the spindle 37 or the conversion part.

[0099] The shoulder 51 forms the longitudinal stop of the threaded ring 33 via the compression spring sleeve 49. At the same time, the compression spring sleeve 49 is held in place.

[0100] In the Figure 6 In the illustrated embodiment, the longitudinal stop is implemented via a flange on the threaded ring 33. The flange can be polygonal. The goal is to ensure that as much diameter as possible is available for the cylinder 21 during hydraulic control.

[0101] Then the actuating forces provided by piston 15 are at their maximum.

[0102] The cylinder 21 is located behind the compression spring sleeve 49. The compression spring sleeve 49 also serves as the front end stop 23 for the piston 15. The draw bolt 13 can also be moved axially in other ways to tighten or loosen the clamping system (e.g., via eccentrics, wedges, etc.).

[0103] In connection with the cylinder structure, the necessary seals are shown in the piston 15 and also in the compression spring sleeve 49, for sealing the piston rod (= rear end of the tension bolt).

[0104] In this exemplary embodiment, the piston 15 is connected to the tension bolt 13 as a single piece. Depending on the design, however, a multi-part design may also be appropriate. In this case, the only important thing is that the piston 15 and the tension bolt 13 are connected to each other in the axial direction.

[0105] From the Figures 1 to 7It can also be seen that the tension bolt 13 is drilled through in the axial direction. The axial bore 55 (see Figure 7 ) in the draw bolt 13 serves to convey a fluid (cooling lubricant (KSS)) or a fluid-air mixture (minimal quantity lubrication). The fluid is guided via a connection point from the accessories (housing, spindle 37, etc.) through the actuating unit (cylinder 21 and piston 15) into the draw bolt 13.

[0106] The stop plate 11 at the front end VE of the tension bolt 13 has one or more through holes. This is where the fluid is transferred to the adjacent components (in this example, adapter 1) that are to be supplied with fluid.

[0107] The design of this transfer can be sealed, channeled or, as shown here, without sealing or channeling.

[0108] Based on the Figures 2 to 5The clamping of the self-locking clamping system according to the invention will now be explained.

[0109] The Figure 2 shows the clamping system in a position in which the tension bolt 13 is compared to the position in Figure 1 shown open position has been moved slightly to the right. This can be seen, for example, in the gap between the end stop 23 and the piston 15. The draw bolt 13 has traveled the same distance. The clamping segments 25 come into contact with their front lugs 27 on the first conical section 103 of the draw bolt 13. This means that the clamping segments 25 are moved radially outwards with their front ends. The clamping segments 25 still rest with their rear lugs 29 on the third cylindrical section 111. The axial movement of the draw bolt 13 therefore causes a first tilting movement of the clamping segments 25. The pivot point of the tilting movement is located on the rear lugs 29. This increases the enveloping circle diameter of the front clamping claws 31.

[0110] The first conical section 103 has an angle of inclination of 30° to 60° and preferably 45°. The clamping segments 25 are designed in the region of the front nose 27 at the contact point with the first conical section 103 such that they have at least a two-point support over a wide area and cannot tilt. The shape of the first contact surface 121 (see Figure 8 ) a cone or a slightly spherical cone contour to prevent pure edge supports.

[0111] The front clamping claws 31 of the clamping segments 25 do not yet have contact with the clamping groove 7 in the hollow shaft 5.

[0112] The hollow shaft 5 is held in contact with the stop plate 11 of the draw bolt 13 by the machine operator, but preferably by a handling device (not shown), such as a handling robot. This means that the adapter 1, and with it the hollow shaft 5, together with the draw bolt 13, also retracts into the centering seat until the hollow shaft 5 comes into contact with the conical section of the centering seat 3. After that, it can initially no longer move in the axial direction. This first axial retraction movement reduces the distance between the flat surface 9 of the adapter 1 and the contact surface of the centering seat 3 to a few 1 / 10 of a mm.

