Patent Publication Number: US-2019168428-A1

Title: Filling Injector and Method for Operating a Filling Injector

Description:
The present invention relates to a filling injector for a plastics machine and a method for operating such a filling injector. 
     Plastics machines can, for example, be injection molding machines, but can also be machines for producing plastics from granulated foam. 
     DE 38 31 600 C1 has disclosed a method and a device for dispensing thermoplastic foam granules into the mold cavity of a mold; the primary goal is to be able to dispense thermoplastic foam granules, namely propellant-containing foam granules, as needed from a storage receptacle both at atmospheric pressure and at a positive pressure into an evacuated mold as well as to dispense non-expandable, compressible foam granules at positive pressure into a mold that is at an equally high pressure and in so doing, to save compressed air and reduce the filling time. This is achieved in that the foam granules remaining in the filling injectors and in the supply lines after the end of the filling procedure are blown back into an additional receptacle that is unpressurized and independent of the storage receptacle. The foam granules are dispensed into the mold cavity by a filling injector, whose closing piston can selectively open or close the supply opening of the mold cavity. Via a 2/2-port directional-control valve, compressed air from a compressed air source is pushed through injector nozzles mounted inside the filling injector, which causes foam granules to be sucked from the outlet opening of a storage receptacle via supply lines, a distributor housing, and a closing mechanism and pushed through the supply opening into the mold cavity when the closing piston is retracted. This is acted on with compressed air via a 3/2-port directional-control valve. 
     DE 197 47 645 A1 has also disclosed a method for producing a foam body and has disclosed the foam body; here, too, granulated foams are processed and the mold cavity is filled with foam granules of a predetermined granulation. The filling takes place by means of one or more fillers that are embodied as injectors and that are acted on with compressed air. The foam granules are sucked from a storage receptacle, not shown, and are blown into the mold cavity by means of the compressed air. In order to obtain a good filling, the mold cavity is evacuated during this procedure. 
     The use of filling injectors is also known from DE 10 2008 016 883 A1. 
     DE 299 19 328 U1 relates to a filling injector for rigid foam molding machines and DE 79 28 606 U1 also relates to a filling injector, in particular for feeding pre-foamed, still expandable, small-granule styrene polymers. In these two filling injectors, a piston rod has a smaller diameter than the piston. 
     WO 2013/182555 A1 relates to a method for transporting foamed thermoplastic polymer particles from a receptacle through at least one tube; to transport the foamed thermoplastic polymer particles, a gas flow is fed through the tube and the foamed thermoplastic polymer particles are wetted with a water-containing lubricant. The lubricant must contain water. The necessary pressure is produced by means of air or nitrogen. 
     DE 10 2009 024 278 A1 discloses a filling device for filling a mold with plastic granules made of thermoplastic plastic. In this case, an actuating piston is provided, which is connected to a closing piston and can move the latter. The actuating piston here has a contoured casing wall in which longitudinally extending air ducts are provided. In an open position, the closing piston is slid into an air duct. The closing piston is dimensioned so that between the closing piston and the air duct, an annular duct is formed, which functions as an outlet nozzle. Air that flows into an opening is guided through this outlet nozzle. 
     WO 2015/091906 A1 has disclosed a filling injector for filling a mold with plastic granules. The injector has a front part and a base part, which are positioned axially one after the other. The front part has an injector opening and an injector head, which are connected to each other via an internal tube; a casing tube is positioned around the internal tube. The base part has an intrinsically known pneumatic drive element, which is embodied with a square cross-section and has two compressed air connections. When the compressed air connections are actuated, an actuating piston is moved forward or backward in the drive element. A piston rod is coupled to the actuating piston. The drive element is thus embodied as a piston/cylinder unit, with a closing piston being positioned at the end of the piston rod oriented away from the actuating piston. At the opposite end, the pneumatic drive device is placed against a guide device. The guide device has a guide housing with a guide housing front part and a guide housing back part. 
