US 3701611 A
Description (OCR text may contain errors)
Oct. 31, 1972 E. LAMBRECHT 3,701,511
MARINE PROPELLER WITH RESILIENT HUB STRUCTURE Filed Dec. 21, 1970 w HG.
INVENTOR RALPH E. LAMBRECHT ATTOR EY United rates Patent O 3,701,611 MARINE PROPELLER WITH RESILIENT HUB STRUCTURE Ralph E. Lambrecht, Lake Bluff, Ill., assignor to Outboard Marine Corporation, Waukegan, Ill. Filed Dec. 21, 1970, Ser. No. 99,882 Int. Cl. B6311 21/26 US. Cl. 416-134 6 Claims ABSTRACT OF THE DISCLOSURE A marine propeller and hub structure for absorbing sudden rotational loads which may be applied to the propeller when it strikes a submerged object. The hub structure for'the propeller includes an inner hub, a plurality of ribs extending radially outwardly from the inner hub and an outer hub joined to the inner hub by the radially extending ribs. The propeller assembly is completed by a plurality of blades extending outwardly from the outer hub. The ribs of the hub structure are flexible enough to provide a resilient cushioning eifect in the propeller hub structure when a blade strikes an underwater obstacle.
BACKGROUND OF THE INVENTION When a marine propeller strikes an underwater obstacle it often causes extensive damage to the propeller itself or to the propeller driving mechanism. In the past, resilient drive connections between various parts in the propeller assembly such as slip clutch mechanisms have been provided to absorb these sudden torque forces transmitted through the propeller when it strikes such an obstacle. In order to absorb the excessive torque forces through slippage, the previous drive assemblies and connections have been expensive to manufacture and complicated in structure. This invention is a simple, economical propeller that provides a resilient cushioning effect in one integral part of the propeller rather than between various connecting parts in the propeller.
SUMMARY OF THE INVENTION The invention relates to a marine propeller adapted to operate immersed in Water and more particularly to an improved marine propeller having a hub structure that is resilient to excessive torque loads.
A primary object of this invention is a marine propeller for absorbing excessive torque loads thereby reducing the damage to the blades and/or possible damage to the mechanism driving the propeller.
A further object is a propeller and hub structure that provides a resilient cushioning eifect in the hub structure when the propeller strikes an underwater object.
Another object is an improved marine propeller that may be fabricated in one piece from one of the memory plastics.
Another object is a propeller that is simple in structure and economical to manufacture.
Other objects and advantages will be apparent from the following description and accompanying drawings for this invention.
FIG. 1 is a partial axial section view through the hub structure of a marine propeller in accordance with the invention.
FIG. 2 is a section view taken along lines 22 of FIG. 1.
FIG. 3 is a section view of another embodiment of this invention showing deflection of the radially extending ribs when they are under excessive torque loads.
DETAILED DESCRIPTION Referring to the drawings in more detail it will be seen that the marine propeller 10 includes a hub structure 12 and a plurality of blades 24 extending radially outwardly from the hub structure to provide the driving force to propel a watercraft (not shown). The hub structure 12 may be adapted to be mounted on a sleeve around a propeller shaft 14 such as the bushing 16 shown in FIGS. 1 and 2. The hub structure may also be adapted to be mounted directly on the propeller shaft 14 as shown in FIG. 3.
The hub structure 12 includes a means for providing a resilient cushioning effect when the propeller 10 hits a submerged object. The hub structure 12 is comprised of an inner hub 18, a plurality of ribs 20 extending radially outwardly from the inner hub, and an outer hub 22 joined to the inner hub by the radially extending ribs. The hub structure and particularly the ribs .20 are adapted to provide a means for deflection in the propeller 10 when it is subject to excessive torque loads.
FIG. 1 is a partial section view showing in detail the propeller 10 and particularly the hub structure 12. The propeller shaft 14 is tranversely bored to receive a shear pin 28 in a conventional manner. The bushing 16 is mounted on the propeller shaft 14 for common rotary movement with the shaft. The inner hub as shown at 18 is mounted around the bushing 16. The inner hub 18 is posi tively connected to the bushing by any number of locking means such as the use of pins, splines, or knurls. FIG. 1 shows the outer surface of the bushing 16 as having knurls which are adapted to interconnect with complementary knurls on the inner surface of the inner hub 18. The shear pin 18 passes through the bushing 16 to positively drive both the bushing and the inner hub from the propeller shaft 14 while the shear pin remains intact.
In accordance with the invention, the outer hub 22 forms part of the hub structure 12. As shown the outer hub 22 is located in radially outwardly spaced relationship to the inner hub 18. The outer hub 22'is connected to the inner hub by the plurality of radially extending ribs .20. A plurality of blades 24 extend outwardly from the outer hub 22 in a conventional manner. It is important to note that the ribs 20 must be rigid enough to withstand the normal rotational forces transmitted to the hub structure by the rotating propeller blades 20 but flex-i ible enough to deflect when the blades strike a submerged object.
As shown in FIG. 1, the inner hub 18, ribs 20, outer hub 22 and blades 24 may all be fabricated as one integral piece. The fabrication of the hub structure 12 and blades 24 as one integral piece may be accomplished by injection molding the propeller assemblyfrom any one of the commonly known memory plastics.
