Abstract:
A filling apparatus for axial powder presses with a filling device includes a filler drive plate, a filling shoe arranged in particular on the side of the press, and a powder feeding device. The filling device can be moved forward and backward on a filler plate by means of an actuator, and in a filling position the filling shoe can be pressed against the filler plate respectively against a die surface embedded therein. According to the invention, the filling shoe is only loosely coupled to the filler drive plate, thus allowing the filling shoe to be subjected to a controlled and uniform adjusting force.

Description:
FIELD OF THE INVENTION 
     The invention relates to a filling apparatus for presses and a method for operating such a press. More particularly, the invention relates to a filling apparatus for axial powder presses. 
     BACKGROUND OF THE INVENTION 
     For filling a powder press with powder, especially ceramic powder and iron powder, a filling device is moved between each pressing operation over an opening in a filler plate, or over an opening in a die plate embedded in the filler plate of a die set, to fill the opening with powder. Prior to compacting the powder, the filling device is withdrawn to a rest position next to the press. For moving the filling device, there are different known actuating mechanisms, such as crank or spindle mechanisms, which are driven, for example, hydraulically or electromechanically, as well as hydraulic cylinders or servomotors. 
     The filling apparatus comprises a filling shoe firmly mounted on a filler main body of a filler drive and configured to move forward and backward together with it on the filler plate. Into a centrally arranged opening of the filling shoe there is introduced a filling tube which is rigidly connected to the filling shoe and to the filler drive. At the end of the filling tube projecting out from the filling shoe there is fixed a hose through which powder is fed from a hopper. The hopper is normally arranged above the filling apparatus and laterally at the press. 
     For filling the die with powder, the filling shoe must be moved over the opening in the die plate and be pressed firmly against it in order to be able to ensure safe, uniform and adequate filling of the die. The contact pressure must be sufficiently high to prevent powder from entering between the filling shoe and the filler plate. The required pressure must be particularly high, if, during displacement of the filling apparatus, the hose, which is normally partly filled with heavy powder, and the hopper are swiveled together with the filling apparatus and exert in particular on the filling shoe a force acting in opposite direction to the displacement and tilting the filling shoe. 
     For pressing the filling shoe against the filler plate, two methods are commonly used. According to the first method, the filler drive, together with the filling shoe is pressed at an angle from above onto the filler plate or die plate, whereby the total own weight of the filling apparatus rests on the filling shoe and at the same time has a negative effect on guidance in that it acts tilting like a lever. In another method the whole filler drive with the filling shoe is mounted for a swiveling movement around a mounting axis arranged outside the whole apparatus. 
     It is a disadvantage that onto the filler plate and onto the die and through the latter onto the die set of the press there acts a non-centric pressure at an angle from above or a tensile force at an angle from below which can lead to malfunction, wear and faulty pressing. In addition the apparatuses are of complex structure, difficult to adjust, and have to be replaced more or less completely at regular intervals because the filling shoe is often made of plastic and wears quickly as it is pulled over the filler plate, especially if, due to tilting, remnants of powder enter between the filling shoe and the filler plate. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to propose a filling apparatus, especially for axial powder presses, which has a simple structure and allows uniform contact pressure of the filling shoe onto the filler plate and/or die plate. 
     This object is solved by a filling apparatus having a filling device comprising a filler main body, a filling shoe arranged on the side of the press, and a powder feeding device. The filling device can be moved forward and backward on or above a filler plate and the filling shoe can be pressed in at least one filling position against the filler plate or a die embedded therein. The filling shoe is coupled to the filler main body of the filling device. 
     As a result of uncoupling, i.e., the separable adjustable coupling of the filling shoe to the filler drive plate, the filling shoe can be pressed against the filler plate with a uniform distribution of pressure. In addition, a pressure force may be adjustable and may be dosed accurately, wherein the weight of the whole filling apparatus no longer rests on the filler plate. This structure is also designed to avoid that the filling shoe rests on the filler plate in a tilted position. Furthermore, it is possible to replace the filling shoe individually and without much expenditure for installation work. 
     Advantageous configurations are the subject matter of dependent claims. 
     Coupling of the filling shoe to the filler drive plate via a frame permits the filling shoe to be pressed against the filler plate with good possibility of control. Forces acting, for example, from the filling hose onto the filling apparatus as the latter is being pushed, will no longer be transferred onto the filling shoe. 
