US1649297A - Compressor - Google Patents

Description

Nov. l5, 1927. 1,649,297

s. T. NELSON coMPREssoR Filed July 6, 1922 2 Sheets-Sheet. 1

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Nov. 15, 1927.

5. T. N ELSON COMPRESSOR Filed July 6. 1922 2 Sheets-Sheet 2 ftluru ug'.

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Patented Nov. 15, 1927.

UNITED STATES 1,649,297 PATENT OFFICE.

SVEN' T. NELSON. OF CHICAGO, ILLINOIS, ASSIGNOR TO`` SULLIVAN MACHINERY COI- PANY, A CORPORATION OF MASSACHUSETTS.

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Application led July 8,

My invention relates to compressors, and more particularly to compressor systems provided with means for effecting a progressive unloading thereof whereby with a constant speed drive it may be possible for the compressor output to be varied in such manner as to maintain the discharge line pressure within certain desired limits.

An object of my invention is to provide an improved compressor mechanism. Another object of my invention is to provide an improved compressor mechanism having improved partial or step by step unloading means. A further object of my invention is to provide an improved compressor system having improved means for effecting a step by step unloading of the entire system in which less of complication is involved than in such systems o other types. Other ob* fleets and advantages of my invention will ereinafter more fully appear.

In the accompanying drawings I have shown for purposes of illustration one form which my invention may assume in practice.

In these drawings,-

Fig. 1 is a diagrammatic view 0I a compressor system provided with the illustrative form of my invention.

Fig. 2 is a view in central vertical section through the intake 'unloading means provided for use on the low pressure cylinders of the compressor units, certain parts being shown in elevation. i

Fig. 3 is a central vertical section through the pilot mechanism controlling the operation of my improved system.

Fig. 4 is an elevation of the same viewed from a different angle.

In the form of my invention shown for purposes of illustration in the accompanying drawings I have shown it embodied in a twin angle compound compressor system which comprises a pair of angle compound compressors 1 and 2, each having low pressure cylinders 3 and high pressure cylinders 4, the low pressure cylinders being supplied with air from intake lines 5 and discharging throu h intercoolers 6 to the high pressure c vlin ers 4 which, in turn, discharge by way of discharge lines 7 to a receiver or other point of storage or use.

In the customary construction the compressors l and 2 are driven from a common crank shaft 8. but in order to permit the more intelligible disclosure of the piping 1922. Serial No. 573,152.

system employed, I have shown the compresser umts 1 and 2 set one behind the other instead of in their customary relation. As each of the units is the same in its general details and as it is by the particular nature of the piping connections with the pilot mechanism that the progressive or step by step unloadin of the system is accomplished, it will suee if I describe the unloadin mechanism for one compressor and thenv escribe the control connections and pilot valve for both units.

Accordingly, considering the compressor unit 1 and noting particularly Fig. 2, it will be observed that the intake line 5 communicates with a casing 9 transversely of which there extend partition members 9 and 10, the partition members 9 and 10 being connected at about the lon 'tudinal ce.nter of the casing 9 by a vertical partition 11 so that separate chambers 12 and 13 are formed and these chambers 12 and 13 communicate respectively withthe inlet valve for the front and rear ends of' the low pressure cylinder 3. Above the partition 10 1s a chamber 14 which vis connected with the chamber below the partition 9 in a manner which will shortly be made apparent. The partitions 9 and 10 at opposite sides of the partition 11 are traversed by circular ports 15 and 16, which orts are surrounded b valve seats 17' an k18 the ports being ldentical at each side of the partition 11, and the upper ports being somewhat larger than the lower to permit the insertion of the valve mechanism. Slidable throu h the o enings 15 and 16 are valve mem ers whic for urposes of convenience will be designated) 20 for the rear end of the cylinder and 21 for the front end thereof, these valve members each comprising a pair of circular valve seat portions 22 and 23 which are respectively adapted to seat u n ythe seats 17 and 18 'and from each of t e valve seating ortions 22 and 23 there depend supported y suitable ribs 24 and 25, gui ing portions 26 and 27 which serve to maintain the valves 20 and 21 properly centered withintheir seats during reclprocation thereof. The valves are hollow throughout their length as indi stems 30 which are connected as at 31 to cross arms 32, these latter being in turn connected by springs 33 with cross arms 34 arranged at the top of operating cylinders 35 which are mounted as indicated at 36 upon heads 37 closing the top of the casing 9. Within the cylinders 35 there are pistons 38 reciprocable, these pistons engaging stems 39 connected with the stems 30 and being operative to force the valves 20 or 21, as the case may be, closed on admission of air to their cylinders 35. Suitable stops 42 limit the upward travel of the pistons 38.

