The present invention relates to an emptying device, hereafter sometimes emptying unit, for powder bags used in powder spray coating apparatus, hereafter sometimes powder spray coating facility.
Powder manufacturers supply spray coating powders in powder containers which frequently are bags to spray coating enterprises. The coating powder is sprayed in a spray coating facility onto the objects to be coated. Then the coating powder is thermally fused on the coated objects. Powder bags may be of conventional shapes. They also may be in the form of a plastic tube or hose fused at the bottom and top and cut open when being used/emptied.
Frequently the powder bags remain in a dimensionally stable cardboard box in the spray coating facility, in the particular vendor powder bag, while coating powder is removed from it.
The invention seeks to allow efficiently and effectively emptying soft, flexible powder bags even in the absence of dimensionally stable cardboard boxes.
According to an aspect of the invention, a powder-bag emptying unit for powder spray coating facilities comprises a bag-receiving hopper which is designed to receive a powder bag. The bag-receiving hopper is narrower at its bottom than at its top. The hopper wall keeps the powder bag dimensionally stable and in a fixed position in which a bag aperture is situated at the top end of the bag. The bag-receiving hopper is fitted at its lower end at the hopper center with a hopper opening which is open downward and permits coating powder to drop out of it. The bag-receiving hopper further is fitted with at least one vibrator to shake said bag-receiving hopper.
Illustratively, a hopper angle of the hopper inside surface is between 45° and 90°.
Illustratively, the hopper further comprises a center axis that extends vertically.
Illustratively, the bag-receiving hopper is oriented on at least one weight sensor for measuring the weight of the bag-receiving hopper including the hopper contents.
Illustratively, the at least one weight sensor is connected to a signal generator for generating a signal based on the measured weight.
Further illustratively, the powder-bag emptying unit comprises an outer retaining element to grip the upper bag segment near an aperture edge of the bag aperture and an inner retaining element for insertion into the upper bag segment near its aperture edge. The two retaining elements are stretchable relative to each other to clamp the upper bag segment between them. The upper inner retaining element comprises a downward pointing passage to pass a powder feed pipe.
Illustratively, the aperture edge retaining means is mechanically connected to a height adjusting device and can be moved up and down by said device.
Illustratively, the powder feed pipe is connected to a height adjusting device and can be moved up and down by said height adjusting device.
Further illustratively, the powder-bag emptying unit includes an outer retaining element to grip the upper bag end segment near the aperture edge of the bag aperture and an inner retaining element for insertion into the upper bag end segment near its aperture edge. The two retaining elements are mutually stretchable to insert the upper bag end segment between them. The inner retaining element comprises at least one of a powder feed pipe and a pipe containing a powder feed pipe. The pipe is inserted downward through the bag aperture into the powder bag situated in the bag-receiving hopper.
Illustratively, the aperture edge retaining means is connected mechanically to a height adjusting device and the retaining means can be moved up and down by the height adjusting device.
Illustratively, a lower end of the powder feed pipe points toward the lower hopper end and is displaceable downward into the vicinity of the lower hopper end.
Illustratively, the powder feed pipe is oriented along the hopper center axis, points in a longitudinal direction of said axis, and can be displaced along the longitudinal direction of said axis.
Illustratively, the powder feed pipe is oriented parallel to the inside surface of the receiving-bag hopper and is displaceable up and down parallel to the hopper inside surface.
Illustratively, an inside cross-sectional dimension of the bag-receiving hopper orthogonal to the hopper center axis is at least 50% smaller at the lower hopper end than at the upper hopper end.
Further illustratively, the powder-bag emptying unit includes a powder pump mounted at the upper end of the powder feed pipe.
Illustratively, the bag-receiving hopper is mounted in a manner to be laterally displaceable into different positions.
The present invention is elucidated below by the description of illustrative embodiments in relation to the appended drawings.
Illustratively such injectors are known from the European patent document EP 0 412 289 B1.
The powder pumps also may be the kind which consecutively move small powder doses by means of compressed air, each small powder dose (quantity of powder) being stored in a powder chamber and then being expelled by compressed air from the powder chamber. The compressed air remains behind the powder dose and pushes it ahead. This kind of pump is sometimes called a compressed air thrust pump or plug moving pump because the compressed air propels the stored powder dose like a plug or stopper through a pump outlet conduit. Various kinds of such powder pumps moving compact coating powder illustratively are known from the following documents: DE 103 53 968 A1; U.S. Pat. No. 6,508,610 B2; US 2006/0193704 A1; DE 101 45 448 A1 and WO 2005/051549 A1.
