Controls For Spooling Apparatus

Abstract

A digital count is converted to an analog signal for application to a servo for driving spooling apparatus. The duration during which the spooling occurs is clocked. In the event the clocked duration gets to be too long, or short, the reference for the digital-to-analog converter is adjusted, respectively to increase or decrease the input to the servo. At one point during spooling, the count is gradually reduced (down-counting) to a certain level corresponding to a low spooling speed. The duration for low speed spooling is also clocked, and the time for starting down-counting is regulated to keep constant the duration for low speed spooling.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to spooling machines and, in particular, to improved apparatus for controlling the operation of a spooling machine.

2. Description Relative to the Prior Art

Consider the high speed winding of small spools, say, of photographic film and/or paper, the wound spools to be virtually continuously fed to packaging equipment in a fully automated system. The spools, from a customer-acceptance standpoint, must be similarly wound; and such winding must be very carefully kept in step with other packaging procedures for optimum efficiency.

A supply of film and/or paper is provided with appropriate indicia such as markings, or notches or the like, which define discrete lengths of film and/or paper to be wound into respective spools, there being means for separating just-wound spools from the supply. The markings, or notches or the like, are used to signal the start and stop of the spooling procedure ... but the actual spooling operation may be subject to various adverse influences. For example, the input to the spooling drive may drift, causing the spooling operation either to get ahead of, or behind, other packaging procedures; or assuming, say, that the spooling drive is hydraulic, the temperature or viscosity, etc, of the hydraulic fluid may change, again causing the spooling operation to lead or lag other packaging procedures.

SUMMARY OF THE INVENTION

To assure the in-step winding of successive similarly wound spools, the invention proposes to clock the time it takes for notches (or markings) to start and stop discrete spooling procedures and, when the clocked duration is greater, or less, than a predetermined time, or range of times (and which occurrences are hereinafter sometimes called clock differentials), to increase or decrease, respectively, the input to the spooling drive, thereby to keep the winding duration, from spool-to-spool, the same.

In a presently preferred form of the invention, the increase, or decrease, of the spooling drive input is effected by varying, in accordance with clock differentials, the reference that is applied to a digital-to-analog converter, the input to which is a count representing a desired spooling speed, and the output of which is applied to the spooling drive. By varying the reference for the digital-to-analog converter, as indicated, the speed count is effectively multiplied by a clock-duration variable, causing the output of the digital-to-analog converter to be a variable that maintains the spooling speed to keep constant the spooling duration.

To avoid the problems of possibly having to adjust, up or down, the reference for the digital-to-analog converter after each spooling cycle, the invention further proposes to use as a reference for the digital-to-analog converter, the analog equivalent of a (preset) count that is increased and decreased respectively whenever a preset up-down counter fills and empties in response to successive clock-durations which are too long and too short. Therefore, so long as the successive clock-durations remain within a predetermined range of times, the up-down counter never fills or empties and, attendantly, the reference for the digital-to-analog converter remains invariant.

The braking of the spooling operation has a direct bearing on the timing of other procedures associated with the spooling operation. Apparatus according to the invention employs the prior art speed profile depicted in United States Pat. No. 2.776,094 (FIG. 32), assigned to the instant assignee, whereby high speed spooling is first ordered, followed by a gradual lessening thereof to an ordered low spooling speed, from which quick braking can be easily effected. The invention proposes that the aforesaid count that is representative of a desired spooling speed appear in and be provided by a downcounter: A notch (or marking) in the paper or film being spooled first causes a high count to be applied to the downcounter for high speed spooling; thereafter, the notch causes the application of down-countng pulses to the counter until a low-speed spooling count is reached; and then, while spooling continues at low speed, the notch causes the counter to be cleared, thus causing the low spooling speed to drop quickly to zero.

As noted above, the timeliness of the spooling cycle, and the braking thereof, has a direct bearing on other procedures. Given controls for holding each spooling operation to a certain duration, and means for abruptly braking the spooling operation, for sake of efficiency, it is incumbent to keep the duration of low speed spooling quite short. To this end, the invention further proposes to control tightly the duration of low speed spooling, whereby whenever the duration of low speed spooling is more or less than a certain (short) amount, or range of amounts, the invention provides means for shifting the time for switching from high speed to low speed spooling, thereby to keep the duration of low speed spooling constant.

OBJECT OF THE INVENTION

To assure efficient and timely spooling of discrete lengths of web material .

