Patent Publication Number: US-9415980-B2

Title: Lift crane with mast-raising mechanism

Description:
PRIORITY CLAIM 
     The present application claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 61/932,060 filed Jan. 27, 2014 and titled Lift Crane With Mast-Raising Mechanism and U.S. Provisional Patent Application Ser. No. 61/937,421 filed Feb. 7, 2014 and titled Lift Crane With Mast-Raising Mechanism, the disclosures of which are incorporated in their entirety by this reference. 
    
    
     BACKGROUND 
     The present application relates to construction equipment, such as cranes. In particular, the present application relates to a crane having arms for raising a mast, i.e., a self-raising mast. The present application also relates to a method of self-raising the mast and assembling the crane. 
     Construction equipment, such as cranes or excavators, must often be moved from one job site to another. Moving a crane or an excavator can be a formidable task when the machine is large and heavy. For example, highway limits on vehicle-axle loads must be observed, and overhead obstacles can dictate long, inconvenient routings to the job site. 
     One solution to improving the mobility of large construction machines, such as cranes, is to disassemble them into smaller, more easily handled components. The separate components can then be transported to the new job site where they are reassembled. 
     The typical practice has been to use an assist crane to disassemble the crane into the separate components. The assist crane is then used to load the components onto their respective transport trailers. Once at the new job site, another assist crane is used to unload the components and reassemble the crane. 
     As the components for a large crane can weigh in excess of 80,000 lbs., the capacity of the assist crane required represents a very significant transport expense. As a result, designers have attempted to develop self-handling systems for assembling and disassembling cranes. The majority of the self-handling systems developed thus far have been directed to smaller cranes that only need to be disassembled into a few components. 
     The development of self-handling systems for larger cranes, however, has met with limited success. One reason for this is that larger cranes need to be disassembled into numerous components, thus requiring time-consuming disassembly and reassembly procedures. For example, a large capacity crane typically uses a complicated and cumbersome rigging system to control the angle of the boom. Boom rigging system components such as the equalizer, the mast, and wire rope rigging are heavy and difficult to disassemble for transport. 
     Another reason for the limited success of prior art self-assembling cranes is that they typically rely on additional crane components that are used only for assembling and disassembling the crane. For example, some self-assembling cranes require additional wire rope guides and sheaves on the boom butt so that a load hoist line can be used with the boom butt to lift various crane components during the assembly process. 
     An example of a prior art method for assembling and disassembling a typical large capacity crawler crane is disclosed in U.S. Pat. No. 5,484,069, titled “Process For Self-Disassembling A Crawler Crane” (“the &#39;069 patent”). In particular, this patent is directed to a type of crawler crane having a mast that is supported by a backhitch. 
     Another example of a prior art method for assembling and is assembling a different type of crawler crane is disclosed in U.S. Pat. No. 6,062,405, titled “Hydraulic Boom Hoist Cylinder Crane” (“the&#39;405 patent”). This patent is directed to a type of crane that utilizes hydraulic cylinders to control the angle of the boom. 
     The &#39;069 patent and the&#39;405 patent are both examples of self-assembling cranes that require the use of the boom butt to lift and position components for assembly on to the crane. As a consequence, additional sheaves must be included on the boom butt for the self-assembling procedure. It is therefore desirable to provide a crane and method of self-assembly which eliminates, or at least reduces, the use of the boom butt during the self-assembling procedure. 
     In addition to the above, some types of cranes utilize a moving or live mast. A crane having a moving or live mast is connected directly to the boom by one or more boom pendants. The boom angle is controlled by boom hoist rigging, which is connected between the mast and the upper works of the crane. The mast and the boom move together as the boom angle is changed. The mast must typically be disconnected from the boom and stored horizontally on top of the crane for transport between job sites. Moreover, the masts on these types of cranes are often very long and heavy, and are consequently difficult to handle during the assembly process. It is therefore desirable to provide a crane having a self-raising mast. It is also desirable to provide a system and method of controlling the mast self-raising procedure that is safe, efficient and easy to implement. 
     Another of the challenges to having a self-raising mast is the limited space on a crane&#39;s upper works or rotating bed in which to install the raising mechanism. For example, it is desirable to install a linear actuator, such as a hydraulic cylinder with an extension rod, that provides as nearly perpendicular force to the mast throughout its course of travel as possible. Of course, since the mast typically rotates about a fixed point on the rotating bed, the force of the cylinder rarely is perpendicular. That said, when the mast is positioned in a near horizontal position it is most efficient for the hydraulic cylinder to be positioned near vertically so that the extension rod presses most closely to a perpendicular position relative to the mast. The problem, however, with such an arrangement is that the hydraulic cylinder extends through a portion or all of the rotating bed. There simply may not be sufficient space to position the hydraulic cylinder vertically, then. 
