JP5740162B2 - Sheave device for crane - Google Patents

Description

  The present invention relates to a sheave device used in a crane, and more particularly to a crane sheave device that can be suitably employed as a sheave used in a vehicle-mounted crane.

As for the hook part of a crane, the wire rope front-end | tip is being fixed to the hook part via the sheave (fixed pulley) of a boom front-end | tip part. Here, in this type of hook part, when lifting a heavy load, if the crane winch hoisting capacity is the same and the output of the crane is the same, the hook part also has a sheave (moving pulley). Is provided to boost the pulling force (see, for example, Patent Document 1).
The hook portion described in Patent Document 1 is wound up to the boom tip portion of the crane as it is, and is stored in contact with the lower surface of the boom tip portion. According to such a configuration, the lifting ability can be improved at a low cost while maintaining the labor saving of the actuator mechanism. Therefore, it is generally used because of its high cost advantage.

Japanese Patent Laid-Open No. 2001-270685

  By the way, the diameter limit of the sheaves of the boom tip and the hook is determined based on the diameter of the wire rope used. This is because if the diameter is below the limit, the bending stress applied to the wire rope becomes larger than allowable, and an early fatigue disconnection occurs in the wire rope, resulting in a shortened life. For example, in a vehicle-mounted crane, according to the Labor Standards Bureau of the Ministry of Health, Labor and Welfare “Mobile Crane Structure Standard”, when the wire rope is wound around a sheave, the diameter of the center circle (pitch circle) of the wire rope and the diameter of the wire rope The ratio (“D / d value”) is defined to be used above a certain value. Therefore, the limit of the diameter of the sheave diameter is naturally determined from the prescribed ratio depending on the diameter of the wire rope to be used.

  Therefore, as shown in FIG. 9, the hook portion 125 similar to the above-described Patent Document 1 is wound up to the boom tip portion 7 s of the crane as it is after the crane work, and is brought into contact with the lower surface of the boom tip portion 7 s for storage. When this is done, the storage length L2 from the center of the sheave 130 of the boom tip 7s to the center of the hook 13 of the hook portion 125 (hereinafter also referred to as “storage distance”) L2 depends on the diameter of the wire rope 12 used. The length of the sheave 130 is a certain length or more from the definition of the limit dimension of the diameter (radius R).

In this case, since the distance L2 at the time of storage is long simply by bringing the hook portion 125 into contact with the lower surface of the boom tip 7s, for example, in a vehicle-mounted crane, the visibility of the driver when the vehicle is traveling when the front of the boom is stored It becomes defective. In addition, the loading height of the load becomes low when rearwardly stored. Therefore, after the hook portion is brought into contact with the boom tip, measures have been taken such as separately providing a storage device for rotating the hook portion so as to be parallel to the boom longitudinal direction.
Therefore, the present invention has been made paying attention to such a problem, and in a state where the hook portion is in contact with the bottom surface of the boom tip, when the boom is retracted forward, the driving view when the hook is retracted is obtained. An object of the present invention is to provide a crane sheave device that is good and can increase the loading height of the load when stored rearward.

In order to solve the above-described problems, the present invention provides a sheave device used in a crane having a boom pivotably supported, and the sheave device is provided at a boom tip so as to function as a fixed pulley. One sheave device and a second sheave device provided on the hook portion so as to act as a moving pulley, and the first sheave device is arranged around the main shaft center of the boom tip portion according to the undulation of the boom. a first support member which is rotatably supported, said first support rotatably the pivoted by a plurality having an arrangement of semicircular convex upward first rolling wheel, and said plurality of comprising first and a first circular arc track section having a first track belt winding the entire track roller of the second sheave apparatus includes a second support crane hook is connected The second support is pivotally supported by the second support. A plurality of second rolling wheels having a downwardly convex semicircular arc arrangement, and a second arcuate track portion having a second track belt that winds the entire plurality of second wheels. , wherein each first and second plurality of track rollers is composed of a loaded rolling wheel for receiving a load crane wire rope is wound, and a support track roller for supporting the track belt is not under load side, each The load roller centers have an arrangement along one circular arc, and the wire rope is wound around the outer periphery of the race belt around which each load roller is wound.
Here, it is preferable that the ratio of the diameter of the center circle of the wire rope hung around the load wheel portion to the diameter of the wire rope is secured to a certain value (for example, “D / d value”) or more.

