EP2388228A1

EP2388228A1 - Boom telescoping control unit

Info

Publication number: EP2388228A1
Application number: EP11166318A
Authority: EP
Inventors: Koichi Shimomura; Jumpei Yamada
Original assignee: Kobelco Cranes Co Ltd
Current assignee: Kobelco Cranes Co Ltd
Priority date: 2010-05-18
Filing date: 2011-05-17
Publication date: 2011-11-23
Anticipated expiration: 2031-05-17
Also published as: JP4998589B2; JP2011241037A; EP2388228B1

Abstract

Provided is a boom telescoping control unit (40) for controlling a telescoping operation of a telescopic boom (10) having a plurality of movable boom members (12b to 12e). The boom telescoping control unit (40) comprises automatic telescoping control means (41) to perform an automatic telescoping control for sequentially moving the movable boom members (12b to 12e) according to a regular boom-telescoping sequence; individual telescoping control means (42) to perform an individual telescoping control for moving only a manually selected one of the movable boom members individually; control switching means (45) including a selector switch (32) for selecting between the automatic telescoping control and the individual telescoping control, wherein the control switching means switches, based on the selection by the selector switch, between the two telescoping controls; automatic-telescoping-control switching prohibition means (43) operative to make a prohibition against switching from the individual telescoping control to the automatic telescoping control, irrespective of the selection by the selector switch (32), under a condition that, when the telescopic control selected by the selector switch (32) is switched from the individual telescoping control to the automatic telescoping control, the movable boom members (12b to 12e) have been moved in a sequence different from the regular boom-telescoping sequence; and switching-prohibition release means (44) to release the prohibition when the entire telescopic boom (10) has been brought into a maximally retracted or extended state.

Description

FIELD OF THE INVENTION

The present invention relates to a boom telescoping control unit for controlling a telescopic motion (extension and retraction) of a telescopic boom having a plurality of boom members capable of relative displacement to telescopically extend and retract the boom.

