US2548501A - Hydraulic pump - Google Patents

Description

April 10, 1951 T. SIMPSON ET AL HYDRAULIC PUMP 5 Sheets-Sheet 5 Filed Dec. 5, 1947 April l0, 1951 T. `szMFsoN ET Ai.

HYDRAULIC PUMP 5 Sheets-Sheet 1 Filed DeC. 3, 1947 April 10, 1951 T. SIMPSON Er AL HYDRAULIC PUMP 5 SheetsSheet 2 Filed Deo. 3, 1947 mw. MW

April 10, T SlMPSON ET AL HYDRAULIC PUMP Filed Dec. 3, 1947 5 Shee'ts-Sheet 5 T. SIMPSON Er AL HYDRAULIC PUMP April 10, 1951 5 Sheets-Sheet 4 Filed Dec. 3, 1947 Patented Apr. 10, 1951 UNITED STATES :PATENT oF-FICE .HYDRAULIC PUMP ApplicationDecember 3, 1947, Serial No. 789,494

.In Greatritan August 19, 1947 (Cl.` S-38) '7 Claims.

1 This invention relates to hydraulic pumps, and has for -its object'to provide means whereby the delivery of the pump maybe varied. 'The Ainven- Ytion relates particularly, though Anot exclusively,

to a variable deliverydhydraulic `pump .whichsprom .duces a constant ow .of liquid lat .airate .determinedby the settingwof a delivery controlling means.

The hydraulic pump iaceording Vtothe invention comprises a` rotaryicam shaftand acam on-said vshaft arranged ito actuate the pump rto cause it -to `deliver liquid, said .cam being .shaft to turn therewith and operating to reciprocate both plungers in their respective barrels, and means for adjusting ,the-cam .longitudinally in relationto the cam shaft, the/cam .being shaped so that, in all positions-.of adjustment,.it vcauses diierential operation of the two pump units so that the two units ,togetherproducaa constant .rate ofiiow of liquidin the .deliverylina While as .the cam is moved in relation'to ,the -shaft the stroke of eachplunger in its barrel, and'therefore `the delivery of the pump, is Yprogressively increased or diminished according'to the direction oi movement of the cam.

Preferably the `pump .comprisesa number of pairs of pump units grouped .around the cam;

shaft with theirbarrels nearlyparallel thereto, the output of eachpair of pumpunitsibeingtaken .to a .common delivery .line .allotted v.to `that Apair of pumpunits land thecam acting en the .plungers through the agency of pivotedrocker arms `carrying rollers or "the likeior engaging Athe cam and tappets for. actuating theplungers, the arrangement `being such that each pair of pumpunits .produces a constant ,'ow of liquid in its delivery "line at a rate determined" by the positioncf the f cam on the cam shaft. `The rate of flowoi Yliquid of coursealso depends on the speed ofrotation of the cam shaft. n

The cam may conveniently be connected to .a piston Working in'a cylinder 'and lspring urged ',in one direction, the spring being 'counterbalanced by fluid pressure in the 'cylinder acting `on *the piston. By varying this -iiuidfpressur-ethe'position of the cam, :and therefore theA delivery vof -thepumping units,l canzbe ivaried.

A preferred-'form of variable delivery constant kflow hydraulic pumpaccording'to the invention for use in injecting fuel into the combustion chamber of va gas turbine, will now be described in detail, `by way of example, with reference to the accompanying drawings, in which:

Fig. l is afront elevation of the pump,

*Fig `2 is a section on the line II-l in Fig. l,

Figs. 3, 4 and5 are 'respectively sections taken on the lines III-III, IV-IV and -V-V'in Fig. 2,

Fig. 6 is a section taken 4on the line -Vl-VTI in Fig. 1,

Fig. '7 is a diagrammatic sectional viewon a Vlarger scale, taken on the line-VII-LVII inFig. 4,

and

Fig. 8 =is a diagrammatic view showing the "means yfor supplying controlling pressure to the mechanism for varying the delivery of `the pump.

Like reference characters denote like parts throughout the iigureS.

