Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F21/00—Devices for conveying sheets through printing apparatus or machines
  • B41F21/08—Combinations of endless conveyors and grippers

Definitions

• This invention relates to improvements in conveyor systems of the type disclosed in Dahlgren Patent No. 3, 644 , 261 , entitled “STRAIGHT FEED PRESS " and Dahlgren Patent No. 3, 847 , 079 , entitled “METHOD OF PRINTING SHEETS” .
• the disclosure of each of the aforementioned patents is incorporated herein by reference in its entirety for all purposes.
• the aforementioned patents disclosed a sheet fed printing press which incorporated a straight through and continuous sheet transfer principle , similar to the feeding style of a web-fed printing press , whereby sheets were grasped by gripper bars carried by flexible steel tapes or bands which extended around drive wheels for moving the sheets through a plurality of printing towers .
• the expansion of various materials are dependent upon the temperature, although for design purposes constant mean values are usually employed for design purposes. If lengths, areas, and volumes are at a standard temperature, the approximate change in dimensions of the material will be considered to be a function of the change in temperature. At best, such, design criteria provides only approximate dimensions and resultant inaccuracy in speed and location of parts. Even though all components of the printing press may be constructed of materials having an identical co-efficient of thermal expansion, the dimensions of various components of the system may change non-uniformly which results in further variation of the speed and location of various parts of the system which is detrimental to registration of the press.
• the method and apparatus disclosed herein relates to an improved conveyor system and register computer to provide automatic register between an endless conveyor surface and a printing cylinder.
• the method of maintaining endless surfaces on two members, at least one of which is circular, in a precisely synchronized relationship, in rolling relation with a surface on the other member comprises the steps of: moving the surface of the circular member in rolling relation with the surface of the other member; periodically comparing the position of a reference point an the circular member with a reference point on the other member to determine the spacing between the reference points; and adjusting the length of one of the endless surfaces to reduce spacing between the points on the respective members as they move in rolling relationship.
• the improved method is accomplished by adjusting the length of elastic flexible bands carrying gripper bars through the printing press to maintain the gripper bars and sheets carried by the gripper bars in synchronized relationship with the printing cylinders.
• the apparatus for accomplishing this method includes a pair of endless flexible bands driven by circular wheels, and gripper bars extending between the Bands and spaced longitudinally thereof, for carrying sheets.
• Each, of the bands extends around and is driven by a drive wheel.
• the band is maintained in tension by at least cne idler wheel for causing a portion of the Band to extend along a precisely defined path.
• Reference pins are attached to the drive wheel and to each band of the conveyor so that the reference pins will be positioned in a known relationship relative to each, other when the conveyor and printing cylinders in a press are registered. Sensors are positioned to generate signals when each of the reference pins move adjacent thereto. The signals are compared and delivered through a computer to a an actuator for adjusting spacing between the drive wheel and the idler wheel to adjust the length of the Band. Thus, the length, of the path, along which, the reference pin carried by the conveyor, is varied to maintain registration Batween the reference pin ⁇ n the conveyor and the reference pin en the drive wheel.
• a primary object of the invention is to provide an aidless conveyor and another endless member , at least cne of which is circular, in a moving registered relationship even though the circumference of the circular member varies under normal operating conditions.
• Another object of the invention is to provide a conveyor for a sheet-fed printing press wherein the length of the conveyor is capable of adjustment for purposes of registering the conveyor with printing cylinders to provide a sheet-fed press in which the sheet is continuously gripped by a single set of grippers from the time the sheet enters the press at the feeder until it reaches the delivery station.
• a further object of the invention is to provide a conveyor for a sheet-fed printing press , the length of the conveyor being adjustable for maintaining registry between sheet's moving at a constant speed by the conveyor along a path, which is adjustable in length.
