US3058426A

US3058426A - Hydraulic control system

Info

Publication number: US3058426A
Application number: US707024A
Authority: US
Inventors: John H Province
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1958-01-03
Filing date: 1958-01-03
Publication date: 1962-10-16
Anticipated expiration: 1979-10-16

Description

Oct. 16, 1962 J. H. PROVINCE 3,058,426

HYDRAULIC CONTROL SYSTEM Filed Jan. 3, 1958 2 Sheer.s-5heerI l 2 Sheets-Sheet 2 Filed Jan. 5, 1958 INVENTOR 1.H. PROVINCE BY n,

ATTORNEYS.

United States Patent Olifice 3,058,426 Patented Oct. 16, 1952 3,058,426 RAUIJIC CNTROL SYSTEM John H. Province, Bartlesville, kla., vassigner to Phillips Petroleum Company, a corporation Delaware Filed Jan. 3, 1958, Ser. No. 707,024 3 Claims. (Cl. 103-17) This invention relates to a control system for hydraulic pumps. In one aspect it relates to a hydraulic system to operate -pipe tongs, rotary air couplings, derricks, and other equipment. In another aspect it relates to an irnproved means of control of a prime mover or motor for providing power for operating the above-mentioned equipment.

In oil well servicing operations it is common practice to obtain the power needed to operate the hoist winch, tubing tongs and other units from the truck motor. Modern well servicing units often employ hydraulic pumps for the operation of derr'icks and other equipment. Thus, a suitable hydraulic pump normally is available on a servicing rig. For this reason I operate a derrick hoist, tubing tongs, and other equipment hydraulicially. The hydraulic pump employed to energize the tubing tongs and other equipment is frequently driven by the same truck motor which energizes the hoisting winch. This dual functioning of the motor creates certain difliculties because the motor must be operated at a considerably higher speed when operating the winch than when coupled to the hydraulic pump. In order to prevent the hydraulic pump from being driven at an excessively high speed when the engine is driving the winch, a pneumatically operated clutch system is provided to disengage the drive shaft of the truck from the hydraulic pump when the speed of the motor exceeds a predetermined value. An air coupling is employed in the clutch system.

Accordingly, it is an object of this invention to provide an improved control system for use with a well servicing rig.

Another object is to provide an improved control system to operate tubing tongs and other equipment from the source of hydraulic fluid under pressure.

Another object of this invention is to provide an automatic control system for operating the prime mover or motor which drives a hydraulic pressure iluid pump to increase the motor and pump speed under conditions requiring large volumes of high pressure actuating fluid.

Yet another object of this invention is to provide such an automatic control system which is responsive to hydraulic pressure for increasing hydraulic pressure fluid ilow for operating a hydraulic unit requiring a large volume of pressure fluid.

Other objects, advantages and features of this invention will become apparent from the following detailed description which, taken with the attached drawing, forms a part of this specification.

In the drawing FIGURE 1 is a schematic representation of a preferred embodiment of the control system of this invention.

FIGURE 2 is a longitudinal view, partly in section, of a portion of the apparatus of FIGURE 1.

FIGURE 3 is an elevational view, partly in section7 of a normally closed pressure switch of FIGURE 1.

FlGURE 4 illustrates in diagrammatic form, a pair of electrical contacts suitable for substitution in the housing illustrated in FIGURE 3 to provide a normally open pressure switch.

FIGURE 5 is an elevational view, partly in section, of a solenoid valve of FIGURE 1.

Specifically, my invention is directed to a control system to regulate the speed of a variable speed driving member comprising in combination, a hydraulic lluid pump driven by said driving member, means for controlling flow of actuating fluid to said driving member, a source of electromotive force, an electrical circuit for communication of electromotive force from said source to said means, a conduit for transmitting pressure fluid, said pump being adapted to pressure `said pressure fluid through said conduit, a pressure switch, the switch of said pressure switch being disposed in said electrical circuit, the pressure sensing element of said pressure switch being in operative communication with pressure iluid in said conduit, said pressure sensing element being adapted to close said switch in response to an increase of pressure of said pressure fluid in said conduit above a predetermined pressure thereby actuating said means to increase ilow of actuating fluid to said driving member and said pressure sensing element being adapted to open said switch in response to a decrease in pressure of said pressure fluid in said conduit below said predetermined pressure to throttle flow of actuating fluid to said driving member.

