US2517452A - Fluid driven centrifugal machine - Google Patents

Description

Aug. L, 1950 F. s'rmo'r 2,517,

FLUID DRIVEN CENTRIFUGAL MACHINE Original Filed Oct. 13, 1945 s Sheets-Sheet 1 VALVE No./

Fig.1.

VAL 1/! N02 NOZZZE IVU.

FEEDER/CK .frwar 7'0 NOZZLE Aug. L 1950 F. STINDT FLUID DRIVEN CENTRIFUGAL- MACHINE Original Filed Oct. 13, 1943 3 Sheets-Sheet 2 SPEED OF sac/(7- 1' 5 550 OFJET EFF/C/ENCY cum/5 0F LARGE BUCKET WHEEL (OPPOSITE NOZZLE No-/) CENTR/FUGAL SPEED W W M E m m mm ma .m

T0 lVuZZLE FEEDER/CK I .fT/A/DT A1 4 S MAJ T0 NazzLE VAL l/E No.2

Aug, 1,, W5 F. STINDT 5 3 FLUID DRIVEN CENTRIFUGAL MACHINE Original Filed Oct. 13, 1943 3 Sheets-Sheetfi 6/ /62 TIM/5R1 SOT/M59322 8,5

#02215 Ala-2 22 aim/M Patented Aug. 1, 1950 FLUID DRIVENCENTRIFUGAL MACHINE Frederick Stindt, Cliffside Park, N. J.

Continuation of application Serial No. 506,085,

ctober13, 1943. This application December 26, 1945, Serial No. 637,245

4 Claims.

This invention relates to centrifugal machine and more specifically to fluid-driven centrifugal machines. The present application is a continuation of aplication Serial No. 506,085 filed October 13, 1943, now abandoned; l f

It is the principal object of this invention to provide means for improving the operation and efficiency of fluid-driven centrifugal machines and particularly of centrifugal machines used in the manufacture of sugar. e i

In the manufacture of sugar, centrifugal machines are utilized which go through many complete operating cycles each hour. In each cycle, the machine is accelerated to full speed, allowed to run at this speed for a few minutes and then quickly brought to rest. During the unloading operation, the machine isturned at low speed. While various forms of drive havelbeen used, a hydraulic or water drive isused extensively for centrifugals drying slow draining materials requiring relatively high centrifugal force. The maintenance charges of hydraulic centrifugals are very low and they have been found to be the most economical type for drying certain types of materials, such as corn sugar. Water driven centrifugals have the further advantage that they usually have fewer moving parts than any other type. On the other hand, the usual water-driven centrifugal has the disadvantages that (1) its rate of acceleration with any reasonable amount of power is slow, (2) its overall efficiency is not as high as that of the electrically driven machines, and (3) frequently, insufficient torque for the low speed required for unloading is available when the only source of usable power is that required to keep the centrifugal running at full speed (this is particularly true in the case of slow drying materials). The present invention in one of its primary aspects is concerned with the problem of reducing these three disadvantages and thus improving the competitive position of the water-driven centrifugal.

For any given fluid pressure there is a Pelton impulse wheel or a turbine wheel diameter which will give the most efficient performance at any given speed. In centrifugals used heretofore, the fluid operated driving means which is most efiicient on the average during acceleration is not the most efficient when running at high speed, a

operating speeds than the region of high, efflwhich is somewhat less than full or rated speed of thecentrifugal machine, the efficiency tapering 2 a i ciency in present day centrifugals and which is incapable of overspeeding.

In accordance with a specific embodiment of the present invention, which is described by way of example for illustrative purposes, a centrifugal is provided which has two or more fluid-operated driving means, one having a point of maximum elficiency ator near the normal operating speed of the centrifugal and the other (or others) hav drivingmeans, such as reaction type turbines,

can be employed. Moreover, one or more of the driving means caneach comprise more than one wheel or turbine.