According to the sheave device according to the present invention, it comprises a circular arc track portion comprising a first and second plurality of rolling wheels that are rotatably pivotally supported to the support each and the plurality of rolling wheels, cranes wire It consists of a load wheel that receives the load on which the rope is wound, and a support wheel that supports the track belt on the side that is not subjected to the load, and each load wheel center has a line along one arc and each load Since the wire rope is configured to be wound around the outer periphery of the track belt that surrounds the wheels, the entire arc track portion is reduced while reducing the diameter of each load wheel of the first and second supports. It is possible to maintain a curvature at which the bending stress applied to the wire rope does not become larger than allowable.
Furthermore, according to the sheave device according to the present invention, the first sheave device includes a first support body rotatably supported around the center of the main shaft of the boom tip portion according to the undulation of the boom, and the first sheave device. A plurality of first rolling wheels pivotally supported by a support body and having an upwardly convex semicircular arc arrangement, and a first track belt for winding the plurality of first rolling wheels as a whole; The second sheave device includes a second support body to which a hook of a crane is coupled, and is pivotally supported by the second support body to be downward. Since it comprises a second arc raceway portion having a plurality of second rolling wheels having a convex semicircular arc arrangement and a second raceway belt that winds the entire plurality of second rolling wheels. Since the second sheave device is a semicircle projecting downward, the upper semicircle portion can be eliminated, and the first sheave device It can be dispensed with bottom semi-circular portion by a semicircular convex upward. For this reason, the distance for storing can be shortened, so that when the hook is in contact with the bottom surface of the boom tip, the driving visibility is good when retracting the front of the boom and when loading the rear. The loading height of objects can be increased.

It is a figure explaining one embodiment of vehicles with a vehicle loading crane provided with a sheave device for cranes concerning the present invention. FIG. 2 is an enlarged view of a main part (a part of a sheave device) in FIG. 1 and a part thereof is broken, and shows a state in which a hook part is suspended from a tip part of a boom. It is a figure explaining a hook part and its sheave device, The figure (a) is a B arrow view in (b), (b) is a front view, (c) is a right view. It is a figure explaining the sheave device of a boom front-end | tip part, The figure (a) is the front view, (b) is a right view of (a). It is explanatory drawing of the piece which comprises the track belt of the circular arc track part of the sheave device concerning the present invention, the figure (a) is the top view, (b) is the left side view, (c) is the front view, (d) Is a right side view, and (e) is a bottom view. It is a figure which expands and shows the principal part (part of a sheave device) of FIG. 1, The figure (a) shows the storage state which made the hook part contact | abut to a boom front-end | tip part, and the figure (b) Shows a part of (a) broken. It is A arrow line view in Fig.6 (a), In the same figure, a part is fracture | ruptured and shown. It is a figure explaining operation | movement of the sheave apparatus of this invention, The figure has shown the state which hung the boom part from the boom front-end | tip part, and the state which stood up the boom. It is a figure which expands and shows the conventional sheave part for cranes (it respond | corresponds to the sheave apparatus of this invention), and the figure has shown the state at the time of storage which wound up the hook part to the boom tip part.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate.
As shown in FIG. 1, the vehicle-equipped crane-equipped vehicle 1 has a loading platform 5 on a chassis frame 3 behind the host vehicle. A torii gate 5a is attached to the front end portion of the loading platform 5 to prevent contact with members on the cab 1a side such as cargo loaded on the loading platform 5. A vehicle-mounted crane (hereinafter simply referred to as “crane”) 15 is mounted between the torii 5a and the cab 1a.

  The crane 15 has a base 4 mounted horizontally on the chassis frame 3 of the vehicle. A pair of outriggers 2 are attached to the base 4 so as to project to the left and right. Further, a column 6 is erected on the base 4 so as to be able to turn by driving a turning hydraulic motor 5. A boom 7 is provided at the upper end of the column 6 so that it can be raised and lowered by the operation of the boom expansion / contraction hydraulic cylinder 8 and the boom raising / lowering hydraulic cylinder 9.

  The column 6 is provided with a winch 11 that can be driven by a winch hydraulic motor 10. Then, the wire rope 12 is guided from the winch 11 to the boom tip 30, and the wire rope 12 is hung on the hook 20 via the sheave device 35 of the boom tip 30, and the hook 20 is wound up by the winch 11. Lowering is done. In addition, this crane 15 is a specification in which the boom 7 is stored with the attitude | position toward the loading platform 5 side, as shown in the figure.