     Alternatively, the linear actuator, such as a hydraulic cylinder or other raising mechanism, could be positioned at an angle to the mast rather than nearly vertically. Thus, the closer to parallel the linear actuator lies to the mast, the less vertical space within the rotating bed that the linear actuator occupies. The drawback to this solution, however, is that the closer to parallel that the actuator lies relative to the mast, the force normal to the mast that the actuator applies decreases. In other words, it is relatively more difficult for an actuator, such as a hydraulic cylinder, of a given size to raise a mast when it is positioned more closely to parallel with the mast. 
     To overcome this, and to apply a greater force normal to the mast, one can increase the size and/or capacity of the cylinder. This would result in more force being applied normal to the mast, but much of the additional capacity of the larger hydraulic cylinder is wasted because it is applied in a direction parallel to the mast. Further, the benefits of packaging the cylinder at an angle to the mast in terms of providing greater available space in the rotating bed are defeated, in part, by increasing the size/capacity of the hydraulic cylinder. In other words, solving the problem of space in the vertical direction of the rotating bed may simply create a problem of insufficient space in an angled and/or horizontal direction of the rotating bed. 
     In U.S. Pat. No. 6,695,158, titled “Crane With Self-Raising Mast” (the “&#39;158 patent”), a crane has an upper works rotatably mounted on a lower works, a boom pivotally mounted on the upper works, a mast pivotally mounted on the upper works and pendantly connected to the boom, and boom hoist rigging connected to the mast for controlling the angle of the boom. The invention further comprises a self-raising mast assembly for controlling the position of the mast when the mast is not connected to the boom. The self-raising mast assembly comprises a mast raising yoke, a hydraulic mast raise cylinder, and a hydraulic system. 
     The &#39;158 solves some of the issues discussed with the prior art, but it involves several components that rotate and are pinned together, increasing the complexity of the mechanism. Further, it involves positing the hydraulic cylinder in relatively vertical position within the rotating bed of the crane, which consumes a significant amount of vertical space in the rotating bed. 
     It is therefore desirable to provide a crane and method of self-assembly which is mechanically simple relative to the prior art and reduces the amount of space into which it is packaged or positioned within the rotating bed. 
     BRIEF SUMMARY 
     A mobile lift crane has an upper works or rotating bed rotatably mounted on a lower works or carbody, a boom pivotally mounted on the upper works, a mast pivotally mounted on the upper works and connected to the boom, and boom hoist rigging connected to the mast for controlling the angle of the boom. The invention further comprises a self-raising mast assembly for controlling the position of the mast when the mast is not connected to the boom. 
     An embodiment of a mast-raising mechanism for raising a mast of a mobile lift crane from a stowed position for travel to an operating position includes a bearing surface coupled to a lower surface of the mast. A linear actuator is extendable to raise the mast. In some embodiments, the linear actuator is a hydraulic cylinder, although other linear actuators such as a drive screw and nut, rack and pinion, winches and pulleys, and other types of linear actuators are contemplated. In the embodiment of a hydraulic cylinder, the cylinder includes a first end pivotally coupled to a rotating bed of the crane and a second end spaced apart from the first end. A first arm includes a first end pivotably coupled to the second end of the hydraulic cylinder. The first end includes a plate oriented to press against the bearing surface to raise the mast when the hydraulic cylinder is extended, and a second end spaced apart from the first end. A second arm includes a first end proximate the second end of the first arm, and a second end spaced apart from the first end. The second end of the second arm is pivotably connected to the rotating bed. A biasing mechanism couples the second end of the first arm to the first end of the second arm and urges the first arm towards the second arm. In some embodiments, the second end of the first arm abuts the first end of the second arm when the mast is stowed, but the second end of the first arm does not abut the first end of the second arm when the hydraulic cylinder extends and presses the first end of the first arm against the bearing surface 
     Another embodiment of a mast-raising mechanism for raising a mast of a mobile lift crane from a stowed position for travel to an operating position includes a bearing surface coupled to a lower surface of the mast. A hydraulic cylinder is extendable to raise the mast. The hydraulic cylinder includes a first end pivotally coupled to a rotating bed of the crane and a second end spaced apart from the first end. A first arm includes a first end pivotably coupled to the second end of the hydraulic cylinder. The first end includes a plate oriented to press against the bearing surface to raise the mast when the hydraulic cylinder is extended and closes a gap that exists between the bearing surface and the plate of the first arm when the mast is stowed. The first arm also includes a second end spaced apart from the first end. A second arm includes a first end proximate the second end of the first arm, and a second end spaced apart from the first end. The second end of the second arm is pivotably connected to the rotating bed. A biasing mechanism couples the second end of the first arm to the first end of the second arm and urges the first arm towards the second arm. 
