US2302847A - Pumping apparatus - Google Patents

Description

Nov.'24, 1942. FERGUSON 2,302,847

I PUMPING APPARATUS Filed May 12, 1937 I 5 Sheets-Sheet l r I I 2017 JEN/6n 5 07. aflzarand 7 .N 1942 A. D. FERGUSON 2502 847 IIPUMPING APPARATUS Filed May 12', 195'? sSMQtS-snQQt 2 Nov. 24, 1942. A. D. FERGUSON' I PUMPING APPARATUS Filed May 12, 1937 3 Sheets-Sheet dhranderflizywaiz.

Patented Nov. 24, 1942 zsmm some arransrus Alexander D. Ferguson, Michigan City, Ind., assignor to Sullivan Machinery Company, a corporation of Massachusetts Application May 1:, 1037, Serial 110.142,. Claims. (oi, sac-2s) My invention relates to pumping apparatus,

' and more particularly to pumping apparatus having improved means for effecting a variable delivery of pumped fluid while maintaining an approximately uniform rate of actuation;

' It is naturally desirable, if economically practicable, to provide a pumping apparatus in which a wide variation in the quantity of fluid pumped may be effected while at the same time maintaining emcient operation and avoiding excessive heating of the COmPXGSSlbIB fluid being pumped. Numerous attempts in this direction have been made, and I have devised an improved apparatus working on this general principle and adapted to effect partial unloading of pumping apparatus, such as an air compressor, by interrupting admission through the inlet for all or a deflnite part of the suction strokes of the pump piston, and I have provided improved controlling means which enables a variation in the portion of the suction strokes during which no fluid enters the pump cylinder, and have made the control, in a preferred form, automatic, in accordance with the variations in pressure of the pump discharge.

Apparatus for controlling unloading which does not alter materially the structure of the inlet and discharge valve mechanism per se and which may be merely superimposed upon them, is obviously ofa very advantageous nature, and I have provided a device which, while allowing the use of automatic inlet valve devices, permits the interruption of the intake 01 fluid to be pumped, at substantially any desired point in the suction stroke, thereby reducing the quantity of pumped fluid delivered upon each of the compression strokes of the pump or compressor. .Desirably, such an apparatus assumes the form of an auxiliary shut-oil valve which may be caused to seat virtually instantaneously, but which, when unseated, neither interferes with the efficient working of the compressor nor is subjected to forces making it diflicult to maintain it in open position. Desirably, means is provided for electrically controlling such a valve, and the controlling means may advantageously comprise means actuated in synchronismwith the compressor or pump in such a way as to insure the rupting admission of fluid to the pump at a substantially uniform time in the working cycle, while allowing it to become operative to interrupt the intake of fluid at any point during the suction stroke, depending upon the value of the pump discharge pressure. The contr may be made directly responsive to the discharge pressure, if desired, by a servo-motor controlling the position of a suitable contact device, or may be made responsive to the variations in pressure of the pump discharge-over and above a certain minimum value, as, for example, by providing a suitable pop type valve which will open, let us say, when the compressor discharge pressure attains a value of one hundred pounds and simply permit the building up at its discharge side of pressures in excess of one hundred pounds.

An object of my invention is to provide an im= proved pumping apparatus. .Another object of my invention is to provide an improved pumping "apparatus having improved means for varying the duration of, and, if desired, wholly interrupting, the intake of fluid to be pumped during each cycle of operation of said pumping apparatus. I

A further object of my invention is to provide an improved pumping apparatus having automatic inlet and discharge valves and improved means so-to-speak superimposed upon the inlet valve mechanism and operative to cut ofl automatically the access of fluid to be pumped, to said inlet valve, at a desired time in the suction stroke of the pumping'apparatus. -A still further object of my invention is to provide an improved auxrendering inoperative of the device for interiliary unloading apparatus of the electrically operated type embodying a valve which is movable to interrupt the access of fluid to be pumped, to the inlet valve mechanism of the pump. Yet a further object of my invention is to providean improved auxiliary valve device controlling the admissionof fluid tobe pumped, toapump cylinder, having improved controlling means regulating the'portions of a suction stroke during which the same is operative. Still another object of my invention is to provide an improved flow-controlling valve particularly adapted for use in controlling the unloading of a pump or compressor, having improved electrical actuating means and of an improved construction, whereby the same is free from harmful interference with fluid flow and likewise subjected degree to-the influence of flowing fluid. Other objects and advantages oi my invention will hereinaiter more fully appear.