BACKGROUND ART

Heretofore, there has been known a machine equipped with a telescopic boom, such as a wheel crane, a rough terrain crane or an all terrain crane. The telescopic boom comprises a single fixed boom member constituting a base end thereof and a plurality of movable boom members provided on the side of a distal end of the fixed boom member, that is, on the side of a boom point. The movable boom members are adapted to be moved by a hydraulic cylinder (telescopic cylinder) in a telescoping direction (a direction in which the entire telescopic boom is to be telescopically extended and retracted). To extend and retract the type of telescopic boom, the member to be driven (hereinafter referred to as "target boom member") has to be selected among a plurality of movable boom members constituting the telescopic boom.
JP 9-2781A discloses a control unit for automatically switching a target boom member among a plurality of boom members constituting a telescopic boom. This control unit imparts to the boom members a extending motion sequentially in order from one thereof closest to a boom foot (this boom member is the thickest or largest-diameter one) for extending the telescopic boom, while imparting to the boom members a retracting motion sequentially in order from one thereof closest to a boom point (this boom member is the thinnest or smallest-diameter one) for retracting the telescopic boom. In this specification, the predetermined target-boom-member switching sequence for an automatic telescoping control as described above will be called "regular boom-telescoping sequence", and the displacement amount of each of the movable boom members in an extension direction when the movable boom members are moved in the regular boom-telescoping sequence (the details will be described later) will be called "regular extension amount".
While the automatic telescoping control as described above is effective for a normal crane operation, it is desirable to allow an operator performing maintenance, repair or the like of the telescopic boom to manually select the target boom member, i.e., select one of the movable boom members to be driven. As a control unit for realizing such manual selection of the target boom member, there may be imagined a device capable of performing both of an automatic telescoping control for automatically moving the movable boom members in the telescoping direction according to the regular boom-telescoping sequence and an individual telescoping control for driving only one of the movable boom members manually selected by an operator, in the telescoping direction, while allowing the two telescoping controls to be manually and selectively switched.
The thus imagined control unit, however, would have a problem of difficulty in switching the control from the individual telescoping control into the automatic telescoping control. Since the individual telescoping control involves operations of the respective movable boom members in an irregular sequence different from the regular boom-telescoping sequence and the movable boom members intend to have their respective actual extension amount different from a regular extension amount thereof, the shift from the individual telescoping control to the automatic telescoping control cannot be performed immediately upon the selection of the automatic telescoping control by an operator. Particularly, in a crane equipped with the above telescopic boom and a moment limiting device for limiting a movement of the telescopic boom based on a preset crane capacity, the shift from the individual telescoping control to the automatic telescoping control may make it difficult to ensure the safety by the moment limiting device. Specifically, because the crane capacity is generally set on an assumption that each of the movable boom members has a regular extension amount, the crane operation in an irregular telescoping state where each of the movable boom members has a displacement amount different from the regular extension amount may prevent the moment limiting device from adequate limitation of the movement of the telescopic boom.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a boom telescoping control unit capable of both of an automatic telescoping control for a telescopic boom comprising a plurality of movable boom members and an individual telescoping control of each of the movable boom members based on a manual selection thereof, while allowing the shift from the individual telescoping control to the automatic telescoping control to be performed in an easy and safe manner.
To achieve the above object, the present invention provides a boom telescoping control unit for controlling a telescopic motion of a telescopic boom having a plurality of movable boom members capable of relative displacement to each other to extend and retract the entire telescopic boom. The control unit comprises: automatic telescoping control means operative to sequentially make the movable boom members be moved in a telescoping direction of the telescopic boom according to a predetermined regular boom-telescoping sequence to automatically extend and retract the telescopic boom; individual telescoping control means operative to make only a manually selected one of the movable boom members be moved, individually, in the telescoping direction of the telescopic boom; control switching means including a selector switch for selecting a telescoping control from an automatic telescoping control performed by the automatic telescoping control means and an individual telescoping control performed by the individual telescoping control means, the control switching means being operative to switch the telescoping control to be performed between the automatic telescoping control and the individual telescoping control; automatic-telescoping-control switching prohibition means operative to make a prohibition against switching from the individual telescoping control to the automatic telescoping control irrespective of the selection by the selector switch, on condition that the movable boom members have been moved in a sequence different from the regular boom-telescoping sequence when the telescoping control selected by the selector switch is switched from the individual telescoping control to the automatic telescoping control; and switching-prohibition release means operative to release the prohibition by the control switching prohibition means at the time when the entire telescopic boom is brought into a maximally retracted state or an maximally extended state.
The above "regular boom-telescoping sequence" is preferably a sequence in which the movable boom members are moved in an extending direction in order from the movable boom member closest to a boom foot, that is, closest to a base end of the telescopic boom, to the movable boom member closest to a boom point, that is, closest to a distal end of the telescopic boom, for extending the telescopic boom while the movable boom members are moved in a retracting direction in order from the movable boom member closest to the boom point to the movable boom member closest to the boom foot for retracting the telescopic boom.
