US2316173A - Sheet making apparatus - Google Patents

Description

April 13, 1943.

' E. M. KRATZ SHEET MAKING APPARATUS Filed May 19, 1939 7 Sheets-Sheet 1 1210mm. jl LGatz.

April 13, 1943.

i mmll HM E; M. KRATZ SHEET MAKING APPARATUS Filed May 19, 1939 7 Sheets-Sheet 2 "Hill April 13, 1943. E. M. KRATZ ,3

SHEET MAKING APPARATUS Filed May 19, 1939 7 Sheets-Sheet 5 I 5 ml :11:-

liu/antofi I SHEET MAKING APPARATUS Filed May 19, 1939 Sheets-Sheet 4 W /l7d0uand .1

April 13, 1943. E. M. KRATZ SHEET MAKING APPARATUS 7 Sheets-Sheet 5 Filed May 19, 1939 Edema/ad M fiaz JZM zz m vf y @375.

April 13, 1943. E. M. KRATZ SHEET MAKING APPARATUS '7 Sheets-Sheet 6 "Til/072K37 JcZOWdMJGaLZ @Ww M W Filed May 19, 1939 April 13, 1943. E. M. KRATZ SHEET MAKING APPARATUS Filed May 19, 1939 20 7 Sheets-Sheet '7 Patented Apr. 13, 1943 2,310,113 snaa'r MAKING APPARATUS Edouard M. Kratz, Gary, ImL, assignor to Kraft Cheese Company, a corporation of Delaware Application May 19, 1939, Serial No. 274,481

7 Claims.

This invention relates to apparatus for making webs or sheets and it is in part a continuation. of my co-pendlng application Serial No. 229,509.

The main objects of this invention are to provide mechanism which will facilitate the production of sheets or webs of uniform thickness; to provide mechanism for automatically controlling the operating condition of mechanism which is subject to variation due to various causes, including changes in temperature; and, in general, to provide improved apparatus for the purpose set forth.

Other objects and advantages of the invention will be understood by reference to the following specification and accompanying drawings (7 sheets) wherein there is disclosed the improved apparatus of the character indicated.

In the drawings:

Figure 1 is a diagrammatic representation of the improved sheet-forming apparatus;

Figures 2, 3 and 4 are more or less diagrammatic illustrations on an enlarged scale of various portions of the apparatus as shown in Figure' 1;

Figure 5 is a plan view of a portion of the receiving end of the apparatus;

Figure 6 is a sectional view on the line 6-6 of Figure 5;

Figure 7 is an end elevation of the receiving end of the apparatus; Figures 8, 9 and 10 are sections, respectively, on the lines 8-8, 9-9 and Ill-l of Figure Figure 11 is a fragmentary perspective of the receiving end of the apparatus;

Figure 12 is a side elvation, of mechanism for automatically controlling the tautness and curling of a drying belt;

Figures 13, 14 and 15 are sections, respectively, on the lines l3--l3, I' l-44 and l5|5 on Figure 12;

Figure 16 is an elevation of electrical switch mechanism forming a part of the apparatus;

Figures 17, 18 and 18 are sections, respectively, on the lines i'|l1, I8--l8 and l9-I9 on Figure 16;

Figure 20 is a plan of the rear end portion of the apparatus; and

Figure 21 is a side elevation of the apparatus shown in Figure 20, certain parts being shown in section to more fully illustrate the construction.

stance where uniformity of thickness is difficult of achievement because of a normal tendency of the material from which the sheeting is formed to flow or run on the forming belt.

The apparatus herein shown comprises an elongated oven designated in its entirety 25, the

ness of the belt, so that its catenary curve may be maintained substantially constant, notwithstanding changes in the length of the belt due to expansion or contraction. The sheet formed on the belt is delivered from the lower reach of the belt and wound on suitable reels near the receiving end of the machine by suitable mechanism indicated generally at 23.