• Figure 1 is a side elevational view of the operator side of the printing press
• Figure 2 is a top plan view of the printing press having inkers and dampeners removed therefrom;
• Figure 3 is a diagrammatic view illustrating the relationship of the sheet conveyor to printing cylinders ;
• Figure 4 is a diagrammatic view of a sheet conveyor which is properly registered;
• Figure 5 is a diagrammatic view similar to Figure 4 in which the path of the sheet conveyor is too short;
• Figure 6 is a diagrammatic view similar to Figure 4 in which the length of the sheet conveyor is too long;
• Figure 7 is an enlarged cross-sectional view taken along line 7-7 of Figure 2;
• Figure 8 is cross- sectional view taken along line 8-8 of Figure 7;
• Figure 2 is an elevational view looking in the direction of arrows 9-9 in Figure 7;
• Figure 10 is a diagrammatic section of the operator side of the conveyor system;
• Figure 11 is a diagrammatic top plan view of the conveyor system;
• Figure 12 is a diagrammatic elevational view of the gear side of the conveyor system
• Figure 13 is a diagrammatic view of the register computer
• Figure 14 is a graphic illustration upon wh ich conveyor revolutions are plotted as the abscissa and on which, the band position error , expressed in units of length, are plotted as th e ordinate ;
• Figure 15 is a series of bar graphs indicating time on the horizontal scale ;
• Figure 1 is a wiring diagram of the registration computer interface .
• Figure 17 is a wiring diagram of the motor controller. Numeral references are employed to designate like parts throughout the various figures of the drawing . DESCRIPTION OF A PREFERRED EMBODIMENT
• the numeral 1 generally designates a sheet- fed, multi-color, perfecting, lithographic printing press of the type disclosed in U. S. Patent No. 3,847,079.
• a feeder mechanism 2 delivers sheets of un printed paper from a stack 4 to a swing gripper 6.
• the swing gripper 6 accelerates individual sheets 5 to the velocity of gripper bars 8 carried by a sheet transfer mechanism 10.
• the sheet transfer mechanism 10 comprises drive wheels 12a and 12b adjacent the feeder end of the press and idler wheels 14a and 14b adjacent the delivery end of the printing press.
• the wheels carry tapes or Bands 16a and 16b, having gripper bars 8 mounted therebetween for moving individual sheets 5 through the printing press.
• a pair of printing towers 18 and 20 are provided to give the press a multi-color, perfecting printing capability. It should be appreciated that any number of printing towers may be employed for printing additonal colors or for coating sheets.
• Individual sheets 5 are gripped by a delivery mechanism 22 as they are released by gripper bars 8 to form a stack 24 of printed sheets.
• each printing tower 18 and 20 has a side frame 26 on the operator side of the press and a side frame 28 on the drive side of the press , joined by tie bars 30 , to form a strong rigid frame structure upon which various components of the press are mounted.
• Feeder 2 and delivery 22 have side frames 2a and 22a on the operator side of the press and side frames 2b and 22b on the drive side of the press, respectively.
• Tie plates 31 join the side frames of feeder 2 , printing tower 18 , printing tower 20 and delivery 22 adj acent opposite sides of the printing press.
• Each printing tower 18 and 20 is provided with an upper plate cylinder 38 U and a lower plate cylinder 38L, an upper blanket cylinder 48U and a lower blanket cylinder 48 L.
• the upper and lower blanket cylinders 48U and 48L serve the dual function of a printing cylinder and a back-up cylinder and engage opposite sides of sheets 5, as best illustrated in Figure 3, carried through the printing press by gripper bars 8 extending between bands 16a and 16b .
• Each blanket cylinder 48U and 48L has a gap 49 formed therein to permit movement of gripper bars 8 therebetween.
• each plate cylinder 38U and 38 L is equipped with, plate clamps to facilitate securing a printing plate thereto and that each blanket cylinder 48U and 48L is equipped with clamps for securing a blanket thereto.
• inking systems and dampening systems for applying ink and dampen ing fluid to lithographic printing plates are not illustrated.
• circumferential and lateral register adjustments for the various cylinders are not illustrated.
• the provision of other and further conventional components is deemed to be within the skill of a press manufacturer.
• the conveyor system is illustrated in combination with a lithographic printing press
• the conveyor may be employed in any rotary print ing system, for example , in which an image is applied by a printing plate to a blanket cylinder and offset onto a sheet , or , printed directly from a planographic printing plate , letter press , relief or intaglio pring ing plate or printing cylinder to a sheet .
• the conveyor system may be employed with a mechanism for performing operations other than printing, for example , cutting, folding, slitting, punching, reading indicia and the like .
