US2882915A - Centrifugal hydraulic governor - Google Patents

Description

R. C. DARNELL CENTRIFUGAL HYDRAULIC GOVERNOR April 2 1, 1959 5 sheets-snaai 14 vFiled sept. 50, 1949 @NRV We.) N um 3500.. Emo taux *CSQ S SO LOCLN Omv D NN uw,

l INVENTOR Qex C. Dar/76H ATTORNEY April 21, 1959 R. c. DARNELL 2,882,915 CENTRIFUGAL HynRAuLrc GOVERNOR Filed Sept. 30, 1949 5 Sheets-Sheet 2 76g; zzz,

INVENTOR Qex C. Dafne# BY @m o; (QM.

ATTORNEY R. C. DARNELL CENTRI'FUGAL HYDRAULIC GOVERNOR April 2l, 1959 5 Sheets-Sheet 5 Filed Sept. 50. 1949 INVENTOR Qex C DarneH L (QM,

ATTOREY April 21,` 1959 R. c. DARNELL 2,882,915

CENTRIFUGAL HYDRAULIC GOVERNOR I Filed Sept. 50, 1949 5 Sheets-Sheet 4 INVENT OR @aux C. Dafne/l @www ATTORNEY April 2l, 1959 R.- c. DARNELL CENTRIFUGAL HYDRAULIC GOVERNOR 5 Sheets-Sheet 5 Filed Sept. 50, 1949 x25' mme ATTORNEYS The present invention relates to improvements in governors for regulating the speed of operation of prime movers, such as internal combustion engines in which a throttle valve is employed to govern the speed.

One of the objects of the invention is to provide a centrifugal hydraulic governor having improved load line characteristics adjacent to the point of no load throttle position to give stable operation with the elimination of hunting and surges.

Another object is to provide an improved master speed responsive unit in a centrifugal governor which is capable of speed adjustment while the prime mover is running.

Another object is to provide a governor in which the degree of control pressure transformed to the centrifugal element as a counter-action is increased in the iinal stages of throttle closing adjacent to the no load position to require increasing engine speed at an acelerated rate to eiect the nal closing of the throttle.

A further object of the invention is to provide an improved and compact master or speed responsive unit for governors of the type described in which the uid pressure for the pressure responsive or slave unit and the increase in speed of operation of the centrifugal element is accomplished through common means.

A still further object is to provide an improved pressure responsive or slave unit in a governor of the type described in which the characteristic of the regulation of load line curve at the nal stages of throttle closing at, or near, the no load position, assumes an exponential form.

Another object of the invention resides in the provision of a novel variable area diaphragm actuator for carrying out the broadly stated principles of the preceding paragraph.

A still further object is found in the provision of a novel, compact, inexpensive, combined pump, centrifugal and valving master or speed responsive unit for centrifugal hydraulic governors used upon prime movers.

A further object of the invention is to provide a simplied bumper spring arrangement for the pressure responsive unit.

A still further object is to provide a speed responsive unit which readily adapts itself to both clockwise and counterclockwise rotation.

These and other objects and advantages residing in the speciiic construction, arrangement, and combination of parts will more clearly appear from a consideration of the following specification and the appended claims.

In the drawings:

Fig. I is a brake horse power curve diagram in which the characteristics of the present invention are graphically illustrated relative to the inlluence upon the load line,

Fig. II shows an internal combustion engine equipped with the present invention,

Fig. III is a cross sectional view through the master "2,882,915 Patented Apr. 21, 1959 or speed sensitive unit of the governor, taken on line III- III of Fig. IX,

Fig. IV is an end view of Fig. III and rotated taken from the right,

Fig. V is an end view taken from the right of Fig. III, illustrating the construction of the centrifugal valve assembly, as viewed with the end plate removed,

Fig. Va is a view similar to Fig. V with the end plate in position,

Fig. VI is a cross-sectional View taken on line VI-VI of Fig. HI to show the gear pump,

Fig. VII is a cross-sectional View taken on line VII-VII of Fig. III,

Fig. VIII is a cross-sectional view taken on line VIII-VIII of Fig. VII with the rotated valve mechanism removed,

Fig. IX is an enlarged side elevational view of the mounting of the speed responsive unit shown in Fig. II,

Fig. X is a plan view of the pressure responsive unit, and

Fig. XI is a vertical cross-sectional view taken on line XI-XI of Fig. X.

