US2668700A - Drier for printing presses - Google Patents

Description

Feb. 9, 1954 R. G. ZIMMERMAN DRIER FOR PRINTING PRESSES 9 sheets-sheet 1 Filed May 25, 1949 .mml

Inventor Pz'chard G.

mmerman Feb 9, 1954 R. G. ZIMMERMAN 2,668,700

DRIER FOR PRINTING PRESSES Filed May 25, 1949 '9 sheets-sheet 2 UML mv HRM Ina/en lor'L Richard G -mmerman /bg Cua, E219?, MJ* lA/ Feb. 9, 1954 R, G, ZIMMERMAN 2,668,700

DRIER FOR PRINTING PRESSES Filed May 25, 1949 9 Sheets-Sheet 3 Im/entor Richard. G. )im rnerrnarl Feb. 9,

R. G. ZIMMERMAN DRIER FOR PRINTING PRESSES Filed May 25, 1949 9 Sheets-Sheet 4 PRESS `SM5-51; Alva ConrnoLLe-n RosITIo/v EMERGENCY STOP ,z FROM FULL .SPEED unmsn ASSEMBLY IMMEDIATELY RErRAcTs 'D Gas TuIrNL-o Orr Ama BuRNERs FLUSHED UNTIL BUTTON B PRESSE!) EMERGENCY STOP FRoM PARTIAL SPEED BURNER ASSEMBLY IMHEDIATELY RsrRAcTs Gns TuRIvEn OFF Anp BuRIvERs FLusHEo UNTIL Burro/v B hasta Fnass `SPEED AND CoIvTIQoLLgR Pos/Tio TIME 1 Inl/enter fichar-d 6. immerrnan Feb- 9, l954 R. G. zlMMl-:RMAN 2,668,700

DRIER FOR PRINTING PRESSES Filed May 25, 1949 9 Sheets-Sheeil 6 Ina/en tor Richard L'mmerh-ran Feb- 9, 1954 R. G. Z1MMERMAN 2,668,700

DRIER FOR PRINTING PRESSES Filed May 25, 1949 9 sheets-sheet v m/en for 000000000000000000 .OAL QV` Richard brim-arman vel L OW\\\QM.\%\ E Wigm ll mmfww bvm.

i .rv/ |Ql 1 \V 09.6%@

v MMBOJQ l9l Feb. 9, 1954 R. G. ZIMMERMAN 2,668,700

DRIER FOR PRINTING PRESSES Filed May 25, 1949 9 sheets-sheet s LI L3 DRUM CONTACTS H0 TaR C /kcwr invent?" RL'charo( G. Zimmerman www Feb. 9, 1954 R. G. ZIMMERMAN l 2,668,700

DRIER FOR PRINTING PRESSES Filed May 25, 1949 9 Sheets-Sheet 9 r A l 1 I nl: 4- l 1 i TLF I'T Bl I Uil gwen ,64 man l Inventor* Richard mmerman Patented Feb. 9, 1954 UNITED VDRIER FOB PRINTING PRESSES Richard G, Zimmerman, Lawrence, Kans.

ApplicationMay '25, 1949, Serial N 0.- 95,340'

(Cl. "26S-f3) 1.6 llainis. VYl

The present invention relates Lto printing presses vand more particularly rto aheaters .for .drying the ink film.

Throughout the course of printing :press de velopment there has been a sharp line .of .des marcation between newspaper presses and magazine presses. Newspaper presses enable high speed printing not only of newspapers but of otherr printed matter where quality .and appearance are not of paramount importance. Such printing is done/on absorbent paper and using non-drying ink. Because of the absorption of `the ink inthe pores -oi Mthe paper, the printing .fis characteristically dull and even the brighter colors are dead -and lifeless. Furthermorathe ink lm 4must be "kept 'relatively thin since the absorbent quality of lthe paper-is limitedetherewise smearingwill result.

'For high vvquality printing #of heavy lms V.and brilliant colors it has in the past Abeen necessary to'resort to the more expensive and complicated magazine press. Magazine printing -isfdone y*with driable ink usuallyhav-ing avol-atile soiventand on coated or non-absorbentfpaper.

Whenus'ing volatile lso'la'ent inks, 'the inlrmust be ys .rtiiicially dried, this being conventionaiiy done by ,theuse'of steam drum-sor by gasburners. Steam drums 'are disadvantageous'since they are extremely expensive, oi heavyeonstructien, and require 'a large amount of'space, r`to `say 'nothing of the problem of furnishing steam. Infaddition since. drying depends apen conducted heat, 'the velocity of the web must Abe kept relatively low. Conventional gas burners-'also haverather-seripps limitations. Even'where the `flarne is plegvyedgdirectly `on the web, the dryingprocess issuperpial and ineiiicient. Solvent is driven from the 'su-rface of vthe film and not from ythe body o f the lm or .from the pores 'ci the "paper, .and the maximum speed 'is -aconsequenbly limited An even more vimportant limitation has to do swith operation at reduced .Speeds or upon .emergency shutdown. The normal heat output combined with the heat stored in the burners -and surrounding metal .parts ,frequently results scorching when the web is slowed'and `(3.0llflplete burnout when the lweb is brought to .ainorevsndden stop. The surface of the jini; alter drying by .conventionalgas burners is A,often excessively rough to .the touch .and the iiame ,playing ,on

the web :tends .to introduce wrinkles, giving .rise

to luneven Y.dry-ing .and Ascoren streaks. .ln ,addition, conventional burner -araneements 4reallife frequent maintenance .and replacement dile v1to the extreme operating temperatures.

vBecause of `the :expense :.of a magazine press many printing establishments have attempted to do 'high-quality worknn .La :newspaper press by using inks having a volatile solvent. However, this involves so :many .disadvantages and corn.-v plications that it Ahas-never before been accQr-h plished vfrom :a practical standpoint. in .the'first place the vavailable room :in .the kvicinity .of .a newspaper press lis severely restricted and 'cone ventional VAheaters for dry-ing 'the ink .cannotv be accommodated. Even when such heaters are used it -is=necessary vto reduce theispeed consider: ably from the normal value lin order to insure that the ink is dried suiiiciently so as not to stick tothe successive roliers with which the printed face comes vintocontact. Iffenough heat .is ap.-

pl-ied to thepaper to dry-'the inkrat the normal web speeds, it lis foundthat vthe paper will .in-.-Y

variably beseorchedfas the press is slowed down to a stop.

