US3017116A - Electrostatic spraying device - Google Patents

Description

Jan. 16, 1962 E. o. NORRIS ELECTROSTATIC SPRAYING DEVICE Filed July 23, 1958 3 Sheets-Sheet 1 i Flt?) mmsn/roe EDWARD 0. n/oee/s ATTORNL-Y Jan. 16, 1962 E. o. NORRIS ELECTROSTATIC SPRAYING DEVICE 3 Sheets-Sheet 2 Filed July 23, 1958 Jan. 16, 1962 E. o. NORRIS ELECTROSTATIC SPRAYING DEVICE 5 Sheets-Sheet 3 Filed July 23, 1958 INVENTOR F EDWAED O. NORRIS A T'TOR/VE Y United States Patent 3,017,116 ELECTROSTATIC SPRAYING DEVICE Edward 0. Norris, Ledgemoor Lane, Westport, Conn. Filed July 23, 1958, Ser. No. 750,471 6 Claims. (Cl. 23915) The present invention relates to rotary spraying devices wherein liquid for painting or otherwise coating or treating a surface is fed to an atomizing distributor head operating at high speed, and is atomized and projected by said distributor head in the form of an annular or fan shaped spray against the surface to be sprayed. The present invention is an improvement over the multiple atomizing disc type of centrifugal spray device shown and described in US. Patent No. 2,545,488.

One object of the present invention is to provide a new and improved rotary spray device of the multiple atomizing disc type capable of projecting a spray of increased depth along its axis of rotation without materially increasing the size of the device.

A further object is to provide a new and improved rotary spray device, which can be efficiently controlled to vary selectively the concentration and distribution of the material across the depth of the spray.

Another object is to provide a new and improved rotary spray device which can be easily controlled quickly, as for example, for cyclic automatic operations to project a spray of any desired density at any selected periods.

Another object is to provide an automatic method and apparatus by which a spray is applied to articles, such as hollow drum shells, under controls, which stop and start the projection of the spray and/or vary its density at predetermined intervals in accordance with the relative positions of the articles and the spray device.

In accordance with certain features of the present invention, the spray device of the present invention comprises a plurality of rotary atomizer axially spaced dished discs in the form of rings, arranged in two opposed sets, each set consisting of one disc or a plurality of nesting discs, and the concave sides of the discs in the two sets facing axially opposite directions away from each other. A rotary spreader is provided inside the two sets of discs with a discharge edge or rim extending obliquely across the inner annular inlet edges or rims of said discs, to distribute the coating material from said discharge spreader rim to each of said inlet disc rims in predetermined proportions. The inlet edges or rims of the atomizing discs are bevelled or otherwise contoured to assure the required distribution of material delivered to said discs from said spreader.

The atomizer discs have discharge rims flaring in axially opposite directions away from each other in the two sets, so that the spray diverges depthwise along the axis of rotation, thereby assuring a thicker spray for wider impingement stripe coverage and also permitting a wider distribution of the material as to assure a spray of lighter density, where such is required, as for example in connection with the coating of certain contours and shapes to be described.

As a further feature of the present invention, the centrifugal spray device of the multiple atomizer disc type is employed in connection with an electrostatic field to assist and improve the centrifugal coating function of the spray device.

As another feature, in conjunction with the electrostatic field, means are provided to controllably distribute the coating material to each disc in such a manner, that the discs having the strongest field, efiect, receive and atomize the greater portion of the material.

As a further feature, to assist and improve the centn'fugal coating function of the multiple disc spray device described when employed in connection with an electrostatic field, the disc assembly is given a convex axial contour with the centrally disposed discs having the largest external diameters and the top and bottom rings the smallest diameters.

As another feature, the discharge edge of the spreader inside the stack of discs is serrated to increase the effective discharge length of said edge, to effect more uniform distribution of the spray material to the discs and to permit control of the rate of feed through a wider range.

Certain types of articles have certain conformations which are diflicult to spray properly, especially where automatic operations are involved, Without loss of spray material or without over-spraying certain parts of the article. For example, a certain type of drum or tubular shell has an edge or r-im section at the top or head end rolled back externally to form a bead or curl. In coating the interior of such a shell, it is also desirable to coat not only the interior of the curled rim but also the exterior. With the drum shell arranged to move axially relative to the spray device and the spray device located inside the shell, it is desirable to apply to the interior surfaces of the drum shell heavy material at a relatively high linear speed of movement between the drum shell and the spray device and also to coat not only the interior of the curled rim but also the exterior. In accordance with the present invention, this result is attained by creating an electrostatic field to cause the spray particles to be electrostatically deflected around the outside of the drum shell and the spray to be wrapped around the curled rim. Since the spray device is operated with a heavy spray for the interior of the drum shell, the application of this heavy spray for the electrostatic wrap around has the disadvantage of creating material losses towards the end of the drum shell. Moreover, the heavy particles are more diflicult to deflect electrostatically around the curled end of the drum shell.

