US2346764A - Method and apparatus for making sheet material - Google Patents

Description

April 18, 1944. E M KRATZ 2,346,764

METHOD AND APPARATUS FOR MAKING SHEET MATERIAL Filed Sept. 12, 193B 9 Sheets-Sheet 1 April 1s, 1944. E M KRATZ 2,346,764

METHOD AND APPARATUS FOR MAKING SHEET MATERIAL Filed Sept. 12, 1938 9 Sheets-Sheet 2 HHHHII :QQ

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METHOD AND APPARATUS FOR MAKING SHEET MATERIAL Filed Sept. 12, 1958 9 Sheets-Sheet 4 E. M KRA-rz Apri 1s, 1944.,

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METHOD AND APPARATUS FOR MAKING SHEET MATERIAL Filed Sept. l2, 1938 9 Sheets-Shea?I 6 Ap@ as, w44.,

E. M. RRA-rz l METHOD AND APPARATUS FOR MAKING ySHEET MATERIAL Flled Sept 12, 1958 E. M. KRA-rz -pril 18, 1944.

METHOD AND APPARATUS FOR MAKING SHEET MATERIAL Filed Sept. 12, 19258 9 Sheets-Sheet 8 u 1 1 u f E. M. KRATZ April Is, 1944.

9 Sheets-Sheet 9 Filed Sept. 12, l1938 METHOD AND APPARATUS FOR MAKING SHEET MATERIAL' QN, Q a

KQN MVN Patented Apr. 18, 1944 -METHOD AND APPARATUS FOR MAKING SHEET MATERIAL Edouard M. Kratz, Gary, Ind.,

assignor, by mesne assignments, to Carbide and Carbon Chemicals Corporation, New York, N. Y.,

of New York a corporation Application September 12, 1938, Serial No. 229,509

3 Claims.

This invention relates to an improved method and apparatus for making webs or sheets from lm forming materials such as casein or synthetic resin solutions, for example.

The main objects of the invention are to provide a method and apparatus by which high speed production of sheeting or webbing of the character indicated may be carried on; to provide a method and apparatus for the purpose indicated whereby a sheet or web of very thin but uniform thickness may be produced; to provide a method and means whereby a soft and pliable sheet may be formed; and in general, it is the object of this invention to provide an improved method and apparatus for the purpose indicated.

Other objects and advantages of the invention will be understood by reference to the following specification land accompanying drawings (9 sheets) wherein there is illustrated the improved apparatus for making sheet material by the improved method.

In the drawings:

. Figure 1 is a more or less diagrammaticrepresentation of the improved apparatus.

Figures 2, 3 and 4 are longitudinal sections respectively, Figures 2 and 4 illustrating the opposite end portions and Figure 3 illustrating the portions of the apparatus intermediate the opposite -end portions.

Figure 5 is a perspective illustrating the portions of the apparatus where the liquid material is delivered to it for formation into a sheet.

Figure 6 is a side elevation of the mechanism shown in Figure 5 together with certain other mechanism at the receiving end of the apparatus.

Figure 'I is an elevation of an end portion of the apparatus as indicated by the line 'lof Figure 6.

Figure 8 is a sectional illustration showing in detail the arrangement for delivering the liquid material to the apparatus and for forming the sheet from such liquid material.

Figure 9 is a perspective illustrating an arrangement for controlling sidewise shifting of a belt or band on which the sheet material is car-` ried for drying purposes.`

Figure 10 is a section on the line lll-I0 of Figure 3.

Figures l1 and 12 are sections respectively on thelines Il-H and I2-I2 of Figure 10.

Figure 13 is a section on theline |3-l3 of Figure 1l.

Figures 14 and l5 are plan and side views of a portion of the apparatus for drying the sheet material.`

Figures 16 and 17 are sections respectively on the lines Iii-I6 and Il-i'i of Figure 14.

Figures 18 and 19 are plan and side elevations of the intermediate portion of the drying apparatus.

Figures 20 and 21 are sections respectively on the lines 2li-20 and 2i-2I of Figure 18.

Figures 22 and 23 are plan and side views respectively of another portion of the drying apparatus.

Figure 24 is a section on the line 22-24 of Figure 22.

