MOUNT FOR A BOAT PROPULSION UNIT

Abstract

A mount for a boat propulsion unit comprises a collar for mounting around an aperture in a boat's hull, the collar having an annular groove on an inner surface thereof; a first mating part for mounting an inboard portion of a propulsion unit to the boat; and a second mating part, connectable to the first mating part, for mounting an outboard portion of a propulsion unit to the boat. The first and second mating parts are connectable through the collar and are configured such that when they are connected they form an external annular recess in an outer surface and an annular gasket is located partly in the groove and partly in the recess to form a seal there-between.

Description

FIELD OF THE INVENTION

This invention relates to a mount for a boat propulsion unit. Particularly, but not exclusively, the invention relates to a mount for mounting an inboard propulsion unit in a boat hull.

BACKGROUND TO THE INVENTION

Aspects of the present invention are particularly concerned with the mounting of electric propulsion units that consist of a saildrive projecting from the bottom of a boat's hull and that have an inboard motor mounted above the saildrive. In essence, a saildrive can be considered as a sailboat's equivalent of a motorboat's sterndrive, which projects from the stern of a boat and usually has a drive mounted outside of the hull (and is therefore also known as an outdrive). A saildrive is significantly different to a traditional inboard motor since it is not connected to the motor via a standard propeller shaft. Instead, inside a saildrive casing there is normally an L-gear that consists of a vertical (pinion) shaft, a horizontal (propeller) shaft and a bevel gear. A compact electric motor can then be positioned above the saildrive with the motor drive shaft extending downwardly through the hull to create a very compact unit maximizing the space in inside the boat.

An electric propulsion unit, such as that described above incorporating a saildrive, is normally rigidly mounted to the bottom of a boat either directly to the hull or onto a motor bed. Such a rigid mounting is fairly easy to achieve, however, a disadvantage is that a rigid mounting will transfer any vibrations caused by the propeller directly to the structures of the boat. This may result in noise, vibrations and, in the worst case, damage to some structures. It will also be understood that it is necessary to seal the gap between the drive/propulsion unit and the hull to prevent water ingress.

U.S. Pat. No. 7,690,959 discloses a mount suitable for a very large inboard drive unit. A simplified illustration of this arrangement is provided in FIG. 1 which shows a cross-section through one side of the mount 10. A first mounting plate 12 is provided on an upper portion of the boat drive unit and has an upwardly facing frustoconical mounting surface 14. A second mounting plate 16 is provided within the hull and has a downwardly facing frustoconical mounting surface 18. A mounting collar 20 is provided in the boat hull and includes a peripheral flange 22 extending inwardly of the collar and having a first frustoconical mounting surface 24 facing upwardly and second frustoconical mounting surface 26 facing downwardly. Two compressible rings 28 are provided between the mounting surfaces 24, 26 of the collar 20 and the respective mounting surfaces 14, 18 of the first and second mounting plates 12, 16. Thus, it can be seen that, in use, each of the rings 28 will be compressed between opposed parallel surfaces such that each ring 28 will be subjected to forces applied substantially through its centre (i.e. from a contact point at one side of the ring 28 to a contact point at the diametrically opposite side of the ring 28). In other words, the first and second mounting plates 12, 16 in this arrangement provide a compressive force directly through each ring 28 to the collar 20 to seal the gap there-between.

European patent application No. EP 0,811,511 discloses another mounting system for use with a sterndrive propulsion unit and which employs a very similar sealing arrangement to that described above.

It is an aim of the present invention to provide an alternative mount for a boat propulsion unit.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a mount for a boat propulsion unit comprising:

• • a collar for mounting around an aperture in a boat's hull, the collar having an annular groove on an inner surface thereof;
  • a first mating part for mounting an inboard portion of a propulsion unit to the boat;
  • a second mating part, connectable to the first mating part, for mounting an outboard portion of a propulsion unit to the boat;
  • the first and second mating parts being connectable through the collar and being configured such that when they are connected they form an external annular recess in an outer surface; and
  • an annular gasket locatable partly in said groove and partly in said recess to form a seal there-between.

