Abstract:
The invention relates to a device for supporting a first machine part when a second machine part is subjected to force, the second machine part being mounted on the first machine part or being accommodated therein, in particular device for supporting a shaft ( 1 ) having a tension rod ( 2 ), which can be displaced in the axial direction, when the tension rod ( 2 ) is subjected to force, for example for changing parts of tools mounted on the shaft in automatic processing machines, a first adjustable component being provided for introducing a counterforce into the first machine part for the purpose of supporting the first machine part in a stable position, and a second adjustable component being provided for subjecting the second machine part to force.

Description:
FIELD OF THE INVENTION 
     The invention relates to a device for supporting a first machine part when a second machine part is subjected to force. The second machine part is mounted on the first machine part. The device supports a shaft having a tension rod, which can be displaced in the axial direction, when the tension rod is subjected to force. 
     BACKGROUND OF THE INVENTION 
     In the case of rotating systems, it is generally required for a force to be introduced when at a standstill, and any contact between the rotating part and the force-introducing unit has to be avoided during the rotation. This is the case with part-changing mechanisms on rotating parts, for example in the case of spindles in automatic processing machines. In this case, the housing and the piston rod of the unit for introducing the force are conventionally arranged in a manner such that they can be displaced freely, and there is a fixed collar on the rotating machine part, against which the parts, which are provided with a gripping means, for example in the form of ratchet levers, and are connected to the cylinder housing, come to bear first and thus enclose the force flux within themselves before the force-introducing actuating force becomes effective. Solutions of this type frequently require considerable structural space. 
     Another solution, but one which is fairly unfavourable, is to support the forces which act outwards in the mounting of the rotating machine part without an internal frictional connection, which has a negative effect on the accuracy, the wear and the running properties. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     The invention is based on the object of providing a particularly compact device for supporting a first machine when a second machine part is subjected to force. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The device according to the invention comprises a first component which can be adjusted hydraulically, pneumatically or in an electrically powered/electromagnetic manner via a threaded drive, for introducing a counterforce into the first machine part for the purpose of supporting the first machine part in a stable position, and a second component which can be adjusted powered/electromagnetic manner via a threaded drive, for subjecting the second machine part to force. The first and second components are activated at the same time and, in the manner of two cylinders acting counter to each other, equalize the internal force flux, in a manner similar to how this happens when a syringe is actuated. 
     In this case, the first and second components can have a piston arrangement, a diaphragm cylinder or an electromagnetic/electrically powered adjusting mechanism. 
     In the case of a design as a piston arrangement, the relief piston of the first component for introducing a counterforce is placed against a collar connected fixedly to the first machine part. At the same time, the relief piston comes to bear against the cylinder housing on a surface which is coordinated precisely in terms of size with the collar, which supports the counterforce of the relief piston, with the result that force is not introduced into the first machine part during support of the latter when the second machine part is subjected to force. 
     At the same time, in the second component a release piston, which is intended to move the second machine part in or on the first machine part, is subjected to pressure. The release piston first of all comes to bear against the second machine part and then displaces the second machine part relative to the positionally fixed first machine part. The force which is introduced via the release piston is held by the relief piston, which bears against the collar of the first machine part, with the result that the force flux is enclosed within it. 
     The first and second components advantageously have diaphragm cylinders, which results in a particularly short constructional length which can easily be sealed. The diaphragm cylinders can be automatically resilient or can be brought into the starting position by an additional spring arrangement. 
     An adjusting mechanism which can be activated in a particularly simple manner is achieved with an electromagnetic or electrically powered adjustment. This saves on structural space for hydraulic or pneumatic supply ducts, with the result that an electromagnetic/electrically powered adjustment can be used, for example, in the case of multi-stage adjusting systems. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following description the invention will be described in more detail with reference to the appended drawings. In the drawings 
     FIG. 1 shows a cross section of the device having diaphragm cylinders, 
     FIG. 2 shows a cross section of the device having a piston arrangement, 
     FIG. 3 a  shows a first embodiment of a diaphragm part according to FIG. 1, 
     FIG. 3 b  shows a second embodiment of a diaphragm part according to FIG. 1, 
     FIG. 4 shows an illustration of a diaphragm cylinder according to FIG. 1 having a diaphragm part according FIG. 3 b,    
     FIG. 5 shows a cross section of the device having electromagnetic/electrically powered adjustment, and 
     FIG. 6 shows a schematic illustration of an embodiment having electromagnetic/electrically powered adjustment. 
    
    
     In FIG. 1, the device according to the invention is illustrated in an embodiment having diaphragm cylinders. Mounted in a rotatably mounted shaft  1  (first machine part) is a tension rod  2  (second machine part) which can be displaced in the axial direction, is held under tension by means of a spring assembly  3  and in the process holds or securely clamps a part, for example a replaceable tool (not depicted), which is mounted on the other end of the shaft. 
