GB2134215A - Mill rolls - Google Patents

Abstract

To improve the juice extraction from sugar cane in a roll mill at least one of the rolls 1 is formed with an array of radial apertures 4 extending from the bases of the pressing grooves 10 to respective axial channels 3, wherefrom sucrose expressed from the sugar can may be withdrawn. The lower roll may be of a similar construction. <IMAGE>

Description

SPECIFICATION Mill rolls This invention relates to mill rolls of the kind which may be usedforthe grinding and juice extraction of sugar cane and the like.

The object ofthe invention isto provide a mill roll with meansthatwill improve juice recoverythrough efficient drainage In accordance with this invention a mill roll ofthe type generally usedforthegrinding and juice extrac tion of sugar cane and the like has a plurality of peripheral grooves formed circumferentially therein with a number of holes extending from the bottom of these grooves into interior channels through which drainage of a further portion ofthe extracted juice is effected during milling.

In orderthatthe invention may be readily understood, an embodimentthereofwill now be described by way of example with reference to the accompanying drawings in which: Fig. 1 is an elevation of a cane mill roll ofthe present invention partly sectional along its longitudinal axis; Fig. 2 is a diagrammatic side elevation view of a two roll cane mill embodying the present invention, and Fig. 3 is a fragmentary sectional viewthrough the mill structure shown in Fig. 2, the section being taken approximately along a straight line joining the axes of both rolls.

In the drawings, the two-roll cane mill of Fig. 2 is shown equipped with atop roll 1 embodying the present invention and a conventonal bottom roll 5 provided with so-called "messchaert grooves" 6. Top roll 1 has a number of peripheral V-shaped grooves 10 formed circumferentiallytherein, all like bottom roll 5 which has a number of similar grooves 9 intermeshing with grooves 10 of roller 1.

As is well known in the sugar industry, the purpose of a mill is to grind the cane whilst extracting the sucrose contained therein. Efficient grinding of the cane is desirable since it opens the cells containing the sucrose which is then more readily diluted by the so-called "imbibition process" before being extracted by the mills. This grinding effect is due mainly to the shearing action exerted on the cane bythe rolls as a result ofthe relative difference in peripheral speeds of their V-shaped intermeshing groovesfora given diameter and speed of rotation of the rolls.These grooves have the furtheradvantage of increasing the capacity ofthe mill by exerting a better grip on the material being processed whilst allowing more ofthe latterto pass th rough a given mill opening as compared to rolls having smooth surfaces.

But the effectiveness of a given mill does not depend only on its ability to grind the cane. Byfar, the most important is its abilityto extract an optimum amountcfjuicefromthe cane. This can only be achieved by'keeping reabsorption at a minimum through an efficient juice drainage system.

In conventional mills, juice drainage is invariably effected by means ofthe messchaert grooves which, however, can only be useful when provided to the bottom roll or rolls of a mill. Butthissystem is still far from satisfactory since a great portion of the juice already extracted istrapped at the top part of the incoming cane blanket whilst reabsorption bythe outgoing cane blanket is inevitable and that which constitutes a serious drawback seemingly inherent to all mills.

The following will explain the way in which drainage is effected by means ofthe messchaertgrooves and the main causes of reabsorption: supposing that a cane blanket 14 is fed continuously into the mill of Fig.

2 whose rolls 1 and 5 rotate in the direction of arrows 19and20 respectively; most of the juice contained in the cane being squeezed by rolls 1 and 5will tend to follow back towards the left into blanket 14whilst part of it will escape, somewhere around location 22, via grooves 6, in direction of arrow 8, whereas that portion of the extracted juice lying atthe top part of blanket 14, somewhere around location 21, can only escape by percolating down through the latter to grooves 6. But since blanket 14 is constantly moving towards the entrance ofthe mill, the undrained material at location 21 enters the nip causing highly pressurized liquid pockets to be formed and entrained past the nip and out at exit 23 ofthe mill where reabsorption ofthejuice bytheoutgoing cane blanket 15 occurs.

In the present invention, the mill of Fig. 2 has its top roll provided with a number of peripheral V-shaped grooves 10 formed circumferentially therein and a plurality of holes 4conveniently spaced and extending substantially radially from the bottom 11 of each groove 10 into interior channels 3 conveniently disposed throughoutthe length of roll 1. These holes 4 and channels 3 provide an additional egress through which most of the juice which would otherwise be trapped and entrained pastthe nip ofthe mill to cuase reabsorption, can readily flow out. Consequently, the efficiency of the mill is considerably improved as a result of its higherjuice extraction and grinding capacity, the latter being due to a bettergripexerted bythe rolls on the relatively drier material going past the nip.

Due to the squeezing action exerted bythe rolls on the cane atthe nip of the mill, heavy pressures are developed, and to which is subjected the juice going past holes 4 and channels 3. As a result, clogging of these passages by the fine fibers or other impurities which would tend to flowthrough with the juice, is obviated.

In the accompanying drawings, a preferred construction of roll 1 is illustrated which consists of having a shaft 2 on which is rigidly mounted an intermediate cylindrical body 13 (which may be of steel, cast iron, reinforced concrete or any other suitable material) at the periphery of which are conveniently spaced a numberof channels 3 extend ing throughoutthe length of roll 1. An outer steel cylindrical shell 12 (which could also be of any other suitable material) is rigidly mounted, in turn, around body 13 and has a number of peripheral V-shaped grooves 10 formed circumferentiallytherein.The sides of grooves 10 are preferably roughened by means of spot-welds 24 with a viewto minimizing wear and slippage. From the bottom of each groove 10, and conveniently spaced are a plurality of holes 4 which extend through shell 12 into channels 3. The walls of holes 4 are convergenttowards the periphery of shell 12, whereas the walls of channels 3 are divergenttowards the ends of roll 1,to provide each of said holes 4and channels 3with increasing crosssectional dimension in the direction ofthe fluid flow, thereby reducing the likelihood of clogging of such passages during operation.

Fig. 3 shows an alternative method of setting the holes4which consists of having holes 16 drilled and tapped before screwing in place inserts 17 containing the holes 4.

While I have shown and described a present embodiment of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied within the scope ofthefollowing claims. For example, shell 1 may also be provided with cross grooves of the "Chevron" or "Kay" type at its periphery with a view to further preventing slippage.

Claims (6)

1. A mill roll for use in combination with one or more rolls in a mill for grinding a material, such as sugar cane and the like, while extracting the juice therefrom, comprising a rigid body having a plurality of peripheral grooves formed circumferentiallythereon, a plurality of channels within the body ofthe roll extending axially ofthe roll throughoutthe roll body, a plurality of holes extending substantially radially from the bottom of said grooves and communicating with said channels, whereby, during operation, the passage of extracted juice through the holes and channels tends to increasethe recovery of juices.

2. A mill roll according to claim 1 wherein the walls of said peripheral grooves are roughened to minimize wear and slippage.

3. A mill roll according to claim 1 or 2 wherein the walls of said holes are divergent in the radially inward direction so that said holes have increasing cross sectional dimension in said radially inward direction.

4. A mill roll according to claim 1,2 or3wherein thewallsofsaid channels are divergenttowardsthe ends of said rolls so that said channels have increasing cross-sectional dimensions in directions towards the ends of said roll.

5. A mill roll substantially as hereinbefore de scribed with reference to the accompanying drawings.

6. The steps orfeatures disclosed herein or any combination thereof.