Seal Arrangement Between an Outdrive Unit and a Hull of a Vessel

This invention relates to a seal arrangement between an outdrive unit and a hull of a vessel such as a sailing boat.

The applicant's U.K. Pat. No. 1,569,661 (sealing date Aug. 20, 1981) has disclosed a sealing arrangement shown in FIG. 1, wherein an outdrive unit 1 comprising an upper unit 2 and a lower unit 3 is shown in vertical section. An end of an input shaft 4 arranged in the upper unit 2 is connected to an engine (not shown), and the other end of the shaft 4 is connected to a drive shaft 5 through a dog clutch mechanism 6 operable between forward, neutral and reverse positions. The drive shaft 5 is connected to a propeller shaft 7 through a bevel gear mechanism 8 arranged in the lower end of the lower unit 3.

The outdrive unit 1 passes through an opening 10 in a hull 9 of a vessel, and is installed on an installation bed 11 of the hull 9 by means of pairs of brackets 12 with vibration isolating rubbers 13 or other vibration-proof means therebetween. The lower unit 3 projects downward and out of the hull 9 through the opening 10. An annular seal flange 14 is secured to the bed 9 by bolts (not shown). An outer edge of an annular rubber diaphragm seal 15 is pinched and secured between the flange 14 and the bed 9. The inner edge of the seal 15 is pinched and secured between the upper unit 2 and the lower unit 3. The seal 15 covers and seals the opening 10. A radially middle portion 15a of the seal 15 is bent and projects upward, whereby flexibility and damping effect are increased.

The radially inner portion of the flange 14 is situated above the diaphragm seal 15 and projects toward the outdrive unit 1. The seal flange 14 has a groove 14a at the inner edge thereof, into which a radially outer portion of a ring seal 16 having an inverse U-shaped section is fitted. The radially inner portion of the ring seal 16 is elastically pressed to the cylindrical surface of the outdrive unit 1. Thus, a double seal arrangement is performed by the diaphragm seal 15 and the ring seal 16.

In the above arrangement, since the lower diaphragm seal 15 has the bent portion 15a projecting upward (or downward), and therefore has sufficient elasticity, the vibration of the engine is not transmitted to the hull 9 through the diaphragm seal 15. However, since the outer portion of the ring seal 16 is engaged into the groove 14a in the flange 14, and the inner portion thereof is strongly pressed to the outdrive unit 1, the ring seal 16 has less elasticity, which results in a disadvantage that the vibration of the engine is transmitted to the hull 9 through the ring seal 16.

In order to dissolve the above disadvantage, the applicant has developed a structure shown in FIG. 2, which is not the invention. In FIG. 2, an annular lip 16a is formed at the inner edge of the ring seal 16 fitted into the groove 14a in the seal flange 14. The lip 16a is pressed to the outer surface of the outdrive unit 1. In this structure, when the outdrive unit 1 swings forward or rearward by thrust during forward driving or reverse driving, a part of the soft lip 16a is further compressed and deformed, and another part may be parted from the outdrive unit 1. Therefore the ring seal 16 may not function as sealing means.

Accordingly, it is an object of the invention to provide an improved seal arrangement, overcoming the above-noted disadvantages, wherein both ends of an upper ring seal are fastened to an outdrive unit and an inner edge of an annular seal flange, respectively.

Another object of the invention is to detect water entered into the space between the upper ring seal and a lower diaphragm seal by means of a water sensor arranged therebetween and connected to warning means, when the lower diaphragm seal is torn or cracked.

Other and further objects, features and advantages of the invention will appear more fully from the following description of the preferred embodiments of the invention.

FIG. 1 is a vertical section view of a known seal arrangement according to the applicant's U.K. Pat. No. 1,569,661.

FIG. 2 is a fragmentary vertical section view of another seal arrangement developed by the applicant, which is not the invention.

FIG. 3 is a fragmentary vertical section view of a seal arrangement according to the invention.

