1. Field of the Invention
The present invention relates to a crane in which a strut, to which a jib support pendant is connected, is installed at one or both of a leading end portion of a boom and a base end portion of a jib provided on a leading end side of the boom, so that the strut can be rotationally moved in a front-back direction.
2. Description of the Related Art
A luffing crane includes a crane main body including a lower traveling member and an upper slewing member, and a front attachment including a boom (main jib) with a foot thereof attached to the upper slewing member for derricking, a luffing jib (hereinafter simply referred to as a jib) with a foot thereof attached to a leading end portion (boom top) of the boom for rotational movement in an up-down direction, and a jib derricking apparatus.
Base ends of a front strut (also referred to as a front post) and a rear strut (also referred to as a rear post) are attached to the jib derricking apparatus near the foot of the jib or at the boom top and outside a direction in which the jib bends with respect to the boom so that the front strut is located closer to the jib than the rear strut and that the base end portions are rotationally movable in a front-back direction. For the operation and attitude of the struts, a direction in which the strut is proximate to the jib is hereinafter referred to as front, and a direction in which the strut is proximate to the boom is hereinafter referred to as back or rear.
A leading end portion of the front strut is joined to a leading end portion of the jib via a jib supporting leading end side pendant with a length dimension set to a certain value. A leading end portion of the rear strut is connected to a base end portion of the boom via a jib supporting base end side pendant with a length dimension set to a certain value.
Moreover, the leading end portion of the front strut and the leading end portion of the rear strut each include a plurality of sheaves. A jib hoist includes the sheaves of each strut and a wire rope paid out from a jib drum mounted on the crane main body and passed between the sheaves so as to form a plurality of strands.
For the luffing crane, the pieces into which the front attachment is disassembled are normally transported to the site, where the pieces are assembled into the front attachment, which is then attached to the crane main body.
In the assembly of the front attachment, the boom and the jib are sequentially connected to the crane main body on the ground so as to be linearly arranged. Subsequently, the jib derricking apparatus is assembled.
In the assembly of the jib derricking apparatus, first, the base end portions of the front strut and the rear strut are attached to the vicinity of the foot of the jib or to the boom top so as to be rotationally movable in the front-back direction. Then, over the front strut leaned forward along the jib, the rear strut is placed in an angular attitude in which an acute angle is subtended between the front strut and the rear strut. A wiring operation is then performed in which a jib-hoisting wire rope drawn out from the jib drum is passed around the sheaves at the leading end portion of the front strut and the sheaves at the leading end portion of the rear strut.
Then, the rear strut is rotationally moved backward and placed in a backward leaning attitude in which an acute angle is subtended between the rear strut and the boom.
Then, the leading end portion of the backward-leaning rear strut is connected to a second end portion of the base end side pendant with a first end portion thereof connected to the base end portion of the boom, the base end side pendant being disposed above the boom in a slackened manner.
Thereafter, the rear strut is rotationally moved forward to tense the base end side pendant.
After the base end side pendant is tensed, opposite end portions of the leading end side pendant are connected between the leading end portion of the front strut leaned forward along the jib and the leading end portion of the jib.
As means for rotationally moving the rear strut in the front-back direction, a configuration has been proposed in which a cylinder is interposed and attached between a longitudinally intermediate portion of the rear strut and a position on the boom close to the leading end thereof. Such a configuration allows the rear strut to rotationally move forward and backward in conjunction with an extending operation and a contracting operation, respectively, of the cylinder (see, for example, Japanese Patent Application Laid-open No. H8-48489).
However, since the base end side pendant attached between the base end portion of the boom and the leading end portion of the rear strut is set to a certain given length dimension, the tension of the base end side pendant increases rapidly with decreasing degree of slack of the base end side pendant during an operation of rotationally moving the rear strut in the backward leaning angular attitude forward to tense the slack base end side pendant. Thus, when the base end side pendant is tensed, a force needed to rotationally move the rear strut forward gradually increases.
