Abstract:
Method and apparatus for furnishing process machines with liquid color from a supply thereof provides a loop conduit having respective ends receiving liquid color from the supply and discharging liquid color back into the supply, pumping liquid color through the loop conduit and discharging liquid color from the loop conduit at an intermediate position into a reservoir associated with a process machine upon liquid color level in the reservoir being at a low level limit.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This patent application claims the benefit of the priority of U.S. provisional application Ser. No. 61/939,816 filed 14 Feb. 2014 in the name of Stephen B. Maguire and entitled “Liquid Color Closed Loop Automatic Refill System”; the priority is claimed under 35 USC 119 and 35 USC 120. 
    
    
     BACKGROUND OF THE INVENTION 
     Liquid color is metered from containers. When the liquid runs out and a process machine, namely an injection molding machine or extruder, is operating producing plastic parts, there is a time period where no color is being metered, and production parts must be scrapped because they do not get the required color. One solution is to alarm when color level is low, and change the liquid color container before the liquid color runs out. However, this results in the remaining liquid color being wasted, or a mess due to spillage, when transferring the remaining liquid color into the new container. 
     A better solution is to simply refill the container before the liquid color runs out. Currently available systems for doing this involve a level sensor to detect low level in the primary container, and then a reserve container and pump standing by for refilling the primary container. 
     The reserve container may be small, but preferably is large enough to last for many weeks. Two thousand pound capacity totes are standard in the industry. 
     This reserve container may be very close, or may be located at some distance. In either case a pump is required for the reserve container for transferring the liquid color into the primary container. 
     Factories always have many process machines. Each requires its own primary supply of color, and its own metering pump. In current systems if, for example, 5 process machines are running and automatic refill of these containers is desired, then each process machine requires its own “reserve” container and a reserve pump as well. This need for 5 reserve containers and 5 pumps is still present even if all process machines are running the same color. 
     SUMMARY OF THE INVENTION 
     When multiple process machines are running the same color, a more efficient system as provided by the instant invention is to have one large reserve container with a pump to resupply all primary containers. 
     That is how the system of this invention works. One large reserve container is preferably used to refill each of the primary containers when any one of the primary containers runs low on liquid color. 
     As a further refinement, this invention preferably also incorporates a closed loop system to supply liquid color to all of the process machines. Liquid is preferably continuously pumped out through a piping system that reaches all of the process machines and then returns to the reserve container. This assures a constant supply of “fresh” liquid color, with no risk of the liquid color settling or separating in the liquid color supply lines. (Settling can occur when liquid color heavily loaded with pigment is left sitting in the liquid color supply conduit.) As an added benefit, this continuous flow also assures continuous turnover of liquid color and mixing of the liquid color in the reserve container. 
     When a primary container requires liquid color, the invention preferably uses a diverter valve to divert the liquid color flow from the circulation loop into the selected primary container. As an additional feature, to allow refill to occur as rapidly as possible, the invention preferably increases the pump rate of the circulation pump to its maximum. When not refilling a container the recirculation pump rate is slowed to a rate that is reasonable and that conserves energy, or in the most preferred practice of the invention, conserves compressed air that is preferably used to drive the pump. 
     As an added feature of the invention, metering systems, with one located at each process machine, use load cells to control metering gravimetrically. The load cells are also available to signal the proper time for refill to occur. Level sensors can be used in place of the load cells. 
     In one of its aspects, this invention provides a method for furnishing process machines with liquid color from a supply thereof where the method preferably commences with providing a loop conduit having respective ends receiving liquid color from the supply and discharging liquid color into the supply. The method preferably proceeds with pumping liquid color through the loop conduit. The method then discharges liquid color from the loop conduit at an intermediate position thereon into a reservoir associated with a process machine upon the process machine signaling a need for liquid color. 
     The method may further include providing at least one valve in the conduit for discharging liquid color therefrom and discharging liquid color from the loop conduit by actuating the valve. 