Referring now to the drawing and specifically to FIG- URE 1, reference numeral 10 identities a truck motor which is employed to energize a well servicing unit. The speed of a motor is controlled by a butterfly valve in carburetor 11. This valve is positioned by a pneumatically operated controller 13. This controller 13 is actuated by pressure air supplied from the storage tank 14. Tank 14 is connected to an air compressor, not shown, by a line 15. A line 16 extends from tank 14 to the inlet of a throttle valve 17. Air inlet in controller 13 is connected to tank 14 through a line 18 provided with a 3-way solenoid operated valve 23. The outlet of throttle valve 17 is connected to a second air inlet 111 of controller 13 by a line 21. Solenoid valve 23 is controlled by a solenoid 24 which is energized from a voltage source 25. One terminal of voltage source 25 is connected to ground as is one terminal of solenoid 24. The second terminal of voltage source 25 is connected to a second terminal of solenoid 24 by a lead wire 27 provided with a switch 28. Switch 28 is a manually operable switch. A line 22 communicates valve 23 with the atmosphere for venting purposes. In the absence of power, that is, when switch 28 is open, a line 19 communicates through valve Z3 and

lines

13 and 16 with tank 14. When solenoid 24 is energized, by closing switch 28, line 19 communicates through valve 23 and line 22 to the atmosphere.

The drive shaft of engine 10 is connected through a suitable power take-oft" 29 and a shaft 311 to one member of a clutch 31. A `second member of clutch 31 is connected by a shaft 32 through a coupling or swivel 34 to a hydraulic pump 33. Clutch 31 is engaged by the application of pneumatic pressure thereto through coupling 34. Air pressure for energizing clutch 31 is supplied from a second storage `35 which is connected to line `15 by a line 36 provided with a pressure reducing valve 37. The pressure in tank 35 is less than the pressure in tank 14. Tank 35 is connected to coupling 34 by a line 3S having a solenoid operated 3-way valve 39, conduit 38a, an oiler 40, a conduit 3811, a quick release valve 41 and conduit 38e. Valve 39 is energized by a `solenoid 43 which has one terminal connected to the ground. The second terminal is connected to the second terminal of voltage source 25 by a lead 44 which is provided with a manually operated switch 46 and a normally closed pressure operated switch 47. Pressure switch 47 is controlled by the pressure from line 21 through a line 48, pressure above a predetermined value opening the electrical switch 47 and below this value allowing the switch to close.

The quick relief valve 41 is a standard 3-way quick relief valve, more fully illustrated on pages 133 and 134 of the Bendix-Westinghouse Maintenance Manual Number B-W 1116 published in 1952` by the Bendix-Westinghouse Automotive Air-Brake Company. This valve 41 is not necessary to the operation of the system and may be dispensed with, its main purpose being to allow air to vent to the atmosphere through opening 41a (when open) faster than it could vent through line 381;, oiler 40, line 38a, valve 39 and vent line 39a, thereby yallowing clutch 31 to release quickly without slipping thereby reducing frictional `wear during releasing. Valve 41 consists of a body having a chamber (not shown) with an air supply inlet and preliminary exhaust line 38b, a quick nir release outlet opening 41a disposed opposite 38b, and a line 38C connecting one side of the chamber to clutch 31. There is a valve seat around 38h and 41a in the chamber, 4and a valve head having a flexible yannular rim is biased by a spring cord. When pressure in 38b is high, the valve head closes opening 41a and air from 38b passes the liexible rim into line 38C to engage clutch 31. When pressure in clutch 31 kbalances the high pressure in 38.6, the flexible rim closes 38b while the valve head closes 41a. When pressure in 38b falls below that in 38C, the valve head unseats, aided by the spring, opening outlet 41ato clutch line 38C allowing quick release of air to the atmosphere. When high pressure returns to line 3Sb, the valve head closes opening 41a and pressure air passes the flexible rim into 38C repeating the cycle.

