US2648806A - Motor control for centrifuges - Google Patents

Description

Aug. 11, 1953 c. F. DlNLEY MOTOR CONTROL FOR CENTRIFUGES 2 Shets-Sheet 1 Filed Marbh 24, 1948 m m. m V m ATTORNEYS.

g 1953 c. F. DINLEY MOTOR. CONTROL FOR CENTRIFUGES Filed March 24/ 1948 2 Sheets-Sheet 2 WQZOUMW I mSC. ON

2: om em 3. om ow om 2 0 2 1 x m Nb ok we com Uum Q P5o ONN on? com com ooh cam com OON u mwuza w "mm w m0. E NF N .d mm m w m w m .A m, W Y B -NNHW Patented Aug. 11, 1953 MOTOR CONTROL FOR CENTRIFUGES- Clarence F. Dinley, Detroit, Mich., assignorto .Detrex Corporation, Detroit, Mich., a. corporation ,of Michigan Application March "24, 1948, Serial No. 16,868

Claims. 1.

This invention is concerned with the driving of machinery suc'h'as rotary extractors or driers', cement mixers, steel mills, agitators, turbines, printing presses, etc, by means of electric motors.

The operation of such machines at high speeds is usually attended by excessive vibration due, for the most part, to uneven or unbalanced distribution of the materials undergoing treatment in them. The vibration so induced is not only objectionable from the standpoint of the noise incidently created, but also by reason of the rapid wear it occasions in the machines so driven.

My invention has for its chief aim to overcome the above mentioned drawbacks. This desideratom is realized in practice as hereinafter more fully set forth, through provision of automatic means whereby the voltage impressed on. the driving motors is changed step by step and the different voltages maintained for difierentintervals for development of variant prescribed torque values requisite to the acceleration of the centrifuges at such rates that the load is aflorded ample opportunity to adjust itself before the desired maximum speed is reached.

Other objects and attendant advantages will appear from the following detailed description of the attached drawings, wherein: Fig. l is a diagrammatic view showing by Way of example, a centrifuge with driving mechanism therefor embodying my invention; and

Fig. 2 is a graph showing a prescribed torque curve in accordance with which the potential impressed upon the motor is changed at varying intervals to start the centrifuge and control its acceleration in accordance with my improved method.

Referring in greater detail, first more especially to Fig. 1 of these illustrations, the numeral 5 represents a centrifuge which may be thehorizontal axis cylinderic drum of an extractor such as is used in dry cleaning operations to expel entrained moisture from a mass of textile materials or articles 5 placed within it subsequent to treatment with solvent fluid. At M is indicated an electric motor which will be understood to be of a variable speed alternating current type, and which is relied upon to drive the centrifuge 5 through a mechanical connection in the form of a chain or belt 8.

The means which I have devised for controlling the driving motor M of an organization such as above exemplified, includes an auto transformer 9 which, by means of leads 9a and 9b, is connected across the conductors 110 and H of a 220 volt power line, and which is shown-ashaving 220 volt, 130 volt and 160 'volt taps, one ter minal ll of the motor M being connected by a conductor l3 directly to the side ll! of the power line. The control means further includes a retary timer T whereof the shaft I ,6 is arranged to be driven, through speed reduction gearing IT, by a small synchronous motor designated M Secured to the shaft of the timer T are pairs of rotary earns 19, 2!); 2i, 22; 23, 24; 25, 2B and 21, 28 for actuating corresponding pairs of downwardly spring biased switch contacts [9a, a; 21a, 22a; 23a, 24a; 25a, 26a. and 21a, 28a.

Through conductors l9b, 21b, 23b, and 25b, the switch contacts 19a, 21a, 23a, and 25a are all connected to a lead 30 extending from the conductor II of the power line; and through other leads 26b, 22b, 24b, and 26b th switch contacts 291;, 22a, 24a, and 260. are connected to corresponding terminals of the magnet coils 3!, 36, 4| and 460i relays R, R, R2 and R3 respectively, the other terminals of said coils being all connected to a conductor 39 which extends to the lead 9110f the transformer 9. Contact 32 of relay R is connected, through a lead 52, to the lead 9a, of transformer 9; and contact 33, through a lead 53 to the contact 39 of relay R. Contact 3'! of relay R is connected, through a lead 51, to the 130 volt tap of transformer 9; contact 38, through a lead 55, to contact 44 of relay R2; and contact 40, through leads and 51', to one terminal 58 of motor M. Contact 42 of relay R2 is connected, through a lead 59, to the 160 volt tap of transformer 55; contact 43, through a lead 66, to contact 49 of relay R3; and contact 45, through a lead 6|, to the conductor 51. Contact 41 of relay R3 is connected, through a lead 83, to the 220 volt tap of transformer 9; while the contacts 48 and 58 are connected together and to the conductor 5'1.

Switch contact 21a of the timer T is connected, through a lead Zlb, to the terminal 53 of the synchronous motor M, the other terminal 154 of said motor being connected, through a lead 65, to the line conductor H. The switch contact 28a is connected, through a lead 231), to the line conductor to; and bridging the leads 2'"), 23b is a conductor in which is interposed a push buttonswitch 8'! for starting the timer motor M.