Referring to the drawings, in Fig. I is shown a typical horsepower curve of a prime mover equipped with a governor. In the illustration, that portion a-b of the curve is the Zone of operation without governor iniluence up to 3,000 rpm. in the example taken. rl`he curve portion b-cd represents the governor or load line curve. It will be noted that the curve portion b-c substantially follows the straight line characteristics while the curve portion c-d assumes exponential characteristics. The point d on the curve b-c-d indicates the no load position with the throttle valve in idle position. The change of speed between full and no load for the governor is indicated as 3,000 to 3,125 r.p.m. which is by Way of example only. It is the structure which provides the curve portion c-d with exponential characteristics which distinguishes the present invention over prior practices now in general use on the market.

In Fig. Il, an internal combustion engine 10 is shown equipped with a distributor drive 12 which is geared to the master or speed responsive unit 14 of the combined governor and carburetor. Obviously, other sources of drive from the engine 10 may be used. While the principles of the present invention are adapted for sandwich type of governor association with the carburetor, they are particularly intended for embodiment in a combination carburetor-governor structure with the carburetor idle stop a part ofthe pressure responsive or slave unit 16 of the governor.

Oil from the lubrication system 20 is piped to the connection 22 (Fig. VII) and passes through the screen 24 and out one of the holes 2.6 depending upon the direction of rotation of the governor.

As shown the holes 26 are enlarged to take plugs 28 and 28 which are interchangeable as are the plugs 28" and connector 112, threadably received in the enlarged threaded outer ends of the holes 26. Holes 30 connect the pressure and suction sides of the gear pump with the holes 26 and extend into the plane of the annular groove 66 with communication therewith being provided through holes 30 shown cross-drilled in Fig. VIII and plugged at 30".

With clockwise rotation of the gear 36 as viewed in Fig. IV the solid plug 28 is press fitted in one of the holes 26 while the angularly ported plug 28 is inserted in the other hole with the port 28 opening into the hole 30 in the direction of the suction side of the gear pump; the plug 28 closing the portion of the hole 30 communicating with the associated hole 30. Where the installation of the unit 14 is such that it is more convenient to drive 3 the gear 36 counter-clockwise, the parts rst described are reversed, for example, the plugs 28s and 28 change places as do the plugs 28 and connection 112.

Formed as an integral part of the unit 14, the gear pump comprises a large gear 36 with internal teeth and a hub 38 having a square hole 39 to receive with a degree olf-tolerance the square end of the shaft 40 driven by the gears (not shown) which are in turn driven from the distributor drive 12 at one-half engine speed. This arrangement permits a degree of misalignment between the gear 36 and the shaft 40. The gear 46 of the gear pump meshes with and is driven by the gear 36 at engine speed. As the distributor shaft is driven at one-half engine speed, gear 46 of the gear pump meshes with and is preferably driven by the gear 36 atfor near engine speed to provide a practical-range of rotation within which to effect regulation without needlessly burdening the master unit and rendering it sensitive to parasitical and other disturbing inuences.

