Double drum traction winch

Abstract

A double drum traction winch of which the rotatable drums are both provided with adjustable grooves is provided. Each drum includes multiple, for example three or more, curved segments, each segment defining a section of a circumferential groove, such that multiple circumferential grooves on the outer surface of the drum are each composed of several curved segments. The curved segments are each movably supported by a core body for movement in a substantial radial direction relative to the rotational axis of the drum. An actuator mechanism for the curved segments is provided, that includes actuators that cause essentially radial displacement of the curved segments, such that the circumference of the grooves can be adjusted.

Claims

1. A double drum traction winch comprising: two rotatable drums including first and second rotatable drums; a frame supporting the first and second rotatable drums such that a wire can be wound about the two rotatable drums, wherein the two rotatable drums each have a rotational axis and an outer surface; and one or more drives for rotating the first and second rotatable drums about their respective rotational axis, wherein each of the first and second rotatable drums comprises: a core body, mounted in the frame for rotation about the rotational axis of the rotatable drum by said one or more drives; a plurality of circumferential grooves formed on the outer surface, each of the plurality of circumferential grooves being defined by a plurality of curved segments movably supported on the core body for movement in a substantial radial direction perpendicular to the rotational axis of the rotatable drum, wherein the plurality of circumferential grooves extend parallel to each other and perpendicular to the rotational axis of the rotatable drum, for carrying the wire that is wound about both rotatable drums, and wherein in use, the tension in the wire carried by the plurality of circumferential grooves increases with each groove the wire passes through from a low tension end of each rotatable drum, where tension in the carried wire is low, towards a high tension end of each rotatable drum, where the tension in the carried wire is high, the plurality of circumferential grooves including a low tension circumferential groove located at the low tension end of the rotatable drum and a high tension circumferential groove located at the high tension end of the rotatable drum; an actuator mechanism comprising actuators configured to move the plurality of circumferential grooves in a plane perpendicular to the rotational axis of the rotatable drum between a radially inward position and a radially outward position relative to the rotational axis of the rotatable drum without moving the plurality of circumferential grooves in a direction along the rotational axis, to adapt the circumferential length of the circumferential grooves defined by the plurality of curved segments.

2. The double drum traction winch according to claim 1, wherein each of the plurality of circumferential grooves is defined by at least four curved segments.

3. The double drum traction winch according to claim 1, wherein the plurality of curved segments are each at one end shaped for supporting an overlying end of an adjacent one of the plurality of curved segments, and at the opposite end are each shaped for engaging another adjacent one of the plurality of curved segments for support, such that the plurality of curved segments that define one circumferential groove overlap each other and are at one end supported by an adjacent one of the plurality of curved segments and at an opposite end support an adjacent one of the plurality of curved segments.

4. The double drum traction winch according to claim 1, wherein each of the plurality of circumferential grooves includes a plurality of groove sections, each of the plurality of groove sections being defined by one of the plurality of curved segment, and wherein the actuator mechanism is provided with a control system adapted to operate the actuators while the first and second rotatable drums carry the wire and are rotated, such that each of the plurality of curved segments is moved in the substantial radial direction only when the groove section defined by said curved segment only partially carries the wire or when the groove section defined by said curved segment does not carry the wire.

5. The double drum traction winch according to claim 1, wherein the plurality of curved segments are arranged parallel in rows along the longitudinal axis of the rotatable drums and wherein the actuators are common to such a row of curved segments for moving the curved segments of the row of the plurality of curved segments simultaneously.

6. The double drum traction winch according to claim 5, wherein for each of the first and second rotatable drums, the actuators of the actuator mechanism each comprise a cam shaft supported by the core body of the respective rotatable drum, the cam shaft extending in a direction parallel to the rotational axis of the respective rotatable drum, and each cam shaft interacting with a row of curved segments for simultaneous movement in the radial direction of the row of curved segments by rotating the cam shaft.

7. The double drum traction winch according to claim 1, wherein for each of the first and second rotatable drums, the actuator mechanism is adapted to move the plurality of curved segments of the respective rotatable drum relative to each other at a predetermined and fixed ratio to adjust a circumferential length of each circumferential groove in relation to a predetermined non-linear elastic behaviour of the wire.