The configuration disclosed in Japanese Patent Application Laid-open No. H8-48489 is such that the rear strut is rotationally moved forward by pushing the longitudinally intermediate portion of the rear strut forward from the rear side by the extending operation of the cylinder interposed between the rear strut and the boom. Thus, when the base end side pendant is tensed, in use of the cylinder the longitudinally intermediate portion of the rear strut needs to be pushed forward by a force in a pushing direction stronger than the tense of the base end side pendant, which acts on the leading end portion of the strut.
Thus, the rear strut is subjected to a heavy bending load by a force exerted on the longitudinally intermediate portion by the cylinder when the base end side pendant is tensed. This leads to the need for a bending strength sufficient to resist the bending load. Hence, disadvantageously, the components of the rear strut correspondingly need to be larger and heavier.
Furthermore, according to the conventional configuration, the cylinder is subjected to a load in a compressing direction as a force reactive to the strong force in the pushing direction, and thus needs to be strong enough to resist buckling.
Thus, an object of the present invention is to provide a crane which can eliminate the need to place a bending load on the longitudinally intermediate portion of the strut when the slack jib support pendant is tensed by rotationally moving the strut connected to the leading end portion of the pendant, which enables a reduction in the structural bending strength of the strut and thus in the weight of the strut, and which can prevent the load in the compressing direction from acting on a member connected to the strut to transmit, to the strut, a force applied by the direct acting apparatus to tense the pendant.
To achieve the above-described object, an aspect of the present invention provides a crane including: a boom; a jib that is provided on a leading end side of the boom; and a strut that is provided at one or both of a leading end portion of the boom and a base end portion of the jib, and to which a jib support pendant is connected, wherein the strut, to which the pendant is connected, is provided with strut rotationally moving means having: a first bar-like member rotationally connected, at a first end portion thereof on one side, to a leading end portion of the strut on an opposite side thereof to a side on which the pendant is connected; and a direct acting apparatus that applies, to the first bar-like member, a force pulling the first bar-like member toward the other side along a longitudinal direction of the first bar-like member.
According to a second aspect of the invention, in the above-described configuration, the strut rotationally moving means serves as a toggle mechanism in which an articulated portion is pushed and pulled by a force of the direct acting apparatus, this articulated portion being formed by connecting, in a stretchable manner, a second end portion of the first bar-like member, whose first end portion is connected to the leading end portion of the strut, with a second bar-like member which is different from the first bar-like member.
According to a third aspect of the invention, in the above-described configuration, the toggle mechanism pushes and pulls the articulated portion of the first bar-like member and the second bar-like member by means of an articulated-portion-driving toggle-mechanism having two link pieces joined together so as to rotate freely and a direct acting apparatus connected to a joining portion between the link pieces.
According to a fourth aspect of the invention, in the above-described configuration, a first link piece of the two link pieces of the articulated-portion-driving toggle-mechanism which is proximate to the strut provided with the strut rotationally moving means is provided so as to have a rotation center disposed coaxially with a rotation center of the strut, and the first link piece comprises means for removably locking the first link piece on the strut so that the first link piece is rotationally moved integrally with the strut.
A according to a fifth aspect of the invention, in the above-described configuration, the first bar-like member, the first end portion of which is connected to the leading end portion of the strut, comprises a contraction mechanism provided in a middle in the longitudinal direction of the first bar-like member and enabling the first bar-like member to contract all over a length thereof.
The crane according to the present invention exerts the following excellent effects.
(1) In an operation of rotationally moving, after the connection of the pendant, the strut in a direction toward the opposite side of the strut to the side, on which the pendant is connected, to tense the pendant, a heavy bending load can be prevented from acting on the strut. Thus, compared to a conventional case where the longitudinally intermediate portion of the strut is pushed against the tension of the pendant, the aspect of the present invention enables a reduction in the structural bending strength of the strut and in the weight of the strut.
(2) When the pendant is tensed, only a tensile load acts on the bar-like member in a longitudinal direction thereof. This eliminates the need to take into account possible buckling of the first bar-like member caused by compression and allows the bending rigidity of the first bar-like member to be set to a small value, enabling a reduction in the weight of the bar-like member.
