| CLAIMS 1. A lifting ,low-cost transom stern drive unit for boats built using common machine tools and coreless sand casting that can be used when the boat is running or lifted when beached, comprising: a. a top gear box cover; b. one or more driving bevel gears; c. a dog clutch; d. a vertical drive shaft; e. a cp-axial oil pump and drives it; f. a pinion item; g- a bottom cover; h. an anti-cavitation plate; i. a mounting base that houses the entire setup; j- a bottom drive cover; k. a hanging bracket for the pivot; 1. a transom mounting plate; m. a stern; n. an oil level window; o. a lifting ram; and P- a vertical pivot hinge for the lifting ram. 2. A stern drive unit of claim 1 wherein the lay shaft supplies power from the inboard engine. 3. A stern drive unit of claim 1 wherein the dog clutch which works on a spline shaft that enables the dog clutch to engage a drive gear, which reverses the rotation on the drive pinion carried on a vertical transmission shaft. 4. A stern drive unit of claim 1 wherein the pinion item at the end of the drive shaft which engages with the crown wheel carried on a propeller shaft, which in turn drives the propeller 5. A stern drive unit of claim 1 wherein the bottom cover prevents ingress of water into the assembly. 6. A stern drive unit of claim 1 wherein the anti-cavitation plate is bolted to a structural unit that holds a rigid vertical plate which is integrated with it. 7. A stern drive unit of claim 1 wherein the oil level window enables easy and external monitoring of oil levels. A stern drive unit of claim 1 wherein the lifting ram lifts the transom drive propeller above the height of the keel to allow the boat to be beached without dismantling the stern drive. 9. A stern drive unit of claim 8 wherein the ram can be operated manually. 10. A stern drive unit of claim 8 wherein the ram can be operated by other means including hydraulic or electrical . 11. A stern drive unit of claim 1 wherein the vertical drive shaft passes though a coaxial oil pump and drives it. 12. A stern drive unit of claim 11 wherein having the oil pump work co-axially on the drive shaft enables oil circulation between the gear housing at the top and bottom thereby enabling cooling of oil by the submerged portion casing which is always in contact with water. 13. A stern drive unit of claim 1 wherein the driving bevel gears are inter-connected by straps and placed on the pedestal, additionally providing sufficient rigidity to the system and preventing flexing of the pedestal bearing under load. 14. A stern drive unit of claim 1 wherein the transom drive can be used in all kind of boats and marine propulsion needs. |
BACKGROUND OF THE INVENTION
This invention describes a stern drive unit whose manufacturing costs are ameliorated by only requiring the use of relatively simpler machinery and hand tools.
DESCRIPTION OF PRIOR ART
A stern drive is a form of marine propulsion, and has been in use for many decades. Typically, a stem drive comprises an engine which is located inboard just forward of the transom (stem) and provides power to the drive unit located outside the hull. This drive unit resembles the bottom half of an outboard motor, and is composed of two sub-units: the upper unit which contains a drive shaft the connects through the transom to the engine and transmits power to a gearbox; the lower unit bolts onto the bottom of the upper unit and contains a vertical driveshaft that transmits power from the upper unit gearbox to the lower unit gear box, which connects to the propeller shaft. Thus, the outdrive carries power from the inboard engine, typically mounted above the waterline, outboard through the transom and downward to the propeller below the waterline.
US200822067A1 discloses a Stern Drive, in particular for twin-propeller boats which is characterized by the separation of the mechanical units from the supporting structure. The supporting structure consists of arms carrying sleeves to support the mechanical units, where the arms are integrated into a plate, which is fixed with the keel of the boat. The stem-drive has the advantage of being light in weight, and can be used with different keel configurations economically, and with minimal modifications. This model of the stem- drive enables the best utilization of space, as it is compact and small in size. The invention eliminates the need to use a transmission device, which helps in controlling costs. US3841257A discloses a High Perfromance Stern Drive wherein the invention relates to a marine propulsion device (e.g. a stern-drive), suitable for use in racing applications. The stern-drive includes a hinge pin which connects a mounting bracket to a mounting plate, which enables a vertical swinging movement about a horizontal tilt axis, within a certain allowable range (so as to ensure that the propeller remains under the water). This movement allows for the optimization of the performance by allowing transmission of power to the propeller without interruptions. The stern-drive has the advantages of being low weight, and economical, and simultaneously simple in design, and strong. US5326294A discloses a Stern Drive for Boats wherein the invention relates to a stern drive unit, useful for submerging a propeller and rudder below the surface of the water. The stern drive unit comprises a pivotal arm, a propeller shaft, a transom fitting, a , stuffing box, a rudder and a means for rotating it, and a means for adjusting the angle of the pivotal arm with respect to the transom. The invention overcomes the problem of a high possibility of damage to the stern drive parts, due to exposure to salt water, as the , critical parts are prevented from being exposed to salt water, in this design. In addition, , the stern drive also has a provision for water intake, which can be used to provide water for cooling the engine. The vertical movement of the stern drive gives stability to the boat and makes the operation economical.
