Patent Application
20170305507
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The present invention relates to a device suitable for placement in a mounted condition on a floating object, comprising a mounting structure and a tiltable arm having a free extremity and a pivot point supported by said mounting structure, wherein said arm connects to suspension and/or support means for controlling the arm's inclination with respect to the horizon, and wherein said suspension and/or support means comprise at least one spring, wherein opposite extremities of the said spring share connecting points with said arm and with said mounting structure.
Such a device is known from WO93/11036 and is for instance used for transfer of personnel or cargo between a fixed or floating installation and a boat in a high sea. According to this document the tiltable arm or boom is pivoted around a horizontal axis of the installation, wherein one outer end of the boom projects over a position to which a boat deck can be maneuvered. An approximately vertical rope or wire connection of approximately constant length is applied between the deck and the outer end of the boom, wherein the outer end of the boom is upwardly suspended around the horizontal axis by means of a passive spring device, thus keeping the rope or wire taut despite the movements of the boat in the waves. The rope or wire connection also serves as a guide rope or guide wire for transport means in the form of a chute like rescue sock, slide, lift, stairway, gangway or the like between the outer end of the boom and the boat deck. The spring device comprises an hydraulic cylinder, wherein claim 3 of WO93/11036 teaches that the spring characteristic can be adjusted by altering the amount of gas and/or liquid in the accumulator with pump and/or valve devices provided for this purpose.
A disadvantage of the known device is that maintaining the arm's free extremity at a predefined position with reference to the boat deck requires the application of said rope or wire which is relatively cumbersome, and which inherently provides an unsafe situation when the rope or wire breaks. In WO93/11036 a passive spring is engaged in an unbalanced configuration, meaning the free extremity of the arm, gangway or access bridge is maintained by the passive spring in only one predetermined inclination of the arm. Once the arm is in any other inclination the passive spring will cause acceleration forces towards the predetermined inclination. When the floating object on which the arm is mounted is subjected to motions due to waves, and when the free extremity of the arm is not connected to a fixed point, these acceleration forces can be very high due to amplification (the acceleration forces due to the spring are amplified by the acceleration forces due to waves). Moreover the acceleration forces are unpredictable and dependent on an irregular wave pattern. This can result in unpredictable and dangerous movements of the free extremity of the arm. In WO93/11036 the passive spring connected to the arm has therefore the drawback of requiring a secondary force to stabilize the free extremity of the arm, such as a connection to a fixed point.
WO2011/154730 discloses a gangway assembly for a vessel comprising a gangway, a pivotably mounted base, a sensor arrangement two sense movement of the vessel, an end portion of the gangway pivotably connected to the base and an actuator connected to the gangway responsive to signals from the sensor arrangement to control the vertical position of an opposite end portion of the gangway so as to compensate for vertical movement of the vessel, and the base arranged to respond to and compensate for roll of the vessel.
WO2013/174886 discloses a gangway system for providing passage between the structure and an independent vessel, comprising a pedestal for mounting to said vessel; a gangway comprising an inboard root hingedly mounted to the pedestal, and an outboard end for interfacing with the structure; a processor and one or more sensors configured to report to the processor and a control system responsive to signals from the processor, wherein a ram is applied responsive to signals from the control system and mounted on the pedestal for adjusting the vertical position of the gangway outboard end; and a ram response to signals from the control system and mounted on the gangway for adjusting the horizontal position of the gangway outboard end.
WO00/15489 discloses a mooring arrangement for mooring a vessel against a structure, comprising a connecting means, a maneuvering member arranged at a first end of the connecting means for adjusting the angle between the connecting means and the horizontal plane, and a locking device arranged at a second end of the connecting means for fastening the vessel to the structure when mooring.
WO2007/120039 discloses the vessel provided with a motion platform and means applied to the platform for compensating motions of the vessel, wherein actuators are applied sensitive to signals from a control system to move the platform with reference to the vessel. Further a passive pressure element is provided to the platform in order to support this platform at least partly.
It is one of the objectives of the invention to arrange that the device according to the preamble is embodied such that a free extremity of the arm can be maintained more easily at a desired position with improved energy efficiency.
It is another object of the invention to maintain the free extremity of the arm at a desired position also when the arm has no connection with a fixed point, and to avoid unpredictable and dangerous movements of the arm, wherein the arm is resistant to irregular and unknown wave patterns.
Another objective is to provide that the device is operationally safe at all circumstances; meaning that with a power failure the construction with the tiltable arm remains essentially balanced.
A still further objective is to provide that the device has improved handling capability for heavier weights and/or longer arms.
Further objectives and advantages of the invention will become apparent from the following disclosure.
