Abstract:
The tool has a tool shank (which may be hollow) ( 14 ), whilst the machine spindle has a connecting sleeve ( 20 ) containing a recess ( 18 ) to accommodate the tool shank. A clamping mechanism ( 22 ) is located in the area between the tool shank ( 14 ) and the connecting sleeve ( 20 ). This mechanism has at least one clamping element ( 24 ″), with radial movement, which acts as a wedge drive, providing axial clamping movement between the tool shank ( 14 ) and connecting sleeve ( 20 ). The clamping mechanism comprises an actuating nut ( 26 ), which screws onto an exterior thread ( 28 ) on the connecting sleeve ( 20 ) and is coaxial in relation to the spindle axis. During the clamping procedure, the axial movement of the actuating nut can be converted into the radial movement of the clamping element ( 24 ″), with the help of at least one connecting link ( 30 ″).

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a device for releasably connecting a tool to a machine spindle, comprising a tool shank projecting on the tool, a connecting sleeve projecting on the spindle coaxially to the spindle axis and having a recess for accommodating the tool shank, and a clamping mechanism which engages in the region between tool shank and connecting sleeve and has at least one essentially radially movable clamping element, the radial movement of which can be converted, preferably in the manner of a wedge drive, into an axial clamping movement between tool shank and connecting sleeve. In this case, the connecting sleeve need not be arranged directly on the machine sleeve. It may also be arranged on an adapter piece which can be releasably connected to a machine spindle. On the other hand, the tool shank need not be arranged directly on the tool either. It may be formed by an adapter piece connected to the tool. 
     The task of the clamping mechanism engaging in the region between tool shank and connecting sleeve is to connect the tool to the machine spindle in a rotationally locked manner by means of the at least one radially movable clamping element. When the clamping element is actuated by means of a suitable actuating mechanism, its radial movement is converted into an axial clamping movement between tool shank and connecting sleeve. In the process, taper clamping and/or flat-face clamping occurs between the clamping faces, facing one another, of the tool shank and the connecting sleeve. Pull rods, for example, are used to actuate the clamping mechanism, these pull rods passing through the machine spindle and engaging in the tool shank and being actuated from the machine side. Furthermore, it is known to actuate the clamping elements by means of screws or plungers which can be actuated radially from outside. This type of actuation has the disadvantage that a preset orientation of the spindle is necessary in order to be able to get to the actuating screws. This disadvantage has an adverse effect in particular in the case of multi-spindle heads. 
     BRIEF SUMMARY OF THE INVENTION 
     Starting therefrom, the object of the invention is to improve the known device of the type specified at the beginning to the effect that it is possible to actuate the clamping mechanism independently of the machine without a specific orientation of the spindle being necessary for this purpose. 
     To achieve this object, the combination of features specified in patent claim 1 are proposed. Advantageous refinements and developments of the invention follow from the dependent claims. 
     The solution according to the invention is based on the idea that the clamping mechanism comprises an actuating nut which is screwed onto an external thread, coaxial to the spindle axis, of the connecting sleeve and the axial movement of which, during the clamping operation, with at least one intermediate member in between, can be converted into the radial movement of the clamping element. This measure achieves the effect that the clamping mechanism can be actuated via the actuating nut irrespective of the orientation of the spindle in the circumferential direction. In this case, the intermediate member is advantageously designed as a wedge drive. In order to achieve flat-face clamping between the tool shank and the connecting sleeve, it is advantageous if the tool shank is defined at its root by a radially projecting annular surface, against which the connecting sleeve can be pressed with its free end face under the effect of the clamping mechanism. 