In the accompanying drawings, in which one iorm of my invention is shown for purposes of illustration,

Fla. 1 is a view, partially in side elevation and partially in section, showing a pumping apparatus constructed in accordance with my invention.

toaminimum view through a combined inlet and discharge valve mechanism arranged at one end of a compressor cylinder and provided with improved controlling means constructed in accordance with the illustrative embodiment of the invention.

Fig. 3 is a view, with parts broken away, primarily on the plane of the section line 3-3 of Fig. 2.

Fig. 4 is a section on the plane of the line 4-4 01 Fig. 3.

Fig. 5 is a section on the plane of the line 5--5 of Fi 2.

Fig. 6 is a top view, but with certain parts shown in section, of a portion of the electrical controlling apparatus.

Fig.7 is a side view of the same apparatus, with parts broken away, this view being taken on the plane of the section line 1-1 of Fig. 6.

Fig. 8 is a fragmentary section on the plane of the line 88 of Fig. 7.

Fig. 9 is a fragmentary section on the plane of the line 8-9 of Fig. 7.

Fig. 10 is a section on the plane of the line l0 ll of Fig. 6, with the view turned through 90 so that the parts correspond to Fig. 8.

Fig. 11 is a section on the plane of the line li-H of Fig. 7.

Fig. 12 is a section on the l2l2 of ig. 6.

Fig. 13 is a wiring diagram.

Fig. 14 is a diagrammatic view showing a deslrable mode of controlling pressure supply.

In the drawings, a suitable base 1 supports a compressor, generally designated 2, having a cylplane 01' the line inder, generally designated 3, containing in its bore 4 a piston Land discharging through a line 3' to a suitable point of use or storage, herein exemplifled by the receiver 1. The compressor cylinder has heads 8 and 9 providing intake chambers l0, and has a discharge chamber II which is connected with the discharge line 6. Suitable automatic inlet and discharge valve mechanisms l2 and I3 are provided at each end of the compressor cylinder-herein, the compressor is of the double-acting type- -each being supported by a stud l4 and held to said stud by suitable nuts 15 and i8.

The discharge valve mechanism l3 comprises a usual ported seat element I1, a guard element It, a guide element i9, and annular valve 20, and a suitably flexed valve spring 2|; the parts being held in cooperative relation ,by cap screws 22. The inlet valve mechanism i2 diflers from a usual inlet valve mechanism frequently used in such compressors, only in that the seat element is made of non-magnetic material, such as brass, aluminum, or the like. Herein, it will be noted that this valve mechanism comprises a ported seat element providing a seat 25 surrounding ports 21 and adapted to have a valve 28 cooperate therewith. The valve is normally maintained in closed position by a spring 29, which is in turn held in position by a guard plate 30. The movements of the valve are guided by a suitable guide element 3| which is clamped between the seat element 25 and the guard element 30 by cap screws 32.

Obviously, upon the suction strokes of the piston 5, air or other fluid to be pumped will pass from the intake chamber l0 through the ports 21, past the unseated valve 28, and into the compressor cylinder; and upon the discharge strokes the compressed fluid will unseat the valve 20 and pass to the discharge chamber ii and through the discharge line 6 to the receiver 1.

electromagnet 38 associated with said valve; said valve element 31, however, when released adapted to seat upon coaxial seat surfaces 39, upon the member 25, between which the ports 21 extend.

