US3334611A

US3334611A - Puddle coater

Info

Publication number: US3334611A
Application number: US325577A
Authority: US
Inventors: Daniel J Nechrony; George L Loehrl
Original assignee: Beloit Corp
Current assignee: Beloit Corp
Priority date: 1963-11-22
Filing date: 1963-11-22
Publication date: 1967-08-08
Anticipated expiration: 1984-08-08

Description

- g 1957 m. J. NECHRONY ETAIL 3,334,611

PUDDLE COATER .3 Sheets-$heet 1 Filed Nov. 22, 1963 INVENTORS JflfeC/Z 66012962 if. L 06 Aug- 8. 1 67 n J. NECHRONY ETAL PUDDLB COATER 3 $heets-$heet 2 Filed Nov. 22, 1963 I I INVENTORS azzze l JIVTscfzrozzg 660156 $.11 06 l l [URN/1 Yb 8, 1967 a. J. NECHRONY ETAL 3,334,611

PUDDLE COATER Filed Nov. 22, 1963 6 Sheets-Sheet 5 I INVENTOR5 flame 1 Jjifecjzz ozqg Jay 5 1 99 L. L oefzz z A; an V \NEYS United States Patent Ofifice 3,334,611 Patented Aug. 8, 1967 3,334,611 PUDDLE COATER Daniel J. Nechrony, Whitewater, and George L. Loehrl, Beloit, Wis., assignors to Beloit Corporation, Beloit, Wis, a corporation of Wisconsin Filed Nov. 22, 1963, Ser. No. 325,577 Claims. (Cl. 118-70) This invention relates to improvements in paper machines and more particularly relates to an improved mechanism for imparting a high quality coated surface of uniform smoothness to a traveling web of paper.

A principal object of the invention is to provide an improved device for more uniformly coating traveling webs of paper.

Another object of the invention is to provide an improved coater for traveling webs of paper and the like, for coating the web on the puddle principle, and arranged with a view toward fineness and accuracy in control of the position of the coater blade with respect to the web.

A further object of the invention is to provide an improved form of coater for coating paper webs on the puddle principle, in which a doctor back and coating blade form a part of the coating channel and in which the accuracy of loading the coating blade is increased over prior coaters.

A still further object of the invention is to provide a novel and improved form of puddle coater for traveling webs of paper so arranged as to accommodate ready cleaning of the puddle coating channel and a more accurate adjustment of the coating blade with respect to the traveling web.

A still further object of the invention is to improve upon the puddle coaters heretofore in use utilizing a coating blade controlling coating of the web, by providing a wiper blade on the outgoing side of the coating blade and a spray between the coating blade and wiper blade, in which the spray and wiper blade are effective to dilute the coating material on the backing roll and wipe coating material therefrom, upon the breaking of a web.

These and other objects of the invention will appear from time to time as the following specification proceeds and with reference to the accompanying drawings where- 111: 1

FIGURE 1 is a view in side elevation of a coater constructed in accordance with the principles of the present invention showing the coating blade in operative association with a web passing about a backup roll.

FIGURE 2 is a fragmentary view in side elevation somewhat similar to FIGURE 1, but showing the doctor back coating channel and coating blade withdrawn from the backup roll;

FIGURE 3 is a fragmentary front elevational view of one side portion of the coater shown in FIGURES 1 and 2, with certain parts broken away and certain other parts shown in vertical section; and

FIGURE 4 is a fragmentary detail side elevational view of the stop structure and limit switch control shown in FIGURE 3.

In the embodiment of the invention illustrated in the drawings, we have shown a puddle coater constructed in accordance with the principles of the present invention and including a pair of laterally spaced vertically extending posts 10, 10 having bearing supports 11 supported adjacent the upper ends thereof and extending forwardly therefrom. The bearing supports 11 form supports for the bearings (not shown) of a backing roll 12 having a web W trained thereabout. The backing roll 12 may be a rubber covered roll and may be driven in a manner well known to those skilled in the art and is no part of the present invention, except insofar as it forms a backing for the traveling web, so need not herein be shown or described further.

A frame structure 13 extends forwardly of each post 10. The frame structures 13 are suitably connected together and are spaced outwardly of the ends of the backing roll 12 and form a support for a doctor back 15, trunnioned therebetween for movement toward and withdrawal from the backing roll 12.

