Steering Cylinder and Steering System for Outboard Engines

This application claims the benefit of priority of India Patent Application No. 202521045528 filed on May 12, 2025, the contents of which are all incorporated by reference as if fully set forth herein in their entirety.

The present invention relates to a steering cylinder. More particularly, the present disclosure relates to a steering cylinder and a steering system for an outboard engine for marine vessels such as boats.

Marine vessels such as boats are generally mounted with an outboard engine which is used to steer the boat. Conventional outboard engine is generally supported by an engine bracket, which is supported pivotably on a tilt tube (a through tube). The tilt tube extends along a horizontal tilt axis, around which the outboard engine may tilt. The tilt tube extends through a clamp bracket, which is fixed to a boat hull. In operation, the outboard engine may turn or steer around a steering axis, which is perpendicular to the engine bracket. In general, the boat may be steered either hydraulically by using a hydraulic cylinder or mechanically by using push-pull cables.

The hydraulic cylinder may include a hollow piston rod configured to be connected to a link arm. The link arm may be coupled to the tiller arm which in turn may be coupled to a rudder. Conventionally, the hydraulic cylinder may be operated to move the steering arm by changing the position of the link arm. upon movement of the link arm, the position of the rudder may be changed to steer the boat. The hydraulic cylinder is generally installed co-axially with the outboard engine with the help of brackets which takes more space. Further, in case of replacement of the hydraulic cylinder, the whole outboard engine may need to be serviced at a service station which is time-consuming and expensive.

United States Patent Publication No. 62,76,977 discloses hydraulic actuator for an outboard motor system in which the cylinder and piston of the actuator are disposed within a cylindrical cavity inside a cylindrical portion of a swivel bracket. The piston within the cylinder of the actuator is attached to at least one rod that extends through clearance holes of a clamp bracket and is connectable to a steering arm of an outboard motor. The one or more rods attached to the piston are aligned coaxially with an axis of rotation about which the swivel bracket rotates when the outboard motor is trimmed. As a result, no relative movement occurs between the outboard motor, the rod attached to the piston of the actuator, and the swivel bracket during rotation of the outboard motor about the axis of rotation.

In an embodiment, the present disclosure relates to a steering cylinder for an outboard engine of a marine vessel. The steering cylinder includes a first cylinder including a first fluid port and a second fluid port. The first fluid port is positioned on a first end cap, and the first cylinder defines a first space. Further, the steering cylinder includes a second cylinder defining a first end and a second end opposite the first end. The second cylinder defines a second space housing a hollow piston. The second cylinder is configured to move with respect to the first cylinder. The steering cylinder further includes a hollow piston rod positioned at least partially within the first space and defining a first end and a second end, the first end being fluidly coupled with the first fluid port and the second end being coupled to the hollow piston. The steering cylinder is configured to actuate between an extended position and a retracted position to steer the marine vessel. In the extended position, the second cylinder is configured to move away from the first end cap, and in the retracted position, the second cylinder is configured to move towards the first end cap.

In another embodiment, the present disclosure relates to a steering system for steering an outboard engine of a marine vessel. The steering system includes a tilt tube coupled to the outboard engine. The steering system further includes a link arm defining a first end and a second end. The steering system includes a tiller arm coupled between the second end of the link arm and a rudder of the outboard engine. The steering system further includes a steering cylinder coupled to the first end of the link arm. The steering cylinder includes a first cylinder including a first fluid port and a second fluid port. The first fluid port is positioned on a first end cap, and the first cylinder defines a first space. Further, the steering cylinder includes a second cylinder defining a first end and a second end opposite the first end. The second cylinder defines a second space housing a hollow piston. The second cylinder is configured to move with respect to the first cylinder. The steering cylinder further includes a hollow piston rod positioned at least partially within the first space and defining a first end and a second end, the first end being fluidly coupled with the first fluid port and the second end being coupled to the hollow piston. The steering cylinder is configured to actuate between an extended position and a retracted position to steer the marine vessel. In the extended position, the second cylinder is configured to move away from the first end cap, and in the retracted position, the second cylinder is configured to move towards the first end cap.

