WO2017018883A1

WO2017018883A1 - Rotary chain tensioner

Info

Publication number: WO2017018883A1
Application number: PCT/NL2016/050557
Authority: WO
Inventors: André REXWINKEL; Maurits VAN WEZEL
Original assignee: Ihc Holland Ie B.V.
Priority date: 2015-07-28
Filing date: 2016-07-28
Publication date: 2017-02-02
Also published as: NL2015233B1

Abstract

A rotary chain tensioner (10) includes a base frame (14); a wheel (16) rotatingly connected to the base frame at a wheel axis (44) and able to receive a chain (12); a pivoting arm (18) with a first arm end (20) pivotally connected to the base frame at an arm pivot axis (46); a hook (24) rotatably mounted to a second arm end (22) of the pivoting arm for securing to the chain; a first cylinder (26) with a first end (28) pivotally mounted to the base frame and a second end (30) pivotally mounted to the pivoting arm for moving the pivoting arm; and a chain stopper (38). The wheel axis is offset from the arm pivot axis.

Description

ROTARY CHAIN TENSIONER

BACKGROUND

Off-shore structures or vessels, such as those used in the oil and gas industry, often use cable or chains for various tasks including anchoring the structure or vessel to the seabed, and lifting or lowering loads. When a chain is used, a specific device can be used to tension the chain and guide it into or out of a chain locker.

One such device can be seen in U.S. Pat. No. 6,655,661, which discloses a rotating jack winch for heaving in or paying out chains. The device includes a frame, a rotating chain wheel with pockets for supporting the chain, an upper gripping device, a lower locking device, and a cylinder for lifting the chain. The upper gripping device includes a pawl for locking the chain into the pocket chain wheel, and is supported in a bracket which is pivotally supported with the same axis of rotation as the chain wheel. The cylinder is pivotally supported in the bracket and the frame. The device works by pushing the chain around the pocket wheel using the cylinder and the upper gripping device, with the pawl of the upper gripping device working with the pocket to engage a vertical link and move the chain. Because the upper gripping device is connected to the frame at the same axis of rotation as the pocket wheel, the upper gripping device with the pawl follow the same path allowing the pawl and pocket to remain engaged while pushing. The cylinder is connected to a frame and extends below the frame so that it is able to exert sufficient force for the pushing of the upper gripping device and chain. Because the cylinder extends below the frame, there may be need for reinforcement due to the large cylinder force beyond the envelope of the jack winch and therefore presumably outside the hull. The long stroke to follow the pocket wheel for proper engagement between the pawl and pocket also means that buckling may be an issue with the cylinder. A similar device is shown in WO 2013/132004, which discloses a holding device for anchoring a vessel. The holding device has a swivel arm that is rotatable about a common axis as the holding device and a locking arm for pulling in or releasing chain.

SUMMARY

A rotary chain tensioner includes a base frame; a wheel rotatingly connected to the base frame at a wheel axis and able to receive a chain; a pivoting arm with a first arm end pivotally connected to the base frame at an arm pivot axis; a hook rotatably mounted to a second arm end of the pivoting arm for securing to the chain; a first cylinder with a first end pivotally mounted to the base frame and a second end pivotally mounted to the pivoting arm for moving the pivoting arm; and a chain stopper. The wheel axis is offset from the arm pivot axis. Such an offset enables a compact rotary tensioner which is able to have all components at or above the base frame while ensuring the cylinder is able to provide sufficient force at a relatively constant rate throughout a stroke. The offset axes allow for using a cylinder at or above the base frame to move the pivoting arm and hook while ensuring the pivoting arm and hook are able to make a secure connection and provide a steady force for pulling in or letting out the chain. Because the rotary chain tensioner is able to be more compact and fully supported by the base frame, it is easier to move and easily supported, for example by the hull of a vessel. The pulling movement system also enables for easier access to rotary chain tensioner components, which can be useful for routine maintenance, fixing

components, etc.

According to an embodiment, the rotary chain tensioner further comprises a second cylinder with a first end pivotally mounted to the base frame and a second end pivotally mounted to the pivoting arm for moving the pivoting arm. Such a second cylinder can support the need for additional forces in the system and/or balancing forces in the rotary chain tensioner.

According to an embodiment, the pivoting arm comprises first and second pivoting arms connected to each other in parallel and to the hook on the second ends. According to an embodiment, one or more of the first and second cylinders also move the hook.

According to an embodiment, the rotary chain tensioner further comprises a hook movement system for rotating the hook about a pivot point. Optionally, the hook movement system comprises one or more cylinders. Such a separate hook movement system that may include one or more cylinders can provide for precise control of the movements of the hook.

