Lifting crane with movable counterweight

Abstract

To provide an improved counterweight device for a mobile lift crane. The lifting cleaner 410 includes a counterweight support frame 432 included in a rotating bed 420, a counterweight unit 435 including a trolley 470 supported on the counterweight support frame in a manner that allows it to move relative to the rotating bed, and a counterweight unit movement device that moves the counterweight unit toward and away from the boom 422. The counterweight unit movement device includes at least one motor that drives a gear 474 connected to the trolley, such that when the motor rotates the gear, the gear engages with a set of teeth 436 on the counterweight support frame, moving the trolley relative to the rotating bed. The counterweight unit 435 is movable to a position where the center of gravity of the counterweight unit 435 is forward of the rear tipping fulcrum.

Description

Technical Field

[0001] The present application relates to a lifting crane, and more particularly to a mobile lifting crane having a counterweight that can be moved to various positions in order to balance the coupling moment between the boom and the load on the crane.

Background Art

[0002] Lifting cranes typically include a counterweight to assist in balancing the crane when the crane lowers the boom and / or lifts the load. A counterweight may also be provided on the car body to prevent the counterweight provided at the rear of the crane from tipping backward when the load is not being lifted. Additionally, a supplemental counterweight attachment, such as a counterweight trailer, may be added to further enhance the lifting capacity of the mobile lifting crane. Since the load often generates various moments by approaching or moving away from the center of rotation of the crane during the gripping, moving, and installation operations of the crane, it is advantageous for the counterweight, including the supplemental counterweight attachment, to also be moved back and forth with respect to the center of rotation of the crane. In this way, less counterweight can be used than would be required if the counterweight had to be maintained at a fixed distance.

[0003] The above typical example is the Terex Demag CC8800 crane equipped with a superlift attachment. This crane has a total counterweight of 1020 metric tons, consisting of a 100-metric-ton carbody counterweight, a 280-metric-ton superstructure counterweight, and a 640-metric-ton auxiliary counterweight attachment. The auxiliary counterweight can be moved closer or farther away by telescoping members. All of this counterweight enables lifting heavy loads, but must be transported as soon as it is disassembled for the crane to move to a new job site. Within the US over-the-road transport limits, 15 trucks are required to transport a 300-metric-ton counterweight.

[0004] Since the crane needs to be mobile, any auxiliary counterweight attachment also needs to be mobile. However, it is common practice to support these auxiliary counterweights on the ground away from the main crane when there is no load on the hook, otherwise the auxiliary counterweight will generate a moment and the crane will tip backwards. Therefore, if the crane needs to move with no load on the hook, the auxiliary counterweight attachment must also be able to move on the ground. This means that the ground must be prepared and cleaned, and frame members must be placed in a fixed position for the rotation or movement of the auxiliary counterweight unit. Therefore, it is advantageous for the crane design to have a movable counterweight that does not need to be supported by the ground except by the crane's crawlers.

[0005] U.S. Patent No. 7,546,928 discloses several embodiments of a mobile lifting crane having a position-variable counterweight that exhibits high capacity with a relatively small amount of counterweight, and in which the movable counterweight does not need to be supported by the ground. These embodiments provide a great improvement over high-capacity crane designs, and at the same time, there are low-capacity cranes that desire to increase the capacity of the crane without increasing the total amount of the crane's counterweight, especially when the counterweight does not need to be supported by the ground during crane operation. Further, the crane in the '928 patent has a fixed lattice mast structure, and the counterweight is suspended from this mast structure by a tension member. There may be cases where it is advantageous for a mobile lifting crane not to have a fixed mast structure. This is because a lattice mast structure requires additional members to be transported to the work site and a tall fixed mast may be an obstacle that requires a vehicle height limit when the crane is being relocated.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 1

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Therefore, it is necessary to further improve the counterweight device of the mobile lifting crane.

Means for Solving the Problems

[0008] A mobile lifting crane for relatively low-capacity cranes and its operating method are invented, which uses a smaller total counterweight amount compared to other cranes of the same capacity but can still lift loads comparable to those of cranes that are still mobile and use a much larger total counterweight amount. In a first aspect, the present invention relates to a lifting crane. The lifting crane includes a car body, a movable ground engaging member attached to the car body to enable the crane to move on the ground, a rotating floor coupled to the car body so as to be rotatable about a rotation axis and having a counterweight support frame, a boom pivotally attached about a fixed boom hinge point at the front portion of the rotating floor and having a load lifting wire rope for handling loads, a boom hoisting device coupled to the rotating floor and the boom to be able to change the angle of the boom with respect to the rotation plane of the rotating floor, a counterweight unit supported on the counterweight support frame in a movable state with respect to the counterweight support frame, and a counterweight unit moving device coupled between the rotating floor and the counterweight unit to be able to move the counterweight unit closer to or farther from the boom. The crane is structured such that when the counterweight unit is moved to correct changes in the coupling moment between the boom and the load during the operation of the crane, the moment generated by the counterweight unit acts mainly on the rotating floor via the counterweight support frame.

[0009] In a second aspect, the present invention relates to a lifting crane. The crane includes a car body, a ground engaging member for lifting the car body from the ground, a rotating floor coupled to the car body so as to be rotatable about a rotation axis and having a fixed rear portion, a boom pivotally attached to the front portion of the rotating floor and having a load lifting wire rope for handling a load, a mast coupled to the rotating floor, and a length adjustable boom hoisting rigging coupled between the mast and the boom so as to be able to change the angle of the boom with respect to the rotation plane of the rotating floor, a counterweight support beam movably coupled to the rotating floor, a counterweight support beam moving device coupled between the counterweight support beam and the rotating floor so as to be able to move the counterweight support beam away from the rotational coupling portion between the rotating floor and the car body in the longitudinal direction of the rotating floor and extending rearward of the fixed rear portion of the rotating floor, a tension member coupled between the mast and the counterweight support beam, a counterweight unit supported on the counterweight support beam in a movable manner with respect to the counterweight support beam, and a counterweight unit moving device coupled between the counterweight support beam and the counterweight unit so as to be able to move the counterweight unit closer to or farther away from the boom, and the counterweight unit is configured to be movable to and held at a position in front of the top of the mast or movable to and held at a position behind the top of the mast.

[0010] The third aspect of the present invention relates to a crane. The crane, when in an assembled state, comprises a car body having a movable ground engaging member, a rotating floor rotatably coupled to the car body so as to be able to pivot about a rotation axis with respect to the ground engaging member, and a boom pivotally attached to a front portion of the rotating floor and from which a lifting wire rope extends, and is shaped to be assembled by two different counterweight assembly structure options i) and ii). In the first counterweight assembly structure option i), a first counterweight moving device moves a first counterweight unit between a first position and a second position, the first position being a position where the first counterweight unit approaches the rotation axis as close as possible for the first counterweight assembly structure option and forms a first distance from the rotation axis, and the second position being a position where the first counterweight unit moves as far away from the rotation axis as possible for the first counterweight assembly structure option and forms a second distance from the rotation axis. In the second counterweight assembly structure option ii), a second counterweight moving device moves a second counterweight unit between a third position and a fourth position, the third position being a position where the second counterweight unit approaches the rotation axis as close as possible for the second counterweight assembly structure option and forms a third distance from the rotation axis, and the fourth position being a position where the second counterweight unit moves as far away from the rotation axis as possible in the second counterweight assembly structure option and forms a fourth distance from the rotation axis, and further, the fourth distance is longer than the second distance, and the difference between the third distance and the fourth distance is larger than the difference between the first distance and the second distance.

[0011] The fourth aspect of the present invention relates to a lifting crane. The lifting crane includes a car body, a ground engaging member for lifting the car body from the ground, a turntable rotatably coupled to the car body, a counterweight support beam nested in the turntable and configured such that a rear portion of the counterweight support beam can extend away from a rotational coupling portion between the turntable and the car body, a boom pivotally attached to a front portion of the turntable and equipped with a load lifting wire rope for handling loads, a mast coupled to the turntable, with a boom hoisting rig having an adjustable length coupled between the mast and the boom and configured to change the angle of the boom relative to the rotational plane of the turntable, a tension member coupled between the mast and the counterweight support beam, a counterweight unit supported on the counterweight support beam in a movable manner relative to the counterweight support beam, and a counterweight moving device configured to move the counterweight unit towards a position in front of the top of the mast towards the boom or away from the boom to a position behind the top of the mast, and the counterweight moving device is configured to move the counterweight unit relative to the rear of the counterweight support beam and move the rear portion of the counterweight support beam relative to the turntable.

[0012] In a fifth aspect, the present invention relates to a lifting crane. The lifting crane includes a car body to which a movable ground engaging member enabling the crane to move on the ground is attached, a rotating floor coupled to the car body so as to be rotatable about a rotation axis and configured to be able to swing with respect to the movable ground engaging member, a boom pivotally attached to a front portion of the rotating floor and provided with a load lifting wire rope for handling a load, a mast having a first end pivotally attached to the rotating floor, and a boom hoisting device including a pendant coupled between the mast and the boom, wherein the boom and the mast are interconnected by a rigging of a fixed length between the boom and the mast, and the boom hoisting device is attached between the mast and the rotating floor and is configured to be able to change the angle of the boom with respect to the rotation plane of the rotating floor, a movable counterweight unit supported on the rotating floor, and a counterweight moving device coupled between the rotating floor and the counterweight unit and configured to be able to move the counterweight unit closer to or farther from the boom.

[0013] In a sixth aspect, the present invention relates to a mobile lifting crane. The lifting crane includes a car body provided with a movable ground engaging member, a rotating floor rotatably coupled to the car body about a rotation axis and configured such that the rotating floor can swing with respect to the movable ground engaging member, a boom pivotally attached to a front portion of the rotating floor, and an upper structure counterweight unit that rotates with the rotating floor and is never supported by the ground except being indirectly supported by the movable ground engaging member of the car body during the grasping, moving, and installation operations of the crane, and i) the ratio of the weight of the upper structure counterweight unit to ii) the total weight of the crane with a basic boom length is greater than 52%.

[0014] In a seventh aspect, the present invention relates to a method of operating a mobile lifting crane. The mobile lifting crane includes a car body having a movable ground engaging member, a rotating floor rotatably coupled to the car body and configured to swivel relative to the movable ground engaging member, a boom pivotally attached to a front portion of the rotating floor and from which a lifting wire rope extends, a movable counterweight support beam, and a movable counterweight unit supported on the movable counterweight support beam. The method includes steps of grasping, moving, and installing a load. The movable counterweight unit is assisted to balance the coupling moment between the boom and the load by approaching or moving away from the front portion of the rotating floor during the grasping, moving, and installing operations. The counterweight remains on the counterweight support beam during the grasping, moving, and installing operations, and both the counterweight support beam and the counterweight unit move to balance the crane when the coupling moment between the boom and the load changes.