     A preferred refinement of the invention provides for at least one clamping element to be designed as a clamping bolt which is radially guided in a guide bore passing through the sleeve wall of the connecting sleeve and has a wedge surface at its end projecting outward beyond the guide bore, and for the intermediate member to be designed as an axially displaceable intermediate ring which is arranged in a non-rotatable manner on the outside of the connecting sleeve between the actuating nut and the clamping bolt and has a wedge surface bearing against and complementary to the wedge surface of the clamping bolt. In this case, the wedge surface of the clamping element and/or of the intermediate member is expediently subdivided into a steeper adjusting bevel and a flatter clamping bevel with regard to the displacement direction of the intermediate member. The wedge surfaces of the intermediate ring may be defined by two lateral guide surfaces which face one another in the circumferential direction, are oriented in an axially parallel manner, laterally overlap the projecting end of the clamping bolt and in the process form an anti-rotation locking means for the intermediate member, the intermediate ring expediently being axially guided on the outer surface of the connecting sleeve outside the wedge surfaces defined by the lateral guide surfaces. An axial supporting bearing designed as a plain or rolling-contact bearing may be arranged in the abutting region between the actuating nut and the intermediate ring. This facilitates the axial displacement of the intermediate ring by the actuating nut. Furthermore, the actuating nut may carry an annular extension piece which axially overlaps the intermediate ring on the outside and may be integrally formed in one piece on the actuating nut or connected to the latter as a separate part, in particular screwed, adhesively bonded, brazed on or shrunk on. In order to facilitate the detaching operation, it is advantageous if the annular extension piece has a driver engaging behind the intermediate ring at an annular shoulder remote from the actuating nut. The risk of contamination from outside is reduced if an annular cap projecting radially beyond the connecting sleeve and fixed to the latter is arranged on that side of the guide bores which is axially opposite the actuating nut. In this case, the annular extension piece of the actuating nut may axially overlap the annular cap at its circumferential surface. A further improvement in this respect can be achieved if a radially acting sealing ring is arranged between annular cap and annular extension piece. In order to achieve antirotation locking of the clamping bolt in the guide bores, it is advantageous if the clamping bolt, on its guide surface opposite the wedge surface, has a radially oriented guide groove in which a guide pin projecting beyond the annular cap engages in an axially parallel manner. 
     In a further preferred refinement of the invention, the clamping bolt has a tapered extension bearing against an internal taper on the tool-shank side. In addition, the tool shank may have a transverse bore in which at least one floating bolt having an internal taper is arranged in a displaceable manner. In order to achieve flat-face clamping, it is advantageous if the internal taper on the tool-shank side and the tapered extension on the clamping-bolt side are offset axially in the clamping direction during the clamping operation. In a preferred refinement of this embodiment variant, the clamping mechanism has two clamping bolts which are of identical design, are radially guided in diametrically opposite guide bores of the connecting sleeve, are displaceable by the actuating nut via the intermediate ring provided with two diametrically opposite wedge surfaces and each engage by means of their inwardly pointing tapered extension in a respective end internal taper of the floating bolt. 
     A further advantageous embodiment variant of the invention provides for the at least one clamping element to be designed as a clamping claw which, at its one end, has an anchor part, which can be supported on an inner shoulder of the connecting sleeve, and, at its other end, has a claw part which reaches into a cavity of the tool shank and can be pivoted there into an inner recess, the claw part and the boundary wall of the inner recess having wedge surfaces which are complementary to one another and via which the radial movement of the claw part can be converted into an axial clamping movement between tool shank and connecting sleeve. In this case, the intermediate member is designed as a plunger which is arranged in a non-rotatable manner in the interior of the connecting sleeve and the tool shank, has a complementary wedge surface bearing against an inner wedge surface of the clamping claw and is axially displaceable indirectly via the actuating nut between a release position and a clamping position. In this arrangement, the actuating nut is expediently coupled to the plunger via a transverse bolt which passes through at least one elongated hole, oriented in an axially parallel manner, of the connecting sleeve, in which case the transverse bolt can pass through an elongated hole, oriented in an essentially axially parallel manner, in the clamping element. At least two clamping elements of said type arranged in the circumferential direction at equal angular distances from one another and designed as clamping claws are advantageously provided. In addition, the plunger may at the same time be designed as an ejector which is effective during the release operation and which for this purpose may have an ejector head bearing against an inner surface of the tool shank. 
     A preferred refinement of the invention provides for the transverse bolt to be mounted with its ends in a thrust ring which is guided in a non-rotatable manner on the connecting sleeve and in such a way as to be axially displaceable via the actuating nut. The thrust ring may have two diametrically opposite recesses for accommodating the transverse-bolt ends, in which case the thrust ring, which overlaps the transverse-bolt ends on the outside, can be connected in each case via a radial pin to the transverse-bolt ends. 
