US2221789A - Pumping apparatus - Google Patents

Description

No 19, 1940' A. D. FERGUSON '2,221,789

PUMPING APPARATUS Filed Jan. 24, 1936 Patented Nov. 19, 1940 UNITED STATES PU'llIPING APPARATUS Alexander D. Ferguson, Michigan City, Ind., assignor to Sullivan Machinery Company, a corporation of Massachusetts Application January 24, 1936, Serial No. 60,581

8 Claims.

My invention relates to pumping apparatus for compressible fluids, and from another aspect to improved unloading means for such pumping apparatus.

It is common practice to provide for compound compressors total-intake-closure type unloading means for the low pressure cylinder and to unload the high pressure cylinder by holding open the inlet valves of the latter. Such a compressor should have provision made in its controlling means to effect a small time delay between the closure of the compressor intake and the unloading of the high pressure cylinder, in order that the partially compressed fluid in the intercooler may be compressed in the high pressure cylinder and discharged to the receiver or discharge line of the compressor, thereby effecting a small but desirable economy. It is also desirable, however, not to have this delay so long that the intercooler pressure will be pumped down too far before the high pressure cylinder is un-` loaded. After complete unloading is effected, there is a tendency for the intercooler pressure gradually to build up due to leakage past the intake unloader valve and the absence, due to the holding open of the inlet valves of the high pressure cylinder, of the continuous removal of air from the intercooler by the high pressure cylinder; and accordingly there are likely to be periodic poppings of the safety valve which is provided on the intercooler, an annoying and at times definitely undesirable thing. Were the safety valve omitted, for the purpose of preventing the popping mentioned, the range of compression in the low pressure cylinder might develop to an excessive one; and it is therefore desirable to provide for a venting of the intercooler after complete unloading is effected, and to maintain the intercooler vented throughout the period of unloaded operation, and then to terminate the venting at the desired time.

An object of my invention is to provide an improved compound compressor. Another object of my invention is to provide an improved compound compressor having improved unloading means. It is a further object of my invention to provide an improved controlling means foreflecting the functions pointed outabove as desirable, in the control of loading and unloading of a compressor. It is a still further' object of my invention to provide an improved unloading means for a compound compressor, in which a single discharge-pressure-responsive pilot valve has associated therewith auxiliary apparatus whereby fluid supply for unloading both the low and high pressure cylinders is sequentially delivered, and whereby venting of the intercooler is effected throughout the unloaded operation. Other objects and advantages of the invention Will hereinafter more fully appear.

f In the accompanying drawing, in which one illustrative embodiment of the invention has been shown- Fig. 1 is a side elevational view of a multi-stage compressor in which the illustrative embodiment 10y of the invention is incorporated.

Fig. 2 is a vertical section, on an enlarged scale, through the secondary control device which governs the time of high pressure cylinder unloading and venting of the intercooler, and also 15 through the total-intake-closure unloader valve associated with the low pressure cylinder.

Fig. 3 is a view, similar to Fig. 2, b-ut with some of theparts omitted, showing the apparatus in` a different working position.

Fig. 4 is a small fragmentary sectional view through theunloading apparatus associated with an inlet valve of a high pressure cylinder.

Fig. 5` is a` fragmentary enlarged sectional View, on a plane similar to that of Fig. 2, to make 25 details of construction clearer. I

Referring to the drawings, it will be seen that.

a compound compressor I has a frame 2, a driving shaft 3, a flywheel II,V herein shown as beltdriven, a low pressure cylinder 5, a high pressure cylinder 6, and an intercooler l.

Air is admitted to thelow pressure cylinder 5l under the control of van unloading mechanism, generally designated 8 and ofthe total-intakeclosure type; and the low pressure cylinder discharges through a connection 9 to the intercooler l.l From the intercooler the air is led to the inlet valves of the high pressure cylinder through a connection Ill and, after compression in the high pressure cylinder,` is discharged through a discharge line I I to a receiver R. rThe intercooler is provided, as usual, with a pressure gauge I2 and a pop safety valve I3. The high pressure cylinder 6 is provided with inlet-valve-v opening unloading mechanisms, of which onej unit is shown in Fig. 4. The intake-closure-type unloading mechanism 8 includes a casing I6 providing a space I'I to which air initially has access. The intake space of the low pressure cylinder Vis connected with a space I 8 which is partitioned 50 off by a wall I 9 having alined openings 20 and 2|, from thespace Il. A double-beat valve ele. ment 22, normally held in open position bya spring 2 3, is movable by a piston 24 reciprocablef;

