US2571815A - Apparatus for and method of drying - Google Patents

Description

Oct. 16, 1951 R. A. BENOIT EI'AL 2,571,815

APPARATUS FOR AND msmoo OF DRYING Filed July 12, 1947 4 Sheets-Sheet 2 INVENTOR. QMl A. BEND/T EDOUAQD Ze/J. BENO/T Oct. 16, 1951 R. A. BENOIT EIAL APPARATUS FOR AND METHOD OF DRYING 4 Sheets-Sheet 3 Filed July 12, 1947 INVENTOR. IQEMI A. GENO/T DOUA20 LEQBENOH Oct. 16, 1951 BENQIT r 2,571,815

APPARATUS FOR AND METHOD OF DRYING Filed July 12, 1947 4 Sheets-Sheet 4 IN VEN TOR. R [M/ A Bf/VO/T 0 00,420 is 5 Lama/r Patented Get. 16, 1951 APPARATUS FOR AND METHOD OF DRYING Beml A. Benoit and Edouard Le B. Benoit, New York, N. Y.

Application July 12, 1947, Serial No. 760,604 1'7 Claims. (CL 34-18) The present invention relates to drying apparatus, and has special reference to apparatus for drying printing ink as the printed material leaves the printing press, and further relates to a method of drying. I

One of the objects of the invention is to provide an apparatus 01 this character which is simple in construction, capable of uniformly and expeditiously drying the material, economical in operation, and capable of being easily and conveniently controlled to meet different conditions.

Another of the objects of the'invention is to provide a novel and improved method of drying.

The several features of the invention, whereby these and other objects may be attained, will be readily understood from the following description and accompanying drawings, in which:

Figure 1 is a longitudinal sectional elevation, partly diagrammatical, taken substantially on the line Il of Fig. 2, of an apparatus embodying features of the invention in their preferred form;

Fi 2 is a sectional plan view, taken substantially on the line 22 of Fig. l

Fig. 3 i a transverse sectional view, taken substantially on the line 3-3 of Fig. 1;

Fig. 4 is a view in perspective of one section of a heating unit forming a component part of the apparatus;

Fig. 5 is a sectional view taken on the line 5-5 of Fi 4;

Fig. 5a is a view corresponding to Fig. 5 of a modified form;

Fig. 6 is a diagrammatical view illustrating the wiring of the electric resistance elements of the heating units;

Figs. '7, 8 and 9 are views corresponding to Fig. 1 of modified forms; and

Fig. 10 is a view corresponding to Fig. 4 of one of the sections of heating units illustrated in Fig. 9.

The drying apparatus illustrated in the drawings is particularly adapted for use in drying printing ink as the printed material leaves the printing press, but it will be apparent, that it may also be used for drying other material which may be fed through the apparatus in sheet or web form or supported on a conveyor belt.

As shown, the apparatus comprises a drying chamber having a bottom wall 2, a. top wall 4.

side walls Ii, and front and rear end walls 8 and ID, said wall being made of suitable heat-insulating material. The front and rear end walls are respectively provided with openings l2 and I4 through which the material it to be treated enters and leaves the drying chamber.

The side walls 6 are made in upper and lower sections which have their ends mounted to slide vertically in guideways adjacent the front and rear end walls. Each guideway is formed by means of an angle iron l8 that is secured to the vertical edge of the associated end wall and to a channel-beam 20 secured across the upper portion of the end wall; and by an angle iron 22 which is secured to the cross-beam 20, the tour angle irons 22 extending below the drying chamber so as to provide supporting legs therefor.

With this construction, it will be apparent that the sections of each side wall may be moved toward each other so as to provide a closed wall, or may be moved away from each other to provide an opening between them so as to permit access into the drying chamber.

The apparatus is provided with upper and lower banks of heating units 26 between which the material I6 passes. The heating units of each bank are arranged transversely of the drying chamber and the path of movement of the material I6, and are spaced apart. The spaces between the heating units of each bank are closed or partially closed and the units are supported by means of angle irons 28 having their vertical sides spaced apart to provide air passages 30 between them extending across the drying chamber and leading into by-pass ducts 3| above and below the banks of heating units. Controllable dampers 33 are provided to regulate the air passages 30 and to close completely if so desired.

