US2553063A

US2553063A - Hydraulic pump

Info

Publication number: US2553063A
Application number: US83348A
Authority: US
Inventors: Simpson Thomas; Edwards Thomas; Greenland Leonard Sidney
Original assignee: HM Hobson Ltd
Current assignee: HM Hobson Ltd
Priority date: 1949-01-19
Filing date: 1949-03-25
Publication date: 1951-05-15
Anticipated expiration: 1968-05-15

Description

May 15, 1951 T. slMPsoN ET AL 2,553,063

HYDRAULIC PUMP Filed March 25, 1949 6 Sheets-Sheet 1 May 15, 1951 T. SIMPSON ETAL. 2,553,063

` HYDRAULIC PUMP Filed March 25, 1949 6 Sheets-Sheet 2 May 15, 1951 T. SIMPSON ET AL 2,553,063

HYDRAULIC PUMP Filed Maron 25, 1949 s sneexs-sheet s T. SIMPSON ET AL May l5, 1951 v HYDRAULIC PUMP 6 sheets-sheet 4 Filed March 25, 1949 May 15, 1951 T. slMPsoN ET AL 2,553,063

HYDRAULIC PUMP Filed March 25, 1949 6 Sheets-Sheet 5 May 15, 1951 Filed March 25, 1949 T. SIMPSON ET AL HYDRAULIC PUMP 6 Sheets-Sheet 6 al @s Q I Il *I l il l G d@ l :g l 1@ @@f 4;' OQ j M Patented May 15, 1951 HYDRAULIC PUMP Thomas Simpson,

Pattingham,

near Wolverhampton, Thomas Edwards, Bilsbrook, near Wolverhampton, and Leonard Sidney Greenland, Compton, Wolverhampton, England, assignors to H. M. Hobson Limited, London, England, a company of Great Britain Application March 25, 1949, Serial No. 83,348 In Great Britain January 19, 1949 6 Claims.

This invention relates to hydraulic pumps' of the kind comprising at least one pair of pumping units of the barrel and plunger type having their outlets connected to a common delivery line and a cam mechanism, common to the two units, for imparting movementI to the plungers, the cam mechanism being such that the units are eiiective to produce a constant rate of ilow of liquid in the common delivery line.

One form of hydraulic pump of the above kind is described in our U. S. application Serial No. 789,494, which matured into Patent No. 2,548,501 on April 10, 1951, and, as explained in that application, the cam mechanism is so designed that while one plunger of each coupled pair is executing a suction stroke, the other is executing a delivery stroke to discharge liquid into the common delivery line at constant speed, while, when the discharge from the one unit is increasing immediately following its suction stroke, that of the other is correspondingly decreasing, and when the discharge from one unit is decreasing, immediately prior to the suction stroke, that of the other unit is correspondingly increasing.

One object of this invention is to provide a convenien't form of regulating mechanism for varying the delivery of the pump. A further object is to provi-de a regulating mechanism such that, in the zero delivery condition, the pump barrels will contain the minimum quantity of liquid.

In the pump according to the invention the pump barrels are disposed radially inV relation to the cam shaft and the regulating mechanism comprises a sleeve surrounding the cam mechanism,v a plurality of rocker arms, for imparting movement to the plungers, each rocker arm being pivoted to the sleeve on an axis parallel to the axis of the cam shaft and carrying a follower which projects through an aperture in the sleeve and Acoacts with the cam mechanism, and means for rotating the sleeve in relation tc the cam shaft.

As the sleeve is turned, the distance between the pivot of each rocker arm and the zone of contact between that rocker arm and its associated plunger or plungers will be varied, and therefore the stroke of the plungers will he changed. When the sleeve is turned into a position such that the pivots' of the rocker arms are opposite the centre lines of the plungers no delivery takes place and it is preferred to arrange that, in this condition, the plungers are at the outer ends of their barrels (i. e. in the positions they occupy at the end of the delivery stroke) so that the barrels are empty of liquid. As the sleeve is turned from this position, the stroke imparted to the plungers by the cam mechanism, and therefore the delivery of the pump, will be progressively increased. There is therefore no danger of disturbance arising from cavitation, due to trapped air, in the liquid at the minimum delivery condition, when such cavitation would be particularly harmful in the case-of a fuel pump.

