US2551838A - Speed control system for centrifugals - Google Patents

Description

May 8, 1951 R. .1. HUSER rrAL 2,551,838

SPEED CONTROL SYSTEM FOBl CENTRIFUGALS Filed June 2l, 1947 2 Sheets-Sheet 1 INVENTORS Afc//mra J /rmrf ,444W vzw May 8, 1951 R. .1. HusER Er AL 2,551,838

SPEED CONTROL SYSTEM FOR CENTRIFUGALS Filed June 21, 1947 2 Sheets-Sheet 2 5 SEC.

OFF ON l0 SEC MINUTES r P72 PT/ 5 zoo RPM START 45o sHTFr Low To HTGH |500 coAsTlNG. STARTS REGEN. BRAKE STAR-rs n OFF MECHANJCAL BRAKE ON MACHINE STOFS Ma/M HTTOR/YEYJ Patented May 8, 1951 UNITE-D STATES PATENT OFFICE .SPEED CONTROL SYSTEM FOR 'CENTRIFUGAL'S ApplicatonfJuneZl, 1947, Serial No. 756,307

4 Claims.

'This invention relates to a system or apparaitus for the control of centrifugal apparatus, particularly of the type used 1in sugar reiineries, and is especially concerned with the control fof the speed of the centriugals used therein.

In sugar centrifugals, the loaded basket must be accelerated Ato running lspeed in an .extremely short period, the complete cycle being .as short :as two minutes and less. `When the basket :is iconnected directly to an Velectric motor, a very high load is placed on'the -motordue `to the high acceleration required of the 'loaded basket. If a iiui'd coupling is interposed between the electric driving motor and the basket, a very high-loadfalso `is placed on the motor yduring acceleration unless some special arrangement of the fluid coupling is employed. Some of said Huid coupling :special arrangements do not transmit power through the coupling in the most efficient Vmanner throughout the acceleration of the basket. Standard :electric motors -will not function properly lunder the aforementioned high load conditions because there is insufficient time for fthe 'motor to cool after the completion of each cycle and before the next cycle is started, 'the cycles -off operation `-nor i mally being frequently repeated. Consequently, it has been the general practice -to use specially designed and constructed expensive electric -motors for individually driven electrically operated sugar centrifugals.

When alternating current motors are used, vthe speed of the motor is lgoverned -by the construction of the motor, number 'of poles, and vthe frequency of the power supply. For example, standard alternating current v60-cycle motors have rated or vsynchronous speeds of i800 and 1200 R. P. M. for 4 and v6 pole motors, respectively, with full load running speeds slightly thereunder. Frequently it has been found that sugar will be undertreated when subjected to a centrifuging speed of near 1200 R. P. M. only, whereas the sugar will be overtreated at a speed near 1800 R. P. M. When the sugar is overtreated, it may be packed so hard as to caused'iiliculty inthe discharging operation.

One of Athe objects of the invention is to provide a control apparatus whereby standard electric motors can be employed without the necessity of using specially built motors l'to withstand the heavy load requirements of :acceleration in sugar and similar type centrluga'ls.

Another of the object `of the invention is `to provide a system and apparatus wherein centrifugal speeds below vthe rated speed "of an ralternating current driving motor can lbe attained, as fde- .2 sired, to suit the processing requirements of particular materials.

A Afurther Vobject vris to save power, increase motor operating efficiency, and avoid overloading of the rmotor .in the use -of heavy motor-driven centrifugal machines.

One of the features of the invention in aidirect connected `drive is the -use of a 'standard electric `eration `of heavy motor-driven `centrifugal imachines. Power is supplied to the motor at the beginning of the acceleration, and, at the end of .a predetermined time :period .permitting the centrifugal -to reach the desired speed below the normal running Ispeed `of the motor, power is cut off Vto the motor and thecentrifugal is allowed to coast under its own momentum until the purging or .separation of materials, washing, or l-orther operations are completed. Thus, the centrifugal can -be voperated at almost any `desired speed below :the operating speed of the electric motor de pending upon the time the accelerating power iis supplied to fthe motor.

'The Iaccelerating power is applied to the mo'- tor only for a short time :during the cycle, and therefore the motor will have an opportunity to cool between intervals of heavy power applica,- tion. In addition to said opportunity to cool between power applications, the cooling rate :of the motor will `be higher dueto rotation during the coasting period as compared with the cooling rate of a motor at standstill.

