US2225291A

US2225291A - Load controlling apparatus for compressors

Info

Publication number: US2225291A
Application number: US299486A
Authority: US
Inventors: William T Alderson
Original assignee: Ingersoll Rand Co
Current assignee: Ingersoll Rand Co
Priority date: 1939-10-14
Filing date: 1939-10-14
Publication date: 1940-12-17
Anticipated expiration: 1957-12-17

Description

Dec. 17, 19.40. w. 'r. ALDERsoN 2,225,291

LOAD CONTROLLING APPARATUS FOR COMPRESSORS Filed on. 14, 1959 s Sheets-Sheet 1 INVENTOR m5- ATTORNEY.

William Til'ldez'fim Dec. 17, 1940, w. T. ALDERSON 2,225,291

LOAD CONTROLLING APPARATUS FOR COMPRESSORS Filed 0c@@ 14, 1939 S-Shggts-Sheet 2 INVENTORL mum/0T1: ldersoul HlS ATTORNEY.

Dec. 17, 1940.

w. T. 'ALDERSON LOAD CONTROLLING APPARATUS FOR COMPRESSORS I Filed Oct. 14, 1939 3 Sheets-Shoet 3 INVENTOR A T W m HIS ATTORNEY.

Patented Dec. 17, 1940 UNITED STATES PATENT OFFICE LOAD con-momma mans-ms ron courasssons Applicatiir0et0ber 14, 1939, Serial No. 299,486

18Cl'aims- This invention relates to compressors, and more particularly to load controlling apparatus for machines of this character.

The invention'is particularly applicable for use in connection with compressor systems employing a plurality of compressors discharging into a common receiver and where the demand of the 7 work for which the pressure fluid is intended may vary to a considerable degree.

10,. In installations of this type if the demand for pressure fluid is moderate only one machine need be operated and whenever the demand for pressure fluid exceeds the capacity of one compressor other compressors may be brought into operation.

.16 In accordance with the present invention, the

initiation of operation of an additional com-.

pressor or compressors, as necessitated by themcreasing demand upon the pressure fluid in storage, is effected automatically and in such wire a: .that whenever the consumption of pressure fluid lowers the storage pressure to a predetermined sors in accordance with the. demand upon thesupply of storage pressure. H

A further object is to confine the load o'on- I 35 trolling function to the last of a group of com-- pressors to be set in operation, irrespective of the number of compressors included in the group. Other objects will be in part obvious and in part pointed out hereinafter.

Inthe drawings accompanying this speeiflba- 'tion and in which similar reference n refer to similar parts, p

Figure 1 is a diagrammatic view of a group or compressors equipped with load controlling ap-' 45 paratus constructed in accordance with the practice of the invention effecting sequential" 1 starting and stopping of the compressors.

Figure 2 is a diagrammatic view, partly in section, of one of the compressors and its load 50 controlling apparatus shown in Figure 1, and

Figure 3-.is a longitudinal elevation, partly broken away, of a detail. v

Referring to the drawings, and at first more particularly toFigure 1, 20, 2| and 22 are multistage compressors which accordingly have low.

(CL 23Q-17) and high'pressure cylinders 23 and 2!, respectively, and may be suitably connected to discharge into a common storage receiver '25. Each compressor has an individual driving motor 26, and

an intercooler 21 through which the fluid passes 6 from the lowpressure .cylinder 23 to the high pressure cylinder 24 for removing the heat generated by compression. In order to enable the load on the compressor cylinders to be changed or controlled gradually, each cylinder-is provided with suitable load controlling devices consisting, in the present instance, of clearancechambers and valves for controlling them. The valves and the clearance chambers are brought into action in pairs and one chamber 16' and associated'valve of a pair is located in the low pressure cylinder while the other chamber and its valve are located in the high pressure cylinder. Thus, a clearance chamber 28 and a valve 29 controlling it are located adjacent the go crank-end of the low pressure cylinder and avalve 2| and a chamber 28 are located adjacent the outer end of the high pressure cylinder.

