Marine propulsion – Screw propeller – Propulsion unit casing
Reexamination Certificate
1999-08-04
2001-05-22
Avila, Stephen (Department: 3617)
Marine propulsion
Screw propeller
Propulsion unit casing
C440S078000
Reexamination Certificate
active
06234855
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a driveshaft housing for an outboard motor, and more particularly to an improved driveshaft housing for an outboard motor that is reinforced against expansion and contraction force exerted thereon.
2. Description of Related Art
A conventional outboard motor generally includes a power head, a driveshaft housing and a lower unit. The power head contains an internal combustion engine. The driveshaft housing depends from the power head and contains a driveshaft that is driven by said engine. In particular, a crankshaft of the engine drives the driveshaft. Since the crankshaft extends generally vertically in the power head, the driveshaft also extends generally vertically in the driveshaft housing. The lower unit depends from the driveshaft housing and contains a propulsion device such as a propeller. The driveshaft drives the propulsion device through a conventional transmission. Thus, the watercraft associated with the outboard motor is propelled by the outboard motor.
The engine usually has an exhaust system for discharging exhaust gases from its combustion chamber(s) to the body of water surrounding the outboard motor. The exhaust system has an exhaust conduit that extends through the driveshaft housing and the lower unit. Exhaust gases flow through the exhaust conduit downwardly and are finally discharged to the body of water through an opening, for example, formed in a propeller hub.
The exhaust gases, immediately after discharged from the engine into the exhaust conduit, have tremendous expansion pressure and this pressure acts on the wall of the driveshaft housing as well as on any internal walls within the driveshaft housing that define the exhaust conduit. The discharge of the exhaust gases intermittently and repeatedly occurs every exhaust stroke of the engine. Accordingly, the housing walls will be intermittently and repeatedly stressed by the fluctuating expansion pressures.
In the meantime, the driveshaft housing is configured generally as an oval shell in a plan view with its major axis extending between fore and aft ends of the housing. The lateral or side wall portions, therefore, are weaker (i.e., less rigid) than the fore and aft wall portions. If rigidity of these portions is not sufficient, vibration occurs when the aforenoted expansion pressure acts upon them. In addition, the engine per se generates relatively large vibration and this vibration is also transmitted to the housing shell. Hence, the lateral walls tend also to be stressed by these vibrations. If the frequency of the vibrations is consistent with the inherent frequency of vibration of the housing shell, resonance will occur and this results in discernable noise.
SUMMARY OF THE INVENTION
It is appreciated that the vibration and the sound in consequence can be prevented if thickness of the housing wall is increased. This structure, however, also increases the weight of the driveshaft housing and the total weight of the outboard motor performance suffers as a result. A need therefore exists for a driveshaft housing of an outboard motor that can withstand the noted vibrations without significantly increasing weight of the outboard motor.
In accordance with one aspect of this invention, an outboard motor comprises a power head. The power head contains an internal combustion engine. A driveshaft housing depends from the power head. The driveshaft housing contains a driveshaft driven by the engine and extending generally vertically. A lower unit depends from the driveshaft housing. The lower unit contains a propulsion device driven by the driveshaft for propelling an associated watercraft. The engine includes an exhaust system for discharging exhaust gases from the engine. The exhaust system has an exhaust conduit extending, at least in part, through the driveshaft housing. The driveshaft housing has at least two side wall portions. The driveshaft housing also has a rib transversely extending from one side wall portion to the other side wall portion and between the driveshaft and the exhaust conduit.
In accordance with another aspect of this invention, an outboard motor comprises a power head. The power head contains an internal combustion engine. A driveshaft housing depends from the power head. The driveshaft housing contains a driveshaft driven by the engine. The driveshaft extends generally vertically through at least a front portion of said driveshaft housing located forward of a central longitudinal axis of the driveshaft housing. A lower unit depends from the driveshaft housing. The lower unit contains a propulsion device driven by the driveshaft for propelling an associated watercraft. Means are provided for reinforcing the driveshaft housing against force transversely acting thereon. The means for reinforcing the driveshaft housing are disposed within the front portion of said driveshaft housing.
Further aspects, features and advantages of this invention will become apparent from the detailed description of the preferred embodiment which follows.
REFERENCES:
patent: 3025824 (1962-03-01), Foster
patent: 3434447 (1969-03-01), Christensen et al.
patent: 3908579 (1975-09-01), Miller et al.
patent: 4723926 (1988-02-01), Uehara
patent: 5026309 (1991-06-01), Onoue
Suzuki Hiroyuki
Watanabe Kazuhiko
Avila Stephen
Knobbe Martens Olson & Bear LLP
Sanshin Kogyo Kabushiki Kaisha
LandOfFree
Driveshaft housing for outboard motor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Driveshaft housing for outboard motor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Driveshaft housing for outboard motor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2540322