In accordance with one aspect of the invention, the time of application o'f power for acceleration 'in a direct-connected electric-driven `centrifugal can be governed by a timer K'arrangement which operates at 'the `end of `a predetermined time to interrupt the supplygof power 'to the lelectric drive motor or to 'interrupt the driving action thereof before the potential or running speed of the Velectric motor is reached by the :centrifugal basket. The predetermined time is adjustably selectable so that the centrifugal can be operated to reach any desired operating speed.

When a hydraulic coupling for #fluid drive is used to connect the 'electric motor with the .centrifugal basket, the system of the 'present invention vcan be applied so as to interrupt the 'flow 'of oil to the coupling at a predetermined time after acceleration istarts, `and thus the 'operating speed of the 4centrifugal basket can be made less the potential or running speed of the driving motor or potential speed of the driving apparatus.

Another feature of the invention is the provision of a cycle control arrangement wherein, in consequence of the movement of a single control device such as a starting button, a control timer and a process timer are started and these can time, when low and high speed motor windings are employed, the shift from low to high speed windings to the drive motor, the time of acceleration until power to the motor or fluid to a coupling is cut 01T, the time of coasting, application of regenerative braking if used, application ofA the mechanical brake, and other desired operations.

vantages of the invention will become apparent from the following description andl drawings which are merely exemplary.

In the drawings: i Fig. 1 is a schematicview partially in Sectio lof one form of theinvention; i

Fig. 2 is a schematic wiring diagram of a icircuit that may be employedin carrying out the invention.

-1 Fig. 3 is a diagrammatic View of the face of a control timer suitable Vfor use in the circuit of Fig. 2.

Fig.`4 is a diagrammatic view of the face of a process timer that may be used in -the circuit of Fig. 2.

In the direct driven centrifugal of Fig. 1, elecl tric motor 2n drives suspended rotatable gyratory basket 2l through shaft 2'2, the motor being directly connected to said shaft and basket. Brake vdrum 23 has braker bands 24, the brake bands being movable to grip brake drum 23 by means' of apparatus attached to bracket 25 as will be vdescribed hereafter, lthe bands being'hinged at bracket 26 to the machine frame in a well known manner.

As explained in detail in the copending application Serial No. 756,308 filed June 21, 1947, the brake bands can be expanded or contractedl rela'- tive to the brake drum by means of an operating device such as the torque motor 23 moving link 29, link 2S operating the brake applying mechanism shown diagrammatically at 30. A torque motor is a motor which rotates in a limited arc upon application of electric power thereto, the torque motor having an arm connected to -the shaft thereof to which link 29 can be fastened.

A hydraulic cylinder, as described in said afore-mentioned application Serial No. 756,308, also may be used to operate the brake applying mechanism, as well as any other suitable apparatus. When a hydraulic cylinder is employed, the applications of pressure thereto may be controlled by a solenoid.

As yan aid to the operator, ab tachometer 34 ofsome suitable description may be employed, said tachometer being connected to give an'indication of the speed of the centrifugal basket.

One form of wiring diagram and controlV Circuit whichmay be used ,is v'shown in Fig. :Zasaid or distinguishing subscripts or letters.

vswitches operable by the process and control 'I'hese and other objects, features, andad- -15 and high speed windings.

circuit omitting such features as the basket wash water control, the syrup separator control, etc. As is well known in the art, a solenoid can be used to operate a plunger or other mechanism connected mechanically to any number of switch operators. In the accompanying drawing, the mechanical connection is omitted in the interests of clarity, the switches operated by a solenoid being given the same numeral with appropriate The timers will be identified by the reference characters PT and CT, respectively, with distinguishving subscripts.

Power -is supplied from a three phase source of alternating current Ilm to the main driving motor 20 having separate connections for the low Power for the control circuit is taken from mtransformer m2 to bus bars |03 and IBG of the` control apparatus. The control apparatus may be located inthe control lbox indicated schematically` at SI in Fig. 1, suitable motor switches being located in the control boxv 32, and the starting and resetV but-y tons being located at a convenient Apoint `3,3 as desired. Itis evident that the control apparatus and control buttons may be grouped and placed as convenient. I

In order to start the basket centrifugal from rest, or to start the automatic control and acceleration of the centrifugal after the basket has been loaded and Yis revolving slowly, the start push button IID is depressed which will energize starting relay solenoid I I I to close holding switch IIIa around starting button IIJ, switch IIIa being operatively connected .with solenoid I I I.

