GB741313A - Improvements in or relating to spray coating of articles - Google Patents

Abstract

<PICT:0741313/III/1> <PICT:0741313/III/2> <PICT:0741313/III/3> <PICT:0741313/III/4> <PICT:0741313/III/5> Articles are electrostatically coated by atomizing finely divided coating material particles from a curved atomizing zone and causing the particles to move along divergent paths lying generally parallel to a plane in which the atomizing zone lies to form a spray which at a distance from the atomizing zone has the pattern of an elongated band, moving the articles bodily along predetermined paths wholly exterior to the atomizing zone and generally longitudinal of the spray-pattern band, and creating an electrical charge differential between the articles and the atomized particles leaving the atomizing zone. In the apparatus shown in Figs. 1, 2 and 3, articles 11 are carried by a conveyer 10 in arcuate paths around two atomizing devices 12 and 13, carried on a support 14 comprising a column 15 to which is secured a horizontal arm to which is fixed a horizontal bracket 17 made of insulating material. The bracket 17 is provided with tubular metallic sleeves 18 and 19 which slidably carry hollow support rods 20 and 21 within which are mounted metal drive shafts 22, 23, to which are fixed pulleys 24, 25, connected by a belt 26, the shaft 23 being connected to a motor 30 through a further belt 28 and pulleys 27, 29. At the lower ends of the shafts 22, 23 are atomizing means comprising sheet metal discs 31, to the upper surfaces of which coating material is delivered from containers 36, 40 by pumps 35, 39 through tubing 32, 37 of plastic, rubber or other insulating material. If both atomizing means are to spray the same coating material, tubes may be connected to the same pump. The atomizing means are reciprocated vertically, the support columns 20 and 21 being carried on an insulating cross bar 42, which is supported by a bracket 43 having a pin-and-slot connection with an arm 44, pivoted at 46 on the column 15 and given a swinging movement by a pneumatic piston-and-cylinder device 47, the extent of the movement being determined by a micro-switch 53 mounted on a rod 52 carried by an extension 51 of the arm 44 and connected to an electrically operated valve 60 which controls the flow of compressed air to the device 47. The limits between which the micro-switch 53 operates are determined by adjustable dogs 56, 57 on a rod 58. The depth of the spray pattern may be increased by providing the discs 31 with corrugated edges, by mounting them on their shafts at angles other than 90 degrees, or by tilting both shaft and disc relative to the plane of the path of movement of the articles. The sleeves 18 and 19 are connected to the live terminal of a power pack 71, the other terminal being earthed, as is the conveyer 10. The articles 11 are caused to rotate during their travel. In the apparatus shown in Fig. 5, the articles 81 are conveyed around two fixed atomizers 82, 83. The atomizer 82 is positioned above the articles and includes a bell-type head 84, fixed to a hollow shaft and rotated, through gearing contained in a housing 86, and an insulating shaft 87, by a motor 88. The housing 86 is connected to the live terminal of a power pack 89, the other terminal being earthed. The atomizer 83 is similar, but is positioned below the articles. The hollow shafts 85 of both atomizers are supplied with coating material from a common source 96 by a pump 97 through tubing 98, 99, 100. The conveyer comprises a channel member 101 having spaced flanges 102, 103 on its upper side. The articles 81 are carried on rods 104 which pass between the flanges 102, 103 and are secured to rollers 105 which are rotatably mounted on links 106, pivoted together at the location of the rollers. Contact of the rollers with the sides of the channel at the curved portions thereof causes the rollers to rotate. Specification 710,852 is referred to.