US2294410A - Pumping apparatus - Google Patents

Description

P 1942- R. r-:. LAMBERTON 2,294,410

PUMPING APPARATU S Filed Dec. 13, 1940 4 Sheets-Sheet l iw' 3" MM:

p 1942- R. E. LAMBERTON 2,294,410

PUMPING APPARATUS Filed'Dec. 13, 1940 4 Sheets-Sheet 2 I v Kw. Z.

:0 HIGH PRESSURE CYLINDER UNLUADERS [immzfaza- Z M/pZzEL/mzmim M A7 WWW y Patented Sept. 1, 1942 UNITED STATES PATENT OFFICE PUMPING APPARATUS Application December 13, 1940, Serial No. 370,043

(Cl. 2303l) 15 Claims.

My invention relates to pumping apparatus, and more particularly to prime mover driven pumping apparatus having means controlling the quantity of fluid delivered thereby, first by controlling the speed of operation in accordance with variations in discharge pressure, and subsequently by unloading the pumping device when a predetermined maximum discharge pressure is attained, such unloading being attended by reduction in speed of the apparatus in a preferred embodiment of the invention.

An object of my invention is to provide an improved pumping apparatus. Another object is to provide an improved mechanism for controlling the speed of a pump in accordance with receiver pressure. A further object is to provide an improved prime mover driven pumping apparatus having improved output control mechanism. Still another object is to provide an improved mechanism responsive to discharge pressure variations for effecting a step by step control of the speed of a prime mover connected in driving relation with a compressor. Yet another objeet is to provide an improved mechanism responsive to discharge pressure for efiecting a step by step decrease in the speed of a compressor or other pumping apparatus as the discharge pressure increases and at a predetermined discharge pressure eliecting an unloading of the compressor or the pumping apparatus and a reduction of its operating speed to a desired value. These and other objects of the invention will, however, hereinafter more fully appear.

In the accompanying drawings there is shown for purposes of illustration one form which the invention may assume in practice.

In these drawings,

Fig. 1 is a side elevational view of a portable compressor having the illustrative embodiment of the improved control apparatus associated therewith.

Fig. 2 is an enlarged fragmentary plan view of the compressor shown in Fig. 1.

Fig. 3 is an enlarged vertical sectional view of the pilot valve mechanism, taken on the plane of the line 3-3 of Fig. 2.

Fig. 4 is a horizontal sectional View through a portion of the pilot valve mechanism, other parts being shown in elevation, the view being taken on the line 44 of Fig. 3.

Fig. 5 is a vertical sectional View of one of the pilot valves, taken on the line 5-.5 of Fig. 4.

Fig. 6 is an enlarged fragmentary side elevational view of the prime mover and the throttle control mechanism therefor.

Fig. 7 is an enlarged sectional view of a portion of the throttle control mechanism, taken on line 'l'l of Fig. 6.

Fig. 8 is an enlarged cross sectional view of the throttle control mechanism, taken on line 8-8 of Fig. 6.

Fig. 9 is a sectional View taken on the plane of the line 9-9 of Fig. 8.

Fig. 10 is an enlarged fragmentary sectional view of one of the compressor cylinders and the unloading means therefor.

In the illustrative embodiment of the invention shown in the drawings, the same is shown incorporated in a portable compressor mechanism, but it will of course be understood that the invention is applicable to other varieties of pumping apparatus and to other types of compressor-s.

In the drawings, the compressor I is shown as of the reciprocating piston and cylinder type, and the compressor illustrated is of the twostage four-cylinder V type. The compressor l is connected in any suitable manner to'the drive shaft of a prime mover 2 herein shown of the Diesel type, though it will be obvious that the invention is not limited to Diesel type motors nor even to internal combustion operated apparatus. The compressor 1 and prime mover "2 are herein shown as mounted on the frame 3 of a wheeled truck. The high pressure cylinders of the compressor are not shown, but the low pressure cylinders are arranged at the opposite side of a V from the high pressure cylinders and are shown at 5. The cylinders are severally provided with inlet and discharge valves, and the general arrangement of these valves may be seen in Fig. 10, which shows a section through one of the low pressure cylinders. Here it will be observed that an inlet valve 6 is provided to control the flow of fluid from the intake passage 1 to a cylinder bore 8, and a discharge valve 9 is provided for controlling the discharge of fluid from the cylinder bore to a discharge passage l0. Reciprocable in each cylinder bore is a piston l2 which is driven in any usual manner by the crankshaft of the prime mover. During normal operation of the compressor, fluid is taken into the cylinder bores past the inlet valves on the suction strokes of the pistons and is discharged past the discharge valves on the compression strokes. As shown in Fig. 1, fluid from the low pressure cylinder discharge passages is delivered to a conduit M, and passes into an intercooler I from which it it returned to the intake side of the high pressure cylinders through a conduit I 5, and the fluid is finally delivered from the discharge side of the high pressure cylinders through a conduit D to the receiver R.