The oven 25 is supplied with hot air through suitable inlets and by suitable mechanism as more fully explained in my aforesaid pending application and suitable outlets and connections to permit re-circulation of the air are, of course, contemplated. Inasmuch as these are fully explained in my said co-pending application they will not be detailed herein.

The receiving end of the machine (see Figures 5 to 11, inclusive) comprises the roller or drum 21, joumalled for rotation in suitable bearings which are supported by side frames 3! of the apparatus. The drum 21 is rotated at suitable speed by means of an electric motor 32 which, through suitable driving connections, drives a worm 33 and a worm-wheel 34 which are carried by the shaft of the drum 2''.

For supporting certain parts about to be explained, upstanding brackets 35 are mounted on the journal brackets 30 and rigidly bolted thereto so as to maintain a fixed relation to the drum 21. A doctor blade 36 is pivotally mounted at its ends in vertically elongated blocks 3'! through the agency of short studs 38 which project from the ends of the doctor blade and fit suitable bearing openings in the said blocks 31. The blocks 31 are vertically slidably mounted in the brackets 35 by being fitted into ways provided in said brackets. For holding the doctor blade 36 in normal vertical position, there are provided latch members 39 pivoted on the respective blocks 31 and urged by suitable spring means as indicated to move toward the lower edge of the doctor blade so as to cause the latter to enter retaining notches such as indicated at .40 in the respective latches, thereby a point where the belt is supported by the drum 21. Each roller 4| is rotatably mounted by means of a suitable shaft in a bracket 42, which, in front view, is of H-form so as to present a transversely extending cross-bar 43 and spaced legs extending upwardly and downwardly therefrom. The roller 4| is journalled between the depending pair of legs as clearly shown. Each bracket 42 is vertically slidably mounted on the front of the doctor blade 38 by having its upwardly extending legs fitted in ways formed on the front of the doctor blade by means of a forwardly extending blocklike portion 44 and an outer cross-head portion 45. The block portion 44 and cross-head portion 45 may be formed of one piece or of separate parts suitably secured together by bolts, welding, or otherwise, and the block part 44 is rigidly secured to the doctor blade 36 in any suitable manner, but preferably by recessing the block into the doctor blade and then bolting or welding so as to insure permanent and fixed attachment. A set screw indicated at 46 is threaded vertically through the mounting block 44 and is adapted to engage the cross-bar 43 of the roller bracket 42, so that corresponding adjustment will be effected of the roller bracket 42 relative to the doctor blade 36.

To facilitate adjustment of the roller bracket 42 and the supporting roller 43 at each end of the doctor blade, there is provided in association with each of theadjusting screws 42 a plate 41 suitably mounted on the upper edge of the doctor blade and provided with a suitably graduated scale 48 which is adapted to be read in connection with the free end of a handle 49 which is secured to the adjusting screw 46 to facilitate turning thereof. It will be apparent that by adjusting each screw to the same extent as is made easy by the provision of the scales just referred to, the doctor blade will be uniformly adjusted throughout its length with reference to the surface of the belt 26. Similarly, in the event that it is discovered that the sheet being produced on the belt is either thicker or thinner than desired at one side than at the other, it is a simple matter to adjust the corresponding side of the doctor blade to the proper extent to eliminate the excess or deficient thickness.

A plurality of nozzles such as indicated at 50 tively the latter being suitably secured to the upstanding brackets 35. The attendant of the front end of the machine may occasionally shift the nozzles laterally such movement being permitted by the swinging arm supports for the cross-bar 52 and if desired power-driven means may be provided for maintaining a continuous lateral shifting movement of the nozzles.

For controlling the spread of the liquid delivered by the nozzles 50 to the belt 26 there are provided side guides 56 56 the same being suitably secured to the inside edges of the respective brackets 42. The lower edges of the said guides 66 are curved as indicated at 51 to fit the curvature of the belt 26 and the relationship of the said bottom edges 51 to the rollers 4| is such that th bottom edges of the guides will rest on or be close enough to the surface of the belt 26 to prevent the liquid from passing between the lower edges of the guides and the belt.

