US1536915A - Centrifugal machine - Google Patents

Description

May 5, 1925. 1,536,915

C.A.OLCOTT CENTRIF'UGAL MACHINE Filed June 5, 1921 2 Sheets-Sheet 1 x/MW ATTORNEYS May 5, 1925.

1,536,915 c. A. OLCOTT CENTR IFUGAL MAC-HI NE Filed June 5, 1921 2 Sheets-Sheet 2 IHVENTDR JWW monnsv s Patented May 5, 1925.

UNITED STATES CHARLES A. OLC-OT'I, OF YORK,

ASSIGNOR T0 S. S. HEPWORTH COMPANY,

OF NEW YORK, N. Y., A CORPORATION OF NEW YORK. CENTRIFUGAL MACHINE.

Application filed .Tune 8,

To all whom it may concern:

Be it known that I, CHARLES A. OLco'rr, a citizen of the United States of America, residing at New York city, in the county of New York and State of New ventedcertain new and useful in Centrifugal Machines, of lowing is a specification.

My invention relates to centrifugal machines, and particularly to a centrifugal driven by an associated electric motor through a slip clutch-preferably by an induction motor through a slip clutch of the centrifugal type. Among the objects of my invention are (let) to provide a centrifugal machine layout such that while the motor employed is of the single speed type (viz., a motor which under no load has a sub- Improvements which the folstantia'lly constant speed at various volt ages) different rates of acceleration of the centrifugal basket are obtained by selectively predetermining the voltage impressed upon the motor, and thus changing the' torque exerted by the motor through the slip clutch upon the centrifugal basket or the like; (2nd) to provide means for impressing upon the motor a voltage different from any of the selected acceleration voltages, but such as to exert upon the basket, through the centrifugal clutch, a torque sufficient to rotate the basket at a speed appropriate for the discharge of material therefrom by a. mechanical unloader, the drag of which causes the clutch to slip and the basket to lag behind the motor; (3rd) to provide means by which the shop foreman, or other appropriate oflicial, may predetermine and set the voltage to be impressed upon the motor to obtain appropriate acceleration of the basket for the particular material under treatment, While the machine attendant has no control over the voltage of the motor current, his control being limited merely to switching the foreman-regulated current on and off the motor.

In the accompanying drawings Fig. 1 is a side elevation partially in section of a centrifugal unit from a battery to which my invention may be advantageously applied; and

Fig. 2 is a diagram of a battery of centrifugals illustrating the motor control for the group.

The present invention is particularly applicable to centrifugals for drying sugar and York, have in- 1921. Serial No. 474,842

which are general] run at a speed one thousand revo utions per min- When drying first sugars and other materials of slmilar properties, it is desirable to reach this s eed as soon as possible after starting, in or or that the dr ing operation ma be completed as quick y as possible rand thus to secure as great an output as possible. With some materials, such as low grade sugars and the like, a slower acceleration of the ile for first sugars the b perio of from three he advantages which result from different rates of acceleration upon various grades of material will be apparent from the following considerations; Take, for example, a solid material suspended in a very viscous mother liquor, such as low grade sugar suspended in molasses. When such a mixture is brought rapidly to speed in a centrifugal basket, the solid material packs against the side of the basket, forming a mass that is relatively impervious to the thick molasses. On account of the fact that the crystals are heavier than the molasses, they move toward the screen at the side of the basket very rapidly. Therefore. when the machine reaches full speed rapidly, the crystals not only form an impervious wall between the molasses and the screen, but also are still further compressed by the weight of which has not yet found its way, through the screenand out of the basket. As a result of this additional pressure, the solid mass is even more impervious than it would have been '1 1d it not been subjected to the pressure resulting from the centrifugal force on the molasses. If the basket is brought to s eed slowly, the crystals do not pass rapidly through the molasses vehicle and pack so rapidly against the basket wall. A lar er amount of molasses therefore escapes efore the crystals form a wall between the molasses and screen. Furthermore, the crystals being subjected to less centrifugal force, do not form an impervious mass. B the time the machine reaches full spee most of the molasses has escaped through the screen. There is therefore no great basket is preferable moisture in which ings are too complicated l to so motor mentioned, and to employ resistance material being treated is in this condition, with a relatively small amount of molasses,