Any suitable type of unloading mechanism for the compressor may be provided, such as intake closure mechanism for the low pressure cylinders and relief apparatus for the high pressure cylinders, but in the illustrative embodiment of the invention, I have shown an unloading mechanism of the so-called sweep-control type; that is to say, devices are provided in association with the inlet valves of each cylinder for the purpose of unseating the inlet valves and maintaining them open when unloading is to be effected.

The unloading mechanisms associated with the several cylinders are generally of the same type, and the unloading mechanism associated with one of the low pressure cylinders is also disclosed in Fig. 10. Here it will be noted that aplunger I8 yield-ably held in retracted position by a spring I9 is movable in a chamber 20 mounted on the cylinder head. Rods or fingers 2| are movable with the plunger and are forced, upon the supply of pressure fluid to the chamber 20, into engagement with the inlet valve to hold it from its seat to effect unloading of the compressor cylinder. Pressure fluid supplied through a conduit 23, herein shown as connected to the receiver R, is deliverable upon the attainment of a maximum predetermined compressor discharge pressure under the control of a pilot valve mechanism generally designated 24, through a conduit 25 communicating with the several chambers 26, to effect unloading of all of the cylinders of the compressor at the same time.

The operation of the prime mover 2 is governed through a conventional control mechanism, generally designated 21 and having a control lever 21' projecting therefrom. In Fig. 1 the lever 21 is shown in what may be called fullload position, and movements of the lever clockwise in Fig. 1 slow down the engine and compressor and ultimately, after passing through an idling position, will stop the engine in the extreme right hand position of the lever 27'. The lever 21' is operable by a link or rod 28 which is connected to an arm 28 pivoted at 28 in any suitable way upon a stationary axis. A manually controlled arm 29 is movable to control the position of the arm 28, being securable by a nut 29' in difierent positions to limit the maximum speed of the unit, if desired. Normally, however, the arm 29 remains in the position shown in Fig. 6, and the control of the operation of the prime mover is eifected exclusively by a pressure responsive device 36, to which discharge pressure is supplied under the control of the pilot valve mechanism 24 in a manner hereafter to be described, to effect a step by step control of engine speed.