A further guide for controlling the supply of liquid to the belt is provided in the form of an angle iron member 58 the same extending transversely between the side guide members 56 56 and being positioned with its legs extending downwardly and in opposite directions as best shown in Figure 10. For supporting the transverse member 58 each of the side guides 56 is provided with a shoulder formation 59 adapted to receive the ends of the cross-member 58. A spring-pressed hook such as 68 is pivoted on each of the side guides 56 and is adapted to cooperate with the supporting shoulder 59 to retain the cross-member 58 in operative position, The said cross-member serves the purpose of preventing the liquid delivered from the nozzles 58 from flowing down the curved front portion of the belt 26 as it travels upwardly and rearwardly around the drum 21. In other words, the cross-member 58 serves wth the side guides 56 to maintain a shallow pood of liquid in front of the doctor blade 36 so as to insure an adequate supply of the liquid at all times over the entire length of the doctor blade between the side guides 56'.

For cleaning purposes, the doctor blade 36 is lower edge of \the doctor blade.

When the doctor blade has been rocked toa position such as shown in Figure 11, it is more accessible for cleaning and the roller bracket 42 and parts carried thereby may readily be separated from the doctor blade as clearly shown in Figure 11. Also, as shown in Figure 11, when the roller brackets 42 are disengaged from the doctor blade, the said brackets and their attached side guides 56 may readily be separated from the cross-bar 58. Also, it will be observed that without separating the side guides 56 from the doctor blade, the cross-bar 58 may be removed by releasing the anchoring hooks 68.

Hence, cleaning of the apparatus is clearly' facilitated.

The belt-supporting roller 28 at the rear end of the apparatus is journalled in suitable bearing brackets 6| which are slidably mounted on side frames 62. By adjusting the roller 28 toward or from the drum 21 at the front end of the apparatus, the tautness and position of the belt 26 within the oven 25 may be controlled. Such adjustment may be effected either manually or by power means. For this purpose there is provided. in association with each of the slidably mounted bearings 6|, a screw-threaded rod 63 which is suitably'connected at one end to the slidable bearing member 6| or to the shaft of the roller 28 adjacent the slidable bearing 6|. The screw-threaded rod 63 threadedly engages an internally threaded, elongated sleeve 64 which comprises an intermediate enlarged portion 65 and endwis'e extensions 66 and 61.

The endwise extension 66 is journalled in a bearing 68 formed integrally or rigidly secured in fixed position on the adjacent side frame 62.

the extremity of the sleeve portion 68 serves to prevent withdrawal of said sleeve portion fro bearing 88 and a suitable anti-frictionbearing II is interposed between the enlarged portion 65 and the adjacent end of said bearing 68. The other sleeve extension 61 has keyed to it a miter gear H which has rigidly connected to it 'a hand wheel 12. The miter gear H is adapted to be rotated manually through the agency of the hand wheel 12 to thereby turn the threaded sleeve to mesh with the respectively adjacent miter gears II. It will be apparent that when the electric motor 13 is energized, the shaft 11 will be driven and the screw-threaded rods 63 caused to move forwardly or rearwardly in accordance with the rotation imparted to the threaded sleeves by reason of the miter gear connections H and 18..

The electric motor 13 is of the reversible type Q so that it may be selectively actuated in both directions to effect either forward or rearward adjustment of the roll 28. Normally, it is desired to effect uniform adjustment of both ends of the roll 28 so as to maintain the normal parallelism of the roll 28 with the front end roll 11. However, occasionally, as for example when installing a new belt26, it is advantageous if either side of the roll 28 may be adjusted independently of the other side. To permitsuch independent adjustment, the gears H and the hand wheels 12 are keyed to the sleeve portion 81 as already explained, so that either hand wheel and its associated gear may be moved outwardly along the sleeve portion 8'! sufficiently to disengage the corresponding miter gear 18. When the gear is thus disengaged, the motor 13 may be actuated to adjust the opposite side of the roller 28, or, in the alternative, the side of the roll corresponding to the disengaged gears H and 18 may be manually adjusted through the agency of the hand wheel 12. Such manual adjustment is facilitated when the gears H and 18 are disengaged, since .by breaking the driving connection between the gear H and the gear 18 no part of the manual force applied to the hand wheel 12 would be transmitted to the shaft 11 and motor 13. The central enlarged portion 65 of each sleeve may ad- .vantageously be provided with graduated scale markings indicated at 19 for cooperation with a facilitate measured adjustment of the screw 63 and corresponding end of the roll 28.