(3) The strut rotationally moving means is configured to serve as a toggle mechanism in which the articulated portion is pushed and pulled by the direct acting apparatus, the articulated portion including the first bar-like member with the first end portion thereof connected to the leading end portion of the strut and the second bar-like member connected to the second end portion of the first bar-like member, the first bar-like member and the second bar-like member being connected together in a stretchable manner. This allows a force acting on the articulated portion to be made weaker than a force needed to directly pull the leading end portion of the strut toward the second end side of the first bar-like member along the longitudinal direction thereof against a tension of the pendant. This enables a reduction in a force to be exerted by the direct acting apparatus and thus in the size and weight of the direct acting apparatus.
(4) As means for exerting a pushing and pulling force on the articulated portion of the toggle mechanism in (3), the articulated-portion-driving toggle-mechanism is adopted which includes the two link pieces rotationally movably connected together and the direct acting apparatus connected to the joining portion between the link pieces. This enables a further reduction in the force to be exerted by the direct acting apparatus.
(5) In the articulated-portion-driving toggle-mechanism, the first link piece of the two link pieces which is proximate to the strut with the strut rotationally moving means is provided so as to have the rotation center disposed coaxially with the rotation center of the strut, and the first link piece includes the means for removably locking the first link piece on the strut so that the first link piece is rotationally movable integrally with the strut. Thus, the direct acting apparatus of the strut rotationally moving means can be utilized to rotationally move the strut forward and backward between an attitude in which the strut is leaned in a direction opposite toward the opposite side of the strut to the side, on which the pendant is connected, and an attitude in which the strut leans toward the side of the strut with the pendant connected thereto. Therefore, in the operation of rotationally moving the strut, the position of center of gravity of the strut can be directly controlled, allowing the strut to be stably rotationally moved.
(6) The first bar-like member with the first end portion thereof connected to the leading end portion of the strut includes the contraction mechanism provided in the middle in the longitudinal direction of the first bar-like member and enabling the first bar-like member to contract all over the length thereof. Due to this configuration, when the strut is leaned in a direction toward the opposite side of the strut to the side on which the pendant is connected, it is possible to prevent the bar-lime member from being stretched.
Embodiments of the present invention will be described below with reference to the drawings.
First, a configuration of a luffing jib crane will be described in brief as an example of the crane according to the present invention.
As shown in an assembled state in
The jib derricking apparatus 5 includes a front strut 6 with a base end portion thereof attached to a support frame 4a provided at a foot of the jib 4 so that the base end portion is rotationally movable in a front-back direction, and a rear strut 7 with a base end portion thereof attached to a support frame 3a provided at a top of the boom 3 so that the base end portion is rotationally movable in a front-back direction.
Moreover, the front strut 6 is connected to a leading end portion of the jib 4 at a leading end portion of the front strut 6 via a jib supporting leading end side pendant (not shown in the drawings) with a length dimension thereof set to a certain value. The rear strut 7 is connected to a base end portion of the boom 3 at a leading end portion of the rear strut 7 via a jib supporting base end side pendant 8 with a length dimension thereof set to a certain value.
A jib hoist 12 includes a sheave 9 provided at the leading end portion of the front strut 6, a sheave 10 provided at the leading end portion of the rear strut 7, and a wire rope 11 paid out from a jib drum (not shown in the drawings) mounted on the crane main body 1 and passed between the sheaves 9 and 10 so as to form a plurality of strands.
In the luffing jib crane configured as described above, assembly of the jib derricking apparatus 5 needs rotational movement of the rear strut 7 in the front-back direction as shown in a procedure shown in
Thus, the rear strut 7 of the jib derricking apparatus 5 includes such a jib derricking apparatus assembly apparatus (hereinafter referred to as an assembly apparatus) 13 as shown in
A base end portion of a cylinder 14 serving as a direct acting apparatus is attached to the assembly apparatus 13 at a certain distance from a position on a support frame 3a on the boom 3 side where the base end portion of the rear strut 7 is attached toward a position on the support frame 3a where a foot of the jib 4 is attached so that the base end portion can swing in the front-back direction.