• the sheet transfer mechanism 10 hereinbefore briefly described, includes drive wheels, 12a and 12b connected to an axle 13 adj acent the feeder 2 of the printing press and idler wheels 14a and 14b rotatably secured about an axle 15 adjacent sheet delivery mechanism 22.
• Band 16a adjacent the operator side of the printing press , extends around wheels 12a and 14a
• band 16b adjacent the drive side of the press , extends about wheels 12b and 14b.
• axle 13 is driven and traction between the surfaces of wheels 12a and 12b and bands 16a and 16b, respectively, imparts motion to the bands .
• the conveyor system 10 is a mechanical device that carries the sheet 5 through the printing press 1. For proper printing to occur, the conveyor system 10 must offer mechanical repeatability of the sheet relative to each, printing tower 18 and 20 .
• the bands 16a and 16b have been formed with good results from a strip of steel material 3. 500 inches wide and 0.042 inch thick to provide a cross-sectional area of 0.147 square inches for each band.
• the band material is preferably a 1095 carbon steel , heat treated to a hardness of Rockwell C 47 and has a modulus of elasticity of 30x10 6 pounds per square inch.
• each of the strips of material are joined together by a riveted aircraft-type splice joint consisting of two plates, one Eeing 0.020 inch thick and the other being 0.035 inch thick secured by flat-head hi-shear rivets extended through countersunk holes in the band to opposite sides of the band.
• the thinner plate will deflect before the thicker plate for distributing the load and the tension in the band to the rivets in a uniform manner to enhance the fatigue life of the joint.
• Outer peripheries of wheels 12a, 12b, 14a and 14b are of substantially identical construction, each having a flange 11 secured to opposite sides thereof to form a groove into which tapes 16 extend. Flanges 11 merely prevent lateral movement of tapes 16 relative to wheels 12 and 14.
• wheels 14 at the delivery end of the printing press are freely rotatahle about the non-rotatable axle 15 and have an inner hub 27 having a passage formed therethrough to receive the outer races 18 of bearings 22a and 22b.
• the inner races 21 of each of the bearings 22a and 22b are secured to axle 15.
• Each axle 15 has a hub 15a for restraining bearings 22a and 22b against inward movement on axle 15.
• a retainer sleeve 28 extends around the outer end of axle 15 and engages the inner race 21 of the outer bearing 22a.
• Sleeve 28 is captured by a lock nut 29 threadedly secured to the outer end of a journal 30 on the outer extremity of axle 15.
• Sleeve 28 extends through and is secured in an opening 32 formed in bearing block 35 which is secured by bolts 36 to support pins 40 .
• a single set screw 38 is provided on one side of the press only .
• Brackets 42 and 44 have spaced aligned apertures formed therein in which, bearings 43 and 45 are secured. Opposite ends of support pins 40 are slidahly secured in bearings 43 and 45 to permit movement of bearing block 35 and shaft 15 . Brackets 42 and 45 are secured fay bolts 46 to side frames 22a and 22b of delivery station 22. As illustrated in Figure 8, a bearing retainer disc 22c is secured by screws 22d to tape wheel 14b for restraining the outer race 18 of bearing 22a against outer movement, A grease seal 22e is urged into sealing relation with bearing disc 22c and sleeve 28 to retain lubricating oil adjacent to bearings 22a and 22b. The innex races 21 of bearings 22a and 22b are pre-loaded relative to outer races 18 by adjusting nut 29 and the outer races are separated by spacer 18a.
• Drive wheel 14a is similarly mounted on the opposite end of axle 15 , as illustrated in Figure 9.
• bracket 44 has an aperture formed in a central portion thereof in which a bearing 50 is secured between lock plates 52 and 53 to prevent long itudinal movement of drive screw 55 relative to bracket
• Drive screw 55 is of conventional design and has a ball screw portion 56 formed on the inner end thereof.
• a ball nut 58 is secured by screws 59 to member 60 which is in turn secured by screws 62 to bearing block. 35.
• the ball screw 56 and ball nut 58 are of conventional design and are available from Saginaw Steering Gear Division of General Motors Corporation , Actuator Products Group , Saginaw, Michigan.
• the ball bearing screw is a force and motion transfer device belonging to the family of power transmission screws . It replaces the sliding friction of the conventional power screw with, the rolling friction of ball bearings .
• the ball bearings circulate in hardened steel races formed by concave helical grooves in the screw and nut.