Figures 25 and 26 correspond respectively to Figures 1 and 4 of the drawings but show a modified arrangement.

Figures 2'7 and 28 are side and end views, respectively, of a form of device which may be employed if desired for conveyor belt guiding purposes, and

Figure 29 is an end view of an alternative means for maintaining a conveyor belt in transversely ilat condition.

The improved apparatus herein contemplated embodies a metallic belt 25 which may be of brass, stainless steel or other metals provided with a suitably polished or otherwise treated, coated or plated surface. If brass is employed it may be buied to a very high polish and if a steel is employed in the belt a satisfactory surface may be provided by plating the belt with nickel or some other metal which produces a satisfactory, smooth finish. In one embodiment of the apparatus the conveyor 25 is approximately one hundred and sixty feet long. The lm forming solution is delivered to the belt where it passes around a drum 25. The solution is spread to form a illm of the desired thickness on the conveyor belt 25 which carries the film into a drying oven. As shown in Figure 1, the oven is represented in its entirety at 21.

The oven 2l is divided into three sections, each of which is supplied with hot air, the arrangement including means whereby the temperature of the air supplied to each section may be controlled and adjusted independently of the other sections.

The conveyor belt 25 is supported at one end by the drum 26 and at its other end by a drum or roller 28. The film of materialadheres to the belt to such an extent that the 111m will continue to travel with the belt on its return reach until the lm is separated from the belt and conducted to winding mechanism indicated at 29.

ported solely by the rolls or drums 2l and 23. The oven 21 is shaped longitudinally to correspond to the common catenary curve of the belt, thereby avoiding the provision of excess space in the oven which would absorb some of the heat supplied to it and thereby hinder the drying operation. 'I'he oven 21 may be made of suitable material, for example, galvanized sheet metal on an angle iron or like frame structure. The oven may and preferably should be provided with suitable thermal insulation to assist in maintaining the desired temperatures therein. Such details of the oven construction are not herein illustrated since they are not a part of the present invention.

When the protein sheet is to be formed from a base of casein solution, the` casein solution or dispersion has added to it a predetermined proportion of formaldehyde, or other suitable hardening or setting agent. The solution, or dispersion, begins to set almost as soon as formaldehyde is added to it. It is desirable that the solution be delivered to the sheet or web forming apparatus before the solution sets to any appreciable extent. Accordingly, the present apparatus provides for the mixing of the casein solution with the proper amount of formaldehyde at a point immediately preceding the delivery of the solution to the forming apparatus.

As best shown in Figure 5, the casein solution is conducted to the apparatus b y a pipe line 30 which is connected with any suitable source of supply. The pipe line 39 conducts the material to a pump 3i which is actuated by an electric motor 32 to a suitable speed reducing device 33 and a variable speed driving device 34. 'I'he pump 3l delivers the casein solution through a pipe line 35 to a mixing device 35 which is actuated by electric motor 31 or by other suitable means. The formaldehyde solution is conducted from a suitable source of supply by a pipe line 38 to a pump 39 which is actuated by the motor 32 through the speed reducing and speed controlling units 33 and 34. 'I'he pump 39 delivers the formaldehyde through a pipe line 49 into the mixer. By suitable valves not herein illustrated, or by proper selection of the capacities of the pumps 3i and 39, the proportion of the fonnaldehyde and casein solutions may be accurately controlled. Also, the volume of these materials delivered to the mixture may be controlled by adiustment of the speed controlling device 34.

The casein and formaldehyde mixture is delivered by a pipe line 4| from the mixer 36 to a header or manifold 42, which is provided with a multiplicity of (in this case 8) discharge outlets which are respectively connected by exible hoses such as 43 to nozzles or delivery pipes 44.

When synthetic resin and other lm forming solutions are employed, the foregoing described arrangement for injecting the hardening, or any similar agent, into the solution immediately before delivery thereof to the lm forming belt, may not be required. I

The nozzles 44 are mounted so that their relationship to the surface of the belt 25 may be adjusted to produce the desired results. As shown in Figures 5 and 8, each of the nozzles is carried by a block 45, each of which is mounted on a rod 46. The blocks 45 may be provided with setscrews (not shown) for locking the blocks and the nozzles in any desired position of adjustment relative to the conveyor belt, or if preferred, the blocks 45 may be xedly mounted on the said rod '2,340,764 As indicated in Figure l, the belt 25 is sup-` 43 and the rod mounted for rotatable adiustmcnt so that all of the nozzles may be simultaneously adjusted relative to the conveyor belt. It will, of course, be understood that both forms of `adjustment may be provided.

