Abstract:
The present invention, in one embodiment, is a system for receiving and delivering into a base the radial loads imposed on a crane where the crane has a center post operably connected to the base with a generally cylindrical outer bearing surface and the crane rotates in at least a partial circle around the axis of the center post. The system comprises three or more radial load rollers arranged in a linked sequence in an arc at the outer bearing surface of the center post. Each radial load roller includes an axle and an axis of rotation that is generally parallel to the axis of the center post. The system also comprises a means for anchoring a first radial load roller at one end of the arc and anchoring a second radial load roller at the other end of the arc. The system also comprises links connecting each roller between the first and the second radial rollers to its adjacent rollers to form a flexible chain of said rollers. Finally, the system comprises a means for tensioning the linked radial load rollers to draw each radial load roller into rolling contact with the outer bearing surface and to equalize substantially the radial forces exerted by the radial rollers on the outer bearing surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority from U.S. Provisional Patent Application No. 60/450,081, filed on Feb. 25, 2003, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus and methods for resisting thrust loads on a crane. More specifically, the present invention relates to a bearing system for resisting radial (i.e., horizontal) thrust loads from a boom on a post crane. 
     Ships and offshore platforms need cranes to rapidly and safely load and off-load various material and personnel. Affixable, pedestal-type cranes with a center post have been very popular in marine type applications. On a post crane, the superstructure and boom of the crane rotate on bearings about the axis of the post. 
     The post serves as the crane&#39;s structural base for resisting the thrust loads and overturning moments experienced by the crane. The thrust loads are transferred from the boom to the post via the bearings on which the superstructure rotates about the axis of the post. Specifically, vertical thrust loads are transferred from the boom to the post via a container ring bearing, which comprises a plurality of rollers. Radial (i.e., horizontal) thrust loads are transferred from the boom to the post via the radial bearing ring comprising a plurality of rollers, which rollably engage the outer circumference of the post. 
     While the post crane has many advantages over other types of cranes in a marine environment, the ability to achieve equal bearing loading about the bearings, especially the radial bearing ring, has been challenging. Failure to achieve equal loading about the bearings can result in uneven bearing roller wear, which can lead to premature repairs and downtime for the crane or even catastrophic failure of the crane. 
     To achieve equal roller loading about the radial bearing ring, manufacturers have had to rely on precision machining of the bearing ring and its rollers or structures that permit elastic deflections. Both options are less than desirable due to their expense. Also, the commercially available precision bearings with integral rings are limited in size to 6.5 meters in diameter, which in turn limits the load capacity of the crane. There is a need in the art for a more cost effective means of achieving equal roller loading about the radial bearing ring. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention, in one embodiment, is a system for receiving and delivering into a base the radial loads imposed on a crane where the crane has a center post operably connected to the base with a generally cylindrical outer bearing surface and the crane rotates in at least a partial circle around the axis of the center post. The system comprises three or more radial load rollers arranged in a linked sequence in an arc at the outer bearing surface of the center post. Each radial load roller includes an axle and an axis of rotation that is generally parallel to the axis of the center post. The system also comprises a means for anchoring a first radial load roller at one end of the arc and anchoring a second radial load roller at the other end of the arc. The system also comprises links connecting each roller between the first and the second radial rollers to its adjacent rollers to form a flexible chain of said rollers. Finally, the system comprises a means for tensioning the linked radial load rollers to draw each radial load roller into rolling contact with the outer bearing surface and to equalize substantially the radial forces exerted by the radial rollers on the outer bearing surface. 
     In another embodiment of the aforementioned system, the links connecting each roller between the first and second rollers comprise pivoting links and fixed links. Each roller between the first and second rollers is connected by pivoting links to one of its adjacent rollers and by fixed links to the other of its adjacent rollers. 
     The present invention, in another embodiment, is a method for receiving and delivering into a base the radial loads imposed on a crane where the crane has a center post connectable to a base with a generally cylindrical outer bearing surface and the crane rotates in at least a partial circle around the axis of the center post. The method comprises providing a linked sequence of three or more radial load rollers arranged in an arc at the outer bearing surface of the center post. Each radial roller has an axle and an axis of rotation that is generally parallel to the axis of the center post. The method also comprises providing a means for anchoring a first radial load roller at one end of the arc and anchoring a second radial load roller at the other end of the arc. The method also comprises connecting each roller between the first and the second radial rollers with links to its adjacent rollers to form a flexible chain of said rollers. Finally, the method comprises providing a means for tensioning the sequence of radial load rollers to draw each radial load roller into rolling contact with the outer bearing surface and causing the pivoting and fixed links to equalize substantially the radial forces exerted by the radial rollers on the outer bearing surface. 