Here, as shown in an enlarged view in FIG. 2, the sheave device 25 and the sheave device 35 according to the present invention are respectively employed in the sheave portions of the hook portion 20 and the boom tip portion 30. Hereinafter, the hook 20 and the boom tip 30 will be described with reference to FIGS.
As shown in FIG. 2, the hook unit 20 includes a hook 13, a trunnion pin 23, and a sheave device 25. Note that a weight plate 22 for an over-winding alarm device is provided on the upper portion of the hook portion 20. The trunnion pin 23 that connects the support 21 is provided so that the hook 13 can perform a pendulum-shaped rotation F and a rotation K about a substantially horizontal axis (see FIG. 3C). The structure of the hook 13 itself and the structure of the trunnion pin itself connecting the hook 13 are not different from the conventional one. As shown in FIG. 3, the sheave device 25 includes an arcuate track portion 26 having a plurality of small-diameter rollers 26a and 26c and a crawler-like track belt 26b around which the plurality of rollers are wound.

  Specifically, the sheave device 25 has a pair of support bodies 21 that are arranged side by side in the front-rear direction with the hook 13 interposed therebetween in order to hang four wire ropes 12. Each support body 21 is formed in a box shape having an opening on the upper surface on the boom tip 30 side in order to pivotally support a plurality of small-diameter rolling wheels 26a and 26c. The upper portion is connected by a connecting portion 24.

  Each support body 21 includes a side plate 21a having a downwardly convex semi-elliptical shape, a back plate 21b on the hook portion side, and a guide plate 21c formed along the convex semi-elliptical shape. In order to prevent the wire rope 12 (see FIG. 2) from coming off the track belt 26b, the guide plate 21c is provided in an arc shape covering the entire outer peripheral portion of the arc track portion 26 from the side surface of the support 21 to the lower surface. ing. And the back surface board 21b consists of a planar board | plate in order to contact | abut with the support body 38 (refer FIG. 2) of the sheave apparatus 35 by the side of the boom front-end | tip part 30 side. A trunnion pin 23 of the hook 13 passes through the substantially central portion of each support body 21 coaxially with the center circle of the wire rope 12 hung around the circular arc track portion 26. And inside each support body 21 so that the trunnion pin 23 may be enclosed, it is substantially semicircular shape toward the downward direction at equal intervals along a predetermined circular arc, and the rolling wheel 26a of several rolling wheels 26a and 26c. Are arranged.

  Specifically, each of the wheels 26a and 26c is pivotally supported by a wheel support shaft 27 so as to be rotatable. The plurality of wheels 26a, 26c are a load wheel 26a that receives the load around which the wire rope 12 is wound via the track belt 26b, and a support wheel 26c that supports the track belt 26b on the side not receiving the load. It consists of. In this example, a small wheel having the same diameter is adopted as each of the plurality of wheels 26a and 26c, and nine load wheels 26a and two support wheels 26c are arranged. . By mounting many small rollers on the arc track portion 26, the gap between the wheels can be reduced, and the entire arc track portion 26 can be made compact. In addition, if a larger roller than this is employ | adopted, the response | compatibility to the winding speed performance of a wire rope will become high. Moreover, if it is a medium-sized wheel, it will perform about the middle performance of both large and small wheels. Further, a plurality of different diameter wheels may be combined.

The number of small-diameter load rolling wheels 26a constituting the arcuate track portion 26 can be three or more, preferably four or more, and more preferably five or more. In the example of the present embodiment, since nine load rollers 26a are arranged, the wire rope 12 is wound around the plurality of load rollers 26a via the track belt 26b constituting the arc track portion 26. Therefore, smooth winding is possible.
Here, the track belt 26b is composed of a plurality of pieces (shoe) 28 (14 pieces in this example), and one connecting pin 28p (see FIG. 5) through which both ends of the adjacent pieces 28 penetrate in the width direction. 3 (c)), it is formed in a ring shape as a whole.

  Specifically, as shown in FIG. 5, each piece 28 constituting the track belt 26b has a piece main body 28t having a U-shaped cross section. And the groove part 28u of this piece main-body part 28t is a groove | channel matched with the diameter of the wire rope 12 so that the wire rope 12 may be wound, guiding smoothly. Each piece 28 has an annular connection arm 28a (left side of (c)) and a pair of connection arms 28b and 28b (right side of (c)) for pivoting with other adjacent pieces 28. On each end face in the direction connected to. The connecting arm 28a and the pair of connecting arms 28b are formed to have a width that can be pivotably fitted to each other, and in a fitted state, the connecting arms 28a and a pair of connecting arms 28b are inserted into through holes 28c, 28d formed in the connecting arms 28a, 28b, 28b. The connecting pins 28p (see FIG. 3C) are inserted from the axial direction, and the respective pieces 28 are connected in an annular shape.

