US3680529A - System for selectively coating webs - Google Patents

Abstract

Apparatus is disclosed for applying a coating, or the like, to one part of a web which is formed of spliced-together parts. Each web part has a different light transmission quality; and a splice detector produces pulses, the widths of which are characteristic of such transmissions. A pulse width discrimination circuit detects pulses wider than a given amount; and when a splice passes the detector, causing a pulse-width change, coating is effected. A circuit is provided for distinguishing between different kinds of splices.

Description

United States Patent P/e coal Francis 14 1 Aug. 1, 1972 [54] SYSTEM FOR SELECTIVELY 2,961,990 11/1960 Wruck ..118/2 COATING WEBS 3,143,017 8/1964 Donnell ..83/211 [72] Inventor: Richard H. Francis, Webster, NY. Primary Examiner john P. McIntosh [73] Assignee: Eastman Kodak Company, Attorney-W. T. French, R. F. Crocker and Robert F.

Rochester, N.Y. Cody [22] Filed: March 4, 1971 [57] ABSTRACT [21] Appl' 120931 Apparatus is disclosed for applying a coating, or the like, to one part of a web which is formed of spliced- 52 us. 01. ..11s/s,11s/9,11s/11 together P Each web part has a different light 51 Int. Cl ..B05c 11/00 transmission q y; and a splice detector Produces [58] Field of Search "118/8, 2 9 250/219 FR pulses, the widths of which are characteristic of such 250/219 83/211 transmissions. A pulse width discrimination circuit detects pulses wider than a given amount; and when a splice passes the detector, causing a pulse-width [56] References cued change, coating is effected. A circuit is provided for UNITED ES PATENT distinguishing between different kinds of splices.

I 2,551,329 5/1951 Klemola ..118/8 9 Claims, 3 Drawing Figures 62 g? Coal/17g I Control/er minnow: Han 3.680.529

sum 1 OF 2 Coal/77g can fra/Ier 'RICHARD H. FRANCIS INVENTOR.

ATTORNEY SYSTEM FOR SELECTIVELY COATING WEBS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates in general to apparatus for coating webs; in particular, the invention provides a device for selectively applying a coating to a web that is comprised of, say, two different kinds of webs, the coating to be applied to one kind, but not to the other kind, of web.

2. Description Relative to the Prior Art The coating of a paper web with a photographic emulsion is an environment within which the invention is especially useful:

As is the practice, a tough plastic leader is spliced to the end of a large roll of paper which is to be emulsioncoated, the leader being threaded through a pre-coat conditioning alley, then through a coating alley, and then through a drying alley to a windup station. Because of the labyrinthine nature and length of the alleys, the leader is about 70.0 feet long. Absent the use of the leader, i.e. with paper extending from roll to windup, a large section of the paper will not be emulsioncoated, and would therefore be waste. Use of the leader, on the other hand, (i.e. without the practice of the invention), means that part of the leader will be emulsion-coated, again causing costly waste.

SUMMARY OF THE INVENTION Apparatus, according to the invention detects the splice between the paper web and the plastic leader, and in response thereto causes timely operation of a coating hopper to apply emulsion exclusively to the paper web:

An infrared pulser transmits a train of light pulses through a web to an infrared receiver. The received pulses are amplified, shaped (one way for the plastic leader, and another way for the paper), and, depending on such shaping, pulses of respective widths are produced and applied to a relay, the relay being cooperative to signal the operation of the coating hopper. The optical transmission of the plastic, vis-a-vis the paper, indicates the kind of pulse width definition which is effected: plastic causes narrow pulses to be produced; paper causes wider pulses to be produced. By properly defining the width of the narrow pulses, i.e. the energy therein, to a point just below the pull-in threshold for the relay, the wider pulses will alone trigger the relay for the application of emulsion to the a er. p ince the plastic leader is quite long, it is itself frequently comprised of spliced plastic parts. To avoid the problem of intermittently operating the coating hopper to apply emulsion in response to plastic-toplastic splices, the invention further proposes a splicediscrimination circuit, whereby plastic-to-plastic splices are ignored, but plastic-to-paper splices effect operation of the coating hopper: Operation of the splice-discrimination circuit is based on the fact that a short duration signal change occurs when a plastic-toplastic splice passes an inspection station, whereas when a plastic-to-paper splice passes such station, the duration of signal change is thereafter virtually contin-uous. The invention proposes that the detected splice signal be applied in parallel to an AND circuit, one branch of which has a time delay therein which is longer than the time that it takes a plastic-to-plastic splice to pass the inspection station. Thus, when a plastic-to-plastic splice passes the inspection station, one, or the other (but not both), of the AND circuit input branches is excited; contrarily, when a plastic-topaper splice passes the inspection station, the AND circuit, after the time delay, has both of its input branches continuously excited, causing it to produce an output for operation of the coating hopper.