     Injectors of this kind for filling a mold with plastic granules are often embodied in a modular fashion so that different front parts can be combined with different back parts. 
     In addition, filling injectors of this kind are highly stressed components, which, along with regular maintenance work, also require a corresponding replacement of expendable parts. 
     In filling injectors, the orifice and the tubing component of the bottom part of the injector head remain mounted on or in the mold permanently. The injector head top part, cylinder piston, closing piston, and all of the moving expendable parts (e.g. bearings) are replaced regularly. 
     The injector head bottom part and the injector head top part are usually provided with a quick release coupling, which is secured with a clamp; in other words, they are connected in a detachable way. 
     A separate filler is supplied with each supplied mold. The replaceable parts, however, are often swapped out during operation. For this reason, during production, confusion often arises as to which individual parts of the respective injectors have actually been used. In order to counteract this, in some production plants, the expendable parts are replaced every week, regardless of whether or not a replacement is needed. 
     Devices for manufacturing granulated foam parts are disclosed by DE 10 2014 117 332 A1, DE 19637349 A1, EP 082 913 1, and EP 224 103 B1. 
     The object of the invention is to create a filling injector with which the maintenance can be standardized, the maintenance costs can be reduced, and the maintenance can be made more reproducible. 
     The object is attained with a filling injector for a mold having the features of claim  1 . 
     Advantageous modifications are disclosed in the dependent claims. 
     The invention therefore relates to a filling injector for a mold having an injector housing, which has a cylindrical cavity in which a closing piston unit is supported in movable fashion; the injector housing has a supply for plastic granules leading to the cavity and at an end oriented toward the mold, has a mold opening for supplying the plastic material to a mold; in a closed position, the closing piston unit is slid so far forward that it closes the mold opening and in an open position, it is retracted from the cylindrical cavity at least in the region between the supply and the mold opening; and inside the injector housing, a sensor is provided for detecting a predetermined detection position of the closing piston unit and a counting device for counting the number of detection positions of the closing piston unit in which it is placed. 
     The invention also relates to a filling injector in which the injector housing is composed of an injector tube and an injector cap that closes the injector tube at the end remote from the mold opening. The injector cap can advantageously be embodied separately from the injector tube or also be embodied as integrally connected to the injector tube. 
     In another advantageous embodiment, the injector tube is composed of a front injector tube section, which has the mold opening, and a rear injector tube section and these sections are detachably coupled to each other. 
     In another advantageous embodiment, between the front injector tube section and the rear injector tube section a front injector head and a rear injector head can be provided, between which the detachable connection is produced. 
     The invention also relates to a filling injector in which the front or rear injector head has one air connection and the injector cap has another air connection, and the closing piston unit has an actuating piston positioned in the rear tube section in order to move the closing piston unit forward or backward by means of a corresponding supply of compressed air through one of the two air connections. 
     It is also advantageous if the closing piston unit is coupled in captive fashion to the rear injector section. This means that when the rear injector tube section is detached, the closing piston unit is suspended on it, even though it is loose. 
     The rear injector head, the rear injector tube section, and the injector cap in this case comprise a structural whole, which can be easily replaced as a unit. In this case, it is advantageous that a subsequently produced identification number is practically always allocated to this unit. 
     It is also advantageous that the filling injector has a power supply for operating the sensor and the counting device. 
     The power supply can also advantageously be a battery and/or an electromagnetic induction unit that converts a part of the movement energy of the closing piston unit into electrical energy. 
     It is also advantageous if the filling injector has a data interface for transmitting a counter reading. 
     The data interface advantageously has a radio interface for contactless transmission of a counter reading or is embodied as such an interface. 
     In another advantageous embodiment, the filling injector has a display device for displaying one or more operating states, which correspond for example to a predetermined counter reading of the counting device or a predetermined state of a power supply. 
     It is advantageous if the predetermined position of the closing piston unit is the open position in which the closing piston unit is preferably maximally retracted. 