For the purpose of greater convenience in subsequent reference to the unloading system as a Whole, the unloading mechanism for the crank end of the low pressure cylinder of unit No. 1 will be designated generally 43, that for the head end thereof 44, that for the crank end of the low pressure cylinder of the unit No. 2, 45, and that for its head end 46.

It will be obvious that any suitable type of inlet or discharge valves may be employed upon the several cylinders, the mode of operation of my mechanism being absolutely independent of the nature of the valves used. On the high pressure cylinder, the unloading mechanism for the upper and lower ends respectively are designated, for unit number 1, 49 and 50, and for unit number 2, 51 and 52. These unloading mechanisms are of the well known intake closure type and comprise casings 8 connected by brush passages 7 with the lines from the intercooler and each container mechanism, similar to that in thel chambers 12 and 13, controlling the commu-l nication between the intercooler and the ends of the cylinders 4. Each of the mechanisms 49. 50, 51 and 52 is operated by mechanism similar to the parts designated 30 to 42, inclusive, and described in connection with the low pressure cylinder unloading mechanism. As this construction is obvious, it has not been thought necessary to describe it in detail. For the purpose ot' controlling the operation of my improved unloading system, I employ a pilot valve mechanism which is the invention of one Alexander D. Ferguson and which is described and claimed 1n his copending application, Serial No. 581,253, filed Aug. 11, 1922.

This pilot valve mechanism is generally designated and comprises a series of valveY members which are annular in construction and which are designated respectivel 101, 102, 103 and 104, which valve mem ers are controlled by means which I Shall now more specifically describe. The valve members 101 to 104 respectively are arranged to cooperate with seats 105, 106, 107, and 108, the several seats being plane, and each containing an annular groove 109,*the several annular grooves 109 communicating respectively by passages respectively numbered 110, 111, 112, and 113 with pipes 114, 115, 116, and 117, which pipes I shall hereafter refer to again. Each of the seats to 108, inclusive, is traversed by a central passageway, these passageways bein r of uuiorm diameter and being indicate at' 118. Extending longitudinally through the several passageways mentioned is a stem formed at its top with a plunger or piston 121 upon which a spring 122 housed in the casing 123 and adjustable by means of a follower 124 roacts. Forme upon the stem 120 is a collar 125 which is adapted to engage after a predetermined movement from a nriven lower position, which will be more fu y described later, the valve member 101 and lift it from its seat 105. Resting upon the top of the valve member 101 is a sleeve 126 which is of slightly less length than the distance between t e valve member 101 and the valve member 102 when both are seated. This sleeve is adapted to be raised on upward movement of the valve 101 and after suiiicient upward movement to engage and lift the valve member 102. A similar sleeve cooperating with the valve 103 in a similar manner and designated 127 is superimposed on the valve 102 and a further similar sleeve 128 is arranged to be lifted by the valve member 103 and to raise the valve member 104. The piston 121 is slidable in a cylinder 129 formed in the casing 123 and fluid pressure from a suitable source is conducted by a passage 130 to chambers 131, 132, 133, and 134 in which the valve members 101 to 104 respective] are located. This pressure normally ten s, of course, to maintain the several valve members seated and as it will be observed that cach of the valve members is raised successively alone from its seat and as it will be observed that the valve members are all of substantially equal diameter with the piston 121, it will be apparent that the pressure of air acting beneath the piston 121 is such as to practically neutralize the Work necessary in raising one of the valve members ofi' its seat. The stem 120 passes through a suitable bore 136 downward into a space formed between a pair of support members 137 formed integral with a support 138. Secured to the support 138 is an expansible diaphragm chamber 139 to whose interior 140 fluid may be conducted by a passage 141 and a series of grooves 142 formed in a member 143 which threadedly engags the lower head 144 of the diaphragm cham er and holds it lixedly in position on the member 138. The member 143 is traversed by a passage 145 through which a lunger 146, alined with the stem 120 and liaving suitable sealing grooves 147 snugly extends, the plunger 146 engaging at 1.48 the upper head 149 of the diaphragm chamber. The plunger 146 is provided at its lower end with a handle 150 and is traversed lil lill

by a series of four arallel transverse passageways 151, 152, 1 3, and 154. The member 143 is provided with a depending sleeve 155 in which a series of holes 156,157, 158 and 159 are formed, these holes being so spaced relative to each other and to the "holes 151 to 154 that the hole 151 will register with the, hole 159 with a very sli ht up- Ward4 movement of the stem 146, whi e progressively further upward movement of the stemr`146 will successively cause registration of the holes 152 and 158, 153 and 157, and 154 and 156. When the first of these pairs of holes regster, valve 101 is unseated and as each successive pair of holes is brought into register an ad itional valve is opened. The function of this mechanism will ,be shortly explained.