     In another one of its aspects, this invention preferably provides apparatus for furnishing process machines with liquid color where the apparatus preferably includes a supply of liquid color, a loop conduit for carrying liquid color with the loop conduit preferably running from the supply to the process machines and back to the supply, a pump for circulating liquid color around the loop, a detector for sensing when liquid color is needed by an associated process machine, and a valve in the loop for diverting liquid color from the loop to the associated process machine upon the detector sensing the need for replenishment. In an apparatus aspect of the invention, a solenoid is preferably provided for actuating the valve. Furthermore in an apparatus aspect of the invention, segments of the loop conduit are preferably structurally mounted adjacent to one another such that liquid color travels in opposite directions in the mounted segments and the valve is in one of the segments. 
     In still another one of its aspects, this invention provides a method for furnishing process machines such as injection molding presses, compression molding presses and extruders, and ancillary machines such as receivers and gravimetric blenders, with liquid color from a supply of liquid color. In one of these method aspects, the invention proceeds by providing a loop conduit having respective ends receiving liquid color from the supply and discharging liquid color back into the supply, and discharging liquid color from the conduit loop at an intermediate position thereon into a reservoir associated with a process machine upon the process machine signaling a need for liquid color. 
     The method may further include intermittently mixing liquid color in the supply or continuously mixing liquid color in the supply. 
     In yet another one of its aspects, the method may further include increasing pumping speed whenever liquid color is being discharged from the loop conduit into a reservoir associated with a process machine. The method may further include providing at least one diverter valve in the conduit for discharging liquid color from the conduit, and specifically discharging the liquid color from the liquid conduit by actuating the diverter valve. 
     In still another aspect of the invention, the invention embraces the steps of sensing weight of the reservoir and upon sensed weight of the reservoir falling below a pre-selected value, actuating a diverter valve to discharge liquid color from the conduit to replenish the reservoir. 
     The method may further embrace sensing the weight of the reservoir and upon sensed reservoir weight falling below a pre-selected value, discharging liquid color from the conduit to replenish the reservoir. 
     The method may further embrace the step of increasing pumping speed upon sensed reservoir weight decreasing to within a pre-selected amount of the pre-selected level and decreasing pumping speed upon sensed reservoir weight increasing to at least the pre-determined level. 
     In another one of its aspects, this invention provides a method for furnishing process machines with liquid color from a supply by providing a loop conduit having respective ends receiving liquid color from the supply and discharging liquid color into the supply, pumping liquid color through the loop conduit, mixing liquid color in the supply, providing at least one valve in the conduit for discharging liquid color therefrom, discharging liquid color from the loop conduit into a reservoir associated with the process machine by opening a valve in the loop conduit upon the process machine signaling a need for liquid color, halting discharge of liquid color from the loop conduit, and increasing pumping speed upon sensed reservoir weight decreasing to within a pre-selected amount of the pre-selected level but decreasing pumping speed upon sensed reservoir weight increasing to at least the pre-determined level. 
     In still yet another one of its aspects, this invention provides apparatus for furnishing process machines with liquid color where the apparatus includes a loop conduit for carrying liquid color running from the supply to the process machines and back to the supply, a pump for circulating liquid color around the loop, a detector for sensing when additional liquid color is needed by an associated process machine, and a valve in the loop for diverting liquid color from the loop to the associated process machine upon the detector sensing the need for replenishment. The apparatus may further include a reservoir associated with each process machine for temporarily storing liquid color received from the loop conduit until needed by the process machine and a load cell for detecting the weight of the reservoir and hence the amount of liquid color therein. 
     The apparatus may further preferably include a solenoid for actuating the valve. 
     In one more aspect of the apparatus, segments of the loop conduit may be structurally mounted adjacent to one another such that liquid color travels at opposite directions in the mounted segments and the valve is in one of those segments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of apparatus embodying the method for practicing aspects of the invention. 
         FIG. 2  is an artist&#39;s rendition, in isometric form, of apparatus manifesting aspects of the invention and showing a number of process machines receiving liquid color in accordance with the invention. 
         FIG. 3  is an isometric drawing of a portion of a loop conduit of the invention, with a diverter valve positioned therein, with the conduit and the diverter valve mounted on a common support structure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings in general and to  FIG. 1  in particular, apparatus embodying the invention and suitable for practice the method aspects of the invention is designated generally  10  and includes a loop conduit  12  leading from a liquid color supply  16  to a pump  14 . From the pump  14 , the loop conduit  12  proceeds to a diverter valve  18  and from diverter valve  18  on around to the liquid color supply  16  to deposit liquid color that has not been diverted by valve  18  back into liquid color supply  16 . Diverter valve  18 , when actuated, diverts liquid color from loop conduit  12  down through supply conduit  28  into a reservoir or holding tank  20 . 
