Mounting of an auxiliary propelling device to a shaft

Abstract: For an existing propeller system having a propeller, propeller shaft (3) and propeller boss (2), and a tightening nut (5) screwed at the end of the shaft, an auxiliary structure for attachment thereto, having an auxiliary boss (A) being approximately cylindrical to enclose tightly said nut (5) of the existing propeller system and having an internal partition (A2) with a central through-hole (31). Various ways of pressing the partition against the nut are provided.

Description: The invention relates to a propeller system. To improve the propelling efficiency in existing boats, the technique of providing an auxiliary propelling device such as an AT fin (Addition Thruster Fin) at the rudder behind an ordinary propeller, or the technique of providing an auxiliary propelling device such as a PBCF (Propeller Boss Cup Fin) immediately behind the propeller to improve the efficiency of the propeller itself, have been proposed. But, in latter case, the axial space associated with the ordinary propeller shaft is very limited, and therefore it is necessary to enlarge the propeller shaft or to have a new propeller shaft. An object of the invention is to propose a propeller system having an auxiliary propelling device that can improve propelling performance without modification, or with minor modification, of an existing propeller shaft. DE-B-1293056 discloses a propeller system including a propeller shaft, a propeller including a propeller boss mounted on the shaft and a tightening nut threaded onto the shaft and maintaining the propeller boss thereon. US-A-4391567 also discloses a propeller system including a propeller shaft, a propeller including a propeller boss mounted on the shaft and means for maintaining the propeller boss on the shaft. According to the present invention there is provided a propeller system including a propeller shaft, a propeller including a propeller boss mounted on the shaft, a tightening nut threaded onto the shaft and maintaining the propeller boss thereon, and an auxiliary propeller device comprising: a cylindrical auxiliary propeller boss member having an interior divided into axially spaced first and second interior portions by an integral internal partition of said boss member, said boss member being fitted over the tightening nut and an end of the propeller shaft with said first interior portion forming means for accommodating therein the tightening nut; and an auxiliary tightening member at least partially accommodated in said second interior portion, said auxiliary tightening member defining means cooperating with the end of the shaft for forcing said internal partition in a direction to press against the tightening nut; said boss member having at a front end thereof at least one convex portion forming means which, when said auxiliary tightening member forces said internal partition in said direction, cooperates with a complementary concave portion of the propeller boss to fix said boss member to the propeller boss rotationally relative thereto and to prevent relative rotational displacement therebetween upon rotation of the propeller shaft. The invention can improve propelling performance in high speed boats or fishing boats, which requires no or little modification of the existing propeller shaft system. Preferably, said boss member and said internal partition comprise a unitary one-piece structure of the same material. Preferably, said internal partition has therethrough a central through-hole. In one embodiment of the invention said auxiliary tightening member comprises a bolt extending through said through-hole to be threaded into a screw hole in the end of the shaft, said bolt having a head positioned in said second interior portion and operable upon threaded tightening of said bolt to force said internal partition in said direction. In another embodiment of the invention said auxiliary tightening means comprises a nut positioned in said second interior portion and operable to be threadably tightened over an end portion of the shaft to extend through said through-hole to thereby force said internal partition in said direction. Preferably, said boss member has an interior step portion to engage an edge of a ring to be positioned on the shaft between the propeller boss and the tightening nut. Preferred embodiments of the invention will be described in conjunction with the following Figures: Fig. 1 shows a partial sectional view of the boat propelling portion before assembly with an auxiliary propelling device; Fig. 2 shows a partial sectional view of the first embodiment of the assembly structure of the auxiliary propelling device of the invention as mounted on the propelling portion of Fig. 1; Fig. 3 shows a partial sectional view of