Patent Publication Number: US-2023152144-A1

Title: Weighing and transporting device and method for transporting and detecting mass flow rates of bulk materials

Description:
PRIORITY CLAIM 
     This application claims to German Patent Application No. DE 10 2021 129 497.5, filed Nov. 12, 2021, which is expressly incorporated by reference herein. 
     BACKGROUND 
     The present disclosure relates to a weighing and transporting devices and a method for transporting and detecting mass flow rates of bulk material. 
     SUMMARY 
     According to the present disclosure, a weighing container enclosing a weighing container volume is closable at its upper inlet and lower outlet. At the upper end of the so closable weighing container the vacuum connection and the material suction coupling are connected. In the filling cycles the air stream with bulk material is fed, with the weighing container volume closed, directly to the weighing container volume. Thus, the weighing container itself is also used as receiving container or receptacle respectively (or “separator”) for receiving the transported air stream with the bulk material. 
     To initiate a filling cycle the weighing container is closed at its upper inlet and lower outlet. Thereafter, in the filling cycle, the weighing container is filled with the bulk material up to a point where a suitable filling level is reached. Subsequently, the filling cycle is terminated and the weighing cycle is initiated. To initiate the weighing cycle the lower outlet and the upper inlet are opened so that the weighing container can subsequently discharge the contained bulk material continuously downwards, where it will be discharged via the impact means to a collecting hopper and from this to the transport region, e.g., directly to a barrel extruder or an upstream screw conveyor. 
     Thus, the weighing and transport device is small in size, in particular, in the vertical direction significantly smaller than comparative systems in which a storage container and suction conveyor system are mounted above the weighing device. The vacuum conveyor, which may be formed in the upper region, with a receiving container or material separator container respectively is combined functionally or integrated respectively with the downstream storage container and weighing container. This makes it possible to use it even in confined spaces, e.g., next to the extruder, so that a short feeding path to the extruder is made possible thereby providing a precise determination of mass throughput. 
     Moreover, a rapid change of materials is made possible because it is only the weighing container with downstream collecting hopper that is being filled. While, comparatively, the filled material separator container, storage container, and weighing container is emptied first, according to the present disclosure, it is possible to directly empty the weighing container with the collecting hopper and, e.g., another material can be fed in. This also allows, e.g., for a quicker change of colors, i.e., a change of the fed-in dye. Thus, corrections, e.g., in coloring can be carried out faster. This allows for a high degree of flexibility both in positioning as well as in material throughput. 
     Moreover, the technical equipment is smaller due to the omission of additional stages. 
     For closing the upper inlet and the lower outlet of the weighing container an actuator is provided. In principle, the actuator may be designed multi-piece and close the upper inlet using one actuator means and the lower outlet using a further actuator means. The actuator initially causes a relative adjustment, whereby, in particular, one closing means each may be adjusted at the top and/or at the bottom, and/or the weighing container may be adjusted upwards and/or downwards in relation to the closing means. Thus, it is possible, e.g., to also adjust the weighing container downwards so as to block the lower outlet. 
     According to one embodiment, a closing means is moved from below against the lower outlet, and then the weighing container with the closing means is adjusted upwards. 
     In illustrative embodiments, the impact means, e.g., an impact cone, is moved directly vertically against the lower outlet of the weighing container so that no additional closing means should be employed here. Thus, it is possible, in particular, to also use the actuator for this adjustment which anyway serves for adjusting an outlet gap between the lower outlet and the impact means and thereby, e.g., for adjusting for differing material shapes and sizes, e.g., granulate, flakes etc. 
     According to one embodiment, the weighing container is moved directly vertically upwards against a seal, in particular, a casket at an upper support means, thereby closing its upper inlet in a sealing manner. 
     According to one embodiment, the actuator of the impact means causes a common adjustment both of the impact means against the lower outlet and the weighing container upwards against the upper abutment at the support means. Hereby, in particular, a consistent adjustment motion of the actuator can be carried out, which initially moves the impact means against the lower outlet and subsequently presses the impact means with the material container upwards against the support means. Thus, only the common actuator, e.g., a pneumatic actuating cylinder, needs to be triggered to adjust into the filling position. Thus, s quick and secure adjustment is made possible at little additional expense, in particular, by means of the actuator use anyway to adjust the outlet gap. 
     The actuator actuates a drawbar which is guided from above through the support means vertically through the weighing container to the impact means, thus initially pressing the impact means against the lower outlet and subsequently taking along the weighing container. 