A leading end portion of an actuation rod (piston rod) 14a of the cylinder 14 is joined to a link plate 15 serving as a link piece with a substantially triangular cross section as shown in
The link plate 15 shaped substantially like a triangle includes a second pin hole 18 formed in a second corner portion of the link plate 15 positioned above the first corner portion in the attitude shown in
Moreover, the link plate 15 includes an engagement recess portion 20 formed in a third corner portion that projects forward (a direction away from the boom 3) in the attitude shown in
Thus, the link plate 15 is rotationally moved in the front-back direction around the pin 19, which is suitable for the second pin hole 18, by locking the engagement recess portion 20 over the engagement pin 22 attached to the bracket 21 for the rear strut 7 and moving the portion of the rear strut 7 closer to the base end portion thereof in the front-back direction. In this state, the first pin hole 16 in the link plate 15 with the actuation rod 14a of the cylinder 14 connected thereto is located offset from a longitudinal direction of the rear strut 7.
Thus, in the state shown in
Moreover, as shown in
That is, the strut rotationally moving means 23 includes, for example, as the bar-like member, a first link bar 24 having an overall length slightly larger than the overall length of the rear strut 7, and one end in the longitudinal direction thereof is connected to a front end of the leading end portion of the rear strut 7 so that the first link bar 24 is rotationally movable in the front-back direction.
Furthermore, a first end portion of a second link bar 25 serving as a different bar-like member is connected, for rotational movement in the front-back direction, to a position at a certain distance from a position on the support frame 3a at the top of the boom 3 where the base end portion of the rear strut 7 is attached toward a position on the support frame 3a where a foot of the jib 4 is attached. Second end portions of the first link bar 24 and the second link bar 25 are joined together via a joining pin 26 in a stretchable manner. As shown in
Moreover, the articulated portion of the link bars 24 and 25 includes means for displacing the articulated portion in a direction in which the articulated portion is made closer to or separated from the support frame 3a of the boom 3. A toggle mechanism for rotationally moving the whole rear strut 7 forward is formed by pulling the leading end portion of the rear strut 7 in a longitudinal direction of the first link bar 24 in conjunction with displacement of the articulated portion of the link bars 24 and 25 in a direction in which the articulated portion is separated from the support frame 3a on the boom 3 side, that is, the forward displacement of the articulated portion by the means for displacing the articulated portion of the link bars 24 and 25.
For example, as shown in
Thus, when the engagement pin 22 installed in the bracket 21 of the rear strut 7 is removed to unlock the engagement recess portion 20 of the link plate 15 from the bracket 21, a contracting operation of the cylinder 14 rotationally moves the link plate 15 forward around the second pin hole 18. When the link plate 15 rotationally moves forward, a part positioned between the second pin hole 18 and the third pin hole 27 (hereinafter referred to as the part of the link plate 15) functions as a link. Thus, serving as the link, the part of the link plate 15 and the third link bar 28 both in a bent state stretch, and this allows formation of an articulated-portion-driving toggle-mechanism for pushing and displacing the articulated portion of the first and second link bars 24 and 25 in a direction in which the articulated portion is separated from the support frame 3a of the boom 3.
The length dimensions of the part of the link plate 15 and the third link bar 28, functioning as links, are set such that a contracting operation of the cylinder 14 allows the rear strut 7 to be placed in an attitude in which the base end side pendant 8 connected to the leading end portion of the rear strut 7 is tensed, via the articulated-portion-driving toggle-mechanism with the part of the link plate 15 and the third link bar 28 and the toggle mechanism with the first and second link bars 24 and 25, driven by the articulated-portion-driving toggle-mechanism, as shown in
Moreover, in the state shown in
As shown in
When the jib derricking apparatus 5 is assembled in the crane according to the embodiment the present invention including the strut rotationally moving means 23 integrated with the assembly apparatus 13 configured as described above, the boom 3 and the jib 4, forming the front attachment 2, are preliminarily sequentially joined to the crane main body 1, as shown in
Moreover, in the assembly apparatus 13, the engagement recess portion 20 of the link plate 15 is pre-locked around the engagement pin 22 installed on the corresponding bracket 21 of the rear strut 7.