Preferably the sleeve is coupled to the vane of a vane-type servo motor to which liquid is supplied for the purpose of rotating the sleeve in relation to the cam shaft.

One form of pump according to the invention, which is intended as a fuel pump for injecting lfuel into the combustion chamber o a gas turbine, will now be described in detail, by way of example, withY reference to the accompanying drawings, in which- Fig. 1 is a diagram showing the pump, the mechanism for supplying fuel to the pump and thence to the turbine, and the mechanism for adjusting the delivery of the pump,

Fig. 2 is a section on the line II-II in Fig. 1,

Fig. 3 is a side elevation of the pump,

Fig. 4 is a longitudinal section through the centre line of the pump,

Fig. 5 is a section on the line V-V in Fig. 3, showing the pump set for maximum delivery,

Fig. 6 is a section, similar to that of Fig, 5, through part of the pump, but showing it set for zero delivery,

Fig. 7 is a section on the line VII-VII in Fig. 3,

Fig. 8 is a section on the line VIII-V111 in Fig. 4, and

Fig. 9 is a section on the line IX-D in Fig. 5.

Like reference numerals designate like parts throughout the figures. F

The hydraulic pump is shown at ID in Fig, 1 and comprises, as later explained, I6 radially disposed pumping units of the barrel and plunger type, which are coupled in pairs to eight .delivery lines H, by which fuel is pumped to eight injection nozzles i2 in the gas turbine. These delivery lines are shown purely diagrammatically in Fig. l, and are attached to the eight delivery outlets i3 shown in Fig. '7. As later described, the pump is so designed that each coupled pair of pumping units maintains, for each setting of the pump, a constant rate of flow in the associated delivery line il. The rate of flow in each delivery line may, however, as described later be adjusted from zero to a given maximum by 3 rotation of a servo vane I4 (Fig. 1) in its housing I5.

Fuel is supplied, from a reservoir I6, to the pump I by a gear wheel pump I1 driven by the turbine which feeds the fuel along a pipe I8 to the pump I0 at some convenient pressure, e. g. lbs/sq. in. The pipe I8 communicates with an inlet I9 shown in Figs. 3, 4 and 9. The pump I1 is tted with the usual relief valve 20 (Fig. 1), to allow excess fuel to be returned to the reservoir I6.

The position of the servo vane I4 in its housing I5 is controlled by a regulating valve 2l (Fig. l) which is movable axially in a sleeve 22, rotatably mounted in la. housing 23, by means of a regulating lever 24, pivoted at and having a cam face I24 abutting against the stern of the valve 2|. The sleeve 22 carries a .coupling dog 26, which is held by a spring 4I in engagement with a slot 21 nthe boss 23 of the servo vane I4, the dog 26 f being shown uncoupled from the slot 21 in Fig. 1 for purposes of clarity. The spring 4I also holds the valve stem in engagement with the cam face I 24.

A pipe 29 conducts fuel under pressure from the pipe I-8 to an annular port 36 in the housing 23, and a similar annular port 3| in the housing 23 communicates with an exhaust pipe 32 leading to the reservoir I6.

Pipes

33, 34, communicating respectively with annular ports 35, -36 in the housing 23 of the same form as the ports 30, 3|, lead to points in the housing I5 on opposite sides of the servo vane I4. The ports 35, 36 are shown most clearly in Fig. 2.

-

Radial ports

31, 38, 39 and 40 in the sleeve 22 communicate respectively with the ports 30, 3|. and 36 in the housing 23. Y

The stem of valve 2| carries a pair of

end discs

42, 43 which t closely within the sleeve 22 and fare pierced by holes 44, 45 respectively. Between the

end discs

42, 43 extend two helical lands 46, 41, the outer surfaces of which are in contact with the inner surface of the sleeve 22, and which divide the space between the

end discs

42, 43 into two

chambers

48, 49. Chamber 48 is in constant communication with the pressure pipe 29 through hole 44 and ports 31, 30, and chamber 49 is in constant communication with the exhaust pipe 32 through hole 45 and ports 38, 3I. The lands 46, 41 normally seal the ports 39, 4D respectively.

