US2796678A

US2796678A - Control device for paper driers

Info

Publication number: US2796678A
Application number: US459648A
Authority: US
Inventors: Lewis A Mckeown
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-10-01
Filing date: 1954-10-01
Publication date: 1957-06-25
Anticipated expiration: 1974-06-25

Description

June 25, 1957 L, A. M KEOWN CONTROL DEVICE FOR PAPER DRIERS' s Sheets-Sheet 1 4 Filed Oct. 1, 1954 IN VEjV TOR. LEW/5 ,4. M KEOW/V J1me 1957 L. A. MQKEOWN 9 78 CONTROL DEVICE FOR PAPER DRIERS INVENTOR.

LEW/S ,4, MC/(L-OWN BY MM.

A r row/Er L. A. M KEOWN CONTROL DEVICE FOR PAPER DRIERS June 25, 1957 5 Shets-Sheet 3 Filed Oct. 1, 1954 Fig.8.

INVENTOR. LEW/.5 /4./VCKOWN BY ma ,4 7'7'0R/VEY United States atcnt CONTROL DEVICE FOR PAPER DRIERS Lewis A. McKeown, Plattsburg, N. Y.

Application October 1, 1954, Serial No. 459,648

14 Claims. (Cl. 34-43) This invention relates to control devices for paper making machines and is particularly directed to novel means for detecting breakage of the web of paper in the drier rolls and for breaking the web at the wet end of the drying apparatus when such breakage occurs.

In the paper manufacturing industry, the most common type of drying machines embody a number of heated drier rolls. The paper stock after being formed into a continuous sheet or web is passed to the drier and about the drier rolls. In modern machines, the paper is pulled through the drier rolls and travels at high speeds, sometimes in excess of 1000 feet per minute. The wet sheet is quite fragile and at times may break as it is traveling over the drier rolls. When such a break occurs the free end of the web tends to adhere to the drying roll which it engages and, therefore, it builds up on the roll and beneath the protecting felt blanket which passes about the outer sides of the rolls.

As soon as a break is discovered, the operator at the wet end of the drier must break the Web at the couch to prevent additional paper from being drawn into the drier. However, the operator at the wet end has numerous duties to perform and is seldom in a position to note the occurrence of a break in the Web. As a result, the break frequently is not discovered until the broken end of the web appears at the dry end of the machine. The delay thus occurring often allows a large amount of paper to build up and become tangled about the rolls whereupon the entire plant must then be shut down and every bit of tangled paper removed before normal operations can be resumed. Obviously, the sooner the flow of paper can be stopped after a break in the web occurs the less paper will be tangled in the rolls and the sooner the mill can be returned to production.

Numerous mechanical and electrical alarm systems have been suggested heretofore to overcome this problem, however, none of these has been very successful. The requirements which any alarm system must meet in order to gain acceptance are extremely rigorous. For example, the temperature in the vicinity of the drier rolls is quite high and the air is extremely dusty. Moreover, the area in which such devices can be located is quite limited due to the close spacing of the rolls and the location of the mechanical drives for the rolls. Furthermore, the paper vibrates quite severely as it travels through the drying machine.

Oviously, no device can be used which will mark or spoil the paper, whereas optical and mechanical systems of the prior art have become clogged with dust and soon become faulty and uncertain in operation.

These disadvantages of prior art devices are overcome with the present invention and mechanism is provided which will set off a warning signal the instant a break occurs. Further, the equipment serves to break the sheet at the wet end of the drying machine so that no additional paper willbe drawn into the drier to tangle about the rolls. The device of the present invention is not affected by heat, dust or the vibration of the sheet and may readily be installed on either new or existing machines without modification thereof. At the same'time, the device requires very little maintenance and is easy to service, if necessary. Moreover, the device preferably an alarm and activating mechanism which breaks the sheet at the couch.

Accordingly, it is an object of the present invention to provide a novel device which will promptly detect a break in a web of paper traveling through a drying machine in a paper mill.

Another object of the present invention is to provide a novel device which will detect a break in a web of paper traveling through the rolls of a drier in a paper mill and which may readily be installed in either new or existing paper machines without modification thereof.

