variable swash plate hydraulic pump pricelist

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There are typically three types of hydraulic pump constructions found in mobile hydraulic applications. These include gear, piston, and vane; however, there are also clutch pumps, dump pumps, and pumps for refuse vehicles such as dry valve pumps and Muncie Power Products’ Live PakTM.

The hydraulic pump is the component of the hydraulic system that takes mechanical energy and converts it into fluid energy in the form of oil flow. This mechanical energy is taken from what is called the prime mover (a turning force) such as the power take-off or directly from the truck engine.

With each hydraulic pump, the pump will be of either a uni-rotational or bi-rotational design. As its name implies, a uni-rotational pump is designed to operate in one direction of shaft rotation. On the other hand, a bi-rotational pump has the ability to operate in either direction.

For truck-mounted hydraulic systems, the most common design in use is the gear pump. This design is characterized as having fewer moving parts, being easy to service, more tolerant of contamination than other designs and relatively inexpensive. Gear pumps are fixed displacement, also called positive displacement, pumps. This means the same volume of flow is produced with each rotation of the pump’s shaft. Gear pumps are rated in terms of the pump’s maximum pressure rating, cubic inch displacement and maximum input speed limitation.

Generally, gear pumps are used in open center hydraulic systems. Gear pumps trap oil in the areas between the teeth of the pump’s two gears and the body of the pump, transport it around the circumference of the gear cavity and then force it through the outlet port as the gears mesh. Behind the brass alloy thrust plates, or wear plates, a small amount of pressurized oil pushes the plates tightly against the gear ends to improve pump efficiency.

A cylinder block containing pistons that move in and out is housed within a piston pump. It’s the movement of these pistons that draw oil from the supply port and then force it through the outlet. The angle of the swash plate, which the slipper end of the piston rides against, determines the length of the piston’s stroke. While the swash plate remains stationary, the cylinder block, encompassing the pistons, rotates with the pump’s input shaft. The pump displacement is then determined by the total volume of the pump’s cylinders. Fixed and variable displacement designs are both available.

With a fixed displacement piston pump, the swash plate is nonadjustable. Its proportional output flow to input shaft speed is like that of a gear pump and like a gear pump, the fixed displacement piston pump is used within open center hydraulic systems.

As previously mentioned, piston pumps are also used within applications like snow and ice control where it may be desirable to vary system flow without varying engine speed. This is where the variable displacement piston pump comes into play – when the hydraulic flow requirements will vary based on operating conditions. Unlike the fixed displacement design, the swash plate is not fixed and its angle can be adjusted by a pressure signal from the directional valve via a compensator.

Vane pumps were, at one time, commonly used on utility vehicles such as aerial buckets and ladders. Today, the vane pump is not commonly found on these mobile (truck-mounted) hydraulic systems as gear pumps are more widely accepted and available.

Within a vane pump, as the input shaft rotates it causes oil to be picked up between the vanes of the pump which is then transported to the pump’s outlet side. This is similar to how gear pumps work, but there is one set of vanes – versus a pair of gears – on a rotating cartridge in the pump housing. As the area between the vanes decreases on the outlet side and increases on the inlet side of the pump, oil is drawn in through the supply port and expelled through the outlet as the vane cartridge rotates due to the change in area.

Input shaft rotates, causing oil to be picked up between the vanes of the pump which is then transported to pump outlet side as area between vanes decreases on outlet side and increases on inlet side to draw oil through supply port and expel though outlet as vane cartridge rotates

A clutch pump is a small displacement gear pump equipped with a belt-driven, electromagnetic clutch, much like that found on a car’s air conditioner compressor. It is engaged when the operator turns on a switch inside the truck cab. Clutch pumps are frequently used where a transmission power take-off aperture is not provided or is not easily accessible. Common applications include aerial bucket trucks, wreckers and hay spikes. As a general rule clutch pumps cannot be used where pump output flows are in excess of 15 GPM as the engine drive belt is subject to slipping under higher loads.

What separates this pump from the traditional gear pump is its built-in pressure relief assembly and an integral three-position, three-way directional control valve. The dump pump is unsuited for continuous-duty applications because of its narrow, internal paths and the subsequent likelihood of excessive heat generation.

Dump pumps are often direct mounted to the power take-off; however, it is vital that the direct-coupled pumps be rigidly supported with an installer-supplied bracket to the transmission case with the pump’s weight at 70 lbs. With a dump pump, either a two- or three-line installation must be selected (two-line and three-line refer to the number of hoses used to plumb the pump); however, a dump pump can easily be converted from a two- to three-line installation. This is accomplished by inserting an inexpensive sleeve into the pump’s inlet port and uncapping the return port.