in a cy1inder25, to close the openings 20 and 2 I, 55:

and thereby close communication between space |1 and space |3, and thus effect unloading of the low pressure cylinder by the total closing of the intake to the latter. The high pressure cylinder is provided with inlet valves 21 normally held in closed position by springs 2S and controlling communication between spaces 29 connected through the passage l0 with the intercooler, and spaces 3|! communicating directly with the cylinder l0 proper. Plungers 3| are adapted to actuate ngers 32 to open and maintain open the inlet valves of the high pressure cylinder, and connections 33 are provided to effect communication between the plungers and a source of pressure uid supply or a point of exhaust, through a connection 34 and the apparatus hereinafter described. A pilot valve 3E, which may be of any suitable type and which is herein illustrated as a so-called RC pilot valve, well known in commerce, is arranged to control communication between the receiver R and a pipe 31, and between said pipe 31 and the atmosphere; being operative automatically in a well known manner, when the receiver pressure rises to a predetermined maximum value, to open communication between the receiver and the line 31, and so to supply fluid from the receiverto that line, and being operative, upon a predetermined drop in pressure below said predetermined maximum, to interrupt 3.0 the communication previously established and to vent the pipe 31 to atmosphere.

The pipe 31 leads to a controlling apparatus, generally designated 38, and the connection 34 also leads to this controlling apparatus, but to 35 a diierent point therein. The controlling apparatus 38 is mounted upon the top lof a cylinder member 39 in which the cylinder bore 25 is formed, and includes a lower portion 40 having a small bore 4| therein, in which a plunger 42 4'0 is reciprocable. The lower end of the bore 4| is provided with a check-valve-receiving cage member 43 containing a check valve44 which is unseatable to provide a large communication, through a passage 45,l between the cylinder bore 45 25 and the bore 4|. A lateral connection 46 connects the pipe 31 with bore 4|, and also has communication through a small passage 41 directly with the cylinder bore 25. Accordingly, pressure may ilow from the pipe 31 to the cylinder bore 25 through the small communication 41; and through the much greater cumulative flow area provided by this passage 41 and the passage 45 when the valve 44 is unseated, fluid may flow out of cylinder 25 under proper pressure conditions. It should further be noted that should plunger 42 cover the mouth of 46, actuating pressure may attain access to the bottom of said plunger through passage 41, cylinder 25, and the passages in the cage 43. The member 38 also includes an upper end portion 49, and

this is provided with a plunger-receiving chamber 50 which is coaxial with and communicates with bore 4|. An annular groove 5| is arranged in portion 49, herein substantially midway between the ends of chamber 5U, and a small longitudinal groove 52 extends upwardly from groove 5|v to the top of chamber 50. A plunger 53 has an upper portion 54 tting the bore 50 and a lower portion 55 of reduced diameter, and a 0 shoulder 5S is provided at the adjacent ends of the portions 54 and 55. When the plunger 53 is in upper position, as shown in Fig. 2, the space around the plunger portion 55s-provides communication between groove 5| vand the lower end 75" of the chamber 5U. When the plunger is in its bottom position, groove 5| is cut off from communication with the bottom part of chamber 50. A connection 51 connects groove 5| with the interior of the intercooler, and may lead to any point in the air passages between the low 5 pressure discharge valves and the high pressure inlet Valves. Pipe 34 opens into bore 4| at a point 58 uncovered when plunger 42 is in top position. A passage 59 extends from the bottom of chamber 5l! to the chamber I1. 1U

The mode of operation of the apparatus described will be readily understood from what has been said. Let it be assumed that the compressor is operating loaded. Under these circumstances the pilot mechanism 36 will connect the 15 pipe 31 to atmosphere. Accordingly, passage 43 will be connected to atmosphere and passage 41 connected to atmosphere. Therefore, chamber 25 will be connected to atmosphere and the plunger or piston 24 will be maintained in the 20 raised position shown in Fig. 3 by the action of the spring 23 upon the double-beat valve 22. The plunger 42 will be in bottom position, as shown in Fig. 3, and accordingly intercooler pressure admitted to the chamber 50 through the connection 25 51 will act upon the top of plunger 53 and maintain the latter in its bottom position. The port 58 being, in the depressed position of the plunger 42, uncovered, there will be established a coinmunication between the space at the backs of 3U the plungers 3| through the pipes 33 and 34, the port 58, the bore 4|, the chamber 50 and the connection 59 to the atmosphere, and accordingly no pressure will be exerted upon the inlet valves of the high pressure cylinder for the purpose of unloading the latter, and accordingly since, as above noted, the double-beat valve 22 is in open position, the compressor will operate fully loaded.