     In order to replace this tool, the tension rod  2  has to be displaced counter to the spring force of the spring assembly  3  in the direction  35 . For this purpose, the rotational movement of the shaft  1  is brought to a standstill. The pressure chamber  5  of the release piston  4  (second component for introducing force) is subjected to a pressure medium and moves the non-rotating release piston  4  counter to the tension rod  2  in the direction  35  by the distance a, which is necessary so as to prevent, when the shaft  1  is rotated, any contact between the rotating shaft  1  (or tension rod  2 ) and piston  4 . After the stroke a, the force of pressure builds up at the release piston  4  to the extent necessary in order to displace the tension rod  2  counter to the spring assembly  3  to a sufficient extent axially in the direction  35  that the tool (not depicted) at the other end of the shaft  1  is released. Since the spring assembly  3  is supported in the shaft  1 , this release force which is introduced also acts on the shaft  1 , and therefore on the mounting with which the shaft  1  is mounted in the machine body. In order to avoid this axial additional load on the mounting, the shaft  1  is supported. 
     According to the invention, a collar  6  is provided for this purpose, which collar is connected fixedly to the shaft  1  and against whose plane bearing surface  7  the relief piston  8  (first component) bears, and therefore prevents any axial displacement of the shaft  1 . The relief piston  8  is placed at the same time against the bearing surface  7  and against a stop surface  9  on the housing part  10 . The free stroke b of the relief piston  8  to the bearing surface  7  and stop surface  9  is exactly the same, with the result that the shaft  1  is held in its position by the relief piston  8  via the collar  6  in a play-free and force-free manner. 
     The pressure which has built up in the pressure chamber  11  produces a force on the relief piston  8 , which is greater than the release force of the release piston  4  and is supported on the stop surface  9 . In this case, as illustrated in FIG. 1, the release force can be produced in an inherently closed (hydraulic) system or can act on the tension rod  2  from the outside. 
     The relief piston  8  is part of a subassembly which comprises the housing  12  together with the pressure chamber  11  and the orifices  13  for the inflow of the pressure medium of the diaphragm  14 . The diaphragm  14  is connected to the housing  12  via the clamping ring  15  and in a leakproof manner to the annular relief piston  8  along a narrow annular surface  16 . The relief piston  8  seals off the pressure chamber  11  with respect to the housing  12  by the sealing ring  17 . When subjected to pressure, the relief piston  8  completes the short stroke movement b and is pulled back into its neutral position illustrated by the resilient diaphragm when the pressure is shut off. The diaphragm  14  is an annular disc made of thin, resilient material, preferably spring band steel, and interacts with the relief piston  8  as a piston which is of sufficiently large dimensions in order to apply the required axial counterforce, and pulls the relief piston  8  into the neutral position when unpressurized. 
     The release piston  4  faces the relief piston  8  and is connected via the housing part  10 . The release force of the release piston  4  is produced in the pressure chamber  5 . The pressure medium, which is supplied through the orifices  18 , presses against the diaphragm  19 , which is tightly clamped on its outer diameter between the housing part  10  and the housing part  20  of the release unit and is connected on its inner diameter to the release piston  4 , and moves the release piston  4  in the direction  35  towards the tension rod  2 . 
     After the idle stroke distance a, which is the safety distance which is necessary in order to prevent any contact between the tension rod  2  and release piston  4  while the shaft  1  is rotating, the release piston  4  presses against the tension rod  2  and displaces the latter relative to the shaft  1 , after overcoming the spring force of the spring assembly  3 , in order to enable the tool to be released and replaced. In the process, the shaft  1  is supported by the relief piston  8 , which bears against the shaft collar  6 , with the result that the shaft remains force-free. The force flux is inherently enclosed by the release piston  4  via the shaft collar  6 , the relief piston  8  and the connected housing parts  12 ,  10  and  20 . 
     Since the stroke of the release piston  4  is significantly larger than that of the relief piston  8 , a two-part diaphragm can be provided. The tear-resistant, but very flexible, diaphragm  19  comprises a reinforced, rubber-coated fabric and is supported against bulging by the diaphragm part  21 . This diaphragm part  21  preferably consists of a metal plate or very firm plastic, and is slit in a suitable manner starting from the inner edge radially as far as the clamping diameter in order to increase the axial mobility (cf. FIG. 3 a ). 
     The resetting movement of the diaphragms is achieved by means of springs  22  which press against the collar  23  on the release piston  4 . The release unit is sealed off between the housing  20  and release piston  4  by the sealing ring  24 . The diaphragm surface of the release unit (second component) is, in order to obtain good axial mobility, significantly larger than the diaphragm surface of the relief unit (first component) for introducing the counterforce. Accordingly, the pressure chambers  11  and  5  are supplied with different pressures through the orifices  13  and  18 . 
