Patent Publication Number: US-2010107434-A1

Title: Drying hopper

Description:
TECHNICAL FIELD  
     The present invention relates to a drying hopper, and particularly relates to a drying hopper which is used for dehumidification drying of resin materials for use with an injection molding machine, or the like. 
     BACKGROUND ART  
     Conventionally, resin materials for use with an injection molding machine, or the like are dehumidification-dried in a drying hopper before being supplied to a injection molding machine, or the like, for injection molding thereof 
     Hereinbelow, the schematic configuration of an example of conventional art pertaining to this type of drying hopper will be explained with reference to an accompanying drawing  FIG. 3 . 
     As shown in the same drawing, a drying hopper  30  is comprised of a hopper main body  33  which is tower-shaped (cylindrical or square tube-shaped), having a material charging port  31  at a top portion thereof and a material discharging port  32  at a bottom portion thereof; a material dispersion element  34  which is disposed within this hopper main body  33  for dispersing granular resin materials P, such as polycarbonate resin materials, or the like, dropped from the material charging port  31  within the hopper main body  33  to cause them to fall down toward the material discharging port  32 , being formed of a mesh material capable of air ventilation into a pyramid (for example, an octahedron produced by vertically symmetrically jointing two rectangular pyramids to each other); a dry air supply tube  35  which is disposed ranging from the top portion of the hopper main body  33  to a top portion of the material dispersion element  34  for feeding heated dry air having a low dew-point temperature from a dehumidification drying machine (not shown) into the material dispersion element  34 ; and a dry air returning port  36  which is provided at the top portion of the hopper main body  33 . 
     The dry air which has been fed into the material dispersion element  34  is passed through a mesh portion of this material dispersion element  34 , being contacted with a number of resin materials P dispersed while being dropped within the hopper main body  33  for absorbing the moisture contained in the resin materials P while being passed through between resin materials P, before being returned from the dry air returning port  36  to a dehumidification drying machine (not shown). 
     The above-stated conventional drying hopper  30  is configured such that the dry air discharged from the material dispersion element  34  in the hopper main body  33  absorbs the moisture in the resin materials P before being returned from the dry air returning port  36  to the dehumidification drying machine. 
     However, the period of time during which the dry air is contacted with the resin materials P is so short that the resin materials P cannot be sufficiently dried, and thus there have been problems that the dry air which has not yet used up its moisture absorption capacity is discharged as it is, the resin materials P is required to be dried once again, part of the moisture absorption capacity of the dry air is wasted, and the like. 
     In the patent document 1, there is proposed a drying apparatus having a hopper comprised of a right circular cylinder-shaped first cylindrical part in the upper section thereof; a tapered cylindrical part which is connected to a bottom part of the first cylindrical part, being gradually tapered downward; and a right circular cylinder-shaped second cylindrical part which is connected to a bottom portion of the tapered cylindrical part, and a bottom portion of which is formed in the shape of an inverted cone, being provided with a hot blast supply tube for supplying hot blast for the inverted cone-shaped portion of the hopper, a first cold blast supply tube and a second blast supply tube for supplying cold blast for the hopper, and the like. 
     The drying apparatus of this patent document 1 has been of a complicated construction as a whole, requiring, in addition to the hopper itself with a complicated construction, accessory elements, including the hot blast supply tube, the first cold blast supply tube, the second cold blast supply tube. 
     [Patent Document 1] Japanese Patent Laid-Open Publication No. 2001-294294 
     DESCRIPTION OF THE INVENTION  
     Problems to be Solved by the Invention  
     The problems to be solved by the present invention lie in the fact that no drying hoppers are available which have a simplified construction of the hopper itself, and allows the absorption capacity of the dry air to be effectively utilized for improved drying efficiency with the time for drying the resin materials being shortened. 
