US2993432A

US2993432A - Calender air doctor

Info

Publication number: US2993432A
Application number: US708881A
Authority: US
Inventors: Casper E Youngchild
Original assignee: Beloit Iron Works Inc
Current assignee: Beloit Iron Works Inc
Priority date: 1958-01-14
Filing date: 1958-01-14
Publication date: 1961-07-25
Anticipated expiration: 1978-07-25

Description

July 25, 1961 c. E. YOUNGCHILD 2,993,432

CALENDER AIR DOCTOR Filed Jan. 14, 1958 2 Sheets-Sheet 2.

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fi M, 4 *W United States Patent 2,993,432 CALENDER AIR DOCTOR Casper E. Youngchild, Appleton, Wis., assignor to Beloit Iron Works, Beloit, Wis, a corporation of Wisconsin Filed Jan. 14, 1958, Ser. No. 708,881 2 Claims. (Cl. 100-93) This invention relates to the portion of a paper machine or paper converting machine known as the calender or calender stack, and more particularly, to an improved nip pressure control in calenders.

Although the instant invention may have utility in other fields including the pressing, smoothing, ironing or the like treatment of a strip of flexible material, a particularly preferred use is in the paper machine or paper converting machine calender. The operation of such calenders is well known and understood in the art. The purpose of the calender is to compact the paper to some extent and to give it a fine smooth finish. This effect is obtained on both sides of the paper by the use of friction and pressure. The calender stack comprises a plurality of upright or vertically aligned calender rolls. One or more of such rolls is driven and the drive arrangement is such that there is a certain amount of slip between the rolls at each of the nips defined thereby so that a substantial amount of friction acts on the paper as it passes through each of the calender nips. A controlled amount of pressure is also applied.

It is conventional practice in the operation of a calender to raise the temperature of a particular local circumference of a calender roll in order to increase the calender loading or pressure at that point. The rise in temperature creates an increase in the diameter of the roll at that point and, therefore, a much higher loading on the paper web passing through the nip at that particular point. Friction blocks have been used for this purpose occasionally, but such blocks tend to disintegrate and pass pants through the nips in the calender.

Some calender stacks are provided with rolls which are bored for the introduction of steam. The entire roll is heated in this way and cooling air may be blown on the roll locally in order to reduce the diameter at a particular spot. Any of the aforementioned temperature control devices are employed to compensate for inequalities or streaks which show up on the reel as hard ridges in the Winding roll.

The instant invention is based upon a novel solution to the problem here involved. The instant invention resides in the use of a hollow doctor back or beam which carries the doctor blade. This hollow beam is equipped to serve as an air manifold. It is equipped with a plurality of spaced air or gas outlets extending the full length of the roll adjacent the doctor blade. Hot or cold air is connected to the manifold and a plurality of valve means mounted in association with each of the spaced gas outlets controls the amount of gas or air flowing through an individual outlet and thus the amount of heating or cooling effect applied to the calender roll. The operator may easily observe the windup roll and notice any inequalities which may appear. Compensation is easily and effectively made for such inequalities by mere adjustment of the valve means mounted in the manifold so as to obtain a desired heating or cooling effect in a particular localized area of the calender roll. For example, if a hard ridge starts to appear on the windup roll at a given location, then the operator adjusts the valves in the manifold along the portion of the calender nip aligned with this imperfection, so as to heat up a portion of a calender roll in this area, thereby to increase the nip pressure.

The doctor is, of course, mounted in close running relation to a calender roll at the ofi-running side of the calender nip; and this keeps the calender roll perfectly clean at this region of the off-running side of the nip. The longitudinally spaced gas outlets in the manifold mounting the doctor blade are aimed at the calender roll along a line at the off-running side of the doctor blade, whereat uniform cleanness of the calender roll surface is obtained for best control in the heating or cooling of the calender roll by the application of the gas or air.

It is therefore an important object of the instant invention to provide an improved calender, and more particularly, an improved calender wherein improved means are provided for controlling the loading along the full length of calender nips therein.

Another object of the instant invention is to provide an improved calender comprising a calender roll, a doctor mounted in close running relation to said roll, means mounting said doctor and providing spaced gas outlets extending the length of said doctor aimed at said roll for effecting localized temperature control along the length of the roll, and gas flow control means for each of said outlets.