The invention is not restricted to one of the known kinds of pumps.
A source of compressed air 6 is used to generate the compressed air to pneumatically move the coating powder and fluidize it, said source being connected to the various components by corresponding pressure adjusting elements 8 such as pressure regulators and/or valves.
Fresh powder from the manufacturer is fed from a manufacturer's container—which may be a small container 12, for instance a dimensionally stable container or a bag holding for instance 10 to 50 kg powder, for instance 25 kg, or for instance a large container 14 also dimensionally stable or a bag, holding for instance between 100 kg and 1,000 kg powder—by means of a powder pump 4 in a fresh powder conduit 16 or 18 to a sieve 10. The sieve 10 may be fitted with a vibrator 11. Herein the expressions “small container” and “large container” denote both dimensionally stable containers and those which are not, such as flexible bags, unless specified otherwise.
The coating powder sifted through the sieve 10 is moved by gravity or by a powder pump 4 through one or more powder feed conduits 20 through powder intake apertures 26 into an intermediate receptacle chamber 22 of a dimensionally stable intermediate receptacle 24. Illustratively, the volume subtended by the intermediate receptacle 22 is substantially smaller than that of the fresh powder small container 12.
In an illustrative embodiment of the invention, the powder pump 4 of the at least one powder feed conduit 20 leading to the intermediate receptacle 24 is a compressed air pump. In this instance the initial segment of the powder feed conduit 20 may serve as a pump chamber which receives the powder sifted through the sieve 10 as it drops through a valve, for instance a pinch valve. Once this pump chamber contains a given powder dose, the powder feed conduit 20 is shut off from the sieve 10 due to valve closure. Next the powder dose is forced by compressed air through the powder feed conduit 20 into the intermediate receptacle chamber 22.
Illustratively, the powder intake apertures 26 are configured in a sidewall of the intermediate receptacle 24, illustratively near the bottom of the intermediate receptacle chamber 22, so that, when compressed air flushes the intermediate receptacle chamber 22, even powder residues at the bottom can be expelled through the powder intake apertures 26, and for that purpose the powder feed conduits 20 illustratively are separated from the sieve 10 and directed into a waste bin as indicated by a dashed arrow 28 in
Powder pumps 4, for instance injectors, are connected to one or more powder outlet apertures 36 to move coating powder through powder conduits 38 to the sprayers 40. The sprayers 40 may be fitted with spray nozzles or rotary atomizers to spray coating powder 42 onto the object 2 to be coated, said object being situated in a coating cabin 43. Illustratively, the powder outlet apertures 36 are situated in a wall that is opposite the wall containing the powder intake apertures 26. Illustratively, the powder outlet apertures 36 also are configured near the bottom of the intermediate receptacle chamber 22
Illustratively, the size of the intermediate receptacle chamber 22 allows storing coating powder in amounts between 1.0 and 12 kg, illustratively between 2.0 and 8.0 kg. In other words, the size of the intermediate receptacle chamber 22 illustratively is between 500 and 30,000 cm3, illustratively between 2,000 and 20,000 cm3. The size of the intermediate receptacle chamber 22 is selected as a function of the number of powder outlet apertures 36 and of powder conduits 38 connected to them in a manner to permit continuous spray coating while also permitting rapidly cleaning the intermediate receptacle chamber 22 in pauses of operation for purposes of powder changes, illustratively in automated manner. The intermediate receptacle chamber 22 may be fitted with a fluidizing means to fluidize the coating powder.
Coating powder 42 failing to adhere to the object 2 is aspirated as excess powder through an excess powder conduit 44 by means of a flow of suction air from a blower 46 into a cyclone separator 48. In the cyclone separator, the excess powder is separated as much as possible from the suction flow. The separated powder proportion is then moved as recovered powder from the cyclone separator 48 through a recovery powder conduit 50 to the sieve 10 and from there it passes through said sieve either by itself or being admixed to fresh powder through the powder feed conduits 20 and once more into the intermediate receptacle chamber 22.
Depending on the kind of powder and/or the intensity of powder soiling, the powder recovery conduit 50 also may be separated from the sieve 10 and move the recovery powder into a waste bin as schematically indicated by a dashed line 51 in
The intermediate receptacle 24 may be fitted with one or more sensors, for instance two sensors S1 and/or S2 to control feeding coating powder into the intermediate receptacle chamber 22 by means of the control 3 and the powder pumps 4 in the powder feed conduits 20. Illustratively the lower sensor Si detects a lower powder level limit and the upper sensor S2 detects an upper powder level limit.
The lower end segment 48-2 of the cyclone separator 48 can be designed and used as a recovery powder supply silo and be used as such and be fitted for that purpose with one or several, illustratively two, sensors S3 and/or S4 which are operationally connected to the control 3. As a result the fresh powder feed through the fresh powder feed conduits 16 and 18 may be stopped, especially in automated manner, until enough recovery powder shall accumulate in the cyclone separator 48 to feed through the sieve 10 enough recovery powder into the intermediate receptacle chamber 22 for spray coating using the sprayer 40. Once the recovery powder becomes insufficient in the cyclone separator 48 for such operation, the switchover to the fresh powder supply through the fresh powder conduits 16 or 18 may automatically kick in. The invention also offers the possibility to simultaneously feed fresh and recovery powders to the sieve 10 to admix them to one another.
The exhaust air of the cyclone separator 48 passes through an exhaust air conduit 54 into a post filtration system 56 and therein through one or more filter elements 58 to arrive at the blower 46 and then into the atmosphere. The filter elements 58 may be filter bags or filter cartridges or filter plates or similar elements. Ordinarily the powder separated from the air flow by means of the filter elements 58 is waste powder and drops by gravity into a waste bin, or, as shown in
Depending on the kind of powder and on the powder coating conditions, the waste powder also may be recovered and moved to the sieve 10 in order to be recirculated into the coating circuit. This feature is schematically indicated in
Typically only cyclone separators 48 and the post filtration system 56 are used for multicolor operation, wherein different colors each are sprayed only for a short time, and the waste powder of the post filtration system 56 is moved into the waste bin 62. In general the powder separating efficiency of the cyclone separator 48 is less than that of the post filtration system 56, but cleaning is more rapid than in the post filtration system 56. As regards monochrome operation, wherein the same powder is used for a long time, the cyclone separator 48 may be dispensed with, and the excess powder conduit 44 instead of the exhaust air conduit 54 may be connected to the post filtration system 56, and the waste conduits 60, which in this instance contain recovery powder, are connected as powder recovery conduits to the sieve 10. Typically the cyclone separator 48 is used in combination with the post filtration system 56 in monochrome operation only when the coating powder entails problems. In such eventuality only the recovery powder of the cyclone separator 48 is moved through the powder recovery conduit 50 to the sieve 10 whereas the waste powder of the post filtration system 56 is moved into the waste bin 62 or into another waste bin, said waste bin being optionally free of waste conduits 60 and directly positioned underneath an outlet aperture of the post filtration system 56.
The lower end of the cyclone equipment 48 may be fitted with an outlet valve 64, for instance a pinch valve. Moreover fluidizing means 66 to fluidize the coating powder may be configured above said outlet valve 64, in or at the lower end segment 48-2, constituted as a supply container of the cyclone separator 48. The fluidizing means 66 contains at least one fluidizing wall 80 made of material comprising open pores or fitted with narrow boreholes, this material being permeable to compressed air but not to the coating powder. The fluidizing wall 80 is situated between the powder path and a fluidizing compressed air chamber 81. The fluidizing compressed air chamber 81 may be connected by a compressed air adjusting element 8 to the compressed air source 6.
For the purpose of evacuating fresh coating powder by suction, the fresh powder conduit 16 and/or 18 may be connected to allow powder flow at its upstream end either directly or through the powder pump 4 to a powder feed pipe 70, said pipe being dippable into the vendor's container 12 or 14. The powder pump 4 may be mounted at the beginning of, the end of or in between in the fresh powder conduit 16 or 18 or at the upper or lower end of the powder moving pipe 70.
A small fresh powder container in the form of a fresh powder bag 12 is shown in
Two or more small containers 12 may be configured each in one bag-receiving hopper 74, also two or more large containers 14 operating alternately. This feature allows rapidly changing from one small container 12 to another or one large container 14.
The invention may be modified in a number of ways without restricting it. For instance the sieve 10 may be integrated into the intermediate receptacle 24. Alternatively the sieve 10 may be omitted when the fresh powder quality is high enough. In that case a separate sieve may be used to sift the recovery powder of the conduits 44 and 50, illustratively upstream or downstream of the cyclone separator 48 or in it. Again, sifting the recovery powder will not be required when its quality is adequate for re-use.
The illustrated embodiment of the invention provides an emptying unit fitted with a bag-receiving hopper 74. Illustrative embodiments of the emptying unit are illustrated in the
The hopper conical angle a at the inside of the bag-receiving hopper 74, also illustratively at its outside surface, illustratively is between 45 and 90°, illustratively between 50 and 70°, illustratively about 60°. The powder bag 12 may be in the form of a plastic sheet/pouch, illustratively a large plastic tube which at its lower end is fused together and there constitutes the lower bag end. This pouch also may be fused shut at its upper end. In that case the lower bag end must be cut open to remove coating powder. Illustratively, the hopper angle is selected so that as the quantity of powder in the powder bag decreases, the powder particles are able to slide by gravity down the bag wall.
The hopper center axis 108 of the bag-receiving hopper 74 illustratively is vertical. In other embodiments, however, the hopper center axis 108 also may be oblique as long the hopper-like inside surface of this hopper runs everywhere obliquely upwards.
As shown in the Figures, the cross section of the bag-receiving hopper 74 orthogonal to the hopper center axis 108 illustratively is circular everywhere regardless of height, though it is understood other cross sections also may be used, for instance oval or polygonal cross sections.
In another embodiment of the invention, the bag-receiving hopper 74 is fitted with at least one weight sensor measuring the weight of the bag-receiving hopper 74 including its contents, in particular the quantity of powder. The at least one weight sensor may be designed to optically display the weight and/or the signal generator, for instance the control 3, which is operationally connected to said sensor, may be designed to generate a signal based on the measured weight. In an embodiment of the invention, this signal shall be generated whenever a given minimum weight has been reached or was fallen short of. Moreover signals may also be generated as a function of two or more different weights of powder, for instance one signal indicating the minimum weight will materialize imminently and/or that the powder bag shall soon be empty.
In
The signal generated by the weighing system 76 or 112 or by the control 3 operationally connected to said system and based on the measured weight illustratively may be acoustic or optical, letting an operator know that the powder bag 12 is nearly empty and needs replacing. The weighing system 76 or 112 per se or the control 3 connected to it may furthermore be designed in a manner that in addition to or in lieu of said acoustic and/or optic signals, they shall also generate control signals driving the powder feed as a function of the measured powder weight when measuring predetermined weight values. One signal may be an early warning to an operator that the powder bag 12 soon shall be empty and must be replaced. Also such a signal may be used to stop the fresh powder feed from the powder bag 12 and instead feeding its recovery powder from the lower end segment 48-2 of the cyclone separator 48—designed as a supply container—to the sieve 10, provided that a sensor S3 or S4 situated there, if there are two sensors for instance the upper sensor S3, does transmit the information to the control 3 that enough recovery powder is present in the supply container 48-2 of the cyclone separator 48, and provided that the sensor S1 of the intermediate receptacle 24 does transmit a “powder needed” signal to the control 3.
The bag-receiving hopper 74 may be fitted with one or several vibrators 78 to shake the bag-receiving hopper 74 in order to shake coating powder off the bag wall and to boost the replenishment of coating powder sliding into the powder bag as the powder quantity in the powder bag is decreasing.
The inner retaining element 116-2 may be fitted with a top to bottom feedthrough aperture 120 passing the powder feed pipe 70. The aperture edge retaining means 116 illustratively is designed as a guide for guiding the powder feed pipe 70 moving in the pipe's longitudinal direction.
The aperture edge retaining means 116 may be stationary. Illustratively, however, it is mechanically linked to a height-adjusting device 122 that illustratively is automatically controlled to move said retaining means up and down.
Illustratively, the powder feed pipe 70 is vertically displaceable in freely moving manner whereby it can dip by gravity into the powder bag 12 and will track the downward moving powder level. However the powder pipe 70 also may be mechanically linked to a height adjusting device 124 to be moved up and down by said device.
The two height adjusting devices 124 and 122 illustratively are mounted to a vertical guide bar 125 and are vertically adjustable along it.
The bag-receiving hopper 74, the weighing system 76 or 112 and the guide system 125, 122, 124 illustratively are configured on a base plate 121. This base plate may be fitted with wheels/casters 123 to facilitate moving it.
The embodiment of
The bag aperture retaining means 126 of
In each illustrative embodiment, the powder feed pipe 70 points down by its lower end as far as the lower hopper end or is displaceable into the vicinity of said hopper end to allow aspirating coating powder even from the very bottom of the powder bag.
In the illustrative embodiments shown in the drawings, the powder pipe 70 is configured along the hopper center axis and displaceable up and down along that axis.
Illustratively, the upper bag end is closed by means of the bag aperture retaining means 116 of
The powder feed pipe 70 may be a single pipe or a plurality of powder pipes.
The powder pump 4 moving fresh powder out of the powder bag 12 may be configured in the fresh powder conduit 16 or, in the illustrated embodiment, at the upper end of the powder feed pipe 70 as illustratively shown by means of an injector in
The bag-receiving hopper 74 may be closed at its lower end. Illustratively, however, it is fitted at its lower end with a downward pointing hopper opening 144. Coating powder that accidentally leaves the powder bag and moves into the bag-receiving hopper 74 is able to drop out of this lower hopper opening 144. This lower hopper opening furthermore offers the feasibility of opening the powder bag in the bag-receiving hopper 74 at its lowest bag site, for instance to pierce it open or to cut off a downward bag snippet in order to remove coating powder, in particular residual powder, in the downward direction.
Regardless of whether a hopper opening 144 is or is not present, the bottom diameter of the bag-receiving hopper 74 is substantially smaller than that of the powder bag 12. The diameter of the upper hopper end is at least as large as that of the powder bag 12. The inside cross-sectional dimension of the bag-receiving hopper 74 perpendicularly to the hopper center axis 108 is substantially less at the lower hopper end than at the upper one, being illustratively 50% or less, illustratively 25% or less, illustratively 10% or less than the cross-sectional dimension at the upper end.
The bag-receiving hopper 74 preferably shall be conical and circular over its full height. Other shapes than circular, for instance oval or polygonal ones, also are possible. The bag-receiving hopper 74 may comprise a non-conical segment at its lower and/or upper ends.
The appropriate respective frequencies of the vibrator 78 driving the bag-receiving hopper 74 and of the vibrator 11 driving the sieve 10 may be determined empirically. Illustratively mechanical vibrators run as fast as 120 Hz. Pneumatic vibrators for instance run at frequencies as high as 18 kHz. Ultrasonic vibrators run at frequencies as high as 34 kHz.
Components already found in previously discussed embodiments and shown again in
The powder pump 4 of the fresh powder conduit 16 illustratively is an injector or a compressed-air thrust pump (plug moving pump) and is oriented at the upper end of the powder feed pipe 70. Jointly with the powder pump 4 of the fresh powder conduit 16, also illustratively jointly with a fluidizing air pipe 132, the powder feed pipe 70 is mounted to be freely vertically displaceable, so that this sub-assembly is able by gravity to automatically track the powder level in the powder bag.
A weighing scale or at least one of the weighing cells 76-1, 76-2 and 76-3 may be configured between the bag-receiving hopper 74 and the pivot beam 200 or between the pivot beam 200 and the guide bar 125 or underneath the guide bar 125.
An optical weight display or another weight signal from the scale 112 or the weighing cells 76-1, 76-2 and 76-3 can be nulled in all embodiments of the invention when the bag-receiving hopper 74 is devoid of any powder bag 12 and be tared in this manner. Therefore when a powder bag 12 rests in the bag-receiving hopper 74, the weight display/signal from the scale/weighing cells only indicates the weight of the powder bag 12, not the additional weight of the bag-receiving hopper 74.
Number | Date | Country | Kind |
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10 2007 005 307.1 | Feb 2007 | DE | national |
This application is a continuation of U.S. Ser. No. 12/023,296 filed Jan. 31, 2008, now abandoned. U.S. Ser. No. 12/023,296 claims the benefit under the Paris Convention of the Feb. 2, 2007 filing date of German patent application DE 10 2007 005 307.1. The disclosures of both of U.S. Ser. No. 12/023,296 and DE 10 2007 005 307.1 is hereby incorporated in their entireties herein by reference.
Number | Date | Country | |
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Parent | 12023296 | Jan 2008 | US |
Child | 13234661 | US |