Cutter suction dredgers (CSDs) are floating vessels (boats, barges, etc.) with tools that are used to dredge the beds of rivers, lakes, and other bodies of water. CSDs use a rotating cutter head at the end of an elongated structure called a ladder to break up sand, rock, dirt, and gravel. The material broken up by the cutter head is sucked into a suction conduit and transported up the ladder to the vessel. The material can then be transported away to a dumping site.
A motor is coupled to and is configured to rotate the cutter head via a shaft that runs through the ladder. When the cutter head is in use, the shaft experiences radial forces and thrust forces due to the angle of the ladder. Bearings can be used to react the forces to protect the shaft and motor.
In one set of embodiments, a cutter suction dredger includes a vessel configured to float on water, a ladder extending away from the vessel, the ladder comprising a proximal end coupled to the vessel and a distal end configured to be raised and lowered, a cutter head positioned at the distal end of the ladder and configured to contact a bed of a body of water to cut into and break up the bed, and a bearing assembly. The bearing assembly includes a first spherical thrust bearing configured to resist thrust forces generated by the cutter head contacting the bed of the body of water, a second spherical thrust bearing positioned opposite the first spherical thrust bearing, a symmetrical spherical bearing positioned between the first spherical thrust bearing and the second spherical thrust bearing, and a housing surrounding the first spherical thrust bearing, the second spherical thrust bearing, and the symmetrical spherical bearing, the housing mounted to the ladder. The cutter suction dredger further includes a shaft extending along the ladder and through the first spherical thrust bearing, the second spherical thrust bearing, the symmetrical spherical bearing, and the housing, the cutter head coupled to a distal end of the shaft.
In another set of embodiments, a dredging assembly includes a cutter head coupled to a shaft, the cutter head configured to be pressed, by the shaft, into a bed of a body of water to cut into and break up the bed and a bearing assembly rotatably supporting the shaft. The bearing assembly includes a first spherical thrust bearing that receives the shaft and is configured to resist thrust forces generated by the cutter head contacting the bed of the body of water, a second spherical thrust bearing positioned opposite the first spherical thrust bearing, a symmetrical spherical bearing positioned between the first spherical thrust bearing and the second spherical thrust bearing, and a housing surrounding the first spherical thrust bearing, the second spherical thrust bearing, and the symmetrical spherical bearing, the housing configured to be mounted to a ladder of a cutter suction dredger.
It will be recognized that the Figures are the schematic representations for purposes of illustration. The Figures are provided for the purpose of illustrating one or more implementations with the explicit understanding that the Figures will not be used to limit the scope of the meaning of the claims.
Referring to
A cutter head 114 is positioned at the end of the ladder 108. The cutter head 114 is coupled to a shaft 116 that runs along or runs through the inside of the ladder 108 to a motor 118. The motor 118 may be positioned in the vessel or may be positioned in the ladder 108 near the cutter head 114. The motor 118 is configured to rotate the shaft 116 and the cutter head 114. The rotating cutter head 114 contacts and is pressed into the bed 110 to cut into and break up the materials of the bed 110. A bearing assembly 120 is positioned in the ladder 108 near the cutter head 114 to react the radial and thrust forces resulting from pressing the cutter head 114 into the bed 110. In some embodiments, the cutter suction dredger 100 may include multiple motors 118 coupled to a gearbox to rotate the shaft 116. The shaft 116 may comprise multiple sections, for example, multiple sections joined at their respective ends by couplings.
Various conventional bearing assemblies include a radial bearing sandwiched between two cylindrical roller thrust bearings. While the cylindrical roller thrust bearings include a spherical washer to account for misalignment between the shaft 116 and the bearings, the spherical washers typically do not share a common pivot point. The loading can become unbalanced and the spherical surfaces can experience non-uniform contact, causing unequal loading and added stress. The radial bearing can also experience a non-uniform load distribution. The bearings are typically lubricated with grease, which, in addition to the misalignment, can cause the bearing to operate in the boundary lubrication condition rather than the hydrodynamic lubrication condition.
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The first outer raceway 132 includes a first spherical surface 140 on which the first plurality of asymmetrical rollers 128 roll to allow rotation of the first inner raceway 136, as well as the shaft 116, relative to the first outer raceway 132. The second outer raceway 134 includes a second spherical surface 142 on which the second plurality of asymmetrical rollers 130 roll to allow rotation of the second inner raceway 138, as well as the shaft 116, relative to the second outer raceway 134.