The ends of each pair of angle irons 28 are secured to a block 32, and the several blocks 32 at each side of each bank are secured to an angle iron 36. Each angle iron 36 is secured by bolts 40 to a section of the associated side wall 6.

The banks of heating units together with the associated sections of the side walls are adapted to be moved toward and from the path of the material It by mechanism that is operable from outside of the drying chamber.

This mechanism comprises walking-beam levers l2 operatively connected with the ends of the sides of the banks of heating units. The walking-beam levers 42 at each side of the drying chamber are fulcrumed on pins 44 between spaced angle irons 46 that are secured at their ends to the cross-beams 20. The lower flanges 48 of the inner angleirons 46 extend beneath the outer margins of the top wall 4 of the drying chamber and are secured thereto so as to support said wall (Fig. 3). The lower flanges 50 of the outer angle-irons 46 have their outer edges extending adjacent the side walls of the heating 38 associated with. the upper bank of heating units, and its lower end has a nut screw-threaded thereon. The other lower arm of each walkingbeam lever 42 is pivotally connected with the upper end of a link or rod 58. The lower end portion of this rod 58 extends freely through one of the air passages 30 associated with the upper bank of heating units and through the underlying air passage 30 of the lower bank of heatin units, and has a nut screw-threaded on its lower end.

The upper arms of the walking-beam levers 42 at each side of the heating chamber are pivotally connected to the ends of an angle-iron 60, and the two angle-irons 80 are secured together by means of a cross-beam B2. A centrally located channel-iron 64 is secured to the top of the beam 82, and a depending handle 66 has its upper end secured to this angle-iron and its lower .end .is arranged in a convenient position to be grasped by the operator of the drier.

With this construction, by means of the handle 66 the walking-beam levers 42 may be turned and through the connecting rods 56 and 58 the banks of heating units, together with the associated sections of the side walls may be moved toward and from the path of travel of the material l6 that is being treated. Such provision for adjusting the positions of the banks of heating units and sections of the side walls not only enables the units to be adjusted toward and from the work but also enables access to be quickly had to the units and the interior of the drying chamber. As shown in Figs. 1 and 3 the side angle-irons 60 are at the limit of their forward movement and thus limit the movement of the banks of heating units toward each other. By adjustment of the nuts on the lower ends of therods 58 and 58 the positions of the banks of heating units with relation to the work may be varied as desired to meet difierent conditions.

In the drawings each unit is shown made in two sections that are arranged end-to-end but the number of sections may be varied for different widths of drying chambers, and in some instances a single section may be employed. Each section has a horizontal wall 68 and vertical side walls 10, which walls may be made of suitable refractory material. The wall 68 is shown made of two longitudinally extending parts which have projecting flanges 12 that are secured by bolts 14 to each other and to the side walls. The inner sides of the side walls are provided with longitudinally extending inwardly opening grooves 16 which receive rods 18 about which is coiled electric resistance fiat wire or ribbon 88 having terminals 82. The outer sides of the side walls 70 are provided with longitudinally extending grooves 84.

In assembling the parts of each section, the rods 18 areheld in proper spaced position and the ribbon 80 coiled thereabout as shown. The rods with the ribbon are then slipped into the grooves 16 which are of greater diameter than the rods,

sistance ribbon and folded into several layers are positioned at diagonally opposite corners and in a manner to extend outwardly between the joints 0! the horizontal wall and the side walls so as to firmly hold them in position. with the parts thus assembled, the ribbon is firmly gripped about the support rods 18 and by the lips of the grooves 16 and thus the coils of the ribbon are firmly held in proper spaced relationship.

In winding the resistance element for each of the several sections of a heating unit, the diagonal arrangement of the terminals and winding are alternated on each successive section. As the sections are placed end to end in proper sequence, a terminal of one section always pairs with a terminal of an adjoining section. Thus each successive pair of terminals alternate from one side of the heating unit to the other. The two bare wire electrical conductors 86 are placed lengthwise on each side of the heating unit and positioned to enable each associated pair of terminals to be conveniently connected thereto. The elements of the several sections of each unit are thereby connected in parallel. The connections between the several element terminals and the conductors assist in supporting and holding the conductors in their proper position. Also by providing extra heavy conductors they in turn give additional support to the individual heater sections, particularly should they become dam aged by excessive cracking when in service. The ceramic construction of the parts of the heater section serves the purpose of an insulator from one conductor to another and from the conductors to ground or to supporting angles 28. This arrangement precludes the use of other types of insulation which will not withstand the high temperatures encountered in the drying chamber. Also this construction enables the conductors to be removed with each unit upon-disconnecting the conductors from their circuit leads, thus making it unnecessary to' disconnect the heating elements from the conductors.