     As measuring signals, for one thing, a measuring force of weighing cells is detected whose temporal changes can be evaluated such as material throughput during the weighing cycle. To that end, the measuring cells housed at the support means may directly weigh the material container. Further, the measuring signal of a filling level sensor is detected which is formed, in particular, at the underside of the support means thereby detecting the filling level in the weighing container from above. Thus, both measuring means, the weighing cells and the level sensor, can be housed directly at the support means, e.g., a support plate, whereby the actuator too may be affixed to the support means. This allows for a simple and common assembly and contacting of both the actuator and the measuring means, in particular, without the spatial separation in some installations. In the weighing cycle the support means is spatially de-coupled to a large extent from the weighing container so that there is no interference affecting the measuring signals. 
     The level sensor may be designed in different ways. It may measure the distance of the bulk material to the sensor as a distance meter, e.g., as an optical distance meter, e.g., laser, or based on radar, in particular, radar distance meter, e.g., as direct or indirect time-of-flight measurement, and/or as ultrasound distance meter. 
     Some embodiments of the filling level sensor are a capacitive and/or inductive design, in particular, by determining changes of a capacity depending on the filling level or, respectively, inductively by measuring an inductivity which changes as a function of the filling level. A capacitive or inductive level sensor may also reliably detect from above, in particular, the bulk material lying below it even in the event of turbulence in the air stream, whereby these sensors can still be designed cost-efficiently and do not easily get dirty by the filling material. According to the present disclosure, preferably, such capacitive or inductive sensors may be affixed to the upper support plate and directed downwards, something that is not yet possible in this manner with the above-mentioned comparative systems with laterally provided sensors. 
     The controlling and detecting of the measuring signals as well as the initiation of the cycles is carried out by means of a controller means which detects the measured value of the filling level in the filling cycle and terminates the filling cycle upon reaching a threshold value of the filling level by closing a vacuum valve and triggering the actuator to open the weighing container at the top and at the bottom, thereby initiating the weighing cycle. 
     In the weighing cycle the measuring force signal is detected and evaluated. When the measuring force signal reaches a lower minimum value an empty weighing container is detected and the weighing cycle is terminated in that the weighing container is closed. The next filling cycle commences by subsequent opening of the vacuum valve. 
     According to one embodiment, the impact means is realized as an impact cone. 
     According to one embodiment, the impact means closes the lower outlet in an airtight manner. 
     According to a preferred embodiment, the actuator is a pneumatic actuating cylinder. 
     According to one embodiment, the upper guides are provided in the area of receptacles of weighing cells. 
     According to one embodiment, the level sensor is designed in accordance with one or more of the following embodiments: 
     capacitive, in particular, by determining changes in a capacitance depending on the filling level,
         inductive, in particular, by measuring an inductance that changes depending on the filling level,   as an optical distance meter, e.g., laser,   as a radar, in particular, radar distance meter, e.g., as direct or indirect time-of-flight measurement,   as an ultrasound distance meter.       

     According to one embodiment, the method comprises the steps an upwards adjustment of the impact means is carried out in a first partial motion of an actuator and, subsequently, the upwards adjustment of the weighing container is carried out in a second partial motion of the same actuator, in particular, in a continuous motion. 
     According to one embodiment, the bulk material is selected from the group consisting of plastic pellets, plastic granulate, and plastic flakes. 
     According to one embodiment, the bulk material is selected from the group comprising plastic pellets, plastic granulate, and plastic flakes. 
     Additional features of the present disclosure will become apparent to those skilled in the art upon consideration of illustrative embodiments exemplifying the best mode of carrying out the disclosure as presently perceived. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
       The detailed description particularly refers to the accompanying figures in which: 
         FIG.  1    shows a weighing and transporting device according to an embodiment of the present disclosure in a weighing cycle; 
         FIG.  2    shows the weighing and transporting device from  FIG.  1    at section A-A; 
         FIG.  3    shows weighing and transporting device from  FIGS.  1 ,  2    in a filling cycle; 
         FIG.  4    shows the weighing and transporting device from  FIG.  3    at section B-B; 
         FIG.  5    shows is a time diagram of the successive cycles; and 
         FIG.  6    shows a comparative weighing and transporting device. 
     
    
    
     DETAILED DESCRIPTION 
     Weighing and transporting devices of this type serve, in particular, to draw in granulated bulk material, e.g., plastic granulate or plastic pellets, determine the mass flow rate and discharge the bulk material continuously towards a downstream transport region of a production machine. The transport region of the production machine transports received bulk material continuously, e.g., towards the extruder which subsequently extrudes the plastic product. 
     Hereby, for one thing, a continuous output of the bulk material towards the transport region should be provided, so that there is no interruption in the production process. Moreover, the mass flow rate as masse per time unit should be determined with sufficed accuracy in order to adjust the production parameters with precision. 