Turning first to 1Fig.-8, the variable delivery constant flow hydraulic pump iii issupplied with 'fuelat a-suitable pressure, from a tank 'ii through anwinlet line' 'l2 by agear pump I3. The pump lil comprises, as later described, six `pairs of pumping units, leach of which pairs vis arranged to discharge fuel at constant speed into-'a delivery line I4 common to that pain-'and leading `to an injection nozzle i5. The delivery of `the pump f-is controlledfalso as later described, 'by a piston vHi housed in -a 4cylinder l1 vand-exposed to .the pressurefof a spring I8. The cylinder il has an inletportI'Lzcommunicating, via a pipe 25.3 having therein a restriction 12I, with the inlet Aline "l2, Yand an outlet port 22 communicating with a pipe T23 through-Which liquid is returned to the tank Y'H. rlThe liquid pressure acts on the piston i5 in opposition tothe spring i8, and therefore the Lpositionfoi the piston I6 in its cylinder' il, 'is dewtermine'd by the :position of a needle valve 24, which in turn controls the effective area of an `oriceli through which theiuel iiows v:from vthe outlet port 22 to the return lin-e 23. The ystern 2t o'f'the needle Ivalve 2d isvpressed .by aspring 2l intocontact with a v'cam 28, the position of lWhich can be adjusted to alter the liquid .presrsureiacting on thefpiston 5,1by'mcving a .pilots control'lever 2t vabout .a pivot ist'.

Turning new to Fig.y 2, thecasing of pump fli is constitutedby :ascentre member 31, and apair of end members .32, 33 suitablyV secured together. IThecylinderll isprovided. in the centrermember l 23|. The pumpl'l@ is actuated by. acarnshaftfi,

mounted inabearing and having azsplined end 36 to carry a gear wheel through whichrotary motion is imparted to the cam shaft from the turbine. The cam shaft 34 is formed with splines 68 engaging corresponding splines on a cam 31, which is supported in bearings 38, 3@ and the forward or left hand end of which is coupled by a thrust bearing 40 to the piston I6. As shown in Fig. 2, the spring I3 is mounted in compression within the hollow interior of piston I6, a thrustbearing 4I being disposed between the rear end of the spring IE and the forward end of the cam shaft 34.

The spring I8 thus tends to move the piston I5 and therefore the cam 31 forwardly, 'or to the left as seen in Fig. 2. As the liquid pressure exerted on the piston I6 is varied, by adjustment of the needle valve 24 (Fig. 8), the cam 31 will be adjusted lengthwise in relation to the cam shaft 34.

The pump 10 includes twelve pumping units of the barrel and plunger type, each comprising a barrel 42 and a plunger 43 mounted to reciprocate in the barrel 42 so as to execute alternate suction and delivery strokes. The barrels 42 are mounted within the centre member 3I and are equally spaced around the cylinder 16, being inclined to the axis of the cylinder with their forward ends nearer said axis than their rear ends. Fuel is admitted to the forward ends of the barrels 42 through an inlet 44, for connection to the inlet line 12 (Fig. 8). The fuel passes from inlet 44 via passages 45 to an annular duct 45 and thence into a plurality of passages 41 aligned with the barrels 42. The admission of fuel from each passage 41 to the associated barrel 42 is controlled by an inlet valve 48 normally held closed by a spring 49. When, however, any of the plungers 43 is executing a suction stroke, the associated valve 48 opens to allow fuel to enter the forward end of the associated barrel. Inlet valves 48 of course close when their associated plungers 43 are executing delivery strokes.

The plungers 43 receive reciprocating movement from the cam 31, as the latter rotates, through the agency of six rocker arms 50, each rocker arm being associated with a pair of adjacent plungers. Each rocker arm 50 is pivoted on a pin 52 and carries a roller 5I which contacts with the cam 31. The rocker arms 5U are, see Fig. 3, of T-shape and each carries a pair of tappets 53 for actuating the associated pair of plungers 43. Springs 54 (Fig. 2) associated with the plungers 43 maintain the rollers 5I in Contact with the cam 31 and urge the plungers in the direction to execute a suction stroke, the plungers being positively actuated by the cam 31 to perform delivery strokes against the action of their springs 54. The pivot pins 52 (see Fig. 3) are accommodated each in one of six rocker supports 55 which t side by side in the interior of the casing member SI and are held in position by plates 55 and bolts 51.

