R OBI m 6 w 53 1 1 E5 m row In J? x no: 256 0651 n:. nn 55:3 1 7 1 P56 A. N. a moEmuzmw N. C. PICKERING DIGITAL QUANTITY MEASURING APPARATUS Filed Jan. 5, 1967 Dec. 2, 1969 BY NORMAN c; PICKERING ATTORNEY mv NEE oh United States Patent 3,481,520 DIGITAL QUANTITY MEASURING APPARATUS Norman C. Pickering, Sag Harbor, N.Y., assignor, by mesne assignments, to General Time Corporation, Stamford, Conn.
Filed Jan. 3, 1967, Ser. No. 606,981 Int. Cl. B26d 5/40, 7/28 US. Cl. 225-4 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to automatic process control devices and in particular to such devices used for controlling the cutting of uniform lengths of sheeting from a moving length of sheet material.
Although the device will be described as embodied in a perforated sheet bursting means, it will be appreciated that the principles can be applied to many repetitive operations where it is desired to actuate a device having some finite operating time and which is intended to act on uniform quantities of a work material.
A need exists for devices which will accurately cut lengths of a continuous sheet into units of predetermined length. One such system relies on marks placed on the sheet material which are sensed by a sensing device, such as a photoelectric cell, and which will instruct a cutter to cut the sheet. Typical of such applications are rolled paper goods which have imprinted thereon forms, labels and other indicia. Since it takes time for the cutter (or other device) to operate, it is necessary to initiate operation of the cutter prior to the time of actual cutting. The time advance between initiation and completion corresponds to the operating time of the device. In prior art systems, if there is any variation in the speed of the sheet material passing through the apparatus or variation in the actuating time of the cutter, then there will be an error. Should the speed increase, more material will pass through the apparatus and the cutters will overcut the length desired; similarly with the converse. This invention is concerned with the elimination of such errors.
The present invention employs a digital length measuring system wherein pulses are generated relative to the material being measured and the pulses are counted to determine the preset cutoff point. The length of time required for the operation of the mechanical cutting operation being constant, any variation in the velocity of the sheet material is self-compensated in the apparatus.
In the separation of perforated multiple business forms, instead of a cutter it is customary to employ a pair of rotating clamping rolls which are brought together and clamp the paper, the differential speed being suflicient to burst the forms at the perforation. If the pulses are counted from the leading edge of the sheet to the preset point, the length of time required to actuate the mechanisms to cut or burst the paper would result in an addition to the preset length, and the sheet of material would be excessively long. The excess length would, of course, correspond to the amount of material that passes during the length of time required for the mechanical bursting device to contact and interrupt the moving sheet. The amount of material in error is a function directly propor- "ice tional to speed and to the length of time required to contact the material. In general, the length of time required for the mechanical cutting or bursting device to contact the sheet is constant and may readily be compensated for, by arranging for the actuation to be initiated this constant time prior to the material cut-off area arriving at the cutter or burst region.
The major factor contributing to errors is then the material speed variations. Thus, in order to compensate for the variations in material speed, the mechanical cutting or bursting device must be instructed to correspondingly operate earlier or later. Thus, if the material velocity is greater than average, the device must be actuated earlier, and if the velocity were less, than the device must be initiated later. The length of time that the operation of the mechanical cutolf device must be initiated ahead of actual cut-olf time is equal to the number of pulses that would be generated during the time that it takes the mechanical cutoff device to contact the paper or other material comprising the sheet at the speed the sheet is moving. The present invention provides an apparatus for instructing the cutting device to operate in this fashion.
It is an object of this invention to provide improved means for controlling the operation of a processing means.
It is another object of this invention to provide an accurate cutoff control means for the accurtae cutting of lengths of material from a supply roll.
It is a different object to provide an accurate control means which is self-compensating for variations in velocity of the work piece.
A specific object of the invention is to provide an improved digital measuring system for automatic processing means.
These and other features, objects and advantages of the invention will, in part, be pointed out with particularity and will, in part, become obvious from the following more detailed description of the invention, taken in conjunction with the accompanying drawing, which forms an integral part thereof.
The drawing shows a circuit diagram of an embodiment of this invention.
