GB801345A - Improved method and apparatus for expanding tubular metal articles - Google Patents

Abstract

801,345. Forging; expanding pistons. MOTOR SPECIALTIES, Ltd. Feb. 17, 1956 [Feb. 22, 1955 ; May 9, 1955], No. 4975/56. Classes 83 (2) and 83 (4). A method of expanding a tubular metal article having a curved surface, such as a piston, comprises placing a convex surface of the metal article on a convex anvil, Fig. 2, striking the concave surface of the article nearest to the anvil with a first hammer 31a to produce an initial depression with a raised edge on said concave surface, and while the first hammer is still engaged in the depression, hammering the raised edge thereof by second hammers 31b flanking the first hammer, to expand the metal away from the initial depression, Fig. 3. The cylindrical anvil 2 is rotatably mounted in supports 3, Fig. 4, and the piston 6 to be expanded is supported thereon by bearing members 4c mounted on calliper arms 4 pivotally mounted at their lower ends. These arms carry toothed quadrants 11, Fig. 7, which engage roller chains 9 on a vertically slidable member 8 which is biased downwardly by a spring 13. The roller chains 9 are pressed outwardly by rubber buffers 10 which are themselves compressed by a strip 12. The two calliper arms are therefore spring biased inwardly and are moved simultaneously. The inward movement is limited by screws 5a or by a removable stop 5b, Fig. 4. The three hammers 31 are pivotally mounted at 32 on a support 24 which is vertically adjustable on a bracket 16 by a handle 27 secured to a vertical worm 25, Fig. 14 (not shown) ; a spring-loaded brake 29 prevents rotation of the worm. The bracket 16 is adjust-' able longitudinally of a base plate 1 by a sprocket 20 engaging a rack 21 on the base, the sprocket being turned by a handle 17. The hammers 31 are biased downwardly by front springs 40 and rear springs 35 which are adjustable in tension by a nut 38. The hammers are raised against their springs by cam rollers 47 mounted on a cam shaft 45 carrying a pulley 45a driven by an electric motor. The rollers 47 engage the tail ends of the hammer to raise their tips 33 and subsequently suddenly release them. The tail end of the middle or first hammer 31a. is shorter than that of the flanking hammers whereby the middle hammer is released first by the rollers. A limiting stop 48a is provided for the downward movement of the hammer heads 33 and the latter may be raised manually, for setting of the piston 6, by a pivoted lever 44. A setting plate 51 for the piston is provided adjacent the anvil 2. The procedure for expanding a piston by the peening hammers is described.