Now let it be imagined that the compressor "im discharge pressure rises to the desired upper limit and that, accordingly, the pilot valve mechanism 36 operates in its well known manner to close the communication of the pipe 31 with the atmosphere and to open communication between T545 the receiver and the pipe 31. Pressure will then ow through the connection 31 into the passage 4G and will flow through the passage 41 into the cylinder 25 and push the piston 24 downward and move the double-beat intake closure valve r5h 22 to the position of Fig. 2, and thereby unload the low pressure cylinder. Pressure will also act upon the lower end of the plunger 42; whether directly through the connection 46, or through the connection 41, the piston chamber 25 and .'55 through the cage member 43, is immaterial. This pressure will, it is noted, act on a relatively small area, and, as above noted, during the loaded operation of the compressor the upper end of the relatively large plunger 53 is subjected to interi60 cooler pressure. The area ratios are such that until intercooler pressure has been materially reduced, receiver pressure acting on the lower end of the plunger 42 will be unable to overcome the pressure acting upon the upper end of the plung- 65 er 53. Now, since the low pressure cylinder has been unloaded by having its intake completely closed, no more air will be supplied to the intercooler, but the compressor will none the less be continued in operation and the high pressure cylinder, which has not been unloaded, will rapidly pump down the intercooler pressure, and. since the space above the plunger 53 is connected through the grooves 52 and 5| and connection 51 with the intercooler, the pressure above 75 the plunger 53 will also be rapidly reduced.

When this pressure has been suiiiciently reduced so that the force exerted by the plunger 42 is sucient to overcome lthe weight of the plunger 53 .and the residual pressure upon the top of the latter, the plunger 42 will rise to the position shown in Fig. 2 and pressure will ilow from the bore 4l through the passage 58, pipe 34, and pipes 33 toact upon the high pressure inlet valve openingplungers 3|, and the high pressure cylinder will then be also unloaded. It will be observed that due to this delayed action, the air in the intercooler will not be lost to any serious extent, but will be conserved, for it will be noted that the intercooler pressure will be brought down tobut little above atmospheric pressure before complete unloading takes place. Now observing the position of the parts in Fig. 2, which corresponds to complete unloading, it will be noted that the interior of the intercooler is connected through the pipe 51, groove 5I, and longitudinal groove 52 with the upper end of the plunger chamber 50, and that the intercooler is also connected through the pipe 51, groove 5|, and the space about the reduced end 55 of the plunger 53 with the lower end of the chamber 50 and so through the connection 59 with the atmosphere. Therefore, if there be any leakage of air into the low pressure cylinder with a resultant discharge of that air to the intercooler, intercooler pressure will not be able to build up above atmospheric pressure because the pressure will freely discharge to the space I1 which is in communication with the atmosphere in the ordinary compressor. It should be borne in mind that the communication with the atmosphere last described was not established until the intercooler pressure was brought down nearly to atmospheric pressure, and so but little air previ- 40 ous-1y pumped into the intercooler escaped to atmosphere when that connection was established. We may now consider briefly what occurs when the receiver pressure drops down to the desired minimum value. When this occurs, pilot valve 45 36 will cut oi communication of the pipe 31 with the receiver and vent the pipe 31 to atmosphere. This will ven-t the pressure rapidly through the dual communication, through 41 and the passages in cage 43, of the piston chamber 25 With 50 the passage 46 and connection 31. The intake closure valve 22 will, therefore, be promptly moved to open position by the spring 23, which will be able to overcome the reduced pressure exerted by the piston 24. The plunger 42, relieved of receiver pressure, will also promptly be moved downwardly by the weight of the plunger 53, whose upper end Will be subjected through the longitudinalgroove 52 to at least as high a pressure as the pressure acting upon the lower end of the plunger 53. When the plunger 53 moves down a short distance, communication between the pipe 51 and the passage 59 will be cut oil, and the intercooler will no longer be connected with the atmosphere, and the pressure 65 building up within the intercooler as the compressor operates loaded will quickly pass to the top of the plunger 53 and hold the same rrnly seated. Obviously, any air which may not escape through port 58 and bore 4l and pipe 31 back to 70 the pilot Valve will quickly pass, in the lowered position of the plunger 42, from behind the unloading plungers 3l to atmosphere through bore 4|, chamber 50 and passage 59.