With the sections thus formed, upon removing or sliding open the sections of one of the side walls of the drying chamber, the sections of each heating unit may be easily slid into position endto-end as shown, the grooves 84 of the side walls receiving the edges of the horizontal portions of the associated angle-irons 28. Previously to sliding the, sections of each unit into position, their terminals 82 may be connected in parallel to the electric conductors 86. The ends of the conductors of the several units of each bank extend outwardly through apertures in each of the sections of one of the side walls and the circuit connections therewith (not shown) may be enclosed by casings 88 removably secured by bolts 89 to the sections of the side walls.

The material l6 before entering the drying chamber, passes between closely spaced air baflles or scoops 90. As the material enters the drying chamber through the inlet opening I2, it passes between closely spaced scoops 92 secured to the foremost angle-irons 28.

After leaving the drying chamber, the material passes through an exhaust chamber 94, and between air nozzles 98 which are inclined forwardly so as to direct air at an angle against the direction of travel of the material. The chamber 94 is in communication with. the by-pass ducts 3| through the outlet opening l4. The

chamber 04 is connected with controllatae suction means through a conduit '5. Air is supplied under pressure to the nozzles I through conduits In the operation of the drier, the scoops Iii serve to regulate the amount of cold air entering the drying chamber. The scoops 92 break up the incoming cold air and the films of entrained air moving with the web in such a manner that part of the cold air passes into the spaces betweenthe heating units, and the remaining cold air is diverted in the by-pass ducts ll above and below the heating units. This cold air entering the drying chamber takes two separate paths of travel at each side of the material, one path being between the material and the adjacent heating elements and the other path being through the associated bypass duct. The proportion of air into each path may be controlled by adjustment of the scoops 92 which may be accomplished upon adjustment of the bank of heating elements toward and from the material, or may be separately accomplished as by bending the scoops. We have found it practicable to place the scoops 92 as close as of an inch in case of printing material in web form, and with such material it is preferable to place them as close to the web as practicable so as to reduce to a minimum the amount of cold air passing betweenthe web and the heating units.

As the web with the thus regulated quantity of air films approaches the space between the first set of heating units, the abrupt edges of the forward side walls of the heating units serve to break up the film of air at each side of the web into two parts, one part being diverted through the air passage 30 into the associated bypass duct ii, and the remainder of'the film entering the space between the web and the heating unit. The front side wall of the heating unit in addition to serving as a baiiie to break up and cause turbulence of the film of air, also as it is previously heated by radiation from the heating element serves to preheat the air entering the heating unit.

Also, the side walls of the heating units preheat the web by radiation as it passes between the forward side walls of the front end units. The web, therefore, is preheated by the side walls, or bafiies, in two waysone through the preheated air because of its turbulent action, and the other by radiation. As the web passes between the resistance elements of the first units, the preheated air films expand rapidly because of the intense heat of the resistance elements and also because of leaving the restricted space between the web and the front side walls of the heating units. This creates further agitation and turbulence of the air films which are thereby heated to a high temperature by the resistance elements, and also because of such turbulence of the air, maximum heat is transferred from the air to the surfaces of the web. The resistance elements being at a temperature of approximately 1700 degrees F. serves also to radiate heat to the web. the radiant heat penetrating through the material of the web.

As the web and films leave the first set of heating units, the closely spaced rear side walls of the units still further heat the films of air and web.

As the web passes to the spaces between the first two sets of heating units, the films of air and the gases or fumes from the web tend to again expand and to be by-passed through the temperature.

airilleadingfromsaidspacesand into the bypass ducts II in the same manner as occurred as the films of air approached the front walls of the first heating units as above described. The operation is repeated as the web successively passes between the remain heating units.

Thus eflective means is provided for breaking up the films of entrained air moving with the web as it passes through the drying chamber and to by-pass the excess air and the gas and fumes from the web into the by-pass ducts above and below the banks of heating units.