     In yet another embodiment, a mast-raising mechanism for raising a mast of a mobile lift crane from a stowed position for travel to an operating position includes a bearing surface coupled to a lower surface of the mast. A hydraulic cylinder is extendable to raise the mast. The hydraulic cylinder includes a first end pivotally coupled to a rotating bed of the crane and a second end spaced apart from the first end. 
     A first arm includes a first end pivotably coupled to the second end of the hydraulic cylinder. The first end includes a plate oriented to press against the bearing surface to raise the mast when the hydraulic cylinder is extended and closes a gap that exists between the bearing surface and the plate of the first arm when the mast is stowed. The first arm also includes a second end spaced apart from the first end. The first arm includes an end plate proximate the second end of the first arm, the end plate having a first side, a second side spaced apart from the first side, and at least one hole extending through the first side and the second side. 
     A second arm includes a first end proximate the second end of the first arm, and a second end spaced apart from the first end. The second end of the second arm is pivotably connected to the rotating bed. The second arm also includes an outer plate proximate the first end of the second arm. The outer plate has a first side, a second side spaced apart from the first side, and at least one hole extending through the first side and the second side. 
     A biasing mechanism couples the second end of the first arm to the first end of the second arm and urges the first arm towards the second arm. The biasing mechanism includes a rod extending through each of the holes of the end plate and the outer plate. The rod is coupled to at least the end plate. In some embodiments, the biasing mechanism includes a spring disposed at least partly around the rod. 
     Yet another embodiment comprises a mobile lift crane that incorporates any of the embodiments of the mast-raising mechanism. The lift crane itself includes movable ground engaging members mounted on a carbody that allow the crane to move over the ground, a rotating bed rotatably mounted on the carbody, a boom pivotally mounted on the rotating bed, and a mast pivotally connected to the rotating bed. 
     Various embodiments of the invention also include methods of raising and lowering a mast-raising mechanism in order to raise a mast on a crane. 
     For example, an embodiment of a method of using any of the disclosed embodiments of the mast-raising mechanism include extending the hydraulic cylinder to open a gap between the second end of the first arm and the first end of the second arm, urging the first end of the first arm against the bearing surface to raise the mast to an operating position, retracting the hydraulic cylinder at least partly under the influence of the biasing mechanism urging the first arm towards the second arm, and closing the gap between the second end of the first arm and the first end of the second arm. Embodiments of the method include stowing the hydraulic cylinder, the first arm, and the second arm in the rotating bed. 
     The mast-raising mechanism and method permits the mast to be raised and lowered during the assembly process without the need for a separate crane, and overcomes many of the problems identified above. In particular, the self-raising mast assembly and method permits the mast to be raised from and lowered to a stored position on the rearward portion of the upper works. 
     These and other advantages, as well as the invention itself, will become more easily understood in view of the attached drawings and apparent in the details of construction and operation as more fully described and claimed below. Moreover, it should be appreciated that several aspects of the invention can be used with other types of cranes, machines or equipment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a right side elevation view of a mobile lift crane that includes an embodiment of a mast-raising mechanism. 
         FIG. 2  is a right side elevation view of the rotating bed of the crane of  FIG. 1  with the mast in a stable upright position and with several elements removed for clarity. 
         FIG. 3  is a top perspective view of the rotating bed and the biasing mechanism of the crane of  FIG. 1  with the mast and several other elements removed for clarity. 
         FIG. 4  is a side elevation view of the rotating bed and the biasing mechanism of the crane of  FIG. 1  with the mast and several other elements removed for clarity. 
         FIG. 5  is a partial cross-section A-A viewed from below of the biasing mechanism illustrated in  FIG. 4 . 
         FIG. 6  is a top perspective view of a first arm of the biasing mechanism. 
         FIG. 7  is a top elevation view of the first arm of  FIG. 6 . 
         FIG. 8  is a side elevation view of the first arm of  FIG. 6 . 
         FIG. 9  is a rear elevation view of the first arm of  FIG. 6 . 
         FIG. 10  is a top perspective view of a second arm of the biasing mechanism. 
         FIG. 11  is a side elevation view of the second arm of  FIG. 10 . 
         FIG. 12  is a top elevation view of the second arm of  FIG. 10 . 
         FIG. 13  is a front elevation view of the second arm of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     The present invention will now be further described. In the following passages, different aspects of the embodiments of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous. 
     Several terms used in the specification and claims have a meaning defined as follows. 
     The term “rotating bed” refers to the upperworks of the crane (the part that rotates with respect to the carbody), but does not include the boom or any lattice mast structure. The rotating bed may be made up of multiple parts. For example, for purposes of the present invention, the adapter plate disclosed in U.S. Pat. No. 5,176,267 would be considered to be part of the rotating bed of the crane on which it is used. Also, if a crane is taken apart for transportation between job sites, the rotating bed, as that term is used herein, may be transported in more than one piece. Further, when a component, such as a counterweight support frame is attached to the remainder of the rotating bed in a manner that it stays fixed to the remainder of the rotating bed until completely removed, it can be considered to be part of the rotating bed. 