As another feature of the present invention, means are provided for controlling the rate of feed of material to the spray device cyclically in accordance with the position of said spray device in relation to the drum shell or other article to be sprayed. For example, at or near the ends of the relative travels of the drum shell and the spray device, where there is travel reversal involved, the temporary pause created by such reversal may cause overspray or loss of material, and the feed of material is in accordance with the present invention shut off, or its rate materially reduced by automatic control. Also, where a curled rim at the end of the drum shell is to be externally sprayed, the rate of feed of material to the spray device is reduced when the spray device is in the vicinity of the region of the plane of said curled rim to create a spray of lighter density. The particles in such a spray being smaller and lighter, they are more easily deflected by electrostatic action, so that the spray will wrap around the rim more effectively. This assures proper coating of the interior of the drum shell and also of the outside of the curled rim.

The specific centrifugal spray device of the multiple disc type described above is particularly adaptable for the automatically controlled system described. However, as far as certain aspects of the invention are concerned, any other suitable type of spray device may be employed in connection with the control features described.

Various other objects, features and advantages of the invention are apparent from the following specification and from the accompanying drawings, in which:

FIG. 1 is a longitudinal section through the distributor of a spray device constituting one embodiment of the present invention;

FIG. 2 is a fragmentary view of the distributor o FIG. 1 shown partily in longitudinal section and partly in elevation;

FIG. 3 is a fragmentary longitudinal section of another form of centrifugal atomizer rings embodying the present invention, and useful especially in connection with the use of an electrostatic field;

FIG. 4 is -a diagrammatic illustration of a system involving the automatic control of a spray device in accordance with the present invention, and illustrated in connection with the coating of drum shells to apply protec tive lining coatings to the interior thereof; and

FIG. 5 is an enlargement of part of the automatic control system illustrated in FIG. 4, and especially the drum shell conveyor means and the position of the spray device in relation thereto.

Referring to FIGS. 1 and 2 of the drawings, the distributor centrifugal spray head is mounted on a fixed tubular housing 10, which is secured to casing of a motor 11 (FIG. 5) and to the casing of a reduction gearing, if such is employed. Extending axially through the housing is a shaft 12 driven from the motor 11 and supported in said housing by ball bearings 13 and roller bearings 14. This shaft 12 carries near One end a distributor spray head unit comprising a series of atomizer discs 15, 16, 17, 18 and 19 in the form of rings axially spaced along said shaft and secured to frame pieces 20 and 21 mounted on said shaft. The frame piece 20 forms a cover for one end of the distributor head and comprises a peripheral fiat ring section 22 axially spaced from the outer end atomizer disc 19 and parallel thereto and a center dome section 23 with a center hub 24 embracing the outer end of the shaft 12 and seated on an annular shoulder 25 formed on said shaft. A locking nut 26 threaded on the outer end of the shaft 12 and bearing against the cover 20 secures the cover to the shaft for rotation therewith.

The other frame piece 21 serves as a cover for the other end of the distributor spray head and comprises a peripheral flat ring section 27 axially spaced from the inner end atomizer disc and parallel thereto and a center conical section 28 around the housing 10 serving as a splash guard. The atomizer discs 15-19 and the two covers and 21 are secured together as a rotatable unit by means of screw and washer assemblies 30.

The atomizer discs 1519 have their main body sections 34 flat and parallel to each other to form passageways 35 between the confronting faces thereof in planes substantially at right angles to their axis of rotation coextensive with the axis a of the shaft 12, and have center coaxial openings centered with respect to the axis of the shaft 12 and all having substantially the same diameter, except for some bevelled contours on the circular edges of said openings to be described. These openings conjointly define around the shaft 12 the inlet cylindrical chamber or eye 36 of the distributor head and located in said chamber is a rotary material spreader 37. This spreader 37 is rotatably supported on a ball bearing 40 for rotation with the shaft 12 and is in the form of a cup with its concavity facing generally the inner end of the distributor spray head. An annular discharge edge or lip 38 on the spreader 37 serves to deliver and distribute the coating material from the spreader to the atomizer discs 15-19.

