TW201318922A - Method for preventing pack-out in pumping system - Google Patents

Abstract

A method for preventing pack-out in a system for pumping hybrid hot-melt material comprises monitoring activity of a pump that pumps hybrid hot-melt material, shutting off a heater that melts pumped hybrid hot-melt material at an inactivity threshold level, and relieving pump pressure.

Description

Method of avoiding crowding in the pumping system

The present invention relates generally to pumping systems for hot melt materials, such as their pumping systems for dispensing adhesives used in packaging. More particularly, the present invention relates to a control method for operating a pumping system for dispensing a mixed hot melt material.

The hot melt system is conventionally operated to melt solid polymer particles, after which the molten liquid particles are passed to a pump system for routing to a dispenser. These systems require heating the molten liquid along the entire route from one of the unheated hoppers to the dispenser. This requires the use of multiple heaters in the system. For example, a hopper, a pump, and a manifold are configured in a single unit with heating, and a heated hose connects the manifold to a dispenser. Heaters increase the power consumption of such systems, thereby increasing the cost of operation. Recent advances in the hot melt technology have been directed to the use of a mixed composition in which a heterogeneously dispersed polymeric microparticle is suspended in an adsorbent liquid component, as described in U.S. Patent No. 7,285,583, issued to <RTIgt;Stumphauzer et al. . In a dispensing system for such mixed compositions, no heat is applied to the composition prior to dispensing (usually just prior to entering the dispenser), such as by Stumphauzer et al. of HB Fuller. U.S. Patent No. 7,221,859.

The mixed composition dispensing unit undergoes a phenomenon known as "crowding" in which the liquid component is evacuated from the pumping unit and the solid polymeric particles are retained in the pump. When the pumping system is placed in a standby mode (where the pump is pressurized but not pumped When the material is melted, the pressure within the pump can cause the liquid component to flow back through the seal to the low pressure region of the pump and leak. In the case where only solid particles remain, the pump mechanism has a tendency to lock. Maintenance is therefore required to remove clogging particles that cause delays in the production line. Prior art systems that have been developed to address crowding have involved continuously recycling material through a pump in a feedback loop to avoid backflow of liquid components, even when no molten material is dispensed. Typically, an orifice is provided in the recirculation loop to maintain the back pressure for dispensing, but it permits some flow recirculation. These systems increase the complexity of the overall system and have increased power requirements, thereby first eliminating some of the benefits of the hybrid composition hot melt system. Therefore, there is a need for one of the improved hot melt dispensing systems.

The present invention is directed to a method for avoiding crowding in a system for pumping a mixed hot melt material. The method includes: monitoring the activity of a pump pumping one of the mixed hot melt materials; shutting down one of the heaters pumping the mixed hot melt material at an inactive threshold level; and releasing the pump pressure.

1 is a schematic illustration of a hot melt dispensing system 10 including a pump assembly 12, a heater 14 and a dispenser 16 for use with a mixed hot melt composition. The pump assembly 12 is fluidly coupled to the heater 14 by a fluid line 18. Pump assembly 12 is electronically coupled to heater 14 via communication line 20. Heater 14 is coupled to dispenser 16 at coupler 22.

The pump assembly 12, described in greater detail with respect to FIG. 2, includes a mechanical pump that provides one of the motive flow of one of the liquid materials to the heater 14. In the illustrated embodiment, the liquid material comprises a mixed hot melt adhesive composition ("mixed combination The mixed hot-melt adhesive composition comprises a hetero-dispersed polymeric microparticle suspended in an adsorbent liquid component, as described in U.S. Patent No. 7,285,583 to Stumpuuzer et al. However, the invention can be used with pumping systems that dispense any type of mixed composition in which solid particles are mixed in a liquid material. The electronics within the pump assembly 12 operate the pump to provide the desired flow of mixed material to the heater 14. The electronics also operate the heater 14 to provide the necessary amount of heat output to melt the dispersed polymeric particles within the hot melt adhesive composition thereby activating the binder material. In one embodiment, the heater 14 includes an in-line heater in which the coupler 22 uninterruptedly engages the fluid line 18 to the outlet valve of the dispenser 16. For example, the heater 14 can include a heater of the type as set forth in U.S. Patent No. 7,221,859 to Stumpuuzer et al. The molten mixture of hot melt adhesive flows into a dispenser 16 that is capable of applying the adhesive in a controlled manner. The dispenser 16 can include a hand-held gun that is directly manually operated or a module that is operated by a controller that is part of an automated program. Thus, in a particular application, hot melt adhesive can be applied to surfaces such as packages, boxes, and the like.