Rotating with the gear 36 is a speed responsive valve mechanism comprising a housing 48 with stem portion 50in which the stub shaft 52-is press-tted and to which the gear 46 is keyed as at 54. The stem portion 50 rotates in the sleeved bore 56 of the body portion of the unit 14. The unit'14 has an enlarged chamber 58 in which thehousing 60 of the centrifugal poppet valve 62 rotates. The recirculating path of the oil through the unit 14 is partially defined by the passage 64 extending between the annular groove 66 and the valve port 68 and a passage 70-extending between the'valve chamber 72 and the annular groove 74 in the face 76 of the gear 36. One or more holes 78 in the groove 74 drain the oil back into the crankcase through the annular groove 80 having holes 82 opening into the housing 84 and connecting with the crankcase. The pressure side of the gear pump connects with the annular groove 66 through the holes 30.

As more clearly shown in Fig. III and V, the centrifugal valve mechanism comprises a weight member 88 ported at 90 on opposite sides of the valve 62 carried in the weight member 88. The weight 88 is supported for radial movement in the ways 92. The centrifugal forces tend to move the weight 88 toward the port 68 to restrict the area of the port 68 thus increasing the pressure of the oil in the passage 30.

The structure for holding the weight 88 in the position shown in Fig. III and resisting the centrifugal forces comprises a spring 94 housed in an adjustable holder 96 and acting against a seat 98 of a U-frame 100 (see Fig. V) having its legI portions anchored in the weight 88. The holder 96 has an angular face portion 102 with which the pointed end 104 of the adjustment screw 106 co-acts to regulate the compression of the spring 94. Elongated slots 103 (see Fig. Va) in the plate 10S receive the Shanks of the locking screws 108 engaged in threaded holes 110 of the holder 96. In practice, with the engine running and the screws S loose, the adjustment screw 106 is manipulated to obtain the desired regulation on the spring 94. The screws 108 are then tightened down to hold the spring holder 96 in its adjusted position and thereafter the adjustment screw 106 may be backed off if desired to remove all contact between the surface 102 and the pointed end 104 of the screw which might produce objectionable wear, if parts were permitted to run in contact with each other following the initial adjustment,V for any appreciable .length of time.

The end cover l of the unit 14 is held in position by capscrews 17. A11 integral ,spider portion 19 carries the` central threaded boss 21 in which the adjustment screw, 106. is manipulated. A removable adjustment cover.23 has a turned outer ange seated against the gasket 25 in the groove 27. Cover 23 is apertured to beA received over the threadedstud portion 29 of the boss 21., A nut 31 holds the cover 23 in position with a sealing ring33-being provided between an annulus 35 ofv 4, the cover 23 and a circular portion 37 of the stud portion 29 to seal against oilseepage along the thread.

To protect the governor mechanism against excessive pressure which may develop in service on a -down grade where the speed of the engine 10 may exceed the no load speed of the governor, a by-pass valve 39 has been provided between the passages 64 and 70. As shown in Fig. III, the valve 39 is held to the seat 41 by a spring 43. A balance weight 45 takes the thrust of the spring 43 and substantially counterbalances the weight 88 and valve 62 within the range of its limited movement which is the order of .010. Oil passing the valve 62 ows around the body ofthe valve 39 by virtue of'a recess 47 in the passage 70. Bleeder ports 49 and 51 are provided to avoid any possible pressure built up that might develop on axial thrust between the fixed intermediate body portion 53 and the stem portion 50. Passage 55 is rrswiflvd for drainage fram. the Chamber 58.

Av conduit structure 112l hydraulically connects the unit 14 with the pressure-responsive or slave unit 16 of Fig. Xl and communicates with the chamber 114 disposed onthe pressurev side of the diaphragm 116. A build up of pressure in the passage 30 as a result of the movement of the valve 62into restricting relationship withl the port 68 results in an increase of pressure Within the chamber 114 which acts against the diaphragm 116. As shown, the central portion, of the diaphragm is connected to one end of an elongated tubular sheet metal spring housing 118. Permanently fixed to the housing 118 intermediate its ends is a sheet metal spring seat 120 having an offsetear 122. Between the spring seat 120 and the dia.- phragm y116 is a sheet metal stamping 124, centrally perforated to receive the housing 118 and being of slightly funneled coniguration to provide a progressive supporting surface for the diaphragm 116 as the diaphragm is urged to the right as viewed in Fig. XI by pressure in the chamber 114.