FIG. 2 is a section view taken along lines 2-2 of FIG. 1, showing an end view of the propeller 10 and the hub structure 12 for this invention. It will be noted that the propeller 10 is shown as having two blades 24. The propeller of thi invention is adapted for use with a marine propulsion unit of any horsepower however, it is probably best adapted for an outboard motor having a relatively low horsepower output.
FIG. 2 clearly shows the disposition and shape of the ribs 20 for connecting the inner hub 18 to the outer hub 22. The plurality of ribs 20 are radially disposed in relationship to the propeller shaft 14. The ribs 20 each have an inner end 30 and an outer end 32 with a mid-section 34 therebetween. The mid-section 34 is thicker in cross section than the ends providing a larger cross sectional area for added strength to keep the hub structure 12 from collapsing under various loading conditions. The disposition and shape of the ribs 20 is important as it allows the propeller to deflect under excessive loads thereby allowing the propeller to withstand shock and torque loads without any permanent deformation to the propeller.
The resilient cushion effect provided by the hub structure 12 when it strikes an under water obstacle substantially reduces the amount of blade damage and substantially eliminates damage to the expensive mechanism driving the propeller. Among other advantages this provides a safety feature as loss of a propeller blade or the driving mechanism can result in a propellent that will not function effectively and thus lead to a disabled craft.
FIG. 3 shows another embodiment of the hub structure 12 for this invention. In this embodiment an inner hub 18 is splined directly to the propeller shaft 14 for common rotary movement with the shaft. The splines 36 of the inner hub fit into key-ways formed by complimentary splines 38 on the propeller shaft 14.
A plurality of radially extending ribs 20 join the inner hub 18 to an outer hub 22. The outer hub 22 is adapted to carry the usual propeller blades (not shown). In this embodiment the ribs 20 are shown under deflection as would occur if a blade of the propeller struck an underwater obstacle.
It should be noted that the hub structure 12 and the blades 24 may be fabricated as two separate parts. For example, the hub structure 12 shown in FIG. 3 may be extruded as a separate piece from one of the memory plastics. The blade 24 may be fabricated separately and attached to the outer hub 22 in any conventional manner.
All or a part of the propeller 10 can be made from one of the commonly known memory plastics. More specifically, the ribs 20 alone or the hub structure 12 alone or the hub structure and blades 24 can be made from one of the commonly known memory plastics. The plastic resin utilized should have high impact strength and dimensional stability. In addition, it should be substantially non-water absorbent. Polyethylene and polypropylene are two plastic resins which have been found to work well.
It is important to note that the plurality of ribs 20 must be able to absorb the stress of operation without flexing while providing a resilient cushioning effect in the hub structure 12 when the propeller hits an underwater object. Therefore, .the material used for the ribs 20 must be able to withstand repeated flexing without cracking.
In addition, it is important to note that the propeller for this invention may be used with an exhaust system that discharges exhaust through a snout when using a cap 25 as shown in FIG. 1 or it can be effectively used with a through the hub propeller exhaust system.
Various features of the invention are set forth in the following claims.
What is claimed is:
1. A hub structure for a marine propeller, said hub structure being constructed in one piece from one of the memory plastics and including an inner hub adapted to be mounted on a propeller shaft for common rotary movement with the propeller shaft, means for providing a'resilient cushioning effect when the propeller hits a submerged object including a plurality of ribs extending radially outwardly from said inner hub, and an outer hub joined to said inner hub by said radially extending ribs and located in radially outwardly spaced relationship to said inner hub.
2. A hub structure in accordance with claim 1 wherein each said rib has an inner end connected to said inner hub, an outer end connected to said outer hub, and a mid-section therebetween of larger cross sectional area than either of said ends.
3. A hub structure in accordance with claim 1 wherein said inner hub includes interlocking splines connected to the propeller shaft to provide positive driving engagement between the propeller shaft and said inner hub.
4. A hub structure in accordance with claim 1 further including a plurality of blades extending integrally and outwardly from said outer hub.
5. A propeller assembly for use with a marine propulsion unit for driving a watercraft, said propeller assembly including a propeller shaft, a bushing mounted on said propeller shaft for common rotary movement with said shaft, and a unitary member fabricated in one piece from one of the memory plastics including an inner hub mounted around said bushing in positive driving engagement with said bushing, means for providing a resilient cushioning effect in the propeller assembly when the propeller hits a submerged object including a plurality of ribs extending radially outwardly from said inner hub, an outer hub joined to said inner hub by said radially extending ribs and located in radially outwardly spaced relationship to said inner hub, and a plurality of blades extending outwardly from said outer hub to provide a thrust force to drive the watercraft.
6. A propeller assembly in accordance with claim 5 wherein each said rib has an inner end connected to said inner hub, an outer end connected to said outer hub, and a mid-section therebet-ween of larger cross sectional area than either of said ends.
References Cited UNITED STATES PATENTS 2,235,605 3/1941 Bugatti 416l34 2,543,396 2/1951 Wolff 6427 R X 3,012,767 12/1961 Jones 6427 R X 3,133,596 5/1964 Berliner 416-24 A X 3,245,476 4/1966 Rodwick 4l6241 A 3,318,388 5/1967 Bihlmire 416-240 X 3,477,794 11/1969 Abbott et al 416l34 3,563,670 2/1971 Knuth 41693 M 3,584,969 6/1971 Aiki 416132 EVERETTE A. POWELL, JR., Primary Examiner US. Cl. X.R.