Embodiments of the invention effectively provide a flexible mounting arrangement in which the traditionally separate elements required for fixing two parts together and sealing the space between them is combined in a single component by way of the gasket of the present invention. Thus, the gasket serves to provide a watertight seal between the collar and the first and second parts; acts as a flexible (“floating”) mounting for the propulsion unit in the boat's hull; and also serves to transfer the power generated by the propulsion unit to the boat. An advantage of the present invention is that the gasket can absorb (or at least dampen) vibrations and thereby prevent (or minimise) the transfer of such vibrations from the propulsion unit to the boat since there is no rigid fixing or hard contact between the boat and the propulsion unit. The mount requires only a few discrete components and has a simple construction making it quick and easy to install. There is also no need for any electrical connections between the boat and the propulsion unit. Furthermore, the mount can be made to be compact and light and yet strong.

In use, the first and second mating parts may be configured to apply a force to compress the gasket when the first and second mating parts are connected. The force may be applied generally vertically through a portion of the gasket received in the recess. Thus, the force to compress the gasket may be transmitted through the innermost side of the gasket causing the gasket to expand radially outwardly into the groove to seal against the collar.

The applicants have found that the shape of the groove in the collar and the shape of the recess formed by the first and second mating parts can influence the power transfer and vibration dampening properties of the mount. Accordingly, the shapes of the groove and recess should be careful chosen to provide the desired properties.

The groove and the recess may have similar or different cross-sections.

The groove and/or the recess may be generally V-shaped or C-shaped. Thus, the groove and/or the recess may be formed by two inclined annular surfaces having an angle of less than 180 degrees there-between. The angle may be between 180 degrees and 90 degrees but is preferably 90 degrees or less. The inclined surfaces may join via a curved interface or a straight (e.g. vertical) interface. In certain embodiments, the groove and/or recess may be part-circular, for example, hemispherical.

The gasket may comprise rubber and may be in form of an O-ring. As above, the type of rubber employed in the gasket may influence the power transfer and vibration dampening properties of the mount.

The gasket may be substantially toroidal forming a circle in plan view. Alternatively, the gasket may be substantially oval, obround or elongated in plan view. The use of an oval, obround or elongated gasket may be particularly advantageous since it has been found that approximately 80% of the forces applied to the gasket in use are likely to be in the forwards and backwards directions and these can be most effectively managed by having a gasket elongated in the forwards and backwards directions.

It will be understood that the plan view shape of the groove and the recess will be required to correspond to the shape of the gasket so that the gasket can be partly received in the groove and the recess, when in use. Although not strictly necessary, the shapes of the collar and/or the first and second mating parts may also generally correspond to the shape of the gasket in plan view.

The gasket may have a vertical cross-section that is substantially circular. However, other cross-sections may be employed to impart specific characteristics to the gasket (e.g. to influence the compression characteristics and/or the load transfer characteristics of the gasket).

The collar may be substantially cylindrical or may be constituted by a substantially oval, obround or elongate section of tubing. As above, the applicants have found that the shape and size of the collar can affect the power transfer and vibration dampening properties of the mount and so these should also be carefully chosen to provide the desired results.

The collar may be affixed in a hole in the boat's hull or it may be integrally formed with the hull (e.g. by moulding the hull including the collar from glass reinforced plastic). Alternatively, the collar may be laminated in the boats hull. Where the collar is a discrete component for affixing to the hull, it may be formed from glass reinforced plastic, steel, aluminium or other durable materials.

The first and second mating parts may be made of metal and may be configured to form a continuous channel there-through.

The first mating part may be provided on a motor and the second mating part may be provided on a propeller unit such as a saildrive.

The first and second mating parts may be connectable via an attachment mechanism which may comprise complementary inter-engaging parts and may be configured for screwing the first and second parts together. Alternatively, the attachment mechanism may be constituted by a bayonet-type or other mechanical fastening.

The propulsion unit may be in the form of an inboard propulsion unit, an outboard propulsion unit, an electric propulsion unit, an internal combustion propulsion unit, a saildrive propulsion unit or a so-called propulsion pod unit.

According to a second aspect of the present invention there is provided a boat propulsion unit comprising a mount according to the first aspect of the present invention.

According to a third aspect of the present invention there is provided a boat comprising a mount according to the first aspect of the present invention.