[0113] Alternatively, the design also allows the adapter 1 to be mounted in the Figure 1remains in the starting position shown. Even then, sufficient space is available between the front clamping claws 31 and the clamping groove 7 of the hollow shaft 5 for the first travel section described here. This allows the front clamping claws 31 of the clamping segments 25 to engage the clamping groove 7 unhindered.

[0114] During this first partial movement, the intermediate disc 47 is pressed against the end face of the threaded ring 33 by the compression spring 45, thus remaining axially stationary. If no intermediate disc 47 is present, the front end of the compression spring remains in contact with the threaded ring 33.

[0115] In the Figure 3 The clamping system is shown in a position in which the tension bolt 13 is opposite the Figure 2 shown position 2 has moved slightly further to the right.

[0116] In this position, the front lugs 27 have moved further outward over the first conical section 103 until they reach the first cylindrical section 101 of the draw bolt 13. At the same time, the front clamping claws 31 of the clamping segments 25 have moved outward into the clamping groove 7; this creates a positive connection between the front clamping claws 31 and the clamping groove 7, which can transmit forces in the axial direction.

[0117] In parallel, in this phase of the clamping process, the rear lugs 29 of the clamping segments 25 also move outwards over the third cone section 109. This causes a first "large" radial stroke of the rear end of the clamping jaws 25.

[0118] The third conical section 109 preferably has an inclination angle of 45°, which can be in a range between 30° and 60°. Preferably, the inclination angles of the first conical section 103 and the third conical section 109 are the same. An inclination angle of 45° has also proven effective for the first conical section 103.

[0119] The rear clamping claw 41, or the fifth contact surface 133 of the clamping segments 25, is always in contact with the cone 43 of the threaded ring 33. The cone 43 of the threaded ring 33 has its largest diameter toward the rear end. The cone sections 103, 107, and 109 have their largest diameters toward the front end. In other words: The cone 43 of the threaded ring 33 and the cone sections 103, 107, and 109 are oriented in opposite directions.

[0120] Therefore, the radial movement of the rear lugs 29 on the third conical section 109 causes a large first clamping stroke of the clamping segments 25, and thus also of the adapter 1, in the axial direction. This is achieved through the interaction of the inner cone 43 of the threaded ring 33 with the fifth contact surface 133 of the clamping segments 25, as well as the rear lugs 29 with the third conical section 109.

[0121] The angle of inclination of the cone 43 in the threaded ring 33 to the central axis is preferably 30° to 35°. Angles of inclination from 20° to 60° are possible. By varying the angle of inclination, the force-to-motion conversion can be optimized.

[0122] At inclination angles of 30° for the cone 43, the conversion of the diameter change in the area of ​​the third cone section 109 and (at a later stage of the clamping process) the second cone section 107 of the draw bolt 13 into an axial displacement of the clamping segments 25 is amplified by a factor of approximately 1.7. A smaller inclination angle increases this factor; however, at the expense of a decreasing clamping force and an increased surface pressure between the clamping segment 25 and the draw bolt 13. Increasing the inclination leads to a reduction of the factor.

[0123] The distance between the front and rear lugs 27, 29 is coordinated such that, at the end of the path of the rear lug 29 over the third conical section 109, the front lug 27 is located on the first cylindrical section 101 of the tension bolt 13. As a result, the front clamping claws 31 of the clamping segments 25 are radially locked in the circumferential clamping groove 7.

[0124] If the adapter 1 has been held in its axial starting position by the operator or, as a rule, by a handling system (e.g., a robot), it is now pulled into the centering holder 3. At this stage, the handling system is no longer required to hold the adapter.

[0125] Since the clamping segments 25 move backwards in the axial direction due to the retraction movement of the tension bolt 13 and the resulting clamping stroke of the adapter 1, the stop disc 47 is pressed backwards against the force of the pre-tensioned compression spring 45: This means that the stop disc no longer presses against the threaded ring 33, as is the case in the Figure 3 is clearly visible.

[0126] In the Figure 4 In the next step, the third section of the path shown, the (axial) clamping force required for clamping between the hollow shaft 5 and the centering mount 3 is generated. In addition, a self-locking of the clamping system is created.