As mentioned, valve 41 is not necessary, and may be eliminated as when either one of

electrical switches

46 or 47 is open, solenoid 43 moves valve 39 to connect line 38a to vent line 39a and air is released to the atmosphere through line 381;, oiler 40, line 38a, valve 39 and vent line 39a, while valve 39 is closed to line 38. When both

switches

46 and 47 are closed, solenoid 43 actuates valve 39 to close vent line 39a and connect line 38 and 38a, supplying air under pressure from tank to valve 41 and line 38C to clutch 31 to engage said clutch.

The inlet of pump 33 is supplied with hydraulic iluid ,from an oil storage tank 50 by a line 51 provided with a iilter 52. A lluid leakage line 49 returns leakage oil from pump 33 to tank 50. The outlet of pump 33 is connected by a line 53 to a iirst port 54 of a valve 55. A second port 56 of valve 55 is connected with a rst port 57 of a second valve 58 by a line 59. The second port 60 of valve 5S is connected by a line 61 to a first port 62 of a third valve 63. A second port 64 of valve 63 is connected by a line 66 to a fluid opening 69 of a hydraulic motor 67. Motor 67 is connected with a gear box 68 which drives a tubing tongs, not sho-wn. A second fluid opening 70 of motor 67 -is connected by a line 71 to a third port 73 in valve 63. A fourth port 74 in valve 63 is connected by a line 76, a check valve 77 and a line 78 through a third port 80 of valve 58. The fourth port 81 of valve 58 is connected by

lines

82 and 83 to the oil tank 50.

Ports

80 and 74 of

respective valves

58 and 63 are connected by line 78, a centering valve 85 and line 76. A third port 87 in valve 55 communicates through a line 88 to supply hydraulic fluid to other apparatus, not shown, Which may be employed on the rig. The fluid supplied by line 88 is returned through a line 89 and line 83 to supply tank 50. The fourth port 90 of valve 55 is also connected to return line 83 by' a line 91. Line 59, which connects ports 56 `and 57 of the

respective valve

55 and 58, is connected to tank 50 by a line 92 provided with a pressure relief valve 93. The connection between the ports in

valve

55, 58 and 63 are described hereinafter.

The valves S5, 58, 63 and tubing tongs, not shown, are fully described in U.S. Patent 2,780,950 over which this present application is an improvement.

Air coupling or swivel 34 and clutch 31 are also described in detail in Patent 2,780,950. The purpose of coupling 34 is to introduce air from line 38 to FIGURE 4 1 into a passage in shaft 32. This air pressure in turn actuates clutch 31 to connect

shafts

30 and 32.

It might be stated that

valves

58 and 63 are very similar to valve 55. The centering va-lve mentioned above, is also fully described in Patent 2,780,950.

The tubing tongs described in said patent are power tongs which are adapted to be energized by hydraulic motor 67 in accordance with the procedure Ifully described in said patent.

An electrical circuit 27a is provided for connecting voltage source 25 with solenoid 24. This circuit 27a is provided with a manually operable switch 103 and a pressure actuated switch 162. A pressure sensitive element 1li-1 communicates with pressure in line 92 for actuation of pressure actuated switch 102. Normally, pressure sensitive element 101 and switch 102 are combined in a single unit, such a unit being commercially available.

Details of the pneu-matically operated controller 13 are illustrated in FIGURE 2.