A further object of the present invention is to provide novel means for detecting a break in a sheet of paper traveling through the drying machine in a paper mill which means is not affected by heat, dust or vibration of the sheet and which requires little maintenance and is simple to service.

A specific object of the present invention is to provide a novel device which will automatically detect a break in a sheet of paper traveling through a drier and simultaneously set otf a signal, break the sheet at the couch and automatically reset itself for renewed functioning when operation of the drier is resumed.

These and other objects and features of the present invention will be apparent from the following description thereof taken in connection with the figures of the accompanying drawings. t

In the drawings:

Fig. 1 is a perspective View of a drier equipped with the device of the present invention and having the frame removed for clarity;

V Fig. 2 is a perspective of a portion of the drier of Fig. 1;

Fig. 3 is .a side elevation of the detecting device of Fig. 2;

Fig. 4 is a schematic view showing the relative positions of the drier rolls, paper web, felt blanket and the.

detector element of Figs. 1 and 3;

Fig. 5 is a perspective of a modified detector mecha nism;

Fig. 6 is a perspective of a detail of the detecting mechanism of Fig. 5;

Fig. 7 is a left side elevation partly in section of a portion of the mechanism of Fig. 5 with the side of the dust box removed for clarity;

Fig. 8 is a front elevation of the mechanism of Fig. 7 with the front of the dust box removed for clarity;

Fig. 9 is a view similar to Fig. 8 showing the parts inthe positions they take when the solenoid is activated;

Fig. 10 is a schematic View showing the relative positions of the drier rolls, paper sheet and the detector element of the mechanism of Fig. 5; i

Fig. 11 is a wiring diagram of the electrical circuit of the present invention;

Fig. 12 is a schematic view of the sheet breaking mechanism at the couch; and

Fig. 13 is a wiring diagram of a modified form of thedetecting circuit included in Fig. 11.

In that form of the invention chosen for purposes of Patented June 25, 1957 in upper and lower tiers and about which the web of poper being manufactured successively passes as it is dried. A felt web or blanket 6 passes over the drier rolls 2'-o'f rhe'upp'er tier and under the adjac'e'nt'snziall roll whereas, felt blanket 8 passes under the drier rolls 2 of the lower tier'and' over the adjacent roll 10 in a similar manner. The'paper web 4 is thus held between the drier rolls andthe felt blanket during the greater part of its travel and is only exposed during a small arc of contact with each roll and as it moves from one roll to another.

Since the webof paper may break at any point, it is desirable to detect a break in the web as soon as possible sd-thatthe delay can be minimized. However, it is not possible to detect a break in the web while it is covered with the blanket and, therefore, the detecting means must be located between the upper and lower tiers of drier rolls where the sheet is exposed for contact by a detecting element. In order to detect a break. as soon as possible, detectors, indicated ge'nerally'at 12, may be positioned adjacent one or more of the drier rolls 2 so that, as soon a as. the sheet is no longer passing about, a drier roll 2, the nearest the detector 12 will be operative to give an alarm. To afford the greatest protection, one of the detectors 12 should be positioned adjacent each of the drier rolls 2. In

this way, an alarmfwill be given instantaneously and the 1 time lost from production will be minimized.

.Due to the proximity of the various elements in the drier, the space available for the detector mechanism is quite small asv seen in Fig. 2. For these reasons, the detector illustrated'in Figs. 2-4 is preferably employed. As seen in Figs. 2 and 3, the detector 12 comprises an arm 14 which is-pivotally mounted at 16 between its ends on asupport lS secured to the frame 20 of the drying machine. The end 24 of arm 14 extends into the drier between one of the drier rolls 2 and the adjacent small rollQlO so as to be movable about hinge 16 toward and away from that portion of the drier roll wherein the web ofp'aper is exposed but is still supported by the roll. The opposite end of arm 14, beyond the hinged supporting point,,16, is provided with a counterweight 22 which is adjustable to slightly overbalance'the long arm 24 of arm 14 so that, due to gravity, there is a slight tendency for end 24, of 14 to rise. However, when the detector is ,mountedadjacent one of the drier rolls of the lower tier, as seen in Fig. 1, counterweight 22 is adjusted to slightly underbalance end 24 of arm 14' so that, under gravity, end 2 4 will fall to contact the web 4 on drier roll 2 but the full weight of arm 14 will not be applied to the web as this might cause scratching of the web.

