Clamping system with polygonal receptacle for hollow shafts

Abstract

A spindle for polygonal hollow shaft tapers is proposed, which allows optimal use of the spindle interior for accommodating a clamping system and optional cylinder structures.

Description

[Technical field]

[0001] Clamping systems with hollow shafts and complementary shaped centering mounts, for example according to ISO 12164 or ISO 26623, have proven themselves on the market for many years. [Background technology]

[0002] Among others, they are used in driven or stationary tool holders. The centering mount and the clamping system are then integrated in the spindle of the driven tool holder or in the housing of the tool holder. In the following, the term "spindle" is used for the rotating and non-rotating receptacles of the clamping system and the centering receptacle. The hollow shaft is part of an adapter that carries, for example, a drill, a milling cutter, a turning tool or another tool.

[0003] To transmit the required torque between the spindle and the adapter and to achieve a defined position of the tool with repeatable accuracy, centering receptacles have been used for decades in the form of truncated cones with a polygonal cross section (hereinafter also called inner polygon), the hollow shaft of the adapter having a complementary outer contour (hereinafter also called outer polygon).

[0004] Known clamping systems for clamping such polygonal hollow shafts comprise a collet consisting of a number of clamping segments. The clamping segments are arranged around a tension bolt. Axial movement of the tension bolt relative to the clamping segments presses them radially outwards into a groove in the hollow shaft. This initially results in a positive locking fit of the front ends of the clamping segments with the hollow shaft. Further movement of the tension bolt generates an axial clamping force which acts on the hollow shaft of the adapter, such that the adapter is pulled into the centering mount. An example of such a clamping system is known from EP 2 164 662.

[0005] Similar clamping systems are known from EP 1 924 379 B1 and DE 196 18 610 A1.

[0006] The force required for clamping and releasing is provided, for example, by a cylinder structure in an automatic system. This cylinder structure, which is fluidly (for example pneumatically or hydraulically) actuated, must also be integrated into the spindle. It is clear that the installation space available for the clamping system and the cylinder structure, for example in a driven spindle, is very limited, both radially and axially. Even in the case of standing tool holders, the available space for the clamping system is becoming smaller and smaller due to the ever narrower installation space. The installation space must therefore be optimally utilized here too.

[0007] The attachment of the clamping system and optional cylinder structure to the spindle must in most cases be achieved by a centering receptacle (internal polygon) in order to achieve a very compact radial design. Summary of the Invention

[0008] The present invention aims to provide a clamping system which allows to make the best possible use of the installation space available on a rotatably mounted or fixed spindle. Furthermore, the installation of the clamping system and the cylinder structure should be easy and time-saving. In case of overhaul or repair, the clamping system and the cylinder structure should be easily removable.

[0009] According to the invention, this object is achieved by a rotatably mounted or fixed spindle, said spindle comprising a centering receptacle, an annular groove and a receiving hole for actuating a clamping system, said centering receptacle designed as a polygonal inner cone and accommodating an adapter having a polygonal outer contour and a hollow shaft, said centering system comprising a collar, said clamping system comprising a collar, said collar having a polygonal outer contour or said outer contour being formed by a plurality of lugs distributed around the circumference, said collar fitting through said centering receptacle in at least one rotational position, and by rotating said collar relative to the spindle into at least one locking position a secure locking fit is established in at least one axial direction between said collar and said annular groove.

[0010] As a result of this type of locking mechanism, by way of bayonet closure in the annular groove of the housing or collar, the diameter of the receiving hole, and therefore of the installable housing or clamping system, can be maximized, which can be of the same size or only slightly smaller than the inscribed circle of the smallest inner polygon of the centering receptacle.

[0011] For the actual axial fixation of the collar on the spindle, the space directly behind the centering receptacle is formed as an annular groove, where the centering receptacle has its smallest diameter at the transition between the centering receptacle and the receiving bore. The installation space requirements of the locking mechanism according to the invention are therefore minimal.

[0012] It is particularly advantageous to be able to maximize the outer diameter of the clamping system and possibly the cylinder structure located behind the clamping system, which gives design freedom to the designer of the clamping system and the cylinder structure, and also increases the actuation force that the cylinder structure can provide to clamp or release the clamping system, since the cylinder structure can be installed with a larger piston diameter.

[0013] A further advantage is the reduced number of components. The collar and the annular groove can be well controlled in production. Furthermore, due to this low number of parts and its construction, the axial transmission of forces by the clamping system to the spindle is extremely stiff.

[0014] Since the axial fixing of the clamping system can be performed in one place, i.e. in the collar or the annular groove, in both directions, very narrow tolerances can be selected here, which allows very precise axial positioning of the clamping system and the cylinder structure to be achieved without increased manufacturing efforts.

[0015] In an advantageous development of the invention, the diameter of the annular groove is equal to or somewhat larger than the circumference of the outer contour of the collar.