This unit comprises a housing unit 112 in which are provided

pistons

113 and 117. Piston 113 has a reduced diameter portion indicated at 126. Air pressure in space 114 acts lon the adjacent surface of piston 113. The area ot piston 113 facing space 114 is relatively large in comparison to the area of a circle having as its diameter the smallest diameter of annular surface 12S. A compression spring 115 is installed as illustrated and biases piston 113 in a direction from left to right. Reference numeral 116 identifies the space from which air from inlet 111 presses against piston 117. An O-ring 127 seals space 116 from space 114. Piston 117 is attached to shaft 118 as illustrated. Shaft 118 is not att-ached to piston 113 but instead is free to move independently of piston 113 except as hereinafter described. The right-hand end of shaft 118 communicates with a compression spring 119, the right-hand end of which is held in position by a nut 128. Nut 128 is provided with a threaded opening 122 for accommodation of a throttle rod 123 (see FiGURE 1) for actuating the buttery valve of the carburetor 11. Shaft 118 is provided with a shoulder or flange 129 for contacting the enlarged end 124 of sleeve 121. A cornpression spring is provided as illustrated for biasing sleeve 121 in a direction from right to left of FIGURE 2.

In the operation of the pneumatic operated controller 13 of FIGURE 2, high pressure air introduced into space 114 through air inlet 110 presses against surface 125 of piston 113 and compresses spring 115 to hold the piston 1.13 against the nut at the left end lof housing 112. Under this condition piston 117 will also move to the left under the pressure of spring 119 and spring 120 will force sleeve 121 to the left with the result that the buttery valve of carburetor 11 will be closed to such an extent that the engine will operate at normal idling speed. If air pressure is removed from space 114, as would happen when valve 23 (FIGURE 1) is actuated to vent space 114, then piston 113 will be urged to the right by spring 115. As piston 113 moves to the right, shaft 11S also moves to the right. When ange 129 contacts enlarged portion 124 of sleeve 121, sleeve 121 and nut 128 will also move to the right. However, sleeve 121 will move to the right only a short distance because the shoulder of piston 113 will contact or lapproach the right-hand end of space 114 and further movement will be prevented. This small amount of movement of sleeve 121 is sutcient to open the butterfly valve of carburetor 11 a small amount which, in turn, will cause the engine to speed up to a fast idle. Sufficient engine speed is then available to supply fluid to the power tongs by way of motor 67. When it is desired to speed up the engine independently of the fast idle operation just described, high pressure air is admitted to space 116 by way of inlet 111. Pressure of the air against piston 117 initially forces the piston and rod 118 to the right. When flange 129 contacts enlarged end 124 of sleeve 121, additional air pressure is required to move sleeve 121 against the force of spring 120. This additional air pressure lis readily supplied by throttle valve 17 via pipe 21 and the sleeve 121 is moved to the right as far as required up to and including the full open position of buttery valve 11.

FIGURE 3 illustrates in detail construction of the pressure switch 47 disposed in electrical circuit 44 or" FIG- URE 1. The working parts of this switch are enclosed within a case 140, this case being divided into two portions by a flexible diaphragm 151. The portion of the case above diaphragm 151 represents a uid-tight portion while the portion below the diaphragm may or may not be huid-tight. As used in the apparatus of FIGURE l the tluid-tight portion of the pressure switch is provided with a threaded opening 147 for accommodation of pipe or line 48. This switch is illustrated in FIGURE 3 of course as being included within circuit 44. The upper portion or the fluid-tight portion is sealed against leakage to the atmosphere by use of a exible sealing washer 148 which is held in place by a metal or other rigid Washer 149. A rod 141 extends through these several washers and serves as a connection to which one lead of circuit 44 is attached. This rod extends into the casing and terminates as one contact point of a pair of contact points 146. These contact points are normally closed contact points.

kThe lower portion of the switch includes rod 145, to the lower portion of which is connected the other terminal ot`circuit 44. This circuit is completed between the lower of the two contact points 146 and rod 145 by a member 142, and

metal washers

152 and 144, and spring 143.-

Washer 144 rests upon a iiexible washer 150.

FIGURE 4 is intended to represent a pressure operative switch in general similar to switch illustrated in FIG- URE 3 with the exception that it is a normally open switch. Like reference numerals in FIGURES 3 and 4 identify similar pieces of apparatus.