A resilient, electrically conductive detecting element, such as a light spring wireor flat strip 26, is mounted adjacent the tip of end 24 of arm 14. The pivot 16 about which arm 14 is movable is preferably positioned at an angle of about as shown in Fig. 2, so that the action of counterweight, 22 and the. angular mounting of,,..arm

14'"w'ill cause" detecting element 26' to movein a sideward and upward direction into contact with that portion of the web' of paper 4 ,whichjis exposedbut still supported by the drier roll 2. The detecting element therefore normallytends to assume the solid line position of Fig. 4. Howevehwh'eln' the paper sheet 2 is being threaded into the drier, or in other instances in which it is undesirable for the detector to be in contact with, the drier roll 2 or papersheet 4, the ar'tn14 can be withdrawnto the dotted line position of Fig. 4. Of course, when the detector is applied to one of the drier rolls of the lower tier, these directions will be'reversedand' end 24 of arm 14 will move downward and sideward to contact the paper and will -be withdrawn sidewar'df and upward to a position adjacent felt blanket 8.

, To facilitatethe withdrawal of-a'rni 11:4, a solenoid 28 is mounted adjacent the short end ofar'rn 14 in any suit: able mannenas by bracket 3 0, .Solenoid28 acts upon a movable member 32 which isjconnecteias by free moying'jchain 34, to the. short end of 14; When solenoid" 28 is energized, it' raises member 32 thereby tector is mounted adjacent a drier roll in the lower tier.

In such a case, member 32 is raised by gravity and lowered when solenoid 28 is activated, since member 32 is mounted on the short end of arm 14 and counterweight 22 is adjusted to underbalance end 24 of arm- 14. Member 32 is preferably provided with

stops

36 and 38 to the detecting circuit is connected to the drier roll 2 in any suitable manner. During normal operations, the

a paper sheet 4. will pass between detecting element 26 and the drier roll' 2. Since paper has well known di-electric properties, the sheet 4 will act as an insulator and no current will flow in the detecting circuit. Should the paper sheet break, however, detecting element 26 would contact the drier roll thereby completing the detecting circuit which would set off the alarm. As pointed out above, if a' detector 12 is located adjacent each of the drier rolls 2 in the drying machine, the alarm will be given almost instantaneously when a break occurs. Consequently, the sheet 4 can be broken at the couch more rapidly and the amount of paper becoming tangled, and, thus, the time lost from production, will be substantially reduced.

While the detector 12 described above is adequate in' most instances, there are occasionally situations where it will not beent irely satisfactory. For example, if the drier rollsshould become dirty, detecting element 26 may not beable to establish proper contact with the roll and no alarm will be given; While this situation rarely occurs near the dry end of the drying machine, it does occasionally happe'n near the wet end. To overcome such a possibility, the detector shown in Figs. 5l0 may be substit'u'ted for that described above. I

As seen inFig. 5, the modified detector comprises a tubular arm 44' which extends between one 'of the drier rolls 2 and'the" adjacent small roll 10 in substantially the same manner as arm 14 of the detector of Figs. 1-4. Arm" 44 is not movable, however, but is rigidly secured adjacent one end thereof to the frame of the drying machinebysupport46 and projects perpendicularly from the support A dust box 48 is mounted on the end of arm 44 and; protects thedetector mechanism from dust. The detecting element, in this case, is a rodlike member 50 which extends freely through tubular arm 44 into dust box 48 and is formed with the opposite ends 52 and 54 thereof extending perpendicularly from the' body 560i the rod 50 and at right angles to each other, as seen in Fig. 6. If desired, a cap 58 may be provided closing the end of arm 44 and having a small hole formed therein through which rod 50 may project, as indicated in Fig. 5. Also, the cap 58 may be provided with a guard 60 extending beyond the end 52 of rod 50 to direct any loose paper away fromend 52 of rod 50. With this construction, end 52 of rod 50 rests gently against the sheet 4 of paper. being manufactured, as shown in Fig. 10. The weight of rod SOis supported by arm 44. Thus, the only, pressure on sheet 4 iscaused by gravity acting upon