The roll 28 and the described adjusting mechanism are housed in an enclosure indicated at 8! (Figures 1, 20 and 21) the same being c nnected to the oven 28 by suitable passageways 82, 82 for the upper and lower reaches of the belt 28.

Inasmuch as the sheet is formed on the outside surface of the belt 26, it will be understood that on the upper reach of the belt the sheet is located on the upper surface thereof and that on the lower reach of the belt the sheet is on the lower surface thereof. Under these circumstances the upper reach of the belt may be supthe ' 3 ported from below by means of suitably journalled rollers 83 disposed at such locations as experience shows to be most desirable. In Figures 2, 3 and 4 of the drawings, such supporting rollers are indicated at spaced intervals throughout the length of the oven. Each of the rollers 88 may be supported on a shaft such as 84 which is suitably supported by means of brackets indicated at 85 forming a part of or securedto the oven framework.

Associated with each of the supporting rollers 83 are grooved rollers 88, 86 journalled on a bracket such as indicated at 81, supported from a bearing member 88 on the shaft 84. Each roller 81 receives in its peripheral groove an edge portion of the belt 28 see Figures 12 and 13) and thereby serves to maintain the belt flat and in engagement with the roller 83 across the entire width thereof. By this means the normal tendency for the belt to curl transversely is overcome. By thus maintaining the belt fiat and in eve/substantially horizontal plane), there is no i or at least only a negligible) tendency for the sheetforming liquid to run on the belt. Hence the production of sheeting of uniform thickness is facilitated. The bracket 81 is preferably pivotally mounted intermediate its ends on the bearing 88, so that the bracket arm 81 may pivot sufficiently to permit the rollers 88 to bear equally on the edge of the belt26.

Control of curling tendency of the lower reach of the belt is of less importance than of the upper reach, since the sheet is well set by the time the sheet-forming material reaches the rear end of the belt and begins its return travel on the lower reach thereof. However, I have found that control of the lateral position of the belt, or in other words, control of migrating tendencies of the belt, may be advantageously effected by action on the lower reach of the belt. Preferably, such controlling action is effected on the lower reach of the belt at a point located about one-third of the distance from the front end of the apparatus to the rear end thereof. It is to be understood that the stated distance is not critical but it is advantageous in that it effectively maintains the belt within permissible limits of movement crosswise of the receiving end of the drum 21, which limits are somewhat less than corresponding limits on the roll 28 at the rear end of the apparatus.

The mechanism for controlling the belt by action on its lower reach comprises a pair of rollers 89, 89 which extend transversely over and in engagement with the upper surface of the lower reach of the belt 26. Said rollers 89. 89 are equipped with endwise extending shafts which are journalled in suitable bearing members 90, 99 to which are connected angle iron side members 9|, 9|. The angle iron side members 9! are thvs supported by the lower reach of the belt 26 through the agency of the rollers 89. 89. Ai a cent each end of each of the s de members 91. there are, pivoted intermediate their ends, arms 92, each of which has rotatably secured to i s ends peripherally grooved rollers 93. The rollers 93 receive in their peripheral grooves the marginal edge portions of the belt 26 so as to ma ntain. the belt flat and in engagement with the surface of the rollers 89, 89 across their entire lengths The position of the supporting rollers 89 and of the edge-engaging rollers 93 in the direction extending transversely of the widths of the oven 25 is fixed by means of a frame 94 which has a transversely extending bar 96 pivoted at its ends to the adjacent sid members 9i approximately midwaybetween the ends thereof. The said frame 94 also has a transversely extending member 96 pivoted at its opposite ends to the walls of the oven as best shown in Figure 14, so as to prevent shifting of the frame transversely of the oven chamber. By the same token, the rollersupported side members 9I are prevented from shifting transversely and hence, through the edge-engaging rollers 93, serve to maintain the belt in a substantially fixed path of travel.