8. The double drum traction winch according to claim 1, wherein the actuator mechanism is provided with a control system comprising one or more sensors for detecting a speed of the wire and/or tension in the wire carried by the rotatable drum, and wherein the control system is adapted to operate the actuators such that the plurality of curved segments are positioned in dependence of the actual tension and thus the stretch of the wire for forming grooves having a circumferential length such that a surface of the curved segment carrying the wire has substantially the same speed as the wire.

9. The double drum traction winch according to claim 1, wherein a diameter of the rotatable drum is at least 2 meter, and a position of each of the plurality of curved segments can be adjusted in the radial direction at least over a range of up to 10 mm.

10. The double drum traction winch according to claim 1, wherein for each of the first and second rotatable drums, the core body supports at fixed angularly spaced locations cam shafts that extend parallel to and at equal radial distance from the rotation axis of the respective rotatable drum, wherein the curved segments of a first row of curved segments each have a first end cooperating with a first cam shaft to displace said first end substantially in radial direction, the curved segments of the first row each have a second end supported by a first end of a curved segment of an adjacent second row of curved segments, and a second cam shaft cooperates with the first ends of the curved segments of the second row to displace said first ends of the curved segments of the second row in the radial direction.

11. The double drum traction winch according to claim 10, wherein for each cam shaft a cam shaft actuator is provided on the core body, and wherein said cam shaft actuators are operable independent from one another.

12. A method of using a double drum traction winch according to claim 1 in off-shore operations.

13. A vessel provided with a double drum traction winch according to claim 1.

14. A method for reducing wire slip on a double drum traction winch, the method comprising the steps of: providing a double drum traction winch according to claim 1; providing a storage drum with a wire to be carried by the double drum traction winch; adjusting the radial position of the plurality of curved segments and thus adjusting the circumferential length of each of the plurality of circumferential grooves defined by the plurality of curved segments; guiding the wire from the storage drum to the traction winch, winding the wire about the two traction drums such that the wire is carried by the plurality of circumferential grooves; guiding the wire from the traction winch to a first load, and connecting the wire to the first load; lifting or lowering the first load using the traction winch and the wire.

15. The method according to claim 14, comprising the step of adjusting circumferences the plurality of circumferential grooves simultaneously, by adjusting radial positions of the plurality of curved segments, while the first and second rotatable drums are carrying the wire.

16. The method according to claim 15, comprising the step of dynamically adjusting the circumferences the plurality of circumferential grooves simultaneously, by adjusting the radial positions of the plurality of curved segments while the first and second rotatable drums are rotated, wherein each of the plurality of circumferential grooves includes a plurality of groove sections, each of the plurality of groove sections being defined by one of the plurality of curved segment, and each of the plurality of curved segments is moved in the substantial radial direction only when the groove section defined by said curved segment only partially carries the wire or when the groove section defined by said curved segment does not carry the wire, and wherein positions of the plurality of curved segments defining one circumferential groove is adjusted in a consecutive fashion along the circumferential length of the one circumferential groove.

Description

(1) The invention will be explained in more detail with reference to the drawing, in which:

(2) FIG. 1 shows a top view, partially in cross section, of a double drum traction winch according to the invention;

(3) FIG. 2 shows a frontal view of the traction winch of FIG. 1;

(4) FIG. 3 shows a frontal view in cross section of a drum of the traction winch of FIG. 1;

(5) FIG. 4 shows a perspective view of curved segments of a drum of the traction winch of FIG. 1;

(6) FIG. 5 shows a partial top view in cross section of the traction winch of FIG. 1, in which two outer sides of the drums, i.e. the sides of the drum carrying a wire, are shown in cross section; and

(7) FIG. 6 shows a schematic view of some curved segments in cross section at different positions.

(8) FIG. 1 shows a top view of a double drum traction winch 1 according to the invention. FIG. 2 shows a frontal view of the same traction winch.

(9) The double drum traction winch 1 comprises a frame 2 supporting a first rotatable drum, or afterward drum 3 and a second rotatable drum, or forward drum 4. In the figure the left drum 4 is shown in cross section. With the traction winch in use, a wire is wound about the two drums. For clarity reasons the wire 5 is not fully shown in these figures, only the sections extending to and from the winch are depicted in FIG. 1. It is observed that a skilled person is known with the general working principles of a double drum traction winch and with the way a wire is carried by such a winch. This will therefore not be extensively discussed.

