Device, use, and method for reducing horizontal and vertical vibrations

Abstract

The present invention relates to a device, use of device, and method of reducing vibrations in a structure. The method comprises a step of rotating a first element (11) in a first rotational plane (P1) and a second element (22) in a second rotational plane (P2) parallel to the first rotational plane (P1) around the rotational axis (2). The first element (11) has a first mass (M1) arranged with a distance (R1) from the rotary axis (2) in the first rotational plane (P1), and the second element (22) has a second mass (M2) arranged at a second distance (R2) from the rotary axis (2) in the second rotational plane (P2). The first and second element (11,22) are rotated in opposite directions around the rotational axis (2) with the centres of mass passing a line extending from the rotational axis (2) and outwards in a predetermined direction.

Description

[0001] Device, use, and method for reducing horizontal and vertical vibrations

[0002] Field of the Invention

[0003] The present invention relates to a device, use of device, and method of reducing vibrations in a structure. The method comprises a step of rotating a first element in a first rotational plane and a second element in a second rotational plane parallel to the first rotational plane around the rotational axis.

[0004] The first element has a first mass arranged with a distance from the rotary axis in the first rotational plane, and the second element has a second mass arranged at a second distance from the rotary axis in the second rotational plane.

[0005] The first and second element are rotated in opposite directions around the rotational axis with the centres of mass passing a line extending from the rotational axis and outwards in a predetermined direction.

[0006] Background of the Invention

[0007] Vibration-compensating devices for counteracting harmonic vibrations from an excitation source, such as vibrations generated by an engine of a vessel, are known to be comprise rotary bodies arranged either to rotate about a horizontally arranged axis for reducing vibrations in the vertical plane or to rotate about a vertically arranged axis for reducing vibrations in the horizontal plane.

[0008] As marine vessels are known to optimize the size and weight of its components, there is a need for compact, multifunctional, and adjustable vibration compensating devices.

[0009] Object of the Invention

[0010] It is an objective of the present disclosure to achieve a device and method to overcome the above-mentioned drawbacks.

[0011] One objective of the present disclosure is to achieve a device and a method for reducing vibrations in a structure in a predetermined direction.

[0012] Further objectives of the present disclosure are to use the device to reduce vibrations in a horizontal plane and / or use the device on a marine vessel. Description of the Invention

[0013] One objective of the invention is achieved by a method of reducing vibrations in a structure in a predetermined direction perpendicular to a rotational axis. The method comprises a step of rotating a first element in a first rotational plane and a second element in a second rotational plane around the common rotational axis. The first and second rotational planes are parallel planes arranged perpendicular to the rotational axis.

[0014] The first element has a first mass and is arranged with its centre of mass at a first distance from the rotary axis in the first rotational plane, and the second element has a second mass with its centre of mass arranged at a second distance from the rotary axis in the second rotational plane.

[0015] The first and second elements are arranged such that the first distance multiplied by the first mass is the same as the second distance multiplied by the second mass.

[0016] The first element and the second element are rotated in opposite directions around the rotational axis with the centres of mass passing at the same time a line extending from the rotational axis and outwards in the predetermined direction.

[0017] The rotation of the first element is driven by a first drive unit, and the rotation of the second element is driven by a second drive unit.

[0018] Alternatively, one objective of the invention is achieved by a method of reducing vibrations in a structure in a predetermined direction perpendicular to a rotational axis. The method comprises a step of rotating a first element in a first rotational plane and a second element in a second rotational plane around the rotational axis. The first and second rotational planes is parallel planes arranged perpendicular to the rotational axis.

[0019] The first element has a first mass and is arranged with its centre of mass at a first distance from the rotary axis in the first rotational plane, and the second element has a second mass with its centre of mass arranged at a second distance from the rotary axis in the second rotational plane.

[0020] The first and second elements are disposed such that the first distance multiplied by the first mass is the same as the second distance multiplied by the second mass. The first element and the second element are rotated in opposite directions around the rotational axis with the centres of mass passing - at the same time - a line extending from the rotational axis and outwards in the predetermined direction.

[0021] The centres of mass passing - at the same time - a line extending from the rotational axis and outwards in the predetermined direction may define a phase angle. Said phase angle may be the phase angle between the synchronized first and second element and the top dead centre of the main engine.

[0022] The centres of mass from the first element and the second element passing - at the same time - a line extending from the rotational axis and outwards in the predetermined direction, may ensure that the first and second element consistently passes each other in predetermined passing positions depending on the specific vibration reduction requirement.

[0023] The first element and the second element may be rotated in opposite directions at the same rotational speed around the rotational axis with the centres of mass passing - at the same time - a line extending from the rotational axis and outwards in the predetermined direction.

[0024] The first drive unit may be a motor configured for rotating the first element around the common rotational axis. The second drive unit may be a motor configured for rotating the second element around the common rotational axis.

[0025] The first element may be connected to a first drive shaft arranged along the rotational axis. The first drive unit may drive the rotation of the first drive shaft, and thus the first element, around the rotational axis. The first drive unit may be attached to the first drive shaft by means of a belt, e.g. a poly chain.

[0026] The second element may be connected to a second drive shaft arranged along the rotational axis. The second drive unit may drive the rotation of the second drive shaft, and thus the second element, around the rotational axis. The second drive unit may be attached to the second drive shaft by means of a belt, e.g. a timing belt.