Assuming now that the lever 24 is moved anticlockwise about its pivot 25, so pushing the valve 2I to the left as seen in Fig. l, the land 46 will unmask the port 3S, connecting it to the pressure chamber 48, and the land 41 will unmask the port 40 and connect it to the exhaust chamber 43. Fuel under pressure will consequently flow through the

ports

39, 35 and the pipe 33 to the housingV i5 causing the servo vane I4 to rotate anticlockwise, expelling fuel to the exhaust chamber 49 through the pipe 34 and ports 36, 40. As the servo vane I4 rotates, it will cause the sleeve 22 to rotate with it until the

ports

39, 46 catch up with the lands 46, 41 and are again masked by those lands. The sleeve 22 thus acts as a followup mechanism, and the movement of the servo vane I5 will cease when it has assumed a position corresponding to and determined by the position of the lever 24.y

If the lever 24 is moved clockwise about its pivot 25, the valve 2I will be moved to the right by the spring 4I. The port 39, when unmasked by the "land 46, will now be connected to the exhaust 'chamber 49 and the port 40, when unmasked by 4 its land 41, will be connected to the pressure chamber 43. Consequently fuel will flow to the exhaust through the pipe 33.

ports 39, 40, so terminating the movement of the servo Vvane I4 Vwhen it has reached the position corresponding to that determined by the lever 24.

The servo vane and its housing are shown in ,Y

more detail in Fig. 7. The housing I5 has inlets 50, 5I, which Iare connected respectively to the

pipes

33, 34 and. the vane is duplicated, compris- Ving two Vanes I4, I4' mounted on a common hub 28 rotatable between

arcuate members

52, 53 in the housing on a central sleeve 51 (Fig. 4). The t space to the right of the vane I4 communicates with the space to the left of the vane I4 via a hole 54 in the boss 28, an annular space 55 within the boss and another hole 56 in the boss. l The space Vto the left of the vane I4 communicates with the space to the right of the vane.V I4' in similar fashion via holes, not shown, in the boss 218 corresponding with

holes

54, 56 and an annular space 58 shown in Fig. 4.

The pump Il! comprises a main cylindrical body 59 (Fig. 9), to one end of which is fitted the housing lI5 of the vane servo motor. Mounted centrally in the main body is a cam shaft 66 carrying two cams 6I, 62 and mounted inbearings 63, 64. The cam shaft is splined to a drive shaft 65 (see also Fig. 1) by which it is driven from the turbine.

Within the main body 59 (see in particular Figs. 4 and 5) are disposed sixteen'pumping units of the barrel and plunger type, these being divided into four groups, each comprising four.. pump barrels 66 arranged in line. The barrels extend radially in relation to the cam shaft '63, fand the groups are spaced apart as clearly shown in Fig. 5. Surrounding the cams 6I, 62 is a regulating sleeve 61, best seen in Fig. 9, having at one end dogs which project through circumferential slots in an end wall 10 of the housing I5, and engage cooperating dogs on the hub 2,8 of the servo vane. In Fig. 8 a pair of dogs y69 fixed to the hub 28 are shown projecting through a circumferential slot 68 in the end Wall 1B and engaging a dog 1I on the sleeve 61. Another pair of dogs on the hub 23, not shown in Fig. 8, but diametrically opposite the dogs 69 project through another slot similar to the slot 68 and engage another dog on the sleeve 61 similar to the dog 1I. When therefore the servo vane I4 rotates as al'- `ready described, in response to movement of the regulating lever 24 (Fig. llthe sleeve 61 will rotagte with it; L