[0127] During the further axial movement of the draw bolt 13 backward, the front nose 27 moves on the first cylindrical portion 101 of the draw bolt 13. The second and third conical portions 107, 109 of the draw bolt 13 are pulled further into the clamping segments 25.

[0128] Depending on the design of the clamping groove 7, the first cylindrical region 101 can also be designed as a cone with a positive inclination angle α of less than or equal to 4° in order to further improve the relationship between the travel of the draw bolt 13 and the axial clamping travel of the clamping segments 25. However, it is also possible to design the first cylindrical section 101 as a cone with a negative inclination angle α of less than or equal to 2° in order to enhance the self-locking effect later in the clamping process.

[0129] In the illustrated embodiment, with a cylindrical first cylinder section between the clamping claws 31 and the clamping groove 7, an axial movement initially occurs in the area of ​​the front clamping claws 31 until the clamping position is reached, and then no further axial displacement occurs. The front area of ​​the clamping segments 25 (front nose 27, front clamping claw 31) can now be considered a joint.

[0130] As the tension bolt 13 progresses, the rear lugs 29 of the clamping segments 25 are no longer pushed outwards by the third conical section 109, but by the second conical section 107.

[0131] The second cone section 107 has a much smaller inclination angle than the third cone section 109. Ideally, the second cone section 107 has an inclination angle of less than arctan (µ). "µ" is the friction coefficient of the material pairing of clamping segments 25 and draw bolt 13. In many cases (and under normal friction conditions), an inclination angle of 3° to 4° is well suited. This range can or must be functionally adapted through the use of (DLC) coatings or targeted lubrication.

[0132] Due to the inclination on the second cone section, the rear lugs 29 of the clamping segments 25 are moved radially further outwards.

[0133] The wedge effect between the rear clamping claw 41, or the fifth contact surface 133, and the cone 43 of the threaded ring 33 first leads to an axial movement to the clamping position and then to an axially acting clamping force in the clamping segments 25, which is absorbed by the front clamping claws 31 and the clamping groove 7 and introduced into the hollow shaft 5 or the adapter 1. This high clamping force results in the desired axial clamping between the hollow shaft 7 and the centering mount 3.

[0134] In the Figure 5 the clamping system according to the invention is shown in the clamping position with self-locking.

[0135] The actuating unit (here the cylinder assembly with piston 15 and cylinder 21) has built up the necessary actuating force and can now be released. In the case of the cylinder assembly, the fluid pressure can be reduced or depressurized.

[0136] The clamping segments 25 are positively connected to the adapter 1 or its hollow shaft 5 via the front clamping claws 31 in the clamping groove 7.

[0137] At the same time, the front lugs 27 rest against the first cylindrical section 101 of the tension bolt 13. The front area of ​​the clamping segments 25 is thus supported in the radial direction.

[0138] The rear clamping jaws 41 of the clamping segments 25 rest against the inner cone 43 of the threaded ring 33. At the same time, the rear lugs 29 of the collet segments 25 rest against the second cone section 107 of the draw bolt 13.

[0139] This creates, as already mentioned in connection with the Figure 4explained, a large axial clamping force in the clamping segments 25. Thus, the clamping segments 25 are subjected to tensile stress; ie the rear area of ​​the clamping segments 25 pulls on the front area of ​​the clamping segments 25 and, via the positive locking in the clamping groove 7, thus also on the adapter 1. This results in the desired axial clamping with high clamping force between the hollow shaft 5 and the centering holder 3.

[0140] Due to the conical and even non-circular design (ISO 26623, Capto) of the interface between the adapter and the centering mount in this example, the components are subjected to axial, radial, and rotational tension. In systems with flat surfaces (e.g., ISO 26623 and ISO 12164), this also results in preloading of the components.

[0141] In addition, the angle of inclination of the cone 43 also causes large radial forces on the rear clamping claws 41, which transfer them via the rear lugs 29 to the second cone section 107 of the tension bolt 13.