In yet another embodiment, the present disclosure relates to a marine vessel comprising an outboard engine mounted on a hull of the marine vessel. The marine vessel includes a steering system for steering the outboard engine. The steering system includes a tilt tube coupled to the outboard engine. The steering system further includes a link arm defining a first end and a second end. The steering system includes a tiller arm coupled between the second end of the link arm and a rudder of the outboard engine. The steering system further includes a steering cylinder coupled to the first end of the link arm. The steering cylinder includes a first cylinder including a first fluid port and a second fluid port. The first fluid port is positioned on a first end cap, and the first cylinder defines a first space. Further, the steering cylinder includes a second cylinder defining a first end and a second end opposite the first end. The second cylinder defines a second space housing a hollow piston. The second cylinder is configured to move with respect to the first cylinder. The steering cylinder further includes a hollow piston rod positioned at least partially within the first space and defining a first end and a second end, the first end being fluidly coupled with the first fluid port and the second end being coupled to the hollow piston. The steering cylinder is configured to actuate between an extended position and a retracted position to steer the marine vessel. In the extended position, the second cylinder is configured to move away from the first end cap, and in the retracted position, the second cylinder is configured to move towards the first end cap.

Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present disclosure.

Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Generally, corresponding reference numbers may be used throughout the drawings to refer to the same or corresponding parts could refer to one or more comparable components used in the same and/or different depicted embodiments.

Referring to, an exemplary marine vesselis shown. The marine vesselmay be a boat′. The marine vesselincludes a hulland an outboard enginemounted on the hullof the marine vessel. The outboard enginemay be used to propel the marine vessel. For example, the outboard enginemay be used to propel the boat′ in water.

Referring to, the outboard enginemay include a propellerand a steering system. The propellermay operate to propel the boatin forward and reverse directions. Further, the steering systemmay be configured to steer the outboard engineof the marine vessel. In an example, the steering systemmay include a steering cylinder, a tilt tube, a link arm, a tiller arm, and a rudder.

In an example, the steering cylindermay be coupled within the tilt tube. The steering cylindermay be a hydraulic cylinder which is hydraulically connected with a steering wheelof the boat′. In an example, a portion of the steering cylindermay be positioned within the tilt tube. In an example, the tilt tubeis coupled to the outboard engineby using a bracket assemblymounted on the outboard engine. The bracket assemblymay be mounted on the outboard engineby using a fastening means or by welding. In an example, the tilt tubemay extends along a horizontal axis through the bracket assembly.

The bracket assemblymay be mounted on a hullof the boat′. In an example, the bracket assemblymay include a clamp bracketand a swivel bracket. In an example, the bracket assemblymay include a first clamp bracket′ and a second clamp bracket″. In an example, the clamp bracketmay be fitted with fastening means such as bolts to the hullof the boat. The outboard enginemay be fitted on the swivel bracket. In an example, the swivel bracketand the clamp bracketmay be coupled together like a hinge and may rotate (0-90 deg) about a hinge. In such an example, the tilt tubemay act like a hinge pin.

The link armdefines a first endand a second endopposite the first end. In an example, the steering cylindermay be coupled to the link arm. In an example, the first endof the link armmay be coupled to the steering cylinderto move the link armby the steering cylinder. Further, the second endof the link armmay be coupled to the tiller arm. The tiller armmay be coupled between the second endof the link armand the rudderof the outboard engine. In an example, the steering systemmay include one or more hydraulic lines (not shown) connected between the steering cylinderand the steering wheelof the boat′.

In an example, the steering wheelmay be turned to steer the boat′ in a desired direction. The steering wheelmay allow the steering cylinderto move in a direction relative to the steering wheel. For example, the steering wheelmay allow a hydraulic fluid to flow through the hydraulic lines to move the steering cylinder. The steering cylindermay be configured to then move the link armwhich in turn moves the tiller arm. The tiller armmay move the rudderwhich steers the boat′ in a desired direction. For example, the ruddermay turn the boat′ in the direction in which the steering wheelis turned.

