Hydraulic trim/tilt system for outboard propulsion units

Claim 2

A hydraulic system for trimming and tilting of outboard drive units for boats, comprising pump means adapted to deliver fluid under pressure from a fluid sump to a double acting cylinderpiston assembly, said cylinder-piston assembly being arranged between said tiltable drive unit and the boat or a stationary part of the drive, characterized by a valve unit, said valve unit being adjustable between a first position in which the chamber at the piston rod end of the cylinder is disconnected from communication with said sump and connected to communicate with the chamber at the piston end of the cylinder, and a second position in which said chamber at said piston rod end of said cylinder is disconnected from communication with said chamber at said piston end of said cylinder and connected to communicate with said sump.

Claim 3

In a hydraulic system for trimming and tilting an outboard drive leg for boats about a horizontal tilt axis comprising a hydraulic fluid sump, a double acting hydraulic cylinder-piston assembly including a piston rod and having a cylinder with a piston therein dividing the space in the cylinder into a first chamber at the piston end and a second chamber at the piston rod end of said cylinder, means connecting said cylinder-piston assembly between said leg and said boat and spanning said axis, and a source of pressure fluid connected to said first chamber, valve means connected to said sump and to each of said chambers adjustablE between two positions in the first of which said valve means closes connection between said second chamber and said sump and opens a connection between said chambers and in the second of which it closes connection between said chambers and opens a connection from said second chamber to said sump.

Claim 4

In a hydraulic system for trimming and tilting an outboard drive leg for boats about a horizontal tilt axis comprising a hydraulic fluid sump, a double acting hydraulic cylinder-piston assembly including a piston rod and having a cylinder with a piston therein dividing the space in the cylinder into a first chamber at the piston end and a second chamber at the piston rod end of said cylinder, means connecting said cylinder-piston assembly between said leg and said boat and spanning said axis, and a source of pressure fluid connected to said first chamber, valve means connected to said sump and to each of said chambers adjustablE between two positions in the first of which said valve means closes connection between said second chamber and said sump and opens a connection between said chambers and in the second of which it closes connection between said chambers and opens a connection from said second chamber to said sump.

Claim 5

A hydraulic system according to claim 2, characterized in that said valve means comprises pressure sensing means for automatic adjustment of said valve means from said first to said second positions in response to a pressure in the system in excess of a predetermined pressure.

Claim 6

A hydraulic system according to claim 3, characterized in that the pressure sensing means is operative to adjust said valve means to said first position in response to said system pressure being less than said predetermined pressure which is characteristic of a low load on the piston rod, fluid being delivered to said first chamber partly from said source and partly from said second chamber when said valve is in said first position, and to adjust said valve means to said second position in response to such system pressure being in excess of said predetermined pressure which is characteristic of a relatively higher load on the piston rod, fluid being delivered to said first chamber only from said source and fluid displaced from said second chamber being returned to said sump when said valve is in said second position.

Claim 7

A hydraulic system according to claim 4, characterized in that said pressure sensing means comprises two spring biased control pistons disposed in a housing of said valve means, one of said control pistons being operative to establish communication between said chambers in response to said pressure below said predetermined pressure, the other of said control pistons being operative to establish communication between said second chamber and said sump in response to an increase of said pressure to above said predetermined pressure, said valve means comprising a back pressure valve for interrupting the communication between said first chamber and said second chamber in response to such increase of the pressure.

Claim 8

A hydraulic system according to claim 5, characterized in that the spring biasing said second piston is adjustable for adjustment of said predetermined pressure at which the communication between said second chamber of the cylinder and said sump is established.