US3045921A - Electrostatic spraying apparatus - Google Patents

Description

July 24, 1962 H. HEUSCHKEL ELECTROSTATIC SPRAYING APPARATUS Filed Oct. 28. 1960 8 Arm 2 m H 22 7 3 7 22 2 9 A w 8 All EJQJ.

INVENTOR. Hans Heuschkel United States Patent Ofifice 3,945,921 Patented July 24, 1962 3,045,921 ELECTROSTATIC SPRAYENG APPARATUS Hans Heuschkel, Ravensburg, Germany, assignor to Escher Wyss G.m.b.H., Ravensburg, Germany, a corporation of Germany Filed Oct. 28, 1960, Ser. No. 65,617 Claims priority, application Germany Nov. 3, 1959 11 Claims. (Cl. 239-132) Electrostatic spraying apparatus are known in which the material being sprayed flows out between the edges of two blades. The said blades are so screwed to the two sides of a base support as to enclose together with the latter a space of triangular cross-section which serves to receive the material to be sprayed. The edges of the two blades form the spraying edges, from which the maten'al is sprayed by electrostatic forces on to the object to be provided with a surface coating.

However, it has been found, especially in the spraying of molten material, that it is often necessary to vary the gap width in order to improve the spraying pattern. With the apparatus heretofore known, it has been necessary for this purpose to interrupt the spraying operation, to empty the gap and, after slackening of the securing screws of the blades, to re-adjust the gap width. The gap was then realigned and the apparatus filled with the material to be sprayed before the operation was resumed.

The invention relates to an electrostatic spraying apparatus in which the material to be sprayed flows out between the edges of two blades, forming the spraying edges, and has for its object so to design the apparatus that it can be adapted for the use of different types of spraying material or for different modes of operation with out the slackening of screws or the like, while being of simple construction and easy to dismantle for the purpose of cleaning. According to the invention, this is achieved by virtue of the fact that at least one of the two blades is arranged to be rotatable about an axis extending parallel to the spraying edge.

A constructional example of the subject of the invention is illustrated in simplified form in the drawings, in which:

FIGURE 1 is an axial longitudinal section through the apparatus, and

FIGURE 2 is a section along the line IIII of FIG- URE 1.

Two blades 1 and 2 are arranged to define between their edges a spraying gap 3. The blade edges form the spraying edges. The blade 1 is secured by screws 4 to a substantially cylindrical hollow supporting body 5 fixedly disposed in space, of which the axis extends parallel to the spraying edge and which extends along the entire length of the latter. Blade 1, however, may also be integrally formed with the body 5. The blade 2 has on the side opposite the edge, i.e. on the blade root, an extension 6 which is appropriately guided at an angle somewhat larger than 180 on the circular cylindrical outer surface of the hollow body 5, in such a manner that the blade 2 can be rotated about the axis of the hollow body 5. Owing to the guiding at an angle amounting to more than 180, lifting of the blade 1 from the supporting body 5 is prevented. With a smaller guiding angle, it would be deisrable to provide a spring for pressing the blade against the guide surface.

The two blades 1 and 2 have between them a wedgeshaped space 7 which is axially bounded by two end walls 8 and 9. The said space 7 is sealed by the extension 6 of the blade 2 in the peripheral direction of the hollow body 5. The guide surface extends over the entire length of the blade and serves at the same time as a sealing surface for the space 7 for the medium to be sprayed.

A tubular member 10 is screwed through the end wall 8 into the hollow body 5. A nut 11 engages with a screwthread provided on the outside of the tubular member 10 and presses the end wall 8 against the hollow body 5.

A tubular member 12 is axially screwed through the opposite end wall 9 into the hollow body 5. A knurled nut 14 mounted on a connecting branch 13 of the said tubular member '12 compresses a spring 15, which thus presses the end wall 9 against the hollow body 5 and the two blades 1 and 2.

The end faces of the hollow body 5 and of the two blades 1 and 2, which bear against the end walls 8 and 9, are ground together so as to provide a seal for the chamber 7 with the also ground end walls.

A pin 16 which locates the blade 1 in relation to the end wall 9, and a corresponding pin on the side of the end wall 8 prevents turning of the blade 1 and of the hollow body 5 toward the two end walls. The end walls, however, allow angular displacement of the blade 2.