Closing of the circuit to bus barsv m3 and IIIA rwill cause energization of low speed solenoid I I2 which will close circuits through connected contacts II2c, II'Zd and IIZe to the low speed windings of drive motor 20. The process timer, which will be described hereafter, will have its clutch solenoid II3 energized and will have operating motor H4 thereof started, switch PTO, connected with the process timer operating mechanism, -being normally closed at the beginning of the cycle. solenoid vI I5 energized and its control motor IIS started, switch contact I I2a connected with solenoid I I2 having.v been closed upon energization of solenoid II2 and switch C'Io being normally 4closed at the beginning of the cycle. Ihe manner in which the timers operate the switches will be described hereafter. .l In the drive motor 2l] shown, a low and high speed winding are used and the low speed winding is energized first so that provision must be made to shift to the high speed winding at the desired time. If, for example, the motor has a rated high speed of 1800 R. P. M. andthe full rotation of the low speed winding is 900 R. fast acceleration being desired, the timing of. the relay circuits may be arranged so that there will be a shift from the low to the high speed winding of the driving motor when ,the driving motor reaches about 450 R. P. M., lthe exact speedof shift being a matter of choice,--motor characteristics, and other variable factors. Loading of the basket may be carried out before this shift, usually at a speed of about 200 R. P. M., either while the basket is being accelerated on the low speed winding, or while the motor idlesand is jogged to about such a speed, through successive movements ,of start button I IIIand circuit @senseless .button '.09 .ibevre .Starting the.

The control timer will have its clutch actual :treating cycle. The .reset button is normally closed and only opened momentarily to permit the circuit to reset. In the particular process'and control timers, a clutch connects the switch operating motor with the switch operators. When a motor is stopped, the switch operator will remain at its stopped position as long as the .clutch remains engaged. I1" the clutch is disengaged, the switches will be returned to zero by suitable means. The resistances |23 may be employed Vwith any suitable control for energizing the low speed windings therethrough, so as to modify the torque at very low speeds, where a very low speed of the centrifugal is required, such as for discharging between :successive running periods.

The aforementioned speed 'winding shift can be accomplished by the control timer switch CTi being closed by the control timer after a Vpredetermined interval folicwing the start of the cycle, the control timer having been started at the beginning of the cycle by being connected across control bus wires m3, 104. Immediately after, or at the time switch CT1 closes, switch GT2 is lset to be opened by the control timer .so as to deenergize the low speed solenoid H2, 'contact H8b connected to solenoid H8 having been opened at the beginning of the cycle 'because of energization of solenoid II 8, switch FTQ being closed. Opening of contact GT2 will allow high speed solenoid vI Il to become energized because GT2 deenergizes low speed solenoid H2 so that switch conta-ct H213 connected to solenoid H2 will close and complete the circuit to solenoid Ii l, normally open switch Contact IIa having been closed when the start button was depressed. Energization of high speed solenoid i I7 will 'close contacts H'Ic, Hld, Hic, HU and 'I'i'ig to connect the high speed windings of main driving motor 29 to the source of power, said solenoid being operatively connected to switches Ille, d, e, f, g. Low speed switch contacts 112e, I IM. and H2e operatively connected to solenoid 'I I2 were opened upon de-energization of low speed :solenoid H2. upon deenergization of solenoid H2 and stop the control timer motor H6, but the control timer will not reset itself inasmuch as the clutch vsolenoid H .remains energized.

At the end of a predetermined time., which is 1' that necessary to accelerate the driving motor and centrifugal to the desired operating speed, switch PTl of the process timer will be opened thereby and de-energize solenoid I l?, thus opening the operatively connected high speed contacts H1c, II'Id, IIle, H-If and Ille, cutting citpower to the drive motor and causing the driving motor to coast.

Brake cooling water solenoid I i9 was energized when yswitch C'I1 was closed by the control timer, switch H8a having `been previously closed, so as to open a valve supplying cooling water to the brake drum in a manner similar to that disclosed in the patent to Roberts, No. Re. 22,686. Solenoid H9 will remain energized so as to continue the supply of cooling water to the brake drum during the coasting operation because said solenoid is shunted across switch PT1, solenoid I Il and switch contact H212.

At the end of the predetermined coasting period, switch PTz is opened by the process timer, which has continued to run, since the start of .the cycle so as to de-energize solenoid H8, which .in turn opens the connected contact Ha to interrupt the supply of current to `brake cooling water Switch contact H2@ also will open solenoid H9 and thus shut the water supply valve for brake cooling. Normally closed fcontact H81), which was opened by the energized solenoid -I I8 at the beginning of the cycle, also will close and thus connect the low speed solenoid H2 to the bus bars. Closing of contact -I I8b by de-energiza-tion vof solenoid H8 will thus close the connected low `speed winding switch contacts H2c, H2d and H2e to the source of power VI'IlI) so that the lmotor vwill be subjected to regenerative braking, switch -contact Illa having closed upon de-energization of the high speed .solenoid III, it being noted that switch `GT2 was opened previously during the acceleration period.