     Means for Solving the Problems  
     The drying hopper pertaining to the present invention provides, as a most important feature, that it comprises: 
     a tube-shaped hopper main body having a material charging port at a top portion thereof and a material discharging port at a bottom portion thereof; 
     hopper parts arranged in a plurality of stages in this order at intervals from top to bottom within this hopper main body, each being formed substantially in the shape of an inverted cone, and through which dry air is capable of being ventilated, and granular resin materials are capable of being passed; 
     material dispersion elements arranged in a plurality of stages for dispersing the granular resin materials that are each disposed under the material charging port, and above the top surface of the respective hopper parts arranged in a plurality of stages; and 
     a dry air supply/discharge system which forms a dry air ventilation path running from the bottom portion of the hopper main body to above the material dispersion element at the uppermost stage through the hopper parts arranged in a plurality of stages and leading to the outside of the hopper main body, 
     the counter-flow contact over a plurality of stages of a number of granular resin materials dispersed and dropped in the hopper main body with the dry air causing the moisture contained in the granular resin materials to be absorbed and removed by the dry air before the number of granular resin materials are discharged from the material discharging port. 
     Advantages of the Invention  
     According to the invention stated in claim  1 , a counter-flow contact over a plurality of stages of a number of granular resin materials with dry air within the hopper main body for a long period of time as compared to that attainable under the conventional art allows the moisture contained in the number of granular resin materials to be effectively absorbed by the dry air such that the number of granular resin materials are thoroughly dried before being discharged to the outside of the drying hopper to be fed to an injection molding machine, or the like, for being injection molded, simplification of the configuration has been realized, and a high-performance drying hopper which, when comprehensively viewed, contributes to shortening the drying time can be realized and provided. 
     According to the invention stated in claim  2 , on the basis of a simple configuration in which, within the hopper main body, inverted cone-shaped hopper parts are arranged in three stages, and cone-shaped material dispersion elements are arranged in three stages, a drying hopper which offers the same advantages as those of the invention stated in claim  1  can be realized and provided. 
     According to the invention stated in claim  3 , the same advantages as those of the invention stated in claim  2  are offered; in addition, the air flow rate for the dry air and the dew-point temperature of the same are monitored by the air flow meter and the dew-point hygrometer, respectively, and when the measurement is not suitable, the alarming device gives an alarm, thus a drying hopper which can realize the proper quality control of the resin materials to be fed to an injection molding machine, or the like can be realized and provided. 
     BEST MODE FOR CARRYING OUT THE INVENTION 
     It is an object of the present invention to realize and provide a drying hopper which, with the construction of the hopper itself being simplified, allows the absorption capacity of the dry air to be effectively utilized for improving the drying efficiency and the drying time for the resin materials to be shortened. 
     The drying hopper of the present invention has achieved the above-stated purpose by a scheme comprising a tube-shaped hopper main body having a material charging port at a top portion thereof and a material discharging port at a bottom portion thereof; a first hopper part, a second hopper part and a third hopper part which are arranged in this order at intervals from top to bottom within this hopper main body, each being formed substantially in the shape of an inverted cone, and through which dry air is capable of being ventilated, and granular resin materials are capable of being passed; first to third material dispersion elements for dispersing the granular resin materials that are each disposed under the material charging port, and above the top surface of the respective first to third hopper parts; a dry air supply/discharge system which forms a dry air ventilation path running from the bottom portion of the hopper main body to above the first material dispersion element at the uppermost stage through the third hopper part, the second hopper part, and the first hopper part, and leading to the outside of the hopper main body, the counter-flow contact over three stages of a number of granular resin materials dispersed and dropped over three stages in the hopper main body with the dry air causing the moisture contained in the granular resin materials to be absorbed and removed by the dry air before the number of granular resin materials are discharged from the material discharging port. 
     Embodiment 
     Hereinbelow, a drying hopper pertaining to an embodiment of the present invention will be explained in detail with reference to  FIG. 1  and  FIG. 2 . 
     As shown in  FIG. 1 , a drying hopper  1  pertaining to the present embodiment is comprised of a tower-shaped (for example, cylindrical) hopper main body  2  having a material charging port  3  at a top portion thereof and a material discharging port  4  at a bottom portion thereof; and a first hopper part  5 , a second hopper part  6 , and a third hopper part  7  which are arranged in this order at intervals from top to bottom within this hopper main body  2 , each being formed substantially in the shape of an inverted cone. 
     The first hopper part  5  is formed, as a whole, of a mesh material through which air can be ventilated, and in the central area of a bottom portion of the first hopper part  5 , a cylindrical flow pass tube part  5   a  through which granular resin materials P of, for example, polycarbonate resin, or the like are passed is provided. 
