US20140263451A1

US20140263451A1 - Variable orifice outlet assembly

Info

Publication number: US20140263451A1
Application number: US13/837,147
Authority: US
Inventors: Daniel P. Ross; Paul R. Quam; Robert J. Lind; Douglas B. Farrow; John S. Lihwa; Joseph E. Tix; Mark J. Brudevold; Mark T. Weinberger; Mark W. Sheahan; Shaun M. Cook; Nicholas D. Long; Michael J. Sebion
Original assignee: Graco Minnesota Inc
Current assignee: Graco Minnesota Inc
Priority date: 2013-03-15
Filing date: 2013-03-15
Publication date: 2014-09-18
Also published as: WO2014143106A1; TW201434538A

Abstract

A pumping system comprises a pump, first and second channels, a valve, and an actuator. The pump pumps fluid according to a pumping cycle. The first channel has a first fluid flow orifice with a first diameter, while the second channel has a second fluid flow orifice with a second diameter greater than the first diameter. The valve is configured to direct fluid from the pump to the first channel in a first state, and to the second channel in a second state. The actuator is configured to switch the valve into the first state during a high pressure period of the pumping cycle, and into the second state during a low pressure period of the pumping cycle.

Description

BACKGROUND

The present disclosure relates generally to systems for dispensing hot melt adhesive. More particularly, the present disclosure relates to a pump outlet assembly for pressure control.
Hot melt dispensing systems are typically used in manufacturing assembly lines to automatically disperse an adhesive used in the construction of packaging materials such as boxes, cartons and the like. Hot melt dispensing systems conventionally comprise a material tank, heating elements, a pump, and a dispenser. Solid polymer pellets are melted in the tank using a heating element before being supplied to the dispenser by the pump.
It is desirable in many hot melt applications that adhesive be dispensed at a substantially constant rate so as to provide a uniform layer of adhesive. Accordingly, conventional hot melt systems often use heated supply systems wherein the pump and dispenser are connected by a heated hose. The pump (typically a linear displacement piston pump with a single reciprocating piston) discharges melted adhesive from the tank with pressure that varies over the course of each pumping cycle. The hose carries melted adhesive from the pump to the dispenser, and acts as a fluid accumulator or pressure dampener to alleviate changes in pressure over the course of the pumping cycle of the pump.

SUMMARY

According to one embodiment of the present invention, a pumping system comprises a pump, first and second channels, a valve, and an actuator. The pump pumps fluid according to a pumping cycle. The first channel has a first fluid flow orifice with a first diameter, while the second channel has a second fluid flow orifice with a second diameter greater than the first diameter. The valve is configured to direct fluid from the pump to the first channel in a first state, and to the second channel in a second state. The actuator is configured to switch the valve into the first state during a high pressure period of the pumping cycle, and into the second state during a low pressure period of the pumping cycle.
According to a second embodiment of the present invention, an adhesive system comprises a melt system, a pump, a dispenser, and an outlet assembly. The melt system melts adhesive, and the pump pumps the adhesive from the melt system according to a pumping cycle. The dispenser is configured to receive and dispense the adhesive from the pump. The outlet assembly is disposed between the pump and the dispenser to smooth melted adhesive pressure at the dispenser by routing the adhesive through a first diameter orifice during a first portion of the pumping cycle, and through a second diameter orifice during a second portion of the pumping cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a system for dispensing hot melt adhesive.

FIG. 2 is a simplified cross-sectional view of an outlet assembly for the system of FIG. 1.

FIG. 3 is an exemplary graph of inlet and outlet pressure in the outlet assembly of FIG. 2 as a function of time.

