CA1276918C - Powder delivery system - Google Patents
Powder delivery systemInfo
- Publication number
- CA1276918C CA1276918C CA000497687A CA497687A CA1276918C CA 1276918 C CA1276918 C CA 1276918C CA 000497687 A CA000497687 A CA 000497687A CA 497687 A CA497687 A CA 497687A CA 1276918 C CA1276918 C CA 1276918C
- Authority
- CA
- Canada
- Prior art keywords
- powder
- hopper
- auxiliary
- primary
- pump
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
- B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
- B05B7/1404—Arrangements for supplying particulate material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
- B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
- B05B7/1404—Arrangements for supplying particulate material
- B05B7/1472—Powder extracted from a powder container in a direction substantially opposite to gravity by a suction device dipped into the powder
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
- B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
- B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
- B05B7/1404—Arrangements for supplying particulate material
- B05B7/1477—Arrangements for supplying particulate material means for supplying to several spray apparatus
Landscapes
- Nozzles (AREA)
- Air Transport Of Granular Materials (AREA)
Abstract
Abstract of the Disclosure A method and apparatus for pumping air entrained solid particulate powder material from a hopper to a dispenser so as to maintain a steady rate of flow of powder to the dispenser. The apparatus comprises a primary fluidized bed hopper from which powder is pumped to an auxiliary and much smaller capacity auxiliary fluidized bed hopper. The powder is then supplied from the auxiliary hopper to the dispenser.
Description
~ . ~
3, ~zt7 POWDER DELIVERY SYSTEM
.
This invention relates to systems for supplying air entrained solid particulate powder material to powder spray guns or dispensers. More particularlyj this invention relates to an improved system for supplying an even flow of powder from a fluidized powder source to a powder spray gun or dispenser. ~
Characteristically, powder is supplied to a powder spray gun through a pneumatic conveyor line within which there is a powder pump containing a low pressure venturi pumping chamber. This chamber is intersected by a powder supply passage through which powder is supplied to the pump from a fluidized bed hopper. In order to meter or control the rate of flow of powder from the fluidized bed into the venturi pumping chamber, such pumps conventionally include a metering air flow passage operable to inject a controllefl flow of air into the powder supply passage.
The pressure of this metering air flow controls the amount of air which is mixed with the powder entering the pump, and consequently the rate of flow of powder from the pump.
~7 . ;,. ~ , .. ..
., ~ ` ` ~I.;Z'7~
One of the shortcomings of all powder spray systems, including systems incorporating powder p`umps of the type described hereinabove, is that the powder ejected from the spray gun of the system commonly flows unevenly from the gun. There are periodic puEfs or clouds of powder ejected from the gun and periodic reductions in the density of powder ejected from the gun. Such periodic increases or decreases in powder density sprayed from the gun result in uneven application of powder to a target substrate to which the powder is applied. Consequently, such random changes in powder density are very undesirable.
There have been numerous attempts ~o minimize or reduce these random changes of powder density sprayed from a powder spray gun. Such attempts have taken the form of changes in the design of the powder spray gun, changes in the design and configuration of the powder pump, etc. Most of these changes have improved the situation somewhat, but have not cured the problem.
It has been an objective of this invention to provide an improved powder spray system wherein inadvertent or random changes in the flow rate of powder dispensed from a powder spray gun or dispenser of the system are minimized or eliminated.
This invention is in part predicated upon the discovery that one source of uneven flow of powder from a powder spray gun or dispenser of a powder spray system is the configuration of the system between the fluidized bed source of powder and the dispensing gun.
That portion of the system has heretoore simply consisted of a siphon tube for supplying powder from the fluidized bed to a powder pump, the pump, and a long supply hose connecting the pump to the gun. It has therefore been an objective of this invention to eliminate powder flow variances which have heretofore been attributable to the configuration of this portion of the system.
These objectives are achieved, and this invention is predicated in part upon the concept of supplying powder from the powder pump through a hose to an auxiliary fluidized bed of powder located near the dispensing gun, and then supplying the powder to the gun from the auxiliary fluidized bed through an auxiliary powder pump and a relatively short hose. By utilizing an auxiliary fluidized bed and an auxiliary powder pump located near the dispensing gun outlet of the system, erratic powder flow heretofore attributable to the relatively long length of hose betwéen the pump and the gun, and to a varying level of powder within the fluidized bed source of powder, have been reduced or completely eliminated.
I have found that a substantial portion of the flow variances within a conventional prior art powder spray system are attributable to two sour~es.
These sources are the relatively long hose between the 76~
pump and the gun and the varying level of powder in the fluidized bed source of powder to the system`. A
long hose between the pump and the gun creates flow variances as a result of loops and curves which inevitably occur in such long hoses. Powder collects in these loops or curves and eventually restricts flow through the hose until a pressure build-up behind the powder restriction breaks the restriction away and causes a resulting puff of powder to be dispensed from the gun while simultaneously causing a ~pressure 3 increase in the hose and a resulting increase in the flow of powder to the gun. Thereafter, the powder again begins to collect in the curve or loop of t~e hose from which it had just broken away, until it forms a restriction in the hose, breaks free, causes another puff of powder, etc.