     The second hopper part  6  is formed substantially in the shape of an inverted cone, an inverted cone-shaped inner cone part  6   b  formed of a mesh material through which air can be ventilated being connected to an outer edge part  6   c  formed of a sheet material outside of the inner cone part  6   b , and in the central area of a bottom portion of the second hopper part  6 , a cylindrical flow pass tube part  6   a  through which resin materials P are passed is provided. 
     The third hopper part  7  is formed substantially in the shape of an inverted cone, an inverted cone-shaped inner cone part  7   b  formed of a mesh material through which air can be ventilated being connected to an outer edge part  7   c  formed of a sheet material outside of the inner cone part  7   b , and in the bottom part of the inverted cone-shaped inner cone part  7   b , an opening part  7   a  is provided, being opposed to the material discharging port  4 . 
     And, these members are dimensioned such that the air ventilation area is increased in the order of the mesh regions for the inner cone part  7   b , inner cone part  6   b , and first hopper part  5 . 
     Within the hopper main body  2  in the drying hopper  1  pertaining to the present embodiment, there is disposed above the flow pass tube part  5   a  of the first hopper part  5  and under the material charging port  3  a first material dispersion element  8  contoured in the shape of a circular cone or a pyramid (for example, an octahedron produced by jointing quadrangular pyramids vertically symmetrically) for dispersing the granular resin materials P dropped from the material charging port  3  before they being dropped into the flow pass tube part  5   a.    
     In addition, within the hopper main body  2 , there is disposed between the first hopper part  5  and the second hopper part  6  a second material dispersion element  9  contoured in the shape of a circular cone or a pyramid (for example, an octahedron produced by jointing quadrangular pyramids vertically symmetrically) for dispersing the granular resin materials P dropped before they being dropped into the flow pass tube part  6   a.    
     Further, within the hopper main body  2 , there is disposed between the second hopper part  6  and the third hopper part  7  a third material dispersion element  10  contoured in the shape of a circular cone or a pyramid (for example, substantially a hexahedron) for dispersing the granular resin materials P dropped before they being dropped into the material discharging port  4  through the opening part  7   a.    
     Further, in the drying hopper  1  pertaining to the present embodiment, in the bottom portion of the hopper main body  2 , a dry air supply tube  11  is provided, and at the upper end of the hopper main body  2 , a dry air returning port  12  is provided. 
     To the dry air supply tube  11  are connected an air flow meter  13  for measuring the air flow rate for the dry air, and a dew-point hygrometer  14  for measuring the dew-point temperature (the temperature at which the water vapor contained in the air is started to be changed into water drops). 
     In the area of the dry air returning port  12 , a filter  15  for catching, the powdered matters, and the like, in the dry air is disposed. 
     To the dry air supply tube  11 , the discharge side of a dehumidification drying machine (not shown) for generating dry air (dehumidification air) at a temperature of −30° C. to −45° C. is connected, while, to the dry air returning port  12 , the suction side of the dehumidification drying machine is connected, such that the dry air is circulated. 
       FIG. 2  is a diagram illustrating a control system for the drying hopper  1  pertaining to the present embodiment. This control system has a control unit  17  which takes in data of the air flow rate for the dry air that is measured by the air flow meter  13 , and that of the dew-point temperature measured by the dew-point hygrometer  14 , and an alarming device  16  which is connected to this control unit  17  for issuing a buzzer sound, or the like, the control unit  17  comparing the data of the air flow rate and that of dew-point temperature with the predetermined proper value of air flow rate, and the predetermined proper value of dew-point temperature, respectively, and when the result of the comparison is not suitable, driving the alarming device  16  for giving an alarm. 
     Next, the function and advantages of the drying hopper  1  pertaining to the present embodiment will be described. 
     In the drying hopper  1  pertaining to the present embodiment, a number of granular resin materials P charged from the material charging port  3  into the hopper main body  2  are dispersed by the first material dispersion element  8  along the tapered surface or in all the four directions to be led to the first hopper part  5 , being dropped along the slope thereof, and further being passed through the flow pass tube part  5   a  to be dropped onto the second material dispersion element  9 . 