The nozzle supporting rod 43 is carried in this instance by means of a pair of hangers 41-41 which are vertically slidably mounted in members 43-43. I'he members 43-42 are in turn horizontally slidably mounted in a bar 4I. The bar 43 is supported for reciprocation in a direction transverse to the travel of the conveyor belt 25. For this purpose the bar 49 is supported by bearing members 50 which are carried by a U- shaped frame element Il. The U-shaped member 5| is pivotally mounted at the free ends of its side legs 52-52 on a rod 53 which is carried by suitable bracket arms 54-54 which are formed integral with or attached to conveniently located frame portions of the apparatus.

n To eil'ect reciprocation of the bar 43 and thereby reciprocation of the nozzles 44 crosswise of the direction oftravel of the belt 25, the bar is connected by means of a link Il to a crank pin 5t carried by a rotatably driven member 51. The latter may be mounted for rotation in any conveniently provided bracket and it may be driven by any suitable arrangement. It will be observed that the revolution of the crank pin 53 will be transmitted by the link 55 to the bar 43 which will be reciprocated accordingly.

The U-shaped element 5I is provided with rollers such as 58 which are adapted to engage the marginal portions of the surface of the drum 23 beyond the respective edges of the conveyor belt 25. A doctor blade 53 is adjustably mounted on a transversely extending supporting member 60. The supporting member 89 is provided with laterally extending arms Gl-GI which are pivotally mounted at their free ends on a rod B2 which is mounted at its ends in the side members 52 of the U-shaped member. Provision for adjusting the doctor blade carrying member 6a vertically relativev to the conveyor member 25 consists in this instance of screws such as 63 which threadedly engage suitably tapped openings in the opposite end portions of the supporting member 60. 'I'he screws 63 may be turned until their lower ends rest on the U-shaped member 58. It will be apparent that by adjusting the screws 63, the doctor blade and its supporting member El) may be adjusted to or from the conveyor member 25. A lock nut or similar device indicated at 64 may be provided on the screws 63 for locking the latter in the desired adjusted position.

The member 69 is preferably made hollow as indicated in Figure 8 and a heating medium such as hot water may be supplied therethrough by a exible hose connection 65 and drained therefrom 'by a similar connection indicated at 6B. 'Ihe drum 26 is also preferably hollow and adapted to have its temperature controlled by supplying to the interior of the drum hot water or the like, the same being supplied through a supply pipe 61 and drained therefrom by a pipe t8.

The doctor blade 59 may be secured to the supporting member through the agency of screws such as indicated at 69. Provision for adjusting the doctor blade relative to the supporting member 60 may include screws such as indicated at 10 provided withheaded ends 1i which t into slots or grooves 12 provided in the doctor blade 59. The screws 19 threadedly engage a suitably tapped opening in bosses such as indicated at 19 which may be carried by the supporting member 80. The upper ends of the screws are preferably squared or otherwise treated as indicated at 14 to facilitate turning of the screws. By turning the screws 14 after loosening the screws 69, the doctor blade 59 may be adjusted. As indicated in Figure 5. the last de, scribed adjusting means is supplied at relatively short intervals along the length of the doctor blade so that accurate localized adjustment of the doctor blade may be made. By this means accuracy or uniformity-of the thickness of the fllm of material permitted to pass under the doctor blade on the conveyor belt may be accurately controlled.

By mounting the nozzles on a pivotally mounted frame such as the frame it is made very easy to swing the entire delivery mechanism and doctoring mechanism upwardly away from the conveyor belt to facilitate cleaning or other operations on the belt or drum or adjacent parts of the apparatus. Also, by mounting the nozzles M for reciprocation transversely, the formation of ridges in the casein solution adjacent the doctor blade is eliminated. It will be understood that in the event that the delivery nozzles were to remain stationary, the material delivered to the conveyor belt would spread l put approximately uniformly on the belt but 'that where adjacent streams of the material come together they would tend to pile up to form ridges of material. Formation of such ridges is somewhat objectionable in that it tends to interfere with uniformity of the Web formed on the apparatus.