     The term “mast” refers to a structure that is attached to the rotating bed and is part of the boom hoist system. The mast is used to create an elevated point above the other parts of the rotating bed through which a line of action is established so that the boom hoist system is not trying to pull the boom up along a line nearly through the boom hinge pin during a set-up operation. In this regard, a gantry or some other elevated structure on the rotating bed can serve as a mast. The mast may be a fixed mast, a derrick mast or a live mast, depending on the embodiment of the invention. A live mast is one that has fixed length pendants between the mast and the boom during normal crane pick, move and set operations, and the angle of the boom is changed by changing the angle of the mast. A fixed mast is designed to stay at a fixed angle with respect to the rotating bed during normal crane pick, move and set operations. (However, a small degree of movement may occur in a fixed mast if the balance of the counterweight moment and the combined boom and load moment change so that the mast is pulled backward by the counterweight. In that case mast stops are used to hold the mast up, but those mast stops may allow for a small degree of movement.) Of course a mast which is fixed during normal crane operations may be pivotal during crane set-up operations. A derrick mast is one that has adjustable length boom hoist rigging between the mast and the boom, thus allowing the angle of the boom with respect to the plane of rotation of the rotating bed to be changed, but also is connected to the rotating bed in a pivotal fashion, and is connected to the rear of the rotating bed with an adjustable-length connection. A derrick mast may be used as a fixed mast by keeping the angle of the derrick mast with respect to the rotating bed constant during a pick, move and set operation. 
     In some instances, a mast is stowed within or upon the rotating body while the crane is transported between job sites. The mast is stowed substantially horizontally either facing towards the front portion or, more typically, the rear portion of the rotating bed to reduce the height of the components of the crane to ensure that the components meet any over-the-road travel restrictions for height. By substantially horizontal, it is meant that the mast can be stored with its long axis parallel to the ground, as well as in those circumstances in which the long axis of the mast slopes several degrees above or below parallel. For example, for purposes of this application, the long axis of the mast may slope ±20 degrees above or below true horizontal and still fall within the scope of the term “substantially horizontal.” 
     The front of the rotating bed is defined as the portion of the rotating bed that is between the axis of rotation of the rotating bed and the position of the load when a load is being lifted. The rear of the rotating bed includes everything opposite the axis of rotation from the front of the rotating bed. The terms “front” and “rear” (or modifications thereof such as “rearward”) referring to other parts of the rotating bed, or things connected thereto, such as the mast, are taken from this same context, regardless of the actual position of the rotating bed with respect to the ground engaging members. 
     The moveable ground engaging members are defined as members that are designed to remain engaged with the ground while the crane moves over the ground, such as tires or crawlers, but does not include ground engaging members that are designed to be stationary with respect to the ground, or be lifted from contact with the ground when they are moved, such as a ring on a ring supported crane and outriggers commonly found on truck mounted cranes. 
     Embodiments of the present invention find application in all types of cranes or construction machines, including those with both a fixed mast and a live mast. That said, the following description describes a mast-raising mechanism with respect to the crawler crane  10  of  FIG. 1 . 
     The crawler crane  10  includes an upper works  12  having a rotating bed  14  that is rotatably connected to a lower works  16  by a swing bearing  18 . The lower works  16  includes a car body  20 , counterweights  22 , and ground engaging members  24 . Illustrated in  FIG. 1  are crawlers, although term ground engaging members encompasses things such as tires, for example. In addition, while only one ground engaging member  24  is visible, an identical ground engaging member  24  exists on the other side of crane  10 . Further, the disclosure is not limited to only two ground engaging members  24 . Rather, crane  10  may employ a plurality of ground engaging members, such as 3, 4, or more. 
     The rotating bed  14  includes a boom  26  pivotally connected to the rotating bed  14 . The boom  26  comprises a boom top  28  and a tapered boom butt  30 . The boom  26  may also include one or more boom inserts  32  connected between the boom top  28  and the boom butt  30  to increase the overall length of the boom  26 . While  FIG. 1  illustrates a lattice style boom  26 , other known types of booms, such as round, oval, and/or telescoping type booms fall within the scope of the disclosure. A mast  34  is pivotally connected to the rotating bed  14 . The boom  26  is connected to the mast  34  by one or more boom pendants  36 . 
     The angle of the boom  26  is controlled by boom hoist rigging  38  connected between the upper works  12  and the mast  34 . While not illustrated, the-boom hoist rigging  38  comprises a boom hoist rope that passes (reeved) around a sheave assembly on the upper end of the mast and a sheave assembly on the rear end of the rotating bed  14 . One end of the boom hoist rope is typically anchored to the rotating bed  14 , while the other end is anchored to and wrapped around the boom hoist drum. 