     In another embodiment of the aforementioned method, the links used to connect each roller between the first and second rollers to its adjacent rollers are pivoting links and fixed links. Each roller between the first and second rollers is connected by pivoting links to one of its adjacent rollers and by fixed links to the other of its adjacent rollers. 
     The present invention, in another embodiment, is a bearing system including a bearing surface forming a circumference about a first axis, and a roller chain encompassing at least a segment of the bearing surface. The roller chain includes a first roller, a second roller, a third roller, a first member, and a second member. Each roller includes a rotational axis and a roller surface. The rotational axis for each roller is generally parallel to the first axis, and each roller surface is in rollable contact with the bearing surface. The rollers are radially offset from each other along the bearing surface. The first member interlinks the first and second rollers and maintains the offset distance between the first and second rollers. The second member interlinks the second and third rollers and maintains the offset distance between the second and third rollers. 
     In one embodiment, the first member is non-rotational relative to the rotational axes of the first and second rollers, and the second member is rotational relative to the rotational axes of the second and third rollers. In another embodiment, the first member is rotational relative to the rotational axes of the first and second rollers, and the second member is rotational relative to the rotational axes of the second and third rollers. 
     The present invention, in another embodiment, is a method of delivering radial loads from a first structure into a bearing surface of a second structure. The bearing surface forms a circumference about a first axis and the first structure is rotationally displaceable about the first axis. The method includes routing a roller chain along at least a circumferential segment of the bearing surface. The roller chain has a first end, a second end, and a plurality of flexibly interlinked rollers between the first and second ends. Each roller includes an axis of rotation that is generally parallel to the first axis. The method further includes operably connecting the first end of the roller chain to a first point on the first structure, operably connecting the second end of the roller chain to a second point on the first structure, and causing each roller to rollably contact the bearing surface. 
     In one embodiment, during operation, the roller chain radially displaces along the bearing surface as the first structure rotates about the first axis. As the roller chain displaces along the bearing surface, the rollers rollably travel along the bearing surface. 
     While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. As will be realized, the invention is capable of modifications in various obvious aspects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation view of a post crane. 
         FIG. 2  is a detailed side elevation of the superstructure of the crane shown in  FIG. 1 . 
         FIG. 3  is a detailed cross-sectional view of  FIG. 2 . 
         FIG. 4A  is a detailed cross-section elevation of the chain segment located within cloud A of  FIG. 3 . 
         FIG. 4B  is a detailed cross-section elevation of an alternate embodiment of the chain segment located within cloud A of  FIG. 3 . 
         FIG. 5  is a cross-section plan view of half of the post and machine deck taken across section line AA in  FIG. 2 . 
         FIG. 6  is a detailed cross-sectional view of  FIG. 2  in another embodiment of the invention. 
         FIG. 7  is a cross-section plan view of half of the post and machine deck taken across section line AA in  FIG. 2  in another embodiment of the invention. 
         FIG. 8  is a lateral cross-section elevation view of the roller chain bearing, wherein the view cuts across the pivot link plates between two rollers. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a side elevation view of a post crane  1  having a tapered post  5 , a boom  10 , a swivel post-head  15  swivelly mounted on top of the tapered post  5 , and a superstructure  20 . The boom  10  is pivotally connected to the superstructure  20  at the boom foot  22  and supported by wire rope  25  running from the swivel post-head  15  to locations on the boom  10 . The post  5  may be rigidly mounted to any desired supporting structure or base (not shown) such as a pedestal of an off-shore platform, a ship deck, a moveable vehicular frame, a permanent foundation embedded in the earth, or any other structure. The superstructure  20  and swivel post-head  15  may rotate about the vertical axis  30  of the tapered post  5 , thereby allowing the boom  10  to displace radially about the vertical axis  30  of the post  5 . The post  5  supports the superstructure  20  and serves as the primary structure for resisting the thrust loads, radial loads, and overturning moments experienced by the crane  1 . 
       FIG. 2  is a detailed side elevation of the superstructure  20  and more clearly shows the connection of the boom  10  to a boom pivot point  32  on the boom foot  22 . Below the superstructure  20 , a support collar  35  is connected to the post  5  and encompasses the outer circumference of the post  5 . The support collar  35  supports a container ring  40 , which encircles the outer circumference of the post  5 . An annular ring  45 , which is part of the superstructure  20  and encircles the outer circumference of the post  5 , rides on the container ring  40 . The annular ring  45  supports a machine deck  50  to which the boom foot  22  is mounted. 