By thus by-passing such excess air away from the' web and the heating elements, the total heat requirements are materially reduced. The bodies formed by the side walls of the heating units absorb heat from the resistance elements, and as they extend the full width of the web and are closer to the web than the resistance elements, they effectively assist in heating the air and the web as they pass between them. Such baiiies are so formed and placed at such an angle to the web, as to agitate the films of air adhering to the web and simultaneously radiate and impart heat to the air films and web. These baffies in so disturbing the air film destroy its harmful insulating properties as well as to reduce the air fiow along the web. The air having been reduced in quantity and preheated by the bames requires a proportionally smaller amount of heat to bring it up to treating temperature and, therefore, the heating load on the resistance elements is reduced, thereby maintaining a higher surface temperature with consequently higher radiating qualities. This is particularly beneficial in effecting penetration of heat through the web by radiation. This, two-fold heat saving has been accomplished, namely, less air to heat and higher radiating and penetrating qualities.

Also, by arranging a multiple of electrical heating units asdescribed, with the resistance elements as close to the moving web as is practicable, while providing exhaust passages above and below the banks of heating units, permits the use of an exhaust system at the web-leaving end of the drier without unnecessarily increasing the amount of air passing between the heating units and the web. The use of the bypass ducts and the outer drier housing results in 'a definite saving in heat requirement since only the air passing between the web and heating units need be heated to the required treating The excess air thus exhausted is not directly exposed to the high temperature of the resistance elements. This exhaust ar, therefore, accomplishes its work of removing the fumes and gases without being heated to the temperature required for treating the web, and it has been found that the heat saved is in some cases as high as 25% of thetotal heat load. The passage of the web between the inclined nozzles insures efiective removal of any remaining fumes or gases from the web before the web leaves the drier.

With the arrangement of the sections of the heating units and thearrangement of the windings of the resistance elements thereof as described, and illustrated in Fig. 6, a uniform heat coverage of the web is maintained which is especially advantageous wheen operating close to the web. By having the terminals of adjacent sections lead from the same point of their conductor, complete electrical protecton for the resistance elements is maintained since no voltage difl'erence exists between successive elements of the sections. Thus. there is no danger of current flowing from one resistance element to the other, and thereby arcing or burning out is eliminated when the sections with their resistance elements are placed in operation end-toend in the heating unit. Also. by making each heating unit up of a plurality of sections as illustrated and described, injury to the units due to expansion or warping is avoided. Each section may be easily removed from its heating unit for replacement and repair. The use of heavy bare conductors which serve the dual purpose of supplying current for the sections and as an additional means of support for the ceramic parts in case they should be excessively damaged by cracking, makes a convenient and relatively inexpensive safety measure. The web to be treated is in some cases as close as from the heatin: units and consequently the sections which may crack from undue heat must be well supported at all times so as not to damage the web. The assembly of the sections of the heating unit and the supporting means therefor ensures proper functioning of all parts irrespective of injury thereto caused by overheating. The heating units not only effectively insulate the resistance elements but also effectively shield the bare conductors associated with the units, it being unnecessary to individually insulate the conductor. It has been found that only insulators of high temperature ceramic or porcelain will withstand the high temperatures of the heating units. This arrangement therefore provides proper insulation conveniently and inexpensively.

The provision for simultaneously adjusting the units toward and from each other, enables the drier to be readily adjusted for difierent thicknesses and quality of work, and enables the quantity of air passing between the web and the heating units to be varied to meet different conditions. Also, as such adjustment may be effected from a point outside of the drying chamber and while the drier is operating, it enables the units to be separated when the feeding of the web is stopped so as to prevent burning or scorching of the web. While it is preferred to use two banks of heating units. in some instances a single bank may be employed.

The heating units may be of various heat intensities in order to subject the paper to the most efilcient drying temperature at all points during its travel between the several banks of heating units. In most instances it has been found more economical to have the first pair of heating units of high heat intensity so as to rapidly heat the moist web at the start of its passage between the banks of heating units. The heat intensities of the other units may be of a substantially lesser amount and preferably of decreasing intensity from front to rear of the banks so as to decrease the amount of heat to which the paper is subjected as it loses its moisture. By means of the decreasing intensity of radiation thus obtained from front to rear of the banks the paper is brought up to a safe drying temperature quickly and is maintained at this temperature resulting in high efficiency and good quality work.