DETAILED DESCRIPTION

FIG. 1 is a schematic view of system 10, which is a system for dispensing hot melt adhesive. System 10 includes cold section 12, hot section 14, air source 16, air control valve 17, and controller 18. In the embodiment shown in FIG. 1, cold section 12 includes container 20 and feed assembly 22, which includes vacuum assembly 24, feed hose 26, and inlet 28. In the embodiment shown in FIG. 1, hot section 14 includes melt system 30, pump 32, and dispenser 34. Air source 16 is a source of compressed air supplied to components of system 10 in both cold section 12 and hot section 14. Air control valve 17 is connected to air source 16 via air hose 35A, and selectively controls air flow from air source 16 through air hose 35B to vacuum assembly 24 and through air hose 35C to motor 36 of pump 32. Air hose 35D connects air source 16 to dispenser 34, bypassing air control valve 17. Controller 18 is connected in communication with various components of system 10, such as air control valve 17, melt system 30, pump 32, and/or dispenser 34, for controlling operation of system 10.
Components of cold section 12 can be operated at room temperature, without being heated. Container 20 can be a hopper for containing a quantity of solid adhesive pellets for use by system 10. Suitable adhesives can include, for example, a thermoplastic polymer glue such as ethylene vinyl acetate (EVA) or metallocene. Feed assembly 22 connects container 20 to hot section 14 for delivering the solid adhesive pellets from container 20 to hot section 14. Feed assembly 22 includes vacuum assembly 24 and feed hose 26. Vacuum assembly 24 is positioned in container 20. Compressed air from air source 16 and air control valve 17 is delivered to vacuum assembly 24 to create a vacuum, inducing flow of solid adhesive pellets into inlet 28 of vacuum assembly 24 and then through feed hose 26 to hot section 14. Feed hose 26 is a tube or other passage sized with a diameter substantially larger than that of the solid adhesive pellets to allow the solid adhesive pellets to flow freely through feed hose 26. Feed hose 26 connects vacuum assembly 24 to hot section 14.
Solid adhesive pellets are delivered from feed hose 26 to melt system 30. Melt system 30 can include a container (not shown) and resistive heating elements (not shown) for melting the solid adhesive pellets to form a hot melt adhesive in liquid form. Melt system 30 can be sized to have a relatively small adhesive volume, for example about 0.5 liters, and configured to melt solid adhesive pellets in a relatively short period of time. Pump 32 is driven by motor 36 to pump hot melt adhesive from melt system 30, through supply hose 38, to dispenser 34. Motor 36 can be an air motor driven by pulses of compressed air from air source 16 and air control valve 17. Pump 32 can, for instance, be a linear displacement pump such as a double-action piston pump driven by motor 36. In the illustrated embodiment, dispenser 34 includes manifold 40 and dispensing module 42. Hot melt adhesive from pump 32 is received in manifold 40 and dispensed via module 42. Dispenser 34 can selectively discharge hot melt adhesive whereby the hot melt adhesive is sprayed out outlet 44 of module 42 onto an object, such as a package, a case, or another object benefiting from hot melt adhesive dispensed by system 10. Module 42 can be one of multiple modules that are part of dispenser 34. In an alternative embodiment, dispenser 34 can have a different configuration, such as a handheld gun-type dispenser. Some or all of the components in hot section 14, including melt system 30, pump 32, supply hose 38, and dispenser 34, can be heated to keep the hot melt adhesive in a liquid state throughout hot section 14 during the dispensing process.
System 10 can be part of an industrial process, for example, for packaging and sealing cardboard packages and/or cases of packages. In alternative embodiments, system 10 can be modified as necessary for a particular industrial process application. For example, in one embodiment (not shown), pump 32 can be separated from melt system 30 and instead attached to dispenser 34. Supply hose 38 can then connect melt system 30 to pump 32.
Outlet assembly 100 connects pump 32 to supply hose 38. Outlet assembly 100 is a variable orifice outlet assembly configured to reduce variation in fluid pressure at supply hose 38 and manifold 40 across the pumping cycle of pump 32. Outlet assembly 100 is described in detail below, with respect to FIGS. 2 and 3.