Many dump bodies can function adequately with a two-line installation if not left operating too long in neutral. When left operating in neutral for too long however, the most common dump pump failure occurs due to high temperatures. To prevent this failure, a three-line installation can be selected – which also provides additional benefits.

Pumps for refuse equipment include both dry valve and Live Pak pumps. Both conserve fuel while in the OFF mode, but have the ability to provide full flow when work is required. While both have designs based on that of standard gear pumps, the dry valve and Like Pak pumps incorporate additional, special valving.

Primarily used on refuse equipment, dry valve pumps are large displacement, front crankshaft-driven pumps. The dry valve pump encompasses a plunger-type valve in the pump inlet port. This special plunger-type valve restricts flow in the OFF mode and allows full flow in the ON mode. As a result, the horsepower draw is lowered, which saves fuel when the hydraulic system is not in use.

In the closed position, the dry valve allows just enough oil to pass through to maintain lubrication of the pump. This oil is then returned to the reservoir through a bleed valve and small return line. A bleed valve that is fully functioning is critical to the life of this type of pump, as pump failure induced by cavitation will result if the bleed valve becomes clogged by contaminates. Muncie Power Products also offer a butterfly-style dry valve, which eliminates the bleed valve requirement and allows for improved system efficiency.

It’s important to note that with the dry valve, wear plates and shaft seals differ from standard gear pumps. Trying to fit a standard gear pump to a dry valve likely will result in premature pump failure.

Encompasses plunger-type valve in the pump inlet port restricting flow in OFF mode, but allows full flow in ON mode lowering horsepower draw to save fuel when not in use

Wear plates and shaft seals differ from standard gear pumps – trying to fit standard gear pump to dry valve likely will result in premature pump failure

Live Pak pumps are also primarily used on refuse equipment and are engine crankshaft driven; however, the inlet on a Live Pak pump is not outfitted with a shut-off valve. With a Live Pak pump, the outlet incorporates a flow limiting valve. This is called a Live Pak valve. The valve acts as an unloading valve in OFF mode and a flow limiting valve in the ON mode. As a result, the hydraulic system speed is limited to keep within safe operating parameters.

Outlet incorporates flow limiting valve called Live Pak valve – acts as an unloading valve in OFF mode and flow limiting valve in ON mode restricting hydraulic system speed to keep within safe operating parameters

Ledluc et a1. 5] Mar. 25, 1975 [54] HYDRAULIC SWASI-ll PLATE PUMP 3,512,178 5/1970 Russell 417/218 [76] Inventors: Gerard Leduc, 88, rue dAlsace, Saint-Die; Michel Leduc, 54 Aze ailles both of France Filed: June 15, 1973 849,380 9/1960 United Kingdom 91/506 1 PP 370,545 Primary E.\"aminerWi11iam L. Freeh Assistant ExaminerGregry LaPointe [30] Foreign Application Priority Data Attorney, Agent, or Firm-Darby & Darby June 16, 1972 France 72.21752 Oct. 27 1972 France 72.38168 [57] ABSTRACT Swash plate pump comprising a rotatable swash plate 52 us. (:1. 417/222, 417/270 the inclination of which is Controlled y a hydraulic 1511 Int. Cl. F04b 49/00 j means The l means is in win Controlled y 11 [58] Field of Sear h 417/212 218 222 270; slide valve which detects the variations in the delivery 91/506; 60/452 pressures of the pump and causes a high or a low pressure to actuate the jack means, whereby the inclina- [56] References Ci d tion of the swash plate is modified and consequently 1E6 output Of thebpump The S11C1 VLliVC fur- 3.835228 /1958 Parr et a1. 417/222 t er upon y bprmg" 3.304.886 2/1967 Roberts 417/222 23 Claims, 12 Drawing Figures 13 i2 3 1 79 18 22 l 21 W 31 24 7 1 25 l 9 fl ..2 F; l

HYDRAULIC SWASH PLATE PUMP BRIEF SUMMARY OF THE INVENTION The present invention relates to improvements in hydraulic pumps of variable cubic capacity and particularly to pumps of the type such as described in US. Pat. No. 3,575,534 and having as its title Constant torque hydraulic pump. The pump described in this patent is a pump having a rotatable swash plate, of which the inclination is modified by means of a hydraulic jack, of

The present invention concerns a pump operating by the same general principle, but comprising a distribution system which is considerably improved as compared with that described in US. Pat. No. 3,575,534 of Feb. 5, 1969.