While it is known that radiant heatersare par: t-icularly -eieetive in Vthe drying of iilms because of the -penetrationof fthe 'heat below the Ysiniface of the Yrilrns, attempts to ruse radiant heaters in printing presses have ybeenr fou-nd in general :to be disappointing; and impractical,V the vpossibilities of scorching on ls`l1ut=down ibeing greatly fin! creased. rvThe reason for l:this rwill be apparent when -it is -considered'that -a radiant lheater lby its very `nature f-must operate `in fthe fred-ff or radiating temperatnrevrange. Particularly when using gaS-iired radiant burners it is found that the radiating element ldoes not l--irnrnediately all to a safe temperature when the supply nof fuel is eut on in Atl-ie normal way, but `continues lfor some time to radiate .'.energy lat `a lrate which lis more 1than suicient to cause scorching. 4Any attempts -to `reduce the 'residual revelation by cuttingdownen theoapacity of the -fburnerswiilL of `coli-rise, produce la corresponding. sacrifice .of heat under normal running conditions, particu;- 1arl-y the extremely high speed rconditions .characteristic of a newspaper press. 1=Inanendeavor to overcome theseiects of Vtlc-ie residual heat and to controlfthe Vheat under reduced speed conditions elaborate pivoting and llinllsalge iarr-ange.u ments have fbeen used so lthat the 'burners are twisted "bodily .to vdirect the YYresidual iieat .away from the web. 'This ingeneral .requires that the individua/'l Lburners be :manipuiated which :leads to mechanical -.complexity,` excessive cost large volumetric `.recluirements. Besides, Aany burner .movement ini/pires l jarring @ne material of which the radiating surfaces flfmed.

Where attempts have been made to mount conventional burner arrangements in confined spaces nearby parts of the press are so overheated that rubber rollers, lubricated bearings and other parts of the press are put in jeopardy to say nothing of the discomfort of the press operators. Additional difficulties arise from the problem of disposing of the fumes and inflammable condensate in the ducts.

Accordingly it is an object of the invention to provide an improved dryer for a printing press which is capable of large heat output enabling drying of magazine-type inks at high speeds, even at speeds approaching the standard operating speed of a modern newspaper press. It is another object to provide a high capacity web drier in which radiation and convectionare so embodies an improved burner arrangement in which the burners are mounted for movement as a unit, minimizing the number of moving parts. It is a related object to provide a dryer which is safe and fool-proof in operation but which is nevertheless simple and straight-forward and in which the cost per foot of drying the web is reduced to a minimum. It is a more detailed object of the invention to provide a burner construction `and arrangement which is extremely long-lived in spite of extreme operating conditions, and which requires a small fraction of the replacement and maintenance demanded by conventional web dryers.

co-ordinated that scorching is avoided under all conditions, both transient and steady state, which may be encountered in the practical operation of a press. More particularly, it is an object to provide a dryer employing radiant heat in which the temperature is brought to a safe level when the press is brought slowly to a halt or suddenly stopped as under emergency conditions. It is a further object to provide a dryer which is of large heating capacity but Which nevertheless occupies less volume than conventional dryers, being adapted for installation on existing newspaper and magazine presses with a minimum of modification thereof and Without danger of overheating the rubber rollers or any other parts of the press.

It is still another object to provide a gas-tired dryer for volatile inks in which the gas is more eiciently utilized than in conventional dryers. It is a related object to produce a gas-fired dryer capable of not only evaporating solvent from the surface of an ink lm but which is also effective to drive the solvent from the body of the film and from the paper itself, the freed solvent being then completely burned to furnish additional heat and to prevent the solvent from passing into the atmosphere or from condensing in the exhaust ducts to form a re hazard and to endangerV exhaust fans and other equipment.

It is a further object of the invention to provide a dryer having gas-fired burners with an improved arrangement for co-ordinating the supply of gas and supply of cooling air with the speed of the web. In one aspect it is an object to coordinate the degree of exhaust with the supply of cooling air.

It is an object to provide a novel control scheme which acts automatically upon varying the speed of the web driving motor to cause the valves supplying the burners as well as the burner positioning means to go through a predetermined cycle of operations both upon increasing the speed of the Web and upon slowing down the web prior to shut-down for maintaining the web at a safe drying temperature. Y y

It is an object allied with the foregoing to provide a radiant dryer in which the latent heat that is stored under normal running conditions is not only kept to a minimum but safely utilized during deceleration for drying purposes, with t; e remainder of the latent heat being so completely dissipated after the press comes to a stop that the danger of scorching is eliminated. In one of its aspects it is an object of the invention to provide a control scheme in which the timing of the operations may be manually controlled by an operator.

It is a further object to provide a drier which Other objects and advantages will become apparent upon reference to the speciiication and to the detailed drawings appended hereto in which:

- Figure 1 is a diagrammatic side elevation of amagazine press including driers embodying the present invention.

Fig. 2 isa detailed elevation of a web drier as.

used in the magazine press of Fig. 1 with the near side wall partially .removed to Vshow the burner assembly.

Fig. 3 is a more or less diagrammatic representation of the improved dryer installed on a conventional newspaper press.

Fig. 4 is a partial face view ofthe burner as` sembly. Y

Fig. 5 shows in perspective several successive burner faces.

Fig. 6 is a horizontal section of a line of v burners taken along the line -6-6 inFig. 2.

Fig. 6a is a fragmentary detail view along line tia-'6a of Fig. 6 showing clamping means fory maintaining the burner manifold in assembledv position.

Fig. 7 is a vertical section looking along the` line 1-1 in Fig. 4.

Fig. 8 is an enlarged fragmentary section taken along the line 8-8 in Fig. 4.

Fig. 9 is a rear view of the burner assembly Fig. 13 is a burner valve control circuit as included in block form in Fig. 12.

Fig. 14 shows a control circuit for the motor which positions the burner assembly and included in block form in Fig. 12

Fig. 15 shows graphically the operating sequence of the control circuit on starting up the press.

Fig. 16 shows a typical operating sequence on slowing the press to a normal stop.

Figs. 1'7 and 18 show the sequence during any emergency stop from full and partial speed conditions, respectively.

Referring to Figure 1 there is shown a portion of a magazine pressZil. Theincoming web 2| passes over a first impression cylinder 22 and the iirst side of the web is printed by a plate cylinder 24. The printed'web then passes down- Wardly into a dryer indicated generally at 25. This dryer is constructed in accordance with' the present invention and is shown in detail in the figures to be discussed. The web then passes around `cooling drums 26, 21 and .into .a subsequent section of the press so Vthat the remaining side .of vthe web Amay be printed. This is accomplished by 'plate cylindersill, 3|, the web passing around an vimpression cylinder 32. If desired, .a conventional oil offset arrangement 33rnay be .used in conjunction with the `impression cylinder 32. The web subsequently passes upwardly through a .dryer 34 whichI is similar to that .previously vreferred to and around cooling drums 35, 36. The outgoing run cf the web may then 'befed into a slitter, cut-off cylinder and folder as required for putting the printed vmatter into la form for distribution.