The other primary source of varying flow from a conventionally configurated prior art powder flow system, the varying level of powder contained in the fluidized bed source of powder, cause~ flow variances as a result of differing pressures being required to draw powder into the powder pump as the powder level changes in the fluidized bed. In fact though, the vacuum within the pump tending to draw powder into the pump does not change with the differing level of powder in the fluidized bed hopper.
Instead, the vacuum pressure remains the same but the .
quantity of powder drawn into the pump changes as the level of powder in the hopper changes.
According to the practice of this invention, the powder spray system comprises a primary fluidized bed hopper source of powder and a smaller capacity auxiliary fluidized bed hopper located adjacent or near the powdér dispensing guns. A venturi style pump and a connecting hose transport powder from the primary hopper to the auxiliary hopper and an auxiliary venturi style powder pump and connecting hose transport the powder from the auxiliary hopper to a dispensing gun. There is an ovexflow pipe which extends between the auxiliary hopper and the primar~
hopper and which functions to maintain a fixed level of powder in the auxiliary hopper.
The practice of this invention with its use of an auxiliary fluidized bed hopper and an auxiliary venturi pump located closely adjacent the powder spray gun of a powder spray system enables both of the above identified sources of powder flow variances to be eliminated. Any flow variances which occur in the long hose between the primary hopper and the auxiliary hopper do not affect the flow rate between 'the auxiliary powder pump and the spray gun. Furthermore, the use of an overflow pipe between the auxiliary fluidized bed hopper and the primary fluidized bed hopper enables the level of powder in the auxiliary hopper to be maintained at a fixed level so long as an ~276~
excess amount of powder is supplied to the auxiliary fluidized bed. Thereby, flow variances attribut`able ! to the changing level of powder in the supply hopper are eliminated.
These and other objects and advantages~of this invention will be more readily apparent rom the following description of the drawings in which:
Fig. 1 is a schematic view of a powder spray system incorporating the auxiliary powder hopper and auxiliary powder pump of this invention~
Referring now to the figure, there is illustrated a powder spray system 10 for dispensing solid particulate powder material from a plurality ~
spray guns 12. Three guns 12 are illustrated but the system i5 equally applicable to the spraying of powder from a single gun or from a substantially greater number of guns 12. The guns 12 per se form no part of the invention of this application and are well known in the prior art. One such gun which is suitable for use in this application is illustrated and described in U. S. Patent No. 4,380,320 of Thomas E. Hollstein, et al for "Electrostatic Powder Spray Gun Nozzle", assigned to the assignee of this application.
The system 10, in addition to the guns 12, comprises a primary or supply hopper 14, an auxiliary hopper 16, as well as a primary pneumatic pump 18 for pumping powder from the primary hopper 14 to the auxiliary 16, and a plurality of auxiliary pneumatic - 7 ~
pumps 20 for pumping powder from the auxiliary hopper 16 to the guns 12. The pneumatic pumps 18 and 20 are conventional powder pumps which per se form no part of the invention of this application. One such pump which is suitable for use in this application is illustrated and described in U.S.
Patent No. 3,746,254 of Lane S. Duncan, et al for "Powder Spray System", assigned to the assignee of this application.
Another, and a preferred pump, useful in this system is illustrated and described in co-pending Canadian patent application Serial No. 489,024, filed August 20, 1985 and entitled "Improved Venturi Powder Pump", also assigned to the assignee of this application.
The hoppers 14 and 16 are also conventional fluidizing bed hoppers and per se form no part of the inven-tion of thi~ application. Both of these hoppers 14, 16 have an enclosed chamber 24 in the ba~e of the hopper and an air pervious ceiling 26 in the chamber. When high pressure air is admitted into the inlet 28 of the chambers 24, such air passes through the ceiling 26 of the closed chamber 24 and is operative to fluidize powder 30 contained in the hopper above the closed chamber 24.
The two hoppers differ only in that the auxiliary hopper is much smaller in size and capacity than is the supply hopper 14. In one preferred embodiment wherein the auxiliary hopper 16 supplies powder to eight guns 12, the auxiliary hopper 16 has a rm/
-8- l~
volume equal to approximately l/16th the volume of the supply hopper 14.
The two hoppers 14 and 16 also differ in that the supply hopper 14 has a vent 34 in its top wall while the auY~iliary hopper has no such vent.
Instead, the auxiliary hopper 16 is vented ~ia an overflow tube 36 which extends from the interior of the au~iliary hopper 16 downwardly through the closed chamber 24 of the hopper 16 and through ~he top wall 38 of the supply hopper 14. As explained more fully hereinafter, this overflow tube 36 functions to vent the auxiliary hopper 16 as well as to transport all excess powder from the auxiliary hopper 16 back to the supply hopper. This overflow tube also functions to maintain a fixed level of fluidized powder within the auxiliary hopper 16.