     The mast  34  supports the connection between the boom hoist rigging  38  and the boom pendants  36  at a location that is distanced from the axis of the boom  26  to optimize the forces in the boom pendants  36  and the boom hoist rigging  38 . This arrangement also permits the boom hoist rigging  38  to impart a force having a component that is perpendicular to the axis of the boom  26 . This force is transferred to the end of the boom  26  by the boom pendants  36 . Because the weight of the boom  26  is significantly greater than the weight of the mast  34  and the boom hoist rigging  38 , the boom hoist rope and the boom pendants  36  are always in tension as long as the boom  26  is within the normal operating range of the crane  10 . Conversely, the mast  34  is always in compression as long as the boom  26  is within the normal operating range of the crane  10 . A boom backstop  48  is provided to prevent the boom  26  from exceeding a safe operating position. 
     Rotation of the boom hoist drum in one direction (e.g., clockwise) will retract the boom hoist rope, thereby shortening the length of the boom hoist rigging  38  and causing the upper end of the mast  34  to be pulled towards the rear of the rotating body. This in turn raises the end of the boom  26  (i.e., increases the boom angle). Likewise, rotation of the boom hoist drum in the opposite direction (e.g., counter-clockwise) will payout the boom hoist rope, thereby increasing the length of the boom hoist rigging  38  and allowing the upper end of the mast  34  to be pulled away from rear of the rotating bed  14  by the weight of the boom  26 . This action results in the lowering of the end of the boom  26  (i.e., decreases the boom angle). 
     The upper works  12  further includes one or more load hoist lines  50  for lifting loads. Each load hoist line  50  is passed (reeved) around a load hoist line drum (not illustrated) supported on the rotating bed  14  of the upper works  12 . The load hoist line drums are rotated to either pay out or retrieve the load hoist lines  50 . The load hoist lines  50  are reeved around one or a plurality of boom top sheaves  54  located at the upper end of the boom top  28 . The boom may also include one or more wire rope guides  56  attached to upper surface of the boom  26  to prevent the load hoist lines  50  from interfering with the lattice structure of the boom  26 . A hook block (not shown) is typically attached to each load hoist line  50 . 
     The rotating body  14  or the upper works  12  further includes a power plant, such as a diesel engine (not illustrated), and a counterweight assembly  22 . The power plant supplies power for the various mechanical and hydraulic operations of the crane  10 , including movement of the ground engaging members  24 , rotation of the rotating bed  14 , rotation of the load hoist line drums, and rotation of the boom hoist drum. Operation of the various functions of the crane  10  is controlled from the operator&#39;s cab  60 . 
     Referring to  FIG. 2 , the mast  34  in this embodiment comprises a frame having two spaced apart rectangular legs or arms that are not visible in the plan view. Further, masts of different shapes, including round and oval tubular shapes fall are encompassed in this disclosure. The mast  34  should not interfere with the operation of the load hoist lines  50  or the boom backstop  48 . In addition, the mast  34  should be configured so as to permit the mast  34  to be lowered to an approximately or substantially horizontal stored position on top of the rotating body  12  or, depending on the configuration of the rotating body  12 , within a recess  70  ( FIG. 3 ) in the rotating body  14 . This permits the overall height of the disassembled crane  10  to be minimized so that highway height restrictions will not be violated during transport to and from the job site. As will be explained below, the mast  34  is ordinarily not disassembled from the crane  10  during transport. The mast  34  should also be configured so as to permit the mast  34  to be lowered to an approximately horizontal fully rearward position towards the rear portion  72  of the rotating bed  14 . Nonetheless, the mast  34  can also be configured to be rotated, lowered, and stowed in a forward direction towards the front portion  74  of the rotating bed  14 . 
       FIG. 2  illustrates the rotating bed  14  with all but the mast  34  and the mast-raising mechanism  100  removed for clarity. The mast  34  is illustrated in a stable upright position after the mast-raising mechanism  100  has raised it from its stowed position. At this point, the mast-raising mechanism  100  could be retracted and stowed. 
     The mast-raising mechanism  100  includes a bearing surface  104  that is coupled to a lower surface  37  of the mast  34 . It is important to consider that the lower surface  37  is referred to as such in deference to its position on the lower side of the mast  34  when the mast  34  is rotated rearward and is substantially horizontal in its stowed position. The bearing surface  104  can be attached to the lower surface  37  through welding, other known methods, or it can simply be an integral component of the lower surface  37 . The bearing surface  104  is substantially vertically oriented and perpendicular to a long-axis  35  of the mast  34  when the mast  34  is in its stowed position. The bearing surface  104  is oriented in this manner, in part, to provide a surface that is oriented more closely to normal or perpendicular to the force F that the mast-raising mechanism  100  applies to the bearing surface  104  to raise the mast  34 . This configuration is an improvement over the prior art in which a mast-raising mechanism might apply a force to the lower surface of the mast, which is oriented more closely to parallel to the force, which resulted in a relatively small normal component of the force to actually raise the mast. 