[0015] In an eighth aspect, the present invention relates to a method of increasing the capacity of a crane. The method comprises: a) providing a crane having a lifting crane with a first capacity, the crane including a car body to which a movable ground-engaging member enabling movement on the ground is attached, a rotating floor rotatably coupled to the car body about a rotational axis and configured to slew relative to the movable ground-engaging member, a boom pivotally attached to a front portion of the rotating floor and provided with a load-lifting wire rope for handling loads, and a movable counterweight unit supported on the rotating floor and including a number of counterweights stacked on one another and movable from a first position to a second position farther from the boom than the first position; b) removing at least some of the counterweights from the crane; c) attaching a counterweight support beam to the rotating floor and adding it to the crane; and d) returning at least some of the counterweights removed in step b) to the crane to provide a crane having a second capacity greater than the first capacity, such that the returned counterweights are supported on the counterweight support beam and are movable to a third position farther from the boom than the second position.

[0016] In the hoisting crane of the present invention, the counterweight can be arranged far forward so that an extremely small rearward moment is generated on the crane when there is no load on the hook. As a result, the car body does not need to have a spare counterweight attached. This large counterweight can be positioned far rearward so as to balance heavy loads. On the other hand, in one embodiment of the present invention, the load is lifted without the need for a lattice mast from which the counterweight is suspended. Rather, in some embodiments, the rotating floor is provided with a counterweight support frame on which the counterweight can move rearward. In some embodiments, it is interesting that the basic model crane can also be provided with a lattice mast and a movable counterweight support beam, and is designed to further enhance the capacity of the crane. Similar to the large-capacity crane of U.S. Patent No. 7,546,928, another advantage of the preferred embodiment of the present invention is that the crane does not need to place the counterweight on the ground when installing its load. There is no need for a spare counterweight unit that requires a trailer, and there is no constraint that the ground for such a trailer must be prepared.

[0017] These and other advantages of the present invention, together with the present invention itself, can be more easily understood with reference to the accompanying drawings.

Brief Description of the Drawings

[0018]

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DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be further described below. In the following sections, various aspects of the present invention are defined in more detail. The aspects thus defined can be combined with any other aspect unless clearly indicated to the contrary. In particular, any feature shown as being preferred or advantageous can be combined with any other feature shown as being preferred or advantageous.

[0020] Some of the terms used in this specification and the claims have the meanings defined below.

[0021] The term "rotating bed" refers to the upper structure of the crane (the part that rotates with respect to the car body), but does not include the boom or lattice structure mast. The rotating bed can be made up of a number of plates. For example, for the purposes of the present invention, the adapter plate disclosed in U.S. Patent No. 5,176,267 can be considered part of the rotating bed of the crane in which the adapter plate is used. Further, if the crane is disassembled for transportation between work sites, the rotating bed used here can be transported as two or more parts. Further, if a component such as the counterweight support frame shown in Figure 24 is attached to the remaining part of the rotating bed in such a form that it remains fixed to the remaining part of the rotating bed until it is completely removed, this component can be considered part of the rotating bed.

[0022] The term "mast" refers to a structure attached to the slewing platform or a part of the boom hoisting device. The mast is used to form a higher part above other parts of the slewing platform, and the line of action is formed through this higher part so that the boom hoisting device does not pull up the boom along the line passing through the hinge pin of the boom during the assembly operation. In this regard, a gantry or any other lifting structure on the slewing platform can function as a mast. The mast can be a fixed mast, a derrick mast or a live mast according to the embodiments of the present invention. A live mast has a pendant of a fixed length between the mast and the boom and the angle of the boom can be changed by changing the angle of the mast during the grasping, moving and installing operations of a normal crane. A fixed mast is designed to remain at a fixed angle relative to the slewing platform during the grasping, moving and installing operations of a normal crane. (However, if the balance between the moment of the counterweight and the combined moment of the boom and the load changes and the mast is pulled backward by the counterweight, a little movement may occur within the fixed mast. In this case, mast stops are used to raise the mast, but these mast stops allow a small amount of movement.) Of course, the mast that is fixed during the operation of a normal crane can pivot during the assembly operation of the crane. A derrick mast is equipped with a boom hoisting rigging with adjustable length between the mast and the boom, allows the angle of the boom relative to the rotating surface of the slewing platform to change, but is pivotally connected to the slewing platform and is connected to the rear of the slewing platform in a form where the length can be adjusted. A derrick mast can be used as a fixed mast by keeping the angle of the derrick mast relative to the slewing platform constant during the grasping, moving and installing operations.

[0023] The front part of the rotating bed is defined as the part of the rotating bed that is between the axis of rotation of the rotating bed and the position of the load when the load is being lifted. The rear part of the rotating bed mostly comprises the side opposite to the front part of the rotating bed with respect to the axis of rotation. The terms "front" and "rear" (or variant terms such as "towards the rear") indicating other parts of the rotating bed or things coupled thereto, e.g. the mast, are drawn from the same situation regardless of the actual position of the rotating bed relative to the ground engaging member.

[0024] The most rearward fixed part of the rotating bed is designed not to move relative to the rest of the rotating bed during the gripping, moving and installation operations of a normal crane and is defined as the part of the rotating bed that is furthest from the centre line of rotation between the rotating bed and the carbody.

[0025] The tail swing of a crane is used to represent the distance from the crane's axis of rotation to the farthest part of the slewing platform (or other components that rotate with the slewing platform). The tail swing is defined by the part of the crane that rotates with the slewing platform, is behind the axis of rotation relative to the boom, and forms the widest arc when the crane rotates about a rotatable joint between the carbody and the slewing platform. When the rear corner of the slewing platform is located 25 feet (7.62 meters) from the axis of rotation, the crane is said to have a 25-foot (7.62-meter) tail swing, and there are no obstacles within the tail swing distance when the crane is assembled in its operating state. In many cranes, a fixed counterweight is attached behind the slewing platform and constitutes the farthest part of the slewing platform and defines the tail swing of the crane. On cranes equipped with a movable counterweight, the counterweight that is moved rearward to compensate for a larger load often increases the tail swing of the crane. It must be remembered that the width of the upper rear part of the crane can affect the tail swing. This is because the distance from this part to the axis of rotation is a function of how far rearward this part is on the slewing platform and how far laterally this part is from the centerline of the crane.

[0026] The position of the counterweight unit is defined as the center of gravity of the combination of all counterweight elements and the retaining tray to which the counterweight is attached or otherwise moves with the counterweight. All counterweights on a crane that are interconnected to move simultaneously are treated as a single counterweight unit for determining the center of gravity.

[0027] The term "superstructure counterweight" means a counterweight that is attached to the slewing platform and rotates with the slewing platform during the lifting, moving, and installation operations of the crane. These can be a stack of individual counterweights. Superstructure counterweights can often be removed from the rest of the slewing platform. The term "superstructure counterweight unit" includes the superstructure counterweight and a tray for holding the individual counterweights. When the counterweight is movable, the "superstructure counterweight unit" includes a member that always moves with the counterweight. For example, in the embodiments shown in FIGS. 38 to 60, the superstructure counterweight unit includes a tray 533, individual counterweights stacked on the tray, and a trolley 570 (since it moves with the counterweight). The outer frame member 532 is not part of the superstructure counterweight. This is because the counterweight unit can move independently of the outer frame member 532.

[0028] The term "gross weight of the crane" means the weight of the crane with no load on the hook, but when the crane is assembled for special lifting purposes, it includes the weight of all components of the crane. Thus, the gross weight of a mobile lifting crane includes not only the counterweights included in the crane for lifting, but also the crawlers, car body, car body counterweight, slewing platform, mast provided, all rigging and winch drums, and the weight of all other normal crane components such as all other accessories on the crane that move with the crane when the assembled crane moves on the ground.

[0029] The term "gross weight of the crane with the basic boom length" means the gross weight of the crane when the basic boom defined below is constructed.

[0030] The top of the mast is defined as the most rearward position on the mast, which is the position where the wire or tension member supported by the mast is suspended.

[0031] The coupling moment between the boom and the load is defined as the moment about the center of rotation of the slewing platform generated by the self-weight of the boom, including the load suspension wire rope, hook block, and the load suspended from the boom. When no load is attached to the load suspension wire rope, the coupling moment between the boom and the load is the moment generated by the self-weight of the boom. This moment takes into account the length of the boom, the angle of the boom, and the radius of the load.

[0032] The movable ground-engaging member is defined as a member such as a tire or crawler designed to remain engaged with the ground when the crane moves on the ground, but does not include a ground-engaging member designed to remain stationary with respect to the ground or to be lifted from contact with the ground when the ground-engaging member is moved, such as the ring on a ring-supported crane and the outriggers commonly found on truck-mounted cranes.

[0033] The term "movement" indicating the operation of the crane includes the movement of the crane with respect to the ground. This movement of the crane is either a traveling operation in which the crane traverses a certain distance on the ground on the movable ground-engaging member, a slewing operation in which the slewing platform rotates with respect to the ground, or a combination of the traveling operation and the slewing operation.

[0034] The term "center of gravity of the boom" indicates the central point at which the boom can be balanced. When calculating the center of gravity, all components attached to the boom structure that must be lifted when the boom is first lifted must be considered, such as components like the pulley attached to the boom top for the load suspension wire rope.

[0035] Since the boom can have various cross-sectional shapes, a centerline is designed where the compressive load is preferably distributed, and the term "boom angle" means the angle of the centerline of the boom with respect to the horizontal.

[0036] The term "basic boom length" is the length of the shortest boom structure that the crane manufacturer has specified as acceptable for use in a given crane model.

[0037] The term "horizontal boom angle" indicates that the boom is at a right angle or very nearly at a right angle to the direction of gravity. Similarly, the term "parallel to the ground" has the same meaning. Both of these terms have the meaning that, even taking into account small variations that occur in the normal crane assembly and usage methods, a person skilled in the art still considers it to be horizontal. For example, when the boom is first assembled on the ground before being lifted into the working position, it is considered to be at a horizontal boom angle even if the ground is not exactly horizontal or even if part of the boom is on a block. The boom can be slightly above or slightly below an exactly horizontal position depending on the blocks being used and is still considered to be at a horizontal boom angle and parallel to the ground.