Actually, pumps providing separate rates of flow are being used to an ever-increasing extent: for example, with a pump having six pistons, it is possible to split up the flow of the pump into two separate flows, each supplied by three pistons, or even with a pump having nine pistons, into three flows each supplied by three pistons. It is quite obvious that, in these cases, it is necessary to have a valve capable of forming the sum of the pressures obtaining in the three circuits so as to act as a function of the torque necessary for driving the pump.

The distribution system described in US Pat. No. 3,575,534 would make it necessary, when the pump is one having several flows, to have a valve body having as many stages as there are flows or deliveries; it would only be possible to obtain a satisfactory functioning of such a system at the cost of complex, delicate and troublesome means.

Another object of the invention is to permit the manufacture of the pumps to be standardised, a single pump head being capable of being used with different bodies having three, or six, or nine pistons.

A last object of the invention is to permit the supply of the pump to be achieved by an axial bore in the pump body, this considerably improving the volumetric yield thereof, but is not possible with a pump such as that which is described in US. Pat. No. 3,575,534.

FIG. 9 is a longitudinal sectional view along the line AA of FIG. 10 of a 12-piston pump, grouped into four deliveries, comprising the improvements according to the present addition;

DETAILED DESCRIPTION Referring to FIG. 1, it is seen that the pump is in two parts: the pump body 1, comprising the pumping pistons 3, and the pump head 2, comprising the driving shaft 4 which, by means of a pin 5, supports the swash plate 6. When the shaft 4 is driven in rotation by a motor (not shown) it drives the swash plate 6, which alternately pushes back the pistons 3, which are countersupported by springs 7. As the"swash plate 6 is pivoted on a pin 5, its inclination can be modified, the travel of the pistons 3 decreasing as a function of the decrease in the angle of the plate 6.

The modifications in the inclination of the plate 6 are caused by a hydraulic jack formed by a piston 8 sliding in a bore 8a drilled axially in the shaft 4 and possibly provided with a sleeve or liner 812, so that during operation, the plate receives the thrust of the pistons 3 on one side and thrust of the piston 8 on the other side.

When there is an odd number of pistons 3, for example five pistons, the thrust exerted by the front face of the plate is alternately caused by two or three pistons, and the result thereof is a high frequency pulsation of the pressure obtaining at the rear of the piston 8, which pulsation cancels out the frictional effects of the various movable elements of the system. By way of example, with a pump having five pistons, the thrust experienced by the front face of the swash plate oscillates by 2.5 i 20%, and this, when the shaft 4 is turning at 1,500 rpm, corresponds to a pulsation at a frequency of 250 cycles per second.

When there is an even number of pistons 3, for example, six pistons, and when the pump is a double-acting pump, the swash plate 6 also experiences high frequency pressure pulsations when the two deliveries are not at the same pressure. When the two deliveries are at the same pressure, or when the pump has a single delivery, there is also a high frequency pulsation which arises from the fact that, because of compressibility phenomena which are shown at the pressures under consideration, the travel of the pistons with a rise in pressure is not symmetrical with that with a fall in pressure, relatively to the line of maximum slope of the plate.

Referring to FIGS. 2 and 4, it is seen that the swash plate 6 comprises a central blind hole 9 which communicates by way of a passage 10 with a crescent-shaped passage 11, over which the studs 12 of the pistons 3 pass at the time of rotation of the plate 6. When the studs 12 pass over the crescent-shaped passage 11, the pistons 3 are in their suction stroke and the liquid surrounding the plate 6 in the chamber 13 is drawn into the bores in which the said pistons 3 are sliding.

A plurality of bores 14 have been placed along the path traversed by the studs 12 in the part corresponding to the delivery, each bore being provided with a non-return valve and communicating with a central chamber 16 which is drilled in the rear face of the swash plate 6 (FIG. 2).

The result of this arrangement is that when the pump is a pump having several rates of flow, the pressure obtaining in the chamber 16 is always the strongest of the pressures obtaining in the circuits connected to the said pump.

By referring to FIGS. 5 and 6, it will be seen that the pin 5 on which the swash plate 6 is pivoted comprises along its longitudinal axis a duct 34 which communicates with the said chamber 16 through a duct 35 and a passage 35a, drilled in the body of the swash plate 6. As is shown in FIGS. 7 and 8, there are passages 36 and 37 radiating from the two ends of the duct 34 towards the bearings 38 carried by the supporting shaft 4, in which the pin 5 is journalled. The passages 36 are directed towards the face of the plate 6, against which the pistons 3 are adapted to bear, and the passages 37 are directed towards the face of the plate 6, against which the piston 8 is bearing. The purpose of this lack of symmetry is to balance at least partially the torsional force to which the pin 5 is subjected, because the force of the pistons 3 on the plate 6 is unsymmetrical.