(10) In the embodiment shown, the first drum 3 is located near a storage drum (not shown) from which the traction winch receives the wire 5, of which part 5a is shown in the figure. The wire passes below the first drum 3, without touching it, towards the second drum 4. On the second drum 4 it is received in a first groove 7a and guided about the drum, back towards the first drum 3, about which it is guided by a first groove 8a back towards a second groove on the second drum, etc. In the embodiment shown the part of the wire 5 is guided from the last groove 8i of the first drum down below the second drum, without touching it, towards the load supported by the wire 5. Thus, the wire makes 9 turns about the two drums, passing eighteen grooves, 9 per drum, in total.

(11) In the embodiment shown, the rotational axis of the first drum is tilted relative to the rotational axis of the second drum such that a circumferential groove of the second drum guides a wire wound about both drums from a first circumferential groove on the first drum to a second circumferential groove on the first drum. By thus positioning the drums, the wires can be transferred between the drums over a short distance, i.e. the drums can be positioned close together, without extensive bending of the wires and/or extensive friction between the flanges of the grooves and the wires.

(12) It is observed that the invention can be used with types of winches that differ form the one shown in FIGS. 1 and 2, for example winches having another configuration, different number of grooves and/or turns as well as different configurations for guiding of the wire towards and from the drum, etc.

(13) The rotatable drums 3,4 each comprise a core body 10, mounted in the frame 2 for rotation about the rotational axis 9 of the drum by drives. More in particular, a main shaft 19 is provided for each drum, on which a drum body 20 is mounted via roller bearings 21. The double drum traction winch 1 shown comprises multiple drives 6 for rotating the drums about their respective rotational axis. In the particular embodiment shown, both drums are provided with four drives. Other configurations are possible and are not considered inventive in view of the prior art.

(14) The outer surface of each drum is provided with parallel circumferential grooves 7, 8 perpendicular to the rotational axis 9 of the respective drums for, when in use, carrying the wire that is wound about both drums.

(15) It is observed that normally a wire between the storage winch and the winch is already under tension, so called back tension, to initiate grip of the wire on the surface of the drum of the traction winch. The tension in the wire 5 carried by the grooves increases with each groove it passes through, from a low tension end of a drum, where tension in the carried wire is low, towards a high tension end of a drum, were the tension in the carried wire is high. Typically, tension in the wire is lowest in the first groove of the winch, receiving the wire form the storage drum, and highest in the last groove of the winch, from which it is guided towards the load.

(16) Thus the low tension ends of the drums are typically those at the side of the winch where the wire is fed from the storage winch to the traction drum, in the top view in FIG. 1 the upper ends, and the high tension ends of the drums are those at the side of the winch where the wire is fed towards the load, in the top view in figure one the lower ends. This is also shown in FIG. 5 in which the load distribution along the grooves of the drums is indicated for a typical load.

(17) FIG. 5 shows a top view in cross section of the two outer sides of the drums, i.e. the sides of the drum carrying a wire, of the traction winch of FIG. 1. For example, in the particular embodiment shown in FIG. 5, the load distribution along the grooves of the drums, i.e. the development of the tension in a particular wire carried by the grooves, for a typical load is as follows.

(18) The wire on the first groove 7a of drum 4 is subjected to a linepull of 600-667 kN. When the wire enters the groove, the tension in the wire, the so called back pull, is 600 kN. When the wire leaves the groove, the tensions has increased to 667 kN. The linepull in the first groove 8a on drum 3 is 667-741 kN. The line pull in the subsequent groove on drum 4 is 741-823 kN. The linepull in the subsequent groove on drum 3 is 823-915 kN. The line pull in the subsequent groove on drum 4 is 915-1016 kN. The linepull in the subsequent groove on drum 3 is 1016-1129 kN. The line pull in the subsequent groove on drum 4 is 1129-1255 kN. The linepull in the subsequent groove on drum 3 is 1255-1394 kN. The line pull in the subsequent groove on drum 4 is 1394-1549 kN. The linepull in the subsequent groove on drum 3 is 1549-1721 kN. The line pull in the subsequent groove on drum 4 is 1721-1913 kN. The linepull in the subsequent groove on drum 3 is 1913-2125 kN. The line pull in the subsequent groove on drum 4 is 2125-2362 kN. The linepull in the subsequent groove on drum 3 is 2362-2624 kN. The line pull in the subsequent groove on drum 4 is 2624-2916 kN. The linepull in the subsequent groove on drum 3 is 2916-3240 kN. The line pull in the subsequent groove on drum 4 is 3240-3600 kN. The linepull in the last groove 8i on drum 3 is 3600-4000 kN. Thus, the line pull of the wire on the traction winch is over the traction winch gradually increased from 600 kN to 4000 kN.