OBJECT OF THE INVENTION To improve the efficiency and economy of apparatus for coating webs.

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

FIG. 1 is a schematic diagram illustrating a circuit for practicing the invention,

FIG. 2 is a logical circuit diagram illustrating apparatus for providing the splice-discrimination technique of the invention, and

FIG. 3 is a series of pulse diagrams useful for describing the invention.

Referring to the Figures, a supply of paper 10 is threaded through a labyrinth 12 within which various conditioning operations are performed to prepare the paper, say, for emulsion-coating. The lead end 14 of the paper has spliced thereto, at 16, a tough plastic leader 18 which, as indicated above, is approximately 700 feet long, and transmits light fairly well. The leader-and-paper together comprise a continuous web 19 that runs past a splice detection station 20, and past an emulsion-coating station 22, being thence fed through an emulsion-drying station 24 to a web takeup station 26. A distance X obtains between the splice detection station 20 and the coating station 22.

The splice detection station 20 is comprised of an infrared pulse transmitter 28 and receiver 30, which are so disposed on opposite sides of the web 19 that light pulses are transmitted through the web to the receiver 30:

An astable multivibrator 32 applies a train of voltage pulses, via a coupling circuit 34, to a two-stage (Darlington) amplifier 36. The second stage of the amplifier 36 has its collector-emitter circuit serially connected to a light-emitting diode 38, whereby, whenever the amplifier second stage is pulsed into conduction, a current pulse passes through the diode 38, causing an infrared light pulse of a given amplitude (waveform A, FIG. 3) to be applied through the web 19 to a phototransistor 40. The amplitude of the light pulse input to the phototransistor 40 depends on the optical transmission characteristics of the web 19.

Consider that the phototransistor 40 secs light pulses which are transmitted through the plastic leader: Because of the relatively good transmission characteristics of the leader 18, strong voltage pulses (waveform B, FIG. 3) are applied to the base of a transistor 44, causing the transistor 44 to discharge a normally charged capacitor 46 to ground. Thereafter, the capacitor 46 recharges, causing a series of generally sawtooth signals (waveform C, FIG. 3) to be applied to the base of a transistor 48. At the moment each sawtooth signal raises to a level C, the transistor 48 is gated into conduction, thereby effectively grounding the collector of the transistor 48 until the end of each such sawtooth signal. Attendantly, the collector signal of the transistor 48 periodically drops from a high level to a low level (waveform D, FIG. 3), causing a transistor 50 coupled to receive the output of the transistor 48 to produce pulses (waveform E, FIG. 3) of 5 a given width. The coupling circuit into the transistor 50 comprises first and second potentiometers 52,54, the potentiometer 52 being set to regulate the amplitude of the input to the transistor 50 (to cancel the effects of ambient light received by the phototransistor 40), and the potentiometer 54, in conjunction with a feedback capacitor 56, being set to change the widthwise dimensions of the pulses appearing at the collector of the transistor 50, whereby the energy of each such pulse will be just insufficient to overcome the choke effect of, and pull in, a relay 58.

Consider now the passage of the plastic-to-paper splice 16 by the splice detection station 20: As soon as the splice 16 reaches the detection station 20, the light pulse signals received by the phototransistor 40 drop in intensity (waveform F, FIG. 3) and, attendantly, the capacitor 46 is barely periodically discharged. Because the capacitor 46 is, for all intents and purposes, continually charged (waveform G, FIG. 3), the transistor 48 substantially continually conducts, causing its collector output to be virtually nil (waveform H, FIG. 3). Thus, a virtually continuous voltage (waveform I, FIG. 3), i.e. wide pulses with brief discontinuities therebetween, appears at the collector of the transistor 50 to pull-in the relay 58 (waveform J, FIG. 3), such discontinuities in the collector (50) voltage being ignored, again because of the choke effect of the relay 58.