At the .end of a short predetermined period suitable for the regenerative braking, switch CTg will be closed by the control timer, the control timer having been started again upon the beginning of the regenerative braking inasmuch as the energization of the low speed solenoid H2 has caused switch contact I I2C. again to close. Closing of switch ICTs will energize solenoid 'I 2E, which will open connected switch contact I29a inthe low speed relay circuit and thus stop the regenerative braking. At the same time, switch contact |2017 operated by solenoid |20 will be closed .and thus energize the brake motor solenoid I2I. Energization of solenoid IZI can be used to cause energization of switch contacts I2 la, I2Ib and I2Ic to energize the brake Vsetting torque motor 28 or to energize a solenoid controlling the admission of air to a :duid pressure operated brake cylinder as disclosed in copending application, Serial No. 756,308.

Thus, the machine is no longer subject to driving torque, and the friction brake bands 24 are applied to the brake drum 23 so as to bring the machine to rest.

After the centrifugal cornes to rest, other operations, as desired, may be performed and the circuit reset for the next cycle by momentarily depressing the reset button |09 which will reset both of the timers by de-energizing the clutches and thus permit the timers to return to zero.

Various types of timers may be used and various arrangements thereof made. In the preferred form, a composite unit type, such as is known as the Multiex, and diagrammatically illustrated in Figs. 3 and 4, can be employed, it being understood that separate timers or time delay switches may be used for each of the timing functions. The Multiflex timer is well known and does not need to be described in detail except to point out that in the Yform shown in Fig. 3, four individually timed switches are available, and in Fig. 4, three are available. The timers have their own motivating mechanism and clutch for engaging the saine with the switch operators. The operation of each of the contacts or circuits can be set vby the adjustment of the on detent or ofi detent with respect to a timing scale shown on the face of the timer so that the timing action or circuit closing will occur ,at any desired interval according to the setting of the on detent and will terminate at any desired interval with relation to the time started. When the on detent is placed above the upper limit of the scale, its corresponding contact is closed when the timer is started or energized. If the oir detent is below the lower limit of the scale, its corresponding circuit, vafter having been closed according to the setting of the on detent, will stay closed until the timer is deenergized or reset. One form of the Multiflex timermay be seen in U. S. Patent No. 2,175,864 issued October 10, 1939. l

As an example of one type of suitable operat ing cycle, reference may be made to Fig. 5, wherein a scale of minutes is shown in relation to various operations for bringing a polyphase induction motor having a synchronous speed of`1800 R. P M. up to 1500 R. P. M. It is understood, of course, that other speeds may be chosen and other intervals employed, the cycle shown being merely illustrative of one type of fast sugar centrifuging cycle.

Assuming that the start button has just been depressed following a loading of the basket leaving the basket turning at about 200 R. P. M., a period of 10 seconds is allowed before the motor windings are shifted from low to high speed. It is assumed that the motor will reach a speed of aboutr450 R. P. M. during the 10 seconds. the end of about 40 seconds after the shift to the high speed winding (50 seconds after starting the cycle), the motor will have reached the desired speed of 1500 R. P. M., and at this time coasting switch PT1 is set to open so as to interrupt the driving action by de-energizing the motor and allowing the centrifugal and motor to coast. It is to be understood that the time for reaching these various speeds will depend upon the size of motor, characteristics thereof, weight of charge in the centrifugal, and other variables, but that these variables are relatively constant for any given conditions of use of a given machine.

The motor may be allowed to coast for 30 seconds and the washing, if it is to be used, may take place during this period, such not being shown or described herein as it does not constitute a part of this invention. At the end of the coasting period of 30 seconds, the regenerative braking is started when switch PTz opens and can continue for l seconds, following which the regenerative braking is turned off by closing of switch CTa, whereupon the mechanical brake is set.