The powder pumps 18 and 20 are all identical except that the powder pumps 20 of the auxiliary hopper may be of smaller capacity than the pump 18 of the supply hopper 14. Each of these powder pumps has an inlet port 40, an outlet port 42, and an atomizi~g air inlet port 44. Additionally, each of these pumps has a powder flow passage 46 therein through which powder is drawn into a venturi pumping chambex 4~ of the pump via a siphon tube 50 which connects the inlet 52 of the powder flow passage 46 to the fluidized bed 30 of powder from which the pump draws powder. The supply hopper pump 18 draws powder from the hopper 14 ,. . .. .... .
~.2~6~
g and pumps it into the auxiliary hopp~r 16 via a transfer conduit 54 while the auxiliary hopper p`~mps 20 draw powder from the auxiliary hopper 16 and pump it to the dispensing guns 12 via short transfer hoses 56.
The inlet ports 40 of the pumps 18, 20 are connected via air lines 58 to a source of high pressure air 60 while the atomizing air inlet ports 44 of the pumps are connected to the same high pressure air source via air lines 62. Internally oE each pump there is a small air orifice through which the high pressure air from the source 60 flows into the ventùri pumping chamber 48 so ar. to create a low pressu~e within that venturi pumping chamber. That low pressure is operative to draw powder via the siphon tubes 50 upwardly into the venturi pumping chambers 48 of the pumps such that the powder can then be transported via the hose 54 from the pump 18 to the hopper 16, or in the case of the pumps 20, via the hoses 56 to the dispensing guns 12.
As is explained more fully in the above identified U. S. Patent No. 3,746,254, or in my co-pending application Serial No. ~ , the pressure o~ air supplied to the port 40 controls the quantity of powder drawn upwardly through the siphon tube into.the venturi pumping chamber 48 of the pump, and the pressure of air supplied to port 44 controls the ratio of air to powder mix within the pump.
Typically, each of the air lines 58, 62 contains a pressure regulator (not shown) through which the air pressure supplied to the inlet ports 44 may be adjusted so as to control the amount of vacuum drawn within the venturi pumping chamber 48 of the pump and the relative air to powder mix supplied to the venturi chamber through the powder flow passage 46 of the pump.
In operation of the powder dispensing system 10, high pressure air is supplied from the source 60 to the inlet ports 40, 44 of the powder pumps 18, 20, and to the inlet ports 28 of the air chambers 24 of the hoppers 14 and 16. The high pressure air supplied to the inlet port 28 of the hoppers 14, 16 is operative to fluidize all of the powder 30 contained in the supply hopper 14 and the auxiliary hopper 16.
The fluidized powder 30 in the supply hopper 14 is drawn via the siphon tube 50 upwardly into the venturi pumping chamber 48 of the pump 18. This powder is then transported from the supply hopper pump 18 via the relatively long transfer hose 54 to the powder inlet 68 of the auxiliary hopper 16. The fluidiæed powder in the auxiliary hopper 16 is in turn pumped by the auxiliary pump 20 to the dispenser guns 12 via~the relatively short hoses 56. In practice, an excess quantity of powder is pumped from the primary or supply hopper 14 to the auxiliary hopper 16, which excess is greater than the capacity of all of the pumps ~0. As a result, excess fluidized powder flows through the inlet 70 of the over-flow tube 36 back to the supply hopper 14. The level of powder within the auxiliary hopper 16 is thus always maintained at a fixed level, that of the top edge of the inlet 70 of the overflow tube.
A powder pump 72 may be associated with the overflow line 36 in the event that gravity is insufficient to carry the overflow powder to the primary~ hopper. Such a pump may be required in installation where there is substantial distance between the two hoppers or where the primary hopper is not located beneath the auxiliary hopper~ In the eve~t that a powder pump 72 is associated with the overflow line 36, a vent (not shown) would be provided in the top of the auxiliary hopper in order to maintain ambient pressure in the auxiliary hopper.
Prior to this invention, it has been the practice to pump powder directly from the supply or primary hopper 14 to the guns 12. There was no intermediate or auxiliary hopper 16 in the system. I
have found that the long hoses which hereto extended from the supply hopper 18 to the guns, as well as the constantly changing level of powder within the supply hopper 14, both contributed to and created a problem of varying powder flow from the guns. Specifically, I
have found that a long hose extending from the pump of the supply hopper to the gun had numerous curved or , ~.27~9~
looped sections wherein powder collected and tended to restrict flow through the long hose. This restri~cted flo~ in turn caused a pressure drop in the hose to the gun with a resultant drop in the ~uantity o~ powder being pumped from the supply hopper to the gun.
Periodically through, the pressure behind the powder created restriction built up to the point that it caused the restriction to break, thereby causing a high density puff of powder to be dispensed from the gun. This in turn resulted in a temporary in~crease in the flow of air and powder from the pump to the gun because of the sudden increase in air flow through the hose. Then the restriction would again build up ~n the hose at the same point at which it had just broken free and the process was repeated.
