US1920985A - Pump controlling mechanism - Google Patents

Description

Aug. 8, 1933. w HUGHES 1,920,985

PUMP CONTROLLING MECHANISM Filed Jan. 21, 1930 2 Sheets-Sheet l FI'GJ. 7

[/IVE/YTORZ WILL/HI? E. HUGHES.

Aug. 8, 1933. w. E. HUGHES PUMP CONTROLLING MECHANISM 2 Sheets-Sheet 2 Filed Jan. 21, 1930 WILL/HM E. HUGHES.

Patented Aug. 8, 1933 7 1,920,985 Puliir CONTROLLING MECHANISM 7 William E. Hughes Chicago, Ill.,assignor to Sullivan MachineryCompany, a, Corporation of Massachusetts Application January 21, 1930. Serial No. 422,429

20 Claims.

This invention relates to controlling mechanism for an electrically driven compressor for starting and stopping the motor automatically in accordance with the demands for air. More particularly my invention relates to controlling mechanism for a synchronous motor connected to a compressor for driving thesame, to start and stop the motor.

when air is required or when the demand for air decreases- One object of my invention isto provide improved controlling means for automatically stopping and starting a motor driving a compressor which is arranged to shut down the motor for a long period 'shouldthe demand for pressure fluid be but small. A further object of my invention is to provide improved automatic start and stop control mechanism for a synchronous motor connected to drive a compressor. A still further object of my invention is to provide an improved control mechanism for-1a synchronous motor 'which drives a compressor and is arranged to automatically start and stop the synchronousmm tor in accordance with-the demands for pressure fluid. A more specific object of my invention is to providestart and stop control mechanism for 1 such a synchronous motor which need not be started and stopped in rapid succession when the demand for pressure'fluid falls 01f. Further objects of my invention will become apparent in'the course of the ensuing description and will bemore particularly pointed out in the accompanying drawings. V l

I have, disclosed for purposes of illustration one embodiment which my invention may assume in the -accompanying drawings, in'which Fig; 1 is a diagrammatic viewof a compressor directly connected to a synchronous motor to be driven by the latter.

Fig. 2 is a wiringdiagram of controlling mechanism for stopping and starting sucha synchronous motor in accordance with the principles of my invention. r y I In Fig. 1 there isdisclosed a compound compressor having a low pressure cylinder 6 and a high pressure cylinder '7. An intercooler 8 is provided through which the fluid compressed bythe low pressure cylinder 6 flows to the high pressure cylinder '7; Discharge from thecompressor takes place through a conduit 9 into a receiver tank 10. Asynchronous motorll is directly connected to the crank shaft-12 of the compressorto drive the latter. A valve 13 is arranged inthe inlet 14 of the lowipressure cylinder, beingactuated by "a spindle 15 connected to the piston 16 of a servo motor 17. When the servomotor is actuated to bring the valve 13 to olosedposition, the admission of air or other fluid to the low'pressurecylinder 6 is completely out on and the compressor is thereby unloaded. Fluid for actuating the servo motor 17 is delivered thereto by means of a pipe .18 under the control of a pilot valve 19, the pilot valve being connected tothe receiver tank lbv by'a pipe20. The pilot valve 19 may be set for a predetermined range of pressure within which it is desired that the compressor shallnormally'operate. For example, the pilot valve 19 may be set so that fluid isdelivered through pipe 18 to unload the compressor when the pressure in the receiver tankreaches 100 pounds, and to vent fluid from the servo motor 17 when the pressure has dropped again to 90 pounds. 1

The pilot valve 19' is equipped with a solenoid 21 which moves the pilot valve mechanism into position to Vent the servo motor 1'7 whenever the said solenoid 21 is deenergized. In other words, the compressor runs unloaded at all times when the solenoid 21 is deenergized. My improved controlling mechanism isdesigned to cooperate with the solenoid 21 to'energize the same when the motor 11 is synchronized on the line, the solenoid 21 being deenergized whenever the ;motor is stopped and receiving current only when the motor has been broughtup to speed and synchronized so as to be able to carry the full load or the compressor.