ends

52 and 54 of rod 50 and tending torotate rod 50 about itsaxis; W I

Within dust box 4 8,' rod 5 0 passes through a' hole 62 adjacent one end of a support 64 which is formed of electrically conductive material and is secured to, but in- 'sulated from, the dust box 48. Rod is freely rotatable within hole 62 but is maintained constantly in electrical contact with support 64. Solenoid 66, mounted upon an insulating panel 68 which is secured to the dust box 48, may be energized through wires 70 to raise arm 72 to the position illustrated in Fig. 9. Upon demagnetization of the solenoid 66, arm 72 falls by gravity. to the position shown in Figs. 7 and 8. Arm 72 hasa portion 74 projecting perpendicularly from the lower end thereof and is provided with

stops

76 and 78, which may be adjustable, to restrict its length of travel. Therefore, when solenoid 66 is energized, arm 72 is raised causing portion 74 thereof to raise end 54 of rod 59 to the position shown in dotted lines in Fig. 7. This causes rod 50"to pivot about its axis moving end 52 thereof out of the way to permit the drying machine to be rethreaded.

One side of'the detecting circuit is connected to-support 64 by wire 80 while the other side of the circuit is connected by wire 82 to the body of solenoid 66. Under normal conditions, end 52 'of rod 50 bears lightly against paper sheet 4 and end 54 is held a slight distance away from portion '74 of arm 72, as seen in full linesin Fig. 7. Should-the sheet 4 break, end 52 of rod 56 will fall causing rod 50 to pivot about its axis, and, thus, allowing end 54 .to strike portion 74 of arm 72 and completing the detecting circuit through support 64, end 54 of rod 50, arm 72; and the body of solenoid 66.

As stated above, when the sheet breaks during the dry- 7 ing operation, it must be broken at the wet end of the drying machine in order to reduce the amount of paper becoming tangled in the drier rolls. The sooner this is done, the less time will be lost from production. Accordingly, with the present invention, as soon as a break occurs, circuits are immediately initiated to simultaneously and automatically break the sheet at the couch, move the detectors out of the way, set off an alarm and reset the mechanism so that all the operator need do to rearm the detectors is to push a single button. In order to accomplish this, the circuit shown in Fig. 1-1 is used. Preferably, 16 volts alternating current is used in the detector circuits since this reduces the danger of injury to workmen in the event they should accidentally get shocked while clearing the tangled paper from the drier rolls.

As seen in Fig. 11, current from power lines 84 passes through a normally closed push button switch 86 and a low amperage fuse 88. Push button 86 is preferably located adjacent the couch and serves as a reset button. From the fuse 88, current passes through the normally closed contacts 98 of relay 92 and, thence, to stepdown transformer 94 which supplies 16 volt current to the detecting circuit. For simplicity, only two detectors are shown, designated generally at 96 and 98, although, in practice, any desired number of detectors may be used. Also, any type of detectors may be used although those types described above are preferred.

When the sheet breaks in the drying machine, the detecting circuit is completed through one of the detectors and current flows through relay 1% closing contacts 102. This permits the volt current to energize relay 104 closing contacts 186, which maintains relay 104 energized throughout the procedure, and contacts 108 which initiate the following series of operations. Closing of contacts 108 permits current to energize relay 92 thereby opening contacts 90 so that no current can flow to transformer 94. This eliminates the flow of 16 volt vurrent in the detecting circuit and prevents possible firehazards. Closing of contacts 108 also energizes solenoids 111) and 112 of

detectors

96 and 98 thus causing the detecting elements of the detectors to be withdrawn as described above. In addition, current passing contact 188 lights a warning light 114. Light 114 may, obviously, be placed in any desirable location, however, it is generally preferable to place it adjacent the machine tenders desk to inform him that the sheet has broken in the drying machine and the automatic sheet breaker is at'work. Fin-' ally, when contacts 108 close, current is permitted to flow through normally closed contacts 116 to energize relay 118. Relay 118 then closes contacts 120 and 122. Contacts 120, upon closing, pass current to energize solenoid 124 which actuates air valve 126 causing air under pressure in air line 128 to pass through jets 130 and break the paper sheet 4 adjacent the couch rolls 132 as seen in Fig. 12.

