Marine propulsion – Screw propeller – Having transmission
Reexamination Certificate
1999-08-24
2001-01-23
Basinger, Sherman (Department: 3612)
Marine propulsion
Screw propeller
Having transmission
C440S080000, C416S129000
Reexamination Certificate
active
06176750
ABSTRACT:
BACKGROUND OF THE INVENTION
Certain marine propulsion units, such as outboard drives and inboard/outboard stern drives, utilize a forward-neutral-reverse transmission along with twin propellers. The typical twin propeller system includes a vertical drive shaft which is operably connected to the engine and is journaled for rotation in the lower gearcase. The lower end of the drive shaft carries a pinion which drives a pair of coaxial bevel gears that are located in the lower torpedo-shaped section of the gearcase. Inner and outer propeller shafts are mounted concentrically in the lower section and each propeller shaft carries a propeller, with the propeller of the outer shaft being located forwardly of the propeller of the inner shaft.
U.S. Pat. No. 4,793,773 is directed to a twin propeller propulsion system in which both propellers are rotated at the same speed, but in opposite directions, during forward movement of the watercraft. With this system, a mechanism is provided to disconnect the outer propeller shaft when the watercraft is moved in the reverse direction. Thus, with the system shown in the aforementioned patent, both propellers are operated during forward movement of the watercraft, but only the inner propeller shaft and the rear propeller are operated during reverse movement.
Co-pending U.S. Pat. application Ser. No. 08/719,633, filed Sep. 25, 1996, now U.S. Pat. No. 5,766,047 is directed to a twin propeller marine propulsion system in which, during forward movement of the watercraft, only one of the propellers is driven at low engine speed and the second propeller is driven when the engine speed reaches a pre-selected elevated value.
In accordance with the construction of the aforementioned patent application, a sliding clutch mechanism having forward neutral and reverse positions is employed to selectively engage the inner propeller shaft with the bevel gears to thereby rotate the inner propeller shaft and the rear propeller in both the forward and reverse directions. In addition, a hydraulically operated multiple disc clutch located in the lower torpedo section is employed to selectively cause engagement of one of the bevel gears with the outer propeller shaft when the engine speed reaches a pre-selected elevated value, normally in the range of 3,500 rpm to 7,000 rpm, to thereby cause the second or forward propeller to rotate in the opposite direction from the rear propeller. With this construction, only the rear propeller is driven at low forward speeds, while at high forward speeds both propellers are driven.
As described in the aforementioned patent application, the multiple disc clutch is moved to the engaged position at the pre-selected elevated engine speed by supplying pressurized fluid to a piston which engages the multiple clutch discs and moves the discs to a contacting or driving position. With this construction, only a single propeller is operable at low speeds, and once the pre-selected elevated engine speed has been achieved, the second propeller is then driven, resulting in a significant improvement in acceleration of the watercraft when getting on plane.
SUMMARY OF THE INVENTION
The invention is directed to an improved hydraulic system for a twin propeller marine propulsion unit of the type described in pending U.S. patent application, Ser. No. 08/719,633, filed Sep. 25, 1996 now U.S. Pat. No. 5,766,047.
The propulsion unit includes a vertical drive shaft that is journaled in the lower gearcase. The lower end of the drive shaft carries a beveled pinion gear that drives a pair of coaxial annular bevel gears located in the lower torpedo section of the gearcase. Inner and outer propeller shafts are journaled concentrically within the torpedo section and each propeller shaft carries a propeller with the propeller on the inner shaft being located to the rear of the propeller on the outer shaft.
A sliding clutch mechanism having forward, neutral and reverse positions is employed to selectively engage the inner propeller shaft with the bevel gears to thereby rotate the inner propeller shaft and the rear propeller in both forward and reverse directions. In addition, a hydraulically operated multiple disc clutch located in the lower torpedo section is employed to selectively cause engagement of one of the bevel gears with the outer propeller shaft when the engine reaches a pre-selected elevated value normally in the range of about 3,500 rpm to 7,000 rpm, to thereby cause the second or forward propeller to rotate in the opposite direction from the rear propeller. Thus, at low forward speeds only the rear propeller is driven, while at high forward speeds, both propellers are driven.
In accordance with the invention, an improved hydraulic system located within the gearcase is employed to supply pressurized fluid to a piston which acts to engage the multiple disc clutch and move the clutch to a contacting or driving position. The hydraulic fluid is pressurized through operation of a pump that is operably connected to the inner propeller shaft, so that rotation of the inner propeller shaft in the forward direction of watercraft movement will drive the pump to pressurize the fluid. The inlet to the pump communicates with a fluid reservoir or sump which is located in the gearcase, while the outlet of the pump is connected through a hydraulic line or conduit to the piston of the multiple disc clutch. As a feature of the invention, a strainer, pressure regulator, and valve mechanism are mounted within the gearcase and are located in series in the hydraulic line.
The strainer includes a generally cylindrical screen element which serves to filter out foreign particles in the hydraulic fluid. In addition, the strainer incorporates a provision for by-passing the fluid around the screen element when there is a substantial pressure drop across the screen element which can occur at low ambient temperatures or if the screen element is clogged.
The pressure regulator, which is located downstream from the strainer, includes a generally cylindrical casing which houses a plunger having a flat face which is exposed to the pressure of the fluid in the hydraulic line. On an increase in pressure in the fluid above a pre-selected value, the plunger will be moved outwardly against a spring biasing force to expose an outlet in the casing, thereby diverting fluid to the sump or reservoir in the gearcase.
The valve mechanism, which is located downstream of the pressure regulator, includes a valve body which is preferably formed integrally with the casing of the pressure regulator. The valve mechanism includes a solenoid operated valve member. At idle or low engine speed, the valve member is held in a dumping position by the energized solenoid so that the fluid is dumped to the reservoir and the pressure of the fluid being supplied to the piston of the multi-disc clutch is insufficient to actuate the piston and engage the clutch. When the engine speed increases to a preselected elevated value, a conventional engine speed sensor acts to deenergize the solenoid, and the valve member will then be biased to a second or clutching position where the fluid will be delivered to the piston of the multi-disc clutch to cause engagement of the clutch and thus effect operation of the outer propeller shaft and its propeller.
As a feature of the invention, a pair of concentrically mounted springs interconnect the valve member and the valve body. A first of the springs has a substantially lesser force than the second spring and the first spring acts to urge the valve to the clutching position. When the valve member is moved toward the dumping position by operation of the solenoid, the initial movement of the solenoid plunger will compress the lighter spring and further movement of the plunger will cause compression of the heavier spring. The use of the two springs results in the combined spring force throughout the stroke of the solenoid plunger being a substantial portion of the force of the solenoid throughout the stroke of the solenoid plunger, so that the clutch will be actuated with a minimum ti
Alexander Charles F.
McCormick Daniel F.
Andrus Sceales Starke & Sawall LLP
Basinger Sherman
Brunswick Corporation
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