My improved mechanism is furthermore designed to start and stop. the motor in accordance with the demands for pressure fluid. ,I have provided a pair of pressure switches 22 and 23. The. pressure switch 22 is designed to operate within a range of pounds to approximately pounds in the illustrative embodiment disclosed herein in which the pilot valve 19 operates within a range of 90 pounds and pounds; Pressure switchg23 closes at a pressureof 90 pounds and. opens lat a pressure of 100 pounds in the illustrative embodiment disclosed herein. The synchronous motor 11 is supplied with alternating current by way of three lead wires 24, 25 and 26. -A main linecontactor switch 27 is arranged to disconnect or. connect the lines 24, 25 and 26 to the lines'28, 29 and 30 respectively whichare connected tothe rotating field of the motor. A solenoid 31 is connected to the actuating lever3l of the switch 27v so as to close the same when current flows through the solenoid 31 to actuate the same. Such current is supplied by means of a control circuit which includes the wire 32 connected to'themain lead 26, a wire 33, a wire 34 and a manually the synchonous motor if the pressure acting on pressure switch 22 be below 80 pounds. The circuit is completed through switch 22, a wire 36, wire 37, the switch 38 of timing relay 39, a wire 40, an overload relay 41, and wire 42 which is connected to the main lead wire 24. The overload relay is or a well-known type .having .a coil 43 inserted'inthe main lead line 24. The time relay 39 is of a well-known type which is designed to open the switch 38 after current flows for a predetermined length of time, for example five minutes, through its coil 44.

The pressure switch 23 is designed to control the flow of current throughcoil 44; and controls for this purpose a circuit including a wire 45 connected to the motor terminal 30, a wire 46, awire 47 and the holding coil 48 of a normally closed magnetic switch 49. This circuit is completed by way of a wire 50 and a wire 51 which is connected to the motor terminal 29. When no current flows through the coil 48 the magnetic switch 49 isclosed and .current flows by 'w'ayrof wires 45 andAGfthemagnetiC switch 49, wiref52, the coil 44, .wire153 and wire 51 to the motor terminal 29. As has beenabove explained, if current flows through the coil .44 for a longer'period than the predetermined amount .(which'in this embodiment is set as fiveminutes) the'switch 38 will be opened breaking thecontrol circuit and deenersizing. the coil 31 so as to openfth'e switch27.

\ Anexciter 54 is provided for supplying "direct current to the field 55 of the synchronous motor 11. As shown in Fig. 2, the circuit connecting exciter. 54, to. the. field 55 is'broken at the field contactor 56. When the switch 56, is closed current flows from the exciter through'lines 57 and 58 to thefield 55.and'returnsbywey ofiwires 59,-.60, the switch 56-and wire 61. The cont actor 5 6.is openedand closed by a solenoid 62 to which currentissupplied by, way of a wire 63 connected to the main lead wire 26. The circuit is completed through .a line 64, a switch [65, wire 66, wire 34,.switch 35', wires 36and 37, switch 38, wire 40, switch 41, and wire .42 which is'connected to line 24. It will thus'be seen that if the control circuit ior'the motor be broken, the solenoidjfiZ will at once he deenergize'd'. It will furthermore benoted that the solenoid 62fcannot be energized untilthe switch 65 is closed. A differentialrelay 68 is providedfor controlling the switch 65. One side of this relay is supplied with current by ' wires 45, 69,70,34, switchv 35 etc., the circuit being completed to mainiead wire .24 when the, main control circuitis closed. The

other side or the difierential relay is supplied with alternating current which is induced in the held 55 as soon as the revolving fieldis setup in the motorll by'closing switch 27. This current flows by way of wire 58, wire 71, switch72, wirev 73, to the, differential relay and returns by wire. '14 and wire '59 to the field 55. Theirequency of this induced alternating current at first is relatively high due to the, motor armature being at a stand-still. However, as the armature is brought up to 'nearitssynchronous speed, due to the use oft usual amorti'seur windings or a usualstar ing motor if desired,the frequency of the induced current is reduced to a very low value asthe slippage between the armaturea'nd rotating field is now small'and accordingly the two sides. of the dilierential relay are supplied with current of difierent frequency. As is well understood in the art, the relay.68 is then operative to closeswitch '65, whereupon coil BZis'energized so as to close switch so and'open switch 72. Closure of switch 56 supplies direct current to field 55 whereupon the armature is pulled into step so that the motor operates synchronously. It is, of course, unnecessary to continue the flow of current through the difierential relay 68 when the motor is once synchronized and placed across the line.