According to an embodiment, the wheel pivot axis is located 500 mm or more from the arm pivot axis. Optionally, the wheel pivot axis is located 1000 mm or more from the arm pivot axis. These offset ranges can be ideal for specific chain sizes or other system requirements, and the offset range can vary according to the axes, the hook, the chain, forces within the system, etc.

According to an embodiment, the base frame comprises a base with the first end of the first cylinder being mounted to the base. By mounting the first cylinder to a base of the base frame, the base frame is fully able to support the forces in rotary chain tensioner, and the cylinder does not need to extend beneath the base, thereby reducing or eliminating the need for extra room and/or reinforcement under the rotary chain tensioner.

According to an embodiment, the first cylinder comprises a hydraulic cylinder.

According to an embodiment, the wheel comprises a sprocket wheel. A sprocket wheel is able to engage particular chain links with the sprockets, thereby securing a stronger connection to the chain to assist in letting out or pulling in the chain.

According to an embodiment, the chain stopper is mounted to the base frame.

Mounting the chain stopper to the base frame provides the chain stopper with support needed and keeps the rotary chain tensioner in a compact package.

According to a further aspect of the invention, a method of tensioning or paying out a chain with a rotary chain tensioner comprises the steps of a) connecting a chain stopper to a chain which extends over a wheel; b) securing a hook connected to the pivoting arm to a chain link of the chain; c) releasing a chain stopper; d) retracting or extending the pivoting arm using at least one cylinder to move the chain; e) connecting the chain stopper to the chain; and f) disengaging the hook from the chain. The rotary chain tensioner includes the pivoting arm with a pivoting arm axis and a wheel with a wheel axis. The pivoting arm axis is offset from the wheel axis, which allows the rotary chain tensioner to have a compact envelope and provide the needed force for tensioning or paying out a chain. The method also allows for a short cylinder stroke making buckling less of an issue, and a relatively short pivoting arm, keeping it less susceptible to bending.

According to an embodiment, the hook is secured, engaged and/or disengaged using a hook movement system. Such a hook movement system can optionally comprise one or more cylinders.

According to an embodiment, step b) of securing a hook connected to the pivoting arm to a chain link of the chain further comprises engaging the hook with the chain by partially retracting the hook with a pivoting arm and at least one cylinder of the rotary chain tensioner. Such a movement can ensure the hook is fully engaged with the chain to secure the chain to the wheel for paying out or tensioning movements.

According to an embodiment, the method is used for paying out a chain by extending the pivoting arm in step d) and the method is used for tensioning a chain by retracting the pivoting arm in step d).

According to an embodiment, step f) comprises extending the pivoting arm until the chain rests on the chain stopper and then disengaging the hook from a chain link. This can help to prevent any possible impact damage on the chain stopper, which may occur if the chain were just released at this point without moving pivoting arm.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. la is a perspective side view of a rotary chain tensioner.

Fig. lb is a perspective rear view of the rotary chain tensioner of Fig. la.

Fig. lc is a perspective top view of the rotary chain tensioner of Fig. la.

Figs. 2a-2c shows perspective side views of a rotary chain tensioner during a tensioning operation.

Fig. 3 shows a graph of the cylinder force over a stroke for a rotary chain tensioner with different axes arrangement between a pivoting arm and a sprocket wheel.

DETAILED DESCRIPTION

Fig. la shows a side view of rotary chain tensioner 10 and chain 12, Fig. lb shows a perspective rear view of rotary chain tensioner 10 and chain 12, and Fig. lc shows a perspective top view of rotary chain tensioner 10 and chain 12. Rotary chain tensioner 10 includes base frame 14 with base 15, sprocket wheel 16, pivoting arm 18 with first arm end 20 and second arm end 22, hook 24, first cylinder 26 with first end 28 and second end 30, second cylinder 32 with first end 34 and second end 36 and chain stopper 38. Chain 12 includes chain links 40.

Base 15 is a generally planar portion which forms the base and lowermost part of rotary chain tensioner 10. Base frame 14 (with base 15) supports the various components of rotary chain tensioner 10, and can be made of a variety of materials, for example, steel. Sprocket wheel 16 is rotatably connected to base frame at wheel axis 44, and acts to guide movement of chain 12. Sprockets are arranged around sprocket wheel 16 for engaging chain links 40.

Chain stopper 28 is connected to base frame 14, generally at the location where chain 12 enters rotary chain tensioner 10, for example from a mooring line. Chain stopper 28 can be an extending pawl or another type of device which can engage and stop chain 12, locking chain 12 movement. It can include a number of components to help in locking chain 12 movement, including one or more cylinders.