(19) The low tension ends of the drums are typically those at the side of the winch where the wire is fed from the storage winch to the traction drum, in the top view in FIG. 1 the upper ends, and the high tension ends of the drums are those at the side of the winch where the wire is fed towards the load, in the top view in FIG. 1 the lower ends.

(20) However, it is observed that which end of the drum is the low tension end, and which end of the drum is the high tension end, may change due to the loading of the drum, more in particular to the load supported by the wire and the tension in the wire fed to the drum from a storage winch.

(21) For example when the carried wire does not support a load the tension in the wire between load and winch may be lower than the tension in the wire between storage drum and winch. In this situation it is possible that the tension in the wire in the last groove of the winch, located at the high tension end of a drum, is smaller than the tension in the wire in the first groove of the winch, located at the low tension end of a drum.

(22) The rotatable drums 3, 4 of the traction winch 1 according to the invention are drums with adjustable grooves 7,8. The drums comprise multiple curved segments 11, each segment defining a section of a circumferential groove, such that multiple circumferential grooves of the drums are each composed of several curved segments. These curved segments are shown in FIG. 3 in a frontal view in cross section of a drum according to the invention shown. Furthermore, FIG. 4 shows the curved segments of a drum according to the invention in perspective view.

(23) The curved segments 11 comprise a support body at the side facing towards the drum, and a groove for carrying a wire at their opposite side. In the embodiment shown, the curved segments 11 are furthermore provided with a circular opening 17 for receiving a camshaft supporting the curved segments. By connecting the curved segment to the cam shaft via the circular opening the cam shaft does not only support the curved segment in a radial direction, forces directed alternative directions, for example in a tangential direction, can also be transferred from the curved segment to the drum and the frame of the traction winch.

(24) In the particular embodiment shown each drum comprises eight parallel rows of nine curved segments. The curved segments together form nine circumferential grooves on the outer surface of the drum. Each groove is formed by eight curved segments.

(25) The curved segments 11 are each movably supported on the core body of the drum for movement in a substantial radial direction relative to the rotational axis of the drum. The substantially radial direction is indicated in FIG. 3 for one row of curved segments with double arrow 18.

(26) An actuator mechanism is provided for the curved segments 11. The actuator mechanism comprises actuators that cause essentially radial displacement of the curved segments. In the embodiment shown, the core body 10 of the drums 3,4 supports at fixed angularly spaced locations cam shafts 12 that extend parallel to and at equal radial distance from the rotation axis 9 of the respective drums. The cam shafts are rotated with drives 13, mounted on the side of the drums.

(27) With the actuator mechanism according to the invention, the curved segments 11 can be moved into an outward position to increase the circumference of the grooves 7,8, and into an inward position to reduce the circumference of the grooves 7,8. In the particular embodiment shown, the curved segments 11 are in contact with cams of the cam shafts 12 such that by rotating the camshafts the curved segments are moved in the radial direction.

(28) In the embodiment shown, the curved segments are arranged parallel in rows along the longitudinal axis of the drum and the actuators of the actuator mechanism are common to such a row of curved segments. Thus one actuator can move a row of curved segments simultaneously. In an alternative embodiment one actuator is provided for a set of grooves, for example for each set of curved segments forming a groove, or each curved segment is provided with a separate actuator for individually positioning the curved segments.

(29) It is observed the in practice the trajectory of radial displacement of the curved segments is small compared to the diameter of the drum. For example, a drum having a diameter of 2.6 meters can be provided with curved segments that can be moved in the radial direction over a trajectory of 15 mm. In general, a relative small displacement of the curved segments will be sufficient to cope with the elongation of the wires used.

