Motors: expansible chamber type – Working member position responsive motive fluid control – Exhaust control
Patent
1995-05-01
1996-12-17
Ryznic, John E.
Motors: expansible chamber type
Working member position responsive motive fluid control
Exhaust control
91422, 440 61, F15B 1522, F15B 1108, B63H 5125
Patent
active
055842259
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a hydraulic piston-cylinder device, especially intended for trimming or tipping an outboard type boat propeller drive, comprising a cylinder, a piston displaceable in the cylinder, dividing the interior of the cylinder into two cylinder chambers, and a piston rod joined to the piston and extending out through an opening in one cylinder end wall, said piston having at least one axial through-passage with stop valve means permitting fluid to flow in one direction through the piston from one cylinder chamber to the other.
In, for example, one known boat propeller drive, a pair of trim and tip cylinders of the type described above are arranged between the drive shield and and rig, each cylinder being articulated in the shield and engaging the rig with the associated piston rod. When trimming out or tipping up the rig, hydraulic fluid is supplied to the cylinder chamber on the piston side, whereupon the cylinder chamber on the piston rod side is drained to a tank. If the rig during operation strikes an object in the water, which forces the rig to be tipped up, hydraulic fluid can flow through the passage in the piston from the cylinder chamber on the piston rod side to the opposite cylinder chamber if the force on the rig is so great that the fluid pressure created on the piston rod side exceeds the pressure on the opposite side, which permits rapid extension of the piston rod and rapid tipping of the rig. In this manner, the risk of serious damage to the rig is reduced when running aground, for example. In a known design of a boat propeller drive of the type described, a rubber buffer is used between the shield and the rig as an end abutment so that rapid tipping of the rig will not cause damage to the drive.
The purpose of the present invention is to achieve a piston-cylinder device of the type described by way of introduction which is particularly, but not exclusively, intended to be used in a tippable boat propeller drive by making it possible to vary the resistance to piston movement caused by an external force, depending on the position of the piston in the cylinder.
This is achieved according to the invention by virtue of the fact that constricting means cooperating with the piston are arranged, after a certain piston movement in the direction resulting in fluid flow from one cylinder chamber to the other via the check valve means to reduce the flow-through the area of the axial passage to brake continued piston movement.
A piston-cylinder device of this type can, for example, be used as a trim and tip cylinder in a boat propeller drive so that if the rig collides with a floating object or runs aground, it will provide less resistance to piston movement during initial tipping up of the rig and, after a certain piston movement, representing a certain tipping up angle, will increase this resistance and provide controlled breaking of the swing movement, so that, inter alia, the need for a rubber buffer is eliminated.
The invention will be described in more detail with reference to examples shown in the accompanying drawings, where
FIG. 1 shows a schematic side view of a boat propeller drive of outboard type,
FIG. 2 shows a partially sectioned side-view of certain components in the rig suspension of the drive, and
FIG. 3 is a longitudinal section through one embodiment of a piston-cylinder device according to the invention.
FIG. 1 shows a propeller drive which is known per se of so-called Aquamatic.RTM. type, comprising a shield 1 designed to be solidly mounted in an opening in a boat transom. A propeller rig, generally designated 2, is suspended in a forked supporting bracket 3, which is pivotally mounted in the shield 1 for pivotal movement about a horizontal pivot axis 4. A pair of hydraulic piston-cylinder devices 5 (one shown in FIG. 2) are arranged symmetrically relative to a centre plane of the propeller drive. Each cylinder is pivotally mounted in the shield 1, while the associated piston rod 7 is mounted in the supporting element 3. The cylinder 6 is coupled into a h
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Arvidsson Lennart
Bergquist Anders
Larsson Stig
Uhlander Lennart
AB Volvo Penta
Ryznic John E.
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