Incident to temperature changes in the oven, especially when first commencing the operation of the apparatus and when stopping the same, the conveyor belt 26 expands or contracts to such an extent that the vertical position of the reaches of the belt may vary considerably. Most of such variation is reflected in the lower reach of the belt since the upper reach is positively supported by the transverse rollers 83. The extent of change in the length of the belt upon expansion is suflicient to cause the lower reach of the belt to very closely approach the bottom of the oven chamber unless the chamber is made much larger than is desirable for efficiency in respect of temperature control. Inasmuch as the formed sheet is on the bottom face of the lower reach of the belt, it is apparent that it is highly objectionable if, the lower reach sags closely enough to the bottom of the oven to either touch the same or pick up dust. or other foreign matter from the bottom of the oven chamber merely incident to the air currents induced by the travel of the belt. The vertical position of the lower reach of the belt may be controlled by adjusting the rear roller 28 to take up the expanded length of the belt and thereby maintain the lower reach in a predetermined normal position between the top and bottom of the oven chamber for the lower reach of the belt.

' For this purpose, electrical switch mechanism indicated in its entirety at 91 is provided and connected tothe lower reach of the belt 26' so as to be governed by the vertical position of the latter. The switch mechanism 91 is in turn connected tothe electric motor I3 which, when energized, efiects adjustment of the rear or belt take-up roller 28. 2 I

As best shown in Figures 16 and 18, the switch mechanism 91 comprises two gangs 98 and 99 of switch elements, in this instance mercury switch tubes, the same being mounted on suitable brackets I and I0 I, respectively, which are mounted for rocking movement on a supporting pivot pin I02. As shown in Figure 16, the switch members are in off-position, the mercury content of each switch unit being disposed in the outer ends of the respective switch tubes. The weight of the mercury content of the switch tubes is suflicient to maintain the tubes in their off-position in which they are supported by means of stop-pins such as indicated at I03. Additional stop-pins such as indicated at I00 are provided for supporting the switch units in their on-position as indicated in dotted lines with respect to the switch gang 98. The switch gangs 98 and 99 are adapted to be controlled by means of rock levers I05 and I06, respectively, which are pivotally mounted on a common pivot pin I01. The free ends of the arms I05 and I06 are equipped with upwardly projecting extensions I08 and I09, respectively.

The said extensions I09 and I09 have their upper ends bent to provide ears such as indicated at 0 which project over the top surface of the pivoted switch-supporting bracket members I00 and IOI, respectively. Said extensions are also bent so as to provide shoulders III which extend transversely across the adjacent end flange of the respective members I00 and IOI. It will be seen that as an incident to rocking movement of the arm I05 and I06, the corresponding extension I08 or I09 will, on upward movement of the free end of the arm, engage and move the outer side of the overlying switch-supporting bracket I00 or IM upwardly so as to cause the mercury content of the respective switch tubes to flow to the other end thereof, to thereby close an electric circuit in a well-known manner,

Similarly, when the upwardly moved arm I05 or I06 is restored to its initial position, the ear H0 at the upper end of the upper. extension will engage the top of the switch-supporting bracket to rock the, same downwardly to its initial position.