the boat propelling portion before assembly with auxiliary propelling device; Fig. 4 shows a partial sectional view of the second embodiment of the assembly structure of the auxiliary propelling device of the invention as mounted on the propelling portion of Fig. 3. First embodiment Fig. 1 shows the assembly structure of an ordinary propeller of a double-nut type. The fixture of propeller boss 2 (propeller blades not shown) to propeller shaft 3 is of the ordinary double-nut type. In other words, key 4 locks propeller boss 2 to propeller shaft 3 with respect to rotational movement. Tightening nut 5 is screwed onto screw portion 31 at the end of propeller shaft 3 against propeller boss 2. Tightening nut 6 is screwed onto screw portion 31 of propeller shaft 3 against tightening nut 5 in a reinforcing manner. Herein, the term "screw portion" will be understood to mean a threaded portion which is profiled to accept a nut or similarly threaded component in a complementary and tight relationship. Fig. 2 shows the assembly structure of an ordinary propeller of the double-nut type with the auxiliary propelling device A mounted thereon. On the internal peripheral surface of the rear end of boss part A1 of auxiliary propelling device A, internal partition A2 is formed with a through-hole at the center. One or more convex parts A3 are formed at the front end of boss part A1. Screw hole 32, having the same axis as the propeller shaft, is formed at end part of propeller shaft 3. Corresponding to the one or more convex parts A3 are one or more complementary concave parts 21 formed at the rear end of propeller boss 2. To install auxiliary propelling device A to ordinary propeller 1 of the double-nut type shown in Fig. 1, boss portion A1 of auxiliary propelling device A is fitted over and fitted with nut 5 and nut 6 at the end of propeller shaft 3. The convex part A3 of boss A1 of auxiliary propelling device A is engaged in a tightly complementary way with a corresponding concave part 21 of propeller boss 2. Assembly bolt 7 is screwed through spring washer 8 and screw hole 32 at the end of propeller shaft 3, the head 71 of bolt 7 abuts the rear end of internal partition A2, to thereby clamp internal partition A2 of auxiliary propelling device A with head 71 of assembly bolt 7. Thus boss A1 of auxiliary propelling device A is fixed rigidly to propeller shaft 3. Furthermore, boss A1 of auxiliary propelling device A is fixed very firmly in the radial direction because the gap formed between the external peripheral surface of nut 5 and the inner peripheral surface of boss A1 of auxiliary propelling device A, is very small. This assembly structure of auxiliary propelling device and propeller boss 2 rotate in the same direction at the same rotating speed. The result is that the plurality of blades set in almost the same radial direction (not shown) to each of boss A1 and 2, can generate thrust efficiently. Second embodiment Fig. 3 shows propeller 1 fixed with a tightening nut to prevent loosening at the end portion. Propeller boss 2 (propeller blades not shown) is fixed to propeller shaft 3 as follows. Propeller boss 2 is mounted onto propeller shaft 3 by means of key 4, tightening nut 5' and ring 10. Said tightening nut 5' screwed on screw portion 31 formed at end of propeller shaft 3 in a way similar to that described above regarding the first embodiment. Fig. 4 shows the assembly structure of auxiliary propelling device A mounted immediately behind propeller 1. On the internal peripheral surface of the rear end of boss part A1 of auxiliary propelling device A, internal partition A2 is formed with a through-hole at the center. One or more convex parts A3 are formed at the front end of boss part A1. This convex part A3 part engages in a tightly complementary concave part 21 formed in the rear end of propeller boss 2. Sectional part A4 is formed on the inner surface of the front end of boss portion A1 to engage ring 10. Tightening 7' nut fixes auxiliary propelling device A to propeller shaft 3. Tightening nut 7' is a pocket nut with the same screw size as tightening nut 5'. Nut 7' is formed with an angular head 73' on top of cap part 72'. Main part nut 71' is round shaped with an outer dimension about the same as the inner dimension of boss part A1 of auxiliary propelling device A. To fix the auxiliary propelling device A to propeller 1 with a tightening nut to prevent loosening as shown in Fig. 3, tightening nut 5 is fixed to shaft 3 and the front end of boss portion A1 of auxiliary propelling device A has concave part A3. Convex part A3 of boss A1 is engaged in a tightly complementary way with concave part 21 of propeller boss 2. Section part A4 of boss A1 of auxiliary propelling device A engages ring 10. Next, for the part of screw portion 31 at