Winch or hoist system with clutch adjustment

1. A clutch for driving a winch, the clutch comprising:

an input shaft for connection to a drive means and being operatively connected to at least one input friction plate for rotation therewith;

an output shaft for driving the winch and being operatively connected to at least one output friction plate for rotation therewith;

a biasing member arranged to provide a biasing force that pushes the at least one input friction plate and the at least one output friction plate into contact with each other so that torque can be transferred from the input shaft to the output shaft via the input and output friction plates; and

a plunger disposed co-axially with and axially moveable relative to the output shaft, wherein axial displacement of the plunger relative to the output shaft causes the biasing force to vary;

wherein the biasing member is at least one disc springs positioned around the output shaft.

2. The clutch of claim 1 , wherein the plunger is disposed inside a plunger housing that is co-axial with and fixed axially relative to the output shaft.

3. The clutch of claim 2 , wherein axial displacement of the plunger is communicated to the biasing member hydraulically.

4. The clutch of claim 1 , wherein axial displacement of the plunger is communicated to the biasing member mechanically.

5. A clutch for driving a winch, the clutch comprising:

an input shaft for connection to a drive means and being operatively connected to at least one input friction plate for rotation therewith;

an output shaft for driving the winch and being operatively connected to at least one output friction plate for rotation therewith;

a biasing member arranged to provide a biasing force that pushes the at least one input friction plate and the at least one output friction plate into contact with each other so that torque can be transferred from the input shaft to the output shaft via the input and output friction plates; and

a plunger disposed co-axially with and axially moveable relative to the output shaft, wherein axial displacement of the plunger relative to the output shaft causes the biasing force to vary;

wherein axial displacement of the plunger is communicated to the biasing member mechanically;

wherein the plunger further comprises projections extending radially therefrom, said projections extending through apertures in the output shaft to allow mechanical communication with the biasing member.

6. A clutch for driving a winch, the clutch comprising:

an input shaft for connection to a drive means and being operatively connected to at least one input friction plate for rotation therewith;

an output shaft for driving the winch and being operatively connected to at least one output friction plate for rotation therewith;

a biasing member arranged to provide a biasing force that pushes the at least one input friction plate and the at least one output friction plate into contact with each other so that torque can be transferred from the input shaft to the output shaft via the input and output friction plates; and

a plunger disposed co-axially with and axially moveable relative to the output shaft, wherein axial displacement of the plunger relative to the output shaft causes the biasing force to vary;

wherein the plunger is disposed inside a plunger housing that is co-axial with and fixed axially relative to the output shaft;

wherein axial displacement of the plunger is communicated to the biasing member hydraulically;

wherein the output shaft further comprises:

an output shaft flange forming at least a first chamber for receiving hydraulic fluid; and

first channels disposed through the output shaft, allowing fluid communication between the first chamber and an interior of the plunger housing; and wherein:

the clutch further comprises a piston being disposed at least partially in the first chamber forming a fluid-tight seal therewith, the piston being axially moveable in the first chamber relative to the output shaft and in mechanical communication with the biasing member; and wherein

the plunger housing further comprises second channels disposed therethrough, allowing fluid communication with the first channels in the output shaft.

7. The clutch of claim 6 , wherein a second chamber for receiving hydraulic fluid is formed within the plunger housing.

8. The clutch of claim 7 , wherein the first and second channels allow communication of hydraulic fluid between the first and second chambers.

9. The clutch of claim 8 , wherein hydraulic fluid is communicated between the chambers due to axial displacement of the plunger within the second chamber.

10. A winch assembly, comprising:

a clutch, the clutch including:

an input shaft for connection to a drive means and being operatively connected to at least one input friction plate for rotation therewith;

an output shaft for driving the winch and being operatively connected to at least one output friction plate for rotation therewith;

a biasing member arranged to provide a biasing force that pushes the at least one input friction plate and the at least one output friction plate into contact with each other so that torque can be transferred from the input shaft to the output shaft via the input and output friction plates; and

a plunger disposed co-axially with and axially moveable relative to the output shaft, wherein axial displacement of the plunger relative to the output shaft causes the biasing force to vary;

a motor operatively connected to the input shaft;

a drum operatively connected to the output shaft for rotation about a drum axis;

a cable attached to the drum and windable therearound to create a varying effective drum radius; and

an arm having a first end operatively connected to the drum, such that its radial position, relative to the drum axis, changes as the effective drum radius varies, and a second end operatively connected to the plunger.

11. The winch assembly of claim 10 , wherein the radial displacement of the first end of the arm is communicated to the plunger to provide axial displacement thereof.

12. The winch assembly of claim 11 , wherein the communication is provided by at least one of a mechanical connection and a hydraulic connection.

13. The winch assembly of claim 10 , wherein the arm is pivotally attached at a point between the first and second ends of the arm to a static structure, and the winch assembly further comprises:

a roller operatively connected to the first end of the arm for rotation thereabouts, wherein the roller is arranged to rest on an outer surface of an outermost layer of cable on the drum; and

at least one of a mechanical or hydraulic connection is provided at the second end of the arm, to communicate displacement of the second end of the arm to the plunger to provide axial displacement thereof.

14. A method of adjusting a clutch torque setting for a clutch of claim 1 when in use in a winch assembly, the clutch including: an input shaft for connection to a drive means and being operatively connected to at least one input friction plate for rotation therewith; an output shaft for driving the winch and being operatively connected to at least one output friction plate for rotation therewith, a biasing member arranged to provide a biasing force that pushes the at least one input friction plate and the at least one output friction plate into contact with each other so that torque can be transferred from the input shaft to the output shaft via the input and output friction plates; and a plunger disposed co-axially with and axially moveable relative to the output shaft, wherein axial displacement of the plunger relative to the output shaft causes the biasing force to vary; the method comprising the steps of:

reeling in or reeling out a cable attached to a winch drum;

communicating variation in an effective drum radius caused by the reeling in or reeling out of the cable to generate the axial displacement of the plunger; and

communicating the axial displacement of the plunger to the biasing member to vary the biasing force.

15. The method of claim 14 , wherein the step of communicating variation in the effective drum radius comprises, detecting said variation via radial displacement of a pivoted arm in operative communication with an outer surface of an outermost layer of a cable laid on the drum.

16. The method of claim 15 , wherein the step of communicating variation in the effective drum radius to the plunger further comprises providing at least one of a mechanical or hydraulic connection from the arm to the plunger, wherein the connection translates the radial displacement of the arm to axial displacement of the plunger.