• drive screw 55 on the gear side of the printing press is driven by a remotely controlled stepper motor 75a and drive screw 55 on the operator side of the press is driven by a remotely controlled stepper motor 75b .
• Stepper motors 75a and 75b are of conventional design and are commercially available under the trademark "SLO-SYN" D.C. Stepper Motor, manufactured by The Superior Electric Company of bristol , Connecticut.
• a suitable gear reducer such as an "Ohio 20 :1" worm gear, right angle drive 75c is preferably mounted between the stepper motors 75a and 75b and each of the drive screws 55 to attain a desired angle of rotation of ball screw 56 for imparting a specified distance of movement to bearing block 35 upon each step of the stepper motor.
• Stepper motors 75 a and 75b are employed for moving the slide blocks 35 at the delivery end of the press for moving the non-driven wheels 14a and 14b which are independently rotatable and independentally horizontally adjustable.
• stepper motor 75a or 75b changes the distance between axes of axles 13 and 15 a distance of 0.00 005 inches.
• the resulting change in length of band 16a or 16b is 2 times the change in the distance between the axes or 0. 0001 inch per step of the stepper motor .
• each of the idler wheels 14a and 14b is equipped with a separate stepper motor to permit adjustment of the distance between the axes of wheels 12a and 14a independently of the adjustment of the distance between the axes of wheels 12b and 14b.
• the length of bands 16a and 16b are independently adjustable .
• Initial band tension has been chosen to be 1 , 800 pounds in each band. This tension is achieved by manufacturing the individual bands to a length shorter than the desired installed length. Each band is elongated during installation to the desired length . As hereinbefore described, the distance between the axes of wheels 12a and 14a is adj ustable to deflect the band to the final length.
• a conveyor system wh ich has been constructed for testing employed wheels 12a, 12b , 14a , and 14b having a diameter of 47. 958 inches plus the thickness of the band which was 0.042 inch, and thus provided a nominal pitch line diameter of 48.000 inches.
• the length of band driven by each drive wheel 12a and 12b during one revolution is 48. 000 inches times ⁇ . This figure is approximately 150. 7263 inches.
• 38U and 38L was 3 : 1 while the ratio of the drive wheel to a 24 gripper bar system is 8 : 1. Multiplying 150. 7963 by 8 gives 1206. 3705 inches for the nominal final length of the band. The manufactured length of the band to achieve a 1, 800 pound pre-load on the band, was
• idler wheels I4a and 14b cannot be made exactly the same diameter as drive wheels 12a and 12b. Therefore , no two pairs or two systems of bands and wheels can perform identically in practice. Therefore, idler wheels 14a and 14b. are mounted to rotate independently of each, other at the delivery end of the press.
• Axle 13 at the feeder end of the press is driven , as hereinbefore described and axle 13 is secured to maintain axle 15 in an established position.
• This is desirable because swing grippers 16 must register with the conveyor 10 for feeding sheets to the sheet conveyor.
• shaft 15 can be moved independently by stepper motors 75a and 75b , axle 15 may not be maintained in a precisely aligned parallel relationship o to driven axle 13.
• Drive wheels 12a and 12b are rigidly secured to drive axle 13 to maintain the timing of band 16a relative to band 16b .
• the timing of the idler wheels 14a and 14b relative to each other is a variable that is unpredictable .
• the two idler wheels 14a and 14b are allowed to rotate freely and independently of each other since their speed of revolution will vary according to the actual diameter of the respective wheels .
• the main function of the conveyor system is to afford repeatability of the sheet relative to each printing tower 18 and 20. Mechanical repeat of conveyor bands 16a and 16b relative to drive wheels 12a and 12b occurs every eight revolutions of the drive wheels . Therefore , the length, of the band is 8 times the theoretical circumference of drive wheels 12a and 12b.
• the band 16a or 16b is not equal to exactly eight times the circumference of drive wheels 12a and 12b , then the mechanical repeat every eight revolutions of drive wheels 12a and 12b would not exist .
• an error will be noticed in the repeat of drive wheels 12a and 12b relative to the bands 16a and 16b. If this error is monitored , it will be seen that the error will accumulate with each cycle as a function of the error in the center distance between axes of axles 13 and 15 or the error in the length of the band.
