GB974443A - Improvements in or relating to oscillatory cutting knives - Google Patents

Abstract

974,443. Cutting apparatus. J. E. THOMPSON. Oct. 25, 1963 [July 26, 1962], No. 28813/62. Heading B4B. An oscillatory cutting knife assembly comprises a knife 1 oscillatable about an axis and co-operating with a die 3 so as to cut material, e.g. a strand, web, or rod, passing between them, the knife being mounted on a spring- loaded arm 5, of which one end co-operates with a pivotable pawl 9 mounted on a rod 8 and actuable by a pneumatic or hydraulic cylinder arrangement, so that the pawl moves the knife in one direction only to perform a cutting operation, while the knife is returned in the other direction under the influence of the spring loading. As described, the rotary knife 1 is of quarter cylindrical shape extended to form a yoke from which trunnions 2 project, and is mounted so that a strip of material may pass over the die and beneath the knife along a line 4. In operation, air is applied to the cylinder moving the piston and rod 8 to the right and compressing the springs 11. Material to be cut is fed along the path 4 past the die 3 and knife 1 until the leading edge of the material abuts a flag 16 of a control valve. The material moves the flag so that a sleeve 15 of the valve is turned to register a slot 17 with a slot 19 in a hollow spindle 18 in the valve, to release the air pressure, and the piston and rod move under the influence of the springs 11, so that the pawl 9 engages a roller 7 on the arm 5 to move the arm against its loading spring 6, and the knife 1 cuts the material. The pawl 9 rides under the roller and, when it has passed, the arm 5 moves under the action of the spring 6 to lift the cutting edge of the knife clear of the die 3. The piston 8 is then retracted by feeding air to the cylinder, and when the pawl 9 abuts the roller 7 it is pivotally displaced on the rod 8 so as to ride under the roller and not move the arm. The pawl 9 is then returned to its initial position by a spring 10. The piston continues its movement until the springs 11 are again compressed and the knife is then ready for a further cutting cycle. The apparatus may be modified by including a collar on the piston-rod, and a spring between the collar and the cylinder, instead of the springs 11, or a two-armed spider carrying spring-loaded rods, with air applied to the other side of the piston, and the knife arm 5 may be mounted above or below the knife. An hydraulic cylinder may be used for high speed cutting, and the piston and cylinder arrangement may be operated by a timing means related to the speed of travel of the material instead of by a flag-operated control-valve.