US1747144A - Centrifugal basket - Google Patents

Description

2 Sheets-Sheet E. ROBERTS CENTRIFUGAL BASKET Filed June 5. 1925 /11 vevjo 7'.

Feb. 11, 1930.

Feb. 11, 1930. E. ROBERTS 1,747,144

CENTRIFUGAL BASKET Filed June 5. 1925 2 Sheets-Sheet 2 Patented Feb. 11, 1930 UNITED STATES PATENT OFFICE EUGENE ROBERTS, OF SALT LAKE CITY, UTAH, ASSIGNOR TO THE WESTERN STATES p MACHINE COMPANY, OF SALT LAKE CITY, UTAH, A CORPORATION OF UTAH CEN TRIFUGAL BASKET Application led .Tune 5,

This invention relates to centrifugall baskets, and is intended to provide a special construction to overcome certain practical diiiiculties experienced in the centrifugal separation of solids held in suspension in liquids by more thoroughly and efficiently purging the solid crystals or grains of sugar or like substance from the associated liquid.

In the centrifugal separation of the syrup from the solid grains or crystals of sugar, the material under the action of centrifugal force tends to build up against the basket wall in concentric vertical rings or bands with the denser material outside and the lighter inside, the liquid with oftentimes a light scum on its inner surface forming the inside layer or ring. In consequence the relatively light liquid was required to force its way through a surrounding wall of sugar crystals which had separated from the liquid and moved toward the basket wall. This action necessarily prolonged the period of syrup extraction and resulted in imperfect elimination of the syrup.

The present invention is intended to improve the operation and shorten the period of centrifugal separation, and also prevents a material reduction in the amount of water used in washing the sugar, thereby saving waste. n

Vith these objects in view the invention comprises a centrifugal basket having an inwardly projecting cap-ring and an annular filter element secured to said cap-ring under such arrangement as to form intermediate drainage space communicating with suitable discharge outlets and so steeply inclined to the horizontal as to permit the free escape of the liquid, while efficiently retaining the solid grains sub-tending the cap-ring, the filtering element being supported so as to prevent buckling and breaking of the fine screen member which prevents the passage of the solid particles, while allowing free escape of the liquid.

This and other features of the present invention will be described in the following specification and will be defined in the claims hereto annexed. l

In the accompanying drawings I have il- 1925. Serial No. 35,139.

lustrated the preferred construction and arrangement embodying the principles of this invention, and also a construction and arrangement of the invention applicable to eX- isting centrifugal machines so as to avoid the shipping and rebuilding of those machines away from the factory.

In the drawings:

Figure l shows, in vertical central section, a centrifugal basket embodying my invention.

Figure 2 is a similar section on an enlarged scale of the upper portion of one side of such a basket. Y

Figure 3 is an underneath view of a. Vportion of the cap ring and filter element in assembled position; i

Figure 4 is an enlarged detail view illustrating the bridge plate construction.

Figure 5 is a vertical section of a construction applied to an existing type of basket, the middle portion of the basket being broken away to permit showing on an enlarged scale.

Figure 6 is a. plan view of one ofthe brackets used in supporting the lter element, as arranged in Figure 5.

In the application of my invention, according to the form illustrated in Figures l to 4, I employ a perforated basket of a form commonly used in sugar mills for suspension from a gyratory shaft. In this case, a portion of the shaft is shown at l, the lower end being made of the usual hub shape 2, for insertion into the open spider 3, formed in the central portion of the bottom plate or ring 4. The cylindrical wall of the basket is secured to the bottom 4, in the usual manner, and, in this case, comprises an inner wall 5 provided with discharge openings at intervals of approximately one inch apart, and being re-inforced by means of peripheral reinforcing bands 9 between which are located peripheral bands 6 of sheet material having perforations registering with the perforations 8 in the wall 5. y

The bottom ring and the top ring l0 serve, as usual, to confine the liquid introduced from escaping around the edges of the peripheral wall. I prefer to make the cap ring so that its peripheral portion is almost or quite fiat, while its inner portion is steeply inclined and is recessed to form a drainage space having communication with suitable liquid-discharge outlets. Inside the cap-ring is secured a filtering element forming an inner cover for the intermediate drainage space and steeply inclined to the horizontal to allow the centrifugally impelled liquid content to freely escape through the filter into the drainage spa-ce out of the basket.

During the centrifugal stratification of the mingled solid and liquid constituents, the liquid tends to accumulate more rapidly than it can percolate through the rsurrounding sugar wall and with the above described arrangement of steeply inclined filter screen overlapping the top, the accumulating liquid will run readily off through the top when the filter cap overlaps or projects inwardly over this interior ring of liquid. At the same time it affords perfect drainage for that portion of the walled-up mass of sugar that was previously only imperfectly drained and purged, and permits the inner circle of liquid to quickly run 0H and be filtered instead of having to force its way through the whole thickness of the sugar wall.

The cap ring 10 has its outer or nearly fiat portion l0a imperforate and secured to the surrounding basket-wall, in the usual manner. Its inner portion l()b is steeply ininclined and is recessed to afford drainage space or clearance, as shown at 10c. Each edge of this clearance or drainage space is formed with a ledge or shoulder l1 to support the edges of the annular filter element which, in this case, comprises a steeply inclined relatively stiff bridge member or plate 12, provided with closely arranged, relatively coarse perforations, and a thin, fine foraminous filter screen 13 which is secured to the inner face of the bridge-plate so as to cover its coarser perforations and prevent the escape of sugar grains through them.