[0142] Because the angle of inclination of the second conical section 107 is chosen to be very small according to the invention, the radial forces transmitted from the rear lugs 29 to the second conical section 107 of the draw bolt 13 cause the draw bolt 13 to be locked in this position. Without an external force, the draw bolt 13 cannot change its position relative to the clamping segments 25 and the adapter 1. This means that the clamping system according to the invention is self-locking in the clamped position.

[0143] This means that the cylinder assembly can be depressurized after the clamping process has been completed; likewise, no spring is required to continuously exert an actuating force on the tension bolt 13 in the direction of the clamping position.

[0144] This is very advantageous because it is not necessary to supply the cylinder assembly with pressurized hydraulic fluid while the spindle 37 is driven and rotating.

[0145] The supply of the cylinder assembly with pressurized hydraulic fluid while the spindle 37 rotates is technically very demanding and requires a lot of installation space.

[0146] Due to the self-locking design in the area of ​​the second cone section, the initiated clamping force is maintained even if the actuating force of the cylinder assembly drops to zero.

[0147] Due to the force amplification of the clamping system according to the invention, the clamping force is 3 to 4 times greater than the actuating force in the pulling direction applied by the cylinder structure.

[0148] In the Figure 6A further embodiment is shown, which functionally corresponds to the first embodiment. One difference is that the centering mount 3 is not designed as a separate component, but is integrated into the spindle housing 37.

[0149] In this embodiment, the entire clamping system is designed so compactly that it can be mounted through the inner diameter of the centering mount 3, i.e., from the front. This makes it possible to construct the centering mount with the surrounding parts of the tool holder as a single piece, eliminating the need for a two-part design.

[0150] In the Figures 9 and 10 A "miscible clamping" of an adapter 1 is shown. These figures illustrate the advantageous property of the clamping system according to the invention, which deflects backward in such a case and thus prevents damage to the clamping system.

[0151] In the Figure 9the adapter 1 has not been pushed far enough into the centering recess 3, so that the front clamping claws 31 cannot engage in the clamping groove of the hollow shaft 5; their movement radially outwards is hindered by the hollow shaft 5.

[0152] As a result, the front lugs 27 do not reach the first cylindrical section 101 of the draw bolt 13. They remain on the first conical section 103 and follow the axial movement of the draw bolt 13. As a result, the clamping segments 25 press so hard against the intermediate disk 47 that it compresses the compression spring 45. As a result, the clamping segments 25 can deflect backward in the event of incorrect clamping and are not damaged.

[0153] In the Figure 10 For the sake of clarity, no reference symbols are shown. Figure 10 the tension bolt 13 is compared to the Figure 9further backward and has taken the clamping segments 25 with it against the force of the compression spring 45 until the front clamping claws 31 at the end of the hollow shaft 5 or the insertion bevel on the hollow shaft 5 move radially outwards again and thus the clamping segments 25 can slide from the first conical section 103 onto the first cylindrical section 101. As soon as this has happened, the clamping segments 25 are independent of the movement of the draw bolt 13 and can slide freely on the cylindrical section 101. By applying pressure to the compression spring 45 (with or without the intermediate disk 47), the clamping segments 25 are pressed towards the adapter 1 and push the adapter 1 out of the centering holder 3.

[0154] This is achieved via the spring force of compression spring 45. Other systems do not have this integrated emergency function. This emergency function is a great advantage, since with other systems the segments cannot deflect sufficiently and are destroyed or severely damaged by the forces present within the system.

[0155] The integrated emergency function can effectively prevent dangers and damage, among other things, in the error example explained below: Assumption: The adapter 1 is pulled into the centering recess 3 even though the clamping segments 25 are not in the correct position, i.e., in the clamping groove 7. This would result in the system appearing to be correctly clamped even though there is no clamping, and the adapter could fall out due to machining forces. The inventive design also prevents this scenario!

[0156] The ejection also prevents the adapter 1 from remaining unclamped in the centering holder 3 and the flat surfaces of 1 and 3 from touching each other.

[0157] This emergency ejection is particularly important because, during automatic operation, it provides direct feedback as to whether the clamping has been correctly performed. This is often achieved by a so-called flat contact check, which checks whether the flat surface 9 of the adapter 1 and the flat surface of the centering fixture 3 are touching.