[0016] To secure the positive locking fit according to the invention against unintentional release, a recess is formed in the collar. A fixing pin, which fits into the recess, is inserted into a hole (threaded or non-threaded) in the spindle. In this way, a positive locking fit and a releasable anti-rotation lock of the collar and thus of the clamping system to the spindle is created.

[0017] The fixing pin can be designed, for example, as a threaded pin. Other one or two part designs can always be realised, as long as the basic functions of positive locking engagement and releasable anti-rotation lock are maintained.

[0018] In a preferred development, the recesses are arranged at the high points of the polygonal collar or at the lugs of the collar.

[0019] Furthermore, it is advantageous if the width of the annular groove is equal to or slightly greater than the width of the collar. The difference between the width of the annular groove and the width of the collar results in an axial play in which the clamping system is placed on the spindle. Very low axial play of less than 0.1 mm can be easily realized. An axial play of 0.05 mm can also be realized. If the width of the annular groove is 0.02 mm to 0.05 mm wider than the collar, this is considered "equivalent". The play prevents clamping of the collar on the annular groove and facilitates assembly.

[0020] The receiving bore of the spindle can be designed as a polygon, at least in cross section. Then, more installation space inside the spindle becomes available for the clamping system and the optional cylinder structure. The piston or pistons of the cylinder structure can also be designed as a polygon.

[0021] If the receiving hole of the spindle is designed at least cross-sectionally as a polygon, the collar or the collar and the housing can rotate relative to the rest of the clamping system (4) or the cylinder structure (6). The collar then acts like a locking ring and forms an axial stop in the clamping direction. The piston and the rest of the system then rest on the entire surface of the polygonal contour of the hole and can use the entire cross section of the polygonal receiving hole.

[0022] In another advantageous embodiment of the invention, the optional cylinder structure comprises a piston rod having a central bore for supplying cooling lubricant to a tool clamped in the clamping system, the piston rod passing through the seal support and terminating in a supply space of the spindle.

[0023] The seal support separates the supply space in which the cooling lubricant is arranged from the cylinder structure, so that the fluid working medium (e.g., compressed air or working fluid) of the cylinder structure and the cooling lubricant in the supply space do not come into contact with each other. Even if the cooling lubricant is used in the cylinder structure, it must not be mixed with the cooling lubricant in the supply space because the cooling lubricant used in the cylinder structure has a higher purity requirement.

[0024] A particularly advantageous embodiment of the invention provides that the sealing support comprises a flange and a threaded section with an external thread, between which an annular groove is formed. In the region of the threaded section, a gap is formed between the piston rod and the sealing support, and at least one hole connects the annular groove and the gap to each other. In this way, it is possible to transport the cooling lubricant from the outside, i.e. from the spindle, to the annular groove, through the at least one hole and the gap to the supply space in a very easy and space-saving manner.

[0025] According to the invention, at least one hole is provided in the spindle, opening into the space bounded by the annular groove and the spindle, through which the cooling lubricant is conveyed to the sealing support or to the annular groove.

[0026] To hydraulically separate the feed space from the cylinder structure, at least one seal is arranged on the flange of the seal support, which seals the piston rod against the feed space. In a further advantageous development of the invention, a stationary seal can be arranged on the flange, which seals the flange of the seal support against the spindle.

[0027] Further advantages and advantageous embodiments of the invention can be found in the following drawings, the description and the claims. All features disclosed in the drawings, their description and the claims may be essential to the invention, both individually and in any combination with one another. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a longitudinal section showing a first exemplary embodiment of the present invention. [Diagram 2] FIG. 2 shows a front view of the first exemplary embodiment in different (assembly) positions. [Diagram 3] FIG. 3 illustrates another exemplary embodiment of the present invention. [Figure 4] FIG. 4 is a simplified diagram of a tool holder for a machining center. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] In the context of the present invention, the term "adapter" is used as a general term for all components or assemblies that can be clamped in the polygonal centering receptacle 7 of the spindle 1 with the aid of the clamping system according to the invention. This can be a tool (e.g. drill, milling cutter, turning tool), an adapter (drill chuck, collet holder, cutting chuck for receiving indexable inserts), a device, etc.

[0030] As already mentioned several times, the invention is described with reference to a rotatably mounted spindle 1. However, the first spindle may also be a fixed spindle.

[0031] At its end facing the centering receptacle 7, the adapter 2 has an outer contour of a conical polygon, which is also referred to below as the outer polygon. The centering receptacle 7 is shaped complementarily to the outer polygon of the adapter 2. The shape of the centering receptacle 7 is therefore also referred to as an inner polygon. This polygonal connection has been established on the market for many years and is standardized, for example in ISO 26623.

[0032] The adapter 2 comprises a hollow shaft 102 of a profile which interacts with a clamping system 4 of the spindle 1. These hollow shaft clamping systems have also been known to those skilled in the art for many years, for example from the descriptions given in the documents introduced above.