The spreader 37 although rotated by the shaft 12 and with the shaft at the same high angular velocity, has the general plane of its discharge edge '38 inclined in relation to the planes at right angles to the axis a of the shaft, so that said discharge edge plane extends across the inner peripheral edges of the stacked atomizer discs 1519. Also, the spreader 37 is adjustable about an axis which is tilted in relation to the axis a of rotation of the atomizer discs 15-19, and the general plane of the discharge edge 38 of the spreader is at an angle to the tilted axis other than an angle of 90, so that adjustable rotation of the spreader about the tilted axis changes the angle of this general edge plane in relation to the general plane of the atomizer discs. Adjustment of this angle of tilt of the general plane of the discharge edge 38 in relation to the axis a of the atomizer discs 1519 is for the purpose to be described.

Referring more specifically to the structure and mount of the spreader 37, this spreader is supported on the ball bearing 40 as described, and has an annular flange 41 supporting the inner race of this ball bearing. The outer race of the ball bearing 40 is secured to a bearing cap 42 threaded or otherwise made fast to a sleeve 43, which embraces a collar 44 secured to the end of the tubular housing 10, as for example, by threading, and which is adjustably secured to said collar by a set screw 45 impinging in a groove 46 in said collar. Although the part of the collar 44 embraced by the sleeve 43 is cylindrical, its axis is inclined in relation to the axis of the shaft 12, and as indicated by the lines a and b in FIG. 1 the axis of the sleeve 43 is disposed at an angle to the axis of the spreader 37 as indicated by the lines 15 and c in FIG. 1 so that the general plane of the discharge edge 38 of the spreader 37 is tilted at an angle to the plane at right angles to said tilted axis for the adjusting purpose indicated above.

The spreader 37 rotates through bearing 40 about an axis 0 at right angles to the general plane of the discharge edge 38 of said spreader and the axis center of this bearing in the center plane of the bearing at right angles to this axis 0 is on the axis a of the shaft 12. In other words, a plane through the center of the bearing 40 and at right angles to the axis 0 will pass through the intersecting point of said axis c and the shaft axis a, as shown in FIGS. 1 and 2. This axial arrangement assures against radial displacement of the spreader 37 relative to the atomizer discs 1519, as they are rotated in unison.

The spreader 37 is driven from the shaft 12 for rotation therewith. For that purpose, a spring drive is provided comprising a tapering coil spring 50 around the shaft 12 having its smaller end seated in an annular shoulder recess, forming part of said shaft and anchored thereto for rotation therewith. The larger end of this spring 50 bears against a frame wall of the spreader through a metal bearing ring and a washer of friction material, such as leather, to form a yieldable friction drive connection with the spreader.

The spreader 37 because of its tilted position in relation to the general planes of the atomizer discs 15-19, extends partly into the dome space of the cover 20 and has an annular flange 55 therein defining an annular trough 56 into which the coating material is fed. This coating material is delivered to the trough 56 through a feed tube 57, which is detachably secured by a screw 58 to a collar 60 fastened to the housing 10 by a set screw 61. This feed tube 57 terminates in the spreading trough 56 in a nozzle 62 having its end turned in the direction of rotation of the spreader 37.

The discharge edge 38 forms the outer boundary edge of the trough 56 and the walls 63 of said trough are curved radially outwardly towards said discharge edge to cause coating material delivered to said trough to fiow smoothly by centrifugal action along said curved wall towards said discharge edge.

If the spreader discharge edge 38 were continuous, each segment thereof cooperating with the single atomizer disc opposite thereto for discharge to said disc would be comparatively short and the material spread along such a segment would have correspondingly greater concentration thereallong. This continuous edge construction cuts down the range of control of the feed material to the atomizer discs 15-19. In order to equalize the spreading of the coating material along the discharge edge 38 of the spreader 37 more evenly and to afford a greater range of control of the feed rate to the atomizer discs 15-19, this edge has a series of serrations 64, serving to increase the effective discharge length of this spreader edge 38.

The inclined discharge spreader edge 38 at its high and low regions extend along the inner annular edges 65 of the atomizer discs at the top and bottom of the disc stack, while the intermediate regions of said discharge edge cut across the inner annular edges 65 of the intermediate atomizer discs at a greater angle, this angle increasing as the middle disc of the stack is approached. As a result, there is a tendency for this discharge spreader edge 38 to project more material onto the top and bottom discs of the stack than onto the center discs. To compensate for this tendency, the inner annular edges 65 of the atomizer discs have angular contours shown as single bevels facing the middle plane of the stack and disposed to deflect some of the projected material from the top and bottom dis-c areas and towards the more central disc areas, and the center atomizer disc 15 has its inner annular edge 65 doubly bevelled to facilitate entry of the material into the field of action of said center disc and to deflect excess material towards the adjoining discs 16 and 18. :This bevel contouring of the inner edges 65 of the atomizer discs 1519 serves to equalize the distribution of the coating material to these discs.