Referring to the drawing, there is shown an electronic counter 12 which can be preset to provide an output signal whenever itreceives a number of pulses indicative of the desired length. Such preset counters are commercially available. One suitable device is Modular Instrument Corporation, Syosset, New York, Model 7TO5. These pulses are generated by the rotation of a sensing roll 14 of known diameter against which the sheet material 16 is drawn, so that as the material passes between clamping rolls 14 and 15, a toothed wheel 18 coupled to roll 14 passes by transducer 20 and generates a pulse P each time a tooth passes. The pulses generated in transducer 20 are applied to both input channels 21 and 22. Channel 21 is a conventional one and the count signal is transmitted directly to the counter 12 through gate 28. The opening of gate 28 is controlled by the interruption of the light beam from light 26 normally passing onto photocell 27. The interruption of the light beam is indication that the leading edge of the sheet is in postion. It will be noted that photocell 27 triggers gate 42 to provide a gate-on signal Q to gate 28 through flip-flop 33 when the light from source 26 does not impinge on photocell 27. Flip-flop 33 acts as a memory for gate 28 turning on gate 28 until a stop signal is received from counter 12.
The counter will continue counting until the preset count is reached. After counter 12 has reached its preset count, a stop signal is generated by the counter which is simultaneously fed to gate 28 through flip-flop 33 to interrupt transmission of pulses to the preset counter and to reset pulse generator 29, which provides a signal to cause the preset counter 12 to reset to zero count. A signal is also generated by the reset pulse generator 29 which open gate 30 temporarily and then closes the gate 30 after a time delay of, say, 30 milliseconds. The time delay is preset corresponding to the length of time required for the mechanical cutolf device to contact the sheet. The length of time setting is adjustable to allow minor corrections in this time setting. During the time the timed gate 30 is open pulses are applied to the counter at a rate proportional to the rate of the passage of material between the rolls. The number of pulses that have now accumulated in the counter are equal to the number of pulses generated during the length of time required for the mechanical cutofi device to contact the sheet after first actuation. After bursting, the light beam impinges on the photocell 27 and, as soon as the next sheet breaks the light beam, gate 28 is placed in a conducting condition and the counter starts to count on to the already accumulated count. Counter 12 will reach the preset count in a time less than that corresponding to the length of the sheet to a degree corresponding to the number of counts previously accumulated as a result of pulses passing through timed gate 20.
In the drawing there is shown an actuator 32 which, upon receiving a signal from the counter 12, brings clamping rolls 34, 36 together onto sheet 16 through the action of linkage 38. It will be understood that the mechanical arrangement shown is merely schematic of the actual mechanism in present usage in industry.
In actual operation the apparatus functions as follows. The sheet 16 is driven at a given speed past rollers 14, 15. Pulses are generated at a rate directly proportional to the distance traveled by the sheet. The distance traveled is a time function of the speed of the sheet. During a given time the distance is directly proportional to the speed of the sheet and thus the pulses are also directly proportional to the speed of the sheet. As the speed increases more pulses are generated and conversely with a decrease of speed less pulses are generated.
The sheet 16 proceeds past auxiliary rollers 46, 47 toward the cutting rollers 34, 36 when the sheets are cut to the desired lengths. The time required for the cutting rollers to operate is predetermined and the number of pulses produced during that time is calculated and a corresponding correction made. For example, assume that the lengths of sheet desired would traverse pulses and that the time required for the cutters to operate would be equivalent to the production of two pulses. In this instance correction would be made by having the cutter actuated after 8 pulses.
A counter is preset to count the number of pulses corresponding to the desired length of paper. Two separate gates 28, 30 receive the pulses from two separate channels 21, 22. After the cutters have been actuated, gate 30 passes to the counter the number of pulses produced until the cutters actually burst the paper. After bursting, photocell 27 opens gate 28 and the number of pulses produced as the sheet advances are now added to the previous num ber counted.
In the above example the counter would count two pulses from the time of actuation until the time of cutting. These pulses would pass through gate 30. It would then count 8 additional pulses through gate 28 and then actuate the cutters again.
The counting of the pulses from the time of actuation until cutting provides a system of self-compensation. Should the speed of the sheet increase, the counter would count the increased number of pulses from the time of actuation until cutting. Thus, for example, should 3 pulses be counted, then the next time the cutters would be actuated after 7 additional pulses. Thus the actuation of the cutters responds to the speed of the sheet.
An important feature of the invention is that it provides a self-compensating device, one that will compensate for variations in the velocity of the sheet 16 as it passes over sensing roll 14. If we consider the situations in which this sheet velocity increases beyond a norm, then a greater number of pulses will be transmitted through timed gate 30 to the preset counter than if the velocity of the sheet 16 is below the norm. Thus, if the sheet is traveling at a faster rate, clamping rolls 34 and 36 will be closed earlier. If it is traveling at a lower rate than the norm, then clamping rolls 34 and 36 will be closed at a later time because it will take the preset counter longer to accumulate a suflicient number of counts for it to be actuated.
When first beginning the apparatus, the counter should be advanced that number of pulses corresponding to the number of pulses which would be produced from the time of actuation until cutting. Then the system proceeds in normal fashion.