Further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more embodiments of the invention and are not to be construed as limiting the invention. In the drawings:
The invention is embodied in a device and a method to balance a tiltable arm comprising a free extremity and having a pivot point on a mounting structure which is supported by a floating object, in accordance with one or more of the appended claims.
In a first aspect of the invention the device is embodied with the feature that the spring is a passive spring and is arranged to balance the arm so as to substantially stabilize a position of a free extremity of the arm during movements of the floating object. A major advantage of this is that hardly any energy will be required for maintaining the free extremity of the arm at the desired position or orientation. Preferably then the free extremity of the arm distant from the mounting structure is arranged to carry or support a payload, wherein the spring is arranged to balance the arm including said payload.
Without being bound to any particular theory the inventors contemplate that in the invention the moment generated by the force of gravity on the arm relative to the pivot point with the mounting structure is to be substantially compensated by a moment generated on the arm relative to said pivot point by the spring in any inclination the arm assumes, so that the spring is arranged to balance the arm in any inclination it assumes, meaning that the force of gravity on the arm and the force of the spring on the arm cancel each other out and do not change or influence the position of the free extremity of the arm. In that situation it is the inertia of the arm which ensures maintaining the position of the free extremity of the arm during movements of the floating object due to waves at any wave frequency and in high sea states.
Suitably the spring is a gas spring comprising a gas container or a hydro-pneumatic spring comprising a gas container and an oil container. The inventors have found that particularly this type of spring is best equipped to balance heavy loads without much energy consumption, if any at all.
Without excluding any other possible embodiments it is in a particular embodiment preferable that with the mounting structure being level, the said pivot point of the tiltable arm with the mounting structure and the connecting point of the at least one spring with the mounting structure are positioned on a straight imaginary vertical line above each other. This construction is particularly suitable for marine applications wherein it is possible to stabilize the position of the free extremity of the arm with a very little amount of energy (if any at all), and this applies to heave, and pitch or roll depending on the arm's direction with reference to the object on which it is mounted.
In order to enable the device to adequately compensate all possible motions due to the waves at least a part of the mounting structure carrying the tiltable arm is rotatable with reference to the object.
It is advantageous that at least one of the connecting points of the spring with the arm and with the mounting structure is adjustable in position along the arm respectively the mounting structure, and/or a spring constant of said spring is adjustable. In this way it is easily possible to compensate for different loads to which the arm is subjected, and for compensating imbalance due to extensions or reductions in length of the arm.
It is preferable that the device comprises at least a first positioning actuator for the arm in addition to the adjustable spring. The position of the free extremity of the arm can then easily be adjusted and relatively small forces due to motion of the object or frictional forces can be compensated.
Further to optimize the reach of the device of the invention it is preferable that the arm is articulated.
In one preferred embodiment of the device of the invention the arm has at least two parts that are displaceable with reference to each other. Advantageously the at least two parts of the arm are longitudinally displaceable with reference to each other and/or said at least two parts of the arm are angularly displaceable with reference to each other. Suitably the at least two parts of the arm are angularly displaceable with reference to each other in a substantially horizontal plane and/or in a substantially vertical plane. These features contribute to securing the reach of the arm and enabling that the arm's extremity is controllable as to its position.
In all embodiments it is preferred that the at least two parts of the arm are arranged to be displaced with reference to each other so as to maintain the free extremity of the arm which lies distant from the mounting structure, at a predetermined and possibly variable position and/or orientation.
Further it is preferable that the mounting structure is arranged to be pivotably mountable or placeable on the object.
Appropriately in the mounted condition the mounting structure is mounted and connected with at least one hinge to the object. This optimizes the maneuverability of the mounting structure with reference to the object and increases its capability to counter motions due to the waves.
In one suitable embodiment the mounting structure is provided with a gimbal for mounting and connecting it to the object.
Further it may be beneficial that in the mounted condition the device is provided with at least a second actuator for pivoting the mounting structure with reference to the object.
Suitably further the device is provided with at least one sensor for monitoring an orientation of the free extremity of the arm distant from the mounting structure and/or of the mounting structure, wherein the device is further provided with a control system receiving signals from said at least one sensor, which control system based on said signals drivingly connects to the said first positioning actuator for the arm to maintain its free extremity at a predetermined position and/or orientation.
It is further beneficial that in the mounted condition the at least one sensor is equipped for monitoring an orientation of the floating object, and that the control system receives signals relating to the orientation of the floating object, which control system based on said signals drivingly connects to the said first positioning actuator for the arm to maintain its free extremity at a predetermined position and/or orientation.
It is further preferred that the control system drivingly connects to means for positioning at least one of the connecting points of the spring with the arm and with the mounting structure respectively and/or for adjusting a spring constant of said spring to maintain the free extremity of the arm at a predetermined position and/or orientation.