the end of propeller shaft 3 which is not screwed with tightening nut 5', tightening nut 7' is screwed through spring washer 8' from the rear end of boss portion A1 of auxiliary propelling device A. In other words, inserting a box wrench into angular head 73' of tightening nut 7' and screwing tightening nut 7' onto screw part 31 of propeller shaft 3, by contacting strongly end surface of tightening nut 7' with internal partition A2 of boss A1 of auxiliary propelling device A. Then boss A1 of auxiliary propelling device A will be fixed completely in the axial direction of propeller shaft 3. Convex part A3 of boss A1 of auxiliary propelling device A engages in a tightly complementary way a corresponding concave part 21 of propeller boss 2. With the additional locking mechanism provided by key 4, propeller 1 and auxiliary propelling device A will be also be fixed in the rotating direction of propeller shaft 3. Furthermore, through two places respectively at ring 10 and main part nut 71' of pocket nut 7', boss A1 of auxiliary propelling device A is constructed to be effectively integral with propeller shaft 3 and also fixed with propeller shaft 3 in the radial direction due to centrifugal force. Therefore, in the second embodiment, auxiliary propelling device A can be fixed immediately behind propeller boss 2 without restructuring the existing propeller shaft system. Thrust can be generated efficiently with a plurality of blades equipped in almost radial configuration at each boss A1 and boss 2 (not shown) by rotating same number of rotations in almost same direction between boss A1 of auxiliary propelling device A and propeller boss 2. While a particular embodiment of the invention has been disclosed, it is to be understood that various different modifications are possible and are contemplated as being within the true spirit and scope of the claims.

Claims: A propeller system including a propeller shaft (3), a propeller including a propeller boss (2) mounted on the shaft (3), a tightening nut (5 or 5') threaded onto the shaft (3) and maintaining the propeller boss (2) thereon, and an auxiliary propeller device comprising: a cylindrical auxiliary propeller boss member (A1) having an interior divided into axially spaced first and second interior portions by an integral internal partition (A2) of said boss member (A1), said boss member (A1) being fitted over the tightening nut (5 or 5') and an end (31) of the propeller shaft (3) with said first interior portion forming means for accommodating therein the tightening nut (5 or 5'); and an auxiliary tightening member (71 or 71') at least partially accommodated in said second interior portion, said auxiliary tightening member defining means cooperating with the end (31) of the shaft (3) for forcing said internal partition (A2) in a direction to press against the tightening nut; said boss member (A1) having at a front end thereof at least one convex portion (A3) forming means which, when said auxiliary tightening member forces said internal partition (A2) in said direction, cooperates with a complementary concave portion (21) of the propeller boss (2) to fix said boss member (A1) to the propeller boss (2) rotationally relative thereto and to prevent relative rotational displacement therebetween upon rotation of the propeller shaft (3). A propeller system as claimed in claim 1, wherein said boss member (A1) and said internal partition (A2) comprise a unitary one-piece structure of the same material. A propeller system as claimed in claim 1 or claim 2, wherein said internal partition (A2) has therethrough a central through-hole. A propeller system as claimed in claim 3, wherein said auxiliary tightening member comprises a bolt (7) extending through said through-hole to be threaded into a screw hole (32) in the end of the shaft (3), said bolt (7) having a head (71) positioned in said second interior portion and operable upon threaded tightening of said bolt (7) to force said internal partition (A2) in said direction. A propeller system as claimed in claim 3, wherein said auxiliary tightening means comprises a nut (7') positioned in said second interior portion and operable to be threadably tightened over an end portion (31) of the shaft (3) to extend through said through-hole to thereby force said internal partition (A2) in said direction. A propeller system as claimed in claim 5, wherein said boss member (Al) has an interior step portion to engage an edge of a ring (10) to be positioned on the shaft (3) between the propeller boss (2) and the tightening nut (5').

Inventors: NISHIYAMA SHIGEKI, NISHIYAMA, SHIGEKI, Nishiyama, Shigeki, c/o Mikado Propeller Co. Ltd.
Applicants: MIKADO PROPELLER, MIKADO PROPELLER CO., LTD.
Application year: 1995
Main classification: B63H23
IPC codes: B63H1, B63H23