Referring to FIG. 1, it is seen that the chamber 13 is supplied with liquid originating from a reservoir through a duct 17 in the pump body 1 along the axis of this latter, this being favourable to the supply of the blind hole 9 and consequently of the crescent-shaped passage 11.

This arrangement in which the liquid arrives through a duct opening perpendicularly of the centre of the chamber 13 assists the supply to the crescent-shaped passage 11 by a centrifugal action of the hydraulic liquid, and cancels out the distrubing effect which is due to the movement of the pistons.

This stud 18 comprises an annular recess 19 facing the plate 6 and an annular recess 20 facing the spherical head of the piston 8. These two recesses are supplied with oil under pressure coming from the chamber 16 through a conduit 21 comprising a calibrated passage 22.

The piston 8 and the rod 24, together with the bore 8a, define an annular chamber 23. The said piston 8 carries a valve which receives the high pressure and the low pressure and which causes one or the other to communicate with the said chamber 23 for actuating the piston 8 in one direction or the other, so as to modify the inclination of the swash plate 6 and hence to adapt the rate of flow delivered by the pump.

The swash plate 6 receives on one face a thrust which is caused by the pistons 3, which thrust is balanced by that of the piston 8. If the outlet pressures (in the case of a pump with 2 x 3 pistons delivering two independent rates of flow) are called P, and P and ifs is the total section of the piston 8, the balancing pressure p in the chambers 23 and 26 is a function of P, and P in the form:

In the particular case where the pump has two identical rates of flow, that is to say: S, S, S, then there is obtained This pressure p acts on the slide valve 29 in opposition with the spring 30; in the balanced state, these two forces are equal.

When one of the pressures P, and P increases, the thrust on the plate 6 likewise increases, and this has the effect of increasing the balancing pressure p in the chambers 23 and 26. The effect of the increase in the pressure in the chamber 26 is to drive in the slide valve 29, which brings the conduits 32 and 31 into communication, in such a way that the high pressure obtaining in the chamber 16 is directed into the chamber 23. The piston 8 then starts to be displaced towards the right at a speed determined by the speed at which the slide valve is driven in, this movement of said valve being continued as long as there is lack of equilibrium between the pressure in the chamber 26 and the action of the spring 30.

If the pressure P rises to 400 bars, as a result of an increasing force in one of the installations supplied by the pump, an identical calculation shows that the pressure p rises to p 262.9 bars approximately.

In practice, the determination of the-characteristics of the spring for obtaining the desired relation is effected experimentally, point by point. A spring of very weak rigidity will give a cubic capacity which varies little as a function of the pressure and as a result one will come close to a pump which cancels out its rate of flow at constant pressure; in any case, a spring of constant rigidity will give a torque on the shaft of which the value will decrease in proportion as the pressures increase, that is to say, as the cubic capacities become smaller; in order to obtain a constant torque, it will be necessary to use a spring of which the rigidity is increased at the same time as the amount of flexion.

EXAMPLE A double delivery pump has been developed which comprises six equal pistons 3 with a diameter of 31.00 mm, delivering at maximum cubic capacity (maximum inclination of the plate 6) two equal rates of flow of 50 cc/revolution. The piston 8 has a diameter of 60 mm, the rod 24 has a diameter of 18 mm and the slide valve 29 a diameter of 6 mm.

In the pump which is shown in the previous FIG- URES, the valve receives the high pressure through the conduit 32 which discharges at the middle of the bearing stud 18, which encloses the chamber 16 in which obtains the highest of the delivery pressures.

In accordance with a modified construction which is shown in FIGS. 9 to 12, the strongest delivery pressure is selected by non-return valves 40 placed in the pump body 1 immediately downstream of the pistons 3.

The pump comprises 12 pistons 3 which are grouped in threes so that the pump has four independent delivery flows: the first delivery is supplied by the pistons 3a, the second by the pistons 3b, the third by the piston 30 and the fourth by the pistons 3d; the deliveries of the pistons of a single group are connected with one another downstream of the non-return valves 42a, 42b, 42c, 42:] by conduits 41, such as 41a for the pistons 3a.

This pressure, thus selected, is carried through a conduit 44 drilled in the casing 1-2 of the pump as far as a passage 45 drilled in the jack 8, opening on to the slide member 29 of the valve.

This supporting stud 18 is preferably biconical and receives, on the one hand, the spherical head of the jack 8 and, on the other hand, the spherical part of a hub 48 placed at the back of the swash plate 6. Formed in the body of this hub 48 is a passage 35a which communicates with the passage 35.