FIG. 2 illustrates outlet assembly 100 disposed between pump 32 and supply hose 38. In the depicted embodiment, outlet assembly 100 comprises inlet plenum 102, first passage 104, second passage 106, outlet plenum 108, valve 110 (with shuttle 112 and first and second openings 114 and 116, respectively), actuator 118, first orifice plug 120 (with first orifice 124) and second orifice plug 122 (with second orifice 126). Outlet assembly 100 is a variable orifice outlet assembly configured to selectively switch between two (or more, in alternative embodiments) fluid paths from pump 32 to supply hose 38.
Pump 32 pumps hot melted adhesive from melt system 30 into inlet plenum 102 of outlet assembly 100 at inlet pressure P_I. Inlet plenum 102 and outlet plenum 108 are chambers, passage, or reservoirs that accumulate liquid adhesive. Inlet pressure P_Iof liquid adhesive entering inlet plenum 102 varies as a function of the pumping cycle of pump 32 (see FIG. 3, discussed below). In an exemplary embodiment, pump 32 is a linear displacement double-action piston pump. As pump 32 reciprocates between up- and down-strokes, liquid is forced into inlet plenum 102. During changeover between strokes of pump 32, inlet pressure P_Itemporarily drops. Opposite strokes of pump 32 may also differ somewhat in pumping pressure.
Valve 110 is a switching valve that provides a path from inlet plenum 102 to either first passage 104 or second passage 106. In the depicted embodiment, valve 110 is a shuttle valve with sliding shuttle 112 having first and second openings 114 and 116. Inlet and outlet plena 102 and 108 are depicted as forked passages having separate branches leading respectively to and from inlet first passage 104 and second passage 106. First passage 104 includes first orifice 124, while second passage 106 includes second orifice 126. First and second orifices 124 and 126 are apertures narrower than first and second openings 114 and 116 and first and second passages 104 and 106. First and second orifices 124 and 126 have diameters selected to produce desired permanent pressure drops ΔP₁and ΔP₂, respectively, between inlet plenum 102 and outlet plenum 108, as described in further detail below. First and second passages 104 and 106 have identical diameters, as do first and second openings 114 and 116, such that the diameters of first and second orifices 124 and 126 determine the difference between ΔP₁and ΔP₂.
In the depicted embodiment, valve 110 has first and second valve states V1 and V2 corresponding to locations of sliding shuttle 112. Valve 110 is shown in first valve state V1, wherein sliding shuttle 112 aligns first opening 114 with first passage 104 and seals second passage 106, thereby providing a fluid path from inlet plenum 102 to outlet plenum 108 via first passage 104 and first orifice 124. In second valve state V2 (not shown), shuttle 112 aligns second opening 116 with second passage 106 and seals first passage 104, thereby providing a fluid path from inlet plenum 102 to outlet plenum 108 via second passage 106 and second orifice 126. In alternative embodiments, valve 110 may, for instance, be a ball valve or similar valve type with a single configurable or redirectable opening instead of separate first and second openings 114 and 116. When valve 110 is in first valve state V1, the permanent pressure drop between inlet and outlet plena 102 and 108 is ΔP₁, as described above. When valve 110 is in second valve state V2, the permanent pressure drop between inlet and outlet plena 102 and 108 is ΔP₂. Actuator 118 switches valve 110 between first and second valve states V1 and V2 over the course of the pumping cycle of pump 32. As described in further detail below, valve state V1 is used during each sustained stroke of pump 32, while valve state V2 is used during pump changeover.
Actuator 118 is a valve actuator such as a motor-driven or hydraulic actuator coupled to valve 110. Actuator 118 drives valve 110 in accordance with control line cl, a mechanical or electrical control line that matches states of valve 110 to the cycle of pump 32 as described in further detail below with respect to FIG. 3. Control line cl can, for instance, be a hydraulic pilot line driven by changes in pump pressure within pump 32, and actuator 118 can be a hydraulic switch. Alternatively, actuator 118 can be an electrical switch and control line cl can be an electrical line carrying electrical signals to actuator 118. These electrical signals may be provided by controller 18 so as to synchronize actuator 118 with the commanded pump cycle (discussed above with respect to FIG. 1) of pump 32, or may reflect pressure readings from a pressure sensor within or adjoining pump 32. By switching valve 102 between valve states V1 and V2, actuator 118 controls whether fluid flowing through outlet assembly 100 passes through first orifice 124 or second orifice 126. In this way, actuator 118 controls whether the pressure drop between inlet and outlet plena 102 and 108 is ΔP₁(corresponding to valve state V1) or ΔP₂(corresponding to valve state V2).