(30) Furthermore, the drum can be configured such that the curved segments at the high tension end of a drum can be moved in the radial direction over a larger trajectory than the curved segments on the low tension end of the drum or visa versa. Also it is possible to provide the drum with adaptable grooves only, or with some fixed grooves, i.e. non adaptable, and some adaptable grooves. In an embodiment only one groove of the set of drums is not adjustable, i.e. the groove that receives the wire from the storage drum or the groove from which the wire is fed to the load.

(31) In an embodiment according to the invention, elongation in the wire carried by the drums is met by increasing the diameter of the grooves. With an increase in tension the elongation of the wire increases. Since the tension in the wire increases along the drum, the diameter of the grooves of the drum in an embodiment increases per groove from the low tension end of the drum towards the high tension end of the drum. Thus, the drums are provided with a treaded surface formed by grooves of increasing diameter. Due to the increase in groove diameter, the circumferential length of the grooves increases and the increase in length of the wire is met. The elongation of the wire leads to an increase in the speed of the wire towards the high tension end of a drum. Slip of the wire along the surface of the drum, more in particular in the grooves, is substantially prevented since the diameter of the groves increases towards the high tension end of the drum, and thus the speed of the surface of the drum increases towards the high tension end of the drum.

(32) In addition to moving the curved segments into an inward and outward position, the actuator mechanism according to the invention allows the curved segments to be positioned such that the circumference of a groove at the low tension end of the drum is smaller than the circumference of a groove at the high tension end of the drum.

(33) This treaded surface can be obtained by reducing the circumference of the grooves towards the low tension end of the drum, by increasing the circumference of the grooves towards the high tension end of the drum, or by a combination of both. With the latter solution, the diameter of the grooves at the low tension end of the drums is reduced, and at the high tension end of the drums is increased.

(34) In the particular embodiment shown in FIGS. 1 and 2, the actuator mechanism is provided with cams of increasing size along each camshafts supporting the curved segments. Thus, by rotating the cam shaft, the drums can be provided with a treaded surface formed by grooves having an increasing diameter.

(35) In the particular embodiment shown, the cams are shaped such that the curved segments can also be positioned in an initial position in which all grooves on a drum have the same diameter. This position is shown in the top view in FIG. 1.

(36) In the particular embodiment shown, the actuator mechanism is configured for moving the curved segments at the low tension end of the drums inward, and thus to reduce the diameter of the grooves at the low tension ends of the drums, to meet elongation of the wire under increased tension.

(37) Shown in figure. 5, is a top view in cross section of the two outer sides of the drums of the traction winch of FIG. 1. It is observed that the grooves are shown in an initial position, in which they all have the same diameter. In use, the radius of the grooves towards the low tension end will be reduced, to match the tension in the wire, such that the radius of the grooves in the direction from the high tension end to the low tension end of the drum gradually reduces.

(38) For example, in the embodiment shown in FIG. 5, the trajectory of displacement of the curved segments is as follows.

(39) The curved segments of the first groove 7a of drum 4 can be moved in the radial direction over a distance of 15 mm. The curved segments of the first groove 8a of drum 3 can be moved in the radial direction over a distance of 14.67 mm. The curved segments of the subsequent groove of drum 4 can be moved in the radial direction over a distance of 14.30 mm. The curved segments of the subsequent groove of drum 3 can be moved in the radial direction over a distance of 13.89 mm. The curved segments of the subsequent groove of drum 4 can be moved in the radial direction over a distance of 13.44 mm. The curved segments of the subsequent groove of drum 3 can be moved in the radial direction over a distance of 12.93 mm. The curved segments of the subsequent groove of drum 4 can be moved in the radial direction over a distance of 12.37 mm. The curved segments of the subsequent groove of drum 3 can be moved in the radial direction over a distance of 11.74 mm. The curved segments of the subsequent groove of drum 4 can be moved in the radial direction over a distance of 11.05 mm. The curved segments of the subsequent groove of drum 3 can be moved in the radial direction over a distance of 10.27 mm. The curved segments of the subsequent groove of drum 4 can be moved in the radial direction over a distance of 9.41 mm. The curved segments of the subsequent groove of drum 3 can be moved in the radial direction over a distance of 8.46 mm. The curved segments of the subsequent groove of drum 4 can be moved in the radial direction over a distance of 7.40 mm. The curved segments of the subsequent groove of drum 3 can be moved in the radial direction over a distance of 6.21 mm. The curved segments of the subsequent groove of drum 4 can be moved in the radial direction over a distance of 4.90 mm. The curved segments of the subsequent groove of drum 3 can be moved in the radial direction over a distance of 3.44 mm. The curved segments of the subsequent groove of drum 4 can be moved in the radial direction over a distance of 1.81 mm. The curved segments of the subsequent groove of drum 3 can be moved in the radial direction over a distance of 0.00 mm. The curved segments can thus be adjusted to compensate for any elongation of the wire due to increased tension, and thus prevent slippage of the wire over the surface of the drum, more in particular slippage in the respective grooves.