It may still be further beneficial that the control system drivingly connects to means for displacing the at least two parts of the arm with reference to each other so as to maintain the free extremity of the arm distant from the mounting structure at a predetermined position and/or orientation.
The adequacy of the device of the invention may be further promoted in that the control system drivingly connects to the second actuator for pivoting the mounting structure with reference to the object to maintain the free extremity of the arm at a predetermined position and/or orientation.
Even further it may be beneficial that in the mounted condition the control system drivingly connects to means for extending the mounting structure upwards with reference to the object to maintain the free extremity of the arm at a predetermined position and/or orientation.
Still further it may be beneficial that in the mounted condition the control system drivingly connects to means for rotating the mounting structure with reference to the object to maintain the free extremity of the arm at a predetermined position and/or orientation.
The invention will hereinafter be further elucidated with reference to the drawing of exemplary embodiments of a device according to the invention that is not limiting as to the appended claims.
Whenever in the figures the same reference numerals are applied, these numerals refer to the same parts.
Making first reference to
A floating object 7 is subjected to the motions of waves 100. In practice, the floating object 7 is mostly a ship, a vessel or a working platform. Drawn in
Due to waves 100, the floating object 7 is subjected to motions of:
heave 1001, a motion parallel to the vertical axis 1000,
yaw 1002, a rolling motion revolving around the vertical axis 1000,
surge 2001, a motion parallel to the y-axis 2000,
roll 2002, a rolling motion revolving around the y-axis 2000,
sway 3001, a motion parallel to the x-axis 3000,
pitch 3002 a rolling motion revolving around the x-axis 3000.
The arm 2 is mounted on the floating object 7 by a mounting structure 8 in a pivot point 3. The upper part of the mounting structure 81 may be enabled to make a rotating movement 802 revolving around the spring base 80 in the swivel point 82 of the mounting structure 8. The upper part of the mounting structure 81 may slide along the mounting base 80 in the direction of the mounting structure 8 in order to extend the mounting structure 8 in a direction 800 of the mounting structure 8 in order to increase the working height of the arm 2. In this figure the direction of the vertical axis 1000 is parallel to the direction 800 of the mounting structure 8.
The arm 2 is further connected to the mounting structure 8 by a spring 6 in a spring base point 60 located on the mounting structure 8 and a spring mounting point 61 located on the arm 2. When the floating object 7 is level, the spring base point 60 (the connection point of the spring 6 with the mounting structure 8) and the pivot point 3 are positioned on a straight imaginary vertical line 800 above each other. The spring base point 60 may be movable along the mounting structure 8, the spring mounting point 61 may be movable along the arm 2. The spring 6 may be a conventional coil spring, but in practice, as depicted in
The arm's free extremity 4 may be constructed to transfer a payload 5 (cargo or staff) between the floating object 7 and a connection point 40 or vice versa. The connection point 40 may be located on a fixed object as shown in this
The arm 2 comprises at least one arm segment 20 but may also be articulated, comprising a second arm segment 21 or even multiple arm segments. In this
The arm 2 may further be connected to the mounting structure 8 by a positioning actuator 9. The positioning actuator 9 is depicted in this
In practice the positioning actuator 9 and/or the spring 6 may also be connected to the mounting structure 8 below the pivot point 3 as depicted in
The arm 2 extends in a direction 200, and an inclination angle 202 is defined between the direction 200 and the vertical axis 1000. In this
Changing the length of the arm 2 and/or a change in the force payload 5 exerted on the arm 2 may be counteracted by the positioning actuator 9 and/or by adjusting the spring. The spring may be adjusted by moving one of the spring connection points 60, 61 or both, and/or by changing the spring constant of the spring 6.
The payload 5 is shown as carried on the free extremity 4 but may also be suspended underneath the free extremity 4 by means of a rope or wire, or by means of a hoisting system with pulleys or other conventional hoisting means. The payload 5 may also be connected to any other part of the arm 2 and may be moved along the arm 2 and connected or disconnected at any time.
In use, while the pivot point 3 is subjected to heave 1001, the position of the free extremity 4 along the vertical 1000 axis is maintained stationary substantially by the spring 6. The pivot point 3 will repetitively move up and down due to the waves 100, but the spring 6 will maintain the vertical position of the free extremity 4 stationary along the vertical axis 1000, accumulating and releasing the energy for the continuous changes of the inclination 202 of the arm 2. Due to the configuration of the spring 6 it generates a moment in the pivot point 3 counteracting the forces of gravity on the arm 2 and—when applicable—its payload 5, in any inclination 202 of the arm 2. Therefore, the energy required to maintain the position of the free extremity 4 along the vertical axis 1000 stationary during heave 1001 is delivered substantially by the spring 6.