The pilot valve mechanism 24 may now be described, with particular reference to Figs. 3, 4 and 5. Here it will be noted that the member 3| is secured to a stationary mounting, herein to the side of the prime mover 2, as by bolts 32. The member 3| provides a chamber 33 to whose interior the conduit 23 conducts compressor discharge pressure, Opening from the chamber 33 through the side of the member 3| are threaded bores 34, 35 and 36 in which short pipe connections 31, 38 and 39 are threaded. Mounted on the outer ends of the connections 31, 38 and 39 respectively are pilot valve devices 40, 4| and 42 set to operate at different compressor discharge pressures. The three pilot valve devices are similar in construction, and each comprises a body member 44 having bores 45 and 46 opening through its opposite ends and communicating with each other through a reduced opening 41 surrounded by a flange 48. Attached to the end of the body member 44 in which the bore 45 is formed is a cap 50 held in place as by screws 49. A plug 5! is threaded into an opening in the cap 56 and is in turn provided with an opening within which the outer end of the respective one of the conduits 31, 38 and 39 is received. Accordingly it will be apparent that the pilot valve device is supported by the plug 5| and the cap 56. A strainer 53 is clamped between the plug 5| and the cap 50 to prevent impurities entering the bore 45. The cap 50 has an opening 55 therethrough through which fluid is adapted to enter the bore 45 when the pilot valve proper, later described, is unseated. Reciprocable in the bore 45 is a piston type valve 56 having adjacent each end thereof a collar portion 51 in close sliding fit with the walls of the bore, and between these collar portions the valve is reduced in diameter to provide an annular space 58 between the valves and the walls of the bore 45. The valve 56 at its end toward the chamber 33 is adapted to engage a valve seat 60 formed on the cap 50 and surrounding the passage 55; and in this, the closed position of the pilot valve, no fluid may pass from the chamber 33 to the bore 45. The valve 56 when in its opposite position is adapted to engage a surface on the flange 48 and to cut off communication between the bore 45 and the opening 41. The collar portions 51 of the valve 56 are traversed by openings 63, and through these openings the annular space 58 is communicable alternatively in the opposite positions of the valve 56 with the passage 55 and the passage 41. The valve 56 is normally maintained closed when the pressure in the chamber 33 is below the value requisite to open the valve by means of a stem 65 projecting into a recess 66 in the valve and extending outwardly through the opening 41 and into the bore 46. A plug 68 is threaded into the bore 46 and has an opening 69 through which the valve stem extends, with a substantial clearance around the valve stem. A coiled spring 10 surrounds the valve stem and acts at one end against the plug 68 and at its other end against an abutment H fixed to the valve stem and so normally yieldingl holds the valve against the seat 66 on the cap 5!]. Threaded on the outer end of the valve stem is a nut 13 which may be used to retract the stem 65 and hold it retracted, and thus enable the valve 56 to be maintained open continuously.

Opening through the side of the body member 44 approximately midway between the ends of the bore 45 is a passage 15. This passage is connected, in the position of the parts shown in Fig. 5, with atmosphere through the annular space 58, the right hand series of openings 63, the opening 41, the bore or chamber 46 and the opening 69. If the pressure of the fluid conducted from the chamber 33 to the end of the valve 56 is sufiicient to overcome the force of the spring 76, the valve will be moved from its seat 60 into abutment with the flange 48 and pressure fluid will flow through the opening 63 in the left hand collar portion 51 to the space 58 where it may enter the passage 15. If the pressure of the fluid drops below that of the spring, the valve will be moved back onto its seat E9 to cut off the flow of pressure fluid from the chamber 33 into the bore 45, and the bore 45 will be vented as above explained. It may be noted that when the valve 56 is opened and forced against the flange 48, there is an increase in the effective area subjected to pressure from the chamber 33 so that a predetermined drop in pressure will be requisite from the value necessary to open the valve 55, before it will close again. It will be evident that by adjusting the plug 58 the pressure exerted by the spring I may be changed, and with it the pressure necessary to open the valve. As above explained, by adjusting the nut 73 in the direction to withdraw the valve stem from engagement with the valve, the valve 59 may be-freed from the pressure which normally holds it seated, and then the pressure fluid in chamber 33 will. immediately act to move the valve from its seat 69 and pressure fluid will be supplied to the passage I5.

I have described the construction and mode of operation of one of the three pilot valve devices 49, II and 42, and it will be understood that the structures of the other two may desirably be the same. The seatings of these pilot valve devices, however, are different, as will shortly be explained. The several passages it in the different pilot valve devices are connected, as will now be explained, with the pressure responsive device 39. Conduits Ill and T3 connect the passages I5 of the pilot valve devices 49 and ll with the pressure responsive device 95. The passage I5 of the pilot valve device 92 is connected through a conduit I9 to a valve mechanism generally designated 89 where it opens into a chamber 8|, and a conduit 82 leads from the chamber 8! directly to the pressure responsive device 39, As will shortly be explained, the conduits 11, I3 and 82 lead to different portions of the pressure responsive device 39, and the pressure transmitted through them affects different parts of that device. The conduit 25 leading to the compressor unloading mechanisms is connected through a connecting element, herein in the form of an elbow 93, with a chamber 84 in the valve mechanism 99. A spring pressed valve 85 controls communication between the chambers 8| and 8 3, through a passage 89. A manually adjustable needle valve 81 controls communication between chambers 8| and 99, through passages 89 and 99. It will be observed that when the pilot valve 42 is operated to deliver pressure fluid to the chamber BI, the fluid will flow immediately through the conduit 92 to the pressure responsive device 39, and will also cause the spring pressed valve 85 to be unseated and to permit the passage of pressure fluid through the chamber 86, connecting element 83 and conduit 25 to the unloading mechanisms. When the chamber 8! is connected to atmosphere through the conduit I9 and the pilot valve device 42, pressure fluid is vented freely from the conduit 92-to effect an immediate speeding'up of the engine as will be later explained, but the fluid which has passed to the compressor unloading mechanisms through the conduit 25 escapes relatively slowly past the needle valve 81, back to the chamber 9|, and accordingly reloading of the compressor will be somewhat delayed, thereby providing an opportunity for the engine to speed up and become ready to handle the load of the-compressor when the latter is reloaded.

