Marine propulsion – Screw propeller – Having transmission
Reexamination Certificate
2001-12-31
2003-11-25
Morano, S. Joseph (Department: 3617)
Marine propulsion
Screw propeller
Having transmission
C474S113000, C474S135000
Reexamination Certificate
active
06652336
ABSTRACT:
FIELD OF INVENTION
This invention generally relates to marine recreational watercraft propulsion, and more particularly, to a power transmission device that transfers power from a single inboard engine, to multiple spaced apart impellers.
BACKGROUND OF THE INVENTION
It is well known throughout the boating industry that the propelling of a watercraft with at least two spaced apart impellers offers significant advantages over the propelling of a craft with only one impeller. The use of multiple spaced apart impellers, with independent forward and reverse thrust control, can vastly improve low speed docking maneuverability. The use of multiple impellers can improve speeds and the handling of watercraft as well. There are many more advantages of using multiple spaced apart impellers. More will become evident throughout this disclosure.
The long time, and still current practice within the boating industry, is to align and couple a singular inboard engine to a singular impeller drive. Therefore to achieve the benefits of multiple impellers, one must also install multiple engines. This unfortunately is not practical, or even possible in smaller and less expensive watercraft.
To try and remedy this situation, several devices were invented. These inventions provide means for the connection of a single inboard engine to two or more independent impeller drives. This concept potentially provides for the advantages of larger multi-engine crafts within the smaller single engine crafts. Despite many attempts however, none have ever been deployed in common use throughout the recreational boating industry. This includes inventions by Wosenitz (U.S. Pat. No. 2,371,013) filed in March of 1943, to the more recent invention by Caricof, et al. (U.S. Pat. No. 5,649,8440) issued on Jul. 22, 1997. The prior arts have all failed in this regard due to some known design shortcomings, which the present invention overcomes.
DISCUSSION OF PRIOR ART
In the field of this invention, as best as currently known, the only power transmission device that provides a stand-alone modular type of arrangement is the invention by Caricof et al. For the purpose of this disclosure, a stand-alone type of arrangement is one where the components of the power transfer system are basically assembled into a modular form, or device. The stand-alone arrangement is needed to allow universal application in various manufacturers' watercrafts, with various types of engines and impeller drives. To be successful however, this arrangement must also be designed to allow use of the most current installation practices. Inventions such as the one by Wosenitz, and one by Sable, (U.S. Pat. No. 3,289,628) do not use a stand-alone arrangement, which prevents widespread acceptance of these inventions for use throughout the industry, especially within the recreational boating industry.
The invention by Caricof, et al., entitled DUAL DRIVE FOR POWER BOATS comes closest to providing an acceptable device, but falls short due to a few, but critical design shortcomings. The invention comprises a housing, supporting three main shafts, which are one input shaft and two output shafts. The shafts are connected for rotation by chains. Engine power enters through the input shaft, then exits out the two output shafts, for driving of two impellers. The shortcomings are explained below.
The first shortcoming of this prior art is the use of chains and sprockets. Chains by definition are a series of metal links connected to one another, used for transmission of mechanical power. The use of chains, for the purpose of powering a marine watercraft, requires continuous lubrication. This in turn requires the use of an oil filled and tightly sealed enclosure, or housing, as the inventors illustrate. This presents issues and concerns to the industry, which include concerns of leaks, ingress of moisture, corrosion, and oil contamination, which all lead to reliability problems. Furthermore, it provides difficulties in servicing and maintaining the device, especially within the very limited confines of a marine engine compartment.
A second shortcoming is the use of three shafts. With chains, this requires use of two separate chains with two sets of sprockets, adding additional and unwanted, weight, size, and cost to the device. This is unacceptable when considering use in small, and low cost watercrafts.
Thirdly, the inventors also teach to mount the two output shafts utilizing non-concentric adjustable bearing housings, allowing for varying of the axes of rotation. Adjustment is required with the use of chains, for the periodic take-up of chain slack. Removal of slack is accomplished through the varying and increasing of the spacing, or center distance, between the shafts. The adjustable bearing housings are the inventors' means to remove slack after assembly, then to periodically adjust for the wear and stretch of the chains throughout the life of the device. In a device such as this, wear and stretch are accelerated by the high centrifugal forces, caused when moving heavy chains through the speeds observed within this type of transmission device. Periodic adjustments must therefore be made to minimize backlash, and to prevent disengagement of the chains from their sprockets. The need for this adjustment is one of the greatest shortcomings of this particular prior art. This is also true for any other prior art utilizing chains, or using this type of adjustment. The reasons are explained below.
Adjusting of shaft center distance within a marine engine compartment would be very difficult, but even more important is that the adjustment eliminates the ability to employ this device in practice with today's direct plug-in type of impeller drives. These drives, which are also referred to as plug-in sterndrives, are the ones most demanded by the industry for use within inboard powered recreational watercraft. This type of drive however, requires for precise, and permanent location of the transmission output shafts. This is necessary to maintain concentric alignments between the transmission and the impeller drives which are mounted to the hull of the craft, specifically between the transmission output shafts, and the impeller input shafts, which insert directly into couplings mounted on those output shafts. This plug-in arrangement is demanded because it is the most compact and most cost efficient means of connection to a sterndrive today. This method will be illustrated and discussed in more detail later.
Furthermore, one cannot employ this device with any impeller drive in the smaller recreational watercrafts. This is due to the additional room required for significant lengths of universal drive shafts, needed to transfer power from the device to the impeller drives. Caricof et al. in their
FIG. 1
, as parts 17 and 19, illustrate these lengthy drive shafts. These long shafts must be used to compensate for misalignments caused by the adjustments in shaft center distance.
Accordingly, when considering use of this prior art, especially within the smaller and less expensive recreational watercrafts, the shortcomings are:
a) the excessive weight, size, and cost associated with the use of multiple sets of heavy steel chains and sprockets;
b) the additional complexity and cost of using a second output shaft, with all its associated parts;
c) the need and concerns of continuous lubrication;
d) the requirement for a tightly sealed and oil filled enclosure;
e) the need for periodic and difficult maintenance;
f) and, this unacceptable adjustment in shaft center distance.
Improvements and Advantages of the Present Invention
A collection of several features was assembled to overcome the shortcomings of the above prior art, as well as other prior arts. In addition, further improvements have been developed to help promote the use of the present invention throughout the boating industry. These will be discussed below and throughout the remaining sections.
The first feature for improvement is a synchronous belt. In contrast to a series of metal links, a belt by definition is a
Morano S. Joseph
Olson Lars A.
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