it can be run at the high speed in thecentrifugal machine without any great degree of packing of the solid mass, and the residual molasses can therefore escape much more easil than if the acceleration had been rapi p r Let us now consider a free draining material such as a high grade sugar suspends in a molasses much less viscous than that to be separated from low grade sugar. It is desirable to accelerate the basket containing such material rapidly, for the following reasons:

1. Because the accelerating period comprises a large percentage of the total time required to dry the charge, and therefore a reduction of this period reduces the time required to dry the charge and consequently increases the output of the machine;

2. It is desirable to have the material wall up in thebasket before all of the mother liquor is thrown off. If the basket is accelerated slowly,

most of the mother liquor will leave the basket before the solid material is walled up, with the result that the solid material being deprived of the it has been suspended will no longer flow upward by centrifugal force, and the wall of material will be relatively thick at the bottom and thin at the top; thus causing uneven drying, and if the material is to be washed in the asket, great difliculty in washing it efi'ectively.

It has heretofore been proposed by Mackintosh (United States Patent No. 1,342, t05) to provide an alternating current induction motor having different windings to secure two motor speeds-one a working speed and the other an unloading speed. He has also suggested a centrifu al clutch connection between the motor an the basket to permit the lag of the basket, through slip at the clutch, during the unloading operation. This layout has'several disadvantages, however. In the first place the double wound motor is-initially expensive, and the windto permit rewind ing or repair of the motor in the ordinary sho of a centrifugal operating plant. Second y, the working torque of definitely fixed and inflexible, and since this fact results in a uniform rate of acceleration regardless of the character of the material treated in the basket, the utility of the Mackintosh arrangement is practically restricted to the treatment of that material for which the one rate of acceleration provided is appropriate.

It has also been proposed b 'tute a D. 0. motor Mackintosh or the A. O.

the motor is asses in the motor circuit to obtain the This type of motor is unsatisfactory for many reasons, and the resistance adds to the expense and difficulties of maintenance.

M invention is based primarily upon two considerations. 1st, that the torque of a single s eed motor of the alternating cur rent in uction type may be controlled by varying the voltage impressed on the motor, and 2nd, that a motor-load connection 0 the centrifugal clutch type, permits the motor to come rapidly to speed which applies the clutch to the load but thereafter accelerates both motor and the load only in'proportion to the torque exerted by the motor, the latter being itself braked by the load imposed through the centrifugal clutch. Therefore, if the voltage impressed on the motor be lower, the torque of the motor at the clutch is reduced and both motor an basket come more slowly to full speed than when the motor torque is hi gh, incident to a higher voltage impressed on the motor.

should be borne in mind that during two speeds.

It the first portion of the accelerating period, the rotor of the motor revolves at a substantially constant speed while the basket is revolving at a lower, but increasing speed, the clutch slipping meanwhile. The speed of the rotor is that at which the torque of the motor equals the torque of the slip clutch. This torque is the torque which 18 effective in accelerating the basket. The torque transmitted by a centrifugal slip clutch increases when the speed of the driving member of the clutch is increased and likewise decreases when the speed of the driving member is decreased. The torque of the alternating current induction motor, at any given speed, increases when the voltage impressed upon the motor is increased, and decreases when the voltage is decreased. Therefore the speed at which the rotor of the motor revolves while the clutch is slipping, is relatively high, and the torque transmitted by the clutch is relatively great when hi her voltage .is impressed on the motor. ikewise the rate of rotation of the rotor is relatively low, and the torque trans mitted by the clutch is relatively less when lower. voltage is impressed on the motor.

