WO2004085245A1

WO2004085245A1 - Power transmission system

Info

Publication number: WO2004085245A1
Application number: PCT/ZA2004/000034
Authority: WO
Inventors: Michael Alan Beachy Head
Original assignee: Michael Alan Beachy Head
Priority date: 2003-03-26
Filing date: 2004-03-25
Publication date: 2004-10-07

Abstract

The present invention provides a stem drive comprising an input shaft (12), an upper gear set (18) including an input gear (118) driven by the input shaft, an output gear (22) and an intermediate gear (20) which transmits drive from the input gear (118) to the output gear (22). The intermediate gear is rotatable about a horizontal axis. An inclined drive shaft (100) extends downwardly from the gear (18) set and driven by the output gear (22). A lower gear set (102) driven by the drive shaft (100). A housing (98) carries the output gear (22), the lower gear set (102) and the drive shaft (100). The housing (98) is pivotable in an arc about the horizontal axis of the gear (20). The drive can further include two co-axial shafts that are rotated in opposite directions by the gear set (18). A reversing drive (98) permits the shaft (100) to be clutched to a selected one of the co-axial shafts.

Description

POWER TRANSMISSION SYSTEM

FIELD OF THE INVENTION

THIS INVENTION relates to a power transmission system,

BACKGROUND TO THE INVENTION

In the transmission of power there is frequently a need for not only forward drive but also for reverse drive with a neutral, disengaged position between forward drive and reverse drive. A vast number of gear boxes have been proposed for this purpose and these are often preceded in the power train by a clutch which isolates the gear box from the drive motor to enable reverse or one of the forward gears to be engaged.

In marine drives, gear boxes are not used in the way that they are in, for example, road vehicles. Drive is transmitted directly to the propeller through a drive system which has only one gear ratio. The ability to move away from a stopped condition, and to run at full speed without gear ratios, is achieved by changing propeller pitch from fine to coarse as the rotational speed of the drive train increases. The ability to reverse the direction of rotation of the propeller is, however, still required.

In Figures 1 and 2 a conventional stern drive layout is illustrated. The transom of the vessel is designated T, the transom guard TG and the output shaft of the motor OS. A double universal joint is shown at U1 and U2.

An upper gear set is shown at G1 and the lower gear set at G2. Both gear sets are within the main housing designated H. The vertical drive shaft between the gear sets is designated V, the propeller shaft P and the two contra rotating propellers P1 and P2.

In its normal drive condition, the stern drive is as shown in Figure 1. For steering purposes the entire housing H is swung left or right about the vertical axis A1 which passes through the joint U1. Variations of the housing's angle take place about the horizontal axis A2 which passes through the joint U2.

Universal joints are undesirable in that they are prone to failure and difficult to maintain. They are difficult to align and cause vibrations when turning or changing pitch.

Despite all the proposals that have been made regarding marine drive configurations, there is still a need in the marine drive industry for a drive which overcomes the shortcomings of the conventional stern drive. There is also a need for a drive which can reverse the direction of rotation of a propeller and be of such a configuration that it is in line with the drive shaft. The present invention provides an improved stern drive and a reversible drive which, of course, can be used not only as a marine drive but in any circumstances where the direction of rotation of the output member of the power train needs to be reversed. BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the present invention there is provided a drive comprising a first shaft, means for rotating the first shaft in one direction, a second shaft co-axial with the first shaft, means for turning the second shaft in the opposite direction to the first shaft, a drive output member, and means for selectively clutching the first shaft or the second shaft to said output member.

The clutching means can comprise clutch elements carried by the shafts and further clutch elements carried by the output member.

Said second shaft can be within the first shaft and have a portion which protrudes from said first shaft, elements for selectively clutching the second shaft to the output member being carried by said protruding portion.

In a preferred embodiment the drive comprises a first cone, said first input shaft rotating said first cone in one direction, a second cone co-axial with the first cone, said second drive shaft for rotating said second cone in the opposite direction to the first cone, the cones tapering in opposite directions, a casing fast in rotation with said drive output member and having a first conical surface for clutching engagement with the first cone and a second conical surface for clutching engagement with the second cone, and means for displacing said casing axially with respect to said shafts to bring one or other of said cones into clutching engagement with the respective conical surface of said casing. According to a further aspect of the present invention there is provided a stem drive comprising an input shaft, an upper gear set including an input gear driven by said input shaft, an output gear and an intermediate gear which transmits drive from said input gear to said output gear, the intermediate gear being rotatable about a horizontal axis, an inclined drive shaft extending downwardly from said gear set and driven by said output gear, a lower gear set driven by said drive shaft, and a housing carrying said output gear, said lower gear set and said drive shaft, said housing being pivotable in an arc about said horizontal axis of said intermediate gear.

Said output gear is preferably co-axial with said inclined drive shaft.