Midway in its length the sleeve 61 has four bosses 12 (Fig. 9), within which are mounted `pivot pins 16 (Fig. 5), spaced 90 apart and extending parallel to the axis of the sleeve. On each pivot pin 16 is mounted a pair of rocker arms 11 (see also Fig. 9), one on each'side of the boss 12. These rocker arms 11 extend more or less circumferentially in relation to the sleeve. Each rocker arm 11 carries at its outer end a yroller 18 mounted on roller bearings (not shown) The rollers 18 coact with the cams 5I, 62, four with each cam (seeFig. 5) and are held .incontact with the cams by tension springs '19 extending between adjacent. rocker arms. 'As shown -in Fig. 5 four tension springs 19 are associated with each group of four rollers 18. The outer 521 facesf of the. rocker arms. 1-1 abut against. the inner ends of' the pump-plungers 88 which are loaded by compression springs 8| which press them inwardly. into contactwith the rocker arms 'H'. EachV rocker arm 11 coacts with two. adjoining plungers 3) of one of the above-mentioned groups as shown in Fig. 4.

VAsthe cams 6l, 62 rotate, the rocker arms 'il are rocked to force the plungers 88 outwards to execute delivery strokes, whereafter their springs 8| return them to execute suction strokes.

Thefuel inlet I9 is atthe housing end of. the main body and communicates, via a pair of openings 82 (Fig. '7 and Fig. 9), with eight. axial. fuel inlet passages 83 in the .main body, two of the inlet passages being associated with. each group of barrels, as shown vin Fig. 5.v Oneinlet passage 83 for each group. communicates (see Fig. 9), by a duct 84 normally closed by anY inlet valve 85 (see Fig. 5), with the outer. end of the first and thirdv barrels 66 reading. from the left hand side of Fig. 9. The other inlet passage communicates in similar fashion with the second and fourth barrels of the group. Each inlet valve 85. opens, against thev action of. a spring. 88, when the associated plunger 88 is executing a suction stroke.

Thus, considering the uppermost group of four pumping units, the inlets of the units marked A and B in Fig. 4 communicate, as shown in Fig. 9, with the right hand one of the two upper inlet passages 83 shown. in Fig. 5, while the inlets of the other two top pumping units, marked C and. D in. Fig. 4, communicate with the left hand one of the two inlet passages 83 shown in Fig. 5.

In the case of the bottom group of four pumping units, the inlet connections are reversed, as will be clear from Fig. 4, the right hand botytom inlet passage 83 as seen in Fig. 5 com-municating with the bottom pumping units C and D and the left hand bottom inlet passageV 82 communicating with the bottom pumping units A and B.

Also associated with each group of four pumping units is a pair'of discharge passages 8'! (Fig. 5). In the case of the uppermost group of barrels, the right hand discharge passage 8l shown in Fig. 5 communicates with the barrels cf the second and fourth units of the group, reading from the left in Fig. 4 and marked C and D, by means of a discharge valve 88 normally held closed by a spring 89. Each discharge' valve 88 opens, against its spring 89, when the associated plunger is executing a delivery stroke to allow fuel tc flow out of the bump barrel into the associated discharge passage 8T. The other two barrels, i. e. the barrels of units A and B, communicate in precisely the same fashion with the left hand discharge passage 31- in Fig. 5.

The discharge connections of the bottom group of pumping units are also reversed. Thus, as will be clear from Fig. 5, units C and D discharge into the left handV bottom passage 8l, while units A and B discharge into the right hand bottom passage 81. The eight discharge passages 8l lead to the eight delivery outlets I3" already mentioned to which are connected the eight delivery lines l i.

As will be apparent fromv Fig. 9, the inletA and discharge valves, 85, 88, are reversed in position Sacar@ by Letters Patent is..

for successive pumping units of the upper and bottom groups reading from the left in Fig. 9. Thus, for the upper group, the inlet valves 85 are located to the left, as seen in Fig. 5, of the units C and D, and to the right of units A and B.

similarly, in the bottom group the inlet valves are to the left (as seen in Fig. 5) of the units- A `and B and tothe right of units C and D.

