US 3409137 A
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Description (OCR text may contain errors)
Nov. 5, 1968 F. w. SCHNEIDER v 3,409,137
PUSHER TYPE CENTRIFUGE WITH A WASHING DEVICE FOR THE CENTRIFUGED MATERIAL Original Filed Aug. 24, 19 1 2 Sheets-Sheet 1 Nov.'5, 1968 F. w. SCHNEIDER 3,409,137
PUSHER TYPE CENTRIFUGE WITH A WASHING DEVICE FOR THE CENTRIFUGED MATERIAL Original Filed Aug. 24, 1961 2 Sheets-Sheet 2 In 14 .555; 20 M 2 22 A A I I4a H 14b v I jm emorz' IF Wm United States Patent 2 Claims. of. 210-213 ABSTRACT OF THE DISCLOSURE A pusher type centrifuge with a washing device for the centrifuged material, which comprises a housing and a centrifugal drum rotatably mounted in the housing to constitute a first member. Two cylindrical screen portions, having different diameters, extend axially from the centrifugal drum. A pusher plate is disposed within the housing and rotates coaxially with, as well as reciprocates relative to the centrifugal drum, the pusher plate constituting a second member. A conically outwardly widening solid-walled portion is secured to one of the members and is disposed at a greater radial range relative to the rotating axis than the outermost radius of the pusher plate, as well as extending from one of the cylindrical screen portions to the other of the cylindrical screen portions. An inwardly widening acceleration funnel is secured to one of the members for joint rotation therewith. A feeding pipe leads into the acceleration funnel and a washing pipe is arranged for feeding washing liquid toward the solid-walled portion.
This is a continuation application to my co-pending patent application Ser. No. 133,664, filed on Aug. 24, 1961, and now abandoned.
The present invention relates to a pusher-type centrifuge with a washing device for the centrifuged material.
Single-stage, as well as multi-stage pusher-type centrifuges are known for the continuous separation of liquidsolids mixtures.
In a single-stage pusher-type centrifuge a pusher plate reciprocates axially along a portion of the inner wall of the centrifugal drum during the rotation of the cylindrical or conical centrifugal drum which is covered with screens and, thereby, the filter cake, which is deposited on the inner wall, is gradually conveyed to the discharge end of the centrifugal drum, where it is thrown out into the collecting chamber for the solids.
In a multi-stage pusher-type centrifuge several cylindrical or conical filter-drum parts are fitted telescopically one inside the other and connected to two systems, reciprocating axially relative to each other in such manner, that any two immediately adjacent drum parts belong to different systems. The end faces of all inner drum parts operate then always as pusher members for the discharge of the filter cake which is deposited on the inner wall of the outwardly adjoining adjacent outer drum part.
It has been found, that in the centrifuging of hard granular or crystalline materials, single-stage pusher-type centrifuges with a cylindrical filter are superior to multistage pusher-type centrifuges with cylindrical filters and are also superior to the pusher type centrifuges with tapered filters in that they provide a low residual moisture and a high yield of solids. This advantage is explained by the fact that in single-stage pusher-type centrifuges with a cylindrical filter part, the filter cake is 3,409,137 Patented Nov. 5, 1968 built up once only, that is it is not turned over several times and, due to the fact that a bridge formation of its particles takes place, it holds back even fine materials.
Multi-stage pusher-type centrifuges are used advantageously, when the filter cake must be washed or when vlscous or thixotropic substances are to be centrifuged. The better effect of the multi-stage pusher-type centrifuges for these materials resides in the multiple restratification and loosening of the filter cake during each transfer from one drum to the next drum of larger diameter. The loosening encourages the penetration of the washing liqaid and the removal of the originally bonded interstitial liquid or mother liquor. Since the loosening and restratification are restricted to a relatively small area, a plurality of washing stages, that is, drum stages, must be arranged in series when larger quantities of washing liquid are to be bonded. Thus, pusher-type centrifuges with a total of eight stages are known, which entail rather high manu facturing costs due to their involved construction. Due to the always new building up of the filter cake, upon the transfer from one drum to the next, as well as due to the great number of ring slots between the sliding rings and the screens, a high solids loss in the filtrate must be ac cepted in the multi-stage pusher-type centrifuge and, thereby, a lower yield of solids.
The heaviest losses of solids are found in multi-stage pusher-type centrifuges with conical filter drums, because in this structure the loss of solids occurs not only in the annular gaps between the thrust rings and the drums, but also to a great extent on the conical filter part itself, because of the continuous loosening of the cake. The centrifuging of fine material is possible only to a limited extent in these centrifuges even with modest requirements concerning the yield of solids.
It is one object of the present invention to provide pusher-type centrifuges with a washing device for the centrifuged material which avoid the drawbacks of the multi-stage pusher-type centrifuges concerning the washingpossibilities, the filtrate loss and the construction thereof.