As best shown in Figure 5, the drum 26 (and thereby the belt 25) is driven from a suitable source of power such as an electric motor indicated at 15. The motor 15 is suitably connected to a variable speed controlling unit 16 which in turn drives suitably journalled shaft 11. The shaft 11 is equipped with a worm gear 18 which meshes with a worm wheel 19 mounted on the tubular shaft 80 of the drum 26.

The shaft 11 is also connected through the agency of suitable gear connections enclosed in a housing such as indicated at 8| to a shaft 82. The shaft 82 extends transversely of the machine and is equipped at the opposite side of the apparatus with a pulley or sprocket represented at 83 which is connected by a chain or belt designated 84 to means for driving the rotating member 51.

It will be evident that a supply of casein and formaldehyde solution delivered vto the band or belt 25 by the nozzles twill be formed into a web of uniform thickness on the belt incident to the travel of the belt under the doctor blade. The web of material on the belt enters the upper v portion of the adjacent end of the drying oven 21 as best shown in Figure l.

It is subjected to heat as soon as it enters the drying oven. Hot air is initially supplied to the oven adjacent the other or far end thereof, that is adjacent the belt supporting roll or drum 28.

Fior convenience, in reference to the latter end of the apparatus, it will be identified by the reference numeral 85.

Referring to Figures 22 :to 2.4, inclusive, it will be seen that there is provided a blower 88 connected by a conduit 81 to branching conduits 68, 89 and 90. The conduits 88, ,89 and 90 are respectively connected to the end portion 85 of the oven near the top, central and bottom portions thereof as shown. By this arrangement a desirable uniformity of the distribution of hot air is obtained in the oven. 'I'he blower 86 is connected to a heating unit 9| which preheats air supplied thereto through a suitable filtering device indicated at 92. By employing the filtering device 92, dust and other foreign matter is adequately removed from the air which is heated and delivered to the oven so that the protein sheet formed on the conveyor belt is kept clean and free from dust and other matter which might impair' its finish. Suitable thermostatic controls (not shown) may be provided for governing the temperature to which the air is heated by the heating unit 9|.

A similar heating arrangement is provided for supplying hot air to the intermediate portion of the oven. such arrangement being illustrated in Figures 18 to 21, inclusive. By reference to the last mentioned figures it will be seen that there is provided a blower 98 which is connected by a conduit 94 to conduit branches 95, 96

and 91, which enter the oven 21 by means of delivery nozzles which direct the air away from the adjacent exhaust connections as most clearly shown in Figure 19. Ihe air supplied to the branches 95, 96 and 91 is obtained primarily from the adjacent end portion of the furnace to which hot air is supplied by the blower 86. For this purpose there is provided a conduit 98 which has vertically spaced exhaust connections indicated at 99-99 to the oven immediately preceding the point to which hot air is delivered thereto by the branches 95, 96 and 91. The conduit 98 also has an intermediate connection indicated at |00 which connects with both the upper and lower sections of the furnace. By reference to Figures 1 to 4, inclusive, it will be observed that the oven is provided interiorly with hollow sheet metal fillers designated |0|, |02, and |03, respectively, which in effect divide-the furnace into upper and lower passes for the upper and lower reaches of the conveyor belt 25. By providing the inlet and transverse 'wall in the oven intermediate the adjacent ends of the fillers |0|, |02 and |03. It is likely that some of the hot air from one section of the furnace passes directly into the other section but the volume thereof is so small that it has no objectionable effect on the re-heated air which is supplied through conduits such as 95, 96 and 91.

A fresh supply of air may also be injected into the furnace by the blower 93, and an intake |04 being suitably connected to the conduit 98 for this purpose. The inlet IM is also preferably provided with means for filtering the fresh air drawn into the system and a heating unit |05, similar to the heating unit 9|, is provided for heating the air delivered to it by the conduit 98.