Other and further objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed disclosure thereof and the drawings attached hereto.

On the drawings:

FIGURE 1 is essentially a diagrammatic view showing a calender stack embodying the instant invention in elevation;

FIGURE 2 is a fragmentary top plan view taken substantially along the line l III of FIGURE 1 showing the doctor back;

FIGURE 3 is an elevational view of the doctor back of FIGURE 2 taken substantially along the line III--III; and

FIGURE 4 is a cross-sectional view of the doctor back of FIGURE 2 taken substantially along the line IVIV, with the valve means shown in detail (the valve means having been omitted from FIGURES 2 and 3 for purposes of simplification).

As shown on the drawings:

As shown in FIGURE 1, a calender stack indicated generally by the reference numeral 10 comprises a bottom roll 11 and a plurality of superimposed calender rolls 12 through 17 defining a plurality of superimposed nips N1 through N-6. The web W passes over the top roll 17 through the first nip N-l around the second roll 16 through the second nip N-2, etc., until the web finally passes through the bottom nip N6 and out to the windup (not shown).

As indicated in FIGURE 1, the

rolls

12, 13, 14 and 15 are each furnished with a

doctor

18, 19, 20 and 21, respectively, which is mounted in close running relation to the particular roll with which it is associated. As will be noted, the doctor 21 is associated with the roll 15 and it is mounted in close running relation thereto at the offrunning side of the nip N-3. The doctor 21 is mounted on a doctor back, indicated generally at 22. Although the details of the doctor back 22 will be discussed in connection with FIGURES 2 through 4, it will be noted that the doctor back 22 is a hollow beam that is connected through a line 23 to a source of gas, in this case cold air CA. The cold air passes from the source CA through the line 23 and into the hollow doctor back 22. From there it is forced through outlets 24 against the surface of the roll 15 at the off-running side of the doctor 21. Optionally, the interior of the roll 15 may be heated, for example, by steam through a line 25 from a source S. In this way the chilling effect of the cold air CA coming through selected outlets or nozzles 24 is very pronounced on the roll 15 and there is a substantial temperature differential between the heated portions of the roll 15 and the chilled or cooled portions exposed directly to a blast of cold air through a nozzle 24. Actually, the chilling effeet of cold air alone (without the use of steam in the interior of the roll 15) will also produce a desirable temperature control effect. This is shown in connection with the doctor back 26 which mounts the doctor 19 in association with the roll 13. Cold air flowing through nozzles or outlets 27 in the doctor back 26 will result in the desired local temperature control in the roll 13so as to obtain localized control of the diameter of the roll 13.

If it is desired to eliminate a localized high spot" or portion of excessive thickness in the web W, the cold air coming from the nozzle 24 is reduced by valve means 28 at the particular area of this high spot and the tem perature of the peripheral port-ion of the roll 15 in this region increases. Thisresults in an increase in the diameter of the roll 15 at this region and much greater loading at the nips N-2 or N-3 or both. Additional increase in the loading of the web at the nips N-4 or N-5 or both may also be obtained by reducing the cold air flow through selected outlets 27 (using selected valve means 29).

Referring now to FIGURES 2, 3 and 4, it will be seen that the doctor back 22 of FIGURES 2 and 3 is provided with a top inlet 30 (which is connected to the cold air inlet line 23) and the doctor back 22 is provided with a plurality of air outlets 24a, 24b, 24c, 240., etc. These outlets 24a, 24b, etc. are spaced longitudinally of the roll so that each may serve a longitudinally spaced peripheral portion of the surface. A reduction of the cold air fiow at the outlet24a while the cold air flow is maintained at the outlet 2412 results in a slight increase in the diameter of the roll just opposite the outlet 24a, so that greater loading at the press nip is obtained in this region.