In FIG. 3, wherein members corresponding to those in FIGS. 1 and 2 bear like reference numerals, an annular seal flange 14 has an upward vertical end 17 of cylindrical form at the radially inner edge thereof around an outdrive unit 1. A lower part of the vertical end 17 has a smaller diameter than the upper part, and an annular stepped surface 17a faced downward is formed between the upper and lower parts of the cylindrical outer surface of the vertical end 17. A similar stepped surface 1a faced downward is formed at the outer surface of the outdrive unit 1. The surface 1a is formed at a position slightly below the position of the surface 17a. A thin ring seal 18 of a diaphragm, which is made from rubber or other elastic material, has, for example, a substantially inverse U-shaped section or other section. The outer cylindrical wall of the ring seal 18 has an inner surface, at the lower end of which an annular stepped surface 19b faced upward is formed. The inner cylindrical wall of the ring seal 18 has an inner surface, at the lower end of which an annular stepped surface 19a faced upward is formed. The ends of the cylindrical walls of the ring seal 18 are fitted and fastened to the outer surfaces of the vertical end 17 and the outdrive unit 1 respectively by bands 21. The stepped surfaces 19a and 19b of the ring seal 18 are engaged to the stepped surfaces 1a and 17a of the outdrive unit 1 and the vertical end 17 of the seal flange 14, respectively. In this manner, a space 20 between the outdrive unit 1 and the seal flange 14 is sealed by the ring seal 18. Both ends of each fastening band 21 are set and connected together by set screws 22. Cloth for reinforcement may be arranged on or inside the surface of the ring seal 18. The lower diaphragm seal 15 has the required, sufficient strength. However, since the ring seal 18 is employed as an auxiliary, extremely high strength is not required for the ring seal 18. Therefore such ring seal 18 is preferably employed that is softer than the diaphragm seal 15, so that vibration may efficiently be absorbed.

The seal flange has a threaded hole 25 at the radially middle portion, into which electric water sensor 26 is screwed. The sensor 26 has two electric terminals 27 situated in a space 28 between the diaphragm seal 15 and the ring seal 18 as well as the seal flange 14. The sensor 26 is connected through amplifier circuit (not shown) to warning means such as a warning lamp (illuminant diode), a buzzer and/or the like mounted on an instrument panel in a control room.

As stated hereinbefore, since the ring seal 18 is fastened to the outdrive unit 1 and the seal flange 14, the outdrive unit 1 does not part from the ring seal 18, even when the outdrive unit 1 is swung by the thrust. Furthermore, since the ring seal 18 is of diaphragm type made from the elastic material, and the ends thereof are fixed to the unit 1 and the flange 14, the ring seal 18 has sufficient elasticity. Thus, the ring seal 18 can prevent the vibration of the engine and the outdrive unit 1 from being transmitted to the hull.

Further, according to the embodiment in FIG. 3, since the electric water sensor 26 connected to the warning means is arranged in the space 28 between the both seals 15 and 18, in the event of such accident that the lower seal 15 is torn or cracked and, therefore, water enters into the space 28, both terminals 27 are electrically connected to each other through the water. By this operation, the sensor 26 detects the entry of the water, and the warning means gives an alarm. Thus the safety and reliability can increase, because the cracked seal 15 can be exchanged before starting on a long cruise, and if not so, the ship can safely go on cruising to the nearest port with using the upper ring seal 18.

Said applicant's U.K. Pat. No. 1569661 has disclosed a water sensor having a float in a space between two seals. Such sensor of float type may be employed instead of the sensor 26 having the terminals 27 for detecting the entry of the water. However, the sensor of float type has large size, and furthermore, may give a mis-alarm when the float inclines during rolling and pitching. On the contrary, the sensor 26 in FIG. 3 has small size, and is not influenced by rolling and pitching. Therefore it is preferable to employ the sensor 26 in FIG. 3.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form may been changed in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.