In Fig. 3, the settings of the control timer to correspond with the above cycle of operations are shown schematically. The switch contact CTO is on from the beginning of the cycle and the off detent is arranged so that it will openapproximately seconds before the end of the range of the control timer. The purpose of this is to de-energize the control timer so that it cannot be left on indeterm-inately. The on detent of CT1 is set for operation l0 seconds after the starting of the control timer and serves to shift the driving motor from low to high speed in conjunction with the opening of C'Iz, the off detent of GT2 being set to operate at the same time as, or immediately after, CT1 closes. Upon shift to the high speed winding, the control timer will be stopped inasmuch as switch contact H211 is opened, but the timer will not reset.

The process timer of Fig. 4 also was started at the sam-e time as the contr-o1 timer and runs continuously. Switch PTo is normally closed before the timer is started and the off detent thereof is set approximately 5 seconds before the end of the 5 minute period for the purpose of turning off the timer in a manner similar to the control timer. Switch PTi is set to be on when the timer starts and to be opened at an appropriate time, say 50 seconds after starting the operation. This serves to cut oli' the power to the high speed winding andallow the coasting to start. It is evident that the coasting switch PT1 may be set for operation by the process timer a predetermined time interval in accordance with the particular speed to be used. Switch PTz is set to be opened at a predetermined time after the coasting contact opens; in the particular cycle shown, this interval being set for 30 seconds. When switch PTz is opened, regenerative braking is started due to re-energization of the low speed solenoid. The control timer also is restarted inasmuch as switch I|2a again is closed by the low speed solenoid. The regenerative braking will be continued for an interval governed by the setting of switch GT3, GT3 being arranged in the particular cycle shown 10 seconds later than the position of the 01T detent of GT2. GT3 is arranged to close at the time interval required for regenerative braking after operation of GT2. When CTs is closed, the control timer will stop because the low speed winding is de-energized and switch contact H2a opened.

All of the usual necessary adjustments can be made on the process timer because PT1 governs the length of time from the starting of the cycle until coasting starts and PTz governs the time of coasting. These two times can be adjusted as desired for the sugar involved.

In the event an electric drive is used with a hydraulic coupling, the timer switches governing acceleration and coasting can be employed to cut oiT the supply of oil to the fluid coupling at the end of the predetermined time necessary for the centrifugal to reach the desired speed. In Fig. 6, the motor 35 drives basket 35 through a iluid coupling 3l, in a manner similar to that disclosed in the copending application of Joseph Hertrich, Serial No. 435,023, filed March 1'?, 1942, now U. S. Patent No. 2,441,356, or as disclosed in Fig. 1 of his copending application Serial No. 713,329, filed November 30, 1946. The pump 38 takes oil or fluid from tank 39 and delivers the same to the three-way valve 40. The three-way valve has pipe lil returning to the storage tank 39 and pipe llZ leading to the coupling. The coupling continuously discharges oil. The control mechanism can be used to cut 01T the supply of oil to the fluid coupling at the desired time, thus interrupting torque transmission to the motor while allowing the driving motor to continue running under no load, by positioning the three-way valve to return the oil to the storage tank instead of supplying it into the coupling. This may be done by using a three-way solenoid valve at l0 with the solenoid connected in a control circuit like that of Fi 2 in the relation occupied by relay solenoid Ill thereof. In such an embodiment, a single speed motor is used so that but one set of windings and motor controls are provided in 'the position of said circuit occupied bythe low speed windings, and the speed shifting and related control timer elements thereof are eliminated.

The coasting control for a fluid coupling drive also can be used in conjunction with other types of controls for the uid coupling. An example of another type of control is one for the regulation of the accelerating torque of the drive by control of the iluid supply to the coupling in response to the torque reaction on the motor frame and an opposing control force, as disclosed in said copending application Serial No. 435,023. In a iiuid coupling drive, it is particularly desirable to have a tachometer such as indicated at I3 to-shc'w the'- speedreached by the centrifugal basket, in= order to assist. in acicurately predetermining the desired setting for timer contact PT1.

Itis to be understood that the illustrated embodiments of the combination and details'thereof may' be4 varied without4 departing from the spirit of theA invention except as defined 'inl th appended claims.

We claim:

l. In a suspended centrifugal machine adapted for operation to and from a high speed of rotation in each of frequently repeated cycles, the combination of a basket-carrying spindle, a rotary driving system connected therewith to drive the same, said system including activating means connected therewith shiftable to respective positions at which said drive is inactive and is active to apply its full accelerating torque to said spindle, braking means normally inactive but movable to retard rotation of said spindle, control means including starting means connected with said activating means movable to shift the activating means to said drive-active position upon actuation of the starting means, an adjustable timing system connected with said control means and said activating means started in action when said control means is moved so to shift said activating means, said timing system including a timer element connected with said activating means acting as a predetermined time after starting the timing system to shift said activating means to said drive-inactive position, so that said spindle then may coast under its own momentum at a desired high centrifuging speed, and another timer element connected with said braking means acting to move the same at a predetermined time after the action of the first-mentioned timer element, so that said spindle is stopped after a period of coasting sufficient to complete the centrifuging at high speed.