According to a fourth aspect of the present invention there is provided a method of mounting a propulsion unit on a boat comprising:

• • providing a collar around an aperture in a hull of the boat, the collar having an annular groove on an inner surface thereof;
  • locating an annular gasket in the collar so that the gasket partly resides in said groove;
  • providing a first mating part on an inboard portion of a propulsion unit and a second mating part, connectable to the first mating part, on an outboard portion of a propulsion unit; and
  • connecting the first and second mating parts through the collar so that the first and second mating parts form an external annular recess in which said gasket is partly located.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the present invention will now be described in detail with reference to the accompanying drawings, in which:

FIG. 1 shows a cross-sectional view of one side of a prior art mounting arrangement for a boat propulsion unit;

FIG. 2A shows an exploded view of a mount according to a first embodiment of the present invention;

FIG. 2B shows a part cross-sectional view of an assembled mount, similar to that shown in FIG. 2A, when attached to an inboard motor and saildrive of a boat according to a second embodiment of the present invention;

FIG. 3 shows a part cross-sectional view of a mount similar to that shown in FIG. 2A when assembled;

FIG. 4 shows an enlarged cross-sectional view of a portion of the mount of FIG. 2B showing that the gasket is located in a groove having faces angled 90 degrees apart;

FIG. 5 shows an enlarged cross-sectional view of a portion of a mount according to a third embodiment of the present invention, wherein a gasket is located in a groove having faces angled 75 degrees apart;

FIG. 6 shows an enlarged cross-sectional view of a portion of a mount according to a fourth embodiment of the present invention, wherein a gasket is located in a groove having hemispherical faces;

FIG. 7A shows an enlarged cross-sectional view of the mount of FIG. 2B, showing an attachment mechanism prior to assembly of the mount; and

FIG. 7B shows a view similar to that shown in FIG. 7A after the attachment mechanism has been employed to assemble the mount.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

With reference to FIG. 2A, there is illustrated a mount 30 for a boat propulsion unit (not shown) according to a first embodiment of the present invention. The mount 30 comprises a hollow generally cylindrical collar 32 (also known as a motor bed). In this embodiment, the collar 32 is designed to be integrally moulded within a hole in the bottom of a boat's hull (not shown). The collar 32 includes an inner annular groove 34 configured to partly receive an annular rubber gasket in the form of O-ring 36. In this particular embodiment, the collar 32 also includes an annular bulge 37 on its external surface, to accommodate the inner annular groove 34.

It will be noted from FIG. 2A that the mount 30 has a generally obround shape when viewed from above. As stated previously, this shape is advantageous in handling the forwards and backwards forces applied to the mount 30 when in use.

The mount 30 further comprises an upper part 38 configured for attachment to an inboard motor or its housing (not shown) and a lower part 40 configured for attachment to a saildrive unit (not shown). Although not shown in the Figures, the upper part 38 and the lower part 40 will be hollow in practice to allow a motor drive shaft to extend through the mount 30 to operate the saildrive. The upper and lower parts 38, 40 also include an attachment mechanism (not shown) which is described below in relation to FIGS. 7A and 7B.

In use, the upper and lower parts 38, 40 are attached together by inserting the upper part 38 into the collar 32 from within the boat and inserting the lower part 40 into the collar 32 from below the boat. The parts 38, 40 are shaped in such way that they will form a recess into which the gasket 36 will be partly located so that the parts 38, 40 can apply pressure on the gasket 36 when they are engaged and tightened together. This constant pressure (pre-stress) will serve to provide a watertight seal between the hull and the propulsion unit as well as providing a flexible mounting for the unit. It will be understood that a suitable pressure will required in order keep the mount 30 properly sealed also when thrust is applied to the boat.

In this particular embodiment, the upper part 38 has a downwardly extending frustoconical surface 42 terminating in a short cylindrical surface 44. The lower part 40 has an upwardly extending frustoconical surface 46 also terminating in a short cylindrical surface 48. The frustoconical surfaces 42, 46 are inclined such that they form an angle there-between of approximately 90 degrees when the upper and lower parts 38, 40 are engaged.

The applicants have determined several ways to adjust the vibration dampening and sealing properties of the mount 30. More specifically, they have discovered that by increasing the size of the collar 32 and parts 38, 40 the mount 30 can be configured to suit larger or more powerful propulsion units. In addition, the shape of the collar 32 can be changed depending on the nature of the drive to be used. A fixed drive is thought to benefit from an oval shaped mounting (as per FIG. 2A) while a round collar 32 is believed to be suitable for a rotating drive or pod-type propulsion unit.