Referring to, the steering cylinderaccording to an embodiment will now be discussed. The steering cylindermay include a first cylinderand a second cylinder. In an embodiment, the first cylindermay be an outer cylinder′ and the second cylindermay be an inner cylinder′. The first cylindermay be coupled with the tilt tubeby fastening means such as a lock nutas shown in. The outer cylinder′ may define a first inner walland a first outer wall′. The outer cylinder′ may include a first end capon a first side.

The steering cylindermay be coupled to the tilt tube. In an example, the steering cylindermay be coupled to the tilt tubeby using a lock nut. The lock nutmay be configured to engage the steering cylinderto a threaded portionof the tilt tube. In an example, the threaded portionmay be formed at ends(for example, a first end′ and a second end″) of the tilt tube. Further, the tilt tubemay be coupled to an end cap. In an example, the second end′ of the tilt tubemay be coupled with the end cap. The end capmay prevent water, dirt and/or debris from entering the steering cylinder. In an example, the first cylinderfurther defines a first space.

The second cylinder(e.g., the inner cylinder′) may be partially mounted within the tilt tube. For example, the inner cylinder′ may be configured to partially move within the tilt tube. In an example, the second cylinder(e.g., the inner cylinder) defines a first endand a second endopposite the first end. In an example, the second cylinderdefines a second space. For example, the inner cylinder′ may define a second inner walland a second outer wall′ to define the second space. In an embodiment, the second spacemay be volumetrically same as that of first space, thereby making it as a balanced-type steering cylinder.

In an example, the second cylinderis configured to move with respect to the first cylinder. In an example, the second cylindermay be configured to partially move within the first cylinder. In an example, the inner cylinder′ may be configured to move within the outer cylinder′. For example, the inner cylinder′ may define a stroke length, L, configured to move within the outer cylinder′. Further, the second endof the inner cylinder′ may be coupled to the link arm. In an example, the second endof the inner cylinder′ may be coupled to a rod endwhich may be coupled to the first endof the link arm.

The steering cylindermay further include a first piston. In an example, the first pistonmay be positioned within the first spaceand coupled to the first endof the inner cylinder′. In an example, the first pistonmay be received within the outer cylinder′. Further, the first pistonmay include a side wallthat may be in contact with the first inner wallof the outer cylinder′ and may move within the outer cylinder′. In an example, the first pistonmay include one or more piston sealscoupled between the first pistonand the first inner wallof the outer cylinder′. In an example, the first pistonmay be a hollow piston′.

The steering cylindermay further include a second pistonand a hollow piston rodcoupled to the second pistonand passes through the first piston. In an example, the second pistonis a hollow piston′. In an example, the second spaceof the second cylindermay house the hollow piston′. The second piston(e.g., the hollow piston′) may be received within the inner cylinder′. In an example the hollow piston′ may allow the hydraulic fluid to be passed therethrough. Further, the hollow piston′ may be coupled with the second inner wallof the inner cylinder′ and may move within the inner cylinder′. In an example, the second pistonmay include one or more piston sealscoupled between the second pistonand the second inner wallof the inner cylinder′.

In an example, the hollow piston rodis positioned at least partially within the first spaceof the first cylinder. The hollow piston roddefines a first endand a second endopposite the first end. In an example, the hollow piston rodalong with the second pistonmay be fixed with respect to the first end capof the outer cylinder′. For example, the inner cylinder′ may move over the second piston(e.g., over the hollow piston′).

The first cylinder(e.g., the outer cylinder′) further includes a first fluid portand a second fluid port. The first fluid portis positioned on the first end cap. The first fluid portmay be coupled to the hollow piston rodwhich allows the hydraulic fluid to pass through the hollow piston rodand into the inner cylinder′. In an example, the first endof the hollow piston rodis fluidly coupled with the first fluid portand the second endof the hollow piston rodis coupled to the hollow piston′. For example, the first fluid portmay be configured to allow the fluid to move into and out of the inner cylinder′ and the hollow piston rod.