Similarly, a clearance chamber 30 and a valve 3| are located at the outer end of the low pressure cylinder and a similarly designated clearance chamber and a valve lie adjacent the crank end of the high pressure cylinder. In like manner, a clearance chamber 32 and its clearance valve 33 are arranged adjacent the outer end of the low so pressure cylinder, as for example diametrically opposite the chamber 30, and a chamber 32 and its valve 33 are located adjacent the crank end of the high pressure cylinder opposite the cham- I ber and at the outer end ofthe high pressure 3&- cylinder. In the longitudinal plane of the chamber 301s a chamber 34 and a valve 35 and the other chamber 34 of the last mentionedpair and its valve 85 lie adjacent the crank end of the low pressure cylinder inthe longitudinal plane 40 of the adjacent clearance chamber 30.

The pairs of clearance valves 29, Si, 33 and a 35 are connected; respectively, by

conduits

36, 31,

3! and 39 which lead to a regulator 40 of the type illustrated in United States Patent No.

1,430,578 to C. W. Metzgar, dated October 3, 1922, and comprises a casing 4| having a series of valve chambers 42 containing main valves 43 which control the supply of pressure fluid to the clearance valves in the compressor cylinders. The main valves are in turn controlled by an auxiliary V valve 44 connected to a weighted lever 45 pivoted The diaphragm 48, plunger 41, pin 4' and lever 45 or each regulator constitute an actuator there-v for so that when the diaphragm 48 is subjected to storage pressure the lever 44 and attached valve 44 are caused to rise and fall in accordance with the variations in the pressure in the storage receiver. Thus, when the demand for fluid substantially equals the discharge output of the compressor the valve 44 assumes a low position in the casing 4|. In this position the valve 44 communicates its chamber 44 with ports or passages 50, II, 82 and 53 leading to the lowerends 01' v the valve chambers 42. The main valves 44 will -'-open to communicate the chambers 34 with the I then be raised to admit pressure fluid through the conduits 34, ll, "and I! to the clearance valves for holding them closed to prevent the passage of fluid from the compressor cylinders into the clearance chambers.

The various elements controlling the clearance chambers remain in substantially the positions described until the pressure fluid in the storage receiver 25 rises above the predetermined value. The pressure fluid acting against the diaphragm .44 then raises the lever 45 and thus the valve 44,. 'As the valve 44 proceeds upwardly it uncovers, first, the port 53 to exhaust the pressure fluid beneath the main valve 43 controlling the conduit 38.

Simultaneously, with the uncovering oi the port 53 the valve 44 places the lowermost port I4 0! a group of "ports, leading to the upper ends of the valve chambers 42, to admit pressure fluid above the main valve 43 controlling the conduit 39. This main valve is then shifted to new position toexhaust the pressure fluid ironithe clearance valves 15. The valves 35 will then high and low .pressure cylinders and the load of the compressor will thereby be reduced by onequarter.

Upon the continued increase in pressure of the fluid acting against the diaphragm 48 the valve 44 will be raised to new positions and will successively uncover the ports II, it and It to communicate the lower portions oi the main valves 43 with the atmosphere, and to successively place other ports, II, 84- and I1, 01' the group including port 44, in communication with pressure fluid supply to shift the main valves 43 downwardly for exhausting the pressure fluid from the clearance valves which they control.

L'Ihis operation or the regulator may continue,

until all the clearance valves have been released and the compressor will then be iully'unloaded.

In-so-iar as the .regulation of the clearance valves is concerned each regulator operates in its characteristic manner, as described in the aforementioned patent and again somewhat briefly in the above description. However, in accordance with the practiceot the invention, the regulators perform additional: duties including those of effecting the starting and the stopping of compressors other than those for which they control'the load. To this end each regulator casing 4i is provided with valve chambers II and I! containing, respectively, valves 44 and II which may be replicas of the valves 43 and accordingly have

end heads

42 and 48, the outer ends or which-constitute pressure suriaces 44 and II, respectively. t

The spaces between the heads and 43 serve. as supply chambers 44 and are inconstant com-- munication with the valve chamber 44 through passages 41 in the casing 4|. Each valve II and ii carries a bridge 44 having a channel it tor tween the lowermost ends of the bridges 68 and .the heads." serve as passages for communicating the chambers 66 with the ports 10.