Operation The'several cams of the timer Tare adjusted circumferentially and set on the shaft 16 to determine an operative cycle of the motor M as follows;

,Let it be assumed that the time required for extraction is four minutes and that the timer is designed to turn through a complete rotation for each extraction cycle. Upon pressing the push button 61, the synchronous motor M is set in motion to rotate the timer shaft iii in the direction indicated by the arrow on one of the cams. In a second or so after starting, the high point of the cam 2'! is advanced from beneath the switch contact 27a which is thereby suddenly freed to drop and close upon the contact 28a so that the motor M keeps running after release of the push button 61. point of cam l9 will pass beyond the switch contact 59a allowing the latter to drop and close upon the contact 2011, with consequent current flow through the magnet coil 3| of relay R by way of conductors 20b, 39 and 9?). By actuation of the relay R, the armature thereof closes the contacts 32 and 33 so that current at 220 volts will pass through the motor M, the course of the current, starting with the line conductor 1 i, being by way of the conductor 9a, contacts 32 and'tS of relay R, conductor 53, armature and contacts 39, if) of relay R, conductors 53, motor M and con ductor l3 to the power line conductor iii. ihe setting of the cam 2i is such that, after the e?- piration of six seconds from the time of closing the contacts 19a, 20a, its high point will underpass the switch contact 2M whereupon the latter, in dropping, will close upon the contact 22a.

During this interval of six seconds at the 220 volt potential, sufficient torque is developed in the motor M to overcome the inertia of the centrifuge 5 and bring it to a rotative speed of approximately 725 R. P. M. at the point a on the torque curve A of the graph in Fig. 2. Upon closing of the switch contacts Zia, 22a, current will flow from the power line conductor H, by way of conductors 3i], iilb, 22b, coil 36 of relay R and conductors 39 and 9b, to power line conductor iii. By consequent actuation of relay R, the armature of the latter breaks with the contacts 39, 49 and makes with the contacts 3?; 33 where upon current at 130 volts will be impressed upon the motor M, the current flow being from the power line conductor H by way of conductor to, the large portion of transformer 9,-conductor 5?, armature and contacts 37, 38 of relay R, conductor 55, armature and contacts 5 5, 55 of relay R2, conductors 5| and 5! through the motor M, and thence through the conductor i3 to the line conductor iii. The setting of the timer cam 23 is such that at the expiration of twenty-nine seconds from the time of closing of the contacts 25a, 22a, its high point will clear the contact 23, which in dropping, will close upon the contact 2 3a. During the aforementioned interval of twenty-nine seconds with supply of current at 130 volts to the motor .M, the requisite torque will be developed to accelerate the centrifuge 5 at a relatively low rate from 725 R. P. M. from the point a on the torque curve A of the graph in Fig. 2 to 1080 R. P. M. at the point a By closing of the switch contacts 23a, E ia, current will flow from the power line conductor i! by way of the conductors 38, 23b, 2th through coil M of relay R2, and from thence through the conductors 39 and 9a to the power line conductor l8. By ensuing actuation of relay R2 its armature will break with contacts 44, 45 and make with contacts 42, 53. Current at 160 volts will thereupon flow from power line conductor H, by way of the lead 9a, through a large part of the transformer 9, then by way of conductor Immediately thereupon, the high ductor 68, armature and contacts 49, 59 of relay 4 R3, and conductor 517 to motor M, and then from the latter to the power line conductor it. At this higher voltage, sufficient torque will be developed in the motor to further accelerate the centrifuge, still at a relatively slow rate as before, from 1080 R. P. M. at the point a to 1590 R. P. M. at the point a on the torque curve A of the graph. This voltage will be maintained for fifty-one seconds when the high point of the timer cam 25 will underpass and release switch contact 25 to close upon contact 251). When this occurs, current will flow from power line conductor H by way or" conductors 30, 25b, 25b to coil 36 of relay R3, and

, from the latter, through conductors 38 and 9b,

to the power line conductor 99. Upon resultant actuation of the relay R3, a new circuit will be established through motor M with current flow at 220 volts, by way of conductor 9a, transformer 9, conductor 63, armature and contacts 41, 48 of relay R3, and conductors 5?, I3. The torque there-by developed will accelerate the centrifuge 5 within about ten seconds from a speed of 1500 R, P. M. at the point a on the torque curve A to the desired maximum speed of 1800 R. P. M, at the point a at which it will thereafter be maintained until the completion of the extraction cycle. By controlling the acceleration in this way between the points a and a through stepwise increase in the voltage impressed upon motor M, the material being extracted is afforded the opportunity to adjust itself within the centrifuge before the latter attains the desired maximum speed, so that no vibration and noise will attend its operation when it is finally driven at full speed.

