ARTICULATED HALFSHAFT FOR AN AMPHIBIAN
An articulated shaft for an amphibian drive line that includes at least three shaft portions, and at least three points of articulation, wherein the articulated shaft is movable between a protracted position for use of the amphibian on land and a retracted position for use of the amphibian on water.
The present invention relates to an articulated halfshaft particularly suitable for use in an amphibian capable of travel on land and water. More particularly, the articulated halfshaft is suitable for use with at least one retractable wheel or track drive in a high speed amphibian capable of planing on water. The present invention also relates to an amphibian incorporating such an articulated halfshaft.
It is known, for example from U.S. Pat. No. 5,531,179 of the present applicant, for amphibians to have wheel and suspension assemblies which are retractable, so that the wheels are raised above the water line when the amphibian is operated on water. This reduces hydrodynamic resistance (drag) and allows for increased speed. The amphibian can then operate in a planing mode on water, and not just in a displacement mode only. However, known halfshafts, and in particular those used in automotive applications, have limited ability in terms of the angles of articulation possible. Furthermore, there are servicing and reliability issues when transmitting power and/or rotation at speed at increased angles of articulation.
Prior art automotive halfshafts generally comprises two constant velocity (hereinafter “CV”) joints arranged in a spaced apart manner, joined by stub and/or intermediate shafts. The resulting driveshaft is commonly known as a halfshaft, axleshaft, CV shaft or CV axle. Whilst the halfshaft may transmit power and provide drive to a supported wheel in the manner of a driveshaft, it may also be used simply to support a wheel and not provide any power transmission or drive.
The use of CV joints permits limited articulation at two points in the halfshaft such that vertical movement of a wheel is possible, usually supported via a suspension assembly. Splined connection of the stub and/or intermediate shafts or plunging CV joints may be used to accommodate geometry changes on movement of the wheel. Such an arrangement provides for bump and rebound, so as to improve the ride and handling characteristics of a vehicle. It also provides for a substantially constant rotating speed of a shaft over a range of angles between input and output.
However, the degree of articulation achievable is limited due to the geometrical constraints of known articulating joints (CV joints, Rzeppa joints, tripod joints, Hooke's joints, Thompson CV joints and universal joints) since mechanical resistance to rotation and even geometric lock can occur beyond operational angles. Ultimately, this gives rise to servicing issues and failure of the articulating joint when it is operated at the larger angles of the limited articulation available. Such limitations do not present a problem in automotive applications where the amount of vertical travel of a wheel to be accommodated is limited. Furthermore, in amphibians where the dead rise angle of the hull is low (e.g. 0 to 5 degrees), it is still possible to retract the wheels sufficiently (wheel axle angles generally of between 15 and 45 degrees above the horizontal) to enable planing when the amphibian is operated on the water.
However, there remains a need to retract wheel and track drives yet further, to achieve wheel or track axle angles of 90 degrees or more above the horizontal. This is of particular benefit in amphibians where the dead rise angle of the hull is more severe (e.g. 10 degrees or more), and/or where there is a need for improved ground clearance which in turn requires a greater height of upright in the suspension assembly.
This presents significant problems in terms of the degree of articulation required (not to mention also the additional articulation about a vertical axis required for steering), packaging, weight distribution and also in terms of how the resulting power transmission pathways can be realised.
The present invention seeks to address the aforementioned problems.
SUMMARY OF THE INVENTIONAccordingly, the present invention provides, in a first aspect an articulated shaft for an amphibian driveline, the articulated shaft comprising:
at least three shaft portions; and
at least three points of articulation, wherein:
the articulated shaft is movable between a protracted position for use of the amphibian on land and a retracted position for use of the amphibian on water.
In a second aspect, the present invention provides an amphibian comprising the articulated shaft.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.
Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:
For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in
Where the wheel 9 is also a steered wheel, the outer CV joint 7 has an additional function, as illustrated in
To maintain a consistent track dimension between the left and right wheels on a given axle, the effective length of the wheel driveshaft must be able to alter as the wheel travels up and down in bump and rebound. This is achieved on a typical road car (e.g. with front wheels which provide drive and steering) by using a plunge type joint as the inner CV joint 3, and a fixed joint as the outer CV joint 7. Whilst a plunge joint can provide for changes in the effective length of the driveshaft, a plunge joint can only operate within a more limited range of driveshaft angles, because the driveshaft will contact the outer sleeve when these angles are exceeded, as can be seen from the indicated angle αC in
In view of the foregoing, it will be appreciated that the need to retract wheel and track drives yet further, to wheel or track axle angles of 90 degrees or more above the horizontal, presents significant problems, not least in terms of the angle of articulation desired, packaging and weight.
Referring next to
The halfshaft 10 is illustrated schematically in protracted, semi-retracted and fully retracted positions in
Referring next to
The halfshaft 100 is illustrated schematically in protracted, semi-retracted and fully retracted positions in
It will thus be appreciated that the articulated halfshaft 10, 100 according to the present invention can provide for significant angles of articulation between input and output. Furthermore, it is also capable of providing drive (transmitting power) and/or a constant speed of rotation between input and output at these significant angles of articulation, yet does so without suffering from the known geometrical problems (mechanical resistance and lockup) of prior art halfshafts.
Retractable wheel and suspension assemblies (selected parts are omitted from the attached Figures for clarity) as described in the applicant's patents and patent applications are particularly suitable for use with the articulated halfshaft 10, 100 of the present invention.