In the above-described initial state, when the assembly of the jib derricking apparatus 5 is started, first, the cylinder 14 is extended by a certain distance as shown in
Thus, a gap is formed between the sheave 10 at the leading end portion of the rear strut 7 and the sheave 9 at the leading end portion of the front strut 6. In this state, a wiring operation is performed in which the wire rope 11 for the jib hoist 12 paid out from the jib drum (not shown in the drawings) on the crane main body 1 is passed between the sheaves 9 and 10 of the front and rear struts 6 and 7 so as to form a predetermined number of strands.
Then, as shown in
When the rear strut 7 is placed in the backward leaning attitude as described above, an upper ends portion of the rear strut 7 is connected to the second end portion of the base end side pendant 8 disposed over the boom 3 in a slackened manner with the first end portion thereof connected to the base end portion of the boom 3.
Then, the engagement pin 22 around which the engagement recess portion 20 of the link plate 15 is locked is removed from the bracket 21. Thus, the link plate 15 is unlocked from the rear strut 7. This allows the load of the rear strut 7 to be received by, instead of the link plate 15, the toggle mechanism with the first and second link bars 24 and 25 of the strut rotationally moving means 23 and the articulated-portion-driving toggle-mechanism including the part of the link plate 15 and the third link bar 28 and configured to drive the articulated portion (the articulated portion of the link bars 24 and 25 joined together via the joining pin 26) of the toggle mechanism by the cylinder 14.
Subsequently, in the operation of the strut rotationally moving means 23, the cylinder 14 is contracted as shown in
After the base end side pendant 8 is tensed as described above, opposite end portions of the leading end side pendant (not shown in the drawings) may be connected between the leading end portion of the front strut 6 leaning forward along the jib 4 and the leading end portion of the jib 4 to complete the assembly of the jib derricking apparatus 5 as in the conventional art.
The jib derricking apparatus 5 may be disassembled by carrying out a procedure reverse to the assembly procedure.
Thus, according to the crane according to the present invention, when an operation is performed in which the rear strut 7 with the base end side pendant 8 connected thereto is rotationally moved forward to tense the base end side pendant 8, the strut rotationally moving means 23 pulls the leading end portion of the rear strut 7 forward. This prevents a heavy bending load from acting on the rear strut 7. Thus, the embodiment of the present invention enables a reduction in the structural bending strength of the rear strut 7 compared to the conventional technique in which the base end side pendant 8 is pushed forward at a middle position thereof against the tension of the base end side pendant 8 to tense the base end side pendant 8. Hence, the weight of the rear strut 7 can be reduced.
Furthermore, the first link bar 24, which pulls the leading end portion of the rear strut 7 forward against the tension of the base end side pendant 8, is subjected only to a tensile load in the longitudinal direction of the first link bar 24. This eliminates the need to take into account possible buckling of the first link bar 24 caused by compression and allows the bending rigidity of the first link bar 24 to be set to a small value, enabling a reduction in the weight of the first link bar 24.
The above-described configuration uses the toggle mechanism configured to push the articulated portion of the first link bar 24 and the second link bar 25 in order to pull the leading end portion of the rear strut 7 forward. Thus, a force exerted forward on the articulated portion of the link bars 24 and 25 can be reduced below a force needed to pull the leading end portion of the rear strut 7 to the second end portion of the first link bar 24 along the longitudinal direction thereof against the tension of the base end side pendant 8.
Moreover, as means for pushing the articulated portion of the first and second link bars 24 and 25, the articulated-portion driving toggle-mechanism is used which includes the third link bar 28 and the part of the link plate 15 rotationally moving the articulated portion by the contracting operation of the cylinder 14. Thus, a force needed for the contracting operation of the cylinder 14 can be made further weaker than a force pushing the articulated portion of the first and second link bars 24 and 25 to pull the leading end portion of the rear strut 7 against the tension of the base end side pendant 8. Therefore, the cylinder 14 is subjected only to a load in a pulling direction when the rear strut 7 is rotationally moved forward to tense the base end side pendant 8. This eliminates the need to take possible buckling of this member into account and allows the bending rigidity of the member to be set to a small value.