The amperage curve B on the graph shows how the current supplied to the motor M from the time of starting at 220 volts and through the changes in the voltage first to 130, then to and finally back to 220 during the successive acceleration periods of six. twenty-nine, fifty-one, and ten seconds. During the remainder of the timer rotation, which takes about two minutes and forty seconds, the cams 2Q, 22, 2t, and 26 gradually raise the contacts Zea, 2 3a and 26a, keeping them closed with the contacts lSa, Zia, 23a and 25a respectively. At the completion of the rotation, the high points of the cams 2t, 22, 2 5-, and 25 underpass the switch contacts 260:, 22a, 24a and 25a and simultaneously release them to fall away from the contacts lilo, 2 Id, 230., and 25a, whereby all the circuits to motor M are broken as in Fig. 1. Also at the sam time, the high point of cam 28 will underpass the contact 28a which, in dropping, will interrupt the circuit through the synchronous motor M, likewise as shown in Fig. 1 with consequent completion or" the cycle,

It is to be understood that the values herein used to exemplify my invention are subject to wide variation in actual practice depending upon the capacities and sizes of the driven machines, the materials which are to be extracted, and the ratings of the driving motors. I do not, moreover, consider myself restricted to the employment of the specific circuit control devices which have been shown and described by way of illustration, since in practice, these may be replaced by equivalents capable of performing like functions as will be readily understood by those skilled in the art of electric motor control.

Having thus described my invention, I claim:

1. The method of accelerating a single phase A. C. electric motor-driven centrifuge or the like with an initially unbalanced load, which comprises impressing upon the motor line voltage for a short time interval sufficient for development of requisite torque to start rotation of the centrifuge, then reducing the voltage to a point for development of requisite torque for acceleration of the centrifuge at a different rate during a predetermined time interval, and thereafter increasing the impressed voltage step by step up to line voltage for development of different degrees of torque requisite for acceleration of the centrifuge at correspondingly different rates during different predetermined time periods whereby the initially unbalanced load is afforded the opportunity to adjust itself within the centrifuge before the latter attains the desired maximum speed.

2. In mechanism for accelerating an electric motor-driven centrifugal with an initially unbalanced load from rest to full speed, a transformer connected across a power line and having a plurality of diflerent voltage taps; normally-open switches respectively interposed in conductors connected to individual taps of the transformer in a wiring system containing the motor; and cycle timing means comprising a shaft with rotary cams thereon arranged to actuate the several switches in succession, an electric motor with reduction gearing for driving the shaft, a manual starting switch in circuit with the motor, a normally open auxiliary switch connected in parallel with the manual switch, and an additional cam on the timer shaft for closing the auxiliary switch upon starting of the latter motor and for opening said auxiliary switch at the completion of a single rotation of the cam shaft.

3. In mechanism for accelerating an electric motor-driven centrifuge with an initially unbalanced load from rest to full speed, a transformer connected across a power line and having a plurality of different voltage taps; normally-open relays interposed respectively in conductors connected to the individual taps of the transformer and one in a conductor independent of the transformer comprised in a circuit containing the motor; and cycle timing means including normallyopen switches interposed with the actuating coils of the respective relays in conductors of another circuit, a shaft with rotary cams thereon arranged to selectively actuate the several switches, an electric motor with reduction gearing for driving the shaft, a manual switch in circuit with the motor, a normally-open auxiliary switch connected in parallel with the manual switch, and an additional cam on the shaft for closing the auxiliary switch upon starting of the latter motor and for opening said auxiliary switch at the completion of a single rotation of the cam shaft.

4. In mechanism for accelerating an electric motor driven centrifuge with an initially unbalanced load from rest to full speed, a transformer connected across a power line and having a plurality of different voltage taps; normally-open relays interposed in conductors connected to the respective taps of the transformer in a wiring circuit containing the motor; and cycle timing means including separate normally-open switches interposed with the coils of the relays in conductors in parallel in another circuit of the wiring system, a shaft with rotary cams thereon arranged to selectively actuate the switches to cause closing in turn of the corresponding relays for impression upon the motor for different time intervals, of different voltages through the respective taps of the transformer, and means for turning the shaft through a complete rotation for each operating cycle of the centrifuge.

5. In mechanism for accelerating an electric motor driven centrifuge with an initially unbalanced load from rest to full speed, a transformer connected across a power line and having a plurality of different voltage taps; normally-open relays interposed in conductors connected to the respective taps of the transformer and one in a conductor independent of the transformer comprised in a circuit containing the motor; and cycle timing means including normally-open switches interposed with the coils of the respective relays in conductors of another circuit and cycle timing means comprising a shaft with rotary cams thereon for selectively closing the several switches to cause closing, in turn, of the corresponding relays for impression upon the motor for different time periods, of different voltages through the different taps of the transformer and of full line voltage by way of the aforesaid separate conductor, and means for turning the shaft through a complete rotation for each operating cycle of the centrifuge.

CLARENCE F. DIN'LEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 762,738 Meyer June 14, 1904 1,851,716 McLenegan Mar. 29, 1932 1,932,280 McLenegan Oct. 24, 1933 2,237,008 McNairy Apr. 1, 1941 2,295,355 Prescott Sept. 8, 1942 2,480,589 McKenney Aug. 30, 1949 2,492,350 Blume et al Dec. 2'7, 1949

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