Abstract:
An indicator system is provided for use with a blown-in dust transfer system. A dust collector collects dust, where it accumulates at an airlock feeder. When the feeder moves, accumulated dust is dispensed into an introduction chamber. A blower moves air through an introduction chamber where the dust particles become entrained in the moving air. The dust and air mixture are moved into a removable storage container where the dust particles fall out of the moving air. Return air that is mostly devoid of dust returns to the introduction chamber. Between the storage container and the introduction chamber is a sensor that detects dust in the return air. If the level of dust reaches a certain amount the sensor detects it and an operator is notified that the storage container is full.

Description:
BACKGROUND OF THE INVENTION 
     In sawmill, woodworking, or other related industries, sawdust is a natural byproduct that must be dealt with on a regular basis. Sawdust is typically vacuumed out and sent to a dust collector, where it is stored until it can be hauled away. Once the level of sawdust reaches a threshold, it is emptied, typically into a trailer or other mobile storage device. Because sawdust is relatively lightweight and would easily blow out when the trailer is transported, an open top trailer is undesirable. Additionally, in order to load an open top trailer, the dust collector must be raised off of the ground far enough to allow the trailer to drive underneath, creating additional expense and difficulty in servicing. Trailers in the art are enclosed with rear doors that have two holes cut through them. One hole receives the sawdust and the other is for return air that is displaced from the trailer as the sawdust is loaded. Currently, no system exists that controls the dispensing of sawdust, and the process must be manually monitored to prevent the trailer from becoming overfilled, thereby overwhelming the feeding system. The user relies on a visual observation of the dust that is present in the return line or physically stopping the system to observe directly the amount of dust in the trailer. Relying on watching dust presence in the return line is subjective and subject to error based on environmental conditions and buildup in a transparent portion of the return line. When the process is not watched, an inadvertent user could not stop the process in time, overfilling the trailer and filling all of the tubing with sawdust, creating a downtime and possible equipment damage. Disassembling and clearing out the system after it is packed with dust is time consuming and difficult, idling production and adding unnecessary expense. Further, stopping and starting the process for periodic inspection is time consuming, wasteful, and creates premature wear and tear on the equipment. An improved system is needed. 
     SUMMARY OF THE INVENTION 
     The present disclosure describes a closed loop system that indicates when the trailer has reached a predetermined fill level. A feeder and airlock located at the bottom of a dust collector dispenses a controlled amount of sawdust into a stream of air that is moved by a blower. The stream of air passes underneath the dispensed controlled amount of sawdust, where falling sawdust becomes mixed and suspended in the stream of air. The stream of air with entrained sawdust is blown into a trailer, where the sawdust falls to the trailer&#39;s floor. The air returns back to the feeder, passing a density sensor, where more sawdust is added by the feeder. As the trailer fills with sawdust, the amount of dust in the return air increases. When the sensor detects a predetermined density of sawdust in the return air, the system alerts the user that the trailer is at capacity. Further, an optional control system is integrated with the sensor and automatically controls the blower and feeder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment of this invention has been chosen wherein: 
         FIG. 1  is an overall side view of the system; 
         FIG. 2  is a partial view  2  of the system in  FIG. 1 ; 
         FIG. 3  is a section view  3 - 3  of the return line in  FIG. 2 ; 
         FIG. 4  is a graph of the density of the return line vs the fill level of the trailer; and 
         FIG. 5  is a block diagram of the control system. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A dust bin indicator system  10  as shown in  FIG. 1  collects dust  12  or other bulk particulate byproduct from a dust collector  14  and moves it into a storage and transportation container, such as a trailer  16 . The dust collector  14  collects dust  12  from an external source, such as sanders, grinders, or other process equipment, where it accumulates in a tapered lower portion  18 . The dust collector  14  can only fill to a certain point before it becomes ineffective or damaged, so regular emptying is necessary. Dust collectors  14  are known in the art and commonly have a tapered lower portion  18  where dust  12  or other accumulated material can be emptied. The tapered lower portion  18  is typically conical but can be pyramidal. Dust  12  collects at the lowest point. At the bottom of the lower portion  18  is a device for metering the dust  12 , typically called a rotary feeder  20 . The rotary feeder  20  also serves as an air lock. The purpose of the rotary feeder  20  is to prevent all of the dust  12  present in the lower portion  18  from travelling into an introduction chamber  30 . Another purpose of the rotary feeder  20  is to prevent airflow present in the dust collector  14  from exchanging with airflow that may be present in the introduction chamber  30 . The rotary feeder  20  has an inlet side  22  and an outlet side  24  with a metering device such as an auger  26  located between the two. The auger  26  is typically rotated by a motor  25  to dispense the dust  12  from the inlet  22  to the outlet  24 . It is contemplated that other metering devices are used, such as a screw-type auger, moving chamber, or a trap door. It is further contemplated that the auger  26  is driven through other means, such as hydraulics. 
     As shown in  FIG. 2 , the outlet side  24  of the rotary feeder  20  dispenses a metered amount of dust  28  into the top of the introduction chamber  30  at a dust inlet  32 . The introduction chamber  30  introduces the metered amount of dust  28  into a stream of moving air  34 . The stream of moving air  34  moves across the introduction chamber  30  with the dust inlet  32  being located directly above. The metered amount of dust  28  falls directly into the stream of moving air  34 . The stream of moving air  34  moves from the air inlet  36  and mixes with the metered amount of dust  28  to form a dust/air mixture  38  that exits the outlet  40 . In the dust/air mixture  38 , dust particles are entrained with the stream of moving air and remain suspended as long as the moving air  34  is moving sufficiently. 