As a relatively large amount of power is required for accelerating the basket containing the sugar and syrup while, only a small amount of power is required for keeping it up to speed, in one specific arrangement the two bucket wheels, one being larger than the other, are. supplied with water during most, of the acceleration and the larger one is shut off just before the machine reaches full speed and the acceleration is concluded and the machine is driven at full speed i by the smaller bucket wheel alone. In a second ,arrangement, the larger bucket wheel alone is used during the initial accelerating period and the smaller, one alone thereafter. -The larger bucket wheel has an efficiency vs. speed characteristic curve which is substantially parabolic, that is, ithas a maximum efficiency at a speed off. on both sides of this maximum. Byway of example, consider that the full or rated speed, I of the centrifugal machine is 1800 R. P. M. The larger bucket wheel has a maximum efliciency of about 80%..at about 1200 R. P. M. and. the efficiency tapers off sharply thereafter to an efficiency of about at 1800B. RM. Between 800 and 1600 R. P. M., the efficiency is or more.

'The smaller bucket wheel has an efliciency of about 30% at 800 R. P. M. and reaches maximum efliciency of about at around 1800 R. P.

M. The use of the larger bucket wheel during acceleration not only providesgreater efllciency unloading. By using two driving means, the region of high eifioiency, say 60% or more, is greatly extended. Moreover, in each of these arrangements, overspeeding or running, away of the machine is prevented. It is well known that there is a safe speed for a centrifugal machine which must not be exceeded, otherwise there is the hazard that the basket may blow up. In each of the present arrangements, when the machine reaches a top speed the larger wheel will develop practically no power, thus producing a 100% protection against overspeeding even ifaboth bucket wheels are still operating. This is inmarked contrast to one well-known type of centrifugal employing a single bucket wheel and a plurality of nozzles. In the usual design of this latter arrangement, if the two nozzles remain in operation for too long a time the safe speed will be exceeded and hence the safety of the machine depends upon the 100% effectiveness of the automatic control which shuts ofi one nozzle before full speed is reached. (If the two nozzles do not have enough power to cause overspeeding then they will not have enough power to accelerate to top speed with the desired rapidity.) The first time that this automatic control fails to operate (and since no machine is perfect, such a failure will ultimately occur), the machine is apt to reach adangerous speed. In the arrangements according to this invention, even though automatic control means are provided as described below, the safety of the machine does not depend upon it.

For the control of the water flow to the two nozzles, a novel valve mechanism is provided. This mechanism comprises, in the first arrangement, a 3-Way 3-port plug valve connected to branch lines leading to both nozzles. In one position of the valve, water flows to both nozzles while in a second position water flows to the nozzle opposite the smaller bucket wheel but is cut off from the nozzle opposite the larger bucket wheel. In the second arrangement, a 3-way 2-port plug valve is so arranged that in one position water flows only to the nozzle opposite the larger bucket wheel while in the second position water flows only to the nozzle opposite the smaller bucket wheel. In each case, the valve is automatically operated from its first to its second position when the machinereaches a predetermined point in its cycle of operation, which point may be determined by the speed of the machine or by the elapsed time from the start of the cycle. In one form of the invention, a scoop is positioned to pick up water when the machine exceeds a predetermined speed and, by means of a float mechanism, the valve can be operated a predetermined time after water begins to strike the scoop. The position of the scoop can be varied to control the speed at which it is desired to operate the valve. In another form of the invention, electrical timing .means are provided for actuating the valve and applying a brake to the machine.v

' The invention will be more readily understood by referring to the following description, taken in connection with the accompanying drawings forming a part thereof, in which:

Fig. 1 is a schematic view of a water-driven centrifugal machine in accordance with the invention, the machine employing, merely by way of example, two. bucket wheels of the Pelton type;

Fig. 2 shows one position of a 3-Way '3-port valve functioning as valve No. 2 in the arrangement of Fig. 1, in which position both bucket wheels are supplied with water;

Fig. 3 shows a second position of the valve of Fig. 2, in which position nozzle No. 1 (opposite one bucket wheel) is cut off while nozzle No. 2 (opposite the other bucket wheel) is supplied with water;

Figs. 4 and 5 are schematic diagrams to aid in understanding the invention;

Fig. 6 is a graphical representation showing the emciency of the large bucket wheel (opposite nozzle No. 1) plotted against centrifugal speed;

