Patent GB-656567-A (GB)
Title: Improvements in methods and means for blast-treating castings, forgings and like articles
IPC: B24C3/08
Filed: 1948-02-29
Abstract: 656,567. Abrasive blast. PANGBORN CORPORATION. Feb. 29, 1948, No. 6364. Convention date, Nov. 15, 1946. [Class 60] [Also in Groups XXX and XXXVII] A method of blasttreating castings, forgings &c. consists in moving the articles to be treated rapidly to a blasting zone, then slowly through the zone, and thereafter rapidly away from the zone to a succeeding zone or to a point of delivery, the articles being preferably rotated at least during the treating operation. The articles are conveyed in a closed path by spaced work supports C, Figs. 2 and 4, which are suspended by rollers from a guide rail B and linked together by a driving chain A. The zone through which the articles pass comprises a housing D which may be provided with swinging doors or labyrinth passages and is fitted in its side wall with a plurality of devices F for projecting abrasive or other particles across the path of the articles; these projectors are arranged at different elevations, as shown in Fig. 4, and are spaced apart at the same distances as are the supports C. Each support C comprises a hanger 21, 22, Fig. 8, extending through a link 23 of the chain A and secured at its lower end to a bracket 24 carrying spaced bearings 25 for rotatably supporting the work-holding shaft 26. The roof of the housing D is slotted to receive the travelling shafts 26 and is fitted with spaced channels 30 which are engaged by guide rollers 31 on the brackets 24; plates 32 fixed to the channels 30 co-operate with plates 33, 34 on the brackets to seal the slot. The main drive sprocket 55 of the chain A is adapted to be driven by either a slow-speed motor 46, Fig. 11, through reduction gearing 51 and a pawl-and-ratchet drive 53, or a fast-drive motor 47 connected through reduction gearing 58 and a second pawl-and-ratchet drive 60. After closure of switches 61, 62, 63, a relay switch 64 in the circuit of the motor 47 remains open and the articles are traversed at slow speed by the motor 46. Mounted on the chain A adjacent each of the supports C is a hanger X, Fig. 8, which in addition to carrying guide rollers 31, is provided with a cam 37 for operating a normally-closed switch 38 and normallyopen switch 39 as shown in Fig. 11 so as to control the speed of travel of the articles. When the article carried by one support has passed through the blast stream of the first projector F, one of the cams 37 actuates the switch 39 so as to close the relay switch 64 and energize the fast-drive motor 47; the shaft 54 of the sprocket 55 then turns freely in the slowly-rotating drive unit 53. As the next article reaches the first blast stream (and the first article reaches the second stream), a cam 37 actuates the switch 38 so as to open the switch 64 and cause the articles to be moved only by the motor 46. The switch 39 is included in a circuit with a holding relay 65 which maintains a closed circuit for the motor 47 until the other switch 38 is again opened by the next cam. Additional switches are provided for permitting the blasting of articles for other than the preset period or dealing with articles of unusual size. While the articles are in the housing D they are caused to rotate by means of a motor-driven chain Y, Fig. 2, which passes over spockets 41 on the roof of the housing D and meshes with sprockets 28, Fig. 8, on the work-holding shafts 26; the chain Y also meshes with guide sprockets 36 freely rotatable on the hangers X. The chain Y may travel in the same direction as the chain A or in the opposite direction, and in the former case the result is that the article is rotated slowly as it passes to. and from the blast streams at a rapid rate and rapidly as it passes slowly through the streams. The articles may rotate one or more complete turns while travelling through each stream. In a modified driving arrangement, (Fig. 12, not shown), a speed-reduction unit, which drives the chain A through a chain drive, is adapted to be driven by both motors, the drive from the slow-drive motor being through a clutch which slips when the fast-drive motor is operating. The housing D is provided with hoppers K for collecting spent particles which are passed by shoots L and elevator M to a separator N for collection in a storage hopper P. Solenoid-controlled valves Q permit passage of the material from the hopper P to the projectors F. A replenishing bin U for adding fresh material, and a dust exhaust duct, may also be provided. After passing through the blasting zone the articles may be further treated inside or outside the housing D in zones providing for manual touch-up, nozzleblasting, inversion of the articles to dump blastant therefrom, and the application of protective coatings to the articles.