The sixteen pump barrels 66. are. thus coupled in pairs to the eight discharge passages 83. Thus, the barrels of the upper units A and B are connected to one discharge passage 83 and those of upper units C and. D to another discharge passage 83.

The barrels of upper units A and B are, however, associated with different cams, the plunger cf unit A being actuated by the left hand cam 8| as seen in Fig. 4. and that of unit B the4 right hand. cam 82. The cams 6l, 62 are of the same shape, but. are displaced in phase. When, therefore, the plunger ofv unit A is executing a suctionstroke, that of unit B will he executing a delivery stroke.

.The shapeof the cams El, 82 is such that, when the discharge from either of the units A and B is increasing. immediately following its suction stroke, thatv oi" the. other .unit is correspondingly decreasing, while when the discharge from. one unit. is.deereasing,-imlnediately prior. to the. suction. stroke, that ofthe other unit is correspondinglyincreasing. The rateof flow of. fuel 'Ln eachv delivery line is: thus .maintained constant at a value determined, as later explained, 'oy-the,

esition ofA the sleevev Si in relation to the cam shaft 68.

Precisely the. same is true of the. other pair .of coupled upper units C and. D; and also the two pairs. of vcoupled bottom. units A. and. B andv C and D.

The arrangement of the. side groups of units is preciselyv similar, as willhev apparent. from Fig. 5, the units. again being grouped inpairs, one unit of each pair being. actuated bya. different one of the two cams 5i, 82,.discharging into a common delivery passage 87.

The. rate at which fuel is delivered by the pump i8 depends upon the position of. the regulating sleeve Si.. When this sleeve occupies the position, shown in Fig. 6, in which the. axes of i the pivot pins le intersect the axes of the pump barrels' 6.8, there will be no delivery from the barrels, the plungers 88 then being maintained at the outer ends of the. barrels. This corresponds with one end position of the vane Eli in itshousing l5. When the Vane i4 is moved towardsthe other end of its housing l5, the sleeve *W is turned to increase progressively the effective lengths of the rocker arms l?, so progressively increasing the stroke of the plungers 88 until finally it reaches thevmaximumdelivery position shown in Fig. 5. The sleeve 8'! is, of course, cut away where necessary, as. clearly shown in Figs. 5 and 6, to enable the rol-1ers i8 to coact with the cams 6l, 82'.

By rotation of the sleeve 81 therefore, the ilow from the pump lc can be adjusted from zero to maximum, the pump always delivering uuid. at a definite rate, which remains constant at a value determined by the position of the sleeve Si. Moreover, when the sleeve is set for zero delivery, the pump plungers 88 are maintained in. their outermost positions in which the pump barrels are substantially empty of fuel.

What we claim as our invention and desire to l. A; hydraulic comprising av cam shaft. having' thereon two cams, at least one pair oi pumping'units, each includinga plunger .mounted to reciprocate in a barrel, a common delivery line associated with each of said pairs of pump- 7 ing unitsand receiving the discharge therefrom, a regulating sleeve surrounding the cam shaft and rotatable in relation thereto, rocker arms pivoted on the sleeve for imparting reciprocating movement from the cams to the plungers, one of the plungers of each of said pairs of pumping units receiving movement from one of the cams and the other plunger of that pair receiving movement from the other cam and, the cams ben ing of the same shape but displaced 180 in phase and shaped so that each pair of pumping units produces, for a given setting of the regulating sleeve, a constant flow of liquid in the associated common delivery line at a rate determined by the position of rotational adjustment of said sleeve in relation to said shaft, and manually operable means for rotating the regulating sleeve in relation to the cam shaft to vary the effective length of the rocker arms and therefore the delivery of the pump.