Fig. '7 is a graphical representation showing the efiiciency of the small bucket wheel (opposite nozzle No. 2) plotted against centrifugal speed;

Fig. 8 is a plan view of a portion of the centrifugal machine shown in Fig. 1;

Fig. 9 shows one position of a 3-way 2-port valve functioning as valve No. 2 in the arrangement of Fig. 1, in which position only nozzle No. 1 is supplied with fluid;

Fig. 10 shows a second position of the valve of Fig. 9, in which position only nozzle No. 2 is supplied with fluid; and

Fig. 11 is a schematic view of a modification of the arrangement of Fig. 1, in which modification electrical means are provided as valve-control means.

Referring more specifically to the drawings, Fig. 1 shows, in schematic form and by way of example for illustrative purposes, a waterdriven, sugar-centrifugal machine 20 comprising a rotating basket 2| for the sugar-bearing material, a spindle 22 attached to the basket 2| and carrying an impulse member 23 which includes a large bucket wheel 24 and a small bucket wheel 25. A housing 26 surrounds the upper part of the machine 20. Driving fluid for the bucket wheels is admitted to the housing 25 through nozzle 21 (nozzle No. 1) opposite the 'large bucket wheel 24 and through nozzle 28 (nozzle No. 2) opposite the small bucket wheel 25. These bucket wheels are preferably of the conventional impulse wheel type known as Pelton wheels. A scoop 29, the purpose of which will be hereinafter described in detail, is positioned opposite the large bucket wheel 24 to pick up water after the speed of the machine attains a certain value. The exhaust fluid passes out of the housing 2% through pipe 30. The machine is braked at the desired times by suitable brake members 43 surrounding the spindle 22.

Fluid is supplied to the nozzles 21 and 28 from a main pipe 3i which is connected through a pipe 32, a valve 33 (sometimes call d valve N0. 1), a pipe 34, and valve 35 (sometimes called valve No. 2) to pipes 36 and 3? which are respectively connected to nozzles No. 1 and No. 2. Valve No. 2 may he of the type represented in Figs. 2 and 3 (3-way S-port valve) or it may be of the type represented in Figs. 9 and 10 (3-way 2-port valve). Both of these types are well-known and do not require detailed explanation. Valve No. 2 is adapted to be operated by the water which ispicked up by the scoop 2'9. This water passes through the pipe 33 to a, chamber 39 having a float 48 therein. The float is attached to lever 41 which operates valve No. 2 from a first position to a second position. While the float is here shown as operating the valve directly, if desired the float can operate a trip permitting a spring to operate the valve. Such an arrangement is shown in Patent 753,155 issued Feb. .23, to J, W, Macfarlane.

Before explaining the operation of the arrangement shown in Fig. 1, it appears advisable to first point out some of the elementary factors afiecting the efiiciency of impulse wheels so that the advantages of the present invention will be better understood. Reference will now be made to Figs. 4 and 5. In Fig. 4 a water wheel W is shown attached to the spindle S and carrying buckets B. Impinging on this wheel is a jet J from the nozzle N. In Fig. 5 is represented what happens when the water jet impinges on a bucket. The water proceeds from the nozzle with the velocity V1, strikes a bucket 13 and makes practically a 180 degree turn, coming out of the bucket with velocity V3. If the bucket is at rest and there are no losses, the water will come out of the bucket as fast as it went in, and thus V3 will equal V1. If the bucket B movestoward the right as the result of the force ofthe jet. it will attain a certain velocity V2 and the jet, although it has an absolute velocity of V1, will have a velocity relative to the bucket of V1Vz. This means that if the jet has an absolute velocit of 100 feet per second and the bucket is moving to the right at feet per second, the speed of the jet relative to the speed of the bucket is 90 feet per second. Therefore the velocity of the water leaving the bucket will be 90 feet per second relative to the bucket, but since the bucket is moving 10 feet per second,

