Patent GB-1251503-A (GB)
IPC: G01B15/02
Filed: 1968-10-18
Abstract: 1,251,503. Statistical computers for moving sheets. INDUSTRIAL NUCLEONICS CORP. 18 Oct., 1968 [13 Nov., 1967], No. 49627/68. Heading G4A. In apparatus for determining statistical data of the properties of a sheet (e.g. paper, steel, plastic film) moving through a machine by cyclically scanning a detector across the moving sheet at right angles to derive a profile measurement, it is shown by mathematics that the short term variance in the machine direction V X(ST)  and the cross direction variance V Y  are given by where V X(LT)  = long term machine direction V X(T)  = total machine direction variance V Z  = average profile variance where n is a number of scans (#Z i /#Z) is average value of n in the scan Z is the average of the n averages of the detected scan readings i is every successive integer from 1 to n, and the measurement is effected at a number N of zones disposed across the sheet for each scan, so that total variance in machine direction V X(T)  is determined by summing the N variances for the n scans. In Fig. 1 a nuclear radiation gauge 11 measures the base weight of a paper sheet 12 translated in longitudinal direction 15 by translation normally to the sheet edges by motor 14 so that the gauge defines in one scan the hypotenuse of a triangle defined by the forward and transverse sheet movements during scan. The gauge output develops in circuit 16 a D.C. base weight signal, the sheet is divided into 3 cross direction sampling zones, and scanned 4 times by the gauge to establish a sequence. Larger numbers of zones and scans may be utilized over a predetermined time period. In Fig. 2, each scan is represented by a diagonal 21 displaced in time from preceding and succeeding scans to permit flyback, and derives at 16 a profile indication of base weight variation, containing base weight information in cross and machine directions. During a scan the signals contain short term machine direction variance V X(ST)  an average value of which is derived over several scans by computing total machine direction and long term machine direction variances, and subtracting the latter from the former, while cross direction variance V y  is derived by subtracting profile variance from short term machine direction variance. Long term machine direction variance is calculated by averaging the profile measurements of each of the four scans and calculating the variance of the four averages, while total machine direction variance is calculated by computing the variances in each of the three zones 1 to 3 for the four scans 1 to 4 and averaging the variances. Thus the total variance of the sheet covered by the four scans of the detector is derived as V t =V y +V x (t). Motor 14 is linked to pulse transducer 22 generating a pulse when gauge 11 is situated at the centre of each of the three zones, which pulses sampling gate 23 coupling the measurement output of 16 through A/D converter 24 deriving parallel multibit words representing the derived base weight signal, which are applied to memory 25 having e.g. 12 cells equal in number to the product of the number of sampling zones and scans necessary for meaningful variance data and each storing one multibit word. Output of pulse transducer 22 is coupled as advance column input to the memory, and thereafter as gauge 11 crosses each zone, data is written into a different memory column, and a microswitch 26 operated by completion of a gauge scan, derives a binary one signal coupled to a memory advance row input, resetting the column read-in position; whereby on completion of each scan the memory row receiving data is advanced and the cell receiving data corresponds to gauge position in machine direction and cross direction of the sheet. After memory 25 has received data corresponding to the third column and fourth row, sense read-in network 26 is connected to the third column and fourth row cell to generate an output signal in response to data being read in, and pulses controller 27 to initiate computation after delay allowing for an entire word to be read in to the third column and fourth row. The controller has internal clock and shift register sequentially deriving control signals at inputs or outputs 28, 29, 30. The four base weight profile signals in each column are non-destructively read out in three successive cycles to computer 31 in response to controller 27. Successive cycles of four base weight profile signals, derive digital multibit words representing variance which are added in accumulator 33, whose output is fed into divider matrix 35 in response to a controller signal; whereby a multibit digital signal representing average zone variance of sheet 12 is fed to register 36; which stores a binary multibit word representing the total machine direction variance of sheet 12 for the four scans of gauge 11, i.e. V X(T) . Thereafter, controller 27 is advanced to read the memory contents into variance computer 32 over