US2279431A - Compressor control means - Google Patents

Description

April 14, 1942. B. s. AIKMAN COMPRESSOR' CONTROL MEANS` Fild Aug. 31, 1940 m Yw R m A @N VO Mmm Y N N u W Q u, n wd B /V N y wm Mm. I Nm,` mm um ..T\ mm. u *N mw;

ATTORNEY Patented Apr. 14, 1942 UNITEDN sTTsELs This invention relates to fluid compressor systems and more particularlyto that type of system employing means, including an unloading or primary reservoir, for relieving the compressor of load in starting, due to back pressure of'f'luid and associated parts of the system. 'The comi pressor in starting is of course subject to the pressurek in the system, and consequently the motor starts under a considerable load, thereby consuming a `corresponding heavy current which sometimes causes damage to the motor.

As shown in E. H. Dewson Patent No. 1,060,588, issued May`.6, 1913, it has been proposed to obviate lthis diiculty by compressing the fluid into s an unloading orprimary reservoir or receptacle connected to the usual 'storage Vreservoir and system through a non-return check valve, and by providing means for releasing fluid from the primary reservoir when the motor is cut out and the pump stops, so that, when the motor is started, the pump operates under alight load while the speed of the motor is increasing to normal.

reservoir, therefore the primary reservoir must be charged with fluid to the pressure of the main reservoir. This has been found objectionable in that it wastes air and requires the .pump to oper- In this arrangement the supply of uid to the main reservoir is by way of the primary".I

ate longer than necessary. This objectionable l feature was recognized, for in the patent ,a modication is disclosed in' which the vprimary reservoir will be maintained partially charged so as to conserve air, but in doing this the compressor will, in starting, be subjected to considerable lead,` which is of course objectionable.

The principal object of the invention is .to provide a fluid compressor system of the above mentioned type in which the unloading or primary i reservoir -will be cut out of communication with the compressor when a predetermined low pressure, i. e., when a pressure lower than the main storage reservoir pressure, is built up inv the Aprimary reservoir, thereby conserving air and at thevsame timehastening the inowiof fluidi-rom the compressor to the main reservoir.

V In the accompanying drawing, thesinglelgure y is a .diagrammatic'viem partly in section, of Vra fluid compressorsystem embodying t'herinvention.

According to system may comprise an electrically.y drivenair compressor I, a storage reservoir'Z and an. electric compressor governor 3 connected to` the storage reservoir bya pipeIl.

According-tothe invention, a 'compressorlunf loading apparatus 5 is interposed inthe. usual conduit 6 which leads from the outlet port ofthe compressor to the main .storage reservoir 2, which apparatus is locatedat a point between the corn'- Pressor and a non-return check valve device 1 interposed in the conduit '6 -to prevent -back ow of fluidY from the storage reservoir to the unloading apparatus andthe compressor. f i

The electric compressor governor 3 may, r,in many respects be quite similar in `construction to any ordinary-form .of electric compressorgovernor.4 l ing 9 containing a Vregulating diaphragm -I for As shown, this governor comprises a cas:-

actuating a control slide valve II. The diaphragm is subject to theopposing pressures of uid ina chamberv I2 andthat exerted vby `a control spring vI3, the chamber I2 being in constant open communication with thefstorage reservoir-2 by way of pipe 4. 4The slidevalve II ,is operative at one time to admit fluidA under pressure from chamber I 2 `to ya' chamber I 4, whichfchamber contains an actuating Apiston I5 of a motor i l control switch, hereinafter more full-y described,

and at the Sametime connects an exhaust portV I and anunloading Valve mechanism-24. 1

The pipe connector 2I is interposed `in the conduit B and is provided with a passage 25'which forms a part of the conduit. This passage is in constant communication with a passage 26 leading to the pipe 20.

the drawing, .the .uid compressor 3| formed on the casing for controlling comy f munication between the chamber V29' andthe un-H loading or primary reservoir -23. The pipe-y ychamber 23 to the unloading reservoir 23. The

value of the spring 88 may be such that when the pressure of reservoir 23 has been increased, to approximately ten pounds it will yield to the action of the piston 34. It should here be mentioned that the diameter of the inner seated area of the valve. and the diameter of the actuating piston are substantially equal and that while the valve is open the pressure on the opposite sides of the valve will be equal.