I have found that by utilizing the auxiliary hopper 16 between the supply hopper and the guns, and preferably close to the guns, the erratic powder flow from the guns created by these powder created restrictions in the hose are minimized or substantially eliminated. I have also found that the use of the auxiliary hopper 16 assists in maintaining an even flow of powder from the guns 20 by maintaining a fixed level of powder in the hopper from which powder is supplied to the guns 20. The level of powder in the supply hopper is subject to change, and that change, prior to this invention, causes changes in the powder flow from the guns 20. These changing :~2~3L8 powder flows were the result of the changing ~ir pressur~ required to draw powder from the fluid`ized bed of powder into the venturi pumping chamber 48 of the pump~ As the level of powder in the fluidized bed iB lowered a greater vacuum is required to pull powder from that bed into the venturi chamber or as the level is raised a lesser vacuum is required. But, the vacuu~ in the venturi pumping chamber of the pump does not change with changing levels of powder in the fluidized bed. Instead, the powder flow from the pump varies. By utilizing the invention of this application, with the fixed level of powder in the auxiliary hopper, this source of varying powder 1bw from the gun is eliminated.
~ hile I have described only a single preferred embodiment of my invention, persons skilled in the art to which this invention pertains will appreciate numerous changes and modifications which may be made without departing from the spirit of my invention. Therefore, I do not intend to he limited except by the scope of the following appended claims:
:.~
3, ~zt7 POWDER DELIVERY SYSTEM
.
This invention relates to systems for supplying air entrained solid particulate powder material to powder spray guns or dispensers. More particularlyj this invention relates to an improved system for supplying an even flow of powder from a fluidized powder source to a powder spray gun or dispenser. ~
Characteristically, powder is supplied to a powder spray gun through a pneumatic conveyor line within which there is a powder pump containing a low pressure venturi pumping chamber. This chamber is intersected by a powder supply passage through which powder is supplied to the pump from a fluidized bed hopper. In order to meter or control the rate of flow of powder from the fluidized bed into the venturi pumping chamber, such pumps conventionally include a metering air flow passage operable to inject a controllefl flow of air into the powder supply passage.
The pressure of this metering air flow controls the amount of air which is mixed with the powder entering the pump, and consequently the rate of flow of powder from the pump.
~7 . ;,. ~ , .. ..
., ~ ` ` ~I.;Z'7~
One of the shortcomings of all powder spray systems, including systems incorporating powder p`umps of the type described hereinabove, is that the powder ejected from the spray gun of the system commonly flows unevenly from the gun. There are periodic puEfs or clouds of powder ejected from the gun and periodic reductions in the density of powder ejected from the gun. Such periodic increases or decreases in powder density sprayed from the gun result in uneven application of powder to a target substrate to which the powder is applied. Consequently, such random changes in powder density are very undesirable.
There have been numerous attempts ~o minimize or reduce these random changes of powder density sprayed from a powder spray gun. Such attempts have taken the form of changes in the design of the powder spray gun, changes in the design and configuration of the powder pump, etc. Most of these changes have improved the situation somewhat, but have not cured the problem.
It has been an objective of this invention to provide an improved powder spray system wherein inadvertent or random changes in the flow rate of powder dispensed from a powder spray gun or dispenser of the system are minimized or eliminated.
This invention is in part predicated upon the discovery that one source of uneven flow of powder from a powder spray gun or dispenser of a powder spray system is the configuration of the system between the fluidized bed source of powder and the dispensing gun.
That portion of the system has heretoore simply consisted of a siphon tube for supplying powder from the fluidized bed to a powder pump, the pump, and a long supply hose connecting the pump to the gun. It has therefore been an objective of this invention to eliminate powder flow variances which have heretofore been attributable to the configuration of this portion of the system.
These objectives are achieved, and this invention is predicated in part upon the concept of supplying powder from the powder pump through a hose to an auxiliary fluidized bed of powder located near the dispensing gun, and then supplying the powder to the gun from the auxiliary fluidized bed through an auxiliary powder pump and a relatively short hose. By utilizing an auxiliary fluidized bed and an auxiliary powder pump located near the dispensing gun outlet of the system, erratic powder flow heretofore attributable to the relatively long length of hose betwéen the pump and the gun, and to a varying level of powder within the fluidized bed source of powder, have been reduced or completely eliminated.
I have found that a substantial portion of the flow variances within a conventional prior art powder spray system are attributable to two sour~es.
These sources are the relatively long hose between the 76~
pump and the gun and the varying level of powder in the fluidized bed source of powder to the system`. A
long hose between the pump and the gun creates flow variances as a result of loops and curves which inevitably occur in such long hoses. Powder collects in these loops or curves and eventually restricts flow through the hose until a pressure build-up behind the powder restriction breaks the restriction away and causes a resulting puff of powder to be dispensed from the gun while simultaneously causing a ~pressure 3 increase in the hose and a resulting increase in the flow of powder to the gun. Thereafter, the powder again begins to collect in the curve or loop of t~e hose from which it had just broken away, until it forms a restriction in the hose, breaks free, causes another puff of powder, etc.