Obviously, if desired, solenoid 124 may release a shear or other means for breaking the sheet. It has been found, however, that high pressure air, for example, 80 pounds per square inch, will serve very eifectively and requires less care and maintenance than other sheet breakers. Furthermore, an air blast is preferable in a device which automatically resets since it does not have to be replaced orrearmed but is ready for a second operation as soon as it is shut off from' the first. To shut off the air blast, current from contacts 120 also passes through a thermal resistor 134 which creates heat while passing only a very small current. As thermal resistor 134 heats up, it acts upon thermally responsive contact 136 which is connected in parallel with thermal resistor 134 and which expands and finally closes. The resistances of thermal resistor 134 and thermally responsive contact 136 should be carefully chosen since the current passed by thermal resistor 134 should be insuflicient to energize relay 138, whereas the relay 138 should be operated by the current passed upon closing of contact 136. Also, a definite period of time, for example, ten seconds, should be required for thermal resistor 134 to generate enough heat to cause contact 136 to close. While resistor 134 is heating up, solenoid 124 will remain energized and the air blast will be directed at the sheet. Since the current through resistor 134 is not sufficient to actuate relay 138, the'current leaks off to the ground. However, when contact 136 closes, a considerably larger amount of current can flow and,, since resistor 140 prevents its flowing directly to the ground, the current will flow through Wire 142 and contacts 122 to energize relay 138 before passing tothe ground. When relay 138 is energized, it causes' contacts 116 to move to the dotted line position. This causse relay 118 to deenergize, opening contacts 120 and 122 which demagnetizesrelay 124, thus, shutting off the air blast. 4 v When the drier rolls have been cleared and production has been resumed, the operator can rearm the detector by simply pressing push button 86. This breaks the current to relay 104 thereby opening

contacts

106 and 108.. When contacts 108 open,

solenoids

110 and 12 are de magnetized, allowing the detecting elements to move'into= their sheet engaging positions, and relay 92 is deenergized,; thus closing contacts 90 and allowing current to flow to step down transformer 94 which reestablishes the 16 volt: current in the detecting circuit; Also, upon opening of contacts 108, warning light 114 is extinguished and relay 138 is deenergized, allowing contacts 116 to return to the solid line position. Thus, the entire mechanism is returned to the condition it had prior to breaking of the sheet and the device is ready to repeat the operations described above in the event of subsequent sheet breakage.

While the device described above functions very well, it is conceivable that the detectorcould be triggered by a small hole in the sheet passing under the detecting element. Where this presents a problem, two or more of the detectors may easily be connected in series so' that it is necessary for both'of the detectors to be triggered before the automatic sheet breaker is set into operation= Thus, as seen in Fig; 13, both

detector

144 and 146 would have to be triggered simultaneously before the detecting circuit would be completed. Detectors 144 and .146 may be of either of the types described above and, furthermore, may either be positioned in spaced relation adjacent the same drier roll, or, if desired, detector 144 may be located adjacent one drier roll. while detector 146 is located adjacent' another drier roll.