As shown in FIGURES 1 and 3, the frame structure 13 includes a base 16 having a housing 17 extending upwardly therefrom. The housing 17 has bearing supports 19, 19 extending upwardly from the top thereof and forming bearing supports for a trunnion shaft 20. The trunnion shafts 20 are provided at opposite ends of the doctor back 15 and form trunnion supports for said doctor back 15 in a manner which will hereinafter more clearly appear as this specification proceeds. The doctor back 15 is supported and loaded at each end, and the supporting and loading structures for each end of the doctor back are the same so the supporting and loading structure for one end only need herein be shown and described.

As shown in FIGURES 1 and 3, a boss 21 is mounted on the shaft 20 between the bearing supports 19 and has a lever arm 22 extending angularly upwardly and rearwardly therefrom. The boss 21 is keyed or otherwise secured to the shaft 20 and is rocked about the axis of said shaft by operation of a piston rod 23 extensible from a fluid pressure cylinder 24. The cylinder 24 is enclosed within the housing 17 and is trunnioned thereto intermediate its ends on trunnion pins 25 (FIGURE 1). The lever arm 22 is shown as being bifurcated and as having a connector 26 on the upper end of the piston rod 23, extending between the furcations thereof and pivotally connected thereto, as by a pivot pin 27. The shaft 20 has a boss 29 keyed or otherwise secured to its inner end.

The boss 29 is shown in FIGURE 3 as being formed integrally with a lever 30. The lever 30, as shown in FIG- URE 1, has an arm portion 31 extending from the boss 29 in a forwardly and downwardly inclined direction and terminating into an angularly upwardly extending arm portion 32 having a bearing boss 33 extending inwardly or rearwardly of the end thereof and formed integrally therewith. The bearing boss 33 forms a bearing support for a pin 35 forming a trunning support for an arm or plate 36 extending along one side of the doctor back 15 (FIGURE 3) and forming a support for one end thereof. The arm or plate 36 has a ledge 37 extending outwardly therefrom at right angles with respect thereto and facing a plate or ledge 39 on the inside of the arm portion 32. A fluid pressure operated diaphragm 40, shown as being in the form of an air spring of a conventional construction, is mounted between the

ledges

37 and 39. The diaphragm or air spring 40 may be supplied with air under pressure to delicately load the doctor back 15 and a doctor or coating blade 41 into engagement with the web W trained about the backing roll 12, for certain coating applications, or to be accurately spaced from said backing roll for certain other coating applications as will hereinafter more clearly appear as this specification proceeds.

An adjustable stop 43, which may be a micrometer stop of a form well known to those skilled in the art, is mounted on the ledge 37 and extends at right angles with respect to said ledge in a rearward direction for engagement with a stop arm 44 projecting upwardly of the arm portion 31 of the arm 30. The stop 43 and stop arm 44 determine the spacing or pressure: of engagement of the coating blade with the web W.

The angle'of the blade 41 with respect to a line tangent to the periphery of the backing roll 12 is shown in FIG- 3 URE 1 as being 52. This angle has been found to produce good results for most coating applications although the blade angle need not be confined to this angle and the angle may be varied as conditions require. The axis of the pivot pin is shown as being spaced above a line A extended from the top surface of the blade 41. This places the coaxial axes of the arms 36, supporting opposite ends of the doctor back 15 and the doctor blade 41, in such relation with respect to the paper web W as to attain an efiicient blade angle, to effect uniform smoothing of the coating on the web and hold the blade 41 from digging into the web. The blade angle may, however, be varied by sliding the bearing supports along the top of the housing and then retaining the bearing supports in position in a suitable manner.

A stop 45 is shown as being threaded in the ledge 39 and as extending through said ledge 39 toward the ledge 37. The stop 45 may be locked in position with respect to the ledge 39 as by a lock nut 46, and serves to prevent complete collapse of the diaphragm 40.

The diaphragm 40 may be used by itself to load the blade 41 and in certain instances the diaphragm 40 may be dispensed with and the micrometer stop 43 may serve to adjust the blade 41 either to engage or be spaced from the periphery of the backing roll 12. The stop 45 may also limit relative movement between the

arms

36 and 30 in a direction to collapse the diaphragm. The use of these two stops without the diaphragm is particularly advantageous where it is desired to leave a gap between the outer edge of the blade 41 and the backing roll 12 for certain coating applications. A fitting 47 is threaded in the ledge 39 and forms an inlet for the diaphragm 40.

