The present invention relates to marine propeller technology, and more particularly to a two-piece axle bushing and a marine propeller using this design of two-piece axle bushing.

Structurally, a conventional marine propeller generally comprises a propeller hub, a plurality of propeller blades radially connected to the periphery of the propeller hub, and an axle bushing mounted in the propeller hub. During operation, the engine transmits power to the axle bushing through a drive shaft, causing the axle bushing to rotate the propeller hub. During rotation of the propeller hub, the propeller blades are rotated to create thrust in water.

Conventional axle bushings for marine propeller are generally made from a hard material (such as metal). If a marine propeller hits an external object during its operation, the axle bushing can become brittle, and may even cause damage to the drive shaft. If the axle bushing has become brittle, it can no longer drive the propeller hub to rotate smoothly, affecting power transmission effects. Further, if the drive shaft outputs a high torque, the axle bushing can become brittle. Therefore, conventional axle bushings are not suitable for use with a high horsepower engine.

In order to settle the aforesaid problem, Taiwan Patent M310175, invented by the present inventor, discloses an axle bushing, which comprises a metal layer and a shock-absorbing layer fixedly surrounding the metal layer. The axle bushing, on the one hand, is connected to the drive shaft of the engine by the metal layer, and, on the other hand, fastened to the axle hole of the propeller hub by the shock-absorbing layer. Thus, if the propeller hub hits an external object during its operation, the shock-absorbing layer of the axle bushing absorbs shocks, avoiding embrittlement of the metal layer and protecting the drive shaft against damage. However, according to the aforesaid prior art patent design, in the moment the engine starts up, the output torque of the drive shaft of the engine will be directly transmitted to the propeller hub without leaving any buffering time in the power transmission process, causing sudden vibration of the marine propeller due to a high impact.

The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a two-piece axle bushing for marine propeller, which utilizes soft start-up to effectively reduce vibration in the moment the engine starts up, thereby enhancing marine propeller start-up stability and smoothness.

To achieve this and other objects of the present invention, a two-piece axle bushing for marine propeller comprises a first transmission member and a second transmission member. The first transmission member comprises an accommodation chamber, at least two longitudinal inner ribs equiangularly spaced around an inner perimeter of the accommodation chamber and radially projecting toward the inside of the accommodation chamber at a predetermined distance, and a buffer space defined inside the accommodation chamber between each two adjacent longitudinal inner ribs. The second transmission member comprises a tube shaft and a shock absorber. The tube shaft comprises a first transmission segment, and a second transmission segment connected to the first transmission segment. The first transmission segment is inserted into the accommodation chamber of the first transmission member, comprising at least one longitudinal outer rib located at an outer perimeter thereof and respectively movably inserted into one respective buffer space of the first transmission member and selectively engageable with one longitudinal inner rib. The shock absorber fixedly surrounds the outer perimeter of the second transmission segment.

Thus, in the moment the engine starts up, the second transmission member will be driven to rotate by the drive shaft of the engine, and the first transmission member will be rotated with the second transmission member only after the longitudinal outer ribs of the tube shaft of the second transmission member have been put into engagement with the longitudinal inner ribs of the first transmission member. As soon as the first transmission member is rotated with the second transmission member, the output torque of the engine can be transmitted to the marine propeller, causing the marine propeller to create thrust in water. Thus, the two-piece axle bushing of the present invention can generate power hysteresis effects when the engine starts up, reducing vibration due to a sudden high torque and further enhancing start-up stability and smoothness of the marine propeller. Further, subject to the shock absorbing effect of the shock absorber of the second transmission member, the two-piece axle bushing can absorb shocks if the marine propeller hits an external object accidentally, protecting the tube shaft of the second transmission member and the drive shaft of the engine against damage.