The pressure fluid supply to the valves iii and BI is also controlled by the auxiliary valve 44, and to this end the casing 4| is provided with a passage 13 that extends from the lowermost part of the valve chamber 58 to a point in the valve chamber 4! below the lowermost oi! the ports leading to the valve chambers 42. Owing to this arrangement, when the auxiliary valve moves below the port 53 the passage 13 will be open to the pressure fluid supply between the headsoi the auxiliary valve, and at the beginning of the upward movement of the auxiliary valve 44 the passage 13 will be communicated with the atmosphere before the port 53 is uncovered.

The lowermost end of the valve chamber 59 is supplied in a similar manner but the passage 14 which conveys pressure fluid thereto opens into the valve chamber 49 at a point above the port 5D so that the said passage F4 will be uncovered by the valve to communicate it with pressure fluid supply before the valve uncovers the'port 50 to supply pressure fluid to its asso-'; ciated main valve 43. -More specifically, the? passage [4 lies intermediate the passages leadiii: to the main valves 43 and the supply port l.

15 of the valve chamber 49. .4 w

Passages are also provided in the casing H for conveying pressure fluid ,to the upper ends oi the valve chambers I8 and 59 from the valve chamber 49. Thepassag'e serving this function for the valve chamber 54, and which is designated I8, communicates with the valve chamber the valve chamber 4!. The passage designated 11 and leading to the upper-end oi the valve chamber 5!, on the other hand, opens into the valve chamber," at a point above the group of passages controlling the upper ends of the main valves so that when the auxiliary valve descends said passage 11 will be the first to be communipassages openinginto thevalve chamber 48 to be communicated with pressure fluid supply.

- The valves and 4| are structurally identical and serve, respectively, as initial steps in the automatic starting and stopping of the ,com-

sure fluid from the valve chamber 54 to the switch ll but is provided with an oriflce I! to cated with the atmosphere and when the auxiliary valve 44 ris'es it will bethe last one oi! the assure a slow exhaust of fluid from the pressure switch 19.

From the foregoing it will be apparent that when the valve 60 of an operating compressor is positioned to admit pressure fluid into a conduit 18 the pressure switch I9 of the motor intended to be started, shown in somewhat fuller detail in Figure 2 as comprising a spring opposed bellows 83 for actuating the movable contactor motor. This action of the switch I9 will take .place automatically since it is controlled by the regulator of its associated compressor and said regulator itself is constantly subjected to and acts in response to the value of the storage pressure.

Any of the motors 26 of the compressors may be started by the action of a regulator butmeans are also provided to effect manual starting of the motors. These means preferably comprise starting devices, for each motor, of the character forming the subject matter of United States Patent No. 1,761,578, granted to C. W. Metzgar, June 3, 1930. Each starting device comprises a valve mechanism including a casing 85 containing a rotary valve 86 having a handle 81 for its manipulation. The handle 61 has a head 88 which, as may be ascertained by reference to the last mentioned patent, is so related with the valve 86 that both will turn in unison.

In the outer side of the head 88 is a cam sur- '86 occupies one position the rod 9| will seat against the end of the head 68 to retain the contactor 90 out of engagement with the contactors 93, and in another position of the valve 86 the cam surface 89 will be in a position permitting the contactor 90 to engage. the contactors' 83.

The valve 86 is of the three-way type and its function, in the present instance, is to control the flow of pressure fluid employed to retain the auxiliary valve 44 of the regulator of the associated compressor, when idle, in a position to maintain a full supply of pressure fluid in the upper ends of all the valve chambers in the regulator casing M to press the valves therein to their lowermost limiting positions. The device employed for this purpose comprises a cylinder 96 shown, for sin!- plicity of illustration, as being attached to the casing 4|, and within the cylinder 96 is a piston 91 having a rod 98 on its upper end to engage the lever 45 of the regulator. A conduit 99 leads from the cylinder 96, beneath the piston 91, to the valve casing 85 and is controlled by the valve 86 which has a port I00 extending diametrically 5 therethrough and a lateral port IOI branching from the port I00.