The shape of the groove 34 in the collar 32, the shape of the recess formed by the parts 38, 40, the tightness of the engagement between the parts 38, 40 as well as the size of the gap between the collar 32 and parts 38, 40 are all considered to affect the “hardness” (or flexibility) of the mount 30. The more free space the gasket 36 has to deform into, the softer the mounting will be. A powerful unit may require a relatively hard mounting to keep movement of the propulsion unit to an acceptable level. By carefully choosing a combination of these properties a suitable level of vibration dampening can be achieved.

FIG. 2B shows a part cross-sectional view of an assembled mount 50, similar to that shown in FIG. 2A, when attached to a propulsion unit comprising an inboard motor 52 and saildrive 54 of a boat 56, according to a second embodiment of the present invention. The mount 50 comprises a hollow obround cylindrical collar 58 affixed within a hole in the bottom of the boat's hull 56. The collar 58 includes an inner annular V-shaped groove 60 configured to partly receive an annular rubber gasket in the form of O-ring 62.

As above, the mount 50 further comprises an upper part 64 which, in this case, is attached to the inboard motor 52 and a lower part 66 which, in this case, is attached to the saildrive 54. Also as described above, the upper part 64 and the lower part 66 will be hollow in practice to allow a motor drive shaft (not shown) to extend through the mount 50 to operate the saildrive 54 and the upper and lower parts 64, 66 also include an attachment mechanism (not shown) which is described below in relation to FIGS. 7A and 7B. The upper part 66 has a downwardly extending frustoconical surface 70 which mates with an upwardly extending frustoconical surface 72 of the lower part 66 to form a recess 74 in which the O-ring 62 is partly engaged. As above, the frustoconical surfaces 70, 72 are inclined such that they form an angle there-between of approximately 90 degrees when the upper and lower parts 64, 66 are engaged.

FIG. 3 shows a part cross-sectional view of a mount 80, similar to that shown in FIG. 2A, when assembled. The mount 80 is identical to that shown in FIG. 2A except that the mount 80 includes a collar 82 which has a thicker wall than the collar 32 and, as such, no external bulge is required in the collar 82 in order to provide for the annular groove 34.

FIG. 4 shows an enlarged cross-sectional view of a portion of the mount 50 of FIG. 2B showing the gasket 62 located in the groove 60, which is formed by inclined surfaces 90, 92 angled 90 degrees apart. As described above, the frustoconical surfaces 70, 72 of the upper and lower parts 64, 66 in this embodiment are inclined such that they form an angle of 90 degrees there-between when the upper and lower parts 64, 66 are engaged.

Although it is not evident from FIG. 4, it will be understood that when the first and second parts 64, 66 are attached to each other they will form a compressive force substantially vertically through the portion of the gasket 62 trapped there-between. This will cause the gasket 62 to bulge in a substantially outwardly direction so as to form a tight sealing fit within the groove 60.

FIGS. 5 and 6 show alternative shapes of grooves and recesses that may be employed in embodiments of the present invention. In each case, only one side portion of the mount is shown to illustrate the shapes of the grooves and recesses. In each case, the remainder of the mount is identical to that shown in FIG. 2B and so like reference numerals will be employed where appropriate.

FIG. 5 shows a mount 100, similar to that of FIG. 4 but wherein the inclined surfaces 90′, 92′ of the groove 60′ are angled 75 degrees apart and the frustoconical surfaces 70′, 72′ (forming the recess 74′) are also angled 75 degrees apart. Power vectors are also illustrated in FIG. 5 to show that the forces applied by the upper and lower parts 64′, 66′ in this embodiment are again directed generally vertically through the innermost side of the gasket 62.

FIG. 6 shows a further mount 110 wherein the groove 60″ and the recess 74″ each have respective hemispherical surfaces 112, 114 facing towards each other and enclosing the gasket 62 there-between. As per previous figures, for ease of clarity, the gasket 62 is not shown in a compression. It will, however, be understood that in use, the attachment of the first and second parts will exert a compressive force on the gasket 62 to ensure that it forms a sealing relationship with the collar.

FIGS. 7A and 7B show enlarged cross-sectional views of the mount 50 of FIG. 2B, before and after the first and second parts 64, 66 are attached. In this case an attachment mechanism is provided which comprises two screws 120 which are arranged to pass upwardly through respective holes 122 in the second part 66 to screw into complementary screw-threaded apertures 124 in the first part 64. In other embodiments, screws may be provided through the first part 64 into the second part 66.