The second fluid portmay work as both an inlet and an outlet port depending upon desired motion of the steering cylinder. For example, when the second fluid portworks as the inlet port, the first pistonmay move towards the first end capof the outer cylinder′ (see). In an example, when the second fluid portworks as the outlet port, the hydraulic fluid may move from the first fluid portthrough the hollow piston rodand the second piston(e.g., hollow piston rodand the hollow piston′) to the rod endto move the inner cylinder′ away from the first end cap(see).

The first fluid portmay be configured to allow the fluid to move into and out of the inner cylinder′. In an example, the first fluid portmay work as both an inlet and an outlet port depending upon desired motion of the inner cylinder′. For example, when the first fluid portworks as the inlet port, the first pistonmay move away from the first end capof the outer cylinder′ (see). Similarly, when the first fluid portworks as the outlet port, the first pistonmay move towards the first end cap(see).

The steering cylindermay further include a first hydraulic adaptercoupled to the first fluid portand a second hydraulic adaptercoupled to the second fluid port. In an example, the first hydraulic adaptermay be mounted on the first end capof the outer cylinder′. The hydraulic lines may be coupled to the first fluid portand the second fluid port. In an example, the hydraulic lines may facilitate the hydraulic fluid to flow into and out of the steering cylinderthrough the first fluid portand the second fluid port. In an example, the hydraulic fluid may be any fluid known in the art such as, but not limited to, a mineral oil or the like.

In an embodiment, the steering cylindermay include various sealing means such as an O-ring, a wiper seal, and the like. The sealing means may facilitate prevention of leakages, maintain the hydraulic fluid pressure, and ensure proper functionality of the steering cylinder. Although some examples of sealing means have been provided, however, any sealing means known in the art may be contemplated.

The steering cylinderis configured to actuate between an extended position and a retracted position to steer the marine vessel. In an example, in the extended position, the second cylinderis configured to move away from the first end cap. For example, in the extended position, the inner cylinder′ along with the first pistonis configured to move away from the first end cap. In an example, in the extended position the hydraulic fluid may flow into the second spacefrom the first fluid portto move the first pistonalong with the inner cylinder′ away from the first end cap. In an example, the hydraulic fluid flows into the second spacethrough the hollow piston rodand the hollow piston′.

Further, in the retracted position, the second cylinderis configured to move towards the first end cap. For example, in the retracted position, the inner cylinder′ along with the first pistonis configured to move towards the first end cap. In an example, in the retracted position, the hydraulic fluid may flow into the first spacefrom the second fluid portto move the first pistonalong with the inner cylinder′ towards the first end cap.

For example, in operation, the steering cylindermay be configured to turn the boat′ upon an action of the steering wheel. In an example, when a user turns the steering wheelof the boat′, a helm pump (connected to the hydraulic lines and the steering wheel) may generate a pressure in the hydraulic fluid. The hydraulic fluid may be moved within the steering cylinderto turn the boat′. In an example, the helm pump may facilitate the hydraulic fluid to be moved within the steering cylinderdepending on the direction (may be left or right) of the steering wheeland/or a number of rotations of the steering wheel.

In an example, the turning of the steering wheelmay lead to either supply of the hydraulic fluid to the steering cylinder, and/or discharge of the hydraulic fluid out of the steering cylinderdepending upon the direction and the amount in which the steering wheelis turned. For example, the supply/or discharge of the hydraulic fluid may take place respectively from the first fluid portor the second fluid port.

Referring now to, a working of the steering systemwill now be explained.refers to a first configuration of the steering system. In the first configuration, when the steering wheelis turned from starboard side to port side, the hydraulic fluid may be supplied to the second fluid port. At this time, the second fluid portmay act as an inlet port. The hydraulic fluid fills within a first spacedefined within the outer cylinder′ and applies a force on the first piston. The inner cylinder′ may act as a piston rod for the first pistonand move the first pistontowards the first end capof the steering cylinder.

