JP2726236B2 - Jib crane rear post support device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jib crane, and more particularly to a rear post supporting device for a jib crane.

[0002]

2. Description of the Related Art A conventional rear post supporting device for a jib crane will be described with reference to FIG. The figure shows a boom head portion, and a jiblower 2 is provided at the front (left in the figure) of a boom head 1 attached to the tip of a boom (not shown).
And a front post 3 are pivotally connected, and a jib extension (not shown) is connected to the jib blower 2. A rear post 4 is pivotally mounted on the center upper portion of the boom head 1, and a rear post supporting device 5 is interposed between the rear post 4 and the boom head 1.

[0003] The rear post supporting device 5 has a telescopic double tube structure, and a compression coil spring 8 is interposed between an outer cylinder 6 and an inner cylinder 7. During standby, the rear post supporting device 5 supports the weight of the rear post 4 and the weight of the jib elevating rope spanned between the rear post 4 and the front post 3 and the rear post supporting cable spanned between the rear post 4 and the body.

On the other hand, during the lifting operation, a load is applied in a direction to raise the tip of the rear post 4 via the jib elevating rope due to the load of the suspended load, and the rear post rotates due to elongation of the rear post supporting cable and the like. The rear post supporting device 5 expands and contracts in accordance with the fluctuation of the load to absorb the elongation of the rear post supporting cable and the jib elevating rope.

[0005]

The conventional rear post supporting apparatus uses a spring to support the weight of the rear post and the lifting load of the jib elevating rope, so that a large spring is required as the crane apparatus becomes larger. The weight and mounting space of the rear post supporting device increase, and mounting becomes difficult.

Therefore, there arises a technical problem to be solved in order to improve the handling efficiency by miniaturizing the rear post supporting device as much as possible and to improve the working efficiency. The present invention solves the above-mentioned problem. The purpose is to:

[0007]

SUMMARY OF THE INVENTION The present invention is proposed to achieve the above object, and a rear post supporting apparatus for a jib crane which is interposed between a rear post pivotally attached to a tip portion of a boom and the boom. The internal cylinder loosely fitted to the external cylinder of the two-stage telescopic cylinder is made expandable and contractable by hydraulic pressure, the piston and the piston rod internally fitted to the internal cylinder are freely movable, and one end of the two-stage telescopic cylinder is An object of the present invention is to provide a jib crane rear post supporting device that is locked to a boom and the other end is locked to the rear post.

[0008]

The rear post supporting device of the present invention has a two-stage telescopic structure, and the inner cylinder of the first stage can be expanded and contracted by hydraulic pressure. Further, the piston fitted inside the internal cylinder is shut off from the hydraulic system, and expands and contracts by an external force. When the rear post is raised to a predetermined posture by supplying pressure oil to the external cylinder during assembly of the jib crane, the second stage piston rod is contracted due to the weight of the rear post. The rear post is maintained at a predetermined angle by closing the open / close valve or cock of the external cylinder and disconnecting it from the hydraulic pressure source while holding the pressure oil. When a rotational moment in the upright direction is applied to the rear post via a jib elevating rope or the like due to a load at the time of the lifting operation, the freely movable piston rod of the rear post supporting device extends, and the rear post freely rotates. When the suspended load lands and the lifting load disappears, the weight of the rear post and cables causes the piston rod to contract, and the rear post returns to the initial position.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 shows a jib crane 11 in which a tower boom 14 is pivotally mounted on an upper revolving structure 13 of a traveling body 12, and a jib 16 and a rear post 17 are pivotally mounted on a boom head 15 of the tower boom 14 which stands up. A rear post supporting device 18 of a telescopic type is interposed between the rear post 17 and the boom head 15, and a tip end of the rear post 17 and a cable link 14a at a lower portion of the tower boom 14 are connected by splittable rear post supporting cables 19a, 19b. ing. Also, the tip of the jib 16 and the front post 20 are connected by a jib support cable 21.
Pulley devices 22 and 23 provided at the front end portions of the front post 20 and the rear post 17 respectively have jib raising ropes 24.
The end of the jib raising rope 24 is fixed to a jib hoisting drum 25 of the upper swing body 13.