Hot air is supplied to the receiving end portion of the furnace by means of a'blower |06. The blower |06 receives the hot air from a conduit |01 which has exhaust connections I08|08 to the upper and lower passes of the intermediate section of the furnace and also an intermediate connection |09. The hot air drawn from the intermediate furnace section is blown by the blower |06 through a delivery conduit IIO to branch conduits |I| and H2, which communicate as best shown in Figures 3. 15 and 17 with the upper chamber or pass of the furnace.

To more effectively separate the upper and lower passes of the furnace from each other, there is provided a divider H3 as indicated. For practical purposes it is neither necessary nor desirable to reheat the air before its delivery to the receiving end portion of the furnace wherefor there is provided `no means for heating the air delivered by the blower |06; however, it will be understood that if it should be desired to reheat the air, heating units such as 9| and |05 may be provided and suitably interposed in the air circuit.

The lower section or pass of the furnace under the receiving end portion of the upper pass is preferably supplied with tempered and hunildied air supplied thereto by an air conditioning unit II4. The air conditioning unit |I4 may include a suitable blower for impelling the air therethrough and it is connected by means of a conduit I I to an outlet in the delivery end portion of the lower pass of the furnace, as indicated at II6. 'Ihe air exhausted from the delivery end of the lower pass of the furnace through the conduit I I 6 is returned to the lower pass of the furnace through a conduit I I1 which has branches IIB and IIS, respectively, connected as indicated at and |2| to the top and bottom of the lower pass of the furnace as best shown in Figures 3, 15 and 17. Dampers such as indicated at I22 may be provided in the various conduits wherever desired for controlling the volume or Velocity of the air drawn from and delivered to the various portions of the furnace.

It has been found that a metal conveyor belt or band such as tends to curl transversely of its length, i. e. buckle so that on its upper reach it is lower in its middle than at its edges. For the purpose of counteracting the tendency of the belt to buckle as explained, there is provided straightening apparatus shown in Figures 10 to 13, inclusive. Such apparatus is located at a convenient point,'preferably about the middle of the length oi' the conveyor or at the closest point of the catenary curve of the belt. The device in its entirety is indicated at |23 in Figure 3 and a similar device for straightening the lower-reach of the belt is indicated at |24.

The device |23 for counteracting the tendency of the upper reach of the belt to buckle comprises a pair of rolls |25-I25 which are rotatably mounted at their opposite ends in angle iron or other suitable frame pieces |26. The frame pieces |28 and the parts carried thereby are provided with axially vertical bearing elements |21 which slidably fit on vertically extending guide rods |28. The guide rods |28 are supported by means of suitable brackets as indicated in Figure 10 which are in turn secured to the frame work or sides of the oven. The rolls I25-I25 underlie the upper reach of the conveyor band 25 and the latter is maintained in contact with the rolls |25 across the entire width of the band by means of a series of grooved rollers |29 which are rotatably mounted on the frame members |26. The grooves in the rollers |29 are made deep enough to receive suiciently wide marginal portions of the belt to prevent said marginal portions from springing out of the grooves. Hence the frame members |26 and the parts carried thereby are, in eiect, suspended from the side marginal portions of the conveyor belt. The weight of the straightening apparatus is such that it is enough to hold the conveyor band to a substantially fiat condition transversely of its length and in which condition the band will engage the entire length of the rolls |25. The weight of the straightening device is not suincient to effect inverted buckling, the latter being resisted by the support of the rolls |25. It will k` i c be observed that the straightening apparatus described more or less floats on the guide members I28-|28, the device being supported by the engagement of the grooved rollers |29 with the opposite margins of the belt.

The lower or return reach of the belt has the same tendency to buckle but themarginal portions of the belt in the lower reach tend to assume a position lower than the central portion of the belt. For the purpose of resisting such tendency in the lower reach of the belt a floating structure substantially like that above described is employed but the rolls |25 are replaced by rolls |30 which engage the top surface of the lower 'reach of the belt. The device, is, however, more or less iioatingly supported by engagement of grooved rollers such as |29 with the marginal portions of the conveyor belt.

