Patent GB-1230102-A (GB)
IPC: B23D36/00
Filed: 1967-04-29
Abstract: 1,230,102. Controlling flying shears. BRITISH STEEL CORP (HOLDINGS) Ltd. 22 April, 1968 [29 April, 1967], No. 19870/67. Heading B3W. In a method of, and apparatus for, controlling the cutting of a bloom or billet into billets or bars of a predetermined acceptable range of lengths, e.g. a nominal length + or - 1 foot, after rolling in a hot mill, a first bloom or billet is advanced through the mill, one or more billets or bars are cut off by flying shears and used to calibrate a length-measuring and-indicating device to the speed of advance and crosssection of the bloom or billet through the mill, the actual crop end length remaining when the next bloom or billet has been cut into the maximum number of bars or billets of precise nominal length is measured and applied to the device as a correcting factor so that the device can be used to predict the crop end length of subsequent successive blooms or billets of the same nominal cross-section if they were to be cut into billets or bars of the nominal length and, if the predicted length is outside the acceptable range, to vary the length of cut of the flying shears to obtain the maximum number of bars or billets of said predetermined acceptable length with minimum crop end wastage. As shown, Fig. 8, a rolling mill has a normally open flag switch B and a normally closed flag switch C at the entrance end and flying shears 13 at the other end, the spacing being such that the rear end of a bloom of normal length has still to pass the switch B when the flying shears make its first cut to crop the front discard, the rear discard having been cropped before the bloom enters the mill. If the bloom is to be cut into billets of nominal length l, the line L-L denotes where the last cut would be made, leaving a rolled crop end length c which will vary from bloom to bloom since the actual lengths of blooms of the same nominal length differ. The distance between the line L-L and the flag switch B, however, will be constant for blooms of the same cross-section to be rolled into the same number of billets of the same nominal length l. This distance is represented by c - r where :- c = the predicted crop end length; r=the distance between the rear end of the bloom and the switch B when the first cut is made. Once the distance c - r has been determined by recording the length r on a measuring and indicating device and measuring the actual crop end length c of a trial bloom cut into billets of precise nominal length l, the crop end length c of subsequent similar blooms can be predicted. merely by recording the distance r for the bloom on said device and adding the constant value c - r to it. The measuring and indicating device (Figs. 6, 7 and 9) comprises a cursor 24 rotatable by a motor (25), preferably a pulseoperated electric motor, about a pivot 21 on a billet length adjusting dial 19, marked in foot lengths at 27 in front of which is a transparent short billet length correction dial 20. Movement of the cursor 24 is initiated at the moment the flying shears 13 make their first cut. To calibrate the device one or more billets cut from a trial bloom is/are measured against the distance travelled by the cursor and the speed of the motor (25) adjusted if necessary, by means of a control knob (55), (Fig. 6, not shown). A further trial bloom is then cut up to establish the value c - r as described. An electric control circuit is so arranged that the first cut of the flying shears only initiates cursor movement if flag switch C has already been closed by the passage past it of the rear end of the bloom, which will be the case with blooms of normal length. Cursor movement is terminated by passage of the end of the bloom past switch B, the cursor having reached position (24<SP>1</SP>), Fig. 9 (not shown). The dial 19 is then rotated anticlockwise through the distance c - r to bring the point 28 on the dial at which the cursor was in its initial zero position to a new position (28<SP>1</SP>), spaced from cursor position (24<SP>1</SP>) by length c. The shear operator then adjusts the frequency of cut of the shears by the amount indicated (in inches as shown in Fig. 7) by whichever of markings 31a-31g on transparent cursor 24 is nearest to whichever of curved lines 30a-30i on the dial indicates the number of billets remaining to be cut. Two series of lines 30a-30i are provided, those on the right-hand side of Fig. 7 indicating the amount to be added to the nominal billet length l and those on the left-hand side of Fig. 7 indicating the amount to be deducted when the length c is so little less than the nominal length I that by such deduction an additional billet of acceptable length can be cut. If when an abnormally long bloom is being rolled the flag switch C is still open when the first cut is made, cursor movement is initiated at the first cut after the switch C is closed, the same number of billets then remaining to be cut to which the length adjustment can be applied as when the very first cut is made in a bloom of normal length. If the crop end length c recorded on dial 19 is greater than the nominal length l, e.g. if a bloom is being cut into very short billets, so that at least one billet more than the estimated number can be cut, the short billet length correction dial 20 is rotated through a peripheral distance corresponding to the nominal aggregated length of the extra billet(s) and length correction is applied to the true length c by using dial 20 in similar manner to dial 19. The markings on the dials 19 and 20 are in different colours. In the simplest control circuit, Fig. 3, not shown, the dials 19, 20 have to be rotated, and the cursor 24 re-set, manually. Alternative control circuitry shown in Figs. 10, 10a, 10b and 11 allows for semi-automatic operation and for automatic re-setting of the cursor. The circuit, which is conventional, includes main and re-set pulse generators (33), (36), respectively, the latter causing fast operation of motor (25) to return cursor 24 to zero position and being under the overriding control of a three-position switch (37), Fig. 6. A cam switch arrangement (Fig. 6a, not shown) provided for retaining the cursor 24 in zero position can be overridden by manual control button (45) if the cursor fails to return to zero position. For blooms so short that the rear end passes and thus opens the switch B before the first cut is made a pulse emitter/batch counter (47), Fig. 11 (not shown), produces an initial pulse count Z corresponding to the distance c - r for a normal length bloom, followed by a succession of pulse counts Y which produce an output pulse Y in the control circuit of the cursor motor (25) corresponding to the nominal length l. The first cut of the shears then initiates cursor movement and the next Y pulse ends it, the cursor having travelled through the distance c. The circuit of Fig. 11 includes a display device (51) for indicating the difference between the number of billets/bars which could be cut from the short bloom/billet compared with a bloom/billet of average length. The flying shears are operated by eccentrics and the flag switches B and C may be replaced by photo-cells.