The relay 58 is adapted to actuate a coating control circuit 60: So long as plastic leader 18 is the transmission medium for the light pulses produced by the lightemitting diode 38, narrow pulses which are insufficient to pull-in the relay 58 are produced; as soon, however, as paper attenuates such light pulses, wider pulses are produced by the transistor 50, causing the relay 58 to close a switch 580 to apply a detected splice signal to the coating control circuit 60.

As noted above, it frequently obtains that the plastic leader 18 is itself made of a number of spliced sections. To avoid turning on a coating controller 61, which operates a coating hopper 63, in response to plastic-t0- plastic splices, the invention provides for the application of the detected splice signal to a pair of relays 62,64, one of which (64) is a time delay relay (waveforms J and K, FIG. 3). The time delay of the relay 64 is longer than the time it takes a plastic-toplastic splice to passthe splice detection station 20, while running the web at a normal coating speed; and the switch contacts 62a,64a of the relays 62,64 are serially connected to an AND gate 68.

For a steady state light pulse change, as will occur for a plastic-to-paper splice, both relays eventually get simultaneously energized, causing their respective serially-connected switches to apply a gate-opening signal to the AND gate 68. For a brief light pulse change, as will occur for a plastic-to-plastic splice, one (62), and then the other (64), of the relays is intermittently actuated, causing the AND gate 68 to remain closed.

FIG. 2 illustrates the logical functions performed by the relays 62,64, and their respective switches; and

similar character notations, save for primes, have been used for the corresponding parts of FIGS. 1 and 2.

With the gate 68 open, a pulser 70 applies pulses to a counter 72, the number of such pulses being representative of the length of web 19 that runs past the splice detection station 20 after a splice has been detected. When the count of the counter 72 reaches a count corresponding to the distance X between the splice detection station 20 and the coating station 22, a pulse is applied to a self-holding relay 74, causing the coating controller 61 to operate the coating hopper 63 (waveform L, FIG. 3).

As will be appreciated from the above, several features bear heavily on the operation of apparatus according to the invention: One feature is the idea of defining pulse widths characteristic of different web materials, whereby a coating control circuit may be gated, or not, into operation when one, but not the other, web material is seen; another feature is the idea of using the choke effect of a relay to prevent actuation of the relay for narrow, but not wide, pulses; another feature is the idea of logically combining a coating command signal with a time delayed coating command signal (which time delay is greater than the time it takes for a false splice to pass a splice detection station), to prevent operation of a coating hopper in response to such false splice.

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, apparatus according to the invention could be used to turn on other web-treating equipment (e. g. corona dischargers, etc.

What is claimed is:

1. In a system for applying a coating or the like to a moving web which is comprised of, at least, one part which is to be coated, and a second part which is not to be coated, said system including:

a. means (22) for applying said coating to said web,

b. signal responsive means (61) for controlling the operation of said means for applying said coating, and

c. means for applying a signal to said controlling means,

said signal applying means being comprised of:

a. means (38) disposed to one side of said web for generating a train of light pulses, and for transmitting said light pulses through said web,

b. means (20) disposed to the other side of said web for receiving said light pulses which are transmitted through said web,

0. circuit means (50) cooperative with said receiving means for producing a train of electrical pulses having widths corresponding to the attenuation of said light pulses by said web,

d. pulse width discriminating means (58) responsive to electrical pulses of a given pulse width for producing a coating command signal, and

e. means (60) for applying said coating command signal to said signal responsive means 61).

2. The improved system of claim 1 wherein said pulse width discriminating means is a relay having a pull-in threshold which is sufficient to prevent the said relay from being actuated by pulses having widths less than a certain amount.

3. The improved system of claim 1 wherein said means for applying said coating command signal to said signal responsive means comprises AND gate means having first and second inputs, said second input having time delay means therein, and said two inputs being both adapted to receive said coating command signal, said AND gate means having its output applied to trigger the operation of said signal responsive means.

4. The improved system of claim 1,

a. wherein said pulse width discriminating means is a relay having a pull-in threshold which is sufi'icient to prevent the said relay from being actuated by pulses having widths less than a certain amount, and

. wherein said means for applying said coating command signal to said signal responsive means comprises AND gate means having first and second inputs, said second input having time delay means therein, and said two inputs being both adapted to receive said coating command signal, said AND gate means having its outputs applied to trigger the operation of said signal responsive means.

