US3007519A

US3007519A - Cleaning systems for paper making machines

Info

Publication number: US3007519A
Application number: US661475A
Authority: US
Inventors: Robert F Hollis
Original assignee: Alton Box Board Co
Current assignee: Alton Box Board Co
Priority date: 1957-05-24
Filing date: 1957-05-24
Publication date: 1961-11-07
Anticipated expiration: 1978-11-07

Description

Nov. 7, 1961 R. F. HOLLIS 3,007,519

CLEANING SYSTEMS FOR PAPER MAKING MACHINES Filed May 24, 1957 I I l I l l 1 a 5 7 i J g .5 15 I l x 55 K I la I. 1. wa 5/ United States Patent 3,007,519 CLEANING SYSTEMS FOR PAPER MAKING MACHINES Robert F. Hollis, Alton, Ill., assignor to Alton Box Board Company, Alton, Ill., a corporation of Delaware Filed May 24, 1957, Ser'. No. 661,475 2 Claims. (Cl. 162-380) This invention relates to cleaning systems for paper making machines, and more particularly to a vat cleaning system where the rate of flow and consistency of the stock e Patented Nov. 7, 1961 the stufi box to the mixing tank, whereas consistency is manually controlled at'the output valve from the tank. Automatic control of flow and stock consistency through the cleaner is achieved by providing the level controller on the mixing tank which is connected to vary the flow of the white water into the tank. Once the level controller is properly adjusted to hold the level in the tank adjacent the top of the dam, there need not be any further change and the machine tender need notworry about the cleaner.

In operation, the system automatically insures that stock of proper consistency will be fed through the cleaner, regardless of the machine tender adjustments of the flow from the stud box or of consistency of the stock fed to the vat. For example, under a condition of low rate of flow and high consistency at the vat, a portion of the conventional practice, the high consistency stock'is drawn from a stuff box supplied by the refining machines and fed to the mixing tank. So-called white water drawn from inside the cylinder of a vat is fed under control of a machine tenders valve into the mixing tank to dilute the stock to proper consistency. The output from the mixing tank is then fed to the cylindervat through a machine screen which serves toremove some of the solid contaminants and improve separation of the fibers. Themachine load is set by the machine tender by. ad-

justment of theflow from the stuff box'to the mixing parent from and in part pointed out in the following tank.

While the system is. relatively simple to-control, the screen cleaning section is not entirely satisfactory, since the screens tend to incorporate large air bubbles intothe stock, which later show up in. the product. the rate of flow and consistency of the stock in passing through screens may vary, it is not uncommon to find that the screen is a bottleneck when the stock is fed at a high rate of flow and low consistency, or to find that Also, since the cleaning action is inadequate when the rate of flow is low and stock consistency high.

Although other types of cleaning systems, especially centrifugal cleaners, are more efiicient, they present control problems because the flow through such a cleaner should be relatively uniform and the consistency of the stock must be held below a predetermined value in order to obtain maximum efficiency coupled with proper cleaning action. Consequently, the use of such cleaners has usually meant complications for the machine tender in controlling various additional valves, or it has meantan elaborate and expensive system of control. advantages are particularly noticeable in vat cleaning systems for cylinder type machines since such machines may have as many as eight cylinder vats, each of which requires its own cleaning system and control valves.

Accordingly, one of the objects of the present inven- 7 tion is to provide a relatively inexpensive vat cleaning unit, which has the simplicity of manual control of a conventional screen system but which is more efficient in its cleaning action. Although other features of the invention will be brought out in the following description, briefly, high consistency stock is fed from the stuff box to a mixing tank which is divided by a vertical dam into two sections. The high consistency stock is fed into one section along with the white water fromthe cylinder so that the stock is diluted before being fed to a centrifugal cleaner. The output from the cleaner is then fed into the other section of the mixing tank, and the cleaned stock is fed from this section through a-machine tender control valve to the cylinder vat. 'The'machine load is controlled, as before, by adjusting the rate of flow from cleaned stock will flow over the dam of the mixing tank and be recirculated in the cleaner. In this respect, the control is not only automatic but provides for additional cleaning of the stock. When the flow of stock to the vat is increased at the machine tender valve, White water flow from the vat also increases, some of which passes over the dam into the section containing the cleaned stock and the other portion of which serves to dilute the high consistency stock received from the stulf box. In other words, the level controller automatically insures that there will be a proper dilution of the stock before it is fed to the cleaner regardless of the rate offlow from the stuff box or the consistency of the stock fed to the cylinder vat.

"Other features of the invention will be in part apdetailed description, taken in connection w-ith'the accompanying drawing, in which:

The single figure is a diagrammatic View illustrating a vat cleaning system incorporating the invent-ion.