     It is also advantageous if the closing piston unit is provided with a magnet element and the sensor for detecting the predetermined position is a magnet sensor. 
     It is advantageous if the injector housing is provided with a contact sensor that detects the predetermined position of the closing piston unit by contacting the closing piston unit. 
     The counting device can advantageously be embodied to count multiple counter readings, with at least part of the counter readings being resettable. 
     The counting device can also be advantageously coupled to an identification device, which contains an identification code. 
     According to the invention, the maintenance of the filling injectors should be simplified so that a higher reliability of the machines is achieved. In addition, improper manipulations and also the use of counterfeit parts or other unsuitable replacement parts or the replacement of parts that have already worn too far should be prevented. 
     Consequently, the overall objective is a so-called “preventive maintenance,” which means that in order to prevent excessive wear, parts are replaced at fixed intervals such as every week, which does incur high costs, but should prevent replacements from being made too late or incorrectly and thus on the one hand reducing quality and on the other, possibly resulting in failures at inopportune times. This approach improves predictability so that the maintenance can be scheduled at convenient times, e.g. during mold replacement or a production stop due to vacation or during weekend hours. Up to this point, it was not possible to know exactly when filling injectors required maintenance. 
     The steps according to the invention can also prevent counterfeit parts or pirated copies from being used, which can damage the entire machine when they fail, without providing any information about this to the machine manufacturer. 
     Consequently, as one measure of the invention, each expendable part of the filling injector is provided with an ID. Such an ID includes, for example, the production date, the model, and possibly other things in a coded form. 
     Since additional electrical lines leading to the filling injector are rejected on the market, a contact transmitter and contact receiver are provided in or on the filling injector. For example, the device can be a solenoid switch device or the like. In particular, it can be a magnet as the contact transmitter and an induction coil, Hall sensor, or reed contact as the contact receiver. 
     By means of these, the cycles are counted in a contactless and autonomous fashion. Alternatively, cycles can be counted with existing end contacts. But this entails a significant wiring cost; in this case, the measurement is carried out in a machine-specific way, but not in a filling injector-specific way. This is not preferable since when a filling injector is replaced, the cycles of another filling injector are also detected at the same time. 
     Preferably, a counting device is used, which functions autonomously, with the power supply being connected to the filling injector itself. Consequently, according to the invention, a battery can be used for this or for example the piston movement can be used to produce electrical energy by means of an induction coil. There are also other possibilities for energy harvesting in filling injectors. 
     According to the invention, a printed circuit board is provided, which is positioned on the filling injector so that it cannot be replaced or manipulated from the outside. This printed circuit board has an antenna, an RFID chip, and a microcontroller. With an RFID reader, data can be retrieved contactlessly, with the possibility, after maintenance or repair work by authorized repair personnel at the maintenance facility, of resetting the counter, in particular resetting it to zero. In this case, it is advantageous if it is not the overall counter reading that is set to zero, but rather only the number cycles since the last maintenance. By means of coding in the RFID connection between the chip and the reader, it is also possible to determine if unauthorized attempts have been made to access the printed circuit board or the data on the printed circuit board. 
     According to the invention, an optical display can be provided, which displays the status of the battery, the functionality of the electronics, and/or the maintenance status. In the simplest case, the optical display can, for example, be an LED display, which is on or off and/or flashes at certain intervals and/or lights up in different colors as a function of particular operating states. 
     Preferably, the device is positioned on the filling injector so that it cannot be nondestructively removed or opened. For example, the printed circuit board, the antenna, and other sensor parts such as magnet parts can be encapsulated in the corresponding component; the battery can also be encapsulated. Particularly if the battery has a service life that is longer than a maintenance interval for replacement of the corresponding part of the filling injector in which the battery is embedded. 