Leading from the forward end of each barrel 42 (see Figs. 4 and 7) is a lateral passage 53 communicating with an outlet port 53 normally held closed by an outlet valve 6l! loaded by a spring 51. On the delivery stroke of any plunger 43, its associated outlet valve 66 opens to allow fuel to pass to an outlet passage 6I. Of the twelve outlet passages 6I, six terminate in outlet spigots 52, while the other six are sealed by screw plugs B3, the spigots 62 and plugs S3 being arranged alternately around the circumference of the pump as clearly shown in Fig. 1. The six outlet spigots 62 are connected to the six delivery lines I4 (Fig. 8).

CII

Each of the closed outlet passages 6l is connected to one of the spigoted outlet passages 6I by a channel 64 (Fig. 1). Each channel 64 communicates at its opposite ends in annular spaces 65 (Figs. 1 and 7), surroundingI the outlet passages 6I and communicating therewith via radial passages 66.

Considering the barrels 42 as Ibeing numbered clockwise consecutively from 1-l2, as seen from the front end, as marked in Figs. 3 and 4, it will be notedv that the rocker arms 50 (see Fig. 3) are common to the following adjoining pairs of barrels 1, 2; 3, 4; 5, 6; and so on. The channels 64, which connect the barrels in pairs to the common outlet spigots 62, extend between the following pairs of barrels (see Fig. 1) 1, 8; 2, '1; 3, 10; 4, 9; 5, 12; and 6, 11.

The cam 31 is so shaped that, for each position thereof in relation to the cam shaft 34, the delivery from each pair .of coupled barrels 42 into its common delivery line I4 through spigot 62 is at a constant rate throughout the cycle. Due to the shaping of cam 31, the one plunger 43 of the pair will be executing a suction stroke while the other is executing a delivery stroke at constant delivery; and an increase or decrease of delivery by either plunger, as it changes from a suction to a delivery stroke or vice versa, is compensated by a corresponding decrease or increase in the delivery from the other plunger. As the rocker arms 5B are common each to a pair of barrels 42, two adjoining plungers at any time will be executing a suction stroke and the diametrically opposite pair of adjoining plungers will be executing a delivery stroke. Thus, when the plungers in barrels 1 and 2 are executing a suction stroke those in barrels 8 and '1 will be executing a delivery stroke. As however barrels 1 and 8 have a common delivery line, and barrels 2 and '7 likewise have a common delivery line, the rate of flow in each delivery line will be constant and determined in magnitude lby the position of the cam 31 in relation to the cam shaft 34, which, in turn, as already explained, is kdetermined by the liquid pressure acting on the piston I6.

When the cam 31 is in its most rearward position on the cam shaft 34, no delivery is taking place and the plungers are at the forward ends of their barrels, a circular section of cam operating on the rocker arms 50. When the pilots lever 29 (Figi. 8) is moved to lower the needle valve 24, and increase the effective area of orifice 25, the liquid pressure acting on the piston I6 is reduced. As the cam 31 is, in consequence, shifted forwardly on the cam shaft 34 by the spring I8, portions of the cam 31 of progressively diminishing cross sectional area, but always of shape appropriate for constant rate of iiow from each coupled pair of barrels, are brought progressively into cooperation with the rocker arms 50. The strokes of the plungers 43 are thus progressively increased, with consequent progressive increase in the rate of flow through the delivery lines I4 and to the injection nozzles I5 coupled thereto.

It will be noted that, when no discharge is taking place, the plungers 43 are at the forward ends of their barrels 42, i. e. the ends at which the inlets are provided. As delivery commences, the quantity of fuel in the barrels 43 gradually increases from substantially zero to that corresponding to maximum stroke. There is therefore no danger of disturbance arising from cavitation, due to trapped air, in the fuel at the minimum delivery condition, when such cavitationwould be particularly harmful.

What we claim as our invention and desire to secure by Letters Patent is:

1. A hydraulic pump comprising` a cam shaft, a plurality of barrels lgrouped around the cam shaft, a reciprocating plunger in each barrel, a cam mounted on the cam shaft to turn therewith and operative on the plungers to impart alternate suction and delivery strokes to the plungers, and means for adjusting the cam on the cam shaft in the axial direction of the cam shaft, to vary the stroke imparted by the cam to the plungers, said barrels being grouped in pairs with the barrels constituting each pair located on opposite sides of the cam shaft and arranged to discharge into a common delivery line and the cam being proled so that the rate of flow of liquid in each delivery line is constant and determined in magnitude by the position of axial adjustment of the cam in relation to the cam shaft.