The other primary source of varying flow from a conventionally configurated prior art powder flow system, the varying level of powder contained in the fluidized bed source of powder, cause~ flow variances as a result of differing pressures being required to draw powder into the powder pump as the powder level changes in the fluidized bed. In fact though, the vacuum within the pump tending to draw powder into the pump does not change with the differing level of powder in the fluidized bed hopper.
Instead, the vacuum pressure remains the same but the .
quantity of powder drawn into the pump changes as the level of powder in the hopper changes.
According to the practice of this invention, the powder spray system comprises a primary fluidized bed hopper source of powder and a smaller capacity auxiliary fluidized bed hopper located adjacent or near the powdér dispensing guns. A venturi style pump and a connecting hose transport powder from the primary hopper to the auxiliary hopper and an auxiliary venturi style powder pump and connecting hose transport the powder from the auxiliary hopper to a dispensing gun. There is an ovexflow pipe which extends between the auxiliary hopper and the primar~
hopper and which functions to maintain a fixed level of powder in the auxiliary hopper.
The practice of this invention with its use of an auxiliary fluidized bed hopper and an auxiliary venturi pump located closely adjacent the powder spray gun of a powder spray system enables both of the above identified sources of powder flow variances to be eliminated. Any flow variances which occur in the long hose between the primary hopper and the auxiliary hopper do not affect the flow rate between 'the auxiliary powder pump and the spray gun. Furthermore, the use of an overflow pipe between the auxiliary fluidized bed hopper and the primary fluidized bed hopper enables the level of powder in the auxiliary hopper to be maintained at a fixed level so long as an ~276~
excess amount of powder is supplied to the auxiliary fluidized bed. Thereby, flow variances attribut`able ! to the changing level of powder in the supply hopper are eliminated.
These and other objects and advantages~of this invention will be more readily apparent rom the following description of the drawings in which:
Fig. 1 is a schematic view of a powder spray system incorporating the auxiliary powder hopper and auxiliary powder pump of this invention~
Referring now to the figure, there is illustrated a powder spray system 10 for dispensing solid particulate powder material from a plurality ~
spray guns 12. Three guns 12 are illustrated but the system i5 equally applicable to the spraying of powder from a single gun or from a substantially greater number of guns 12. The guns 12 per se form no part of the invention of this application and are well known in the prior art. One such gun which is suitable for use in this application is illustrated and described in U. S. Patent No. 4,380,320 of Thomas E. Hollstein, et al for "Electrostatic Powder Spray Gun Nozzle", assigned to the assignee of this application.
The system 10, in addition to the guns 12, comprises a primary or supply hopper 14, an auxiliary hopper 16, as well as a primary pneumatic pump 18 for pumping powder from the primary hopper 14 to the auxiliary 16, and a plurality of auxiliary pneumatic - 7 ~
pumps 20 for pumping powder from the auxiliary hopper 16 to the guns 12. The pneumatic pumps 18 and 20 are conventional powder pumps which per se form no part of the invention of this application. One such pump which is suitable for use in this application is illustrated and described in U.S.
Patent No. 3,746,254 of Lane S. Duncan, et al for "Powder Spray System", assigned to the assignee of this application.
Another, and a preferred pump, useful in this system is illustrated and described in co-pending Canadian patent application Serial No. 489,024, filed August 20, 1985 and entitled "Improved Venturi Powder Pump", also assigned to the assignee of this application.
The hoppers 14 and 16 are also conventional fluidizing bed hoppers and per se form no part of the inven-tion of thi~ application. Both of these hoppers 14, 16 have an enclosed chamber 24 in the ba~e of the hopper and an air pervious ceiling 26 in the chamber. When high pressure air is admitted into the inlet 28 of the chambers 24, such air passes through the ceiling 26 of the closed chamber 24 and is operative to fluidize powder 30 contained in the hopper above the closed chamber 24.
The two hoppers differ only in that the auxiliary hopper is much smaller in size and capacity than is the supply hopper 14. In one preferred embodiment wherein the auxiliary hopper 16 supplies powder to eight guns 12, the auxiliary hopper 16 has a rm/
-8- l~
volume equal to approximately l/16th the volume of the supply hopper 14.
The two hoppers 14 and 16 also differ in that the supply hopper 14 has a vent 34 in its top wall while the auY~iliary hopper has no such vent.
Instead, the auxiliary hopper 16 is vented ~ia an overflow tube 36 which extends from the interior of the au~iliary hopper 16 downwardly through the closed chamber 24 of the hopper 16 and through ~he top wall 38 of the supply hopper 14. As explained more fully hereinafter, this overflow tube 36 functions to vent the auxiliary hopper 16 as well as to transport all excess powder from the auxiliary hopper 16 back to the supply hopper. This overflow tube also functions to maintain a fixed level of fluidized powder within the auxiliary hopper 16.
The powder pumps 18 and 20 are all identical except that the powder pumps 20 of the auxiliary hopper may be of smaller capacity than the pump 18 of the supply hopper 14. Each of these powder pumps has an inlet port 40, an outlet port 42, and an atomizi~g air inlet port 44. Additionally, each of these pumps has a powder flow passage 46 therein through which powder is drawn into a venturi pumping chambex 4~ of the pump via a siphon tube 50 which connects the inlet 52 of the powder flow passage 46 to the fluidized bed 30 of powder from which the pump draws powder. The supply hopper pump 18 draws powder from the hopper 14 ,. . .. .... .