The medium to be sprayed is introduced. through a duct 17 extending through the tubular member 10 and the interior of the body 5, into a cross member 18 extending through the centre of the body 5 and passes from the said cross member through a bore 19 extending through the cross member 18 and the wall of the hollow body 5, and through a slot 20 formed in the extension 6 of the blade 2 into the spraying space 7, whereafter it is sprayed through the gap 3 between the edges of the blades 1 and 2 by electrostatic forces. For producing these forces, the spraying apparatus is brought by means not shown to a high negative electrical potential in relation to the object to be sprayed.

The extension 6 is provided with two ribs 21 on the side opposite to the spraying space 7. Secured to the said ribs is a trough 22 surrounding the hollow body at a distance therefrom. The said trough serves to receive spraying medium overflowing at the spraying gap 3. The trough is sealed from the end walls 8 and 9 by flanges 23. A branch 24 disposed on the end wall 8 serves to carry away the spraying medium taken up by the trough 22.

In addition, a fork 25 is secured on the side of the end wall 9 to one of the ribs 21 of the extension 6 of the blade 2 by screws 26 through the trough 22. Eccentrically and rotatably mounted in the end wall 9 is a pin 27 which extends into the fork 25. The said pin can be rotated by means of a knob 28 provided on the outside of the end wall 9 and serves for the fine adjustment of the angular position of the rotatable blade 1. By actuation of the rotatable knob 28, the blade 2 can be turned through the fork 25 about the axis of the hollow body 5, whereby the width of the gap 3 is varied. The width of the gap 3 can thus be readily adapted during operation to the medium employed for the spraying in each instance or to other variations of the state of operation.

Since some spraying liquids, such as paraffin, must be applied in the warm state and cooling thereof must be avoided as it flows through the apparatus, means are also provided in the illustrated apparatus for the supply of a heating medium, for example hot oil. The said heating medium is introduced through a branch 29 into the annular space between the duct 17 and the tubular member 10 and thereafter flows through the interior of the hollow body 5, so that all the parts by which the medium to be sprayed is guided to the spraying gap 3 are heated. The cross member 18 is formed With apertures 30 for the passage of the heating medium. The heating medium thereafter flows away through the tubular member 12 and through a central bore in the branch 13. The interior of the hollow body thus serves as a passage for the heating medium. This form of heating is very effective, but in some cases it may be sufficient to provide, for example, a heating conductor extending through the chamber 7 for the material to be sprayed.

In the spraying of varnishes and of molten products, considerable distances between the spraying gap and the object to be sprayed are often necessary in order to obtain a fine distribution of the medium being sprayed. In such cases, the loss of solvent, the cooling and solidification of the liquid molten material and the oxidation of additives sometimes contained in the medium being sprayed have a very disadvantageous effect.

For this reason, the illustrated apparatus is provided with a housing wall portion 31 which surrounds the hollow body 5 and the trough 22 with some clearance and which has a connection 32 for the supply of a gaseous medium into its interior. The housing 31 is secured to the end wall 8 by way of a flange 33 by means of screws 34. The housing 31 consists substantially of a tube which is arranged eccentrically in relation to the hollow body 5 and which has on the side closer to the spraying gap an aperture extending over its entire length for the passage of the two blades 1 and 2.. Gaps 35 are left free on either side between the housing 31 and the blades 1 and 2 in the said aperture, through which gaps the gaseous medium supplied can escape in the direction of the spraying edges. It is thus possible to blow, for example, hot air, nitrogen or a mixture of air and solvent past the spraying gap 3 and thus to afford protection tothe sprayed jet against the ambient air.

In addition, in the described arrangement the end walls 8 and 9 extend upward above the spraying edge. At a short distance from the spraying gap, apertures 36 extend in the end walls parallel to the spraying gap, into which apertures straight cylindrical electrodes 37 slotted on one side can be introduced for the lateral limitation of the sprayed jet.

The apparatus can readily be dismantled for the purpose of cleaning. After unscrewing the knurled nut 14, the spring 15, the end wall 9 and the blade 2 can readily be withdrawn. The interior of the gap is then readily accessible and can be well cleaned.

Instead of only one blade, if desired, both blades may be arranged to be rotatable about axes extending parallel to the spraying edges.