inputs responsive to each of the three columns of 25 and to the four rows in sequence; the signals being applied from the memory twice, once for computation of profile and once for long term machine direction variance. Initially, the average profile variance over four scans, #V Z  is calculated by computing and summing successive profile variances and dividing by 4, thereafter feeding the signal to register 37 in response to controller 27, which thereafter initiates four sequential operations each reading three simultaneous words from memory 25 to computer 32, which calculates long term machine direction variance in response to equation 3 for storage in register 38. From total machine direction, average profile, and long term machine direction variance components stored in registers 36, 37, 38 there are calculated total variance, short term machine direction variance, and cross direction variance in accordance with equations 1 and 2 by combining stored profile variance and long term machine direction variance signals in adder matrix 41 whose total variance output is stored in register 42; by supplying contents of register 36 as a one input to subtraction matrix 43 whose other input is connected to output of register 38. The resultant short term machine variance signal is stored in register 44 and registers 37, 36 supply inputs to subtraction matrix 45; the output of which is an input to the adder matrix 46. The second input to the latter is the output of register 38, and it develops a binary representation of the cross direction variance of the sheet averaged over four detector scans which is coupled to register 47, so that registers 36, 37, 38, 42, 44, 47 store and indicate the variance components of total machine direction, average profile over four scans of gauge 11, long term machine direction over the four scans, total for the four scans of gauge 11, average short term machine direction for the four scans, and average cross direction for the four scans. The variance computer 31 (Fig. 3) responsive to the four simultaneous columnar outputs of memory 25 calculates the average values thereof, subtracts the individual inputs from the average, squares the resultant, sums the squares, and divides by 4 to give variance. The inputs are switched over 4-pole2- throw electronic switch 51 operated by controller 27 to adder matrix 52 deriving a single multibit binary output word divided by 4 in matrix 53; whose output is coupled during averaging over electronic 1-pole2- throw switch 54 operated by controller 27 to the subtrahend inputs of subtraction matrices 55-58; whose minuend inputs are responsive to the read outs from the four rows of the specific column of memory 25. Thus each matrix derives a digital multibit word representing deviation from average basic weight signal for a given zone over the four scans of gauge 11 across sheet 12. Such signals are squared in matrices 61 to 64 and memorized until controller 27 energizes switch 54 to decouple matrix 53 from inputs of matrices 55-58. Switch 51 is also activated to couple memorized signals to adder 52 with exclusion of signals from memory 25. A binary signal derived from the normally open contact of switch 54 represents the variance of the four values for the zone from memory 25, and is coupled to accumulator 33, and on completion of each variance computation controller 27 signals memory 25 to advance the column being read; switches 51, 54 being activated to apply contents of a second memory column to adding matrix 52 while output of division matrix 63 is coupled to subtraction matrices 55-58 so that the computer 31 derives sequentially three multibit binary words, each indicating variance across the width of sheet 12 in each of the three zones. Profile variance indications for each scan is calculated (Fig. 4) by deriving under control of 27 three parallel multibit words from each row of memory 25, applied over 3-pole2- throw switch 71 controlled by 27 to adder matrix 72. Initially the sum of the sampled values for the 3 zones of each scan of gauge 11 across sheet 12 is applied to ¸ 3 matrix 73, whose output represents average profile base weight for the scan applied in parallel to electronic 1-pole 2- throw switch 74 and electronic multiplex switch 175 controlled from 27, so that each average profile signal is applied to a distinct output of the switch which correspond to the number of scans of gauge 11; the four switch outputs being applied to four cell memory 176 for later long term machine variance computation. Average profile base weight outputs of matrix 73 are applied over normally closed switch 74 to inputs of subtraction matrices 75-77 including further inputs responsive to three zone basis weight signals read out from the appropriate row of memory 25; each matrix deriving multibit binary signal indicating deviation of base weight from average for a particular scan; such signals being squared at 78 to 80 and memorized for readout controlled by 27 to adder matrix 72