As another important feature of the present invention, the atomizer discs 1519 are constructed and arranged to impart a divergent axial spread to the spray particles. For that purpose, the atomizer discs 1519 are dished or coned shaped and are mounted into two sets, the rings of the two sets being arranged with the concave sides facing axially away from each other, so that the two sets will be back to back. Where increase in the material handling capacity of the spray device is required, each set of discs will consist of more than one atomizer disc, as shown in the present embodiment, and the discs in each set will be nested in spaced relationship.

Referring more specifically to the structure of the atomizer discs 15-19 shown in 'FIG. 1, five discs are shown for the purpose of illustration, discs 15 and 16 nesting and forming one set, discs 18 and 19 nesting and forming the other set, and the middle disc 17 being bifunctional and belonging to both sets. The discs 15, 16, 18 and 19 are provided with flat bases 34 parallel to each other and peripheral conical discharge rims 66 and 67, the rims 66 of the two atomizer discs 15 and 16 extending parallel to each other and slanting away from the planes of their bases 34 radially outwardly and axially inwardly of the spray head and the rims 66 of the two atomizer discs 18 and 1 9 slanting away from theplanes of their bases 34 radially outwardly and axially outwardly of the spray device. As a result, the atomizer discs of the two sets will be arranged b ack to back, with their concave sides facing opposite directions away from each other.

The center atomizer disc 17 has a base 3 4 similar to the bases 34 of the other atomizer discs 15, 16, 18 and 19 but has double peripheral conical rims 67 merging at their larger 'base ends and flaring in opposite directions from the base 34 of said center disc, one of said rims 67 being parallel to the rims 66 of the atomizer discs 15 and 16, and the other rim 67 being parallel to the rims '66 of the atomizer discs 18 and 19. This center disc 17 is in eifect, therefore, two discs in back to back contact with their concave sides facing axially away from each other.

As a result of the disc construction and arrangement described the spray projected from the peripheries of the atomizer discs 1519 will diverge axially and therefore will deposit a wider stripe on the article being coated. This will permit the article being coated to be moved relative to the spray device at a greater speed, permits the production of a spray having a lighter density for the purpose to be described, and permits better control of the distribution of the material across the depth of the spray.

To assist centrifugal action in atomizing and directing the spray in the right direction, and to improve in other respects the centrifugal coating function of the spray device, an electrostatic field may be employed. For that purpose, the atomizing discs =1519 may be of non-conducting material, as for example, nylon, the cover plates 20 and 21 and the locking nut 26 may also be made of non-conducting material, as for example of phenolic composition and the spreader 37 may be made of conductive material and may be connected to a high voltage line to form one side of the electrostatic field, so that the coating material is electrostatically charged as it leaves the peripheral discharge edge or lip 38 of this spreader, to be received and centrifugally atomized by the atomizer discs 17-19. The other side of the electrostatic field is established where the article to be coated is located, and this article for that purpose, may be grounded or otherwise connected in the circuit of the high voltage line connecting into the spreader 37.

To connect the spreader 37 to the high voltage line, there is an electrical connection from the source of high voltage through a conductor or electrode 70 to a binding post 71 on the housing 10, so that the high voltage current is conducted along the housing and/ or along the shaft 12, through the collar 44, sleeve 43, bearing cap 42, bearing 40, flange 41 to the walls of the annular spreader trough 56 where the particles of coating material are charged.

In the spray device of FIGS. 1 and 2, the discs 1519 are of a uniform diameter, and if this spray device is employed in connection with an electrostatic field, as described, the electrostatic field will have the greatest concentration on the discharge peripheries of the outer (top) and inner (bottom) discs 15 and 19. This variation in the concentration or strength of the electrostatic field can be compensated for by adjusting the angle of the spreader 37 in relation to the general planes of the atomizer discs 15-49, so that greater proportions of the material is handled by these inner and outer discs. This adjustment can be effected by loosening the screw 45 and turning the spreader 37 about the collar 44 until the spreader tilts in the direction to attain the desired distribution to the disc. In the position in which the bearing 40 of the spreader 37 has its axis along the line 0, the angle of the spreader will be near its limit, and the inner and outer atomizer discs 15 and 19 will receive a greater proportion of the coating material. To decrease the proportion of coating material received by these inner and outer atomizer discs 15 and 19, the spreader 37 will be adjusted at a lesser angle, for example, at an angle at which the axis of the bearing 40 is along the line b.