  Here, the pitch circle of the wire rope 12 when being wound around one conventional large sheave is determined by the “mobile crane structure standard”, but from the arrangement of the plurality of wheels 26a, 26c. In the circular arc track portion 26, the centers of the load rolling wheels 26 a are arranged along one circular arc so that the overall diameter of the circular arc track portion 26 is equal to or larger than the diameter ratio of the wire rope 12 to be used. And the wire rope 12 is wound around the outer peripheral side of the circular arc track portion 26 (crawler-shaped track belt 26b), and the center of the wire rope 12 looped around the circular arc track portion 26 is configured. The ratio between the diameter of the circle and the diameter of the wire rope 12 is secured to a certain value or more. And the wire rope 12 is hung around the circular arc track parts 26 and 26 of the adjacent support bodies 21 and 21, respectively. The proximal end of the wire rope 12 is fixed to the winch 11 (see FIG. 1), and the distal end of the wire rope 12 is fixed to the wire end fixing device 31 (see FIG. 7) of the boom distal end portion 30.

Next, the sheave device 35 of the boom tip 30 will be described.
As shown in FIG. 2, the sheave device 35 is provided at the same position as the conventional sheave mounting position (the center position of the main shaft 40). As shown in FIG. 2, the structure is similar to the sheave device 25, and is a support 38, and an arcuate track portion 36 in which each load wheel 36a is pivotally supported by a wheel support shaft 33. And a boss 37 through which the main shaft 40 is inserted.

  Specifically, as shown in FIG. 4, the support 38 has two side plates 38 a that form a convex semicircular shape at the top. An insertion hole for the main shaft 40 is formed at the center of the lower side of these side plates 38 a, and the peripheral edges of the insertion holes of the two side plates 38 a are fixed to both end surfaces of the boss 37 coaxially with the boss 37. Has been. In addition, the lower surface 38b of the semicircular side plate 38a has a planar shape so as to come into contact with the back plate 21b on the hook portion 20 side when the hook portion 20 is stored. The roller support shaft 33 is attached along the circumferential direction so that the two side plates 38a are coaxial along the convex semicircular periphery of the side plate 38a. Since the height of the boss 37 is the distance between the two side plates 38a, when the circular arc track portion 36 is provided between the side plates 38a, the gaps that allow each load roller 36a to rotate smoothly. The height is considered.

Here, also in the sheave device 35, the plurality of rollers 36a and 36c and the track belt 26b wound around the entire rollers 36a and 36c are configured in the same manner as the circular arc track portion 26 of the sheave device 25 described above. Therefore, the description of the circular arc track portion 36 will be omitted as appropriate.
The arc track portions 36 are arranged such that the centers of the load rolling wheels 36a are arranged along one arc so that the arc track portion 36 as a whole has a diameter equal to or larger than the diameter ratio of the wire rope 12 to be used. And the wire rope 12 is wound around the outer circumference of the arcuate track portion 36. The diameter of the center circle of the wire rope 12 hung around the arcuate track portion 26 and the wire rope 12 The ratio with the diameter is secured above a certain value.

  As described above, in this embodiment, four wire ropes 12 are hooked on the hook portion 20. Therefore, as shown in FIG. 6, the support 38 of the sheave device 35 is disposed so as to rotate 90 ° with respect to the sheave device 25 of the hook portion 20. Two sets of the boom tip end portion 30 that are spaced apart from each other in the axial direction of the main shaft 40 are provided. The width is adjusted to be the same as that between the sheaves 26a. Furthermore, on the same axis as the main shaft 40 (on the left side in the figure), a wire terminal fixing device 31 is provided for processing the tip of the wire rope 12 in the boom in order to fix the terminal of the wire rope 12 (this (For the structure of a kind of wire terminal fixing device, see Japanese Patent No. 2503141).

  Here, as the winch 11 is rolled up and down, the sheave device 35 of the boom tip 30 is also rotated. That is, the sheave device 35 itself may rotate due to the tension of the wire rope 12. Therefore, in the example of the present embodiment, the rotation prevention stopper 29 is provided on the side plate 38a of the sheave device 35 (see FIG. 4), and the guide plate 39 is provided on the boom 7 side (see FIG. 6). The rotation position is regulated by bringing a rotation prevention stopper 29 into contact with the end face (see FIGS. 6 and 8).