At ambient room temperature, the liquid material is sufficiently viscous to flow from the pump system 12 to the heater 14 at pump pressure. Therefore, the fluid line 18 is neither heated nor insulated. Heater 14 provides all of the heat input required to activate the mixed composition into a homogenous, viscous hot melt adhesive. The hot melt adhesive also flows from the heater 14 through the coupler 22 to the dispenser 16 under pressure from the pump system 12. The heater 14 provides sufficient heat output and is coupled to the dispenser 16 in a suitable manner such that the heat from the heater 14 maintains the mixed composition in the dispenser 16 in a melted state. In the state. However, in other embodiments, the dispenser 16 is provided with a separate heating element. Moreover, in some configurations, the coupler 22 can include a heated hose or the like. Any inline heating system as is known in the art, such as resistive heating elements, can be used. In such embodiments, the heaters are controlled relative to the present invention in a manner similar to one of the heaters 14. Thus, the dispenser 16 receives the mixed composition in one of the conditions for preparation. This system is superior to prior art solid particle systems in that it eliminates the need in the art to pass through the entire pump system and heat the mixed composition outside the dispenser.

The hot melt dispensing system 10 can thus be subjected to continuous or uninterrupted operation to dispense hot melt adhesive while only requiring a small amount of mixed composition to be activated between the heater 14 and the dispenser 16. The activated (heated) mixed composition immediately turns into a homogeneous solid material after cooling to room temperature. The solid material can be remelted into a hot melt adhesive, but cannot be reverted to the mixed composition as originally provided. Therefore, it is undesirable for any heated and activated mixed composition to flow back into fluid line 18 or pump system 12. In a conventional prior art system, this occurrence would require heating any component of the system into which the activated mixed composition enters to expel the coagulated gel. This usually does not occur as long as the prior art system is used continuously or uninterruptedly in short intervals. However, if the prior art system is left idle for a period of time, the activated mixed composition from the heater can migrate back to where it can solidify and plug one of the fluid lines of the system. In addition, these systems can be individually subjected to a full charge condition. The present invention provides a method of controlling one of the systems 10 for avoiding a crowded condition whereby the activated mixed composition from the heater 14 is prevented from migrating back through the system 10.

2 is a diagram showing the interconnection of the mixed material container 24, the hopper 26, the motor 28, the pump 30, the fluid outlet block 32, the relief valve 33, and the electronics 34 that perform control of the hot melt dispensing system 10. A schematic of one of the pump assemblies 12. Pump 30 includes an inlet 36, an outlet 38, and fluid lines 40 and 42. The relief valve 33 is positioned within the return line 44 that connects the fluid outlet block 32 to the hopper 26. Electronic device 34 includes communication circuitry 20 that is coupled to position sensor 46, relief valve 33, and motor 28.

Pump 30 includes a pump for pressurizing liquid material from hopper 26. Pump 30 can include any conventional pump as is known in the art. For example, in one embodiment, pump 30 can include a positive displacement pump (such as a diaphragm pump or a linear displacement piston pump). Pump 30 is driven by motor 28, which may include any conventional motor known in the art. For example, motor 28 may include a pneumatic motor or an electric motor that rotates a shaft member for powering pump 30. Electronic device 34 selectively operates motor 28 to drive pump 30 based on an operator input or a stylized schedule.

The inlet 36 of the pump 30 is fluidly coupled to the hopper 26 by a fluid line 40, such as. The hopper 26 includes a container or receptacle that holds the hot melt material container 24 and directs material to the inlet 36 of the pump 30. For example, the hopper 26 can have a funnel shape or can have a separate pump to prime the pump 30. As mentioned above, the hot melt material container 24 includes a mixed composition comprising one of the heterogeneously dispersed polymeric particles suspended in an absorbent liquid component. In one embodiment, the material container 24 includes a liner bag package that can be placed into or on the hopper 26. The outlet 38 of the pump 30 is fluidly coupled to the fluid outlet block 32 by a fluid line 42. Fluid outlet block 32 includes receiving from The fluid of pump 30 directs the pressurized fluid to a fluid manifold of fluid line 18 and return line 44. Fluid line 18 extends to a heater and dispenser such as heater 14 and dispenser 16 (Fig. 1). The return line 44 extends to the material hopper 26. The flow through the return line 44 is controlled by a release valve 33 that is selectively operable by the electronics 34.

