Patent Publication Number: US-6662617-B2

Title: Press for transforming work pieces

Description:
This application claims the priority of Germany Application No. 10045312.0 filed Sep. 12, 2000, the disclosure of which is expressly incorporated by reference herein. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The invention relates to a press as well as a process for transforming work pieces. 
     A press with a safety shutdown is known from DE 197 01 282 A1 where the drive of the tappet is disengaged by means of a coupling apparatus which receives a signal from a monitoring apparatus if the force exerted upon the tappet deviates from a specified standard value by more than a specified amount. Among other things, it can also be provided with this press that the monitoring apparatus shuts down one or more extractors. 
     But it is not indicated in this document how this shutdown of the extractor is to be undertaken. It is, however, unambiguous that the shutdown can only be undertaken in connection with shutting down the tappet and consequently can only be undertaken only when a disturbance arises in the area of the tappet. 
     It is the object of the present invention to create a press for transforming work pieces where in the event of a disturbance in the area of the extractor elements, damage to the extractor elements of the entire press are avoided. 
     Through at least one measuring sensor which in accordance with the invention is arranged within the lever linkage, the force acting upon at least one extractor element is measured, owing to which at any point in time there is a monitoring on the sequence of the extraction process. 
     In this way, the triggering apparatus of the invention having the measuring sensor can then disengage the coupling if the height of the force measured deviates from a standard force value specified at a certain point of the motion of the extractor element by a specific amount. In this way, in the event of a disturbance in the area of at least one extractor element, the drive apparatus is disconnected from the extractor element, and the extractor element is shut down. In this way, damage to the extractor element or the entire press can be avoided in cases in which disturbances arise in the region of the extractor element. 
     Through the process of the invention for transforming work pieces, it is possible to shut down the extractor element already before reaching a maximal force, since already when a certain tolerance is exceeded, that is, a recognizable tendency toward higher emerging forces, the flow of power between the drive apparatus and the extractor element is interrupted. 
     In an advantageous refinement of the process of the invention, the possibility offers itself of undertaking an adaptation of the force standard values for each operating point in connection with changes of the force acting from the drive apparatus on the extractor element which can arise owing to the shape of the lever linkage. Here the functions of the force or the path of the drive apparatus traversed and the extractor element are adapted to each other, which can be designated as “dynamization.” 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantageous configurations and refinements of the invention emerge from the remaining dependent claims as well as the embodiment represented below on the basis of the drawings in terms of principles, wherein: 
     FIG. 1 is a schematic representation of an extraction system of the press of the invention; 
     FIG. 2 is an alternate embodiment of the extraction system of FIG.  1 . 
     FIG. 3 depicts an extractor element with a part of the associated lever linkage in a first embodiment; 
     FIG. 4 is a further detailed construction and arrangement of the first embodiment of FIG.  3 . 
     FIG. 5 shows an extractor element with a part of the associated lever linkage in a second embodiment; and. 
     FIG. 6 is a modification of the second embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows an extractor system  1  which has several rod-like extractor elements  1   a . The extractor system  1  is a component of a press for transforming work pieces  3 , and the extractor elements  1   a  are provided to extract the work pieces  3  out of a lower tool  4  which is an element of a further tool  5 . The tool  5  moreover has an upper tool  6  in an inherently familiar manner which is or can be provided with an extractor system  1  in a way not represented and is installed on a tappet  7 . The tappet  7  executes a stroke motion characterized with an arrow “A” in order to transform the work pieces  3 , and is for this purpose connected with a not represented drive apparatus. Basically an eccentric press, a toggle-lever press or any other desired press  2  can be used as press  2 . 
     The extractor system  1  or the extractor elements  1   a  are connected with a drive apparatus  9  through a lever linkage  8  whereby the drive facility  9  is either connected with the aforementioned drive facility for the tappet  7  or is identical with the same. The drive apparatus  9 , here a curve-controlled eccentric drive apparatus, has a drive shaft  9   a  which rotates in accordance with the arrow designated with “B.” Between the drive apparatus  9  and the lever linkage  8 , there is located a coupling  10 , which is the present case is formed by a hydraulic piston/cylinder unit, and has a cylinder  10   a  as well as a piston  10   b.  An actuation lever  11  is mounted on the piston  10   b  which is connected with a rocker arm  12  or acts upon the same. The rocker arm  12  consists of two arms  12   a  and  12   b  which are arranged on both sides of an approximately central point of rotation  13  of the rocker arm  12 , whereby arm  12   a  is installed on actuation lever  11  and arm  12   b  actuates an individual extractor element  1   a.  In the present case, the extractor elements  1   a  are thus activated when the piston  10   a  moves out and consequently exerts pressure on the actuation lever  11 . As already mentioned above, the work piece  3  is ejected in this way. Of course, a moving out of the extractor element  1   a  when piston  10   b  moves in, and consequently a traction stress upon the actuation lever  11 , would also be possible. 
     Between arm  12   b  of the rocker arm  12  and extractor element  1   a,  a measuring sensor  14  is situated, which is part of a triggering apparatus  15 . Moreover, the triggering apparatus  15  has an evaluation apparatus  16  connected with the measuring sensor as well as a memory apparatus  17  and a valve  18 . The measuring sensor  14  is in a position to measure continuously the force acting on the extractor element  1   a,  and forwards the force measured to the evaluation apparatus  16 . In the evaluation apparatus  16 , the force values measured are constantly compared with standard values entered into the memory apparatus  17  for forces arising in the normal case and with a deviation of a measured force value by a specific value from the associated standard value, the triggering apparatus  15  ensures that the coupling  10  is disengaged. The amount by which the actual force values may deviate from the stored standard values is stored in the memory apparatus  17  as so called envelopes and can be freely programmed for any point. If several evaluation elements la with assigned lever linkages  8  are present, as this is here the case, then each of these extractor elements  1   a  is allocated a corresponding trigger apparatus  15 . Of course, only one extractor element  1   a  could be provided. 