The invention is illustrated as employed as a stock cleaner at one vat of a multi-cylinder paper making machine. The system can be made into a compact unit which is preferably used as a substitute for the more conventional paper machine screen, and there would be one such unit for each vat of the paper making machine. A counterfiow type of vat is shown in the drawing to include a chest or housing 1 and a rotary cylinder 3 which cooperates with the felt 5 and couch roll 7. The fibrous stock is fed in atone end of the vat so as to flow over a dam 9 where it is then picked up by a rotary cylinder. Water is withdrawn from inside the cylinder through return pipes 11 and 13. As the water is Withdrawn, the fibers mat against the wire cylinder and are then transferred to the felt. A shower pipe 15 is mounted in the vat adjacent the cylinder on the side thereof which is leaving the felt.

The drawing also shows a so-called stuif box 17, which is supplied from one or more of the jord-ans or other refining engines (not shown). The refining machines operate best at a stock consistency of around two or three percent, hence it has been necmsary to dilute the stock before being fed to the vat. The consistency of the stock fed into the vat is usually under onepercent but may be varied, depending upon a particular machine and the the stock from the stuif box. The diluted stock is commonly fed from the mixing tank through a paper machine screen (not shown) to the head box 21 of the machine. A gate valve is generally provided on the outlet pipe 13 from the vat to control the level within the vat, and a '1 machine tenders valve was provided on the return pipe 11 to control the amount of water to be fed into the mixing tank, and thereby the consistency of the stock.

The screen type of cleaner had the function of removing some of the contaminants and of improving the separation of the fibers just before they enter the vat. Such cleaning and dispersion is desirable at the vat, but the screen device tends to introduce an excessive amount of air into the stock. In other words, the stock would pick up large bubbles which would later appear in the paper. Moreover, the consistency of the stock and the rate of flow through the machine vary considerably, and these variations necessarily interfere with the efficiency of the screening operation, even assuming the screen is an efiicient cleaning device to begin with. For example, under a condition of operation involving a high rate of flow of relatively free stock, the screen tends to become a bottleneck in which case it may be necessary to bypass it entirely. At the other extreme of relatively low rate of flow and high stock consistency, the cleaning action becomes unsatisfactory. In other Words, a satisfactory cleaning machine should operate at a relatively uniform rate of flow and with a stock consistency not exceeding a predetermined value, depending upon the nature of the cleaning machine. On the other hand, the screen cleaning system does have the advantage of simplicity, especially from the view point of control by the machine tender. There were only two valves to worry about, the first controlling the rate of flow from the stud box to the mixer, the second controlling the amount of water fed into the mixer or the consistency of the stock supplied to the vat.

Other types of cleaners are more efficient in their operation and their cleaning action, and the invention particularly contemplates the use of a centrifugal cleaner where the stock is fed tangentially into a conical housing so as to be whirled around in a vortex. The heavier contaminants collect against the wall of the housing and are drawn oiT through a bottom port as tailings, while the lighter cleaned components or accepts accumulate in the center and flow out through a top port. This type of cleaning system also has other advantages over the screen type (less air in the stock and improved fiber separation at the cleaner pump), but it is even more sensitive. It is considered necessary to maintain a uniform capacity rate of flow and to hold the stock consistency within predetermined limits.

Referring to the drawing, stock from the stuff box 17 is drawn down through a valve 53 and pipe 31 to one end of a mixing tank 23. Accordingly, the uncleaned stock tends to accumulate in one section on the right side of the tank, and this stock is drawn out through a pipe 25. The line 25 connects with the input of cleaner 22 and includes an open-impeller cleaner pump 27 and throttle valve 29 to permit control over the rate of flow and pressure in accordance with the rating of the cleaner.

The mixing tank 23 includes a dam 33, so as to provide a second section at the other end (-left side of the drawing) into which the clean stock is conveyed by a pipe 35 may be provided on one side of the tank to receive the sensing element 47 of a controller 49. A small supply of water may then be fed into the top of this tube at A to purge the tube of fibers and insure proper functioning of the instrument. The controller 49 could be of the pneumatic type and is connected to actuate a valve 51, which is connected in the White water return line 11 from the vat to the mixing tank. The level controller is adjusted to maintain the fluid level in the tank slightly above the dam 33, and it will be'noted that fluid may flow over the dam 33 in either direction.

