EP0731054A1

EP0731054A1 - Mobile reach tower crane

Info

Publication number: EP0731054A1
Application number: EP95900915A
Authority: EP
Inventors: Hiroyuki Sawabe; Shinichi Ohta; Takeshi Ushioda
Original assignee: Komatsu Ltd; Komatsu MEC Corp; Komatsu MEC KK
Current assignee: Komatsu Ltd; Komatsu MEC Corp; Komatsu MEC KK
Priority date: 1993-11-26
Filing date: 1994-11-18
Publication date: 1996-09-11
Also published as: TW302016U; CN1136304A; KR960705733A; JPH07144884A; CN1037425C; WO1995014632A1; EP0731054A4

Abstract

A mobile reach tower crane capable of improving general versatility by using in a normal crane operation and a tower crane operation, and of ensuring safety during work by defining various limitations in response to each operation mode. A main hook (21) is provided to a base boom (61) of a second boom (6), and an auxiliary hook (22) is provided to a upper-end boom (62) of the second boom (6). An operation mode B with use of the main hook (21) or an operation mode A with use of the auxiliary hook (22) can be chosen, in which limitations of the derrick angle, length of the boom, rated load, and boom revolving speed may be defined in each operation mode.

Description

TECHNICAL FIELD

This invention relates to a mobile reach tower crane and, more particularly, to a mobile reach tower crane improved in general versatility as a crane.

BACKGROUND ART

Conventionally, a crane truck, provided with an extendable second boom at the upper end of an extendable first boom, has been facilitated to operate as a tower crane by extending and luffing the second boom and standing the first boom in an approximately upright state.
However, the aforementioned crane truck is designed only for using as the tower crane. In consequence, only one hook can be used, so that a working area and load quantity are limited, resulting in a disadvantage whereby, for example, work is impossible when both the main and auxiliary hooks are used. And further, there is a disadvantage of inferior general versatility, such as a slow revolving speed adapted to the tower crane.

DISCLOSURE OF THE INVENTION

The present invention is for resolving the aforementioned disadvantages of the conventional art, accordingly, it is an object of the present invention to provide a mobile reach tower crane having high general versatility capable of including the main hook and auxiliary hook and changing a revolving speed in response to the selected operation to be able to operate both as a normal crane and the tower crane.
A mobile reach tower crane according to the present invention is characterized by including a main hook provided at a base boom of the second boom, and a auxiliary hook provided at an upper-end boom of the second boom. The controller includes an operation-mode selection switch to choose through the operation-mode selection switch between operation modes of an operation mode B carrying out work with one of the main hook and the auxiliary hook by fixing the first boom and the second boom in a straight line and an operation mode A carrying out work with the auxiliary hook while the first boom stands approximately upright and the second boom is extended and derricked, and limitations in the derrick angles, lengths, rated loads, and boom revolving speeds for the first boom and the second boom may be defined in response to each operation mode selected. The limitation in the boom revolving speed in the operation mode A may be defined at a lower specified value than the limitation in the boom revolving speed in the operation mode B. Further, the controller outputs a stop signal to an automatic stop system to automatically stop an operating drive when values of the derrick angle, the length of the boom, the suspended load and the boom revolving speed exceed specified values during operation.
As for the mobile reach tower crane having the above structure, both of the normal crane operation using the main hook or the auxiliary hook and the tower crane operation can be carried out, resulting in improved general versatility. By selecting the operation mode, the limitations of derrick angle, the length of the boom, rated load, the boom revolving speed and so on can be defined in response to each operation mode, and further, when the limitation exceeds the specified value, the operation is automatically stopped, consequently, work is carried out in safety without considering what the operation mode is.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is a side elevational view of a mobile reach tower crane in an operation mode B according to the preferred embodiment of the present invention;
Fig. 2 is a side elevational view of the mobile reach tower crane in an operation mode A according to the preferred embodiment;
Fig. 3 is a fragmentary diagram of an oil hydraulic circuit capable of selecting a boom revolving speed based on each operation mode according to the preferred embodiment;
Fig. 4 is a block diagram showing a control system of the mobile reach tower crane according to the preferred embodiment;
Fig. 5 is a flow chart showing the action of the mobile reach tower crane according to the preferred embodiment;
Fig. 6 is a fragmentary diagram of the oil hydraulic circuit when a pump shown with Z in Fig. 3 is changed to a variable pump; and
Fig. 7 is a fragmentary diagram of a pilot pressure control when the main control valve shown with Z in Fig. 3 is changed to another control.