     A load cell  22  senses the weight of reservoir or holding tank  20  and thereby senses the weight of liquid color within reservoir or holding tank  20 . Load cell  22  may be supported by structure resting on a floor  26 . It is to be understood that any suitable structure may be used for supporting load cell  22  in a position to sense the weight of reservoir or holding tank  20 . 
     An agitator or mixer  24  is provided for mixing liquid color within a supply  16 . Agitator or mixer  24  is depicted only schematically. Agitator or mixer  24  is conventionally motor-driven. 
     Diverter valve  18  is preferably actuated by solenoid  30 . Upon actuation of valve  18  by solenoid  30 , liquid color flowing through loop conduit  12  is diverted to flow down through supply conduit  28  into reservoir or holding tank  20 , rather than flowing around the remainder of loop conduit  12  and back into liquid color supply  16 . 
     Solenoid  30  actuates diverter valve  18  to open diverter valve  18  to permit flow of liquid color through supply conduit  28  into reservoir  20  upon sensed weight of reservoir  20  being low, indicating a low level of liquid color within reservoir  20 . Weight sensing is performed by load cell  22 . Once load cell  22 , which continuously senses weight of reservoir or holding tank  20 , senses that reservoir or holding tank  20  is beginning to approach its maximum capacity for liquid color, a signal is sent to solenoid  30 . The signal de-actuates diverter valve  18  whereupon no liquid color is permitted to flow into supply conduit  28 , but rather liquid color continues to flow through valve  18  around loop conduit  12  and back to liquid color supply  16 . 
     The invention further embraces regulation of the speed of pump  14 . Desirably the speed of pump  14  is increased upon the sensed weight of reservoir  20  decreasing to within a pre-selected amount of a pre-selected low level, but speed of pump  14  is decreased upon the sensed weight of reservoir  20  increasing to at least a pre-determined high level. 
     The invention further embraces regulation of the mixing or agitation provided by agitator/mixer  24  for liquid color in liquid color supply  16 . A feed line  38  leads from reservoir or holding tank  20  to the associated process machine to supply liquid color to the process machine, as indicated by the arrow in  FIG. 1 . 
     Referring now to  FIG. 2  which is an artist&#39;s rendition of the manner in which the invention and apparatus embodying the invention might be installed in a plastic injection molding facility, apparatus in accordance with the invention is designated generally  10  with the loop conduit designated generally  12  and a pump designated generally  14  being associated with a reservoir or holding tank  20 , all as illustrated in  FIG. 2 . Valves  18  are provided for diverting liquid color from loop conduit  12  into individual reserve or holding tanks  20  with one such reserve or holding tank  20  being associated with each one of the process machines  34 , which in the drawing are illustrated as injection molding presses. Valves  18  are not visible in  FIG. 2 . 
     Liquid color is delivered from individual reservoirs or holding tanks  20  to the process machines  34  by supply conduits  38 . There is one supply conduit  38  for each reservoir/holding tank  20 -process machine  34  combination as illustrated in  FIG. 2 . Weight of each reservoir or holding tank  20  is measured by an associated load cell  22  located preferably below reservoir or holding tank  20 . There is preferably an individual load cell  22  for each reservoir or holding tank  20 . Load cells  22  are supported by suitable structure, which also supports the associated reservoir or holding tank  20  and which preferably rests on a floor  26  of the facility in which process machines  34  are located. 
     An agitator or mixer is provided for liquid color residing in liquid color supply  16 . Hoppers  36  associated with each one of process machines  34 , in this case injection molding presses, retain granular resin until the granular resin is needed by the molding machine for the manufacture of plastic parts. 
     Each reservoir/holding tank  20  is connected to loop conduit  12  by a supply conduit  28  leading downwardly from a diverter valve, not shown in  FIG. 2 , that when actuated by a solenoid, not shown in  FIG. 2 , diverts liquid color from loop conduit  12  downwardly through supply conduit  28  into reservoir or holding tank  20 . 
     A feed line  38  is provided for each of the reservoir/holding tank-process machine combinations as illustrated in  FIG. 2 . 