Referring now to the pressure responsive device 39 and more particularly to Figs. 6 to 9, it will be noted that a cylinder block 93 is attached to a stationary part, herein to the side, of the prime mover, as by bolts 94; and attached to one end of the cylinder block, as by bolts 95, is a casing member 96. Formed in the cylinder block are parallel bores 91, 98 and 99 so arranged that points in their axes lying in a plane to which said axes are perpendicular lie at the corners of an equilateral triangle. Reciprocably contained within the bores are plungers I09, IOI and I52. The conduits I1, I8 and 82 are respectively connected throug the connecting elements I94, I95 and I99 in communication with the bores 91, 99 and 99 at the ends of these bores remote from the casing 99. Clamped between the cylinder block 93 and the casing 96 is a plate I9! cooperating with the casing 99 to form a chamber I93. Openings I99 are provided in this plate, through which the plungers may be projected into the chamber I09. A circular plate I I9 is supported for reciprocation in the chamber I98 by means of alined stems III, H2 herein formed integrally with the plate and guided respectively within a bore [I3 formed in the cylinder block and an opening H4 in the casing member 95. The common axial line of the stems I I I, H2 is parallel to the axes of the plungers I99, I95, E92 and equidistant from each of the three last mentioned axes. The radial dimension of the plate is such that the plate laps a small amount over the inner edges of the plungers I99, IQI, Ifl2so that each of these plungers upon projection from its respective cylinder will be operative to move the plate H9 and with it the rod or stem II2. A coiled spring [I6 acts between the casing member and the plate and normally holds the latter against the ends of the plungers. Stop screws H8 are threaded through openings H9 in the casing member 95 and are so positioned that the plate H0 is free to move without engaging any of these screws. The screws are, however, also so positioned that they will be severally engaged by the outer portions of the plungers I99, IIJI, I92 when these plungers have moved predetermined distances. The stop screws are held in their adjusted positions by lock nuts I29. The several stop screws are held in adjusted positions as follows: The stop screw which is associated with the plunger I99 is so arranged that the plunger I90, after moving the plate H9 but a short distance, will engage its stop screw. The stop screw associated with the plunger I9I permits that plunger to move the plate H9 a short additional distance before the plunger I9! engages its stop screw. The stop screw associated with the plunger I92 permits the plunger I92 to move the plate I It still further before the plunger engages its stop screw.

From what has been said it will be apparent that the plunger I99 is adapted to move the plate Hi3 a predetermined distance and then to be stopped. The plunger IGI is adapted to move the plate HG an additional distance and then to be stopped. The plunger I92 is adapted to impart a still further movement to the plate I I6, and then to be stopped. It will be evident that each of the plungers is supplied with air from one of the pilot valve devices previously described, and each constitutes a servo-motor device.

Attached to the end of the stem I I2 through aconnecting element I22 (Fig. 6) is a rod I23 which is attached in turn to the link 28 extending between the motor control device 2'! and the manually controlled arm 29. The link 28 is ;yielding1y urged by a spring I24 in a direction to cause full speed, full load operation of the motor, the end of the spring I24 not connected to the bent rod I23 being connected to a stationary point, as at I25.