A de ic for d te t n we b eaka i t e dr eta p pe l; said dev c comp in d e t me 9 id:%di6 i i d ie r ol iq a d'dri and contactin e what Pap ein u a u ed, e e tr l cuit means'connected to said detecting means, and a warnns d i e nc ud n mea s ope abl upo completion f a d cir ui o b eak ng a dw b a jac t the wet end of said drier, said detecting-means being movable uponbreakage of said web to complete said circuit and actuate said warning .device, and means responsive to completion of said circuit for withdrawing and deenergizing-said detecting means to facilitate rethreading said web into said drier. i

. 2. A device for detecting web breakage in the drier of a paper mill, said device comprising a detecting arm located adjacent one of the drier rolls of said drier and extending substantially parallel to the axis of said drier rolls, said arm being pivotally supported adjacent one end thereof, a counterweight mounted on said one end of said detecting arm and being of such weight as to slightly overbalance the other end of said detecting arm, a-deteoting element projecting from said other end of said detecting arm and normally contacting the web of paper beinglmanufactured, an electrical circuit connecting said detecting element and said drier roll, and a web breaking device operable upon completion of said circuit, said detecting element being movable to contact said drier roll upon breakage yof said Web,there'by completing said cir cui't and setting .off said web breaking device. a

"3. A dev'ce for detectmg Web breakage in the drier of a paper mill, said device comprising a detecting arm locatedadjacent-one of the drier rolls of said drier and ex tending substantially parallel to the axis of said drier roll, a vertical support pivotally connected to said detecting arm'adjacent one end ofsaid detecting arm, said detecting arm extending substantially perpendicularly from said support in opposite directions and at an angle to the axis of sa id support, a counterweight mounted on said one end of said detecting arm and beingof such'weight as to 'slightlyloverbalance the other end of said detecting arm, 'a detecting element extending substantially perpendicularly from s'aidother end of said detecting arm 7 and normally contacting the Web ,ofrpaperb'eing manufactured, an electrical circuit connecting said detecting element and said drier roll, and a web breaking device operable .upon completion of saidfoircuit, said detecting element'beingmovable upon breakage of said web to coritact said drier. roll, thereby completing said circuit and setting olf said web breaking device.

4; A device for'deteeting' web breakage in the drier of a paper mill, said device comprising a detecting arm lo.- cated adjacent one of the drier rolls of said drier and extending substantially parallel to the axis of said drier roll, a vertical supportpivotally connected to said detecting armadjacent one end of said detecting arm, said detecting arm -exte'nding substantially perpendicularly from said support in opposite directions and at an angle to the axis of said supportpa counterweight mounted on said one end of said detecting arm and being of such weight as 'to slightly overbalanee the other end of said detecting arm, adetecting element extending substantially perpendicularly from said other end'of" said detecting arm and normally contacting the-web of paper being manufactured, an electrical circuit connecting said detecting element and said drier roll, 'a web. breaking: device operable upon completion of 'said circuit, saiddetectingelement being movable upon 'breakag'e'fof said web to contactsaid drier roll, thereby completing said'cirouit and' setting off said web breaking device, and means connected to said detecting arm for causing said detecting arm to pivot about said support for Withdrawing said detecting element and thus facilitating rethreading of said web into said drier.

5. A device for detecting web breakage in a paper mill, said device comprising'an electrically conductive detecting element in the form of a rod with the end portions thereof extending perpendicularly from the intermediate portion of the rod, said detecting element being rotatable about the axis of said intermediate portion and having one of said end portions normally contacting the web of paper and being held in an elevated position by said web, an electrical circuit having one end thereof maintained in continuous electrical contact with said detecting element and the other end of said circuit being located adjacent the end portion ofsaid detecting element opposite from said one of said end portions, a web breaking device operable upon completion of said circuit, whereby upon breakage of said web, said detecting element will be caused by gravity acting on said end portions thereof to rotate about said axis thereof, allowing the end portion thereof opposite said one of said end portions to contact said other end of said circuit thus completing said 7 circuit and setting off said web breaking device, and means for'rotating said detectingelement about said axis thereof to elevate said one end portion above the web contacting position thereof to facilitate rethreading said web.