In operation, the machine load is controlled as before by adjusting valve 53 at the output of the stuff box, the amount and condition of such stock being designated B. The machine tender utilizes valve 39, to produce the desired consistency at the machine, as will be more apparent. Gate valve 55 in the output line '13 is adjusted v to maintain a proper level within the vat 1, and of course,

I tank 23 through pipe 25 to the cleaner 22 and this flow is designated C. The tailings are drawn oil from the bottom of the cleaner, as indicated at D, whereas the cleaned output or accepts designated E are conveyed by pipe 35 to the other section of the mixing tank. Clean stock is drawn oifby pipe 37 from this section of the tank, as

indicated at F, although the amount drawn off may be greater or less than the amount E entering the tank. The difference is accounted for by a flow over the dam 33. In the case where the amount F drawn olf is less than the amount of entering clean stock E, a portion G will flow clockwise into the first section of the tank and be recirculated to the cleaner. Conversely, if the amount drawn oil at F is greater than the amount entering at E, someof the white water in the tank will flow over the dam in the reverse counterclockwise direction, as indicated in the drawing. The counterclockwise flow is essentially white water supplied by pipe 11, as indicated. atH. Consequently, the consistency of the stock entering the vat is determined indirectly by the rate of flow, a small flow resulting in high consistency and a large flow resulting in lower consistency.

The flow out of the machine head box 21,will be the same as that entering, hence the stock input to the vat is represented by F. An additional amount of water is supplied by the shower 15, as indicated and is designated I.

The output from the vat consists of the stock on the felt connected with the accepts outlet of the cleaner. As indi- 7' cated, the tailings are drawn oif at the bottom of the cleaner and may be fed back to a breaker beater (not shown), which is a conventional component in the paper making process, or the tailings may be separately treated.

A pipe 37 extending from the clean section of the tank 23 is connected through a machine tenders valve 39 to the head box 21 for a vat of the paper making machine. Accordingly, the machine tender rnay visually inspect the stock as it passes into the vat. In addition, the head box serves to release some of the larger air bubbles from the stock.

Finally, the invention contemplates the use of an automatic level controller which is arranged to vary the flow of White water into the mixing tank in response to fluctuations of fluid in the tank. Such level controllers are well k wn in the art. For examp n pen t be 45 web, which is designated J, white water drawn from inside the screen through pipe 11 as represented by H, and an additional amount of white water drawn ofi through the pipe 13 as indicated at K.

In order to illustrate the operation of the system under varying conditions, the following tables may be helpful.

Example 1 Rate of Load or Stock flow, Tons Con- Gal. per Per sistency, Minute Day Percent Example 2 Rate of Load or Stock flow, Tons Con- Gal. per Per sistency, Minute Day Percent Example 3 Rate of Load or Stock flow, Tons Con- Gal. per Per sistency, Minute Day Percent 1 0 0 111 20 3 650 20 0 52 25 l 625 19 0. 51 632 19 0.50 7 0 0 546 0 0 I, .1, Ksame as in preceding example.

Example 4 Rate of Load or Stock flow, ons Con- Gal. per Per sistency, Minute Day Percent In view of the above, the construction, operation and advantages of the disclosed system will be readily apparent to those skilled in the art. Although one physical embodiment is disclosed, it should be understood the invention is subject to various modifications or adaptations Without departing from the spirit of the invention or the scope thereof, as set forth in the claims.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. In vat stock cleaning apparatus of the character described, wherein stock supplied from a stuif box is cleaned before being fed to a vat of a cylinder-type paper making machine, the improvement comprising a mixing tank having a dam dividing it into first and second sections, means supplying stock from said stuif box to said first section of the mixing tank, a centrifugal cleaner, means including a pump conveying stock from said first section of the mixing tank to the cleaning device, means conveying stock from said cleaning device to the second section of the mixing tank, said second section of the mixing tank being connected to supply stock to the vat of the paper making machine, a controller for sensing the level of the fluid within the first section of the mixing tank, a water supply line extending from the vat to said first section of the mixing tank, and controller-actuated valvemeans interconnected in said Water-supply line to vary the flow of Water to the first tank section in response to fluctuations of the liquid level, said controller being adapted to maintain the level above the top of said dam.

2. Apparatus as set forth in claim 1, further including a machine tenders valve interconnected between the secend section of the mixing tank and said vat.

References Cited in the file of this patent UNITED STATES PATENTS 1,026,819 McIntyre May 21, 1912 1,472,238 Berkey Oct. 30, 1923 1,653,125 Schur Dec. 20, 1927 1,670,874 Bankus May 22, 1928 1,853,849 De Cew Apr. 12, 1932 1,868,291 OConnor July 19, 1932 2,060,685 Murphy Nov. 10, 1936 2,156,445 Baxter May 2, 1939 2,312,706 Freeman Mar. 2, 1943 2,540,301 Staege Feb. 6, 1951 2,609,732 Breyfogle Sept. 9, 1952 FOREIGN PATENTS 703,618 France May 4, 1931