     For this purpose, comparative weighing and transporting devices comprise an upper vacuum feeder with a material separator in which a vacuum is created via a vacuum connection so that an air stream with bulk material is fed to the material separator via a material suction coupling. The bulk material can become deposited in the material separator and is fed downwards to a storage container. Hereby a level sensor is provided in the material separator which measures the filling level so that the vacuum transport is terminated when a filling level threshold is reached. This causes the vacuum in the material separator to collapse so that an outlet flap kept closed by the vacuum opens by virtue of the weight of the bulk material resting on top of it. Subsequently, the bulk material is discharged into the storage container and from there via, e.g., a spiral hose downwards to a weighing means with a weighing container. In the weighing means the weight of the weighing container with the bulk material contained therein is continuously measured thereby determining the mass flow rate as mass per time unit. 
     This results in an accordingly high build caused by the vacuum feeder, the downstream storage container, and the weighing means with the weighing container. In come production facilities, however, the space available is at a premium so that it may be a problem to position the weighing and transport device. Thus, when the available space is small, a continuous gravimetry may possibly not be use. However, it is generally viewed as problematic to position the weighing and transport device at a greater distance from the production machine because, when there are longer transport regions to the production machine, the measuring accuracy is reduced and re-segregations of the mixed material may occur. 
     The present disclosure is based on the object of creating a weighing and transport device and a method for transporting and detecting mass flow rates of bulk material allowing for vacuum conveying as well as a precise weighing of the bulk material. 
     This task is solved by a weighing and transport device and a method according to the independent claims. The sub-claims specify preferred further developments. The method according to the present disclosure may be carried out, in particular, using a weighing and transport device according to the present disclosure. 
     Thus, according to the present disclosure, a weighing container enclosing a weighing container volume is closable at its upper inlet and lower outlet. At the upper end of the so closable weighing container the vacuum connection and the material suction coupling are connected. In the filling cycles the air stream with bulk material is fed, with the weighing container volume closed, directly to the weighing container volume. Thus, the weighing container itself is also used as receiving container or receptacle respectively (or “separator”) for receiving the transported air stream with the bulk material. 
     To initiate a filling cycle the weighing container is closed at its upper inlet and lower outlet. Thereafter, in the filling cycle, the weighing container is filled with the bulk material up to a point where a suitable filling level is reached. Subsequently, the filling cycle is terminated and the weighing cycle is initiated. To initiate the weighing cycle the lower outlet and the upper inlet are opened so that the weighing container can subsequently discharge the contained bulk material continuously downwards, where it will be discharged via the impact means to a collecting hopper and from this to the transport region, e.g., directly to a barrel extruder or an upstream screw conveyor. 
     Thus, using the present disclosure, a few advantages are attained: 
     Thus, the weighing and transport device is small in size, in particular, in the vertical direction significantly smaller than comparative systems in which a storage container and suction conveyor system are mounted above the weighing device. The vacuum conveyor, which may be formed in the upper region, with a receiving container or material separator container respectively is combined functionally or integrated respectively with the downstream storage container and weighing container. This makes it possible to use it even in confined spaces, e.g., next to the extruder, so that a short feeding path to the extruder is made possible thereby providing a precise determination of mass throughput. 
     Moreover, a rapid change of materials is made possible because it is only the weighing container with downstream collecting hopper that is being filled. While, comparatively, the filled material separator container, storage container, and weighing container should be emptied first, according to the present disclosure, it is possible to directly empty the weighing container with the collecting hopper and, e.g., another material can be fed in. This also allows, e.g., for a quicker change of colors, i.e., a change of the fed-in dye. Thus, corrections, e.g., in coloring can be carried out faster. This allows for a high degree of flexibility both in positioning as well as in material throughput. 
     Moreover, the technical equipment is smaller due to the omission of additional stages. 
     For closing the upper inlet and the lower outlet of the weighing container an actuator is provided. In principle, the actuator may be designed multi-piece and close the upper inlet using one actuator means and the lower outlet using a further actuator means. The actuator initially causes a relative adjustment, whereby, in particular, one closing means each may be adjusted at the top and/or at the bottom, and/or the weighing container may be adjusted upwards and/or downwards in relation to the closing means. Thus, it is possible, e.g., to also adjust the weighing container downwards so as to block the lower outlet. 
     According to a preferred embodiment, a closing means is moved from below against the lower outlet, and then the weighing container with the closing means is adjusted upwards. 
     According to an advantageous further development, the impact means, e.g., an impact cone, is moved directly vertically against the lower outlet of the weighing container so that no additional closing means should be employed here. Thus, it is possible, in particular, to also use the actuator for this adjustment which anyway serves for adjusting an outlet gap between the lower outlet and the impact means and thereby, e.g., for adjusting for differing material shapes and sizes, e.g., granulate, flakes etc. 
