GB2239488A

GB2239488A - Hydraulic actuator for marine drives

Info

Publication number: GB2239488A
Application number: GB8928661A
Authority: GB
Inventors: Colin Turner
Original assignee: MARINEX IND Ltd
Current assignee: MARINEX IND Ltd
Priority date: 1989-12-19
Filing date: 1989-12-19
Publication date: 1991-07-03
Anticipated expiration: 2009-12-19
Also published as: GB2239488B; GB8928661D0

Abstract

A hydraulic actuator (1, 11) intended to operate while an autopilot is in the drive mode, is adapted to be coupled to marine steering linkage (3) powered by a conventional power steering system (7) comprising a valve (6) operated by a push-pull cable (5). The actuator includes a directional hydraulic cylinder (1) connected by a piston rod (2) to the linkage (3) and by a bracket (9), adapted to suit different types of power steering, to the valve (6). The hydraulic cylinder (1) is fed with hydraulic fluid from an electrically driven pump (10) connected to an hydraulic reservoir (11) operable to open and close ports (16-19) allowing hydraulic fluid to flow selectively through the shuttle valve to move the actuator cylinder in the required direction With the shuttle in its shown position, fluid can flow between the ends of the cylinder (1), thereby allowing normal power steering control. <IMAGE>

Description

HYDRAULIC AICTUATOR FOR MARINE DRIVES This invention relates to an hydraulic actuator for marine drives and more particularly to an hydraulic actuator unit to operate power assisted steering systems under automatic pilot control.

Existing power assisted steering systems fitted to inboard/outboard marine drives for watercraft are normally manually actuated by a push-pull cable system.

The actuation of the cable operates a directional hydraulic valve to engage or disengage the power assisted steering to steer the watercraft.

An aim of the present invention is to provide an hydraulic actuator for operating power assisted steering systems under autopilot control whilst allowing the motor of a watercraft to be backdriven so that it can still be steered normally.

According to the present invention there is provided an hydraulic actuator for marine drives comprising an hydraulic cylinder, an electrically driven hydraulic pump for supplying hydraulic fluid to the cylinder an hydraulic reservoir and a shuttle valve, wherein the shuttle valve includes a housing and a shuttle slidable in the housing to open and close ports in the housing allowing hydraulic fluid to flow selectively through the shuttle valve to operate the actuator.

Preferably, the hydraulic pump and valve assembly is mounted on the body of the cylinder but can be remotely mounted if required.

The invention also extends to a power assisted steering system when fitted with an hydraulic actuator as set forth above.

An embodiment of the present invention will now be described, by way of example only with reference to the accompanying diagrammatic drawings, in which: Fig. 1 is a perspective view of a typical power assisted system for marine craft fitted with an hydraulic actuator according to the invention; Fig. 2 is a schematic sectional view of the hydraulic actuator shown in Fig 1; Fig 3 is an enlarged cross-section of the shuttle valve in a neutral position; Fig. 4 is a similar view to Fig. 3 of the shuttle valve in a first loaded position; and Fig. 5 is a similar view to Figs. 3 and 4 of the shuttle valve in a second loaded position.

The hydraulic actuator system shown in Fig. l comprises a directional hydraulic cylinder 1 connected via a piston rod 2 with one end of the steering linkage 3 and clamped to a valve actuator 4 at the other end of the power steering unit. The cylinder 1 is connected to the valve by a bracket 9 which can be adapted to suit different types of power steering systems.

In the conventional power steering system operation of the unit is actuated by a push-pull cable 5, which in turn transmits a relatively small linear movement to a directional hydraulic valve 6. Operation of this valve operates the power steering 7 to move the linkage 3 of the steering system.

The hydraulic actuator of the present invention is intended to operate in parallel with the push-pull cable 5 and comprises the hydraulic cylinder 1 connected with an electrically operated hydraulic pump reservoir 18 (see Fig. 2) and a shuttle valve generally indicated at 11.