2. A hydraulic pump comprising a cam shaft, a plurality of barrels grouped around the cam shaft, each having an inlet and an outlet port at the same end thereof, a cam mounted on the cam shaft, to rotate therewith and capable of axial adjustment in relation to the cam shaft, rockers between the plungers and the cam for imparting delivery strokes to the plungers on rotation of the cam shaft, and springsfor returning the plungers to enable them Vto execute suction strokes. said cam having a circular portion adapted in one position of axial adjustment of the cam to coa-ct with the rockers to maintain all the plungers in end-of-delivery stroke position and thus adjust the pump for `zero delivery, and said cam being effective, when moved axially of the cam shaft and away from said position, progressively to increase the stroke of said plungers.

3. A hydraulic pump as claimed in claim l, wherein each barrel has inlet and outlet ports at the same end of its barrel, and comprising rockers for imparting delivery strokes from the cam to the plunger and springs for returning the plungers to enable them to perform suction strokes, said cam having a circular portion adapted in one position of axial adjustment of the cam to coact with the rockers to maintain all the plungers in end-of-delivery stroke position and thus adjust the pump for Zero delivery and said cam being effective, when moved axially ofthe cam shaft and away from said position, progressively to increase the stroke of said plungers.

4. A hydraulic pump comprising a cam shaft, a plurality of barrels grouped around the cam shaft, a reciprocating plunger in each barrel, a cam mounted on the cam shaft to turn therewith and operative on the plungers to impart alternate suction and delivery strokes to the plungers, a piston coupled to said cam, a cylinder housing said piston, a spring for urging said piston in one direction in its cylinder, means for subjecting the piston to liquid pressure to balance the spring pressure, and means for varying the magnitude of said liquid pressure and so adjusting the cam on the cam shaft in the axial direction of the cam shaft, said barrels being grouped in pairs with the barrels constituting each pair located on opposite sides of the cam shaft and arranged to discharge into a common delivery line and the cam being profiled so that the rate of ilow of liquid in each delivery line is constant and determined in magnitude by the position of axial adjustment of the cam in relation to the cam shaft.

5. A hydraulic pump comprising a cam shaft, a plurality of barrels grouped around the cam shaft, each barrel having an inlet port and an outlet port at the end thereof remote from the cam shaft, a reciprocating plunger in each barrel arranged to execute therein alternate suction and delivery strokes, a cam mounted to turn with the cam shaft and arranged to impart delivery strokes to the plungers as the cam shaft rotates, springs for returning the plungers to enable them to execute suction strokes, a piston coupled to said cam, a cylinder housing said piston, a spring for urging said piston in one direction in its cylinder, means for subjecting the piston to liquid pressure to balance the spring pressure, and means for varying the magnitude of said liquid pressure and so adjusting the cam axially of the cam shaft, said cam having a circular portion adapted in one position of axial adjustment of the cam to maintain all the plungers in end-ofdelivery stroke position and thus adjust the pump for zero delivery, and said cam being effective, when moved axially of the cam shaft and away from said position, progressively to increase the stroke of said plungers.

6. A hydraulic pump as claimed in claim-5, comprising a pump for feeding liquid into the cylinder to exert pressure on the piston in opposition to the spring, an outlet line for leading liquid away from the cylinder, a valve for controlling the effective area of an orifice in the outlet line, and means for adjusting the position of said valve so as to vary the liquid pressure exerted on the piston.

7. A hydraulic pump as claimed in claim 5, comprising an inlet line for supplying fuel under pressure to the pump, a pipe connecting the cylinder to the inlet line so as to supply fluid pressure to the piston, an outlet line for leading fuel away from the cylinder, a valve for controlling the effective area of an orice in the outlet line and means for adjusting the position of said valve so as to vary the liquid pressure exerted on the piston.

THOMAS SIMPSON. LEONARD SIDNEY GREENLAND. THOMAS EDWARDS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,071,800 Mock Feb. 23, 1937 2,169,456 Wahlmark Aug. 15, 1939 FOREIGN PATENTS Number Country Date 366,097 Italy 1938

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