The valves 86 control both the admission to and the exhaust of fluid from the cylinders 86, the

0 latter taking place througha'n exhaust pipe I02" attached to each casing 85. Pressure fluid is conveyed to a casing 85 by a conduit I03 attached 84, will be closed to complete the circuit to its for controlling communication between the supply conduit I04 and the valve 86. Each valve mechanism I05 controlsthe flow of pressure fluid to and from a valve 86. It comprises. a casing I06 having a chamber I01 to accommodate a valve I08 which seats upon a spring I09, in the lower part of the casing I06, for actuating the valve I08 toward the upper part of the casing I06. The valve has end heads I I0 and the outer end of the upper head IIO constitutes an actuating surface III to and from which pressure fluid is conveyed by a conduit II 2 connected to the conduit I8 between the check valve 8i and the valve 60 so that pressure fluid will flow unrestrictedly to and from the actuating surface II I.

The heads IIO of the valve I08 are suitably spaced to uncover the several branches of the conduit I03 in order to permit the flow of fluid through the valve chamber I01 from one branch to the other of said conduit and also to afford communication between the branch I03 leading from the valve mechanism I05 to the valve 86 with an atmospheric exhaust pipe H3 attached to the casing I06 below the conduit leading to the valve 86.

In accordance with a well known practice, each compressor unit is provided with devices, variously located, for further assuring the complete unloading of the compressors after the clearance valves have ,been opened to communicate the clearance chambers with the compressor cylinders. I Included among these devices are cylinder relief valves II4, of a well known type, attached to the high pressure cylinder to permit the' exhaust therefrom of such pressure fluid as may leak from storage into the cylinder. Thereceivers arealso provided with relief valves N5, of a well known type, to permit the partial exhaust of the fluid delivered to the receivers by the low pressure cylinders during the starting of a compressor, thereby preventing the imposition of a heavy load upon the motors while accelerating.

During the. normal operation of the compressors both the relief valves H4 and H5 of a compressor are held closed, however, by pressure fluid controlled by a common valve means which also controls the supply of pressure fluid to the valve chamber 49 of the'regulator. The valve mechanism illustrated to, perform this service is of the three-way type comprising a casing II6 having a chamber III to which is connected a conduit II8 that leads to the relief valves I I4 and- H5 and to the port I5 in the valve chamber 49. In the chamber II! is a valve H9, in the form of a ball, for controlling communication between the conduit II8'and a supply pipe I20 connected to the valve chamber, and at the opposite end of the valve chamber is a second seating surface I23 uponwhich the valve seats whenever the conduit H8 and the pipe I20 are in communication with each other. The valve II9 descends by gravity to the latter seat and is actuated into engagement with the seat I22 by a piston I24 containing a spring I25 which seats against a shoulder I26 in the casingv II6 to move the piston I24 downwardly in the chamber I 21 containing" the piston. A rod I28 is interposed between the piston I24 and the valve II3 to actuate and hold the latter against the seat I22.

The rod I23 extends slidably through the wall I25 and loosely through an aperture I23 merging 5 with the valve seat I23, and opening into the lower part of the aperture I23 is an exhaust pipe I30 to communicate the aperture I23 with the atmosphere. Y