The angle adjusting features of the spreader 37 are also useful in connection with spray devices not having electrostatic assistance, to distribute the material to the diiferent atomizer discs in the desired proportions.

As indicated above, in the embodiment of FIGS. .1 and 2, where the discs are all of the same diameter, the distribution of the electrostatic field on the disc peripheries may be uneven, the peripheries of the inner and outer discs 15 and 19 attaining greater concentration. FIG. 3 shows a modified form of spray device in which a more uniform electrostatic field distribution on the disc peripheries is attained. In this construction, the atomizer dis-cs 15a, 16a, 17a, 18a and 19a are similar to the discs in the construction of FIGS. 1 and 2 and are similarly arranged, except that the external diameters of the discs very, increasing progressively from the inner and outer discs 15a and 19a to the centrally disposed ones 17a, so that the disc stack has a convex axial contour on its periphery with the centrally disposed disc having the largest external diameter and the inner and outer discs 15 and 19 the smallest diameter.

FIGS. 4 and 5 show an automatic commercial system, in which the multiple disc type of spray device shown in FIGS. l3 may be applied. For purposes of illustration, there is shown a tubular shell and more specifically a common form of drum shell 75, which may have a capacity of about 55 gallons, and which in most present mill operations is coated internally with a protective lining material before the top and bottom heads are attached. This drum shell 75 is supported horizontally on a wheeled carriage 76, riding on tracks 77 and moved back and forth axially of the shell through one spraying cycle by any suitable means, as for example, an air cylinder 78. The drum shell 75 is moved axially in one direction past the field of operation of a spray head 79 located axially of the shell, so that said shell passes over the spray head to expose the inner surface of the shell to the coating action of the spray from said device. At the end of one stroke, in which the shell 75 has traversed a distance equal substantially to its own length during which travel the full length of said shell has been subjected to the spraying action of the spray head 79, the carriage 76 is reversed to carry the drum shell past the field of operation of the spray head for the full length of the drum shell, whereupon the drum shell 75 is rolled off the carriage and replaced by the next drum shell 75 to be internally coated.

The spray head 79 is illustrated as being similiar to that shown in FIGS. 1-3 and comprises the non-rotatable housing 10 supported on a standard 80 and extending along the axis of the drum shell 75 to be coated. This housing 10 connects into the casing of the motor 11 driving shaft 12, which extends along said housing to the spray head, as described in connection with FIGS. 1 and 2. A supply tube 81 connected to solenoid valves 82 and 83 and thence to a material supply source under pressure is shown spirally wrapped around a non-con ducting sleeve 81a and connecting or merging into the feed tube 57 of FIGS. 1-3, to deliver the coating material under pressure to the spreader 37 This spiral wrapping of the supply tube 81 insures adequate conduit length between the high voltage charged atomizer in the distributor head and the grounded solenoid valve 83, when materials having some electrical conductivity are being handled, so that the charges are not carried back to the solenoid valve with enough strength to interfere with its proper operation.

The insulated high voltage line or electrode 70 con nects to the shaft 12 through binding post 71 in the housing 10 as described, and conducts the charge to the charging point in the spreader 37, as described. The drum shell 75 is grounded to attract the charged particles of the spray.

The spraying unit illustrated is part of a completely automatic machine in a steel drum line, where the uncoated shells are automatically fed successively onto the carriage 76 at the end of each spray cycle, while the carriage 76 is in the extreme dot and dash line position shown at the right of FIG. 5.

The drum shells 75 are shaped to require special feed controls according to the position of the drum shell in relation to the spray head 79. The upper rim 86 of most drum shells is curled or rolled over, so that the gasketed cover fits smoothly over this curled rim, and this cur should be coated with protecting lining material at least over 75% of its external extent. In accordance with the present invention, this coating of not only the inside of the curled rim 86 but also at least a major part of the outside of the curled rim is achieved while the inside of the drum shell is being coated near its rim end and is effected by automatic control of the feed of the spray material, so that when coating is being carried out in the vicinity of the rim end, the charged particles are small enough and light enough to be deflected by electrostatic action around the rim 86 of the drum shell to the outside thereof. This electrostatic wrap around effect of the charged particles causes the outsides of the curls to be adequately coated on their outside. The control 8 system to be described is designed to permit periodic variations in the feed of the material during certain coating phases to accomplish the result described.

