US 2411138 A
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Nov. 12, 1946.l
y E. ROBERTS CENTRIFUGAL MIXER 'APPARATUS Filed March 27, 1943 lNvEToR EUGENE ROBERTS wat@ `ATTOR N EYS Patented Nov; 12, 1946 2,411,13-8 CENTRIFUGAL MIXER APPARATUS Eugene Roberts, Hastings, N. Y., assignor to The Western States Machine Company, Hamilton, Ohio, a corporation of Utah Application March 27, 1943, Serial No. 480,789 c claims. ci. 12v- 17) This invention relates to mixer apparatus for use at sugar centrifugal stations, in refineries and raw cane and beet sugar factories, to hold massecuites and magmas in proper condition for centrifugal treatment. More particularly, the invention deals with improvements in mixer installations of the types disclosed in United States Patents Nos. 2,086,951, Re. 20,556, 2,128,873 and 2,206,237, which embody means for heating and stirring the mixture of sugar crystals'and syrup held in the mixer tank, awaiting or en route for delivery to adjacent centrifugal machines, so as i to predetermine and keep approximately uniform the viscosity and purging qualities of the many centrifugal charges drawn successively from the mixer during the period of hours usually needed to process an entire run or Vacuum pan strike.
In the use of such mixer installations made with conventional forms of mixer tanks there has continued to be some trouble due to centrifugal charges of irregular consistency sometimes being delivered from the mixer. For example, the sugar crystals sometimes are not uniformly distributed in their suspending syrup, and when such a charge is admitted into a slowly rotating centrifugal basket, the crystals tend to lodge in the bottom of the basket and form an uneven or conical sugar Wall that cannot be centrifuged emciently, instead of walling up evenly under centrifugal force. Such trouble is particularly evident in the treatment of higher purity or white sugar massecuites-the so-called free-purging massecuites.
The object of my present invention, therefore, is to provide improved mixer apparatus of the type described by which to avoid irregularities which still occur in the use of known mixer equipment, and 'thereby to increase the emclency of sugar centrifugal work and related sugar factory operations,
I have found that troubles of the kind above mentioned are caused to a. large extent'by the presence of relatively dormant portions or pockets of massecuite in the prior mixer apparatus during the processing of charges drawn from a batch held in the mixer. These dormant portions are not subjectto the same heating and stirring effects as the main body of massecuite awaiting centrifugal treatment, so that a relative settling of sugar crystals in the syrup and other physical changes occur, with the lapse of time, which cause some portions of the massecuite charged to the centrifugals toi-,liffer in consistency from other portions.
One of the main minces of this trouble is the long goosenecks or loading conduits of conventional mixer structures. These extend from the tank proper to the loading gates adjacent the centrifugal machines, and they each hold a substantial portion of the massecuite in a dormant condition during the time periods between successive centrifugal charging operations.y The duration of this condition is enough in many cases to cause objectionable changes in the massecuite quality. Another source of trouble is the corners or lower inside end portions of the usual mixer tank, which may hold pockets of massecuite next to the tank wall in a relatively dormant condition despite the action of rotary heating and stirring means.
According to the present invention, I overcome the irregularities and troubles referred to by providing an improved `mixer apparatus of the type described which comprises heating and stirring means for controlling the condition of massecuite or magma to be delivered from the mixer, togetherwith means to keep all of the massecuite that is ready for centrifugal treatment in circulation and subject substantially uniformly to the action of the heating and stirring means. More particularly, the mixer is constructed to keep all massecuite awaiting treatment in motion and under the influence of the heating and stirring means by maintaining a forced circulation of the 'massecuite substantially to the inside faces of My apparatus thus prevents the loading gates. heated massecuite., from resting in a relatively dormant condition and distributes such cooling and settling effects as occur through all of the' mass being conditioned for centrifugal treatment. This enables cooling and settling effects to be avoided, or overcome automatically, through the control and operation of the heating and stirring means.
Other features, objects and advantages hereof are set forth particularly in the appended claims and will become apparent from the following detailed description of preferred embodiments of my invention, when considered in connection with the accompanying drawing wherein,
Figure 1 is a diagrammatic front elevation, with some parts broken away to reveal inside structure, illustrating one form of the improved l mixer apparatus;
Figure 2 is an end View, partly in section, taken substantially along line 2--2 of Figure l;
Figure 3 is a fragmentary front elevation show ing another form of the improved apparatus;
Figure 4 is an end view, partly in section, taken substantially along line M of Figure 3; and
Figure 5 is an inclined horizontal section along line 5-5 of Figure 4.