Turning now to Fig. 2 the dryer 34 and the associated drums 35, y3| are Vset forth in :greater detail. The dryer includes a burner assembly I4|!! which iis vpreferably enclosed in `a box-iike housing 4| and arranged parallel to the vertical run 'of the web 2|. The burner assembly includes lines of burners which extend horizontally and spaced vertically fromone another along the web. r'Ihese lines designated lil- 30 inclusive, project radiant heat voutwardly in the direction of vthe web. Arranged parallel to the web on the opposite side from the burner assembly is a `back-up plate 6| which serves to reect the heat back onto the web and to conduct away the unrelectedheat.

Before `proceeding with the more detailed structural features it will be helpful to refer briefly to Fig. 3 which shows an 'equivalent installation ina newspaper press. Corresponding elements will be designated with the same reference numerals used in the magazine press but with the subscript a. The printing unit 23a includes two printing couples for printing on both sides of the web. The incoming web Zla is fed around an impression cylinder 22a and the web is printed on its first side by a plate cylinder 23a.. The web subsequently passes upwardly through a dryer V25a and around water filled vcooling drums 26a, 21a. The web next passes downwardly into contact with the second impression cylinder 32a which co-operates with a plate cylinder 30a. An oil offset arrangement 33a rides in contact with the impression cylinder 32a. After the second impression has been made the web rises vertically through a dryer Sta after which it passes about cooling drums 35a, 35a. After thus being printed on both sides, the web 2|a leaves the press unit for subsequent slitting and folding and combination with other similar webs. Since the dryer installation may be substantially identical in the two types of presses the subsequent discussion will concern itself only with the installation as made in a magazinepress.

In accordance with one of the aspects of the invention means are provided for generating radiant heat at refractory surfaces having low heat storage capacity and for maintaining the burner mounting, the fuel supply lines, and other metal objects within the region of radiation at a temperature which is extremely low compared'to that of the burner. The manner in which this is VAaccomplished in the present instance will lbe made clear vby inspection of Figs. 2 and 5 to-S inclusive. Each'of the burners inthe lines 5| to V60 has a refractory face -pcrtion l1li which is heated to brilliant red heat by the combustion of gas-air mix in contact therewith. Centrally arranged in the face portion and serving to `physically support it isia stem 1|.. lThe Alatter is threaded `into a tubular manifold 12 of lrectangularsection which supports a L:lineof burners.- The .refractory burner .ma-` terial is vreinforced .bynmetal vwalls ,16, 11 which are .anchore'd'by screws or the like'tothemanifold v12'. These walls rare preferably of light gauge metaland perforated to reduce heat trans` mission as well as Vthe amount ,of heat which may Vbe storedtherein. Direct .rearward -low yof heatfrom the burner .is reduced by spacing 'the` .Ihe manifolds for the various lines of burners are all mounted in intimate thermal contact with a ',backplate 13 which is preferably formed of copper or othergood conducting metal. .In `con-y tact with the back` plate 13 aresuccessive convolutionsfof a vcooling coil 'Hl which conducts cooling water. The cooling coilmay also .be formed of copper sweated or brazed tothe conductive back plate '13.

In lorder to :minimize the direct transfer of heat Ato the back vplate 13 and the horizontally arranged manifolds 12, the spaces :betweenthe manifolds are lled with high temperature inf sulation 83 having extremely low heat storage capacity. Preferably such insulation'consists `of a series ofslabs or layers of asbestos, the layers being retained in lplace by the overhang of the edges of the burners as shown.

While it is possible to use various types lof burners 'having refractory heat radiating surfaces the illustrated form of burner has been-found to work out most satisfactorily. The construction of theindividual burners isset forth in some detail in Figs. 5 and 8. Here it will be seen that theA face portion 16 -of the burners `isfcupped to vform a recess 80. Centrally positioned within therecess and at the end of the stem y'|| is a nozzle -8l. A concave deflector 32 .positioned opposite the nozzle serves to deflect the gas-air mix downwardly into the recess so that it is burned .in intimate contact with the refractory material. In axial section the burners are generally cylindrical but attened on opposite sides sc thatV the individual burners may be stacked side vby side with the recessesof successive burnersintersecting one another. This produces a -continuous band of radiation across the entire vWidth of .the webv and also facilitates lighting the burners Asince the iiame from a pilot will quickly travel from one end ofthe line to the other. y

'I-o complete the discussion of the burner-.as sembly All, it includes at each 'end an upright channel 62 (Figo) which is covered with applate 63 welded or otherwise xed thereto. The channel includesvcooling coils 64. In order thatvan entire line of burners including its manifold may be maintained in contact with the back plate yet readily .removed from i the burner assembly, a clamp 65 lis used at each end ofthe vmanifold which is so constructedfas to Xenable forward withdrawal. In the present instance the clamp, which is C-shaped, is `mounted on vthe plate :.63 withits open side facing forwardly for receiving astub projection 66. The latter is 'butt Welded to the closed'end of the manifold 12. VAs'shown inthe detailed View Fig. 6a, the open side of the clamp -65 is spanned by means 'of a removableA bridgeBEWhich is maintained in place bysuitable bolts or the like 68. To facilitate withdrawalgof aburnerline, the pipes 69 supplying vgas ythereto extend rearwardly from the manifold and pass through suitable apertures in the back plate 13V of the cover plate 15. It will be understood that each of the pipes 69 is threaded so that it may be readily disconnected from the supply line. It will be apparent then, that any one of the lines of burners may be withdrawn for maintenance or replacement merely by uncoupling the rear ends of the pipes 69, removing the bridges 61 and drawing the selected burner lines forwardly.

Since all of the burner assembly parts having any substantial heat storage capacity are not only shielded against the direct transference of heat from the burners but are in intimate heat transferring relation to the cooling coils 14, it will be apparent that they will be kept at a low temperature. The surface presented toward the web by the burner assembly is formed almost entirely of refractory burner faces and insulating material, all having low heat storage capacity. Y

On the opposite side of the web from the burner assembly 43 is the back-up plate 6| providing a reflecting surface 85. For the purpose of completely enclosing the web and defining an air flow channel about the web as well as for preventing the escape of heat to the surrounding portions of the press, the back-up plate abuts a pair of side walls 81 which are spaced from one another just sufficiently to enable the slidable reception of the burner assembly 40 between them. In order to conduct away the excess heat striking the back-up plate 6| and the side walls 81, cooling coils 86, 88 are provided. These coils are preferably of copper or similar good conducting metal and are fastened in place by sweating or brazing. The side walls are preferably mounted for edgewise sliding on the press frame so as to provide access to the web for threading and inspection.