The carburetor throttle valve controlling the speed of operation of the internal combustion 'engine is actuated by rotation of the shaft 126. The arm 128 is fired to the shaft 126 and carries a crank pin 128 to which the rod 130 is connected at its outer end through an adjustment bolt 130. At one end of the rod 130 is a spring seat 132 against which the follow spring 134 acts. lt will be understood that the open end 118 of the housing 118 is provided with an inturn ears flange 136 upon which the opposite end of the spring 134 is supported, the ears 136 being, formed inwardly and the spring is threaded through the end 118.

The spring 138 acting against the spring seat 120 holds the housing 118 in the full load position shown in Fig. Xl

and the diaphragm k116 :in what may also be referred to as the full load position., A rivet 118" holds the housing 118 and diaphragm 116 in assembled form and provides an abutment for the adjustable stop 116 which in practice is sealed at the factory by the plug 116". At the samel time the spring 134 is acting against the seat 132 to hold the rod 130 in its inner-most position within the housing 118. As shown in Fig. XI the shaft 126 has been permitted to rotate by some remote means, as for example, the foot accelerator of an automobile, with the rod 130 being moved to its extreme position in one direction hold-` ing the throttle valve in its full open position. If the operator now lets up on the foot accelerator the usual accelerator spr-ing (not shown) which is stronger than the spring 134 will compress the latter and the arm 128will rotate clockwise as viewed in Fig. Xl until ,the` carburetor idle stop 140; isv engaged by the bumper 140' on the bolt 130'.

lt will be understood that the housing 118 is guided for axial movement in the aperture 124 of the plate 124 and by the wall of the borey 16. Angular movement of the rod 130 takes place within the opening 118.

ln the` example, the. governor is `supposed to take over the control of the throttle valve when the r.p.m. of the engine exceeds 3,000. Restriction of the port 68 by the valve 62 due to the centrifugal action upon the weight 88, builds up pressure in the passage 30 and the chamber 114 and will result in the diaphragm 116 being moved from the position shown in Pig. X1 toward the plate 124. Such movement carries with it the housing 118 together with the rod 130 to rotate the shaft 126 in a direction to close the throttle valve. As the engagement between the exible diaphragm 116 and the backing plate 124 progressively takes place from the periphery of the diaphragm 116 radially inward, the area of the diaphragm 116 which is subject to pressure in the chamber 114 effectively being exerted against the housing 118 is progressively decreased.

Through the adjustment 116 the initial position of the diaphragm 116 relative to the backing plate 124 is provided. It will be noted that the end plate 142, in whichthe adjustment 116 is threadedly mounted, concentrically supports and changes the peripheral portions of the diaphragm 116 and plate 124. Cap screws 144 hold the plate 142 to the body of the unit 16. A piloting flange is indicated at 142'.

As the diaphragm 116 is wrapped over the surface of the plate 124 by the progressively increasing pressure required in chamber 114, compression of the spring 138 is taking place to reduce the extent of the lost motion connection between the ear 122 land the adjustable bumper spring 146 mounted on the reduced end 148 of the axial adjustable shaft 150 threaded at 152 into a tapped hole 154. The spring 13S may be of straight rate or it may be of variable rate or pitch depending upon the desired characteristics of the governor. Engagement between the ear 122 and the end of the bumper spring 146 preferably takes place just short of the no load position of the throttle valve to improve stability at the most critical point in the operation of the governor.

As heretofore mentioned, the valve 62 is `of such construction that it is subjected to the transformed pressure developed in chamber 114. The spring 94 may be of either straight or variable rate as .in the case of the spring 138 and for similar reasons.