It is another object of the present invention to provide pusher-type centrifuges with a washing device for the centrifuged material with a rotating shell of a centrifugal drum and a cylindrical screen part, followed in the discharge direction by a conically widening solid-walled part, secured to a pusher plate, or the cylindrical screen part secured to the pusher plate to which solid-walled part the washing liquid is fed, and a suitably wider cylindrical filter part which follows the comically diverging walled part.
The formation of the washing zone as a conical solidwalled part causes a loosening of the filter cake and, thereby, an improved washing possibility without additional filtrate loss. This solid-walled part can be rigidly connected with the two adjacent cylindrical screen parts or may be made axially displaceable relative to one or both of these parts, whereupon a one-, twoor at the most three-stage pusher-type centrifuge, thus a comparatively simple construction, results.
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 multistage pusher-type centrifuges are disclosed:
FIGURE 1 is an axial section of a pusher-type centrifuge, in accordance with the present invention, and illustrated as a three-stage pusher-type centrifuge;
FIG. 2 is an axial section of a three-stage pushertype centrifuge and discloses another embodiment compared with that of FIG. 1; and
FIG. 3 is an axial section of a two-stage pusher-type centrifuge. V
Multistage pusher-type centrifuges are disclosed, serving to separate liquids from materials which start to flow under the influence of the washing liquid, for instance which have a fine grain amorphous characteristic. Such materials are unable to transmit the axial thrust required for the discharge of the material within the range of the washing zone.
Referring now in particular to FIG. I of the drawings, the centrifuge comprises a housing 27' and is divided into an axially immovable centrifugal drum 1 which consists of two axially immovable cylindrical filter portions 12 and 13, the filter portion 12 being connected with the centrifugal drum 1' by means of stays 12a which extend through bores 140 of a pusher plate 14. A conical solidwalled portion 15 having an angle of 20 to 40, reciprocates in the axial direction together with the pusher plate 14 connected thereto by stays 15a and simultaneously rotates with the pusher plate 14 and stays 15 and with the centrifugal drum 1'. A hollow drum shaft 1a is rotatably mounted in the housing 27' by means of ball bearings 1b secured to the housing 27. A reciprocating shaft 14a is mounted for axial reciprocating movement and simultaneous rotation with the hollow drum shaft 1a in the latter by means of slide bearings 14b. The hollow drum shaft 1a is rigidly secured to the centrifugal drum 1 to rotate jointly with the hollow drum shaft 1a. The reciprocating shaft 14a is secured to the pusher plate 14, whereby rotation as well as axial reciprocating movement is conferred to the pusher plate 14, as well as to the conical solid-walled portion 15 connected with the pusher plate 14. The solids are taken up in this embodiment, upon moving to the right stepwise by the axially reciprocating pusher plate 14, which is sealed at its periphery by piston ring-like members 8 consisting of elastic material and thereby reaches the conical solid-walled portion 15 during its axial movement along the first screen portion 12 of the centrifugal drum 1' and the comparatively long washing zone along the solid-walled portion 15 of the pusher plate 14, from the end faces of the filter portion 12 operating as a pusher ring and of the solid-walled portion 15 and moved forwardly to the collecting chamber 11'. A feeding pipe 5 for the material to be centrifuged enters the housing 27 and terminates in an acceleration funnel 6, which is connected with the pusher plate 14 by means of stays 7' and rotates with the latter together with the centrifugal drum 1. At the solid-walled portion 15 of the filter cake is loosened due to the continuous increase of the diameter of the portion 15, whereby the penetration of washing liquid simultaneously fed by means of a pipe 9' and the nozzle 10 is favored. Due to the formation of the conical portion as a solid wall, neither a passage of solids, nor a filtrate loss occurs in the loosening and washing zone. The washing liquid flows along the inner portion of the solid-walled portion 15 into a cylindrical screen portion 13 projecting axially from the solid-walled portion 15, in which portion 13 the cake is no longer subjected to any turn-over movements, which could start or favor the passage of solids through the screen openings. The cake is centrifuged dry from the cylindrical filter portion 13, the centrifuged liquid being caught in the filtrate collecting chamber and the solids at the right end are finally thrown out into the collecting chamber 11' for the solids.