the absolute velocity of the water leaving the bucket will be 80 feet per second. Now let it be assumed that the bucket is moving to the right at a speed one-half the speed of the jet, that is, V2 is equal to /2 V1. The jet with an absolute velocity of 100 feet per second has a velocity relative to the bucket of only 50 feet per second. The water comes out of the bucket with a speed relative to the bucket of 50 feet per second, but as the bucket is moving 50 feet per second to the right, the absolute speed of the water leaving the bucket is zero. This obviously is a condition of highest efficiency because the water will have all its kinetic energy removed and will have imparted all its energy to the bucket. Of course, with the wheel revolving, this condition takes place with one bucket after another so that the condition is practically continuous. It is for this reason that it can be stated that, with an impulse wheel, maximum. efliciency is obtained when the speed of the buckets is about one-half the speed of the jet. This figure is not strictly correct because, due to losses and to the fact that the water never makes a complete 180 degree turn, the actual speed of maximum efficiency is about 47 of the speed of the jet.

If it is considered that the bucket moves toward the right at a speed more than one-half the speed of the jet, it is obvious that the water leaving the bucket has an absolute velocity due to its following the bucket around. Thus the efficiency of a water wheel increases with its speed up to approximately one-half speed and then begins to decrease. This condition is shown in Fig. 6.

Inasmuch as it is desirable to have the average efficiency of water wheels as high as possible, centrifugal impulse wheels have been designed on a sort of compromise basis, that is, the top running speed is usually in excess of the speed of maximum efficiency. This permits utilization of the efficiency condition on both sides of the maximum in the eficiency curve, as represented by the shaded area in the curve of Fig. 6. Ina high speed machine, however, it is desirable to have the wheel at maximum efiiciency while the centrifugal is running at full speed on account of the relatively higher amount of power required to overcome windage and friction, as the windage and friction values are much higher for high speed machines (1800 R. P. M.) than they are for 1200 R. P. M. machines. Thus the present day machines are now built for a speedefiiciency curve as shown in Fig. 7, but it will be noted that, during acceleration, advantage is not taken of the efficiency condition on both sides of the peak of the curve.

In a specific form chosen to illustrate the present invention, two bucket wheels 24 and 25 are provided as shown in Fig. 1. During acceleration the large bucket wheel 24 is utilized to a speed up to about 1600 R. P. M., for example.

This large bucket wheel, as shown in Fig. 6, has

.celeration but also makes this acceleration more rapid, making the sugar wall up better. It also provides a higher torque for the rotation required during the unloading operation. The greatest efficiency would result from consecutive use of each wheel (or turbine) alone. However,

at some sacrifice in efiiciency, more rapid acceleration can be achieved by using two or more at the same time and dropping the slower speed wheel (or turbine) out of action as the speed of the centrifugal increases.

While valve No. 2 controlling the flow of water to the two nozzles Zl and 28 maybe manually controlled, it is preferable to control the operation of the valve by automatic means. It should be clearly understood, however, that the invention is not limited to any specific form of automatic valve operating system. While two different forms have been shown in the drawings, one in Fig. l and the other in Fig. 11, it will be readily apparent that arrangements employing other forms of valve operating systems are within the scope of the invention.

In the arrangement of Fig. l, for the control of the water to the two nozzles, valve No. 2 can have the form shown in Figs. 2 and 3 or that shown in Figs. 9 and 10. Considering first the 3-way B-port valve shown in Figs. 2 and 3, this valve is a straight-way plug valve which when open (the position shown in Fig. 2) supplies water to both nozzles, but which when shifted to the position shown in Fig. 3 by the valve-operating mechanism to be described below will cut off water from nozzle No. 1 but will continue to pass water to nozzle No. 2. The operation of the arrangement shown in Fig. l with the valve of Figs. Zand 3 isas follows: valve No. 1 is turnedby hand or by suitable mechanical or electrical means, to its ON position to admit water from the header pipe 31 and the pipe 32 to the pipe 34 and valve No. Valve No. 2 is in the position shown in Fig. 2 and water flows to both nozzles.

This means that while the centrifugal machine 20 is accelcrating, both nozzles are functioning and the. machine accelerates rapidly clue to power derived from the larger bucket Whee124 assistedby a atom-e52 smaller amount of power from the smaller wheel.

