US2720355A - Unloading control apparatus for air compressors - Google Patents

Description

06L R WIDMYER UNLOADING CONTROL APPARATUS FOR AIR COMPRESSORS Filed May 29, 1951 Compressor Unlooder 6 Cam pressor Mo+o r 5 Compressor i INV TOR. Rob ert G. ZUL dmyez- BY qalzfmx AT TOENEY United States PatefitO 2,720,355 UNLOADING CONTRO APPARATUsFOR Ark t COMPRESSORS Widrnyer, Irwin, Pa.,, assignor to. Westinghouse Air Brake Company, a corporation of Pennsylvania Application May29, 1951, Serial N; 228,877- 2 Claims. (Cl. 230-18) Description Ref erringto'the drawing, the reference numeral, 1 designates an air compressor driven through such as a flexible belt 2' by an electric motor 3 to deliver compressed air to, a fluid pressure storage reservoir 4 via the usual valve 5. The compressor 1 is provided with the,

usual unloader device 6 whichwill respond to receipt of fluidunderpressu're in an unloader control conduit 7 to uhload the compressor in the well-known manner by such as holding its exhaust valve open, for example, and said delvice6 will respond to venting of conduit 7 to atmos phere to] loadthe compressor for deliveringcornpressed air; othe reservoir 4. The usual line starter 8 provides forcojnnec'ting and disconnecting the motor 3 to and from the line.

Ihefline starter 8, for sake of illustration, schematically In'ay co rnprise a plurali'ty of switches 9, biasedto open,

positions by a spring 941, for making and breakingelectrical"cbnnection between respective motor wires 10, ;con 3 nected to motor 3, and respective line wires llwhichare ada ed robe connected to a ,suitable source of electrical energy (not shown) for operating the motor In thefl drawinglthree line wires and three motor wiresindicate three phase. operation of motor 3, but the control appara: tus embodying the invention will just as rcadilyyadapt itselfto use with such as two wire feed to the compressor motorin, which case only two switches 9 needbe includedin the line starter 8. Each of the switches 9, operahlyconneeted by means of such as linkage 12 to a soleiioid 13 common to all for operation in unisonto respcctive closed positions upon energization of the solenoid andtofrespeotive open positions upon deenergiza'tion of said solenoid. l n

Acc ording to the invention, for controlling operation of jtlien1otor 3, the control apparatus is provided witha WlI f 61fi; Wh iCh CQllStitntlfpOHllCCtS one terminal of the soleno 13 to one of the line wires 11 While electrical connection of the opposite end of said solenoid to another.

of said, line .wires t o complete electrical circuitthroug'h tlr'elsolenoid for energizing same is effected by closure of,

a manual switch 15 and either a switch 16 associated with.

a pressure responsive device 1791 another manualswitch.

thefjlatter two switches 16 and 18 being; connected 18- el 'rri 'lly inparallel with each other and in series with th sw ch15 land solenoid 13.

est terminal or the" switch 15 is connected via a wire 2,720,355 Patented Oct. 11, 1955 2 19th afres pective 'lirie wire 11 otherthanthe line wire 11 towhic'hfwirel t is connected, and/ he, opposite terminal of theswitch 'is connected to one terminal of both the switch 16 and the switch 18 by means of a wire 20. and. bi nch s'thereof. Opposite terminals of bothswitches 16 and';18",are"connec'ted electrically one with. the other a'ndwith the respective terminal of solenoid 13 by a wire 21 and branches thereofi.

ThQPI'eS SilPB responsive device 17 comprises a fluid pressure actuator which may be in the form of a cylinder 22 having reciprocably disposed therein a snap-acting piston subject opposingly to pressure of fluid ina pressure chamber 24 at one side and to force of a compression spring 25 disposed in a non-pressure chamber 26 at its opposite side. The pistoh'23 is'operatively connected, by means of such as a piston rod 27., to the switch 16 and the pressure chamber 24 is connected bymeans of a fluid pressure conduit 28 and branches thereof to. the reservoir 4 so that reservoir pressure will be present constantly in said} pressure chamber. The initial compression of the spring; 25 is such relative to the area ofpiston 23 exposed to pressure of reservoir fluid in pressure chamber 24 that said piston will move from the repose position in which it is shownin the drawing toward chamber 26 to cause opening of the switch 16 when the pressure of fluid in the reservoir 4 has been re-established at a desired level. In response to reduction inreservoir pressure in chamber 24 to a certain value, the spring 2 5 will return the piston 23 to its repose position in which it is shown in' the drawing with. the switch. 16 again closed.