[0033] Therefore, it is assumed that the polygonal connection of the adapter 2 and centering receptacle 7, the clamping system 4 and the cylinder structure 6 are known and only those aspects relevant to the present invention will be described.

[0034] The spindle 1 may, for example, be part of a driven tool holder. That is, the spindle 1 must be designed relatively compact in order to fit into the limited installation space of the tool holder. The installation space potentially available inside the spindle 1 is therefore radially limited by the outer diameter and length of the spindle 1.

[0035] Nevertheless, the clamping system 4 arranged on the spindle 1 must fix the adapter 2 with its hollow shaft in the centering receptacle 7 in such a way that very good concentricity and axial run-out of the adapter 2 or the tool attached to it is always ensured. Furthermore, the torque required for machining, as well as the resulting radial and axial forces, must be reliably transmitted from the adapter 2 to the spindle 1. High clamping forces are therefore required axially, and the adapter 2 and the spindle 1 are clamped against each other in order to transmit the resulting forces, torsion and bending moments.

[0036] The clamping system 4 is typically clamped and released by a cylinder arrangement 6 which is fluidly (e.g. pneumatically or hydraulically) actuated and which is also integrated in the spindle 1. It is located behind the clamping system 4 in a stepped receiving bore 9 of the spindle 1. Alternatively, any other system for applying high axial forces can be used.

[0037] The cylinder structure 6 and the clamping system 4 are attached from the front, i.e. by means of a centering receptacle 7 (internal polygon) of the spindle 1. As a result, the maximum diameter of the clamping system 4 and the cylinder structure 6 and the maximum diameter of the receiving hole 9 cannot be larger than the smallest inscribed circle of the centering receptacle 7.

[0038] The cylinder structure 6 comprises a piston rod 3 which transitions to or is connected to a tension bolt 5 of the clamping system 4. The cylinder structure 6 must provide a relatively large operating force to the piston rod 3. An effective means for increasing the operating force is to increase the diameter of the piston of the cylinder structure 6. However, the maximum diameter is predetermined by the diameter of the receiving hole 9. Therefore, the diameter of the receiving hole 9 should be as large as possible.

[0039] In Figure 1, the clamping system 4 and the cylinder arrangement 6 are shown in two separate locations. Below the centerline, the clamping system 4 is shown in the released position. Above the centerline, the clamping system 4 is shown in the clamped position.

[0040] 1, it is clear that the tension bolt 5 pivots at least one clamping segment 33. When clamping the clamping system 4, the front ends of the clamping segments 33 are pivoted radially outwardly so as to dip into the grooves of the hollow shaft 102.

[0041] To ensure both manual and automatic clamping processes, the front end of the tension bolt 5 acts as a stop for the adapter 2 .

[0042] The centering receptacle 7 is designed as an internal polygon. It can be an integral part of the spindle 1. However, it can also be a separate part that is inserted into the spindle 1.

[0043] A portion of the receiving bore 9 adjacent the centering receptacle 7 receives the clamping system 4. A further adjacent section of the receiving bore 9 receives the cylinder structure 6.

[0044] Where the receiving hole 9 receives the clamping system 4 and the cylinder structure 6, it is designed as a cylindrical hole with a shoulder 13. In the illustrated exemplary embodiment, the receiving hole 9 is designed as a blind hole on the right side of Fig. 1, although this does not have to be the case.

[0045] It can also be seen in FIG. 1 that the clamping force acting on the adapter 2 is transmitted from the clamping segment 33 via the conical contact surface 34 to the spring housing 19 and from there to the collar 67 .

[0046] The exemplary embodiment of the spindle 1 according to the invention shown in Fig. 1 allows for the mounting of the clamping system 4 and the cylindrical structure 6 by means of a polygonal centering receptacle 7, where the outer diameter of the clamping system 4 and the cylindrical structure 6 is approximately the same size as the smallest inscribed circle of the centering receptacle 7. As a result, the outer diameter of the clamping system 4 and the cylindrical structure 6 can be maximized.

[0047] As already mentioned, the centering receptacle 7 is designed as a polygon (for example according to ISO 26623), which can be seen, for example, by a closer inspection of figure 1, in that the distance between lines 7.1 and 7.2 of the centering receptacle 7 is of a different magnitude than the central line shown in dashed dots.

[0048] A shoulder 60, arranged concentrically to the center line, is indicated at 60 on the end face of the spindle 1. The line 7.1 marked the high point of the inner polygon of the centering receptacle 7. The radial distance between the shoulder 60 and the line 7.1 is therefore smaller than the radial distance between the shoulder 60 and the line 7.2, which marks the low point of the polygon. The points belonging to the lines 7.1 and 7.2 are marked in Fig. 2b.

[0049] Adjacent to the polygonal centering receptacle 7, an annular groove 65 is formed in the spindle 1. This circular annular groove 65 is arranged concentrically about the center line. It has a diameter equal to or greater than the circumference of the smallest inner polygon of the centering receptacle 7.