2. In a suspended centrifugal machine adapted for operation to and from a high speed of rotation in each of frequently repeated cycles, the combination of a basket-carrying spindle, a rotary driving system connected therewith having a full accelerating torque and speed which drive the spindle to more than a predetermined high centrifuging speed, said system including activating means connected therewith shiftable to respective positions at which said drive is inactive and is active to apply its full accelerating torque to said spindle, braking means normally inactive but movable to retard rotation of said spindle, control means including starting means connected with said activating means movable to shift the same to said drive-active position upon activation of the starting means, an adjustable timing system connected with said control means and moved thereby into action upon movement of said control means to activate the driving system, said timing system including a timer element connected with said activating means acting at a predetermined time after starting the timing system to shift said activating means to said drive-inactive position after a predetermined period of application of said full accelerating torque, during which said predetermined centrifuging speed is reached, so that said spindle then may coast under its own momentum, and another timer element connected with said braking means acting to move the same at a predetermined time after the action of the first-mentioned timer element, sol that saidi s'pindlef is' stopped after a periodik off coasting; sufficient tocomplete the centrifuging at-highfspeedf Y A 3 lin aususpendedi centrifugal machine-adapt"- ed for operation to and from a high speed of rotation in e'achyof frequently repeated cycles, the 4confibi'n'ation of a basket-carrying spindle, a rotary electric driving motor directly connected with said spindle, said motor having a full accelerating.. torque ande speed which. drivev the spindle to more than a predetermined higlr centrifuging speed, a power supply switch mechanism connected with said motor and shiftable to respective positions at which the motor is deenergized and is energized to apply its full accelerating torque to said spindle, braking means normally inactive but movable to retard rotation of said spindle, control means including a cycle starting element connected with said switch mechanism movable to shift the same to said motor-energizing position When said cycle starting element is activated, an adjustable timing system connected with said control means and moved into action upon movement of said control means so to shift said switch mechanism, said timing system including a timer element connected with said switch mechanism acting at a predetermined time after starting the timing system to shift said switch mechanism to said motor-deenergized position after a predetermined period of application of said full accelerating torque, during which predetermined high centrifuging speed is reached, so that said spindle then may coast under its own momentum, and another timer element connected with said braking means acting to move the same at a predetermined time after the action of the first-mentioned timer element, so that the machine is stopped after a period of coasting sufficient to complete the centrifuging at high speed.

4. In a suspended centrifugal machine adapted for operation to and from a high speed of rotation in each of frequently repeated cycles, the combination of a basket-carrying spindle, a rotary driving system including an electric driving motor and a hydraulic coupling for transmitting torque from said motor to said spindle, a power supply switch mechanism connected with said motor to energize the same and adapted normally to be left in motor-energizing position, lling control means connected with said hydraulic coupling shiftable to respective positions at which the same is emptied and is lled to apply the full accelerating torque of said system to said spindle, braking means normally inactive ybut movable to retard rotation of said spindle, control means including a manually operable starting element connected with said filling control means movable to shift the same to said coupling-lled position upon activation of said starting element, an adjustable timing system connected with said manually operable control means and moved thereby into action upon movement thereof so to shift said filling control means, said timing system including a timer element connected with said lling control means acting at a predetermined time after starting the timing system to shift said iilling control means to said coupling-emptied position, so that said spindle may coast under its own momentum, with said motor continuing energized and running, after a predetermined period of application of said full accelerating torque imparting a desired high centrifuging speed, and another timer element connected with said braking means acting i1 to move the same at a predetermined time after UNITED STATES .PATENTS the action of the first-mentioned timer element, Number NameA 1 f Date so that said spindle is stopped after a period of 1 866 499 n Hen. July 5, 1932. coasting sufficient to complete the centrifuging 2148320 Olcott Feb 21 1939 at high Speed 5 2152562 oloott s/Iar. '28 1939 RICHARD J- HUSER- 2,175,864 Anderson oon. 1o, 1939 ANTHONY H- STUHLREYER- 2,280,916 Johnson Apr. 28, 1942 REFERENCES CITED 2,338,053 Olcott Dec. 28, 1943 The following references are of record in the 10 le of this patent:

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