The compressor I continues to operate to supply uid under pressure to conduit 6 so that the bracket is provided with stop lugs 32 which, when the valve is unseated, maintainsthe outer 'faceof the valve head spaced away from the passage 21,

so as to at all times ensure the free ilow of uid to orv from the chamber 29.

The unloading valve is provided. with-a stem 3,3 which extends across the interioroi the unloading reseiivoir j 23 and at its endis provided with an actuatingpiston 3 4whi-chis operatively mounted in a cylinder 35 formed in the-casing of thereservoin. Exteriorly of said casing there is adjustably secured to the outer end of the cylinder, by `means of screw threads, a cap 36 which, together with the outer face of the piston, de'ne a chamber 31 which is constantly open to theatmosphere by way'of ports 5I) provided in the cap.

Contained in the' chamber 31 'and interposed between and operatively engaging the outer face ofthepistonandan inner suriaceof the cap is arelativelylightspring38 whichbiases the piston initsvalve unseating direction.

i Operation f-Assu'ming that'the fluidunder pressure in the storage reservoir 2 and in the connected governorchamber -I2 is depleted to some pressure below the opposing pressurejof the control spring I3, the various operating parts of the governor '3 willfbein the position shown in the drawing,

pressure in the conduit is now quickly built up to a degree in excess of the opposing pressure of fluid-in the storage reservoir 2, thus ensuring flow of-iiuid through the check valve device 1 to the storage reservoir, thereby increasing the pressure in the storage reservoir and consequently the pressure of duid in chamber I2 until the pressure in this chamber is suicient to overcome the opposing action-oi the control spring I3, at which time diaphragm Infwill bev deflected downwardly thereby moving slide valve YI I to its lower position. I y

It will be here notedthat thepressure of fluid in chamber 29 'acting on the outer face of the valve 30 willinow maintain the valve seated even though the pressure o f iluid in the unloading orV primary reservoir 23 should'be reduced by leakage of iiuid past the piston 34 to the atmosphere. I v 1 i With the slide valve II in its lower position it establishes communication between chambers I2 and I4' by "Way, of a port which has been uncovered by the valve II. With this communication establishediluid'under pressure ows from chamber I2 to chamber I4 and acts on the piston I5 in opposition'to the force of the spring 4I When the fluid pressure is suflicient to overcome the opposingiforce of the spring the piston I5y is caused to move upwardly, operating the I switch 42-toxits circuit `opening position, thus 'since the diaphragm I8 and connected slide valve 'chamber II will be maintained in this lposition by the control spring I3-. Under these conditions a cavity 40 in the slide valve II will establish communication between chamberr I4 and the atmospheric port `I8, sothat fluid under pressure in chamber I4 will be vented to the atmosphere,

trol switch mechanism, will move the switch actuating piston I5 to its lowermost position in Yysfhich position switch 42 closes the electrical circuit Vfrom, the source ofelectrical energy; not shown, to the `corripre'ssor driving motor.

*Atthe same time, theoperating parts of the unloading apparatus 5 will bein the positions shown 'in the drawing, since the spring'38 holds the valve 30 unseated.