The pilot valve devices 40, 4|, 412 are adjusted by means of the threaded plugs 88 in such a manner that upon the attainment of a certain compressor discharge pressure the valve 56 of the pilot valve device 46 will be unseated and supply pump discharge pressure through the conduit 11 to act upon the plunger I 00. The pilot valve device 4! will be so set that upon the attainment of a higher predetermined compressor discharge pressure its valve 56 will be moved to supply pressure through the conduit 18 to act upon the plunger IOI. When a maximum desired compressor discharge pressure is reached, this will be effective, with the setting which has been given to the pilot valve device 42, to open the valve '56 in the last mentioned pilot valve device andsupply pressure through the conduit I9 to the valve mechanism 83 and, as above eX- plained, this pressure will be transmitted through the connection 82 to act upon the plunger Hi2 and further slow down the engine-this time to a desired idling speed, while fluid also passes to the unloading devices through the conduit 25 and completely unloads the compressor. It will thus be evident that as compressor discharge pressure builds up to the desired range, the compressor will be slowed down somewhat, but if the demand for air does not equal the rate of air delivered at the somewhat reduced speed so attained, compressor discharge pressure will continue to build up, and when a somewhat higher predetermined value is reached, the compressor will be further slowed down. If the air consumption is still below the rate of delivery at this further reduced rate, the discharge pressure will build up still higher, and if it attains the maximum desired value the compressor will be unloaded and slowed down to a suitable idling speed. This will result in a cessation of delivery of air, and when the air consumption causes the pressure to fall to a point sufilcient for the valve 55 of the pilot valve device 52 to close, the compressor driving engine will first speed up and the compressor will then be loaded. If the air demand increases so that the compressor discharge pressure continues to fall off sufiiciently to effect closure of the valve 56 of the pilot valve device 4 I, the compressor will be driven at a higher speed, and if the demand for air is not adequate- 1y supplied at this higher speed, the pilot valve device 39 will ultimately be operated to vent the pressure from the cylinder 97 and the compressor will be brought up to its maximum operating speed,

As illustrating the mode of operation in more detail, the pilot valve device 40 may be set to supply air to the conduit I7 and plunger It!!! on attainment to a compressor discharge pressure of eighty pounds, and the device may be so designed as to interrupt the supply of pressure fluid to the conduit TI and vent it to atmosphere upon a reduction in pressure, say, to seventy-five pounds. The pilot device 4| may be set to supply pressure to the conduit 13 and plunger IIJI when compressor discharge pressure builds up to ninety pounds, and to vent the conduit 18 to atmosphere when the compressor discharge pressure falls oiT to eighty-five pounds.

The pilot valve device 42 may be set to supply pressure through the conduit 79 when a compressor discharge pressure of one hundred. pounds is attained, and to vent the conduit I9 to atmosphere when the compressor discharge pressure falls off to ninety-five pounds. It will be understood that when compressor discharge pressure is acting on the plunger I02, it will also be acting on the plungers IIlI, I90, and that when it ceases to act upon plunger I02 but is still acting on plunger IOI, it will also be acting on plunger I00. Accordingly the plate IIO will be understood to be p e sively moved to the right in Figs. 7 and 9 to effect slowing down of the compressor, and to be progressively returned. by the spring III; in steps to speed up the compressor. To repeat the mode of operation, if the compressor discharge pressure attains to a value sufiicient to open the valve 56 of the pilot valve device 40, the valve 56 will be moved from its seat 6!! and pressure fluid will flow from the chamber 33 through the conduit 3! to the bore 45 and from the latter through some of the passages 63 in the valve to the space 58, and thence through the opening 15 and through the conduit I1 to the bore 91 in the pressure responsive device 39. Pressure fluid then acts on the plunger Hit in the bore 91 and forces the latter to the right, moving with it the plate H0. When the plunger I 90 comes up 'afiainst the end of its associated stop screw I I8 its further movement to the right is interrupted and accordingly the degree to which the compressor will be slowed down will be definitely determined by the amount of movement which the rod I23 can give to the control link 28 and through the latter to the engine drive control with the movement which the plunger Hill is enabled to impart to the plate III]. If the receiver pressure continues to increase, notwithstanding the fact that the engine has been somewhat slowed down, to a value sufficient to open the pilot valve device M, pressure fluid will be supplied in a similar manner through the conduit I8 to the bore 98, where it will force the plunger IllI outwardly until its motion is checked by another one of the bolts H8, the plunger lIlI moving the plate III! further in a direction to slow down the driving engine. When the pressure in the receiver reaches a maximum desired value, the pilot valve 32 will be operated to supply pressure fluid through the conduit I9 to the chamber SI of the valve mechanism 8%). From the chamber 8! the pressure fluid will flow through the conduit 82 to the bore 99 and force theplunger I82 outwardly until its motion is stopped by its associated stop screw H8. This movement of the plunger I02 will cause a movement of the plate H0, stem H2, rod I23 and link sufficient to reduce the speed of the prime moved to a desired idling speed. Concurrently with the slowing down of the engine there will be a complete unloading of the compressor by the passage of pressure fluid from the chamber 8| past the valve 85 through the chamber 84, elbow 83, and conduit 25 to the chambers 20 of the several compressor unloading mechanisms, in which chambers the pressure will act on the plungers I8 to open the inlet valves and unload the compressor cylinders.