5. The improved system of claim 1 wherein said pulse generating and receiving means are, with respect to the direction of web travel, disposed before and spaced from said means for applying said coating by a predetermined distance, and wherein said means (60) for applying said coating command signal to said signal responsive means (61) includes means (70,68,72) responsive to said coating command signal for measuring the length of web that travels past said means for applying said coating after said coating command signal has been produced, and for delaying the operation of said signal responsive means (61) for a time corresponding to said web length.

6. The improved system of claim 5 wherein said pulse width discriminating means is a relay having a pull-in threshold which is sufficient to prevent the said relay from being actuated by pulses having widths less than a certain amount.

7. The improved system of claim 6, wherein said means for applying said coating command signal to said signal responsive means comprises AND gate means having first and second inputs, said second input having time delay means therein, and said two inputs being both adapted to receive said coating command signal, said AND gate means having its outputs applied to trigger the operation of said signal responsive means.

8. The improved system of claim 5, wherein said means for generating and transmitting a train of light pulses produces infrared pulses, and wherein said means for receiving light pulses is responsive to infrared light.

9. The improved system of claim 1, wherein said means for generating and transmitting a train of light pulses produces infrared pulses, and wherein said means for receiving light pulses is responsive to infrared light.

Claims (9)

1. In a system for applying a coating or the like to a moving web which is comprised of, at least, one part which is to be coated, and a second part which is not to be coated, said system including: a. means (22) for applying said coating to said web, b. signal responsive means (61) for controlling the operation of said means for applying said coating, and c. means for applying a signal to said controlling means, said signal applying means being comprised of: a. means (38) disposed to one side of said web for generating a train of light pulses, and for transmitting said light pulses through said web, b. means (20) disposed to the other side of said web for receiving said light pulses which are transmitted through said web, c. circuit means (50) cooperative with said receiving means for producing a train of electrical pulses having widths corresponding to the attenuation of said light pulses by said web, d. pulse width discriminating means (58) responsive to electrical pulses of a given pulse width for producing a coating command signal, and e. means (60) for applying said coating command signal to said signal responsive means (61).

2. The improved system of claim 1 wherein said pulse width discriminating means is a relay having a pull-in threshold which is sufficient to prevent the said relay from being actuated by pulses having widths less than a certain amount.

3. The improved system of claim 1 wherein said means for applying said coating command signal to said signal responsive means comprises AND gate means having first and second inputs, said second input having time delay means therein, and said two inputs being both adapted to receive said coating command signal, said AND gate means having its output applied to trigger the operation of said signal responsive means.

4. The improved system of claim 1, a. wherein said pulse width discriminating means is a relay having a pull-in threshold which is sufficient to prevent the said relay from being actuated by pulses having widths less than a certain amount, and b. wherein said means for applying said coating command signal to said signal responsive means comprises AND gate means having first and second inputs, said second input having time delay means therein, and said two inputs being both adapted to receive said coating command signal, said AND gate means having its outputs applied to trigger the operation of said signal responsive means.

5. The improved system of claim 1 wherein said pulse generating and receiving means are, with respect to the direction of web travel, disposed before and spaced from said means for applying said coating by a predetermined distance, and wherein said means (60) for applying said coating command signal to said signal responsive means (61) includes means (70, 68,72) responsive to said coating command signal for measuring the length of web that travels past said means for applying said coating after said coating command signal has been produced, and for delaying the operation of said signal responsive means (61) for a time corresponding to said web length.

6. The improved system of claim 5 wherein said pulse width discriminating means is a relay having a pull-in threshold which is suffIcient to prevent the said relay from being actuated by pulses having widths less than a certain amount.

7. The improved system of claim 6, wherein said means for applying said coating command signal to said signal responsive means comprises AND gate means having first and second inputs, said second input having time delay means therein, and said two inputs being both adapted to receive said coating command signal, said AND gate means having its outputs applied to trigger the operation of said signal responsive means.

8. The improved system of claim 5, wherein said means for generating and transmitting a train of light pulses produces infrared pulses, and wherein said means for receiving light pulses is responsive to infrared light.

9. The improved system of claim 1, wherein said means for generating and transmitting a train of light pulses produces infrared pulses, and wherein said means for receiving light pulses is responsive to infrared light.

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