2. A hydraulic pump as claimed in claim 1, comprising va plurality of groups of four pumping units, the pumping units of each group being arranged in line in relation to the cam shaft, and the plungers of two pumping units of each group being operated by a common rocker arm from one of the cams while the plungers of the other two pumping units of each group are being operated by a common rocker arm from the other cam, a p'air of inlet passages extending longitudinally of each group of pumping units, and a pair of discharge passages also extending longitudinally of each group of pumping units, the inlet and discharge passages communicating alternately with the pumping units of the group so that a pair of pumping units associated one I with each cam receives liquid from each inlet passage and a pair of pumping units associated one with each cam discharges liquid into each discharge passage. l

'3. A hydraulic pump, comprising a shaft, at least one pair of pumping units, each pumping unit comprising a barrel disposed radially in relation to the shaft, a plunger in the barrel, and an inlet valve and a discharge valve at the outer end of the barrel a delivery outlet associated with each pair of pumping units and arranged rto receive the discharge from both of said pumping units, a cam mechanism on the shaft for reciprocating the plungers in their respective barrels, a regulating sleeve surrounding the cam mechanism, rocker arms pivoted to the sleeve on axes parallel to that of the shaft for imparting move-y ment from the cam mechanism to the plungers,

and means for rotating said sleeve in relation to the shaft so as to vary the effective length of the rocker arms and therefore the delivery of the pump, said cam mechanism being so shaped that the ow of liquid in each of ysaid delivery outlets is constant and determined in magnitude by the position of rotational adjustment of said sleeve in relation to said shaft and all of said plungers being maintained bythe rocker arms in the positions corresponding to the termination of their delivery strokes when said sleeve is postioned with the pivotal axes Yof said rocker arms intersecting the centre lines of said plungers 4; A hydraulic pump, comprising a cam shaft, having thereon two cams, at'least one pair of pumping units, each including a plunger mounted to reciprocate in a barrel, a common delivery line associated with each of said pairs of pump- Uil a regulating sleeve surrounding the cam shaft and rotatable in relation thereto, rocker farms pivoted on the sleeve for imparting reciprocating movement from the cams to the plungers, one of the plungers of each of said pairs of pumping units receiving movement from one of the cams and the other plunger of that pair of receiving movement from the other cam, and the cams be-v ing of the same shape but displaced in phase and shaped so that each pair of pumping units produces, for a given setting of the regulating sleeve, a constant ow of liquid in the associated vcommon delivery line at a rate determined by the position of rotational adjustment of said sleeve in relation to said shaft, means for feeding' fuel to the pump, a vane typeservo motor having Aa vane coupled to said regulating sleeve,'andxman ually operable means for controlling the supply of fuel from said fuel feeding means to said servo motor and thereby effecting rotation of Asaid vane and'sle'eve in relation to said shaft to vary' the eiective length of the rocker arms and vtherefore'the deliveryof said pump.

5. '-Ahydraulic pump as claimed in claim f3, comprising a vane type servo motor, including 'a housing and a vane movable in said housing and coupled t'o the sleeve, a valve casing, aV conduit between each end of said housing and the'valve casing, pressure and return connections to saidv valve casing, a valve in the valve casing which normally interrupts communication between said connections and said conduits, a manually op? erable regulating member for displacing the valve,

according to its direction of movement, to eifect v coupled to the vane and constituting the follow-` up mechanism, and comprises helical lands normally masking a pair of ports in the sleeve and dividing the space therein into pressure and exhaust chambers which are respectively in com7 munication with said pressure and return connections, said ports being in fluid communication with said conduits and the regulating member serving to displace the valve axially to effect all ternative connections of the ports in the ported sleeve to said chambers.

Y THOMAS SIMPSON. THOMAS EDWARDS.' l i LEONARD SIDNEY GREENLAND'.

' REFERENCES 'CITED The following references arejof record inthe le of this patent:

UNITED STATES yPATENTS Number Name Datev 1,719,693 Ernst vJuly 2, 1929 1,859,541 Thaheld May 24, 1932,' 2,260,414 Thaheld Oct. 28, 1941L 2,446,497 Thomas Aug. s, 1943 2,471,195 Christopher M ay 28, 1949 2,479,813 Chamberlain et al. Aug. 23, 1949