[0027] The drive units may be controlled based on individual and common sensor signals and be configured for synchronized rotation. The first drive unit may have master status, and the second drive unit may have slave status. The master drive unit may not control the slave drive unit. The PLC controller may control both the master drive unit and the slave drive unit. A failure in one of the drive units may cause both drive units to fail. Thus, the drive units may run separately but not independently from one another. The PLC controller may be arranged in connection with the master drive unit.

[0028] The device operated in accordance with the method may be a vibration compensator for minimizing damaging vibrations from e.g. two-stroke engines, propellers, etc. Reducing vibrations increases operational flexibility, lowers maintenance costs, reduces fuel consumption and improves crew health on a marine vessel such as a ship.

[0029] The device may be operated with the rotational planes vertically arranged to reduce vibrations in the vertical plane by operating the two elements in a configuration where the centres of mass pass each other so that a net force is generated in the vertical direction or at least with a net force component generated in the vertical direction.

[0030] The device may be operated with the rotational planes vertically arranged to reduce vibrations in the horizontal plane by operating the two elements in a configuration where the centres of mass pass each other so that a net force is generated in the horizontal direction or at least with a net force component generated in the horizontal direction.

[0031] The device may be operated for reducing vibrations in any direction, such as in a horizontal and / or a vertical configuration.

[0032] The device may be operated for reducing vibrations in any direction either in a horizontal or a vertical configuration.

[0033] One advantage of the device being operated for reducing vibrations in any direction, may be achieving a compact device to compensate for vibrations in a variety of directions. Thus, it is possible to change the direction of the resulting harmonic force component from a vertical to a horizontal direction, or vice versa, within a single device having vertically arranged rotational planes. The device being arranged with vertical rotational planes to reduce vibrations in the horizontal plane may further be advantageous in minimizing the horizontal space required to achieve optimal combination of the mass and its distance to the rotation axis, to achieve optimal operation of the device depending on the specific vibration conditions. Common compensation devices are known to comprise horizontal rotational planes for reducing vibrations in the horizontal plane, thus taking up a lot of horizontal space due to the required combination of the mass and its distance to the rotation axis. With the device according to the invention, the required horizontal space may be minimized with the majority of device taking up space in the vertical plane.

[0034] When used in the vertical configuration in accordance with the claimed invention, the resulting force may be substantially sinusoidal. The resulting force may be influenced by the gravitational force acting on the rotating masses and thus the resulting forces may be sinusoidal superposed with the influence of gravitation. Experiments conducted by the applicant have indicated, that the gravitational force acting on the rotating masses is substantially non-significant as the rotational speed is increased, e.g. during normal operation when used to reduce vibrations.

[0035] The direction of the resulting force may be changed during operation and / or at initial start-up by adjusting the position where the centres of mass of the first and second element pass each other e.g. be increasing or decreasing the rotational speed of the first and / or the second element i.e.by introducing a phase lag between the two elements.

[0036] Assuming 0 degrees from the rotational axis is arranged substantially upwards in a vertical direction, if the passing position of the first and second elements centre of mass is located at 0 degrees and at 180 degrees from the rotational axis, the device may substantially reduce vibrations in the vertical plane. If the passing position is located at 90 degrees and 270 degrees from the rotational axis, the device may substantially reduce vibrations in the horizontal plane.

[0037] With a passing position arranged at substantially 0 degrees and 180 degrees, the respective maximal resulting force may substantially be in an upwards direction (substantially 0 degrees) and a downwards direction (substantially 180 degrees), thus substantially reducing vibrations in the vertical plane. In this configuration, the resulting force may be substantially 0 when the centre of mass of the first and second element is arranged at respectively 90 and 270 degrees. The resulting force may be between 0 and the maximum resulting force when the centre of mass of the first and second element is in any other position than 90 and 270 degrees.

[0038] With a passing position arranged at substantially 90 degrees and 270 degrees, it is achieved to substantially reducing vibrations in the horizontal plane. In this configuration, the resulting force may be substantially 0 when the centre of mass of the first and second element is arranged at respectively 0 and 180 degrees. The resulting force may be between 0 and the maximum resulting force when the centre of mass of the first and second element is in any other position than 0 and 180 degrees.

[0039] The device may be configured with passing positions arranged in any angle from the rotational axis depending on the reducing required.

[0040] Adjusting the passing position the direction of the resulting force component of the device is changed and thus the dampening direction can be changed. It may be interesting to change the dampening direction in response to changes in operational conditions of the structure. E.g. in case of the structure being a marine vessel, such operational changes may include changes in the position of cargo load, speed of the vessel, rotational speed of a main engine, weather conditions, water depth etc.

[0041] In one embodiment, the method may further comprise one or more modes for operating the first element and second element. The modes may include: an initial startup mode and / or an operation mode and / or and adjustment mode.

[0042] In one further embodiment of the method, the first element and the second element may be operated in at least an initial startup mode, initiating a swinging motion of each of the first element and the second element until a full rotation of at least one of the first or second element is achieved.

[0043] In one further embodiment of the method, the first element and the second element may be operated in at least an operation mode, wherein the first element and the second element are rotated in opposite directions at the same rotational speed, around the rotational axis.

[0044] In one further embodiment of the method, the first element and the second element may be operated in at least an adjustment mode, wherein the rotational speed of the first element and / or the second element are altered, so that the position where the centres of mass of the first and second element pass each other is in accordance with the predetermined direction.