     For disengaging the coupling  10 , the evaluation apparatus  16  emits a signal to valve  18  constructed as a quick breaking 2/2 way valve which then within a very short time switches over and consequently ensures that the cylinder  10   a  becomes pressureless. In this way, the coupling  10  can transfer no more force to the actuation lever  11 , and the extractor element  1   a  likewise becomes power-free. Such a deviation of actual force from the associated standard value can arise in connection with disturbances in the area of an individual extractor element  1   a  or also in the area of the entire extractor system  1 . Through the disengagement of the coupling  10  described, the extractor elements  1   a  are no longer driven by drive apparatus  9 , owing to which damage to extractor elements  1   a  and the entire press  2  are avoided. 
     In an alternative configuration in accordance with FIG. 2, a preliminary relief apparatus  101 , constructed as a hydraulic cylinder in the present example, is arranged between the extractor pin  1   a  and measuring sensor  14  in the device in accordance with FIG.  1 . The preliminary relief device  101  is relieved through the preliminary relief valve  100 , which is arranged between preliminary relief apparatus  101  and valve  18 . This takes place in the following manner. Valve  18  is opened through relief of the pressure through valve  100  in the hydraulic cylinder  101 . In this way, the pressure in the coupling  10  subsides and is consequently relieved. 
     In FIG. 3, the more exact construction and the arrangement of the measuring sensor  14  in the lever linkage  8  is represented. Thus, measuring sensor  14  is comprised by a cylindrical element  19  which is provided with strain gauges  20  on its periphery and which is accommodated in a recess  21  in rocker arm  12 . Through strain gauges  20 , the force acting on the individual extractor element  1   a  is continuously measured, whereby the connection of the strain gauges  20  with the evaluation apparatus  16  is not explicitly represented in this case. Alternatively, the measuring sensor  14  could also be comprised quartz element arranged within the lever linkage  8 . For amplifying the signals of the strain gauges  20 , a measuring amplifier  22  is situated between measuring sensor  14  and the evaluation apparatus  16  which operates in an inherently familiar manner. The rocker arm  12  and consequently also the measuring sensor  14  accommodated therein is represented in FIG. 3 in both its end positions. 
     The more exact construction and the arrangement of measuring sensor  14  in lever linkage  8  is represented in FIG.  4 . The measuring sensor  14  is thus formed by a cylindrical element  19  which is provided with strain gauges  20  on its periphery and is accommodated in a recess in the rocker arm  12 . The force acting on the individual extractor element  1   a  is continuously measured by strain gauges  20 , whereby the connection of strain gauges  20  with the evaluating apparatus  16  is not explicitly represented in this case. Alternatively, the measuring sensor  14  can also be formed by a quartz element arranged inside the lever linkage  8 . A measuring amplifier  22  which operates in an inherently familiar manner is situated between the measuring sensor  14  and the evaluation device  16  for amplifying the strain gauge  20  signals. The rocker arm  12  and consequently also the measuring sensor  14  accommodated therein is represented in both end positions in FIG.  3 . The preliminary relief element  101  is situated between recess  21  and the cylindrical element  19 . The preliminary relief valve  100  is connected in series after preliminary relief element  101  and is already described in FIG.  2  and opens valve  18  automatically in the event of an overload. 
     FIG. 5 illustrates an extractor system  1  for the upper tool  6  where the lever linkage  8  is constructed as a toggle linkage  8 ′. Here too once gain a rocker arm  12 ′ is provided whose point of rotation  13 ′ nonetheless does not lie in the middle as with rocker arm  12  described above, but outside, and indeed on the side facing the actuation lever  11 ′ likewise provided here. Consequently the extractor element  1   a  is actuated by an area of rocker arm  12 ′ which in relation to the mode of functioning of the lever linkage  8 ′ represents no basic change from the embodiment represented in FIG.  3 . Here too once again a triggering apparatus  15 ′ is provided which has the components already described above, but which are not completely represented. Coupling  10 ′, which is executed in the form of an inherently known pawl coupling, is in the immediate vicinity of rocker arm  12 ′ arranged in the direction of the flow of force in front of the same and within or in front of the actuation lever  11 . Valve  18 ′ is once again directly assigned to coupling  10 ′. 
     Since with toggle linkages  8 ′ of this sort, depending on the position of the drive shaft  9   a ′ of drive apparatus  9 ′, the force arising on the extractor element  1   a  is not proportional to the force occurring on drive shaft  9   a ′, an adaptation of the force standard values is undertaken for each operating point of the extractor element  1   a  in connection with such a deviation, which is imported into the memory apparatus  17 . With the “dynamization” undertaken here, the functions of force or the path of the drive apparatus  9 ′ and the extractor element  1   a  covered are adapted to each other, which once again has effects on the envelopes of the allowable force course. 
     As shown in FIG. 6, the preliminary relief device  101  is arranged between rocker arm  12 ′ and measuring sensor  14 . As already described in FIG. 2, the preliminary relief valve  100  is connected in series after the preliminary relief device  101  and opens the valve  18  automatically in the event of an excess load above the previously set triggering pressure. 
     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.