(40) In an embodiment, the curved segments of a double drum traction winch according to the invention are each at one end shaped for supporting an overlying end of an adjacent curved segment, and at the opposite end are each shaped for engaging a curved segment for support, such that the curved segments forming a groove support each other like overlapping roof tiles. Such an embodiment is shown in the figures, in particular in FIGS. 3 and 4.

(41) In the particular embodiment shown, a first row of curved segments 11a each have a first end 14 of a curved segment 11 cooperating with a first cam shaft 12a to displace said end substantially in an essentially radial direction. Each second end 15 of a segment of the first row 11a is supported by a first end 16 of a segment of an adjacent second row 11b. A second cam shaft 12b cooperates with said first ends 15 of the segments of the second row 11b to displace the ends in the radial direction. Thus, by actuating a single cam shaft the ends of the segments of two rows adjacent rows are moved. Thus, the curved segments can be moved efficiently.

(42) In the embodiment shown, for each cam shaft a cam shaft actuator is provided on the core body, e.g. a hydraulic or electric motor. The cam shafts can thus be rotated individually. Alternatively, one cam shaft actuator is provided for rotating two or more cam shafts. In a further embodiment, said cam shaft actuators are operable independent from one another.

(43) In an embodiment, the actuator mechanism is provided with a control system adapted to operate the actuators while the drums carry a wire. Thus, the drums can be adjusted when the tension in the wire changes, for example when a load is attached to one end of the wire. IN a further embodiment, the actuator mechanism is provided with a control system adapted to operate the actuators while the drums carry a wire and while the drums carrying a wire are rotated. Thus, the drums can be adjusted for example while a load is being lifted or lowered. In a further embodiment, the actuator mechanism is provided with a control system adapted to operate the actuators while the drums carry a wire and are rotated and such that a curved segment is moved in the substantial radial direction only when the groove section of that curved segment only partially carries a wire, in an embodiment is moved only when the groove section of that curved segments does not carry a wire.

(44) For example in the side view in cross section of the drum shown in FIG. 3, two curved segments 11a, 11d partially carry a wire and two curved segments 11b, 11c, both facing the other drum, do not carry a wire. When lowering a load, the drum 4 is rotated in a clockwise direction. Thus, the curved segments come free from the wire at the top side of the drum, and engage the wire at the bottom side of the drum. When adjusting the position of the curved segments, they are preferably moved when they are not carrying a wire, in this case curved segments 11b and 11c. However, it is also possible for segment 11d to already move the end of the curved segment free from wire, while the opposite end of the cured segment still carries a wire. By moving the curved segment, or part of the curved segment, when not carrying a wire, the drives for rotating the cam shaft supporting that curved segment, or part of that curved segment, do not need excessive power and can thus be kept comparatively small in size and light of weight.

(45) In a further embodiment, for adjusting the circumference of a groove a first curved segment is moved at one end only, to form an intermediate between the curved segments defining the previous circumference and the curved segments defining the new circumference. When the circumference of the groove is to be adjusted, for example increased, of a first curved segment the upstream end, i.e. the end firs engaging the wire, is not moved in the radial direction, and the downstream end, i.e. the end that engages the wire last is moved to a new radial position. Of the subsequent curved segment both ends are moved to a new radial position. Thus, the first curved segment forms an intermediate between the old and new circumference, and guides the wire onto the second curved segment which is moved at both ends into the new radial position. By thus adjusting the circumference of the groove and thus guiding the wire, peak tensions in the wire due to sudden changes in the diameter of the groove are prevented.