[0010] As shown in FIG.
8, a first piston 27 is fitted into an outer cylinder 26, a second piston 29 is inserted into an inner cylinder 28 connected to the first piston 27, and a piston rod 30 is connected to the second piston 29. I have. The inner cylinder 28 is provided with partitions 28a, 28a so that no hydraulic pressure acts on the second piston 29. Therefore, the internal cylinder 28 expands and contracts by supplying pressure oil to the extension side port 31 or the contraction side port 32 of the external cylinder 26, but the piston rod 30 remains stationary with respect to the internal cylinder 28 unless external force is applied. I do.

When assembling the jib crane 11, the tower boom 14 shown in FIG. 1 is set in a horizontal state, a hydraulic power source (not shown) is connected to the rear post support device 18, the rear post support device 18 is contracted, and the rear post 17 travels. Turn over to the fuselage 12 side. Then, the distal end of the rear post support cable 19a connected to the rear post 17 and the distal end of the rear post support cable 19b connected to the cable link 14a of the tower boom 14 are connected. After that, the rear post supporting device 18 is extended and the rear post 17 is extended.
Stand almost perpendicular to the tower boom 14.

Subsequently, the hydraulic hose from the hydraulic pressure source connected to the rear post supporting device 18 is disconnected, and the auxiliary tank 33 provided on the boom head 15 is connected to the rear post supporting device 1.
8 contraction side port 32 is connected. Then, the extension side port 31 is closed by a self-sealing valve or a cock, and the internal cylinder 28 is stopped at a position supporting the rear post 17 at a predetermined angle.

Thereafter, the tower boom 14 is raised up to a working posture as shown in FIG. 1, and the rear post 17, the rear post supporting cables 19a and 19b and the jib elevating rope 2
4 is supported by the rear post support device 18,
The piston rod 30 of the rear post support device 18 is in a contracted state by a load, and a load is applied to the internal cylinder 28 via the piston rod 30. The pressure oil in the extension-side oil chamber of the external cylinder 26 is compressed by this load, but since the contraction-side port 32 communicates with the spare tank 33, no negative pressure is generated due to the load fluctuation.

During the lifting operation, the jib support cable 21, the jib elevating rope 24, and the rear post support cables 19a and 19b are extended by the load of the suspended load, and the rear post 17 rotates in the upright direction. The piston rod 30 of the device 18 extends with the rotation of the rear post 17 and does not hinder the movement of the rear post 17,
The rear post 17 and the rear post supporting device 18 are not overloaded.

When the suspended load is released, the rear post 1 is contracted with the contraction of the jib support cable 21, the jib elevating rope 24 and the rear post support cables 19 and 19b.
7, the piston rod 30 of the rear post supporting device 18 returns to the most contracted position, and returns to the initial state.

As described above, the rotational displacement of the rear post 17 due to an external force such as wind or the like during the lifting operation is allowed by the freely movable piston rod 30, and the load is prevented from being concentrated on the rear post 17, thereby protecting the mechanism. is there. Note that the present invention is not limited to the above-described embodiment, and various modifications can be made to the external shape and the like of the rear post support device 18, and it goes without saying that the present invention extends to those modifications. It is.

[0017]

According to the present invention, as described in detail in the above embodiment, the rear post of the jib crane is supported by the rear post supporting device in which the piston rod of the telescopic cylinder is freely movable by an external force. The jib crane can be formed easily without obstructing the rotation of the rear post due to the fluctuation, and can be formed to be smaller than the conventional spring-type rear post supporting device, and can be expanded and contracted by hydraulic pressure.

[Brief description of the drawings]

FIG. 1 is a side view of a jib crane according to an embodiment of the present invention.

FIG. 2 is a partially cutaway side view of the rear post supporting device of the present invention.

FIG. 3 is a side view of a boom head of a jib crane, showing a conventional rear post support device.

[Explanation of symbols]

 11 Jib crane 14 Tower boom 15 Boom head 16 Jib 17 Rear post 18 Rear post support device 19a, 19b Rear post support cable 20 Front post 21 Jib support cable 24 Jib elevating rope 26 External cylinder 27 First piston 28 Internal cylinder 29 Second piston 30 Piston rod

Claims (1)

(57) [Claims] In a rear post supporting device of a jib crane interposed between a rear post pivotally attached to a tip portion of a boom and the boom, an inner cylinder loosely fitted to an outer cylinder of a two-stage telescopic cylinder is expanded and contracted by hydraulic pressure. The two-stage telescopic cylinder has one end locked to the boom and the other end locked to the rear post. Rear post support for jib cranes.