It is usual to encounter in governors of generally accepted design `a progressively increasing tendency toward instability as the load is progressively reduced. Such tendency toward instability is partly contributable to the `accelerated rate at which the reduction in area around the throttle valve 126 and valve 62 takes place as the no load positions of the valves are approached. The other major factor contributing to instability as the governor progresses from full to no load is the progressively increasing fluid pressure actuating the pressure responsive or slave unit.

According to the present invention, the `above mentioned factors have been counteracted to a substantial degree by introducing a condition whereby a progressively increasing rate of pressure change is required to move the diaphragm 116. This has been .accomplished in the illustrated form by (l) the design of the backing plate 124 which in practice may assure numerous shapes and contours to obtain the desired results (as heretofore stated the characteristic of the diaphragm may be supplemented by a spring 138 of variable rate), and (2) the transformation of the increased rate of pressure change from the slave unit 16 to the head of the valve 62. This design results in the exponential characteristic of the portion c-d of the curve of Fig. I and results from the fact that the diaphragm 116 and related parts are so designed that the pressure for each unit of diaphragm deflection increases at a rate to promote a practical constant order of stable governor control as it progresses down or up the load line curve.

I claim:

l. In ya centrifugal hydraulic governor having .a source of hydraulic pressure, the combination with a fluid circulating passageway hydraulically connected to the pressure source, of co-ordinated speed responsive valve means and pressure responsive movable wall structure adapted to regulate lspeed control means and hydraulically connected to the pressure source through said passageway, said valve means including rotatable means in which said passageway is at least partially defined, said valve means being located in and controlling the pressure in that portion of said passageway hydraulically connected to said movable wall structure, said valve means including a port defining a portion of said passageway, an unbalanced valve, means supporting said valve for movement toward said port under centrifugal action upon rotation of said rotatable means to resist the passage of fluid from said source through said passageway and port to increase the pressure in said passageway, the uid under pressure flowing through said port in a direction counter to movement of said unbalanced valve toward said port with said pressure reacting against said unbalanced valve whereby movement of said valve toward said port is resisted by pressure increases in said passageway, spring means carried by said rotatable means and engaging said valve means to continuously yact thereon in a direction opposite the centrifugal `action upon said valve means, said movable wall being in the form of an annular diaphragm having a xed peripheral portion land an axial movable portion within said fixed portion with the maximum movement thereof taking place at the central part of said axial movable portion, a backing plate for said diaphragm, said backing plate in section being trumpet shaped to present a flared surface to said diaphragm with which said -diaphragm progressively contacts inwardly 4from said peripheral portion upon axial movement produced by hydraulic pressure increases to provide a variable effective diaphragm `area subjected to the hydraulic pressure upon valve restriction.

2. In a centrifugal hydraulic governor having a source of hydraulic pressure, the combination with a uid circulating passageway hydraulically connected to the pressure source, of co-ordinated speed responsive valve means and pressure responsive movable Wall structure adapted to regulate speed control means and hydraulically connected to the pressure source through said passageway, said valve means including rotatable means in which said passageway is at least partially defined, said valve means being located in and controlling the pressure in that portion of said passageway hydraulically connected to said movable wall structure, said valve means including a port defining a portion of said passageway, an unbalanced valve, means supporting said valve for movement toward said port under centrifugal action upon rotation of said rotatable means to resist the passage of iluid from said source through said passageway and port to increase the pressure in said passageway, the uid under pressure flowing through said port in a direction counter to movement of said unbalanced valve toward said port with said pressure reacting against said unbalanced valve whereby movement of said valve toward said port is resisted by pressure increases in said passageway, spring means carried by said rotatable means and engaging said valve means to continuously act thereon in a direction opposite the centrifugal action upon said valve means, said movable wall being in the form of an annular diaphragm having a xed peripheral portion and an axial movable portion within said xed portion with the maximum movement thereof taking place at the central part of said axial movable portion, a backing plate for said diaphragm, said backing plate in section being trumpet shaped to present a ared surface to said diaphragm with which said diaphragm progressively contacts inwardly from said peripheral portion upon axial movement produced by hydraulic pressure increases to provide a variable elective diaphragm area subjected to the hydraulic pressnreupon valve restriction, and spring means having a substantially unitary rate reacting against said wall structure counter to said hydraulic pressure whereby progressive movement of said wall structure requires progressively inereasing pressure of exponential curved characteristics.