The center point of a sphere coincident with the spherical surface of the outer race of a spherical roller bearing is called the pressure point of the bearing. Any line normal to the spherical surface of the outer race passes through the pressure point. The first spherical thrust bearing 122 and the second spherical thrust bearing 124 are positioned such that the pressure point of the first spherical thrust bearing 122 is substantially coincident with the pressure point of the second spherical thrust bearing 124. Thus, a center of a sphere coincident with the first spherical surface 140 and the center of a sphere coincident with the second spherical surface 142 are located at approximately the same point 144 on the common axis of rotation 143. In these positions and with the first spherical thrust bearing 122 being the same size as the second spherical thrust bearing 124, a single sphere (e.g., sphere 145) can be coincident with the first spherical surface 140 and the second spherical surface 142. With the first spherical thrust bearing 122 and the second spherical thrust bearing 124 having substantially coincident pressure points, angular misalignment between the housing 121 and shaft 116 simply displaces the first plurality of asymmetrical rollers 128 relative to the first inner race 132 and the first outer race 136 and the second plurality of asymmetrical rollers 130 relative to the second inner race 134 and the second outer race 138 without introducing any load non-uniformity or loss of contact. The first spherical thrust bearing 122 is configured to resist thrust forces in a first direction (e.g., to the left of
The symmetrical spherical bearing 126 has an outer race 146 and an inner race 148. The outer race 146 has a spherical surface 150 with which the inner race 148 is in sliding contact, to allow rotation of the inner race 148 relative to the outer race 146. The symmetrical spherical bearing 126 is positioned such that the center of a sphere (e.g., sphere 147) coincident with the spherical surface 150 is located at approximately a point 144. This point may be referred to as the center point of the symmetrical spherical bearing 126. Thus, the center point of the symmetrical spherical bearing 126 may be substantially coincident with the pressure points of the first spherical thrust bearing 122 and the second spherical thrust bearing 124. The first spherical roller thrust bearing 122, the second spherical roller thrust bearing 124, and the symmetrical spherical bearing 126 all share a common pivot point, the point 144, and the entire assembly operates uniformly when there is alignment error between the shaft centerline and the housing center line.
The bearing assembly 120 can be lubricated with a fluid or semifluid lubricant rather than grease. This may allow the symmetrical spherical bearing 126 to operate in the hydrodynamic lubrication condition. Referring now to
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The bearing assembly 120 is coupled to the ladder 108 at a position distal to the gearbox 412. The output shaft 414 is coupled to a first end 418 of a portion of the shaft 116 that extends through the bearing assembly 120 (e.g., a first portion 416 of the shaft 116) by a first shaft coupling 422. A second end 420 of the first portion 416 of the shaft 116 is coupled to a third portion 424 of the shaft 116 by a second shaft coupling 426. The third portion 424 of the shaft 116 extends to the distal end 404 of the ladder 108. The third portion 424 may extend through one or more additional bearing assemblies 428 coupled to the ladder 108, and may include or be coupled to a distal portion 430 configured to receive a cutter head that dredges the bed of a body of water.
As utilized herein, the terms “approximately,” “about,” “substantially”, and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the disclosure as recited in the appended claims.
It should be noted that the term “exemplary” and variations thereof, as used herein to describe various embodiments, are intended to indicate that such embodiments are possible examples, representations, or illustrations of possible embodiments (and such terms are not intended to connote that such embodiments are necessarily extraordinary or superlative examples).
The term “coupled” and variations thereof, as used herein, means the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent or fixed) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members coupled directly to each other, with the two members coupled to each other using a separate intervening member and any additional intermediate members coupled with one another, or with the two members coupled to each other using an intervening member that is integrally formed as a single unitary body with one of the two members. If “coupled” or variations thereof are modified by an additional term (e.g., directly coupled), the generic definition of “coupled” provided above is modified by the plain language meaning of the additional term (e.g., “directly coupled” means the joining of two members without any separate intervening member), resulting in a narrower definition than the generic definition of “coupled” provided above. Such coupling may be mechanical, electrical, or fluidic.
References herein to the positions of elements (e.g., “top,” “bottom,” “above,” “below”) are merely used to describe the orientation of various elements in the FIGURES. It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure.
It is important to note that the construction and arrangement of the cutter suction dredger 100 and the systems and components thereof as shown in the various exemplary embodiments is illustrative only. Additionally, any element disclosed in one embodiment may be incorporated or utilized with any other embodiment disclosed herein. Although only one example of an element from one embodiment that can be incorporated or utilized in another embodiment has been described above, it should be appreciated that other elements of the various embodiments may be incorporated or utilized with any of the other embodiments disclosed herein.