Now, if the pressure in the receiver be reduced to a value such that the sprin ID of the pilot valve device 42 can force the valve 56 of this device to its seat Bil, the chamber 8| will be connected to atmosphere through the conduit 19, the bore 45, opening 4! and the space 69 surrounding the valve stem 65. Pressure fluid is immediately freely vented through the conduit 82, and the engine control will be actuated by the springs H6 and I24 to speed up the prime mover. Pressure fluid will be vented more slowly from the unloading mechanisms through the conduit 25, past the needle valve 8'! to the chamber 8!; and due to the reduced flow past the valve 81, the delay in the reloading of the compressor will be sufficient to permit the prime mover to be brought up to the necessary increased speed before reloading takes place. It will be appreciated that the plunger Nil, being still under pressure, will check the movement of the plate Iii! to the left, and that a further speeding up of the compressor will not be possible until the cylinder bore 98 is vented. If the pressure in the receiver continues to drop, the pilot valve device 4! will cut off the supply of air to the cylinder 53 and vent that cylinder, and then the springs I 86 and I24 will be enabled to move the link 28 and cause the engine 2 to speed up further. If the compressor discharge pressure falls off still further, the pilot valve device 453 will cut off the supply of air to the cylinder 91 and vent that cylinder, and the plunger me will then be free to move back in its cylinder, permitting the plate Hi! to move back to the position shown in Fig. 7, thereby permitting the springs H6 and I 24 to return the control link 23 to the position shown in Fig. 6 and the prime mover to attain to full operating Speed.

As a result of this invention, it will be noted that there is provided an improved controlling mechanism whereby the speed of the compressor is reduced in steps and in accordance with predetermined compressor discharge pressure increments, and that at a predetermined maximum pressure the compressor will be unloaded and the prime mover will be caused to operate at an idling speed. It will be noted further that by reason of the adjustments provided for the controlling mechanism, there is obtainable an operation of the pilot valves and other mechanism to control the speeds and the unloading of the compressor at any desired pressure values in the receiver or elsewhere in the compressor discharge line. Other uses and advantages of the invention will be clearly apparent to those skilled in the art.

While there is in this application specifically described one form which the 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.

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

1. In a pumping apparatus, in combination, a prime mover, a pump connected for drive by said prime mover, unloading means for said pump, means for controlling the speed of said prime mover, means for actuating said last mentioned means to effect a slowing down of said prime mover upon a predetermined increase in pump discharge pressure, and means for operating said unloading means to effect pump unloading and for further actuating said prime-mover-speedcontrolling means further to slow down said prime mover upon the attainment to a higher predetermined pump discharge pressure, said means for actuating said prime-mover-speedcontrolling means upon successive increases in pump discharge pressure including means responsive to diiferent pump discharge pressures for effecting successive deliveries of operating medium and means energized by the action thereon of the operating medium delivered upon each such delivery to effect a controlling movement of said prime-mover-speed-controlling means to reduce the prime mover speed.

2. In a pumping apparatus, in combination, a prime mover, a pump connected for drive by said prime mover, pressure responsive unloading means for said pump, means for controlling the speed of said prime mover, pressure responsive means acting on said last mentioned means for effecting a slowing down of said prime mover upon a predetermined increase in pump discharge pressure, said pressure responsive means including means providing a plurality of difierent expansible chambers in which pressure fluid works to effect successive movements of said speed controlling means to reduce the speed of said prime mover, and means for operating said unloading means to effect pump unloading and for further actuating said prime-mover-speed-controlling means further to slow down said prime mover upon the-attainment to a higher predetermined pump discharge pressure.