3,. In acentrifugal hydraulic governor having a source 0f Ahydraulic pressure, the combination with a duid circulating passageway hydraulically connected to the pressure source, `of co-ordinated speed responsive valve means andpressure responsive movable wall structure adapted to regulate speed control means and hydraulically connested to the pressure source through Seid passageway, Seid lValve Ymeans including rotatable means in Whih `said passageway Ais at least partially dened, said yalveurneans being locatedin and controlling the pressure in that portion of lsaid passageway hydraulically connected to said movable wall structure, said valve means including a port defining a portion of said passageway, an unbalanced valve, means supporting said valve for movement toward Said `port under centrifugal action upon rotation of said rotatable `means to resist the passage of fluid from said source through said passageway and port to increase the pressure in said passageway, the fluid under pressure nowing through said port in a direction counter to movement of said unbalanced valve toward said port with said pressure reactingagainst4 said unbalanced valve whereby movement of said valve toward said portis resisted by pressure increases in said passageway, spring means carried by said Arotatable means and engaging said valve means tocontinuously act thereon in a direction opposite the centrifugal action upon said valve means, said movable wall being in the form of an annular diaphragm having la Yfixed peripheral portion and an axial movable portion within said fixed portion with the maximum 5 movement thereof taking place at the central part of said 'axial movable portion, a backing plate for said diaphragm, said backing plate in section -being trumpet shaped to present a dared surfacev to said diaphragm .with which said diaphragm Aprogressively contacts inwardly fromsaid peripheral portion upon axialmovement produced by-hydraulic pressure increasesto provideva variable eiectivel diaphragm area subjected to thehydraulic pressure upon valve restriction, said valve part lbeing a poppet valve, the restrictionsurfae of saidpoppet-,vaive being subjected tothe transformed pressure .to which said movable wall structure is, subjected.

4. In a centrifugalhydraulic Vgovernor unit tor controlling the speed of a-primemoverthroughathrottle valve. andjcharacterized by the stability of control` in the nal stages of throttle valve closing, ahydraulic pressure source, and valvernechanism,responsive to speed for controllingthe hydraulic pressure, throttle valve controlling structuregresponsivevto the hydraulic pressure, said structure including a variable area diaphragm `actuatorcomprising amovable diaphragmfand a-iixed backingstructure with which saiddiaphragmpengages with progressively increasinglarea of contactV to progressively decrease the effectivearea ofthe diaphragm subjected Ato hydraulic pressure whereby aprogressively vincreasing pressure is required for final stages of throttle valve c losingof expouentiallcurve characteristics.

5. A centrifugal hydraulic governor unit comprising a fixed part, a rotatable centrifugal actuated valve supported for rotation in said part, an adjustment structure for said valve including an axially adjustable member located in said part land disposed longl the axis of rotation ofsaid valveand` engageablel witha portion of said valve structure toadjust the same while the valve structure is being rotated, and locking means independent of said adjustment structure for holding said valve in different positions of adjustment whereby Asaid adjustment means is-capable-of beingheid out of operation following an -initial adjustment of said valve.