For controllingoperation of the compressor unloader device6, the control apparatus is provided witha solenoid valve device 30 which comprises a valve portion3 1 having 1 formed in a suitable casing asupply chamber 32 con:

nected to the reservoir 4 via the conduit 28, and having a delivery chamber 3'3' connected via a conduit 43 and a volume chamber 44to the unloader control conduit 7. A supply valve 34 disposed in'supply chamber 32 is cooperable with an opening in a partition 35' to control communication between the supply chamber 32 and the delivery chamber 33'. The valve 34 is biased by a spring 36 toward an unseated position in which it is shown in the'dia'wing'in engagement with a stop element 37. The valve 34 isope'rably connected to a' solenoid by the usual linkage such as'a rod 39 extending from the valve into the solenoid to serve as al reciprocable armature. One terminal of the"solenoid3 8 is constantly connected electrically tonne of -thelrnotor wires, 10 by means of a wire 40," whil e the opposite terminal of said solenoid 38 is connectedto another of the motor wires 10 via awire 41,.

a"switch"42and'a wire 43. When the solenoid 38 is energiz'edfaeltion of the spring 36 is overcom e to cause the valve 34 to' mfoveto a seated position closing oifcommunilc'atiori between the supply chamber 32 and the delivery chamber 33,, while deenergization of the solenoid 38 allows spring 36 toopen said valve and again connect the chambers 32,,33one to the other.

Thejswitch 42 is attachedfor reciprocable movement withthe rod 27 coincident with, the switch 16 and is arrangedltobe. disposed in a closedposition in which it is shown in the drawing establishing. electrical circuit through the solenoid 38 when the piston 23 is in its repose position .aforedescribed.

Theswitch 42 will be actuated to an open position disconnecting the wires 41. and 43 electrically one from the othenby movement of piston 23 in response to attainrnent of a certain pressure of fluid in chamber 24, as

aforedescribed,

For controlling release of fluid under pressure from the compressor unloader control conduit 7, a release valve device 45 is provided associated for convenience withthepressure responsive device 17. The device 45, forsakeof illustration, sehematically-- may comprise' a casing having formed therein two chambers 47, 48, separated by a partition49; thechamber47 being constantly' connected to a branch of the conduit 43, and the chamber 48 being constantly connectedto atmosphere byway ofja'port 50 inthe casing. Arelease valve 51, di sposedin chamber, 47 and attached to rod v27, is arranged tofcontrol communication between the chambers 47, 48 via an opening in the partition 49. The valve 51 attains an unseated position opening chamber 47 to chamber 48, as shown in the drawing when piston 23 assumes itS- ICpOS6 position. The rod 27 extends through a suitable opening in casing 46 and carries the valve 51 to a seated position when said rod is caused to move with piston-23 in response to attainment of a certain pressure of; reservoir fluid in chamber 24 as aforedescribed.

Operation ;.Assume" that the switch is open so that electrical circuit. through the solenoid 13 in the line starter 8 is interruptedandthe solenoid therefore deenergized with the .respective switches 9 consequently in their open position .inwhich they are shown in the drawing. With the, 1ir 1 e. .starter.switches 9 open, the motor wires 10 will hefiiscbnnected from the line wires 11 and the compressor motor 3 and therefore compressor 1 will be idle, with consequently no 'fluid under pressure being generatedfor supply to the reservoir 4 which, we will assume isavoid offluid under pressure at this time.

...W. h reservoir 4 void of fluid under pressure, the piston 23 inv the pressure responsive device 17 will be fluid will be increased.

in its, reposeposition in which it is shown in the drawing,

with rod 27 so disposed that switches 16 and 42 willbe closed,-and release valve 51 will be open.

:The closed switch 42 at this time has no effect on solenoid 38 which will be deenergized by reason of the motor wires 10 being disconnected from the line wires 11. With thesolenoid 38 deenergized, the valve 34 will be held open by spring 36 so that the reservoir 4 will be void .of fluid under pressure as assumed, by virtue of connection tjatrnosphere, via conduit 43 and, in device 45, chamber 47, unseated valve 51 chamber 48 and port 50.

j The closed switch 16 has no effect on the starter switch.

so1enoid13 at this time because of the open switch 15 in series. with it.