The invention will be described with reference to the Figures, wherein:

FIG. 1 is a schematic block diagram of apparatus embodying one aspect of the invention,

FIG. 2 is a schematic block diagram of apparatus which, when used in conjunction with apparatus indicated in FIG. 1, provides another aspect of the invention,

FIG. 3 is a schematic block diagram of apparatus which, when used in conjunction with apparatus indicated in FIG. 1, provides still another aspect of the invention,

FIG. 4 illustrates a spooling speed profile provided by apparatus as depicted in FIG. 3,

FIG. 5 is a schematic block diagram of apparatus which, when used in conjunction with apparatus indicated in FIG. 3, provides still another aspect of the invention, and

FIG. 6 illustrates a spooling speed profile according to the teaching of FIG. 5.

Referring to FIG. 1, a web 10 has notches 12,14 which generally define the length of web to be spooled by a spindle 16. The web 10 is fed into a pre-aligned slot in the spindle by means of pinch rollers 20,22. The roller 22 is driven, and positioned to engage the web 10, by a drive 24 which is energized by a flip-flop device 26 in response to actuation of a switch 28. As the lead end of the web 10 enters the slot 18 (i.e., the web travels the distance d), the notch 14 sees a photoelectric device PC-1, which disengages the drive 24 via the flip-flop device 26, and turns on a flip-flop device 30 to signal high speed spooling apparatus 32 into operation. When the notch 14 sees a photoelectric device PC-3, the flip-flop device 30 is turned off (spooling ended), after which a knife 34 is actuated to cut away the just-wound spool, and thus ready the spooling equipment for a next spooling operation. A web supply loop 35 is provided for tensionless spooling of the web 10.

The knife drive and spindle slot alignment, as well as means for providing the supply loop 35, form no part of the present invention. And the function of a photoelectric device PC-2 will be described later in connection with FIGS. 3 through 6.

As soon as the flip-flop device 30 is turned on by the photoelectric device PC-1, a preset count is applied, via gates 36, to a digital-to-analog converter 38, the output of which is applied to actuate a spindle (16)-driving servo 40. The servo 40 may include, as appropriate, a motor, amplifiers, feedback, etc.

Depending on the magnitude of a reference signal applied to the digital-to-analog converter 38, the signal output of the digital-to-analog converter 38 will, when the gates 36 are opened, snap to a high signal plateau P for driving the servo 40 at high speed. Digital-to-analog conversion techniques, as herein applied, are well known; see, for example, "Digital Computer and Control Engineering," McGraw-Hill Book Company, New York, N.Y., 1960, pages 742 through 744, Library of Congress Catalog Card No. 59-15055. In response to its signal input, the servo 40 rapidly runs up to a speed plateau Sp and, when the photoelectric device PC-3 sees the notch 14, the servo input signal is cut to zero, causing the spooling speed to coast down to a stop.

In accordance with the invention, the duration of spooling is clocked: The photoelectric device PC-1, at the start of a spooling peration, actuates a flip-flop device 44, so that clock pulses may be applied via a gate 46 to a counter 47; as soon as the servo has coasted to a stop, the output of a tachometer 48 disappears, causing a signal comparator 50 to trigger the flip-flop device 44 to close the gate 46. Thus, the counter 47 registers a count representing the duration that it takes, from start to finish, for the spooling operation. So long as the clocked duration is within certain limits (i.e., L > C > S), a preset up-down counter 51 applies its preset count to a digital-to-analog converter 52, the output of which is the reference for the digital-to-analog converter 38. Should the clocked duration exceed a preset certain amount (L) -- which can happen as a result of a servo gain change, and the like -- a comparator 54 produces, in response thereto, a pulse to increase the count of the counter 51, whereby the reference output of the digital-to-analog converter 52 will increase to increase the input to, and speed of, the servo 40. Similarly, in the event the clocked duration is less than a preset certain amount (S), a comparator 56 produces a pulse to decrease the reference for the digital-to-analog converter 38; which is to say that the servo 40 input, and speed, decreases. Thus, the input to and the speed of the servo 40 is regulated by the output of the digital-to-analog converter 38, thereby to keep constant the duration that it takes for each spooling operation.

The servo correction technique discussed above presupposes the adjustment of the servo 40 input after each spooling operation. In a preferred form of the invention, the circuit 60 is replaced by the circuit of FIG. 2, whereby only after a "clocked duration drift" of a given amount is the reference for the digital-to-analog converter 38 changed: A preset count is gated (62) into an up-down counter 64. After each spooling cycle, if the clocked duration is more or less than a given amount, or range of amounts, the up-down counter 64 is respectively increased or decreaed, say by one. Only when the counter 64 fills, or empties, is the count of the reference-changing counter 51 increased, or decreased; and so long as the count of the counter 64 drifts up and down within its fill-to-empty range of counts, the reference provided for the digital-to-analog converter 38 remains invariant. In other words, the technique of FIG. 2 obviates the need for continual servo speed correction, and permits slight drift of the servo speed within a prescribed tight range of speeds. An OR gate 66, operative with the gates 62, re-applies the preset count to the up-down counter 64 each time the counter 51 is increased or decreased, thereby to re-establish the reference count for the counter 64.

