PROPELLER AND COUPLING MEMBER

Abstract: This invention relates to an improved design for a plastic propeller (1) and coupling member (10). The inner surface of the coupling member (1) is formed with a keyway (14) which mates with a corresponding key on the propeller shaft. The outer surface of the coupling member (1) is formed with a securing means to attach the propeller to the coupling member. The construction provides ease in replacing damaged propellers and in retrofitting existing metal propellers with plastic propellers.

Description: Background of the Invention This invention relates to screw type propellers and, in particular, to propellers in maritime use. The advantages of plastic propellers over metal propellers are well known. Plastic propellers are lighter, which facilitates storage and handling. Plastic propellers are also simpler to manufacture, which results in a lower cost. Further, a propeller made of an appropriate plastic is not as subject to permanent deformation as is a metal propeller. While contact with underwater objects may cause a portion of the propeller blade to shear or chip away, it is more resistant to chipping or shearing than a metal propeller is to a bending or deformation of its blade edges. Due to the reduced weight of the plastic material, any chips or nicks which do occur have considerably less effect upon the balance of the propeller than deformation or loss of material of its metal counterpart. Lastly, plastic propellers are more resistant to corrosion and erosion and thus have considerably longer lives than metal propellers. Despite the many advantages of plastic propellers, the transition in the trade from metal to plastic has been slow. What is needed is a propeller design making use of the potential advantage of plastic materials which can be easily retrofitted to existing inboard and outboard vessels of virtually any size or hull configuration. Therefore, one objective of the present invention is to provide a plastic propeller which can be easily attached to and removed from the propeller shaft. Another objective of the present invention is to provide a propeller coupling member which would enable a vessel with metal propeller to be retrofitted with a plastic propeller. Other objectives of the present invention will be apparent, to those skilled in the art, from the specification and drawings. SUMMARY OF THE INVENTION The invention comprises a screw-type propeller and a coupling member adapted to attach the propeller to the propeller shaft of a vessel. The coupling member is formed with an inner surface and an outer surface. The inner surface is formed with a first securing means for securing the coupling member to the propeller shaft; the outer surface is formed with a second securing means for securing the coupling member to the propeller. The two securing means are designed to allow easy attachment and removal of the propeller and coupling means from the propeller shaft. In the use of the inboard/outboard or standard outboard engine, the design (fig. 5 & 6) offer exhaust gas release through the coupling hub. One advantage of the present propeller and coupling member design is the ease with which damaged propellers may be replaced. Another advantage of the present invention is the ease with which existing inboard and outboard metal propellers may be replaced with plastic propellers. Other advantages of the present invention will be apparent to those skilled in the art from this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side elevational view of a propeller according to a first embodiment of this invention; Fig. 2 is a detail view of the coupling member according to the first embodiment of this invention; Fig. 3 is a side elevational view of a propeller according to a second embodiment of this invention; Fig. 4 is a detail view of the coupling member according to the second embodiment of this invention; Fig. 5 is a side elevational view of a propeller according to a third embodiment of this invention; and Fig. 6 is a detail view of the coupling member according to the third embodiment of this invention. DETAILED DESCRIPTION OF THE DRAWINGS Referring to Figure l, a plastic propeller 1 having a central hub 2 and radially extending blades 3 is shown. The embodiment in Figures l and 2 is preferred for small inboard and outboard power vessels. The propeller blades and hub may be made as a single, integral piece or formed separately and attached in a known manner. In the preferred embodiment, the propeller blades and hub are injection molded into an integral construction. The shape,number and orientation of the blades will depend on the intended use of the propeller and in particular on the requirements of the user's vessel and the vessel's motive power. The design of these parameters will be apparent to one skilled in the art. The propeller of the present invention may be used both by large vessels with inboard motors and inboard/outboard or outboard with engine speeds below 1000 RPMs, as well as with smaller vessels, with outboard motors and engine speeds of up to approximately 5000 RPMs. The preferred material for the propeller is DuPont ZYTEL, a nylon resin. In particular, ZYTEL ST 801 BK-10 with well-dispersed carbon black has proven to be a particularly effective resin. ZYTEL has many advantageous properties, such as light weight, strength, stiffness and durability. In addition, ZYTEL is well suited for injection molding. Other materials may be used for the propeller, however, without departing from the principles of the invention. The propeller 1 is formed with an inner cylindrical surface 4 for receiving the coupling member 10. Extending radially outward from the cylindrical surface 4 is a plurality of axially extending slots 5 formed within the hub 2. Figure 2 is a detailed drawing of coupling insert 10 accordinq to the first embodiment of the invention. Coupling insert 10 is formed as a cylinder with outer surface 11 and inner surface 12. Extending radially outward from outer surface 11 is a plurality of axially extending splines 13. An axially extending keyway 14 is formed in inner surface 12. The splines 13 are spaced uniformly about the circumference of outer surface 11. No spline is formed in the cylindrical segment opposite keyway 14, however. In the preferred embodiment, coupling member 10 is injection molded from DuPont ZYTEL. Other materials, such as bronze or aluminum, may be used to match the coupling member material with that of the propeller shaft without departing from the principles of the invention. Some users may prefer a hub made of bronze or aluminum in order to match the construction of the propeller drive shaft. Such a preference would be caused by a desire to avoid the electrochemical effect called electrolysis, which can sometimes occur when dissimilar metals are used in a propeller/shaft environment. While the electrolytic effect will not occur if a hub made of ZYTEL is used, hubs made of other metals may nonetheless be desirable merely because of consumer preferences. As exemplary dimensions, in the preferred embodiment the inner diameter of coupling member 10 is 76 mm. The wall thickness of member 10 is 11 mm. Splines 13 each extend radially outward 12,7 mm from outer surface 11 and are 3,2 mm thick. Slots 5 in propeller 1 are formed to mate with splines 13. Keyway 14 in coupling member 10 is 22,2 mm wide and is formed to mate with a matching key on the vessel's propeller shaft. Hub 2 and blades 3 may be any dimension desired. In use, coupling member 10 is secured to the propeller shaft of a vessel by inserting the propeller shaft key (not shown) into the matching keyway 14 in coupling member 10. Propeller 1 is secured to coupling member 10 by inserting splines 13 into the matching slots 5. In this way, existing metal propellers may be replaced with plastic propellers through use of the coupling member of this invention. If plastic propeller 1 is damaged by striking an underwater object, the lightweight propeller can be replaced either on shore or in the water by sliding the propeller off coupling member 10 and inserting a new propeller in its place. This operation is extremely simple and can be performed at sea, even on the largest vessels, by one or two divers wearing appropriate diving gear. Hence, the need to tow a vessel back to shore for dry docking, as well as the extensive down time need to repair prior art propellers, is greatly reduced or eliminated. A second embodiment of the present invention is shown in Figures 3 and 4. This embodiment is preferred for larger vessels, but could also be used in lieu of the first embodiment on smaller vessels. Figure 3 shows a plastic propeller 101 having a central hub 102 and radially extending blades 103. As in the first embodiment, the blades 103 and hub 102 may be formed as an integral piece from DuPont ZYTEL as above. The propeller 101 is formed with an inner surface 104 of substantially square cross-section for receiving coupling member 110. Figure 4 is a detailed drawing of coupling member 110 according to the second embodiment of this invention. Coupling member 110 is formed with a substantially square outer cross-section 111 and a substantially circular inner cross-section 112. An axially extending keyway 114 is formed in inner surface 112. As exemplary dimensions, the inner diameter of coupling member 110 is 76 mm ; the outer diameter varies with the size of the propeller. Keyway 114 has a width of 22,2 mm and a depth matching the height of the propeller shaft key. The diameter of inner surface 104 of propeller 101 is slightly less than the outer diameter of coupling member 10. In use, coupling member 110 is secured to the propeller shaft of a vessel by inserting the propeller shaft key into the matching keyway 114 in coupling member 110. Propeller 101 is secured to coupling member 110 by force fitting inner surface 104 of propeller 101 over outer surface 111 of coupling member 110. A third embodiment of the present invention is shown in Figures 5 and 6. This embodiment is preferred for outboard and inboard/outboard motors having splined propeller shafts. Figure 5 shows a plastic propeller 201 having a central hub 202 and radially extending blades 203. As in the first and second embodiments, the blades 203 and hub 202 may be formed as an integral piece from DuPont ZYTEL. The propeller is formed with an inner surface 204 of substantially square cross-section for receiving coupling member 210. Figure 6 is a detailed drawing of coupling member 210 according to the third embodiment of this invention. Coupling member 210 is formed with a substantially square outer cross-­ section 211. A plurality of axially extending grooves 215 is formed along inner surface 212. One or more axial exhaust ports 216 are formed in coupling member 210 between outer surface 211 and inner surface 212. In use, coupling member 210 is secured to the propeller shaft of a vessel by inserting the propeller shaft splines into the matching slots 215 of coupling member 210. Propeller 201 is secured to coupling member 210 by force fitting inner surface 204 of propeller 201 over outer surface 211 of coupling member 210.