[0038] Stability is mainly related to the state in which the crane can generally remain upright during the lifting operation. The stability against backward tipping of a lifting crane having an upper structure that rotates about a lower structure can be expressed as the ratio of a) the distance between the center of gravity of the entire crane and the axis of rotation to b) the distance between the backward tipping fulcrum (typically, the center of the rearmost roller within the crawler frame of a crawler crane) and the axis of rotation. Thus, if the distance between the center of gravity of the entire crane and the axis of rotation is 3.5 meters and the distance from the axis of rotation to the backward tipping fulcrum is 5 meters, this stability is 0.7. The smaller this ratio, the more stable the crane becomes. Of course, the center of gravity of the crane is a function of the relative magnitudes and relative positions of the centers of gravity of the various components of the crane. Therefore, the boom length and weight and the boom angle, as well as the weight and position of the counterweight unit, can significantly affect the position of the center of gravity of the entire crane and thus the stability of the crane. The stability against backward tipping is most affected at large boom angles with no load on the hook. Lifting the boom reduces the stability of the crane against backward tipping. This is because the center of gravity of the boom moves closer to the axis of rotation, and thus the center of gravity of the entire crane can be shifted far behind the axis of rotation. Thus, the larger the numerator of this ratio, the higher the stability value, which indicates lower stability of the crane.

[0039] When determining the center of gravity of the entire crane, it is often useful to determine the contribution rate to the center of gravity by considering the weight of each individual component of the crane and the distance from the reference point of the center of gravity of that component, and then use the sum of the moments about the said reference point generated by each crane component. The individual values in the sum are determined by multiplying the weight of the component by the distance between the center of gravity of the component and the reference point. For the calculation of stability against backward tipping, it is generally done to use the axis of rotation as the reference point when summing to determine the center of gravity of the entire crane.

[0040] When considering the moment generated by the boom, the total weight of the boom, which is located at the center of gravity of the entire boom, is generally divided into two separate weights, namely the weight in the boom butt called "boom butt weight" and the weight in the boom top called "boom top weight". The total weight of the boom is equal to the sum of the boom top weight and the boom butt weight. These weights are determined by calculating the forces that occur when the boom is simply supported at each end. In this case, it is assumed that the load lifting wire rope reaches the boom top but is not looped through it and that the boom straps are connected. Therefore, if one scale is placed under the boom butt at the point where the boom is connected to the rotating floor (boom hinge point) and another scale is placed under the boom top at the point where the boom top pulleys are connected, the combined weight on the two scales is of course the weight of the boom, and the weights on the individual scales are the boom butt weight and the boom top weight respectively.

[0041] Several embodiments of the present invention are shown in the accompanying drawings. A first basic crane model having a first counterweight assembly form is shown in FIGS. 1 to 6. The same basic crane model can be assembled in the second counterweight assembly form shown in FIGS. 13 to 15. Still another variant of the first basic crane with a third counterweight assembly form is shown in FIG. 16. A second basic crane model having a first counterweight assembly form is shown in FIGS. 24 to 28. The same second basic crane model can be assembled in the second counterweight assembly form shown in FIGS. 23 and 38 to 41. FIGS. 17 to 22 show a third basic crane model assembled in a counterweight assembly form similar to the second counterweight assembly form of other basic crane models.

[0042] (Example 1) In the first embodiment shown in FIGS. 1 to 6, the mobile lifting crane 10 includes a lower structure (which can be best seen in FIGS. 4 and 5), also referred to as the car body 12, a ground engaging member for lifting the car body from the ground, and a turntable 20 rotatably coupled to the car body about a rotational axis. The movable ground engaging member on the crane 10 is in the form of two crawlers 14, only one of which can be seen in the side view of FIG. 1. (FIG. 1 is simplified for clarity and does not show the boom and mast.) The other crawler 14 can be seen in the perspective view of FIG. 4 and the rear view of FIG. 5. In the crane 10, the movable ground engaging member can be a set of a number of crawlers, for example, in a form having two crawlers on each side, or can be other movable ground engaging members such as tires. In the crane 10, the crawlers provide forward and rearward tipping points for the crane. FIG. 1 shows the rear tipping point 16 and the forward tipping point 17 of the crane 10.

[0043] The rotating bed 20 is attached to the car body 12 by a swivel ring so that the rotating bed 20 can rotate about an axis relative to the ground engaging member 14. The rotating bed supports the boom 22 pivotally attached in a fixed position on a first portion of the rotating bed and supports the live mast 28 with its first end attached on the rotating bed, and supports a movable counterweight unit 35 having a counterweight 34 in the form of a counterweight tray 33 on a support member. The counterweight in this embodiment is provided as two stacks of individual counterweight members 34 on the support member 33 as shown in FIGS. 4 and 5. The rotating bed has a fixed rearmost portion, which will be described in detail below. In the crane 10, since the counterweight is movable, it does not constitute the fixed rearmost portion of the rotating bed, and even when the counterweight is moved to the rear position, the outer corner of the counterweight 34 is farthest from the rotation center line, thus defining the tail swing of the crane. However, when the counterweight unit 35 is pulled forward as in FIG. 1, the fixed rearmost portion of the rotating bed defines the tail swing of the crane.

[0044] The boom hoisting device on the crane 10 enables the angle of the boom 22 with respect to the rotating surface of the rotating bed 20 to change. In the crane 10, the boom hoisting device includes rigging coupled between the rotating bed 20, the mast 28, and the boom 22. The boom hoisting device includes a boom hoisting drum and a boom hoisting wire rope, and the boom hoisting wire rope is passed between a set of pulleys on the mast and a set of pulleys on the rotating bed. The mast 28 is pivotally coupled to the rotating bed, and the boom hoisting rigging between the mast and the boom includes only a fixed-length member in the form of two sets of pendants 25 (only one of which can be seen in the side view) coupled between the mast 28 and the top of the boom 22. Further, the boom hoisting rigging has multiple portions of the boom hoisting wire rope 27 between a pulley 23 on the rotating bed and a pulley on the second end of the mast 28. Thus, the boom hoisting drum 21 on the rotating bed can be used to wind up or pay out the boom hoisting wire rope 27 to change the angle of the live mast 28 with respect to the rotating bed, and then to change the angle of the boom 22 with respect to the rotating bed 20. (The pulley 23 and the drum 21 are not shown in FIGS. 4 - 6 for clarity of the drawing.) Alternatively, the mast 28 can be used as a fixed mast during normal crane operation. In this case, the boom hoisting wire rope extends between the equalizer and the top of the mast and can change the angle between the mast and the boom.

[0045] The load lifting wire rope 24 for handling the load extends from the boom 22 and supports the hook 26. The rotating floor 20 may also include other elements commonly found on mobile lifting cranes such as the operator's cab and the drum 29 for the compensating wire rope. The load winding drum 13 for the lifting wire rope 24 is preferably attached to the boom butt as shown in FIG. 2. If desired, an additional lifting drum 19 can be attached to the base of the boom 22 as shown in FIGS. 2 and 3. The boom 22 may include a luffing jib or other boom structure pivotally attached to the top of the main boom.

[0046] The counterweight unit 35 is movable relative to the remainder of the rotating floor 20. In the crane 10, the rotating floor 20 includes a counterweight support frame 32, which is preferably in the form of a welded plate best seen in FIGS. 4 - 6. The counterweight support frame 32 supports the movable counterweight unit 35 in a movable state relative to the counterweight support frame 32. The counterweight support frame 32 has an inclined surface provided by the flange 39, and the counterweight unit 35 moves on this surface. This surface is inclined upward with respect to the rotation surface between the rotating floor and the car body as the counterweight support frame extends rearward. The counterweight tray 33 includes rollers 37, and the rollers 37 are placed on the flange 39 welded to the plate structure of the support frame. The rollers 37 are arranged at the top of the counterweight tray 33 such that the tray 33 is suspended downward from the counterweight support frame 32. In the crane 10, the counterweight support frame constitutes the most rearward fixed part of the rotating floor. Further, the counterweight support frame 32 is supported on the rotating floor 20 in such a form that the moment generated by the counterweight unit 35 acts mainly on the rotating floor 20 and in this case only through the counterweight support frame.

[0047] The counterweight moving device is coupled between the rotating floor 20 and the counterweight unit 35 and can move the counterweight unit 35 closer to or farther away from the boom. The counterweight unit 35 is located in front of the most rear fixed part of the rotating floor, and the tail swing of the crane is defined by the most rear fixed position of the rotating floor (as can be seen in FIGS. 1 and 2), and the counterweight unit can move between the position where the counterweight unit defines the tail swing of the crane (as can be seen in FIGS. 3, 4 and 6). As can be seen in FIG. 1, the counterweight unit 35 can move the center of gravity of the counterweight unit closer to, preferably further forward, the rear tipping point 16 of the crane.

[0048] The counterweight moving device within the crane 10 includes a counterweight unit moving device created by a drive motor 40 and a drum provided behind the counterweight support frame 32. The rear counterweight unit moving device includes two identical assemblies spaced apart, as best seen in FIG. 4, and thus it is preferred that the drive motor 40 drives two drums 42. Each assembly of the counterweight unit moving device further includes a flexible tension member that passes around a driven pulley and an idler pulley 41 (as best seen in FIG. 1). The driven pulley is provided by the drum 42. The flexible tension member can be a wire rope 44 as shown or a chain. Of course, if a chain is used, the driven pulley is a chain drive device. Both ends of each flexible tension member are coupled to the counterweight tray 33, as can be seen in FIG. 6, such that the counterweight unit 35 can be pulled as it approaches or moves away from the boom. This is preferably done with a ring 43 at both ends of the wire rope 44 and a hole in the connector 45 on the counterweight tray 33 with a pin passing through the ring and the connector 45. In this way, in the crane 10, the counterweight moving device is coupled between the counterweight support frame 32 and the counterweight unit 35.

[0049] Figure 1 shows the counterweight unit 35 in its most forward position, while Figure 2 shows the counterweight unit 35 in an intermediate position, and Figures 3 - 6 show the counterweight unit 35 in its most rearward position, for example when a large load is suspended from the hook 26 or the boom 22 is pivoted forward to extend the load further away from the turntable. In each of these positions, the crane is configured such that during crane operation, when the counterweight is moved to correct for changes in the combined moment of the boom and the load, the weight of the counterweight unit 35 is transmitted to the turntable only through the counterweight support frame 32. The phrase "only through the counterweight support frame" is meant to distinguish from prior art cranes where a tension member between the top of the mast and the counterweight provides at least some of the support force for the counterweight. Such a prior art crane has a structure disclosed, for example, in U.S. Patent No. 4,953,722, which includes a pendant 149 for a rear connector that attaches behind the support beam 84 to the mast 54 and thus supports the beam 84 at both ends. In crane 10, all of the balancing force provided by the counterweight unit 35 is transmitted to the remainder of the turntable through the counterweight support frame 32. On the other hand, the boom hoisting rigging transmits a force to tip forward from the boom and the load on the hook to the rear of the turntable.