~.2~6~
g and pumps it into the auxiliary hopp~r 16 via a transfer conduit 54 while the auxiliary hopper p`~mps 20 draw powder from the auxiliary hopper 16 and pump it to the dispensing guns 12 via short transfer hoses 56.
The inlet ports 40 of the pumps 18, 20 are connected via air lines 58 to a source of high pressure air 60 while the atomizing air inlet ports 44 of the pumps are connected to the same high pressure air source via air lines 62. Internally oE each pump there is a small air orifice through which the high pressure air from the source 60 flows into the ventùri pumping chamber 48 so ar. to create a low pressu~e within that venturi pumping chamber. That low pressure is operative to draw powder via the siphon tubes 50 upwardly into the venturi pumping chambers 48 of the pumps such that the powder can then be transported via the hose 54 from the pump 18 to the hopper 16, or in the case of the pumps 20, via the hoses 56 to the dispensing guns 12.
As is explained more fully in the above identified U. S. Patent No. 3,746,254, or in my co-pending application Serial No. ~ , the pressure o~ air supplied to the port 40 controls the quantity of powder drawn upwardly through the siphon tube into.the venturi pumping chamber 48 of the pump, and the pressure of air supplied to port 44 controls the ratio of air to powder mix within the pump.
Typically, each of the air lines 58, 62 contains a pressure regulator (not shown) through which the air pressure supplied to the inlet ports 44 may be adjusted so as to control the amount of vacuum drawn within the venturi pumping chamber 48 of the pump and the relative air to powder mix supplied to the venturi chamber through the powder flow passage 46 of the pump.
In operation of the powder dispensing system 10, high pressure air is supplied from the source 60 to the inlet ports 40, 44 of the powder pumps 18, 20, and to the inlet ports 28 of the air chambers 24 of the hoppers 14 and 16. The high pressure air supplied to the inlet port 28 of the hoppers 14, 16 is operative to fluidize all of the powder 30 contained in the supply hopper 14 and the auxiliary hopper 16.
The fluidized powder 30 in the supply hopper 14 is drawn via the siphon tube 50 upwardly into the venturi pumping chamber 48 of the pump 18. This powder is then transported from the supply hopper pump 18 via the relatively long transfer hose 54 to the powder inlet 68 of the auxiliary hopper 16. The fluidiæed powder in the auxiliary hopper 16 is in turn pumped by the auxiliary pump 20 to the dispenser guns 12 via~the relatively short hoses 56. In practice, an excess quantity of powder is pumped from the primary or supply hopper 14 to the auxiliary hopper 16, which excess is greater than the capacity of all of the pumps ~0. As a result, excess fluidized powder flows through the inlet 70 of the over-flow tube 36 back to the supply hopper 14. The level of powder within the auxiliary hopper 16 is thus always maintained at a fixed level, that of the top edge of the inlet 70 of the overflow tube.
A powder pump 72 may be associated with the overflow line 36 in the event that gravity is insufficient to carry the overflow powder to the primary~ hopper. Such a pump may be required in installation where there is substantial distance between the two hoppers or where the primary hopper is not located beneath the auxiliary hopper~ In the eve~t that a powder pump 72 is associated with the overflow line 36, a vent (not shown) would be provided in the top of the auxiliary hopper in order to maintain ambient pressure in the auxiliary hopper.
Prior to this invention, it has been the practice to pump powder directly from the supply or primary hopper 14 to the guns 12. There was no intermediate or auxiliary hopper 16 in the system. I
have found that the long hoses which hereto extended from the supply hopper 18 to the guns, as well as the constantly changing level of powder within the supply hopper 14, both contributed to and created a problem of varying powder flow from the guns. Specifically, I
have found that a long hose extending from the pump of the supply hopper to the gun had numerous curved or , ~.27~9~
looped sections wherein powder collected and tended to restrict flow through the long hose. This restri~cted flo~ in turn caused a pressure drop in the hose to the gun with a resultant drop in the ~uantity o~ powder being pumped from the supply hopper to the gun.
Periodically through, the pressure behind the powder created restriction built up to the point that it caused the restriction to break, thereby causing a high density puff of powder to be dispensed from the gun. This in turn resulted in a temporary in~crease in the flow of air and powder from the pump to the gun because of the sudden increase in air flow through the hose. Then the restriction would again build up ~n the hose at the same point at which it had just broken free and the process was repeated.
