Abstract:
A shrinkage device for rapidly shrinking and outshrinking tools, especially hard metal tools, in so-called shrinkage tension chucks using an induction heating coil, wherein a plurality of shrinkage chucks of paramagnetic or ferromagnetic materials can be positioned on a turntable and brought from a position below the induction coil, which can be lowered, into a cooling position.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a shrinkage device for rapidly shrinking and outshrinking tools, especially hard metal tools, in so-called shrinkage tension chucks of paramagnetic or ferromagnetic materials using an induction heating coil. 
     A shrinkage tension chuck is understood to be a tool seat, for which the tool, which is to be held therein is held owing to the fact that initially the accommodating borehole of the shrinkage tension chuck, which is somewhat smaller than the shaft diameter of the tool, is expanded by being heated and the tool is then inserted, whereupon the chuck is heated once again, so that it contracts around the shaft of the tool, wedging it firmly. Conversely, the tool is removed once again by locally heating the surrounding chuck; because of the unavoidable transfer of heat also to the tool and, with that, of the simultaneous expansion of the latter, it is in most cases of decisive importance that the shrinkage chuck and the tool have different coefficients of expansion and that the heating takes place very rapidly. In the simplest cases, a naked flame or a hot air blower, with long heating times of the order of minutes, is used to heat the shrinkage tension chuck. Furthermore, the heating by heat transfer from a preheated metal piece, slipped over the shrinkage chuck, is also already known but, in practice, can be used successfully only for shrinkage chucks of small dimensions. In addition, the use of an induction heating coil in conjunction with the principle of inductive heating, which has already been known for decades, is also already known. In the latter case, the induction coil is pushed over the shrinkage tension chuck, remaining at a distance from the latter, in order to achieve contactless rapid heating. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a shrinkage device with such an induction heating coil, which makes possible particularly rapidly shrinkage and outshrinkage of tools, even of different dimensions. 
     Pursuant to the invention, this objective is accomplished owing to the fact that a plurality of shrinkage chucks can be positioned on a turntable and brought from a position below the induction heating coil, which can be lowered, into a cooling position. 
     Due to the inventive use of a turntable, rapid shrinkage and outshrinkage can be achieved in a small space, since a heated shrinkage tension chuck, into which the tool is subsequently inserted, can be brought rapidly and simply into a cooling position for achieving the clamping effect and also, conversely, a cooled shrinkage tension chuck is always available, so that, after rapidly being shifted into the operating position below the induction heating coil, it can be heated up for accommodating a tool. 
     Particularly advantageously, the turntable has insertion seats, into which the shrinkage chucks with lateral cool air-supplying grooves can be inserted, through which cooling air can be blown from below past the shrinkage chuck inserted in the seats, so that the shrinkage chucks can be cooled by these means. 
     In this connection, it has proven to be particularly advantageous if guiding connecting pieces for the cooling air are fastened to the underside of the turntable and are opposite the outlets of a ventilator for the cooling air, there being no such outlets for cooling air below the position of the induction heating coil. When the ventilator is switched on, all shrinkage chucks, which are disposed in the insertion seat but do not lie below the induction heating coil, are then cooled constantly. 
     In order to be able to use the inventive shrinkage device for the shrinkage and outshrinkage of tools of any dimensions, provisions can be made in a further development of the invention that the insertion recesses of the cooling plate, formed to correspond to the diameters of the largest shrinkage tension chucks used, are surrounded by recessed, offset shoulders for inserting adapter rings providing a fit for the respective shrinkage chuck. 
     In a corresponding manner, air-conducting sleeves, which can be inserted preferably in the recesses of the turntable surrounding the adapter ring shoulders, taper conically in the upward direction. Over these air-conducting sleeves, the cooling air, blown upward over the cooling air guiding grooves, is passed selectively close past the heated conical upper parts of the shrinkage tension chuck, so that optimum utilization of the cooling air is ensured. 
     When such cooling air sleeves are provided, the formation advantageously is such that they end below the angular flange of the inserted shrinkage chuck, forming a support for the induction heating coil. By these means, the induction heating coil, which has been pushed on, can function as a counter-holding device, so that, when the tool is pulled out of the heated shrinkage tension chuck, the latter is not also lifted from the turntable in the event that a slight clamping action still exists. 
     In order to be able to bring the induction heating coil particularly rapidly and simply into the operating position and, for the purpose of rotating the turntable further once again into an upwardly displaced non-operating position, provisions can be made in a further embodiment of the invention that the induction heating coil is fastened to a supporting arm, which can be displaced vertically at a guiding column, disposed laterally next to the turntable. Preferably, the supporting arm is connected with a counterweight within the hollow guiding column by means of a cable control, which is diverted at the upper end of the guiding column over a roller. By means of this counterweight, the supporting arm can be shifted easily over rollers, without having to provide special locks, for holding the supporting arm in a raised position. Preferably, the guiding column should be surrounded by divided bellows, which are fastened to the top and bottom of the supporting arm and hide the cable control. 