"The'bpen release valve 51.vents the unloader control conduit1'7.to'at1nosphere via volume chamber 44, conduit 43,"and chambers 47, 48 in device 45 so that unlo cler'device 6 will be conditioned to allow for compressi "of 'ai11,by operation of the compressor. I

Assume nowthat it is desired to operate the cornpress or-motor system with .automatic motor cut-off and compressor'unloading when the desired reservoir pressure has been attained. The switch 18 will be allowed td remain open and the switch 15 .will be closed to eifect energizationofthe line starter solenoid 13 through sup-.

plyof electrical energy from the respective line wire 11, wire 19, closed switch 15, wire 20, the closed switch 16in pressure responsive device 17, and the wire. 21.

"Inr'e'sponse to' its energization as above, thesolenoid 13 will effect closure of the respective switches 9, thereby connecting the motor wires 10 to the line wires 11, whereupon the motor 3 is brought into operation for driving the compressor 1 for supplying compressed air via check valve 5 to the reservoir 4.

Immediately upon receipt of electrical energy from I fluid under pressure as generated by operation of the compressor 1 cannot escape to atmosphere via device 30, conduit 43 and the unseated release valve 51 in device 17 and therefore such fluid under pressure delivered by the When the pressure of fluid in the reservoir 4 is thus increased as above and thereby attains a desired value, such pressure as experienced in pressure chamber 24 in device 17 will cause the piston 23 to move rod 27 such that the release valve 51 will be closed to prevent communication of conduit43 to atmosphere; switch 16 will be opened to cut off supply of electrical energy to the line starter solenoid 13 which thus will become deenergized and allow spring 9a to open the switches 9, disconnecting the motor wires 10 from the line wires 11, thereby terminating operation of motor 3 and compressor 1; and switch 42 will be opened to interrupt electrical circuit through the solenoid 38 of device 30, which solenoid thus will become deenergized, if not otherwise deenergized by virtue of cut-ofi of electrical energy to motor wires 10, and the spring 36 will then be allowed to open valve 34, whereupon fluid under pressure from reservoir 4 will'flow via conduit 28, the open valve 34 in device 30, conduit 43, and volume chamber 44 to the unloader control conduit 7 to cause the unloader device 6 to unload the compressor 1 preparatory to operating same again I With switches 15 and 18 remaining closed and open, respectively, with the motor 3 idle and the compressor 1 unloaded, when the pressure of fluid in the reservoir 4 drops below a certain value by supply ofsuch fluid under pressure to-devices (not shown), such pressure as reflected in chamber 24 in device 17 will allow spring 25 to return the piston 23 to its repose position in which it is shown in the drawing, with resultant substantially simultaneous opening of the release valve 51, and closing of switches 16'and 42. v

Closing of ,switch 16 will effect energization of the line starter solenoid 13 to cause closure of switches 9 under pressure to vent from said control pipe whenthe release valve 51 in device 45 is opened as above mentioned.

Ventingof fluid under pressure from the unloader control pipe 7, to allow the unloader device 6 to condition the compressor 1 to deliver compressed air to the reser-.

voir 4,'occurs by way of the volume chamber 44, con;

duit 43,a nd in device 45, the chamber 47, the open r'elease valv e'51, chamber 48 and port 50.

Since the-release valve 51 is opened at substantially the same time that switch 16 closes to bring motor 3 into operation, it is the purpose of the volume chamber 44 to provide such volume of fluid under pressure as will delay depletion of fluid under pressure in the unloader control conduit '7 by way of the release valve 51 when opened,

to give the motor 3 time to come up to speed before the compressor is loaded.

Now assume that it is desired to bring the motor-compressor system into operation with automatic unloading of the compressor 1 and continuous operation of the motor 3; both switches 15 and 18 are then moved to closed position.

Closure of the switch 15 will cause energization of the line switch solenoid 13 via the closed switch 18 which bypasses switch 16 in device 17 to connect the motor wires 10 to the line Wires 11 for operating the motor 3.

If, while the motor 3 is thus brought into operation, the device 17 is in the position in which it is shown in the drawing as a result of reduced reservoir pressure, with switches 16, 42 consequently closed and release valve 51 open, electrical energy supplied to the motor wires will flow via the closed switch 42 to energize solenoid 38 and close valve 34, thereby preventing communication between reservoir 4 and the unloader control conduit 7 vented to atmosphere via volume chamber 44, conduit 43 and the unseated release valve 51.