US6468119B1 discloses a Composite Stern Drive assembly wherein the invention relates to a composite stern drive assembly which comprises a central rigid core, the upper portion of which is connected to the stern, and the lower portion is coupled (directly or indirectly) to a propeller. The rigid core is placed within a housing, which is thin-walled. This design combines the features of both an inboard and outboard engine. A closed-loop system (which eliminates problems of corrosion associated with exposure of the machinery to salt water) to circulate water may be incorporated, which is useful for cooling the engine. The lack of empty spaces in the circulatory system also offers the advantage of elimination of eddy formation and salt water accumulation. The exterior of the stern-drive unit is made of a non-metallic material, thereby minimizing the corrosion of metals caused by exposure to salt water. The stern drive is designed such that there is a transfer of rotary power from the engine to the propeller, which in turn transfers the propelling force to the boat, to enable the boat to move forward. This design makes use of a single hydraulic cylinder, which does not contact the water when the boat is in motion, thereby preventing spray of water on to the boat.
Stern drives which are in use currently have the disadvantages of a high manufacturing cost, due to the complex machinery and sophisticated technology required to produce them. The present invention provides a stern drive system that can be manufactured using relatively simpler machinery and hand tools, thereby cutting down the manufacturing costs.
SUMMARY OF THE INVENTION
The advantages of the present invention are as follows. The transom stern drive of the invention can be made using common machine tools and coreless sand casting, thereby sustainably reducing the manufacturing costs. The bevel gears connected by straps on the pedestal restrict the flexibility of the gear box, thereby providing rigidity while, the pedestal bears a load. As the oil pump works co-axially on the drive shaft, it possible for the oil to circulate between the top and bottom portions of the gear housing, which enables cooling of the oil by the submerged portion of the casing which is always in contact with water.
The oil levels can be monitored with ease externally, by placing the oil window at an appropriate level in the casing. By placing the lifting ram below the vertical pivot point, it is possible to lift the propeller above the keel of the boat, thereby enabling the boat to be beached. Also included is a means to operate the ram, manually or otherwise. The transom stern drive of the invention is a marine propulsion unit, suitable for use in all kinds of boats. BRIEF DESCRIPTION OF FIGURES
Figure 1 shows the power transfer module in the integrated mode.
Figure 2 shows the pedestal carrying the driving bevel gears which are connected by a strap, and provides rigidity.
Figure 3 shows the lifting ram which lifts the transom drive propeller above the height of the keel.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The advantages of a stern drive system over outboards include higher available horsepower per engine and a clean transom with no cutouts for the outboard installation and no protruding power head, which makes for easier ingress and egress for pleasure boat passengers and for easier fishing. The advantages of the stern drive system versus inboards include simpler engineering for boat builders, eliminating the need for them to design propeller shaft and rudder systems; also significant space savings freeing up the boat's interior volume for occupancy space. Because of their practical advantages and attractive cost, stern drives have become extremely popular especially for use in pleasure boats, and there are many models of boats for which stern drive power is the only available propulsion offered. The main drawback of stern drives over straight inboards is that they are more exposed to salt water, which can cause corrosion, and hence high maintenance costs. The present invention overcomes this problem by making use of a protective casing. Figure 1 shows the power transfer module in the integrated mode. The stern drive of the invention is characterized by splitting the power transfer module into two separate independent assemblies, which are fixed on the structural part of the stern drive, which consists of pivot links and brackets. The two units are placed within a suitable casing 8, which prevents the machinery from coming into contact with salt water, and also ensures that the lubricants do not leak outside. It shows a top gear box cover, where the lay shaft supplies power from the inboard engine to the dog clutch 2, which works on a spline shaft. The spline shaft enables the dog clutch 2 to engage a drive gear, which reverses the rotation on the drive pinion 3, carried on a vertical transmission shaft. The vertical drive shaft passes though a co-axial oil pump and drives it. The end of the shaft carries a pinion item which engages with the crown wheel carried on a propeller shaft, which in turn drives the propeller. A bottom cover 8 prevents ingress of water into the assembly. The anti-cavitation plate 5 is bolted to a structural unit 19, and holds a rigid vertical plate which is integrated with it. The entire-set up is placed on a mounting base 4. Also shown in the figure is the bottom drive cover, a hanging bracket for the pivot 12, transom mounting plate 13, stern 14, and oil level window 15. The stern drive consists of a top gear box cover 1, where the lay shaft 17 supplies power from the inboard engine to the dog clutch through a universal joint. The dog clutch works on a spline shaft, which engages one of the drive gears 16. This causes the rotation of the drive pinion to reverse. The drive pinion is carried on a vertical transmission shaft which passes through a coaxial oil pump, and drives it. The other end of the shaft carries a pinion item 10 which engages a crown wheel 9, carried on a propeller shaft 7and drives the propeller 6. The driving bevel gears are inter-connected by one or more straps 20 and placed on the pedestal. This provides a sufficient degree of rigidity to the system and prevents flexing of the pedestal bearing under load. The stern drive further comprises a lifting ram 11 which lifts the transom drive propeller above the height of the keel, as it works on its vertical pivot hinge 18.
Figure 2 shows the vertical transmission shaft 21 which carries the drive pinion and passes through a coaxial oil pump. A pedestal 24 carrying the driving bevel gears which are connected by one or more straps 20 and provides rigidity is also shown alongside an oil pipe 22, lock nuts 23 and an oil pump 25.
Figure 3 shows the Ufting ram 11 which lifts the transom drive propeller above the height of the keel connected to the stern by means of a vertical pivot hinge 18.