Leading from a receiver to which the compressors dischar or from their common discharge' line, 1s a passage or connection 160 controlled b a stop valve 161 and provided with a. strainer 162 to prevent the passage of impurities or solid matter to the valve mechanlsm. Beyond the strainer 162 is a T 163 from which a connection 164 leads to the passa way 130 reviously described. From the o er end ofp the T a connection 165 leads tothe pop valve 166, which pop valve works on the principle of the ordinary safety valve, that is, it opens when a desired pressure is reached in the line 160 and permits a pressure equal to the excess above the desired pressure in line 160 to pass through `the valve before it again closes. The chamber above the valve in, the pop valve 166 communicates with the passage 141 so that a pressure equal to the excess above the seating of the pop valve will be transmitted to the diaphragm chamber 140. Upon the to of the pop valve 166 is a safet valve 16 loaded to prevent building up o more than a desired pressure in the dia hragm chamber 140. A suitable pin ho e leak or adjustable leak such as a pet cock 166', as may be. deslred, is arranged at any suitable point between` the pop valve 166 and the muts of the diaphragm chamber whereb the pressure in the chamberJ 140 wil promptly fall on closure of the pop valve 166. Leakage may also be permitted around the plunger 146, a shoulder 168 thereon then .cooperating with the top of the member^143 in preventlng leakage when the diaphragm 1s collapsed to its smallest dimension.

The several pipes 114, 115, 116, 117, described above, serve to conduct operating luid to cause the proper sequential operation of the several unloadingmeans 43, 44, 45, 46, 49, 50, 51 and 52. The pipe 114 leads by branched connections to the unloading means `44 for the head end of the low pressure cylinder of unit number 1 and tothe unloading means 49 for the head end of the high pressure cylinder 4 of that unit. The

pipe 115 leads to the unloading means 43 for the crank end of the low pressure cylinder of unit number 1 and by a branch to the unloading means 50 for the crank end of the high pressure cylinder 4'of that unit. Passage 116 communicates respectively with the unloading means 46 and 51 for the head ends of the low and high pressure cylinders of unit number 2, and assage 117 serves to conduct fluid to the un oading means designated 45 and 52 for the other ends of the cylinders of unit number 2.

From the fore oing description the mode of o eration of t is mechanism will already be cearly ap arent. To recapitulate, however it may e briefly described as follows:

The compressor may be run when desired to havea certain substantially definite maximum output with progressively less roduction of air as ma be desired. If the emand for air falls off rom full load, the compressor may also be caused to give three-quarters, half, quarter, or no output, being entirely shut down as far as the delivery of compressed airis concerned, althou h the engine speed may remain constant. ,et it be assumed that the maximum demand for air in a given plant is equal to the full output of both the units 1 and 2. During such demand, the receiver ressure or pressure in `the compressor discharge lines will be approximately equal to what is desired and will not exceed the setting of the pop valve 166. Should the demand for air fall ofi' in part, the compressor, lcontinuin to deliver the same amount of air, will bui d up an increased pressure in its discharge line or receiver and the pop valve 166 will open and pressure will pass into the diaphragm chamber 140. This chamber will accordingly increase somewhat in volume in roportion to the pressure that is transmitted) past the tpop' valve 166 and, as its top moves upvvar it will cause the plun er or stem 120 to rise and the collar 125 will ift the valve 101 and duid pressure will be transmitted through the pipe 1-14 to the head end unloading means 44 of4 the low pressure cylinder o unit number 1 and to the unloading means 49 for the head end of the high pressure cylinder 4 of that unit. As a. result, the delivery of air by the compresser plant will be cut down to three-quarters of what was previously being delivered, the unit number 1 then simply operatin as a compound com ressor having a pair o single-acting cylin ers, the crank ends of the low pressure cylinder and of the high pressure cylinder alone operatin to comvpress air. If the demand for air as fallen oil' in such manner as to result in the continued rise of the ressure in the discharge line, despite the reduced out ut of the compressor, a higher pressure wil be transmitted through the pop valve 166 and the stem 120- will be forced upward further, causing'the valve 101 Ato raise the sleeve 118 and lift the valve 102 whereby pressure passes through the line 115 to the unloading means t3 and no further air is thereafter adn'iiltcd to the low pressure cylinder of unit number 1. The mechanism 50 is simultaneously operated to close the intake to the high pressure cylinder of that unit. As a result, unit number l is completely unloaded and supplies no more air to the discharge line. 'l`o guard against high temperatures resulting from possible leakage past the intake closure valves 2() and 2l. mechanism ol' the type shown and described in Patent No. 1,404,170, granted to one Il. C. Johansen, may hc placed in the ll. l. cylinders and will permit t-he discharge ol' such air as might be compressed in either end ot' the high pressure cylinder directly to atmosphere. lt will be 'understood that in the event that the demand for air is such that the single operating unit 2 can supply more pressure fluid than is needed, the unit 2 will be progressively unloaded, the supply of fluid through the pipe 116 taking place on opening ot' the va ve 103 and resulting in the unloading ot the head ends of the high and low pressure cylinders of unit number 2, while, il the demand for air entirely ceases or the pressure in the discharge line gets high enough, the further risc in pressure in the receiver or discharge lines of the compressor will cause the valve 104 to be unseated with a discharge of air to the line 117 to completely unload the unit number 2 by the supply of air to the mechanisms 45 and 52. Thereafter the compressor plant will simply operate idly, no air being discharged by the compressor to its discharge lines. As thedemand for air increases, it will be understood that the discharge pressure will fall and in proportion as the pressure falls the valves 104, 103, 102 and 101, will successively close and there will occur a reloading of the units 1 and 2, beginning with partial reloading of unit number 2, followed by a complete reloading thereof. The next step will be the partial loading of unit number land finally unit number 1 will be fully loaded. The pistons 38 are not absolutely tight fits for their cylinders 35 and accordingly, when no more air is supplied through the pipes 114, 115, 116, and 117, the air under pressure in these pipes will rapidly leak out and reloading will take place due to raising of the unloader pistons b their respective springs. As explained a ove, if desired, by the use of the plunger 146 and a suitable pin which may e inserted through the holes 154 and 156, 153 and 157, 152 and 158, or 151 and 1519, the compressor may be so set as to be incaable of producing more than a. fraction of its full output. Any possibility of damage due to excessive pressures in the chamber 140 will be avoided by the use of safety valve 167.

lt is also possible to practice my invention by dividing each of the units l aud :2 throughout in such manner that each constitutes in effect two separate compressors. It will be observed that. in the form described above the intakes to the low pressure cylinders are separate. The discharge` chambers of the low pressure cylinders may also be separated by a partition or otherwise. The intercoolers may be divided into two separate parts either in the, same outer casing or shell, or entirely distinct. The compressors 1 aud 2 may each then be made into practically two compound compressors, the intakes to thc two ends of the low pressure cylinders being separate, tho discharge from the ends ol the low pressure cylinders being led to the two parts of the intercoolcrs, and the intakes of. the two ends of the high pressure cylinders being connected tothe two parts of the intercoolers. In other words, the compressor units are divided, as it were, so that, save from common mechanical elements, they are as distinct as if built separalelv.

While I have in this application specifically described one form which my invention may 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 other forms without departing from its spirit or the scope of the appended claims.

lVhat I claim as new and desire to secure by Letters Patent is:

1. In combination with a compressor system including two compound compressors running continuously, means for reducing the output of the system comprising means for first partially and subsequently wholly unloading one of said compressors While the other compressor remains completely loaded, and common mechanism for controlling said lill last mentioned means to effect first partial and then total unloading thereby.

2. In combination with a compressor system including two compound compressors running continuously, means for reducing the output ot' the system comprising fractional unloading means for each of the compressors, and common mechanism for con trolling all of said unloading means operative to eil'ect complete unloading of one of the compressors prior tn any unloading of the other.

3. ln combination with a compressor system including two compound compressors` means for varying the output ot said system from its full capacity to zere without discontinuing the running of either of said compressors comprising means for first partially and then wholly unloading one of said compressors while the other compressor remains completely loaded and for thereafter unloading said last mentioned compressor and common mechanism for controlhn sai unloading means to effect unloading 1n the sequence specified.

4. In combination with a compressor sys-V tem including two compound compressors,

means for varying the output of said system from its fullcapacity to zero without 4discontinuing the running of either of said compressors comprising means associated with each compressor for first partially and then totally unloading the same, and common means for controlling said last mentioned means to effect lirst partial and then total unloading of one of said com ressors while the other remains fully loa ed and thereafter progressive unloading of the second compressor.