In'order to coordinate the pilot-valve 19 with synchronizing of the'motor 11 I connect the solenoid 21 in parallel with the coil 62 by means of wires '75 and 76 connected to wires 63 and 64 respectively whereupon it will be seen that the pilot valve effects loading of the compressor when the motor is synchronized. A circuit for shortcircuiting switches 35 and 22 is provided and includ'es wire 77, switch 78 and wire 79 which is connected to the wire 33. The switch '78 is closed when the switch'27is closed.

In the operation of my improved control, assurning that the equipment has been shut down and that the receiver pressure is below 80 pounds, switch'22 will have been already, closed as it closeswhen pressure drops toor below 80 pounds. To initiate operation of the equipment the operator then manually closesswitch 3-3, whereupon motor switch 2'? is closed due tosolenoid'iii being energized by current supplied from main lead 26, wires 32, 33, 34, switch 35, wires 36, 37, nor.- mally closed switch 38, wire 40, overload'switch 41 (which is normally closed) and-wire 42 tornain lead 241 A rotating field is thusv set up inthe synchronous motor and its armature is brought up substantially to its synchronous speed by'the use of ainortiseur windings in a well-known man; ner. When the armature isnear substantially synchronous speed the differential relay mechanism 68 operatesto close, switch 65 thereby energizingsolenoid .62 to open switch '72 and close switch 55 thus supplying the field winding 55 with direct current from exciter 54 and causing the armature to be pulled into step and up'to synchronous speed. ,Withv the motor'being synchronously driventhe compressor isnow in condition to be ,lo'a'dedand this is eiiect'ed by the energizationof solenoid ,2i s'uhstantially simultaneously with the'energization ,o'i solenoid 62, withwhich the solenoid 21 is connected in parallel as by wires,'75f.and 76; Upon energization of solenoid 21, pilQ valve 19, vents pipe lsand cylinder 17 to'atmosphere thereby'permitting un loading valve 'l3'to" open" andcauseloading oi the compressor. v

I Whenthe compressor has increased the receiver pressure to 95 pounds, switch 22 is opened,

but the compressor-continues to operate because upon closurelof wswitchjfrl'lgswitcl'i 78 was also' closledithus'causing mains'witch solenoid 31 to be energized by current supplied from main lead 26 throughwires 32, 33,79, switchj'iii, wires. 77, 37, switchr38, andwires 4i) .and42 connectedto the main lead 24.. nlsdlaslong as the receiver pressure is at'or below 90 pounds notime lllllltlS imposed upon the compressor, operation because the timeelement is, disconnected in thatswitch 23 is arranged to ,close when receiver pressure is at or, below, 90 pounds, thus'energizing coil'48ffof magnetic switch 49 to .open the otherwise 'nor mally closed magnetic switch. Receiver-pressure thereby continues to buildup untilit reaches 100. pounds when pilot valvel9 unloadsiithe cornpressor; andat the same time, or just prior there'- to, switch 23isopened by receiver pressure, there by deenergi'zing'c'oil 48 by breaking the. circuit ineluding wires 45,46, switch 23, magnetic'switch coil 48, wires 50, 51 and terminal29, thus per. mitting magnetic switch 49 to close, whereupon the time relay 39 is startedby current flowing through- wires 45, 46, switch 49, wire 52, coil'44, and wires 53, 51 to terminal 29. After current flows through the time relay coil 44, for say five minutes, timerelay switch 38 is opened automatically, thereby deenergizing main switch coil 31 by breakingits circuit includingmain lead 26, wires 32, 33, 79, 7'7, 37,140, etc.,-and thus causing main switch 27 to be opened and stop operation of the synchronous motor. If, during this five minute period, the receiver pressure drops to or below- 90 pounds, pilot valve 19 operates to reload the compressor and at the same time, or just prior thereto, switch 23 isclosed, thus energizing coil 48, and opening the magnetic switch 49 whereby the time relay coil 44 is de- 1 energized and the five minute period thus preformed:

vented from becoming effective. The compressor will thus continue to operate untilreceiver pressureagain reaches 100 pounds when the abovecycle may-again take place. It may happen ever, 'will not close until receiver pressure drops.

to pounds. When this occurs, there-isreestablished the starting circuit frommainle'a'd 26 though'wires 32,33, 34, switch 35, wires 36, 3'7, switch 38, (which is automaticallyreset after being opened upon expiration of its five minute period) and wire 40 to'lead 24.