In a specific embodiment said input shaft is horizontal and coaxial with said input gear, the axis about which the input shaft and input gear rotate intersecting, and being at right angles to, the horizontal axis about which the intermediate gear rotates.

To enable reverse and forward drive to be obtained, the drive can comprise a first output gear, a second output gear, the first and second output gears being co-axial and being contra rotated by said intermediate gear, a first reversing drive shaft driven by said first gear and a second reversing drive shaft driven by said second gear, a first cone rotated by said first reversing drive shaft, a second cone rotated by said second reversing drive shaft, the cones tapering in opposite directions, a casing fast in rotation with said drive output member and having a first conical surface for clutching engagement with the first cone and a second conical surface for clutching engagement with the second cone , and means for displacing said casing axially with respect to said shafts to bring one or other of said cones into clutching engagement with the respective conical surface of said casing.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which:-

Figure 3 is an axial section through a reversing drive in accordance with the present invention, the drive being in neutral;

Figures 4 and 5 are similar sections showing the drive in forward and reverse;

Figure 6 is a section through the drive's main housing;

Figure 7 illustrates the outer casing of a cone clutch;

Figure 8 illustrates the cones of the cone clutch;

Figures 9 and 10 are a top plan view and an elevation of an actuator;

Figure 11 illustrates a drive train; and

Figure 12 illustrates the drive train incorporated into a stern drive.

DETAILED DESCRIPTION OF THE DRAWINGS

In Figure 3, reference 10 designates a drive which comprises an input shaft 12 driven by a motor (not shown). The shaft 12 is mounted in a bearing 14 and rotates the first bevel gear 16 of gear set 18. The gear 16 rotates an intermediate gear 20 which in turn rotates a further gear 22. The gears 16 and 22 are co-axial.

To ensure balance there can be a further gear co-axial with the gear 20 and in mesh with the gears 16 and 22. The gear 20, or its co-axial gear if one is provided, can constitute the input gear and be fast in rotation with the shaft 12 which thus lies at right angles to the position illustrated.

The gear 22 is mounted on a shaft 24 which is carried by a bearing 26. The outer race of the bearing 14 is carried by a casing 28 of the gear set 18 and the outer race of the bearing 26 is carried by a main housing 30 of the drive 10.

The casing 28 is secured to the housing 30 by bolts 32.

The shaft 12 is extended beyond the gear 22 and is within, and coaxial with, the shaft 24. The shaft 12 has a portion, designated 34 (see particularly Figure 11), which protrudes beyond the end of the shaft 24.

A first cone 36 (see also Figure 8) is fast in rotation with the shaft 24 and a second cone 38 is fast in rotation with the portion 34 of the shaft 12. The cones 36, 38 taper in opposite directions.

The shaft 24 has a keyway 40 and the portion 34 of the shaft 12 has a keyway 42. Keys 44 and 46 of the cones 36, 38 fit in the keyways 40, 42 and thus the cones are rotated by their respective shafts 24, 12.

The cones 36, 38 are within an axially movable outer casing 48 (Figure 7) which comprises two hollow bells 50, 52. The bells 50, 52 have castellated rims which interengage and which are secured together by bolts 54.

The bell 50 includes a cylindrical spigot 56 which runs in the inner race of a bearing 58. The outer race of the bearing 58 is secured to the housing 30. The spigot 56 is free to slide in the inner race of the bearing 58. The shafts 12 and 24 pass with clearance through the spigot 56.

The bell 50 further includes two protruding rings 60, 62 which bound a peripherally extending gap 64 between them.

The bell 52 has a splined spigot 66 and an opening 68 (Figure 7) which connects a bearing space inside the spigot 66 with the hollow interior of the bell.

From the above description it will be appreciated that the casing 48 has two cone-shaped internal surfaces which taper in opposite directions and match the external configuration of the cones 36, 38.

The smaller diameter end 70 (Figure 11) of the shaft 12 passes through the opening 68 and is supported by a bearing (not shown) in the spigot 66. The housing 30 (see Figure 6) comprises two parts designated 72, 74 which are secured together by a set of bolts 76. The casing 48 is within the housing 30. The groove which receives the bearing 26 is designated 78 in Figure 6 and the groove which receives the bearing 58 is designated 80.

An output member 82 of the drive (see Figure 11) includes an internally splined socket 84 which meshes with spigot 66. A bearing 86 (Figures 3 to 5) mounts the member 82 in the housing part 74 of the housing 30. A further internally splined socket 88 of the member 82 meshes with an output shaft (not shown).

A selector 90 (see Figures 3, 4, 5, 9 and 10) enables forward, reverse or neutral to be selected. The selector 90 comprises a rod 92 on which a push or pull can be exerted by a mechanical or hydraulic actuator. A bifurcated bell crank lever 94 mounted at 96 has the ends of its fork in the gap 64 and converts rectilinear movement of the rod 92 to rectilinear movement of the casing 48.