6. A device for detecting web breakage in the drier of a paper mill, said device comprising a cylindrical arm located adjacent one of the drier rolls of said drier and extending substantially parallel to the axis of said roll, said arm being supported adjacent one end thereof, a detecting element formed of a generally Z-shaped rod having a body portion extending generally through said cylindrical arm and being freely rotatable therewithin and having the end portions of said rod projecting substantially erpendicularly from said body portion and approximately at right angles to each other, one of said end portions projecting beyond the end of said cylindrical arm opposite said support and normally engaging the web of paper being manufactured whereby said one end is normally maintained in an elevated position, the other of said end portions extending beyond the end of said cylindrical arm adjacent said support, a dust box mounted on the end of said cylindrical arm and protecting the elements therein against dust, a supporting arm mounted within said dust box and electrically insulated from said box, said supporting arm being formed with a hole therein adjacent one end thereof, said other endportion of said rod extending into said dust box and through said hole in said, supporting arm, said rod being freely rotatable within said hole while maintaining continuous electrical contact with said supporting member, a solenoid mounted within said dust box and electrically insulated therefrom, the armature of said solenoid having an arm extending substantially perpendicularly therefrom and into the path of rotation of said other end of said rod, an electrical circuit having one end thereof connected to said supporting arm and the other end connected to the body of said solenoid, and a web breaking device operable upon completion of said circuit, said circuit being completed upon breakage of said web allowing said one end of said rod to fall by gravity thus rotating said rod about its axis causing said other end of said rod to engage said arm of said armature thereby completing said circuit and setting on said web breaking device, said solenoid being operable to raise said armature causing said arm thereof to raise said other end of said rod above the normal position of said rod thus rotating said rod about the axis thereof to withdraw said one end thereof to facilitate rethreading said web into said drier. V

7. Automatic web breaking mechanism for the drier of a paper'milL'said mechanism comprising means for detecting'breakage of the paper web during the drying operation, a low voltage electrical circuit completed by said detecting means upon breakage of said'web, a high '9 voltage electrical circuit completed in response to completion of said low voltage circuit, means responsive to completion of said high voltage circuit for de-energizing said low voltage circuit, a warning device operable upon completion of said high voltage circuit, means responsive to completion of said high voltage circuit for breaking said web adjacent the wet end of said drier, and means included in said high voltage circuit for breaking said high voltage circuit and re-energizing said low voltage circuit.

8. Automatic web breaking mechanism for the drier of a paper mill, said mechanism comprising means for detecting breakage of the paper web during the drying operation, a low voltage electrical circuit completed by said detecting means upon breakage of said Web, a high voltage electrical circuit completed in response to completion of said low voltage circuit, means responsive to completion of said high voltage circuit for de-energizing said low voltage circuit, a warning device operable upon completion of said high voltage circuit, means responsive to completion of said high voltage circuit for releasing a blast of air under pressure against the Web of paper adjacent the wet end of said drier, means activated by said high voltage circuit for shutting off said air blast after a predetermined length of time, and means included in said high voltage circuit for breaking said high voltage circuit and re-energizing said low voltage circuit.

9. Automatic web breaking mechanism for the drier of a paper mill, said mechanism comprising means for detecting breakage of the paper web during the drying operation, a low voltage electrical circuit completed by said detecting means upon breakage of said web, a high voltage electrical circuit completed in response to completion of said low voltage circuit, means responsive to completion of said high voltage circuit for de-energizing said low voltage circuit, a warning device operable upon completion of said high voltage circuit, means responsive to completion of said high voltage circuit for breaking the web of paper adjacent the wet end of said drier, means responsive to completion of said high voltage circuit for withdrawing said detecting means to facilitate rethreading said web into said drier, and means included in said high voltage circuit for breaking said high voltage circuit thereby re-energizing said low voltage circuit and returning said detecting means to the web engaging position thereof.