It will be evident, from what has been said, 75 that a most satisfactory sequence of operations has been provided for. It will be noted that the apparatus is very simple and has no parts which are likely to become deranged, that the apparatus provides ample ow areas for al1 the needed fluid movements, and that step operation is provided Wherever the same is advantageous.

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

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

1. In combination, a compressor having high and low pressure cylinders and an intercooler, means for closing the intake to the low `pressure cylinder to eiect unloadin-g thereof and including a piston operating at a predetermined compressor discharge pressure to eiect such unloading, and automatically acting means responsive to variations in 4pressure differences between the discharge sides of said low and high pressure cylinders arising f-rom the unloading of the low pressure cylinder for subsequently venting the intercooler to atmosphere and unloading the high pressure cylinder, said automatically acting means including a plunger coaxial with said piston for controlling high .pressure cylinder unloading.

2. In combination, in a pump unloading apparatus, a supporting structure providing alined cylinders, alined pistons in said cylinders oppositely movable to effect unloading of different compressor cylinders, and one having controlling means precluding movement thereof in an unloading effecting direction until after the cylinder controlled by the other is unloaded and Vgoverned by pressure conditions created as a result of operation of the other.

3. In combination, in an apparatus for unloading a high `pressure cylinder of a multi-stage compressor and venting an associated lower pressure cylinder of said compressor, means providing alined bores, a plunger recipr-ocable in one of said bores and controlling unloading of a high pressure cylinder, a larger plunger reciprocable in the other of said bores and controlling venting of an associated lower pressure cylinder, and compressor discharge pressure responsive means for supplying operating `pressure to the end of the rst mentioned plunger away from the other plunger.

4. In combination, a multi-stage compressor having an intercooler, an intake closure type unloader for :the low pressure cylinder, an unloading apparatus ior the hi-gh pressure cylinder eiective to interrupt the discharge of pressure from the intercooler lby said high pressure cylinder, and means for effecting operation of said high .pressure cylinder unloading means and for providing .a venting of the intercooler pressure including a relief valve mounted upon said intake closure type unloader and opened after the latter is closed and the intercooler pressure reduced substantially.

5. In combination, a multi-stage compressor having an intercooler, unloading means for the low pressure cylinder including a cylinder having a piston reciprocable therein, intercooler venting means including a cylinder having a pisinder having a piston -r'eciprocable therein, said last mentioned cylinder having its bore connected at its opposite ends to the bores of said rst and second mentioned cylinders.

6. In combination, a multi-stage compressor having an intercooler, unloading means for the low pressure cylinder including a cylinder having a piston reciprocable therein, intercooler venting means including a cylinder at one end of said first mentioned cylinder and having a piston reciprocable therein, and unloading means for the high pressure cylinder including a cylinder having a piston reciprocable therein, said last mentioned cylinder arranged between said two previously mentioned cylinders and said last mentioned cylinder having its bore connected at its opposite ends to the mutually more proximate ends of the bores of said iirst and second mentioned cylinders.

'7. In combination, a multi-stage compressor having an intercooler, unloading means for the 10W pressure cylinder including a cylinder having a .piston reciprocable therein, intercooler venting means including an alined cylinder having a piston reciprocable therein, and unloading means for the high pressure cylinder including another alined cylinder having a piston reciprocable therein, said last mentioned cylinder having its opposite ends connected respectively to the bores of said first mentioned and second mentioned cylinders.

8. In combination, in a multi-stage compressor, high and low pressure cylinders and an intercooler, means for unloading said 10W pressure cylinder comprising an intake closure unloader for the low pressure cylinder including a pressure-actuated piston, means for effecting interruption of pumping by the high pressure cylinder subsequently to the unloading of said low pressure cylinder and including a pressure-actuated piston, and means for Venting said intercooler simultaneously with .the interruption of pumping by said high pressure cylinder and incl-uding a third piston coaxial With the rst and second mentioned pistons and rigidly attached to and actuated by said second mentioned pist0n.

ALEXANDER D. FERGUSON.

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