(46) In an embodiment, the actuator mechanism is provided with a control system comprising one or more sensors for detecting the wire speed and/or tension in the wire carried by the drum. This control system is furthermore adapted to operate the actuators such that the segments are positioned in dependence of the actual tension in, and thus the stretch of, the wire for forming grooves having a circumferential distance such that the surface of the curved segment carrying the wire has substantially the same speed as the wire. Such a control system allows for automatic adjustment of the position of the curved segments while lifting and/or lowering a load, in particular when the supported load changes during the lifting or lowering operation, for example when lifting and/or lowering a load at great depths.

(47) It is observed that in the embodiment shown the curved segments are positioned such that the radii of the grooves are similar. In use the radii of adjacent curves will differ, with the groove having the smallest radius located at the low tension end of the drum and the groove having the largest radius located at the high tension end of the drum. Thus, the curved segments of a groove can be moved between an inward position for supporting a wire under low tension, and an outward position for supporting a wire under high tension. The minimal inward and maximal outward position are similar for the curved segments forming a groove, but may differ between curved segments forming adjacent grooves.

(48) It is observed that the elastic behaviour of different types of wires differs, due to for example the material(s) used, the weave of the wire and the diameter of the wire. Some wires have a linear elastic behaviour in their entire operational window, others have a non linear elastic behaviour, and others have a linear elastic behaviour along a part of their operational window, for example when supporting light loads, and a non linear elastic behaviour along another part of their operation window, for example when supporting large loads. In an embodiment, the actuators are configured such that the movement of the curved segments is linked to the elastic behaviour of a typical type of wire.

(49) In an embodiment the actuator mechanism is adapted for moving the curved segments of a drum at a predetermined and fixed ratio from one groove to the next groove, to adjust the circumferential distance of each groove in relation to the elastic behaviour of the wire. Thus, the speed at which the curved segment at the high tension end of the drum is moved is higher than the speed of the curved segment at the low tension end of the drum. All segments are thus moved into their next position in the same amount of time. This may for example be achieved by providing a cam shaft with off centre and circular shaped cams.

(50) It is furthermore observed that the stretching behaviour of a wire may not be direct proportional to the tension in the wire along its entire operation window. Thus, when the overall tension in the wire increases, the ratio between the radii of the different grooves may change. In a further preferred embodiment, the actuator mechanism is adapted for moving the curved segments of a drum at a predetermined and changing ratio from one groove to the next groove to adjust the circumferential distance of each groove in relation to a predetermined non-linear elastic behaviour of the wire. Thus, the speed at which a curved segment is moved from the inward position towards the outward position, or visa versa, may differs in relation to the tension in the wire. This may for example be achieved by providing a cam shaft with oval shaped cams.

(51) By using a traction winch according to the invention wire slip on a double drum traction winch can be reduced or even eliminated.

(52) In use, the traction winch is preferably combined with a storage drum holding a wire to be carried by the double drum traction winch. In an embodiment, the radial position of the curved segments is adjusted, and thus the circumferential length of the grooves defined by those curved segments, to fit the specifics of the wire and or the load supported by the wire.

(53) The wire is subsequently guided from the storage drum to the traction winch, and wound about the two traction drums such that the wire is carried by the grooves. The wire is then guided from the traction winch to a load, for example via a crane and/or pulley system, and connected to the load. The wire can then be used for lifting and/or lowering the load using the traction winch.

(54) With a traction winch according to the invention the circumference of the grooves can be adapted by moving the curved segments forming the grooves in a substantial radial direction. Thus, the circumferences of the grooves are adapted to fit the particular wire and the load supported by that wire. Slippage between rope and the drum is thus prevented. This slipping of the wire develops heat and causes extensive wear, especially with synthetic, i.e. light weight, wires. Hence, with a double drum traction winch according to the invention it is possible to use lightweight rope in deep water, e.g. for lowering equipment and placing equipment on the bottom of the sea. By enabling the use of light weight wires the traction winch according to the invention enables an increase in loads to be carried by that wire and/or the water depths to be reached since the part of the load formed by the weight of the wire is reduced. The traction winch according to the invention may alternatively be applied for mooring purposes.

(55) In a method according to the invention, the circumference of multiple grooves is adjusted by adjusting the radial position of multiple curved segments, while the drums are carrying the wire. Thus the grooves, more in particular the radius and circumference of the grooves, are adapted while the wire is supporting a load. In an embodiment the radii of a row of grooves are adjusted simultaneously with an actuator common to the row of grooves.