     Coupling the filling shoe via filling shoe mounting bolts being encompassed by recesses in the bottom of the frame, permits the filling shoe to be pushed in a simple and safe manner across the upper surface of the filler plate even in case of interrupted contact pressure. 
     While the filling shoe is pushed via the frame, a contact pressure adjustable to a lower value may act on the filling shoe ensuring that the filling shoe is pressed firmly enough against the filler plate to prevent remnants of powder from entering between the filling shoe and the filler plate. 
     Furthermore, the filling shoe, being a wearing part made of plastic in the majority of cases and, therefore, having to be replaced several times when producing large quantities of green parts or compact discs, can be removed and replaced quickly by simply lifting the frame from the filling apparatus. 
     Another aspect of the invention involves a filling apparatus having a filling device comprising a filler main body and a powder feeding device. The powder feeding device is adjustably and positionably coupled to the filler main body. 
     Due to the fact that the powder feeding device is mounted to the filler drive plate and not to the filling shoe, the load and the restoring forces of the filling hose, which in addition is filled with heavy powder or remaining quantities of powder, and of the powder feeding hopper, which can be swiveled over a certain angle, are no longer transmitted directly onto the filling shoe but onto the filler drive plate. There is no tilting of the filling shoe, thus avoiding among other things also loss of powder. 
     Fixing the powder feeding device to the filler drive plate by adjustable carriers permits variable adjustment of the outlet opening of the filling tubes above the die. With this structure, the density of the filled powder, in particular iron or ceramic powder, can be adjusted in a simple way not only in the die as a whole but also in individual portions of it. In this way, dies for producing eccentric sintered parts, e.g., for connecting rods, can be filled with powder more individually. 
     In particular, a complete plant can be quickly adapted to different compact discs. On the one hand a suitable filling shoe can be inserted into the filling apparatus without much work involved, on the other hand support of the filling tubes on the adjustable carriers permits simple and quick adjustment and fine adjustment of the outlet openings of the filling tubes. 
     Filling tubes with different—even non-circular—cross sections, make it possible to feed powder or quantities of powder individually to certain areas of the die. By using adjustable flaps in the tubes, this filling effect can be adapted to specific requirements. This, together with the use of more than one filling tube arranged next to each other, permits optimized filling of the die. Therefore, filling pressure and density in particular are individually adjustable. 
     Generally speaking, adjustment of the individual assemblies is easier because the individual adjusting elements are arranged for easy access in front of the press in the area of the filler drive plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment is described in more detail below with reference to the drawing. There is shown in: 
     FIG. 1 a side view of a filling apparatus on a powder press, 
     FIG. 2 a plan view of the filling apparatus of FIG. 1 with the filling hose removed, and 
     FIGS. 3 and 4 cutouts of FIGS. 1 and 2 as enlarged partial sectional views. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As can be seen from FIGS. 1 and 2, a powder press comprises a press frame  1  with a base plate  2  mounted to it. In the press frame  1 , above the base plate  2 , there is arranged and guided a die set  3  adjustable at least in vertical direction. The die set comprises a die bolster  4 , a die plate  5  and a filler plate  6 , whereby these three elements  4 - 6  are firmly connected to each other. The die plate  5  is arranged on the die bolster  4 . The filler plate  6  is arranged on or around the die plate  5  which partly protrudes through filler plate  6 , whereby their surfaces—around an opening  5   a  in the die plate—form a common and plain sliding surface for a filling shoe  15 . On this assembly, there is arranged on the die bolster  4 , for example, a driving feature  7 . On the driving feature  7  there is arranged a filling apparatus or slide driving feature  8  of a slide  11  of a filling apparatus  10  supported directly or supported loosely by a buffer block. For guidance, this slide  11  is mounted on guide rails  9  fixed laterally on the press frame  1  in its vertical respectively longitudinal direction. During pressing, i.e. during the upward or downward movement of the assembly elements  4 - 6  of the press, the slide  11  is correspondingly moved up or down by means of the driving feature  7  and the slide driving feature  8 . 
     On the slide  11 , in particular on its upper surface, there is arranged the filling apparatus proper  10  comprising a filling device  12  on which hoses  13  are mounted on filling tubes  14 . In the structure as shown, a powder to be pressed is fed through two hoses  13  and filling tubes  14  each into the filling shoe  15  of the filling device  12 . 