     A controller  32  is provided for each reservoir or holding tank  20 . Controller  32  actuates solenoid  30  thereby to open diverter valve  18  and permit downward flow of liquid color, under pressure, from loop conduit  12  into reservoir or holding tank  20 . 
       FIG. 3  illustrates a mounting block/diverter valve/loop conduit segment assembly, one of which is provided for each reserve holding tank  20 . Mounting block  44  is mounted on a framework  46  that is associated with and supports reservoir/holding tank  20 , load cell  22  and solenoid  30 . Framework  46  is illustrated and designated so in  FIG. 2 , but is not illustrated in  FIG. 3 . 
     Mounting block  44  supports outbound segment  40  and inbound segment  42  of loop conduit  12 . A diverter valve  18  is provided in the outbound segment of loop conduit  40  and is actuated by solenoid  30 . Upon energizing solenoid  30  and consequent activation of diverter valve  18 , liquid color flowing in the outbound segment  40  of loop conduit  12  is diverted downwardly by valve  18  and flows through supply conduit  28  into a particular reservoir or holding tank with which diverter valve  18  and supply conduit  28  are associated. Arrows A and B in  FIG. 3  denote the direction of flow of liquid color with liquid color flowing outwardly as indicated by arrow A through outbound segment  40  of loop conduit  12  and liquid color returning to supply  16  through inbound segment  42  of loop conduit  12  as indicated by arrow B. 
     During operation, liquid color is desirably pumped continuously by pump  14  out of liquid color supply  16  through loop conduit  12 . With loop conduit  12  being a “continuous” conduit, loop conduit  12  reaches all of process machines  34 , albeit indirectly, through supply conduits  28  and feed lines  38 , with loop conduit  12  then returning to liquid color supply  16 . This assures a constant supply of “fresh” liquid color with no risk of the liquid color settling or separating in the liquid color supply line, namely loop conduit  12 . As an additional benefit, this continuous flow through loop conduit  12  assures continuous turnover of liquid color and mixing of the liquid color in liquid color supply  16 . 
     When a reserve or holding tank  20  requires liquid color, diverter valve  18  is actuated to divert liquid color from loop conduit  12 , specifically from the outbound segment  40  of loop conduit  12 , into the associated reservoir or holding tank  20 . Preferably, when a reservoir or holding tank  20  requires additional liquid color, the speed of pump  14  is increased to drive liquid color through loop conduit  12  faster and at higher pressure, thereby to minimize the time required for liquid color replenishment into reservoir or holding tank  20 . When not refilling a reservoir or holding tank  20 , pump  14  is preferably slowed to a rate that is reasonable and conserves energy, while continuing to circulate liquid color around loop conduit  12 . 
     The metering system, namely the solenoid  30  and controller  32  associated with each reservoir or holding tank  20  uses a load cell  22  to control the metering of liquid color into each reservoir or holding tank  20  gravimetrically. Load cell  20  additionally signals the proper time for refill to occur, namely when the amount of liquid color in reservoir or holding tank  20  is excessively low and there is risk that there will be insufficient liquid color flowing through feed line  38  to satisfy the needs of process machine  34 . While use of load cells is preferable, level sensors in reserve or holding tank  20  may also be used in place of load cells. 
     In another aspect of the invention, a detector may be provided associated with a process machine  34  to indicate when liquid color is needed by that associated process machine. The detector then provides signal to the controller  32  which actuates solenoid  30  to move diverter valve  18  so that liquid color is supplied through supply conduit  28  to reservoir/holding tank  20 . Desirably, a signal is also provided at that time to pump  14  to drive pump  14  at its maximum speed, to provide liquid color at high pressure thereby quickly filling the associated reserve or holding tank  20  and replenishing the liquid color needed by the associated process machine  34 . 
     As illustrated in  FIG. 3 , liquid color preferably moves in opposite directions with respect to mounting block  44 , thereby balancing any stresses on mounting block  44  resulting from the dynamic flow of liquid color in directions A and B in  FIG. 3 . Additionally, pumping speed of pump  14  is desirably increased upon sensed weight of a reservoir or holding tank  20  decreasing to within a pre-selected amount of a pre-selected level, while decreasing pumping speed upon the sensed reservoir weight increasing to at least the pre-determined level as a result of the reservoir or holding tank  20  being filled with liquid color to a pre-determined level.