-6. In zit-*centrifugal hydraulic governor unit having a speed responsive sftnuctu're including a main body portion, .a scar sum-r housed in Said body having a Pair 0f meshing gears of difrierent diari)eter,`` means for driving the gear of larger diameter at one speed while the smaller gear of said pump isbeingdriven at a higher speed, a rotatable member inciuding a centrifugally actuated valve, and a drive connection between said pump and said rotatable member driven by said smaller gear at said hishersneedi 7.. YIn a centrifugal governor, a pressure responsive unit including a movable wall structuresubjected to iluid pressure, continuously nacting spring means resisting movement of saidstructure, a bumper spring disposed to one side of said spring means,- and au actuator for said bumper spring supported for longitudinal unitary movement with said structure and moved thereby, there'being a lost motion connection between said actuator and said bumper spring. y A Y 8. In a centrifugal governor, a pressure responsive unit including ,a movable wall structure subjected to fluid pressure, a compression spring in axial alignment withV the axis .ofmovement of said wall structure, means actuated by said wall structure for compressing said spring, a rbumper spring disposed to one side of`said compression spring, land alateral projection on said means'for engaging with said bumper spring. 4

9. In a hydraulic centrifugal governor, a pressure chamber, a diaphragm defining one wall of said chamber, meanspcripherally supporting said diaphragm for movement in said chamber, `a throttle valve controlmechanism operatively connected to said diaphragm" and actuated thereby, said mechanism including athrottle valve shaft, a crank upon said shaft, a rod connected to said crank, a housing in which a substantial portion of said rod telescopes, a follow spring in said housing and lacting against said rod in said housing in one direction, a spring located exteriorly of said housing and acting upon said housing in the direction of iirst spring, a connection between said housing andrsaid diaphragm,yand means defined in said unit for supporting said housing for axial movement by said diaphragm. i Y

l0. In a hydraulic centrifugal governor, the combination of a speed responsive unit, a pressure responsive unit, a source of hydraulic pressure, a speed responsive valve mechanism including an unbalanced valve, a valve chamber, an inlet into said chamber regulated by said valve, a pressure chamber defined in said pressure responsive unit means dening a hydraulic connection between said chambers, a diaphragm, a throttle control mechanism connected to andvactuated by said diaphragm, spring means continuously acting to resist movement of saidv diaphragm, means associated with said diaphragm for progressively reducing the effective area subjected to pressure in said second chamber, a source of fluid pressure, the .pressure in said pressure responsive chamber being transformed against said valve in said speed responsive chamber, and speed responsive means acting in opposition to said transformed pressure.

ll. In a hydraulic centrifugal governor, a speed responsive unit including a rotatable valve mechanism, a gear pumphaving a pair of meshing gears of different diameter, means for driving said valve mechanism in either direction from the gear of said gear pump kof highest speed, hydraulic conduit means conducting hydraulic fluid to said gear pump, and discharging it to said valve mechanism, said means including conduits communicating with the pressure and vacuum sides of said pumps, inter,changeable means inserted in said pumps depending upon thedirection of rotation thereof, a hydraulic fluid inlet with which said conduits selectively communicates, means for delivering hydraulic fluid to said valve mechanism, said means including a, pair of conduits, means for selectively bringing one or the other of said last .conduits in hydraulic communication with said conduits connecting the pressure side of said pump depending upon the direction of rotation of said pump.

References Cited in the le of this patent UNITED STATES PATENTS Mills Apr. 24, 1888 Huil? Dec. 15, 1908 Kasley July 4, 1916 Pierce July 23, 1918 Kasley Dec. 26, 1922 Wardwell June 10, 1924 HUE June 30, 1931 Johnson Aug. 30, 1932 Hueber Julyv 25, 1933 Singrser June 18, 1935 Tarisien May 25, 1937 Karelitz Nov. 22, 1938 Warner Apr. 18, 1939 Sherrill Sept. 12, 1939 10 Day Aug. 6, Parker Jan. 7, Feilcke Apr. 29, Sexton Oct. 20, Crafts et al. Mar. 23, Mallory Aug. 15, Mallory Aug. 22, Kalin Dec. 12, Mallory Feb. 6, Kostenick Feb. 13, Hoover July 9, Mallory Aug. 20, Haines July 29, Young Dec. 6, Mallory Sept. 12, Christian Oct. 24, Parker Aug. 21,

FOREIGN PATENTS Switzerland Dec. 17,

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