[0045] The initial startup mode may be controlled by an initial startup algorithm.

[0046] The first and second element may be operated in at least the initial start-up mode.

[0047] The initial startup mode may comprise an act of initiating a swinging motion of the first and second element respectively in the first and second rotational plane. The first and second element may swing back and forth without fully rotating.

[0048] The initial startup mode may comprise an act of transitioning the swinging motion of the first and second element to a full rotation. The initial startup algorithm may detect the transition by detecting the first full rotation.

[0049] The adjustment mode may be controlled by an adjustment algorithm.

[0050] The adjustment mode may comprise an act of accelerating or decelerating the rotational speed of the first and second element until reaching a specified rotational speed. This may be performed in steps such as increasing the rotational speed in a first step to 60 rpm and in a second step from 60 to 200 rpm or vice versa to decrease from 200 rpm to 60 rpm in a first step and to a lower speed in a second step.

[0051] The adjustment mode may be combined with the one of the other modes.

[0052] The adjustment mode may be performed between the initial startup mode and the operational mode or in between two operations in the operational mode. E.g. the rotational speed of the elements may be adjusted so that the direction of the resulting force, from an initial direction e.g. 0 and 180 degrees to the predetermined direction, e.g. 90 and 270 degrees. The direction of the resulting force may be changed during operation and / or at initial start-up by adjusting the position where the centres of mass of the first and second element pass each other. This position may be changed by increasing or decreasing the rotational speed of the first and / or the second element, e.g. by introducing a phase lag between the first and second element. The adjustment mode may further comprise an act of synchronising the oppositely directed rotation of the first and second element. The act of synchronising may further comprise an act of rotating the first and second element at the same rotational speed.

[0053] The adjustment mode may comprise an act of accelerating the rotational speed of the first and second element until reaching an operation speed of e.g. 200 rpm.

[0054] The operational speed may be preset or predetermined depending on the type and / or specification of drive unit.

[0055] A common disadvantage of changing the direction of the resulting force component during operation may be accidently enhancing the vibrations.

[0056] One effect of adjusting the direction of the resulting force before acceleration of the first and second element have reached an operational speed may be preventing accidental increasing the level of vibration in the surrounding structure.

[0057] The operation mode may be controlled by a synchronisation algorithm.

[0058] The operation mode may comprise an act of verifying that the direction and magnitude of the resulting force is correct and that the first and second element are synchronised and moving in opposite directions. If verification reveals an error, the adjustment mode may be activated to correct the rotational speed, and / or the resulting force and / or the synchronisation, etc.

[0059] The operation mode may continuously perform the act of verifying once the elements are synchronized and the direction and magnitude of the resulting force is correct, e.g. after an adjustment due to changing operational conditions or after an adjustment following the initial startup.

[0060] When changing the direction of the resulting force component during operation, without enhancing the vibrations, the adjustment mode may comprise one or more acts of:

[0061] - decreasing the rotational speed

[0062] - determining the direction of the resulting force, e.g. from 0 and 180 degrees to 90 and 270 degrees, or vice versa;

[0063] - synchronizing the first and second element;

[0064] - increasing the rotational speed; - controlling and optionally correcting of the synchronization of the first and second element.

[0065] When the resulting force component is adjusted and is correct, the operation mode may continuously verify the resulting force component and check if an adjustment is necessary.

[0066] The need to change the direction of the resulting force may be caused by changing operational conditions, such as a variation in the weather condition, e.g. the arrival of a storm, and / or an increase or decrease in the rotational speed of the main engine.

[0067] When the rotational speed is changed, e.g. when starting the vibration compensating device and / or during operation of said device, the rotational speed of each of the first and second element may be individually adjusted. Thus, each of the first and second element may be individually controlled and comprise individual power drives.

[0068] In one embodiment, the method may comprise acts of:

[0069] - the initial startup mode initiating a swinging motion of each of the first element and the second element before a full rotation of both elements are achieved;

[0070] - the adjustment mode:

[0071] - initially accelerating the rotational speed of the first and second element to an intermediate speed, being slower than a predetermined operational speed;

[0072] - synchronizing the oppositely directed rotation of the first element and the second element so that the position where the centres of mass of the first element and second element pass each other is substantially in accordance with the predetermined direction;

[0073] - accelerating the rotational speed of the first and second element to reach the operational speed;

[0074] - optionally, finetuning oppositely directed rotation of the first element and the second element so that the position where the centres of mass of the first element and second element pass each other is substantially in accordance with the predetermined direction, when reaching the operational speed.

[0075] Said acts of the initial startup mode and the adjustment mode may be executed in sequence followed by the operation mode. The act of initiating a swinging motion may comprise the first and second element swinging back and forth a number of times over a period of time, until reaching a full rotation. A prolonged initial startup mode with multiple swinging motions may be particularly, but not exclusively, advantageous for enabling the use of smaller drive units without compromising the operating performance of the drive units.

[0076] The intermediate speed may be any speed less than an operational speed, such as, but not limited to 40 RPM, 50 RPM, 60 RPM, 70 RPM.

[0077] The act of synchronizing the oppositely directed rotation of the first and second element may determine where the two centres of mass are arranged to pass each other to achieve vibration reduction in the horizontal plane or the vertical plane.