BEST MODE FOR CARRYING OUT THE INVENTION

The preferred embodiment of a mobile reach tower crane according to the present invention will be explained in detail below with reference to the attached drawings.
In Fig. 1, a vehicle body 1 capable of moving by using wheels 2 includes a revolvably revolving superstructure 3, in which a first boom 4 and a drivers cab 5 are attached to the revolving superstructure 3. Incidentally, the vehicle body 1, naturally, is moved by using a crawler belt. The first boom 4 is composed of a multistage boom extending in a multiple of stages, in which the base end of the first boom 4 is rotatably attached on the revolving superstructure 3 to be able to luff with a boom cylinder 23. Further, the upper end of the first boom 4 is rotatably attached with the base end of a second boom 6.
In Fig. 2, the second boom 6 is composed of a multistage boom extending in a multiple of stages. The upper end of the second boom 6 can be luffed with a boom cylinder 7. Wires 8 are respectively suspended from a base boom 61 and an upper-end boom 62 of the second boom 6 to respectively hang a main hook 21 and an auxiliary hook 22 from the upper ends of the wires 8. The base end of the wire 8 is extended along the second boom 6 and the first boom 4, and is wound on a winch 24 provided at the upper side of the base end of the first boom 4.
A tower crane operation mode, carrying out work by using the auxiliary hook 22, will be explained below with reference to Fig. 3. In the case of the tower crane operation mode, conventionally, the boom revolving speed should be defined to be slower than in the case of the normal crane operation mode carrying out work while using the main hook, or else it would be in danger caused by the increased a circumferential speed of a suspender while revolving. Therefore, in the embodiment, the revolving speed can be controlled. That is, when the tower crane operation mode is selected, oil discharge from a pump 32 is adapted to be sent through a flow control valve 33 to a revolving motor 34 by a diverter valve 31. As a result, the revolving speed of the revolving superstructure 3 can be controlled.
The pump 32 shown in Y in Fig. 3 may be changed to a variable pump 35 shown in Fig. 6 to control flow in a pilot line by a magnet diverter valve 36. In a different manner, a part shown as Z in Fig. 3 can be changed to a design as shown in Fig. 7 to control flow in a pilot pressure of the main control valve by a pilot operated valve 38 and a control valve 37.
Further, as shown in Fig. 4, a control system for controlling extension and derrick of the first boom 4 and the second boom 6 includes a controller 10. The controller 10 accepts the length and the angle of the first boom 4 input from a first boom length sensor 12 and a first boom angle sensor 13 which are provided in the first boom 4. The controller 10 accepts the length and the angle of the second boom 6 input from a second boom length sensor 14 and a second boom angle sensor 15, and further accepts a load signal input from a pressure sensor 16 detecting the load and a signal input from a revolving speed sensor 19. The output side of the controller 10 is connected to an automatic stop system 17.
In the control system, an operation mode A and an operation mode B are set. The operation mode A is of a mode in which the first boom 4 stands approximately upright, and the second boom 6 is extended and luffed to be used as the tower crane. The operation mode B is of a mode in which the first boom 4 and the second boom 6 are on a straight line to carry out the normal crane operation. The operation modes A and B are each selected by an operation-mode selection switch 18 (see Fig. 5). More specifically, in the operation mode A, the boom revolving speed caused by the revolving superstructure 3 can be set to be lower than in the operation mode B by controlling the aforementioned oil hydraulic circuit (see Fig. 3). Therefore, a revolving movement speed of the suspender can be controlled, resulting in safeness of work.
The operation of the embodiment will be described below with reference to a flow chart in Fig. 5. In the case of the tower crane operation, the operation mode A is selected through the operation-mode selection switch 18. In the operation mode A, derrick angular limitation for the first boom 4 is defined as, for example, 83-75 degrees, and the derrick angular limitation for the second boom 6 is defined to protect a terrain angle from having a negative value. A rated load table is set at less than 1.4 tons. After the first boom 4 is maintained in an approximately upright state, as shown in Fig. 2, by extending the second boom 6 in the horizontal direction, the auxiliary hook 22 can be used in work. After the starting operation, the controller 10 catches an operating attitude, the actual suspender load, the revolving speed and so on based on signal input from the sensors 12 to 16 and 19. The actual suspender load and so on are compared with parameters defined in the operation mode A. When only one of the values of the actual suspended load and so on exceeds the specified value, an automatic stop signal is output to the automatic stop system 17 to stop the operation, resulting in safeness of work.
In the case of the normal crane operation, the operation mode B is selected through the operation-mode selection switch 18. In the operation mode B, the derrick angular limitation of the second boom 6 is the maximum derrick-up angular ±α°, and the terrain angle is protected from having a negative value. Here, it is desirable that α° is a small angle, for example, a value of a digit. Respectively, the length limitation of the second boom 6 is defined as, for example, shorter than 5.5 m, and the rated load table is defined as, for example, less than 4.9 tons. When only one of the values of the actual suspended load and so on during the operation exceeds the parameter, the stop signal is output to the automatic stop system 17 to stop the operation, resulting in safeness of work.
The present invention, as described thus far, one mobile reach tower crane can be used for both operations of the normal crane operation and the tower crane operation. In consequence, the working area is enlarged as compared with the conventional walking tower crane, resulting in greatly improved general versatility. And further, the specified limitation for the boom derrick angle and so on can be defined in each operation mode, so that the operation can be carried out while measurement values in the operation are compared, resulting in certain safeness.

INDUSTRIAL AVAILABILITY

According to the present invention, a normal crane operation and a tower crane operation can be carried out by only one crane truck, resulting in a mobile reach tower crane capable of enlarging a working area, greatly improved general versatility, and ensuring safeness during operation which is caused by setting various limiting values in each operation mode.

Claims

A mobile reach tower crane, in which a second boom extending in a multiple of stages is provided to derrick at the upper end of a first boom extending in a multiple of stages and derricking and a controller controls, said mobile crane comprising:
a main hook attached at a base boom of the second boom; and

a auxiliary hook attached at an upper-end boom of the second boom.
The mobile reach tower crane according to Claim 1, wherein the controller includes an operation-mode selection switch to choose through the operation-mode selection switch between operation modes of an operation mode B carrying out work with one of said main hook and said auxiliary hook by fixing the first boom and the second boom in a vertical straight line and an operation mode A carrying out work with said auxiliary hook while the first boom stands approximately upright and the second boom is extended and derricked, and is defined with limitations in derrick angle, lengths, rated loads, and boom revolving speeds for the first boom and the second boom in response to each said operation mode selected.
The mobile reach tower crane according to Claim 2, wherein the limitation in the boom revolving speed in said operation mode A is defined at a lower specified value than the limitation in the boom revolving speed in said operation mode B.
The mobile reach tower crane according to Claim 1, wherein the controller outputs a stop signal to an automatic stop system to automatically stop operating drive when actual values of the derrick angle, the length of the boom, suspended load and the boom revolving speed exceed specified values during operation.