3. In a compressor mechanism, in combination, a prime mover, a compressor connected in driving relation with said prime mover, unloading means for said compressor, means for controlling the supply of motive fluid to said prime mover, means including a plurality of sequentially energized servo-motors for effecting a step by step control of said last mentioned means in accordance with predetermined increases in receiver pressure to effect a stepped reduction in the speed of said prime mover, and means for eifecting an unloading operation of said unloading means and an actuation of said second mentioned means to effect prime mover operation at an idling speed upon attainment to a predetermined maximum receiver pressure.

4. In a compressor mechanism, in combination, a prime mover, a compressor connected in drivin relation with said prime mover, pressure responsive unloading means for said compressor, pressure responsive means for controlling the supply of motive fluid to said prime mover including motive fluid supply control means and servo-motor means providing a plurality of surfaces adapted upon successive subjection to pressure fluid to exert successive motive fluid supply controlling forces on said motive fluid supply controlling means to operate the same in the same direction, means responsive to predetermined discharge pressures of said compressor for controlling the supply of pressure fluid to said surfaces of said controlling means, and means responsive to a predetermined maximum discharge pressure of said compressor for controlling the supply of pressure fluid to said unloading means and to said controlling means.

5. In a compressor mechanism, in combination, a prime mover, a compressor connected in driving relation with said prime mover, pressure responsive unloading means for said compressor, pressure responsive means for controlling the supply of motive fluid to said prime mover ineluding motive fluid control means and means providing a plurality of surfaces to which pressure fluid is successively deliverable to exert forces effecting successive adjustments of said motive fluid controlling means to cut down motive fluid supply, and a plurality of pilot valves,

each responsive to a different compressor discharge pressure for controlling the supply of pressure fluid to said controlling means and to said unloading means.

6. In a compressor mechanism, in combination, a prime mover, a compressor connected in driving relation with said prime mover, pressure responsive unloading means for said compressor, pressure responsive means for controlling the supply of motive fluid to said prime mover, said pressure responsive controlling means including an element movable to cut down the supply of motive fluid and operating means for said element including means providing a plurality of surfaces upon which pressure fluid is adapted successively to act to move said surface providing means to operate said element to reduce the motive fluid supply, a plurality of pilot valves, each responsive to a difierent compressor discharge pressure for supplying pressure fluid to said controlling means and thereby effecting a step by step reduction in the speed of said prime mover, and means including one of said pilot valves for supplying pressure fluid to said unloading means at a predetermined maximum compressor discharge pressure.

'7. In a compressor mechanism, in combination, a compressor, an internal combustion engine for driving said compressor, pressure responsive unloading means for said compressor, pressure responsive means operative on the supply of pressure fluid thereto for reducing the supply of operating fluid to said engine, said last mentioned pressure responsive means including means movable to reduce the supply of operating fluid to the engine and means movable by the forces exerted thereon by successive quantities of pressure fluid delivered thereto to move said supply reducing means progressively to reduce the supply of operating fluid, means responsive to predetermined discharge pressures of said compressor for controlling the supply of pressure fluid to said second mentioned pressure responsive means, and means responsive to a predetermined maximum discharge pressure of said compressor for controlling the supply of pressure fluid to said unloading means.

8. In a compressor mechanism, in combination, a compressor, an internal combustion engine for driving said compressor, pressure responsive unloading means for said compressor, pressure responsive means operative on the supply of pressure fluid thereto for reducing the supply of operating fluid to said engine, said last mentioned pressure responsive means including a plurality of expansible chamber operating devices operative successively on pressure fluid supply to them, and moved by pressure fluid so supplied, to reduce the supply of operating fluid to said engine, means responsive to predetermined discharge pressures of said compressor for controllin the supply of pressure fluid to said second mentioned pressure responsive means, and means responsive to a predetermined maximum discharge pressure of said compressor for controlling the supply of pressure fluid to said unloading means and to said second mentioned means.

9. In a compressor mechanism, in combination, a compressor, an internal combustion engine for driving said compressor, pressure responsive unloading means for said compressor, means including a, plurality of plungers, each operative on the supply of pressure fluid thereto for effecting a predetermined reduction in the supply of operating fluid to said engine, means operative at predetermined discharge pressures for sup plying pressure fluid consecutively to said plungers, and means operative at a predetermined maximum discharge pressure for supplying pressure fluid to said unloading means.

