CA2622041A1

CA2622041A1 - Rope tensioner

Info

Publication number: CA2622041A1
Application number: CA 2622041
Authority: CA
Inventors: Guenter Odlozinski
Original assignee: Atlas Copco Craelius AB
Current assignee: Epiroc AB
Priority date: 2008-02-21
Filing date: 2008-02-21
Publication date: 2009-08-21

Abstract

A rope tensioner in a mechanical lifting device with a winch, a holding means, and a rope.
The rope tensioner includes a sheave guiding the rope from the winch to the holding means;
and a driving means operatively driving the sheave resulting in a tension between the sheave and the winch.

Description

Rope Tensioner FIELD OF THE INVENTION

[0001] The present invention relates to a rope tensioner. More particularly, the invention relates to a rope tensioner for maintaining rope tension on a mechanical device that is used to wind up the rope.

BACKGROUND OF THE INVENTION

[0002] Mechanical lifting devices are widely used for loading and unloading of freight; for movement of materials; for assembling of heavy equipment. These mechanical lifting devices are generally equipped with a winch, hoisting ropes and sheaves that can be used both to lift and lower materials. Mechanical lifting devices commonly come in the form of cranes, drill rigs or the like.

[0003] A mechanical lifting device 100 such as a drill rig generally used in the resource industry for exploring for minerals, is shown in Figure 1. A sheave 102 is generally located at a hard to reach height and much higher than a winch 104. A rope 106 is paid out from the winch 104 and pulled back by being rewound on the winch. The rope extends from the winch 104 to the other side of the sheave and is connected to a holding means, for example, a hoisting plug 108.

[0004] In some drill rigs, the hoisting plug is handled manually. The hoisting plug is therefore kept as light as possible. The handler has to move the hoisting plug away from the drill boom when he picks up or lays down drill pipe behind the rig or stacks the rod in the rod rack.
Therefore single lines and hoisting plugs are generally used for easy handling.

[0005] For heavy duty ropes in the mechanical lifting device 100, the diameter of the rope 106 could be up to one inch, therefore the rope 106 may be stiff. On the other hand, the hoisting plug 108 may not be heavy enough, especially when no load is put on the hoisting plug 108, to keep enough rope tension between the winch 104 and the sheave 102.

[0006] In the absence of sufficient rope tension, when the winch 104 winds up the rope 106, the rope 106 may not wind on the winch properly, may snarl at the winch, cross over the rope already wound on the winch, thus causing damage to the rope when the hoisting plug 108 is subsequently raised with a load on it. The snarled rope is often extremely difficult to clear.

[0007] Furthermore, the hoisting plug 108 may need to be pulled down on the other side if it is not heavy enough to pull the stiff wire rope over the sheave.

[0008] US Patent 4,113,237 describes a cable pay-out drive on a crane having a set of three sheaves, one of which is driven in the lowering direction. The pay-out drive pulls the rope off the freely rotatable drum of the crane in the payout direction.

[0009] The cable pay-out drive described in US Patent 4,113,237 is free to idle in the raising direction, therefore there is no rope tension in the raising direction actively provided by the cable pay-out drive. Furthermore drawing a heavy duty cable through a non-linear path defined by three offset sheaves shortens the life of a single heavy duty rope due to the reversing bending caused by the offset sheaves. Furthermore, the construction of three offset sheaves adds complexity and cost, since the existing idler sheave that is required at the top of the boom is not utilized for providing the desired rope tension.

[oolo] Therefore, there is a need to for an improved rope tensioner.
SUMMARY OF THE INVENTION

[0011] It is an object of the invention to provide an improved rope tensioner and a method for providing desired rope tension in a mechanical lifting device.

[0012] In accordance with one embodiment of the present invention, there is provided a rope tensioner in a mechanical lifting device, the mechanical lifting device includes a winch, a holding means, and a rope, the rope tensioner comprises a sheave guiding the rope from the winch to the holding means; and a driving means operatively driving the sheave resulting in a tension between the sheave and the winch.

[0013] In accordance with one embodiment of the present invention, there is provided a method for providing rope tension in a mechanical lifting device, the mechanical lifting device includes a winch, a holding means, and a rope, the method comprising the steps of:
guiding the rope from the winch to the holding means through a sheave; and providing a tension between the sheave and the winch through a driving means operatively driving the sheave.