Since the acceleration of the basket is rapid when the torque of the clutch is at, and

the basket accelerates rapidly or slowly accordin to whether high or low voltage is impress upon the motor. The torque required for discharging, that is, the torque necessary to drive the basket against the drag of a mechanical unloader is usually different from the torque required for accelerating the basket to a drying s eed, and is always less than that require the rapid acceleration of the basket desired for free draining materials such as high of the clutch is less,

the acceleration is slower when t e torque for ass

grade sugar. impre ing on the motor a voltage lower than that used for rapidly accelerating the basket muses a reduced torque of the clutch, and a proper lower voltage will thcrefore causc the clutch to transn'iit the proper torque to drive the basket against the drag of the unloader.

It is thus possible speed motor and a motor-load connection of the centrifugal clutch type, to obtain an installation havin many advantages. A single speed motor of this type is notinitially expensive. Its winding is so simple that it may be rcadil repaired or rewound in the ordinary'shop of the centrifugal plant. Th appliances for varying the voltage to bc impressed upon the motor are of simple and durable character. A flexibility of rate of acceleration of the basket is obtained which makes it possible to handle in the basket materials having markedly different characteristics. and requiring markedly different rates of acceleration. It prevents the relativelv unskilled machine attendant from exercising; any discretionary control over the rate of acceleration of the'baskct, and leaves this'to the judgment of the foreman or other oflicial of experience. It simplifies the work of the attendant at the basket, who has merely to close the motor switch to impress upon the motor the voltage predetermined by the foreman. The invention also makes it possible for the foreman to regulate the acceleration voltage of the cen trifugal independent of the unloading voltage: while for a battery of centrifugals the connections are so arranged that the motor of each machine may be independently accelerated and discharged by the manipulation of switches under the control of the machine attendant.

A centrifugal machine of the present type is indicated in Fig. I. The centrifugal basketis suspended by shaft 6 from hearing 7. and has a clutch cup 8 with which cooperates the centrifugal clutch blocks 9 at the lower end of the shaft 10 of the single speed induction motor 11. The usual band brake 12 and drum 13 on the shaft 6, and the mechanical unloader 14. for the basket are employed. rreferablv a battery of ccntrifugals is mounted on the frame 15 and is controlled as indicatcd in Fig. 2. Each motor 11 is connected by means of a switch 16 to the line wires 17 and 18 leading to the source of power. Suitable means isprovided for selecting the voltage to be impressed on the motor circuit. As indicated, this means consists of a transformer 19 having various taps 20, 21, 22, 23 and 24. A selector switch 25 serves to connect the motor circuit to the transformer through one or other of the several contacts 26, 27 and 28 which lead respectively to the several taps 20, 21 and 22 of the transformer 19.

by the use of a single.

contact be mar w voltage will be imand the latter will Obviously. if the switch with the tap a high pressed upon the motor brin: the ccntrifugal to speed very rapidly. \Vhcrcas, if the switch be connected to the tap 22 for a lower voltage. the basketwill be brought to speed much slower.

f the units of the battery be connected 1n multiple as indicated. each basket 5 is accelerated at the same rate upon the closing of its switch 16, since the same voltage i impressed upon each motor from the motor circuit controlled by the selector switch 25. It is thus possible for the foreman, or other oliicial in authority, to set the selector switch in such position that it will connect to the current source at that voltage which. when impressed upon the several motors of the battery. by the manipulation of the several independent motor switches 16, i

will cause the baskets to accelerate similarl v at that predetermined rate Which is chosen by the foreman as suitable for the treatment of the particular material in hand. The operators at the ccntrifugals thus have no control over the ratc of acceleration of the baskets. and this set rate will be maintained until the foreman shifts the selector switch 25 to another voltage conncction to obtain a different rate of acceleration appropriate for a new batch of material of diflerent character.