As shown in FIG. 7B, when the screws 120 are tightened to secure the first and second parts 64, 66 together, the gasket 62 is compressed within the recess 74 and groove 60 both to seal the mount 50 and to transfer load from the propulsion unit to the boat hull.

Using an O-ring for attaching the propulsion unit to the boat hull is convenient as this kind of mechanical gasket is readily available as a standard part and will thus keep costs down. It is noted that O-rings are normally used only for sealing in either static or dynamic mechanical applications. However, in the present invention the O-ring is employed in a different way since (in addition to sealing the mounting) it will be the component that insures that the whole propulsion unit is secured to the boat as well as helping to dampen any vibrations.

It will be appreciated by persons skilled in the art that various modifications may be made to the above embodiments without departing from the scope of the present invention.

Claims

1. A mount for a boat propulsion unit comprising: a collar for mounting around an aperture in a boat's hull, the collar having an annular groove on an inner surface thereof;a first mating part for mounting an inboard portion of a propulsion unit to the boat;a second mating part, connectable to the first mating part, for mounting an outboard portion of a propulsion unit to the boat;the first and second mating parts being connectable through the collar and being configured such that when they are connected they form an external annular recess in an outer surface; andan annular gasket locatable partly in said groove and partly in said recess to form a seal there-between.

2. The mount according to claim 1 wherein the first and second mating parts are configured to apply a force to compress the gasket when the first and second mating parts are connected.

3. The mount according to claim 1 wherein the first and second mating parts are configured to apply a force to compress the gasket when the first and second mating parts are connected, and wherein the force is applied generally vertically through a portion of the gasket received in the recess.

4. The mount according to claim 1 wherein the first and second mating parts are configured to apply a force to compress the gasket when the first and second mating parts are connected, and wherein the force is applied through the innermost side of the gasket causing the gasket to expand radially outwardly into the groove to seal against the collar.

5. The mount according to claim 1 wherein the groove and the recess have similar cross-sections.

6. The mount according to claim 1 wherein the groove and/or the recess is generally V-shaped or C-shaped.

7. The mount according to claim 1 wherein the groove and/or the recess is formed by two inclined annular surfaces having an angle of less than 180 degrees there-between.

8. The mount according to claim 1 wherein the groove and/or the recess is formed by two inclined annular surfaces having an angle of less than 90 degrees there-between.

9. The mount according to claim 1 wherein the groove and/or the recess is formed by two inclined annular surfaces having an angle of less than 180 degrees there-between, and wherein the inclined surfaces join via a curved or a straight interface.

10. The mount according to claim 1 wherein the groove and/or recess is generally V-shaped or C-shaped, and wherein the groove and/or recess is part-circular.

11. The mount according to claim 1 wherein the gasket is circular, oval, obround or elongated in plan view.

12. The mount according to claim 1 wherein the collar is substantially cylindrical or constituted by a substantially oval, obround or elongate section of tubing.

13. The mount according to claim 1 wherein the collar is integrally formed in a boat's hull.

14. The mount according to claim 1 wherein the first mating part is provided on a motor and the second mating part is provided on a propeller unit.

15. The mount according to claim 1 wherein the first and second mating parts are connectable via an attachment mechanism.

16. The mount according to claim 1 wherein the first and second mating parts are connectable via an attachment mechanism, and wherein the attachment mechanism comprises complementary inter-engaging parts, or is configured for screwing the first and second parts together or is constituted by a bayonet-type fastening.

17. The mount according to claim 1 configured for mounting a propulsion unit in the form of an inboard propulsion unit, an outboard propulsion unit, an electric propulsion unit, an internal combustion propulsion unit, a saildrive propulsion unit or a propulsion pod unit.

18. The mount according to claim 1, the first and second mating parts being configured such that, when connected, they are able to accommodate a motor drive shaft passing axially through the mount.

19. A boat propulsion unit comprising a mount according to claim 1.

20. A boat comprising a mount according to claim 1.

21. A method of mounting a propulsion unit on a boat comprising: providing a collar around an aperture in a hull of the boat, the collar having an annular groove on an inner surface thereof;locating an annular gasket in the collar so that the gasket partly resides in said groove;providing a first mating part on an inboard portion of a propulsion unit and a second mating part, connectable to the first mating part, on an outboard portion of a propulsion unit; andconnecting the first and second mating parts through the collar so that the first and second mating parts form an external annular recess in which said gasket is partly located.