When the motor circuit is broken 'so as to stop the compressor, solenoid 21 is deenergized, thereby positively arranging the mechanism of pilot valve'l9'so' that the passage forthe flow of fluid from the receiver through pipe 20 to pipe- 18 is maintained open and accordingly actuates servo motor 1,? and-unloading valve 13. This makes certain that the compressor may re-start in its unloadedcon'dition. It is thus seen that the following series of pressure operations are perlst-The compressor when operating loaded,

continuesftooperate until receiver pressure is built up to 100 pounds, at'which time switch 23' is'c1osed to start the time relay 39, and simultaneously therewith, or justafterwards, the coinpressor is unloaded by pilot valve 19 and runs idle.

2nd.-With time relayclosed, the compressor idles for say, five minutes, and then stops until receiver pressure drops to 80 pounds when switch 22 closesand the compressor pumps up to 100 pounds v '3rd.-'l-lowever, if receiver pressure drops to or below 99 pounds before expiration of the five I minute period, the pilot valve loads the-compressor and the time relay is disconnected by closure of switch23, whereupon receiverpressure is again built up to 100 pounds. a it will of course be understood that the various pressure limits herein described may be varied in accordance withdesired operating conditions,

and it .willalso be understood that the upper pressure, limit for the time relayswitch 23 may be slightly less than the unloading limit of the pilot valve 19, thereby insuring that the time period will be;v started when the receiver pressure has .drops to 91 pounds. is shut down (by opening of switch 38) withthe j.

pressor. which would be the case if the lower or loading limit of the pilot valve 19 was higher than the pressure at which the pressure switch 23 'is closed to terminate running of the time interval of switch 38. For example, assume the compressor toload at 91 pounds and the running of the time limit to be interrupted only if thepressure drops to pounds. The withdrawal of air or other fluid from the receiver tank 10 may be at so slow a rate that the 5 minute time interval elapses before the pressure in the receiver tank 10 In this case the motor 11 compressor unloaded. But the withdrawal of fluid from the receiver tank 10 may be fast enough to lower thepressure therein to 91 pounds before the '5. minute time interval elapsesj The compressor now resumes pumping of fluid into the 5-;

receiver tank 10. The running of the time period of switch 38 cannot be interrupted, however, un-

less the pressure drops still lower (to 90 pounds) and the compressorinight therefore. be stopped (by opening of switch 38 and the ensuinginterj ruption of. the current supply to the motor 11) I in'loaded-condition. While disconnection of the power'supply to the synchronized motor unloads the compressor through thefldeenergization of solenoid 21, yet this operation may not be in exact coordination, whereby the compressor might be stopped during compressing operations. However, by havingthe coil 44 of the time limit switch 1 disconnected by openingof pressure switch 23 at apressure slightly above the unloading limit this I diiliculty will be avoided. It it is desired to rely uponthe de-energization Of'SOlBl'lOldfZl to unload the compressor, the low limit of the time relay can be set at a pressure below the loading limit'of the pilot valve. In this case, the pres-s sureis pumped to pounds, the pilot valve then unloads the compressor, the motor is; stopped after a predetermined time interval (which may be made much shorter than five minutes if desired), and pumping-is resumed when the receiver pressure falls to 80 pounds.

If such precise adjustment of the pressure switch 23 werepossible that its operationwould coincide exactly with the operation-of the pilot valve l9, in other Words if the pressure switch 23 could be set to open at precisely the same pressure which causes functioning of the pilot valve 19 and to close at precisely the same pressure which causes the pilot valve 19 to vent, the slight differences in pressure limits for operating. the time element would not have to be employed. It will, therefore, be understood that where reference is made to having the pressure limits for the time element the same as the pressure limits for the unloading pilot valve, variations may or may not .i be employed in accordance with the above description. It is also seen that magnetic switch 43, 49

may be eliminated. ifswitch 23 is designed to jmaintained substantially.

47 is connected directly to coil 44, the operation otherwise being as previously described.