• the actual function of repeatability to center distance error is : error equals two times the center distance error . For example , if the center distance is 0. 001 inches more or less than it.
• the error repeat of the band and the drive wheel will be .002 inches.
• An initial position error could also exist with the band mounting on the wheel. In other words, the band could be initially misplaced relative to the wheel 12a or 12b even though the distance between axes
• the position of conveyor bands 16a and 16b relative to the drive wheels 12a and 12b is critical because the bands move the. gripper bars 8 relative to printing cylinders 38U and 38 L.
• the initial 1, 800, pound tension in bands 16a and 16b is established and maintained for two reasons .
• the tractive force is a function of the co-efficient of friction times the force normal to the surface ofthe drive wheels 12a and 12b.
• tension in bands 16a and 16b is required to prevent a loss of tension or frictional driving force during normal thermal build-up of the conveyor system under normal operating conditions .
• the conveyor bands 16a and 16b. were manufactured at an ambient temperature of 72 ° F . , at a length of 1205 , 8883 inches and assuming that the band expands 6 X 10 -6 inches per inch of length per degree
• conveyor bands 15a and 16b are diagrammatically illustrated in relation to a computer for determining errors in locating of bands 16a and 16b relative to printing cylinders and for making adjustment of the lengths of the bands 16 a and 16b for elimination of any error.
• stepping motors As hereinbefore explained, stepping motors
• Photocells 81 , 82 , 83 , 84 and 85 are photoelectric cells particularly adapted to generate signals when a light beam is broken.
• the location of the photoelectric cells 81-85 is optional provided that they are positioned to accomplish the function as set forth hereinafter.
• Photocell 81 is positioned adjacent the gear side of the press such that a pin 81a on gripper bar 8a breaks the light beam.
• Photocell 82 is positioned adjacent the operator side of the press and is positioned such that pin 82a on the end of gripper bar 8a breaks the light beam.
• Photocell 83 is secured to the side frame 2a on the operator side of the press and the light beam is broken by pin 83a secured to drive wheel
• Photocells 84 and 85 are secured to the side frame 2b on the. gear side of the press and are spaced apart such that pin 84a on drive wheel 12b sequentially breaks the light beams of photocells
• signals from photocells 81-85 are delivered through cables 81c -435c to interface or input logic circuitry 86 for modifying the pulses from the photocells to a number which the computer can use.
• Signals from input logic interface board 86 are delivered through a commercially available interface module board 87 , to a microcomputer 88 , to an interface module 89 , to motor controllers 75a and 75b.
• a commercially available power supply 30 is illustrated in combination with the circuitry as will be hereinafter more fully explained.
• the interface module 87 and interface module 89 are commercially available from Motorola, Inc., of Phoenix, Arizona, and are designated "MEX68USM Universal Support Module" which is described in "User's Guide, First Edition, dated 1978.” The Motorola User's
• the microcomputer 88 is commercially available from Motorola, Inc., of Phoenix Arizona, and is re ferred to as "M68MM01, Monoboard Microcomputer 1,
• Micromodule 1 The microcomputer is described in User's Guide MM6801 (D) dated November 1, 1977, which is incorporated herein by reference in its entirety.
• the power supply 90 is commercially available as a "Motorola M68SC with, power supply,” from Motorola,
• The. motor controllers 75a and 75b are available from The Superior Electric Company of Bristol, Connecticut, as a "Slo-Syn, Preset Indexer Module, Type PIM 153" equipped with, a "Slo-Syn, Power Supply, Type MPS
• Figure 15 is a series of bar graphs indi eating time on the horizontal scale to form a timing chart to diagrammatically illustrate operation of the photocells 81-85 and the input to the computer.
• the time sequence of the various signals is indicated adjacent the numeral reference at the left-hand side of the chart corresponding to the respective photocells.
• the elements incorporated into Figures 16 and 17 of the drawings and referred to in Figure 15 include : photocells 81 , 82 , 83 , 84 and 85 ; NAND gate Ul with Schmidt trigger input; optical couplers U28 , U29 , U30 and U31; N ⁇ ND gates U25 , U32 , U35 and U36 ; one-shots
• the first thing that occurs in this system is that a pulse is delivered from one of the photocells 81 or 82 triggered by movement of gripper bar 8 carried by bands 16a and 16b when a pin 81a or 82a on the end of the gripper bar breaks the light beam.