[0078] One effect of synchronizing the oppositely directed rotation of the first and second element after the initial acceleration and before the first and second element have reached an operational speed, may be to prevent accidentally increasing the level of vibration in the surrounding structure. The synchronization may ensure that the position of where the two centres of mass pass each other is arranged to reduce vibrations in the correct plane before accelerating to reach the operational speed to further avoid accidently enhancing the vibrations.

[0079] The operational speed may be any rotational speed such as, but not limited to, between 180 RPM and 300 RPM, e.g. 264 RPM.

[0080] The act of re-synchronizing may be particularly, but not exclusively, advantageous for ensuring that the first and second element is synchronized correctly after reaching the operational speed to achieve the desired reduction of vibrations.

[0081] In one embodiment of the method, the operational speed may be based on a signal from a main engine of a structure. The structure may be any structure such as, but not limited to, a marine vessel e.g. a ship.

[0082] In one embodiment of the method, the operational speed is achieved by RPM detection of the main engine.

[0083] The RPM detector may comprise a sensor arranged to detect the RPM of the main engine. The RPM detector may continuously detect the RPM of the main engine. The sensor may be a speed sensor. Based on information from the RPM detector regarding the current RPM of the main engine, the adjustment algorithm and / or the synchronization algorithm, may control the first and second element accordingly.

[0084] During the adjustment mode, following an initial start-up mode, the act of accelerating the rotational speed of the first and second element to reach the operational speed may be determined by the detected RPM.

[0085] If the detected RPM requires an adjustment during the operation mode, the operation of the first and second element may change from the operation mode to the adjustment mode.

[0086] The drive units may drive the rotational speed of the first and second as a multiple of the frequency of the main engine based on information regarding the detected RPM.

[0087] In one embodiment of the method, the first mass and the second mass may have substantially the same mass.

[0088] One advantage achieved by the first mass and the second mass having substantially the same mass, may be generating a harmonically varying force component in the specified direction depending on the passing position of the centres of mass of the first and second element.

[0089] In a further embodiment of the method, the first element and the second element may each comprise two sub-elements arranged and rotated in the same rotational plane around the rotational axis and may be spaced apart by an angle.

[0090] In a further embodiment of the method, the first element and the second element may each comprise two sub-elements arranged and rotated in parallel rotational planes around the rotational axis. The two sub-elements of the first element may be spaced apart by an angle q>1. The two sub-elements of the second element may be spaced apart by an angle >2.

[0091] Thus, the first element comprises two sub-elements arranged and rotated in parallel rotational planes around the rotational axis. The two sub-elements of the first element may be spaced apart by an angle q>1. Similarly, the second element comprise two sub- elements arranged and rotated in parallel rotational planes around the rotational axis.

[0092] The two sub-elements of the second element may be spaced apart by an angle >2.

[0093] In the context of the invention, the first element ‘comprising’ two sub-elements is to be understood as the two associated sub-elements combined, constitute the first element. Likewise, the second element ‘comprising’ two sub-elements is to be understood as the two associated sub-elements combined, constitute the second element.

[0094] In a further aspect, each of the first or second element may comprise multiple subelements such as three, four or more, where the sub-elements combined, constitute each of the first or second element.

[0095] The angle between the two sub-elements of the first element and / or the second element may be the relative position of the two sub-elements of a sub-element set, extending outwards from the rotational axis.

[0096] The angle >1 may be a flyweight angle between the sub-elements of the first element. The angle >2 may be a flyweight angle between the sub-elements of the second element.

[0097] In a further embodiment, the first distance of the first element’s centre of mass is adjusted by adjusting the angle >1 between the sub-masses of the first element.

[0098] In a further embodiment, the second distance of the second element’s centre of mass is adjusted by adjusting the angle >2 between the sub-masses of the second element.

[0099] The angle (p may be adjusted before and / or during operation for optimal operation.

[0100] The direction of the resulting force generated by the device may be regulated by adjusting the angle (p and thus the position of the centres of mass of the first element and the second element.

[0101] The resulting force may be regulated by adjusting the angle (p and thus the position of the centres of mass of the first element and the second element. Decreasing the angle (p may result in an increased resulting force. Increasing the angle (p may result in a decreased resulting force. One advantage of adjusting the angle (p, may be to enable an increase or decrease of the resulting force component of the device during the operation. As a result, it is possible, during operation, to adjust the magnitude of the compensation to the vibration conditions which apply during changing operational conditions, such as changes in the cargo and speed of a ship as well as the weather conditions and the water depth.

[0102] The sub-elements of the first and second element may be operated individually with the angle (p generally being fixed. The angle (p may be adjusted during operation if inaccuracies arise within the elements resulting in the first distance multiplied by the first mass is no longer the same as the second distance multiplied by the second mass. Adjusting the angle (p may ensure optimal operation by ensuring that the first mass is the same as the second distance multiplied by the second mass.

[0103] In a further embodiment of the method using sub-elements, the rotational speed of each of the sub-elements is adjusted individually in accordance with the specific mode in which is it operated, so that the position where the centres of mass of the first and second element pass each other is in accordance with the predetermined direction.

[0104] The individual adjustment may be performed by using a hydraulic fluid for at least one sub-element to change the flyweight angle (p.

[0105] The phase angle may be the phase angle between the synchronized sub-elements of the first and second element respectively, and the top dead centre of the main engine.

[0106] In one embodiment of the method, the two sub-elements may have the same mass and may be arranged with the centre of mass at the same distance from the rotational axis.

