US2974796A

US2974796A - Centrifugal-type pulp separator

Info

Publication number: US2974796A
Application number: US682050A
Authority: US
Inventors: Jung Johannes
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-09-04
Filing date: 1957-09-04
Publication date: 1961-03-14
Anticipated expiration: 1978-03-14

Description

CENTRIFUGAL-TYPE PULP SEPARATORv Filed Sept. 4, 1957 *ayz-in.

Patented Mar. 14, 1961 CENTRIFUGALTYPE PULP SEPARATOR Johannes Jung, Miltenberg (Main), Germany Filed Sept. 4, 1957, Ser. No. 682,050

'5 Claims. (Cl. 209-284) The present invention relates to a centrifugal-type pulp separator comprising a housing having a stationary cylindrically-shaped screen drum arranged at a certain distance from the inner wall of the housing, and blades inside the screen drum rotating about the drum axis, and in which the pulp enters from the one front side and the coarse-grained parts leave the housing at the opposite end.

In known centrifugal-type separators of this kind the pulp enters the screen drum in axial direction at a height of the shaft. In the drum the pulp is rotated by the blades. This necessitates a power input which is very high as compared to the output of the screen drum. Furthermore, the impacts on the rotating blades resulting from the axial flow of the pulp are of detrimental effect. Furthermore, when feeding the pulp in axial direction at a height of the blade shaft, the screen is not uniformly charged over its total length since the end facing the breast box is not correctly loaded.

To eliminate these disadvantages it has already been proposed to feed the pulp at a height of the screen drum all over its periphery and to bend the ends of the blades which are inclined with respect to the axis, at the point of entry of the pulp so that a shockless entry of the pulp into the impeller is achieved. At the point where sizing takes place, the blades are inclined so as to impart an axial movement to the pulp. By eliminating the impact of the entering pulp on the impeller, power requirements are reduced. As compared to the drum output, however, power input is still considerable since the axially supplied pulp has to be circulated. This reversal of movement takes place gradually, which again has the disadvantage that the drum is less loaded at the point of entry than in its center.

According to another known embodiment, power requirements are reduced in that the screen drum which in conventional separators is stationary, is rotated at a speed somewhat lower than that of a Worm conveyor provided instead of impeller blades. The rotating screen drum itself forms the centrifugal member. The material is supplied at a height of the worm conveyor shaft to a double-walled hopper arranged concentric on the screen drum, the hopper tapering towards the screen drums periphery. In this hopper the axially entering material is transferred, through means of its friction on the wall and without causing any impact, into the direction and speed of rotation of the screen drum. The material is then spread as a uniform layer over all of the inner circumference of the screen drum and smoothly passes over the separating area where the fine fibers and the water are thrown out through the holes of the screen drum due to its rotation. Efliciency is not as high as if the material is thrown against a stationary screen drum by rotating blades. A rotary screen drum considerably complicates the apparatus and increases its manufacturing cost.

It is, therefore, one object of the present invention, to provide a shockless entry of the pulp into the screen drum at a height of its inner wall and all over its periphery, a utilization of the total length of screen, and a reduction of power requirements by arranging a stationary feed pipe for the pulp which is shaped so that a rotary movement is imparted to the pulp which follows the curvature of the screen drum before the pulp enters the drum.

It is of particular advantage to supply the material fiom a breast box through a double-walled pipe in which the space between the two walls through which the material is passed, is provided with spiral channels, guide blades, or the like. These spiral passages impart a rotary movement to the passing material. The spiral is shaped in such a manner that the direction of movement -of the material is the same as the direction of rotation of the impeller blades. By controlling the feed from the breast box into the double-walled pipe, the amount of material flowing into the pipe can be controlled, and by varying the level of the material in the breast box the feed pressure can be varied. If desired, one of the walls of the double-walled pipe may be of conical shape so that the cross-section of passage gradually decreases towards the separator. In these embodiments the front wall of the housing is preferably shaped in such a manner that the pulp can enter the housing from the circumference of the feed pipe. Multiple spirals in the feed pipe take care of distributing the material over the entire inner edge of the screen drum adjacent the feed pipe.