Also, it will be noted that these heating units of lower heat intensity serve as boosters to maintain the air passing between the banks at a substantially uniform temperature. It will be understood, however, that for certain kinds of work it may be desirable to otherwise vary the heat intensities of the various units. Such variation in heat intensities may be accomplished by employing different size element ribbon, by varying the number of turns of the ribbon on each heating unit, or by any other suitable means.

Another advantage of this construction as above described is that the amount of air necessary to be passed between the banks of heating units with the web is reduced to the minimum amount required to carry off the moisture and gases arising from the web during the drying thereof. This not only reduces the amount of equipment necessary to carry off the air and gases exhausted from the drier but results in maximum economy of operation.

It has been found that the drier described above gives high drying efficiency which up to now is only obtained with very low temperature driers and which have been found to be'prohibitive in size in many instances as well as more costly.

This drier also requires less space and costs less than the high temperature driers. The high temperature driers have up to now been considered small but the quality of printing as a direct result of drying is inferior. Also, the high temperature driers are considered hazardous since the paper frequently catches fire. The specific construction of the unit sections has been found to be of considerable practical importance. The resistance ribbon is securely locked in place without the use of spacers for each individual turn and without the use of cement. Also, the sections may be wound of various thicknesses and widths of ribbon elements and of various number of turns or windings and may be connected in parallel as shown, or in series in an electric circuit, depending on the conditions required. The unit sections are of simple and strong construction, and may be easily assembled and individually removed for replacement or repair.

In the form of heating unit section illustrated in Fig. 5A, instead of the resistance ribbon being spaced a substantial distance above the lower edges of the bailles or side walls of the unit as shown in Fig. 5, each element carrying rod is mounted in a groove I6 which opens downwardly and inwardly so as to position the lower edges of the heating element but a slight distance above the lower edges of the baffles or side walls. This construction enables the heating element to be spaced a minimum distance from the web which makes for most economical operation in the case of certain kinds of work. It will be noted that when the resistance elements are thus positioned that the air entering between the names or side walls of each unit is thoroughly agitated as it expands and passes between the strands of the heating element and as it leaves the space above the heatin element.

In the form shown in Fig. 7, the web before entering the drying chamber passes through the suction chamber 10 which may be connected through conduits I02 with controllable suction means. This chamber has an inlet opening I04 through which the web passes and baflies or scoops NE at opposite sides of the web. Also, the rear ends of the top and bottom walls of the drying chamber are provided with damper controlled openings I08.

With this construction the air bypassed through the passages 30 and entering the bypass ducts 3|. instead of passing out through the rear or outlet openin of the drying chamber as in the form above described. will run counter to the travel of the web and be exhausted out through the suction chamber Ill. Also. the air entering through the air males will tend tobedrawnintothedryingchamberand through the exhaust bypass II, the amount of air thus entering the drying chamber depending upon the degree of vacuum in the suction chamber It.

It will be noted that the air thus counterfiower through the'bypass ducts Ii will be directed counter to the flow of entrained air entering with the web into the drying chamber and thus will not only serve to preheat the air and the web but also serve to break up the entrained air and tend to cause it to be exhausted through the conduits ill. Thus the cold films of air entering with the web are broken up and displaced by the air passing through the inlet opening of the drying chamber into the suction chamber, and consequently cold air entering between the banks of heating elements and the web is eliminated. thus effecting a substantial saving inheat.

The amount of air entering the drying chamber through the outlet opening thereof may be controlled by controlling the degree of vacuum in the suction chambers. The damper controlled openings ill when open permit when desired fresh air to be admitted into the rear ends of the bypass ducts 3| which may be desirable in some instances in order to increase the fiow of air therethrough to eliminate the vapors arising from the web or for other .purposes. The fresh air, or combination of fresh air and gases so admitted, during their counter-flow travel through bypass ducts ii are exposed to the high temperature of the back sides of the horizontal walls of the heating units. Thus the entering fresh air is effectively preheated before it comes into contact with the web and entrained air as they enter the drying chamber.