[0107] One advantage achieved by the two sub-elements having substantially the same mass and with their centre of mass arranged with the same distance from the rotational axis, may be generating a harmonically varying force component in the specified direction depending on the passing position of the centres of mass of the first and second element.

[0108] In one embodiment of the method, the elements and / or the sub-elements may have the shape of a sector disk. One advantage of the sector disk shape may be to provide a more compact device by minimizing the distance of the other parts of the elements from the rotational axis.

[0109] The sector disk shape may comprise a central angle between 90 and 190 degrees, preferably between 120 and 180 degrees, and more preferably between 140 and 180 degrees, and even more preferably between 130 and 150 degrees. The moment of force is almost not affected by the last 40 degrees from 140 to 180 degrees.

[0110] The sector disk shape and the distance from the rotational axis may achieve the optimal moment of force and thereby the optimal effect.

[0111] The use of sector disks may be beneficial in placing the elements in close vicinity of each other almost abutting each other to reduce the space of the device along the rotational axis.

[0112] Using sector disks may furthermore have the benefit of being able to mount the elements in direction communication with the rotational axis without introducing any weightbearing arms extending between the masses and the rotational axis.

[0113] The use of substantially identical element for the first and second elements or for the sub-elements may be beneficial for production, assembly, alignment and / or refitting.

[0114] The sub-elements may have other advantageous shapes to increase the mass while minimizing the distance between the first and second element.

[0115] A further objective of the invention is achieved by a device comprising:

[0116] - a first element with a first mass rotatably mounted around a rotational axis with its centre of mass arranged at a first distance from the rotational axis in a first plane perpendicular to the rotational axis,

[0117] - a second element with a second mass rotatably mounted around the rotational axis with its centre of mass arranged at a second distance from the rotational axis in a second plane perpendicular to the rotational axis.

[0118] The first and second elements are disposed such that the first distance multiplied by the first mass is the same as the second distance multiplied by the second mass. The device furthermore comprises one or more drive units configured with drive shafts connected to respectively the first and second elements and configured to for rotating the first and second elements around the common rotational axis.

[0119] In one embodiment, the device may further comprise a control unit in communication with a processor and a computer readable medium having stored one or more of:

[0120] - an initial startup algorithm for controlling the initial startup mode,

[0121] - a synchronisation algorithm for ensuring synchronised rotation of the first and second element during the operational mode,

[0122] - an adjustment algorithm for controlling the adjustment mode.

[0123] The control unit may comprise a controller for operating the one or more drive units for controlling the rotational speed of the elements to be operated in accordance with the intended operation of having the centres of mass passing each other at the same time on a line in the predetermined direction.

[0124] In a further embodiment of the device, the first element and the second element each comprises two sub-elements arranged and rotated in the same rotational plane around the rotational axis and spaced apart by an angle cp1 , >2.

[0125] The device is configured to be operated in accordance with the herein disclosed methods.

[0126] The advantages achieved by the device are substantially the same as the advantages described in relation to the method.

[0127] A yet further objective of the invention is achieved by use of the device, wherein the device is arranged with the rotational planes in a vertical direction for reducing vibrations in a horizontal direction.

[0128] The advantages achieved by the use of the device are substantially the same as the advantages described in relation to the method.

[0129] In one embodiment, the use of the device may be on a marine vessel for reducing vibrations in a direction extending substantially from aft to bow, where the device is arranged with the rotational planes perpendicular to a ship deck along the direction extending from aft to bow. The device being used with vertically arranged rotational planes to reduce vibrations in the horizontal plane may thus minimize the deck space required to achieve optimal combination of the mass and its distance to the rotation axis.

[0130] An advantage of reducing vibrations substantially in a horizontal plane may be achieving operational flexibility, lowers maintenance costs, reduce fuel consumption and improves crew health on the marine vessel.

[0131] In one embodiment, the use of the device may be on a marine vessel for reducing vibrations in a direction extending substantial from starboard to port side, where the device is arranged with the rotational planes perpendicular to a ship deck along the direction extending from starboard to port side. The device may also be used to reduce local vibrations, e.g. on a superstructure.

[0132] A yet further objective of the invention is achieved by a marine vessel comprising the device according to the invention.

[0133] The advantages achieved by the machine vessel comprising the device, are substantially the same as the advantages described in relation to the method.

[0134] Description of the Drawing

[0135] Various examples are described hereinafter with reference to the figures. Like reference numerals refer to like elements throughout. Like elements will, thus, not be described in detail with respect to the description of each figure. It should also be noted that the figures are only intended to facilitate the description of the examples. They are not intended as an exhaustive description of the claimed invention or as a limitation on the scope of the claimed invention. In addition, an illustrated example need not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular example is not necessarily limited to that example and can be practiced in any other examples even if not so illustrated, or if not so explicitly described.

[0136] Exemplary embodiments of the invention are described in the figures, whereon:

[0137] Fig. 1 illustrates a perspective view of two configurations of a device according to the invention, Fig. 2 illustrates the first and second element in two positions wherein the resulting force is 0.

[0138] Fig. 3 illustrates the first and second element in two positions with a vertical maximum resulting force.

[0139] Fig. 4 illustrates the first and second element a position wherein the resulting force is 0.

[0140] Fig. 5 illustrates the first and second element in a position with a horizontal maximum resulting force.