Because of unavoidable inaccuracies in adjustment of the drums or reels 26 and 28 relative to each other, or due to other causes, there is a tendency for the conveyor belt to shift sidewise; to control and counteract such tendency there is provided a guiding or steering roll |3I (see Figures 6 and 9) which underlie the lower reach of the belt at a convenient point outside of the drying furnace. 'Ihe roll |3I is journalled at one end in a suitable bearing |32 and at its other end in a bearing |33 which is mounted for lateral adjustment in a supporting member |34. The bearing |33, in a neutral position, would be so located that the axis of the steering roll |3I would be exactly perpendicular to the length of the belt 25. To steer the belt to one side or the other the roll I3I is adjusted to an inclined position relative to the length of the conveyor belt with the result that it eiects the desired shifting of the belt.

For effecting shifting of the roll I 3| to inclined position for the purpose indicated, there is provided a reversible electric motbr |35 which is equipped with a worm gear |36 meshing with a worm wheel |31. The worm wheel |31 is secured to one end of a shaft |38 which is journalled in a suitable portion of the supporting member |34 and provided with screw threaded engagement with the bearing |33. It will be apparent that when the motor |35 is energized to rotate in either direction, the bearing member |33 will be shifted one way or the other so as to cause the roll |3I to assume the desired angular position.

The operation of the motor |35 is controlled by a gauging device comprising a bell crank |39 which is pivotally mounted intermediate its ends on a suitable post I 40 which is secured to the frame work of the apparatus. The free end of one arm of the bell crank I 39 is equipped with a roller |4| which is grooved to receive the marginal portion of the conveyor belt 25. The free end of the other arm of the bell crank is connected by a spring |42 to a fixed part of the frame work of the apparatus, such spring tending to rock the bell crank I 39 in the proper direction to maintain the roller |4I in engagement with the edge of the conveyor belt. The free end of said other arm of the bell crank is also connected by means of a Wire or rod |43 to a movable switch arm or contact member |44 of a two-way switch I 45. A spring |45 connected between said switch arm |44 and a xed point serves to pull the switch arm 44 in a crosswise direction (as diagrammatically represented in Figure 9) to make contact with a contact element |41 of the switch. Such movement of the switch arm is, of course, permitted only should be noted that the travel of the conveyorwhen the bell crank |39 is rocked by outward movement of the roller |4| resulting from shifting of the conveyor belt in one direction. In the event that the conveyor belt shifts in the other direction and permits the spring |42 to pull the rod |43, the switch arm |44 will be caused to engage the contact element |48 of the switch |45.

The two-way switch |45 is connected with suitable relays indicated at |49 and |50 'which respectively control electrical circuits for operating the motor |35 in opposite directions. It will be seen that by proper adjustment of the twoway switch |45, the extent to which the conveyor belt 25 may shift sidewise may be effectively limited and controlled.

The film which is designated is removed from the conveyor belt 25 closely adjacent the discharge outlet |52 in the drying furnace. The web or sheet of material |5| is guided around upper and lower rolls |53 as best shown in Figures 2 and 6 and then downwardly and horizontally under a guide roll |54. From the guide roll |54 .the sheet |5| passes over aguide roll |55 which has associated with it trimming wheels |56|56 for trinrming the sides of the web so as to provide straight edges and to make the width ofv the sheet uniform throughout its length. As best shown in Figure '1, the trimming Wheels |56 are mounted on a shaft |51 and they cooperate with the opposite ends of the roll |55 for trimming the sheet or web |5| The roll |55 is carried by a shaft |56 which is suitably journalled for rotation and the shaft |51 is also rotatably supported in suitable bearings provided in frame elements as shown. The trimming wheels |58 and the roller |55 are rotated as an incident to the gearing |59 which connects the shafts |51 and |58 and the engagement of a. pulley |60, c arried by the shaft |51, with a driving belt |6|. The belt |6| is driven by a pulley |62 (see Figures 5 and 6) which is carried by a shaft |63 and which shaft is driven by a belt |64. The belt |64 is driven by engagement with a pulley |65 carried by the driven shaft 82'.

The material to be Wound or reeled is wound on a suitable core such as indicated at |66 which may be carried by a shaft |61. The shaft |61 is journalled at one end in a bearing |68 and at its other end is supported in a. suitable clutch element |69 which is connected with the armature of a magnetic coupling device indicated in its entirety at |10.