Suitable means are provided for controll n the supply and exhaust of pressure fluid to and from the chamber I21 for actuating the valve H3 against the seat I22 and to permit the valve II3 to return to the seat I23. To this end the chamber I21 is provided with a conduit I3I which is attached to thecasing I32 of a control valve mechanism having a chamber I33 to accommodate a valve I34. The conduit I3I opens into an intermediate portion oi. the chamber I33, and'opening into the upper end of the chamber 0 is a branch conduit I35 that leads from the pipe I20. The valve I34 is of the ball type adapted to engage a seat I36 in the upper end of the chamber J33 to cut oil communication between the conduits I3I and I35 and also to engage a seat m in the bottom of the chamber I33 at the end of abore I33 extending downwardly through lower end of the plunger rests upon a rocker I42 rotatable in the casing I32 and having an arm I43 which is yieldably connected, as by a spring I44, to the armature I45 of. a solenoid I43. The wires I41 of the solenoid are wired'into the motor field switches, in a well understood manner, so thatthe energization and deenergization of the solenoids takes place automatically in accordance with the operation or the motor switches. In this way the energizationoi the solenoids will not occur during the initial starting of the motors when they are operating as induction motors. This delay is desirable because ,it prevents the loading of the compressors until their motors have attained a speed at which it may be considered practical to apply the load. The function of the valves GI is, more particularly, that of initiating the first step in the stopping of a compressor other than that of which the regulators controlling the valves 3I form a part. For example, the valve SI of the compressor 20 performs this service for the compressor 22, the valve 3| of the compressor 2| performs alike service for the compressor 20 and the valve SI of the compressor 22 acts as the first step in the stopping of the compressor 2|. 1 Each valve 5i controls a conduit I43 that conveys pressure on fluid to and from a reversing valve I43, similar in all respects to the valve mechanism I05.

The reversing valves I43 are interposed in conduits leading from the supply conduit I04 to the several diaphragms 43 of the'reguiators. One of 05 these conduits, designated I50 and controlled by the reversing valve I43 associated with compressor 20, leads to the diaphragm 43 oi compressor 22. The conduit controlled by reversing valve I43 of compressor 2I and designated I5I leads to the diaphragm 43 of compressor 20, and the conduit designated I52 controlled by reversing valve I43 of compressor 22 leads to the diaphragm 43 of compressor 2I.

Interposed in each conduit I50, I5I and I52 15 are volume tanks I53 to maintain ample volumes of pressure fluid closely adjacent the diaphragms 43 oi. the regulators.

In practice, whenever it is intended to set the first one oi the group of compressors in operation, the valve 35 of, say, compressor 20 is ro- 5 tated manually into a position in which the passage in the valve 33 establishes communication between the conduit 33 and the exhaust pipe I02, thereby opening the cylinder 33 to the atmosphere and permitting the lever 45, together 10 with the auxiliary valve 44 attached thereto, to descend. During the rotation of the valve 33 the cam surface 33 of, the head 33 is moved into the longitudinal plane of the rod 3|. The contactor 30 will then be actuated, by itsspring. 15 against the contactors 33, and close the circuit 34 for starting the motor 25 of compressor 20.

when the motor attains synchronous speed the solenoid I43 will become energized to move the armature I45 upwardly and tilt the rocker I42. 20 This movement of the rocker raises the ball valve I34 against the seat I33, thereby opening the chamber I21 to the atmosphere through the conduits I3I and I33 and the associated passages in the casing I32. 25 Upon the exhaust of pressure fluid from the chamber I21 the spring I25 shiits the piston I24 to permit the valve II3 to drop to the seat I23. Pressure fluid then flows from the conduit I20 to the valve chamber I I1 and conduit II3 to the relief valves H4 and H5 and to the valve chamber 43. The relief valves H4 and H5 will be closed by such pressure fluid to prevent the further passage of fluid from the compressor through these elements. During the ensuing descending movement of the lever 45 01 the regulator the auxiliary valve 44 will successively place the upper ends of the valve chambers 42,

53 and 53 in communication with the atmosphere and successively place the ports below the supn ply port I5 in communication with pressure fluid supply. 7

In the present instance, the port first uncovered is that designated I4. When this port is uncovered pressure fluid is admitted beneath the 5 valve 3| which will be raised to place the space I2 in position to. admit pressure fluid into the adjacent port I0. Pressure fluid will then flow through the conduit I43 into the casing I03 of reversing, valve I43 and move its valve I03 to 50 communicate the conduit I50 with the atmosphere through pipe II3 so that the diaphragm 43 of compressor 22 will be open to the atmosphere.

Upon further descending movement of the aux- 55 iliary valve 44 the ports leading to the lower ends of the chambers 42 are successively communicated with pressure fluid supply in the valve chamber 43. The clearance valves of the high and low pressure cylinders will then be closed 50 by the pressure fluid valved to them by the main valves 43 accordingly as one main valve after the other is actuated upwardly in their chambers 42.