Electronic device 34 typically operates hot melt dispensing system 10 in an automated manner. As such, electronic device 34 includes a computer system including one of the processors, memory, graphics display, user interface, memory, and the like as is known in the art. Under normal or typical operating conditions, electronic device 34 maintains system 10 in a state such that the activated (heated) mixing composition can be dispensed at the dispenser. Under these conditions, the motor 28 is active to maintain the pump 30 in a pressurized, operational state. As such, the pump 30 receives the unpressurized fluid from the hopper 26 and maintains the pressurized fluid downstream of the outlet 38. In addition, electronic device 34 activates heater 14 to cause a heat or heat output. Therefore, the mixed composition pushed by the pump 30 to the dispenser 16 first passes through the heater 14. The heat output of the heater 14 causes the suspended polymeric particles in the liquid component to melt, thereby forming a hot melt adhesive. Accordingly, the pressurized and unheated mixed composition is supplied upward to the heater 14, and the pressurized and heated mixed composition is supplied to the heater 14 and the dispenser 16. The dispenser 16 can thus be manually or automatically operated to distribute the activated mixed composition.

However, when the activated mixed composition is not being dispensed, the system 10 is sometimes placed under normal operating conditions (such as in the case of motor 28 and heater 14 operation). If the system 10 is not expected to be used for an extended period of time, such as at the end of a day or a manufacturing shift, it is generally desirable to shut down the entire system. (such as) The short inactivity period between the dispensing operations does not have an effect on the operation of system 10. However, if system 10 is energized for a prolonged period of time without the application of any fluid, system 10 may experience a phenomenon known as "crowding," in which pump 30 becomes filled with the mixed composition. Melted polymeric particles. This phenomenon occurs when the pump 30 is maintained in a state in which there is a pressure difference between the inlet 36 and the outlet 38. This pressure differential can cause the liquid component of the mixed composition to flow back through the system, particularly through the seal of pump 30.

In prior art systems, the pump can become stagnant and the heated mixed composition can be returned from the heater to a fluid line. Once the heated mixed composition moves away from the heater, it solidifies after a period of time, thus plugging the fluid line. This makes the system inoperable, thereby wasting production time. A maintenance system is required to remove the coagulated mixed composition from the fluid line upstream of the heater. The coagulated mixed composition can be remelted by heat, but once it has migrated far enough away from the heater within the fluid line, an external heat source must be introduced to remove the coagulated mixed composition from prior art systems. In the present invention, electronic device 34 performs an operational algorithm to prevent pump 30 from operating under pressure for a prolonged period of time without dispensing a fluid.

3 is a block diagram summarizing one of the methods by which electronic device 34 of FIG. 2 performs to avoid crowding in pump 30. At step 100, the hot melt dispensing system 10 is activated to begin the process of dispensing the activated mixed composition or hot melt adhesive. In particular, electronic device 34 transmits a signal to heater 14 via communication line 20. The heater 14 then activates the mixed composition within the dispenser 16. In one embodiment, the heater 14 is directly coupled to one of the outlet valves of the dispenser 16 such that the heater 14 activates only the mixed composition that is ready to be dispensed. As mentioned And, electronic device 34 also sends a signal to any other heater used in system 10. The mixed composition in line 18 upstream of heater 14 remains unmelted. At step 105, pump 30 is started, such as by electronic device 34 transmitting a signal to motor 28 via communication line 20. Accordingly, pump 30 is operative to deliver the pressurized mixed composition to fluid outlet block 32 and dispenser 16. As such, system 10 is ready to dispense the activated mixed material.

At step 110, the electronic device 34 monitors the pump 30 for activity. In particular, electronic device 34 communicates with position sensor 46 coupled to pump 30 via communication line 20. Position sensor 46 determines the movement of one of the components of pump 30, which provides an indication of whether an active pumping is occurring. For example, position sensor 46 can monitor the position of one of the piston shaft members to displace a linear displacement piston pump. Alternatively, the activity of the pump 30 can be indirectly monitored by monitoring the activity of the dispenser 16. Thus, one of the triggers, actuating levers or nozzles of the dispenser 16 can be provided with a motion sensor or position sensor. Thus, at step 110, electronic device 34 continuously monitors pump 30 to detect activity. The electronic device 34 maintains a counter or clock that is activated when the movement in the pump 30 is stopped. In the illustrated embodiment, electronic device 34 maintains a single clock that determines one of two threshold levels of inactivity of pump 30. In other embodiments, electronic device 34 includes two separate clocks that each individually determine a threshold level.

