GB911698A - Improvements in and relating to shears - Google Patents

Abstract

911,698. Shearing. UNITED ENGINEERING & FOUNDRY CO. Aug. 3, 1961 [Aug. 29, 1960], No. 28219/61. Class 83 (4). A shear has two movable knives, one of which is controlled in movement towards an article to be sheared by means including a feeler device adapted to engage the article and initiate arrest of movement of said one blade at a predetermined spacing from the article. Construction. The shear comprises a frame with guides 11 for an upper knife head 12 which carries a blade 15 and which has guides 13 for a lower knife head 14 carrying a blade 15. A main shaft is journalled in the lower knife head and has eccentrics 18 on which run the big-ends 23 of links 22, the other ends of which are attached to a shaft 21 journalled in the upper knife head 12. When the main shaft rotates the upper knife head descends by gravity until it is arrested in a fixed position relative to a bloom to be sheared and further rotation of the shaft then causes the lower knife head to rise and make the shearing cut. The weight of the upper knife head is partially balanced by hydraulic cylinders 24. A gag 26 has a pressure foot 27 and runs in guides 28 in the lower knife head. The upper end of the gag is pivoted to one end of a lever 30, which is pivoted intermediate its ends on a shaft 31 carried on the upper knife head, and is pivoted at its other end to the push rod 32 of an hydraulic cylinder 29. The gag clamps the bloom to the lower knife head and also serves as a feeler to actuate control mechanism which arrests the upper knife head at a predetermined distance from the bloom. An auxiliary gag lever 33 is pivoted at one end about the same axis as the shaft 31 and at its other end is connected by a link 34 to the gag 26. An auxiliary cylinder 35 is pivoted at 36 on the lever 30 and its pull rod 37 is pivoted at 38 to lever 33. The end of the lever 33 which pivots about the axis 31 is connected by means including a shaft 40 to a stud shaft 43 which carries an arm 45 the outer end of which is pivoted to a push rod 46 which engages the stem 48 of a control valve 39. Operation. At the start of a cycle the knife heads are in the open position, the push rod 32 is in the " out " position, the auxiliary cylinder 35 is holding the auxiliary lever 33 against the lever 30, the lower surface of the pressure foot 27 is level with the bottom of the upper knife 15 and the control valve 39 is closed. When the cycle is initiated fluid is exhausted from the auxiliary cylinder 35 which allows the lever 33 to drop, until a stop 51 engages a pad 52 on the upper knife head, so that the pressure foot is below the upper knife blade 15. As the lever 33 drops the shaft 40 rotates and actuates the valve 39 which permits fluid to exhaust from the cylinder 29 and allows the upper knife head and gag to descend together until the pressure foot 27 contacts the bloom, after which the upper knife head only descends, and produces reverse rotation of the lever 33 which allows the valve 39 to be closed by a spring, and halts the descent of the upper knife blade at a predetermined height above the bloom. As the cycle continues the lower knife blade rises and pushes the bloom and gag upwards so that a pad 53 on the auxiliary lever 33 engages a pad 54 on the lever 30 and rotates it against the action of the cylinder 29, to absorb the initial shock of the shearing blow. This cushioning action continues throughout the remainder of the shearing cut and as the gag descends at the end of the cycle it strips the bloom free of the upper knife head.