The bridge-plate sustains the centrifugal thrust of the sub-tending band of sugar and prevents the buckling and cracking of the fine foraminous screen by affording a smooth supporting surface in contact with the screen. These holes may range, according to conditions, from one-eighth inch to onequarter inch in diameter; that is, the diameter of the hole will equal, or exceed the thickness of the bridge plate. The holes should l not be so large as to allow the thin screen to bulge into them under the pressure of the sugar.

The filter element is preferably made in arcuate sections or segments, and is secured to the inside face of the cap-ring 10 by means of an intermediately located row of'attaching screws l5, which pass through suitable apertures in the filter element, preferably through interposed washers 14, and are tapped. into the cap-ring itself.

It is important to observe the steep inclination of the filter element since, if this should lie in a fiat or nearly horizontal plane, it will not function effectively. Generally speaking, the elevation of the inner edge of the filter element should equal or exceed one-half its inward projectiony from its peripheral edge. In some cases, where the sugar being treated is particularly difficult to purge, an inclination of 45 degrees to thehorizontal may be used advantageously.

Vhile the above described form is the preferred embodiment of my invention, nevertheless, it is desirable to provide means for utilizing this principle in existing baskets having imperforate cap rings of relatively low or flat inclination, and in Figures 5 and 6 I have illustrated a. convenient construction by which baskets of this type may be equipped with my invention.

In this case the cylindrical or peripheral basket-wall 20, with the usual perforations 20a, is provided with the usual re-inforcing bands 2l and a cap-ring 22.

An internally grooved ring 24C is riveted inside the basket-wall a short distance below the cap-ring so as to form a supporting ledge for the outer edge of the filter element. The filter element, as previously described, comprises the coarsely perforated, stiff bridge plate 25 and the fine foraminous filter screen V26, secured to its inner face.

An inner supporting ring or ledge 23 is bolted or riveted to the inner edge of the capring and the filter element is then placed in position between the ledge ring v241 and the ledge ring 23. The filter element is held in place by means of intermediate screws 30 which are tapped into brackets 27, which brackets are placed at intervals around the basket and secured to the basket-wall by means of a peripheral foot or flange 27 b fitting against the inside of the basket-wall, and an inner foot or flange 27a forming surface contact with the outer or upper face of the bridge plate 25. The rivets, through the basket-wall, can be passed directly through the regular perforations 2()a so that no drill- 'ing of the-basket-wall is required and the only drilling necessary is through the inner portion of the cap-ring for the attachment of the inner annular ledge 23.l

It will be seen that withv this arrangement I get a steeply inclined filter element arranged to form a clearance or drainage space intermediate of the filter element and the cap-ring, and having communication through the perforations 2Oa in the basket-wall with the outside of the basket. This arrangement involves a slight loss of space inside the basket which is more than compensated for by the gain in rapidity and efiiciency of the purging operation, due to the more perfect vdrainage of the liquid.

What I claim is:

l. A cap-ring for a centrifugal machine adapted to be secured to the inside of the pe' ripheral wall of the basket to proj ect inwardly therefrom, the outer portion of said ring being imperforate and the inner portion being steeply inclined to the horizontal and recessed on its inner side, an annular filter element secured to said cap-ring in position to form an interior cover for said recessed portion and being steeply inclined to the horizontal to allow free escape of the liquid while preventing the adjacent sugar grains from escaping, substantially as described.

2. A cap-ring for a centrifugal basket em bracing an inclined ring adapted to be secured to the inside of the basket-wall to project inwardly therefrom and provided with an annular recess on its inner face in communication with liquid-discharge outlets, an annular filter element secured to said cap-ring so as to form an interior cover for said recess inclined steeply to the horizontal, said iilter element comprising a relatively stiff bridge-plate provided with closely arranged coarse perforations, and a fine foraminous filter screen secured against the inside smooth surface of said bridge-plate to preventescape of solid particles while aifording free drainage for the liquid content, substantially as described.

3. A cap-ring for a centrifugal basket embracing a relatively flat, outer portion adapted to be secured inside the basket-wall, an inner inclined portion formed with an annular recess between inner and outer annular ledges, an annular perforated filter element interiorly mounted on said ledges and secured to the inclined portion of the cap-ring, said recess communicating with liquid-discharge outlets penetrating the cap-ring to allow free drainage of liquid from the interior of the sugar-wall, substantially as described.

4. In a centrifugal basket, the combination with a cap-ring projecting inwardly from the wall of the basket, an annular filter element secured to said cap-ring so as to leave intermediate drainage space in communication with suitable liquid-discharge openings, said lter element presenting an upwardly inclined surface whose inner edge is elevated above the level of its outer edge a distance not appreciably less than one-half the inward projection of the inner edge from said outer edge, said iilter element comprising a relatively stiff, coarsely perforated bridge member, and a fine foraminous filter screen secured against the inner face of said bridge member, substantially as described.

In witness whereof, I have subscribed the above specification.

EUGENE ROBERTS.

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