25. When the machine, which, by way of example, is designed for a full speed or" 180013.1 M., reaches speed of about 1600 R. P. M. (but other speeds may be selected, .as will be pointed out below), the automatic valve operating mechanism, comprising the scoop as, the pine 38, the chamber 30, the fioat and the valve operating lever 4i, causes valve No. 2 to be moved through 90 degrees to the position shown in Fig. 3. In this position, water flows only to nozzle No. 2 which is opposite the smaller bucket wheel. Thus only the smaller bucket wheel 25 is utilized for driving the centrifugal machine at its rated or normal running speed and the efficiency of this wheel. as shown in Fig. 7, is high at this speed. If both bucket wheels should be left to function, the device will not overspeed since an examinationof Figs. 6 and '7 shows that the efiiciency of the larger bucket wheel drops ofi so fast above 1800 R. P. M. that substantially no power is produced thereby above this speed.

The operation or". the automatic valve operating mechanism shown in Fig. 1 will now be explained, reference being also made to Fig. 8 which is a partial plan View of the bucket wheel Z' -l, the nozzle 2? (nozzle No. 1) and the scoop 29. This scoop is shown in Fig. 1, for the sake of clarity, in a position angularly displaced from its true location which is shown in Fig. 8. The scoop 2'9 consists of a stiff, heavy-walled pipe -0 with the inwardend bent so that the open end faces toward the accelerating nozzle 2?. When the bucket wheel M, having an efficiency curve like that shown in Fig. 6, is rotating at less than 1200 P. M., the water from the buckets is thrown backwards from the bucket in the general direction of the nozzle and thus none of it enters the scoop 20. However, when the speed exceeds 1200 R. P. M., the water carries around with the wheel and s thrown into the scoop from which it is fed through the pipe 38 into the chamber 30. As soon as enough water has passed into the chamber the lever l! operated by the float it causes valve No. 2 to be operated either directly or through a spring trip or switch and solenoid to the position shown in Fig. 8 to cut ofi water from nozzle No. l and hence from the scoop 29. The bucket wheel alone then drives the centrifugal machine until it is time to brake the machine. At this point, valve No. 1 is turned to its OFF position. cutting water from both nozzles, and brake 41 is applied by any well known means. The operation or the brake and of valve No. 1 can be interlocked if desired by any well-known means. When the machine is at rest, valve No. 2 is again placed in the position shown in Fig. 2, the water being drained from the chamber 39 by means of the pet-cock 02.

In order to control the point at which valve No. 2 operates to the position shown in Fig. 3, a variation of the position of the scoop 29 is provided. To make this possible, the pipe 50, as it passes through the wall 5! of the wheel case, is surrounded. by a stuffing box 52. This permits an adjustment of the scoop as it can be pushed toward or away from the bucket wheel 2!; as re quired. The position of the scoop determines the rate at which it picks up water. If it is pulled out a considerable distance away from the wheel 24, it picks up water slowly and thus delays the action of the float for a long period which. of course, maintains the accelerating nozzle 2i in operation while the machine increases its speed considerably higher than .1200 R. P. M., such as, ,for

hydraulically operated.

example, up to 1600 R. -P. M. or even higher. on the other hand, pushing it toward the wheel to the point where there is the greatest amountof water being thrown off causes the float 4-0 to rise more rapidly and thus to shut off the water to the nozzle 2'! a short time after the machine reaches 1200 R. P. M. After the desired point 'for shutting off the nozzle 2'! is determined by trial, the position of the scoop 28 corresponding thereto is fixed by tightening up as much as possible on the stuihng box 52 so that the pipe 50 is firmly held and doesnot move.

vThe operation of the arrangement shown in Fig. 1 with valve No. 2 being of the type shown ,in Figs. 9 and 10 will now be explained. This valve is of the 3-way Z-port type .and'is arranged to permit the passage of water to nozzle No. 1 only-in the position shown in Fig. 9 and to permit the water flow to nozzle No. 2 when the plug of the valve is shifted 90 degrees to the position shown in Fig. 10. Except for the 'fact that only the larger bucket wheel 24 is utilized during the initial acceleration up to about 1600 R. P. M. (instead of both bucket wheels), the operation of the arrangement of Fig. l. utilizing the 3-way Z-port type of valve is the same as described above.