The structure of the device .35 may obviously vary, and herein I have shown the winding 40 0t an electromagnet enclosed in a suitable metallicdesirably steelcasing 4| and having secured to its face a brass, phosphor-bronze, aluminum or other non-magnetic front cover 42. This front cover is grooved, as at 43, to provide a wide annular recess 44 adapted to receive the valve 31, which is of magnetic material. If desired, there may be formed integrally with the cover 42, or separately therefrom, as shown in the drawing, an annular, grooved valve spring receiving and guiding portion 45, having a groove 46 lacing the valve and receiving a suitable transversely or annularly flexed annular spring element 41 which is desirably of non-magnetic material. If the portion be made separately, as indicated in the drawing, from the cover 42, and set into the latter, so to speak, and made of magnetic material, it is desirable that the spring, which is of non-magnetic material, shall be greater in thickness than the depth of the spring-receiving groove, as otherwise the residual magnetism may tend to cause the valve 31 to remain in the position shown in Figs. 2 and 4. It is to be noted that the groove 44 is made 01 such depth, and the spring guiding portions of such small projection, that the valve 31 may occupy a position with-its outer surface in a plane with the outer rim of the cover 42. The cover 42 may be held in position by screws 48 or in some other suitable manner; and the member 41 is desirably traversed by-a series of openings 48 arranged about its axis, in communication with another series of openings 50 in an intermediate member 5|, which is clamped by the .nut [5 between the member 4| and the seat element 25. The member 5i may be formed to provide by its external periphery a guiding action for the inner edge of the valve 31; or, as illustrated, guiding projections 52 may be provided suitably spaced about the inner periphery of the cover member 42 to guide the valve during both its seating and its unseating movements. It will be noted that devices 35 are provided for each end of the double-acting cylinder shown in Fig. 1, and controlling mechanism for each of these devices is also provided so that they may operate in proper relation to the compression cycles of their respective cylinder ends'.

For the purpose of energizing the magnets 40 periodically at appropriate times and maintaining them energized for the desired portions of the suction strokes, the apparatus shown'in Figs. 6 to 13 is provided. Suitably mounted for rotation in a definite timed relation to the crank shaft of the compressor, herein for rotation at the same angular rate with and directly by the compressor crank shaft, is a rotating cylinder 55, which will be noted to be mounted by a flange 56 and a fixed socketed connection 51 coaxial with the fly wheel and crank shaft of the compressor. The member 55 is desirably formed of insulating material, and is provided with a pair of plates 59 and 59 of conducting material mounted upon its periphery. These will be noted to be arranged, so to speak, in staggered relation; that is to say, they are more or less arranged, except for annular portions 60, 60' thereof which will shortly be noted, on opposite arcuate portions of the surface of the cylinder. Plates 59 and 59' include, in addition to the annular portions 60, 60 respectively thereof, tapering portions Bi and Bi respectively, these tapering portions each having a leading edge, numbered 62 and 62 respectively, for the different plates, and a helically disposed trailing edge, numbered 63 and 63' respectively, for the diiferent plates. Accordingly, at the ends of the plates remote from their annular portions the plates die away to points, and at the ends of the tapering portion nearer the annular portions, these tapering portions are approximately 180 in circumferential extent with respect-to the cylinder member 55. The periphery of themember 55 is so formed, as by recessing, that the cylindrically bent plates may have their outer surfaces flush with the cylindrical surface of the cylindrical member. The two plates are electrically connected in any suitable manner, as by the bus bar 64 which may be arranged within the body of the cylinder 55. Each of the plates 59 and 59' has an adjustable brush cooperatingtherewith, and since the plates are electrically connected, a single stationary brush may coact directly with either of the plates and function in conjunction with the adjustable brushes which are individual to the plates. The stationary brush 65 is mounted to cooperate with the annular portion 60 of the plate 59, and the adjustable brushes 86 and 66' cooperate respectively with the plates 59 and 59'. The several brushes are carried upon a stationary carriage generally designated 61, which comprises a pair of parallel supporting rods 68 which extend through relatively stationary support brackets 69. A sliding brush support is mounted to slide upon the rods 68 and carries the sliding brushes 66 and 66. The stationary brush 65 is mounted by means of the spring-actuated brush holder II to contact with the rotating annular portion 60 of the plate 59. The brushes 66 and 86 are resiliently pressed against the periphery of the rotating cylinder 55 and the plates 59 and 59' thereon, by suitable spring brush holders 1! and 12' respectively. Herein, it will be noted that the several brush holders 'are pivotable about pins I3, 13' and 13" and have springs 14, I4 and 14" acting upon them and upon stationary pins 15, I5 and 15" to force the brushes yieldingly against the periphery of the rotating contacts. The brushes 56 and 66' are mounted upon the sliding carriage It, as above noted, and this carriage is movable longitudinally by a rod 11, which carries at one end thereof a piston 10 reciprocable in a cylinder bore 19 formed in a cylinder member 80 which is supported in fixed relation to the frame of the compressor and in parallelism with the guiding rods 68. Suitable spring means 8| is provided normally to maintain the piston 18 in such a position that the brushes 66 and 68' may be in contact with the annular portions 60 and 86' respectively of the plates 59 and 59', when there is no pressure supplied to the cylinder bore 19 in excess of the desired minimum working pressure of the compressor.