[0158] In the Figure 11 Another embodiment is shown in section and without adapter 1. The lower half shows the released state and the upper half the closed state. This embodiment largely corresponds in its design and functionality to the first example of the Figures 1 to 5, so that in this regard, reference is made to the description of the first embodiment. Only the reference numerals necessary to explain the additional details and functions are shown.

[0159] The change essentially concerns the type of preload of the clamping segments 25 in the released state. This ensures (as in the first embodiment) that the clamping segments 25 rest with their inner sides on the outer diameter of the tension bolt 13. However, here the clamping segments 25 are loaded by the compressive force of the spring 45 in such a way that the described contact occurs.

[0160] The compression spring 45 in the rear area is supported on the one hand on one end face of the compression spring sleeve 49 and presses in the state shown in the figure against the intermediate disk 47. The intermediate disk 47 in turn does not rest on the threaded ring 33 in the opened state in this embodiment, but is guided in the compression spring sleeve 49 and always presses on the clamping segments 25. The inner diameter of the intermediate disk 47 is larger in this embodiment than in the Figures 1 to 6 illustrated first embodiment. This allows the stop disc 11 to be connected in one piece to the tension bolt 13 because it now fits through the bore of the intermediate disc 47.

[0161] In detail Y, the rear end of a clamping segment 25 is shown enlarged. As can be seen from this illustration, the clamping segment 25 has a projection 30 extending in the axial direction in the region of the rear nose 29. This projection 30 has no contact with the compression spring 45 and the intermediate disk 47 in the installed state shown. It serves to shorten the overall length because the intermediate disk 47 is arranged above the projection 30 and thus the intermediate disk 47 simultaneously serves as an assembly aid for the clamping segments 25, since these are pre-centered via the inner diameter during assembly.

[0162] As can be seen from detail Z, the intermediate disk 47 is frustoconical on its side facing the clamping segment (see angle β in detail Z). The resulting frustoconical surface is designated 142. This inclined position causes the contact surface between the clamping segment 25 and the intermediate disk 47 to be displaced to the outer diameter of the intermediate disk 47 and to the radially outermost point of the rear clamping claw 41 (see detail Z).

[0163] This results in a maximum lever arm from the contact surface to the pivot point at the contact point of the rear nose 29 to the draw bolt 13. The clamping segments 25 are simultaneously pressed against the cone 43. Due to the resulting total torque around the contact points, the clamping segments 25 are always pivoted in such a way that the front nose 27 is also pressed against the draw bolt 13. This applies not only to the Figure 11shown end positions of the tension bolt 13, but also for all intermediate positions not shown.

[0164] The angle β of the frustoconical surface 142 is selected to be slightly larger than the pivot angle of the clamping segment 25 between the clamped state and the released state, so that the clamping segments 25 rest on the radially outermost point of the rear clamping claw 41 in every position.

[0165] Alternatively or additionally, it is also possible to slightly bevel the rear end of the clamping segment 25 in the area of ​​the rear clamping claw 41 (see angle β in detail Y). The bevel 141 has the same effect as the frustoconical configuration 142 of the intermediate disk 47 on its side facing the clamping segments 25. This often makes it possible to omit the tension spring 39 of the first embodiment. Because the bevel 141 of the clamping claw 41 and the frustoconical configuration 142 of the intermediate disk 47 have the same function, the angle β was used in the description of both examples.

[0166] In the tension bolt 13, a shoulder 48 / a diameter jump is formed, which serves as a (rear) stop for the clamping segments 25. As can be seen in the Figure 11As can be clearly seen, the shoulder 48 acts with the rear lug 29. The shoulder 48 ensures that the clamping segments 25 cannot be displaced relative to one another in the axial direction when opened. For example, if an adapter 1 is accidentally inserted "obliquely" into the centering recess 3 and thereby comes into contact with individual clamping segment(s) 25, these cannot be accidentally pushed backwards but remain in their intended location. To prevent the system from becoming distorted, the shoulder 48 is shifted backwards by a few tenths of a millimeter and normally has no contact with the clamping segments 25.

