JPS6117959B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in screening equipment for screening pulp fibers for papermaking, and in particular to an improved vertical centrifugal screen for pulp stock.

When screening pulp fibers, it is desirable to separate the fibers into individual disaggregated forms. Since the stock as it is fed to the screen usually contains varying amounts of debris and fiber bundles, the main purpose of the screening operation is to ensure that a uniform and pure stock is available for the paper machine. There is no need to remove this kind of impurities. Although the problem of obtaining a pure paper stock applies to all types of fibers, it is particularly troublesome in the case of groundwood fibers. In particular, the present invention provides for feeding the stock into the center of the screen so that the receptacle or employable fibers pass through the openings in the screen and are collected in a housing surrounding the screen, as well as debris, bundles or bundles or dust. Although this paper relates to a vertical centrifugal screen in which the waste material, including wood and bark particles, is retained within the screen and exits through an outlet opening in the housing, other types of screen processing equipment use horizontal It includes screens and vertical screens.

For these modified types of vertical screens, it is important that continuous operation can be achieved without blocking or interfering with the continuous screening flow of stock through the screen. Similarly, it is important for the device to achieve adjustable flow control with structures that are not complex in design and relatively easy to control. Although centrifugal screens of the type described herein can also be used in other industrial sectors, the invention finds particular advantages in the paper industry and will therefore be described in connection with the screening of paper pulp. That's it. The present invention provides an improvement over conventionally used screens by reducing the cost per unit of processing capacity and requiring less space for installation. Additionally, the present invention provides a structure that is more convenient to operate, particularly with respect to adjusting the jet openings that control the flow of stock through the screen treatment mechanism.

It is therefore an object of the present invention to provide an improved structure for centrifugal screens for screening paper pulp.

It is another object of the present invention to provide improved centrifugal efficiency to increase the screen process flow and thereby obtain improved product, as well as to achieve improved centrifugal efficiency without the need for rotationally driving the screen or other components. It is to provide a screen.

According to the principles of the invention, a circumferential slicing aperture is provided to deliver a continuous radial jet at one end of the cylindrical screen, and the radial velocity of the jet is controlled by varying the pressure within the inlet chamber. I can do it. The flow rate can be controlled by changing the slice opening. The jet exiting the slice radially is then redirected downward while experiencing a mostly tangential velocity component by the unique deflector vanes. This results in a swirling flow of liquid along the inner surface of the cylindrical screen. Centrifugal force, determined by the combined effects of jet velocity, spiral angle and container diameter, causes dewatering or screening of the stock. There is no need to incur the construction costs of providing supports and rotary drives. Due to the size of the openings in the cylindrical screen, particles exceeding a certain size limit are retained therein and eventually fall down the screen surface and are collected in the debris compartment. Most of the liquid and the fine particles that pass through the screen are collected in the fines compartment. The idea of the structure is to achieve low manufacturing costs, the structure of which is that the piping supported by the collection compartment serves as a mechanical support for the inlet chamber. While a few of the parts that make up the head assembly require machining, including turning and boring, the remaining parts of the device include standard pipe fittings and simple stainless steel components.

Still other objects, advantages, and features of the invention will become more apparent from the teaching of its principles in conjunction with the disclosure of the preferred embodiments set forth in the specification, claims, and accompanying drawings. It will be.

Hereinafter, the present invention will be explained in detail based on specific examples shown in the accompanying drawings.

As shown in FIG. 1, a sorting or bast screen mechanism is provided having a rotatable cylindrical screen 10 with screening perforations or openings 11. The stock flowing from the top to the bottom of the screen is subjected to a controlled centrifugal flow, and while the acceptor, the pure fibers, passes through these apertures, dust, bundles, bundles, etc. Undesirable substances remain within the screen and fall toward the bottom end.

A rotatable cylindrical screen 10 is contained within a housing 12 and defines an annular space 19 between the screen and the housing through which the receptacle flows downwardly and exits the housing via a fines conduit 20 in the base 13 of the housing. It is starting to form in between. Annular stationary shell 15 at the base of the housing
a provides a series of annular spaces 19 for fines, which spaces communicate with an outlet 20. A seal 23 is provided between the lower end of the cylindrical screen 10 and seated on its annular support base 15a.

In this support base there is a support pipe 15 leading from both radial directions into a central T-tube 16a which supports the central inlet pipe 16. This central inlet pipe is screen 10
It is concentric with the screen and supports the screen at its upper edge. The paper stock is attached to the mounting bracket 1 on the side of the housing.
4 and 17 and flows inwardly up the center of the inlet tube 16 to be distributed by an annular distributor head 18. Once the stock has been distributed at the top, it flows downwardly through the center of the cylindrical screen 10, while its rejects flow, as indicated by the arrow line 21, to the waste outlet, indicated schematically by the arrow 22. . On the other hand, the fines flow downward through the screen as shown by arrow 19a.

In order to improve the movement of the stock and further increase the separation effect, the stock is discharged as an umbrella jet at the slicing openings 30 and distributed under a spiral centrifugal action along the inner surface of the screen.