It will be apparent from the foregoing that the burners and web are surrounded by cooling coils arranged about all four sides. The manner in which these coils are supplied with cold water will be apparent on inspection of Figs. 9 and 10. Fig. 9 shows the arrangement of the cooling coils in the burner assembly while Fig. 10 is a diagrammatic view of the preferred form of circuitory system. It will be noted that the cooling coils 14 and B6 are arranged so that the successive convolutions are horizontal with the cooling water admitted at the bottom and drawn off at the top. This causes any steam which may be generated in these coils to be immediately fiushed out and replaced by the relatively cooler water. The latter avoids uneven cooling or hot spots and correspondingly reduces maintenance to a minimum. As shown in Fig. 10 the water is drawn from a cold water supply line directly into the cooling drums 35, 36 which are thereby kept at a very low temperature. The water exhausted from the cooling drums is then used in the remainder of the system. The cooling coils 64 and 88 arranged along the side walls of the burner assembly are supplied with cooling water independently. Vertical convolutions can be used at this point since the temperature is normally lower and there is less danger of developing steam.

To keep down the heat radiated rearwardly from the burner assembly as Well as to even out the temperature thereof a light metallic cover plate 15 is used. rhe spaces 19 between the coil convolutions may be lled with insulation if' desired to reduce the temperature of the plate 15. Y

. In accordance with one of the aspects of the invention means are provided for turning on the; burners and advancing the burner assembly 4|!A upon accelerating the web and for turning oi theA burners and bodily retracting the burnerassem` bly away from the web when it is brought to av to the web speed setting Will be discussed in av following section. Attention will first be given tov the mechanical positioning arrangement used in the present embodiment as set forth in Fig. 2.l The burner assembly 4B is mounted on suitable Ways which permit the face of the burner assembly to move through a range 9|.

a reduction Worm gear 9s to apply torque to a cross-shaft 95.

obstructedly slots |02 are cut in the side walls 81.`

Turning attention now to the lower portion of Fig. 2, an air blast line |||l is arranged parallel to the lower edge of the burner housing and in a position to direct air upwardly in the space between the burners and the web.

cussed in connection with Fig. 11.

Arranged at the upper end of the burner assembly to exhaust the cooling air as well as theI products of combustion of the gas and ink sol-` vent is an exhaust duct |20. This duct extendsthe width of the press andrhas a series of aperf tures or air inlets |24 along its lower surface. As

will be noted from the profile view of this duct in Fig. 2, the underside is concavely formed so as to closely follow the curvature 0f the cooling drum 35. In this way any vapor which tends tol cling to the moving web is eilectively withdrawn and does not escape into the atmosphere. *In carrying out the invention the exhaust duct |20 includes an additional set of apertures |22 whichv are substantially blocked oiT when the burner assembly Il@ is in its normal position closely adjacent the web. However, upon retraction of the burner assembly the apertures |22 are successively uncovered in order to increase the effective duct area and thus increase the capacity of the exhaust system. Vacuum is produced in the duct |28 by means of a suitable exhaust fan |23 (Fig. 10). As Will be understood by one skilled inthe Ventilating art, the exhaust fan will consume energy in accordance with the area of the inlet duct. It will be clear, therefore, that uncover' ing the ducts |22 serves automatically to increase' the volume of air exhaust from the system;

Movement in this range is affected by meansof ai burner assembly adjusting mechanism indicated generally at 92. This includes a motor 93 driving Rigidly mounted for rotation' With this shaft is a bell crank 96, the latter being connected to the burner assembly 4U by meansl Preferably the line ||0 has a series of holes or nozzles spacedv along its length capable of discharging a'largel volume of air. The valve arrangement for controlling the flow of air to the line'l l0 will be disfeeding a, compressedl air line E33. thelines |39, |33 respectively are dam-pers. |34,; |35V whichA are. adjusted by a combustion conmeans` of anr air by-pass valve |31. Y that the main gas valve |3|V is shut 01T, opening the air by-pass valve |31 will enable air at high In carrying. out another. aspect. of they present inventionmeans are provided for turningoff the burner lines. on` shutdown and for discharging cooling air` directly through the fuel system of the' burnersv and into contact with the radiating surfaces thereof. The effect of this is toA reduce the radiating surfaces immediately to a safe temperature, the action being faciiitated by the low .specific heat of the refractory burner' material.

Inaddition thecooling air is heated by such. con-A tactand.- thevconvected'currentsof heated air are directed from the burner toward the web. Thus, such. latent-heat as may be present in the burners is effectively utilized to complete thedrying as the web is slowed and broughtto a stop.

'Ihesystem here Used in accomplishing the above is setA forth diagrammaticaliy in Fig, l1. 1 Gas issuppliedthrough a liner |3il having a sole- .noid gas valve. tti. p the remaining v ves the system are controlled by means of the control circuit. (Fig. 12) which will be describedv in detail as the discussion pro- The latter valve as well as ceeds. Air is supplied by means of a blower |32 In series4 with troller |236. The latter. is of conventional design capable of producing an optimum fuel-air ratio for all rates of flow. The amount of gas-air miX at the discharge of the combustion controllerv may' be adjusted manually and left in an adjusted position, the generatedv heat being controlled by the other solenoid valves in thesystem. The' damper |35v in the air line is by-passed by velocity to pass through. the system for cooling purposes.

Under normal operating conditions the gas f mixture passes through a mixtureY supply line |40, through avalve. |4| and into-a header |42 which supplies all of the burner manifolds with fuel. Interconnecting the header |42 to the lines of burners are Valves |5.|-|5|| respectively. The air blast line HU which directs air upwardly between. the burners. and the web is connected to the supply line. |40 bymeans of a Valve |49;

in ordervto Vprevent the burners from blowing back when. the supply of gas is cut on, each of thev burners: 54-60 is. provided with an auxiliary valve ld- |10 connected to any desired source'of. compressed air. The latter valves are electrically interlocked with the valves lill-|50 so that'after the Valve is shutoff compressed air is. supplied to the burner for a short interval of time, on the order of rive'` seconds. -in which the interlock is eiected will bey made The manner clear during the discussion of the control diagram in Fig. 112. The compressed air admitted by the.

auxiliary valves iSd-|! assists in bringing the temperature ofthe burner faces down toa value which will not produce scorching of the web. Al-

Y though not shown in the drawings it will be apparent toone skilled in the art that name detectors androther safety devices may bel applied to circuit forl causing operationY of thesev and asl sociated elements in a predetermined sequence isy Assuming l set-.forth in Figs. 12, i3 andv 14. Fig. 12 is a diagram of the rcontroller circuit partially in block formA while Figs. 13 and 14 set forth blocks in greater detail. Voltage for operating the control circuits and motor isy obtained from the thru phase- A. C. lines LI, L2, and L3.