10. Means for detecting web breakage in the drier of a paper mill and automatically breaking the Web adjacent the wet end of said drier, said means comprising a detecting arm located adjacent one of the drier rolls of said drier and extending substantially parallel to the axis of said drier roll, said arm being pivotally supported adjacent one end thereof, a counterweight mounted on said one end of said detecting arm and being of such weight as to slightly overbalance the other end of said detecting arm, a detecting element projecting from said other end of said detecting arm and normally contacting the web of paper being manufactured, a low voltage electrical circuit connected to said detecting element and said drier roll, said detecting element being movable upon breakage of said web to contact drier roll and thereby complete said low voltage circuit, a high voltage electrical circuit completed in response to completion of said low voltage circuit, means responsive to completion of said high voltage circuit for de-energizing said low voltage circuit, a warning device operable upon completion of said high voltage circuit, means responsive to completion of said high voltage circuit for breaking said web adjacent the wet end of said drier, means responsive to completion of said high voltage circuit for causing said detecting arm to pivot about said support for withdrawing said detecting element and, thus facilitating rethreading said web into said drier, and means included in said high voltage circuit for breaking said high voltage circuit thereby re-energizing said low voltage circuit and permitting said detecting arm to 10 pivot about said support to return said detecting element to its web engaging position.

11. Means for detecting web breakage in the drier of a paper mill and automatically breaking the web adjacent the wet end of said drier, said means comprising an electrically conductive detecting element in the form of a rod with the end portions thereof extending perpendicularly from the intermediate portion of the rod, said detecting element being rotatable about the axis of said intermediate portion and having one of said end portions normally engaging the web of paper being manufactured and being held in an elevated position by said sheet, a low voltage electrical circuit having one end thereof maintained in continuous electrical contact with said detecting element and the other end of said low voltage circuit being located adjacent the end portion of said detecting element opposite from said one of said end portions whereby upon breakage of said web, said detecting element will be caused by gravity acting upon said end portions thereof to rotate about said axis thereof, allowing the end portion thereof opposite said one of said end portions to contact said other end of said circuit thus completing said low voltage circuit, a high voltage circuit completed in response to completion of said low voltage circuit, means responsive to completion of said high voltage circuit for de-energizing said low voltage circuit, a warning device operable upon completion of said high voltage circuit, means responsive to completion of said high voltage circuit for breaking said web adjacent the wet end of said drier, means responsive to completion of said high voltage circuit for rotating said detecting element about said axis thereof to elevate said one end portion above the web engaging position thereof to facilitate rethreading said web into said drier, and means included in said high voltage circuit for breaking said high voltage circuit thereby re-energizing said low voltage circuit and permitting said detecting element to rotate about said axis thereof to return to said web engaging position.

12. Automatic web breaking mechanism for a paper mill, said mechanism comprising means for detecting breakage of the paper web, an electrical circuit completed by said detecting means upon breakage of said web, web breaking means operable in response to completion of said circuit, means responsive to completion of said circuit for tie-energizing said detecting means, resetting means operable in response to completion of said circuit for resetting said web breaking means after it has broken said web, and means operable upon momentary interruption of said circuit for re-energizing said detecting means and resetting said mechanism to operation.

13. A device for detecting web breakage on a paper inachine, said detecting device comprising an electrically conductive rod with the end portions thereof extending perpendicularly from the intermediate portion of the rod, one of said end portions normally being maintained in an elevated position by engagement with the web of paper, the other end portion of said rod being housed in a dustproof enclosure, said rod being rotatable about the axis of said intermediate portion thereof upon breakage of said web by gravity acting upon said one of said end portions, and a control circuit having one end thereof connected to said other end portion of said rod inside said enclosure, the opposite end of said circuit being connected to a contact located adjacent said other end portion of said rod inside said enclosure, said circuit being completed upon breakage of said web by said other end portion of said rod engaging said contact as said rod is rotated.

14. A control system for use in a paper mill comprising a low voltage detecting circuit, detecting means in said circuit responsive to breakage of a web of paper passing through the mill, a high voltage circuit controlled by the low voltage circuit, web breaking means icdtai'td by the hi' gh voltage cii'iiit and loeaca at; a Rfii (iit fli-h are me at this patem able upon momentary 1IIIILIPIOD of the hlgh voltage V r circiiit' for resetting the web Br'eaking niefi's ffr 6pm 1399-596 m 261 1916 lion thereofl 5 2,020,056 ,Glbbs Nov. 5, 1935 7 2,074,237 Pierce Mar. 16, 1937 2,085,128 Staeg'e June 29, 1937