[0050] In a preferred embodiment of the present invention, the movable counterweight is never supported by the ground during normal operation. The crane can perform load grasping, moving, and installation operations, in which case the movable counterweight is moved closer to or farther from the front part of the slewing platform by the operation of the hydraulic motor 40 and the drum 42 to assist in moving it during crane operation and balancing the load, but the counterweight is never supported by the ground except indirectly by the movable ground engaging members on the car body. Further, the movable counterweight unit 35 is the only functioning counterweight on the crane. The car body is not provided with any separate functioning counterweight. The fact that the counterweight unit can be moved very close to the center of rotation of the crane means that the counterweight does not generate a large moment to fall backward within this structure, and if it did, the car body would be required to carry an additional counterweight. The phrase "not provided with any separate functioning counterweight" means to distinguish from prior art cranes that are specially designed to be equipped with a large amount of counterweight used to prevent the car body from tipping backward. For example, in the standard model 16000 crane by Manitowoc Crane Company, the car body is provided with a 120,000-pound (54.43-ton) counterweight, and the slewing platform is provided with a 332,000-pound (150.6-ton) superstructure counterweight. In the crane of the present invention, a total of 452,000 pounds (205.0 tons) of counterweight can be used in the movable counterweight unit, but no functioning counterweight is added to the car body.

[0051] The positioning of the counterweight can be manually controlled, or the crane 10 can further include a sensor (not shown) that senses a condition associated with the need to move the counterweight. In the simplest form, the counterweight may be moved in response to a change in the boom angle. In a more advanced method, the combined moment of the boom and load can be used to control the movement of the counterweight, such that the movement of the counterweight is caused by a change in the boom angle or the picking up of a load. If desired, this can be done automatically when a computer processor is connected to the sensor. In this case, a computer processor that controls the counterweight moving device and perhaps other operations of the crane receives a signal from a sensor indicating a condition (such as the boom angle) or some other function indicating a condition (such as the combined moment of the boom and load, i.e., the tension in the boom hoisting rigging indicating the moment of the boom and load about the hinge point of the boom), and controls the position of the counterweight unit. The position of the counterweight can be detected by maintaining the rotational path of the drum 42 or by using a cable and reel structure (not shown). A crane using such a device preferably includes a computer-readable storage medium that is operable to incorporate program code to be performed by a computer processor to control the position of the counterweight unit.

[0052] (Example 2) Figures 13 to 15 show a second embodiment of the crane 10 of the present invention. This embodiment includes a fixed position mast 117 in addition to the live mast 128. The fixed position mast has some disadvantages compared to the crane 10 because the fixed mast structure may require additional components to be supplied to the work site and may require vehicle height restrictions when the crane is repositioned. However, by adding the fixed mast 117, the crane 110 can be provided with other features that enhance the lifting capacity of the crane. Similar to the crane 10, in the crane 110, the car body is not provided with any separate effective counterweights, and the movable counterweight unit is not supported by the ground except being indirectly supported by the movable ground engaging members on the car body during the grasping, moving and installation operations of the crane.

[0053] Crane 110 is made of the same basic crane structure as crane 10, but not only is an additional counterweight support beam 160 added, but also a fixed mast 117 is added. A derrick mast can also be used instead of the fixed mast. The counterweight support beam 160 is shown in FIGS. 7 - 12. The counterweight support beam 160 is movably coupled to the rotating floor 120. Crane 110 has the same structure as the counterweight support beam moving device, and utilizes the structure of moving the counterweight unit 35 on crane 10 as described below. Therefore, in this embodiment, the counterweight moving device includes a counterweight unit moving device and a counterweight support beam moving device. This counterweight support beam moving device is coupled between the counterweight support beam 160 and the rotating floor 120, and is configured such that the counterweight support beam can be moved away from the rotational coupling portion of the rotating floor and the car body with respect to the length of the rotating floor and can extend rearward from the fixed rearmost portion of the rotating floor. As will be described in more detail below, the movement of the counterweight support beam 160 is generally in the horizontal direction and in a direction straight with the length of the counterweight support beam. Crane 110 further includes a tension member 131 coupled between the fixed mast 117 and the counterweight support beam 160. The counterweight unit 135 is supported in a movable form with respect to the counterweight support beam on the counterweight support beam 160. The counterweight unit moving device is coupled between the counterweight support beam 160 and the counterweight unit 135, and can move the counterweight unit closer to or farther away from the boom 122. The counterweight unit 135 can be moved to and held at a position in front of the tip of the fixed mast 117, or can be moved to and held at a position behind the tip of the fixed mast 117.

[0054] Crane 110 is provided with a live mast 128 that is much the same as the live mast 28 on crane 10. However, after the live mast 128 is used to erect the fixed mast 117, it is then made so that its position cannot be changed. To change the boom angle on crane 110, the boom hoist wire rope 115 moves upward from a boom hoist drum 118 attached to the base of mast 117 and is looped between an equalizer 129 and a pulley at the top of the fixed mast 117 to form multiple wire rope portions. The equalizer 129 is coupled to the boom 122 by a pendant 126 of fixed length. The pendant 125 of fixed length couples the top of the fixed mast 117 to the top of the mast 128. The rigging 127 couples the top of the mast 128 through a set of pulleys 123 to the turntable 120 and to a drum 121, just as the boom hoist rigging 27, pulley 23 and drum 21 on crane 10 do. Crane 110 also, although not shown, is provided with a load hoist wire rope and hook block much the same as those used on crane 10.

[0055] The counterweight support beam 160 preferably has a U - shaped configuration made by two spaced - apart side members 162 whose rear portions are interconnected by a cross - beam member 164, as best seen in FIG. 12. The front ends of the two side members 162 are coupled to a counterweight tray 133, which is mounted on a counterweight support frame 132 on the turntable 120 and can be moved using a drive motor and drum provided at the rear of the turntable. This is the same way the counterweight tray 33 is movably mounted on the turntable 20 on crane 10. The counterweight support beam 160 is further provided with a counterweight unit moving device coupled between the counterweight support beam 160 and the counterweight unit 135. Thus, the counterweight unit 135 can move together with and move relative to the counterweight support beam 160.

[0056] The tension member 131 is preferably in the form of two sets of joined flat straps (only one can be seen in side view) attached adjacent to the top of the fixed mast 117 and supports the rear portion of the counterweight support beam 160 in a suspended form. Since the length of the tension member is fixed, when the counterweight support beam 160 is moved rearward, the rear portion of the counterweight support beam will move in an arcuate manner with the position where the tension member 131 is joined to the top of the fixed mast 117 as the center of the arc. Thus, the rear portion of the counterweight support beam will lift slightly when moving rearward. To keep the counterweight support beam 160 as close to horizontal as possible, the surface on the counterweight support frame 132 on the rotating floor 120, on which the counterweight tray 133 moves rearward, has an inclined surface (flange 139 best seen in FIG. 11). This inclined surface is inclined upward with respect to the rotating surface between the rotating floor and the car body such that just as the flange 39 provides an inclined surface on the crane 10, when the counterweight support beam is moved rearward. The path can be machined to conform to the arcuate shape along which the rear portion of the counterweight support beam moves, but more particularly, a simple straight inclined path is used that provides the same height increase that the counterweight support beam 160 experiences when its rear portion is moved to its most rearward position. Thus, the movement of the counterweight support beam 160 is in a substantially horizontal direction and in line with the length of the counterweight support beam. As best seen in FIGS. 7 and 10, the rollers 137 are mounted on the counterweight tray 133 such that the rear roller 137 is at a higher position than the front roller 137 (FIG. 7). In this way, the counterweight tray 133 remains horizontal itself while the rollers 137 are placed on the inclined surface. The support legs 182 are provided as a safety mechanism and can provide support for the counterweight unit in case the load is suddenly removed.However, when the counterweight support beam 160 is positioned at its most forward location (FIG. 13), and thus when the support leg 182 is at its closest position to the ground within the arc formed by pivoting the tension member 131 about the top of the mast 117, the support leg 182 is still at an appropriate distance from the ground (e.g., 15 inches (38.1 centimeters)) and is sized such that it never contacts the ground during normal crane operations, i.e., during pick-up, movement, and placement operations.

[0057] The same structure that moves the counterweight tray 33 within crane 10 is used to move the counterweight tray 133 within crane 110. However, since the counterweight support beam 160 is coupled to the counterweight tray, the counterweight support beam 160 moves with the counterweight tray 133. Thus, the counterweight support beam 160 can be moved to and fixed at infinitely variable positions relative to the rotating floor, meaning that it can be moved to a small movement amount, a large movement amount (less than the maximum movement amount of the counterweight tray 133 on the counterweight support frame 132 on the rotating floor), or any position in between. This is different from other extendable counterweight support surfaces, such as the counterweight support beam 84 in U.S. Patent No. 4,953,722. The counterweight support surface in that U.S. Patent can only be extended to and fixed at two different working positions.

[0058] Figure 9 shows the connection part of the counterweight support beam 160 to the counterweight tray 133. In this embodiment, the individual counterweights 134 are not arranged on the counterweight tray. The lug 179 welded to the side member 162 is connected to the connection part 145 on the counterweight tray 133. Similar to the crane 10 exactly, the wire rope 144 is used to move the counterweight tray 133, and the rings provided at both ends of the wire rope 144 and the holes of the connector 145 on the counterweight tray 133 are pinned together by passing a pin through these rings and the connector 145. At the same position, the pin holds each lug 179 to the connector 145. When the motor rotates the drum on the end of the counterweight support frame 132 on the rotating floor 120, the wire rope 144 is moved back and forth just like when the wire rope 44 moves on the crane 10. The wire rope 144 pulls the connector 145 on the counterweight tray. At the same time, the counterweight support beam 160 is moved by the connection part between the lug 179 and the connector 145.

[0059] Each part of the counterweight 134 is stacked on the counterweight support beam 160 in a movable form, for example, on a sliding wear pad (not shown). When they are in a far forward position, each part of the counterweight is just above the counterweight tray, and the counterweight support beam is attached to the counterweight tray. In this position, just like the counterweight 35, the counterweight unit 135 can move to a position in front of the most rearward position of the fixed rotating floor. Further, since the counterweight support beam 160 can move backward and the counterweight unit 135 can move backward on the counterweight support beam 160, the counterweight unit 135 may be moved to and held at a first position in front of the top of the fixed mast or moved to and held at a second position behind the top of the fixed mast 117.