With the various elementsin the positions de- 05 scribed, the compressor is fully loaded and its discharge output delivered to the storage refluid causes the pressure in the receiver and,

therefore, beneath the diaphragm 43 to fall below a predetermined minimum value the auxiliary valve 44 descends to a position in which it comously, with the actuation of switch I9 pressure fluid is admitted into the associated valve mechanism I05 to press valve I08 downwardly to a position for communicating the branch of conduit I03 leading to valve 88 with the exhaust pipe II3. With the valve 86 in a position to communicate conduits I03 and 99 with each other pressure fluid passes from cylinder 98 of compressor 2| to the atmosphere. The auxiliary valve 44 may then descend to supply pressure fluid to the various valves which it controls to cause the actuation or the devices that serve to apply the load 'to compressor 2|. I

During its downward movement the auxiliary valve uncovers first the passage I4 leading to the associated valve GI to admit pressure fluid thereto for raising said valve. Pressure fluid will then flow from the chamber 88 throughthe space 1-2, the port I and the conduit I48 into the upper end of reversing valve I49, the valve I08 of which will be moved into a position in which it communicates the branch of the conduit II leading from the reversing valve to diaphragm 48 of compressor 20 with the atmosphere. V

The pressure fluid beneath the diaphragm 48 of compressor 20 will then be exhausted to the atmosphere and the regulator remains in posi- ,-tion to maintain full loading of said compressor 20 and to maintain pressure fluid beneath the valves 60 and BI but will not take any part in varying-the load on the compressor 20 or on the combined load of the compressors.

Thereafter, this service will be performed only by the regulator of compressor 2| and said regulator will maintain a partial or full load on its compressor until the consumption of pressure fluid creates a value in the storage receiver 25 below the predetermined minimum,

- When the pressure acting against the dia-'- phragm 48 of compressor 2| reaches this minimum value the auxiliary valve 44 of the active regulator descends and uncovers passage I3 to admit pressure fluid beneath the associated valve 60 for raising it. Pressure fluid then passes through the connected conduit .18 to the pressure switch 19 and to the valve mechanism I05 of compressor 22. After a short period of acceleration of compressor 22 the remaining devices, including the solenoid I48, will act in their proper order to apply the load to the compressor and to communicate the diaphragm 48 of compressor 2| with the atmosphere in the manner previously explained.

The function of load controlling will thereafter be assumed entirely by the regulator of comprese sor 22 and the regulators of compressors 20 and 2| will occupy positions in which they maintain full loads on their respective compressors but will be otherwise inactive and, therefore, unable to cause any variation in the loading of their compressors. I

Inthe event that the combined deliveries of all the compressors oi the group raise the storage pressure'in excess of the predetermined maximum value the pressure beneath'diaphragm 48 of. compressor 22 raises the auxiliary valve 44 to cause unloading of the

cylinders

28 and 24, either partially or fully, in accordance with requirements.

'If the compressor 22 becomes fully unloaded and the receiver pressure continues to rise the auxili- 5 aryvalve 44 of compressor 22 will be elevated fur-. ther to aposition to communicate passage with the valve chamber 49. Pressure fluid then flows against-the pressure surface 84 of valve 8| and moves said valve downwardly to exhaust the pressure fluid acting against pressure surface III of the associated valve I08. This valve will then .be moved in position to permit the flow of pressurefluid through conduit I52 and volume tank to the diaphragm 48 of compressor 2|, thereby rendering its regulator operative. The auxiliary valve 44 of the latter diaphragm will then be raised above the associated passage I3 to open the lower end of valve chamber 58 to atmosphere.