suitable reduced operating pressure bearing a, definite relation to the compressor discharge pressure, may be supplied from the receiver 1 through means herein represented by the fluid delivery connection 82 shown as leading from the receiver to a port 83 in the end of the cylinder 00. As the compressor discharge pressure increases, the piston II will move the carriage II to theright in Figs. 6 and 7 and instead of the magnets 88 being energized throughout the complete cycle of piston movement. the magnets will be energized for progressively smaller portions of the suction strokes of the compressor piston, as the discharge pressure rises. In order to have the desired range of movement of the movable contacts, it will be found better in practice, probably, to use a popf valve in the line 82', to provide a continuous bleed for this line, and to transmit to the cylinder 80 only the excess pressure -above the desired minimum compressor discharge pressure. Such an arrangement is shown in fragmentary detail in Fig. 14, wherein the "pop" valve will be noted to be designated 85 and the bleed port 86.

Any suitable circuits connecting the magnet windings 40, the brushes 65, 66 and and 88' and the source of current, herein represented by the generator G, maybe employed, asior example, those shown in Fig. 13, where it will be noted that the generator is connected by conductor M to, say, the crank end winding 40 and by a branch conductor 88 to the head end winding 48, and by another conductor 89 to the stationary brush 65. The brush 86 is connected by a conductor 80 with the opposite end of the'crank end winding 40, while the brush it is connected by a conductor M to the opposite end ofthe head end winding. 7 v

The mode of operation or the apparatus described will be readily understood. The views or the partsinFigs. l, ZandiandFigaSandi do not correspond with 'each'other, being selected primarily to illustrate the structure, but the diagram oi Fig. 13, and the position of the piston in Fig. l, and of valve 8 in Figs. 2 and 4, do correspond. In the position of the parts shown in Fig. 13, the compressor piston l is just beginning the suction stroke in the crank end of the cylinder. The crank end magnet winding 40 is being supplied with current through a circuit including generator G, conductor 88. stationary contact 85, plate 5!, adjustable brush 88, conductor 80 and the winding 40. Accordingly, the valve plate 11 is held in the unseated position shown in Fig. 2, and air may freely enter the crank end of the compressor cylinder past the valve 28. when the crank shaft has rotated far enough to cause the trailing edge I! or the plate 58 to pass from beneath the adiustablebrush 86, the magnet ll will be deenergized, and the spring I! will start the valve 31 in a closing direction, and the latter will instantly seat upon the surfaces 3 8 and interrupt further inlet of fluid into the compressor cylinder. Accordingly, a partial vacuum will be produced during the remainder of the suction stroke or the piston, and the early portions of the compression stroke for the crank end of this cylinder will simply bring the pressure 20 and force the reduced quantity of iluid taken in into the discharge line 0. During the passage Compressor discharge pressure, or preferably of the piston I from the headend of the cylinder 'of the cylinder, but with a to the crans: end, there will be first an engagement between the contact plate 59 and the ad- Justable brush 66', resulting in the establishment of the circuit energizing the head end. magnet winding iii and holding the head end valve 31 in retracted position, then a release, after a portion of the stroke is completed, of this valve. and an interruption thereby of inlet of fluid to the head end of the cylinder. The cycle for this end of the cylinder will be the same as for the other end phase difierence of 180.