Prior tofdiscussing the functions of the control systemit will be helpful tov refer brieiiy` to the variousA circuit components' and to bring out the ning condition. Speed control is accomplished graduated series ofV twelve points.

relationship between suchv components and the speed. controller used ina conventional printing press. As. appreciated by one'skilled. in the art, a: printing press has a large driving motor and a small. driving motor-'which together act toY vary the speed of the webfrom standstill to full runrneans of a motor driven controller operated by a manual pushbuttonto` cover a series of speed points. 1n describing the present embodiment it is assumed that the controller has a 1n practicing the present invention` a modified controller is used which has an auxiliary contact drum having contacts which are operl.ated in sequence as the web speed controller is moved in the increase and decrease directions. These contacts include the prefix D andare shown along the left hand edge of Fig. 12. The

- present disclosure need not be burdened by a physical showing of the controller.. It will sunice to set forth in tabulated form. the relationship betweenv the speed` points and thev contacts as follows:

Increase speed Controller Point Drum Contact D2 closes. D3-1 closes. D4-l closes. D5 closes. D6 closes. D7 closes. D8 closes. D9 closes. D10 closes. D11 closes. D12 closes.

Under conditions of decreasing web speed, the

drum contactsin Fig. 12 will be operated as follows:

Decrease speed' Controller Point Drumv Contact D12 opens. D11 opens. D10 opens. D9 opone D8 opens. D7 opens. lD6 opens. {D opens.

D42 closes. D4-.1 opens. D3-2 closes. D3-1Y opens, D2 opens.

In order to further tie: in the present circuit with the normal speed control of the web attention isy drawn to the fact that4 three ofthe relays .in Fig., 12am-energized from asource of current external to thediaeram.. These. are a Stop re lay. an Orl7 relayandyan Oif relay.v The Stop relay isenerg-ized Wheneverthe press is 7 5v :runnin-g, regardless whether it is driven by the drum contacts D6 to DIZ inclusive.

jsmall or large driving motor. This relay drops outV whenever the Stop Vemergency button is operated or when a detector switch opens as a V' result of a web break. A suitable current source is provided so that the On rlay is closed whenever the press is accelerated and the Off relay is closed whenever the press is decelerated.

In order to locate the burner assembly suc- A cessively closer to the web as the web speed increases, limit switches LSI, LSZ, LSB, and LSA IZCR, |3CR and MCR. The latter are controlled by the drum contacts in a manner which will become apparent as the discussion proceeds.

Y Referring now to the upper portion of the cir- 1 cuit diagram, solenoid valves IM, |49, I3| and |31 are shown connected to the contacts of a main relay IUCR. It will be recalled that the Q functions of these valves on being energized are as follows:

I III-permits iiow to burner manifold. HIS-admits compressed air to air blast line I ID.

` I3 I-turns on supply of gas from gas line.

I3'I-by-passes air around combustion controller.

Y' the Off condition by manual control, a pushbutton B is used which is connected in a series with the contacts of a relay |8CR. The latter in conjunction with an off limit switch DLS on the press controller operates the restoring circuit in the event the operator does not operate pushbutton B.

In order to operate the individual valves |54| 6|) inclusive for admitting a combustible mix or air to the lines of burners 513-60, sub-control circuits |84|90 are employed. These circuits Y serve also to control the auxiliary valves |64| 1U.

As will be apparent from inspection of the diagram, these circuits are under the control of cuit diagram for the valve control circuit 184 is typical and is shown in detail in Fig 13. It includes a relay MICR for operating the burner solenoid Valve |54 together with a relay MCR for operating the auxiliary valve |64. In order to Y' hlimit the time that the auxiliary valve is open a time delay relay 40T is used having a delayed drop-out on the general order of ve seconds.

The contactor circuit for the motor 93 which adjusts the positioning of the burner assembly is indicated in block form at 200 and shown in detail in Fig. 14. It includes contactors UI and BI for operating the motor in the forward and reverse directions respectively. The motor is protected by an overload device OLI and includes a brake to prevent overtravel when the motor is de-energized. For the purposes of simplicity, only one adjusting motor has been included in the present circuit. It will be understood, however, that the invention is not limited to the use of but one motor and includes the use of additional motors and limit switches for adjusting the remaining burner assemblies which v may be included in a complete set-up. 1 Any additional motor circuits may be conneiiel Paral- The cir- Cil flz

lel across the supply lines LI, L2 and L3, 'and parallel connections may also be made to the y left hand or input side of the associated limit switches.

The above completes the cataloging of the various elements in the controlcircuit. Since control circuits of this general type are well understood by those skilled in this art, the present application will not be burdened by a d etailed recitation of the electrical connections. The latter are specifically set forth in the drawings and the reasons for the same will become apparent in the discussion of the operating sequence.

Control sequence uponl increasing speed M The operation of the control'circuit just discussed for the increasing speed condition may be visualized by reference to Fig. 15 which is a graph of controller position and press speed'as a. function of time. It will be assumed that the Apress ls started from rest and that the controller is moved uniformly from the first position to the twelfth or maximum speed position. 'Ihis causes a progressively increased press speed. Because of the inertia of the rollers in the press, the press speed will lag the movement of the controller as shown. While the press speed is shown to increase linearly, this is merely a simplifying assumption and the actual speed curve may have portions which are concave upwardly or downwardly.

In accordance with one of the aspects of the invention the burner assembly starts out from a position fully retracted from the web, movement of the press controller causing (1) at least a portion of the burners to be lighted, (2) the burner assembly to move up close to the web and (3) the heat generated by the burner assembly to be increased as the web speed setting is increased. In the preferred embodiment the heat produced by the burners is increased by progressive, step-by-step lighting of additional burners so that under full speed running conditions the burners will be fully on and so close to the web that the llame may actually graze the surface thereof. It will be appa-rent to one skilled in the art that the invention in its broader aspects is not limited to an arrangement in which burners are turned on successively but would also include arrangements in which the increased heat output is obtained by increasing the supply of gas-air mixture. The present arrangement is preferred since variation in drying capacity is attained increasing the burner and, while the burner temperature remains relatively constant over the speed range. In Fig. 15 the stepped curve indicates the successive lighting of the burners at the various controller points. The numbers applied to the steps indicate the number of the burners (in the series BI-BU) which are in operation at each point. The manner in which the above operating sequence has been achieved in the present embodiment will be made clear by the following step-by-step description,

When the press is at rest the following conditions prevail:

Valve I3| closed-gas supply turned off.

Valve |4| closed-burner manifold closed.

Valve |37 open-air by-pass turned full on. Valve |49 open-air blast provided by line I0.

'Preferably the press includes provision in the main drive circuit for inchingf This is conl/.emonally accomplished by an "inch button which may oe-operatedl eventhough the main 'controller is' set in the off position. Thus,

the press cylinders -rnayy be--advanced,l say, for

threading the web without having any eiect closed, closure of D2 causesrelay MECH. to be energized. The latter relay'remaing closed because vvof;a circuit which includes a normally closed con'- tacti on relay' l'CR, a normally' open contact on the Stop relay, and; a normally openv or "sealing in contact on relaylCR. Aszsoon as relay l'CR closes-the solenoid. valves are operated 'as'foll'owsz :Valve ilclosedair by--pass turned oit.