on the material in a basket is sufficient- .ly dried, the motor switch 16 is opened at the contacts 31, thus deenera'izing the motor and permitting the operator through the brake 12-43 to bring the basket to a halt.,

or to such speed as will cnal o him to remove the cover from the discharge port at the bottom of the basket. In order to drive the basket for unloading. by means of the mechanical unloader 14, the motor circuit is then closed at the contacts 29 and 30, thus Th 30 which cooperate with the contacts 29 may be those of an independent. motor switch. or the switch 16 maybe a two-position switch. swinging to the line terminals 31 during the acceleration and drving op ration. and to the terminals 29 for unloading. As will be noted. the tap 23 is connected to the transformer at a point which impresses upon the motor circuit a lower voltage than that attordcd by any of the acceleration ta us 20, 21 and 22. e torque averted by the motor is less therefore during unloading than even at the lowest speed of accelera- Ill) ' the unit at upon the nected by switch 16 to the drying line 17 leading to the selector switch 25, whereas the left hand of the group is connected to the discharging line which leads to the tap 523. It will of course be understood that when a very slow acceleration of the basket is desired there may be selector switch taps which afford a voltage lower even than that used for unloading.

Various other ways of accomplishing the same result will occur to those dealing with the problem. without departing from the underlying thoughts which I claim as my invention.

I claim-- 1. A centrifugal machine installation, comprising a centrifugal basket or the like for the reception of material to be treated, an electric motor which under no load has a substantially constant speed at various voltages, a slip clutch connection between the motor and the basket, and master controlled means for selecting and impressing different desired 'vohages upon the motor to cause it to exert a predetermined torque upon the basket through the slip clutch, depending character of the'material fed to the basket and the desired rate of acceleration of the has at for the treatment of ,said material. v

2. A centrifugal machine installation, comprising a centrifugal basket or the like for the reception of material to be treated, an electric motor which under no load has a substantially constant speed at various voltages, a centrifugal slip clutch connection between the motor and the basket. and

master controlled means for impressing different selected voltages upon the motor to cause it to exert a predetermined torque upon the basket through the slip clutch, (leendingupon the character of the material ed to the basket and the desired rate of ac celeration of the basket for the treatment of said material.

3. A centrifugal machine installation, comprising a centrifugal basket or the like 'for the reception of material to be treated, an electric motor which under load has a sub stantially constant speed at various voltages, a slip clutch connection between the motor and the basket, selector means for connecting the motor circuit at different voltages to a source of power, and independent means for making and breaking connection between the motor and the motor circuit at the selected voltage to cause the motor to exert a predetermined torque upon the basket through the slip clutch, depending upon the character of the material fed to the basket and the desired rate of acceleration of the basket for the treatment of said material.

4:. A centrifugal machine installation, comprising a centrifugal basket or the like for the reception of material to be treated,

an electric motor which under no load has a substantially constant speed at various vol ages, a slip clutch connection between the motor and the basket, said clutch affording a variable grip which increases with the speed of the motor, and master controlled means for impressing different ages upon the motor to'causeit to exert a predetermined torque upon the basket through the slip clutch, ;lepending upon the character of the material fed to the basket and the desired rate of acceleration of the basket for the treatment of said material.

'5. A centrifugal machine installation, comprising a centrifugal basket or the like for the reception of material to be treated, an electric motor which under no load has a substantially constant speed at various voltages, a slip clutch connection between the motor and the basket, and master controlled means forimpressing different selected voltages upon the motor to cause it to exert a predetermined torque upon the basket through the slip clutch, depending upon the character of the material fed to the basket and the desired rate of acceleration of the basket for the treatment of said material, in combination with independent means for impressing a difi'erent selected voltage upon the motor to cause it to exert such tor ue upon the centrifugal basket through the s ip clutch that the braking action of a mechanical unloading maybe utilized to cause the basket to lag behind the motor, through the slip clutch connection to the motor.