[0050] In the exemplary embodiment shown, the diameter of the annular groove 65 is approximately as large as the diameter of the "high point" of the inner polygon indicated at 7.1 in FIG. 2b, at the transition between the centering receptacle 7 and the annular groove 65.

[0051] If the polygonal shape of the collar 67 is "cut" at the outer diameter (for example by twisting off the high points), the diameter of the annular groove 65 can be made smaller than the circumference of the polygonal high point 7.1 at the transition between the centering receptacle 7 and the annular groove 65. In any case, the diameter of the annular groove 65 must be somewhat larger than the inner diameter of the smallest polygon, but the axial forces that can be transmitted axially between the collar 67 and the annular groove 65 are then smaller. It is therefore desirable to use the entire polygonal shape and to select the diameter of the annular groove 65 to be large as shown in FIG.

[0052] Due to the polygonal cross section of the centering receptacle 7, the shoulder at the transition between the centering receptacle 7 and the annular groove 65 in the region of the lowest point 7.2 is significantly larger than at the highest point 7.1. Also, a comparison of the distances between the radial lines 7.1 and 7.2 relative to the annular groove 65 shows that the centering receptacle 7 is an internal polygon.

[0053] In this exemplary embodiment, the clamping system 4 comprises a spring housing 19. A collar 67 is formed at the front end of the spring housing 19 (on the left in FIG. 1 ) and in this exemplary embodiment also has a polygonal outer contour (see FIGS. 2 a to c). The outer contour of the collar 67 is dimensioned to be minimally smaller than the smallest inner polygon of the centering receptacle 7. The outer contour of the collar 67 may be, for example, 0.1 mm smaller than the smallest inner polygon of the centering receptacle 7.

[0054] The outer contour of the collar 67 is somewhat smaller than the smallest inner polygon of the centering receptacle 7, so that the spring housing 19 can be inserted with its cylindrical part through the centering receptacle 7 into the part of the receiving hole 9 located behind the annular groove 65, in a rotated position. In this rotated position, the collar 67 fits through the polygonal centering receptacle 7. This situation is shown in FIG. 2a.

[0055] By subsequently rotating the collar 67 relative to the spindle 1, the high point of the collar 67 moves into the annular groove 65. At least one axially acting positive locking fit is thereby formed by the collar 67 between the spring housing 19 and the spindle 1. As a result, the clamping system 4 and the cylinder structure 6 arranged behind the clamping system 4 are axially fixed in the receiving hole 9 in the direction of the centering receptacle 7. In the exemplary embodiment shown in FIG. 1, the clamping system 4 is supported in the other direction by the cylinder structure 6 against the shoulder 13 of the receiving hole 9.

[0056] The insertion of the clamping system 4 and the cylinder arrangement 6 onto the spindle 1 and the subsequent creation of a positive locking fit are shown in three steps in FIG. 2a to FIG. 2c.

[0057] These figures show a plan view of the polygonal centering receptacle 7. The lines belonging to the centering receptacle 7 are designed as dashed-dotted lines. The lines belonging to the collar 67 are solid lines.

[0058] In Figure 2a, the collar 67 is positioned so that its outer contour has a smaller radius at each point than the smallest inner polygon of the centering receptacle 7 at this point. Thus, in the position of the collar 67 shown in Figure 2a, it is possible to displace the collar 67 axially in the direction of the receiving hole 9 by the smallest inner polygon of the centering receptacle 7 until the collar 67 is located in the annular groove 65.

[0059] When the collar 67 is rotated relative to the spindle 1 in this axial position, the high point of the collar 67 fits into the annular groove 65. This results in a positive locking fit between the collar 67 and the spindle 1, acting at least in the axial direction. This situation is shown in FIG. 2b.

[0060] In the illustrated example, the rotation angle is 60° between the rotation positions shown in Figure 2a and Figure 2b, but may vary depending on the shape of the polygon.

[0061] In the exemplary embodiment shown in Fig. 3, the width of the annular groove 65 is slightly larger than the width of the collar 67, allowing the collar 67 to rotate in the annular groove 65. A slight backlash (such as less than 0.1 mm) is tolerated as it does not adversely affect the function. In the exemplary embodiment shown in Fig. 3, the axial fixation of the clamping system 4 and the cylinder structure 6 is performed in both directions via the collar 67 and the annular groove 65, so that very small axial tolerances can be easily realized.

[0062] In the embodiment according to FIG. 1, the width of the annular groove 65 can be designed to be significantly wider than the width of the collar 67. Then only the left shoulder of the annular groove 65 (in the direction of the centering receptacle 7) takes over the axial positioning and force absorbing function. In the opposite direction, the support between the cylinder structure 6 and the spindle 1 can be at another point, for example by the intermediate floor 15 and the shoulder 13 of the receiving hole 9. Here, the axial play depends on the sum of the component tolerances and is somewhat larger than in the exemplary embodiment shown in FIG. 3. Alternatively, the existing play can be adjusted or minimized as desired in FIG. 1, for example by shimming or grinding the components.