The doctor back 15 has a backing arm 49 extending therefrom toward the backing roll 12. The backing arm 49 forms a mounting and backing member for the doctor blade 41, held to said backing arms as by a clamping arm 50. The clamping arm 50 pivots about the axis of a pivot pin 51 seated in the undersurface of the backing arm 49 and is pressed against the doctor blade 41 by a toggle linkage 53 that snaps outwardly to release the doctor blade for blade replacement. The toggle linkage 53 is shown in a blade holding position and is held in this position by an adjustable stud 54, which bears against a lower link 55 of the toggle linkage 53, to maintain it in position for clamping the blade 41 to the backing arm 49 under pressure. The toggle linkage and means for clamping the doctor blade 41 to the backing arm 49 are well known to those skilled in the art so need not herein be shown or described in detail.

The backing arm 49 is a part of a coating channel 56 containing a coating solution. The coating channel 56 extends for the width of the backing roll 12 and has a wall 57 forming the upper surface of the backing arm 49. The wall 57 terminates in a vertical wall 59 extending upwardly to a position above the horizontal center line of the backing roll 12.

The opposite open ends of the coating channel 56 abut gaskets 60 extending along the front and bottom edges of end dams 61. The end dams 61 extend along opposite end portions of the backing roll 12 and forwardly therefrom to close the ends of the coating channel 56. These end dams are pivotally supported on the beari'ng supports 11 on guides 63 extending forwardly of said bearing supports and pivotally connected thereto to accommodate the dams to be swung outwardly at the termination of a coating operation. The guides 63 may also support the end dams 61 for adjustable movement toward and from the axis of the backing roll 12 to adjust said end dams to seal opposite ends of the coating channel 56 when in the position shown in FIG. 1.

A catch-all trough 65 is suitably mounted beneath the end dams 61 and the scraper blade 41 and extends across the roll face, for catching the coating material when the coating blade 41 and coating channel 56 are moved away from the roll. The catch-all 65 is in the form of a trough extending across the backing roll and spaced beneath the scraper blade 41 when in the operative position shown in FIGURE 1.

A stop means is provided to limit movement of the arms toward the backing roll 12, and to provide a rigid structure when the blade 41 is in operative association with the web W. Said stop means comprises a stop screw 67 threaded in a ledge 69 projecting from the inner wall of the housing 17 toward the arm 30. The stop screw 67 is locked in position as by a lock nut 70 and extends through the ledge 69 in position to engage an abutment 71 extending from a depending arm portion 73 of the lever 30, when the lever 30 is in the upright position shown in FIGURE 1.

A limit switch 75 is mounted on a bracket 76 in the space between the outer side of the arm 30 and the adjustment screw 67 to operate a suitable valve (not shown) supplying fluid such as air under pressure to the cylinders 24, to hold pressure in said cylinders as the stop screw 67 engages the abutment 71. The bracket 76 is mounted on a bracket 79 extending outwardly of the inner wall of the housing 17. The limit switch 75 has a pivoted lever 80 having a follower 81 at its free end engageable with the horizontal leg of an angle bracket 83 mounted on the arm portion 73 adjacent the lower end thereof. Adjustment screws 84 extend through slots 85 formed in the vertical leg of the angle bracket 83 to adjust the position of the horizontal leg of said angle bracket with respect to the follower roller 81 in accordance with the position of the adjustment screw 67. The valves for controlling the admission and release of air to and from the head and piston rod ends of the cylinder 24 may be well known forms of electrically operated valves and are no part of the present invention so need not herein be shown or described further.

A wiper blade 88 is spaced from the blade 41 on the outgoing side thereof and is normally out of contact with the backing roll 12, but comes into engagement with said backing roll upon a break in the web W to catch the coating material and clean the coating material from the face of the backing roll 12.

As shown in FIGURES 1 and 2 the wiper blade 88 is mounted on a doctor back 89 by means of a clamping member 90 in a conventional manner. The doctor back 89 extends for the length of the face of the backing roll 12 and is pivoted at its opposite ends on trunnion shafts 91 extending from opposite ends thereof and journalled in bearing brackets 93 mounted on the supports 94 extending inwardly of the housing parts 17.

Cylinders 96 having piston rods 97 extensible therefrom, are provided at each end of the doctor back 89 to move the wiper blade 88 into wiping engagement with the face of the roll 12, as shown in FIGURE 2, and to withdraw said wiper blade from the face of said roll. Each cylinder 96 has spaced connectors 98 depending from its head end and pivotally connected to a connector bracket 99 on a pivot pin 101. The piston rod 97 has a connector 103 on its upper end extending along opposite sides of a lever arm 104 and pivotally connected to said lever arm as by a pivot pin 105. The lever arm 104 is keyed or otherwise secured to the trunnion shaft 91.