     In addition, however, the battery can also be accessible from the outside; in this case, a cover for the battery either cannot be nondestructively opened or a lead seal is provided, which is damaged during opening. It is therefore preferable if the printed circuit board is not a component of such a cover and always remains in the filling injector. Preferably, stored values are not lost during the battery change, but are instead written to a memory in such a way that they persist. In an advantageous embodiment, the cover has a frosted glass screen behind which at least one light-emitting diode or another lighting device is provided. When the light-emitting diode lights up, this illuminates the entire cover, which makes it easier for the machine operator to see this on the machine since the surface is larger. 
     If the device is positioned in the cylinder cap of the filling injector, then the cylinder cap includes the cylinder cap housing, the cover, the battery, and the printed circuit board; the printed circuit board includes all of the electronic components such as the reed contact, the RFID controller, the battery holder, LEDs, the coil serving as an antenna, and sealing rings. Depending on the power supply, i.e. on whether it is supplied by battery or by energy harvesting, the device is consequently designed so that it also has more or fewer LEDs or even no LEDs. 
     The cylinder cap in this case is the component on which the air connection of the cylinder for the closing movement is positioned. The air connection for actuating the cylinder in the opening direction is positioned on the upper part of the injector head. The basic function of the cylinder cap is to close the cylinder and to supply compressed air. With the invention, the cylinder cap is turned into another functional component. 
     With energy harvesting, an additional coil is preferably arranged around the cylinder; the magnet, which is positioned on the piston, is moved by means of the coil. By means of this, electrical energy can be produced, which can be used to operate the electronics. A short-term buffer, such as a capacitor, is advantageous in this case and is primarily important for LEDs since a one-time energy pulse is sufficient for the counting. 
     The invention also relates to a method for operating an above-explained filling injector; when a predetermined number of detection positions is reached, a maintenance signal is emitted. 
     Through the automatic counting and emission of the maintenance signal, the prophylactic replacement of parts of the filling injector that is usually performed in the prior art can be avoided if it is not needed. Through this counting of the detection positions, it is possible for maintenance intervals to be kept in accordance with the actual use of the filling injector. 
     The maintenance signal can be emitted as a light signal by means of a lighting device such as a light-emitting diode that is integrated into the filling injector and/or by means of a radio signal. The radio signal can be produced, for example, by means of an RFID chip. 
     Alternatively or in addition, other functional states of the filling injector can be emitted by means of a corresponding signal (light signal or radio signal), for example indicating the charge state of a battery and/or the functionality or operating state of electronics contained in the filling injector. 
     Preferably, an overall counter reading counts the number of detection positions that can be read by means of the data interface. 
     The method is preferably embodied so that the overall counter reading can never be reset. In addition, a cycle counter reading is provided with which a maintenance cycle can be monitored. This cycle counter reading can be reset to  0  each time maintenance is performed. 
     Preferably, a radio interface, in particular an RFID radio interface, is used as the data interface. 
    
    
     
       The invention will be explained by way of example based on the drawings. 
       In the drawings: 
         FIG. 1  schematically depicts a filling injector in a perspective, partially disassembled view; 
         FIG. 2  shows a detail according to  FIG. 1 , showing an injector head; 
         FIG. 3  is a perspective view of an injector cap and the adjoining tube; 
         FIG. 4  is a partial cut-away perspective view of the cylinder cap according to  FIG. 3 ; 
         FIG. 5  shows a sectional view of the cylinder cap according to  FIG. 4  with a magnet ring to be positioned on the piston. 
     
    
    
     A filling injector  1  for a mold according to the invention has an injector housing  2 , which has a cylindrical cavity  6  in which a closing piston unit  3  is positioned and supported in an axially movable fashion. 
     The injector housing  2  has a supply  4  for foam granules leading to the cavity  6 . 
     At an end of the cylindrical cavity  6  oriented toward the mold, the filling injector  1  has a mold opening  5  for supplying the plastic material to a mold. 
     In an intrinsically known way, in a closed position, the closing piston unit  3  is slid so far forward that it closes the mold opening  5  and in an open position, is retracted from the cylindrical cavity  6  at least in the region between the supply  4  and the mold opening  5 . 