     The filling device  12 , in particular its filling shoe  15 , is mounted on and can be pushed across the filler plate  6  and the die plate  5 . By means of a familiar type actuator  16 , there can be moved among other things the filling shoe  15  in synchronism with the pressing cycle of the press over an opening  5   a  in the die plate  5  into the press in order to fill the die with powder, and the filling shoe  15  can be moved laterally out of the area of the press frame in order to be able to compact the powder filled into the die. This process can be effected by automation, in particular by computer control. 
     As can be seen from FIG. 3 and 4, the filling device  12  comprises a filler main body respectively a filler drive plate  17 , fixed to the press-side end of a piston rod of the actuator  16 . The filler drive plate  17  is moved backward and forward preferably directly above the filler plate  6 , so that there is no friction between these two plates. 
     On the upper surface of the filler drive plate  17  there are supported one or several oblong carriers  20 , in the embodiment shown these are two carriers  20 , designed for holding and positioning one filling tube  14  each. On the end of the carriers  20  on the actuator side there is provided an oblong hole  21  in longitudinal direction of the said carriers, with a carrier journal  22  passing through it and projecting upwards out from the upper surface of the filler drive plate  17 . 
     A setscrew  23  enters at the face side of each carrier  20  and into its oblong hole  21 . By means of the setscrew  23  the carrier journal  22  can be adjusted and positioned in the oblong hole  21  in its longitudinal direction in order to be able to adjust the carrier  20  in its longitudinal direction and parallel to the surface of the filler drive plate  17 . 
     Through each carrier  20  there passes—transversely to its longitudinal direction and parallel to the surface of the filler drive plate  17 —a threaded hole  24 , into which another setscrew  25  is screwed. The shank of this setscrew  25  leads to a stop  26  and abuts against it, whereby the stop  26  is situated on the upper surface of the filler drive plate  17 . 
     Alternatively, there may also protrude, e.g., a bolt  25  laterally from the carriers  20 , said bolt being supported on a stop  26 , which is mounted for rotation around its longitudinal axis on the upper surface of the filler drive plate  17  near to the end on the side of the press. In this way the carriers  20  can also be adjusted and positioned laterally on the surface of the filler drive plate  17 , whereby the carrier journals  22  constitute the center of rotation of the carriers  20 . 
     For repeated adjustment of the positions, e.g., after having replaced a worn component, individual distances can be measured and be compared with values of a table. There may also be scale graduations attached to or worked into the surfaces of individual components. 
     For pressing the carriers  20  against the surface of the filler drive plate  17 , there is formed an opening or through hole  27  at a distance from the oblong hole in each carrier  20 . A threaded bolt  28  protruding upwards from the upper surface of the filler drive plate  17  passes through the through hole  27 . The through hole  27  is dimensioned in such a way that the filling tube  14  situated on the carrier  20  can be brought into any position required above the die plate opening  5   a . The threaded bolt  28  passes further through a spring washer  29  and a tensioning nut  30 . The spring washer  29  is large enough in diameter to ensure that in any position of the carrier it rests on the rim of the through hole  27  on the upper surface of the carrier  20 . By means of the tensioning nut  30  and the spring washer  29  the corresponding carrier  20  can be pressed against the surface of the filler drive plate  17 , in order to apply the carrier  20  against this surface in a way preventing its rotation. 
     Alternatively, instead of the threaded bolt  28  protruding from the filler drive plate  17  and instead of the tensioning nut  30 , there may also, e.g., pass a clamping screw from above through the spring washer  29  and through the through hole  27  of a carrier  20  into a threaded opening of the filler drive plate  17 . Thereby may be arranged a plurality of threaded openings next to each other on the surface of the filler drive plate  17 . 
     At the front end of each of the carriers  20  facing the press there is fixed at least one filling tube  14 . In the embodiment shown, one filling tube  14  each passes through the front end of the carriers  20  facing the press and can be clamped firmly therein. In order to increase throughput, the filling tubes are inclined in a way that on the one hand the angle of inclination is flat enough to permit quick entry of the filling apparatus into the press and quick withdrawal of the filling apparatus  10  out of the press, and that on the other hand the angle of inclination is steep enough to permit uniform and unhindered flow of the powder to be pressed. 
     On the upper end of each filling tube  14  there is fixed one hose  13  each for feeding powder from a hopper or from a dosing device. The lower end of the filling tubes  14  is shaped at an angle to their longitudinal axis in a way that the filling tube rims are arranged essentially parallel to the plane of the die plate  5  and of the filler plate  6  respectively of the die plate opening  5   a  and closely above it. 