Now with the motor lcircuit closed, theL motor operates to drive the compressor so as to supply fluid vunderpressure to the compressor discharge conduit 6. Fluid under'pressure supplied to conduit 6 iiows from passage 25 of the pipe connector vcorrie-title pposingforce of spring 38, at which time the'piston acts to move the unloading valve :mv into 'engagement 'withV the seat 3|., thereby cutting oi the ow of iluid under pressure from a1' spring 4I, forming part of the motor conbringing the motor to a stop.` Y

Further, with the snee valve n in its lower position the cavity 40 in the valve establishes communication' between the'exhaust port I8 and port I9 so that fluid under pressure in pipe 8, chamber 25, connected chamber 29 and adjacent portion ofthe discharge conduit 6 are vented to the atmosphere, check valve 1 preventing back ow of fluid under pressure from the storage reservoir 2 to the conduit 6. When the pressure of fluid in-chamber 29 has been reduced to a pressure lower than the `value of spring 38, that is to say below ten pounds, the spring acting through the medium of `piston 34and stem 33 moves valve 30 awayfrom its seat 3I, thereby connecting the unloading or primary reservoir 23 to chamber 29, so that fluid under pressure in the unloading reservoir 23 is also vented to the atmosphere.

When the pressure inthe reservoir 2 and connected chamber I2 is reduced to a predetermined degree, the diaphragm I0 and connected slide valve I I is moved under the iniiuence of the force to move piston I5 to the position shown in the drawing thereby closing the electrical 'circuit to the compressor motor, so that the compressor will again operate to supply fluid under pressure to the reservoir 2.

It will be noted, that upon starting there is substantially no resistance to the operation of the compressor since the pressure in the discharge conduit 6 on the compressor side of the check 1., unloading or primary reservoir 23 and pipe 8 have been maintained vented during the rest period of the compressor as hereinbefore described. This permits the compressor, therefore, to take up its load gradually, and in fact, to start without imposing an overload on the driving motor.

It will be understood that the unloading or primary reservoir 23 is of such a size as to permit the driving motor of the compressor' to reach its normal speed before the heaviest load is imposed thereon.

From the foregoing description it will now be seen that the apparatus functions to cause the compressor to operate in an unloaded state until the full running speed is attained. It will also be seen that since the pressure obtained in the unloading or primary reservoir is limited to some low degree, such for instance ten pounds, the air loss due to unloading is reduced to a minimum.

While one embodiment of the improved unloading valve means has been illustrated and de'- scribed in detail, it should be understood that the invention is not limited to the exact details of construction disclosed and that numerous changes and modifications may be made without departing from the scope of the following claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is: l,

l. In a pressure control apparatus, vthe coinbination with a compressor and a compressor governor subject to the pressure of fluid discharged by the compressor, of an unloading receptacle into which said compressor compresses fluid, means independent of said governor and subject to the pressure of fluid discharged by said compressor for limiting the pressure of fluid supplied to said receptacle, and other means operated by a moving part of said governor for effecting operation of said means to effect the release of fluid under pressure from `said receptacle.

2. In a pressure control apparatus, the combination with a compressor, a storage reservoir into which said compressor compresses fluid, and a compressor governor subject to storage reservoir pressure, of an unloading device interposed between the compressor and said reservoir comprising a chamber into which said compressor compresses fluid, said device including valve means independent of said governor for limiting the pressure of fluid supplied to said chamber, and means operated by a 'moving part of said governor for effecting operation of said valve means to effect the release of fluid under pressure from said chamber.

3. In a pressure 'control system, the combination with a compressor, a main storage reservoir charged with fluid discharged by said compressor, a conduit through which fluid discharged by said compressor is supplied to said storage reservoir, a check valve located in said conduit and interposed between the storage reservoir and the compressor for preventing back flow of fluid fromV said storage reservoir to the compressor, a governor subject to variations in pressure in said reservoir, said governor having one position for effecting the cutting inandanother posii'li,or.;forl effectingthe. cutting'oiit of said compressor, of-a primary-reservoir connected to said conduit inter-y mediate the check valve and the compressonand charged .with fluid discharged by said compressor to a lower pressure than the pressure in said storage reservoir, means for cutting off the discharge of fluid froml said compressor to said primary reservoir upon an increase in pressure therein to said lower pressure, and valve means operated upon movement of said governor to cutout position for effecting operation of said means to effect the release of fluid under pressure from said primary reservoir.