• the exact time at which pins 81a and 82a trigger photocells 81 and 82 will be dependent upon the position of the respective bands 16a and 16b If hands 16a and 16b are precisely positioned in the desired, registered relationship , photocells 81 and 82 will be triggered simultaneously.
• Photocells 81 and 82 indicate the positions of bands 16a and 16b relative to the member carrying pin 83a which triggers photocell 83. It will be noted that, although, pin 83a is secured to drive wheel 82 , it may be secured directly to printing cylinders 48U or 48L if it is deemed expedient to do so . However , in the illustrated embodiment, the surface speed of drive wheel 12a is synchronized to the surface speed of the printing cylinders 48 U and
• pin 83a is moving in a known relationship to the surface speed of the printing cylinders .
• Reference pin 83a could also be located on drive shaft 67 , on a drive gear or some other part of the press having a known speed relationship relative to the printing cylinders .
• Photocells 84 and 85 are mounted such that the distance between the light beams of the respective cells is precisely known , for example , 0. 314 inches to generate a velocity reference. It will be appreciated that selection of the distance between photocells 84 and 85 is arbitrary. However, the distance moved by pin 84a for triggering photocells 84 and 85 should be the same as the distance pin 83a on drive wheel 12a moves after pin 82a or pin 81a triggers photocells 81 or 82 .
• the photocells are arranged to measure the time between the breaking of a light beams in the respective photocells. By indicating the time sequence of the relative positions of the parts the actual distance between the parts can be computed. However, signals must be generated to indicate numbers with, which, the computer can work, so the input circuitry gives the computer a number and with the components illustrated in Figure 4 correlated with the timing chart illustrated in Figure 5 signals can be generated for stepping motors 75a and 75b for adjusting the time interval for triggering photocells 81-85 as desired.
• pin 81a on gripper bar 8a has broken the light beam in photocell 81 which, has resulted in the generation of a pulse from a one-short circuit that produces an output signal of fixed duration , when an input signal of any duration is applied , which is delivered to logic circuitry.
• the logic circuitry is set up to open counter gate when the band signal occurs and the gate stays open until the reference signal from photocell 83 is received.
• the gate opens the input to the counter and allows a one megahertz crystal controlled signal from the computer to pass through the gate to the counter so that the gate counts cycles of the one megahertz signal from the time between the band pulse , when photocell 81 was triggered, until the reference pulse from photocell 83 is recieved.
• the three counters 91, 92 , and 93 are in one intergrated circuit chip , for example , anintegrated circuit chip known as a Motorola 6840 , Pro gramable Timer Module which will interface directly with computers.
• the count from the first, second and third counters are the numbers with which the computer works.
• the count again is based upon a one megahertz signal (1 x 10 6 cycles per second) so that the number diagraramatically illustrated in the last three lines of Figure 15 of the drawing represents the number of one millionths of seconds that it takes for the pin to pass from one photocell to the other.
• the second counter 92 indicates the time that it takes for the press to move the known distance of 0. 314 inches
• the count on the first and third counters indicates the time that it took for the bands 16a and 16b to move the actual distance travelled by the band during the time interval.
• the distance between photocells 84 and 85 was arbitrarily selected to be 0.314 inches and this distance could be , for example , 2 inches or any other arbitrary figure , so long as the distance is known.
• the computer determines the "error distance " .
• the computer must know the velocity of the press . It is known that velocity is equal to distance divided by time . Since photocells 84 and 85 are positioned 0. 314 inches apart , substituting this number into the equation along with the count in counter 92 , which is the time in micro-seconds that it took the press to pass between photocells 84 and 85 , the velocity of the press can be determined.
• the count in counter 91 indicates time and the velocity of the band is equal to the velocity of the drive wheel , since there is no slippage between the band and the drive wheel.
• the band length or position is 0. 314 inches and it will pass through in the same amount of time that it takes the pin 84a to pass through photocells 84 and 85 which is also 0.314 inches . If the count in counter 92 is subtracted from the count in counter 91 , the difference is equal to the error expressed in time . To determine the distance of the error , the time of the error signal can be substituted into the following "Equation A" :
• the graph indicates that the press was started with the band in the proper position (coordinate 0, 0 ) . After running one revolution , the band was out of position by one unit or 0. 0001 inch (coordinate 1, 1 ) which means that the band was the wrong length.