The magnetic coupling device may be in the form of a modified electric motor to which current may be supplied through an adjustable or variable resistance device |1|. The field portion of the coupling device may be driven by means of a belt |6| as shown in Figures 6 and '1 and as an incident to the magnetic coupling, the armature portion of the device is also driven so ,that the clutch element |69 will impart rotation to the shaft |61 and core |66. The magnetic coupling device |10 may be of any selected form wherefor the details thereof are not herein speciflcally set forth. By varying the strength of the electric current supplied to the coupling device, the tension under which the sheet is wound upon the core may be. varied to suit speciic requirements. If a, strong current is supplied to the coupling device the sheet will be wound tightly on the core, but if a weak current is supplied the sheet will be wound less tightly. It

belt 25 of the machine proceeds at a constant, fixed rate so that by varying the force which rotates the core |66 the winding tension is accordingly varied.

In one practical embodiment of the described apparatus, the conveyor belt 25 is operated at a speed of about fty feet per minute. Transparent casein sheet material may be eiliciently produced with the apparatus and the effective control of the drying conditions in the oven of the variable temperatures in the successive stages of the oven through which the belt travels permit the production of unusually clear, transparent material, free from discoloration by scorching or other causes resulting from the employment of heat for drying purposes. Also, by permitting a gradual increasing of the tem- -perature to which the sheet is subjected in the drying furnace, thorough drying from the surface of the metallic belt to the outer or upper surface of the sheet is effected. In other words, the formation of a moisture retaining skin on the top surface of the sheet as an incident to the immediate application of high temperature is effectively avoided.

Instead of the above described adjustable roll |3| for guiding the belt 25, relatively fixed means may be employed for maintaining the belt in its proper position relative to the receiving end drum 26. Such means is illustrated in Figures 25, 27 and 28.

The relatively fixed guiding means is movable vertically but not substantially movable transversely of the conveyor belt 25. As-shown best in Figures 2'1 and 28, the device comprises a pair of angle iron side members |15, |15, respectively located adjacent the opposite edges of the lower Areach of the belt 25. Tubular rolls |16 extend between the opposite side members and are suitably rotatably mounted in bearings carried by the' said side members. For engaging the opposite edges of the conveyor belt 25, there is provided a pair of grooved wheels |11, |11, each pair of thev said wheels being located substantially in alignment with the axis of each roller |16. The respective grooved wheels |11 are rotatably supported on the ends of arms |18 and are so spaced from each other that the Width of the conveyor belt] 25 ts between them substantially as shown. As best shown in Figure 27, the arms |18 are pivoted at |19 intermediate their ends and grooved wheels such as |11 are mounted on each end of each of the arms |18. By mounting the grooved wheels in the manner explained, self-adjustment of the grooved wheels |11 relative to the side members |15 is permitted to insure satisfactory contact between each of the grooved Wheels and the edge of lthe conveyor belt without requiring a burdensome degree of manufacturing accuracy.

The guiding unit, comprising the side members |15, |15, and attached parts, is more or less floatingly supported, so that it may readily adjust itself to the normal vertical position of the lower reach of the conveyor belt on which it acts. As shown in Figures 25 and 27, the device is located within the last stage of the drying oven and it is connected thereto by means of links such as indicated at |80. The links are pivoted at one end to the walls or frame of the drying oven and at their other ends to the side members |15 through the agency of brackets such as indicated at |8|. The links |80 permit the guiding device to move vertically but restrain it from horizontal travel with the conveyor belt. The weight of the guiding device is suitably counterbalanced so that itdoes not impose a load on the conveyor belt. One way of counter-balancing the guiding device is to provide one or more counter-balancing weights such as |82 connected by suitable ilexible means |88 extending over pulleys such as 84, and connected to the guiding device.

It has been found that the above described guiding mechanism, when mounted within the drying oven at about one-third of the length of the conveyor belt from the receiving end thereof, will be automatically maintained in proper position relative to the drum 26. The maintenance of the belt in predetermined position on the drum 26 is considerably more important than positionl ing of the belt on the drum 28 at the other end of the apparatus.

