US2407343A - Hydraulic pump - Google Patents

Description

Sept 10, 1946- K. EQ PYNE ETAL v l -2,107,3434

HYDRAULIC PUMP 4 Filed July 12, 1944 2 ysheets-sheet 1 2f v f 20,3 f f l/ :x www HH. mm'\\\\\\\\\\\\\\\\\\mummvg; 50 y \\\`Q% 1 he-nrwih` Edward Pyne Clifford Douglas' Pgne. By David Luh'r Leadbeater Sept. 10,1946. K. rsi PYNE r-:rA| 2,407314 3 HYDRAULIC PUMP Filed July 12, 1944 2 sheets-sheet 2 3 mvfrirons.- Klnheh Edward Pyne Cliffar Douglas Pyne David4 Luther" Leadbeater mw l? ATTORNEY Patented Sept. 10, `14946 HYDRAULIC PUMP Kenneth Edward Pyne and Clifford Douglas Pyne, West Wickam,

Leadbeater, Prittlewell, England Application July 12, 1944, Serial No. 544,5,42 vIn Great Britain August 3, 1943 (Cl. S-38) 2 Claims.

The present invention relates to hydraulicv pumps more particularly c-f the type employing reciprocating pistons operated by eccentrics mounted upon the driving shaft'or by ther conventional crankshaft.

An object of the present invention is to provide an automatic control of the stroke of the pump e piston-or pistons so that when the desired pressure is obtained the stroke of the piston or pistons is automatically carried so that the piston or pistons transmit only the required quantity of oil or other pressure fluid to maintain the desired prsure. Y

A further object of the present invention is to provide a pump of the type referred to in which the necessity of by-passing the oilor other pressure fluid through a pressure valve set at the desired pressure back to the reservoir is eliminated. The present invention is characterised by the pro-vision of pressure sensitive means responsive to the pressure of the pressure iluid on the pressure side of the pump which means is adapted to control the stroke of the piston or pistons so that they transmit only the required quantity of pressure fluid to maintain the desired and predetermined pressure.

Conveniently the pressure sensitive means comprises a plunger working within ya cylinder and having its head exposed to the pressure fluid with which it is maintained in contact said plunger being adapted to be moved axially within this cylinder by the uid on a variation of pressure which movement is transmitted to the piston to lift it off or to return it on to the driving eccentric according to whether the pressure is above or below the desired and pre-determined pressure at which the pressure sensitive means has been set to operate. The plunger may conveniently be spring loaded the tension of the spring being adjustable to that pressure at which it is required to operate the pump. The plunger may be connected to transmit its movement to the piston by any suitable means and for example the plungerL is adapted to pivot a centrally fulcrumed link or links the other end of the link or links engaging a yoke member which bears upon shoulders upon the pistons. Conveniently the yoke member may be mounted upon guide rods which reciprocate in guide Ways provided in the body of the pump casing.

The invention will now be described with reference to the accompanying drawings in which:

Figure 1 is a cross-section of an hydraulic pump according to the present invention on the line I-I of Figure 2,

and David Luther Figure 2 is a cross-section of the same pump on the line II-II of Figure 1,

Figure 3 shows a detail in cross-section on the line III-III of Figure 1 and A Figure 4 shows a further detail in cross-section on the line IV-IV of Figure 2.

Mounted in the pump casing I is a driving shaft 2 carried in suitable bearings 3 and 4. This shaft 2 carries eccentric races 5, 6 and I which drive the pump pistons 8, 9 and I9 respectively. These pistons are spring loaded by springs I I, I2

and I3 to maintain them normally in contact with the eccentrics 5, 6 and 1, The pressure lluid is introduced through the conduit I4 and one way Valve I5 to the pump cylinder I6. The pistons pass the ud vfrom there through one-way valve I1 to the outlet conduit I8. Each piston cylinder is connected in thisy manner with the inlet and outlet conduits in accordance with normal practice.

Centrally disposed with respect to the pump pistons 8, 9 and I9 is a side conduit I9 leading oil from the outlet conduit I8. Exposed to this conduit is a plunger 2 0 which works in a cylinder 2I the open end of which is provided with a suitable gland 22 which p-reventskany leakage of oil between the plunger and the cylinder. The rear end of the plunger 20 is securely bolted to a yoke member 23 which extends the lengthv of the interior of the pump casing I and which is carried on guide rods 24 and 25 which work in guide ways 26 and 21 respectively bored in the pump casing I. Each end of the yoke member 23 is turned down to form a circular stud 28 which engages a slot in the upper end of a link 29. Each link 29 is pivoted on a pivot bolt 36 threaded into the wall of the pump casing I.