[0014] Preferably, the driving means is a hydraulic motor.
[0015] Preferably, the mechanical lifting device is a drilling rig.
[0016] Preferably, the tension is predefined.

[0017] Preferably, the holding means is a hoisting plug.

[0018] Preferably, the rope tensioner includes a pressure roller pressing the rope against the sheave.

[0019] Preferably, the driving means is controlled by a winch release circuit.

[0020] Preferably, the rope tensioner includes a means for changing mechanical advantage between the driving means and the sheave.

[0021] Preferably, the means for changing mechanical advantage between the driving means and the sheave is a sprocket and chain mechanism.

[0022] Preferably, the rope tensioner includes a hydraulic pump.
[0023] Preferably, the rope tensioner includes a relief valve.

[0024] This summary of the invention does not necessarily describe all features of the invention.
[0025] BRIEF DESCRIPTION OF THE DRAWINGS

[0026] These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings wherein:

Figure 1 shows a prior art mechanical lifting device;

Figure 2 shows a mechanical lifting device with a rope tensioner in accordance with one embodiment of the present invention;

Figure 3 (A) is a perspective view of a rope tensioner in accordance with one embodiment of the present invention;

Figure 3 (B) is a cut away perspective view of the rope tensioner shown in Figure 3 (A);
and Figure 4 is a schematic of a hydraulic circuit of the rope tensioner in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0027] Reference will now be made in detail to some specific embodiments of the invention including the best modes contemplated by the inventors for carrying out the invention.
Examples of these specific embodiments are illustrated in the accompanying drawings.
While the invention is described in conjunction with these specific embodiments, it will be understood that it is not intended to limit the invention to the described embodiments. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail in order not to unnecessarily obscure the present invention.

[0028] In this specification and the appended claims, the singular forms "a,"
"an," and "the"
include plural references unless the context clearly dictates otherwise.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs.

[0029] The term "rope" is intended to describe wires twisted or braided to improve tensile strength for pulling. Other terms used in the art may include, but not limited to, wire rope, cable, or the like.

[003o] The term "winch" is intended to describe a mechanical device used to wind up a rope or the like. A winch generally comprises a winch drum. Winch may be powered by, but not limited to, electric, hydraulic, pneumatic or internal combustion drives.

[0031] The term "sheave" is intended to describe a wheel with a groove between two flanges around its circumference, whereby the groove generally locates a rope, cable or belt.
Sheave is generally used to change the direction of an applied force, transmit rotational motion, or realize a mechanical advantage in either a linear or rotational system of motion.

[0032] The term "hydraulic motor" is intended to describe a mechanical actuator that converts hydraulic pressure and flow into torque and rotation.

[0033] Figure 2 shows a rope tensioner 202 in accordance with one embodiment of the present invention, in a mechanical lifting device 200, such as a rig.

[0034] Also referring to Figure 3 (A) and (B), the rope tensioner 202 produces a tensioning torque on the sheave 302 so that the rope 106 between the sheave 302 and the winch 104 is always under a specified tension whether the winch and sheave is stationary or lowering the hoisting plug 108. When raising the hoisting plug 108, the tensioning torque on the sheave is overcome by the main winch pull.

[0035] In accordance with one embodiment of the present invention, a driving means, for example a hydraulic motor 304 is used to supply the tensioning torque to the sheave 302. The tensioning torque on the sheave can be produced in a number of ways.
The hydraulic motor 304 may drive the axis 306 of the sheave 302 directly (not shown), or through a means for changing mechanical advantage, for example, a sprocket 308 attached to the sheave 302 and then drive the sprocket 308 by a smaller sprocket 310 mounted on the hydraulic motor 304 as shown in Figure 3 (B). The use of a means for changing mechanical advantage may further provide additional freedom and convenience to place the hydraulic motor at a desired location and connect the hydraulic motor to the sheave. The wire rope may have to be pressed against the sheave so no sliding occurs between the sheave and the rope. The hydraulic motor 304 displacement and sprocket ratio is chosen so that the desired tension is put on the winch 104.

[0036] Pressure rollers may be used to keep the rope 106 in the groove of the sheave 302 and prevent slipping between the rope and the sheave.