When the first pistonmoves toward the first end cap, the hydraulic fluid already present in the inner cylinder′ moves out from the first fluid portthus acting as an outlet port. At this time, the inner cylinder′ may be retracted within the outer cylinder′ towards the first end cap. The movement of the inner cylinder′ towards the first end capmay turn the link armwhich in turn changes the position of the tiller arm. The tiller armmay then move the ruddertowards the starboard side, thus steering the boat′ from starboard side to port side.

refers to a second configuration of the steering system. In the second configuration, when the steering wheelis turned from the port side to the starboard side, the hydraulic fluid is supplied to the first fluid port. At this time, the first fluid portmay act as an inlet port. The hydraulic fluid fills the second spacedefined within the inner cylinder′. The fluid may apply a force on the rod end. The inner cylinder′ may then move with the first pistonaway from the first end capwithin the outer cylinder′ of the steering cylinder.

When the first pistonmoves away from the first end cap, the hydraulic fluid already present in the outer cylinder′ moves out from the second fluid portthus acting as an outlet port. The movement of the inner cylinder′ away from the first end capmay turn the link armwhich in turn changes the position of the tiller arm. The tiller armmay then move the ruddertowards the port side, thus steering the boat′ from the port side to the starboard side.

In an embodiment, the steering cylindermay be a balanced-type steering cylinder. In an example, the steering cylindermay be configured to move from the first configuration to the second configuration for equal number of revolutions of the steering wheelfrom the port side to the starboard side and vice-versa in order to steer the boat′ towards the port side or toward the starboard side. The balancing of the steering cylinderwill now be explained.

The outer cylinder′ and the inner cylinder′ of the steering cylinderare constructed in a way such that a volume of hydraulic fluid inside the outer cylinder′ and the inner cylinder′ is same. In an example, because the volume of the hydraulic fluid is same in both the inner cylinder′ and the outer cylinder′, an equal amount of force may be applied to the first pistonand the second pistonto move the boat′ towards the port side and towards the starboard side. Since, equal forces are required to steer the boat′ in both directions, the steering wheelmay be rotated for equal number of turns to steer the boat′ in both directions, i.e., towards the port side and towards the starboard side.

illustrates an alternate embodiment of the steering cylindershown in. For example, the steering systemmay include a steering cylinder. The steering cylindermay include similar components as that of the steering cylinderand differ in that the steering cylindermay include only a pistonand a hollow piston rod. The steering cylindermay include a first cylinder, and a second cylinderconfigured to move with respect to the first cylinder. In an example, the first cylindermay define the first space.

In an example, the second cylindermay extended or retracted with respect to the first cylinder. In an example, the second cylindermay be partially disposed within the first cylinder. In an example, the second cylindermay be positioned within the tilt tube. The second cylinderincludes the pistonwhich is a hollow piston′. In an example, the second cylinderdefines the second space. The second cylindermay further include a rodcoupled to the hollow pistonsuch that the second cylinderdefines a third space.

In an example, the third spacemay be fluidly coupled with the first spacethrough the hollow piston rod. In an example, the rodmay be partially placed within the second cylinderand may extend out of the second cylinder. For example, the second cylindermay be coupled with the rod endthrough the rod. Further, the steering cylinderincludes a single hydraulic adapter. In an example, the first fluid portand the second fluid portmay be formed on the hydraulic adapter.

