GB2475356A

GB2475356A - Hydraulic pump

Info

Publication number: GB2475356A
Application number: GB1000764A
Authority: GB
Inventors: Roland Store
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-11-13
Filing date: 2010-01-18
Publication date: 2011-05-18
Also published as: GB201000764D0; GB0919849D0

Abstract

There is provided a hydraulic pump, incorporating an actuating mechanism, whereby bearing surfaces 3,4 contact the inner walls of a bi-conic elliptical section cavity 5,6 and subject to driveshaft rotation produce an axial reciprocation of a rotationally constrained piston 1 at the rate of two strokes per single revolution of the driveshaft. The pump may be provided with a rotating sleeve valve to control the flow of fluid.

Description

HYDRAULIC PUMP

This invention relates to a hydraulic pump, which applies pressure to hydraulic fluid in response to the application of rotational power. The special features of this invention can best be understood within the context of a brief general

description as follows.

The pump has two moving parts rontained within an outer assembly. The two moving components comprise a rotating part and a reciprocating part respectively. The reciprocating part consists of an axial piston with a longitudinal stem incorporating four radial projections, which are specially shaped and positioned.

The transverse cross-section of the piston is elliptical in shape arid the piston is slidable in a central axial bore having a matching elliptical cross-section. The elliptical bore ensures that the piston is able to resist torque arising from the interaction of the rotating part and the radial projections on the piston stem. The said radial projections are enclosed in a specially shaped rotatable cavity formed integrally with the driveshaft. In addition to the driveshaft and cavity, the rotating part also incorporates a coaxial cylindrical sleeve valve as a further axial extension of the cavity.

Rotation of the sleeve valve governs the entry and exit of hydraulic fluid to and from the cylinder space by virtue of slotted ports in the extremity of the sleeve.

The mechanism of the invention, as.hereinbef ore described in general terms, enables the piston to make two complete pressure strokes for each single revolution of the driveshaft.

By way of example, the construction of the invention will now be described in more detail with reference to the accompanying diagrams in which: Figure 1 is a longitudinal cross-sectional view in the plane of the central axis of the pump.

Figure 2 is a transverse section showing the arrangement of valve ports.

Figure 3 is a transverse section through the rotating cavity.

Hydraulic Pump -continued Figure 1 shows the piston unit comprising the piston head 1, longitudinal stem 2 and two pairs of radial projections 3 and 4.

The pair of radial projections 3 are mutually at right angles to the pair of radial projections 4. E.ch pair of the radial projections are symmetrically disposed with respect to the central axis of the piston unit and hereinafter each pair is referred to simply as component 3 or component 4 respectively.

The outside surface at the extremity of each radial projection is in contact with the side walls of a surrounding cavity illustrated in Figure 1. As shown in Figure 1, the uppermost part of the cavity is formed as a separate component 6, which is secured within the main component 5 by means of four setscrews 7.

The cavity thus formed within component 5 has side walls which taper away from the central transverse plane of the cavity towards the uppermost and lowermost axial extremities of the cavity as shown in Figure 1. The greatest cross-sectional area occurs midway between the axial extremities of the cavity and the main axis of the cavity is coincident with the central axis of the pump.

The transverse section shown in Figure 3 illustrates the cross-sectional shape of the cavity, which is of an elliptical form. The part of the cavity formed in component 6 and that part formed in the main component 5 are similar in that both are tapered bores of elliptical cross-section and each have a constant side iall angle. With reference to Figure 1 the constant side wall angle conforms to the line of contact between the outermost surface of the two pairs of radial projections and the surrounding wall of the cavity.

Since the cavity as a whole is composed of two identical halves, for clarity the two halves will be referred to as cavity 5 and cavity 6 in accordance with the indications in Figure 1. When the whole cavity is assembled by insertion of component 6, it should be noted that the position of the maximum diameter in each of the two halves mutually coincides.

Hydraulic Pump -continued Concerning assembly of the cavity, the piston stem with radial projections is captive within the cavity and for this to be achieved the internal dimensions of component 6 should permit free passage of piston head 1 during the assembly operation.

With reference to Figure 3, component 4 is shown straddling the narrowest diameter of the cavity. During the operation of the pump, when driveshaft 5 commences to rotate carrying the cavity with it, component 4 will be effectively reorientated to straddle the widest diameter of the cavity after 90 degrees of rotation, and thus facilitates an axial movement of the piston unit.