     The mast-raising mechanism  100  also includes a linear actuator  106  that is extendable to raise the mast  34 . In some embodiments, the linear actuator  106  is a hydraulic cylinder, as illustrated in the figures, although other linear actuators such as a drive screw and nut, rack and pinion, winches and pulleys, and other types of linear actuators are contemplated. Thus, while the concept of a linear actuator encompasses all of these and equivalent features, for convenience reference typically will be made to a hydraulic cylinder. 
     In the illustrated embodiment, the hydraulic cylinder  106  is extendable to raise the mast  34 . The hydraulic cylinder  106  includes a first end  108  pivotally coupled to the rotating bed  14 . For example, the first end  108  typically is the cap end of the hydraulic cylinder  106  and it is pinned or otherwise coupled to a lug or similar structure (not illustrated) on the rotating bed  14 , as known in the art. The rod  110  extends from the body  109  of the hydraulic cylinder to a second end  112  that is spaced apart from the first end  108 . The second end  112  may include a clevis or other similar attachment for pivotably coupling the hydraulic cylinder  106  to a first end  122  of a first arm  120 , as illustrated in  FIGS. 3 and 4 . 
     As illustrated, the hydraulic cylinder  106  is positioned proximate the front portion  74  of the rotating bed  14  so that it might more easily raise the mast  34  from its stowed position in which the mast  34  is pivoted downward towards the rear portion  72  of the rotating bed  14 . The hydraulic cylinder  106 , however, can be positioned at other locations within the rotating bed  14  as design considerations warrant. 
     The first arm  120 , which is part of the mast-raising mechanism  100 , is best illustrated in  FIGS. 6-9  that provide several views of the first arm  120  in isolation. The first arm  120  includes a first end  122  that is pivotably coupled to the second end  112  of the hydraulic cylinder  106 , as noted. 
     The first end  122  includes a plate  126  oriented to press against the bearing surface  104  on the mast  34 . Optionally and as illustrated, the plate  126  is substantially vertically oriented and perpendicular to a long-axis  35  of the mast  34  when the mast  34  is in its stowed position. 
     When the mast-raising mechanism  100  is in its lowered or stowed position, the plate  126  is proximate the bearing surface  104  and in yet other embodiments there exists a gap between the plate  126  and the bearing surface  104 . Stated differently, in one embodiment the first end  122  of the first arm  120  is not physically connected to the bearing surface  104  and/or the mast  34  when the mast-raising mechanism  100  is in its stowed position. In other embodiments, the plate  126  and the bearing surface  104  still are not physically coupled together, but the plate  126  and the bearing surface  104  do contact each other when the mast-raising mechanism  100  is in its stowed position. Alternatively, the plate  126  is coupled to the bearing surface  104  in some manner and, in some instances, may be integrally formed with the bearing surface  104 . 
     When it is desired to raise the mast  34  from its stowed position, the hydraulic cylinder  106  extends and urges the first end  122  of the first arm  120  towards and eventually into contact with the bearing surface  104 . Alternatively, it may be considered that the hydraulic cylinder  106  extends and urges the plate  126  into contact with the bearing surface  104 . Of course, if the plate  126  and the bearing surface  104  are in contact already with the mast  34  in the stowed position, the hydraulic cylinder  106  and urges the first end  122  and the plate  126  against or further into contact with the bearing surface  104 . Of course, it will be understood that in other embodiments the rod  110  of the hydraulic cylinder  106  extends and urges the first end  122  and/or the plate  126  into contact with the bearing surface  104 . Regardless, once the plate  126  contacts the bearing surface  104  the hydraulic cylinder  106  urges the plate  126  and the bearing surface  104  away from the first end  108  of the hydraulic cylinder  106 , thereby raising the mast  34  from its stowed position. 
     Optionally, the first end  120  includes a top plate  132 , and at least one side plate  133 . In this instance, two side plates  133  are illustrated. The side plates  133  optionally include a through hole  134  configured to receive a pin (not illustrated) or other fastening mechanism that couples the first end  122  of the first arm  120  to a clevis or similar structure at the second end  112  of the hydraulic cylinder. In the illustrated embodiment the plate  126 , top plate  132 , and side plates  133  are coupled together, typically through welds or other similar fastening methods. Alternatively, these components may be integrated into a contiguous structure through machining, for example. 
     The first arm  120  includes an end plate  128  proximate the second end  124  of the first arm  120 . The end plate  128  includes a first side  129 , a second side  130  spaced apart from the first side  129 , and at least one hole  131  extending through the first side  129  and the second side  130 .  FIGS. 6 and 9  illustrate two holes  131 , although other embodiments might have only one hole or a plurality of holes. 