     According to a preferred embodiment, the weighing container is moved directly vertically upwards against a seal, in particular, a casket at an upper support means, thereby closing its upper inlet in a sealing manner. 
     According to a particularly preferred embodiment, the actuator of the impact means causes a common adjustment both of the impact means against the lower outlet and the weighing container upwards against the upper abutment at the support means. Hereby, in particular, a consistent adjustment motion of the actuator can be carried out, which initially moves the impact means against the lower outlet and subsequently presses the impact means with the material container upwards against the support means. Thus, only the common actuator, e.g., a pneumatic actuating cylinder, needs to be triggered to adjust into the filling position. Thus, quick and secure adjustment is made possible at little additional expense, in particular, by means of the actuator used anyway to adjust the outlet gap. 
     The actuator preferably actuates a drawbar which is guided from above through the support means vertically through the weighing container to the impact means, thus initially pressing the impact means against the lower outlet and subsequently taking along the weighing container. 
     As measuring signals, for one thing, a measuring force of weighing cells is detected whose temporal changes can be evaluated as material throughput during the weighing cycle. To that end, the measuring cells housed at the support means may directly weigh the material container. Further, the measuring signal of a filling level sensor is detected which is formed, in particular, at the underside of the support means thereby detecting the filling level in the weighing container from above. Thus, both measuring means, the weighing cells and the level sensor, can be housed directly at the support means, e.g., a support plate, whereby the actuator too may be affixed to the support means. This allows for a simple and common assembly and contacting of both the actuator and the measuring means, in particular, without the spatial separation in comparative installations. In the weighing cycle the support means is spatially de-coupled to a large extent from the weighing container so that there is no interference affecting the measuring signals. 
     The level sensor may be designed in different ways: thus, it may measure the distance of the bulk material to the sensor as a distance meter, e.g., as an optical distance meter, e.g., laser, or based on radar, in particular, radar distance meter, e.g., as direct or indirect time-of-flight measurement, and/or as ultrasound distance meter. 
     Particularly preferred embodiments of the filling level sensor are a capacitive and/or inductive design, in particular, by determining changes of a capacity depending on the filling level or, respectively, inductively by measuring an inductivity which changes as a function of the filling level. A capacitive or inductive level sensor may also reliably detect from above, in particular, the bulk material lying below it even in the event of turbulence in the air stream, whereby these sensors can still be designed cost-efficiently and do not easily get dirty by the filling material. According to the present disclosure, preferably, such capacitive or inductive sensors may be affixed to the upper support plate and directed downwards, something that is not yet possible in this manner with the above-mentioned comparative systems with laterally provided sensors. 
     The controlling and detecting of the measuring signals as well as the initiation of the cycles is carried out by means of a controller means which detects the measured value of the filling level in the filling cycle and terminates the filling cycle upon reaching a threshold value of the filling level by closing a vacuum valve and triggering the actuator to open the weighing container at the top and at the bottom, thereby initiating the weighing cycle. 
     In the weighing cycle the measuring force signal is detected and evaluated. When the measuring force signal reaches a lower minimum value an empty weighing container is detected and the weighing cycle is terminated in that the weighing container is closed. The next filling cycle commences by subsequent opening of the vacuum valve. 
     According to a preferred embodiment, the impact means is realized as an impact cone. 
     According to a preferred embodiment, the impact means closes the lower outlet in an airtight manner. 
     According to a preferred embodiment, the actuator is a pneumatic actuating cylinder. 
     According to a preferred embodiment, the upper guides are provided in the area of receptacles of weighing cells. 
     According to a preferred embodiment, the level sensor is designed in accordance with one or more of the following embodiments: 
     capacitive, in particular, by determining changes in a capacitance depending on the filling level,
         inductive, in particular, by measuring an inductance that changes depending on the filling level,   as an optical distance meter, e.g., laser,   as a radar, in particular, radar distance meter, e.g., as direct or indirect time-of-flight measurement,   as an ultrasound distance meter.       

     According to a preferred embodiment, the method comprises the steps an upwards adjustment of the impact means is carried out in a first partial motion of an actuator and, subsequently, the upwards adjustment of the weighing container is carried out in a second partial motion of the same actuator, in particular, in a continuous motion. 
     According to a preferred embodiment, the bulk material is selected from the group consisting of plastic pellets, plastic granulate, and plastic flakes. 
     According to a preferred embodiment, the bulk material is selected from the group comprising plastic pellets, plastic granulate, plastic flakes, and combinations thereof.