     The injector housing  2  is composed of an injector tube  6  and an injector cap  7 . The injector cap  7  closes the injector tube  6  at the end  9  remote from the mold opening  5  or the end  9  diametrically opposite from the mold opening  5  in the axial direction. 
     The injector tube  6  in this case is composed of a front injector tube section  6   a,  which has the mold opening  5 , and a rear injector tube section  6   b,  which has the injector cap  7 . 
     The tube section  6   a  in this case is particularly embodied as significantly longer axially than the rear injector tube section  6   b.    
     Between the front injector tube section  6   a  and the rear injector tube section  6   b,  an injector head  10  is provided to connect the two tube sections  6   a,    6   b.  The injector head  10  has a front injector head  10   a  and a rear injector head  10   b;  the front injector head  10   a  is embodied on the front injector tube section  6   a  and the rear injector head  10   b  is embodied on the rear injector tube section  6   b.    
     The front injector head  10   a  and the rear injector head  10   b  can be detachably connected to each other, as a result of which, the front injector tube section  6   a  and the rear injector tube section  6   b  can also be detachably connected to each other. 
     The front injector head  10   a  and/or the rear injector head  10   b  each have an air connection  11 ,  12 . 
     The injector cap  7  likewise has an air connection  13 , which is embodied so that air can be conveyed through the injector cap  7  into the rear injector tube section  6   b.    
     The closing piston unit  3  has an actuating piston  14  positioned in the rear injector tube section  6   b,  with the actuating piston  14  being positioned at an end that closes the mold opening  5 . 
     Preferably, the closing piston unit  3 , particularly by means of the actuating piston  14 , is coupled to or positioned on the rear injector tube section  6   b  and/or the rear injector head  10   b  in captive fashion. 
     This means that when the rear injector tube section  6   b  is detached, the closing piston unit  3  remains coupled to it; the coupling can even be loose. It is essential that the closing piston unit, the rear injector tube section  6   b,  and the injector cap  7  form a structural whole and can be simply replaced as a unit. In particular, this assembly has one identification number, which is assigned to this unit in order to prevent arbitrary replacement of the individual elements. 
     On the injector housing  2  or in the injector housing  2 , a sensor  8  is provided to detect a predetermined detection position of the closing piston unit  3  and a counting device is provided for counting the number of detection positions of the closing piston unit  3 . It is thus possible to particularly determine what position the closing piston unit  3  is in or how often it has been situated in the detection position. 
     In principle, the detection position can be located at any point on the injector housing. For example, the detection position can be on the mold opening, on or in the tube section  6   a,  in the front injector head  10   a,  in the rear injector head  10   b,  in the rear injector tube section  6   b,  or on the injector cap  7 . In this connection, it should be noted that with the measurement of end stops, i.e. with the measurement at the mold opening or at the injector cap, detection positions are detected that are reached only one time per working stroke. 
     At the other places, the detection position is then selected so that each stroke, i.e. both the forward stroke and the return stroke of the device, is counted. This must be noted. 
     The sensor  8  therefore can be positioned on or in the mold opening  5 , on or in the tube section  6   a,  in the front injector head  10   a,  in the rear injector head  10   b,  in the rear injector tube section  6   b,  or on or in the injector cap  7 . 
     The filling injector can have a power supply  15  for the operation of the sensor  8  and/or a provided counter device. This insures that the filling injector is autonomous relative to the sensor and the counting procedure. 
     In this case, the power supply can be a battery  15  and/or an electromagnetic induction unit. 
     If an electromagnetic induction unit is used, this can convert a part of the movement energy of the closing piston unit  3  into electrical energy, e.g. by means of an inductor. 
     Preferably, storage elements are provided for storing the energy that is produced, for example, by induction; in particular, a capacitor can be used in a known way for this. 