The lever 104 has a depending arm 106 having a stop screw 107 threaded therein and locked thereto as by a lock nut 109. The stop screw 107 is engageable with a stop 110 to limit movement of the wiper blade 88 toward the periphery of the backing roll 12. Each lever arm 104 has a similar depending arm 106 with a stop screw 107 threaded therein.

Fluid under pressure, such as air, may be admitted to and released from the head and piston rod ends of the cylinders 96 under the control of suitable valve means, which may be solenoid operated under the control of a conventional form of web break detector, bringing the wiper blade 88 into wiping engagement with the surface of the roll 12 upon breaking of the web W. The same web break detector may energize the valves controlling the admission of fluid under pressure to the piston rod ends of the cylinders 24, to effect withdrawal of the blade 41 and coating channel 56 from the backing roll 12, into the position shown in FIGURE 2 upon the breaking of a web.

A spray nozzle 111 leading from a pipe 112 is provided to spray the surface of the backing roll upon the breaking of the web, to dilute the coating carried by the backing roll from the region of the recently withdrawn scraper blade 41 and to thereby facilitate the cleaning of coating from the backing roll by the scraper blade 88.

Inoperation of the coater, the wiper blade 41 and coating channel 56 are moved from the position shown in FIGURE 2 to the position shown in FIGURE 1 by the admission of fluid, such as air, to the head ends'of the cylinders 24. As the coating channel 56 is brought into sealing engagement with the gaskets 60 on the end dam 61, the ledge 79 on the depending arm portion 71 will come into engagement with the stop 67 and pressure in the cylinders 24 will solidly hold the arms 30 in the operative position. The limit switch '75 may then be operated to eifect the holding of air in the cylinders 24 to retain the coating channel into sealing engagement with the gaskets 60.

Air may then be supplied to the diaphragms 40 on opposite sides of the doctor back, to bring the blade 41 into close running position against the web W at zero pounds blade pressure. The micrometer 43, which has been retracted, may then be screwed into contact with the stop arm 44. The pressure between the micrometer and the stop arm will also be zero. Where it is desired to increase the pressure of the blade 41 on the web W, air may be supplied to the diaphragms 40 and the micrometer stop 43 may be gradually retracted until the blade 41 contacts the web with the required pressure. Coating material may then be supplied to the coating channel through an inlet pipe 113 and the micrometer may be adjusted until the desired coating weight is obtained.

It is, of course, understood that the coating layer applied and the blade pressure is a function of the position of the micrometer stop 43 rather than a function of the pressure of the diaphragms or air springs ML-so that fluctuation in pressure in the air springs will not influence the blade pressure and the thickness of the layer of coating applied.

It should be understood that when the micrometer stop 43 has once been set, the blade pressure is fixed and will not vary and that the blade can be moved away from the backing roll, as in the case of a web break, and returned against the Web to the position shown in FIG- URE 1.

In many cases, it is desirable to have a gap between the end of the blade 41 and the web and to dispense with the diaphragms 40. In such cases, the required gap may be attained by operation of the micrometer stops 43, and when the proper position of the blade has been attained the stop screws 45 may be turned to engage the ledges 37 and retain the blade in a selected position of adjustment.

It should further be understood that the diaphragms 40 may be used to load the blade 41 independently of the micrometer stops 43, and that these diaphragms may position the blade at the required blade angle and load the blade at the desired blade pressure, in co-operation with the stops 67.

Where the web may break during the coating operation, air is admitted to the piston rod ends of the cylinders 24 under the control of the web break detector, to retract the coating channel 56 and scraper blade 41, and is admitted to the head ends of the cylinders 96 to engage the wiper blade 88 with the web and periphery of the backing roll 12. At the same time the spray nozzles 111 are supplied with water or any other suitable fluid under pressure to dilute the coating and aid the wiper blade 88 in cleaning the backing roll 12.

While we have herein shown and described one form in which our invention may be embodied, it may readily be understood that various modifications and variations in the invention may be attained without departing from the spirit and scope of the novel concepts thereof.