The two solenoid valves 82 and 83 for controlling the flow of coating material from a supply tank to the distributor head of the spray device with their control circuits are shown in greater detail in FIG. 4. These two valves 82 and 83 are connected in series. Valve 82 has an inlet leading from the supply tank and is of a type to open partly for a predetermined period during energization of its controlling solenoid, to permit a low rate of feed of material therethrough during said period, and said valve 82 has a discharge line 91 connecting to the inlet end of the solenoid valve 83. This valve 83 is either fully opened or fully closed, but is normally opened, and has an outlet 92 connecting to the supply tube 81.

The valve 82 is actuated by an air motor 93, which has an advance speed control screw 94 and a return speed control screw 95 adjustable to give a slow stroke and which is electrically controlled from an advance solenoid 96 and a retract solenoid 97. The air motor 93, with its speed controls 94 and 95 and its controlling solenoids 96 and 97, per se, form no part of the present invention, are well known, and are commercially available, as for example, as Bellows BEM Air Motors.

The valve 82 comprises a cylinder 100 having a springpressed piston 101 connected to the piston of the air motor 93 by a piston rod 102 and a cylinder 103 of larger diameter than the cylinder 100, connected thereto and having mounted therein an orifice plate 104 against which the piston 101 seats in closed position of said valve, as shown in FIG. 4. This piston 101 has an axial extension or hub 105 of reduced diameter passing through an orifice 106 of larger diameter in the plate 104 when the valve 82 is in closed position shown. A passageway 107 leads from the inlet end of the cylinder 100 along one side of said cylinder up to the orifice plate 104, where it is entirely blocked off when the piston 101 is seating against said orifice plate. As the piston 101 is moved towards the left by energization of the advance solenoid 96, its initial movement may be slow according to the setting of the speed control 94, and the piston extension 105 will linger in the orifice 106 according to this setting. Under these conditions, the flow through the valve 82 will be restricted to that passing through the annular space between the periphery of this piston extension 105 and the periphery of the orifice 106, so that the rate of feed of the coating material to the spray head will be correspondingly low. This low feed is desirable during the periods when the spray head is acting in the region of the drum shell 75 where the curled rim 86 is located, to effect the electrostatic wrap around of the charged particles as described.

When the piston 101 has moved to the left to the point where its axial extension 105 has emerged from the orifice 106 in the plate 104, the valve 82 will be fully opened and the fiow will be through the fully cleared orifice. The resulting high rate of feed of the material to the spray head 79 is particularly useful during the periods when the interior along the drum shell 75 is being sprayed to effect a heavy deposit on this interior.

The solenoid valve 83 is similar to the solenoid valve 82 except that it has a piston without the axial orifice penetrating extension 105 of valve 82, so that the valve is either fully opened or fully closed. This valve 83 is controlled from an air motor 110 controlled by a solenoid 111. The motor 110 and solenoid 111 are of well known construction, and are commercially available, as for example as Bellows BSKM Air Motors.

Arranged along the path of movement of the carriage 76 are microswitches 112 and 113 actuated successively by a cam 115 and a microswitch 116 actuated by a cam 117 also carried by said carriage. A supply current stepped down in voltage through a transformer 118- is conducted to either of two loops by a hand switch 119.

One of these circuit loops containing the microswitches 112 and 113 is connected into the supply circuit when the switch 119 is in the full position A as shown in FIG. 5. For certain types of drum shells or other articles to be coated, it may not be desirable to have the rate of feed vary as described. For that purpose the microswitch 112, would be rendered in operative by moving the switch 119 from the full line position A shown in FIG. 4, to the dotted position B shown, to disconnect the circuit loop of this microswitch from the current supply line and to connect the other circuit loop into the current supply line. A microswitch 120 in the path of the cam 115 is only in this other circuit loop, and this microswitch serves the purpose to be described. The microswitch 113 is connected to the pivot post of the switch 119, so that it is connected into both circuit loops.

The microswitch 112 is in the circuit of the advance solenoid 96 and when said switch is closed by the cam 115, this solenoid is energized and this moves the piston in the air motor 93 towards the left at a speed depending on the setting of the control 94 and starts the valve 82 opening from the closed position shown.