Rods

141 and 145, contacts 146a, member 142, spring 143 and washer 144 of FIGURE 4 complete the circuit 27a. The normally open contact points are illustrated in FIGURE 4 and are identified by reference numeral 146o. A housing suitable for enclosing the apparatus parts of FGURE 4 is, if desired, similar to that illustrated in FIGURE 3 and accordingly it will not be described in detail. Flexible diaphragm 151 in FIGURE 4 also separates the portion thereabove as a fluid-tight portion of the pressure switch.

In FIGURE 5 is illustrated, tdigramrnatically and in detail, the solenoid 3-way valve 23 of FIGURE l. The solenoid 24 is illustrated as having one terminal connected to circuit 2.7 and the other terminal grounded. The valve portion of this solenoid valve is illustrated as having a common outlet on one side attached to line 19 and an outlet connected to vent line 22. disposed in such a manner that upon how of electrical current through the solenoid the valve is lowered and opened to the iiow of pressure air :from line 19 through the vent line 22. Upon opening circuit 27 the valve raises under the influence of a compression spring 161 to admit pressure air from line 18 through line 19 to the pressure operated controller 13.

In the operation of this hydraulic system and in reference to FIGURE l the manually operable switch 46 is closed to energize solenoid 43. With solenoid 43 energized valve 39 opens to admit air pressure from pipe 38 and tank 35 to rotary coupling or air swivel member 34 and shaft 32 to clutch 31. The application of air pressure to clutch 31 results in shaft 32. being coupled with shaft 3G to drive pump 33. The pneumatically operated controller 13 is set so that with switch 46 closed and switch 28 open, the motor 10 operates at normal idle speed and drives pump y33 at a speed suicient to supply power fluid for the operation of those hydraulic units which require a comparatively small amount of huid, such as a derrick raising mechanism, sucker rod tongs, etc.

When switch 2.8 is closed to complete a circuit through solenoid 24, valve 23 is actuated to vent pressure from line 19 through 22. When solenoid 24 is energized, the valve portion of the valve 23 moves downward against compression of spring 161. The venting of air pressure from line 19 results in opening the butterfly Valve of the carburetor with the motor 10 operating at a fast idle speed thereby driving pump 33 at a faster speed suiiicient to supply power fluid at a desired rate to drive those hydraulic units requiring a larger amount of rluid, such as tubing tongs.

Rotation of shaft 32 drives pump 33 so that hydraulic iiuid is Withdrawn from tank 50 through line 51 and de- =livered to line 53 under pressure. A return line 49 is provided 'between pump 33 and tank 50 for return of fluid which may leak from pump 33. When it is desired to operate any of the auxiliary equipment, not shown, valve 55 is adjusted so that ports 54 and 87 are in corn- Inunication as are ports 56 and 9i). The fiuid under pressure is then transmitted to the auxiliary equipment through a line `S8 and 'is returned therefrom to tank 50 through

lines

89 and 83.

In order to energize power tongs in a forward direction, valve 55 is set such that ports 54 and 56 are in communication as are

ports

37 and 90; Valve 53- is set so that po-

rts

57 and 60 are in communication as are ports and 81. Valve 63 is set so that ports 62 and 64 are in communication as are

ports

73 and 74. Under these conditions, the fluid `from pump 33 passes through line 53, valve 55, line 59, valve 58, line 61, valve 63 and line 66 to the opening 69` of motor 67. Fluid is returned to tank 50 yfrom motor 67 through opening 76, line 71, valve l63, line 76, check valve 77, line 78, valve 53, line 32 and line `83. When each pipe joint has been tightened it is then necessary to remove the tongs from the pipe.

