Trim and tilt apparatus

A trim and tilt system for use with an outboard propulsion unit on a marine craft having a transom. The trim and tilt system comprises a stern bracket configured to be mounted on the transom of the marine craft and a swivel bracket for supporting the outboard propulsion unit. The swivel bracket is pivotally supported on an upper end of the stern bracket. There is also a tilt cylinder unit that has a lower end supported by the stern bracket and an upper end in pivotal engagement with the swivel bracket. The tilt cylinder unit pivotally supports a pair of trim cylinder units. Each of the trim cylinder units is on an opposite side of the tilt cylinder unit. Each said trim cylinder unit has a longitudinal axis, a lower end in pivotal arrangement with the tilt cylinder unit and a trim rod for engagement with the swivel bracket. The swivel bracket has means for aligning the trim rods therewith, whereby the force exerted by the swivel bracket on the trim cylinder unit is substantially along the longitudinal axis. There is also means for actuating the tilt cylinder unit and the trim cylinder units.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a trim and tilt system for use with an outboard motor mounted on a marine craft.

2. Description of Related Art

Conventional trim and tilt systems include a unitary trim and tilt cylinder apparatus, as disclosed in U.S. Pat. No. 5,032,094, issued Jul. 1, 1991 to Sadaji Katogi, hereinafter Katogi. Katogi discloses a trim and tilt system for trimming and tilting an outboard propulsion unit on a boat. The trim and tilt system disclosed by Katogi includes a unitary trim and tilt cylinder apparatus having a tilt cylinder unit and a trim cylinder unit, a stem bracket adapted to be mounted on the transom of the boat, a swivel bracket for supporting the outboard propulsion unit, the swivel bracket being pivotally supported on an upper end of the stem bracket, and a hydraulic pressure circuit for actuating the tilt cylinder unit and the trim cylinder unit. The trim and tilt cylinder apparatus has an upper end pivotally supported on the stern bracket and a lower end pivotally supported on the swivel bracket.

The trim and tilt system disclosed by Katogi has the disadvantage of undue stress being applied to the trim cylinder units at a point of contact of a trim rod of each of the trim cylinder units with the swivel bracket. This excessive stress is in part due to the unitary construction of the trim and tilt cylinder apparatus. As the outboard propulsion unit pivots during the trimming and tilting procedure, the angle of the trim rods of each of the trim cylinder units changes with respect to the swivel bracket. The weight of the propulsion unit is therefore applied to the trim rod through the swivel bracket at various angles throughout the trimming procedure. This leads to a considerable amount of transverse stress being applied between the trim rods and their respective trim cylinders, leading to undue wear and fatigue.

There is therefore a need for a new and improved trim and tilt system that reduces the stress experienced by trim cylinder units during the trimming of a marine propulsion unit.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a trim and tilt system for use with an outboard propulsion unit on a marine craft having a transom. The trim and tilt system comprises a stem bracket configured to be mounted on the transom of the marine craft and a swivel bracket for supporting the outboard propulsion unit. The swivel bracket is pivotally supported on an upper end of the stem bracket. There is also a tilt cylinder unit that has a lower end supported by the stem bracket and an upper end in pivotal engagement with the swivel bracket. The tilt cylinder unit pivotally supports a pair of trim cylinder units. Each of the trim cylinder units is on an opposite side of the tilt cylinder unit. Each said trim cylinder unit has a longitudinal axis, a lower end in pivotal arrangement with the tilt cylinder unit and a trim rod for engagement with the swivel bracket. The swivel bracket has means for aligning the trim rods therewith, whereby the force exerted by the swivel bracket on the trim cylinder unit is substantially along the longitudinal axis. There is also means for actuating the tilt cylinder unit and the trim cylinder units.

According to a second aspect of the present invention there is provided a method of reducing stress on a trim cylinder unit of a trim and tilt system during trimming and tilting of a marine propulsion unit, the stress resulting from the weight of the marine propulsion unit being transmitted through a swivel bracket to the trim cylinder unit, the method comprising the step of transmitting the weight of the marine propulsion unit substantially along the longitudinal axis of the trim cylinder unit throughout the trimming of the marine propulsion unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings and first toFIG. 1there is shown a trim and tilt system, indicated generally by reference numeral10, for trimming and tilting an outboard propulsion unit13. The trim and tilt system10is operatively mounted on a transom11of a marine craft12and operates to position the propulsion unit13between a lower position and an upper position. The trim and tilt system10includes a stem bracket14, a swivel bracket16and a trim and tilt cylinder apparatus which is indicated generally by reference numeral18.