[0060] In this embodiment, the counterweight unit comprises two stacks of counterweights that are moved simultaneously. These stacks each include a counterweight 134 that is identical to the counterweight 34 used in the crane 10 and several additional counterweights 136 (Figs. 10 and 11). These stacks are each placed on a counterweight base plate 163. The counterweight base plate further comprises sliding pads (not shown), which enable the base plate of the counterweight to move on the surface of the side member 162. These rollers can be used instead of the sliding pads. A pair of flexible tension members 173 can each be a chain or wire rope as shown, but these are passed around a driven pulley in the form of a chain drive 176 and an idler pulley 172 (best seen in Figs. 7 and 12). The chain drive 176 is attached to a shaft 178, which is rotated by a gearbox and motor (not shown). Each of the base plates 163 of the counterweights is attached via a connector 189 to a flexible tension member 173 such that the stack of counterweights is pulled towards or away from the front of the counterweight support beam and thus towards or away from the boom 122. (The counterweight base plate 163 is not shown in Fig. 12 for clarity of the figure.)

[0061] Thus, the crane 110 includes a movable counterweight support beam 160 and a movable counterweight unit 135 supported on the counterweight support beam, and the counterweight unit can move independently on the counterweight support beam. The boom angle can be changed, and the crane can perform load grasping, moving, and installation operations. The movable counterweight unit is moved to approach or move away from the front portion of the slewing platform during the change of the boom angle or during the crane's grasping, moving, and installation operations to assist in balancing the combined moment of the boom and the load. First, the counterweight unit 135 moves rearward of the crane while the counterweight support beam remains in its forward position. If further balancing is required, the counterweight unit 135 can remain on the counterweight support beam 160 while the combined moment of the boom and the load is changing, and the counterweight support beam and the counterweight unit can move together to balance the crane when the boom angle is lowered or the load is grasped. Similar to the crane 10, in a preferred embodiment, the counterweight unit 135 can move forward of the fixed rear portion of the slewing platform 120.

[0062] Since a basic crane 10 can be used to manufacture the crane 10, one aspect of the present invention is a crane having a structure assembled by two different counterweight assembly structure options. The first counterweight assembly structure option (crane 10) includes a first counterweight moving device that can move the first counterweight unit 35 between a first position (FIG. 1) and a second position (FIG. 3). In the crane 10, the counterweight assembly structure is the counterweight unit 35 directly supported on the counterweight support frame 32, and the counterweight unit moving device is coupled to move the counterweight unit relative to the counterweight support frame. Regarding the first counterweight assembly structure option, the first position is a position where the first counterweight unit is as close as possible to the axis of rotation. This position forms a first distance from the axis of rotation. Regarding the first counterweight assembly structure option, the second position is a position where the first counterweight unit is as far as possible from the axis of rotation. This distance forms a second distance from the axis of rotation.

[0063] The second counterweight assembly structure option (crane 110) includes a second counterweight moving device, which can move the second counterweight unit 135 between a third position (FIG. 13) and a fourth position (FIG. 15). In crane 110, the counterweight assembly structure includes a counterweight support beam 160 movably coupled to the counterweight support frame 132, and a counterweight unit 135 supported on the counterweight support beam. The counterweight support beam moving device is coupled to move the counterweight support beam relative to the counterweight support frame. Regarding the second counterweight assembly structure option, the third position is a position where the second counterweight unit is as close as possible to the axis of rotation. This position forms a third distance from the axis of rotation. In the second counterweight assembly structure option, the fourth position is a position where the second counterweight unit is as far as possible from the axis of rotation, and this position forms a fourth distance from the axis of rotation.

[0064] As is apparent from the drawings, in cranes 10 and 110, the fourth distance is greater than the second distance, and the difference between the third distance and the fourth distance is greater than the difference between the first distance and the second distance. The difference between the third distance and the fourth distance is preferably at least 1.5 times the difference between the first distance and the second distance, more preferably at least 2 times the difference between the first distance and the second distance, and even more preferably at least 2.5 times the difference between the first distance and the second distance. In a preferred embodiment of the present invention, the difference between the third distance and the fourth distance is at least 3 times the difference between the first distance and the second distance.

[0065] In a preferred embodiment, the crane 10 includes a counterweight tray 33 movably supported on a counterweight support frame 32. In a first option, the counterweight 34 is directly stacked on the counterweight tray 33. In a second option, a counterweight support beam 160 is attached to the counterweight tray 133, and the counterweight 134 is stacked on the counterweight support beam 160. The second counterweight unit typically includes more counterweight boxes than the first counterweight unit. However, although not shown in the illustrated embodiment, the first and second counterweight units can have the same structure.

[0066] (Embodiment 3) FIG. 16 shows a third embodiment of a crane in which all features except one are exactly similar to the crane 110. Therefore, the reference numerals used for each part of the crane 210 in FIG. 16 are the same as those of the parts of the crane 110 with 100 added. For example, the boom 222 on the crane 210 is exactly similar to the boom 122 on the crane 110. Similarly, the boom hoisting wire rope 215, the fixed mast 217, the boom hoisting drum 218, the slewing platform 220, the drum 221, the pulley set 223, the fixed-length pendant 225, the fixed-length pendant 226, the mast 228, the equalizer 229, the tension member 231, and the counterweight unit 235 are exactly the same as their respective components within the crane 110. One difference is that the crane 210 includes an additional counterweight unit 237, and the additional counterweight unit is attached to the rear of the counterweight support beam 260. The additional counterweight unit 237 is used to further increase the lifting capacity of the basic crane 10. This additional counterweight unit moves closer to and farther away from the counterweight support beam 260.

[0067] FIG. 16A shows details of how the auxiliary counterweight is attached to the counterweight support beam 260. The auxiliary counterweight 237 includes a counterweight tray 252, and the counterweight tray 252 is provided with a side panel 254 having a hook element 256. The counterweight support beam 260 is provided with an extension 266 on the rear side of a cross beam member 264 that engages with the side panel 254. A pin 268 within each extension 266 enables the hook member 256 to be coupled to the pin 268 from above by rotational engagement. Each side panel 254 is provided with a bearing surface 258, and the cross beam member 264 is provided with a bearing surface 269, and the bearing surface 269 abuts against the bearing surface 258 to limit rotation when the hook element 256 is engaged with the pin 268, and in this way, the tray 252 is held in the coupled horizontal position.

[0068] (Example 4) Figures 17 to 22 show a fourth embodiment of the crane 310 of the present invention. Similar to the crane 110, the crane 310 includes a car body 312, crawlers 314, a rotating platform 320, a boom 322, a boom hoisting tackle 325, a fixed mast 317, a live mast 328, and a counterweight support beam 360. The counterweight support beam 360 is movably coupled to the rotating platform and can extend the rear portion of the counterweight support beam 360 away from the rotational coupling portion between the rotating platform and the car body. The counterweight unit 335 is supported on the counterweight support beam 360 in a movable form with respect to the counterweight support beam. The tension member 331 is configured to be coupled between the fixed mast and the counterweight support beam 360. The main difference of the crane 310 from the crane 110 is that the counterweight support beam 360 has a telescoping mechanism, and its front portion remains coupled to the rotating platform 320 at all times at the same position. Further, when the telescoping rear portion of the counterweight support beam moves rearward with respect to the rotating platform 320, the counterweight moving device simultaneously moves the counterweight unit 335 rearward with respect to the counterweight support beam 360. In this way, a single drive device moves the counterweight support beam (functioning as a counterweight support beam moving device) with respect to the rotating platform and moves the counterweight unit (functioning as a counterweight unit moving device) with respect to the counterweight support beam.

[0069] As can be best seen in FIG. 20, the counterweight support beam 360 is preferably in a U-shape formed by two spaced-apart side members 362 whose rear portions are interconnected by a cross beam member 364. The front end portions of the two side members 362 are coupled to the rotating platform 320. Each side member 362 is formed by two parts that fit into each other in a telescoping form. FIG. 17 shows these two parts in the retracted position, while FIGS. 18 to 21 show these two parts in the extended position.

[0070] FIG. 19 shows the counterweight support beam 360 itself with the counterweight unit 335 placed thereon, and FIG. 20 shows the counterweight support beam 360 in a state where it is coupled to the slewing platform 320 of the crane 310 but other parts of the crane 310 are removed for clarity and also shows the counterweight support beam moving device. The counterweight support beam moving device includes a telescopic cylinder 355 attached between the slewing platform 320 and the counterweight support beam 360, and a plurality of flexible tension members in the form of a wire rope 373 passing around pulleys 371 and 372. The tension members are coupled to the counterweight unit 335 at the coupling portion 376 and to the counterweight support beam 360 at the coupling portion 378. The counterweight unit 335 can be pulled toward the boom when the telescopic cylinder 355 is shortened to pull the rear portion 364 of the counterweight support beam toward the boom. When this occurs, the pulley 372 on the counterweight support beam 360 must also move forward. Since the wire rope 373 is coupled to both the coupling portions 376 and 378, to move the pulley 372 forward, the wire rope must move in the clockwise direction (as can be seen in the side view of FIG. 21), thereby moving the coupling portion 376 forward, and then, in addition to the movement of the portion of the counterweight support beam itself, the counterweight unit 335 is pulled forward on the counterweight support beam. On the other hand, when the cylinder 355 is extended, the pulley 371 is pushed rearward as the telescopic cylinder is extended and pushes the rear portion of the counterweight support beam away from the boom. As a result, the wire rope 373 is moved in the counterclockwise direction to pull the coupling portion 376 and the counterweight 335 rearward.

[0071] As can be seen in FIG. 17, the rotating bed 320 has a fixed rear portion, and the counterweight unit 335 can move to a position in front of the fixed rear portion of the rotating bed. The counterweight unit 335 can be moved to and held at a position in front of the top of the fixed mast (FIG. 17) or moved to and held at a position behind the top of the fixed mast (FIG. 18) during the grasping, moving, and installation operations of the crane. During this operation, the movable counterweight unit 335 is never supported by the ground except being indirectly supported by the movable ground engaging member 314 on the car body 312. The support leg 382 is provided as a safety mechanism and can provide support for the counterweight unit when the load suddenly disengages. However, the support leg is dimensioned such that when the rear portion 364 of the counterweight support beam 360 is disposed directly below the top of the mast 317 (FIG. 17), and thus when the support leg 382 is at the position closest to the ground within the arc generated by pivoting the tension member 331 about the top of the mast 317, the support leg 382 is still at an appropriate distance from the ground and never contacts the ground during normal crane operations, during the grasping, moving, and installation operations.

[0072] (Examples 5 and 6) FIGS. 23 to 60 show details of another embodiment of a crane that can be assembled with two different counterweight assembly configurations. FIGS. 24 to 28 show a crane 410 with a movable counterweight supported on a counterweight support frame. FIGS. 23 and 38 to 41 show the same crane with a mast and a movable counterweight support beam. In this configuration, the crane is referred to as crane 510.