When the power tongs are employed to unscrew pipe sections valve 58 is positioned such that

ports

57 and 66 are in communication as are ports Si) and 81. Valve 63 is positioned so that

ports

62 and 73 are in communication as are ports 64 and 74. The fluid under pressure is then transmitted from line 59l through valve 53, line 61, valve 63, and line 71 to port 76 of motor 67. Fluid is returned to tank 50 through line 66, valve 63, line 7 6, check valve 77, line 78, valve 58, lines 82 and line 33. In order to center the tubing tongs when operated irthe reverse direction, valve 58 is reversed. Fluid is then transmitted -from line 59 to valves 5S, line 7S, centering stop valve 85, line 76, valve 63 and line 66 to port 63 of motor 67. The return iiuid is transmitted to tank 5@ through line 71, valve 63, line 61, valve 5S, lines 82 and 33.

A Isecond power take-Off 12 is provided near the drive shaft end of engine 10. This power take-orf provides power for pulling casing and for such other uses as require high engine speeds with a mechanical direct drive takeoff, that is, a non-hydraulic drive.

The handle of the reversing valve 63 has a neutral position intermediate its line of movement. When this valve handle is in its right

hand position pipes

61 and 66 are connected and pipes 71 and 76' are connected to permit ilow of hydraulic fluid through motor 67 in one direction. When this valve handle is moved to the left of the center neutral, the motor 67 is reversed by closing oit flow of uid through the pipes just mentioned and connecting pipes 61 to 71 and pipes 66 to 76. In the valve handle neutral or center position pipe 61 is connected to pipe 76 to by-pass completely the motor 67. This by-pass involves passage of hydraulic tluid from pump 33 through pipe 53, valve 55, pipe 59, valve 58, pipe '61, valve 63, pipe 76, check valve 77, pipe 78, valve 58, pipe S2 and pipe 83 to storage 50. tIn this manner the hydraulic liquid is performing no useful work and the pressure from pump to storage is merely that caused by flow through the just mentioned pipes and valves. However, when valve 63 is actuated to operate motor 67, the pressure drop from pump to storage is markedly increased due to the load on motor 67 for operating power tongs, for example. With switch 28 and circuit 27 open and switch 103 in circuit 27a closed, this increase in pressure drop from pump to storage is evidenced in line 92 by an increase in pressure therein. This increase in pressure is sensed by the pressure sensing apparatus 101, and switch 162 is closed thereby, thus venting pressure air from line 19 through the solenoid valve 23 and vent line 22. Upon venting pressure air from line 19, the pneumatic operated controller 13 actuates to allow movement to a piston assembly 112e to the right which movement increases somewhat the ilow of fuel to the engine. Sudicient engine speed is then available to supply fluid to the power tongs by way of motor 67. If it is desired to pull tubing, throttle valve 17 is opened to admit pressure air to line 21 and thence through inlet 111 to piston 117 of pneumatic controller 13 to increase engine speed. Upon opening throttle valve 17 pressure air flows from pipe 21 through pipe 4810 actuate pressure switch 47 to disengage clutch 31 so that pump 33 will be inoperative. It is immaterial whether switch 103 is opened or closed when switch 28 is closed because the latter overrides action of the pressure assembly i-102 in maintaining valve 23 in its venting position. Y

By providing circuit 27a with a pressure switch assembly 101-102, the motor is automatically speeded up an amount sufficient to supply just enough hydraulic fluid from pump 33 to operate power tongs or other hydraulically operable equipment without overspeeding pump 33. By the use of this invention I am able to use hydraulic pump 33 as long as 24 to 30 months between overhaul periods in contrast to need for pump overhauling each 3 to 6 months when my invention is not used.

While certain embodiments of the invention have been described for illustrative purposes, the invention obviously is not limited thereto.