Rather than provide signal and spooling speed profiles for the servo 40, as indicated in FIG. 1, apparatus according to the invention preferably employs a (composite) signal-speed profile like that indicated in FIG. 4: A large signal input is applied to the servo 40 in response to a notch-produced signal from the photoelectric device PC-1, causing the servo speed to run rapidly (dashed line 70) to a high speed plateau; when the notch sees the photoelectric device PC-2, the signal input to the servo 40 is cut gradually to a low level, causing the servo speed to run down gradually to a low speed plateau from which quick braking can be easily effected; and when the photoelectric device PC-3 sees the notch, the signal input to the servo is cut to zero, causing the servo speed to drop extremely quickly to zero (dashed line 72).

To implement the signal-speed profile of FIG. 4, apparatus according to the invention employs the circuit of FIG. 3 as a substitute for the circuit 80 of FIG. 1: In response to the notch-produced signal output of the photoelectric device PC-1, the flip-flop device 30 gates (36') a high plateau preset count into a down counter 82. At the instant the photoelectric device PC-2 sees the notch, a flip-flop device 84 opens a gate 86 to allow clock pulses to pour into the down counter 82, causing the count of the counter 82 to reduce gradually to a low plateau count: the count of the counter 82, as it counts down, is continually compared with a preset count representing a desired low speed plateau; and at the moment the compared counts are equal, a comparator 88 pulses the flip-flop device 84 to close the gate 86. By applying the count of the counter 82 to the digital-to-analog converter 38, the speed profile of FIG. 4 obtains for the servo 40.

For optimum efficiency in the spooling operation, it is desired to run at high speed as long as possible and, conversely, to run at low speed for as short a time as possible: To this end, the invention proposes the substitution of the circuit of FIG. 5 for the circuit 90 of FIG. 3, whereby the duration of slow speed running is clocked and kept within a prescribed range of short times. To keep the duration of slow speed running within its prescribed range, apparatus according to the inventon proposes the effective shifting of the time for actuating down-counting from the high speed plateau to the low speed plateau: a lengthened slow speed duration calling for a double-delay in the start of down-counting (thereby to extend the duration of high speed spooling a bit); a desired, or aim, slow speed duration calling for a single delay in the start of down-counting; and a shortened slow speed duration calling for no delay in the start of down-counting (thereby to shorten the time for high speed spooling at the expense of a lengthened period for slow speed spooling).

At the moment that the down-counter 82 reaches the low plateau count, causing the comparator 88 (FIG. 3) to produce an output pulse, a flip-flop device 100 (FIG. 5) is actuated to open a gate 102 so that clock pulses may be applied to a counter 104. By applying the zero spooling speed signal (comparator 50, FIG. 1) to the flip-flop device 100 at the end of the spooling cycle, the flip-flop device 100 is again actuated to close the gate 102, thereby to produce in the counter 104 a count c representing the duration of slow speed spooling. The slow speed duration count c is compared with a pair of preset reference (long and short) counts 1, is in comparators 106,108 and, depending on which, or neither, of the comparators 106,108 produces a coincidence pulse, one of three flip-flop devices 110, 112,114 is actuated. (The flip-flop device 114 is actuated by a pair of inhibit devices 116,118 acting through an AND gate 120.) A pulse generator 122, in response to a notch-produced signal output from the photoelectric device PC-2 produces three differently phased gating pulses .phi..sub.1,.phi..sub.2,.phi..sub.3, and, depending on whether the slow speed duration is too long, too short, or just right, one of such three gating pulses actuates the flip-flop device 84' to permit down-counting pulses to be applied via the gate 86 to the counter 82. In other words, depending on which (slow speed) duration-indicating flip-flop device 110,112, or 114 has been actuated, one of three AND gates 124, 128, 126, respectively, is opened to permit, via an OR gate 130, one of the three phased gating pulses .phi..sub.3,.phi..sub.1, .phi..sub.2, respectively, to define the start of down-counting. FIG. 6 indicates that the phased gating pulses have the effect of shifting the location for the photoelectric device PC-2 so that the duration for slow speed spooling is, in actuality, determined by the time that the system permits for high speed spooling.