[0073] Similar to the crane 10, the crane 410 includes a carbon body 412, a movable ground engaging member 414 attached to the carbon body that enables the crane 410 to move on the ground, a rotating floor 420 coupled to the carbon body so as to be rotatable about a rotation axis, a boom 422 attached so as to be pivotable about a fixed boom hinge point at the front portion of the rotating floor, a live mast 428 and a boom hoisting rigging 427, and a boom hoisting device provided between a pulley installed on the rotating floor and the boom and coupled so that the angle of the boom with respect to the rotating surface of the rotating floor can be changed. Similar to the crane 10, the boom hoisting device includes a boom hoisting drum and a boom hoisting wire rope wound between a pulley installed on the mast and a pulley installed on the rotating floor. In this embodiment, the rotating floor includes a counterweight support frame 432 removably attached to the remaining portion of the rotating floor 420, as will be described in more detail below. The counterweight unit 435 is supported on the counterweight support frame 432 in a movable state with respect to the frame 432. A counterweight unit moving device, which will also be described in more detail below, is coupled between the rotating floor and the counterweight unit 435 and can move the counterweight unit 435 closer to or farther away from the boom 422. In this structure, similar to the crane 10, during the operation of the crane, when the counterweight unit is moved to correct the change in the coupling moment between the boom and the load, the moment generated by the counterweight unit 435 mainly acts on the rotating floor, but in this case, it acts through the counterweight support frame only.

[0074] The counterweight support frame 432 in this embodiment is disposed below the remainder of the rotating table. The counterweight support frame is made of a welded plate structure, as best seen in FIGS. 29 - 34. This counterweight support frame is removably attached to the remainder of the rotating table. An adapter 450 is used to facilitate the removable coupling between the rotating table 420 and the counterweight support frame 432. The adapter 450 has a hole 452 passing through an ear 454, and the ear 454 fits between lugs 429 on the lower portion of the rotating table 420 to couple the adapter 450, and thus the counterweight support frame 432, to the rotating table 420. The adapter 450 is itself fixed to the counterweight support frame 432 by a pin 456 (as best seen in FIG. 34). By using the pin 456, the adapter 450 can be removed from the counterweight support frame 432, such that the counterweight support frame 432 can be reused within the structure of the crane 510. The front hole 481 functions as a location for pinning the counterweight support frame 432 and the adapter 450 together. The rear hole 483 and the top hole 484 within the counterweight support frame 432 are not used in this embodiment, but are provided such that the counterweight support frame 432 can be used within the structure of the crane 510, as will be described below.

[0075] The counterweight support frame 432 is coupled to the rotating table at the rear via two short links 462. Each link 462 has one end pinned to a lug 464 on the rotating table and the other end pinned between a pair of lugs at the rear of the counterweight support frame 432. Once the front adapter 450 and the rear link 462 are pinned together, the counterweight support frame 432 effectively becomes a removable part of the rotating table of the crane 410.

[0076] In the crane 410, the counterweight unit moving device is coupled between the counterweight support frame 432 as part of the rotating floor and the counterweight unit 435, thereby being coupled between the rotating floor 420 and the counterweight unit 435. The counterweight unit 435 includes a counterweight tray 433 pinned to a movable trolley 470 (Figs. 35 - 37). Similar to the previous embodiment, the counterweight tray is suspended below the counterweight support frame. The tray 433 is pinned within a hole 471 of the trolley 470 (Fig. 31). The hole 471 is larger at the top than at the bottom. The size of the bottom is the same as the outer diameter of a pin (not shown) used to couple the tray 433 and the trolley 470. The larger size at the top allows for easier insertion of the pin.

[0077] The trolley 470 is placed on four vertical rollers 476, and the rollers 476 engage with flanges 438 along both ends of the counterweight support frame 432. The trolley 470 also includes four horizontal rollers 478 (Fig. 33), and these rollers provide lateral positioning of the trolley 470 on the counterweight support frame 432.

[0078] The counterweight unit moving device includes at least one (two in this embodiment) hydraulic motor and gearbox 472, which drive gears 474 each coupled to the trolley 470. The counterweight support frame 432 has a set of teeth 436 on each side (Fig. 29). The gears 474 engage with the teeth 436 provided on the two sides of the counterweight support frame 432, and when the motor and gearbox 472 rotate the gears 474, the trolley 470 is moved relative to the counterweight support frame. In this way, the counterweight unit 435, being mounted on the trolley 470, can move relative to the counterweight support frame 432.

[0079] To facilitate manufacture, several individually replaceable bars 434 (best seen in FIG. 29) can be bolted to the base of the counterweight support frame 432 by socket head cap screws to provide both the flange 438 and the teeth 436. Further, the sides of these bars provide an engagement surface for the horizontal rollers 478, as can be seen in FIG. 33. The surfaces of these bars 434 are preferably hardened to provide relatively good wear resistance against the rollers 476 and 478. The bars 434 are provided with shear block surfaces 439 (FIGS. 32 and 33) to assist in transmitting the load from the rollers 476 on the trolley 470 to the counterweight support frame 432. As can be seen in FIG. 32, the roller 476 is preferably mounted in the same vertical plane as the gear 474

[0080] In a preferred embodiment, the crane is configured such that, during crane operation, when the counterweight unit is moved to correct for changes in the combined moment of the boom and load, the moment on the crane's forward tipping point generated by the counterweight unit is not transmitted to the slewing platform via the mast. Rather, this moment is transmitted to the slewing platform by the counterweight support frame, such as via the pin joints at the lugs 429 and 464, for example.

[0081] Crane 510 is made up of the same components used to manufacture crane 410, but includes an added fixed mast 517 and a movable counterweight support beam 560. Further, the structure that was used as the live mast 428 within crane 410 is no longer used as a live mast. Instead, a boom hoisting rigging 519 is provided between the boom top and the top of the fixed mast 517 to enable changing of the boom angle. A fixed-length pendant 525 connects the top of the fixed mast 517 to the top of mast 528. The rigging 527 and mast 528 are held in a fixed position during normal operation of crane 510. Further, a tension member 531 is added between the top of mast 517 and the counterweight support beam 560. In the drawings, components used in crane 410 that are the same as those in crane 510 have the same reference numerals with 100 added, thus the boom 422 on crane 410 is the boom 522 on crane 510. The counterweight unit 535 is the same as the counterweight 435.

[0082] The counterweight unit 535 on the crane 510 can be moved in two ways. First, similar to the counterweight unit 435, the counterweight unit 535 includes a trolley 570 with rollers 576, and the rollers 576 are placed on the flange of the counterweight support frame 532. However, in this counterweight assembly structure, the counterweight support frame 532 is part of the nested counterweight support beam 560. Therefore, another way to move the counterweight unit 535 is to extend the beam 560 in a nested manner while maintaining the position of the counterweight unit 535 on the frame 532. The first type of movement can be seen by comparing FIGS. 39 and 40, and the second type of movement can be seen by comparing FIGS. 40 and 41. These movements can both be performed separately, but it is not necessary to perform them to the maximum possible extent. However, usually, the counterweight unit 535 is returned as far as possible on the frame 532 before the beam 560 is extended. As can be seen by comparing FIGS. 39 and 41, in the counterweight moving device of the crane 510, the counterweight unit can be moved to a position between the boom hoist pulley on which the counterweight unit is assembled on the turntable and the rotation axis of the car body, or to a position behind the boom hoist pulley on which the counterweight unit is assembled on the turntable.

[0083] The counterweight support beam 560 is preferably made up of three nested beam members, namely, an inner beam member 592, an intermediate beam member 582, and an outer beam member 532 (which is also referred to as the counterweight support frame 532 above). Accordingly, the counterweight support beam moving device consists of a nested frame having at least one inner frame member fitted inside the outer frame member. As shown, it is more preferable that the counterweight support beam includes an intermediate frame member surrounding the inner frame member inside the outer member. The counterweight support beam constitutes the outer frame member of the nested frame which is a part of the counterweight support beam moving device.

[0084] Interestingly, the structure used as the counterweight support frame 432 in the first counterweight assembly structure option (crane 410) can be used as the outer beam member 532 within the counterweight support beam 560 in the second counterweight assembly structure option (crane 510). When the counterweight support frame 432 is used as the outer beam member 532, the outer beam member is provided with additional structures that can be coupled to the base of the beam member and moved relative to the rotating floor 520.

[0085] Since the trolley 570 is exactly the same as the trolley 470 and the outer beam member 532 has the same outer structure as the counterweight support frame 432, the way the counterweight unit 535 moves relative to the outer beam member 532, the structure of the trolley 570, the motor and gearbox 572, and the gear 574 that engages with the teeth provided on the steel bar 534 portion will not be described in detail again. Due to these similarities, in this embodiment, the drive gear coupled to the trolley engages with the teeth on the counterweight support beam 560 to move the trolley relative to the counterweight support beam 560 when the motor rotates the gear 574.

[0086] The counterweight support beam 560 is attached to the remainder of the crane 510 in a manner similar to the way the counterweight support frame 432 is coupled to the remainder of the crane 410. Instead of the short link 462 that couples the lug 466 to the rear of the slewing platform, a tension member 531 is coupled from the top of the fixed mast 517 through the lug 566 to the rear of the counterweight support beam 560. Forwardly, instead of the adapter 450, the inner beam member 592 has a connector 550 at its end. This connector has an ear 554 with a through hole 552, and the connector 550 can be pinned to the underside of the slewing platform 520 such that the adapter 450 is pinned to the slewing platform 420.

[0087] This counterweight support beam moving device preferably comprises a linear actuator in the form of a trunnion-type hydraulic cylinder. The counterweight support beam moving device further comprises a wire rope and a pulley attached to an intermediate frame member and an outer frame member, and the outer frame member is made to move in a dependent manner with respect to the movement of the intermediate frame member with respect to the inner frame member. In a preferred embodiment of the counterweight support beam 560, a double-acting hydraulic cylinder 540 with a rod 542 is coupled between the inner beam member 592 and the intermediate beam member. Thus, when the rod 542 is extended or retracted, the intermediate beam member 582 moves with respect to the inner beam member 592. On the other hand, the outer beam member 532 is coupled to the other beam members in a dependent manner, and the relative movement between the other beam members necessarily and simultaneously causes the movement of the outer beam member 532 with respect to the intermediate beam member 582. The details of the form in which this occurs are best understood in FIGS. 42 - 52, and additional details are shown in FIGS. 53 - 60.

[0088] The inner, intermediate, and outer beam members are each formed into a box structure by welding plates. Rollers 585 and 586 support the inner surface of the outer beam member 532 on the outside of the intermediate beam member 582. Similarly, rollers 587 and 588 support the inside of the intermediate beam member 582 against the outside of the inner beam member 592. When the member 432 is reused as the outer beam member 532 within the crane 510, the holes 481 and 483 provided on both sides of the counterweight support frame 432 are used to attach the rollers 585 and 586.

