Patent GB-1374209-A (GB)
Title: Shearing machines
IPC: B23D25/06
Filed: 1972-05-15
Abstract: 1374209 Flying shears ZDARSKE STROJIRNY A SLEVARNY NARODNI PODNIK 15 May 1972 [16 July 1971] 22653/72 Heading B3W The drive to one of the cutters in a flying shear for shearing strip includes a drive crank rotatable about a fixed axis, and connected to a driven crank arranged to actuate said one cutter and means for adjusting the displacement between the axes of rotation of the drive and the drive in crank for synchronizing the actuation of the cutter with the feed of the strip. Strip is fed to the shear by rollers 51 through straightener rolls 52, a variable speed gear-box 5, having a differential gear in the main transmission gear case 3 and connected to the rolls 51 and 52 by a clutch 42 and a transmission gear case 6, allowing continuous limited range of adjustment of the length of cut. An upper blade holder 12 is pivotable on a main crank 10 which is supported in bearings in side walls 8, 8<SP>1</SP> of a cutter frame. Rigid with the crank 10 is a driven crank 19 connected by a rod 21 to a drive crank 20 connected to the last transmission stage of the gear case 3. Both cranks 19 and 20 have the same throw. Arms 15, 14 connect the holder 12 to a lower blade holder 13, eccentric pivot bolts 16 allowing the cutting clearance between the blades 17 and 18 to be varied. The blade holder 13 is pivoted on a cranked portion of a shaft 11 which is pivoted on the main shear frame 7. The cutter frame 8, 81 is alsopivotally mounted at its lower end on the shaft 11. The shaft is driven via a clutch (40), Fig. 4 (not shown), from the gear case 3 which allows the shaft 11 to be rotated through, e.g. a half or a quarter of the revolutions of main crank 10 for miss-cutting. For cutting the basic length, the axes of rotation of the cranks 19 and 20 are coaxial and the crank 10 rotates at a constant speed. To vary the cut length, the axis of rotation of the crank 19 is displaced relative to that of crank 20, to cause non-uniform angular velocity of the crank 10, by pivoting the cutter frame about the shaft 11 by means of a crankshaft 24, in the feed direction for cutting lengths shorter than the basic length and in the opposite direction for longer lengths. The shaft 24 is driven by a motor 31 and held in the desired position by a brake 33. The adjustment can be carried out with the shear operating at full speed. As shown in Fig. 2, movement of the cutter frame through an angle and from the vertical displaces the axis of rotation of crank 19 from that of crank 20 by an eccentricity -E in the feed direction to reduce the cut length. The required displacement can be read from a scale 30. If the crank 10 is not rotated at a uniform velocity the driven crank 19 can be given a periodic angular acceleration and deceleration during one revolution. The shear can be used for cutting stationary material, e.g. for cropping waste ends or taking samples, by stopping the cutters in their cutting position, i.e. with crank 10 in its bottom dead centre position. The cutters can be adjusted to this position by the main motor 4 using a pointer (39), Fig. 4 (not shown), on the crank 10 or by an an auxiliary drive which is stopped by a sensing device associated with the crank 10. The clutch 40 in the drive to the shaft 11 is disengaged and an auxiliary motor (34), Fig. 4, rotates the shaft 11 to its bottom dead centre position. The shear is now ready for stationary shearing. Strip is fed by an auxiliary motor 43, Fig. 1, and measured by an impulse feeler 49, the feed and straightener rolls being brought to rest by a brake 45. The motor (34) then rotates the shaft 11 one revolution in the opposite sense to that required for flying shearing and the lower blade 18 carries out a shearing stroke whilst the upper blade 17 is stationary. In a simplified embodiment, Fig. 3 (not shown), which is not readily converted to stationary cutting and cannot provide misscutting, the cutters (57), (58) are mounted on drums (54), (55) both of which are rotatably supported in side walls (53) of the cutter frame which is itself pivotally supported on bolts (56). The upper drum is rotated by a twin crank mechanism 19-21 and the lower drum is driven from the upper drum.