Obviously, ii the use of air diminishes to a sufilcient extent so that the compressor discharge pressure builds up to a high enough valueto move the piston 18 far enough to the right in Figs. 6 and 7 to move the adjustable contact members 88 and 66' beyond the points at the extreme right hand ends of the plates 59 and 58', there will be no opening of the valves 31 at any time during the suction strokes of the piston 5, and accordingly the compressor will operate completely unloaded. It may be noted that it the springs 41 should require assistance in effecting virtually instantaneous closure of the valve elements 31',

it would be possible to provide for the access to' certain valve portions of the fluid flowing through the ports 21; but with the extremely short valve movement necessary to effect closing and the use of springs of substantial strength, this will not ordinarily be necessary.

It will be evident that I have shown aiconstruction in which the same cycle, except for the diil'erence in phase, will be effected at both ends of a double-acting compressor cylinder, but it will be evident that this apparatus may be employed with respect to but one end of the compressor cylinder or with single-acting cylinders, if desired. The arrangement is simple; there is no waste of power during the partially unloaded operation of the compressor. There is no development of excessive heat. An exceedingly wide range of partial unloading, and also complete unloading, are possible. The magnet windings 40 are located in a place where they would be continuously maintained cool by the inflowing air, but by proper design these may be made to require no special cooling and they will not materially heat the air entering the compressor cylinder. All the parts are simple in construction, easily repaired or replaced and definite in operation.

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 various other forms without departing from its spirit or the .scope of the appended claims. I

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

1. In combination, in a pumping apparatus, a cylinder, a piston therein, inlet and discharge valves for said cylinder for controlling the flow of fluid to and from said cylinder, and electrically-controlled valve means having controlling means governed by the pump discharge pressure for automatically interrupting inlet of fluid through said inlet valve to said cylinder at difierent times, depending upon the pump discharge pressure, prior to the end of the suction strokes of the pumping apparatus.

2. In combination, in a pumping apparatus, a cylinder, a piston therein, inlet and discharge valves for said cylinder for controlling the flow of fluid to and from said cylinder, and electrically-controlled valve means having controlling means responsive to variations in the pump discharge pressure for automatically interrupting inlet of fluid through said inlet valve to said cylinder for difierent portions, depending upon the pump discharge pressure, of the suction strokes of the pumping apparatus.

3. In combination, in a pumping apparatus, a cylinder, 9, piston therein, inlet and discharge valves for said cylinder for controlling the flow of fluid to and from said cylinder, valve means for interrupting the inlet of fluid through said inlet valve to said cylinder during different portions of the suction strokes of the pumping apparatus,'the extent of such portions depending upon the pump discharge pressure, electromagnetic controlling means for said inlet-interrupting valve means, and pressure fluid actuated means responsive to variations in the pump discharge pressure for automatically variably controlling said electromagnetic controlling means to effect interruption of inlet for increasing portions of the suction strokes as pump discharge pressure increases above a desired minimum.

4. In combination, in a pumping apparatus, a cylinder,a piston, a discharge valve, an inlet valve, an auxiliary valve coaxial with said inlet valve and closable'to cut oil fluid access to said inlet valve, means for shielding said auxiliary valve, when open, from the rush of fluid during inlet to said cylinder, means for continuously biasing said auxiliary valve toward closed position, and a control device for opening and holding open said auxiliary valve, said control device for said auxiliary valve coaxial with the latter.

5. In combination, in a pumping apparatus, a

cylinder, a piston, a discharge valve, an inlet valve, an auxiliary valve coaxial with said inlet valve and closable to cut on fluid access to said inlet valve, and a control magnet for opening and holding open said auxiliary valve during'varying time intervals, said control magnet being arranged coaxial with said auxiliary valve and in the intake space of the pumping apparatus.

6. In combination, in a pumping apparatus, a cylinder, a piston, a discharge valve, an inlet valve, an auxiliary valve coaxial with said inlet valve and closable to cut off fluid access to said inlet valve, means for shielding said auxiliary valve, when open, from the rush oi! fluid during inlet to said cylinder, mean for continuously urging said auxiliary valve towards closed portion, and a control magnet for opening and holding open said auxiliary valve during varying time intervals, said control magnet being arranged coaxial with said auxiliary valve and in the intake space of the pumping apparatus.