In use, because of the action of the spring 6, a positioning actuator 9 is not substantially required to maintain the position of the free extremity 4 along the vertical axis 1000 stationary during the influence of heave 1001. Therefore the device 1 is energy efficient and enables safe operation: maintaining the free extremity 4 substantially stationary along the vertical axis 1000 is not dependent on the continuous supply of energy nor depending on a functional actuation system. However, the positioning actuator 9 may be engaged for relatively small forces required to maintain the free extremity 4 stationary along the vertical axis 1000, such as counteracting friction in the spring 6. In addition the positioning actuator 9 may be engaged to change the inclination 202 of the arm 2 in order to change the position of the free extremity 4 along the vertical axis 1000.
In use, during the influence of motions due to waves 100 as mentioned above, the relative position of the free extremity 4 to the connection point 40 may further be maintained stationary by adjusting the length 201 of the arm 2 and changing the orientation of the mounting structure 8 relative to the floating object 7.
In use, when the length of the arm 2 changes and/or when the influence of the payload 5 on the arm 2 changes, the spring 6 may be adjusted in order to balance the arm 2. This can be done by changing the position of at least one of the spring connecting points 60, 61 and/or by changing the spring constant of the spring 6.
Making reference now to
The arm 2 shown in
With reference to
The arm 2 of the device shown in
With reference to
Due to a rolling motion 2002 (called roll for this direction of the floating object 7), the mounting structure 8 of the device shown in
With reference to
In
In use, during a rolling motion 2002 of the floating object 7, the mounting structure 8 is maintained substantially vertical by the offset actuator 92. By doing so the positioning actuator 9 does not need to counteract acceleration forces due to an offset angle, despite the rolling motion of the floating object 7. The orientation 804 of the hinge 84 is square to the horizontal orientation of the arm 2. This is not a preferred solution because in this configuration, for compensation of the offset angle 301 the offset actuator 92 uses a lot of energy. This is because the moment the arm 2 generates in the hinge 84 needs to be considered. It is preferable to maintain the direction of the orientation of the hinge parallel to the horizontal orientation of the arm 2. Then the offset angle 301 can be compensated with little energy because the moment generated by the arm 2 in the pivot point does not need to be taken in consideration.
Making now reference to
In use, the floating object 7 is subjected to a rolling motion 2002 (roll) and to a rolling motion 2003 (pitch), and the mounting structure 8 is maintained substantially vertical by two offset actuators 91 and 92. In order to change the working position of the arm, the upper part of the mounting structure 81 may be extended or retracted from the mounting base 80.
With further reference to
In
In use, when the length of the arm 2 changes and/or the influence of the payload 5 on the arm 2 changes, the spring constant of the spring 6 may be adjusted in order to balance the arm 2 and—when applicable—its payload 5. This may be done by changing the position of at least one of the spring connection points 60, 61 and/or by changing the spring constant of the spring 6 by adjusting the gas volume and/or the oil volume in the hydro-pneumatic spring.
Turning now to
In this preferred embodiment of
In
The arm 2 of the device shown in
It can be seen that the arm can be accessed by staff or cargo from the deck of a boat 3 during operation of the arm in all angles of the arm and in any horizontal orientation of the arm by simple access means such as a stair 85. The swivel point 82 is below the hinge 83 and its offset actuator 91.
Due to the energy efficient compensation in the device of the invention for heave, pitch and roll (and all other motions due to waves 100 mentioned above), the power supplies 94 and 64 as shown on the deck of the floating object 7 are much smaller compared to the power supplies of known devices. The first arm segment 20, the free extremity 4 and the connection point 40 both comprise guide and connect means 41. The first arm segment 20 is supported by a hydro-pneumatic spring 6 comprising two spring piston 66 and two gas containers 62.
Although the invention has been discussed in the foregoing with reference to several exemplary embodiments of the device of the invention, the invention is not restricted to these particular embodiments which can be varied in many ways without departing from the gist of the invention. The discussed exemplary embodiments shall therefore not be used to construe the appended claims strictly in accordance therewith. On the contrary the embodiments are merely intended to explain the wording of the appended claims without intent to limit the claims to the offered exemplary embodiments. The scope of protection of the invention shall therefore be construed in accordance with the appended claims only, wherein a possible ambiguity in the wording of the claims shall be resolved using the provided examples.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013933 | Dec 2014 | NL | national |
| 2014631 | Apr 2015 | NL | national |
This application is a continuation application of Patent Cooperation Treaty Application No. PCT/NL2015/050838, filed on Dec. 3, 2015, which claims priority to Netherlands Patent Application Nos. 2013933 and 2014631, filed Dec. 5, 2014 and Apr. 14, 2015, respectively, and the specifications and claims thereof are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/NL2015/050838 | Dec 2015 | US |
| Child | 15614217 | US |