Referring now to, working of the steering systemof the second embodiment will now be explained in detail. The steering cylindermay work in two configurations (for e.g., a first configuration and a second configuration).refers to the first configuration for the steering cylinderof the steering system. The first configuration of the steering cylindermay be the extended position of the steering cylinder. In the first configuration, when the hydraulic fluid enters the steering cylinderthrough the second fluid port, the second spaceof the second cylindermay be filled by the hydraulic fluid and may exert a force on the pistonaway from the hydraulic adapter. The movement of the pistonmay move the rod endaway from the hydraulic adapterto tilt the boat′ in a direction respective to the force experienced on the piston. At this time, the hydraulic fluid may exit the third spaceto the first spacethrough the hollow piston rodand finally out of the first fluid port.

refers to the second configuration for the steering cylinderof the steering system. The second configuration of the steering cylindermay be the retracted position of the steering cylinder. In the second configuration, when the hydraulic fluid enters the steering cylinderthrough a first fluid port, the third spaceof the second cylindermay be filled by the hydraulic fluid and exert a force on the pistontowards the hydraulic adapter. The movement of the pistonmay move the rod endtowards the hydraulic adapterto tilt the boat′ in a direction respective to the force experienced on the piston. At this time, the hydraulic fluid already present in the first spacemay exit the first cylinderfrom the second fluid port.

illustrates an alternate embodiment of the steering cylindershown in. For example, the steering systemmay include a steering cylinder. The steering cylindermay include similar components as that of the steering cylinderand differ in that the steering cylindermay include a pistonsuch as a hollow piston′, and a hollow piston rodpassing through the hollow piston′. The steering cylindermay include a first cylinder, and a second cylinderconfigured to move with respect to the first cylinder. In an example, the first cylindermay define the first space.

In an example, the second cylindermay extended or retracted with respect to the first cylinder. In an example, the second cylindermay be partially disposed within the first cylinder. In an example, the second cylindermay be positioned within the tilt tube. The second cylindermay be coupled to the pistonwhich is the hollow piston′. In an example, the second cylinderdefines the second space.

In an example, the second spacemay be fluidly coupled with the first spacethrough the hollow piston rod. In an example, the second cylindermay be coupled with the rod end. Further, the steering cylinderincludes the single hydraulic adapter. In an example, the first fluid portand the second fluid portmay be formed on the hydraulic adapter.

Referring now to, a working of the steering systemof the third embodiment will now be explained in detail. The steering cylindermay work in two configurations (for e.g., a first configuration and a second configuration).refers to the first configuration for the steering cylinderof the steering system. The first configuration of the steering cylindermay be the extended position of the steering cylinder. In the first configuration, when the hydraulic fluid enters the steering cylinderthrough the second fluid portand through the hollow piston rod, the second spacemay be filled by the hydraulic fluid and may exert a force on the pistontowards the hydraulic adapter. The movement of the pistonmay move the rod endtowards the hydraulic adapterto tilt the boat′ in a direction respective to the force experienced on the piston. At this time, the hydraulic fluid may exit the first cylinderdirectly from the first fluid port.

refers to the second configuration for the steering cylinderof the steering system. The second configuration of the steering cylindermay be the extended position of the steering cylinder. In the second configuration, when the hydraulic fluid enters the steering cylinderthrough the first fluid port, the first spacemay be filled by the hydraulic fluid and exert a force on the pistonaway from the hydraulic adapter. The movement of the pistonmay move the rod endaway from the hydraulic adapterto tilt the boat′ in a direction respective to the force experienced on the pistonand the hydraulic fluid may exit the second spacethrough the hollow piston rodand finally out of the second fluid port.

The present disclosure provides the outboard engineand the steering system. The steering systemincludes the steering cylinder,,configured to steer the boat′ toward the port side or the star board side. In an example, the steering cylinder,,may be disposed at least partially within the tilt tube. For example, the steering cylinder,,is configured to partially fit inside the tilt tube.

The fitment of the steering cylinder,,provides lesser space requirements as compared to conventional steering cylinders. Hence the steering cylinder,,may be mounted on any marine vesselirrespective of the size constraints which was there in conventional marine vessels. The configuration of the steering cylinder,,inside the tilt tubealso provides on-site assembly and disassembly of the steering cylinder,,, thus doesn't require dismantling of the entire outboard engine. The steering cylinder,,may be attached to the tilt tubeby any suitable fastening means such as the lock nutfastened on the threaded portionof the tilt tube.