[0141] Fig. 6 illustrates the first and second element a position wherein the resulting force is 0.

[0142] Fig. 7 illustrates the first and second element in a position with a horizontal maximum resulting force.

[0143] Fig. 8 illustrates a sinusoidal curve for resulting forces for reducing vibrations in a vertical and horizontal direction.

[0144] Fig. 9a, b illustrates the device according to an embodiment of the invention.

[0145] Fig. 10 illustrates a cross section (A-A) of the device of fig. 9a.

[0146] Fig.11 illustrates the inside of the device of fig. 9a and 9b.

[0147] Detailed Description of the Invention

[0148] Exemplary examples will now be described more fully hereinafter with reference to the accompanying drawings. In this regard, the present examples may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the examples are merely described below, by referring to the figures, to explain aspects.

[0149] Throughout the specification, when an element is referred to as being “connected” to another element, the element is “directly connected” to the other element, “electrically connected”, “fluidic connected” or “communicatively connected” to the other element with one or more intervening elements interposed there between.

[0150] The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting. As used herein, the terms “comprises" "comprising" "includes" and / or "including" when used in this specification specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this invention pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined in the present specification.

[0151] No Item

[0152] 1 Device

[0153] 2 Rotational axis

[0154] 3 Predetermined direction

[0155] 11 First element

[0156] 31 First drive unit

[0157] 41 First drive shaft

[0158] P1 First rotational plane

[0159] M1 First mass

[0160] R1 First distance

[0161] 51 First sub element

[0162] 22 Second element

[0163] 32 Second drive unit

[0164] 42 Second drive shaft

[0165] P2 Second rotational plane

[0166] M2 Second mass

[0167] R2 Second distance

[0168] 52 Second sub element

[0169] Figure 1-7 illustrates a device configured for being operated in accordance with a method of reducing vibrations in a structure in a predetermined direction 3 perpendicular to a rotational axis 2.

[0170] The method comprises a step of rotating a first element 11 in a first rotational plane P1 and a second element 22 in a second rotational plane P2 around the rotational axis 2.

[0171] The first and second rotational planes P1 , P2 are parallel planes arranged perpendicular to the rotational axis 2, as illustrated in figures 1A and 1 B. The device illustrated in figure 1A comprise a first element 11 which has a first mass M1 and is arranged with its centre of mass at a first distance R1 from the rotary axis 2 in the first rotational plane P1. The second element 22 has a second mass M2 with its centre of mass arranged at a second distance R2 from the rotary axis 2 in the second rotational plane P2.

[0172] The first and second elements 11 ,22 are disposed such that the first distance multiplied by the first mass (R1 x M1) is the same as the second distance multiplied by the second mass (R2 x M2).

[0173] The first element 11 and the second element 22 are rotated in opposite directions as indicated by the white and black arrows in figures 1 , 2, 4, and 6. The first element 11 as indicated by the white arrow is configured for clockwise rotation, while the second element 22 as indicated by the black arrow is configured for counterclockwise rotation.

[0174] The first and second element 11 ,22 are rotated around the rotational axis 2 with the centres of mass passing a line extending from the rotational axis 2 and outwards in the predetermined direction. The first and second element 11 ,22 may be rotated at the same rotational speed around the rotational axis 2.

[0175] The first mass M1 and the second mass M2 may be substantially the same.

[0176] Although not illustrated, the method may further comprise one or more vibration reducing modes. The vibration reducing modes may comprise an initial startup mode, initiating a swinging motion of each of the first element 11 and the second element 22.

[0177] The vibration reducing modes may comprise an operation mode, wherein the first element 11 and the second element 22 are rotated in opposite directions at the same rotational speed, around the rotational axis 2.

[0178] The vibration reducing modes may comprise an adjustment mode, wherein the position where the centres of mass of the first and second element 11 ,22 pass each other is adjusted.

[0179] The device operated in accordance with the method may further comprise a control unit comprising one or more algorithms. The algorithms may comprise an initial startup algorithm for controlling the initial startup mode.

[0180] The algorithms may comprise a synchronisation algorithm for ensuring synchronised rotation of the first and second element 11 ,22 during the operational mode.

[0181] The algorithms may comprise an adjustment algorithm for controlling the adjustment mode.

[0182] Although not illustrated, the method may comprise acts of initial start-up mode and / or the adjustment mode.

[0183] The initial startup mode may comprise an act of initiating a swinging motion of each of the first element 11 and the second element 22 until a full rotation of at least one of the first or second element is achieved.

[0184] The adjustment mode may comprise an act of initially accelerating the rotational speed of the first 11 and second element 22 to an intermediate speed, less than an operational speed.

[0185] The adjustment mode may comprise an act of synchronizing the oppositely directed rotation of the first element 11 and the second element 22 so that the position where the centres of mass of the first element 11 and second element 22 pass each other is in accordance with the predetermined direction 3.

[0186] The adjustment mode may comprise an act of accelerating the rotational speed of the first 11 and / or second element 22 to reach the operational speed.

[0187] The adjustment mode may comprise an act of deaccelerating the rotational speed of the first 11 and / or second element 22 to reach the operational speed.

[0188] The adjustment mode may comprise an act of re-synchronizing at the operational speed.

[0189] The operational speed may be based on a signal from a main engine of a structure.