     The first arm  120  includes at least one, and in the illustrated embodiment, a plurality of guide arms  135  that join the first end  122  to the second end  128 . The guide arms  135  illustrated are plates coupled to the first end  122  and, more specifically, the sides  133 , and the second end  128  and, specifically, the end plate  128 , via welds or other known methods. Alternatively, the guide arms  135  are coupled to the sides  133  through a pin joint, such as a pin-and-hole or a pin-and-slot connection, or other similar connection that provides a controlled measure of play or looseness in the connection between the guide arms  135  and the sides  133 . A connection that provides a designed measure of play may have beneficial use in that it allows the first end  122  and, more specifically, the plate  126 , to better conform to the orientation of the bearing surface  104  so as to provide a greater contact area over which the hydraulic cylinder  106  urges the plate  126  into the bearing surface  104 . Such a connection, therefore, adapts to any slight variations that may occur during the manufacturing process. The guide arms  135  alternatively can be made from bar stock, round stock, tubes, and other shapes as one of skill in the art would appreciate. 
     Optionally, another top plate  136  is coupled to the end plate  131  and the guide arms  135  proximate the second end  124  via welds or other known methods. While illustrated as separate components fastened together, the components  122 - 136  may also be integrated into a contiguous structure through machining, for example. The top plate  136  is illustrated as extending only partly between the second end  124  and the first end  122 , although it optionally extends fully between the second end  124  and the first end  122 . In the latter event, the top plate  136  optionally is coupled to the top plate  132  or is formed integrally with the top plate  132  as a single combined top plate  132 / 136 . 
     The mast-raising mechanism  100  includes a second arm  140  is best illustrated in  FIGS. 10-13 , which provide several views of the second arm  140  in isolation. The second arm  140  includes a first end  142  proximate the second end  128  the first arm  120  and a second end  170  spaced apart from the first end  142 . 
     The second arm  140  includes an outer plate  146  proximate the first end  142  of the second arm  140 . The outer plate  146  includes a first side  148 , a second side  150  spaced apart from the first side  148 , and at least one hole  152  extending through the first side  148  and the second side  150 .  FIGS. 12 and 13  illustrate two holes  152 , although other embodiments might have only one hole or a plurality of holes. 
     As illustrated in  FIGS. 3-5 , the second end  124  of the first arm  120  abuts the first end  142  of the second arm  140  when the mast-raising mechanism  100  is stowed. More particularly, the second side  130  of the end plate  128  abuts the first side  148  of the outer plate  146  when the mast-raising mechanism  100  is in the stowed position. In other embodiments, the end plate  128  and the outer plate  146  are proximate each other, but do not abut, when the mast-raising mechanism  100  is in its stowed position. 
     As discussed above, when it is desired to raise the mast  34  from its stowed position, the hydraulic cylinder  106  extends and urges the first end  122  of the first arm  120  towards and eventually into contact with the bearing surface  104  if the first end  122  is not already in contact with the bearing surface  104 . Regardless, as the hydraulic cylinder extends, the second end  124  of the first arm  120  will move apart from and no longer abut the first end  142  of the second arm  140  if the second end  124  was initially abutting the first end  142 . Stated differently, a gap will open and/or increase (if a gap previously existed) between the second end  124 , specifically the end plate  128 , and the first end  142  of the second arm  140 , specifically the outer plate  146 . 
     The second arm  140  optionally includes an inner plate  154  positioned between the outer plate  146  and the second end  170  of the second arm  140 . Like the outer plate  146 , the inner plate  154  includes a first side  156 , a second side  158 , spaced apart from the first side  156 , and at least one hole  160  extending through the first side  156  and the second side  156 . 
     The second arm  140  optionally includes a top plate  162  and at least one side plate  164 . In this instance, two side plates  164  are illustrated. Further, the side plates optionally comprise a plurality of plates, such as plates  165  and  166 , coupled together to form the side plate  164 . The side plate  164  alternatively can be made from bar stock, round stock, tubes, and other shapes as one of skill in the art would appreciate. The side plates  164  extend from the first end  142  of the second arm to the second end  170  of the first arm. Likewise, the top plate  162  optionally extends from the first end  142  where the top plate  162  is coupled to the outer plate  146 , across and coupled to the inner plate  154  and the side plates  164 , and at least partly to the second end  170  of the second arm  140 . In other words, the top plate  162  may be solid or it may include holes or discontinuities in it. In the illustrated embodiment the outer plate  146 , inner plate  154 , top plate  162 , and side plates  164  are coupled together, typically through welds or other similar fastening methods. Alternatively, these components may be integrated into a contiguous structure through machining, for example. 