Figures 1 and 2 illustrate a mixer installation useful for the; handling andtreatment of white or other free-purgingmassecuite that is to be dropped directly from a vacuum pan (not shown) into a mixer A and held by the mixer in a substantially uniform condition while awaiting treatment, charge by charge, in sugar centrifugals B. The mixer structure includes an elongated tank body 2, which is usually U-shaped in cross-section, together with a. plurality of loading gates 4 and means including conduits 6, 8 and I0 connecting the loading gates with the bottom of the tank so as to maintain a circulation of heated massecuite or magma between suitable heating and stirring means I2 inside the tank and the inside faces of the loading gates. The gates 4 may be of any suitable construction, and are usually operable bymeans such as the levers 5 to open and close charging ports, which they normally cover, and thus deliver charges periodically from the mixer to the respective centrifugals B.
The heatingand stirring means I2 extend lengthwise in the base or lower portion of tank I 2, and coacting rotary stirring means I6 also are provided which extend substantially the full length of the tank in its upper portion. The means I2, as` shown, comprise spiral coils I4 mounted for rotation on a shaft I3, and these coils both heat and stir the massecuite in contact therewith just before delivery of the massecuite .to the centrifugals B.' Other forms of moving coils, however,` may be used, as well as suitable combinations of relatively stationary heating coils with rotary stirring means. Water or other suitable heating fluid at a regulated temperature is circulated through the coils by any suitable means (notshown) for example, as disclosed in United States Patent Reissue No. 20,556.
The upper stirring means I6 comprise horizontal paddles or blades I1 mounted on radial armsl 8 for rotation with a shaft I9. The general arrangement of means I2 land I6 is similar to that disclosed in my United States Patent No. 2,128,873. A common external drive transmission of any suitable type, parts of which are diagrammed at 2l), may be used for driving the means I2 and I6.
The elongated conduit 8, which is spaced below tank 2, as seen in Figures '1 and 2, extends parallel to the tank and to the adjacent centrifugals B, and serves as a header which is connected with the tank bottom near its opposite ends through the vertical conduits 6 and IIl. The loading gates 4 are secured directly to the front face of header l8 so as to deliver massecuite therefrom directly to thecorresponding centrifugal machines.
Inside of header 8 I provide a screw propeller 30, or equivalent means, which is connected at one end vwith suitable driving means such as a chain 32 driven from the same source 20 as the means I2 and` I6.
In some mixer installations the coils I4 may not extend quite to the end walls of the tank 2, so that pockets of massecuite might stay relatively dormant in one or more of the tank corners. Where this condition is likely to occur, such as y iny lthe left-hand corner of the tank shown in Figure 1, I preferably provide a fillet 40 to present a curvedor streamlined surface 4I causing a freer circulation of massecuite relative to the heating tank approxithereof, so that coils. Conduit I opens into the mately at the right hand end wall a. similar llet is not needed at thatpoint in the form shown.
In the use of this apparatus, the heating and stirring means I2 and I6 and the screw propulsion means 30 insideheader 8 are all maintained in continuous rotation at suitable predetermined rates. The means I2 and I6 keep the main body of massecuite in the tank substantially uniform', since the massecuite is constantly agitated and circulated in and between the respective upper and lower paths of rotation of the two devices, and enough heat may be furnished, by the circulation of hot water through the heating coils and the relative motion of massecuite in contact with these coils, to establish the desired temperature conditions for purging and counteract heat losses from the mass held in the tank. In the treatment of white massecuite or the like, the 'desired temperature may be approximately the final temperature existing in the vacuum pan when the strike is dropped into the mixer.
The coils I4 of means I2 tend to move the heated massecuite in a path leading to one end of the tank bottom. The screw means 30 continuously draw `massecuite from that end and circulate it through the conduits 6, 8 and III back to the heating coil, thereby keeping the massecuite being heated in motion at all times, substantially to the inside faces of the loading gates 4. In this way themixer keeps all of the massecuite awaiting centrifugal treatment in a substantially uniform condition of heat and crystal distribution; eliminates dormant masses which heretofore have contributed to false grain formation, settling of crystals and 'irregularity of centrifugal work; and enables temperature and viscsity conditions to be selected and maintained more perfectly than heretofore, in many mixer installations.' 40 The embodiment of Figures 1 and 2 is applicable to conventional mixer installations without necessitating major changes in the form or mounting of the mixer tank. The embodiment of Figures 3, 4 and 5 similarly is applicable for the conversion of conventional mixer apparatus to the improved construction herein disclosed. It will be understood that various other forms may be utilized in adapting the invention to existing installations or in providing entirely new factory installations according to the invention,` whereby all of the many successive charges delivered for centrifugal treatment during the processing of a strike or'run of sugar may be kept at a desired uniform condition by maintaining the whole mass in the lower portion of the mixer in motion relative to the heating means, not only in the tank proper but also substantially to the inside faces of the loading gates. A
The form of apparatus shown in Figures`3, 4
and 5 functions in substantially the same way as the embodiment of Figures 1 and 2, but it differs structurally from the latter in s'ome respects. The lower portion" only of the mixer tank |02 is shown. This has loading gates |04 at the bottom connected with the tank proper through vertically extending conduits or loading chutes or spouts |06, one conduit for each gate. The heating and stirring means I I2, as shown, again comprise spiral coils' II4 mounted for rotation on a T0 shaft |I3 in the lower portion of the tank |02. Instead of circulating the massecuite along the heating coils from one end to the other of the tank and then through a header Aconduit supporting the'loading gates, a horizontal conduit or header |08 is disposed below the tank in back of the gates and is connected with the chutes at points near the gates through respective branch conduits |09; and this header |08 is also connected to the tank bottom through an additional vertical conduit iii).