The form shown in Fig. 8. differs from that of the form first described in that damper controlled conduits lead from the upper and lower exhaust ducts ll preferably midway between the ends of the drying chamber. These conduits are connected with suction means, not shown.

This construction is particularly advantageous in'treating certain kinds of material where an excessive amount of gases or vapors arises therefrom as it permits the gases and vapor to be exhausted in large volume from the bypass conduits.

In the form shown in Fig. 9 the heating units ofeaeh bank are arranged side by side and are of open construction, so as to permit the heating element of each unit to radiate from both sides thereof directly to the web. The web to be treated enters the drying chamber through an inlet opening ill, passes adjacent the under side of the lower bank of heating elements and then leaves the chamber through an opening Ill. The web then passes over a roll Ill, thence returns to the drying chamber through an opening Ill. From this opening the web passes midway between the two banks of heating elements and again leaves the chamber through an opening lll. The web then passes over a roll I22 and re-enters the chamber through an opening I and passes through the chamber in proximity to the top side of the upper bank of heating units and finally leaves the chamber through an is connected with a suitable suction means through a damper controlled conduit Ill. the suction chamber lll enclosing the roll I22 and the portions of the web extending from the roll to the drying chamber. The openings Ill and ill in the rear wall of the drying chamber are in communication with a suction chamber in which is connected with suitable suction means through a damper controlled conduit-I32, this suction chamber enclosing the roll Ill and the portions of the web extending therefrom to the drying chamber.

The rear end of this auction chamber III is provided with a damper controlled opening I34 and the forward end of the forward suction chamber I21 is provided with a damper controlled opening Ill.

This form of the invention is particularly adapted for use where the material is of such a nature as. to permit it to be passed over rolls so as to allow the material to pass a plurality of times through the drying chamber.

It will be noted that the web entering the chamber first passes beneath the lower bank of heating units, then on its next travel through the chamber it passes between the banks of heating units, and finally it passes over the upper bank of heating units. By using a skeleton construction of heating units as will be hereinafter described, the heating elements thereof are capable of radiating heat from both sides thereof so that both portions of the web in their travel in opposite directions through the heating chamber are subjected to radiation from all of the heating elements of each bank.

The suction chambers I 21 and III, and the restricted inlet and outlet openings in the front and rear walls of the drying chamber tend to remove the entrained films of air from the web. In case additional air is required to assist in carrying of! the vapors this may be supplied through the damper controlled openings I and Each heating unit, like in the case of the heating units first described, may be made of sections arranged end to end, on of the sections being shown in Fig. 10. Each section comprises side walls I which are secured together by means of removable cross-bars I" which correspond to the horizontal wall 08 of the section of the heating unit first described except for the skeleton construction. The side walls of adjacent units of each bank are provided with registering grooves 0 which are adapted to be positioned over rods I42 secured to the side walls of the heating chamber. It will be apparent that this form of heating unit may be easily assembled and mounted in the drying chamber similarly to the units first described.

As will be evident to those skilled in the art, our invention permits various modifications without departing from the spirit thereof or the scope of th appended claims.

What we claim is:

1. In a drier of the class described, the combination of a drying chamber having openings in the front and rear ends thereof through which the material to be treated is adapted vto pass as it enters and leaves the chamber, a bank of heating units mounted in the chamber arranged parallel to and in proximity to the path of the material as it travels through the chamber, the heating units extending transversely of the path of the material and being spaced apart, said chamber having an air duct extending over the side of the bank of heating units opposite the path of the material, the frontend of the air duct being in communication with said opening in the front end of the drying chamber, and the rear end of the air duct being in communication with said opening'in the rear end of the drying chamber, members closing the spaces between the heating units of each bank having air passages leading into said air duct, and means for exhausting air from the rear of said air duct whereby the entrained air entering with the material through said opening in the front end of the chamber and the fumes from the material tend to pass through said air passages and into said air duct and to be discharged through said opening in the rear end of the chamber.