FIGURE 4 shows the details of the valve means employed in control of a specific gas outlet, in this case the outlet 24d. As will be seen from FIGURE 4, the doctor back 22 has a generally rectangular cross-section formed by welding to angle irons 22a and 22!; together at welds x (which are airtight welds). An end piece such as the end piece 220 of FIGURE 2 is, of course, provided at opposite ends of the doctor, back 22 to provide a closed hollow chamber C. Incoming gas or air is fed into the chamber C through the inlet described in connection with FIGURES 2 and 3. Each outlet 24 is defined by a short section of pipe 24d which threadedly engages the doctor back at a suitable aperture y in one side of the angle iron 22a. Opposite the individual aperture y there is a smaller aperture y which mounts a threaded tube 31. The threaded tube 31 carries spaced O-

rings

32, 32 which function to mount a valve shaft 33 and seal the same to prevent loss of air under pressure through the tube 31. The valve shaft has a manually graspable handle 34 outside the doctor back 22 for effecting limited axial movement of the shaft 33. The inner extremity of the shaft 33 carries a valve closing element 35 is the form of an oversize rubber washer 35a clamped between the two brass washers 35b, 35b by a screw 35c threadedly engaging the end of the shaft 33.

The doctor blade 21 (shown only fragmentarily) is secured to the doctor back 22 by suitable nut and bolt assemblies 36 as indicated. The gas passes through. the opening y and the pipe section 24d against the roll 15 (shown only fragmentarily) along a portion 15a at the off-running side of the nip N-3 and at the ofif-running side of the doctor 21. The amount or" air passing through each individual opening 1 is controlled by axial movement of the valve shaft 33.

It will also be appreciated that hot air can be employed instead of the cold air previously described in connection with the instant device. For example, as shown in 4 V FIGURE 1, a source of hot air HA may be provided and

lines

37 and 38, respectively, feed the hot air to the backs 39 and 49 which mount the

doctor blades

20 and 18. The structure of the doctor backs 39 and 40 is the same as that shown in connection with FIGURES 2 through 4 and the only difference in function is that hot air rather than cold air is' employed. In such circumstances, additional loading at a region in the press nip is accomplished by opening the valve means 41, for example, in the doctor back 40 to permit greater heating of the desired portion of the roll 12.

It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of the present invention.

I claim as my invention:

1. In a calender, which comprises a plurality of super- 9 imposed rolls defining a plurality of nips, a doctor mounted in close running relation to each of said rolls at the oii-running side of the nip and extending along the length of the roll, a hollow doctor beam mounting each of said doctors, said doctor beam being provided with at least one air inlet and a plurality of air outlets spaced therealong and directing a plurality of air streams at the roll at the off-running side of the doctor and the off-running side of the nip for effecting localized temperature control along the length of the roll, and valve means controlling each of the air outlets, the improvement in said valve means comprising a horizontally slidable shaft member mounted by the doctor beam, an air stream-directing pipe member in each outlet generally transverse to the roll opposite thereto, and an outlet closing member at one end of the shaft movable toward and away from each outlet to control the amount of air released from said doctor beam and through each outlet pipe toward the roll.

2. A calender, which comprises a plurality of superimposed rolls defining a plurality of nips, a doctor mounted in close running relation to each of said rolls at the off-running side of the nip and extending along the length of the roll, a hollow doctor beam mounting each of said doctors, said doctor beam being provided with at least one air inlet and a plurality of air outlets spaced therealong and directing a plurality of air streams at the roll. at the off-running side of the doctor and the elf-running side of the nip for effecting localized temperature control along the length of the roll, and valve means controlling each of the air outlets, the improvement in said valve means comprising an air stream directing pipe member in each outlet generally transverse to the roll opposite thereto, directing air to a selected roll area at the region of contact with the doctor, the pipe member being aligned generally parallel with the doctor blade, a movable shaft member, and an outlet closing member mounted on the shaft member and movable toward and away from closed position in the outlet to control the amount of air released from said doctor beam and through each outlet pipe member toward the roll.

References Cited in the file of this patent UNITED STATES PATENTS 485,534 Dillon Nov. 1, 1892 600,518 Dillon Mar. 15, 1898 680,135 Drew et a1. Aug. 6, 1901 1,326,615 Pope Dec. 30, 1919 1,714,261 Egan et al. May 21, 1929 1,982,571 Clark Nov. 27, 1934 2,130,241 MacLaurin Sept. 13, 1938 2,184,908 Chan Dec. 26, 1939 2,190,941 Gardner Feb. 20, 1940