[0089] To assist in explaining the relative movement of the beams, some of the drawings are shown with some of the plate members removed, similar to FIGS. 45 - 50. As can be best seen in FIGS. 45 and 46, the hydraulic cylinder is attached in a trunnion fashion to the side wall of the inner beam member 592 via a mount 541. The rod portion 542 of the hydraulic cylinder terminates at a head 539, which has a hole through it and can be pinned between lugs 538 that are welded to the back plate of the intermediate beam 582. Thus, when the rod 542 within the hydraulic cylinder 540 is extended or retracted, the intermediate beam member 582 will similarly extend or contract relative to the inner beam member 592.

[0090] The movement of the outer beam member 532 is controlled by a pair of shortening wire ropes 544 and a pair of extending wire ropes 546. One end of the extending wire rope 546 is connected by a connector 545 to the front portion of the outer beam member 532. This extending wire rope passes through a hole 584 that is the same as the unused hole 484 in the counterweight support frame 432. The extending wire rope 546 passes around an extending pulley 596 attached to the rear portion of the intermediate frame member 582. The other end of the extending wire rope 546 is connected by a connector 595 to the rear portion of a counterweight support beam connector 550 disposed at the front portion of the inner beam member 592. When the counterweight support beam 560 is in the shortening mode and the hydraulic cylinder 540 is extended to move the intermediate beam member 582 rearward relative to the inner beam member 592, the extending pulley 596 is pushed rearward together with the intermediate beam member, and the extending wire rope 546 is caused to pass around the extending pulley 596, whereby the front portion of the outer beam member 532 is inevitably pulled rearward by the connector 545. The extending wire rope 546 is connected to the outer beam member 532 at the connector 545 and is connected to the connector 595 at the front portion of the inner beam member 592, but since it passes around the extending pulley 596 attached to the intermediate beam member 582, when one of the moving distances of the intermediate member extends by 1 foot (30.48 centimeters), the outer beam member 532 is extended by 2 feet (60.96 centimeters).

[0091] The shortening wire rope 544 has one end connected to the rear portion of the inner beam member 592 by a connector 543 (Figs. 49 and 56). The shortening wire rope is passed around a shortening pulley 594 attached to the front portion of the intermediate beam member 582. The other end of the shortening wire rope 544 is connected to the rear portion of the outer member 532 by a connector 593. When the counterweight support beam 560 is in the extended mode and the hydraulic cylinder 540 is shortened to move the intermediate beam member 582 forward relative to the inner beam member 592, the shortening pulley 594 is pushed forward by the intermediate beam member and the shortening wire rope 544 is passed around the shortening pulley 594, whereby, necessarily, the rear portion of the outer beam member is pulled forward by the connector 593. The shortening wire rope is connected to the inner beam member at the connector 543 but is passed around the shortening pulley 594 attached to the intermediate beam member 582, so that when the intermediate beam member moves 1 foot (30.48 centimeters), the outer beam member 532 is shortened by 2 feet (60.96 centimeters). The shortening wire rope 544 can be attached to the outer beam member 532 at any point within the beam material behind the location where the shortening pulley 594 is disposed when the beam is shortened. However, by attaching the shortening wire rope 544 at the very rear portion of the outer beam member 532, the connector 593 is more readily accessible when adjustment is required.

[0092] It can be seen from FIGS. 58 and 59 that the roller 588 has a flange on the outside for the purpose of assisting in keeping the beams arranged and aligned side by side. The rollers 585, 586 and 587 also have such flanges. The rollers 585, 586, 587 and 588 are preferably attached to the side of the intermediate beam member 582 by bearings between the roller shafts and the rollers, although the bearings are not shown in the drawings. Further, although not clear from the drawings, those skilled in the art will understand that there is a slight clearance between the side and the top or bottom of the rollers with respect to the beam members supported thereby.

[0093] FIGS. 61 and 62 show not only an alternative structure of the joint between the rear portion of the rotating floor 420 and the counterweight support frame 432 when the crane is assembled without the fixed mast 517 (when the crane is assembled in the first counterweight assembly structure), but also an alternative structure of the joint between the nested counterweight support beam 560 and the tension member 531 when the crane is assembled in the second counterweight assembly structure. Instead of using the short link 462, the support portion at the rear of the rotating floor in the form of the lug 523 is arranged in a position directly pinned to the lug 620 on the outer beam member 532, and the lug 620 is used as a part of the counterweight support beam 560 in the embodiments shown in FIGS. 61 and 62. Similar to the lug 566, each of the lugs 620 is made of two plates having through holes, and the plates are used to form a connection pinned either in the state of the rotating floor (when the crane is assembled in its first counterweight assembly structure) or at the bottom of the tension member 531 (when the crane is assembled in its second counterweight assembly structure). In the first assembly structure, a pin (not shown) passes through the hole 632 of the lug 620 and the hole 562 of the lug 523.

[0094] One of the advantages of the lugs 620 is that these lugs have a top bar 624 and a bottom bar 626 between plates 621 and 622, and these bars engage with the lugs 523 on the rotating floor 520 as shown in FIG. 62 (the left plate is removed for clarity) when the counterweight support beam 560 is shortened to its fullest extent. Thus, the support member 523 on the rear portion of the rotating floor engages with the counterweight beam support engagement portion (bar 624) and is arranged such that when the counterweight beam is in the fully shortened position, this support and support engagement allows the load to be directly transmitted from the counterweight beam to the rotating floor. At a large beam angle with no load on the hook, the moment of the counterweight device may exceed the counteracting moment of the boom and load combination, as can be understood by the fixed mast 517. In this situation, the fixed mast tries to move rearward and compresses the fixed mast stop 529 until the top bar 624 on the lug 620 of the outer beam member engages with the lug 523 on the rotating floor 520. (It should be noted that when the crane is assembled by the mast 517, the pins are not placed in the holes 562 and 632. These holes also just happen to line up when the tension member 531 is pinned to the lug 620 and the counterweight support beam 560 is shortened to its fullest extent.) At this point, the rear portion of the rotating floor carries a portion of the counterweight load and reduces the tendency of the mast 517 to fall further rearward.

[0095] The counterweight unit is preferably movable to a position where the center of gravity of the counterweight unit is within a distance from the axis of rotation that is less than 125% of the distance from the axis of rotation to the rear tipping fulcrum, and more preferably within a distance from the axis of rotation that is less than 110% of the distance from the axis of rotation to the rear tipping fulcrum.

[0096] As described above, conventional mobile lifting cranes generally had a number of counterweight assemblies. The preferred crane has a variable-position counterweight and includes only one counterweight assembly. When a typical design requires a counterweight of 330 metric tons, a crane 10 with a single variable-position counterweight requires a counterweight of approximately 70% of this value, or 230 metric tons, to generate the same load moment. The 30% reduction in counterweight directly reduces the cost of the counterweight, but this cost is partially offset by the cost of the counterweight moving device. Within current US road limits, a 100-metric-ton counterweight requires five trucks for transportation. Thus, reducing the total amount of counterweight can reduce the number of trucks needed to transport the crane between job sites. Since the counterweight is significantly reduced, the maximum ground support is also reduced by the same amount. The counterweight is simply placed rearward to the extent necessary to lift the load. The crane and counterweight are kept as compact as possible and only extended when additional load moment is required. Another feature is the ability to operate with a reduced counterweight in an intermediate position. With a reduced counterweight, a balance is struck with the stability requirements to the rear when no load is hooked to the hook. Then, the variable-position function is switched off and the crane operates as a conventional lifting crane. In a preferred embodiment of the present invention, compared to a crane of comparable ability, the total amount of counterweight can be reduced, or if the total amount of counterweight is the same, the stability of the crane can be increased or the crane can be designed with a smaller footprint. Of course, when manufacturing a new crane model, some combination of all three of these advantages may be used.

[0097] The customer of the crane 410 may first decide to buy and use a crane 410 that only has the counterweight support frame 432 and does not have the inner beam member 592, the intermediate beam member 582, or the fixed mast 517. Subsequently, the crane 410 can be changed to a crane 510 by adding the mast 517 and inserting the inner beam member 592 and the intermediate beam member 582 into the counterweight support frame 432 to form the counterweight support beam 560. Subsequently, when the crane is assembled without the fixed mast 517, the intermediate beam member 582 with the inner beam member 592 can be removed. However, once the counterweight support beam 560 is assembled, it is often left in its original state and used in the crane 410 without being extended, but rather simply used as the counterweight support frame 432.

[0098] In the first counterweight assembly structure option (crane 10 or crane 410), the counterweight unit is not supported by a fixed mast or a derrick mast. Instead, the counterweight unit is supported on a counterweight support frame on the revolving deck. The counterweight moving device includes a counterweight unit moving device coupled to move the counterweight unit relative to the counterweight support frame. In the second counterweight assembly structure option (crane 110 or crane 510), the second counterweight unit is supported by a mast selected from among a fixed mast and a derrick mast. The counterweight support beam is movably coupled to the revolving deck, and the counterweight unit is supported on the counterweight support beam. The counterweight moving device includes a counterweight support beam moving device coupled to be able to move the counterweight support beam relative to the revolving deck. In crane 110, the counterweight support beam is movably coupled to the revolving deck by being movably coupled to a counterweight support frame. In crane 510, the counterweight support beam is movably coupled to the revolving deck by having a nested portion movably coupled to the revolving deck by a front portion of the counterweight support beam.

[0099] In the first counterweight assembly structure option, crane 10 or crane 410 includes a counterweight tray movably supported on a counterweight support frame, and the counterweights are stacked directly on the counterweight tray. In the second counterweight assembly structure option of crane 110, the counterweight support beam is attached to a counterweight tray, and the counterweights are stacked on the counterweight support beam by being stacked on a base plate disposed on the counterweight support beam.

[0100] In the embodiments of the cranes 110 and 510, the method of operating a mobile lifting crane includes steps of picking up, moving, and installing a load, and in these steps, to assist in balancing the moment of the boom and the load, a movable counterweight unit is moved closer to or farther from the front portion of the slewing deck during the picking up, moving, and installing operations, and the counterweight unit remains on the counterweight support beam during the picking up, moving, and installing operations. Both the counterweight support beam and the counterweight unit move when the moment of the boom and the load changes to balance the crane. Further, the counterweight unit can be moved relative to the counterweight support beam during the picking up, moving, and installing operations to assist in balancing the moment of the boom and the load.

[0101] A preferred crane includes a movable superstructure counterweight unit that rotates together with a slewing deck and a counterweight moving device coupled between the slewing deck and the counterweight unit. The counterweight unit is moved to and held in both a forward position and a rearward position and is never supported by the ground except being indirectly supported by a movable ground engaging member on the car body during the picking up, moving, and installing operations of the crane. The ratio of i) the weight of the superstructure counterweight unit to ii) the total weight of the crane having a basic boom length is greater than 52% and preferably greater than 60%. In some embodiments, the counterweight unit is supported on a counterweight support frame provided as part of the slewing deck, and the counterweight unit is movable relative to the counterweight support frame.