Substantially the same effect is brought about in the centrifuge disclosed in FIG. 2 which again comprises a housing 27 In deviation from the embodiment disclosed in FIG. 1, however, the conical solid'walled portion 16 is secured by means of radial stays 17 to the acceleration funnel 18, which in turn is connected to a pusher plate 14 by means of stays 17. A hollow shaft 1a is in this embodiment again mounted in the housing 27 by means of ball bearings lb A reciprocating shaft 14a is axially movable in the hollow shaft 1a by means of slide bear ing 1419 and rotatable with the hollow shaft la The reciprocating shaft 1411 is secured to the pusher plate 14 and axially movable with the latter. The washing liquid is fed through a pipe 19 into a drum 20 which is also connected with the acceleration funnel 18. The shell of the drum 20 is equipped with spray-nozzles 21, which cause hitting uniformly the opposite face of the washing zone with the washing liquid. In order to avoid an overflow of the drum 20, radial bores 22 are provided in the stays 17 through which bores 22 the washing liquid may run off in case of feeding too great quantities thereof, or in case of clogging up of the nozzles 21. The arrangement providing a rotation of the washing nozzles 21 is of advantage, since it prevents the otherwise unavoidable atomization experienced in immovable nozzles, which atomization can penetrate into a collecting chamber 11 for the solids. Screen portions 12 and 13: are secured to the centrifugal drum 1 as disclosed in FIG. 1. A feeding pipe 5 for the material is provided as in the previous embodiments.
Referring now again to the drawings and in particular to FIG. 3, in which a pusher-type centrifuge with two stages is disclosed and comprises a housing 27 and the centrifugal drum 1 carries a screen portion 25. A pusher plate 14 secured to a reciprocating shaft 14a has secured thereto another filter portion 24, to which is connected directly a conical solid-walled portion 23, while the first mentioned filter portion 25, as stated above, is connected with the centrifugal drum '1 A pusher bottom 26 is connected with the centrifugal drum 1 by means of stays which extend through bores 14c of the pusher plate 14 to rotate with the centrifugal drum 1 An acceleration funnel 6 is secured by means of stays 27 to the pusher bottom 26. A reciprocating shaft 14a is again secured to the pusher plate 14 and a hollow shaft 1a is provided in the same manner as disclosed in the previous embodiments by means of ball bearings 1b carrying slide bearings 14b for the reciprocating shaft 14a A washing pipe 9 having a nozzle 10 and a feeding pipe 5 are again arranged. In this embodiment the advantage of a comparatively long washing zone is also present.
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.
1. In a pusher type centrifuge with a washing device for the centrifuged material:
a centrifugal drum rotatably mounted in said housing,
to constitute a first member,
at least one first cylindrical screen portion extending axially from said centrifugal drum,
a pusher-plate disposed within said housing and rotating with and reciprocating relative to said centrifugal grum, said pusher plate constituting a second meman inwardly widening acceleration funnel secured to one of said members for joint rotation therewith,
a conically outwardly widening solid-walled portion secured to one of said members and disposed at a greater radial range relative to the rotating axis than the outermost radius of said pusher plate,
a second cylindrical screen portion of a smaller diameter than that of said first cylindrical screen, and having a radius at least equal with the outermost radius of said pusher plate,
means for feeding said material to be centrifuged toward said acceleration funnel,
means for feeding washing liquid disposed directly opposite said solid-walled portion and feeding washing liquid over substantially the entire area of said solidwalled portion, and
said conically outwardly widening solid-walled portion is secured to said pusher plate.
5 6 2. In a pusher type centrifuge with a washing device said second cylindrical screen portion is secured to said for the centrifuged material: pusher plate at one end and to said solid-walled pora housing, tion at its other end. a centrifugal drum rotatably mounted in said housing,
to constitute a first member, 5 References Cited at least one first cylindrical screen portion extending UNITED STATES PATENTS axially from said centrifugal drum,
a push r-plate disposed Within said housing and rotatguegg ing with and reciprocating relative to said centrifugal 178 7/1958 gg K76) drum, said pusher plate constituting a second memu e ere ber 10 2,883,054 4/1959 Sanchez 210-.377X
an inwardly widening acceleration funnel secured to 2991887 7/1961 Wlrth et 210 376 one of sard members for JOlIlt rotatlon therewith, FOREIGN PATENTS a conically outwardly Widening solid-walled portion secured to one of said members and disposed at a 5 859,429 12/ 1952 Germany. greater radial range relative to the rotating axis than the outermost radius of said pus-her plate, OTHER REFERENCES a second cylindrical screen portion of a smaller dia- German im d li tion No, 1,030,771, May 1958, meter than that of said first cylindrical screen and German printed application No. 1,044,721, November having a radius at least equal with the outermost 20 1958 radius 0f Said Pusher P German printed application No. 1,073,964, January means for feeding said material to be centrifuged 1%() t wa d Said accelfifation funnel, German printed application No. 1,079,551, April 1960.
means for feeding washing liquid disposed directly opposite said solid-walled portion and feeding Washing 25 REUBEN FRIEDMAN, Primary Examiner.
liquid over substantially the entire area of said solid- J L DE CESARE Assistant Examiner walled portion, and 7