The stern bracket14is mounted on the transom11of the marine craft12. The swivel bracket16supports the outboard propulsion unit13, and is pivotally connected with the marine craft12at pivotal connection20which is located at an upper end of the stem bracket14. The trim and tilt cylinder apparatus18has a lower end supported by the stern bracket14and is pivotally connected at an upper end with the swivel bracket14at pivotal connection22, which is best shown inFIGS. 14 and 15.

Referring now toFIGS. 2 to 5, in which the trim and tilt cylinder apparatus18is shown in greater detail, the trim and tilt cylinder apparatus18comprises a tilt cylinder unit24and at least one trim cylinder unit26, of which there are two in this example. The trim cylinder units26are on opposite sides of the tilt cylinder unit24. The tilt cylinder unit24has a tilt cylinder28, a tilt rod30and a piston (not shown) inside the tilt cylinder28which is connected to the tilt rod30. The tilt rod30extends from a top32of the tilt cylinder28. There is a clevis34, in the form of an annular ring in this example, at an end of the tilt rod30that extends from the top32of the tilt cylinder28. The clevis34is pivotally connected with the propulsion unit13, e.g. a motor, of the marine craft12.

Each of the trim cylinder units26has a trim cylinder36, a trim rod38and a piston40, which are best shown inFIG. 6for this example. As shown inFIG. 2, each of the trim cylinder units26has a pivotal connection42with the tilt cylinder unit24. In this example, each of the pivotal connections42of the trim cylinder units26are pivotally independent of each other, allowing the trim cylinder units26to move independently of each other, however this is not a requirement of the present invention. Each of the trims rod38extend out of respective ones of the trim cylinders36at an end opposite to the pivotal connections42. Referring back toFIG. 6, in this example each of the trim rods38has a bore39at an end that extends from respective ones of the trim cylinders. The bore39of each of the trim rods38has a ball bearing44pressed therein. The piston40is connected with the trim rod38and moves along a longitudinal axis of the trim cylinder36.

FIG. 7shows a trim cylinder unit26.1according to another embodiment wherein like parts have been given like reference numerals with the additional numerical designation “.1”. In the embodiment ofFIG. 7the piston40.1is in the form of a washer41and over-molding43. The over-molding43being a resilient member. This embodiment of the trim cylinder unit26.1further allows for a pivotable trim receiver to be threadedly received at an aperture39.1of the trim rod38.1allowing for engagement of the of the trim cylinder unit and projections on the swivel bracket in alternate embodiments of the invention.

FIG. 8shows a trim cylinder unit26.2according to yet another embodiment wherein like parts have been given like reference numerals with the additional numerical designation “.2”. In the embodiment ofFIG. 8the trim cylinder36.2is provided with a bore37at an upper end thereof which hydraulically connects the interior of the trim cylinder36.2to a down gallery53leading to a pumping unit. This permits up relief by allowing fluid to re-circulate, as shown generally by arrows110, when the trim rod38.2is fully extended outside the trim cylinder36.2. This inhibits the generation of high pressures and excessive motor current draw. It will be understood by a person skilled in the art that a similar bore may be provided on the tilt cylinder as a means of providing up relief.

Referring again toFIGS. 2 to 5, in this example, the trim and tilt cylinder apparatus18also includes a pumping unit50and a reservoir52for providing hydraulic fluid to the tilt cylinder unit24and each of the trim cylinder units26. The pumping unit50, the reservoir52, the tilt cylinder unit24, and the trim cylinder units26form a hydraulic circuit. Hydraulic fluid is pumped into and out of the cylinders28and36during operation of the trim and tilt apparatus18in order to move the marine propulsion unit13between the lower position and the upper position during the trim and tilt procedure.

The trim and tilt apparatus18further includes a pair of trim receivers60, each configured with respective ones of the trim cylinder units26. The trim receivers60have a concave surface in this example and are best shown inFIGS. 9 and 10. Each of the trim receivers60has a bore62and is connected with the swivel bracket14at respective pivotal connections63as shown inFIGS. 13,14and15. The pivotal connections63allow pivotation of respective ones of the trim receivers60allowing engagement with respective ones of the trim rods38, as will be explained in more detail below.