[0190] The operational speed may be achieved by RPM detection of the main engine. Figures 1 B to 6 illustrates the first element 11 and the second element 22 each comprising two sub-elements S1 , S2 arranged and rotated in the same rotational plane around the rotational axis 2 and spaced apart by an angle (p.

[0191] The two sub-elements S1 , S2 may have the same mass and be arranged with the centre of mass at the same distance R1 ,R2 from the rotational axis 2.

[0192] The elements 11 ,22 or the sub-elements S1 ,S2 may have the shape of sector disks.

[0193] A device configured for being operated in accordance with the method comprises a first element 11 with a first mass M1 rotatably mounted around a rotational axis 2 with its centre of mass arranged at a first distance R1 from the rotational axis 2 in a first plane P1 perpendicular to the rotational axis 2.

[0194] The device configured for being operated in accordance with the method comprises a second element 22 with a second mass M2 rotatably mounted around the rotational axis 2 with its centre of mass arranged at a second distance R2 from the rotational axis 2 in a second plane P2 perpendicular to the rotational axis 2.

[0195] The first and second elements 11 ,22 are disposed such that the first distance multiplied by the first mass R1 x M1 is the same as the second distance multiplied by the second mass R2 x M2.

[0196] Figures 2 and 3 illustrate a device with vertically arranged rotational planes P1 ,P2 and wherein the device is configured for generating a resulting force in the vertical direction. The passing positions of the centre of mass is arranged at 0 and 180 degrees.

[0197] As illustrated in figure 2A and 2B, the resulting force is substantially 0 when the first and second element 11 ,22 is in rotational position of 90 and 270 degrees. The resulting force is equalized as the angle between the centre of mass of the first and second element 11 ,22 is 180 degrees.

[0198] The first and second element 11 ,22 are arranged in the passing position such that one element is hidden behind the other in figures 3A and 3B. Figure 3A illustrate that the maximum resulting force is in a vertical downwards direction when the first and second element 11 ,22 align in a rotational position of substantially 180 degrees. Figure 3B illustrate that the maximum resulting force is in a vertical upwards direction when the first and second element 11 ,22 align in a rotational position of substantially 0 degrees.

[0199] Figures 4-7 illustrate a device with vertically arranged rotational planes P1 ,P2 and wherein the device is configured for generating a resulting force in the horizontal direction. The passing positions of the centre of mass is arranged at 90 and 270 degrees.

[0200] As illustrated in figure 4 and 6, the resulting force is substantially 0 when the first and second element 11 ,22 is in rotational position of 0 and 180 degrees. The resulting force is equalized as the angle between the centre of mass of the first and second element 11 ,22 is 180 degrees.

[0201] The first and second element 11 ,22 are arranged in the passing position such that one element is hidden behind the other in figures 5 and 7. Figure 5 illustrate that the maximum resulting force is in a horizontal direction to the right, when the first and second element 11 ,22 align in a rotational position of substantially 90 degrees. Figure 7 illustrate that the maximum resulting force is in a horizontal direction to the left, when the first and second element 11 ,22 align in a rotational position of substantially 270 degrees.

[0202] Figure 8 illustrate variations of a harmonically varying resulting force component depending on the passing position and the angle (p.

[0203] In 8A and 8B, the unbroken line indicates the resulting force component in a device configured for reducing vibrations substantially in the vertical plane. The broken line indicates the resulting force component in a device configured for reducing vibrations substantially in the horizontal plane. The angle (p between the sub-elements S1 ,S2 is decreased in figure 8B resulting in an increased maximum resulting force component.

[0204] Figure 8C illustrate a configuration where the passing position of the centres of mass is not arranged in 0 and 180 degrees or in 90 and 270 degrees.

[0205] The device configured for being operated in accordance with the method, arranged with the rotational planes P1 ,P2 in a vertical direction may be used for reducing vibrations in a horizontal direction. The device may be used on a marine vessel for reducing vibrations in a direction extending from aft to bow where the device is arranged with the rotational planes perpendicular to a ship deck along the direction extending from aft to bow.

[0206] Although not illustrated, a marine vessel comprising the device according to the invention is also claimed.

[0207] Figures 9a-11 illustrate the device according to an embodiment of the invention configured for being operated in accordance with a method of reducing vibrations.

[0208] As best seen in figures 10 and 11 , the rotation of the first element 11 is driven by a first drive unit 31 , and the rotation of the second element 22 is driven by a second drive unit 32. As clearly seen in figure 10, the first and second drive units 31 , 32 may be configured with first and second drive shafts 41 , 42 connected to and configured for rotating the first and second elements 11 ,22 around the common rotational axis 2.

[0209] As seen in figure 11 , the first and second drive unit are connected to respectively a first and second drive shaft 41 ,42 (see figure 10) by means of a drive belt.

Claims

CLAIMS1. A method of reducing vibrations in a structure in a predetermined direction (3) perpendicular to a rotational axis (2), comprising a step of rotating a first element (11) in a first rotational plane (P1) and a second element (22) in a second rotational plane (P2) around the common rotational axis (2), said first and second rotational planes (P1 , P2) being parallel planes arranged perpendicular to the rotational axis (2), wherein the first element (11) has a first mass (M1) and is arranged with its centre of mass at a first distance (R1) from the rotary axis (2) in the first rotational plane (P1), and the second element (22) has a second mass (M2) with its centre of mass arranged at a second distance (R2) from the rotary axis (2) in the second rotational plane (P2), wherein first and second elements (11 , 22) are disposed such that the first distance multiplied by the first mass (R1 x M1) is the same as the second distance multiplied by the second mass (R2 x M2), and wherein the first element (11) and the second element (22) are rotated in opposite directions around the rotational axis (2) with the centres of mass passing at the same time a line extending from the rotational axis (2) and outwards in the predetermined direction, wherein the rotation of the first element (11) is driven by a first drive unit (31), and the rotation of the second element (22) is driven by a second drive unit (32).