     A further advantageous refinement of the invention provides for the actuating nut to have an annular extension which axially overlaps the thrust ring and which, on that side of the transverse bolt which is axially opposite the actuating nut, can be rigidly connected to a pull ring driving the transverse bolt in the release direction. A supporting bearing designed as an axial plain or rolling-contact bearing can be arranged both between the actuating nut and the thrust ring and between the pull ring and the thrust ring. 
     A particular solution variant of the invention provides for the thrust ring to have a thread interacting with a thread of the actuating nut and coaxial to the actuating nut. The thrust ring expediently has an external thread interacting with an internal thread of the actuating nut. In this case, the thrust ring and a pull ring arranged on that side of the transverse bolt which is axially opposite the actuating nut may be rigidly connected to one another. 
     It is also advantageous in this embodiment variant that the wedge surface of the plunger and/or the associated wedge surface of the clamping claw has a steeper adjusting bevel and a flatter clamping bevel with regard to the displacement direction of the intermediate member. 
     A preferred refinement of the invention provides for the clamping claws to be arranged with axial clearance in a centering cage which has two pistons which are connected to one another by webs and each engage in a respective cylindrical recess of the tool shank and the connecting sleeve. In this case, the webs may be designed as coolant tubes which pass through the pistons and to which cooling lubricant can be admitted. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The invention is explained in more detail below with reference to the exemplary embodiments shown schematically in the drawing, in which: 
     FIG. 1 shows a section through a tool coupling with actuating nut, an external wedge ring and clamping elements radially displaceable via the wedge ring; 
     FIGS. 2 a  and  2   b  show a plan view and a sectional representation of the actuating nut; 
     FIG. 2 c  shows a section through a driver ring which can be connected to the actuating nut; 
     FIGS. 3 a  and  3   b  show a sectional representation and a plan view of the wedge ring according to FIG. 1; 
     FIGS. 4 a  and  4   b  show a plan view and a section of an annular cap of the coupling device according to FIG. 1; 
     FIGS. 5 a  and  5   b  show two different side views (partly sectioned) of one of the clamping elements of the coupling device according to FIG. 1; 
     FIGS. 6 a  and  6   b  show a side view and a sectional representation of the floating bolt of the coupling device according to FIG. 1; 
     FIGS. 7 a  and  7   b  show a longitudinal section and a cross section through a coupling device modified compared with FIGS. 1 to  6  for tools with internal clamping elements which can be actuated via an actuating nut and a transverse rod; 
     FIG. 7 c  shows the actuating mechanism according to FIG. 7 a  in partially sectioned representation; 
     FIGS. 8 a  to  8   d  each show a clamping mechanism in a half view in accordance with FIG. 7 a , with different embodiment variants of the actuating mechanism having an actuating nut and a transverse rod; 
     FIG. 9 a  shows a representation of the clamping mechanism according to FIG. 7 a , with a further embodiment variant of the actuating mechanism having an actuating nut and a transverse rod; 
     FIGS. 9 c ,  9   d  and  9   e  show three different side views of the clamping mechanism of the coupling device according to FIG. 9 a  in partially sectioned representation. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The coupling devices shown in the drawing are intended for connecting tools  10  or tool adapters to a preferably rotating machine spindle  12  or a spindle adapter  12 ′. For this purpose, the tool  10  has an axially projecting tool shank  14 , whereas a connecting sleeve  20  projecting coaxially to the spindle axis  16  and having a recess  18  for accommodating the tool shank  14  is integrally formed on the machine spindle  12  or on the spindle adapter  12 ′. A clamping mechanism  22  is provided in order to produce the connection, this clamping mechanism  22  engaging in the region between tool shank  14  and connecting sleeve  20  and having at least one essentially radially movable clamping element  24 ′,  24 ″, the radial movement of which, in the manner of a wedge drive, can be converted into an axial clamping movement between the tool shank  14  and connecting sleeve  20 . The clamping mechanism  22  comprises an actuating nut  26  which is screwed onto an external thread  28 , coaxial to the spindle axis  16 , of the connecting sleeve and the axial movement of which, during the clamping operation, with at least one intermediate member  30 ′,  30 ″ in between, can be converted into the radial movement of the at least one clamping element  24 ′,  24 ″. In all the exemplary embodiments shown in the drawing, the intermediate member  30 ′,  30 ″ forms a wedge drive, as will be explained in more detail below. In all the exemplary embodiments, engagement points  32 ′,  32 ″ for wrench actuation, in particular grooves  32 ′ for a hook wrench or bores  32 ″ for a pin wrench, are formed on the outside of the actuating nut  26 . In addition, the outer circumferential surface may be provided with straight knurling  33  or diagonal knurling for providing a better grip. 