     Since, when being subjected to pressure, the volumetric flow in the relief unit is substantially smaller than in the release unit, it is ensured that, when simultaneously subjected to pressure (by means of a common hydraulic system), the relief piston  8  bears against the collar  6  before the release force by means of the release piston  4  becomes effective. In order to monitor the release movement of the tension rod  2 , a signal ring  25  is connected to the tension rod  2 , said signal ring participating in the stroke movement, so that the sensor in the orifice  26 , which sensor is fastened fixedly or adjustably in the housing part  10 , is activated. One or more sensors can be mounted next to one another or offset around the circumference (not depicted). 
     In FIG. 2 the first component has a piston arrangement. The shaft  1  is connected fixedly to the collar  6 . The bearing surface  7  of said collar is at precisely the same distance b from the relief piston  8  as the latter is from the stop surface  9  on the housing cover  34 . The relief piston  8  is subjected to pressure medium through the orifices  13  in the pressure chamber  11  and is moved against the bearing surface  7  and stop surface  9 , where it bears with a force which is greater than the force F of the release piston  4  (not depicted), which force is introduced at the tension-rod head  36  of the tension rod  2 . The relief piston  8  is set back into the starting position by means of the spring force of the spring  37  or, if the relief piston  8  is correspondingly designed as a double-acting piston, by means of the counterpressure (not depicted). 
     FIG. 3 a  shows one possible embodiment of a diaphragm part  21  which supports the flexible diaphragm  19  over its entire surface. The diaphragm part  21  is at the same time concentrically clamped by its outer edge zone together with the diaphragm  19  between the housing parts  10  and  20 . The supporting surface of the diaphragm part  21  for the flexible diaphragm  19  is separated into a multiplicity of sectors  28  by thin, radial slots  27 . The mobility of the individual sectors  28  is made easier, in a hinge-like manner, by the tangential slots  29 , which leave only a sufficiently short connection  30  behind. Since the inner edge of the diaphragm part  21  is free, a supporting element, which overall is readily moveable, is therefore produced, said supporting element being moved to and fro by the compressive force of the diaphragm  19 , on the one hand, and by the restoring force of the spring  22 , on the other hand. 
     FIG. 3 b  shows a further design of a diaphragm part  21 . Here, the supporting surface of the diaphragm part  21  for the flexible diaphragm  19  comprises individual segments  31  which are not connected to one another and are fitted at the outer edge, by means of a cylindrical thickening  32  in the housing part  10 , into an annular groove  33  in a manner such that they can tilt in the axial direction (cf. FIG.  4 ). These segments  31  bear against the flexible diaphragm  19  and are pressed against the diaphragm  19  by means of the spring  22  and the collar  23  on the release piston  4 . In FIG. 4, the two segments  31  and  31   a  of the diaphragm part  21  are also illustrated in a relaxed and actuated (depiction using dashed lines) switching position of the release piston  4 . 
     FIG. 5 shows a further embodiment of the device having electromagnetic/electrically powered adjustment, in order to prevent an axial movement in the force direction F. The axially moveable stop  38  is moved by an electric motor or rotary magnet consisting of the stator  39  and the rotor  40 . The stator  39  is enclosed by a thick-walled sleeve  41  which is pressed into the housing  42 , which in turn is held in a twist-proof manner by the spindle sleeve  43 . The rotor  40  is fastened in a twist-proof manner on the axial part of the stop  38 . The stop  38  is connected rotatably to the housing  42  via the thread  44 , as a result of which, when the stop  38  is rotated by the electric motor/rotary magnet, the axial movement a′ of the stop  38  between the stop surface  45  and the stop surface  46  of the housing part  10  takes place. 
     When the stop  38  is activated, the stop surface  46  and the collar  6  of the shaft  1  are made contact with via its stop surface  45 , and the collar  6  is supported. The deactivated stop  38  bears against the sleeve stop surface  47  of the sleeve  41 . The thread  44  is self-locking, with the result that the stop surface  45  cannot be displaced relative to the stop surface  46  under the load F. The electric motor/rotary magnet is supplied with power via wires (not depicted). 
     FIG. 6, along with FIG. 5 shows a further schematic illustration of an electromagnetic/electrically powered adjustment. A thread  61  is mounted in the air gap between the stator  39  and and rotor  40 . The stop  38  is shown. The stator  39  has an inner part (for example made of plastic) having an inner thread  48  which is screwed to an outer part of the rotor  40  with an outer thread  49 . By this means, the rotor  40  is mounted radially and when rotated in the stator  39  executes the adjusting movement a′ according to FIG.  5 . 
     The electromagnetic/electrically powered adjusting mechanisms depicted in FIGS. 5 and 6 can be combined with all of the arrangements depicted or described in FIGS. 1-4 for activating the release piston  4 .