In this example, each trim receiver60has a first surface64, a second surface66and a receptacle68therebetween. The first and second surfaces64and66are arranged at an inclination with respect to each other with the receptacle68forming a vertex of the concave surface. Each of the trim receivers60is in operative correspondence with respective ones of the trim rods38of the trim cylinder units26. In an another embodiment, the trim receivers may form the shape of a spherical cone as illustrated inFIG. 11, where the radius r varies according to the equation r=R+x, where R is a minimum radius and x=1, 2, 3, 4, etc. Alternately, in yet another embodiment the trim receiver may be in the form of a three-dimensional concave or parabolic receptacle for receiving respective ones of the trim rods.

In this example the trim and tilt cylinder apparatus18further includes a pair of pads74for each of the trim cylinder units26which are best shown inFIGS. 2,3, and4. The pads are aluminum pads in this example, but can be resilient pads in other embodiments, e.g. non-linear springs, non-linear rubber bumpers or polyurethane pads. The pads74may also be inserts which can be installed and removed. The pads74act to limit the pivotation of each of the trim cylinder units26about respective ones of the pivotal connections42. The trim rods38are held in operative engagement with the trim receivers60by limiting the pivotation of the pivotal connections42, as will be explained in more detail below.

In operation, when the propulsion unit13of the marine craft12is to be moved from the lower position to the upper position, the pumping unit50actuates the tilt cylinder unit24and the trim cylinder units26from the position shown inFIG. 13. The tilt rod30extends from the tilt cylinder28causing the swivel bracket16to pivot upwardly about connection22. The trim rods38extend from respective ones of the trim cylinders36causing the ball bearings44on the trim rods38to come into operative engagement with respective ones of the trim receivers60on the swivel bracket thereby pivoting the swivel bracket16upwardly at connection20. This phase of the operation is considered the trimming phase.

The trimming phase ends when the trim rods38are fully extended out of the trim cylinders36, as shown inFIG. 14. After the trim rods38have extended fully out of the trim cylinders36, the tilt rod30continues to pivot the swivel bracket16, and the trim receivers60move away from the ball bearings44of the trim rods38, as shown inFIG. 15. This phase of the operation is considered the tilting phase of the operation. The swivel bracket16continues to pivot at connection20until the tilt rod30is fully extended out of the tilt cylinder28.

Considering now the opposite motion, when the trim and tilt apparatus10moves the marine propulsion unit13between the upper position and the lower position. The pumping unit50actuates the tilt cylinder unit24to retract the tilt rod30into the tilt cylinder28, thereby causing the swivel bracket16to pivot downwardly about the connection22. Eventually the trim receivers60on the swivel bracket16come into contact with respective ones of the ball bearings44on each of the trim rods38.

In this example, the ball bearings44come into contact with one of either the first surface64or the second surface66of respective ones of the trim receivers60, which then guide the trim rods38towards the receptacles68. Normally, the ball bearings44of the trim rods38initially contact the first surface64of respective ones of the trim receivers60. The trim receivers60then pivot so that the force exerted by the trim receivers60on the trim rods38is along the longitudinal axis of the trim cylinder units26.

The pumping unit50continues to actuate the tilt cylinder unit24, and also the trim cylinder units26so that the trim rods38retract into respective ones of the trim cylinders36, until both the tilt rod30and the trim rods38are fully retracted in the respective tilt cylinder28and trim cylinders36, as shown inFIG. 13.

The trim receivers60of the present invention provide the advantage of allowing the trim rods38to self align within the trim receivers60, such that as the propulsion unit13is moved between lower and upper positions the force exerted by the propulsion unit13through the trim receivers60on the trim rods38is substantially along the longitudinal axis of the trim cylinders36and the trim rods38. This minimizes the stress put on the trim cylinder units26as the propulsion unit13is moved between the lower and the upper positions, and also allows the trim cylinder units26to handle a greater load.

Another advantage of the present invention is achieved by the pads74, which limit the pivotal range of the pivotal connections42. The predetermined range of the pivotal connections42ensures that the trim rods38will always come into operative engagement with respective ones of either the first surface64of the trim receiver60, the second surface of the trim receiver66or directly with the receptacle68of the trim reciever.

As will be apparent to those skilled in the art, various modifications may be made within the scope of the appended claims.