Again touching on the basic tenets of the invention -- but not on the preferred circuit details which have been disclosed -- two features singly and together work to provide the instant spooling control; the control of spooling speed in accordance with the clocking of the spooling duration; and the control of, by clocking, a low speed spooling duration which occurs within the overall spooling duration.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. For example, it would be well within the purview of the invention to program a general purpose computer to perform many of the teachings herein described.

Claims

What is claimed is:

1. Apparatus for controlling the spooling of a discrete length of web material having indicia thereon for starting and stopping said spooling comprising:

a. means upon which said spool of web material is formed,

b. servo means for driving said first-named means,

c. clocking means responsive to said indicia for timing the duration of a spooling operation and generating a signal representing said duration, said signal being utilized in a succeeding spooling operation,

d. means for signalling that the said web material has a zero velocity, indicating the completion of said spooling operation,

e. means responsive to said means for signalling for disabling said clocking means,

f. means for providing a signal representing a reference duration, indicating a desired nominal spooling duration,

g. means for comparing said reference duration signal and said signal representing the clocked duration,

h. means for applying an input signal to said servo means, and

i. means responsive to the output of said comparing means for varying the input signal to said servo means to keep constant the duration for said succeeding spooling operation.

2. The apparatus of claim 1,

a. wherein said means for applying a signal to said servo means is a digital-to-analog converter,

b. wherein said means for varying the input to said servo means is means for providing a variable reference signal to said digital-to-analog converter, and

c. wherein said apparatus includes means for applying a spooling speed representative signal to said digital-to-analog converter.

3. The apparatus of claim 1 wherein said means for comparing comprises:

a. an up-down counter,

b. means for presetting said counter,

c. means for increasing and decreasing the count of said counter in response to a clocked duration signal which may be, respectively, greater or less than said duration reference signal, and

d. means cooperative with said up-down counter for increasing and decreasing the input to said servo means when said up-down counter respectively fills and empties.

4. The apparatus of claim 3 wherein said means for increasing and decreasing the servo means input comprises:

a. a presettable up-down counter, the count of which is increased and decreased in response to the filling and emptying of said first-named up-down counter, and

b. a digital-to-analog converter cooperative with said second-named up-down counter for providing said reference for said first-named digital-to-analog converter.

5. The apparatus of claim 2,

a. wherein said means for applying a spooling speed representative signal to said digital-to-analog converter is a presettable down-counter, and

b. wherein said apparatus includes means responsive to said indicia for starting and stopping said spooling for respectively presetting and clearing said downcounter.

6. The apparatus of claim 5 including:

a. clock pulse producing means,

b. means responsive to said indicia for applying said clock pulses to said down-counter after said counter has been preset and before said counter has been cleared, and

c. means cooperative with said down-counter for ending the application of clock pulses to said down-counter when the count of said down-counter has dropped to a predetermined amount.

7. The apparatus of claim 6 including:

a. means for further varying said servo means input signal so that said servo means may have a first high speed plateau and a second low speed plateau,

b. means for clocking, and for producing a signal corresponding to, the duration that said servo means runs at low speed,

c. means for producing a signal representing a low plateau reference duration,

d. means for comparing said low plateau reference duration signal with said clocked low plateau duration signal, and

e. means responsive to said last-named means, and cooperative with said means for further varying said servo means input signal, for adjusting the time for commencing the application of clock pulses to said down counter, thereby to keep constant the duration of the low speed plateau of a succeeding spooling operation.

8. Apparatus including spooling means for spooling a web having indicia thereon that defines the starting and stopping of said spooling, comprising:

a. servo means for driving said spooling means,

b. a signal source for applying a drive signal to said servo means,

c. first and second signal-producing means responsive to said indicia on said web for respectively applying and removing the signal output of said signal source from said servo means,

d. detector means for producing a signal at the moment when said spooling speed becomes zero,

e. means, cooperative with said first signal-producing means and said detector means, for clocking the time difference between the occurrence of signals from said first signal-producing means and said detector means,

f. means for generating a difference signal representing said time difference, and

g. means responsive to said difference signal and to a predetermined reference duration signal for increasing the signal output of said signal source in a succeeding spooling operation when said time difference is more than said predetermined duration, and for decreasing the signal output of said source when said time difference is less than said predetermined duration.

9. The apparatus of claim 8 including:

a. third signal-producing means responsive to said indicia on said web, after said first signal-producing means and before said second signal-producing means produce their respective signals, for reducing to a low plateau the output of said signal source,

b. means for clocking and for generating a signal corresponding to the duration of said low plateau signal, and

c. means responsive to the low plateau clocked duration signal and to a predetermined low plateau reference duration signal for varying the occurrence of the signal output of said third signal-producing means to keep constant the duration of the low plateau signal of a succeeding spooling operation.