In the depicted embodiment, first orifice 124 has a narrower diameter than second orifice 126. As is well known in the art, narrower apertures produce greater permanent pressure drops. Accordingly, ΔP₁across first orifice 124 is greater than permanent pressure drop ΔP₂across second orifice 126. By matching larger pressure drop ΔP₁with periods of high inlet pressure P_I, and smaller pressure drop ΔP₂with periods of low inlet pressure P_I, outlet assembly 100 reduces fluctuation in outlet pressure P_O. To this end, actuator 118 switches valve 100 to valve state V1 during relatively high pressure sustained strokes of pump 32, and to valve state V2 during relatively low pressure changeover periods of pump 32. In this way, outlet assembly 100 produces a relatively uniform outlet pressure P_Othat varies substantially less over the course of each pumping cycle of pump 32 than inlet pressure P_I.
In the depicted embodiment, first and second orifices 124 and 126 pass through first and second orifice plugs 120 and 122, respectively. First and second orifice plugs 120 and 122 are removable inserts that fit into outlet assembly 100 to provide orifices of desired diameters. First and second orifice plugs 120 and 122 may, for instance, be sealed threaded cylindrical components that screw into outlet assembly 100 to situate orifices 124 and 126 in first and second passages 104 and 106, respectively. First and/or second orifice plugs 120 can be swapped out for similar plugs with different diameter orifices so as to tune permanent pressure drops ΔP₁and ΔP₂to achieve reduced variation in outlet pressure P_Oacross the pump cycle of pump 32. In alternative embodiments, first and second orifices 124 and 126 may be permanent structures formed within outlet assembly 100.
Although outlet assembly 100 has been described above as a variable outlet assembly having two separate orifices 124 and 126 with differing diameters, alternative embodiments may include more or fewer apertures. Some alternative embodiments, for instance, may dispense with valve 110 and replace orifices 124 and 126 with a single aperture with continuously variable diameter controllable to compensate for fluctuations in inlet pressure P_Ifrom pump 32. In other embodiments, valve 110 may switch between three or more orifice passages for greater granularity of pressure control as compared to the two-orifice embodiment described above.
FIG. 3 is a graph of an inlet pressure P_Iand outlet pressure P_Oof outlet assembly 100 as a function of time, illustrating the switching of valve 110 from valve state V1 to valve state V2 during pump changover. FIG. 3 is only intended as an illustration of fluid pressure in outlet assembly 100, and is not drawn to scale. As described above with respect to FIG. 2, actuator 118 switches valve 110 of outlet assembly 100 between valve states V1 and V2. Valve state V1 routes fluid through first orifice 124, while valve state V2 routes fluid through second orifice 126. Because first orifice 124 is narrower than second orifice 126, permanent pressure drop ΔP₁in valve state V1 is greater than permanent pressure drop ΔP₂in valve state V2. By switching from valve state V1 to valve state V2 during relatively low pressure pump changeover periods, outlet assembly reduces pressure fluctuation in outlet pressure P_O, as shown. P_Imay experience different pressure drops at the top and bottom changeover of pump 32, as illustrated in FIG. 3. Inlet and outlet plena 102 and 108 can, in some embodiments, act as fluid accumulators, further smoothing the outlet pressure P_Oas a function of time. Outlet assembly 100 thus increases the uniformity of outlet pressure P_O, allowing dispenser 34 to uniformly apply hot melt adhesive. Although outlet assembly 100 has been described as feeding supply hose 38, alternative embodiments may dispense with supply hose 38 and pump adhesive directly into dispenser 34, as outlet assembly 100 substantially obviates the need for the accumulator function of supply hose 38. Outlet assembly 100 thus enables smooth application of adhesive in a more compact system.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