I have found that by utilizing the auxiliary hopper 16 between the supply hopper and the guns, and preferably close to the guns, the erratic powder flow from the guns created by these powder created restrictions in the hose are minimized or substantially eliminated. I have also found that the use of the auxiliary hopper 16 assists in maintaining an even flow of powder from the guns 20 by maintaining a fixed level of powder in the hopper from which powder is supplied to the guns 20. The level of powder in the supply hopper is subject to change, and that change, prior to this invention, causes changes in the powder flow from the guns 20. These changing :~2~3L8 powder flows were the result of the changing ~ir pressur~ required to draw powder from the fluid`ized bed of powder into the venturi pumping chamber 48 of the pump~ As the level of powder in the fluidized bed iB lowered a greater vacuum is required to pull powder from that bed into the venturi chamber or as the level is raised a lesser vacuum is required. But, the vacuu~ in the venturi pumping chamber of the pump does not change with changing levels of powder in the fluidized bed. Instead, the powder flow from the pump varies. By utilizing the invention of this application, with the fixed level of powder in the auxiliary hopper, this source of varying powder 1bw from the gun is eliminated.
~ hile I have described only a single preferred embodiment of my invention, persons skilled in the art to which this invention pertains will appreciate numerous changes and modifications which may be made without departing from the spirit of my invention. Therefore, I do not intend to he limited except by the scope of the following appended claims:
:.~
Claims (6)
1. In combination, a powder spray booth, a powder spray gun for spraying solid particulate powder onto workpieces contained within said booth; a filter module for collecting oversprayed powder from said booth, and a sieve for receiving powder from said filter module and separating said oversprayed powder from coarser particles, a primary fluidized bed hopper for receiving powder from said sieve, said primary hopper having an interior chamber adapted to receive and fluidize powder material, a primary pneumatic powder pump having an inlet port and a discharge port, said primary powder pump having a low pressure venturi pumping chamber contained therein and a powder flow passage intersecting said venturi pumping chamber, said powder flow passage having an inlet connected via a siphon tube to said interior chamber of said primary hopper, means connecting said inlet port of said primary powder pump to a source of high pressure air, an auxiliary fluidized bed hopper having an interior chamber of substantially less capacity than said interior chamber of said primary hopper, said auxiliary fluidized bed hopper being located in close proximity to said powder spray booth, first conduit means connecting said outlet port of said primary powder pump to said interior chamber of said auxiliary hopper, at least one auxiliary pneumatic powder pump having an inlet port and a discharge port, said auxiliary powder pump having a low pressure venturi pumping chamber contained therein and a powder flow pump passage intersecting said venturi pumping chamber, said powder flow passage of said auxiliary powder pump having an inlet connected via a siphon tube to said interior chamber of said auxiliary hopper, second conduit means connecting said outlet port of said auxiliary powder pump to said powder spray gun, said second conduit means being substantially shorter than said first conduit means, and means for maintaining a constant level of fluidized powder in said auxiliary hopper, said means for maintaining a constant level of fluidized powder in said auxiliary hopper comprising an overflow tube extending between said auxiliary hopper and said primary hopper, said overflow tube having an inlet spaced upwardly from the bottom of said interior chamber of said auxiliary hopper.
2. The apparatus of claim 1 which further comprises a plurality of auxiliary powder pumps and a plurality of powder spray guns, each of said auxiliary powder pumps having a powder flow passage connected via a siphon tube to the interior chamber of said auxiliary hopper, and each of said auxiliary powder pumps having an outlet port connected via conduit means to one of said powder spray guns.
3. In combination, a powder spray booth, a powder spray gun for spraying solid particulate powder onto workpieces contained within said booth; a filter module for collecting oversprayed powder from said booth, and a sieve for receiving oversprayed powder from said filter module and separating said oversprayed powder from coarser particles, apparatus for dispensing a relatively constant flow of solid particulate powder from said powder spray gun, which apparatus comprises, means including a relatively large capacity primary hopper for receiving powder from said sieve and for fluidizing said solid particulate powder, a substantially smaller capacity auxiliary hopper, means including a relatively long conduit for supplying said powder from said primary hopper into said auxiliary hopper, means for fluidizing said powder in said auxiliary hopper, means including a relatively short conduit for supplying said solid particulate material from said auxiliary hopper to said powder spray gun, said means for supplying said powder from said primary hopper to said auxiliary hopper being operable to supply a greater quantity of solid particulate powder material to said auxiliary hopper than is supplied from said auxiliary hopper to said spray gun, and means for transporting excess powder from said auxiliary hopper to said primary hopper so as to maintain a substantially constant level of fluidized powder in said auxiliary hopper.
4. In combination, a powder spray booth, a powder spray gun for spraying solid particulate powder onto workpieces contained within said booth; a filter module for collecting oversprayed powder from said booth, a primary fluidized bed hopper for receiving powder from said filter module, said primary hopper having an interior chamber adapted to receive and fluidized powder material, a primary pneumatic powder pump having an inlet port and a discharge port, said primary powder pump having a low pressure venturi pumping chamber contained therein and a powder flow passage intersecting said venturi pumping chamber, said powder flow passage having an inlet connected to said interior chamber of said primary hopper, means connecting said inlet port of said primary powder pump to a source of high pressure air, an auxiliary fluidized bed hopper having an interior chamber of substantially less capacity than said interior chamber of said primary hopper, first conduit means connecting said outlet port of said primary powder pump to said interior chamber of said auxiliary hopper, at least one auxiliary pneumatic powder pump having an inlet port and a discharge port, said auxiliary powder pump having a low pressure venturi pumping chamber contained therein and a powder flow passage intersecting said venturi pumping chamber, said powder flow passage of said auxiliary powder pump having an inlet connected to said interior chamber of said auxiliary hopper, second conduit means connecting said outlet port of said auxiliary powder pump to said powder spray gun, said second conduit means being substantially shorter than said first conduit means, and means for maintaining a constant level of fluidized powder in said auxiliary hopper, said means for maintaining a constant level of fluidized powder in said auxiliary hopper comprising an overflow tube extending between said auxiliary hopper and said primary hopper, said overflow tube having an inlet spaced upwardly from the bottom of said interior chamber of said auxiliary hopper.