     For a better understanding of the relationship between the support collar  35 , the container ring  40 , the annular ring  45 , and the machine deck  50 , reference is now made to  FIG. 3 , which is a detailed cross-sectional view of  FIG. 2 . As shown in  FIG. 3 , the annular ring  45  comprises the machine deck  50 , an outer vertical wall  55 , a roller plate  60 , and a first pair of rails  65 . The machine deck  50  encircles the post  5  and forms the top surface of the annular ring  45 . The outer vertical wall  55  runs from the machine deck  50  and tees into the roller plate  60 . The first pair of rails  65  is connected to the bottom surface of the roller plate  60 . The annular ring  45  and machine deck  50  are rotationally displaceable about the outer circumference of the post  5 . 
     As illustrated in  FIG. 3 , the support collar  35  encompasses, and is connected to, the outer circumference of the post  5 . The support collar  35  comprises a flat upper deck  70  and a second pair of rails  75 . The second pair of rails  75  is mounted on the top of the upper deck  70 . 
     As indicated in  FIG. 3 , the container ring  40  comprises pairs of flanged rollers  80  encircling the outer circumference of the post  5 . The flanged rollers  80  ride on the second pair of rails  75  and the first set of rails  65  ride on the flanged rollers  80 . Thus, the flanged rollers  80  of the container ring  40  support the annular ring  45  above the support collar  35  and allow the annular ring  45  to rotate about the axis  30  of the post  5 . The support collar  35  carries substantially all of the vertical (thrust) loads of the crane  1  into the post  5 . 
     In one embodiment of the invention, as shown in  FIG. 3 , a stewing gear assembly  85 , a first back roller  90 , a second back roller  95 , and a roller chain bearing  100  are located on or above the machine deck  50 . In another embodiment of the invention, the first back roller  90  is not present.  FIG. 3  shows in phantom the elevation location of the boom pivot point  32  relative to the machine deck  50  and the post  5 . The first and second back rollers  90 ,  95  and the roller chain bearing  100  are used to carry radial (i.e., horizontal) loads, which are induced by the thrust of the boom  10 , into the post  5 . The roller chain bearing  100  comprises interlinking chain segments  102 , which have horizontally oriented rollers  105  connected together by pairs of pivot link plates  110  and fixed link plates  115 . As indicated in phantom, the post  5  has structural reinforcement  101  along the interior circumference of the post  5 . This structural reinforcement  101  allows the post  5  to withstand the loads exerted on the post  5  by the rollers  105  of the roller chain bearing  100 . 
     For a better understanding of the structure of the roller chain bearing  100 , reference is now made to  FIG. 4A , which is a detailed cross-section elevation of the chain segment  102  located within cloud A of  FIG. 3 . As shown in  FIG. 4A , the chain segment  102  has two horizontally oriented rollers  105 , a pair of fixed link plates  115 , two vertically oriented roller axles  120 , two pairs of annular bearings  125 , two pairs of annular bearing covers  130 , two pairs of annular bushings  132 , four sets of bolts  135 , and four axle covers  140 . Each chain segment  102  is connected to the pairs of pivot link plates  110  of the adjacent chain segments  102 . Thus, the chain segments  102  anchored to the machine deck  50  at each end of the roller chain bearing  100  will have one adjacent chain segment  102  and, as a result, will be connected to only one pair of pivot link plates  110 . All other chain segments  102  of the roller chain bearing  100  will have two adjacent chain segments  102  and, as a result, will be connected to two pairs of pivot link plates  110 . 
     As illustrated in  FIG. 4A , each roller  105  is rollably supported about a roller axle  120  by a pair of bearings  125 . A bearing cover  130  encircles each roller axle  120  and is located adjacent to the outside surface of each bearing  125 . The end of each roller axle  120  resides in an opening  145  in a fixed link plate  115  near the end of the fixed link plate  115 . The bolts  135  secure a fixed link plate  115  and an axle cover  140  to each end of a roller axle  120 . This prevents a roller axle  120  from rotationally displacing within the opening  145  of a fixed link plate  115 . 
     Each roller axle  120  resides within two bushings  132 , which are located in openings  150  in the pivot link plates  110  near the ends of the pivot link plates  110 . Thus, each pair of pivot link plates  110  may pivot about a roller axle  120  via a pair of bushings  132 . 