Furthermore, the articulated-portion driving toggle-mechanism becomes closer to the toggle mechanism at a timing when the tension of the base end side pendant 8 increases rapidly in conjunction of the forward rotational movement of the rear strut 7 with the base end side pendant 8 connected thereto. Thus, a force exerted by the cylinder 14 via the articulated-portion driving toggle-mechanism can be varied (increased) depending on a variation (increase) in a force needed during the forward rotational movement of the rear strut 7 with the base end side pendant 8 connected thereto. Therefore, the cylinder 14 need not have an excessive margin for the force exerted by the cylinder 14 itself and can thus have a smaller size and a lighter weight than a conventional cylinder configured to push the rear strut 7 forward at a longitudinally middle position thereof against the tension of the base end side pendant 8. Consequently, the crane according to the present invention enables a reduction in costs needed for the cylinder 14.
Moreover, in the specific state as shown in
The assembly apparatus 13 is integrated with the strut rotationally moving means 23 and thus enables both of the following functions to be carried out utilizing the cylinder 14 used by the strut rotationally moving means 23: the function to rotationally move the rear strut 7 forward to tense the base end side pendant 8 and the function to rotationally move the rear strut 7 backward into the backward leaning attitude during a step preceding the step of forward rotational movement. When the rear strut 7 is thus leaned backward, only the weight of the rear strut 7 acts and no strong force in the pushing direction needs to be exerted in order to resist a strong force such as the tension of the base end side pendant 8. Furthermore, when the jib derricking apparatus 5 is disassembled, the assembly apparatus 13 rotationally moves forward the backward-leaning rear strut 7 from which the base end side pendant 8 has been removed, from the backward leaning attitude to the attitude in which the rear strut 7 is leaned forward over and along the jib 4. Also at this time, only the weight of the rear strut 7 acts on the assembly apparatus 13. Thus, the force exerted by the cylinder 14 and the size of the cylinder 14 can be reduced below the force and size of the conventional cylinder without any problem as described above.
Furthermore, in the crane according to the present invention, the cylinder 14 included in the assembly apparatus 13 performs the operation of rotationally moving the rear strut 7 with the base end side pendant 8 not connected thereto forward and backward between the attitude in which the rear strut 7 is leaned forward toward the jib 4 side and the backward leaning attitude as described above. Thus, when the forward-leaning rear strut 7 is leaned backward and when the rear strut 7 is rotationally moved in the opposite direction, the position of center of gravity of the rear strut 7 can be directly controlled. This enables more stable movement than a case where the rear strut 7 is suspended and leaned backward by an accompanying machine.
In the above-described embodiment, the crane according to the present invention includes the strut rotationally moving means 23 integrated with the assembly apparatus 13 so as to enable both of the following functions to be carried out using the common cylinder 14: the function to rotationally move the rear strut 7 forward to tense the base end side pendant 8 and the function to rotationally move the rear strut 7 backward into the backward leaning attitude during the step preceding the step of forward rotational movement. However, if the operation of leaning the rear strut 7 backward is performed by an accompanying machine or a cylinder different from the cylinder used to rotationally move the rear strut 7 forward to tense the base end side pendant 8, the crane according to the present invention may exclusively include the strut rotationally moving means 23 having only the function to rotationally move the rear strut 7 to tense the base end side pendant 8 as shown in
As shown by reference numeral 23A in
A base end portion of the cylinder 32 is rotationally movably supported by the support frame 3a on the boom 3 side.
The link pieces 31a and 31b included in the articulated-portion-driving toggle-mechanism have length dimensions set such that a contracting operation of the cylinder 32 allows a rear strut 7 to be placed, via a toggle mechanism with the first and second link bars 24 and 25 driven by the articulated-portion-driving toggle-mechanism, into an attitude in which a base end side pendant 8 connected to a leading end portion of the rear strut 7 is tensed, as shown in
For convenience of illustration, a jib 4 connected to the top of the boom 3 and members connected to the jib 4 are omitted (this also applies to
The crane according to the present invention including the strut rotationally moving means 23A according to the present embodiment can exert effects similar to the effects of the embodiment shown in
That is, as shown by reference numeral 23B in
The other components are similar to the corresponding components shown in
Similarly to the embodiments shown in
Furthermore, the toggle mechanism with the link bars 24 and 25 allows a force exerted by the cylinder 33 to push an articulated portion of the toggle mechanism forward to tense a base end side pendant 8 to be made weaker than a force needed to pull a leading end portion of the rear strut 7 directly to a second end portion of the link bar 24 along a longitudinal direction thereof against the tension of the base end side pendant 8.