[0063] In the exemplary embodiment shown in Figures 1 and 3, the outer contour of the collar 67 and the inner polygon of the centering receptacle 7 are geometrically similar. However, this does not have to be the case. The collar 67 could, for example, consist of three lugs offset by 120°. It is important that the collar 67 fits through the smallest inner polygon of the centering receptacle 7 in the rotated position and then establishes an axially positive locking fit between the collar 67 and the spindle 1 by rotation.

[0064] For removal of the clamping system 4 and the cylinder structure 6, the collar 67 is simply rotated counterclockwise by 60° from the rotated position shown in FIG. 2b (as shown in FIG. 2a). The positive locking engagement is then released and the collar 67 can be removed forward through the centering receptacle 7. The clamping system 4 and the cylinder structure 6 can then be removed via the centering receptacle 7.

[0065] To ensure this positive locking fit, created by rotation and formed in at least one axial direction, a recess 69 is provided at the high point of the collar 67. The recess 69 is located at 16:00 in Fig. 2a and at 18:00 in Fig. 2b. This corresponds to the mentioned 60° rotation angle.

[0066] In the position of the collar 67 shown in Figures 2b and 2c, a locking pin 71 is rotated into the recess 69 of the collar 67 via the spindle 1. This locking pin 71 is shown in Figures 1 and 2c. This prevents unintentional rotation of the collar 67 relative to the spindle 1.

[0067] The fixing pin 71 is accessible from the end face of the spindle 1. A threaded hole (not numbered) in the spindle 1 runs approximately parallel to the centering receptacle 7 and terminates in annular groove 65 (see Figure 1). When the fixing pin 71 is inserted far enough into the (threaded) hole, its front end projects into the annular groove 65 and fits into a recess 69 in the collar 67. As long as the fixing pin 71 fits into the recess, the spring housing 19 is fixed against rotation.

[0068] Screwing or inserting the fixing pin 71 from the end or front side of the spindle 1 has several advantages.

[0069] In a driven tool holder, the cooling lubricant from the centering receptacle 7 cannot pass through the threaded hole to the rolling bearing (not shown) in which the spindle 1 is held. In this case, the rolling bearing would be damaged.

[0070] Furthermore, the locking pin 71 is easily accessible and can be reached without removing the tool holder, simplifying maintenance or repair of the clamping system.

[0071] A particular weight advantage of the type of axial locking mechanism according to the invention is the maximum diameter of the cylindrical part of the receiving hole 9, which has been explained with reference to figures 1 and 2. This can be best explained with reference to figure 1.

[0072] Comparing line 7.2 (to the left of annular groove 65) at the bottom of FIG. 1 with the adjacent cylindrical portion of receiving hole 9, it can be seen that the diameter of the cylindrical portion of receiving hole 9 is approximately the same size as the inscribed circle diameter of the smallest inner polygon of centering receptacle 7.

[0073] In other words, the locking mechanism according to the invention is connected in the axial direction of the collar 67 to the spring housing 19 here and does not require any extra space in the radial direction on the spindle 1. Also, the axial installation space required is very small. The required installation space corresponds approximately to the width of the annular groove 65.

[0074] A direct positive consequence of maximizing the diameter of the cylindrical portion of the receiving bore 9 is that a larger installation space is available for the cylinder structure 6, i.e. the diameter of the pistons 27 and 31 can be increased, so that a larger actuation force can be provided by the cylinder structure 6 under otherwise identical boundary conditions. Furthermore, the radial installation space of the clamping system has also been maximized, and therefore it can be built more "robust".

[0075] A further advantage of the locking mechanism according to the invention via the collar 67 of the spring housing 19 of the spindle 1 is the reduced number of components.

[0076] The cylinder arrangement 6 is briefly described below with reference to figure 1. Starting from the shoulder 13, an intermediate floor 15 and a cylinder sleeve 17 are arranged in the receiving bore 9.

[0077] Besides the cylinder sleeve 17, a spring housing 19 is provided in the receiving bore 9. The spring housing 19 belongs to the clamping system 4. Accordingly, the intermediate floor 15 of the cylinder structure 6 and the cylinder sleeve 17 are axially fixed by the shoulder 13 of the receiving bore 9 and the spring housing 19. The cylinder sleeve 17 also delimits a pressure chamber 37 of the cylinder structure 6.

[0078] The inner diameter of the intermediate floor 15 has an opening 21. The piston rod 3 protrudes through the opening 21. The opening 21 has a seal 23 formed therein which surrounds the piston rod 3.

[0079] In this exemplary embodiment, the piston rod 3 has a shoulder 25. Starting from the shoulder 25, the piston rod 3 is lined up with a piston 27, a piston rod sleeve 29 and a piston 31.

