US3148145A

US3148145A - Solids discharge centrifuge

Info

Publication number: US3148145A
Application number: US267633A
Authority: US
Inventors: Karl G Reed
Original assignee: Pennsalt Chemical Corp
Current assignee: Pennwalt Corp
Priority date: 1963-03-25
Filing date: 1963-03-25
Publication date: 1964-09-08
Anticipated expiration: 1981-09-08
Also published as: FR1387606A; GB987390A; DE1432845A1

Description

p 8,1964 K. G. REED 3,148,145

SOLIDS DISCHARGE CENTRIFUGE Filed March 25, 1963 INVENTOR.

KARL G. RE D M ATTORNEY United States Patent 3,148,145 SOLIDS DISSHARGE CENTRIFUGE Karl G. Reed, Wayne, Pa., assignor to Pennsalt Chemicais Corporation, a corporation of Pennsylvania Filed Mar. 25, 1963, Ser. No. 267,633 3 Claims. (Cl. 233-7) This invention relates to a centrifuge. More specifically this invention relates to a centrifuge containing an axially disposed conveyor element rotating at a speed different from that of the centrifuge bowl and serving to move solids toward the solids discharge port.

In the centrifugal separation of solids from a liquid it has been quite common to provide a centrifuge bowl with a solids discharge port inward from the liquid discharge port and an axially disposed conveyor element usually in the form of a helical edge which rotates at a speed different from that of the centrifuge bowl to move the solids inward out of the liquid in the bowl to the solids discharge port for discharge. As the solids are moved inward out of the liquid and toward the discharge they drain on an inwardly tapered wall portion and become comparatively dry as they reach the discharge port. An example of a machine operating in this manner is disclosed in the U.S. Patent 2,703,676, which issued March 8, 1955, on an application filed by Fred P. Gooch.

In moving the solids inward out of the liquid and toward the solids discharge port a thrust caused by the resistance to movement of the solids urges the conveyor in a direction away from the solids discharge port. In the prior art machines this thrust has conventionally been borne by a thrust bearing disposed between the conveyor and the end wall of the centrifuge opposite the solids discharge port. This end wall, or front hub, has been, especially in large machines, of necessity, massive to withstand the lateral urging on the periphery of the hub by the bowl shell without bending. Further, extremely rugged connecting means, e.g. bowl shell flanges and many flange bolts, have been required to hold the hub and peripheral wall together. The rugged and massive nature of these parts has been dictated not only by the thrust forces but also by the internal liquid pressure present in the bowl at the juncture of the hub and bowl shell. This heavy structure has increased the power required to accelerate the centrifuge, has increased the expense of construction and has complicated balancing procedures.

In addition to the disadvantages of high strength structures, the location of the thrust bearing elements within the centrifuge has made them inaccessible for easy inspection, repair and replacement. For instance, to merely inspect the thrust bearing in the prior art machines it has been necessary to remove the rotor from its frame, and remove the front hub with the gear box and shaft from the bowl shell. Such procedure has not only consumed excessive time of the repairman and operator, but, more importantly, has had a major effect on the amount of lost production time.

It is, therefore, an object of the present invention to provide a centrifuge of the type described in which the reaction forces generated by the scrolling of solids toward the solids discharge port is in a compressive form borne at the juncture of the bowl shell and the rear hub, or end wall of the machine adjacent the solids discharge port. Since the diameters of the parts at the solids discharge portion of the bowl are significantly less than at the front hub where the forces have previously been borne, the connecting portions, that is the flanges and flange bolts, need not be significantly strengthened. This is especially true in comparison with the juncture of the front hub and bowl shell of the old design, since under the present invention the juncture of the bowl shell and rear hub is inward of the liquid in the bowl and is not subject to liquid pressures.

It is a further object of the invention to provide in the centrifuge of the type described for the easy accessibility of the thrust hearing from the outside of the centrifuge.