     In the exemplary embodiments shown in the drawing, the tool shank  14  is defined at its root by a radially projecting annular surface  34 , against which the free end face  36  of the connecting sleeve  20 , in the manner of flat-face clamping, can be pressed under the action of the clamping mechanism  22 . 
     Two clamping elements  24 ′ designed as clamping bolts are provided in the exemplary embodiment of a tool coupling shown in FIGS. 1 to  7 , and these clamping elements  24 ′ are guided radially in two guide bores  38  located diametrically opposite one another on the connecting sleeve  20  and passing through the sleeve wall and have a wedge surface  40 ′,  40 ″ at their ends projecting radially beyond the relevant guide bore  38 . Here, the intermediate member  30 ′ is designed as an axially displaceable intermediate ring which is arranged in a non-rotatable manner on the outside of the connecting sleeve  20  between the actuating nut  26  and the clamping bolt  24 ′ and has a wedge surface  42 ′,  42 ″ bearing against and complementary to the wedge surface  40 ′,  40 ″ of the clamping bolt  24 ′. The wedge surfaces of the clamping element  24 ′ and of the intermediate member  30 ′ are subdivided into a steeper adjusting bevel  40 ′ or  42 ′, respectively, and a flatter clamping bevel  40 ″,  42 ″ with regard to the displacement direction of the intermediate member  30 ′. As can be seen in particular from FIGS. 3 a  and  b , the wedge surfaces  42 ′,  42 ″ of the annular intermediate member  30 ′ are defined by two lateral guide surfaces  46  which face one another in the circumferential direction, are oriented in an axially parallel manner, laterally overlap the radially projecting end  44  of the clamping element  24 ′ and in the process form an anti-rotation locking means for the intermediate member  30 ′. Outside the wedge surfaces  42 ′,  42 ″ defined by the lateral guide surfaces  46 , the annular intermediate member  30 ′ is axially guided on the outer surface of the connecting sleeve  42  by a cylindrical surface  48 . As can be seen in particular in FIG. 1, a supporting bearing  50  designed as an axial rolling-contact bearing is arranged in the abutting region between the actuating nut  26  and the annular intermediate member  30 ′. 
     The actuating nut  26  carries an annular extension piece  52  which axially overlaps the annular intermediate member  30 ′ on the outside, has a driver  55  engaging behind the intermediate member  30 ′ at an annular shoulder  54  remote from the actuating nut  26  and is connected in a rotationally locked manner to the actuating nut  26  at the location  56 , preferably screwed, adhesively bonded, brazed or integrally formed. In addition, in order to prevent dirt from getting into the guide bores  38 , an annular cap  58  projecting radially beyond the connecting sleeve  20  and fixed to the latter is arranged on that side of the guide bores  38  which is opposite the actuating nut  26 , and the annular extension piece  52  of the actuating nut  26  axially overlaps this annular cap  58  at its circumferential surface. To further improve the sealing effect, a radially acting sealing ring  60  is arranged between annular cap  58  and annular extension piece  52 . 