7. In combination, in a valve mechanism, an inlet valve, a cage element providing a seat for said'valve on one sideand having an opposed seat, an auxiliary valve supported in cooperative relation to said opposed seat, springs tending to close both valves, and means for opening the second valve and holding it open against the action of its respective spring.

8. In combination, in a valve mechanism, an

inlet valve, a cage element providing a seat for said valve on one side and having an opposed seat, an auxiliary valve supported in cooperative relation to said opposed seat, springs tending to close both valves, and means outside the second valve for opening the second valve anda cylinder, a" piston reciprccable therein, dis- 1 spective .spring during .varying time intervals.

10. In combination, a cylinder, a piston, actu-' sting means for said piston including a crank shaft, automatic valve means for said cylinder; auxiliary valve means for eflecting partial or total unloading by interrupting inlet at diiIerent points in, or throughout, the suction strokes of said piston, and magnetic means having a control device rotating with the crank shaft for regulating the time of interruption oi inlet.

11. In combination, a cylinder, a piston, ac-

' tuating means'ior said piston including a crankshaft, automatic valve means for said cylinder, auxiliary valve means for eflecting partial or total unloading by interrupting inlet at diflerent points in, or throughout, the suction strokes of said piston, and magnetic means having a control device rotating with the crankshaft and "a cooperating discharge pressure responsive device movable longitudinally ,of said. crankshaft, tor

' controlling said auxiliary valve means.

12. In. combination, in a pumping apparatus, a cylinder, a piston, a discharge valve, an inlet.

valve, an auxiliary valve closable to cut 01! fluid access to said inlet valve, on eiectromagnet for opening and holding open said auriliary valve when energized, and'means responsive to pump charge valve means for said cylinder, a valve assembly for controlling the flow oi fluid-to said cylinder, said valve assembly comprising a t member having passage means therein for conducting fluid to said cylinder and providing seats at the opposite ends of said passage means, an

inlet valve cooperating with one of said seats and opening in the direction 0! flow of fluid through said passage me'ans towards said cylinder ior c ntroll ng the flow of fluid relative to said cylinder, an auxiliary valve cooperating with the other of said seats and closing in the direction oi flow oi fluid through said passage means towards said cylinder for controlling the flow o! fluid towards said inlet valve, and means cooperating with said auxiliary valve for causing the same to occupy its closed position during progressively increasing portions 0! the suction strokes of said piston with respect, to said inlet valve as compressordischarge pressure rises above a predetermined value.

' 16. In a'pumping mechanism, in combination, I

a cylinder, a piston reciprocable therein, discharge valve means for said cylinder, means for conducting fluid to said cylinder, an

inlet valve opening in the direction 0! flow 0! fluid through said passage means towards said cylinder for controlling the now of fluid relative to said cylinden an auxiliary valve closing in the direction of flow oi fluid through said pe means towards saidcylinder for-controlling the flow oi fluid towards said inlet valve; and cooperating with said auxiliary valve for caus the same to occupy its closed position during pro- .-gressively increasing portions of the suction discharge pressure for continuously energizin laid electromagnet or forenergislng said electromagnct at a predetermined point-in each cycle [or piston operation and tie-energizing said electroardiilerent points varying in once with discharge pressure. ll. In:-eombinatlon, -in a pumping apparatus, a cylinder, 1 piston, a discharge valve, an inlet accordstrokes of said piston with ret to said valve as comprr discharge pressure above a predetermined value, said means cooperating with said auxiliary valve'including yielding f means iormoving the same in one direction d means eii'ective du diflerent portionsoi such suction strokes as compressor discharge pr valve, an auxiliary valve closable to cut. of! fluid accesl'to said inlet valve, means for continuous- I ly urging said auxiliary valve in a closing directiomran velcctromagnet for opening and holding open said auxiliary valve when energized, and means responsive to pump discharge pressure torenergizing said electromagnet at a predetermined-point in'each cycle or piston operation and de-energising said electromagnet at diflerent points varying in accordance with discharge 14. In a. pumping mechanism, in combination,

charge valve means for said cylinder, m,

means for conducting fluid to said cylinder, an

' inlet valve opening in the direction oi flow of .fluid through said passage means towards said cylinder for controlling the flow oi fluid relative to said cylinder, an auxiliary valve closing in the direction of flow of fluid through vSaid passage means towards said cylinder for controlling the flow oi fluid through said passage means towards said inlet valve, and means cooperating with said auxiliary valve for causing the same to occupy its closed position during progressively increasing portions of. the suction strokes of said piston with respect to said inlet valve as compressor discharge pressure rises above a predetermined value.