Valve IM closed-airblast turned oil.v

Valve l 3 l. open-gas admitted from supplyA line.

Valve it! open-gas mixtureadmitted tofburner manifold;

'I'he' valves {5l-53 associated with the nrst three'. lines of burners are' normally open. Burner lines l, 52, 53` fed by such valves are thus lit automatically upon admission of combustible'gas, lacontinuously burning pilot (not shown)y being 'associated With each of theY burner lines. At this point burner valves IM-l-E are closed. Due

'to theV slow movement of the'web at this: time, the radiant heatfrom'the iirst three lines' oi burners is suflicient to produce drying even ythough the burners are in the fully retracted povsition.

On point 3', drum contact'DS-l closesto` run the burner assembly to its semifretracted position approximately six inches from the Web. This results because of the energization ofrelay l ICR which closes the circuit to motor contact'or UI (see Fig. 14). When the burner assembly reaches the six-inch position it automatically opens the Vlimitswitch LS1 and the motor contactor U1 is dropped out, stopping the motor.

On point 4 drum Contact D4. closes.` to pick up relay IZCR. rihis causes the motor contactor Ui. to closeresuiting in addi-tional" forwardmove- .mentV of the. burnerY assembly until the. contacter is. dropped out by the limit switch LSB". At this timethe burner assembly is approximatelythree inches from the web.v

Ori point 5 drum contactA Dcl'oses to energize relay 131GB. whichoperatesrin asimilar manner to. MCR yto runtheburner assembly tothefully advanced. or closed. position. Inths positionthe burner'cerarnio is about 11/24 inches iromtherweh. The 'web is by this time moving at about onequarter speedand' only three lines of burners are lit so that there is no danger of scorching; in spite of the closeness of the burners.

When the controller is moved to point 6 the burner control circuit' its (see Fig; 13) is' enerisized. Relay liliCR is picked up which energizes T4 circuit: liishown inblock-form in: 12.1I This results in the turning- Onof burner' valve IE5; in the samefmanner as'. discussed. above forivalve. |54. kimilarly; theV .remaining valves tti60 are turnedononebyone1as the controller is moved from point 8 to theifulle speed positionat pointi12.

Operation of' dryer under high; speed' runningv conditions The Webf newr is traveling i throughathe press at maximum speed and all of: the burners are ignited-.for applying both radiantl heat and con.- vected. heat to the: webv at close range. It will be helpful. yat this point to. observe the nature of the. drying which` takes place. Referring to -FigspZeg and.particularly-torig, gas iioWs into the manifoldifm from the', associated one of the valves Iii- 160, and; thence through the stem 'H and', nozzle 8i.. The gas flowing through thefnozraleI isdirected toward a cupz-shaped defiecting plate 237i:V and thenl baclrvvardly` in., al smoothptoric l'ayeri along; the refractory material forming the surface.z of the recessv all.y Burning of the gasadjacent' the refractory material of the burner causes such material quickly to become red hot andthe radiantheatxtherefromis beamed along the burner. axis: in; the direction of the web.

Upon. striking the inkt lm the radiantenergy releases solvent fromthe. body; of the iilm.l as Well as from the surface. thereof'. In. addition, any of the solventv which yhasbeen, absorbedv inthe pores ofthe paper isy driven offV into the space surrounding: the Web. The solvent in vaporform is ignited by the burnersV and; serves toincrease the temperature oi the Webabove the point which would result from the action of the burners themselves. Studies` havey shown that before the web completes. its journey through the dryer, substantially allV of the solvent is liberated and hurried.v which noty only contributes to the eiliciency of, the dryerbut preventsthe solvent from beingdischarged: into: the atmosphere or condensing: in the' exhaust ducts to. create a nre hazard. The' convected: heat andthe products of cornbustion are drawnoi at the upper endet. the web bythe exhaust'duct i202 Since the lower: surface of the duct. 29' includes: apertures` |21. closely following the surface of the cooling drum 35, even the combustion products which are drawn along the web: are eiciently removed and no. harmful products are permitted to. escape. into. the` at'- mosphere;

A large portion` of" the heat produced by the burners is drawn. oi'through the exhaust system. Tozfully'understand the advantages ofthe: prestent construction, it will be helpful to trace the dispositionl ofthe remaining heat. A certain portion of the heatA will be usedin raising the temperatureof the web itself. Thisheat is subsequentl'y subtracted'from the web by the cooling vruins 35, 36. The radiated heat Whichpasses through the web strikes the back-up plate ETI (see Fig. 2). Because ofv the reflecting surface thereon most of'thisradiated heat issrefle'cted back onto the webwhere. it servesto: drive; off'additional solvent. Some: heat, however, passes into` the plate 85 whencev it is removed. bythe cooling coil 36'.

Although the: sidewalls 8T and the ends.l ofi the burner assembly are notin the direct radiation path,` a certain amountl of-A heatfrom the. burners will. ow to. the.r` ends` ofJ the burner. assembly. Thefheatiis-removed in this regi'oirbythe;y cooling eoilsll. 88;

Attention may next bergiven; totheow: offhea in the burner assembly itself under normal operating conditions. As previously stated, the refractory surfaces of the burners are rendered red hot. Very little of this heat, however, travels through the refractory material since it is an extremely poor heat conductor. It might be expected that the metallic burner walls 16, 11 (Fig. 8) would conduct heat from the face of the burner'to the manifold. However, because of the thin cross section of these walls and because of the foraminated structure thereof, only a very limited'amount of heat will follow this path. As previously described, the burners are spaced at some distance from the manifold 12 which supplies them. This space indicated at 18 in Fig. 8 is filled with insulating material to minimize the direct rearward flow of heat from the burners. The only remaining metallic heat path, then, from the burner to the manifold is through the stem 1| arranged centrally in the burner and threaded to the manifold. However, it will be apparent that if the cross section of this heat path is kept small, the amount of heat flowing to the Walls of the manifold may be correspondingly reduced.

In the present construction means are provided for keeping the auxiliary portions of the burner assembly far below the temperature of the burner. This is accomplished in great measure by the 'back plate 13 which engages the manifold 12 over an extensive area and which has sweated thereto the cooling coil 1li. On each side of the manifold 12 the layers of insulation 83 prevent the passage of heat to which the latter is subjected as a result of convection and the reiiection of radiant heat from the back-up plate 6|. As a result of the foregoing structure, therefore, it will be appreciated that all of the parts of the burner assembly which have appreciable heat storage capacity remain cool by comparison to the burners which operate at a red heat. Since the back-up plate and the side walls are similarly cooled by water cooling coils, the heated space is eiectively isolated from the rest of the press.