We claim as our invention:

1. In apuddlecoater,

a backing roll adapted to have a web trained partially thereabout, a coating channel, a blade mounted on said coating channel and forming a continuation of the lower wall thereof,

a pair of spaced arms mounted for pivotal movement about an axis disposed beneath but adjacent said backing roll for movement toward and from said backing roll,

lever means supporting said coating channel on said arms and pivotally connecting said coating channel to said arms for movement about an axis disposed outwardly of and above the axis of rotation of said backing roll,

means limiting movement of said arms toward said backing roll,

other means limiting movement of said coating channel and blade about the axis of connection of said coating channel to said arms and spacing said blade from said backing roll,

and a fluid pressure operated diaphragm connected between said arms and said coating channel for selectively loading said blade. 2. The structure of claim 1, wherein a second blade is spaced circumferentially from said first blade on the outgoing side thereof,

wherein power means brings said second blade into engagement with said backing roll upon retractible movement of said first blade upon a web break,

and wherein spray means are provided between said blade and are actuated to spray said backing roll upon the engagement of said second blade with said backing roll upon a web break.

3. A puddle coater comprising a frame, a backing roll journalled in said frame for rotation about a horizontal axis and adapted to have a web partially trained thereabout, a coating channel open at its opposite ends, end dams mounted on said frame and extending from opposite ends of said backing roll for closing the ends of said coating channel, a blade on the lower end of said coating channel and engageable with the web trained about said backing roll, means pivotally mounted on said frame for moving said coating channel and blade toward and from said backing roll about an axis spaced beneath said backing roll and adjacent the outgoing side of said coating channel and for withdrawing said coating channel and blade from said backing roll, other means tilting said coating channel with respect to said means moving said coating channel toward and from said backing roll about an axis spaced above and outwardly of the axis of rotation of said backing roll and loading said blade to engage the Web with a predetermined pressure, a spray on the outgoing side of said blade and a wiper blade on the outgoing side of said spray, said wiper blade and spray being operable to come into operation upon the breaking of a web and retractible movement of said. coating channel and blade.

4. A puddle coater comprising a frame, a backing roll journalled on said frame for rotation about a horizontal axis and adapted to have a web trained thereabout, a coating channel open at its opposite ends, end dams mounted on said frame and extending from said. backing roll for closing the ends of said coating channel, a blade on the lower end portion of said coating channel and forming a continuation of the lower Wall thereof, a pair of spaced arms pivotally mounted on said frame for movement about an axis parallel to the axis of said roll about an axis spaced beneath said backing roll and adjacent the outgoing side of said coating channel, fluid pressure operated cylinder and piston means for moving said arms toward and from said roll for moving said coating channel and blade into operative association with said backing roll and for quickly withdrawing said coating channel and blade therefrom, lever arms pivotally mounted on the outer ends of said arms for movement about an axis parallel to the axis of pivotal movement of said arms and spaced above and outwardly of the axis of rotation of said backing roll and extending inwardly along said arms toward said backing roll and having said coating channel and blade rigidly mounted thereon, fluid pressure operated diaphragms disposed between said arms and said lever arms for moving said lever arms and coating channel and blade with respect to said arms toward said backing roll, means limiting movement of said arms toward said backing roll and providing a rigid support structure for said lever arms and coating channel, and other means limiting the position of said blade with respect to said backing roll and limiting the loading of said blade by said diaphragms.

5. The structure of claim 4, wherein a second wiper blade is pivotally mounted on said frame on the outgoing side of said first blade, wherein fluid pressure operated means are provided for bringing said second wiper blade into engagement with said backing roll upon the breaking of a web, and wherein spray means extend across said backing roll and are disposed between said first and second blades for spraying said backing roll upon the breaking of a web and the withdrawal of said first mentioned blade and coating channel therefrom, to facilitate cleaning of the roll by said scraper blade.

6. In a puddle coater, a backing roll, a web adapted to be trained partially about said backing roll, a frame supporting said backing roll for rotation about a horizontal axis, a doctor back disposed beneath said backing roll and having a coating channel having an inclined bottom wall mounted thereon and movable into juxtaposition with said backing roll, a doctor blade extending from said inclined bottom wall and forming a continuation thereof, a pair of arms pivotally mounted on said frame at opposite ends of said backing roll for movement about an axis parallel to the axis of rotation of said backing roll and spaced therebeneath and closely adjacent said backing roll and extending outwardly of said backing roll and a substantial distance below the axis of rotation thereof, means pivotally mounting said doctor back to the outer ends of said arms for movement about a transverse axis disposed above the axis of rotation of said backing roll at a substantial distance outwardly of the periphery thereof, fluid pressure operated means for moving said doctor back and doctor blade with respect to said arms, stop means cooperating with said fluid pressure operated means determining the loading of said doctor blade, other fluid pressure operated means for moving said arms, doctor blade, coating channel and doctor back into juxtaposition with said backing roll, and stop means limiting movement of said arms toward said backing roll and affording a solid backing for said arms during a coating operation.