[0167] In the Figure 12The front end of another embodiment of a clamping segment 25 is shown. This is a version of the clamping segment 25 for an adapter 1, which has a clamping groove 7 with a circular cross-section. Such clamping grooves are present, for example, in clamping systems according to ISO 26623 (Coromant Capto).

[0168] The front claw 31 comprises a bevel 31.1, which is adapted to an insertion bevel of the adapter 1 (not shown). In the event of incorrect clamping, the clamping segments 25, after being carried backwards by the draw bolt 13, already rest with this bevel 31.1 on the insertion bevel of the adapter 1 and can deflect radially outwards until they can slide from the first conical section (103) onto the first cylindrical section (101). As a result, the entire clamping claw 31 does not have to be pulled axially out of the adapter 1 for this function. This has the advantage that the spring travel of the spring 45 is smaller than in the Figure 10 illustrated embodiment can be selected. Nevertheless, the spring 45 can eject the adapter 1. This reduces the required spring length and thus also the overall length.

[0169] Where the front claw 31 has its largest diameter (see 31.2), it is cylindrical. This short cylindrical section 31.2 is followed by a radius 31.3.

[0170] The cylindrical section 31.2 prevents unwanted radial jamming of the clamping segments 25 between the groove base of the clamping groove 7 and the surface 101 of the tension bolt 13. Typically, the outer diameter of the radius 31.3 is turned by 1 / 10 mm to produce the cylindrical section 31.2.

[0171] The radius 31.3 is selected so that it always corresponds to the smallest possible radius of the clamping groove 7 of the adapter 1. This brings the contact point of the clamping segment(s) 25 on the clamping groove 7 as close as possible to the smallest diameter of the clamping groove 7. This reduces the leverage acting on the clamping segments 25 and improves the force flow.

[0172] Area 31.4 is designed to optimally utilize the free space in the inner contour of adapter 1 and slowly redirect the force flow over the bevel at an angle γ, which is preferably between 10 and 20°, and the adjacent radii R1 and R2. This reduces local stress peaks, increases the fatigue strength of clamping segments 25, and significantly reduces the risk of spontaneous component failure due to axial clamping forces.

[0173] The bevels 125.1 and 125.2 on the inside of the clamping segment 25 are designed in such a way that the cross sections in the clamping segments 25 are maximum, without them being in the open position (see Figure 11 below the center line) against the tension bolt 13 or prevent the clamping segments 25 from folding into the open position. This also reduces the stresses in the clamping segments 25 and increases the fatigue strength of the clamping segments 25.

Claims

1. A clamping device for a hollow shaft (5), in particular a hollow shaft taper with a circular or polygonal outer contour, comprising one or more clamping segments (25) and a tension bolt (13) cooperating with the clamping segments (25), wherein each clamping segment (25) has a front clamping claw (31) at a front end (VE) on its outer side and a front lug (27) on its inner side cooperating with the tension bolt (13), wherein each clamping segment (25) has a rear clamping claw (41) at a rear end (HE) on its outer side and a rear lug (29) on its inner side cooperating with the tension bolt (13), wherein, in the clamping position, the front clamping claw (31) of each clamping segment (25) engages in a clamping groove (7) of the hollow shaft (5) and the rear clamping claw (41) is pressed against a cone (43), wherein, in the open position, the front clamping claw(s) (31) do / does not engage in the clamping groove (7) of the hollow shaft (5), wherein, by means of axial displacement, the tension bolt (13) moves the clamping segment or segments (25) from the clamping position into the open position and from the open position to the clamping position, wherein the clamping segment or segments (25) perform(s) a first pivoting movement during the transition from the open position to the clamping position, such that the front clamping claws (31) of the clamping segments (25) engage in a positively-locking manner in the clamping groove (7) and form a joint for a subsequent second pivoting movement of the clamping segment or segments (25), wherein, during the second pivoting movement, the rear lugs (29) of the clamping segment or segments (25) slide on a third cone section (109) of the tension bolt (13) and press the rear clamping claws (41) of the clamping segments (25) against the cone (43) of the adjacent part / spindle (37) and axially clamp the clamping segment or segments (25), characterized in that, during a further axial movement of the tension bolt (13) following the second pivoting movement, the rear lugs (29) of the clamping segment or segments (25) slide on a second cone section (107) of the tension bolt (13), such that a self-locking effect is produced between the clamping segments (25) and the tension bolt (13).