The rubber rollers, mounted closely adjacent the dryer are kept at about the same temperature as in presses not employing a dryer.

Control sequence-gradually decreasing speed In accordance with one of the aspects of the invention, the burner assembly is retracted and the burners are shut off and flushed with cooling air as an incident to slowing down the press. In the present embodiment a portion of the vburners operating during the normal running of the press are turned off one by one as an incident to decreasing the speed of the press, after which Ithe burner assembly is retracted and the remaining burners are extinguished. Provision is quence or may be deferred until a later time in .65

the event that the dryer has not achieved its normal running temperature. In addition the flushing air is utilized to continue the drying process, so that the latent heat removed in Abringing the burner temperature down from the radiating range is not wasted but on the contrary .isl usefully employed for drying. Finally, after the burner assembly is retracted and the burners have been turned oi, a blast of air is discharged :through space vacated by the burner assembly 75 and additional exhaust ports are uncovered to conduct away the air in the air blast. The manner in which these novel functions are performed will be apparent upon reviewing the step by step operating sequence characteristics of a normal and gradual shut-down. These steps are set forth diagrammatically in Fig. 16 which resembles Fig. 15 previously discussed in that the numerals 1-12 indicate various controller points and the steps show the number of burner lines in operation at each point.

With the controller at point 12, the conditions are the same as existed at the end of the increase cycle: the burners are all in operation and the burner assembly is closely adjacent the web. As the controller is moved to point 11, the solenoid valve |60 is turned off. This results from the fact that contact D|2 opens to drop out a relay in circuit |90, which relay corresponds to relay MICR shown in Fig. 13. Closing of the valve |60 is accompanied by a timed discharge of compressed air through the auxiliary valve |10 associated therewith. The manner in which this occurs may be made clear upon inspection of Fig. 13, where the corresponding circuit is shown. The normally closed contact on relay CR therein completes a circuit through the timing relay 40T, resulting in the picking up of relay MCR. The contacts of the latter relay cause the auxiliary valve |10 to open, thereby causing a discharge of compressed air through the burners in line 60. This compressed air has two effects: The primary effect is to blow out of the burner the combustible air-gas mixture, thereby preventing blow-back in the burners and manifold. In addition the air flowing through the burner nozzles serves to cool the face of the burner to the extent that the temperature of the exhaust air is suciently high to be useful in further dry- Aing the web at the existing speed. The primary cooling effect, however, occurs at a later point due to the effect of the flushing air.

At the end of a predetermined time interval, for example, five seconds, relay 40T drops out thereby opening the circuit to the relay MCR and turning off the valve |10. When the control is moved to point 10, contact D|| opens to deenergize the control circuit |89. This results in an operating sequence which is exactly similar to that mentioned in the preceding paragraph. The net effect is to close the solenoid valve thereby turning off the burner 59 and injecting compressed air into the burner for a short space of time by opening the auxiliary air valve |69.

As the controller next is moved to point 9 and successively down to point 5 the contacts in the series DH1-D6 inclusive cause shutting down of the burner lines 'S8- 54. In each instance an auxiliary source of compressed air is briefly connected to the burner.

When the controller reaches point 4 retracting movement of the burner assembly occurs as follows: The drum contact D4-2 closes and since the off relay contact is closed indicating that the press is being decelerated, relay MCR closes. A normally closed contact on the relay ItCR opens the circuit to the contactor Ul (Fig. 14). Normally open contacts in the relay MCR energize the opposite motor contactor Bl. This causes the motor 93 to rotate until the burner assembly is fully retracted, in the present instance to a distance of twelve inches from the web. At this point the burner assembly operates the limit switch LS4. This drops out contactor BI to stop the motor. Itwill be understood that when The flushing air, after acquiring the latent heat of the burners passes contact with the web to "taper off the drying operation. Simultaneously, dropping out of the Stop relay causes a normally closed contact thereon to energize the relay MCR. This relay energizes the contactor Bl to drive the burner assembly to its retracted position where it is brought to rest by operation of the limit switch LSA. When the controller rotates around to its off position, the 01T limit switch is operated to drop out the relays ISCR, HCR, and IDCR to terminate the ushing and turn on the air blast from line l lli.

While the present construction causes the temperature of the radiant burners to be dropped suddenly, particularly under conditions of emergency shutdown, itis important to note that drying is not terminating so quickly that undried web will pass through the dryer into contact with subsequent rollers in the press. Instead, the latent heat of the burners is utilized to produce convection currents which produce surface drying of the film at a lower temperature level than is normally produced by the radiation. The necessity for removing undried ink from the rollers after an emergency shutdown is thus eliminated.

Provision is made for terminating the flushing and turning on the air blast before the press is brought to a stop. This is accomplished by pressing pushbutton B. The latter deenergizes the relay I8CR which in turn drops out relay HCR to establish the off condition which is as follows:

Valve I 3l closed-gas shut oft.

Valve IM closed-burner manifolds shut off.

Valve I3? open-air by-passed around combustion controller.

Valve M9 open-air blast from line l l0 turned on.

In the event that the operator does not push button B to turn on the air blast, the relay l SCR will be dropped out, in any event, when the controller reaches its oir position. Conditions are then set up corresponding to those listed above.

Providing the pushbutton B and its associated circuits for cutting off the flushing process upon emergency shut-down adds iiexibility to the operation of the dryer. If the press has only been in operation for a short time and the dryer is not up to full operating temperature, the operator may omit pressing button B. In this event the latent heat in the flushing air will continue to have a drying effect on the decelerating web even after the burner radiation is reduced to a, safe point. However, where the press has been operated for a considerable period the operator may not wish to make use of the latent heat and may wish to merely reduce the radiation, following this immediately by an air blast to carry away as much of the heat in the dryer as possible. In such instance, the operator would press button B immediately as the press begins its emergency shut-down. The eiect of flushing the burners by air conducted through them followed by an air blast forming a protector blanket has been found to safeguard the web against scorching even under the most abrupt conditions of shutdown.

In the above discussion it has been assumed that emergency shut-down took place from the normal running speed. It should be noted, howeverl that the emergency circuits are equally useful when the press is operating at a partial speed or during the course of deceleration` Referring to Fig. 18 it will be assumed that the speed controller has been moved down to point 8 when the This corresponds to a press' emergency arises. speed S. 'Ihe eiect of the emergency is to drop out the Stop relay and to run the controller back to its off position. The press speed will suffer a correspondingly sharp decrease as indicated by the break in the press speed curve. As before, the emergency will result in the admission of flushing air to all of the burners to bring them below red heat, and the air blast may be turned on, if desired, prior to the return of the controller to the 0H position by pressing the pushbutton B.