• a plus adjustment of length should increase the band length and a minus adj ustment should shorten the band length . Since the conveyor NOT TO BE TAKEN INTO CONSIDERATION FOR THE PURPOSES OF INTERNATIONAL PROCESSING (SECTION 310(c) (iii) OF THE ADMINISTRATIVE INSTRUCTIONS)
• the position error at this time is negative rather than positive.
• the graph indicates that an adjustment was made which resulted in the position error being four units at the beginning of the ninth revolution.
• the graph indicates what happens when the computer makes adjustments from "Equation B" above.
• the equation accounts for both errors, the position error and the length error, and combines two different adjustments into one adjustment to actually change the band length. First it adjusts for the actual position error.
• the additional 2 units would cause it to be "negative going" to a position error of two units so that at the Beginning of the tenth revolution, the actual position error would Be a plus 2 units.
• the plus 4 that existed at the ninth revoultion, the plus 2 that existed at the tenth revolution inserted into the adjustment equation indicates that the adjustment is a negative 1 unit. In other words, it shortened the band by one unit.
• the band was two units long at the beginning of the tenth revolution. Shortening the band one unit leaves it one unit too long and from the tenth revolution to the eleventh revolution the position would change by one unit, down to one. From the eleventh to the twelveth revolution, after making the adjustment, the band actually would be the right length and it would stay the one unit off of zero because adjustments of less than one unit cannot be made by the stepper motors.
• Equation B tends to dampen out all other factors which minimizes oscillation. Further, if adjustments are made slower than one-half the error the response of the correction will be too slow.
• the adjustment of 0.5 of the error upon each revolution of the band is believed to be an optimum adjustment. However, it will be appreciated that an adjustment of 0.8 or 0.3 of error upon each revolution of the band will operate successfully; however, not as efficiently as the result which is required in making the 0.5 adjustment.
• photocells 81-85 are identical.
• the structure photocell 81 is illustrated in Figure 16.
• LD1 shines on a photo sensitive transistor Q-1 and pin 81a on gripper bar 8 passes between the diode LD1 and the transistor Q-1 breaking the light beam, which in turn causes the transistor Q-1 to conduct less. Decreasing conduction is converted to a voltage change across resistor R2 and the voltage change is felt at the input to a NAND gate U-1.
• a 74132 NAND gate has been used which has a Schmidt trigger input. The Schmidt trigger input switches at a definite voltage, for example, at 2.1 volts.
• the Schmidt trigger U-1 effectivly shortens the switching time of the photo sensitive transistor Q-1.
• the light beam is not blocked instantaneously, but it is blocked and it is most accurate when the voltage from the photo transistor is crossing the 2.1 volt area. So by triggering at that voltage, the definition of the position is in- creased.
• the output of the NAND gate U-1 is delivered through a simple transistor amplifier Q-2, a low impedance output amplifier, and through a cable 81c from the press to the actual computer location.
• the low impedance output amplifier Q-2 driving a photo-coupler U31 in the computer is employed to reduce electrical interference from the press .
• the optical couplers U31 with the low impedance driver Q-2 in effect eliminate interference and the optical coupler is driving another Schmidt trigger input NAND gate U-35 to further eliminate interference.
• the output of the Schmidt trigger U-35 is driving a one- shot U-19 which produces a pulse when it receives the signal trigger from the NAND gate .
• the pulse length from one-shot U-19 is determined by the external components to make the pulse from the photocell 81 of a constant length, of 100 milli-seconds.
• the actual pulse from the photocells 81-85 varies in length, with, the press speed , the slower the press is running, the longer the pulse . It would interfere with, computer operations to switch off at the wrong time. By making the pulse a constant 100 milli-seconds, such, problems have been eliminated.
• Each, photocell 81-85 delivers a signal through, a Schmidt trigger and a one-shot. From there they drive logic circuitry U25. The logic is set up so that if a pulse is received from one of the bands 16a or 16b, either pjhotocell 81 or 82 , then the counter gate output IRQ at terminal K3-1 is held low.
• Any pulse from photocell 81 will hold low true gate 1 of logic element U25 low.