As an alternative to the means |23 and |24 for maintaining the conveyor belt flat transversely, there may be provided a series of device such as shown in Figures 25 and 29. Such devices comprise a tubular roll |85 rotatably mounted at its ends on brackets such as |86, and grooved wheels |87 receiving the opposite edge portions of the conveyor belt 25 and also rotatably mounted on the said brackets ite. As shown in Figure 29, the grooved wheels itl are spaced from each otherv so that the width of the conveyor belt 25 ts between the grooved peripheries of the wheels so that the top and bottom anges of the wheels engage surface portions of the belt to prevent its curling and to maintain the belt in flat condition against the surface of the roll |85. Such devices may be suitably mounted through the agency of brackets |82 on guide rods such as indicated at |82 which may be mounted in the oven structure substantially as above explained for the guide rods H28. However, if preferred, the rollers |85 and associated parts may be floatingly supported by means such as above described for the guiding devices comprising the rollers |16 and the grooved wheels |11. As shown in Figures 25 and 26, a series oi four of the described devices are provided at suitably spaced intervals for maintaining the belt at; more or less may be employed as desired and found advisable.

The described apparatus may be employed as already indicated for the production of sheet material of single ply thickness. However, if desired, the sheeting may be made multi-ply or laminated by the simple expedient of depositing additional coats of the forming liquid on preceding plies, which in that case are not stripped from the belt until the desired number of plies have been formed. Such material, although of laminated construction, will have the characteristics of a relatively heavy single-ply sheet since the new plies tend to fuse themselves to the previously formed plies.

In some cases the rst ply of material may be formed of cellulose acetate or nitrate, or any natural or synthetic resin, or rubber composition to provide a` backing of water-proof or other selected character.

In some instances, it is desired to apply reading material or the like on the lsheet material and this may conveniently be done by printing on the conveyor belt with suitable printing ink 70 or the like which will adhere strongly to the sheet formed on the belt and will be stripped from the latter when the sheet is removed from the belt.

Another method of marking the sheet material which may conveniently be practiced in connection with the formation of the sheeting is to apply the desired reading or display material on the belt with suitable pigmented material such as a paint which is dull or flat, and which strongly adheres to the belt. When a sheet is stripped from a belt bearing such indicia, the sheet will disclose the same indicia in the form of frosted or like areas. corresponding to the pigmented areas on the belt.

It is desirable that means be provided for facilitating the cleaning and polishing of the conveyor belt 25. Such means may comprise a suitable bufling wheel or drum rotatably supported by frame work |8| and driven by means such as an electric motor |92. The buillng drum |90 should preferably be mounted so as to be adiustable toward and from the conveyorl belt so as to permit adjustment of the pressure with which the buillng drum acts on the belt. 'I'he buing device may be operated at any desired time but it is preferable that it be not operated during the production of sheet material .on the belt.

AThe apparatus described may be modified in various ways without sacriilcing the advantages set forth in the foregoing description and without departing from the spirit of the invention, the scope of which should be determined by reference to the following claims, the same being construed as broadly as possible consistent with the state of the art. t

I claim: t

1. The method of making sheet material which consists in forming a iilm oi' liquid material on a conveyor belt, propelling the conveyor belt and the iilm thereon through a multi-stage drying oven, applying successively increased drying temperatures to the web in a series of successive stages of the oven, then subjecting the illm to successively reduced drying temperatures in successive stages of the oven, and thereafter removing the ilnished web from the conveyor belt.

2. The method of making sheet materia; which consists in forming a iilm of liquid material on a conveyor belt, propelling the conveyor belt and the mm thereon through a multistage drying oven, applying successively increased drying temperatures to the web in a series of successive stages of the oven, then sub- Jecting the lm to successively reduced drying temperatures in successive stages of the oven, moistening the air in the last stage of the oven, and thereafter removing the finished web from the conveyor belt.

3. In a machine of the character indicated, the combination of a. conveyor belt, means for propelling said conveyor belt, means for delivering a plurality of streams of predetermined liquid mixture or solution to said conveyor belt, means located in proximity to said nozzles for effecting mixture ofgat least two component solutions, and means for delivering predetermined proportions of' said component solutions to said mixing means.

EDOUARD M. KRATZ.

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