The rock arms I05 and I06 are each provided with downwardly facing, forked extensions. As best shown in Figure 16, the arm I05 is equipped with a. downwardly facing forked extension comprising a long arm H2 and a short arm 3. Similarly, the rock arm I06 is provided with a downwardly facing forked extension comprising a long arm I I4 and a short arm H5. The forked extensions of the arms I05 and I06 cooperate with the upper end of a rock lever H6, whichis secured at its lower end to a rock shaft I I1 suitably journalled in the oven wall. The rock lever II 6 is preferably so made or equipped that its upper end portions may be adjusted as to width so as to thereby permit regulation of the amount of play between the upper end of the rock lever and the cooperating forked arms of the levers 405 and I06. In this instance, such adjustment is provided by equipping the rock arm II6 with an underlying member II8 of substantially the same shape and size as the arm 6, the member I I8, however, being pivotally mounted on the shaft II I instead of fixedly secured thereto as is the arm H6. The arm H6 is provided with a slot H9 and the arm H8 is provided with a threaded hole I20, for receiving a clamping screw I2I which passes through the slot H9 and is adapted to clamp the member H8 in fixed position relative to the lever arm I IS.

The rock shaft III is provided within the oven with an arm I22 and the free end of said arm I22 is connected by means of a link I23 to the adjacent belt-supported side frame 9i. Hence,- in the event that the belt expands and is lengthened, downward movement of the lower reach of the belt will produce a rocking motion in the rock shaft I I7. Such motion will be transmitted to the rock .arm 6. Assuming, for example, that the belt is lengthened so as to cause rocking movement of the shaft II! in a clockwise direction as shown in Figure 16, the rock arm II6 will also rock in a clockwise direction so asto cause its free end to engage the long finger II4 of the forked portion of the rock lever I06, such movement thereupon causing the rock lever I06 to turn on its pivot I01 in a counter-clockwise direction. Incident to such movement, the shoulder III at the outer end of the rock lever I06 will engage the switch bracket IOI and when sufiicient movement has been efiected, the switch gang 99 will be adjusted to its on-position. The electric circuit controlled by the switch gang 99 is such that the motor 13 will be rotated in the proper direction to adjust the belt take-up roller 28 outwardly to thereby tighten the belt and cause the lower reach thereof to be pulled upwardly toward its normal position.

As an incident to the restoration of the lower reach of the belt to a suitably elevated position, the rock shaft III is, of course, rotated in a counter-clockwise direction so as to permit lowering of the rock lever I 08. A suitable spring I24 is provided for causing the rock lever I03 to follow the movement of the arm H6, and as an incident to the engagement of the lip IIO on the extension I09 of the lever with the switch-supporting bracket IOI, said spring will ultimately restore the switch gang 99 to its initial or offposition, whereupon adjustment of the belt takeup roller 28 ceases. It will be observed that when the upper end of the rock arm II6 engages the finger II4 of the lever I06, the said upper end clears the arm II3 of the other switch lever I05 so that the switch gang 98 is not actuated. when the rock lever I06 is in an upwardly adjusted position, the shorter finger II5 of that rock lever is swung to a position in which it will be in the path of return movement of the arm I I6. Hence, in the event that the spring I24 fails to effect return movement of the lever I06, such movement will be effected by engagement of the arm II6 with the said shorter finger II5 of the lever. A stop pin I25 is provided for limiting the downward or clockwise turning movement of the lever I06. A similar spring I24 and a similar stop pin I25 are provided in association with the other rock lever I05 for the same purpose.

Upon shutting down of the apparatus or cool- Ing of the oven and hence cooling of the belt, and incident to shutting down of the apparatus for other reasons, the lower reach of the belt, incident to contraction, will move upwardly and through the described connections effect counter-clockwise rocking of the shaft III. Under such circumstances, the arm I I6 will actuate the rock lever I05 and the switch gang 98 to complete an electric circuit for causing the electric motor 13 to rotate in an opposite diretion for effecting an inward adjustment of the belt takeup roller 28 to slacken the belt. The slackening continues until such time as the rock arm "6* has been returned to a position wherein the lever I05 will have caused the switch gang 98 to be dropped to an off-position, to thereby openthe circuit to the electric motor 13.

A pair of oppositely positioned mercury switch tubes I26 and I 21 may be advantageously mounted on the rock arm 6 so as to control electric circuits for signal lights which will indicateto an attendant of the apparatus whether or not any adjustment of the belt is being effected and in which direction.