     Next, the granular resin materials P are dispersed by the second material dispersion element  9  along the tapered surface or in all the four directions to be led to the second hopper part  6 , being dropped along the slope thereof, and further being passed through the flow pass tube part  6   a  to be dropped onto the third material dispersion element  10 . 
     Further, the granular resin materials P are dispersed by the third material dispersion element  10  along the tapered surface or in all the four directions to be led to the third hopper part  7 , being dropped along the slope thereof, and being passed through the opening part  7   a  to be led to the material discharging port  4  before being discharged outside of the drying hopper  1 . 
     On the other hand, the dry air from the dehumidification drying machine flows in from the dry air supply tube  11  into the hopper main body  2 ; is passed through the inner cone part  7   b  of the third hopper part  7  that is formed of a mesh material, before being raised; next is passed through the inner cone part  6   b  of the second hopper part  6  that is formed of a mesh material, before being raised; further is passed through a mesh portion of the first hopper part  5  before being raised; and is passed through the filter  15  to be led to the dry air returning port  12  before being returned to the dehumidification drying machine. 
     In the drying hopper  1  pertaining to the present embodiment, such a counter-flow contact over three stages in total of a number of granular resin materials P with the dry air within the hopper main body  2  for a long period of time as compared to that attainable under the conventional art allows the moisture contained in the number of granular resin materials P to be effectively absorbed by the dry air such that the number of granular resin materials P are thoroughly dried before being discharged to the outside of the drying hopper  1  to be fed to an injection molding machine, or the like, for being injection molded. 
     In other words, the drying hopper  1  pertaining to the present embodiment allows the moisture absorption capacity of the dry air to be sufficiently utilized as compared to the conventional drying hopper, and when comprehensively viewed, the resin materials P can be sufficiently dried in a short period of time. 
     In addition, according to the drying hopper  1  pertaining to the present embodiment, the air flow rate for the dry air and the dew-point temperature of the same are monitored by the air flow meter  13  and the dew-point hygrometer  14 , respectively, and when the measurement is not suitable, the alarming device  16  gives an alarm, thus the proper quality control of the resin materials P to be fed to an injection molding machine, or the like can be realized. 
     Further, according to the drying hopper  1  pertaining to the present embodiment, minute dust particles produced by the counter-flow contact of the resin materials P with the dry air can be sucked to be removed by the filter  15 , whereby the quality of the resin materials P can be improved. 
     With the drying hopper  1  pertaining to the present embodiment, resin materials P were subjected to drying treatment, using dry air having a temperature of 120° C. and a dew-point temperature of −40° C., and the moisture measurement of the resin materials P was carried out by means of a Karl Fischer moisture meter, which gave a result of 1835 ppm before drying and 294 ppm after drying for 1 hr. 
     The drying hopper  1  pertaining to the present embodiment may be realized, being provided with a two-stage configuration, a four-stage one, or the like, of hopper parts and material dispersion elements as well as the three-stage configuration as described above. 
     INDUSTRIAL APPLICABILITY  
     The present invention is widely applicable to drying treatment of a variety of granular resin materials besides polycarbonate resin materials. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  is a schematic configuration drawing of a drying hopper of an embodiment pertaining to the present invention; 
         FIG. 2  is a schematic block diagram of a control system for the drying hopper of the embodiment pertaining to the present invention; and 
         FIG. 3  is a schematic configuration drawing of a conventional drying hopper. 
     
    
    
     DESCRIPTION OF SYMBOLS  
     
         
           1 : Drying hopper 
           2 : Hopper main body 
           3 : Material charging port 
           4 : Material discharging port 
           5 : First hopper part 
           5   a : Flow pass tube part 
           6 : Second hopper part 
           6   a : Flow pass tube part 
           6   b : Inner cone part 
           6   c : Outer edge part 
           7 : Third hopper part 
           7   a : Opening part 
           7   b : Inner cone part 
           7   c : Outer edge part 
           8 : First material dispersion element 
           9 : Second material dispersion element 
           10 : Third material dispersion element 
           11 : Dry air supply tube 
           12 : Dry air returning port 
           13 : Air flow meter 
           14 : Dew-point hygrometer 
           15 : Filter 
           16 : Alarming device 
           17 : Control unit 
         P: Resin materials