The microswitch 113 is in the circuit of the retract solenoid 97 and when said switch is closed by the cam 115, the solenoid is energized and this moves the piston in the air motor 93 towards the right at a speed depending on the setting of the control 95 and starts closing the fully opened valve 82 towards the position shown.

The microswitch 116 is in the circuit of the solenoid 111, and this circuit is independent of those containing the hand switch 119, so that the operation of this microswitch and this solenoid is not affected by the position of this switch 119. When the microswitch 116 is closed by the cam 117, the solenoid is energized and this moves the piston in the air motor 110 towards the left and this fully closes the valve 83.

The microswitch 120 is in the circuit of the advance solenoid 96 only when the hand switch 119 is in position B, and is actuated by the cam 115 to move the valve 82 into closed position shown to cut off the spray feed.

In operation, the carriage 76 will be in the initial position shown in FIG. 4 with the spray head 79 beyond the rimmed end of the drum shell 75 supported on said carriage. In this initial position of the carriage 76, any spray C projected from the spread head 79 will have its side nearest the drum shell 75 reaching the vicinity of the adjacent rimmed end of the shell, as shown in FIG. 4. A shield 121 around the spray head 79 and around the drum shell 75 will in this initial position of the carriage 76 catch and drain off the excess part of the spray which does not reach the drum shell. Also, in this initial position of the carriage 76, the microswitch 112 is so located as to be engaged by the cam 115, the valve 82 is in completely closed position shown and the valve 83 is in the completely open position shown, so that the spray head 79 has not started to project its spray.

The carriage 76 from the initial position described starts moving the drum shell 75 towards the left, and this immediately causes the cam 115 to close the microswitch 112, energizing thereby the advance solenoid 96, assuming that the hand switch 119 is in the position A shown, and causing thereby the piston 101 of the valve 82 to move slowly from the closed position shown in FIG. 4 towards the left. During this first part of this slow valve opening stroke, the piston hub or extension 105 of the valve 82 remains in the orifice 106 of the plate 104, thereby restricting flow through said orifice, so that the feed of material to the fully opened valve 83 and in turn to the spray head 79 is correspondingly light, creating thereby spray particles which wrap around and coat the exterior of the curled rim 86 by electrostatic wrap around deflection, as described. This limited feed rate is adjusted by the control 94 as described, to coincide with the period while the spray head 79 is still exterior of the shell. The drum shell 75 then moves over the spray head 79 and simultaneously the axial extension or hub emerges from the orifice 106 of the condition, just as the carriage 76 starts to reverse, the

cam 117 reaches and closes the microswitch 116 and this energized the solenoid 111, thereby actuating the air motor and causing the valve 83 to close and shut off the material feed to the spray head 79 during the initial period of carriage reversal. As the carriage 76 moves for its return stroke towards the right, the cam 117 opens the microswitch 116 and then valve 83 fully opens, causing the heavy feed rate to resume. When the carriage 76 reaches a position near the end of its return stroke towards the right, when the spray head 79 is again in the vicinity of the curled rim 86, and the shell starts to move away from the spray head, the cam reaches a position to close the microswitch 113, and this energizes the retract solenoid 97, causing the piston 101 of the valve 82 to move towards the right from fully opened positions, and causing the piston extension or hub 105 to reenter the orifice 106 of the plate 104. This action limits the feed rate for a period depending on the setting of the control 95, thus producing fine, light spray particles, while the spray head 79 is exterior of the shell 75 and is spraying the curled rim 86. The position of the microswitch 113 is preferably such, that the valve 82 starts to close during return movement at substantially the same position of the carriage 76 that the valve 82 reaches fully opened position during the advance movement of the carriage 76, and the two controls 94 and 95 are preferably set to afford the same rate of opening and closing the valve 82.

As the carriage 76 comes to a stop and shell unloading position corresponding to its initial position, the valve 82 reaches a fully closed position, thereby shutting off the feed rate. The drum shell 75 is then automatically unloaded from the carriage 76 and another shell is then rolled onto the carriage for repetition of the cycle.

The above procedure covers the type of operation where the exterior of the curled rim 86 and the interior of the shells 75 have to be coated. However, there are situations where the shells to be lined do not have curled rims. Under these circumstances, the system is adjusted to handle this situation by moving the hand switch 119 from position A to position B and the control screws 94 and 95 are adjusted so that the air motor 93 operates with a fast stroke. With the system so set, the microswitches 113 and will be connected to one current supply line, the microswitch 116 will still be connected to its separate current supply line, and the microswitch 112 will be disengaged from any supply line.