4. In a compressor unloading apparatus, the combination with a compressor, a compressor governor for cutting the compressor into or out of action and a receptacle for receiving fluid supplied by the compressor to permitthe compressor to start operating without load, of` a valve mechanism separate from said governor for controlling the supply of fluid to and the release of fluid from Vsaid receptacle, said mechanism comprising a valve having a cut-oil" position for cutting off the supply of fluid from the compressor to the receptacle, and means operative by fluid in the receptacle for actuating said valve to its cut-off position, and other means for rendering the first mentioned means effective to actuate said valve to its cut-ofi" position upona predetermined increase in the pressure of fluid supplied to said receptacle.

5. In a compressor unloading apparatus, vthe combination with a compressor, a compressor governor having a cut-in position for cutting the compressor into action and a cut-out position for cutting the compressor out of action, :and a receptacle for receiving fluid supplied by the cornpressor to permit the compressor to start operating without load, of a valve mechanism for limiting the supply of fluid to Vsaid receptacle, said vmechanism comprising a valve operative to cutoff the flow of fluid from 'the compressor to the receptacle, a spring, and a movable abutment subject to 'the opposing pressure of fluid in the receptacle` and said spring, for actuating said valve to its cut-off position, and valve lmeans controlled by said governor, and operative in the cut-in position thereof, for `rendering said abutment operative upon a predetermined increase in the pressure of fluid supplied to said receptacle to actuate said valve to `its cut-offl position.

6. In a pressure control apparatus, the combination with a compressor and a Vcompressor governor, of an unloading reservoir into which said compressor compresses fluid to permit the 'com- -pressorto take up its load gradually, of a valve mechanism separate fromthe governor and interposed between the compressor and Athe -unloading reservoir for limiting the supply ofiluid to said reservoir, said mechanism4 comprising'a valve having a cut-oil position for cutting oil said supply, and means subject to the pressure of fluid in said reservoir 'for `.actuating said valve to said cut-off position, and other `means operated by a moving part of saidgovernor for condi# tioning vsaid means.

7. In a pressure control system, the vcombination with a storagereservoir charged with yiluid to a predetermined maximum pressure, a com'- pressor for` supplying fluid under pressure to said reservoir, means subject to the maximum pressure of fluid in the storage reservoir for cutting thecompressor out of action and operative upon a certain reduction in the storage vreservoir vpressurefo'r cutting the compressorinto action, `an unloading-.reservoir for receiving iiuid supplied by the compressor to permit the compressor to start operating without load, of a valve operative to cut off the flow of iluid from the compressor 'to the unloading reservoir, and means operative by fluid in the unloading reservoir at a pressure lower than the reduced `pressure of the storage reservoir for actuating said valve to its cut-off position.

V8. In a pressure control system, the combination with a storage reservoir charged With fluid to a predetermined maximum pressure, a compressor for supplying uid under pressure to said reservoir, means subject to the maximum pressure of fluid in the storage reservoir for cutting the compressor out of action and operative upon a certain reduction in the storage reservoir pressure for' cutting the compressor into action, an unloading reservoir for receiving fluid supplied by the compressor to permit the compressor to start operating without load, of a valve having a cutoiposition for openingv communication between the compressor and the unloading reservoir and a cut-in positionfor closing communication between the compressor and the unloading rreservoir, means for actuatingsaidvalve, said means comprising a movable abutment subject to the opposing pressures of uid under pressure in said unloading reservoir and a spring and operative upon an increase in the pressure of fluid therein to a pressure lower than the reduced pressure of the storage reservoir for actuating said valve to its cut-01T position and operative upon a decrease in the pressure of fluid acting on said compressor to a value below the value of said spring for actuating said valve to its cut-in position, said first mentioned means eifectinga release of uid under pressure acting in said compressor when subject to the maximum pressure of fluid in the storage reservoir.