At step 120, after the electronic device 34 determines that the pump 30 has been idle for a first threshold level (referred to as an "idle" threshold level, the electronic device 34 places the system 10 in an inactive mode. In the standby mode, the electronic device 34 sends a command to the heater 14 via the communication line 20 to reduce the signal of the heat output to the heater 14. The heat output is reduced to avoid one level of activation of the mixed material, This provides a cost savings with reduced energy output. The heat output level is maintained high enough to allow the heater 14 to quickly rise back to the operating temperature when the operation of the system 10 is again desired or desired. When it is known that system 10 will be used again for a short period of time (such as after a maintenance operation or completion of a scheduled interruption), the standby mode can be initiated at a first threshold level. The time limit of the first threshold level can be set and adjusted by the operator of one of the systems 10 at the electronic device 34.

While in the standby mode, electronics 34 continues to monitor the inactivity of pump 30. At step 130, if an additional amount of time exceeds the first "idle" threshold such that a second threshold level or "inactive" threshold is reached, the electronic device 34 begins to shut down the components of the system 10. First, the heater 14 is turned off or powered down at step 150. At step 160, pump 30 is turned off or powered down by electronics 34. In particular, electronic device 34 commands motor 28 and heater 14 to cease operation. Inactivity of the motor 28 causes the pump 30 to no longer actively create a pressure differential between the inlet 36 and the outlet 38, thereby eliminating the condition under which the crowd can occur. Inactivity of the heater 14 avoids melting of the additional mixed composition. In step 170, after a sufficient length of time has elapsed, the mixed composition within heater 14 is ultimately cooled to a temperature at which solidification occurs. As such, the coagulated mixing composition within the heater 14 can be remelted immediately after the heater 14 is activated, but the mixed material in the fluid line 18 that is not far from the heater 14 remains unactivated in a suspended liquid state. Thus, the activated mixed composition is prevented from drifting back or migrating into the fluid line 18 or pump assembly 12. At step 180, pump 30 is depressurized to allow any residual remaining in system 10 (such as lines 42 and 44) to be pressurized. The composition is turned back to the hopper 26 via the back. In particular, the electronic device 34 sends a command release valve 33 to open a signal to the valve. The relief valve 33 can include any suitable automated shut-off valve. Since all of the mixed materials that have been activated will solidify in the heater 14 immediately after cooling, only the unactivated mixed composition will return from the fluid line 18 to the fluid outlet block 32, line 42 and pump 30 when the valve 33 is open. in. As such, the system 10 is fully in one of the deactivated modes in which no pumping and heating occurs and no dispensing system is possible. In this state, the migration back of the liquid component of the mixed composition in the pump 30 is avoided because there is no pressure differential across the inlet 36 and the outlet 38. As such, the system 10 in which the activated mixed composition enters the heat system from which the heater 14 is not available is avoided. In addition, the pump 30 is prevented from being crowded.

At step 190, the electronic device 34 restarts the system 10. Specifically, the power to the pump 30 and the heater 14 is restored. Further, the release valve 33 returns to a closed state. In one embodiment, system 10 is restarted after an operator provides an indication to electronic device 34. In another embodiment, the electronic device 34 restarts the system 10 as part of a pre-programmed schedule. For example, electronic device 34 can place system 10 in an inactive mode and then place it in a deactivated mode at the end of a shift after system 10 has been run. The electronic device 34 can then return the system 10 to an operational state at the beginning of the next shift.

While the invention has been described with respect to the preferred embodiments, the embodiments of the invention

10‧‧‧Hot melt dispensing system/system

12‧‧‧Pump assembly/pump system

14‧‧‧heater

16‧‧‧ dispenser

18‧‧‧Fluid line/pipeline

20‧‧‧Communication lines

22‧‧‧Connector

24‧‧‧Mixed material container/hot melt material container/material container

26‧‧‧Loading hopper/material loading hopper

28‧‧‧Motor

30‧‧‧ pump

32‧‧‧Fluid export block

33‧‧‧Release valve/valve

34‧‧‧Electronic devices

36‧‧‧ Entrance

38‧‧‧Export

40‧‧‧ fluid pipeline

42‧‧‧Fluid line/line

44‧‧‧Return line/line

46‧‧‧ position sensor

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic illustration of one of a hot melt dispensing system comprising a pump assembly, a heater and a dispensing gun for use with a mixed hot melt composition.