First cylinder 26 and second cylinder 32 are pivotally mounted at respective first ends 28, 34 to base frame 14, and particularly base 15. On second ends 30, 36, first and second cylinders 26, 32 are pivotally connected to pivoting arm 18. While the connection is shown at a mid point of pivoting arm 18, the connection can be at another point of pivoting arm. First cylinder 26 and second cylinder 32 can be hydraulic cylinders or other types of cylinders able to exert force on pivoting arm 18 and in some cases hook 24. In some embodiments, hook 24 is moved by one or more separate cylinders.

Pivoting arm 18 is pivotally connected to base frame 14 at arm pivot axis 46 on first arm end 20 and to hook 24 on second arm end 22. In some embodiments, arm 18 can be formed of two separate arms on either side of sprocket wheel 16 and connected together at the connection to hook 24. In that case, they would each have first ends connected to base frame 14 through arm pivot axis 46.

Arm pivot axis 46 is located a distance from wheel axis 44. This distance can be, for example, 500 mm, 1000 mm or more. Such spacing allows for a pivoting arm 18 which can accommodate connections of first cylinder 26 and second cylinder 32 to base frame 14 without having to extend below base 15; and the secure connection of hook 24 to chain links 40 during a rotation.

A tensioning cycle is shown in Figs. 2a-2c. Fig. 2a shows rotary chain tensioner 10 with cylinders 26, 32 and pivoting arm 18 extended and hook 24 in an open position. Chain 12 is around sprocket wheel 16 such that some chain links 40 are engaged by the sprockets and some chain links 40 are between. Chain stopper 38 is connected to chain 12 to hold it in place.

Next, as shown in Fig. 2b, hook 24 is moved to a closed position between two chain links 40. Hook 24 is engaged by partially retracting hook and pivoting arm 18 to form a secure contact between hook 24 and a chain link 40. Hook 24 movements can be facilitated by first and/or second cylinders 26, 32 and/or could be facilitated by one or more separate hook 24 movement systems such as one or more additional cylinders. At this point, chain stopper 38 can be released to a point where clearance is sufficient for chain 12 passage through chain stopper 38. First and second cylinders 26, 32 are retracted, moving chain 12 with them, to a position where chain stopper 38 can be engaged again. This can be, for example, over at least two chain links 40 to such a position as shown in Fig. 2c. At this position, chain stopper 38 is closed to engage chain 12. Pivoting arm 18 is then extended until chain 12 rests on chain stopper 38, after which hook 24 can be disengaged from chain 12 link 40. This helps to prevent impact damage on the chain stopper 38 which may occur if the chain were just released at this point without moving pivoting arm 18. Hook 24 is then moved to an open position to release chain. Next, cylinders 26, 32 and pivoting arm 18 can be extended to the position shown in Fig. 2a for another cycle.

By using a configuration where the axis of rotation of sprocket wheel 16 is offset from arm pivot axis 46 and using first and second cylinders 26, 32 in combination with pivoting arm 18 and hook 24 as a pulling movement system; first and second cylinders 26, 32 are able to connect their first ends 28, 34 to base 15 of base frame 14, thereby allowing for a compact package of rotary chain tensioner 10. This ensures that all components of rotary chain tensioner 10 are supported and located at or above base plate 15, resulting in no force introduction outside the hull of a vessel, thereby leading to less or no extra reinforcement needed to handle the forces of rotary chain tensioner 10. In past systems which used pushing cylinders and a common axis of rotation, the cylinders needed to extend below the frame for the required pushing forces, resulting in a more complicated system that often required reinforcement below the hull where the device reached. The compact package of rotary chain tensioner 10 also makes moving the device easier, and less lifting movement is needed than if rotary chain tensioner components extended below base plate 15.

Additionally, by having a compact package all supported at or above base frame 14, components are more easily accessible. The use of pulling cylinders 26, 32 allows for connection of cylinders 26, 32 to base frame 14 on an opposite side of chain stopper 28, making chain stopper 28 and its associated components also more accessible. This can be helpful in the case that routine maintenance, inspection and/or a repair is needed. The pivoting connection of first cylinder 26 and second cylinder 32 on first ends 28, 34 and second ends 30, 36 allows for a simple support of cylinders 26, 32. Such a set-up has a relatively short cylinder 26, 32 stroke and a relatively short pivoting arm 18, resulting in buckling not being an issue and in the pivoting arm 18 being less susceptible to bending. The use of a sprocket wheel 16 and hook 24 also ensures for a secure connection for pulling in or letting out chain 12. If cylinders 26, 32 were supported with ball-and-socket joints, movement around two axes would be supported, making machining tolerance requirements less strict than if supporting movement around only one axis.