     Moreover, it has proven to be particularly advantageous that the supporting arm has supporting legs for rollers lying against the guiding column, the supporting legs surround the guiding recess for the supporting arm, are elastic at least partially and adjustable by set screws and are disposed in a horizontal plane. The supporting legs can be constructed particularly simply by slots formed in one piece at a frame part inserted in the guiding recess of the supporting arm. In accordance with a particularly preferred embodiment of the invention, four supporting legs, lying against the four sides of the square guiding column over rollers, are disposed at the top and four at the bottom of the guiding recess. 
     Finally, it is also still within the scope of the invention that the supporting arm is provided with a cooling blower, which conducts cooling air, which is aspirated from the end of the supporting arm lying opposite to the induction heating coil, about the inductive heating coil, and permits it to emerge once again through slots in the wall of the supporting arm surrounding it at a distance. The inventive shrinkage device can also be used for demagnetizing tools passed through the induction heating coil by drastically reducing the frequency and voltage, which can easily be accomplished when producing the supply voltage for the induction heating coils by means of a.c. converters, for example, to a frequency of 50 Hertz and a voltage of 5 volts. 
     Moreover, the shrinkage times can also still be approximately halved if the induction coil, preferably formed as a ceramic coil, is adapted to the shape of the tension chuck, that is, to the conical part of the latter for accommodating the tool and, by these means, a tighter magnetic coupling is obtained. Moreover, it is still also within the scope of the invention for monitoring the temperature and switching off the converter at excessively high temperatures, to glue a switch on the ceramic coil, which preferably should be provided at the bottom with an exposed edge for counter-holding during outshrinking. The fact that it is seated directly on the ceramic coil and not on the plastic head has proven to be significantly more advantageous. 
     Further advantages, distinguishing features and details of the invention arise out of the following description of an example as well as from the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a perspective view of an inventive shrinkage device, 
     FIG. 2 shows an enlarged plan view of the turntable for accommodating four shrinkage tension chucks, 
     FIG. 3 shows an enlarged section along the line III—III in FIG. 2, 
     FIG. 4 shows a perspective partial view of the guiding column with the supporting arm for the induction heating coil with the covering bellows removed, 
     FIG. 5 shows an enlarged plan view of the guiding recess of the supporting arm in FIG. 4, and 
     FIG. 6 shows a sectional representation of a ceramic coil, corresponding to the left half of FIG.  3  and adapted to the shape of the shrinkage chuck. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The inventive shrinkage device comprises a housing  2 , disposed on adjustable foot supports  1 , with a turntable  3 , which is disposed on the upper side of the housing  2  and into which four shrinkage tension chucks can be inserted. Aside from the driving mechanism for the turntable and the control device, a further cooling device for the shrinkage tension chuck, described in greater detail below, as well as a converter are disposed in the housing  2 , in order to provide from the voltage, supplied from the outside over the electrical network cable with a three-phase current plug  4 , especially a three-phase voltage, over a.c. converters, from the initially rectified supply voltage, an a.c. voltage of specifiable frequency with a high power of several KW, which can be supplied over cable  57  without using an oscillating circuit or a transformer on the secondary side to the induction heating coil disposed in the interior of the head  5  of a supporting arm  6 . The supporting arm  6  and its vertical displacement at a guiding column  7 , which is normally hidden by divided bellows  8   a ,  8   b , is described further below by means of FIGS. 4 and 5. The turntable  3  is provided with four insertion seats  9   a  to  9   d , into which shrinkage tension chucks  10   a  and  10   c  can be inserted, which are usually provided with an upper conical seating part  11  with an accommodating borehole for a tool  13  and a conical seating part  14 , so that they be fastened in a machine tool. The two parts  11  and  14  are separated by a flange  15 . 