[0037] When the rope 106 has to be pulled off the winch 104, for example when drilling with the hoisting plug attached to the drill rod in a drilling rig, then the work ports of the hydraulic motor 304 are connected so that the sheave is not tensioned during the drilling operation.

[0038] Figure 4 illustrates a exemplary hydraulic circuit to accomplish the desired tensioning torque on the winch 104. Also referring to Figures 3 and 4, the hydraulic motor 304, 402 is pressurized by a constant pressure such as by a pressure compensated pump 404.

When the winch is stationary, the hydraulic motor 304, 402 is in a stall condition and is putting a constant tensioning on the rope between the winch 104 and the sheave 302 of the rope tensioner 202. When the holding means, for example the hoisting plug 108 is lowered, the hydraulic pump 404 puts out enough flow to maintain the desired constant tension on the rope between the winch 104 and the sheave 302 of the rope tensioner 202.

[0039] When the hoisting plug 108 is raised by the winch 104, the hydraulic motor 304, 402 is forced by the force of the winch 104 to turn in the reverse direction and acts a hydraulic pump. The hydraulic motor 304, 402 working as a pump in the reverse direction forces flow over a relief valve 406 since the flow cannot pass over check valve 408.
The set pressure of the relief valve 408 is set so that the relief valve will close at a pressure higher than that produced by hydraulic pump 404. Since the hydraulic motor 304, 402 is acting as a hydraulic pump, the sheave 302 of the rope tensioner 202 provides a resistance so that a rope tension is maintained while the hoisting plug 108 is being raised.

[004o] The hydraulic circuit may further include a valve 410 that is shifted so that the hydraulic motor 304, 402 work ports are connected when the rope 106 is pulled off the winch 104, for example, during the drilling operation. This valve can be opened automatically by the same hydraulic signal that releases the parking brake on the winch so the rope can be pulled off the drum.

[0041] Optionally, provision can be made so that the line 412 from the hydraulic tank to the hydraulic motor 304, 402 will not empty when the hydraulic motor304, 402 is acting as a hydraulic pump while the hoisting plug 108 is being raised.

[0042] The present invention has been described with regard to one or more embodiments.
However, it will be apparent to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as defined in the claims.

Claims

1. A rope tensioner in a mechanical lifting device, the mechanical lifting device including a winch, a holding means, and a rope, the rope tensioner comprising:

a sheave guiding the rope from the winch to the holding means; and a driving means operatively driving the sheave resulting in a tension between the sheave and the winch.

2. The rope tensioner of claim 1, wherein the driving means is a hydraulic motor.

3. The rope tensioner of claim 1, wherein the mechanical lifting device is a drilling rig.

4. The rope tensioner of claim 1, wherein the tension is predefined.

5. The rope tensioner of claim 1, wherein the holding means is a hoisting plug.

6. The rope tensioner of claim 1, further comprising a pressure roller pressing the rope against the sheave.

7. The rope tensioner of claim 1, wherein the driving means is controlled by a winch release circuit.

8. The rope tensioner of claim 1, further comprising a means for changing mechanical advantage between the driving means and the sheave.

9. The rope tensioner of claim 8, wherein the means for changing mechanical advantage between the driving means and the sheave is a sprocket and chain mechanism.

10. The rope tensioner of claim 2, further comprising a hydraulic pump.

11. The rope tensioner of claim 2, further comprising a relief valve.

12. A method for providing rope tension in a mechanical lifting device, the mechanical lifting device including a winch, a holding means, and a rope, the method comprising the steps of:
guiding the rope from the winch to the holding means through a sheave; and providing a tension between the sheave and the winch through a driving means operatively driving the sheave.

13. The method of claim 12, wherein the driving means is a hydraulic motor.

14. The method of claim 12, wherein the mechanical lifting device is a drilling rig.

15. The method of claim 12, wherein the tension is predefined.

16. The method of claim 12, wherein the holding means is a hoisting plug.

17. The method of claim 12, further comprising the step of pressing the rope against the sheave using a pressure roller.

18. The method of claim 12, further comprising the step of controlling the driving means using a winch release circuit.

19. The method of claim 12, further comprising the step of changing mechanical advantage between the driving means and the sheave.

20. The method of claim 12, further comprising the step of changing mechanical advantage between the driving means and the sheave using a sprocket and chain mechanism.