2. In a drier of the class described, the combination of a drying chamber having openings in the front and rear ends thereof through which the material to be treated passes as it enters and leav s the cha r. opposed banks of heating units between which the material passes as it travels through the chamber, the heating units of each bank extending transversely of the material and being spaced apart, said chamber having air ducts respectively arranged adjacent the outer sides of the banks of heating units, members closing the spaces between the heating units of each bank having air passages leading into the associated air duct, nozzles for directing streams of air in a forward direction against opposite sides of the material after it leaves the rear end of the drying chamber, and means comprising an air passage into which said opening in the rear end of the chamber leads and into which said nozzle leads for exhausting air through said opening from said air ducts and to-cause said flow of air from said nozzles.

3. In a drier of the class described, the combination of a drying chamber having openings in the front and rear ends thereof through which the material to be treated passes as it enters and leaves the chamber, a bank of heating units arranged parallel to one side of the path of the material as it passes through the chamber, said heating units extending transversely of said path of the material, each heating unit having a wall parallel to and spaced from said path, baiiies arranged adjacent the longitudinal sides of said wall and having their inner edges in proximity to said path, an air duct arranged adJacent the outer side of said bank of heating units and in communication with the openings in thefront and rear ends of the drying chamber, openings between the heating units leading into said air duct, and an electric heating element arranged between the baffles of the unit.

4. In a drier of the class described, the combination of a drying chamber having openings in the front and rear ends thereof through which the material to be treated is adapted to pass as it enters and leaves the chamber, said chamber having side walls adapted to be closed and opened and when open permitting access to said material, banks of heating units mounted in the chamber 1 between which said material passes, and means operable from outside of the chamber for simultaneously closing and opening said side walls and for moving said banks of heating units toward and from the path of said material.

5. In a drier of the class described, the combination of a drying chamber having openings in the front and rear ends thereof through which the material to be treated is adapted to pass as it enters and leaves the chamber, said chamber having side walls adapted to be closed and opened and when open permitting access to said material. a bank of heating units arranged parallel to the path of said material as it passes through the chamber, and means operable from outside of .the drying chamber for simultaneously closing and opening said side walls; and for moving the bank of units toward and from said path of the material.

6. In a drier of the class described, the combination of a drying chamber having openings in the front and rear ends thereof through which the material to be treated passes as it enters and leaves the chamber, opposed banks of heatin units between which the material passes as it travels through the chamber, the heating units of each bank extending transversely of the material and being spaced apart, said chamber having air ducts respectively arranged over the outer sides of the banks of heating units, the front end of the air duct being in communication with said opening in the front end of the drying chamber, members closing the spaces between the heating units of each bank having air passages leading into the associated air duct, and means for ex hausting air from the chamber through said opening in the rear end thereof whereby the entrained air entering with the material through said opening in the front end of the chamber and the gases from the material tend to pass through said air passages and into said air ducts and to be discharged from the chamber.

7. In a drier of the class described, the combination of a drying chamber having openings in the front and rear ends thereof through which the material to be treated passes as it enters and leaves the chamber, banks of heating units between which the material passes as it travels through the chamber. the heating units of each bank extending transversely of the material, said chamber having bypass ducts arranged adjacent the outer sides of the banks of heating units, and baiiies located between the front end ofthe drying chamber and the front ends of the banks of heating units tending to divert the air entering the chamber with the material into said bypass ducts.

8. A structure according to claim 7 in which suction means is provided for exhausting air from the bypass ducts and from the space between the banks of heating units and the material and causing the air to pass with the material from the drying chamber through said opening in the rear end of said chamber.

9. In a drier of the class described, the combination of a drying chamber having openings in the front and rear ends thereof through which the material to be treated is adapted to pass as it enters and leaves the chamber, said chamber having vertical side walls made in longitudinally extending sections, means for supporting said sections for vertical sliding movement, banks of heating imits mounted in the chamber between which said material passes, and means operable from outside the chamber for simultaneously moving the sections of said side walls toward and from each other and for moving said banks of heating units toward and from each other.

10. In a drier of the class described, the combination of a drying chamber having openings in the front and rear ends thereof through which the material to be treated is adapted to pass as -it enters and-leaves the chamber, banks of heating units between which the material passes as it travels through the chamber, the heating units of each bank extending transversely of the material and being spaced apart, members closing the spaces between said units, air ducts respectively arranged adjacent the outer sides of the banks of heating units, said closure members having air passages leading into the associated air duct, and a suction chamber adjacent the outer side of the front end of the drying chamber through which the material passes before entering the drying chamber, the suction chamber being in communication with said ducts through the opening in the front end of the drying chamber.