5. In combination with a compressor system comprising a pair of angle compound compressors running continuously, means for reducing .the output of the system comprising means for first partially and subsequntly wholly unloading one of said cornpressors while the other compressor remains completely loaded, and common mechanism for controlling said last mentioned means to 1 effect first partial and then total unloading thereby.

6. In combination with a compressor system comprising a pair of angle compound compressors running continuously, means for reducing the out ut of the system comprising fractional un oading means for each of the compressors, and common means for controllin all of said unloadn means operative to e ect complete unloading of one of the compressors prior to any unloading of the other.

7. In combination with a compressor system comprising a twin angle compound compressor, means for partially unloading each angle compound compressor, and common means for controlling all of said unloading means operative to cause unloading of one com ressor completely before any unloading of t e other.

8. In a compressor system including a plurality of continuously running pumping units cooperating in delivering air to a common line, means for serially intercepting iuid flow to said several units comprlsing separate actuators for each unit, and a common pilot mechanism serially controlling said actuators.

9. In combination, a double acting compound compressor and separate valve means controlled by compressor discharge pressure for closing the intake to one end of each of the cylinders thereof, and a single means for controlling each of said valve means.

10. In combination, a double acting compound compressor and separate valve means for closing the intake to one end of each of the cylinders thereof and for thereafter closing the intake to the other end of the low pressure cylinder thereof, and a single means for controlling each of said valve means in the sequence specified.

11. In combination, a double acting compound com ressor and separate valve means controlled y compressor discharge pressure for closin r the intake to one end of each of the cylinders thereof and for thereafter closing the intake to the other end of the low pressure cylinder thereof, and a single means for controlling each of said valve means in the sequence specified.

12. In combination, a double acting compound compressor and separate valve means for closing the intakes to one end of each of the cylinders thereof and for thereafter closing the intakes to the other ends thereof and a single means for controlling each o said valve means in the sequence specilied.

13. In combination, a double acting compound compressor and separate valve means for closing the intakes'to one end of each of the cylinders thereof and for thereafter closing the intakes to the other ends thereof, said means being controlled by variations in compressor discharge pressure, and a single means for controlling each of said Valve means in the sequence specified.

14. In combination, at least two com ound compressors and means for complete y unloading one of said compressors in steps while the other remains com letel loaded and both remain running, an a pi ot valve mechanism effecting complete control of said entire step unloading means.

15. In combination, at least two compound compressors and compressor discharge pressure controlled means for completely unloading one of said compressors in steps while the other remains completely loaded and lboth remain running, and a pilot valve mechanism effecting complete control of said entire step unloading'means.

16. In combination, a. double acting compound compressor, separate valves controllin the flow of air to the intakes to each en of each of the cylinders thereof, and compressor discharge pressure controlled means forcontrolling all of said valves.

17. In combination with a cylinder of a. double acting compressor having inlet means, a casing, a pair o middle chambers therein spaced from either side thereof, a connection between one of said middle chambers and the inlet means for one end of said cylinder, a connection between another of said middle chambers and the inlet means for the other end of said cylinder` a connection between an outer space of said cas-ring and the atmosphere, and separate valve means for controlling the communication between each of said two middle chambers and the third lill chamber, said valve means extending through said middle chambers and being provided with open spaces so as to afford a passageway through said middle chambers whereby free communication to the atmosphere is afforded the other of said outer spaces.

18. In combination with ,a cylinder of a double acting compressor having inlet means, a. casing having a pair of com artments which are so disposed across sai casing as to define additional outside compartments, a connection between one of said pair of compartments and the inlet means for one end of said cylinder, a connection between the other of said pair of compartments and the inlet means for the other end of said cylinder, a connection between one of said outside compartments and the atmos here, and separate valve means for control ing the communication between each of said pair of compartments and said outside compartments, said valve means extending through said pair of chambers and providing passageways whereby free communication to the atmosphere is aiiorded the remainder of said outside compartments.

19. In combination with a cylinder of a double acting compressor having inlet means, a casing whose interior is divided into outer chambers and a pair of intermediate chambers, a connection between one of said pair of intermediate chambers and the inlet means for one end of said cylinder, a connection between the other of said pair of chambers and the inletsmeans for the other end of said cylinder, a connection between one of said outer chambers and th'e atmosphare, and separate valve means for controlling the communication between each of said pair of intermediate chambers and said outer chambers, at least one of said valve means extending through from an outer chamber on one side to an outer chamber on the other side and providing a passageway through which free communication to the atmosphere is afforded.