6. A centrifugal machine installation, comprising a centrifugal basket or the like for the reception of material to be treated, an electric motor which under no load has a substantially constant speed at various voltages, a slip clutch, the grip of which increases as the speed of the motor increases, selector means for connecting a motor lead at different voltages to a. source of power, a fixed connection to the source of power at a diiferent voltage suitable for unloading, and means for energizing the motor at the selected voltage during the working period of the centrifugal and at the fixed voltage for unloading.

7 A battery of centrifugal machines comprising a grou of motors which under no load have a su tantially constant speed at various voltages. a centrifugal basket or the like for each motor, a slip clutch connection between each motor and its corresponding basket, means common to the motor group for supplying the same with current at selected voltage, and means associated with each motor for impressing a different voltage thereon.

selected volt- 8. A battery of centrifugal machines co basket or the like for each motor, a slip clutch connection between each motor and its corresponding basket, and means common to the motor group for varying in unison the voltage of the current supplied thereto, together with independent means associated with each motor for connecting the same to the source of power at a lowered voltage appropriate for driving the motor at a torque suitably reduced for an unloading operation, substantially as descri w-d.

9. A centrifugal machine comprising an electric motor, which at no load has a sub stantially constant speed at various voltages, a centrifugal basket or the like, a friction clutch drive connection between the motor and the basket, means for selecting the voltage impressed upon the motor during the working period of the centrifugal, and independent means for connecting the motor to a source of current at a voltage so reduced as to materially reduce its torque, together with a mechanical unloader serving by its drag to cause the friction clutch to slip at the thus materially reduced torque of the motor, and thus to reduce the speed of the basket to a speed less than that of the motor and to one suitable for unloading.

10. A battery of centrifugal machines.

comprising a group of electric motors which under no load have a substantially constant speed at various voltages, a centrifugal basket or the like for each motor, a slip clutch connection between each motor and its corresponding basket, a transformer having a plurality of tap connections, a selector switch associated with the trans former for energizing the motor circuits in unison at different voltages, in combination with an independent switch ineach motor circui for changing the voltage impressed upon its associated motor.

11. The method of operating a centrifugal driven by a motor which at no load has a substantially constant speed at various voltages, and having a shp clutch connection between the motor and the centrifugal, which comprises predetermining the character of the charge to be placed in the centrifugal basket, selecting the voltage to be impressed upon the motor with reference to the predetermined character of the charge in order to obtain a rate of acceleration of the basket appropriate to etiicient operation upon the charge, impressing the thus predetermined voltage upon the motor during the acceleration period of the centrifugal, decreasing the voltage after the charge has been sufliciently sub'ected to centrifugal ac tion and discharging the centrifugal during the period of reduced torque incident to the decreased voltage.

12. The method of operating a centrifugal driven by a motor which at no load has a substantially constant speed at various voltages, and having :1 slip clutch connection between the motor and the centrifugal'element, which comprises predetermining the character of the char e to be placed in the centrifugal basket, se ecting the voltage to be impressed upon the motor with reference to the predetermined character of the charge in order to obtain a rate of acceleration of the basket appropriate to efficient operation,

upon the charge, impressing the'thus predetermined voltage upon the motor during the acceleration period of the centrifugal, de creasing the voltage after the charge has been sufiiciently subjected to centrifugal action and causing the clutch to sli to reduce the speed of the centrifugal be 0W that incident to the reduced torque exerted thereon by the motor at the lower voltage, for the discharge of the centrifugal.

13. The method of operating a centrifugal driven by a motor which at no load has a substantially constant speed at various voltages, and having a. slip clutch connection between the motor and the centrifugal, which comprises predetermining the character of the charge to be placed in the centrifugal basket, selecting the voltage to be impressed upon the motor with reference to the predetermined character of the charge in order to obtain a rate of acceleration of the basket appropriate to eificient operation upon the charge, and impressing the thus predetermined voltage upon the motor to bring the basket to speed at the predetermined desired rate of acceleration.