     The second end  170  of the second arm is pivotably connected to the rotating bed  14 . For example, the second arm optionally includes at least one lug  172 , and as illustrated, a plurality of lugs  172 , that couple to a corresponding lug  80  ( FIG. 3 ) on the rotating bed  14  through the use of a pin (not illustrated) as will be appreciated. Of course, other types of pivotal connections can be used. 
     The mast-raising mechanism  100  includes a biasing mechanism  180  that couples the second end  124  of the first arm  120  to the first end  142  of the second arm  140 . In addition, the biasing mechanism  180  urges the first arm  120  towards the second arm  140 . Stated differently, the biasing mechanism applies a force to at least one of the first arm  120  and the second arm  140  that urges the first arm  120  and the second arm  140  together. 
     As noted above, the second end  124  of the first arm  120  typically, although not necessarily, abuts the first end  142  of the second arm  140  when the mast-raising mechanism  100  is stowed. This result is at least in part a function of the biasing mechanism  180  urging the first arm  120  and the second arm  140  together. In other words, the biasing mechanism  180  is configured to apply a pre-load to the mast-raising mechanism  100 . 
     Likewise, and as noted, when the mast-raising mechanism  100  is in its lowered or stowed position, the plate  126  is typically in contact with the bearing surface  104 , or at least proximate the bearing surface  104 , and in yet other embodiments there exists a gap between the plate  126  and the bearing surface  104 . This, too, is at least in part a function of the biasing mechanism  180  urging the first arm  120  and the second arm  140  together or, stated differently, urging the first arm  120  away from the bearing surface  104 . Optionally, the pre-load of the biasing mechanism  180  is adjusted to ensure that plate  126  remains in contact with and/or proximate to the bearing surface  104 . 
     Further, the force that the biasing mechanism  180  includes a directional component that acts in a direction opposite to a directional component of the force that the hydraulic cylinder  106  generates. As noted above, when it is desired to raise the mast  34  from its stowed position, the hydraulic cylinder  106  extends and urges the first end  122  of the first arm  120  towards the bearing surface  104  and, if the first end  122  is not at least initially in contact with the bearing surface  104 , eventually into contact with the bearing surface  104 . Thus, the force that the hydraulic cylinder  106  applies to urge the first arm  120  towards the bearing surface  104  must first overcome any pre-load that the biasing mechanism  180  applies to the first arm  120 . 
     Embodiments of the biasing mechanism  180  include various types of springs, hydraulic cylinders and other biasing mechanisms. In some embodiments, the biasing mechanism  180  includes or displays a substantially linear force-displacement relationship, i.e., one that generally follows Hooke&#39;s law. As illustrated, an embodiment of the biasing mechanism  180  includes at least one spring  182 . A plurality of springs  182  are illustrated in  FIG. 5 . 
     In addition, the biasing mechanism  180  includes at least one rod  184  that extends through at least one of the holes  131 ,  152 , and  160  through the end plate  128 , outer plate  146 , and inner plate  154 , respectively. Illustrated in  FIG. 5  are a plurality of rods  184 . The rod  184  is coupled to at least the end plate  128 , and to at least one of the outer plate  146  and the inner plate  154 . As illustrated, the rod  184  is threaded rod, and a threaded nut  186  couples the rod  184  to the end plate  128 . Similarly, a threaded nut  188  couples the rod  184  to the inner plate  154 . Of course, other mechanisms to couple the rod  184  to the end plate  128  and the inner plate  154  can be used. 
     The spring  182  is illustrated disposed around at least a part of the rod  184 . In this embodiment, the spring  182  is positioned between the threaded nut  188  and a spacer  190 , which itself is positioned between the spring  182  and the second side  158  of the inner plate  154 . The threaded nut  188  in this embodiment at least partly compresses the spring  182  against the second side  158  of the inner plate  154 , which provides the pre-load discussed above. Of course, the spring  184  may be positioned differently around the rod  184  relative to the end plate  128 , outer plate  146 , and inner plate  154 . 
     In addition to the embodiments of a crane  10  and mast-raising mechanism  100  discussed above, methods of raising a mast on a crane are also disclosed. On a crane  10  that includes a mast  34  and a mast-raising mechanism  100 , the method includes extending the hydraulic cylinder  106  to open a gap between the second end  124  of the first arm  120  and the first end  142  of the second arm  140 ; urging the first end  122  of the first arm  120  against the bearing surface  104  to raise the mast  34  to a stable upright position; retracting the hydraulic cylinder  106  at least partly under the influence of the biasing mechanism  180  urging the first arm  120  towards the second arm  140 ; and, closing the gap between the second end  128  of the first arm  120  and the first end  142  of the second arm  140 . Further, the method includes at least partly stowing the hydraulic cylinder  106 , the first arm  120 , and the second arm  140  in the rotating bed  14 . 
     It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.