In the event that either ofthe switch units 93 or 99 should fail of operation and adjustmentcontinue, considerable damage might result. In one direction of adjustment the belt 26 might be subjected to such excessive stretching as to cause distortion or other impairment of the belt if not actual breakage thereof. If the adjustment were to continue in the other direction, the belt might come into scraping contact with the bottom of the oven with the result that the s'heet forming surface of the belt might bescratched, dented, or otherwise impaired to such an extent that it may not even be possible to repair the belt and its replacement thus necessitated. In either event, the damage may entail considerable loss not only in respect of the cost of the belt itself, but in respect of the labor required for installation and the loss of production during the time required for repair or replacement.

For the purpose of preventing such a contingency, there is provided a safety device in the form of an electric switch indicated in its entirety at I28 (see Figures 12, 16 and 19), which switch, upon being opened, breaks the electric circuit to the motor I3 so as to prevent operation thereof to eilfect adjustment of the belt take-up roller 28 beyond predetermined limits.

The said switch I 82 comprises a series of contact elements I29 which are fixedly mountedon an insulating base element I30 and respectively connected in the circuit wires of the electric motor I3. A corresponding series of electrical terminals I3I is carried by a strip I32 of insulation material and respectively connected to the electric wires of said circuit as indicated in Figure I3. The terminal-carrying strip I32 is slidably mounted on the side legs- I33, I33 of a bail-like member I34 which is suitably anchored in the insulating material base element I30. A cam element I35 is mounted for rocking movement on the bail element I34 and acts against a saddle I36 which is carried by the slidably mounted terminal-supporting strip I32. In the normal position of the cam I35 as shown in the drawings, the strip I32 is held in an inwardly disposed position, wherein its contact terminals I3l are inengagement with the terminals I29 so as to maintain a circuit through said terminal elements. Suitable compression coil springs I3'I are provided and normally tend to move the terminal-carrying strip I32 outwardly so as to separate said contact elements to thereby open or break the electric circuit.

The cam element I35 is adapted to be controlled by a push rod I38 which is slidably mounted in the oven wall. The inner end of the push rod I38 normally engages a recessed surface portion, I39 of a vertically movable bar I40. The bar I40 is slidably mounted at its upper end in a slot I4I provided in an extension of the push rod guide element, and the lower end of the said bar is pivotally connected as shown at I42 to the adjacent side member I43 of the frame 94.

In the event that the frame 94 is caused to continue upward movement, for example, beyond a normal extent for efiecting correction of the position of the lower reach of the belt 26, a cam surface I44 adjacent the lower end of the recessed seat I39 in the bar I40 will engage and move the push rod I38 outwardly to thereby rock the cam I45 so as to permit the springs I3I to move the contact-carrying member I32 outwardly, thereby breaking the circuit to the electric motor I3 and stopping its operation, notwithstanding the continued maintenance of a closed circuit by the switch gang 98 or 99. Similarly, in the event that the frame 94 continues downward movement beyond a predetermined limited extent, a cam surface I45 adjacent the upper end of the recessed seat I39 in the bar I40 will engage and move the or prevention of curling of the belt constitute im-' portant aids in the production of sheet material of uniform thickness throughout its width. The described controls are of relatively simple construction and they are not likely to get out of order, so that their effectiveness is enhanced .by their durability and eiliciency.

The described mechanism for controlling tautness of the belt is also of considerable importance in apparatus of the type described in view of the improved results obtained when the sheet formed on the belt is dried under conditions which may be maintained substantially constant within the selected operating zone of the belt. The said belt take-up mechanism is also of substantial importance because of its effect in safeguarding the relatively expensive belt from injury and attendant losses as already explained.

The electrical circuits herein referred to are not illustrated inasmuch as they form no part of the present invention and are well-known reversing motor circuits. Furthermore, it will be understood that the circuits for controlling the motor 13 may also be provided with manual switching means, although such manual means is not herein shown.

Changes in the described apparatus may be made 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.