Fig. 11 shows another automatic valve control arrangement-one that is electrically rather than In the arrangement of Fig. 11, the scoop 20 and its associated pieces of apparatus 38, 30, Mi, and ll for operating valve No. 2 have been omitted and replaced by elec trical timers and solenoids for operating valves No. 1 and 2. Elements having the same reference characters in both Figs. 1 and 11 are similar and have similar functions.

The valve operating mechanism of Fig. 11 com-- prises a source of power 60, a first timer 6! (sometimes designated timer No. 1), a second timer .62 (sometimes designated timer No. 2), and solenoids t3, t4, and .05. Timer No. 1 can be of any suitable form, there being many types which are widely used and well known, but has been shown schematically as comprising a field winding 10 for a motor ii, a train of gears '12, a cam 13, and a pair of contacts M and 1-5 closed after a predetermined time by cam l3. The winding 10 is connected in circuit with the power source 6.0, the circuit being closed when the grounded switch lever ill for operating valve No. l is connected to the ON contact ll. Contact i4 is grounded while contact 75 is connected by wire 81 to one terminal of the :field winding 30 of timer No. 2 (which is similar to timer No. 1) and by Wire 88 to one terminal of the winding of solenoid '63, the other terminal of which is connected by wire 89 to'the ungrounded terminal 8'3 of the source 60. Motor 84 is connected through a gear train 82 to rotate cam 83 to close, after a predetermined time, contacts 34 and 85. Contact 84 is grounded while contact 85 is connected (1) by wire to one terminal of the winding of solenoid 65, the other terminal of which is connected by wire 9| to the ungrounded terminal 36 of source 60, (2) by wire 02 to one terminal of the winding of solenoid 6 3, the other terminal of which is connected by wire .lI-l to the ungrounded terminal wire 85 of source and (3) by wire l to a solenoid operated brake mechanism 95, the other terminal of which is connected by connection St to terminal of source til. Valve No. 2 is provided with a lever 9i which is moved to the right or left, depending on which of solenoids i3 and 6.4 is energized, to shift the plug in the valve either from the position shown in Fig. 2 tothat "shownin Fig. 3 or from the position shown in Fig. 9 to that shown inFig. 10, depending On what type of valve mechanism is used. Solenoid 65,

when energized, moves lever 16 from the ON contact H to the OFF contact 18. 7 The operation of the arrangement shown in Fig. 11 is as follows: When the system is at rest, the valve control lever i6 is in its lower or OFF position and valve No. 1 cuts off all flow of water to the pipe, 34. To start the operation, valve No. l is turned on by raising the lever 16 to its ON position (the full line position shown in Fig. 11) and water flows through pipe 34 to valve N0. 2. The lever Bl is in its left-hand or rest position or, in other words, in the full line position shown in Fig. 11, and it remains there until the solenoid 63 is operated later in the running cycle. In this rest position, both valve-Operating solenoids 63 and are deenergized (but due to the bias thereof, the lever member 9'! is in the left-hand position), the brake solenoid 95 is deenergized (the brakes therefore being released), the cams 13 and 33 are in the positions shown in Fig. 11, and the contact pairs 14, i and 84, 85 are open. Fig. ll shows the position of the members at the moment the lever it is turned to the ON position. When the lever 91 is in this left-hand position water flows through pipes 36 and 31 to nozzles No. l and 2, respectively, if the valve of Figs. 2 and 3 is used or through pipe 36 to nozzle No. 1 if the valve of Figs. 9 and is used. The centrifugal machine is therefore quickly accelerated as in the arrangement of Fig. 1.