What is claimed is:

1. An electrostatic spraying apparatus comprising in combination a tubular supporting body of circular crosssection; two blades arranged on said supporting body so as to define a wedge-shaped space for the reception of a medium to be sprayed, said blades having spraying edges which are remote from and Parallel with the axis of said supporting body and which are spaced to define a gap, at least one of said blades having a face conforming with and contiguously engaging the outer peripheral surface of said supporting body, said blade being rotatable about the axis of said supporting body; end walls connected with the supporting body at opposite ends of said blades for closing the ends of the wedge-shaped space; conduit means for supplying the medium to be sprayed into the space; and means for angularly displacing said rotatable blade about the axis of the supporting body to vary the gap between the spraying edges.

2. The combination defined in claim 1 in which the face of said rotatable blade engage the outer peripheral surface of the supporting body throughout an angle of more than 3. The combination defined in claim 2 in which said face of the rotatable blade extends over the entire length of the supporting body and serves as a sealing means for the wedge-shaped space.

4. The combination defined in claim 2 in which the blade face is provided with a fork on the side opposite to said wedge-shaped space with respect to the supporting body; a pin being eccentrically and rotatably mounted in one of said end walls so as to engage with said fork, said pin serving for the fine adjustment of the angular position of the rotatable blade.

5. An electrostatic spraying apparatus comprising in combination a substantially cylindrical hollow supporting body; a first blade rigidly connected to said supporting body in substantially tangential direction, said blade having a free edge extending parallel with the axis of said supporting body; a second blade mounted on said supporting body opposite to said first blade so as to be rotatable about said axis, the free edge of said second blade being parallel with the free edge of the first blade, said blades defining with the supporting body a wedgeshaped space for the reception of medium to be sprayed, end walls closing said wedge-shaped space axially while allowing angular displacement of the rotatable blade; the rotatable blade and the supporting body having circular cylindrical surfaces which bear against one another; means for effecting angular displacement of the rotatable blade relatively to the rigidly connected blade so as to vary the width of the gap; a supply conduit for the medium to be sprayed leading through the interior of the supporting body into said wedge-shaped space; flow connections for leading a heating medium through the interior of the sup porting body; a trough connected to the rotatable blade so as to surround the side opposite to the spraying edges of the supporting body and to receive overflowing spraying medium; a housing enclosing the supporting body and the trough while leaving gaps on both sides of the blades; and a supply conduit for a gaseous medium, leading into said housing.

6. Spraying apparatus comprising in combination a housing having a pair of spaced end walls and a supporting body connected between said end walls; a pair of blades connected with said body and extending outward therefrom, the ends of said blades being adjacent said end walls and the adjacent surfaces of said blades being spaced to define a chamber, said blades having parallel spraying edges which are remote from said supporting body and which are spaced to define a gap, at least one of said blades being rotatable about an axis parallel with and equisdistant from the two spraying edges in all relative positions of said blades; means for supplying a medium to be sprayed to said chamber; and an adjustment means for rotating said blades relative to each other so as to vary the width of the gap between the edges of said blades.

7. Apparatus as defined in claim 6 wherein said supporting body is hollow and extends parallel with said spraying edges over the lengths thereof, and wherein said last mentioned means extends through at least a portion of said supporting body.

8. Apparatus as defined in claim 6 wherein said end walls are movable relative to each other longitudinally of said supporting body, and including means biasing said end walls into engagement with the ends of the blades.

9. Apparatus as defined in claim 6 wherein said housing includes a wall portion arranged about and spaced from said supporting body and at least a portion of said blades, and means for introducing a gaseous medium into the space between said supporting body and said wall 5 6 portion whereby said gaseous medium flows along the References Cited in the file of this patent outer surfaces of said blades and past said spraying edges. UNITED STATES PATENTS 10. Apparatus as defined in claim 9 and further ineluding a trough arranged between and spaced from said 768,095 Twfst 1904 962,209 Gaiior June 21, 1910 supporting body and said Wall portion for collecting spray 5 I ing medium which overflows the spraying edges, and 5 33 et "22 cans for ov' th m d'u f 0 sad 1 P er P g rem mg e Spraying e 1 m r m 1 2,710,773 Sedlacsik June 14, 1955 11. Apparatus as defined in claim 7 and further inolud- 21763575 Bede Sept 1956 ing means for passing 'a heating medium through said 10 2309302 Ransburg 1957 supporting body independently of the spraying medium. 2'893'893 Grouse July 1959

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