I claim:

1. In apparatus of th class described, the combination of a rotatable drum, a belt adapted to travel around saiddrum, means for delivering sheet-forming liquid to said belt, a doctor blade extending transversely of said belt for limiting the depth of sheet-forming liquid carried rearwardly by said belt, side guides extending forwardly from said doctor blade for controlling the spread of said liquid, a member extending transversely between said side guides in proximity to said belt for retaining the liquid in a pool in front of said doctor blade, and means for detachably mounting said transversely extending member on said side guides and said side guides on said doctor blade.

2. In apparatus of the class described, the combination of a rotatable drum, a belt adapted to travel around said drum, a doctor blade associated with said belt for limiting the depth of sheet-forming liquid carried rearwardly by. the belt, adjustable means carried by said doctor blade and engaging said belt for supporting the doctor blade in predetermined, adjusted position relative to the belt, and means for mounting said doctor blade comprising relatively fixed frame members adjacent the opposite ends of said doctor blade, guide members vertically slidably mounted in said frame members, a pivotal connection between the respective ends of said guide blocks.

members adjacent the opposite ends of said doctor blade, guide members vertically slidably mounted in said frame members, and means pivotally connecting the ends of said doctor blade with the respectively adjacent guide members.

4. In apparatus of the class described, the combination of a frame, a drum rotatably mounted in said frame, a belt travelling around said drum, means for delivering sheet-forming liquid to said belt, a doctor blade for limiting the depth of the liquid carried rearwardly by said belt, means for adjustably mounting said doctor blade on said frame, a roller adjustably and detachably mounted on said doctor blade for engaging a portion of said belt overlying said drum so as to support the doctor blade in predetermined position relative to said belt, and means for effecting adjustment of said roller relative to said doctor blade to thereby adjust the position of the doctor 3. In apparatus of the class described, the

combination of a rotatable drum, a belt adapted to travel around said drum, a doctor blade associated with said belt for limiting the depth of sheet-forming liquid carried rearwardly by the belt, adjustable means carried by said doctor blade and engaging said belt for supporting the doctor blade in predetermined adjusted position relative to the belt, and means for mounting said doctor blade comprising relatively fixed frame blade relative to the belt, the detachable mounting of said rolleron said doctor blade serving to permit removal of the roller so as to facilitate cleaning of the apparatus.

5. In apparatus of the class described, a rotatable drum, 9, thin, flexible belt travelling around said drum, means for delivering sheetforming liquid to the belt on said drum, a doctor blade for limiting the depth of the liquid carried rearwardly on said belt, and rollers respectively associated with the opposite ends of said doctor blade with their axes disposed within the crosssectional area of the doctor blade, said rollers being operative to engage a portion of the belt overlying said drum for supporting said doctor blade in predetermined relation to said belt.

6. In apparatus of the class described, the combination of a rotatable drum, a belt travelling around said drum, means for delivering sheet forming liquid to said belt, a doctor blade extending transversely of said belt for limiting the depth of liquid carried rearwardly by said belt, a pair of brackets respectively associated with the opposite ends of said doctor blade and adjustably secured thereto, a roller journalled in each of said brackets for engaging said belt to thereby adjustably support the doctor blade in a selected position relative to the belt, side guides extending forwardly from said brackets for controlling the spread of said liquid, and a liquid-retaining member extending transversely of said belt between said guides and secured thereto so as to be thereby supported in predetermined, fixed relation to said belt.

'7. In apparatus of the class described, a rotatable drum, a thin, flexible belt traveling around said drum, means for delivering sheet-forming liquid to the belt on said drum, a doctor blade for limiting the depth of the liquid carried rearwardly by said belt, and means associated with said doctor blade for engaging a portion of said belt overlying said drum to support the blade in predetermined spaced relation to the belt, said means being positioned relative to the doctor blade so as to engage the belt closely adjacent the plane of the operative edge of the doctor blade so as to transmit to the doctor blade, rises and falls in the surface of the belt substantially at the time said operative edge of the belt is in operative relation to any such rise or fall in the belt, thereby to facilitate the formation of a sheet having substantially uniform thickness.

EDOUARD M. KRATZ.

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