     As can be seen from FIGS. 5 a  and  5   b  in conjunction with FIG. 1, the bolt-shaped clamping elements  24 ′, on their guide surface  62  opposite the wedge surface  40 ′,  40 ″, have a radially oriented guide groove  64 , in which a guide pin  66  projecting beyond the annular cap  58  in an axially parallel manner engages. Furthermore, the bolt-shaped clamping elements  24 ′ have a tapered extension  70  bearing against an internal taper  68  on the tool-shank side. The two internal tapers  68  are arranged on a floating bolt  72  which is arranged so as to be displaceable in a transverse bore  74  of the tool shank  14 . To achieve the above-mentioned flat-face clamping, the internal tapers  68  of the floating bolt  72  and the tapered extensions  70  on the clamping-element side are axially offset in the clamping direction during the clamping operation. 
     To release the tool  10  from the spindle adapter  12 ′, the actuating nut  26  shown in the clamping position in FIG. 1 is slackened by rotating it about the spindle axis  16  until the clamping elements  24 ′, with their tapered extensions  70 , can be displaced radially outward completely out of the internal tapers  68  of the floating bolt  72 . In this position, the tool shank  14  can be pulled axially out of the recess  18  in the connecting sleeve  20 . The coupling of another tool is effected in the reverse order by first of all the tool shank  14  of the relevant tool  10 , with actuating nut  26  slackened, being inserted into the recess  18  of the connecting sleeve  20  and then by the actuating nut  26 , with the intermediate member  30 ′ being displaced, being brought into the clamping position shown in FIG.  1 . 
     In the exemplary embodiments of a tool coupling which are shown in FIGS. 7 to  9 , the clamping elements  24 ″ are designed as clamping claws which, at their one axial end, have an anchor part  82 , which can be supported on an inner shoulder  80  of the connecting sleeve  20 , and, at their other axial end, have a claw part  88  which reaches into a cavity  84  of the tool shank  14  and can be pivoted there into an inner recess  86 . In this case, the claw part  88  and the boundary wall of the inner recess  86  have wedge surfaces  90 ,  92  which are complementary to one another and via which the radial movement of the claw part  88  can be converted into an axial clamping movement between tool shank  14  and connecting sleeve  20 . The intermediate member  30 ″ in these embodiments is designed as a plunger which is arranged in a non-rotatable manner in the interior of the connecting sleeve  20  and the tool shank  14 , has a complementary wedge surface  96 ′,  96 ″ bearing against an inner wedge surface  94 ′,  94 ″ of the clamping claw  24 ″ and is axially displaceable indirectly via the actuating nut  26  between a release position and a clamping position. In this case, the actuating nut  26  is coupled to the plunger-shaped intermediate member  30 ″ via a transverse bolt  102  which passes through elongated holes  98 ,  100 , oriented in an axially parallel manner, in the boundary wall and in the claw-shaped clamping elements  24 ″. In the exemplary embodiments shown in FIGS. 7 to  9 , two claw-shaped clamping elements  24 ″ diametrically opposite one another are provided in each case. 
     In the exemplary embodiments shown in FIGS. 7 to  9 , the tool shank  14  is designed as a hollow taper which can be inserted into the correspondingly tapered recess  18  of the connecting sleeve  20 . In the region of its root, the tool shank  14  is defined by an annular surface  34 , against which the end face  36  of the connecting sleeve  20  bears in the clamped state of the tool  10 . In order to be able to release the frictional connection between tool shank  14  and connecting sleeve  20  during the tool change, the intermediate member  30 ″ designed as plunger is at the same time designed as an ejector which is effective during the release operation. For this purpose, the plunger  30 ″ has an ejector head  106  bearing against an inner surface  104  of the tool shank  14 . 
     In the exemplary embodiments shown in FIGS. 7 to  9 , the transverse bolt  102  is mounted with its ends  108  in a thrust ring  110  which is guided in a non-rotatable manner on the outer surface of the connecting sleeve  20  and in such a way as to be axially displaceable via the actuating nut  26 . In this case, the thrust ring, in accordance with FIGS. 7 a ,  8   a ,  8   c  and  9   a , may have two diametrically opposite recesses  112  for accommodating the transverse-bolt ends  108 . In the case of FIGS. 8 b  and  d , the thrust ring  110 , which overlaps the transverse-bolt ends  108  on the outside, is connected in each case via a radial pin  114  to the transverse-bolt ends  108 . 