[0080] The piston 31 is screwed into the piston rod 3 at the right end of the latter in FIG. 1. The piston 31 differs from the piston 27 in two main respects: it fixes itself axially in the piston rod 3 and constitutes an axial lock for the piston 27 and the piston rod sleeve 29. Also, the outside diameter of the piston 31 runs directly in part of the receiving bore 9 and there is no cylinder sleeve.

[0081] The intermediate floor 15 divides the space bounded by the cylinder sleeve 17 and the receiving bore 9 into two partial chambers. Pistons 27, 31 are arranged in both partial chambers. The pistons 27 or 31 in turn divide the partial chambers into a first pressure chamber 35 and a second pressure chamber 37. Figure 1 shows the cylinder arrangement 6 and the clamping system 4 in two different positions, so that the pressure chambers 35, 37 have different sizes above and below the centre line.

[0082] In the position of the piston rod 3 shown above the centre line in Figure 1, it is at its rightmost stop, which is reached when the piston 31 comes to rest with its end face against the seal support 59. When the first pressure chamber 35 is then filled with pressurised fluid, the volume of the first pressure chamber 35 increases and the piston 31 or 27, and with it the piston rod 3, moves to the left in Figure 1 until it reaches the position shown below the centre line in Figure 1. In this position, the clamping system 4 is released.

[0083] Due to the movement of the piston rod 3 and the pistons 27, 31 the volume of the second pressure chamber 37 decreases. The intermediate floor 15 limits the path of the piston 31 to the left in Figure 1. In this end position the clamping system is open.

[0084] In the extreme positions (above or below the centre line in FIG. 1) the piston 27 has a minimum distance from the flat surface of the intermediate floor 15 or from the flat surface of the cylinder sleeve 17. This has two effects: on the one hand, a defined piston surface is available also in the end positions and so-called "hydraulic coupling" is avoided; on the other hand, overdetermination of the end positions is avoided.

[0085] Two pistons 27 and 31 are attached to the piston rod 3 and are subjected to hydraulic or pneumatic forces F by pressurized fluids located in two first pressure chambers 35. Hydr is supplied, the forces of the pistons 27 and 31 are added. The two pistons are connected in parallel. As a result, the cylinder arrangement 6 can provide a relatively large actuation force for the diameter of the piston 27 that is possible in terms of the installation space.

[0086] If more installation space is available axially, three or more pistons can of course be arranged one behind the other on the piston rod 3, so that the actuation force available at the tension bolt 5 can be further increased or the fluid pressure required to generate the required clamping force can be reduced.

[0087] Now, when the second pressure chamber 37 is pressurized with pressurized fluid, the piston rod 3, and with it the tensioning bolt 5, moves from its extreme left position (below the centre line) to the right hand side, again subject to the application of force exerted by the piston 27 or 31 on the piston rod 3. The movement of the tensioning bolt 5 from the released position to the clamped position pulls the adapter 2 into the centreing receptacle 7. For ease of understanding, FIG. 1 shows the adapter 2 outside the centreing receptacle 7.

[0088] The pressure chambers 35, 37 are supplied via control lines 39, 41. In Figure 1 a first control line 39 is formed in the lower part of the spindle 1 and supplies pressurised fluid to the first pressure chamber 35 of the piston 27, if necessary via a radially extending hole or recess (not numbered) in the spindle 1 and at least one subsequent radial hole (not numbered) in the cylinder sleeve 17.

[0089] Through this first pressure chamber 35 of the piston 27, the fluid is led to the first pressure chamber 35 of the piston 31 via a channel between the piston rod 3 and the piston rod sleeve 29 or the piston 31. As a result, the radial installation space of the right-hand spindle 1 can be reduced and space can be provided for a seal support 59 that can transfer coolant to the spindle 1 if coolant is required in the spindle 1.

[0090] The second pressure chamber 37 is supplied with pressurized fluid as required via a second control line 41 (top of FIG. 1) supplying a radially extending hole or recess (not numbered) in the spindle 1. In the case of the piston 27, the supply line is then led to the pressure chamber 37 via at least one radially inner diameter (not numbered) of the cylinder sleeve 17. In the case of the piston 31, the fluid is led to the fluid space 37 via a groove in the intermediate floor 15.

[0091] Depending on which of the two control lines 39, 41 is supplied with pressurized fluid, the first pressure chamber 35 or the second pressure chamber 37 is pressurized, and accordingly a force toward the left or right in FIG. 1 acts on the pistons 27, 31, which force is transmitted to the tension bolt 5 via the piston rod 3.

[0092] Releasable check valves (not shown) can be present in the control lines 39, 41. As with the control lines 39 and 41, the check valves are preferably arranged opposite each other, i.e. offset by 180° in the circumferential direction. In this way, despite the control lines 39 and 41 and the check valves, the spindle 1 is very well balanced. Even at high rotational speeds, only relatively small dynamic imbalances occur, which can also be relatively easily compensated for by holes in the circumference of the spindle 1.