It is another object of the present invention to provide a marine propeller, which comprises a propeller hub defining therein an axle hole, a plurality of propeller blades equiangularly and radially extended from an outer perimeter of the propeller hub, and a two-piece axle bushing as described above. The two-piece axle bushing is mounted in the axle hole of the propeller hub for connection to a drive shaft of an engine.

Other advantages and features of the present invention will be fully understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference signs denote like components of structure.

• FIG. 1 is an oblique top elevational view of a marine propeller in accordance with a first embodiment of the present invention.
• FIG. 2 is an exploded view of the marine propeller in accordance with the first embodiment of the present invention.
• FIG. 3 is an exploded view of the two-piece axle bushing used in the marine propeller in accordance with the first embodiment of the present invention.
• FIG. 4 is a sectional assembly view of the marine propeller in accordance with the present invention.
• FIG. 5 is a rear end view of the two-piece axle bushing used in the marine propeller in accordance with the present invention.
• FIG. 6 is a transverse sectional view of the two-piece axle bushing used in the marine propeller in accordance with the present invention, illustrating the longitudinal outer ribs of the second transmission member spaced from the longitudinal inner ribs of the first transmission member.
• FIG. 7 is similar to FIG. 6, illustrating the longitudinal outer ribs of the second transmission member respectively engaged with the longitudinal inner ribs of the first transmission member.
• FIG. 8 is similar to FIG. 7, illustrating the first and second transmission members rotated in the reversed direction.

Referring to FIGS. 1 and 2, a marine propeller 10 in accordance with the present invention is shown. The marine propeller 10 comprises a propeller hub 22, four propeller blades 30, and a two-piece axle bushing 40.

The propeller hub 20 comprises an axle hole 22 extended through opposing front and rear ends thereof.

The propeller blades 30 are equiangularly and radially extended from the outer perimeter of the propeller hub 20.

The two-piece axle bushing 40 is mounted in the axle hole 22 of the propeller hub 20, comprising a first transmission member 50 and a second transmission member 60, as shown in FIG. 3.

The first transmission member 50 is made from metal. For use with a high horsepower engine, the first transmission member 50 can be made from stainless steel; for use with a low horsepower engine, the first transmission member 50 can be made from aluminum alloy.

Structurally, the first transmission member 50 comprises an accommodation chamber 52 and four longitudinal inner ribs 54. These four longitudinal inner ribs 54 are equiangularly spaced around an inner perimeter of the accommodation chamber 52 and radially projecting toward the inside of the accommodation chamber 52 at a predetermined distance such that a buffer space 56 is defined inside the accommodation chamber 52 between each two adjacent longitudinal inner ribs 54. Further, as shown in FIG. 6, each longitudinal inner rib 54 comprises two first sloping surfaces 541 respectively located at two opposite sides thereof. Preferably, the first sloping surfaces 541 of each two adjacent longitudinal inner ribs 54 define therebetween a contained angle in the range of 21∼25°. Further, the outer perimeter of the first transmission member 50 consists of multiple first planes 58 connected to one another so that the first transmission member 50 can be engaged with the peripheral wall of the axle hole 22 of the propeller hub 20 by the first planes 58.