     In another embodiment, as indicated in  FIG. 4B , a set of outer pivot link plates  116  (i.e., a second set of pivot link plates) is substituted for the fixed link plates  115 . The end of each roller axle  120  resides within a bushing  132 , which is located in an opening  145  in the outer pivot link plate  116  near the end of a outer pivot link plate  116 . The bolts  135  secure an axle cover  140  to each end of a roller axle  120 . Again, each roller axle  120  resides within two bushings  132 , which are each located in an opening  150  of the pivot link plate  110  near the end of a pivot link plate  110 . Thus, in the embodiment depicted in  FIG. 4B , each pair of pivot link plates  110  and outer pivot link plates  116  may pivot about a roller axle  120  via a pair of bushings  132 . 
     For an understanding of the arrangement of the roller chain bearing  100  and its interaction with the post  5  or, more specifically, the post bearing surface  5 , reference is now made to  FIG. 5 , which is a cross-section plan view of half of the post  5  and machine deck  50  taken across section line AA in  FIG. 2 .  FIG. 5  shows half of a roller chain bearing  100  that, in one embodiment, forms a 180-degree arc about the outer surface of the post  5 .  FIG. 5  also shows a boom foot  22  located at approximately the two o′clock position. This boom foot  22  is one of the two boom feet  22  mounted on the machine deck  50 .  FIG. 5  also shows back rollers  90 ,  95  located at the four-thirty and six o′clock positions and structural reinforcement  101  on the interior circumference of the post  5 . The back rollers  90 ,  95  are two of the three back rollers  90 ,  95  mounted on the machine deck. In other embodiments of the invention, there may be a greater or lesser number of back rollers  90 ,  95 . For example, in one embodiment, the first back roller  90  (i.e., the back roller at the six o&#39;clock position) is not present. The structural reinforcement  101  allows the post bearing surface  5  to withstand the loads exerted on the post bearing surface  5  by the rollers  105  of the roller chain bearing  100  and the back rollers  90 ,  95 . 
     It should be noted that the arrangements of the roller chain bearing  100 , the back rollers  95 , and the boom feet  22  are symmetrical about the axis  30  of the post  5  on a plane that is perpendicular to the axis  30  (i.e., the machine deck  50 ). Thus, if  FIG. 5  were an illustration of the full diameter of the post  5  and the machine deck  50 , in one embodiment, a back roller  95  would be visible at the seven-thirty position and another boom foot  22  would be visible at approximately the ten o&#39;clock position. Also, one would see that the roller chain bearing  100  runs continuously from the three o&#39;clock position, past the twelve o&#39;clock position, to the nine o&#39;clock position. In other words, in one embodiment of the invention, as shown in  FIG. 5 , the roller chain bearing  100  encompasses 180 degrees of the outer surface of the post  5 . In other embodiments, the roller chain bearing  100  encompasses greater or lesser extents of the circumference of the outer surface of the post  5 . For example, in one embodiment, the roller chain bearing  100  encompasses 120 degrees of the outer surface of the post  5 . In another embodiment, the roller chain bearing  100  encompasses 270 degrees of the outer surface of the post  5 . In yet another embodiment, the roller chain bearing  100  encompasses the full 360 degrees of the outer surface of the post  5 . In other embodiments, the circumference segment of the post  5  encompassed by the roller chain bearing  100  ranges from approximately 30 degrees to approximately 360 degrees. 
     In one embodiment of the invention, as illustrated in  FIG. 5 , the last roller axle  120  at the end of the roller chain bearing  100  is anchored in an anchor bracket  155  that is secured to the machine deck  50  and located at the three o&#39;clock position. Again, it should be noted that the arrangement of the roller chain bearing  100  and the back rollers is symmetrical about the axis  30  of the post  5 . Thus, if  FIG. 5  were an illustration of the full diameter of the post  5  and the machine deck  50 , an anchor bracket  155  would be visible at the nine o&#39;clock position. In other embodiments of the invention, the anchor brackets  155  are located at other positions about the outer surface of the post  5 . For example, in one embodiment, the anchor brackets  155  anchoring the ends of the roller chain bearing  100  are located at the seven-thirty and four-thirty positions. In other embodiments, the anchor brackets  155  are located at other locations about the circumference of the post  5 . 