By rotary chain tensioner 10 having a pivoting arm 18 with axis 46 which is offset from sprocket wheel axis 44, the force during cylinders 26, 32 strokes can also be more stable throughout the stroke, as can be seen in Fig. 3. Line 50 shows a graph of cylinder force if the sprocket wheel 16 axis and the pivoting arm 18 axis were the same or very close together. As can be seen in the graph, the force is much higher at the beginning and end of the stroke. Line 52 shows the force in cylinders of rotary chain tensioner 10, where pivoting arm 18 axis 46 and sprocket wheel 16 axis 44 are offset 500 mm. As cylinders 26, 32 extend, the virtual moment arm to the pivot point of pivoting arm 18 at arm pivot axis 46 decreases while the distance of hook 24 to the pivot point of pivoting arm 18 also decreases, resulting in the ratio between these two arms being relatively constant. As can be seen clearly from line 52, the force in such a device 10 is consequently much more stable and lower throughout the stroke. This lower and stable force can lead to a system that is more reliable and has a longer lifespan.

While rotary chain tensioner 10 has been shown and described in relation to tensioning movements, it can also be used for slackening chain 12, which would be roughly the same procedure in reverse. Specifically, the pivoting arm 18 would be extended by cylinders 26, 32 after a connection is made between hook 24 and a chain link 40. While the distance between sprocket wheel axis 44 and arm pivot axis 46 are shown as 500 mm apart, the distance could vary depending on system requirements, including chain size, pulling force, the axes, the hook, other forces within the system, etc.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A rotary chain tensioner comprising:

a base frame;

a wheel rotatingly connected to the base frame at a wheel axis and able to receive a chain;

a pivoting arm with a first arm end pivotally connected to the base frame at an arm pivot axis;

a hook rotatably mounted to a second arm end of the pivoting arm for securing to the chain;

a first cylinder with a first end pivotally mounted to the base frame and a second end pivotally mounted to the pivoting arm for moving the pivoting arm; and

a chain stopper, wherein the wheel axis is offset from the arm pivot axis.

2. The rotary chain tensioner of claim 1, and further comprising:

a second cylinder with a first end pivotally mounted to the base frame and a second end pivotally mounted to the pivoting arm for moving the pivoting arm.

3. The rotary chain tensioner of any of the preceding claims, wherein the pivoting arm comprises first and second pivoting arms connected to each other in parallel and to the hook on the second ends.

4. The rotary chain tensioner of any of claims 2-3, wherein one or more of the first and second cylinders also move the hook.

5. The rotary chain tensioner of any of the preceding claims, and further comprising a hook movement system for rotating the hook about a pivot point.

6. The rotary chain tensioner of claim 5, wherein the hook movement system comprises one or more cylinders.

7. The rotary chain tensioner of any of the preceding claims, wherein the wheel pivot axis is located 500 mm or more from the arm pivot axis.

8. The rotary chain tensioner of any of the preceding claims, wherein the wheel pivot axis is located 1000 mm or more from the arm pivot axis.

9. The rotary chain tensioner of any of the preceding claims, wherein the base frame comprises a base with the first end of the first cylinder being mounted to the base.

10. The rotary chain tensioner of any of the preceding claims, wherein the first cylinder comprises a hydraulic cylinder.

11. The rotary chain tensioner of any of the preceding claims, wherein the wheel comprises a sprocket wheel.

12. The rotary chain tensioner of any of the preceding claims, wherein the chain stopper is mounted to the base frame.

13. A method of tensioning or paying out a chain with a rotary chain tensioner, the rotary chain tensioner with a pivoting arm with a pivot axis and a wheel with a wheel axis, the pivot axis being offset from the wheel axis, the method comprising:

a) connecting a chain stopper to a chain which extends over the wheel;

b) securing a hook connected to the pivoting arm to a chain link of the chain; c) releasing a chain stopper;

d) retracting or extending the pivoting arm using at least one cylinder to move the chain;

e) connecting the chain stopper to the chain; and

f) disengaging the hook from the chain.

14. The method of claim 13, wherein the hook is secured, engaged and/or disengaged using a hook movement system.

15. The method of any of claims 13-14, wherein step b) of securing a hook connected to the pivoting arm to a chain link of the chain further comprises engaging the hook with the chain by partially retracting the hook with the pivoting arm and at least one cylinder of the rotary chain tensioner.

16. The method of any of claims 13-15, wherein the method is used for paying out a chain by extending the pivoting arm in step d) and the method is used for tensioning a chain by retracting the pivoting arm in step d).

17. The method of any of claims 13-6, wherein step f) comprises extending the pivoting arm until the chain rests on the chain stopper and then disengaging the hook from a chain link.