Simultaneously with the shifting of valve 6|, 2o pressure fluid flows from valve chamber 49, through passage I8, into the upper end of valve chamber 58 and moves valve 60 downwardly to open conduit I8 to the atmosphere. Pressure. fluid will then escape from pressure switchv I9 and valve mechanism I05 of compressor 22 to stop said compressor. The valve I08 of valve mechanism I05 will then be actuated by its spring I09 to a position to admit pressure fluid from the supply conduit I 04 through conduits I03 and 99 80 and valve 86 .into cylinderl 96 of compressor 22. The pressure fluid acting against piston9'l will raise lever and auxiliary ,valve '44 to their up-, permost positions for maintaining valve 8| in position to communicate reversing valve I49 with 85 the atmosphere and thereby retain diaphragm 48 of compressorZI in communication with pressure fluid supply;

Thereafter the regulator of compressor ,2I will control the load of its compressor and if the receiver pressure continues to rise will cause unloading of the cylinders of compressor 2| in stepby-step fashion. The latter regulator will then act to efiect full or partial loading and if the storage pressure still continues to rise above the predetermined maximum the auxiliary valve 44 is elevated to its extreme top position to cause actuation of the valves 8| and I 49 for admitting pressure fluid beneath diaphragm 48 of compressor 20 and to open pressure switch 19 and admit pressure fluid beneath piston 91 of compressor 2|, in the manner explained more fully inconnection with the stopping of compressor 22.

Compressor 2| will then also be idle and only compressor 20 will continue to. operate. The load will again 'be controlled by its regulator, and if the volume delivered by compressor 20 continues ing theauxiliary valve 44 to its uppermost limit- 85 ing position.

All the compressors will then be idle. Their cylinders will be fully unloaded and all the valve mechanisms I49 will be in position to admit pressure fluid beneath the diaphragms 48. Thus, whenever it is intended to again start operation or a compressor any one of the valves 88 may be actuated manually to a position for exhausting I pressure fluid from the associated cylinder 98.

The remaining steps in the starting, loading and 7 operation of the compressor will then follow as herelnbefore outlined.

After the pressure fluid has been exhausted from the cylinder 96 the starting valve 86 is moved into a position in which the port I99 communicates the conduits 99 and H13 and with the remaining valves 89 occupying like positions the subsequent starting operation of the remaining compressors and the stopping of all the compressors will take place entirely automatically without further manual attention. Although, as has been stated in the description of the operation of the apparatus, a continued rise in the value of the storage pressure will cause the 15 auxiliary valves of the regulators to ascend progressively to their topmost limitingpositions and successively cause actuation of the various devices serving to unload the compressors, it will be readily appreciated that, upon increased conso sumption in pressure fluid, the regulators may again apply partial or full loads to their compressors, either in an intermediate position or topmost limiting position .of the auxiliary valves as long as sufllcient pressure remains in the pressure switches 19 to keep them from opening the circuits which they control. Thus, an auxiliary valve may be actuated to its topmost limiting po-' sltion but, by reason of the restricted exhaust of pressure fluid from the switches, through the apertures 82 in the check valves 8|, the opening of. the switches will be delayed somewhat, and if the demand for pressure fluid is again increased before the pressure in the switches I9 has dropped below that value at which the switches 33 open the regulators will again operate to apply loads to the compressors before the switch is opened and, therefore, while their respective mo tors are still in operation.

'I claim:

40 1'. The combination of a plurality of compressors, and pressure fluid actuated means acting in response to an increasing demand on the discharge output of an operating compressor to effect the starting of another compressor.

45 2. The combination of a plurality, of compressors, load controlling devices for each compressor, and pressure fluid actuated means acting in response to an increasing demand on the discharge output of an operating compressor to 50 effect the starting of another compressor and its load controlling device.

3. The combination of a plurality of compresing compressor to initiate 'an operating period of another compressor and its regulator.

5. The combination of a plurality oicompresc5 sors, loading devices for the compressors, regulators for controlling the loading devices, means controlled bythe regulator of an operating compressor to initiate the operation of another compressor and its regulator, and means contr'olled' 70 by the regulator of such other compressor to render the regulator 01' the compressor first set in operation inefl'ective to vary, the load 01' its associated compressor.