I claim:

l. A control system for regulating the speed of a variable speed driving member comprising, in combination, a Variable speed driving member having an actuating iiuid flow control valve in operative communication with said driving member, a hydraulic iiuid pump driven by said driving member, a pneumatically operable spring biased controller operatively connected with said actuating iluid 5 ow control valve, a source of pneumatic fluid under a superatmospheric pressure, a rst conduit communicating said source of pneumatic lluid under pressure with said controller, a 3way solenoid valve in said conduit, a source of electromotive force, an electrical circuit communicating said source of electromotive force with the solenoid of said valve, a second conduit leading from said pump for transmission of hydraulic fluid under pressure, a pressure switch, the switch of said pressure switch being disposed in said circuit, the pressure sensing element of said pressure switch being in operative communication with said hydraulic fluid in said second conduit, said pressure sensing element being adapted to close said switch in response to a predetermined pressure of said hydraulic iuid in said second conduit above a pressure produced by a low idling speed of said driving member thereby causing said 3-way valve to vent pneumatic iluid from said controller whereby said spring biases open said actuating fluid flow control valve to increase the speed of said driving member to a fast idling speed, and said pressure sensing element being adapted to open said switch in response to a pressure below said predetermined pressure of said hydraulic fluid in said second conduit thereby causing said 3-way valve to open said -rst conduit to 8 said controller thereby admitting pneumatic iiuid under pressure to said controller thereby actuating said spring loaded controller against its bias' and throttling said actu-ating -iluid flow control valve to decrease the speed of said driving member to a normal idling speed thereby providing said hydraulic i'luid under suiiicient pressure only for light duty service.

2. A control system to regulate speed of a variable speed driving member comprising, in combination, a variable speed driving member, a hydraulic fluid pump driven =by said driving member, a source of pneumatic fluid, a spring loaded pneumatic controller, a iirst conduit communicating said source of pneumatic iluid under pressure with said controller, said pneumatic controller being operatively connected with said driving member for regulating ilow of fuel thereto, an electrically operative 3-way motor valve in said rst conduit, a source of electromotive force, an electrical circuit communicating said source of electromotive force with the motor of said motor valve, a second conduit operably communicating said pump with a point of hydraulicV huid use, a hydraulic uid, in said pump and said second conduit, a pressure switch having a pressure sensing element operatively connected therewith, the switch of said pressure switch being disposed in said electrical circuit and said pressure sensing element being in operative communication with said second conduit, said 3-way valve having a vent, said pressure sensing element upon sensing a pressure higher than a predetermined pressure closing the switch oi the pressure switch to complete said electrical circuit to the motor of said motor valve thereby communicating said iirst conduit intermediate said pneumatic controller and said 3-way valve with said vent whereby the spring of said controller biases said controller in such a manner as to increase the speed of said driving member to a fast idling speed and provides high pressure hydraulic iluid for heavy duty service, and said pressure sensing element upon sensing a pressure below said predetermined pressure opens said switch thereby opening said electrical circuit and thereby communicating said rst conduit intermediate said pneumatic controller and said 3-way valve with the first conduit intermediate said 3way valve and said source of pneumatic uid whereby said pneumatic fluid biases said spring of said controller in such a manner as to decrease the speed of said driving member to a normal idling speed thereby providing hydraulic fluid below said predetermined pressure for normal light duty service.

3. An internal combustion engine throttling control assembly comprising, in combination, a variable speed internal combustion engine, la throttle valve in operative communication with said engine, a pneumatically operable spring loaded controller, said controller being operatively connected with said throttle valve, a source of pneumatic iluid under pressure, a rst conduit communicating said controller with said source of pneumatic fluid under pressure, an electrically operative 3-way motor valve in said conduit, a source of electromotive force, an electrical circuit communicating said source of electromotive force with the motor of said valve, a pressure switch having a pressure sensing element operatively connected with the switch, a hydraulic pump operatively connected lwith said engine, a hydraulic pressure restricting means, a second conduit communicating said pump with said pressure restricting means, hydraulic iiuid in said pump and in said second conduit, said switch being disposed in said circuit, said pressure sensing element operatively communicating with said second conduit and being adapted to close said switch on sensing a pressure above a predetermined pressure thereby Vactuating said motor valve to vent pneumatic iluid under pressure from said controller and actuating said spring loaded controller References Cited in the tile of this patent UNITED STATES PATENTS Ferris etal. Mar. 12, 1918 Dolza et al. Aug. 14, 1951 -Foote Oct. 5, 1953 Province Feb. 12, 1957 Henz Mar. 5, 1957