2. The clamping device according to claim 1, characterized in that a first cylindrical section (101), a first cone section (103), a second cylindrical section (105), the second cone section (107), the third cone section (109), and a third cylindrical section (111) are successively formed on the tension bolt (13), starting at its front end (VE).

3. The clamping device according to one of the preceding claims, characterized in that an angle of inclination of the second cone section (107) is less than 5° or less than the arc tangent (arctan) of the coefficient of friction (µ) of the pairing of the contact surfaces of the clamping segment (25) and the tension bolt (13).

4. The clamping device according to one of the preceding claims, characterized in that the angle of inclination of the second cone section (107) is in a range between 3° and 5°.

5. The clamping device according to one of the preceding claims, characterized in that an angle of inclination of the first cone section (103) and / or an angle of inclination of the third cone section (109) is in a range between 30° and 60°.

6. The clamping device according to claim 5, characterized in that the angle of inclination of the first cone section (103) and / or the angle of inclination of the third cone section (109) is 45°.

7. The clamping device according to one of the preceding claims, characterized in that the second cone section (107) and the third cone section (109) merge into one another without a diameter change and without an intermediate cylindrical section.

8. The clamping device according to one of the preceding claims, characterized in that the front lugs (27) of the clamping segment or segments (25), starting at the front end (VE), have a first contact surface (121) matched to the angle of inclination of the first cone section (103) and a second contact surface (123) matched to the first cylindrical section (101).

9. The clamping device according to one of the preceding claims, characterized in that the rear lugs (29) of the clamping segment or segments (25) have a third contact surface (129) matched to the angle of inclination of the third cone section (109).

10. The clamping device according to one of the preceding claims, characterized in that the rear lugs (29) of the clamping segment or segments (25) have a fourth contact surface (131) matched to the angle of inclination of the second cone section (107).

11. The clamping device according to one of the preceding claims, characterized in that the rear clamping claws (41) have a fifth contact surface (133), and in that the fifth contact surface (133) is matched to the angle of inclination of the cone (43).

12. The clamping device according to one of the preceding claims, characterized in that the angle of inclination of the cone (43) and / or of the fifth contact surface (133) of the clamping segments (25) is in a range of 20° to 45°, and preferably at 30° or at 35°.

13. The clamping device according to one of the preceding claims, characterized in that the clamping segment or segments (25) are supported with their rear end against a spring-loaded intermediate disk (47) or directly against a compression spring (45), such that the clamping segments (25) can deflect in the axial direction if they cannot slide from the first cone section (103) onto the first cylindrical section (101).

14. The clamping device according to one of the preceding claims, characterized in that a stop disk (11) is provided at the front end (VE) of the tension bolt (13).

15. The clamping device according to one of the preceding claims 2 to 14, characterized in that the first cylindrical section (101) has a negative angle of inclination α of small magnitude.

16. The clamping device according to one of the preceding claims 13 to 15, characterized in that the intermediate disk (47) is formed to be frustoconical (142) on its side facing the clamping segment (25).

17. The clamping device according to one of claims 13 to 16, characterized in that clamping segments 25 have a chamfer (141) at their rear ends, at least in some regions.

18. The clamping device according to one of the preceding claims, characterized in that an offset (48) is formed on the tension bolt (13), which offset serves as a stop for the clamping segments (25).

19. The clamping device according to one of the preceding claims, characterized in that the cone (43) is integrated into the adjacent part or the spindle (37) or is designed as a separate component.

20. The clamping device according to one of the preceding claims, characterized in that it is part of a driven or stationary tool holder.

21. The clamping device according to one of the preceding claims, characterized in that it is used on a turret of a lathe.