The gear set 18 is such that the shafts 12, 24 rotate in opposite directions. In the position illustrated in Figure 1 , the drive is in neutral, the cones 36, 38 both being spaced from the inner conical surfaces of the casing 48. By shifting the casing 48 axially, either the cone 36 and bell 50 engage or the cone 38 and the bell 52 engage. Thus the member 82 can selectively be driven in opposite directions by the action of displacing the casing 48 axially. The cones 36, 38 can be replaced by other clutching means such as a set of clutch discs on each shaft 12, 24 and two sets of internal clutch discs carried by the casing 48.

In Figure 12 there is illustrated a stern drive comprises an inboard motor (not shown) which turns the shaft 12 and hence the gear set 18. The reversing drive described above, and designated 98 in Figure 10, is mounted in an inclined position between the gear set 18 and an inclined drive shaft 100 which extends downwardly to a further gear set 102 in a main housing 104. The gear set 102 drives co-axial contra rotating propeller shafts 106, 108 on which twin propellers 110 and 112 are mounted. It will be understood that a single propeller can be provided in which form there is a single shaft driven by a simpler gear set.

The shaft 12 is carried by two sets of bearings 114, 116 and drives a large gear 116 which rotates about the horizontal axis of the shaft 12.

The gear 118 drives the gear 20 (see Figure 3). It will be understood that, in the form shown in Figure 12, the shaft 12 intersects the axis about which the components of the reversing drive 98 rotate at a skew angle and not in an axially aligned configuration as shown in Figure 3. The form shown in Figure 12 also differs from that shown in Figure 3 in the gear 118 (the equivilent of input gear 16) is not rotatable in bearings 14 carried by the casing 28 but in the fixed bearing 116. Hence there is no impediment to two rams designated 120 displacing the main housing in an arc about the axis of the gear 20. When this movement happens the gear 22 moves around the gear 20 thus permitting the line of thrust of the propellers to be adjusted with respect to horizontal.

The gear 118 and bearing 116 are carried by a subsiding housing 122 and the gears 16, 20 and 22 and by the casing 28.

Insofar as steering is concerned, this is achieved by rotating the housing 104 about the axis of the shaft 100. The housing 104 moves with respect to the subsidiary housing 122 so that the geometry of the shaft 12 and gear set 18 is not changed. The gears 16 and 22 simply rotate on their own axes.

Claims

CLAIMS:

1. A drive comprising a first shaft, means for rotating the first shaft in one direction, a second shaft co-axial with the first shaft, means for turning the second shaft in the opposite direction to the first shaft, a drive output member, and means for selectively clutching the first shaft or the second shaft to said output member.

2. A drive shaft system as claimed in claim 1 , wherein the clutching means comprises clutch elements carried by the shafts and further clutch elements carried by the output member.

3. A drive system as claimed in claim 1 or 2, wherein said second shaft is within the first shaft and has a portion which protrudes from said first shaft, elements for selectively clutching the second shaft to the output member being carried by said protruding portion.

4. A drive system as claimed in claim 1 and which comprises a first cone, said first input shaft rotating said first cone in one direction, a second cone co-axial with the first cone, said second drive shaft rotating said second cone in the opposite direction to the first cone, the cones tapering in opposite directions, a casing fast in rotation with said drive output member and having a first conical surface for clutching engagement with the first cone and a second conical surface for clutching engagement with the second cone, and means for displacing said casing axially with respect to said shafts to bring one or other of said cones into clutching engagement with the respective conical surface of said casing.

5. A stern drive comprising an input shaft, an upper gear set including an input gear driven by said input shaft, an output gear and an intermediate gear which transmits drive from said input gear to said output gear, the intermediate gear being rotatable about a horizontal axis, an inclined drive shaft extending downwardly from said gear set and driven by said output gear, a lower gear set driven by said drive shaft, and a housing carrying said output gear, said lower gear set and said drive shaft, said housing being pivotable in an arc about said horizontal axis of said intermediate gear.

6. A stern drive as claimed in claim 5, wherein said output gear is co-axial with said inclined drive shaft.

7. A stern drive as claimed in claim 5 or 6, wherein said input shaft is horizontal and coaxial with said input gear, the axis about which the input shaft and input gear rotate intersecting, and being at right angles to, the horizontal axis about which the intermediate gear rotates.

8. A stern drive as claimed in any one of claims 5 to 7 and comprising a first output gear, a second output gear, the first and second output gears being coaxial and being contra rotated by said intermediate gear, a first reversing drive shaft driven by said first gear and a second reversing drive shaft driven by said second gear, a first cone rotated by said first reversing drive shaft, a second cone rotated by said second reversing drive shaft, the cones tapering in opposite directions, a casing fast in rotation with said drive output member and having a first conical surface for clutching engagement with the first cone and a second conical surface for clutching engagement with the second cone , and means for displacing said casing axially with respect to said shafts to bring one or other of said cones into clutching engagement with the respective conical surface of said casing.