, This modification has two advantages as compared with the embodiment in FIGS. 1 to 8: firstly, the means for selecting the highest delivery pressure are no longer actually placed inside the swash plate, which is more difficult to achieve from the point of view of machining operations, and secondly the hydraulic balancing of the supports of the jack 8 and of the hub or boss 48 on the stud 18 is much better. Actually, in the pump as shown in FIGS. 1 to 8, the pressure obtaining inside the stud 18 is always the highest of the delivery pressures, and this makes necessary the determination of the contact circle between jack 8 and stud 18 as a function of the highest possible delivery pressure, and the result of this is a hydraulic over-balancing of the bearing of the jack on its stud; this over-balancing necessitates the presence of a calibrated leakage flow device, such as that bearing the references 19 to 22.

It may actually be proved to be advantageous in certain cases to have an automatic stopping of the movements of the plate 6 when it reaches the zero delivery position.

means communicating between said control valve means outlet and said jack moving means, said control valve means moving in response to variation of pressure in said chamber and communicating the fluid from one of said first or second inlets to said outlet to move said jack in a direction to change the inclination of the swash plate to maintain a given torque at said driving means in response to a variable delivery pressure, said control valve means also being movable with respect to said jack to vary the flow of the fluid to said jack as the jack moves.

2. A pump as in claim 1 wherein said jack moving means includes restricted passage means (24a, 25-24a, 25) for supplying the fluid to said chamber (2626).

3. A pump as in claim 1 wherein said control means includes a slide valve communicating with and responsive to the pressure in said chamber (26-26) and further comprising spring means for exerting a force on said slide valve means in opposition to the force exerted thereon by the fluid in said chamber.

6. Pump according to claim 3 wherein the jack includes a piston having a surface communicating with said chamber, said piston of the jack controlling the swash plate having a double section of different sizes, said jack moving means including two chambers situated so that one communicates with the large section and the other communicates with the small section of said jack piston, a calibrated passage means providing communication between said two chambers, the chamber situated behind the large section receiving either the high pressure or the low pressure by means of the valve, so that, with equilibrium, the said valve being closed, these two chambers are at the same pressure, which is a function of the delivery pressure.

7. Pump according to claim 6, wherein the slide member of the valve projects into the chamber which communicates with the small section of the jack and is subjected to the pressure obtaining in this chamber, so that any variation of the delivery pressures causes a displacement of the slide member of the valve.

8. Pump according to claim 7, further comprising a fixed stop against which said spring bears said fixed stop comprising a partition separating the two chambers situated behind the jack.

9. Pump according to claim 7, further comprising a fixed stop against which said spring bears said fixed stop comprising a partition separating the two chambers situated behind the control jack of the swash plate, and second spring means bearing on the jack.

10. Pump according to claim 6, further comprising a partition separating said two chambers and wherein said calibrated passage is formed by an annular space provided between the small-section of the jack and an orifice formed in the partition separating the said chambers.

11. Pump according to claim 10, wherein the jack includes a rod having a shoulder extending through said orifice such that the said annular calibrated passage is of variable length.

plate with which said passages communicate, said jack having a piston including a supporting stud for providing communication between said central chamber and a passage formed in the said piston and ending at the valve.

13. Pump according to claim 1 wherein said pump includes delivery pistons and further comprising means for selecting the highest delivery pressure including an assembly of interconnected passages equipped with non-return valves, said passages being located in the casing of the pump body downstream of the delivery pistons.

14. Pump according to claim 13, further comprising additional non-return valves at the outlet of each delivery pistons, said non-return selection valves being located downstream of said additional non-return valves which are located at the outlet of the bore of each delivery piston.

15. Pump according to claim 13, further comprising additional non-return valves at the outlet of each of said delivery pistons, said selection non-return valves being positioned upstream of the additional non return valves.

18. Pump according to claim 1, further comprising first means for applying the highest selected delivery pressure to the valve positioned inside the jack by means, said first means comprising a passage drilled in the casing of the pump body and a passage drilled in the jack.

19. Pump according to claim 18, further comprising ajoint between two passages, said joint including a ring which is centered with friction on the jack and is held immobile to rotation, said ring having a passage providing communication between the said two passages.

20. Pump according to claim 12 wherein the high pressure selected at the passage ending at the valve communicates with a further passage connecting two passage assemblies supplying the said high pressure to the bearings of the said shaft in two diametrically opposite Zones.

23. Pump according to claim 13 wherein means for selecting the high pressure communicates with a passage connecting two passage assemblies supplying the said high pressure to the bearings of the said shaft in two diametrically opposite zones.