GB2079383A - Pumps for hydraulic fluid - Google Patents

Abstract

A reciprocating piston pump 1 for hydraulic fluid comprises a pair of crankshafts 16 rotatable about spaced apart, parallel axes 17, an epicyclic gearbox 20 associated with each crankshaft 16 and hydraulic means 27 Figure 4 operable through the epicyclic gearboxes 20 to cause variation of the mutual phasing of the crankshafts 16, whilst the pump 1 is operating. <IMAGE>

Description

SPECIFICATION Pumps for hydraulic fluid This invention relates to reciprocating piston pumps for hydraulic fluid.

Such pumps are employed for instance to provide hydraulic fluid for mine equipment e.g. roof supports, which equipment of necessity produces a variable demand for fluid, and if it were possible to vary the displacement of a reciprocating piston pump, it would have inherent advantages over similar types of pumps that did not have this capability. Although there exist many variable displacement pumps that operate quite adequately when using an oil as the pumped medium, firstly these are not of the reciprocating piston type and secondly very few are successful when the hydraulic medium is water or a water oil emulsion of 95% water 5% soluble oil which is the standard hydraulic medium of mine roof supports.Therefore as far as mine equipment is concerned reciprocating piston pumps that have not been able to respond adequately to variable delivery demands placed upon them have to some extent been replaced by swash plate pumps, but these are not always satisfactory for various reasons.

According to the present invention, a reciprocating piston pump for hydraulic fluid comprises a pair of crankshafts rotatable about spaced apart, parallel axes, an epicyclic gearbox associated with each crankshaft, and hydraulic means operable through the epicyclic gearboxes to cause variation of the mutual phasing of the crankshafts, whilst the pump is operating.

The pump may have a single piston or multiple pistons, which number determines the number of throws or crankpins of each crankshaft, while the annulus of each gearbox may be geared together, with one annulus rotatable by the hydraulically actuable phase variation means.

The two annu li of the gearboxes may be geared directly together e.g. by providing intermeshing external teeth on each annulus or may be indirectly geared together, e.g. by a common, interposed pinion(s). Conveniently, for the or each piston, connecting rods of the crankshafts may be connected to opposite ends of a beam, which is pivotally attached at a mid-position to an actuator of the piston. The actuator may be an end of a piston rod remote from the piston or alternatively a crosshead.

With one crankshaft at top dead centre (T.D.C.) and the other at bottom dead centre (B.D.C.), crankshaft rotation simply rocks the beam and does not displace the pump actuator, while with both crankshafts identically phased i.e. both simultaneously at T.D.C., reciprocation of the beam, in the direction of displacement of the connecting rods, takes place, with resultant reciprocation of the pump actuator and hence the piston. Thus, with one crankshaft atT.D.C.

while the other crankshaft is at B.D.C., the pump gives zero delivery of fluid, while the location of both crankshafts at T.D.C. may be arranged to give maximum delivery, with intermediate delivery at any selected crankshaft positions between these extremes.

Preferably, apart from the two epicyclic gearboxes, the pump is provided with first stage reduction gearing, driven from a common power source eg. an electric motor. Thus, an output shaft from the electric motor may carry a pinion in mesh with two externally, toothed gearwheels, all rotatable about, spaced, parallel axes. Each gearwheel may carry a sunwheel which forms part of each epicyclic gearbox, which in fact constitutes second stage reduction gearing. The sunwheel may be in mesh with three planet wheels which are simultaneously in mesh with an internally toothed annulus.

The means to rotate one annulus may comprise a gearwheel in mesh with the external teeth of the annulus. This gearwheel may in turn be rotatable under the control of a rack which is in turn displaceable by the hydraulic means. Such hydraulic means may conveniently comprise a linear actuator having a cylinder and a piston. Thus, the phasing of the two crankshafts and hence the pump output is determined by the rack position, which position is preferably determined automatically by the output required from the pump. Thus, a pilot line may extend from the pump output line to the one side of the piston of the linear actuator, whereby the latter may sense the fluid pressure in the output line and displace itself appropriately. Alternatively, oil/water emulsion may be supplied by a services pump.If the pump is pumping an oil/water emulsion, it is desirable that only as small a quantity as possible, commensurate with accurate sensing, is admitted to the linear actuator, to maximisethe life of the latter.

The other side of the piston of the linear actuator is preferably operable on mineral oil for displacement purposes, conveniently supplied from the lubricating oil in the crankcase of the pump.

Conventionally, the or each piston is slidably located in a piston head provided with suitable porting and valves to provide for fluid supply and delivery.

The present invention will now be described in greater detail, by way of examples, with reference to the accompanying drawings, in which: Figure lisa sectional elevation through a pump in accordance with the invention; Figure 2 is a part sectional plan view taken on the line ll-ll of Figure 1; Figure 3 is a section on the line Ill-Ill of Figure 2; Figure 4 is a section on the line IV-IV of Figure 2; and Figure 5 is a section on the line V-V of Figure 2.

