Patent GB-941183-A (GB)
Title: Improvements in and relating to spray coating methods and apparatus
IPC: B05B5/08
Filed: 1959-11-20
Abstract: 941,183. Coating-apparatus. RANSBURG ELECTRO - COATING CORPORATION. Nov. 20, 1959 [Nov. 20, 1958], No. 39429/59. Heading B2B. Apparatus for the spray coating of articles comprises spraying means for forming a spray of liquid coating material particles, a plurality of sources of liquid for delivery to the spraying means, means associated with each source for controlling the delivery of liquid therefrom to the spraying means, a common operator for the delivery-controlling means selectively operable to cause delivery from any one source to the spraying means while preventing delivery from the others, and power-activated means energizable during delivery of coating material from the selected source so as in a predetermined cycle to terminate delivery of liquid from one source, and after a delay to initiate delivery of liquid from a different source. The apparatus may be arranged to supply solvent alone to the spraying means for a period after each lot of coating liquid, to clean the spray head. In the form shown in Fig. 3, paint from each of the containers 40a, 40b or 40c may be fed to an associated port delivering on to the internal face of a rotated electrostatic spraying head 10, e.g. in the case of the container 40a by means of a gear pump 41a, driven by an electric motor 43a. The flow of liquid delivered to the head through the conduit 31a is controlled by a compressed air operated on-off valve 42a, the compressed air for operating this being controlled by an air valve 45a, operated by a solenoid 51a which also controls the motor 43a. Further, a mixture of air and cleaning solvent from a pressurized container 46 may be supplied by a pipe 47 to a port delivering it to the internal surface of the head 10, and, if desired, to a nozzle directed against the external surface, the flow being controlled by a valve 48 operated by a solenoid 52. A cylindrical shroud 16 may be moved forward to surround the head 10 by a compressed air cylinder 19, the supply to which is controlled by a valve 50 operated by a solenoid 53. An electrical control panel 55 provides for operating the solenoids to deliver liquid from the one containers 40a, b or c to the atomizer while preventing delivery from the others, and for terminating the delivery of one paint to the head, supply of cleaning solvent to the head for a predetermined time, and initiating the delivery of another paint; preferably, the shroud is moved into spray-intercepting relation with the head during cleaning, and then retracted. In the apparatus of Fig. 6 a number of compressed air spray guns, such as 60a, 60c, radiate from a hub 61 which is charged to a high electrical potential by a source 73, and supported on an insulating column 62 which can be rotated by a D.C. motor 80 to bring a selected gun opposite an opening in a housing 64, the gun then being flanked by electrodes 74. Each gun is supplied by a paint line such as 75a and compressed air line (e.g. 76a) simultaneously controlled by a solenoid, e.g. 79a. The operation of motor 80 is controlled by a series of positioning solenoids 82a, b, c &c., a motor switch 83 mounted eccentrically on shaft 62, and a motor reversing switch 84. The operation of the apparatus is controlled by a series of push-buttons PB 11, 12, 13 &c. and a relay system contained in a control panel 85. On pressing one of the push buttons, the supply of paint and air to the operative paint-gun is cut off by operation of its associated solenoid 79, and the core of its associated solenoid 82 is retracted, allowing the switch 83 to initiate rotation of the shaft 62 by the motor 80. This movement is terminated by the switch 83 striking the core of another solenoid 82, which has meanwhile been protruded. The appropriate solenoid 79 is then operated to commence spraying of paint of another colour. In order to prevent the air and paint lines becoming tangled, rotation of the shaft 62 is restricted to less than 360 degrees by the switch 84, which, when it strikes a pin, not shown, causes reversal of the motor 80.