[0093] The optionally present releasable check valves ensure that the fluid located in the first pressure chamber 35 and the second pressure chamber 37 is retained there and together with the cylinder structure 6 against the centrifugal forces occurring when the spindle 1 rotates. Moreover, the piston rod 3 and the tension bolt 5 connected thereto are thereby held in their position. This means an additional fixation for the clamping system 4 against unintentional release.

[0094] In the exemplary embodiment shown in FIG. 1, the piston rod 3 and the tension bolt 5 are hollow drilled, so that a through hole or central bore 47 is visible.

[0095] At the right end of the piston rod 3 in FIG. 1, the piston rod 3 passes through a seal support 59 and terminates in the feed space 53 .

[0096] In this exemplary embodiment, the seal support 59 is screwed onto the spindle 1. The seal support 59 consists of a flange 75 and a threaded portion 77 with an external thread.

[0097] An annular groove 79 is formed between the seal support 75 and the threaded portion 77. In the region of the threaded portion 77, a gap is formed between the piston rod 3 and the seal support 59, so that the cooling lubricant can flow from the annular groove 79 through one or more holes 81 through the gap into the feed space 53. From there, the cooling lubricant passes through the through-hole or central hole 47 into the region of the centering receptacle 7 or into the hollow shaft of the adapter 2.

[0098] A moving seal 51 is provided on the seal support 75 and interacts with a sealing portion of the piston rod 3 to prevent unwanted escape of cooling lubricant from the supply space 53 in the direction of the cylinder arrangement 6 and the clamping system 4, while at the same time preventing fluid from escaping from the first pressure chamber 35 into the supply space 53.

[0099] Furthermore, a static seal between the seal support 75 and the spindle 1 is also provided. Both seal the first pressure chamber 35 against the supply space 53. They separate the fluid of the cylinder arrangement 6 from the cooling lubricant.

[0100] This design of the seal support 59 has several advantages.

[0101] It is constructed very compactly (especially axially) because moving and static seals are only required at the seal support 75 and because the gap present in the thread 77 between the seal support 59 and the piston rod 3 is used to transport the cooling lubricant to the feed space 53.

[0102] The seal support 59 is also very advantageous from a manufacturing standpoint and is very easy to install and remove. The seal support 59 is threaded via a pin wrench whose pins enter complementary holes in the end faces of the seal support 59.

[0103] 3 shows another exemplary embodiment of the invention in a central position between the open and the tensioned state. The cylinder structure 6 comprises only one piston 27, which is guided directly in the cylindrical section of the receiving bore 9 and not in the cylinder sleeve 17. With reference to this figure, it can be particularly seen that the diameter of the piston 27 is approximately the same size as the inscribed circle of the centering receptacle 7.

[0104] Because the exemplary embodiment shown in FIG. 3 has fewer components, some details according to the present invention can be better seen.

[0105] Two advantages essential to the present invention can be better explained with reference to FIG.

[0106] In Fig. 3, the diameter D of the receiving hole 9 AB Diameter D AB It can be clearly seen that is just as large as the smallest inscribed circle of the centering receptacle. That is, based on the inscribed circle diameter of the centering receptacle 7 prescribed by the standard, the locking mechanism of the clamping system 4 according to the invention does not require any installation space in the radial direction.

[0107] In the solutions known from the prior art, the diameter of the receiving hole is significantly smaller than the smallest inscribed circle of the centering receptacle, for example due to the presence of a shoulder due to a thread or a stop end.

[0108] Moreover, in this exemplary embodiment, collar 67 absorbs axial forces in both directions. Annular groove 65 is only the minimum width wider than collar 67 necessary for production. Thus, the axial position of spring housing 19, and therefore clamp set 4, can be adjusted very precisely.

[0109] Since the clamping system 4 is axially fixed in both directions by a collar 67 in annular groove 65, the tolerance chain is very short and, as a result, the range of different types of mass-produced spindles 1 is very low.

[0110] In this exemplary embodiment, the piston 27 runs directly over a section of the stepped receiving bore 9. The piston 27 can have a polygonal outer contour rather than a circular one. The relevant part of the stepped receiving bore 9 is therefore also designed as a polygon. As a result, the surface of the piston 27 can be increased, which results in - assuming the same fluid pressure and the same outer dimensions of the spindle 1 - a greater actuation force of the piston 27.

[0111] The arrangement of a tool holder 85 fastened to a turret 83 of a machining center will be described with reference to Fig. 4. In Fig. 4, only one position of the turret 83 is occupied by a tool holder 85. The tool holder 85 carries a cutting tool.