The lower end of each link 29 is similiarly engaged by studs 32 provided on each end of a yoke member 33. This yoke member 33 is apertured to permit the free passage of the rear ends of the pistons 8, 9 and III bearing against the eccentrics .5, 6 and I respectively.

Normally and before the desired pressure at which the pump is to work has been attained, the plunger 26 is maintained in its fully forward position as shown in the drawings by a powerful Si! and locking ring 40 for adjusting the pressure of the spring 34 upon the plunger 20. The spindle 38 is also carried upon a threaded shank 4I which is provided with a knurled knob 42 and locking ring Q3. When it is desired to operate the pump without the automatic device the spindle 36 is screwed up hard against the rear of the cap 35. This prevents the plunger moving rearwardly under influence of the fluid pressure in the side conduit I9. Normally however and when the automatic control is operating the spindle` 33 is screwed back away from the cap 35 to allow the links 2S and the plunger 2o free movement,

The yoke member 33 as stated above permits free movement of the pistons 8, S andv IG over' their full stroke when the plunger 29. is in its forward position and consequently the yoke 33 in its rearward position. However when the pressure of the fluid against the head of the plunger 20 overcomes the pressure of the spring 34 the plunger E@ is moved rearwards. This movement rocks the links 29 to move the yoke member 33 forward to bear against the shoulders 44 provided on each of the pistons 3', 9 and I0 as they move to the rear of their stroke. When the plunger 2! has been moved toits rearmost position the yoke 33 moves to its foremost position and lifts the pistons out of contact with their respective eccentrics. If the pressure drops the yoke 33 is moved backwards to permit the pistons once more to come into driving engagement with their eccentric. Thus when the desired pressure has been reached a balance is set up whereby the pistons are moved over only a portion of their stroke to maintain the pressure of the uid.

The pump according to the present invention may be employed for any purposewhere a pressure delivery of a iiuid is required and more particularly where a constant pressure is maintained. The main advantage of the automatic control of the present invention over the known method of employing a by-pass valve is that full power for the pump is only required as the pres-k sure isbeing built up and once this pressure has been obtained` only that power is needed which is d Cil iii)

fluid at a pre-determined pressure which pump includes a reciprocating piston, a driving eccentric having releasable driving connection with the rear of the piston, spring means for said piston actuating the same rearwardly toward contact with the eccentric and providing the motive power for the suction stroke, a spring loaded plunger the head of which is exposed to and maintained in contact with the pressure nuid on the pressure side of the pump and adapted upon a pre-determined pressure being reached to move axially against the spring loading the plunger, a yoke member at the rear of said piston movable toward thepressure end of the pistonl for reducing the piston stroke, a pivoted link connecting the said plunger and yoke member by which longitudinal movement of the plunger due to pressure thereon swings the link and thereby moves said yoke member toward the pressure end of the piston and lifts the piston oli the eccentric proportionally to the movement of the plunger to reduce or to eliminate the stroke of the piston accordingly.

2. An hydraulic pump for delivering pressure uid at a pre-determined pressure which pump includes a plurality of reciprocating pistons and a like number of driving eccentrics bearing upon the rear of said pistons spring means for maintaining the pistons in` contact with the eccentrics and to return the pistons on the suction stroke, a spring loaded plunger exposed to the pressure of the pressure fluid on the delivery side of the pump, means for adjusting the spring load-ing of the plunger to a pre-determined pressure, a yoke member secured to the plunger, a plurality of pivoted links centrally fulcrumed to the casing of the pump and connected at one end of each to said yoke, a second yoke member pivoted to and at the opposite end of said links said second yoke member being apertured to permit the pistons to pass freely therethrough before the pre-determined pressure is reached and shoulders upon said pistons against which the second yoke member bears upon said pre-determined pressure being reached to. lift said pistons out of driving Contact wholly or partially from said eccentrics.

KENNETH EDWARD PYNE. CLIFFORD DoUGLA-s PYNE. DAVID LUTHER, LEADBEATER.

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