At the upper end of the structure, as shown in FIG. 1 but primarily as shown in FIG.
into a cap structure 28 mounted on the top end of the cap. This cap structure is constructed so that the paper stock is inlet pipe 16.
an upwardly facing cup-shaped annular unit with a radial opening 27 into which the stock then exits radially outwardly beyond an annular lower slice lip 29; The lower slicing lip cooperates with the upper slicing lip 35 to form a circumferential slicing opening 30. Paper stock is this slice opening 3
0 flows radially outwardly through a series of circumferentially spaced spiral deflector vanes 36 (second
(see Figures and Figure 3). These vanes are supported on a peripheral outer flange 45 which is part of the head 18 and which is movable in the vertical direction and whose position determines the dimensions of the slicing aperture 30. The vane 36 is rigidly supported and positioned so that the stock impinges thereon;
Furthermore, the shape is such that the stock can be guided or deflected into a spiral channel along the inner surface of the cylindrical screen 10. An inflatable connecting portion 37 is disposed between the screen 10 and the flange member 45 so that the head 18 can move vertically relative to the screen 10.

The stock is delivered to the mechanism by a controlled pressure or power delivery pump 46 (see FIG. 1), the radial velocity of the stock exiting the slicing opening 30 being controlled by the cup-shaped member 28. Control is achieved by changing the pressure of the stock fed into this mechanism which changes the pressure of the stock in the inlet chamber 28a. The volume is controlled by varying the dimensions of the slice aperture 30, which is varied by positioning the upper slice lip 35. This slice lip can be moved up and down by rotating the handle wheel 41 and positioning the head 18 in the up and down direction. The head has an annular flange 45
The head member 33 supports the cap 31 and slides vertically against the cap 31. The cap 31 has a smooth cylindrical outer surface 32 for receiving an O-ring seal 34 carried by a head member 33.

The head member 33 is attached to the top of the cap 31 at 44
The collar 42 includes a flanged collar 42 that can freely move up and down on a vertical post 43 that is threadedly engaged with the collar 42 . This column 43 receives the rotary handle wheel 41 and is threadedly engaged with it at its upper end. The steering wheel presses on a cup 40 that presses on an annular ring 39 that presses against the top of the air actuator 38. Actuator 38 may be a continuous annular donut or a plurality of inflatable members that are air inflated and provide a downward biasing force to head member 33 that holds flange 42 of collar 42a against the top of ring 39. be able to.
When the handle wheel 41 is tightened, the cup 40 and ring 39 exert downward pressure on the air actuator 38 to push the head member 33 downward, thereby forcing the upper slice lip 35 downward and closing the slice opening 30. It becomes like this. The pneumatic actuator accepts the sudden surge of fluid pressure and temporarily forces the head upwardly so that the slicing aperture 30 can be opened. Air actuator 38 can be collapsed by venting to emergency open the slice opening to release the blockage. In addition, the actuator 38
The pressure can be varied to control the size of the slicing opening and can also be adjusted in relation to the pressure of the stock being pumped by pump 46. The volume of stock fed into the screening chamber is varied by varying the dimensions of the slicing openings.

During operation, stock is conveyed to the screening mechanism by pump 46 through inlets 14 and 17 and flows upwardly in inlet tube 16. At the upper end of the inlet tube, the stock flows through radial openings 26 and 27 and exits through annular slicing opening 30. The stock then impinges on the spiral deflector vanes 36 and is directed down the inside surface of the screen through a spiral channel which enhances the screening effect. Increased speed and centrifugal action can be achieved by increasing the pump 46 delivery pressure. Increasing the flow rate can also be achieved by opening the slicing aperture 30 to a larger size.

The structure is easy to arrange, has a small number of parts, and requires minimal machining. This construction allows the use of standard structures for parts such as the inlet tube 16 and simple castings for the head, and for the cylindrical surface 32 of the cap, surfaces 29, 35 of the slice lip, etc. Only minimal machining is required. The structure is such that it can be easily spaced apart by raising the head 18 relative to the screen, and the housing is constructed to accommodate this action at its upper end.

The applicant therefore provides an improved sorting and bast screen which completes the advantages and features described above and which is capable of continuous operation without frequent attention or cleaning. Let's understand what happened.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram, in vertical section, of a centrifugal screening apparatus embodying the principles of the present invention. FIG. 2 is an enlarged detailed vertical cross-sectional view of the head end of the structure. 3 is a schematic horizontal cross-sectional view taken substantially along the line - of FIG. 2; FIG. 10... Cylindrical screen, 11... Opening, 1
2... Housing, 14, 17... Mounting bracket (inlet), 15... Support piping, 15a... Stationary shell, 16... Central inlet pipe, 16a... Center T-shaped pipe, 18... Distributor head, 19... annular space,
20... Conduit for fine objects, 27... Radial opening, 2
8...Cap structure, 28a...Entrance chamber, 29
... lower slice lip, 30 ... slice opening, 31 ... cap, 33 ... head member, 3
4... O-ring seal, 35... Upper slice lip, 36... Deflector vane, 37... Interrupter, 38... Air actuator, 39... Annular ring, 40... Cup, 41... Handwheel , 42...flange, 42a...collar, 43
...Column, 45...Peripheral outer flange, 46...Delivery pump.

Claims (1)

[Claims] 1 a cylindrical perforated wall screen, an outer enclosing housing containing a fiber receiver passing through the screen from the stock in the screen, an annular outlet at the upper end of the screen and a lower slicing lip; a centrally located concentric stock support conduit; an annular upper slicing lip defining a radially facing slicing opening with the lower lip for discharging the stock into the interior of the screen; means for directing the flow in a spiral direction within said screen; means at the lower end of said housing for removing rejects that do not pass through said screen openings; and means for adjusting said upper lip to adjust the size of said slicing openings. and a power means for controlling centrifugal movement of the stock through the center of the screen.