Other features and objects of the invention will be apparent from the following description of an apparatus embodying the invention and shown in the accompanying drawings wherein the figure is a broken sectional view, partly in elevation, of an apparatus embodying the invention, the liquid level and separated solids being shown in phantom.

Referring more specifically to the drawings, a centrifuge embodying the invention is designated 10 in the figure. It comprises a frame 12 supporting a pair of pillow block bearings 14. Mounted for rotation in the bearings is the rotor or centrifuge bowl 16 comprising a front hub 18 secured at a peripheral flange to the bowl shell 20. At the opposite end the rotor comprises the rear hub or wall 22. A tapered wall portion 20a comprises part of the bowl shell and is secured at its end to the rear hub.

A liquid discharge port 26 is provided in a plate dam 28 secured in the front hub 18. A solids discharge port 30 having the outermost edge of its inner lip disposed inwardly of the outermost margin of the liquid discharge port 26 is disposed adjacent the rear hub 22 in the tapered wall portion 20a.

Rotatably mounted on bearings 32 within the rotor 16 is the conveyor 34. The body of the conveyor 34 is formed with outwardly extending flight portions 36, the edges of which are disposed closely adjacent the inside surface of the rotor shell. Threadedly secured to the rightward end of the conveyor 34 as shown in the figure is the tension element 38 extending in a central hollow portion of the rotor within the rightward bearing 14. As shown, on the side opposite the rightward bearing 14 from the centrifuge bowl the rotor is provided with a pulley means 40 by which the rotor may be driven. Internally the pulley means 40 is formed with a radial shoulder 42 and the tension element 38 is formed with an enlargement presenting a radial shoulder 44 opposing shoulder 42. Intermediate the

shoulders

42 and 44 is disposed in compression the thrust bearing means 46 comprising in the embodiment shown a roller bearing. The seal 40a closes the compartment defined by the pulley means.

As in prior art devices, such as the device of the above-mentioned patent, the rotor shaft extending through the leftward bearing 14 is secured to an appropriate gear box (not shown) containing a suitable gear train by which rotary motion is transmitted at the desired differential to the conveyor shaft 48 which is splined at 50 to drive the conveyor.

The feed tube 52 extends through the tension element 38 and is adapted to deliver feed mixture against the accelerator plate 53 and through the feed port 54 in the conveyor body. At its rightward end the feed tube 52 is supported by a bracket 56. A cover 58 is secured to the frame 12 and collects the separated discharges as is conventional.

In operation with the rotor 16 rotating at an appropriate speed, for instance 4000 r.p.m., and the conveyor driven through the gear box at a suitable differential, the liquid solids mixture is delivered to the rotor through the feed tube 52 and the feed port 54. Under the infiuence of centrifugal force the heavier solids settle in the liquid to form a layer against the bowl shell 20. The clarified liquid passes out the liquid discharge port 26 and thereby establishes the level of liquid in the rotor at the level of the port. The solids are moved by the edges of flights in a rightward direction inward out of the liquid to the solids discharge port 36). In so moving to and out of the port the solids become dry as they drain on the tapered wall portion 29a. By being thus concentrated and dried the solids increase in their resistance to inward movement by the conveyor flights and as a reac tion to the force applied against them the solids urge the entire conveyor in a leftward direction as shown in the figure. The leftward urging creates a tension in the element 38 and a compressive force on the bearing means 46. The compression force is carried through the rotor shaft within the rightward bearing 14 and through the juncture of the tapered wall portion a and the rear hub 22.

Unlike the prior art forms in which the thrust of the conveyor acted against the front hub and required massive flanges and many connectors between the front hub and the bowl shell, under the present arrangement the compressive force is easily absorbed at the juncture of the tapered wall portion 20a and the rear hub 22. This is especially true since unlike the prior forms, at this juncture there is no liquid pressure. Hence the power required to accelerate the present machine and the amount of metal required to build it and hence the expense are significantly less than in prior comparable structures. Further, by having the bearing means 46 outside of the centrifuge it is readily accessible to inspection, repair or replacement. As will be understood, to inspect the bearing means 46 it is merely necessary to remove the feed tube 52, the tension element 38 and the pulley seal 46a.