That is, as shown by reference numeral 23C in
The other components are similar to the corresponding components shown in
As is the case with the embodiment shown in
Furthermore, when the rear strut 7 is rotationally moved forward to tense a base end side pendant 8, the cylinder 36 is subjected only to the load in the pulling direction, eliminating the need to take into account possible buckling of the bar-like member 34 caused by compression and allowing the bending rigidity of the bar-like member 34 to be set to a small value. This enables the size and weight of the cylinder 36 to be reduced below the size and weight of the conventional cylinder used to push an intermediate portion of the rear strut 7 against the tension of the base end side pendant 8. Hence, the embodiment of the present invention enables a reduction in costs needed for the cylinder 36.
The present invention is not limited to the above-described embodiments. The rear strut 7 may be applied to a crane that is supported by a frame attached to the foot side of the jib 4. In this case, the members of the strut rotationally moving means 23, 23A, 23B, or 23C, attached to the support frame 3a on the boom 3 side according to the above-described embodiments, may be attached to the frame on the jib 4 side fixed to the position where the rear strut 7 is rotationally movably attached according to the above-described embodiments.
The illustrated lengths and thicknesses of the boom 3, the jib 4, and the front and rear struts 6 and 7 are for convenience of illustration, and the actual dimensions may be properly set.
Furthermore, the size of the link plate 15 and the lengths and thicknesses of the first link bar 24, the second link bar 25, the third link bar 28, and the link pieces 31a and 31b may be properly changed according to the dimensions of the boom 3, the jib 4, and the front and rear struts 6 and 7.
Additionally, the first link bar 24 according to the embodiments in
In the embodiment in
In the above-described embodiments, the strut rotationally moving means 23, 23A, 23B, and 23C are configured to rotationally move the rear strut 7 forward to tense the base end side pendant 8 after the base end side pendant 8 is connected to the leading end portion of the rear strut 7 leaned backward. However, the strut rotationally moving means 23, 23A, 23B, and 23C may be configured to rotationally move the rear strut 7 backward to tense the leading end side pendant (not shown in the drawings) after the second end on the opposite side of the leading end side pendant to the side, on which one end of the leading end side pendant is connected to the leading end portion of the jib 4, is connected to the leading end portion of the front strut 6 leaned forward. In this case, the components of the strut rotationally moving means 23, 23A, 23B, and 23C may be attached to the front strut 6 and the support frame 4a on the jib 4 side instead of the rear strut 7 and the support frame 3a on the boom 3 side.
The strut rotationally moving means 23, 23A, 23B, and 23C may include a direct acting apparatus such as a ball screw instead of the cylinders 14, 32, 33, and 36.
The present invention is applicable to any type of luffing jib crane such as a type in which the jib drum is provided on an attachment or a mast as long as one or both of the leading end portion of boom 3 and the base end portion of the jib 4 include the front strut 6 and the rear strut 7, to which the jib support pendant is connected, so that the front strut 6 and the rear strut 7 are rotationally movable in the front-back direction. Furthermore, the present invention is applicable to a tower jib crane including a jib provided on a leading end side of a boom and a strut provided at either a leading end portion of the boom or a base end portion of the jib and to which a second end portion of a jib support pendant with a first end portion thereof connected to a leading end side of the jib is connected.
In an applied example of the present invention, wire ropes or other cable-like bodies may replace the first link bar 24 and the second link bar 25 according to the embodiment in
Of course, various changes may be made to the embodiments of the present invention without departing from the spirits of the present invention.
Number | Date | Country | Kind |
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2012-186115 | Aug 2012 | JP | national |