In this type of operation with the switch 119 in position B, the valve 83 fully open and the valve 82 fully closed, the carriage 76 moves from initial position towards the left until the cam 115 engages the microswitch 120 simultaneously with the entrance of the head of the spray head 79 into the shell 75, thus energizing the advance solenoid 96, moving the piston in the air motor 93 towards the left and opening the valve 82. 'Since the controls 94 and 95 are set for rapid movement of the piston of the air motor 93, the valve 82 will open fully almost immediately, causing the heavy feed rate to start almost immediately.

When the carriage 76 reaches near the end of its advance stroke towards the left, the cam 117 engaging the microswitch 116, will close the valve 83 completely and shut off feed to the spray head 79, while the carriage is reversing. gaged by the cam 117 will open fully the valve 83, so that heavy feed to the spray device is resumed for the return stroke. When the carriage 76 reaches a position during the return stroke when the shell starts to move away from the spray head 79, the cam 115 engages the microswitch 113 to immediately shut off the valve 82 and thereby completely shut off the feed to the spray head.

In connection with the control systems described, the multidisc distributor head described and shown in FIGS. 1, 2 and 3 are-particularlynsetul. They lend themselves admirably to thetype of control contemplated in connection with such a system and produce a wide spray band which permits complete and rapid coverage of the articles being coated. However, as far as certain aspects of the invention, other types of spray devices may be employed in connection with the types of control system described.

While the invention hasbeen described with particular reference to specific embodiments, it is to be understood that it is not to be limited thereto, but is to be construed broadly and restricted solely bythe scope of the append-- ed claims. 7

What is claimed is:

1. A sprayhead comprising a plurality of rotary atomizer discs axially spaced and-having outer peripheral discharge'rirnsysaid discs being in the form of rings having central openings ,conjointly defining a chamber, arotary spreader in said chamber having an annular peripheral dischargeedge, means adjustably supporting said spreader in said chamber permitting the angularity of the general plane of said peripheral discharge edge to be adjusted in relation to the axis of said discs, and means for feeding liquid material to said spreader.

2. A spray head comprising a plurality of rotary atom izer discs axially spaced and having outer peripheral discharge rims, said discs being in the form of rings having central openings conjointly defining a chamber, a rotary spreader in said chamber having an annular discharge serrated edge extending generally diagonally across the inner peripheral edges of the discs and adapted to discharge material and distribute material to the inner peripheral edges of said discs, and means for feeding liquid.

material to said spreader.

3. A spray head comprising a plurality of atomizer discs axially spaced and having peripheral discharge rims, said discs being in the form of rings with center openings conjointly defining a chamber, a shaft passing through said openings, means connecting said discs to said shaft for rotation therewith, a spreader in said opening supported on said shaft for rotation therewith and having an After reversal, the microswitch 1116 again enend wall defining an annular trough with its open end facing an axial direction away from the outer end of the spray head, said trough having an annular discharge edge extending generally diagonally across the inner peripheral edges of said discs, and a feed tube passing through the open end of said trough into said trough for delivering liquid material thereto.

4. A spray head comprising a plurality of rotary discs axially spaced and having outer peripheral discharge rims, means for feeding and distributing liquid material to said discs, said discs being in the form of rings having respective center openings conjointly defining a chamber, said material feeding means comprising a rotary spreader in said chamber adapted to project and distribute the material to the inner peripheral edges of said discs, said spreader being made of conductive material, said discs being made of non-conductive material, and electrical charging means comprising means for conducting an electric current to the spreader to electrically charge the particles of the material in said spreader.

5. A spray head comprising a plurality of rotary atomizer discs axially spaced in a stack and having outer peripheral discharge rims, the central discs having a greater external diameter than the outer discs of said stack whereby the outer peripheral-surfaces of said discs conjointly define a convex axial contour, means for feeding and distributing liquid material to said discs, and means for electrically charging the particles of the material to effect electrostatic discharge of the spray from said discs.

6. A spray head comprising a 'plurality'of rotary atomizer discs in the form of rings axially spaced in a stack and having outer peripheral discharge rims and having center openings conjointly defining a chamber, a rotary spreader'in said chamber for discharging material and distributing said material to the inner peripheral edges of said discs, the discs near the ends of said stack having their inner peripheral edges bevelled to face toward the center of the stack to defiect'the material discharged thereon towards the more centrally placed discs, and means for feeding liquid material to said spreader.

' References Cited in the file of this patent UNITED STATES PATENTS 2,922,584 Slatkin Ian. 26, 1960

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