(56) A further method according to the invention comprises the step of dynamically adjusting the circumference of the grooves, in an embodiment simultaneously, by adjusting the radial position of multiple curved segments while the drums are rotated. A curved segment is in an embodiment moved in the substantial radial direction only when the groove of that curved segment partially carries a wire, in an embodiment is moved when the groove of that curved segments does not carry a wire. In this embodiment, the position of the curved segments defining a groove is adjusted in a consecutive fashion along the circumferential distance of the groove. Thus, the curved segments are moved when not, or at least not fully, supporting the wire, which facilitates adjusting the position of the curved segments. For adjusting the radius of a groove, and thus adjusting the position of all curved segments forming the groove, the drum has to rotate over a full 360 degrees.

(57) With a traction winch according to the invention, an increase or decrease in length of a wire caused by the weight of the load supported by that wire is balanced by increasing or reducing the diameter of the grooves supporting the wire and thus extending or reducing the circumferential length of the grooves of the drums, i.e. extending or reducing the distance a wire travels about the drum. Thus the wire is optimal supported along the drum and slippage of the wire is at least reduced compared to a double drum traction winch known from the art.

(58) Furthermore, in an embodiment according to the invention, the circumference of the grooves can be adjusted while lowering or lifting a load. The invention also provides dynamic adjustment of the circumference of the grooves. Thus, the circumference of the grooves can be adjusted while the grooves support a wire, and thus when the tension in the wire changes during lifting and lowering a load.

(59) For example, when lowering an object to a great depth in off shore operations, the load supported by the wire continuously increases. While lowering the object, the length of the supporting wire, i.e. the distance between load and surface, increases, and thus the weight of the supported wire increases. Therefore, the tension in the wire section wound about the drums of the traction winch increases.

(60) With a traction winch according to the invention, the circumference of the grooves can be adapted during the lowering of the load. Thus, the traction winch provides an optimal support for the wire, and prevents slip, for example during the whole trajectory of lowering and/or lifting an object.

(61) A double drum traction winch according to the invention can be used in off-shore operations, for example for abandonment and recovery applications, oceanography, dredging at great depths, or for towing by a tow boat.

(62) The traction winch according to the invention is beneficial since it enables handling any type of rope, e.g. lightweight rope, fibre rope and wires in a very careful manner, without causing damage. The use of fibre rope is particularly beneficial when large ends are required, e.g. for use in deep water, because of its properties being as strong as steel wire but only a fraction of the weight. This means that lightweight fibre rope can handle a substantially better payload in deep water, and, due to its low weight, winches and handling equipment may be applied with much smaller power requirements and dimensions than for steel wire. As a result, energy and space consumption of traction winches on offshore equipment is reduced.

(63) In FIG. 6 the curved segments of adjacent grooves are shown in cross section. The figure is highly schematic and the relative movement of the curved segments is exaggerated for explanatory purposes. The wire supported in the grooves is not shown in the drawing.

(64) FIG. 6a shows the curved segments in an initial position in which all the grooves have the same radius and circumference. Such a position of the curved segments is also shown in FIG. 1.

(65) FIG. 6b shows a situation in which the curved segments towards the high tension end of the drum, i.e. the right in the figure, are moved in an outward position, i.e. upwards in the figure. It is observed that the same affect can be achieved by moving the curved segments towards the low tension end of the drum, i.e. the left in the figure, towards an inward position, i.e. downward in the figure.

(66) FIG. 6c shows a situation in which the curved segments are moved in an outward position, similar to the situation depicted in FIG. 6b, but with more tension in the wire and thus more elongation of that wire. Thus, in the particular situation shown, the curved segments towards the high tension end of the drum are moved further outward for supporting the wire than the curved segments in the situation depicted in FIG. 6b.

(67) FIG. 6d shows the curved segments in a situation in which the high tension end and the low tension end of the drum have switched. Such a switch may occur when the tension in the wire between the traction winch and storage drum is higher than the tension in the wire between the traction winch and the load, for example when a comparatively light load, or no load at all, is supported by the wire. In the depicted situation the tension in the wire is high enough to cause elongation of the wire, and the curved segments towards the low tension end of the drum, i.e. the right in the figure, are moved inward to provide the drum with grooves having a larger circumference towards the high tension end of the drum.