1. A pumping system comprising:

an pump that pumps a fluid according to a pumping cycle;

a first passage with a first orifice having a first diameter;

a second passage with a second orifice having a second diameter greater than the first diameter;

a valve configured to direct the fluid from the pump to the first passage in a first state, and to the second passage in a second state; and

an actuator configured to switch the valve into the first state during a high pressure period of the pumping cycle, and into the second state during a low pressure period of the pumping cycle.

2. The pumping system of claim 1, wherein the first orifice is disposed through a first removable plug in the first passage, and the second orifice is disposed through a second removable plug in the second passage.

3. The pumping system of claim 1, wherein the actuator comprises an electronic switch.

4. The pumping system of claim 3, wherein the electronic switch actuates the valve in response to sensed pressure readings from the pump.

5. The pumping system of claim 3, further comprising:

a pump motor configured to drive the pump; and

a controller configured to control the pump motor and the electronic switch according to the pumping cycle.

6. The pumping system of claim 1, wherein the actuator comprises a hydraulic switch.

7. The pumping system of claim 6, wherein the hydraulic switch is controlled by a hydraulic pilot line driven by changes in pressure in the pump.

8. The pumping system of claim 1, wherein the pump is a double-action piston pump.

9. An adhesive system comprising:

a melt system for melting adhesive;

a pump disposed to pump the adhesive from the melt system according to a pumping cycle;

a dispenser configured to receive and dispense the adhesive from the pump; and

an outlet assembly disposed between the pump and the dispenser to smooth melted adhesive pressure at the dispenser by routing the adhesive through a first diameter orifice during a first portion of the pumping cycle, and through a second diameter orifice during a second portion of the pumping cycle.

10. The adhesive system of claim 9, wherein the first diameter orifice has a narrower diameter than the second diameter orifice, and wherein the outlet assembly further comprises a valve disposed to route the adhesive through the second diameter orifice during changeover of the pump, and through the first diameter orifice otherwise.

11. The adhesive system of claim 10, wherein the valve is a shuttle valve.

12. The adhesive system of claim 10, wherein at least one of the first and second diameter orifices is situated in a removable plug.

13. The adhesive system of claim 9, further comprising a supply hose configured to carry adhesive from the outlet assembly to the dispenser.

14. An outlet assembly for a pump, the outlet assembly comprising:

an inlet plenum disposed to receive fluid from the pump;

an outlet plenum disposed to supply fluid to a downstream component;

a first orifice fluidly disposed between the inlet and outlet plena, and having a first orifice diameter;

a second orifice fluidly disposed between the inlet and outlet plena, and having a second orifice diameter greater than the first orifice diameter;

a valve with two valve states:

a first valve state routing fluid from the inlet plenum to the outlet plenum via the first orifice; and

a second valve state routing fluid from the inlet plenum to the outlet plenum via the second orifice; and

an actuator configured to switch the valve from the first valve state to the second valve state during changeover of the pump.

15. The outlet assembly of claim 14, wherein the first orifice is situated in a first passage connecting the inlet and outlet plena, and the second orifice is situated in a second passage connecting the inlet and outlet plena.

16. The outlet assembly of claim 15, wherein the valve is a shuttle valve disposed to open the inlet plenum to either the first passage or the second passage.

17. The outlet assembly of claim 14, wherein the downstream component is a fluid dispenser.

18. The outlet assembly of claim 14, wherein the fluid is hot melt adhesive.

19. A method for controlling outlet pressure of a pump having a pumping cycle, the method comprising:

directing fluid through a first orifice during a high pressure period of the pumping cycle corresponding to a sustained pump stroke; and

directing fluid through a second orifice wider than the first orifice during a low pressure period of the pumping cycle corresponding to pump changeover.

20. The method of claim 19, wherein:

directing fluid through the first orifice comprises switching a valve to a first valve state that fluidly connects the pump to the first orifice; and

directing fluid through the second orifice comprises switching the valve to a second valve state that fluidly connects the pump to the second orifice.

21. The method of claim 20, further comprising actuating the valve based on pressure in the pump.