Variations of the apparatus shown are possible within the scope of the appended claims. Hence while I have explained my invention with the aid of a particular embodiment thereof, it is to be understood that I do not wish to be limited to the specific structural details illustrated and described from which departure can be made without departing from the spirit and scope of the invention as defined by the following claims.

I claim:

1. A centrifuge comprising:

(a) a rotor mounted to rotate about a horizontal axis and having a pair of end walls and an imperforate peripheral shell with a portion tapering inwardly toward one end, the shell being secured between the end walls, the rotor having a solids discharge port at the said end, the end wall at the said end having a central opening, the other end of the rotor having a liquid discharge port inward from the shell but at a radius greater than the solids discharge port, the said end wall and the shell meeting at an inner juncture, the inner juncture being radially inward from the liquid discharge port, the other end wall and the shell meeting at an outer juncture, the outer juncture being radially outward from the liquid discharge port,

(7)) a conveyor rotatably supported within the rotor, the conveyor having a body portion and a helical edge portion supported by the body portion, the helical edge portion being closely adjacent the shell and adapted in rotating to move solids toward the solids discharge port,

(c) a tension element removably secured to the conveyor and extending through the central opening in the said one end wall,

(d) means to supply feed mixture to the interior of the rotor,

(e) means to drive the rotor and the conveyor at different speeds including a drive shaft on the rotor and surrounding the tension element and presenting a shoulder facing away from the rotor,

(f) enlarged means on the tension element on the opposite side of the shoulder from the rotor, the shoulder and the enlarged means being axially spaced and the enlarged means presenting a second shoulder generally facing the first-mentioned shoulder, and

(g) thrust bearing means having freely rolling elements and disposed in the space and held in axial compression between the shoulders,

whereby the forces developed between the conveyor and the rotor as the conveyor moves the solids toward the solids discharge port appear as a compressive force acting at the inner juncture instead of as a tension force at the outer juncture.

2. A centrifuge as described in claim 1 wherein the conveyor body portion has an axial threaded opening in its end adjacent the said end of the rotor, the tension element is tubular and threaded on one end and has an enlarged head on the other, the threaded end being threadedly received into the last-mentioned opening and the head comprising the enlarged means.

3. A centrifuge comprising:

(b) a conveyor rotatably supported within the rotor, the conveyor having a body portion and a helical edge portion supported by the body portion, the helical edge portion being closely adjacent the shell and adapted in rotating to move solids toward the solids discharge port,

(c) means to supply feed mixture to the interior of the rotor,

(d) means to drive the rotor and the conveyor at different speeds including a tubular drive shaft on the rotor and extending axially out from the said end about the central opening, and presenting a shoulder facing away from the rotor,

(e) thrust bearing means having freely rolling elements and having an inner face abutting about said shoulder and an outer face directed away from the rotor,

(f) force-conducting means extending through the opening in the said end wall and through the tubular drive shaft and including a threaded, readily disassemblable joint and connecting the conveyor and the outer face of the thrust bearing means so that axial thrust of the conveyor in a direction toward the said other end wall is borne by the thrust bearing means,

(References on following page) UNITED STATES PATENTS Whitely et a1. Jan. 22, 1902 Rigler Apr. 18, 1933 Howe Feb. 27, 1945 Messinger Nov. 4, 1947 Hertrich Feb. 22, 1949 Milliken et a1. June 10, 1952 Ritsch Oct. 21, 1952 6 Kuster et a1. Aug. 25, 1953 Crossley Aug. 3, 1954 Gooch Mar. 8, 1955 Cook et a1. Oct. 14, 1958 Harlow Jan. 6, 1959 Gooch Oct. 30, 1962 FOREIGN PATENTS Germany Sept. 27, 1915 Disclaimer 3,148,145-5'1172 G. Reed, Wayne, Pa. SOLIDS DISCHARGE CENTRL FUGE. Patent dated Sept. 8, 1964. Disclaimer filed Mar. 5, 1965, by the assignee, Pennsalt Uhemica-Zs Gowpomtz'on. Hereby enters this disclaimer to claim 3 of said patient.