     The conically extending upper edge  16  of the insertion seat is provided with a plurality of cooling air grooves  17 , through which cooling air can be passed from below past the inserted shrinkage tension chucks. So that, all conventional sizes of shrinkage tension chucks can alternately be shrunk and outshrunk with the help of an inventive shrinkage device, provisions are made pursuant to the invention that the insertion seats  9   a  to  9   d  are surrounded by recessed offset shoulders  18 , into which adapter rings  19  can be inserted, which in each case have the same external but different internal recess diameters, in order to be able to hold alternately shrinkage tension chucks  10   a  to  10   c  with different sizes for different tools on the turntable  3 . Below the insertion seats of the turntable  3 , cooling air guiding connection pieces  20  are disposed. Three of these lie above openings  21  of a plate  23  disposed in front of a cooling fan  22 , while the fourth cooling air guiding connection piece  20   a  of the insertion seat  9   a  lies below the induction heating coil, that is, next to the guiding column  7 , over a closed part of the wall  23 , so that cooling does not take place here. As soon as the turntable is turned further, the cooling air guiding connecting piece of the previously heated shrinkage tension chuck then also reaches a position over an opening  21 , so that cooling automatically sets in then. In order to achieve particularly effective cooling, air conducting sleeves  25 , which taper conically in the upward direction, are inserted in the recessed shoulders  24  of the turntable  3 , surrounding the shoulders  18 . As can be seen particularly in FIG. 3 at the right, cooling air, supplied from below, is passed through the air guiding sleeves  25  directly past the shrinkage tension chuck, so that the latter is also cooled effectively. The air guiding sleeves  25 , which are optionally provided with an upper, reinforcing, inwardly pointing angular flange  28 , terminate below the surface  27  of the flange  15  of the shrinkage tension chuck  10 ,  10   c  so that, in spite of the presence of the air guiding sleeves  25 , it is possible to place the head  5  of the supporting arm  6 , with the induction heating coil  28  disposed therein, directly on the flange  15 , so that, after the tool  13  is heated and pulled out, the whole shrinkage tension chuck  10   a  is not also raised, as long as there is still a slight gripping action between the shrinkage tension chuck and the tool. In the supporting arm  6 , a cooling blower is disposed, which is not shown, aspirates cooling air from the rear in the direction of arrow  29  and passes it between the outer wall  30  of the head  5  and the induction heating coil  28  in the gap  31 , in order to be able to cool the induction heating coil  28  effectively, which is being operated at a high power. The cooling air then emerges once again through slots  32  in the head  35 . 
     The induction heating coil  28  is wound on a bobbin  40  of ceramic, using a high temperature resistant enameled copper wire  41 . At  42 , a switch is recognized, which monitors the temperature, switches off the converter at excessively high temperatures and is glued on to the ceramic body  40  of the induction heating coil  28 . The induction heating coil  28  with the ceramic bobbin  40  is suspended in the head  5 , so that the lower flange  43  of the bobbin is exposed. In the position shown in FIG. 3, the bobbin  40  presses over an edge  44  on to the shrinkage chuck  10   a , so that it is held during outshrinking and not raised from the seat of the turntable  3  when tension is applied to the tool. The induction heating coil  28 , suspended with the upper edge flange of the ceramic bobbin in an annular shoulder  46 , is prevented from twisting in the head  5  by means of a screw, which is not shown. 
     Over a cable control  33 , which is turned around a roller  44  at the upper end of the guiding column  7 , the supporting arm  6  is connected with a counterweight, which is not shown and disposed in the interior of the hollow guiding column  7 , so that the supporting arm can easily be shifted and nevertheless held automatically at different heights. Frame parts  35 , disposed at the top and bottom of the supporting arm  6 , guide the supporting arm  6  at the guiding point  7 . Supporting legs  37 , at the free front ends of which rollers  38  are mounted and which are formed by slots  36  in the frame part  35  and disposed in a horizontal plane, are formed at the frame part  35 . These rollers  38  are in each case at one of the side surfaces  56  of the guiding column  7 , which is constructed as a square. At least some of the supporting legs  36  can be tilted elastically against the side surfaces  56  of the guiding column  7  by set screws  39 , which pass through the frame part  35 , so that the contacting pressure of the rollers can be controlled, in order to bring the requirement of an easily accomplished shifting into conformity with that of a supporting arm  6 , which automatically remains in the position set manually. At the upper frame part  35 , which can be seen in FIG. 5, all four supporting legs  36  can be adjusted by set screws  39 . On the other hand, in the case of an appropriately constructed frame part at the under side of the supporting arm  6 , it is sufficient if only two supporting legs are constructed so that they can be adjusted, while the others may be rigid. As can be seen especially from FIG. 1, the supporting arm  7  is encased by a two-part bellows  8   a ,  8   b , so that, in particular, the control cable  38  is covered. 
     FIG. 6 shows a modified embodiment of an induction heating coil  28 , the ceramic bobbin  40 , corresponding to the conical shape of the seat  11  of the shrinkage tension chuck  10   a , is also constructed conically. This results in a tighter magnetic coupling by means of which the shrinkage times can approximately be halved. 
     The control panel  47  of the inventive shrinkage device comprises a malfunction display  46  and a malfunction acknowledgement  49 , an ON switch  50  for the cooling and an OFF switch  51  for the cooling, a switch  52  for switching on the heating controlled over a time relay  53  and a switch  54  for switching off the heating. A special feature is the post-heating switch  55 , with the help of which, in the event that the automatic heating process has not yet led to complete outshrinkage or that the shrinkage tension chuck has not been expanded sufficiently, so that the tool can be inserted, brief manual reheating becomes possible without having to set the whole heating cycle in motion once again using switch  51 .