Similar to the feed of the pulp, the coarse-grained material remaining in the screen drum' may be discharged. For this purpose, the front side of the housing opposite the feed pipe may be provided with another double-walled pipe through which the coarse-grained material is passed away. When several separators are arranged in a row, the passed-away coarse-grained material can be directly supplied to the following separator. In this case, spirals have to be provided also in this pipe which, however, can be disposed of when the coarse-grained material is fed directly from the separator to a refiner or to another station. In this embodiment the arrangement of several separators in a row, each with a finer mesh scren than the preceding one, is considerably simplified. No special pipes and pumps for the transfer of the material from one separator to the other are necessary. Furthermore, the different separators may 'be successively mounted at the same level.

When for constructional reasons it-is not possible to mount a breast box, the material is supplied to the pipe provided with the spiral passages, through a feed channel or the like.

With these and other objects in View which will become apparent in the following detailed description, the present invention will be clearly understood in connection with the accompanying drawings, in which:

Figure l is an axial section of a centrifugal-type pulp separator having a breast box disposed on the same plane and a double-Walled pipe connecting both members, the space between the double walls serving for the feeding of the material;

Fig. 2 is an axial section similar to that in Fig. 1, wherein, however, the space between the double walls is tapered down in direction towards the separator;-

Fig. 3 is an axial section of a centrifugal-type pulp separator having a higher breast box and a doublewalled pipe connecting both members;

Fig. 4 is an end View of the separator shown in Fig. 3, indicating a spirally shaped pipe connecting the higher breast box with the centrifugal type separator; and

Fig. 5 is an axial section of a plurality of separators disposed in series and each of the separators being connected with the next one by means of a double-walled pipe and a higher breast box feeding the material to the first one of said separators. V

Referring now to the drawings and in particular to Fig. l, the separator comprises a cylindrical housing 1 having a screen drum 2 spaced apart from the inner wall of the housing. Impeller blades 3 are arranged within the screen drum 2. Theshaft 9 carrying the impeller blades 3 is journalled in the front and back sides of the housing 1.

Co-axial with the housing 1 is fixed a double-walled pipe 4 to the front side of the housing, the space between the two walls of the pipe 4 having spiral passages 5. The outer'diameter of the double-walled pipe 4 corresponds with the diameter of the screen drum 2. The front side of the housing 1 to which the double-walled pipe 4 is fixed, is shaped in such a manner that all of the periphery of the pipe 4 is in communication with the inside of the screen drum 2.

The material to be separated is supplied from a breast box 6 through the double-walled pipe 4 to the separator. The material flowing through the space between the two walls of the pipe 4 is put in circular motion by means of the spiral passages 5. The latter are shaped in such a manner that the circular motion corresponds with the direction of rotation of the impeller blades 3. The material fed to the separator through the pipe 4 reaches the inner Wall of the screen drum 2 at its entrance and spreads 'all over its circumference. To achieve perfect operation, the pipe 4 is provided with a multiple spiral. Since the material supplied is already in a circular motion which corresponds with the direction of rotation of the blades 3, the screen drum 2 is not subjected to great stress when receiving the material. For the same reason it is not probable that the blades 3 subject the material to an additional motion.

The speed at which the material flows through the V double-walled pipe 4 corresponds with the pressure existing at the entry of the pipe 4 in the breast box 6 and with the amount of material entering the pipe 4. The pressure may be varied by varying the material level. in the breast box 6, and the amount of material is controlled by a valve means 7 at the inlet of the pipe 4.

It is also possible to control the speed of the material supplied by varying the pitch of the spiral in the doublewalled pipe 4. Preferably, the spiral is shaped in such a manner that its pitch is variable by expanding or compressing the spiral.

By controlling' the speed of the material flowing through the double-walled pipe 4, it is easy to have the material enter the separator at a speed corresponding with the circumferential speed of the impeller blades 3. When these two speeds are synchronized, the stress acting on the screen drum is reduced to a minimum and the danger of the material being subjected to an additional movement is completely eliminated. Thus, careful treatment of the material as well as gentle separation is secured.