In the drawings, a pump 1 for hydraulic fluid comprises three pistons 2 each reciprocable in a cylinder 3 of a pump head 4, with a fluid flow passage 5 provided with a non-return inlet valve 6 and a non-return outlet valve 7. Each piston 2 is connected by a piston rod 8 to a crosshead 9 reciprocable in an enlarged cylinder 10 and carrying a projection 11 in turn carrying a pivot pin 12 by which an actuator of the piston 2, in the form of a rocking beam 13, is indirectly connected to the piston. Each rocking beam 13 carries towards each end thereof a pivot pin 14 for a connecting rod 15 of one of a pairofthreethrowcrankshafts 16 rotatable about spaced apart, parallel axes 17. The crankshafts are shown rotatably supported by bearings 18 carried in walls 19 of the pump 1.With each crankshaft 16 is associated an epicyclic gearbox 20 constituting second stage reduction gearing. Thus, drivably connected to an adjacent end of its associated gearbox is a carrier 21 of the gearbox 20, the carrier also being rotatable about its crankshaft axis 17 and carrying three sunwheels 22 rotatable within an internally toothed annulus 23 and around a sun wheel 24 also rotatable about the axis 17. Each annulus 23 is also externally toothed and in mesh with one another, while one gear of a compound gear 25 is in mesh with the external teeth of one annulus. A rack 26 is in mesh with the other gear of the compound gear 25, and is displaceable by a linear actuator 27 having a mineral oil pressure line 28 supplied e.g. from a service pump (not shown) driven by the pump 1 operable on one side of piston 29.The other side of the piston 29 is supplied with an oil/water emulsion by a line 30 which is responsive to the output of the pump 1 e.g. by being supplied by a further pump (not shown) driven by the pump 1, a fall in pressure in the oil/water emulsion causing the linear actuator 27 to displace to rotate the annuli 23 in a direction to increase the stroke of the pump 1, the resulting increase in pressure subsequently overcoming the mineral oil ioading on the piston 29 to cause rotation of the annuli 23 in their stroke decreasing directions. Such rotations of the annuli alter the phasing of the crankshafts between an in phase, full delivery condition illustrated in Figure 5 where no locking out linear reciprocation of the rocking beam 13 occurs, and a fully out of phase non-delivery condition where no linear receiprocation, but only rocking of the rocking beam 13 is effected by the out of phase reciprocation of the connecting rods 15. Obviously, proportionally controlled delivery occurs when the crankshafts are phased between these extremes. Each sunwheel 24 is connected to a gearwheel 31 in mesh with a common pinion 32, to constitute first stage reduction gearing, the pinion 32 being drivable by an output shaft 33 from a power source e.g. an electric motor (not shown).

Claims (25)

1. A receiprocating piston pump for hydraulic fluid comprising a pairofcrankshafts rotatable about spaced apart, parallel axes, an epicyclic gearbox associated with each crankshaft, and hydraulic means operable through the epicyclic gearboxes to cause variation of the mutual phasing of the crankshafts, whilst the pump is operating.

2. A pump as claimed in Claim 1 having a single piston.

3. A pump as claimed in Claim 1 having multiple pistons.

4. A pump as claimed in Claim 1 having three pistons.

5. A pump as claimed in any preceding Claim, wherein the annulus of each gearbox is geared together, with one annulus rotatable by the hydraulically actuable phase variation means.

6. A pump as claimed in Claim 5, wherein the two annuli of the gearboxes are geared directly together.

7. A pump as claimed in Claim 6, wherein intermeshing external teeth are provided on each annulus.

8. A pump as claimed in Claim 5, wherein the two annuli of the gearboxes are indirectly geared together.

9. A pump as claimed in Claim 8, wherein a common interposed pinion(s) is in mesh with external teeth of each annulus.

10. A pump as claimed in any preceding Claim, wherein for the or each piston, connecting rods of the crankshafts are connected to opposite ends of a beam, which is pivotally attached at a mid-position to an actuator of the piston.

11. A pump as claimed in Claim 10, wherein the actuator is an end of a piston rod remote from the piston.

12. A pump as claimed in Claim 10, wherein the actuator is a crosshead.

13. A pump as claimed in any preceding Claim, provided with first stage reduction gearing.

14. A pump as claimed in Claim 13, wherein an output shaft from a power source carries a pinion in mesh with two externally, toothed gearwheels, all rotatable about spaced, parallel axes.

15. A pump as claimed in Claim 14, wherein each gearwheel carries a sunwheel which forms part of each epicyclic gearbox.

16. A pump as claimed in any preceding Claim, wherein each epicyclic gearbox constitutes second stage reduction gearing and comprises three planet wheels which are simultaneously in mesh with an internally toothed annulus.

17. A pump as claimed in Claim 5 and any Claim appendant thereto, wherein the means to rotate one annulus comprises a gearwheel in mesh with the external teeth of the annulus.

18. A pump as claimed in Claim 17, wherein the gearwheel is in turn rotatable under the control of a rack which is in turn displaceable by the hydraulic means.

19. A pump as claimed in Claim 18, wherein the hydraulic means comprises a linear actuator having a cylinder and a piston.

20. A pump as claimed in Claim 19, wherein the position of the rack is determined automatically by the output required from the pump.

21. A pump as claimed in Claim 20, wherein an oil/water emulsion is applied to one side of the piston and the linear actuator and mineral oil to the other side.

22. A pump a claimed in Claim 21, wherein mineral oil is supplied from a lubrication pump.

23. A pump as claimed in Claim 21, wherein the oil water/emulsion is bled from the pump output.

24. A pump as claimed in Claim 21, wherein the oil/water emulsion is supplied from a services pump.

25. A reciprocating piston pump for hydraulic fluid substantially as hereinbefore described with reference to the accompanying drawings.