While there is in this application specifically described one form which the inventionmay assume in practice, it-will be understood that this form of the same is shown for purposes of illustration and that the invention may, be modified and embodied in various other forms without departing from its spirit'or the scope of the ap pended claims. a

What I claim as new and desire tosecure by Letters Patent is: g A

1. In a compressor system having a prime mover operated compressor provided "with un:

loading mechanism and connected to supply pressure fluid to a receiver, the combination comprising a pilot valve constructed and arranged to effect loading and unloading'of said compressor at predetermined limits of pressure in said receiver, means whereby when the compressor is unloaded it will idle for a limited period of time and then be stopped, and means whereby if thereceiver pressure drops substantially to the loading limit of said pilot valve before'said time period expires means constructed and arranged, when rendered" operative upon occurrence of a predetermined receiver pressure, to determine a limited period of time'and to stop operation of the compressor when said time period expires independently of further pressure control of the time determining means,

and means for initiating operation of said time determining means when receiver, pressure reaches a predetermined maximum value.

I 3. Apparatus for controlling a prime mover operated compressor having load controlling means comprising, in combination, means for loading and unloading said compressor atpredetermined limits of discharge pressure from said compressor, time control means rendered operative at a predetermined pressure limit and render'ed inoperative at another predetermined limit, and means for controlling said time control means so as to render the same operative and arranged to permit said time control means to stop operation of the compressor upon expiration of the predetermined time period even though the compressor discharge pressure remains between the pressure limits at which said time control means is rendered operative or inoperative.

4. Apparatus for controlling a prime mover operated' compressor comprising, in combination, a

pilot valve constructed and arranged to control the loading and'unloading of said compressor at predetermined lower and upper pressure limits respectively, and separately compressor discharge pressure controlled means whereby when the comp ressor isunloaded at said upper pressure limit the compressor is adapted to idle for a predetermined period of time and then automatically be stopped even while the upper pressure limit is 5.Apparatus for controlling a prime mover operated compressor having load controlling mechanismcomprising, in combination, means for loading and unloading the compressor at lower and upper pressurelim'its respectively, time controlling means arranged to stop compressor operation when the compressor idles for a predetermined-length of time between substantially its loading and unloading limits, and means whereby said time controlling means is constructed and arranged to stop the compressor operation at the end of the same predetermined time irrespective of variations in the compressor discharge pressure between said loading and unloading limits.

6. Apparatus for controlling-a prime mover operated compressor comprising, in combination, a pilot valve constructed and arranged to control the loading and unloading of said compressor at predetermined pressure limits, time control mechanism arranged to stop compressor operation a pilot valve constructed and arranged to control the-loading and unloading of said compressor at predetermined pressure limits, time control mechanism arranged to stop compressor operation when the compressor idles unloaded for a predetermined time period, a main switch for controlling saidprime mover, a plurality of main control circuits for controlling said switch and each including said time control mechanism, means whereby one of said control circuits is opened when pressure discharge pressure reaches a. predetermined-value, and .means for opening the other of said circuitsincluding a circuit arranged upon occurrence of a predetermined higherpressure limit to initiate operation of said "time control mechanismwhereby the-second one of said main control circuits is controlled in accordance with a given time period.

8. Apparatus for controlling a prime mover operated compressor comprising, in combination, a solenoid operated controlling means for said prime mover whereby the prime mover may be "started and stopped, time control means for determining a period of time during which said compressor may run idle, main control circuits for said solenoid and each of which includes said time control means, means for opening one of said control circuits when a predetermined compressor discharge pressure obtains, and means for initiating operation of said time control means upon occurrence of a predetermined higher discharge pressure whereby upon expiration of said time period the second one of said maincontrol circuits automatically effects opening of the solenoid controlled means to stop operation of the prime mover and compressor.

9. The combination set forth in claim 8 further characterizedin that said means for opening the first of said main control circuits is reclosed. before the occurrence of a predetermined minimum pressure.

'10. The combination set forth in claim 8 further characterized in that the means for controlling the first of' said main control circuits is arranged to :reclose the same upon occurrence of a predetermined minimum pressure thereby to initiate operationof the prime mover and to plying current to thesynchronous motor including a relay device whereby the breaking of the circuit is normally prevented until the end of a predetermined time interval after unloading of the compressor by said unloading means.