In the embodiment disclosed in Fig. 1 both walls of the pipe 4 are of cylindrical shape. The cross-section of passage is uniform over the total length of the pipe 4. However, if for instance the material is highly diluted, and a big output is to be rendered, it may be of advantage to have one wall of the double-walled pipe 4 tapered down, so that the cross-section of passage is reduced towards the separator. Such an embodiment is disclosed in Fig. 2.

The arrangement of the breast box 6 will depend on the available space. In the embodiments illustrated in Figs. 1 and 2 the breast box 6 is arranged at level with the separators, the material being supplied from the breast box 6 in axial direction, to the double-walled pipe 4. Asshown in a side and a front elevational view in Figs. 3 and the breast b X 6' may also be mounted above the double-walled pipe 4, and the material may be sup- "plied in radial direction from the box 6 to the doublewalled pipe 4 through a spiral pipe .10.

When the coarse-grained material leaving the separator is to be further treated in another screen drum having a finer mesh screen, it is advisable to arrange the outlet of the coarse-grained material at the front side opposite the inlet and to shape it in such a manner that the coarse-grained material is ejected over the entire circumference at a height of the screen of the first separator. The coarse-grained material leaving the separator here, is then passed into a double-walled pipe having spirals inside and being fixed to the front side of the separator, to transfer it into the second separator. In this way, any number of separators, each having a finer mesh screen, may be arranged one after the other, as disclosed in Fig. 5. The coarse-grained material is then passed from one separator to the other without the necessity of employing further pumps and pipes. It might be'necessary to feed water to the pulp for further dilution between the various separators. The separators arranged in a row may be mounted at the same level and close to each other. Space requirements are considerably reduced as compared to the conventional arrangement of several separators working one after the other.

In some cases space conditions may not allow for an arrangement of a breast box with a transfer pipe to :the separator. In these cases a feed channel or pipe leading to the double-walled pipe 4 may be provided instead of a big-capacity box 6.

While I have disclosed several embodiments of the present invention, it is to be understood that these embodiments are given by example only and not in a limiting sense, the scope of the present invention being determined by the objects and the claims.

I claim:

1. .A centrifugal-type pulp separator comprising a housing having an inner wall, a stationary screen drum disposed in said housing spaced apart a predetermined distance from said inner wall and having its axis disposed horizontally, a horizontal shaft axially disposed rotatably in said housing, a plurality of impeller blades keyed to said shaft, a feed pipe disposed adjacent one end of said screen drum and feeding materialtangentially directly to the inner face of said screen drum in the direction of rotation of said impeller blades, said screen drum in conjunction with said impeller blades operating as separating means for said pulp, said material emerging from said screen drum from the opposite end thereof, said feed pipe comprising two substantially contric pipe members, the outer diameter of said feed pipe corresponding with the inner diameter of said screen drum and the inner diameter of said feed pipe being slightly smaller than the outer diameter of said impeller blades, said feed pipe being disposed completely outside said housing and having a spiral intermediate wall extending over the entire length of said feed pipe.

2. The separator, as set forth in claim 1 which includes a breast box supplying said material at a pressure and at an amount to said feed pipe, in order to impart the same rotary speed as said impeller blades to said material when feeding the latter from said feed pipe to said screen drum.

3. The separator, as set forth in claim 1, wherein one of the walls of said feed pipe is tapered, so that its crosssection of passage decreases gradually towards the screen drum.

4. The separator, as set forth in claim 1, which includes a curved pipe mounted to the front face of said feed pipe, said curved pipe being adapted to feed said material to spiral passages, and a breast box supplying said material to said feed pipe by means of said curved pipe and being disposed at ahigher level than that of said screen drum.

5. A set of a plurality of separators, each of said :separators being set forth in claim 1, wherein said separators are disposed .in series, so that said material is fed 6 from one of said separators to the adjacent one of said References Cited in the file of this patent separators through said pipe, and the screen drum of UNITED STATES PATENTS each of said separators having, in the direction of movement of said pulp through said plurality of separators, 1,583,705 Schmldt P 1923 a finer mesh screen than the preceding one of said sep- 5 1,730,057 COX 1930 arators. 1,356,176 Trimbey May 3, 1932