• a pulse from photocell 82 will hold low true gate 3 of logic element 25 low.
• the counter 21 is counting the one Megahertz signal to the computer. They are held low until a pulse from photocell 83 triggers the one-shot U-18 . That signal is inverted at U-24 and used to turn off the 'NAND gates that are producing the low true signal. Now, this is another use of the one hundred milli- seconds pulses.
• the time that it takes for the .314 inches to pass on the press is less than one hundred milli-seconds and by holding these one-shots to one hundred milli-seconds or longer, the computer is given time to reconize the fact that there is a number there to read.
• the computer resets everything before the one-shots have gone back to their normal state.
• Another portion of the logic circuit insures that when all three of these pulses occur simultaneously, then we have a low true high IRQ, which is a signal for the computer that an event has occurred and that the computer needs to do something.
• the IRQ actually means interrupt request. It interrupts the computer and requests that it do something with this information.
• the three signals occur to give that signal immediately following the signal from photocell 83.
• That signal closes the gate to the counters 21 and 93, which means that at that time counters 91 and 93 have the numbers to be used.
• the computer will ignore the extra seven revolutions of wheels 12a and 12b. In other words, unless the pins 81a or 82a on gripper bar 8 carried By bands 16a and 16b trigger photocell 81 or 82, which only happens once per press revolution, the computer does nothing.
• the velocity signal has Been generated eight times. However, it is used only the last time it was generated, so the computer is instructed to hold the velocity signal from photocells 84 and 85 in a reset state until readings from the Bands are received. After getting an IRQ signal the computer becomes active and enables the velocity circuit by applying a signal to U -21 , pin 1. This is actually the clear input to JK flip-flop U21 and the computer is holding it in the clear stage until it gets an interrupt request. It then removes the clear so that it can operate. After removing the clear, the computer does nothing for approximately one hundred thousandths
• Photocell 84 triggers one-shot U-23 which , in turn , provides the signal to the input pin 2 of an AND gate U22. If the input to AND gate U-22 , at pins 1 and 2, is in the true state the output also would be high or true. The signal from photocell 84 turns this signal from terminal 2 of AND gate. U-22 off so that the output is turned off.
• Driving pin 2 of one-shot U20 is set for a very short time period, for example , six microseconds, so that pin 3 of AND gate of U-22 is turned off for six micro-seconds when we get a signal from phtocell 24 and then is turned off again for six micro-seconds when we get a signal at photocell 85. That puts the signal from photocells 84 and 85 an one line out of AND gate U -22 , but not at the same time, to one-shot U-20 , pin 2, that has been adjusted to 0. 7 milli-seconds. In effect, one-shot U-20 stretches the very short pulses into it, making them longer.
• the two pulses are 1. 8 milli-seconds apart so that spacing between the pulses at maximum speed is roughly equal to the pulse width.
• the first pulse triggers the flip-flop causing the not true output, pin 7, to go low and this output is coupled to gate 2 of the counter.
• the counter starts counting from the first pulse . It also triggers one-shot U20 , which in turn, toggles a flip-flop U26 consisting of two sections .
• this flip-flop U26 is fed back to the J input of the JK flip-flop U21, making it possible for the JK flip-flop U21, to turn off , but it cannot turn on again until flip-flop U26 has been reset.
• the second pulse counter is turned off , any noise or one revoultion of the drive wheel which produces two more pulses, connot operate this circuit until the U20 is expired and the computer has output a reset signal to pin 6 of flip-flop U26. This occurs a minimum of 1.8 milliseconds and a maximum of
• the computer After one hundred milli-seconds , the computer reads counters 91, 92 and 93 and starts processing the mathmatics . When it finishes the mathmatics , the computer outputs the adj ustment to the motor controllers, outputs the reset to pin 6 of flip-flop U26 , and then goes into a wait state.
• the circuit and components shown in Figure 17 is a conventional circuit which is commercially available from The Superior Electric Company of Bristol, Conneticut and is described in a publica tion entitled "Instructions for Installation, Operation and Maintenance, SLO-SYN, Preset Indexer Module Type PIM 153" (SE - 147816; MS2105G223) which is incorporated herein by reference in its entirety for all purposes.

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  • 1980-09-12 WO PCT/US1980/001209 patent/WO1982000975A1/en unknown
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