     In addition, in the exemplary embodiment according to FIGS. 7 a  to  c , the thrust ring  110  has an external thread  118  interacting with a further thread  116  of the actuating nut  26  and is rigidly connected to a pull ring  120  arranged on that side of the transverse bolt  102  which is axially opposite the actuating nut. These measures achieve the effect that the transverse bolt is driven axially via the actuating nut both in the clamping direction and in this direction. 
     In the exemplary embodiments shown in FIGS. 8 a  to  d  and  9 , the actuating nut has an annular extension  122  axially overlapping the thrust ring  110 . On that side of the transverse bolt  102  which is axially opposite the actuating nut, the annular extension is connected to a pull ring  120  driving the transverse bolt in the release direction. In each case a supporting bearing  124  designed as a rolling-contact bearing is arranged between the actuating nut  26  and the thrust ring  110 . In the case of FIGS. 8 c  and  d , a supporting bearing  126  designed as a rolling-contact bearing is also located between the pull ring  120  and the thrust ring  110 , whereas in FIGS. 8 a ,  8   b  and  9   a  supporting bearings  126 ′ designed as plain bearings are arranged between pull ring  120  and thrust ring  110 . 
     The inner wedge surfaces  94 ′,  94 ″ of the claw-shaped clamping elements  24 ″, on the one hand, and the associated wedge surfaces  96 ′,  96 ″ of the plunger-shaped intermediate member  30 ″ have a steeper adjusting bevel  94 ′,  96 ′ and a flatter clamping bevel  94 ″,  96 ″ with regard to the displacement direction of the intermediate member  30 ″. 
     As can be seen from FIGS. 9 b  to  e , the clamping claws  24 ″ can be arranged with axial clearance in a centering cage  128  which has two pistons  136 ,  138  which are connected to one another by coolant tubes  130  and each engage in a respective cylindrical recess  132 ,  134  of the tool shank  14  and the connecting sleeve  20 . Via a central bore  140  of the machine spindle  12 , a cooling lubricant can be admitted to the coolant tubes  130  passing through the pistons. The piston  138  is sealed off from the spindle-side cylindrical recess  134  by a radial seal  139  (cf. FIGS. 9 a, c, e ). 
     In FIGS. 7 a ,  8   a  to  d  and  9   a , the coupling devices are shown in their clamping position. To release the coupling device, the actuating nut is rotated in the release direction, for example via the engagement points  32 ′,  32 ″, so that it is displaced together with the transverse bolt  102  and the intermediate member  30 ″ in the direction of the tool shank. In the process, the claw parts  88  of the claw-shaped clamping elements  24 ″, via a spring ring  144  inserted into the circumferential groove  142 , are moved radially inward until their wedge surfaces  92  clear the displacement path for the tool shank  14 . At the same time, the tool shank  14  is released from the connecting sleeve  20  via the ejector head  106 . The replacement with a new tool is effected in the reverse order by the tool  10 , with actuating nut  26  slackened, first of all being inserted with its tool shank  14  into the recess  18  of the connecting sleeve  20 . If the actuating nut is subsequently actuated in the clamping direction, the claw parts  88 , under the wedge effect of the intermediate member  30 ″, pass into the inner recess  86  of the tool shank until the wedge surfaces  90 ,  92  are pressed against one another with clamping being effected axially. 
     In summary, the following may be emphasized: the invention relates to a device for releasably connecting a tool  10  to a machine spindle  12 . The tool has a tool shank  14  which is possibly of hollow design, whereas the machine spindle has a connecting sleeve  20  with a recess  18  for accommodating the tool shank. Located in the region between tool shank  14  and connecting sleeve  20  is a clamping mechanism  22  which has at least one essentially radially movable clamping element  24 ″, the radial movement of which can be converted, in the manner of a wedge drive, into an axial clamping movement between tool shank  14  and connecting sleeve  20 . According to the invention, the clamping mechanism comprises an actuating nut  26  which is screwed onto an external thread  28 , coaxial to the spindle axis, of the connecting sleeve  20  and the axial movement of which, during the clamping operation, with at least one intermediate member  30 ″ in between, can be converted into the radial movement of the clamping element  24 ″.