When valve No. l is turned to the ON position, the circuit starting with source 60, and continuing through field winding it! of timer No. 1, contact 'i'i, switch element it, and ground back to the source til is closed. This starts timer No. 1 running and after a predetermined interval oi time long enough for the machine to reach a speed of 1600 R. P. M.say, for example, one minutecontact "i l rides up on the raised portion of cam wheel i3 and makes contact with contact 15. This places the contact member 15 at ground potential and closes the following circuits: (1) the circuit starting with source til, and continuing through wire 65, wire 89, coil of solenoid 63, wire 88, contacts 15 and i l, and ground back to source til, and (2) the circuit starting with source 50 and continuing through field winding 88 of timer No. 2, wire 81, contacts 15 and 14, and ground back to source 69. The closing of these two circuits causes solenoid S3 to be actuated, moving lever 9'2 to its right hand or dotted position, in which position water flows only to nozzle No. 2 (as shown in Figs. 3 and 10) and also starts timer No. 2 running. After a second predetermined time interval long enough to extract the sugar from its mother liquid-say, for example, four minutes-cam wheel 83 of timer No. 2 causes contacts 8d and 85 to close which closes three circuits. lhese circuits are: (l) the circuit starting with source Eli and continuing through wire 9!, winding of solenoid 353, wire Qt, contacts 85 and 8d, and ground back to source 6%, (2) that starting with source 60 and continuing through wire 95, solenoid operated brake mechanism Q5 (not shown specifically in the drawing but which can be of any well known form), wire 94, contacts 655 and 84, and ground back to source 60, and (3) that starting with source 60 and continuing through wire 86, wire 93, winding of solenoid 54, wire 92, contacts 85 and 84, and ground back to source 60. The closing of the first of these circuits close's'valve No. 1, shutting off all water iromthe centrifugal machine and moving switch lever Hi to the OFF contact i8 which breaks the circuit to timer No. 1. By any well-known reset mechanism (not shown), thecam wheel 13 is returned to its original position breaking conitacts l5 and i4 and breaking thecircuit connectionsto solenoid B3 and to timer No. 2. Cam .wheel 83 is also then resetxby any appropriate .mechanism (not shown). .ciricuitsyenergizes the solenoid operated brake The second of these the left, but if current flows through solenoid winding 63 alone the lever will be moved to its right hand or dotted position.

Various changes can be made and still be within the scope of the invention as indicated by the claims.

What is claimed is:

1. A heavy centrifugal machine for drying sugar bearing and like materials and being of the type which is adapted to be cyclically rapidly accelerated from rest to a normal running speed which is substantially the highest safe speed of said machine, allowed to run at this speed for a time period normally less than an hour and then quickly brought to rest, comprising a rotatable basket for holding the material to be dried, a shaft for supporting said basket, a first water wheel driving means on said shaft for rotating said basket, said driving means having the characteristic that the speed at which it has its highest efficiency substantially coincides with said normal running speed and being adapted to be normally the only source of power for the machine at and immediately around said normal running speed, and a second water wheel driv ing means on said shaft, the wheel of which is of larger diameter than the wheel of the first driving means, for normally providing power during said acceleration period only, said second driving means having the characteristics that the speed at which it has its highest efiiciency is much lower than said normal running speed and that it produces no appreciable amount of power above said normal running speed.

2. The combination of elements as in claim 1 in which each of said two water wheel driving means comprises a bucket wheel.

3. The combination of elements as in. claim 1 in further combination with valve means for making effective the second water wheel driving means during the acceleration period and for making efiective only the first water wheel driving means during the normal running period.

l. The combination of elements as in claim 1 in further combination with valve means for making efi'ective only the second water wheel driving means during the acceleration period and for making effective only the first water wheel driving means during the normal running period.

FREDERICK STINDT.

(References on following page) REFERENCES CITED 7 Ih'e following references are of record in the fire ofthis patent:

UNITED STATES PATENTS Number Name Date MacfarlaJ-ne 1. Feb. 23-, 1904 Dutcher Feb. 20,1906 Tingley -11 Oct. 2, 1906 Ashley 1 Oct. 6, 1908 DOlier Mar. 23, 1915 Number 70 Number Name Date Xardell 1 Apr. 20, 1926 Pecker May 18, 1937 Hazen- Dec. 29, 1942 0100171; Mar. 16, 1943 0100121: Dec. 28, 1943 Olcott Nov. 28,1944 FOREIGN PATENTS Country Date

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