     In an advantageous embodiment of the invention ( FIG. 2 ), the front injector head  10   a  and the rear injector head  10   b  are tube sections that can be axially inserted into each other; a circumferentially extending radial locking groove  20  is provided on one of the injector heads. 
     On the respective other injector head  10   a,    10   b,  a corresponding groove  21  is provided, which, in the fully slid-together or inserted state of the injector heads  10   a,    10   b,  is flush with the groove  20 . A locking clamp  22  can be inserted into the groove  21  and extends through both the grooves  21  and the groove  20  and thus ensures an axial locking of the injector heads  10   a,    10   b  relative to each other. 
     Preferably, at least one centering wedge  23  is provided on the injector head that is inserted into the respective other injector head (the injector head that has the smaller diameter in the insertion region), which centering wedge is embodied so that it is able to engage in a corresponding centering groove  24  on the respective other injector head so that the two injector heads  10   a,    10   b  are affixed relative to each other. 
     In addition, the tube connection between the two injector heads  10   a,    10   b  naturally has seals, which are in particular embodied as O-ring seals or as Dilag seals and guides. 
     In an advantageous embodiment, the sensor and counting device are embodied on the injector cap  7  ( FIGS. 4 &amp; 5 ). 
     To this end, the injector cap  7  is embodied as essentially cylindrical and has a cylindrical compressed air connection  13  coming from an outside  25 ; the cylindrical compressed air connection  13  does not have to be embodied as coaxial. 
     A printed circuit board  27  is positioned between the compressed air connection  13  and a radial outer wall  26 . 
     In particular, an RFID chip and a microcontroller are positioned on the printed circuit board. In addition, the printed circuit board can be provided with a reed contact or Hall sensor that interacts with the magnet ring or other suitable contact transmitters, in order to detect the position and/or the number of positions of the closing piston unit  3 . 
     Preferably, the power supply, particularly the power supply in the form of a battery  15 , is provided adjacent to the printed circuit board  27 . 
     The display  17  is also provided in this region; the display  17  can particularly be embodied in the form of an LED or a plurality of LEDs, which flashes and in particular, flashes with a predetermined color in order to indicate a particular state of the battery and/or the maintenance or another desired parameter. 
     An interface for transmitting the counter reading and in particular a coil or antenna  16  can be arranged around the compressed air connection  13 ; the antenna  16 , the tray  28  for the battery, and the space for the printed circuit board  27  and LEDs  17  are covered by a cover  29 . 
     In order to make the interior visible, the cover  29  can in particular be embodied as transparent or as partially opaque. 
     The cover  29  is positioned on the injector cap  7  particularly so that it can be removed only by causing damage or by damaging a lead seal or the like so that manipulations of the interior are visible and in particular, only maintenance personnel can legitimately replace a damaged cover or a damaged lead seal. 
     In order to rule out the possibility of manipulations of the printed circuit board  27 , the printed circuit board  27  can be embodied of one piece with the injector cap  7  and in particular, can be encapsulated in or cast into the injector cap  7 . 
     If an energy storage device in the form of a battery is eliminated and the energy is provided by means of energy harvesting, then the energy production for example by means of induction can advantageously be used directly for the counting so that an induction coil that detects the movement of the closing piston  3  is simultaneously the sensor  8 . 
     REFERENCE NUMERALS 
       1  filling injector 
       2  injector housing 
       3  closing piston unit 
       4  supply 
       5  mold opening 
       6  cavity 
       7  injector cap 
       8  sensor 
       9  end 
       10   a  injector head 
       10   b  injector head 
       11  air connection 
       12  air connection 
       13  compressed air connection 
       14  actuating piston 
       15  power supply 
       16  data interface 
       17  display 
       18  magnet element 
       20  locking groove 
       21  groove 
       22  locking clamp 
       23  centering wedge 
       24  centering groove 
       25  outside 
       26  outer wall 
       27  printed circuit board 
       28  tray 
       29  cover 
       30  drive element