Whilst not shown, it is possible also to provide decouplers separately or integrated in the transmission illustrated. The provision of decouplers allows drive to the wheels or track drives to be disengaged when the amphibian is operated on water. As decouplers should be mounted rigidly to encourage smoothness of operation, it is preferred that decouplers be used on the inner CV joints. The CV joints may also include a synchromesh unit for smooth engagement and disengagement of said decouplers.
Whilst wheels 400, 600 have predominantly been referred to throughout for use as the land engaging and/or land propulsion means of the amphibian when operated on land, track drives or individual track drives (i.e. to replace a single wheel) may be used as an alternative or in combination with wheels.
Furthermore, it will be appreciated that drive (power) may be provided by internal combustion engines, electric motors, hydraulic motors, or hybrid engines in any suitable location (e.g. hydraulic wheel hub motors).
Although different embodiments of articulated halfshaft 10, 100 according to the present invention have been described above, any one or more or all of the features described (and/or claimed in the appended claims) may be provided in isolation or in various combinations in any of the embodiments. As such, any one or more these features may be removed, substituted and/or added to any of the feature combinations described and/or claimed. For the avoidance of doubt, any of the features of any embodiment may be combined with any other feature from any of the embodiments.
Accordingly, whilst preferred embodiments of the present invention have been described above and illustrated in the drawings, these are by way of example only and non-limiting. It will be appreciated by those skilled in the art that many alternatives are possible within the ambit, spirit and scope of the invention, as set out in the appended claims.
Claims
1. An articulated shaft for an amphibian driveline, the articulated shaft comprising:
- at least three shaft portions; and
- at least three points of articulation, wherein:
- the articulated shaft is movable between a protracted position for use of the amphibian on land and a retracted position for use of the amphibian on water.
2. An articulated shaft as claimed in claim 1 wherein the at least three shaft portions comprise:
- an inner shaft portion;
- a mid shaft portion; and
- an outer shaft portion.
3. An articulated shaft as claimed in claim 2 wherein the inner shaft portion is a differential stub shaft which connects with a differential of the amphibian.
4. An articulated shaft as claimed in claim 2 wherein the mid shaft portion is a mid shaft of variable effective length in use.
5. An articulated shaft as claimed in claim 4 wherein the mid shaft portion comprises two parts provided with mating splines slidably received one within the other to vary the effective length of the mid shaft portion in use.
6. An articulated shaft as claimed in claim 2 wherein the outer shaft portion is a suspension upright stub shaft which connects with a suspension upright of the amphibian.
7. An articulated shaft as claimed in claim 1 wherein the at least three points of articulation each comprise a constant velocity joint.
8. An articulated shaft as claimed in claim 1 wherein at least one of the at least three points of articulation comprises a constant velocity joint.
9. An articulated shaft as claimed in claim 1 wherein at least two of the at least three points of articulation each comprise a constant velocity joint.
10. An articulated shaft as claimed in claim 1 wherein at least three of the at least three points of articulation each comprise a constant velocity joint.
11. An articulated shaft as claimed in claim 1 wherein the total angle of articulation of the shaft achievable between its protracted position for use of the amphibian on land and its retracted position for use of the amphibian on water is at least 45 degrees.
12. An articulated shaft as claimed in claim 1 wherein the total angle of articulation of the shaft achievable between its protracted position for use of the amphibian on land and its retracted position for use of the amphibian on water is at least 65 degrees.
13. An articulated shaft as claimed in claim 1 wherein the total angle of articulation of the shaft achievable between its protracted position for use of the amphibian on land and its retracted position for use of the amphibian on water is at least 85 degrees.
14. An articulated shaft as claimed in claim 1 wherein the shaft is a halfshaft.
15. An articulated shaft as claimed in claim 1 wherein the shaft is a driven shaft.
16. An articulated shaft as claimed in claim 1 wherein the shaft is a non-driven shaft.
17. An amphibian comprising the articulated shaft as claimed in claim 1.
18. An amphibian as claimed in claim 17 wherein the amphibian comprises a powertrain and the shaft forms part of the powertrain of the amphibian.
19. An amphibian as claimed in claim 17 wherein the amphibian comprises:
- at least one prime mover; and
- at least one retractable wheel or track drive, wherein the shaft transmits drive from the at least one primer mover to the at least one retractable wheel or track drive.
20. An amphibian as claimed in claim 18 wherein the powertrain of the amphibian comprises at least one differential.
21. An amphibian as claimed in claim 18 wherein the powertrain of the amphibian comprises at least one decoupler.
22. An amphibian as claimed in claim 18 wherein the powertrain of the amphibian comprises at least one synchromesh.
23. An amphibian as claimed in claim 17 further comprising a retractable suspension assembly.
24. An amphibian as claimed in claim 17 operable in land and marine modes wherein when the amphibian is operated in the marine mode, sufficient hydrodynamic lift is achieved for the amphibian to plane.
25. An amphibian as claimed in claim 17 operable in land and marine modes wherein when the amphibian is operated in the land mode it can be driven in one, two, three or four wheel or track drive.
Type: Application
Filed: Feb 7, 2012
Publication Date: Aug 8, 2013
Inventor: Neil Graham Jenkins (Orchard Lake, MI)
Application Number: 13/367,948
International Classification: B63H 19/08 (20060101);