Patent GB-1322351-A (GB)
Title: Control system for a shearing installation
IPC: B23D36/00
Filed: 1970-06-30
Abstract: 1322351 Controlling shearing apparatus SIEMAG SIEGENER MASCHINENBAU GmbH 30 June 1970 [30 June 1969] 31662/70 Heading G4H [Also in Division B3] Non-deceleration and deceleration phases of the drive means in a control system for a shearing installation are controlled by the counts from impulse generators 11, 12 (Fig. 3) driven from measuring rollers rotating with the rollers pressing the material to be sheared, the pulses from the measuring rollers rotating fastest and slowest being used during the non-deceleration and deceleration phases respectively for deriving the control signals. In the embodiment of Fig. 3 in which the impulse generators comprise non magnetic discs 17 with inserted permanent magnets rotating in front of stationary coils 18, the pulses induced in the coils are counted in counters 21, one counter for each impulse generator. During the non- deceleration phase the counters, initially preset by a register 22, are counted down by the outputs from the impulse generators, the first counter reaching zero passing a pulse via OR gate 28 to operate a device 30 terminating the non-deceleration phase. This pulse also results in gate 33 being opened to count pulses in a counter 34 from one of the impulse generators until all the counters 21 have reached zero when counter 35 closes the gate 33 and resets the counter 34. The count is used to adjust the count in a register 23, (presetting the counters 21 for the deceleration phase) to compensate for slip.  During the deceleration phase the adjusted count in register 23 is read into the counters 21 which are then again counted down, a device 36 terminating this phase only being operated by the output of a counter 35 when all the counters 21 reach zero. Counter 34 counts impulses from one of the generators from the first zero count in one of the counters 21 until the counter 35 delivers its output. If this count exceeds a first reference level (indicating too much slip in the rollers) a warning lamp 38 is lit and if the count has exceeded a second higher reference level a switch 41 is operated to prevent the shearing operation. Rotors 48, 49 of tachogenerators associated with the pressing rollers are connected in series via a resistor 50, the voltage across this resistor being fed to device 51 also actuating the lamp 38 and switch 41. A further counter 47 counts impulses from one of the generators from the time the material passes a light barrier 42 until the end of the deceleration phase. The counter 47 also controls the lamp and switch in accordance with its count. The difference in the counts of the counters 21 at the end of the acceleration phase may be measured by counting in counters 34, 47 the number of high frequency pulses from a generator 56 necessary to return all the counters 21 to zero. In a second embodiment (Fig. 6, not shown) the material passes four light beams (61-64) equispaced along the path of a material and displaced from the position at which the control operation is to occur by the amount of tolerance allowed. Initially the pulses from four impulse generators (11-16) are directed via gates (70) into first counters (73) having a cycle corresponding to the distance between adjacent light barriers. The first counter to recycle, indicating the end of the acceleration phase, gives a signal via a gate (93) to set a bi-stable (95). This enables a counter (97) to count pulses from two of the impulse generators (12, 16) until the count set up in the counter (representing the tolerance range) is reached when the bi-stable is reset. If during the time the bi-stable is set the material passes the first light barrier the resulting signal from a photoresistor (81) is fed via gates (89, 104, 105) to a gate (103) where it is blocked. If however it occurs outside this range a warning device (107) is actuated. Only the first counter to recycle operates the bi-stable since subsequent counter outputs are blocked by a gate (93). If however the time between different counters recycling exceeds the tolerance set up by the count in a counter (111) (indicating too much slip) the output from a counter (92) when the last counter (73) recycles operates the warning device. When the material passes through the third light beam (63) a brake is operated after a delay determined by a device (112) to reduce the material speed to a creeping speed. When the material passes through the fourth barrier (64) the pulses from the impulse generators are directed via gates (75) into second counters (76) which are preset by an amount representing the material to project beyond the last barrier before cutting. A gate (121) is enabled at this time. When all the counters have reached their preset condition, i.e. four pulses have been received by the counter (92) a signal is fed via the enabled gate (121) to a device (122) to stop and cut the material. If however the time delay between the first and fourth signals from the counters (76) exceeds the tolerance range set by the counter (97), gate (103) is not blocked when the counter (92) delivers its output signal and this is consequently applied to the warning device. The light barriers may be replaced by for example mechanical contacts or inductive sensors.