The shuttle 12 of the shuttle valve 11 travels between the closed ends of a housing 13 under the action of the hydraulic flow from the hydraulic pump 10. Coil springs 15 centre the shuttle when there is no flow of hydraulic fluid. The housing 13 has four ports 16, 17, 18 and 19 these are interconnected in different ways depending on the position of the shuttle, see Figures 3, 4 and 5. The shuttle 12 is formed with radial collars 20 positioned to selectively open and close the ports 16 to 19 and control the passage of hydraulic fluid through the shuttle valve to the cylinder 1 via flexible connections 21 and 22.

The hydraulic actuator shuttle valve is operated as shown by the diagrammatic views in Figs. 3 to 5. When the electric motor 23 is not running the shuttle 12 is in a neutral position shown in Fig. 3, the shuttle 12 connects ports 16 and 17 as shown by the cross-hatching 24, allowing the hydraulic cylilnder to move freely, this is the condition in which the unit is operated when the actuator is not required to operate under autopilot control and manual steeriong of the watercraft is being used.

When the motor 23 is switched on the initial hydraulic pressure moves the shuttle 12 to the left, as shown in Fig. 4 or to the right as shown in Fig. 5 depending on the direction of rotation of the hydraulic pump 10 connecting ports 16 to 18 and 17 to 19 allowing the cylinder 1 to move in the appropriate direction thereby operating the power steering valve 6.

As shown in Fig. 4 the shuttle 12 is moved to the left opening ports 19 and 17 to allow delivery of the passage of high pressure hydraulic fluid illustrated by the cross-hatching 25, to flow in the direction of the arrows 26. While allowing the low pressure fluid as shown in cross-hatching 27, to return in the direction of arrows 28. In this position of the shuttle valve is loaded and the hydraulic cylinder is moved activating the power steering system valve to move the steering in one direction.

In the operating position of the shuttle valve shown in Fig. 5, the shuttle 12 is moved to the right allowing the passage of high pressure delivery fluid in the direction of arrows 29 and the return of low pressure fluid in the direction of arrows 30. This loaded position of the shuttle valve activates the hydraulic cylinder 1 to operate the power steering system valve 6 to move the steering in the opposite direction.

The hydraulic actuator is designed to operate while the autopilot is in the drive mode but must allow the normal steering to operate freely when the pilot is not engaged.

Although in the embodiment described and shown in Fig. 1, the hydraulic pump 10 is mounted on the cylinder 1 for ease of installation and for reasons of space restrictions, the pump and shuttle valve assembly can be mounted remote from the cylinder and connected by flexible supply lines.

Various types of brackets can be used to connect the power steering linkage to the hydraulic actuator depending on the make of power steering linkage used.

Claims

CLAIMS:

1. An hydraulic actuator for marine drives, comprising an hydraulic cylinder, an electrically driven hydraulic pump for supplying hydraulic fluid to the cylinder an hydraulic reservoir and a shuttle valve, wherein the shuttle valve includes a housing, and a shuttle slidable in the housing to open and close ports in the housing allowing hydraulic fluid to flow selectively through the shuttle valve to operate the actuator.

2. An hydraulic actuator as claimed in Claim 1, wherein the shuttle is held in a central position by springs and is moved to the required position by the flow of hydraulic fluid.

3. An hydraulic actuator as claimed in Claim 1 or 2 wherein the hydraulic pump assembly is mounted on the actuating cylinder.

4. An hydraulic actuator as claimed in Claim 1 or 2 wherein the hydraulic pump is mounted remote from the actuating cylinder.

5. A power steering system when fitted with an hydraulic actuator as claimed in any preceding claim.

6. A power steering system as claimed in Claim 5, wherein the hydraulic actuator is connected with the power steering linkage by a bracket adapted to be compatible with the power steering linkage.

7. An hydraulic actuator for marine drives, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS: 1. An hydraulic actuator for marine drives, comprising an hydraulic cylinder, an electrically driven hydraulic pump for supplying hydraulic fluid to the cylinder an hydraulic reservoir and a shuttle valve, the shuttle valve including a housing, and a shuttle slidable in the housing to open and close ports in the housing allowing hydraulic fluid to flow selectively through the shuttle valve to operate the actuator, wherein the cylinder is locked in position when the pump is inoperative and is free to run when the electric drive to the pump is not running.