The impetus for the said axial movement is in fact generated by component 3, which begins by straddling the widest diameter of cavity 6 and after 90 degrees of rotation finally straddles the narrowest diameter. The result of the aforesaid reorientation is to produce a force which pulls the piston downward as indicated in Figure 1. A further 90 degrees of rotation in the same direction will produce an axial force which pushes the piston upwards, arising from the relative orientation of the wall of cavity 5 with respect to component 4. After the drivesha.ft has completed 180 degrees of rotation, component 1i. again resumes the position shown in Figure 3 and the cycle is able to conumience again.

As mentioned earlier any tendency for the piston to twist in the cylinder bore is prevented by using a bore of elliptical cross-section, which ensures that the relative movement of the cavity with respect to the radial projections is productive of axial movement only as reflected in the movement of the piston unit.

The pump will function equally well for either clockwise or counter-clockwise rotation of the d.riveshaft, although the direction of fluid flow through the pump will be reversed if the direction of rotation is changed.

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Hydraulic Pump -continued With respect to the supply of hydraulic fluid to and from the cylinder space; Figure 1 showS that the side walls of component 5 extend beyond the cavity 5 & 6 as a coaxial cylindrical extension of the drjveshaft, thus forming an enclosed rotating sleeve. The inlet and outlet pipes are connected to the pump by means of components 12 & 13, which subtend an angle of degrees with respect to thern central axis of the pump as shown in Figure 2. Linear hydraulic channels connect components 12 & 13 directly to the interior cylinder space, while the respective flow in or out of the cylinder is governed by extended ports in the moving sleeve valve 5. The extent of the radial ports formed in sleeve valve 5 are indicated in Figure 1 and Figure 2. The transverse section in Figure 2 shows that there are two diametrically opposed ports in the sleeve, each subtending an angle of approximately 90 degrees with respect to the central axis.

When the piston unit is descending ( reference Figure 1) hydraulic fluid is drawn into the cylinder space during 90 degrees of rotation ( reference Figure 2), whilst during a further degrees of rotation hydraulic fluid is expelled from the cylinder space. The aforementioned cycle is repeated as the dri.veshaft rotates a further 180 degreeS to complete one full revolution.

The outer casing 9 incorporateS a mounting flange adjacent to the driveshaft. The driveshaft extension 5 is rotatable within the outer casing 9 and the driveshaft extension is also rotatable relative to stationary component 8, which bears on the inside surface of the rotating sleeve valve. With reference to Figure 1, component 8, which houses the piston, incorporates a circular flange adjacent to end plate 10. A central boss of similar cross-section to the piston is incorporated as an optional feature of component 10. During assembly the boss is located at the extremity of the cylinder bore. The end plate 10 and flange of component 8 are secured by setscrewS 11 which are threaded into the outer casing 9.

Hydraulic Pump -continued With reference to the forces acting on component 5, Figure 1 shows a thrust bearing 1k at the extremity of the sleeve valve.

Bearing 114' resists axial forces directed away from the driveshaft, whilst tapered roller bearing 15, adjacent to the driveshaft, resists axial loads in the opposite direction. Side loads on the driveshaft are partially absorbed by bearing 15 but are also distributed to the extensive free running surfaces within the body of the pump.

At the point where the driveshaft emerges from the outer casing, a recess is incorporated for the inclusion of an oil seal 16.

The oil seal is retained by a circlip as shown in Figure 1.

Interior channel 17, coaxial with the driveshaft, may be used for applying special lubricants to the operating mechanism.

The outer extremity of the channel is sealed by grub screw 18, located in the end of the driveshaft.

If the difficulties of producing an elliptical section bore and matching piston are toogreat,Lthen a standard circular section bore with matching piston can be used in conjunction with ball bearings constrained to move in axial grooves in both the cylinder wall and the piston stem, so that rotation of the piston in its bore will be prevented while at the same time reciprocating motion of the piston will be unimpeded.

Claims

CLAIMS1) A hydraulic pump, incorporating an actuating mechanism, whereby bearing surfaces contact the inner walls of a bi-conic elliptical section cavity and subject to driveshaft rotation produce an axial reciprocation of a rotationally constrained piston at the rate of two strokes per s±nglettevolution of the driveshaft.
2) In accordance with Claim 1, there is provided a rotating sleeve valve, positioned between the cylinder wall and the outer casing, which, bymeans of ports, controls the flow of hydraulic fluid to and from the cylinder space.
3) In accordance with Claim 1 and Claim 2, there is provided a hydraulic pump described herein by way of example.