If the burster fails to break the sheet, or the optical sensing system fails, or if the forms run out, an alarm system is actuated. The alarm system consists of a unijunction transistor 39 to which an emitter voltage is applied depending upon the condition of flip-flop circuit 31. When the voltage is applied, it is applied through a delay circuit 40 which may be a simple RC circuit whose time constant is adjustable. The time constant is arranged such that the unijunction 39 will fire if the emitter voltage has been applied for a time greater than the maximum time determined possible from the reaching of the actuation point and the time at which the light sensor should cycle through the light to dark transition. The flip-flop 31 is operated when the conditions are met of:
( 1) Actuation of the clamping rolls; and
(2) The light sensor cycling through the dark through light transition.
When the unijunction 39 fires, the alarm 41, symbolized by a bell, is actuated.
When the sheet is interposed between the photocell 27 and lamp 26 so that the photocell is dark, gate 42 produces a signal Q which puts the flip-flop 31 in an off condition. When the counter 12 reaches the actuation point, a stop signal is sent to the fiipfiop 31 and puts it into an on state, such that a voltage is sent to delay circuit 40. The delay circuit is adjusted to delay the voltage for a period corresponding to the time it should take for the cutters to sever the paper and the photocell to go dark again. Should the photocell be light at that time, then the voltage will be applied to fire the unijunction 39 and ring the alarm 41, signifying the absence of the sheet. Should the sheet be cut properly and the photocell go dark by the advancing sheet, the gate 42 will produce a pulse which will shut olf the flip-flop and remove the voltage on the delay circuit 40.
Having thus disclosed the best embodiment of the invention presently contemplated, it is to be understood that various changes and modifications may be made by those skilled in the art without departing from the spirit of the invention.
What is claimed is:
1. A method of controlling severing means for the separation of material into unit lengths from a continuous sheet of material advanced by material advancing means, comprising the steps of:
(a) forming a continuous sequence of electrical pulses as a function of the speed of the advancing material;
(b) counting the number of pulses produced by the advancement of the material;
(c) actuating the severing means when a prescribed number of pulses are produced;
(d) severing the unit length of material; and
(e) counting the number of pulses produced from the time of actuating the severing means until separation occurs wherein the prescribed number of pulses is attained through the combination of the pulses produced from the actuation time to the separation time and subsequently after the separation time.
2. A device for controlling the severing of a continuous web of material into unit lengths comprising:
(a) a material advancing device;
(b) material separation means;
(c) pulse producing means and time dependent gating means associated with the material advancing device where'by the number of said pulses admitted through said gate is a function of the speed of the advancing material;
(d) pulse counting means set to count up to a predetermined number and thereafter actuate the separation means said pulse counting means further including length dependent gate means wherein said time dependent gating means passes the pulses from the time of actuation to the time of actual separation and the length dependent gating means passes the number of pulses from the time of separation until said predetermined number is reached where by said separation means is compensated for changes in the speed of the advancing material; and
(e) resetting means whereby the pulse counting means is reset after actuation.
3. A device for controlling the separation of material into unit lengths comprising:
(a) a set of rollers between which the material ad vances;
(b) pulse generating means coupled to one of said rollers capable of producing pulses as a function of the displacement of the advancing material;
(c) material separation means;
(d) light producing means;
(e) light responsive means capable of producing a first signal as material interrupts the beam from the photo producing means from impinging on to the photo responsive means;
(f) pulse counting means set to count up to a predetermined number of pulses and thereafter produce a second signal;
(g) first and second channel inputs to the pulse counting means;
(h) a first gate in said first channel opened by the first signal and closed by the second signal;
(i) a second gate in said second channel opened by the second signal and set to automatically close when separation occurs;
(j) resetting means controlled by said second signal whereby the pulse counting means is reset after the second signal is produced; and
(k) actuating means responsive to second signal and controlling the separation means whereby the system responds to the speed of the advancing material and compensates for changes in the speed.
4. A device as claimed in claim 3 further including:
(a) a warning device; and
(b) delay means responsive to said first and second signals and controlling said warning device,
whereby should a predetermined time period pass between said second signal and said first signal the warning device is actuated.
References Cited UNITED STATES PATENTS 3,082,368 3/1963 Rowe 83364 X 3,177,749 4/1965 Best et al. 83'20'8 3,322,961 5/1967 Harrison et al 83-364 X 3,040,609 6/ 1962 Bowman 83,294 X FOREIGN PATENTS 624,398 7/ 1961 Canada.
JAMES M. MEISTER, Primary Examiner US. Cl. X.R.