2 is a pump of FIG. 1 showing a hybrid material container, a hopper, a pneumatic motor, a pump, a fluid outlet block, a release valve, and an interconnect that performs control of the hot melt dispensing system. A schematic diagram of the assembly.

3 is a block diagram summarizing one of the methods by which the electronic device of FIG. 2 performs to avoid crowding in the pump assembly.

10‧‧‧Hot melt dispensing system/system

12‧‧‧Pump assembly/pump system

14‧‧‧heater

16‧‧‧ dispenser

18‧‧‧Fluid line/pipeline

20‧‧‧Communication lines

24‧‧‧Mixed material container/hot melt material container/material container

26‧‧‧Loading hopper/material loading hopper

28‧‧‧Motor

30‧‧‧ pump

32‧‧‧Fluid export block

33‧‧‧Release valve/valve

34‧‧‧Electronic devices

36‧‧‧ Entrance

38‧‧‧Export

40‧‧‧ fluid pipeline

42‧‧‧Fluid line/pipeline

44‧‧‧Return line/pipeline

46‧‧‧ position sensor

Claims (25)

A method for avoiding crowding in a system for pumping a mixed material, the method comprising: monitoring activity of a pump pumping a mixed material; shutting down the melt pumping at an inactive threshold level One of the mixed materials heater; and the bleed pump pressure. The method of claim 1, further comprising: solidifying the mixed material in the heater prior to draining the pump pressure. The method of claim 1 wherein the bleed pump pressure comprises routing the pressurized mixed material from a pump outlet to a pump inlet. The method of claim 1 wherein the bleed pump pressure comprises opening a release valve. The method of claim 1, and further comprising: deactivating a motor that drives the pump at the inactive threshold level. The method of claim 1, wherein the inactivity threshold comprises a period of time during which the pump is not in motion. The method of claim 1, and further comprising: reducing the heat output of the heater at an idle threshold level prior to turning off the heater at the inactive threshold. The method of claim 7, wherein the inactivity threshold comprises a period of time longer than a period of time including the idle threshold. The method of claim 1, and further comprising: restarting the system. The method of claim 9, wherein restarting the system comprises: pressurizing the pump; and activating the heater. The method of claim 10, wherein pressurizing the pump comprises: closing a pump release valve; and powering a pump motor. The method of claim 9, wherein restarting the system comprises: automatically restarting the system. The method of claim 1, wherein monitoring the activity of the pump comprises determining a position of a pump shaft member or determining a position of a dispenser rod. A material pumping system comprising: a pump pumping material having an inlet and an outlet; a heater receiving the pumped material from the outlet; and a dispenser receiving the heating from the heater The heated pumped material; and an electronic device that monitors the activity of the pump and is configured to reduce the output of the heater and the pump at an inactive threshold level. The material pumping system of claim 14, wherein the heater is coupled to the dispenser and is separated from the pump outlet by a hose. The material pumping system of claim 14, and further comprising: a position sensor coupled to the pump and in electronic communication with the electronic devices. The material pumping system of claim 14, and further comprising: a release valve positioned to fluidly couple the inlet and the outlet back In the flow line and in electronic communication with the electronic devices. The material pumping system of claim 17, and further comprising: a material hopper connected to the return line between the pump inlet and the pump outlet. The material pumping system of claim 14, and further comprising: a motor configured to drive the pump. The material pumping system of claim 14, wherein: the electronic devices are configured to turn off the heater and the pump after detecting that the pump has been deactivated for a first period of time. The material pumping system of claim 20, wherein: the electronic devices are configured to reduce the output of the heater after detecting that the pump has been deactivated for less than a second period of time of the first period of time . A method for avoiding crowding in a system for pumping a mixed hot melt material, the method comprising: pumping a mixed hot melt material by means of a pump; heating the mixed hot melt material by means of a heater; detecting the Pump activity; determining a first period of inactivity; reducing the heat output of the heater; and depressurizing the pump. The method of claim 22, wherein reducing the heat output of the heater comprises powering down the heater. The method of claim 23, wherein decompressing the pump comprises turning off a pump motor. The method of claim 24, wherein depressurizing the pump further comprises opening a pressure relief valve fluidly coupled to one of the outlets of the pump.