The guide plate 39 has an arc shape with a size of a quadrant, and is arranged on the inner side of the side of the tip of the boom tip 30 in order to prevent the wire rope 12 from coming off the arc track portion 36. It is installed. Thereby, rotation of sheave device 35 itself by the tension of wire rope 12 is prevented.
Further, even when the wire rope 12 is wound too much, a rotation prevention stopper is provided on the arc-shaped end surface of the guide plate 39 so that the hook portion 20 does not rotate to a position where it protrudes beyond the end surface of the boom tip 30. 29 is provided at a position where it abuts (see FIGS. 6B and 8). Further, the guide plate 39 is fixed to the boom side so as to be in sliding contact with the outer peripheral portion of the support 38. As shown in FIG. 7, the arc shape of the guide plate 39 is such that the wire rope 12 does not interfere even when the boom rises and falls from about horizontal (0 °) to an elevation angle of about 80 °.

  That is, when the sheave device 35 according to the present invention is used for the sheave of the boom tip portion 30, the undulation angle of the boom 7 is taken into consideration. In the present embodiment, as shown in the figure, the wire rope 12 is configured to maintain a constant curvature so that the undulation angle is within a range of 0 ° to about 80 °. This makes it possible to always keep the “D / d value” of the wire rope 12 wound around the arcuate track portion 36 constant.

  Next, operations and effects of the sheave device 25 and the sheave device 35 of the crane 15 will be described. In the conventional large-diameter sheave, as shown in an example in FIG. 9, since the sheave is combined with the boom tip and the hook, the wire rope is actually wound around the large-diameter sheave. The half of the sheave was only half, and the other half was still playing although the sheave rotated.

  On the other hand, in the crane 15, the sheave device 25 winds the pair of support bodies 21, the plurality of wheels 26a and 26c provided on each support body 21, and the plurality of wheels 26a and 26c as a whole. And the sheave device 35 includes a pair of supports 38, a plurality of rollers 36a, 36c provided on each support 38, and the plurality of rollers 36a. , 36c, and an arc raceway portion 36 having a raceway belt 36b wound around the whole, and the arc raceway portions 26, 36 are arranged such that the centers of the load rollers 26a, 36a are arranged along one arc. In addition, the wire rope 12 is configured to be wound around the outer peripheral side of the arcuate track portions 26, 36, and the diameter of the center circle of the wire rope 12 wound around the arcuate track portions 26, 36 and the wire rope. Since the ratio of the 12 diameter is secured to a certain value or more, it is possible to maintain the curvature applied bending stresses in the wire rope 12 does not become larger than the acceptable overall circular arc track section 26 and 36. Therefore, since the above-described conventional storage distance L2 can be shortened, in the state where the hook portion 20 is in contact with the lower surface of the boom distal end portion 30, the driving visibility when the hook is stored is improved when the front of the boom is stored. At the time of storage, the loading height of the load (see reference numeral H in FIG. 1) can be increased.

  That is, as shown in FIG. 6 (b), the sheave device 35 includes an arcuate track portion 36 and a load wheel 36a among a plurality of small-diameter rollers 36a and 36c arranged in a substantially semicircular shape (radius R). Therefore, the track belt 36b wound around the load roller 36a also forms a substantially semicircular arc shape (radius R). Therefore, the ratio of the diameter (radius R) of the center circle of the wire rope 12 stretched around the track belt 36b and the diameter of the wire rope 12 can be used with a constant value. This also applies to the sheave device 25.

  Therefore, since the curvature which the bending stress applied to the wire rope 12 does not become larger than an allowance as the arcuate track parts 26 and 36 as a whole can be maintained, the pitch circle of the wire rope 12 hung on the arcuate track parts 26 and 36 ( The radius R) can be secured to a diameter satisfying the diameter ratio “D / d value” of the wire rope to be used, which is defined by the “mobile crane structure standard”.