Claims: 1. - A screw-type propeller assembly comprising a propeller (1, 101, 201); and a coupling member (10, 110, 210) to attach said propeller to the propeller shaft of a vessel, said coupling member being formed with an inner surface and an outer surface, said coupling member having a first securing means on said inner surface for securing said coupling member to said shaft and a second securing means on said outer surface for securing said coupling member to said propeller, said coupling member being further adapted to be easily removable from said shaft and from said propeller. 2. - The propeller assembly of Claim 1, wherein said propeller (1, 101, 201) and said coupling member (10, 110, 210) are formed of nylon resin. 3. - The propeller assembly of Claim 1, wherein said propeller (1, 101, 201) and said coupling member are formed of ZYTEL. 4. - The propeller assembly of anyone of Claims 1 to 3, wherein said coupling member (10) is substantially cylindrical and said second securing means comprises a plurality of axially extending splines (13) disposed on said outer surface (11) of said coupling number (10), said propeller (1) being formed with corres­ ponding slots (5) adapted to be mated with said splines (13). 5. - The propeller assembly of Claim 4, wherein said first securing means comprises an axially extending keyway (14) disposed on said inner surface (12) of said coupling member (10), said keyway (14) being adapted to cooperate with a corresponding key on said propeller shaft. 6. - The propeller assembly of Claim 5, wherein said axially extending splines (13) are spaced uniformly about said outer surface (11) except for the cylindrical segment opposite said keyway (14). 7. - The propeller assembly of anyone of Claims 1 to 3, wherein said coupling member (110) has a substantial­ ly square outer cross-section, said second securing means comprising means on said outer surface (111) adapted for a force fit with said propeller (101). 8. - The propeller assembly of Claim 7, wherein said first securing means comprises an axially extending keyway (114) disposed on said inner surface (112) of said coupling number, said keyway (114) being adapted to cooperate with a corresponding key on said propeller shaft. 9. - The propeller assembly of Claim 7, wherein said first securing means comprises a plurality of axially extending slots (215) disposed along said inner surface (212), said slots (215) being adapted to cooperate with corresponding splines on said propeller shaft. 10. - The propeller assembly of Claim 9, wherein said coupling member (210) is formed with an axially extending exhaust port (216).

Inventors: GEARY, EDWIN S.
Applicants: GEARY, EDWIN S.
Application year: 1987
Main classification: B63H1
IPC codes: B63H23, F16D1, B63H1