[0102] The present invention is particularly applicable to cranes having a capacity of 200 to 1500 metric tons and more preferably 300 to 1200 metric tons.

[0103] It will be understood that the present invention includes a method of enhancing the capacity of a crane. A lifting crane having a first capacity can be modified to become a crane having a second capacity higher than the first capacity. The crane of the first capacity includes a counterweight unit having a number of counterweights stacked on top of each other at their upper ends. The counterweight unit can be moved from a first position to a second position that is farther from the crane boom than the first position. The method includes removing at least some of the counterweights from the crane, adding a counterweight support beam to the crane, and returning at least some of the counterweights to the crane to impart greater capacity thereto. The returned counterweights are supported on the counterweight support beam in such a way that the returned counterweights can move to a third position that is farther from the boom than the second position. As disclosed herein, in some embodiments, the counterweight support beam is attached to the rotating bed by being attached to a counterweight support beam moving device that is directly attached to the rotating bed. The counterweight support beam moving device is coupled between the counterweight support beam and the rotating bed, such that the counterweight support beam can be moved away from the rotational coupling between the rotating bed and the car body in a direction along the length of the rotating bed. In some methods of the present invention, the returned counterweights move to the third position by moving with the counterweight support beam, or by moving relative to the counterweight support beam, or by moving with and relative to the counterweight support beam. As described above, the step of adding the counterweight support beam can include removing an outer frame structure coupled to the rotating bed by an adapter, assembling an inner frame structure nested within the outer frame structure to form a counterweight support beam moving device, and attaching the inner structure to the rotating bed.

[0104] 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. For example, the boom hoisting device can include one or more hydraulic cylinders attached between the boom and the rotating floor to change the angle of the boom. Instead of a live mast or a lattice structure mast, a fixed gantry can be used to support the boom hoisting rigging. In this regard, such a gantry is considered to be a mast for the purposes of the claims. The crane 10 can be modified to include a lattice structure mast as used in the crane 110, in which case it includes a movable counterweight on the counterweight support frame 32 rather than the counterweight support beam 160, and in this case the boom hoisting rigging includes an equalizer between the lattice structure mast and the boom. When the crane is assembled in this way at the work site, relatively small lifts can be made as in the initial assembly, and then the crane 110 can be made by adding the counterweight support beam 160 without having to reassemble the crane again. Further, the various parts of the crane do not always have to be joined directly to each other as shown in the drawings. For example, a tension member can be joined to the mast by joining it to a rear coupler near the position where the rear coupler is joined to the mast. Such changes and modifications can be made without departing from the spirit and scope of the invention and without sacrificing the intended advantages. Accordingly, such changes and modifications are intended to be protected by the appended claims.

Description of the reference numerals

[0105] 10 Hoisting crane, 12 Cabody, 13 Load hoisting drum, 14 Crawler, ground engaging member, 16 Rear tipping point, 17 Front tipping point, 19 Additional hoisting drum, 20 Rotating floor, 21 Boom hoisting drum, 22 Boom, 23 Pulley on the rotating floor, 24 Load hoisting wire rope, 25 pendant, 26 hook, 27 boom hoisting wire rope, 28 live mast, 29 drum for compensating wire rope, 32 counterweight support frame, 33 counterweight tray, 34 counterweight, 35 counterweight unit, 37 roller, 39 flange, 40 drive motor, hydraulic motor, 41 idler pulley, 42 drum, 43 wheel, 44 wire rope, 45 connector, 84 support beam, 54 mast, 110 crane, 115 boom hoisting wire rope, 117 fixed mast, 118 boom hoisting drum, 120 turntable, 122 boom, 125, 126 pendant, 127 rigging, 128 live mast, 129 equalizer, 131 tension member, 133 counterweight tray, 135 counterweight unit, 136 additional counterweight, 137 roller, 139 flange, 144 wire rope, 145 coupling part, connector, 149 pendant for rear connector, 160 counterweight support beam, 162 side member, 163 counterweight base plate, 164 cross beam member, 172 idler pulley, 173 flexible tension member, 176 chain drive, 178 shaft, 179 lug, 182 support leg, 189 connector, 210 crane, 215 boom hoisting wire rope, 217 fixed mast, 218 boom hoisting drum, 220 turntable, 221 drum, 222 boom, 223 pulley set, 225 pendant, 226 pendant, 228 mast, 229 equalizer, 231 tension member, 235 counterweight unit, 237 auxiliary counterweight, additional counterweight unit, 252 counterweight tray, 254 side panel, 256 hook member, 258 bearing surface, 260 counterweight support beam, 264 cross beam member, 266 extension, 268 pin, 269 bearing surface, 310 crane, 312 car body, 314 crawler, ground engaging member, 317 fixed mast, 320 rotating bed, 322 boom, 325 boom hoisting rigging, 328 live mast, 331 tension member, 335 counterweight unit, 355 telescopic cylinder, 360 counterweight support beam, 362 side member, 364 cross beam member, rear part of counterweight support beam, 371, 372 pulleys, 373 wire rope, 376 coupling, 378 coupling, 382 support leg, 410 crane, 412 car body, 414 ground engaging member, 420 rotating bed, 422 boom, 427 boom hoisting rigging, 428 live mast, 429 lug, 432 counterweight support frame, 433 counterweight tray, 434 steel bar, 435 counterweight unit, 436 teeth, 438 flange, 439 shear block surface, 450 adapter, 452 hole, 454 ear, 456 pin, 462 link, 464,466 lag, 470 trolley, 471 hole of trolley 470, 472 gearbox, 474 gear, 476 vertical roller, 478 horizontal roller, 481 front hole, 483 rear hole, 484 top hole in counterweight support frame 432, 510 crane, 517 fixed mast, 519 boom hoisting rigging, 520 rotating bed, 522 boom, 523 lag, 525 pendant, 527 rigging, 528 mast, 529 fixed mast stop, 531 tension member, 532 counterweight support frame, outer beam member, 533 counterweight tray, 534 steel bar, 535 counterweight unit, 538 lag, 539 head, 540 hydraulic cylinder, 541 mount, 542 rod, 543 connector, 544 shortening wire rope, 545 connector, 546 extending wire rope, 550 connector, 552 through hole, 554 ear part, 560 counterweight support beam, 562 hole, 566 lag, 570 trolley, 572 gearbox, 574 gear, 576 roller, 582 intermediate beam member, 584 hole, 585,586 roller, 587,588 roller, 592 inner beam member, 593 connector, 594 shortening pulley, 595 connector, 596 extending pulley, 610 crane, 620 lag, 621,622, plate, 624 bar, 626 bottom bar, 632 hole,

Claims

1. A lifting crane, a) a car body; b) a movable ground engaging member attached to the carbody that enables the lift crane to move over the ground; c) a rotating bed having a forward portion and a rearmost fixed portion, the rotating bed being rotatably connected to the carbody about a rotation axis to provide a rotation plane perpendicular to the axis; d) a boom pivotally mounted to the rotating bed; e) a counterweight support frame included in the rotating bed, the counterweight support frame including a set of teeth directly coupled to a first underside of the counterweight support frame and positioned below the rotating bed; f) a counterweight unit including a trolley and supported on the counterweight support frame in a manner movable relative to the rotating bed; g) a counterweight unit movement device adapted to move the counterweight unit toward and away from the boom, the counterweight unit movement device including at least one motor driving a gear coupled to the trolley, the gear engaging the set of teeth on the counterweight support frame when rotated by the motor to move the trolley relative to the rotating bed so that the counterweight unit can be moved to a position where its center of gravity is in front of the rear tipping fulcrum; h) a counterweight support beam connected to the rotating bed, the outer beam member of the counterweight support beam being formed by the counterweight support frame; and i) a counterweight support beam movement device connected between the counterweight support beam and the rotating bed such that the outer beam member can be moved forward toward the front portion of the rotating bed and rearward beyond the aftmost fixed portion of the rotating bed; A lifting crane equipped with

2. 2. The lift crane of claim 1, wherein the counterweight unit movement device includes a pair of motors, each motor located on opposite sides of the counterweight support frame.

3. 2. The lift crane of claim 1, further comprising a mast coupled to the rotating bed such that when the counterweight unit moves to compensate for changes in combined boom and load moment during crane operation, moments created by the counterweight unit are not transmitted through the mast.

4. 2. The lift crane of claim 1, wherein the counterweight unit is movable between a position where the counterweight unit is forward of the rearmost fixed portion of the rotating bed and a tail swing of the lift crane is defined by the rearmost fixed portion of the rotating bed, and a position where the counterweight unit defines the tail swing of the lift crane.

5. 2. The lift crane of claim 1, wherein the movable ground engaging members comprise crawlers which provide a front tipping fulcrum and a rear tipping fulcrum for the lift crane, and wherein the counterweight unit can be moved to a position where its center of gravity is within a distance from the axis of rotation that is less than 125% of the distance from the axis of rotation to the rear tipping fulcrum.

6. The lift crane of claim 1 further comprising a live mast pivotally coupled to the rotating bed.

7. 2. The lift crane of claim 1, wherein the counterweight unit comprises at least one counterweight stacked on at least one counterweight tray, the counterweight tray suspended below the counterweight support frame.

8. 2. The lift crane of claim 1, further comprising a mast connected to the rotating bed, and an adjustable length boom hoist rigging connected between the mast and the boom that allows the angle of the boom relative to the plane of rotation of the rotating bed to be varied.

9. 9. The lift crane of claim 8, further comprising a tension member coupled between the mast and the counterweight support beam.

10. 2. The lift crane of claim 1, wherein the counterweight unit is supported on the counterweight support beam in a manner that allows it to move relative to the counterweight support beam.

11. The lift crane of claim 1 , wherein the trolley includes at least one of a vertical roller and a horizontal roller.

12. 2. The lift crane of claim 1, wherein said set of tines is formed from multiple sections.

13. 13. The lift crane of claim 12, wherein the sections are bolted to the counterweight support frame.

14. 2. The lift crane of claim 1, wherein the counterweight unit further comprises at least one tray adapted to support a plurality of stacked counterweights, at least one counterweight being disposed on one side of the counterweight support frame and another counterweight being disposed on the other side of the counterweight support frame.

15. 2. The lift crane of claim 1, wherein the counterweight unit is suspended below the rotating bed.

16. 2. The lift crane of claim 1, wherein the counterweight unit supports a plurality of stacked counterweights thereon, at least one counterweight being positioned on one side of the rotating bed and another counterweight being positioned on an opposite side of the rotating bed.

Images