  Then, the wire rope 12 is wound only around the portions of the track belts 26b and 36b that are wound around the respective load rollers 26a and 36a and have a substantially semicircular shape (radius R), thereby efficiently using the sheave device. Thus, half of the occupied size that was played in the conventional large-diameter sheave can be eliminated. Thereby, in the above-described sheave devices 25 and 35, the arc raceways 26 and 36 including the load wheels 26a and 36a, the support wheels 26c and 36c, and the race belts 26b and 36b in the sheave devices 25 and 35 are paired with each other. Therefore, the lift of the crane 15 is increased. Furthermore, when the boom 7 is stored in the vehicle front direction, the distance between the boom 7 and the hook portion 20 can be shortened by the diameter of the conventional large sheave. Therefore, the visibility of the driver when the vehicle is traveling can be improved by the amount that the hook portion 20 is raised upward during storage. Further, as another effect, when the boom 7 is stored in the vehicle rearward direction, the space on the loading platform 5 can be increased by the amount that the hook portion 20 is raised upward during storage. Therefore, there is also an effect that the space on the loading platform can be effectively used, for example, the load can be stacked higher than before.

  In particular, the crane 15 has flat surfaces facing each other of the sheave devices 25, 35. As shown in FIG. 6B, in the retracted state in which the hook portion 20 is in contact with the boom tip portion 30, Since the sheave device 35 of the boom tip 30 rotates about the main shaft 40, the lower surface of the sheave device 35 can be brought into contact with the upper side of the sheave device 25 of the hook portion 20 exactly. Therefore, the above-described conventional storage distance L2 can be shortened to the symbol L1 shown in FIG.

  Therefore, it is preferable to improve the driving field of view when the hook is stored when the boom is stored forward, and to increase the load height (refer to symbol H in FIG. 1) of the load when stored rearward. In addition, since this crane 15 is provided with the wire terminal fixing device 31, since the front-end | tip of the wire rope 12 is processed in a boom by the wire end part fixing device 31 (refer FIG. 7), the sheave device 35 lower surface and The wire rope 12 does not bite when contacting the upper surface of the hook portion 20.

The crane sheave device according to the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the example of the sheave device used for the vehicle-mounted crane has been described. However, the present invention is not limited to this example, and the crane sheave device according to the present invention can be applied to various cranes. . In this example, the four wire ropes are described as an example. However, the present invention is not limited to this, and the wire rope may be used as a sheave device for the two hooks.

DESCRIPTION OF SYMBOLS 1 Vehicle with vehicle-mounted crane 3 Chassis frame 4 Base 6 Column 7 Boom 11 Winch 12 Wire rope 13 Hook 15 Vehicle-mounted crane (crane)
DESCRIPTION OF SYMBOLS 20 Hook part 21 Support body 22 Weight plate 23 Trunnion pin 24 Connection part 25 Sheave device (of hook part) 26 Arc track part (of hook part) 27 Rolling shaft 28 (of hook part) Block 29 Anti-rotation stopper 30 Boom tip 31 Wire end fixing device 32 Overwind alarm device 33 Roller spindle (of the boom tip) 34 Spacer 35 Sheave device 36 (of the boom tip) 36 (Boom tip) Arc track portion 37 Boss (at the tip of the boom) 38 Support body (at the tip of the boom) 39 Guide plate 40 Spindle L1 Storage distance in the sheave device of the present invention L2 Storage distance in the conventional sheave R Wire rope hook Turning radius (= pitch circle of wire rope)

Claims (2)

A sheave device used in a crane having a boom pivotably supported ,
The sheave device includes a first sheave device provided at the tip of the boom so as to work as a fixed pulley, and a second sheave device provided at the hook portion so as to work as a moving pulley,
It said first sheave device, pivotally supported on the first and the support, the first support member which is rotatably supported on the spindle center around the boom tip according to relief of the boom A first arcuate track portion having a plurality of first rolling wheels having a semicircular arc-shaped arrangement that is upwardly convex , and a first track belt that winds the entire plurality of first rolling wheels; With
The second sheave device includes a second support body to which a crane hook is coupled, and a plurality of semicircular arc-shaped arrangements pivotably supported by the second support body and projecting downward. A second arcuate track portion having a second wheel and a second track belt that winds the entire plurality of second wheels,
Each of the first and second plurality of wheels comprises a load wheel that receives a load wound with a wire rope of a crane, and a support wheel that supports the track belt on the side that does not receive the load. A crane sheave characterized in that the center of the wheel has an arrangement along one arc and the wire rope is wound around the outer periphery of the race belt around which each load wheel is wound. apparatus.   The sheave device for a crane according to claim 1, wherein a ratio of a diameter of a central circle of the wire rope hung around the load wheel portion to a diameter of the wire rope is secured to a certain value or more.

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