12. In a compressor system, in combination, a

compressor, unloading means therefor, a driving thereafter cause opening of said switch or not in accordance with the time the compressor operates unloaded including separate compressor discharge pressure responsive devices respectively controlling the unloading means. and the switch. 13. In a compressor system, in combination, a

compressor, unloading means therefor, a driving motor for said compressor, a control switch for said driving motor, and controlling means operative on the attainment of a predetermined comcompressor, unloading means therefona driving motor for said compressor, a control switch for said driving motor, and controlling means operativeon the attainment of a predetermined compressor discharge pressure to cause said unloading means to unload the compressor and to thereafter cause opening of said switch or not in accordance with the time the compressor operates unloaded including separate compressor discharge pressure responsive devices controlling the un-- loading means and the switch, said compressor discharge pressure responsive device'controlling the unloading means having associated therewith means precluding loading except when the driving motor is operating at substantially full speed.

15. In a compressor system, in combination, a compressor, unloading means therefor, a driving motor for said compressor, a control switch for said driving motor, and controlling means operative on the attainment of a predetermined compressor discharge pressure to cause said unloading means'to unload the compressor and to thereafter cause opening of saidswitch or not in accordance, with the time the compressor operates unloaded including a time delay relay controlling running of the motor and operative to interrupt the same when energized for a predetermined time, said controlling means including means for precluding restarting of said motor, if the same be stopped as aforesaid, until after compressor discharge pressure drops materially below the normal reloading value.

16. In a compressor system, in combination, a

compressor, unloading means therefor, a driving motor for said compressor, and controlling means automatically operative to start said compressor when discharge pressure reaches a predetermined minimum, to load the compressor when motor speed reaches a predetermined minimum, to unload'the compressor when compressor discharge pressure reaches a predetermined maximum, and v to stop said motor if the compressor operates unloaded for a predetermined time including means for preventing stopping the motor if a predetermined drop in compressor discharge pressure precedes the expiration of said predetermined time.

1'2. In a compressor system, in combination, a compressor, unloading means therefor, a driving motor for said compressor, a control device controlling driving of said compressor by said driving motor, controlling means for said unloading means operative duringcontinued' driving of said compressor to load the compressor at a predetermined minimum discharge pressure and to unload it at a predetermined maximum discharge pressure, and controlling means for said control device arranged to operate thesame automatically to interrupt compressor drive if the compressor operates unloaded for a predetermined time and including means for precluding operation of said device to reinitiate compressor drive after the automatic interruption thereof until-compressor discharge pressure falls substantially below the predetermined minimum aforesaid.

18. Apparatus for controlling a prime mover operated compressor comprising compressor unloading means having controlling means'operative upon occurrence of a predetermined condition of operation to cause said unloading means to unload the compressor, and means for stopping the compressor after the same operates under substantially said predetermined condition for a given time period including compressor drive interrupting means and controlling means therefor responsive independently of said first mentioned controlling means to a condition of operation of said compressor.

19. Apparatus for controlling a synchronous motor driven compressor comprising, in combination, means responsive'to compressor discharge pressure variations for unloading the compressor;

means for making and breaking a circuit supplying current to the synchronous motor including a relay device whereby the breaking of the circuit is normally prevented until the end of a predetermined time interval after unloading of the compressor by the unloading means, and common means for controlling both said unloading means and said circuit making and breakin means.

20. Apparatus for controlling a synchronous motor driven compressor comprising, in combination, means, responsive to compressor dischargev pressure variations for unloading the compressor,

means for making and breaking a circuit supplying current to the synchronous motor including a relay device whereby the breaking of the circuit is normally prevented until the end of a predetermined time interval after unloading of the compressor by the unloading means, and common fluid pressure responsive means'for controlling both said unloading means and said circuit making and breaking means.

\ WILLIAM E. HUGHES.

CERTIFICATE 6F CORRECTIQN.

Patent No. 1,920, 985. August 8 1933.

WILLIAM E. HUGHES.

y it is hereby certified that ermr appears in the printed s ecification (Pf the above numbered patent requiring correction as follows: Page 1, lifie 95, for "t) read 90+; and line for "190" read 186; and psge 5, line 234, ciam 2:9, strike out the comma after "means"; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and seated this 13th day of Nsvember, I). i934.

Leslie Frazer (Seal) Acting Commissioner of Patents.

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