     In another embodiment, as shown in  FIGS. 6 and 7 , the anchor bracket  155  is located at approximately the four o&#39;clock position. The anchor bracket  155  has a pair of extended link plates  160  that run between the axle  120  of the last roller  105  of the roller chain bearing  100  at the three o&#39;clock position and the anchor bracket  155 . The extended link plates  160  tangentially leave the circumference of the post  5  at the three o&#39;clock position as they run to the anchor bracket  155 . Again, because the anchor bracket  155  arrangement is symmetrical about the circumference of the post  5 , a pair of extended link plates  160  run between the axle  120  of the last roller  105  of the roller chain bearing  100  at the nine o&#39;clock position to an anchor plate  155  located at approximately the eight o&#39;clock position. 
     As illustrated in  FIGS. 3 and 5 , the roller axle  120  located at the anchor bracket  155  is extended and resides in a hole  162  in an anchor block  165 . The hole  162  is off-center from the geometrical center point of the anchor block  165 . Pivoting the anchor block results in a cam-action that allows the roller chain bearing  100  to be adjusted in length about the outer circumference of the post  5  for typical roller wear. 
     As shown in  FIG. 5 , the rollers  105  are evenly distributed along the length of the roller chain bearing  100 . For example, in one embodiment, there is a ten-degree spacing between each roller  105  about the axis  30  of the post  5 . In another embodiment, there is a five-degree spacing between each roller  105  about the axis  30  of the post  5 . In another embodiment, there is a 15-degree spacing between each roller  105  about the axis  30  of the post  5 . In other embodiments, the range of possible equal spacings for the rollers  105  about the axis  30  of the post  5  will be from approximately two degrees to approximately 20 degrees. 
     As illustrated in  FIG. 3 , in one embodiment of the invention, the roller chain bearing  100  is supported above the machine deck  50  and prevented from displacing vertically along the outer circumference of the post  5  by pads  170  located below some or all of the axles  120  of the roller chain bearing  100 . In another embodiment, structural members are secured to the machine deck  50  at various locations adjacent to the outer circumference of the roller chain bearing  100 . The structural members have flanges that extend below the top fixed link plate  115 , thereby supporting the roller chain bearing  100  above the machine deck  50  and preventing the vertical displacement of the roller chain bearing  100  along the outer circumference of the post  5 . In another embodiment, the stiffness and mass of the roller chain bearing  100 , along with the thrust loads exerted on the roller chain bearing  100  by the boom  10 , combine to prevent the vertical displacement of the roller chain bearing  100  without additional structural support. 
     Another means of preventing vertical displacement of the roller chain bearing  100  is illustrated in  FIG. 8 , which is a lateral cross-section elevation view of the roller chain bearing  100 , wherein the view cuts across the pivot link plates  110  between two rollers  105 . As shown in  FIG. 8 , the rollers  105  of the roller chain bearing  100  have flanges  175  for mating with a rail  180  encircling the outer circumference of the post  5 . The rail  180  serves as a post bearing surface. In another embodiment, the roller  105  has a double inclined face for mating with a rail  180  having a V profile. In other embodiments, the roller  105  and rail  180  will have a circle segment or other cross-sectional profiles that will allow the bearing surface of the roller  105  and rail  180  to mate, align and prevent vertical displacement of the roller chain bearing  100  along the outer circumference of the post  5 . 
     As can be seen from  FIG. 5 , as the machine deck  50  of the superstructure  20  rotates about the axis  30  of the post  5 , the back rollers  90 ,  95  and the rollers  105  of the roller chain bearing  100  roll along the outer surface of the circumference of the post  5  and transfer any radial (i.e., horizontal) thrust load from the boom  10  to the post  5 . The pivot link plates  110  of the roller chain bearing  100  allow the roller chain bearing  100  to flex to conform to the outer circumference of the post  5 . In other words, in one embodiment, the roller chain bearing  100  is a series of flexibly linked rollers  105  that form a radial bearing surface that conforms to at least a portion of a radial bearing surface on the outer circumference of the post  5 . 
     The roller chain bearing  100  is advantageous because it provides an effective method of substantially equalizing roller loads without having to rely on precision machining or elastic deflections to equally share roller loads. When a slewing gear assembly  85  that is removable in segments is used, the configuration and location of the roller chain bearing  100  also eases servicing. Specifically, the structure allows the replacement or other servicing of the means of resisting radial (i.e., horizontal) thrust from the boom  10  without having to remove the boom  10 , the machine deck  50 , or superstructure  20 . 
     Although the present invention has been described with reference to preferred embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.