5. The apparatus of claim 4 which further comprises a plurality of auxiliary powder pumps and a plurality of powder spray guns, each of said auxiliary powder pumps having a powder flow passage connected to the interior chamber of said auxiliary hopper, and each of said auxiliary powder pumps having an outlet port connected via conduit means to one of said powder spray guns.
6. In combination, a powder spray booth, a powder spray gun for spraying solid particulate powder onto workpieces contained within said booth; a filter module for collecting oversprayed powder from said booth, apparatus for dispensing a relatively constant flow of solid particulate powder from said powder spray gun, which apparatus comprises, means including a relatively large capacity primary hopper for receiving powder from said filter module and for fluidizing said solid particulate powder, a substantially smaller capacity auxiliary hopper, means including a pump and a relatively long conduit for supplying said powder from said primary hopper into said auxiliary hopper, means for fluidizing said powder in said auxiliary hopper, means including a pump and a relatively short conduit for supplying said solid particulate material from said auxiliary hopper to said powder spray gun, said means for supplying said powder from said primary hopper to said auxiliary hopper being operable to supply a greater quantity of solid particulate powder material to said auxiliary hopper than is supplied from said auxiliary hopper to said spray gun, and means for transporting excess powder from said auxiliary hopper to said primary hopper so as to maintain a substantially constant level of fluidized powder in said auxiliary hopper.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US681,502 | 1976-04-29 | ||
| US68150284A | 1984-12-13 | 1984-12-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1276918C true CA1276918C (en) | 1990-11-27 |
Family
ID=24735542
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000497687A Expired - Lifetime CA1276918C (en) | 1984-12-13 | 1985-12-13 | Powder delivery system |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0185479B1 (en) |
| JP (1) | JPH075189B2 (en) |
| AU (1) | AU568034B2 (en) |
| CA (1) | CA1276918C (en) |
| DE (1) | DE3582411D1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2666753A1 (en) * | 1990-09-18 | 1992-03-20 | Sames Sa | Feed device for a powder-spray apparatus |
| US5474609A (en) * | 1992-06-30 | 1995-12-12 | Nordson Corporation | Methods and apparatus for applying powder to workpieces |
| US5520735A (en) * | 1992-06-30 | 1996-05-28 | Nordson Corporation | Nozzle assembly and system for applying powder to a workpiece |
| DE19913448A1 (en) | 1999-03-25 | 2000-09-28 | Itw Gema Ag | Powder container level probe device |
| CN108545481B (en) * | 2018-05-30 | 2023-11-21 | 泰山石膏(陕西)有限公司 | Energy-saving dry powder supply system |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1494061A (en) * | 1964-10-08 | 1967-09-08 | R L U M G Automation Sa | Improvement in spraying devices for powdery products |
| BE790830A (en) * | 1971-11-02 | 1973-02-15 | Nordson Corp | ELECTROSTATIC SPRAYER |
| GB1521800A (en) * | 1976-12-23 | 1978-08-16 | Coors Container Co | Powder feeder pick-up tube |
| US4380320A (en) * | 1981-02-25 | 1983-04-19 | Nordson Corporation | Electrostatic powder spray gun nozzle |
| JPS58106322U (en) * | 1982-01-13 | 1983-07-20 | 新日本製鐵株式会社 | Continuous cutting device for fine powder |
| JPS58135033A (en) * | 1982-02-03 | 1983-08-11 | Nippon Steel Corp | Gas transport device of pulverized coal |
-
1985
- 1985-11-28 EP EP19850308678 patent/EP0185479B1/en not_active Expired
- 1985-11-28 DE DE8585308678T patent/DE3582411D1/en not_active Expired - Lifetime
- 1985-12-05 AU AU50789/85A patent/AU568034B2/en not_active Ceased
- 1985-12-13 CA CA000497687A patent/CA1276918C/en not_active Expired - Lifetime
- 1985-12-13 JP JP60279376A patent/JPH075189B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH075189B2 (en) | 1995-01-25 |
| JPS61192620A (en) | 1986-08-27 |
| AU568034B2 (en) | 1987-12-10 |
| DE3582411D1 (en) | 1991-05-08 |
| EP0185479A3 (en) | 1987-10-07 |
| EP0185479B1 (en) | 1991-04-03 |
| AU5078985A (en) | 1986-06-19 |
| EP0185479A2 (en) | 1986-06-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |