US 3680528 A
An apparatus for removing excess, airborne powder following the application of a powder material to a moving surface such as a web or sheet wherein a manifold is positioned downstream of the powder application to entrap the airborne powder and the collected powder is removed by the combined action of a fluid stream to move the powder towards the ends of the manifold and a gentle vacuum adjacent the manifold ends to exhaust the powder to, for example, an exhaust trap, and methods for removing excess, airborne powder.
Description (OCR text may contain errors)
1151 3,680,528 1451 Aug, 1, 1972 United States Patent Sanders  APPARATUSFORPOWDERREMOVAL 2,515,223 7/1950 Hollick.......................15/345X 2,757,635 8/1956 Lipsius.........................
118/312 ...ll8/637 X  Inventor: Robert C. Sanders, Syracuse, N.Y.
 Assignee: Oxy-Dry 3,404,418 10/1968 Fantuzzo................ 3,434,416 3/1969 Testone....................
Sprayer Corporation, 118/639 X Chicago, 111. 3,451,376 6/1969 Obuchi et a]. 18/637 ..1 18/637  Filed: April 1, 1970  Appl. No.: 24,523 Primary Examiner-Louis K. Rimrodt Att0meyWo1fe, Hubbard, Leydig, Voit & Osann Related US. Application Data  Continuation-impart of Ser. No. 811,381, ABSTRACT An apparatus for removing excess, airborne March 28, 1969, abandoned. powder following the application of a powder material to a moving surface such as a web or sheet wherein a manifold is positioned downstream of the powder aplication to entrap the airborne powder and the collected powder is removed by the combined action of a fluid stream to move the powder towards the ends of the manifold and a gentle vacuum adjacent the manifold ends to exhaust the powder to, for example, an exhaust trap, and methods for removing excess, airborne powder.
0. 78 mmm 3 001 1 D3 1 20 05 W W S 1m92 T l 0 N mm E mr s M M mmfl u P c s 6 E WWW C T n A mm! m T mm k s uh e D mmm R E mmm T r v I n N L U C d S M U.| .F 11. 2 8 6 555 5 1.11 .1
13 Claims, 4 Drawing Figures 3,287,755 11/1966 Pansini............................15/17 1,850,502 3/1932 l-iilker ...l39/1C APPARATUS FOR POWDER REMOVAL This is a continuation-in-part of copending application Ser. No. 811,381, filed Mar. 28, 1969 now abandoned.
, This invention relates to apparatus for removing airborne powder from the atmosphere and, more particularly to an apparatus that is used in conjunction with the application of a powder to a moving surface to remove the excess, airborne powder following the powder application.
In many industrial situations it is extremely desirable or necessary to deposit a powder material on a moving surface. As one representative example, in the printing industry, it is conventional to apply (generally electrostatically) a powder such as starch onto a moving web or sheet to prevent the smearing of ink. While this powder application effectively prevents smearing, not all of the powder is adherred to the travelling surface. A significant amount remains airborne and eventually collects on the equipment, the walls, ceiling and floor of the press room and even on the individuals in the area.
Where a sheet-fed press is involved, separate gripper bars carry individual sheets and there is a gap between the end of one sheet and the forward end of the next sheet. This causes an intermittent pulsating of the powder which increases the tendency of the powder to stay airborne. This excess powder is often termed fly around.
In a web-fed press, other problems can arise. Thus, powder applicators are generally equipped to dispense the powder over a set distance. And, when a web with a width narrower than that set distance is to have powder deposited thereupon, not only will the air turbulence caused by the moving web cause excess powder to remain airborne but also some of the powder dispensed in areas where there is no moving web below will fall by gravity past the web.
Considerable effort has in the past been directed towards developing apparatus suitable for collecting most or all of this excess powder. Such apparatus have generally involved enclosing the whole area in which the powder was applied and then employing vacuum to transport the powder from adjacent the sheet. Typically, these solutions have proved expensive, have af fected the quality of the powder application itself and installation on the presses have sometimes been difficult because of the available space in the press for installation.
It is accordingly a primary aim of the present invention to provide a method and apparatus for removing excess, airborne powder from a moving surface following the application of powder to that surface which is economical and can remove a significant amount of the excess powder without significantly affecting the desired application of the powder to the sheet.
Another object of the present invention is to provide an apparatus which is sufficiently compact so that it may be easily mounted on most conventional printing presses.
Other objects and advantages of the present invention will become apparent as the following description proceeds, taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a perspective view of one embodiment of the apparatus of the present invention and illustrating the positioning of the apparatus in relation to the powder applicator, a portion of the manifold being partly broken away to illustrate the air or fluid distribution means;
FIG. 2 is a cross-sectional view taken along lines 2- 2 of FIG. 1 and illustrating in greater detail the cabinet for minimizing the escape of any collected powder;
FIG. 3 is a cross-sectional view taken along lines 3- 3 of FIG. 1 and illustrating the positioning of the fluid distribution means in relation to the manifold; and
FIG. 4 is a cross-sectional view taken along lines 4- 4 of FIG. 3 and showing in detail the fluid distribution means.
While the invention is susceptible of various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed, but, on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope and spirit of the invention.
Turning to the figures, FIGS. 1 and 2 illustrate an exemplary embodiment for effecting the removal of airborne powder following the application of the powder to a moving surface without significantly affecting the effectiveness of the powder application itself. As shown, powder 10 is applied to a moving surface 12 by a powder sprayer or applicator 14. Any conventional sprayer may be employed. Electrostatic powder sprayers, such as are illustrated and claimed in U.S. Pat. Nos. 3,273,016, 3,292,045, 3,292,046, 3,341,740 and 3,344,312 may be advantageously employed.
In accordance with one feature of the present invention, a collecting means is provided to entrap at least a significant portion of the airborne powder. As shown, a collecting surface or manifold 16 is provided. The manifold may have any desired shape for the collecting surface providing that it forms an open entrapping enclosure for the powder. The enclosure should allow free ingress while restricting egress. It is preferred to employ an enclosure with a collecting surface that is substantially rectangular in shape, the rectangle being open on the bottom side adjacent the moving surface 12 to achieve optimum performance. However, adequate performance, it is believed, can be provided when the cross section of the surface constitutes other geometrical shapes such as semicircular, parabolic and the like. In the illustrative embodiment, the manifold 16 may have rectangular collecting surface 18 with a width w of 12 inches and a height of 3 inches. Desirably, the manifold should have a length which is substantially equivalent to the maximum side-to-side spray capability of the sprayer itself. Because of the turbulence caused by the high speed motion of the travelling surfaces which will generally be involved, the excess powder particles will concentrate into an area downstream from the powder applicator. The exact positioning of the manifold will vary depending upon the normal operating speed of the sheet or web that is being sprayed. As an example, when used in connection with a sheet-fed press operating at conventional press speeds, it has generally been found suitable to position the manifold 16 about 6 to 8 inches downstream from an electrostatic powder sprayer.
To transport the entrapped powder particles from the enclosure or collecting surface, another feature of the present invention provides the combined action of a fluid such as air to direct the powder outwardly towards the ends of the manifold and a gentle vacuum to pull the powder from adjacent the manifold ends and exhaust the powder without pulling powder away from the sprayed moving surface. It is the combination of these forces that provides successful powder removal without also pulling deposited powder off the moving sheet or web. Thus, the air or other fluid pressure must be sufficient to move the powder outwardly to the manifold ends but not so great that the air stream in effect, begins to function as a vacuum thereby pulling powder away from the sprayed surface. Similarly, the vacuum must be sufficiently gentle to prevent pulling powder away from the sprayed surface while still being sufficient to maintain the movement of the powder particles towards their ultimate collection in an exhaust trap, dispersion into the atmosphere or connection with other exhaust systems. Thus, as is shown, air from a source not shown is passed through an air regulator and filter 20 into lines 22 and 24 and through a fluid distribution tee 26 which is located adjacent the center of manifold 16. The distribution tee 26 has orifices 28, 28 that direct the air or other fluid outward. Desirably, the distribution tee should be substantially in the center of they manifold so that the air pressure will push the particles towards the manifold ends with substantially the same force in both directions. Additionally, it has been found preferable to position the distribution tee close to the top of the interior collecting surface 18 of the manifold in such a manner that the orifices 28, 28' direct the air or other fluid toward surface 18. Optimum performance is achieved when the air flow contacts the collecting surface adjacent the plenums. This can be accomplished by positioning the orifices 28, 28' at angles to the horizontal of about 1 to As a representative example in connection with a sheet-fed press, it has been found adequate if the fluid source provides a pressure of from 3 to pounds per square inch gage with orifices of about one thirty-secondth inch diameter.
It should, however, be appreciated that the distribution tee could have more than one orifice to direct the flow if this is found necessary or desirable. Generally, if multiple orifices are used, they will be employed to direct, at least initially, the air towards the sides of the enclosure rather than straight to the ends of the manifold.
To collect the powder particles that exit from the ends of the manifold there are provided exhaust plenums through which the vacuum is pulled and suitably dimensioned to allow all of the exiting powder drawn by the gentle vacuum to be collected en route to an exhaust trap. The exhaust plenums provide a means to converge and further concentrate the powder stream. To this end, and as is shown, exhaust plenums 30 are provided which have an entrance face 32 with a transverse dimension substantially equivalent to the width w of the manifold and a height also equivalent to the height h of the manifold. As shown, the plenums 30 are connected together with the manifold 16 to provide a continuous system. This can be accomplished by any conventional fastening means such as soldering.
While this minimizes the amount of powder escape, it should be appreciated that satisfactory operation will also result when the manifold and the plenums are not connected. The wedge-shaped plenums concentrate the powder stream which exits the plenums through an exit 34'which may be circular in shape and have a diameter corresponding to the height of plenum entrance face 32. Thus, the height and transverse dimensions of the plenums may be varied if desired. Similarly, while it is desirable to position the plenums 30 at about the same level as the manifold 16, they may be higher or lower if necessary because of the spatial limitations of the equipment with which the subject invention is being employed. The relative height can be varied widely as long as the vacuum remains sufficient to pull the powder stream through the plenums. The same considerations are involved as regards the distance between the manifold ends and the plenum. In the case of a sheet-fed press, the exhaust plenums may, for example, be positioned just outside the path of the gripper bars.
In accordance with another aspect of the present invention, an air curtain is utilized in connection with the manifold to minimize escape of powder from the manifold. Thus, as is shown in FIG. 1, an air curtain 29 comprises an air regulation tube 31 which is positioned adjacent the side of the manifold 16 which is away from the powder sprayer 14. Air, from a source not shown, is supplied to an air regulator 33 to the air regulation tube 31. The air can suitably exit from the air regulation tube by means of a series of spaced orifices. As an example, it has been found satisfactory to employ about 0.030 inch orifices spaced about 1 inches apart. A pressure of about 2 to 6 pounds gage is suitable. It should be appreciated that adequate performance can be achieved without use of the air curtain; but, to obtain optimum benefits from the present invention, the air curtain should be utilized.
The transporting of the powder particles from adjacent the ends of the manifold to the plenums and eventually into an exhaust trap is carried out by providing a means for creating a gentle vacuum. As shown, a blower 36 creates a vacuum which moves the powder stream into the plenums 30, through flexible conduits 38, a T 40, conduit 42 and into an exhaust trap. The length of conduit between the entrance to the distribution tee and each plenum should be substantially the same so that an equal pressure arrangement will be provided. Unequal pressure would result in escape of part of the powder particles.
When employed in conjunction with a system including the examples for the various elements hereinbefore set forth, the flexible conduit may suitably have an inside diameter of about 3 inches and the tee may have an outlet on the blower side of about 4 inches. Heavy duty applications may require the employment of larger diameter conduits and T outlet. The blower itself may suitably operate at a capacity of about 350 cubic feet per minute of air.
In accordance with a further feature of the present invention, the powder particles may be collected in an exhaust trap which is air or fluid permeable to allow the air or fluid to pass therethrough. To this end, the powder collects in an exhaust trap 44, which may suitably be a woven cotton bag that is sufiiciently porous to allow exhaust of the air into the atmosphere. Desirably, the exhaust trap should have a capacity that will be sufficient to minimize the frequency with which it must be cleaned to remove the collected powder. As an example, a trap having a 100 pound capacity could be employed. For optimum operation the powder should not be allowed to occupy more than about 5 to percent of the area of the trap itself. A 100 pound trap, used in connection with depositing starch onto printed sheets in a sheet-fed press could perhaps be expected to collect anywhere from about 2 to about 30 pounds per 120 operating hours. If desired, the powder stream could be joined with any existing exhaust system or could also be vented to the atmosphere.
While the exhaust trap will collect the vast majority of the powder, a small amount can be carried through the woven bag by the air passing therethrough. Pursuant to still another feature of the present invention, an additional barrier to escape of powder into the air may be provided by housing the exhaust trap in an enclosure provided with a filtered egress. Thus, a cabinet 46 is provided to house the exhaust trap 44. The cabinet may be formed with a removable top plate 48 and a gasket 50. The top plate may be fastened to the top edge of the cabinet by any suitable means. An air tight coupling 52 is provided to accommodate the conduit 42. A filter 54 is set in one side of the cabinet in a suitable frame and inregister with an exhaust or egress for the air.
It should be appreciated that the use of a symmetrical system, ie fluid distribution T 26 located in the middle of the manifold and equal length conduits, is preferred due to its simplicity. However, it is within the present invention to vary the respective conduit lengths and position of the tee to provide a system that coordinates the relative vacuum and fluid pressure to achieve removal of the powder. More specifically, within certain limits, the vacuum could be increased on one side relative to the other side (by varying conduit length) and the tee moved closer to the side of least vacuum to still provide for effective removal.
In addition, when dealing with a web-fed press or other situations when the moving surface is not as wide as the set distance of the powder applicator, it may be desirable to include a second manifold 56 and distribution tee 58. This manifold may be positioned below the web or moving surface with the collecting surface facing upwardly. No additional plenums are necessary.
Thus, as has been seen, the present invention provides a unique method and apparatus for removing excess airborne powder following powder application to the surface of a sheet, web or other surface which is travelling at, generally, a high rate of speed. The collection and removal of the powder is achieved without effecting the powder previously deposited upon the moving surface yet is compact and can be easily mounted trib tion means located s 'd manif ld a d i te mediate the ends to direct ii ui towardst eeniiso said manifold, a fluid source for supplying fluid to said fluid distribution means to cause the powder to move towards the ends, a plenum located adjacent each end of said manifold and means to exhaust the powder from adjacent the ends of said manifold through said plenums as powder is moved adjacent the ends.
2. The apparatus of claim 1 which includes an exhaust means comprising an exhaust trap to collect the powder while being sufficiently porous to allow fluid to pass therethrough and means coupling said plenums to said exhaust trap.
3. The apparatus of claim 1 wherein an air curtain is positioned adjacent the side of the manifold downstream from the powder application.
4. The apparatus of claim 1 wherein the plenums and manifold are connected together.
5. The apparatus of claim 1 wherein the fluid distribution means are positioned adjacent the center of said manifold and the vacuum for each end is substantially the same.
6. The apparatus of claim 1 wherein the fluid source is air.
7. The apparatus of claim 1 wherein the manifold has a rectangular collection surface.
8. The apparatus of claim 1 wherein the manifold is located downstream of the powder applicator.
9. The apparatus of claim 7 wherein the manifold is positioned above the moving surface a distance substantially equal to that of the powder applicator.
10. The apparatus of claim 7 wherein a second manifold and fluid distribution means are positioned below the moving surface to collect falling powder and direct it towards said plenums.
11. The apparatus of claim 2 wherein the coupling means is flexible tubing and said vacuum means is positioned between said plenums and said exhaust trap, the length of tubing from each of said plenums to said vacuum means being substantially the same.
12. The apparatus of claim 10 wherein said vacuum means is a blower.
13. The apparatus of claim 2 wherein a closed compartment encloses said exhaust trap, said compartment being provided with an opening and a filter in register therewith to contain the collected powder while providing an egress for the fluid.