     On the end portion of the filler drive plate  17  facing the press, a frame  40  is supported for holding and guiding the filling shoe  15 . The frame  40  comprises two clamps  41  and  42 , preferably arranged laterally to the filler drive plate  17  and in its longitudinal direction. 
     The end portions of the two clamps, facing the filler or actuator, are connected to each other by a square clamp or transverse clamp  43 , with journals  44  on the face of this transverse clamp  43  being mounted in holes of the clamps  41  or  42 . The transverse clamp  43  is arranged above and spaced at a certain distance to the end portion of the filler drive plate  17 , this end portion facing the actuator. The transverse clamp  43  is supported on at least one pressure piece of a piston rod  18  of a short-stroke cylinder  19 . The short-stroke cylinder  19  is fixed on or in the filler drive plate  17  and serves for pressing the transverse clamp  43  of the frame  40  upwards. 
     On the end portion on the side of the press, there are mounted in the clamps  41  and  42  filling shoe mounting bolts  45  protruding laterally from the filling shoe  15 . Mounting of the filling shoe mounting bolts  45  is preferably carried out by a semicircular recess  46  each in the lower surface of the clamps  41  respectively  42 , i.e. in that the recesses  46  in the clamps  41  and  42  rest on the filling shoe mounting bolts  45 . Thus the filling shoe can be removed and replaced very simply and quickly after simply lifting the clamps  41  and  42  respectively the filling device  10  with these clamps. 
     Depending on the desired contact pressure or leverage onto the filling shoe mounting bolts  45 , the clamps  41  and  42  are mounted on the side of the filler drive plate  17  in its central portion or its portion on the side of the press. One clamp mounting bolt  48  each protruding laterally from the filler drive plate  17  serves for mounting the clamps  41  and  42  in a way enabling their swiveling movement. In order to permit arrangement of the filling tubes  14  at a specially small angle of inclination, a portion of the front edge of the filler drive plate  17  is arranged in a position set back to the rear. 
     As the transverse clamp  43  is pressed upwards, the clamps  41  and  42  are swiveled around the clamp mounting bolts  48 . Consequently the ends of the clamps  41  and  42  on the side of the press are swiveled downwards and subject the filling shoe mounting bolts  45  to pressure corresponding to the intensity of pressure of the short-stroke cylinder  19  and of the acting lever of the clamps  41  respectively  42 . After installation of the filling apparatus  10  into the press, the short-stroke cylinder  19  can be activated partly or preferably continuously during operation. 
     In the embodiment shown, the front portion respectively the portion facing the press of the clamps  41  and  42  is larger towards the bottom than their portion facing the actuator. Alternatively there is, however, also possible a different way of mounting the frame  40  on the filler drive plate  17 , e.g., guidance of flat clamps in a groove-type recess in their surface. 
     An example of a pressing cycle comprises the steps of forward respectively inward movement of the filling apparatus  10  across the filler plate  6  into the press, so that the filling shoe  15  is placed above the die plate opening  5   a , firmly pressing the filling shoe  15  onto the die plate  5  by activation of the short-stroke cylinder  19 , filling of the die  5  of the press with powder, optionally partial or complete deactivation of the short-stroke cylinder  19 , withdrawal of the filling apparatus  10  together with the filling shoe  15  out of the press, compaction of the powder in the die to form a green compact by activation of the corresponding pressing punches, and finally, after compaction, deactivation and withdrawal of the pressing punches. Due to the fact that the filling apparatus  10  is mounted on the slide  11 , during pressing, the whole filling apparatus  10  together with the die set  3 , i.e. the filler plate  6 , the die plate  5  and the die bolster  4  is moved, so that there can take place partial overlapping of the above mentioned process steps. Open loop or closed loop control of the individual process steps is effected preferably by a computer which evaluates also measured values of pressure transducers, displacement transducers and acceleration transducers on the plant. 
     In one embodiment, the filling tubes have an elliptic instead of a circular cross section. In this embodiment it is also possible to install an adjustable flap in the filling tubes in order to be able to carry out fine adjustment of the cross section of the tube. In a specially preferred embodiment, adjustment of the flaps is possible by means of an external control adjustable by means of a central computer controlling the whole plant. 
     Furthermore, adjustability of the filling positions can be further improved by means of more than one filling tube with different diameters or different cross sections, in particular if non-centric green parts or compacts have to be produced and the die has to be filled with powder more densely or less densely in certain areas.