9. In a pressure control system, the combination with a storage reservoir charged with fluid to a predetermined maximum pressure, a compressor for supplying iiuid under pressure to said reservoir, a governor comprising a valve mechanism subject to the maximum pressure of fluid in the storage reservoir for cutting the compressor out of action and operative upon a certain reduction in the'storage reservoir pressure for cutting the compressor into action, a conduit through which fluid is supplied'from saidv compressor to the storage reservoir,- of a chamber forming a part of said conduit,` a fluid conducting communication for releasing fluid under pressure from said chamber, said valve mechanism being operative when subject to maximum pressure of fluid in the storage reservoir to open said communication and operative upon said reduction in the storage reservoir pressure to close said communication, an unloading reservoir for receiving fluid supplied by said compressor to permit the compressor to take-up its load gradually,f a valve for controlling communication between the chamber and the unloading reservoir, means for actuating said valve, said `means being operative to close said valve and thereby cut-off the flow of uid from said chamber to said unloading reservoir when the pressure of fluid supplied to the unloading reservoir has been increased to a pressure considerably lower than the reduced pressure in the storage reservoir and to open said valve and thereby permit the ow of duid from the unloading reservoir to the cham- `ber'upon a predetermined reduction in the presage reservoir and said chamber for preventing back flow from said storage reservoir to said chamber.

10. In a pressure control system, the combination with a storage reservoir, of a compressor unloading reservoir, a compressor for supplying fluid under pressure to both of said reservoirs, said unloading reservoir being interposed between said storage reservoir and the compressor, a governor subject to a chosen maximum fluid pressure in the storage reservoir for cutting the compressor out of action and operative upon a certain reduction in the storage reservoir pressure for cutting the compressor into action, and means for isolating the unloading reservoir from the compressor and storage reservoir, said means comprising a valve mechanism operative upon an increase in the pressure of fluid in the unloading reservoir priorto obtaining the maximum pressure in said storage reservoir.

11. In a pressure control system, the combination, with a storage reservoir normally charged with fluid to a maximum chosen pressure, of a compressor unloading reservoir normally at atmospheric pressure, a compressor for supplying uid under pressure to said storage reservoir, said unloading reservoir` being interposed between said storage reservoir` and the compressor and being normally in open communication with the compressor, a compressor governor subject to the pressure of fluid in the storage reservoir for normally cutting the compressor out of action and connecting said unloading reservoir with the atmosphere, said compressor governor being operative upon a reductionin the pressure of uid in the storage reservoir for cutting the compressor into action and for closing the atmospheric communication from the unloading reservoir to the atmosphere, and means operative upon a predetermined increase in the pressure of fluid supplied by the compressor to said unloading reservoir for cutting off the communication between the compressor and the unloading reservoir.

12. An unloading mechanism for a fluid compressor system of the type which permits the compressor in starting to take up its load gradually, said mechanism comprising an unloading chamber for receiving fluid supplied by the compressor, a valve operative to cut off the ow of uid from the compressor to the chamber, and means subject to a chosen increase in the pressure of fluid in said chamber for actuating said valve to its cut-oil position.

13. An unloading mechanism for a fluid compressor system of the type which permits the compressor in starting to take up its load gradually, said mechanism comprising an unloading chamber for receiving uid supplied by the compressor, a valve operative to cut off the iiow of fluid from the compressor to the chamber, and means disposed in said vchamber subject to a chosen increase in the pressure of fiuid in said chamber for actuating said valve to its cut-off position.

A14. An unloading mechanism for a fluid compressor system of the type which permits the compressor in starting to take` up its load gradually, said mechanism comprising an unloading chamber for receiving fluid supplied by the compressor, a valve operative to cut orf the ow of fluid from the compressor to the chamber, and means comprising a movable abutment disposed in said chamber subject to a chosen increase in the pressure of uid in said chamber and an opposing pressure for actuating said valvel a storage reservoir and comprising a chamber for receiving uid supplied by the compressor, a valve having a cut-01T position for cutting off the supply of fluid to said chamber, a spring, a movable abutment mounted in said chamber subject to the opposing pressures of uid in the chamber and that of said spring and being operative upon a chosen increase in the pressure of fluid in the chamber for actuating said valve to its cut-01T 10 position.

BURTON S. AIKMAN.

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