In the boom telescoping control unit of the present invention, the telescoping control for the telescopic boom is prevented from being switched from the individual telescoping control to the automatic telescoping control under a condition that the actual extension amount of any one of the movable boom members is inadequate for the automatic telescoping control. Specifically, in the case that the movable boom members have been moved in a sequence different from the regular boom-telescoping sequence in the individual telescoping control, which may make at least one of the actual extension amounts of the respective movable boom members be different from a regular extension amount thereof as mentioned above, the automatic-telescoping-control switching prohibition means makes a prohibition against switching the telescoping control to the automatic telescoping control, even if the automatic telescoping control is selected by the selector switch.
On the other hand, in the case that the entire telescopic boom have been brought into the maximally retracted state or the maximally extended state, which certainly makes the actual extension amount of each of the movable boom members be equal to the regular extension amount even during the performance of the individual telescoping control, the prohibition against the switching to the automatic telescoping control is released by the switching-prohibition release means. In other words, only a trouble-free control switching is automatically permitted.
Operators normally select the automatic telescoping control for a crane operation. Accordingly, the prohibition against switching to the automatic telescoping control in the above manner inhibits the operators from performing the crane operation under an unsuitable condition that the telescopic boom is irregularly telescoped, i.e., under a condition that each of the movable boom members may have an actual extension amount different from the regular extension amount. This provides enhanced safety in operation.
The switching-prohibition release means may release the prohibition against switching to the automatic telescoping control not only in the case that the entire telescopic boom have been brought into the maximally retracted state or the maximally extended state, but also in another condition for preventing problem from occurring due to switching to the automatic telescoping control. For example, it is permitted that the boom telescoping control unit of the present invention may comprise extension-amount storage means operative to store therein respective actual extension amounts of the movable boom members, and the switching-prohibition release means is operative to release the prohibition on condition that the actual extension amounts stored in the extension-amount storage means become equal to their respective regular extension amounts which are assumed extension amounts of the respective movable boom members when the movable boom members have been telescopically moved in the regular boom-telescoping sequence.
The thus configured switching-prohibition release means releases the prohibition as long as the movable boom members have their respective regular extension amounts, even if the telescopic boom is not maximally retracted or extended. This allows the prohibition to be released, with no problem, in a shorter time as compared with the case where the prohibition against switching to the automatic telescoping control is not released except the condition that the telescopic boom is maximally retracted or extended.
The release of the prohibition in the above configuration is performed not only in the case that the plurality of movable boom members are actually moved in the regular boom-telescoping sequence, but also in the case that the movable boom members are moved in a sequence different from the regular boom-telescoping sequence but their movements eventually let the actual extension amount of each of the movable boom members be equal to the regular extension amount.
The boom telescoping control unit of the present invention can be used suitably also in a crane comprising a moment limiting device adapted to set an allowable value of a hoisting load of the telescopic boom so as to limit a tipping moment produced by a weight of the telescopic boom itself and the hoisting load. In this case, it is preferable that the boom telescoping control unit further comprises crane-capacity limiting means operative to make the moment limiting device set the allowable value of the hoisting load to a lower level, when the prohibition against switching to the automatic telescoping control is made, than a level of the hoisting load when the prohibition is not made. The crane-capacity limiting means lowers the allowable value of the hoisting load set by the moment limiting device under the condition that the prohibition against switching to the automatic telescoping control is made, that is, in a situation where at least one of the movable boom members has an irregular extension amount different from the regular extension amount to thereby make it difficult to estimate the tipping moment, thus enhancing safety in crane operation by the crane.
The present invention also provides a crane having a telescopic boom, the crane comprising: a hydraulic circuit for driving the telescopic boom; a moment limiting device adapted to set an allowable value of a hoisting load for the telescopic boom so as to limit an tipping moment produced by a weight of the telescopic boom itself and the hoisting load; and a boom telescoping control unit adapted to input a control signal into the hydraulic circuit as defined in the appended claim 5, the crane-capacity limiting means of the boom telescoping control unit being operative to make the moment limiting device set the allowable value of the hoisting load to a lower level, when the prohibition against switching to the automatic telescoping control is made, than a level of the hoisting load when the prohibition is not made.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a telescopic boom and a hydraulic circuit associated with a control unit of the present invention.
FIG. 2 is an electrical block diagram showing various signals to be input into and output from the control unit to control the hydraulic circuit in FIG. 1.
FIG. 3 is a flowchart showing a routine of the control by the control unit according to a first embodiment of the present invention
FIG. 4 is a flowchart showing a subroutine of an automatic telescoping control in the control routine in FIG. 3.
FIG. 5 is a flowchart showing a control routine in a control unit according to a second embodiment of the present invention.
FIG. 6 is a flowchart showing a control routine in a control unit according to a third embodiment of the present invention.
FIG. 7 is a flowchart showing a control routine in a control unit according to a fourth embodiment of the present invention.
FIG. 8 is a flowchart showing an automatic telescoping control subroutine in the control routine in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