A screw propeller mechanism |30 inside of header |08 maintains a forced circulation of massecuite from the heating means ||2 through the several conduits substantially to the inside faces of the loading gates. As shown in Figure 5 the propelling means are formed with oppositeiy pitched spiral screw sections |3| and ISI?, respectively, which cause massecuite to be drawn downwardly from tanky |02 through conduit |||l and then to be divided and forced in different paths through the plural sets of connected conduits |09 and |06. Bames |2|| (Figure 4) may be provided at the joints between conduits |08 and |09, to extend toward the loading gates |04 and insure complete circulation of massecuite up to the faces of the gates. A shaft |32 carries the screw means which enforce this circulation.
. I realize that various other forms of mixer apparatus may be made according to my invention, and I intend to define the invention by the appended claims without restriction to non-essential details of the illustrated embodiments.
l. A mixer to hold a mixture of sugar crystals and syrups awaiting centrifugal treatment comprising a tank body, gate means to deliver charges of the mixture to adjacent centrifugal machines, means inside the tank body for heating and stirring the mixture ther'ewithin, and connecting means-between the tank body and said gate means v and having propulsion means therein to maintain a forced circulation-of said mixture from said heating means substantially to the face of said gate means.
2. A mixer to hold sugar massecuite awaiting header spaced below the tank bottom, a plurality of loading gates to deliver charges of massecuite to adjacent centrifugal machines, vertically extending conduits respectively connecting the loading gates-with the tank bottom, other conduits respectively connecting the header with the aforesaid conduits close to the loading gates, additional conduit means directly connecting the header with the tank bottom, and screw propulsion means in the header operative to draw massecuite from' the tank and circulate the massecuite to the gates and through said conduits.
4. A mixer to hold sugar massecuite quite uniform while awaiting centrifugal treatment comprising a tank body having massecuite heating and stirring means therewithin,v a plurality of loading spouts having loading gates thereon at the bottom of the mixer to deliver charges of the massecuite therefrom to adjacent centrifugal machines, a, substantially horizontal header below the tank body connected with the same and with the respective loading spouts adjacent said loading gates, and massecuite propulsion means in said header to maintain a circulation of massecuite therethrough and through said spouts between the gates and the heating means.
5.`A mixer to receive a pan strike of sugar massecuite and hold the same ready for centrifugal treatment, comprising :a tank body having massecuite heating and stirring means therewithin, gate means to deliver charges of the massecuite to adjacent centrifugal machines, conduit means connecting the bottom of the tank body with said gate means, and screw propulsion means to maintain a forced circulation of massecuite through said conduit means.
6. A mixer to hold sugar massecuite awaiting centrifugal treatment comprising an elongated centrifugal treatment comprising an elongated y substantially U-shaped tank having massecuite heating and stirring means disposed lengthwise in the lower portion thereof, an elongated header in spaced relation to the bottom of the tank, conduits connecting the end portions of the header with the tank, means to circulate massecuite from the tank through the header, and a plurality of i "loading gates mounted on the header to deliver charges of massecuite therefrom to adjacent centrifugal machines.
3. A mixer to hold sugar massecuite awaiting centrifugal treatment comprising an elongated tank having massecuite heating and stirring means extending substantially the full length thereof adjacent thel tank bottom. an elongated substantially U-shaped tank having lower rotary heating and stirring means disposed lengthwise in the base thereof and upper rotary stirring means disposed lengthwise above and in coacting relation to said lower means, a plurality of loading gates to deliver charges of the massecuite to adjacent centrifugal machines, conduit means connecting the gates with the tank bottom, said tank having its inside walls approaching the paths of rotation of said lower and upper meansand curved insides at cornersthereof to prevent massecuite lying dormant in the comers, and
means to maintain a forced circulation of massecuite between said lower means and the inside faces of said loading gates through said conduit means..