Since the pushbuttons A and B offer a certain degree of manual control over the drying process, provision is made to insure that these buttons are not operated at such times as will endanger the web. It will be noted, for example, that if button B is operated by accident without preliminary iiushing, the press will stop and ushing will occur automatically to bring the red heat of the burners down to a safe value. In the event that the press is accelerated to a partial speed point, for example point 5, the burner assembly will be closely adjacent the web. Decelerating to point 4 will cause the burner assembly to be run out to the retracted position. After the limit switch LS is operated in such retracted position, the burner assemblies will be turned to the position determined by the controller just as though acceleration were taking place. For exampley if vthe controller has remained on point 4, the `burner assembly will automatically move forward to the B-inch position.

In spite of the high capacity of the dryer described above the volume which it occupies is only a small fraction of that required for conventional dryers used in the past. I'he dryer may be readily accommodated within the frame of a conventional magazine press without any substantial modification thereof. In the case of a newspaper press the dryers are suii'iciently `'small as to enable mounting above the press unit. The supporting frame for the dryer in the latter instance may be very light permitting the dryer to be installed directly on the press frame. No additional floor space is consequently required. One of the factors contributing to the compactness of the present arrangement is the fact that the burner lines are xedly oriented in the burner assembly. This not only facilitates cooling as Will be clear from the foregoing description but also enables the burner lines to be arranged more closely together and permits more efficient placement of insulation while enabling utmost simpliication from a mechanical standpoint. Regardless of whether the dryer is used in a magazine or newspaper press, and in spite of the large amount of heat generated therein, practical experience has shown that heat is eiliciently confined and the surrounding parts of the press are not subjected to high tempera-ture even after many hours of continuous operation.

In the above description it has been assumed for simplicity that the burners are successively turned on and turned off at successive evenly spaced controller positions. It will be apparent to one skilled in the art that the invention is not necessarily limited thereto and the points at 21 which the drum contacts are operated need not correspond to the numbered controller points'.v In a practical installation the drum contacts are so positioned that a sunicient number of the burner lines are turned on to produce the optimum dry'- ing effect for a given controller setting and web speed.

claim as my invention: l. In a dryer for a web a printing' press. a burner assembly comprising a back plate, burner lines arranged on said plate and spaced from one another, each of the burner lines having a longitudinally extending manifold and a burner of .refractory material superimposed thereon for producing radiant heat, said manifolds eachhaving an extended surface in contact with said back plate, high temperature insulation having low heat storage capacity lling the interstices between said manifolds, and a water coolingl line in intimate thermal contact with said back plate for maintaining said plate and said manifolds at a low temperature to minimize the stored heat of the burner assembly after a sustained period of operation.

2. In a dryer for a web in a printing press the combination comprising a burner assembly having a plurality of burner lines therein iixedly oriented to supply radiant heat simultaneously to an extended surface of web, each of said burner lines including a metallic base having a i'ace of refractory material superimposed thereon which is cup-shaped in cross section, means including a" nozzle for conducting combustible gas mix into said cup-shaped face so that the latter becomes radiantly red during combustion of the gas, a cooling pipe having cooling water circulating therein and in intimate thermal contact with said base to maintain it at a low temperature during operation of the burner, said refractory material having low latent heat under normal operating conditions, and means for simultaneously turning oii the supply of gas and ad mitting cooling air directly on the radiating surfaces to quickly reduce the temperature thereof upon shut-down of the press.

3. In a dryer for a web in a printing press a burner assembly including a plurality of burners arranged substantially parallel to the web, said assembly having a series of radiant gas burners mounted thereon and directed toward the web, means for bodily advancing and retracting said burner assembly to change the spacing between the burners and the web, and control means for (l) first turning on said burners in the assembly in sequence and advancing the burner assembly toward the web as an incident to increasing web speed and 2) retracting the burner assembly and turning off said burners in sequence as an incident to decreasing the web speed.

4. In a dryer for a web in a printing press a burner assembly oriented substantially parallel to the web and having a plurality of radiant burners arranged in both directions therealong, lsaid burners being fixedly mounted in said burner assembly so that the radiant heat' generated thereby is directed toward the web, a series of air jets along one edge of the burner assembly and positioned to discharge a blanket of air between the burner assembly and the web, exhaust means along the opposite edge of the burner assembly and means operating incident to a reduction of speed of the web for supplying air to said air jets and for retracting said burner assembly away from the web to provide a channel of large cross section which extends substantially unobstructed 22 between the jets and the exhaust means-for the accommodation of a large volume of air in said blanket.

5. A dryer for a web in a printing press a burner assembly oriented parallel to the web. and having a plurality of radiant burners arranged in both directions therealong, said burners including nozzles for transmitting a combustible mix to the radiant face thereof and xedly mounted in said burner assembly so that the radiant heat generated thereby is directed toward the web, and means operated as incident to a reduction of the speed of the web for bodily retracting said burner assembly from the web, turning off said source of gas, and supplying cooling air to said nozzles for cooling said radiating surfaces.

6. A dryer for a web in a printing press including a burner assembly extending the width of the web and oriented parallel thereto, the burners in said assembly being arranged therein so that radiant heat is directed toward the web, exhaust means including exhaust ducts arranged along one side of the burner assembly and normally covered thereby when the latter is in normal running position, and means for retracting the burner assembly in a direction away from the web so that the exhaust ducts are simultaneously uncovered thereby to facilitate the heat removing action thereof with the result that the temperature of the air adjacent the web is lowered.

7. In a dryer for a web in a printing press the combination comprising a burner assembly having a box-like housing for said burner assembly, said housing including a plurality of gas burners nxedly mounted thereon and having a relatively flat end surface, said housing being open on the side toward said web so that the heat radiated from said burners is applied to the web, an exhaust duct along an edge of said box-like housing and arranged to be normally at least partially covered by the end surface thereof, means including a plurality of air jets arranged along the opposite edge of said housingr for directing an air blanket between the burner assembly and the web, and means for retractins said housing away from said web upon slow down of the web, such retraction serving to uncover an additional area of said exhaust ducts and servingl to increase the cross section ofthe air channel between said web and said housing to facilitate removal of the air from said air4 jets.

8. In a dryer for a web in a printing press a burner assembly comprising in combination a plurality of burner lines arranged horizontally and spaced vertically from one another equidistant from the web, a water-cooled back plate, each ofv said burner lines including a longitudinal manifold of rectangular cross section, a plurality of radiant burners of refractory material spaced along said manifold and in communication therewith, the space between adjacent inanifolds being filled with insulating material' so that substantially the entire face of' said burner assembly is composed of material having poor heat transmission characteristics, and means for normally clamping said manifolds into intimate thermal contact with the water-cooled back plate but permitting a selected burner line to be forwardly withdrawn as a unit for purposes of replacement or maintenance.

9. A system for supplying a gas-nred radiant burner in a printing press web dryer comprising in combination a source of gas, a source oi com-

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