Marine propulsion – Screw propeller – With means effecting or facilitating movement of propulsion...
Reexamination Certificate
2000-04-26
2001-10-23
Basinger, Sherman (Department: 3617)
Marine propulsion
Screw propeller
With means effecting or facilitating movement of propulsion...
C248S641000, C440S059000
Reexamination Certificate
active
06305996
ABSTRACT:
SUMMARY OF THE INVENTION
This invention relates to improvements in marine propulsion systems. It is specifically concerned with improvements in an apparatus for varying the height of an outboard motor on the transom of a boat.
Cavitation is a common problem with marine propulsion systems. Boat motors tend to draw water from the surface, which allows air as well as water to pass through the propeller. This results in cavitation or slippage of the propeller, reducing the efficiency of operation of the motor.
It is therefore important to avoid cavitation when operating marine propulsion systems, such as motor boat propellers. Outboard engines normally include a cavitation plate to prevent cavitation. This plate should be positioned to travel across the surface of the water while the motor is operating. At this location, the cavitation plate prevents air from reaching the propeller.
The height at which a cavitation plate is most effective varies depending upon various factors. A boat operating at low speeds, but requiring maximum thrust, will perform best when the cavitation plate is positioned one to three inches above the bottom of the boat. At higher speeds, however, the stern is lower in the water, and the optimum position for the cavitation plate is typically three to five inches above the bottom of the boat.
My U.S Pat. No. 5,484,311, issued Jan. 16, 1996, describes a variable height outboard motor mount comprising brackets connected respectively to a boat transom and an outboard motor, a fluid actuator for adjusting the relationship between the two frames, and guides comprising rods with vertically spaced bearings for firmly constraining the brackets to relative movement in a straight line.
The motor mount of U.S Pat. No. 5,484,311 has the advantage that it allows the outboard motor to be set to any selected height from a remote location by a closed-loop servo control. However, it also has the disadvantage that it is primarily designed for racing, and is more elaborate and expensive than necessary for fishing or pleasure boats. Height adjustment for improved operating efficiency is nevertheless desirable in the operation of fishing and pleasure boats.
The cost of a variable height outboard motor mount having the advantages of strength afforded by the guide construction described in U.S Pat. No. 5,484,311 can be reduced by eliminating the servo control system, and providing for manual adjustment. However, in a manually controlled outboard motor mount utilizing a hydraulic actuator system any fluid leakage in the actuator, or in its associated pump or valving can permit drift in the height of the outboard motor. Other schemes for manual adjustment can be used, but all are subject to drift as a result of the strong vibrations inevitably accompanying outboard motor operation. The foregoing problems are addressed in my U.S Pat. No. 5,964,627, dated Oct. 12, 1999. However, the outboard motor mount described in U.S Pat. No. 5,964,627 also utilizes rods with vertically spaced bearings for firmly constraining the parts of the motor mount to relative movement in a straight line. The rod and bearing assembly is highly effective for maintaining a rigid relationship between the relatively moving parts of the motor mount, and for providing the strength needed to support very heavy and powerful outboard motors. However, the rods and bearings are expensive and difficult to assemble.
There is a need, therefore, for a simpler and less expensive, variable height outboard motor mount which is capable of withstanding the heavy loads imparted by the weight of the motor and its thrust, and maintaining a rigid relationship between the outboard motor and the boat transom. Accordingly, among the important objects of the invention are cost saving, simplicity of manufacture, ability to withstand heavy loads, and rigidity.
Briefly, the motor mount in accordance with the invention utilizes brackets with cross-braces as its principal structural parts. The brackets have interengaging ribs and recesses to constrain its parts to relative movement in a straight path.
More specifically, the motor mount in accordance with the invention comprises first and second bracket assemblies one being connectible to a boat transom and the other being adapted to support an outboard motor. A screw, a hydraulic mechanism, or other suitable manual or powered actuator is connected to the first and second bracket assemblies for effecting movement of the second bracket assembly relative to the first bracket assembly along a path which is substantially vertical when the one bracket assembly is mounted on the transom of a boat. The first bracket assembly comprises first and second brackets, each having a inner face and an upper and lower end, a first cross brace connected to the first and second brackets adjacent to their upper ends and a second cross brace connected to the first and second brackets adjacent to their lower ends. The second bracket assembly comprises third and fourth brackets, each having an outer face and an upper and lower end, a third cross brace connected to the third and fourth brackets adjacent to their upper ends and a fourth cross brace connected to the third and fourth brackets adjacent to their lower ends. The third and fourth cross braces are situated between the first and second cross braces and the spacing between the third and fourth cross braces is substantially less than the spacing between the first and second cross braces so that the bracket assemblies can move relative to each other through a range in the substantially vertical path. The outer face of the third bracket is engaged with the inner face of the first bracket and the outer face of the fourth bracket is engaged with the inner face of the second bracket. The engaging inner and outer faces of the brackets have interengaging ribs and recesses constraining the bracket assemblies to relative movement along the substantially vertical path.
In a preferred embodiment, the inner face of at least one of the first and second brackets, and preferably the inner face of each, has a recess elongated in the direction of the substantially vertical path. Each recess has a side surface extending transverse to the inner face of its bracket, and the outer face of the engaging bracket has a rib also elongated in the direction of the path. The rib has a side surface extending transverse to the outer face of its bracket. The side surfaces are in sliding engagement with each other and prevent relative movement of the engaging brackets in at least one direction which is both parallel to their respective inner and outer faces and transverse to the direction of the substantially vertical path.
The interengagement of the ribs and recesses of the brackets provides the motor mount with a high degree of strength and the capability of withstanding the weight and thrust of a large, powerful outboard motor, without the need for the rod and bearing structure of U.S Pat. Nos. 5,484,311 and 5,964,627.
Ends of the first and second cross braces are preferably received in the recesses of the first and second brackets, with faces of the first and second cross braces in engagement with side surfaces of the recesses. The cross braces are constrained by side surfaces of the recesses against movement in directions which are both parallel to the inner faces of the first and second bracket and transverse to the substantially vertical path. Taking advantage of the recesses of the brackets to receive ends of the cross braces provides an exceptionally strong bracket assembly.
In the preferred embodiment, screws extend through the first and second brackets in directions perpendicular to the inner faces of the first and second brackets adjacent to the upper and lower ends thereof. The screws adjacent to the upper ends of the first and second brackets are threaded into the first cross brace, and the screws adjacent to the lower ends of the first and second brackets are threaded into the second cross brace.
In the preferred embodiment, each of the first and second brackets has a slot exte
Basinger Sherman
Detwiler Industries Incorporated
Howson & Howson
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