7. A puddle coater, in accordance with claim 6, wherein a wiper blade is pivotally mounted on said frame for movement into and out of engagement with said backing roll on the outgoing side of said doctor blade, wherein a spray extends across said backing roll between said doctor blade and said wiper blade and is effective to spray 8 said backing roll upon withdrawal of said doctor blade from said roll and the engagement of said wiper blade with said roll upon a break in the web being coated.

8. A puddle coater, in accordance with claim 6 wherein end dams are mounted on said frame and extend along opposite ends of said backing roll beyond the periphery thereof and have-sealing engagement with said coating channel upon movement of said coating channel into operative association with said backup roll, and wherein a catch-all extends across said backing roll beneath said doctor blade and is carried by said end dams for catching coating falling from said coating channel upon withdrawal of said coating channel from said backing roll.

'9. A puddle coater, in accordance with claim 8 wherein a spray extends across said backing roll beneath said doctor back and catch-all and is directed to spray said backing roll to dilute any coating material thereon upon a web break, and wherein a wiper blade is disposed on the outgoing side of said spray and is effective upon a web break to wipe said backing r-oll upon the withdrawal of said doctor back and coating channel therefrom.

10. In a puddle coater, a backing roll, a web adapted to be trained partially about said backing roll, a frame supporting said backing roll for rotation about a horizontal axis, a doctor back disposed beneath said backing roll and having a coating channel having an inclined bottom Wall mounted thereon and movable into juxtaposition With said backing roll, a doctor blade extending from said inclined bottom wall and forming a continuation thereof, a pair of arms pivotally mounted on said frame at opposite ends of said backing roll for movement about an axis parallel to the axis of rotation of said backing roll and spaced therebeneath, means pivotally mounting said doctor back to the outer ends of said arms, fluid pressure operated means for moving said doctor back and doctor blade with respect to said arms, stop means cooperating with said fluid pressure operated means determining the loading of said doctor blade, other fluid pressure operated means for moving said arms, doctor blade, coating channel and doctor back into juxtaposition with said backing roll, stop means limiting movement of said arms toward said backing roll and affording a solid backing for said arms during a coating operation, the axes of pivotal connection of said means pivotally mounting said doctor back to the outer ends of said arms being spaced a substantial distance above a line extended from said blade when said arms are in engagement with said stop means, and positioning said blade in such relation with respect to said web as to avoid the digging of said blade into said web in all positions of adjustment of said blade with respect to said arms.

References (Iited UNITED STATES PATENTS 3,030,917 4/1962 Brown et a1 1l84l3 3,079,889 3/1963 Jacobs et al. 118-413 X 3,128,207 4/1964 Schmitt. 3,152,918 10/1964 Kraus. 3,169,082 2/1965 Krikorian 118413 3,220,377 11/1965 Good 118126 X CHARLES A. WILLMUTH, Primary Examiner.

I. P. MCINTOSH, Assistant Examiner.

Claims

1. IN A PUDDLE COATER, A BACKING ROLL ADAPTED TO HAVE A WEB TRAINED PARTIALLY THEREABOUT, A COATING CHANNEL, A BLADE MOUNTED ON SAID COATING CHANNEL AND FORMING A CONTINUATION OF THE LOWER WALL THEREOF, A PAIR OF SPACED ARMS MOUNTED FOR PIVOTAL MOVEMENT ABOUT AN AXIS DISPOSED BENEATH BUT ADJACENT SAID BACKING ROLL FOR MOVEMENT TOWARD AND FORM SAID BACKING ROLL, LEVER MEANS SUPPORTING SAID COATING CHANNEL ON SAID ARMS AND PIVOTALLY CONNECTING SAID COATING CHANNEL TO SAID ARMS FOR MOVEMENT ABOUT AN AXIS DISPOSED OUTWARDLY OF AND ABOVE THE AXIS OF ROTATION OF SAID BACKING ROLL, MEANS LIMITING MOVEMENT OF SAID ARMS TOWARD SAID BACKING ROLL,