11. A structure according to claim in which means is provided for directing air into the drying chamber through said opening in the rear end wall thereof, the air tending to impinge against the sides of the material.

12. A structure according to claim 10 in which damper controlled openings are provided in the top and bottom walls of the drying chamber.

13. In a drier of the class described, the combination of a drying chamber having openings in the front and rear ends thereof through which the material passes as it enters and leaves the chamber, banks of heating units arranged parallel and spaced apart, the heating units of each bank extending transversely of the chamber, and conveyor rolls adjacent the outer sides of the ends of the drying chamber, whereby the material enters the chamber through one of the openings in the front end thereof, passes adjacent the outer side of one of the banks of heating units, leaves the chamber through one of the openings in the rear end thereof, then passes over the conveyor roll at the rear of the chamber, then enters the chamber through another one of the openings in the rear end wall thereof, passes between the banks of heating elements, leaves the chamber through another one of said openings in the front end thereof, then passes over the roll adjacent the front end of the chamber, reenters the chamber through another opening in the front end thereof, passes over the outer side of the other bank of heating units, and then leaves the chamber through anotherone of said openings in the rear end thereof.

14. A structure according to claim 13 in which air chambers respectively enclose the rolls at the ends of the chamber and the portions of the material extending from the rolls into the chamber.

15. In a dryer of the class described, the combination of a drying chamber having openings in the front and rear ends thereof through which the material to be treated passes as it enters and leaves the chamber, a bank of heating units arranged parallel to one side of the path of the material as it passes through the chamber, said heating units extending transversely of said path of the material, each heating unit having a wall parallel to and spaced from said path, baiiles arranged adjacent the longitudinal sides of said wall and having their inner edges in proximity to said path, an electric heating element extending over the inner side of said wall and between said bafflee, the backs of said heating units together with the walls of said chamber forming an air duct having its front and rear ends in communication with said openings in the front and rear ends of said chamber, and suction means in communication with said opening in the rear end of said chamber for exhausting air entering through said opening in the front end of the chamber through said air duct, and between the material and said heating units as the material passes through the chamber, said bailies serving to break up and agitate the air that passes between the material and the heating units.

16. The method of drying sheet material of the class described which comprises passing the material between banks of heating units located in a heating chamber having openings in its front and rear ends through which the material enters and leaves the chamber, exhausting air from the chamber through said opening in the rear end thereof so as to cause air to flow through the chamber and to enter and leave the chamber through the openings in the front and rear ends thereof respectively, diverting portions of the air thus entering the chamber through bypass ducts extending over the outer sides of the banks of heating units, and directing the air passing through said ducts against the material as the material passes beyond said banks of heating units and approaches said opening in the rear end of the chamber.

17. The method of drying material of the class described which comprises, passing the material parallel to the heating surface of a bank of heating units located in and extending longitudinally of a heating chamber having openings in its front and rear ends through which the material enters and leaves the chamber, exhausting air from the chamber through said opening in the rear end thereof so as to cause air to pass through the chamber and to enter and leave the chamber through said openings in the front and rear ends thereof respectively, diverting a portion of the air thus entering the chamber through a bypass duct extending over the outer side of the bank of heating units, and directing the air passing through said duct against the material as the material passes beyond said bank of heating units and approaches'said opening in the rear end of the chamber.

REMI A. BENOIT. EDOUARD LE B. BENOIT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 784,854 Grace Mar. 14, 1905 1,469,048 Nelson Sept. 25, 1923 1,571,282 Leculier Feb. 2, 1926 1,819,109 Miller Aug. 18, 1931 1,827,508 Cope Oct. 13, 1931 1,881,241 Potensa Oct. 4, 1932 2,000,546 Woodsome May 7, 1935 2,038,457 Venturini Apr. 21, 1936 2,220,928 Kienle et a1 Nov. 12, 1940 2,256,727 Sloane Sept. 23, 1941 2,268,986 Hess et al. Jan. 6, 1942 2,268,988 Hess et al. Jan. 6, 1942 2,308,239 Bell Jan. 12, 1943 2,325,950 Greene et al Aug, 3, 1943 FOREIGN PATENTS Number Country Date 386,840 Great Britain Jan. 26, 1933

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