In testimony whereof I have signed my name to this specification.

CHARLES A. OLCOTT.

basket or the like for each motor, a sli clutch connection between each motor an its corresponding basket, and means common to the motor group for varying in unison the voltage of'the current supp led thereto, together with independent means associated with each motor for connecting the same to the, source of power at a lowered voltage appropriate for driving the motor at a torque suitably-reduced for an unloading operation, substantially as described.

9. VA centrifugal machine comprising an electric motor, which at no load has a substantially constant speed at various voltages, 'a centrifugal basket or the like, a friction clutch drive connection between the motor and the basket, means for selecting-the voltage impressed upon the motor'during the working period of the centrifugal, and independent means for connectingthe motor to a source of current at a voltage so reduced as to materially reduce its torque, to-

ether with av mechanical unloader serving 5 its drag to cause the friction clutch to w of the motor, and thus to reduce the speed of the basket to a speed less than that of the motor and to one suitable for unloading.

10. A battery of centrifugal machines. comprisin a group of electric motors which .under no oad have a substantially constant speed at various voltages, 1a centrifu al basket or the like for each motor, a slip clutch connection betwcen'each motorand its corresponding. basket, a transformer having a. lurahty of tap connections, a-

' selector switch associated with the transformer for energizin the motorcircuits in unison at dilferent votages, in combination with an independent switch in'.each motor to the predetermined character of the charge p at' the thus materially reduced torquetion and causing the clutch to sli in order to obtain a rate of acceleration of the basket appropriate to eflicient operation upon the charge, impressing the thus pre determined v tage upon the motor during the acceleration eriod of the centrifu al,

"decreasing the v0 tage after the charge as been sufliciently subjected to centrifu al action and discharging the centrifu a1 uring the period of reduced torque inci cut to the decreased voltage. v

'12. The method of operating a centrifugal driven by a motor which at no load has a substantially constant speed at various voltages, and having a slipclutch connection between the motor and the centrifugal element, which com rises predeterminmg the character of the c urge to be placed in the centrifugal basket, se ecting the voltage to be impressed upon the motor with reference to the predetermined character of the charge in order ,to obtain a rate of acceleration of the basket appropriate to efiicient operation.

' -13. The method'of operating a centrifugal driven by a motor which at no load has a substantially constant speed at various voltages, andflhaving a slip clutch connection between the motor and the centrifugal, which comprises predetermining the character of the charge to be placed in the centrifugal basket, selecting the voltage to be impressed upon the motor with reference to the predetermined character of the charge inorder to obtain a rate of acceleration of the basket appropriate to efiicient o oration upon the'charge, and impressing e thus 'redetermined voltage u on the motor to ring the basket to sp at the prede ter-.

'rnin'eddesired rate of acceleration.

'name to .this specification.

4 GHABLES A. OLCOTT.

of Correcti'on. f

is hereby certified that" Letters Patent No. 1,536,915, granted May 5, 1925,- upon the a plicatidn of Charles'A. Oloott; of New York, 'N. Y., for an improvement in entrifugal'Machines an error appears in the a line 49 quiring correction. as follows: age

printed specification reclaim 3, a tar-the word under insert the word no; and that the said letters l atent should be read-with this correction Signed and sealed this 2d day oi June, D. 1925.

therein that the same may conform to the record of the case in the Patent KARL'FENNING, Acting b'ommissimwr of Patents.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,536,915, granted May 5, 1925,

upon the applicatidn of Charles A. ()loott; of New York, N. Y., for an improvement in Centrifugal Machines, an error appears in the rinted specification requiring correction. as follows: Page 4 line 49, claim 3, a ter the word under insert the word no; and that the said Letters Patent should be read with this c0rrection therein that the same may conform to the record of the case in the Patent ()fiiee. l

Signed and sealed this 2d day of June, D. 1925.

[amp] KARL FENNIN G,

Aeting Commissioner of Patents.

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