10. In a compressor mechanism, in combination, a compressor, an internal combustion engine for driving said compressor, pressure responsive unloading means for said compressor, means including a plurality of plungers each operative on the supply of pressure fluid thereto for effecting a predetermined reduction in the supply of operating fluid to said engine, means in cluding a plurality of pilot valves, one for each of said plungers, operative at different predetermined compressor discharge pressures for supplying pressure fluid to said plungers, and means, including the one of said pilot valves operative at the maximum discharge pressure, for supplying pressure fluid to said unloading means.

11. In a compressor mechanism, in combination, a compressor, an internal combustion engine for driving said compressor, pressure responsive unloading means for said compressor, means including a plurality of plungers each operative on the supply of pressure fluid thereto for effecting a predetermined reduction in the supply of operatin fluid to said engine, means including a plurality of pilot valves, one for each of said plungers, responsive to different compressor discharge pressures for supplying pressure fluid to and venting pressure fluid from said plungers, and means, including the one of said pilot valves operative at the maximum discharge pressure, for supplying pressure fluid to said unloading means at said maximum discharge pressure and for venting pressure fluid from said unloading means after a predetermined time delay on reduction of the discharge pressure a predetermined amount below the maximum value.

12. In a pump controlling apparatus, an element movable to alter the output of the compressor, a plurality of pressure fluid operated devices for actuating said element, means for limiting the movement of said devices individually providing different degrees of movement for the several devices, and means, operative upon the attainment of diiferent predetermined pump discharge pressures, for supplying fluid successively to said different devices in a given order as the pump discharge pressure increases and for ventin fluid from said devices in reverse order upon the attainment of different predetermined relatively lower pump discharge pressures as the pump discharge pressure falls.

13. In a pumping apparatus, in combination, a, prime mover, a pump connected for drive by said prime mover, unloading means for said pump, means for controlling the speed of said prime mover, means for actuating said last mentioned means to efiect a slowing down of said prime mover upon a predetermined increase in pump discharge pressure, and means for operating said unloading means to effect pump unloading and for further actuating said prime-moverspeed-controlling means further to slow down said prime mover upon the attainment to a higher predetermined pump discharge pressure, said means for actuating said prime-mover-speedcontrolling means upon successive increases in pump discharge pressure including means responsive to different pump discharge pressures for efiecting successive deliveries of operating medium and expansible chamber devices in which trolling means to reduce the speed of said prime mover.

14. In a pumping apparatus, in combination, a prime mover, a pump connected for driving by said prime mover, unloading means for said pump, means for controlling the speed of said prime mover, means for actuating said last mentioned means to effect a slowing down of said prime mover upon a predetermined increase in pump discharge pressure, and means for operating said unloadin means to efiect pump unloading and for further actuating said prime-moverspeed-controlling means further to slow down said prime mover upon attainment to a higher predetermined discharge pressure, said means for actuating said prime-mover-speed-controlling means upon successive increases in pump discharge pressure including devices responsive to diflerent pump discharge pressures for controlling flow of fluid under pressure and expansible chamber means providing a plurality of working chambers relative to which said devices control the flow of operating fluid and each having a movable bounding wall operatively connected with said prime-mover-speed-controlling means and movable to effect progressive slowing down of said prime mover upon like control of the fluid flow relative thereto by said devices.

15. In a pumping apparatus, in combination, a pump, an engine for driving said pump, unloading means for said compressor including a fluid actuated element movable to efiect unloading, a throttle for said engine, a plurality of fluid actuated members each movable to move said throttle and severally operative to move it different amounts, whereby upon sequential supply of fluid to said fluid actuated members said throttle will be moved in steps in a closing direction, a lurality of pilot valves, one for each of said fluid actuated elements, for passing fluid to said fluid actuated members successively as pump discharge pressure rises and for venting fluid from them in reverse order as pump discharge pressure falls, and a connection controlled by the pilot valve last to pass fluid to and first to vent fluid from its fluid actuated member for delivering fluid to said fluid actuated element to effect 5 unloading.

RALPH E. LAMBERTON.

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