     The dust/air mixture  38  then proceeds down a pipe  42  toward the inlet  44  of a blower  48 . The blower  48  draws air in through the inlet  44  using negative pressure and drives it out of an outlet  46  with positive pressure. The blower  48 , as shown, drives the dust/air mixture  38  from the outlet  48  to a supply line  50 . The supply line  50  transfers the dust/air mixture  38  into an inlet  52  on the trailer  16 . The trailer  16  is moveable with the supply line  50  being able to disconnect in order to relocate the trailer  16 . The pressurized dust/air mixture  38  enters the cavity of the trailer  16 , where the dust  12  falls out of the moving air and settles as shown in  FIG. 1 . Because the trailer  16  is closed from escaping air, return air  54  that is mostly free of dust exits an outlet  56  and then moves into a return line  58 . Like the supply line  50  being able to disconnect, the return line  58  is able to disconnect to allow the trailer to be moved. Because the blower  48  is pulling air from the introduction chamber  30 , and the rotary feeder  20  does not allow significant air flow through it, the air is pulled through the return line  58 , creating a loop of circulating air. This closed loop is visible in  FIGS. 1 and 5 . The closed loop prevents any dust  12  that remains present in the return air  54  from escaping. 
     The return air  54  moves through the return line  58 , where it then passes a density sensor  60  as shown in  FIGS. 1-3 and 5 . The density sensor  60  as shown is a retroreflective. A retroreflective sensor works by sending out a beam of light, reflecting it off of a certain type of reflector, and then received to determine if the beam is blocked. As shown in  FIG. 3 , a portion of the sensor  60  sends out a light beam, where it bounces off of a reflector  62  and is then received by another portion. The reflector  62  is usually placed opposite the sensor  60  with the return air  54  passing directly between the two. The sensor  60  then calculates the difference in the intensity of the light as sent to the intensity of the light as received. It is contemplated that another sensor type is used such as a through beam (where there is a transmitter on one side and a receiver on the other side). If a through beam sensor is utilized, the reflector  62  would be replaced with a transmitter and the density sensor  60  would be a receiver only. Other sensors that detect the dust density in the return air  54  are contemplated, such as capacitive or ultrasonic. It is further contemplated that a reflective sensor is utilized that reflects off of dust  12  in the dust/air mixture  38  to detect the density of the return air  54 . 
     The sensor  60  as shown is located in the return line  58 , but could be located in the introduction chamber  30 , as long as it is located before the metered amount of dust  28  is mixed into the stream of moving air  34 . The sensor  60  is shown in the return line  58  in close proximity to the introduction chamber  30  but could be located anywhere in the return line  58 . 
     Further an additional sensor (not shown) could be located in the supply line  50 , the pipe  42 , or the blower  48  to detect the density of dust  12  as it is introduced into the system  10 . The additional sensor could alert the user that the dust collector  14  is empty or the feeder  20  is not properly functioning. Additional sensors are further contemplated to allow better control over the system  10  and improve the user&#39;s monitoring capabilities. 
     A control system  64 , as shown in  FIG. 5 , receives the signal from the density sensor  60  and indicates its output to the user. The control system  64  alerts the user with a visual indicator, such as a strobe light or a sound such as a bell or siren. The user then decides to turn off the blower  48  and/or the rotary feeder  20 . It is further contemplated that the control system  64  directly controls the blower  48  and rotary feeder  20 . In the event that the control system  64  directly controls the blower  48  and rotary feeder  20 , the rotary feeder  20  would be disabled to stop the flow of the metered amount of dust  28  from entering the introduction chamber  30 , then the blower  48  would be disabled to stop the flow of air. At that point, the user would be alerted through indicator lights  68 , a siren  70 , or both. The user would be safe to disconnect the supply line  50  and the return line  58  and move the trailer  16 . Any additional sensors could be utilized to allow the control system  64  to cycle the rotary feeder  20  on and off to better control the amount of dust  12  as it is dispensed into the introduction chamber  30 . 
     As is shown in  FIG. 1 , the trailer  16  is moved into position and the supply line  50  and return line  58  are attached. The trailer  16  begins as an empty container. At that point, the blower  48  is turned on, thereby circulating air through the supply line  50 , the return line  58 , the introduction chamber  30 , and the pipe  42 . The trailer  16  begins to fills up with dust  12  from the dust collector  14 . As the trailer  16  continues to fill with dust  12 , there is less room for the dust  12  to fall out of the dust/air mixture  38 . At that point, more dust  12  begins to travel through the return line  58 . A graph of the density of dust in the return air  54  based on the fill level of the trailer  16  is shown in  FIG. 4 . A trip point  66  is set by either the sensor  60  or the control system  64  that either indicates to the user that the trailer  16  is full or it directly controls the blower and rotary feeder  20 . 
     While the blower  48  as shown in  FIGS. 1 and 5  is located between the introduction chamber  30  and the supply line  50 , it is contemplated that the blower  48  is located in the return line  58  ahead of the introduction chamber  30 . In this event, the dust  12  would mix with the return air  54  to form the dust/air mixture  38  under positive pressure. This arrangement would be especially helpful if the dust  12  were abrasive or otherwise harmful to the blower  48 . 
     It is understood that while certain aspects of the disclosed subject matter have been shown and described, the disclosed subject matter is not limited thereto and encompasses various other embodiments and aspects. No specific limitation with respect to the specific embodiments disclosed herein is intended or should be inferred. Modifications may be made to the disclosed subject matter as set forth in the following claims.