Patent Publication Number: US-2015064297-A1

Title: Extruder having a vacuum feeder

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to extrusion technology, and more particularly to an extruder equipped with a vacuum feeder. 
     2. Description of the Related Art 
     In most conventional extruders, the screw generally defines a feeding section, a mixing section, and a discharging section. In some extruders, one or two exhaust holes are made in the mixing section of the screw for discharging water from the applied plastic material. Waste plastic materials such as waste plastic bags or waste plastic films may carry a certain amount of water after washing. Even treated through dehydration and drying processes, residual water left among waste plastic bags or films still cannot be completely dried out. In consequently, a large amount of water vapor will be produced during the melt-mixing process. This water vapor can be mixed in the molten plastic material. Although exhaust holes are provided for exhaust of water vapor, this arrangement cannot guarantee that water vapor can be completely dried out. This is the major drawback of conventional extruders. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide an extruder having a vacuum feeder, which effectively reduces the residual water contained in the applied material. 
     It is another object of the present invention to provide an extruder having a vacuum feeder, which makes the feed more smoothly. 
     To achieve these and other objects of the present invention, an extruder having a vacuum feeder of the present invention comprises a machine base, a cylinder shaped like a long tube and connected with one end thereof to the machine base and defining a feeding section adjacent to the machine base, a feed port at the feeding section and a discharge port at an opposite end thereof, a screw pivotally connected with one end thereof to the machine base and accommodated in the cylinder and rotatable in the cylinder by an external force, a feed tank having a top through hole located at a top side thereof and a bottom through hole located at a bottom side thereof and connected to the feed port of the cylinder, a control valve mounted in the top through hole of the feed tank and operable to open or close the feed tank, and a vacuum pump connected to the feeding section of the cylinder through a piping and operable to pump air out of the feeding section and to further leave a vacuum in the feeding section. 
     Other advantages and features of the present invention will be fully understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference signs denote like components of structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic structural view of an extruder having a vacuum feeder in accordance with a first embodiment of the present invention. 
         FIG. 2  is a front view of an extruder having a vacuum feeder in accordance with a first embodiment of the present invention. 
         FIG. 3  is a top view of the extruder in accordance with the second embodiment of the present invention. 
         FIG. 4  is a schematic structural view of the extruder in accordance with the second embodiment of the present invention. 
         FIG. 5  is a horizontal sectional view of a part of the second embodiment of the present invention, illustrating the structure of the bearing block and the feeding section of the cylinder. 
         FIG. 6  is a sectional view taken along line  6 - 6  of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1-4 , an extruder having a vacuum feeder in accordance with a first embodiment of the present invention is shown. This first embodiment is a natural gravity feed type design, comprising: 
     a machine base  10 ; 
     a cylinder  20  shaped like a long tube and connected with one end thereof to the machine base  10 , and defining a feeding section  21  adjacent to the machine base  10 , a feed port  22  at the feeding section  21 , and a discharge port (not shown) at an opposite end thereof; 
     a screw  30  pivotally connected with one end thereof to the machine base  10  and accommodated in the cylinder  20  and rotatable in the cylinder  20  by an external force; 
     a feed tank  40  having a top through hole  42  located at a top side thereof and a bottom through hole  41  located at a bottom side thereof and connected to the feed port  22  of the cylinder  20 ; 
     a control valve  50  mounted in the top through hole  42  at the top side of the feed tank  40  and operable to open or close the feed tank  40 ; and 
     a vacuum pump  60  connected to the feeding section  21  of the cylinder  20  through a piping  61  and operable to pump air out of the feeding section  21  and to further leave a vacuum in the feeding section  21 . 
     Further, the screw  30  comprises a grooved area  31  pivotally coupled to the machine base  10  adjacent to the cylinder  20 . The cylinder  20  further comprises a through hole  23  corresponding to the grooved area  31 . The vacuum pump  60  is connected to the through hole  23  of the cylinder  20  by the piping  61 , and kept in communication with the feeding section  21  of the cylinder  20  through the gaps in the pivot connection area between the screw  30  and the machine base  10 . An O-ring  11  and a V-shaped gasket ring  12  are mounted in the connection area between the machine base  10  and the screw  30  to prevent leakage. Further, the machine base  10  has a gear train (not shown) mounted therein and drivable by a motor (not shown) to rotate the screw  30 . 
     In this embodiment, a storage hopper or feed piping can be connected to the top side of the control valve  50 . When in use, open the control valve  50  to let the prepared material fall into the feed tank  40 . When the material in the feed tank  40  reaches a predetermined elevation, the control valve  50  is turned off automatically. At this time, the vacuum pump  60  keeps pumping, enabling the material to fall to the inside of the feeding section  21  of the cylinder  20  automatically subject to the double action of the force of gravity and vacuum suction. Further, the vacuum effect enables the water contained in the material in the feed tank  40  and the feeding section  21  to be evaporated easily, and the generated water vapor can also be drawn out by vacuum, thereby lowering the moisture content of the material to further improve the speed and quality of the production. 
       FIGS. 2-6  illustrate an extruder having a vacuum feeder in accordance with a second embodiment. To facilitate explanation, like reference signs designate like components throughout the specification. The extruder in accordance with this second embodiment also comprises a machine base  10 , a cylinder  20 , a screw  30 , a feed tank  40 , a control valve  50 , and a vacuum pump  60 . The structures of these components and their relationship are same as the aforesaid first embodiment. The cylinder  20  also comprises a feeding section  21  and a feed port  22 . The screw  30  also comprises a grooved area  31 . The cylinder  20  also comprises a through hole  23  corresponding to the grooved area  31  of the screw  30 . The vacuum pump  60  is also connected to the through hole  23  by a piping  61 . The major characteristics of this second embodiment are outlined hereinafter. 
     A force feed screw  70  is mounted within the feed tank  40 , and adapted to propel the applied material into the feeding section  21  of the cylinder  20 . The feeding section  21  of the cylinder  20  is equipped with a bearing block  80  at one lateral side thereof for the connection of the force feed screw  70  pivotally. The feed tank  40  is mounted on the bearing block  80 . The bearing block  80  defines therein an accommodation chamber  81 . The accommodation chamber  81  is kept in communication with the feed port  22  of the cylinder  20 , i.e., the feed port  22  is disposed at one lateral side relative to the cylinder  20 . A storage tank  90  is provided at the top side of the control valve  50 . A feed piping  95  is connected to the top side of the storage tank  90 . Further, a sensor  43  is mounted at the bottom side of the feed tank  40  for upper-limit material level detection, and a sensor  91  is mounted in a top side in the storage tank  90  for lower-limit material level detection. Thus, when the level of the supplied material in the feed tank  40  drops the sensing level of the upper level sensor  43 , the control valve  50  is turned on automatically. After a predetermined set time, the storage material in the storage tank  90  automatically falls to the inside of the feed tank  40 . Thereafter, the control valve  50  is automatically turned off to close the feed tank  40 , and at the same time, the feed piping  95  is opened for enabling the prepared material to be delivered into the inside of the storage tank  90 . After the material in the storage tank  90  reaches the sensing level of the lower level sensor  91 , the feed piping  95  is closed automatically. Subject to the functioning of the vacuum pump  60 , the water content in the material inside the feed tank  40  can be rapidly evaporated and drawn out, and thus, the applied material can be well dried, facilitating the subsequent processing operations and smoothening the material feeding.