[Ofiieial Gazette June 15,1965] Disclaimer 3,1&8,145.Karl G. Reed, Wayne, Pa. SOLIDS DISCHARGE 'CENTRI- FUGE. Patent dated Sept. 8, 1964:. Disclaimer filed June 9, 1965, by the assignee, Pennsalt Ohemioals Corpomtion. Hereby enters this disclaimer to claim 1 of said patent.

[Ofice'al Gazette September 14, 1965.]

Claims

1. A CENTRIFUGE COMPRISING: (A) A ROTOR MOUNTED TO ROTATE ABOUT A HORIZONTAL AXIS AND HAVING A PAIR OF END WALLS AND AN IMPERFORATE PERIPHERAL SHELL WITH A PORTION TAPERING INWARDLY TOWARD ONE END, THE SHELL BEING SECURED BETWEEN THE END WALLS, THE ROTOR HAVING A SOLIDS DISCHARGE PORT AT THE SAID END, THE END WALL AT THE SAID END HAVING A CENTRAL OPENING, THE OTHER END, OF THE ROTOR HAVING A LIQUID DISCHARGE PORT INWARD FROM THE SHELL BUT AT A RADIUS GREATER THAN THE SOLIDS DISCHARGE PORT, THE SAID END WALL AND THE SHELL MEETING AT AN INNER JUNCTURE, THE INNER JUNCTION BEING RADIALLY INWARD FROM THE LIQUID DISCHARGE PORT, THE OTHER END WALL AND THE SHELL MEETING AT AN OUTER JUNCTION, THE OUTER JUNCTURE BEING RADIALLY OUTWARD FROM THE LIQUID DISCHARGE PORT, (B) A CONVEYOR ROTATABLY SUPPORTED WITHIN THE ROTOR, THE CONVEYOR HAVING A BODY PORTION AND A HELICAL EDGE PORTION SUPPORTED BY THE BODY PORTION, THE HELICAL EDGE PORTION BEING CLOSELY ADJACENT THE SHELL AND ADAPTED IN ROTATING TO MOVE SOLIDS TOWARD THE SOLIDS DISCHARGE PORT, (C) A TENSION ELEMENT REMOVABLY SECURED TO THE CONVEYOR AND EXTENDING THROUGH THE CENTRAL OPENING IN THE SAID ONE END WALL, (D) MEANS TO SUPPLY FEED MIXTURE TO THE INTERIOR OF THE ROTOR, (E) MEANS TO PROVIDE THE ROTOR AND THE CONVEYOR AT DIFFERENT SPEEDS INCLUDING A DRIVE SHAFT ON THE ROTOR AND SURROUNDING THE TENSION ELEMENT AND PRESENTING A SHOULDER FACING AWAY FROM THE ROTOR, (F) ENLARGED MEANS ON THE TENSION ELEMENT ON THE OPPOSITE SIDE OF THE SHOULDER FROM THE ROTOR, THE SHOULDER AND THE ENLARGED MEANS BEING AXIALLY SPACED AND THE ENLARGED MEANS PRESENTING A SECOND SHOULDER GENERALLY FACING THE FIRST-MENTIONED SHOULDER, AND (G) THRUST BEARING MEANS HAVING FREELY ROLLING ELEMENTS AND DISPOSED IN THE SPACE AND HELD IN AXIAL COMPRESSION BETWEEN THE SHOULDERS, WHEREBY THE FORCES DEVELOPED BETWEEN THE CONVEYOR AND THE ROTOR AS THE CONVEYOR MOVES THE SOLIDS TOWARD THE SOLIDS DISCHARGE PORT APPEAR AS A COMPRESSIVE FORCE ACTING AT THE INNER JUNCTURE INSTEAD OF AS A TENSION FORCE AT THE OUTER JUNCTION.