2. The method according to claim 1 wherein the first mass (M1) and the second mass (M2) are substantially the same.

3. The method according to any of the preceding claims, wherein the first element (11) and second element (11) are operated in at least:- an initial startup mode, initiating a swinging motion of each of the first element (11) and the second element (22) until a full rotation of at least one of the first or second element is achieved.

4. The method according to any of the preceding claims, wherein the first element (11) and second element (11) are operated in at least:- an operation mode, wherein the first element (11) and the second element (22) are rotated in opposite directions at the same velocity, around the rotational axis (2).

5. The method according to any of the preceding claims, wherein the first element (11) and second element (11) are operated in at least:- an adjustment mode, wherein the speed of the first element (11) and / or the second element (22) are altered, so that the position where the centres of mass of the first and second element (11 ,22) pass each other is in accordance with the predetermined direction (3).

6. The method according to claim 3 or 4 or 5, comprises acts of:- the initial startup mode initiating a swinging motion of each of the first element (11) and the second element (22) until a full rotation of at least one of the first or second element is achieved;- the adjustment mode:- initially accelerating the rotational speed of the first (11) and second element (22) to an intermediate speed, less than a predetermined operational speed;- synchronizing the oppositely directed rotation of the first element (11) and the second element (22) so that the position where the centres of mass of the first element (11) and second element (22) pass each other is in accordance with the predetermined direction (3);- accelerating the rotational speed of the first (11) and second element (22) to reach the operational speed;- optionally, re-synchronizing at the operational speed.

7. The method according to claim 6, wherein the operational speed is based on a signal from a main engine of a structure.

8. The method according to claim 7, wherein the operational speed is achieved by RPM detection of the main engine.

9. The method according to any of the preceding claims wherein the first element (11) and the second element (22) each comprises two sub-elements (S1 , S2) arranged and rotated in parallel rotational planes around the rotational axis (2), and wherein the two sub-elements (S1 ,S2) are spaced apart by an angle (cp1 , cp2).

10. The method according to claim 9, wherein the first distance (R1) of the first element’s centre of mass is adjusted by adjusting the angle (cp1 ) and / or wherein the second distance (R2) of the second element’s centre of mass is adjusted by adjusting the angle (q>2).

11. The method according to claim 9 or 10 wherein the rotational speed of each of the sub-elements is adjusted individually in accordance with the specific mode in which is it operated, so that the position where the centres of mass of the first and second element (11 ,22) pass each other is in accordance with the predetermined direction.

12. The method according to any of claims 9 to 11 , wherein the two sub-elements (S1 , S2) have the same mass and are arranged with the centre of mass at the same distance (R1 , R2) from the rotational axis (2).

13. The method according to any of the preceding claims, wherein the elements (11 , 22) and / or the sub-elements (S1 , S2) have the shape of sector disks.

14. A device comprising:- a first element (11) with a first mass (M1) rotatably mounted around a rotational axis (2) with its centre of mass arranged at a first distance (R1) from the rotational axis (2) in a first plane (P1) perpendicular to the rotational axis (2),- a second element (22) with a second mass (M2) rotatably mounted around the rotational axis (2) with its centre of mass arranged at a second distance (R2) from the rotational axis (2) in a second plane (P2) perpendicular to the rotational axis (2), wherein first and second elements (11 , 22) are disposed such that the first distance multiplied by the first mass (R1 x M1) is the same as the second distance multiplied by the second mass (R2 x M2), and- one or more drive units (31 , 32) configured with drive shafts (41 , 42) connected to and configured to for rotating the first and second elements (11 ,22) around the common rotational axis (2), wherein the device (1) is configured to be operated in accordance with the method of claim 1 , 2, 3, 4, 5, 6, 7, 8 or 13.

15. The device according to claim 14, further comprising a control unit for communication with a processor and a computer readable medium having stored one or more of:- an initial startup algorithm for controlling the initial startup mode,- a synchronisation algorithm for ensuring synchronised rotation of the first and second element (11 ,22) during the operational mode,- an adjustment algorithm for controlling the adjustment mode, causing the device to be operated in accordance with the method of any of claims 4 - 8.

16. The device according to claim 14 or 15 wherein the first element (11) and the second element (22) each comprises two sub-elements (S1 , S2) arranged and rotated in the same rotational plane around the rotational axis (2) and spaced apart by an angle (cp1 , cp2), and wherein the device is configured to be operated in accordance with the method of any of claims 9-13.

17. Use of the device according to any of claims 14 to 16, wherein the device is arranged with the rotational planes (P1 , P2) in a vertical direction for reducing vibrations in a horizontal direction.

18. Use of the device according to claim 16 on a marine vessel for reducing vibrations in a direction extending substantially from aft to bow, where the device is arranged with the rotational planes perpendicular to a ship deck along the direction extending from aft to bow.

19. A marine vessel comprising the device according to any of claims 14 - 16.

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