With the control conduit 7 vented, the unloader device 6 will be conditioned to load the compressor 1 so that the compressor in turning over with the motor 3 in operation will deliver fluid to the reservoir 4 and thereby increase pressure of fluid therein.

Again, in response to attainment of a certain desired pressure of fluid in the reservoir 4, the device 17 will respond to move rod 27 to open switches 16, 42 and to close the release valve 51.

Opening of the switch 42 will effect deenergization of the solenoid 38 to unseat valve 34 for supplying fluid under pressure to conduit 43 and, via chamber 44, to the unloader control pipe 7 for causing device 6 to unload the compressor 1.

At the same time, closure of the release valve 51 will prevent escape of the fluid under pressure supplied to the conduit 43 as above described.

Opening of the switch 16 with switch 18 closed has no influence on the line starter solenoid 13 which will remain energized by supply of electrical line energy via wire 19, switch 15, wire 20, the closed switch 18 and the Wire 21, so that the motor 3, hence compressor 1, will continue to operate inetlectively without supplying compressed air to the reservoir 4.

When the reservoir pressure drops a certain degree, the device 17 will respond to close switch 42 for energizing solenoid 38 to close valve 34 for preventing loss of reservoir fluid via the release valve 51 which is opened at the time said switch is closed.

Opening of the release valve 51 will vent the fluid under pressure from the unloader control conduit 7 to cause the device 6 to again load the compressor 1 being constantly operated by the continuously running motor 3.

The system may be shut down intentionally by opening switch to deenergize line starter solenoid 13 for opening switches 9 to stop the motor 3.

It should be pointed out that the reservoir 4 will vent to atmosphere via open valve 34 and release valve 51 when the system is shut down during operation of the compressor under load by opening switch 15; the compressor operates under load at reduced reservoir pressure by virtue of repose position of piston 23 in which release valve 51 is open to vent unloader control conduit 7 to allow unloader device 6 to load the compressor, and when electric current is cut-off to motor wires 10 at this time, solenoid 38 becomes deenergized and allows valve 34 to be unseated, thereby connecting reservoir 4 to conduit 43, thence to atmosphere via open valve 51.

The reservoir 4 thus will become void of fluid under pressure, and when the system is again brought into operation, even though the unloader control pipe 7 is vented via said open valve 51 and the unloader device 6 therefore conditioned to load the compressor 1, the compressor at time of starting will in effect be unloaded by virtue of absence of back pressure in reservoir 4 against which it has to pump.

Summary Thus it will be seen that I have provided a relatively simple and improved apparatus for controlling operation of a motor-compressor system.

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

l. A fluid compressor system comprising a storage reservoir, a fluid compressor for supplying fluid under pressure to said reservoir, a compressor unloader device responsive to pressurization and depressurization of a compressor unloader control conduit to unload and load, respectively, said compressor, electric motor means operatively connected to said compressor, motor wires connected to said motor, line wires from a source of electrical energy, switch means having an operating solenoid and effective upon energization and de-energization, re spectively, of said solenoid for connecting and disconnecting said motor wires to and from said line wires, circuit means connected to said line wires controlling energization and de-energization of said solenoid including a first switch and a second switch connected in series one with the other, an unloader-control supply valve biased toward an open position to establish supply connection of said unloader control conduit to said reservoir and operable to a closed position to disestablish said supply connection, supply valve actuating solenoid means energizable to close said supply valve, circuit means connected to said motor wires for controlling energization and de-energization of said valve actuating solenoid means including a third switch, an unloader-control vent valve operable to open and closed position to establish and disestablish, respectively, connection of said unloader control conduit to the atmosphere, and a movable abutment mechanically connected to the second and third switches and to said vent valve, said abutment being biased toward a position in which the second and third switches are closed and said vent valve is open and being operable responsively to pressure of fluid in said reservoir above a certain value to open the second and third switches and to close said vent valve.

2. The combination as set forth in claim 1, including a fourth switch connected in parallel with said second switch, and a volume chamber means constantly open to said unloader control conduit to delay loading of the compressor upon starting of the motor driving same.

References Cited in the file of this patent UNITED STATES PATENTS 1,786,367 Sanford Dec. 23, 193 1,864,132 Halleck June 21, 1932 1,914,594 Clapp June 20, 1933 2,134,693 Bartholomew Nov. 1, 1938 2,167,369 Paullin, Jr. July 25, 1939 2,191,908 Evelyn Feb. 27, 1940 2,221,857 Bartholomew Nov. 19, 1940

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