The second transmission member 60 comprises a tube shaft 70. The tube shaft 70 is made from metal. For use with a high horsepower engine, the tube shaft 70 can be made from stainless steel; for use with a low horsepower engine, the tube shaft 70 can be made from aluminum alloy. Structurally, the tube shaft 70 comprises a first transmission segment 71, and a second transmission segment 72 connected to the first transmission segment 71. The first transmission segment 71 of the tube shaft 70 is inserted into the accommodation chamber 52 of the first transmission member 50. The second transmission member 60 further comprises a shock absorber 80 fixedly surrounding the second transmission segment 72 of the tube shaft 70, and an internal gear 73 formed integral with the inner perimeter of the second transmission segment 72 of the tube shaft 70 (see FIG. 4 and FIG. 5). The internal gear 73 is meshed with a drive shaft (not shown) of an engine (not shown) so that the tube shaft 70 is rotatable by the drive shaft of the engine. As shown in FIGS. 5 and 6, the tube shaft 70 further comprises four longitudinal outer ribs 74 and four bearing portions 75. These four longitudinal outer ribs 74 are equiangularly spaced around an inner perimeter of the first transmission segment 71 and radially projecting toward the outside of the first transmission segment 71 at a predetermined distance. Further, each longitudinal outer rib 74 comprises two second sloping surfaces 742 respectively located at two opposite sides thereof. The longitudinal outer ribs 74 of the tube shaft 70 are respectively engaged in the buffer spaces 56 inside the first transmission member 50. When the longitudinal outer ribs 74 of the tube shaft 70 are respectively engaged with one respective longitudinal inner rib 54 of the first transmission member 50, as shown in FIG. 7, the second sloping surface 742 of each longitudinal outer rib 74 is abutted against one first sloping surface 541 of one respective longitudinal inner rib 54. At this time, the tube shaft 70 can drive the first transmission member 50 to rotate. As the bearing portions 75 extend radially from the outer perimeter of the second transmission segment 72 a predetermined distance, they assist the tube shaft 70 to bear an output torque from the drive shaft of the engine.

As shown in FIG. 3 and FIG. 5, the shock absorber 80 of the second transmission member 60 is made from, but not limited to, rubber. The shock absorber 80 fixedly surrounds the outer perimeter of the second transmission segment 72 of the tube shaft 70 over the bearing portions 75, and, the outer perimeter of the shock absorber 80 consists of multiple second planes 82 that are connected to one another and respectively disposed in line with the first planes 58 of the first transmission member 50 in a flush manner so that the shock absorber 80 can be engaged peripheral wall of the axle hole 22 of the propeller hub 20 by the second planes 82.

Thus, when the engine is started up, subject to the engagement relationship between the drive shaft of the engine and the tube shaft 70, the drive shaft of the engine drives the second transmission member 60 to rotate. At the beginning the second transmission member 60 starts to rotate, the longitudinal outer ribs 74 of the second transmission member 60 are disposed in the respective buffer spaces 56 and not engaged with the longitudinal inner ribs 54 of the first transmission member 50, as shown in FIG. 6, before engagement between the longitudinal outer ribs 74 of the second transmission member 60 and the longitudinal inner ribs 54 of the first transmission member 50, the first transmission member 50 and the propeller hub 20 are immovable. Once the second transmission member 60 is rotated to the angular position where the longitudinal outer ribs 74 of the second transmission member 60 are respectively engaged with the longitudinal inner ribs 54 of the first transmission member 50, as shown in FIGS. 7 and 8, the first transmission member 50 begins to rotate with the second transmission member 60. When the first transmission member 50 begins to rotate with the second transmission member 60, the first transmission member 50 and the second transmission member 60 can then transfer the output torque of the engine to the propeller hub 20, causing the propeller blades 30 to rotate with the propeller hub 20 and to further generate a propelling force.

On the other hand, if the marine propeller 10 hits an external object, the shock absorber 80 that fixedly surrounds the outer perimeter of the second transmission segment 72 of the tube shaft 70 over the bearing portions 75 can absorb the shocks thus produced, preventing breaking of the metal tube shaft 70 due to excessively high vibration level and simultaneously giving good protection to the drive shaft. Further, by means of the bearing portions 75, the tube shaft 70 of the second transmission member 60 can bear the output torque of the drive shaft of the engine, and thus, the marine propeller 10 is practical for use with a high horsepower engine.

In conclusion, subject to the design of the buffer spaces 56, the two-piece axle bushing 40 can achieve a soft start-up effect to effectively reduce vibration of the marine propeller 10 in the moment the engine starts up, thereby enhancing start-up stability and smoothness of the marine propeller 10. Further, the two-piece axle bushing 40 not only can absorb shocks to protect the engine but also can bear a high torque for high horsepower application.

Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.