20. In combination with a double acting compressor cylinder provided with inlet means, acasing whose interior is divided into a plurality of chambers, a connection between one of said chambers and the inlet means for one end of said cylinder, a connection between another of said chambers and the inlet means for the other end of said cl linder, a connection between a third one o said chambers and the atmosphere, separate valve means for controlling the communication between each of said first two chambers and the third chamber, and a serially operative multiple valve pilot mechanism controlling said valve means.

21. In a compressor system includin a plurality of continuously running pumplng units cooperating in delivering air to a common line, means for serially interce ting fluid How to said several units comprlsing separate Huid actuators for each unit and a common pilot valve serially controlling said actuators.

22. In a pumping system including a. lurality of compressor units each adapte to discharge into a common discharge line, means associated with each unit operable to unload the same, and common control means for controlling said units operative automatically to successively unload said units.

In testimony whereof I affix my signature.

SVEN T. NELSON.

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chamber, said valve means extending through said middle chambers and being provided with open spaces so as to aiford a. passageway through said middle chambers whereby free communication to the atmosphere is afforded the other of said outer spaces.

18. In combination with a cylinder of a double acting compressor having inlet means, a. casing having a pair of com artments which are so disposed across sai casing as to define additional outside compartments, a connection between one of said pair of compartments and the inlet means for one end of said cylinder, a connection between the other of said pair of compartments and the inlet means for the other end of said cylinder, a connection between one of said outside compartments and the atmos here, and separate valve means for control ing the communication between each of said pair of compartments and said outside compartments, said valve means extending through said pair of chambers and providing passageways whereby free communication to the atmosphere is afforded the remainder of said outside compartments.

19. In combination with a cylinder of a double acting compressor having inlet means, a casing whose interior is divided into outer chambers and n pair of intermediate chambers, a connection between one of said pair of intermediate chambers and the inlet means for one end of said cylinder, a connection between the other of said pair of chambers and the inlet means for the other end of said cylinder, a connection between one of said outer chambers and the atmosphere, and separate valve means for controlling the communicatlon between each of said pair of intermediate chambers and said outer chambers, at least one of said valve means extendingr through from an outer chamber on one side to an outer chamber on the other side and providing a passageway through which free communication to the atmosphere is afforded. y

20. In combination with a double acting compressor cylinder provided with inlet means, acasing whose interior is divided into a plurality of chambers, a connection between one of said chambers and the inlet means for one end of said cylinder, a connection between another of said chambers and the inlet means for the other end of said cylinder, a connection between a third one of said chambers and the atmosphere, separate valve means for controlling the communication between each of said first two chambers and the third chamber, and a serially operative multiple valve pilot mechanism controlling said valve means.

21. In a compressor system including a plurality of continuously running pumping units cooperating in elivcring air to a common line, means for serially intercepting fluid flow to said several units compris` ing separate fluid actuators for each unit and a common pilot valve serially controlling said actuators.

22. In a pumping system including a lurality of compressor units each adapte to discharge into a common discharge line,

means associated with each unit operable to unload the same, and common control means for controlling said units operative automatically to successively unload said units.

In testimony whereof I affix my signature.

SVEN T. NELSON.

Cexticate oL Correction.

Patent No. 1,649,297-

SVEN T. NELSON.`

Granted November 15, 1927, to

cioatwn of the above It is hereby ertified that error appears in the Prlnted spelne 34, for the word i correction as fo Il 4, line 89, :tor the word fxriinns therem lid LettersY Patenthould be read wlth thlgselclfrrec isdn conform to the record of the case 1n the a Ooes.

' and sealed this 10th day of January, A, D. 1

[mrd

Hows: Pg@ g, md for; and that th that the Sm M, J. MooRE. Acting of m' Certificate of Correction. Patent N o. 1,649,297. Granted November 15, 1927, to

SVEN T. NELSON.

It s hereby certified that error appears in the printed specification of the above numbered patent .requiring correction as follows: Page 2 line 34, for the word brush read branch; page 4, line 89, for the word from read for; and that the said Letters Patent'should be read with these corrections therein that the Same ma. conform to the record of the case in the Patent Oee.

and and Sealed this 10th day pf January, A. D. 1928.

[Inail i .M1 J. MOORE,

Acting Owlmlsnom of Pam.

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