[0112] A spindle 87 with a jaw chuck as shown carries the workpiece so that it can be rotated in the configuration shown. [Explanation of symbols]

[0113] 1 Spindle 2 Adapter 3 Piston rod 4 Clamping System 5 Tension bolt 6 Cylinder structure 7 Centering Receptacle 7.1 Lines 7.2 Lines 9 Receiving hole 11 Recess 13 Shoulder of receiving hole 15 Middle Floor 17 Cylinder sleeve 19 Spring housing 21 Aperture 23 Seal 25 Shoulder of piston rod 3 27 Piston 29 Piston rod sleeve 31 Piston 33 Clamp Segment 34 Conical contact surface 35 First Pressure Chamber 37 Second Pressure Chamber 39 First Control Line 41 Second Control Line 47 Through hole or central hole 51 Seal 53 Supply Space 55 holes 59 Seal Support 60 Shoulder 65 Annular groove 67 Color 69 Recess 71 Fixing pin 75 Seal Support 77 Threaded part 79 Annular groove 81 holes 83 Turret 85 Tool holder 87 Machining center spindle 102 Hollow Shaft D AB Receptacle hole 9 diameter

Claims

1. 1. A spindle having a recess (11), a centering receptacle (7) for an adapter (2) having a polygonal outer profile and a hollow shaft, an annular groove (65) and a receiving hole (9), wherein a clamping system (4) is arranged in the receiving hole (9), the clamping system (4) having a collar (67) having a polygonal outer profile or the outer profile is formed by a plurality of lugs, the collar (67) being mounted through the centering receptacle (7) in at least one position, and wherein a positive locking fit in at least one direction between the collar (67) and the annular groove (65) is established by rotation of the collar (67) relative to the spindle (1).

2. 2. Spindle according to claim 1, characterized in that the diameter of said annular groove (65) is equal to or greater than the circumference of said collar (67).

3. 3. Spindle according to claim 1 or 2, characterized in that the width of the annular groove (65) is equal to or greater than the width of the collar (67).

4. 3. Spindle according to claim 1 or 2, characterized in that the inscribed circle of the smallest polygon of the centering receptacle (7) is smaller than the circumference of the collar (67).

5. 3. Spindle according to claim 1 or 2, characterized in that the annular groove (65) is arranged at the transition between the centering receptacle (7) and the receiving hole (9).

6. 3. The spindle according to claim 1 or 2, characterized in that the collar (67) is formed at the front end of the housing (19), and the collar (67) or the housing (19) is fixed against rotation of the spindle (1) with a positive locking fit.

7. 7. Spindle according to claim 6, characterized in that a fixing pin (71) is inserted into the spindle (1), said fixing pin (71) fitting into a recess in said collar (67).

8. 8. Spindle according to claim 7, characterized in that recesses (69) are arranged at the high points of the polygonal collar (67).

9. 8. Spindle according to claim 7, characterized in that recesses (69) are arranged in the lugs of the collar (67).

10. 7. Spindle according to claim 6, characterized in that a fixing pin (71) is inserted into the spindle (1), said fixing pin (71) fitting into the annular groove (65) adjacent to a high point (7.1) or lug of the collar (67).

11. 3. Spindle according to claim 1 or 2, characterized in that the receiving bore (9) is designed as a polygon at least in cross section.

12. 3. Spindle according to claim 1 or 2, characterized in that if the receiving bore (9) is designed as a polygon, the piston or pistons (27) are designed as a front polygon.

13. 3. Spindle according to claim 1 or 2, characterized in that the collar (67) and the housing (19) are rotatable relative to the rest of the clamping system (4) or to a cylinder structure (6) arranged in the receiving hole (9).

14. 3. The spindle according to claim 1 or 2, wherein a cylinder structure (6) for actuating a clamping system (4) is arranged in the receiving hole (9), the cylinder structure (6) is provided with a piston rod (3), the piston rod (3) has a central hole (47) for supplying a medium to a tool clamped by the clamping system (4), the piston rod (3) passes through a seal support (59) and terminates in a supply space (53) of the spindle (1).

15. 15. Spindle according to claim 14, characterized in that the seal support (59) comprises a flange (75) and a threaded portion (77) having an external thread, an annular groove (79) is formed between the flange (75) and the threaded portion (77), a gap is formed in the region of the threaded portion (77) between the piston rod (3) and the seal support (59), and at least one hole (81) connects the annular groove (79) and the gap to each other.

16. 16. Spindle according to claim 15, characterized in that at least one hole (55) is provided in the spindle (1), said hole (55) opening into a space bounded by the annular groove (79) and the spindle (1).

17. Spindle according to claim 14, characterized in that at least one seal (51) is arranged on the seal support (59).

18. 3. Spindle according to claim 1 or 2, characterized in that it is part of a driven or stationary tool holder.

19. 3. Tool holder comprising a spindle (1) and a mechanical interface for fastening to the turret of a lathe or machining center, characterized in that the tool holder comprises a spindle (1) according to claim 1 or 2.

20. 20. Tool holder according to claim 19, characterized in that the spindle (1) is rotatably mounted or fixed to the tool holder.

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