. a cylinder, .a piston reciprocabletherein, disvariesior overcoming said yielding means and moving said auxiliary valve in the o rection.

17.- In a pumping 111 in combination, a cylinder, apiston recip ocable therein, charge valve means for said cylinder, '1 means for conducting fluid to said cylinder, an

inlet valve 0 in the direction of flow of fluid through said 1. means towards said cylinder for controlling the flow of fluid relative to said cylinder, an auxiliaryvalve closing-in the direction oi flow oifluid through said u means towards said cylinder for controlling e flow o! fluid towards said inletwalve, and means cooperating with said auxiliary valve for causing the same to occupy its closed position d progressively increasing portions of the suction strokes-oi said piston with respect to said inlet valve as compressor discharge pressure rises above a predetermined value. said means cooper= ating with said auxiliary valve including yielding means for moving the same in one direction,

means operative on the delivery of operating medium thereto for moving said auxiliary valve in the opposite direction, and means governed by compressor discharge pressure for effecting delivery oi. operating medium to said last mentioned means-during different portions of the suction strokes oi said piston relative to said inlet valve a predetermined value.

15. In a pumping mechanism, in combination, (6 18. In a pumping mec, in combination,

it at a cylinder, a piston reciprocable therein, discharge valve means for said cylinder, a valve assembly for controlling the flow of fluid to said cylinder, said valve assembly having passage means therein for conducting fluid to said cylinder, an inlet valve opening in the direction of fluid flow through said passage means for controllingthe flow of fluid relative to said cylinder, an auxiliary valve closing in the direction 01 fluid flow through said passage means for controlling the flow of fluid to said inlet valve, and controlling means for said auxiliary valve including means for effecting opening of said auxiliary valve during portions of the cycles of reciprocatory movement of said piston in said cylinder, means for eflecting closure of said auxiliary valve during the remaining portions of the cycles of reciprocatory movement of said piston in said cylinder, and means governed by compressor discharge pressure for varying said portions inversely.

19. 'In a pumping mechanism, in combination, a cylinder, a piston reciprocable therein, a valve assembly for controlling thesflow of fluid to said cylinder, said valve assembly having passage.

means therein for conducting fluid to said cylinder, an inlet valve opening in the direction of fluid flow through said passage means for controlling the flow o1 fluid relative to said cylinder, an auxiliary valve closing in the direction of fluid flow through said passage means for controlling the flow of fluid to said inlet valve, and means for opening said auxiliary valve during portions of the suction strokes of said piston and for closing the same during subsequent-portions of the same suction strokes when compressor discharge pressure exceeds a predetermined value, said last mentioned means including means responsive to compressor discharge pressure variations for altering the proportions of such suction strokes during which said auxiliary valve is open.

20. In combination, in a pumping apparatus,

a cylinder, 8. piston reciprocable in said cylinder, 7

a discharge valve, and valve mechanism for controlling the flow oi! fluid to said cylinder, said valve mechanism including avalve plate traversed by an intake port and having an annular valve seat surrounding said intake port at one side of said plate and another annular .valve seat surrounding said intake port at the other side of said valve plate, an annular inlet valve cooperating with the valve seat surrounding the cylinder end of said port and opening when the pressure on said inlet, valve adjacent said intake port exceeds the pressure on said valve adjacent said cylinder for admitting-fluid to the latter, an annular valve coaxial with said inlet valve and cooperating with the other annular valve seat. for controlling the flow of fluid to said inlet valve,

and means for eflecting a closure of said last mentioned valve during portions of the suction strokes of said piston varying with compressor discharge pressure.

ALEXANDER D. I IIZIRtGUS ON.

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