6. The combination of a plurality of compres- 7 sors discharging into a common receiver, load controlling means for each compressor, means for automatically initiating sequential operation of the compressors in response to an increasing demand upon the pressure fluid in the receiver, and means to render allbut one of the load con- 5 trolling means ineflective to vary the combined load of the compressors. l

7. The combination of a plurality of compressors discharging into a common receiver, load controlling means for eachcompressor, pressure 10 actuated means controlled by the load controlling means of an operating compressor upon an increasing demand for initiating the operation of another compressor and its load controlling means, and means actuated by pressure fluid 15 valved by the load controlling means of such other compressor to render the load controlling device of the compressor first set in operation ineilfective to vary its load.

'8. The combination or a plurality of compreso Sors discharging into a common receiver, load controll s means for each compressor, means for automatically initiating sequential operation 0!. the compressors and their load controlling means inresponsetoanincreasingdemandsndmeans g controlled by the load controlling means and acting during the starting of a compressor to render the load controlling means otanother operating compressor ineflective to vary. the load of such other operating compressor. 30

9. Thecombination or a plurality oi compressors into a common receiver, regulators for controlling the loads or the compressors, pressure actuated valve means controlled by the regulator 01 an operating compressor for initiating the operation of another compressor, and a valve actuated by pressure fluid valved by the regulator of another compressor, during the starting thereof for rendering the regulator of the said operating compressor ineflective to vary the load of said operating compressor.

10. The combination of a plurality of compressors discharging into a common receiver, regulators for controlling the loads of the compressors, manually operable means for initiating the operation of a compressor and its regulator, and pressure actuatedvalve means, controlled by the regulator of such operating compressor for initiating the starting of another compressor.

11. The combination of a plurality of compressors discharging into a common receiver, motors for driving the compressors, power supply controlling means for the motors, and pressure fluid actuated means acting in response to a predetermined pressure value in such common receiver to to eflect the actuation of the power controlling means of an idle motor to start such idle motor.

12. The combination of a plurality of compressors discharging into a common receiver, motors for driving the compressors, pressure fluid actuo0 ated switches for the motors, pressure fluid actuated valves for admitting and exhausting pressure fluid to and from the pressure actuated switches, and means operating in response to an increasing demand on an operating compressor to eifect g5 actuation of a valve for admitting pressure fluid toaswitchforstartingthemotorotanother compressor.

19. The combination of a plurality of compressors discharging into a common receiver, motors for driving the compressors, pressure actuated switches for the motors,conduits for conveying pressure. fluid to and from the switches, valves to control the conduits, load controllingmeans for the compressors operating in response to an 7 increasing demand on an operating compressor to effect actuation of. a valve for admitting pressure fluid to a switch for starting the motor of another compressor, and means in the conduits for restricting the exhaust of fluid from the switches.

14. The combination of a plurality of compressors discharging into a common receiver, and

means actuated by the pressure fluid discharged from the compressors acting automatically for sequentially stopping the compressors upon the attainment of a predetermined pressure value in such common receiver.

15. The combination of a plurality of comp'res sors discharging into a common receiver, means for sequentially stopping the compressors; and means for controlling the loads of the compressors and to effect actuation of the first said means upon the attainment of a predetermined pressure value in such common receiver.

16. The combination of a plurality of compressors, a storage receiver for the compressors, means for sequentially efiecting the starting of the compressors, means for sequentially efiecting the stopping of the compressors, and pressure fluid actuated means acting responsively to the pressure within the storage receiver to effect actuation of the first mentioned means whenever the pressure in the storage receiver reaches a predetermined minimum value and to efiect actuation of the second mentioned means whenever the pressure in the storage receiver reaches a predetermind maximum value.

17-. The combination of a plurality of compressors, a storage receiver therefor; means for sequentially eifecting the starting of the compressors, means for sequentially effecting the stopping of the compressors, and regulators for controlling the loads of the compressors and for controlling both of said means.

18. The combination of a plurality of compressors, a storage receiver therefor, pressure actuated means for sequentially eflecting the starting of the compressors, pressure actuated means for sequentially efiecting the stopping of the compressors, and regulators acting in response to the pressure within the storage receiver to control the loads of the compressors and to efiect the actuation of both said means respectively as the pressure within the storage receiver reaches a certain predetermined low value and a certain predetermined high' value.

wrrm /r T. ALDERSON.