There will be explained various embodiments according to the invention with reference to the drawings. The following embodiments are applied in common to a crane which comprises a telescopic boom 10 shown in FIG. 1 and a telescopic drive mechanism for telescopically driving the telescopic boom 10. In other words, the crane is provided with a boom telescoping control unit according to the present invention, namely, a control unit 40.
The telescopic boom 10 is a box-shaped boom, for example, used in a crane, comprising a plurality of boom members telescopically arranged. Specifically, the telescopic boom 10 comprises a single fixed boom member 11, which is a member on the side of a boom foot which is positioned at a base end of the telescopic boom 10 and mounted to a crane body not shown (the fixed boom member 11 is also called "base boom member" or "first boom member"), and a movable boom member assembly 12 provided on the side of a distal end of the fixed boom member 11, that is, on the side of a boom point which is positioned at a distal end of the telescopic boom 10. The movable boom member assembly 12 includes a plurality of movable boom members. The specific number of movable boom members according to the invention is not limited. The movable boom member assembly 12 shown in FIG. 1 comprises a second boom member 12b, a third boom member 12c, a fourth boom member 12d and a fifth boom member 12e, which are arranged in this order from the boom foot to the boom point of the telescopic boom 10.
The telescopic drive mechanism includes a first telescopic cylinder 16, a second telescopic cylinder 18, and a hydraulic circuit 20. The first and second telescopic cylinders 16 and 18 are connected to the movable boom members to move the movable boom member assembly 12 in a telescoping direction. In other words, the telescopic boom 10 shown in FIG. 1 is telescopically driven in a two-step manner.
The first telescopic cylinder 16 is adapted to move the second boom member 12b and the third boom member 12c of the movable boom member assembly 12. Specifically, the first telescopic cylinder 16 has a base portion 16c, an intermediate portion 16b adapted to be axially telescoped with respect to the base portion 16c, and a head portion 16a adapted to be axially telescoped with respect to the intermediate portion 16b; the head portion 16a, the intermediate portion 16b and the head portion 16c are coupled to the fixed boom member 11, the second boom member 12b and the third boom member 12c, respectively.
Similarly, the second telescopic cylinder 18 is adapted to move the fourth boom member 12d and the fifth boom member 12e of the movable boom member assembly 12. Specifically, the second telescopic cylinder 18 has a base portion 18e, an intermediate portion 18d adapted to be axially telescoped with respect to the base portion 18e, and a head portion 18c adapted to be axially telescoped with respect to the intermediate portion 18d; the head portion 18c, the intermediate portion 18d and the head portion 18e are coupled to the third boom member 12c, the fourth boom member 12d and the fifth boom member 12e, respectively.
The hydraulic circuit 20 is adapted to supply hydraulic fluid to the first and second telescopic cylinders 16 and 18 to impart a telescopic motion to each of the movable boom members comprised in the movable boom member assembly 12, i.e., to extend and retract the first and second telescopic cylinders 16 and 18. Specifically, the hydraulic circuit 20 comprises: a tank 20T which reserves hydraulic fluid; a hydraulic pump 20P adapted to discharge therefrom the hydraulic fluid reserved in the tank 20T; a extension/retraction selector valve 21 connected to a downstream side of the hydraulic pump 20P (the downstream side of the hydraulic pump 20P will hereinafter be referred to generally as "downstream side"); a cylinder selector valve 22 provided on a downstream side of the extension/retraction selector valve 21; and first and second cylinder- telescoping control valves 26 and 28 each connected to a downstream side of the cylinder selector valve 22, the first and second telescopic cylinders 16 and 18 being connected to respective downstream sides of the first and second cylinder- telescoping control valves 26 and 28. The first and second cylinders 16 and 18 discharge return fluid, which is returned to the tank 20T through the extension/retraction selector valve 21.
The extension/retraction selector valve 21 is adapted to switch an fluid passage between the hydraulic pump 20P and the cylinder selector valve 22 so as to allow a movement direction of the first telescopic cylinder 16 or the second telescopic cylinder 18 to be selected between an extension direction and a retraction direction. The cylinder selector valve 22 is adapted to switch an fluid passage on the downstream side of the extension/retraction selector valve 21 between a passage for leading hydraulic fluid from the extension/retraction selector valve 21 to the first cylinder-telescoping control valve 26 and a passage for leading the hydraulic fluid to the second cylinder-telescoping control valve 28. The first cylinder-telescoping control valve 26 is adapted to switch an fluid passage from the cylinder selector valve 22 to the first telescopic cylinder 16 between a passage for moving the intermediate portion 16b of the first telescopic cylinder 16 and a passage for moving the head portion 16a of the first telescopic cylinder 16. Similarly, the second cylinder-telescoping control valve 28 is adapted to switch an fluid passage from the cylinder selector valve 22 to the second telescopic cylinder 18 between a passage for moving the intermediate portion 18d of the second telescopic cylinder 18 and a passage for moving the head portion 18c of the second telescopic cylinder 18.
The control unit 40 controls the driving of the telescopic boom 10 by the first and second hydraulic cylinders 16 and 18 and the hydraulic circuit 20. Specifically, the control unit 40 is operative to input after-mentioned control signals 21 s, 22s, 26s and 28s into the extension/retraction selector valve 21, the cylinder selector valve 22, the first cylinder-telescoping control valve 26 and the second cylinder- telescoping control valve 28 included in the hydraulic circuit 20, respectively, to thereby control supply/discharge of the hydraulic fluid to/from each of the first and second hydraulic cylinders 16 and 18, thus controlling the telescoping operation of the telescopic boom 10.
The control unit 40 has an automatic telescoping control section 41, an individual telescoping control section 42, a control switching section 45, an automatic-telescoping-control switching prohibition section 43, and a switching-prohibition release section 44, as shown in FIG. 3. While details of each operation of the sections will be described later, an outline thereof is as follows.
The automatic telescoping control section 41 is operative to perform an automatic telescoping control for sequentially making the boom members 12b to 12e of the movable boom member assembly 12 be moved, in a telescoping direction of the telescopic boom 10, according to a predetermined regular boom-telescoping sequence to automatically and telescopically move the telescopic boom.
The individual telescoping control section 42 is operative to perform an individual telescoping control for moving only a manually selected one of the boom members 12b to 12e, individually, in the telescoping direction of the telescopic boom 10.
The control switching section 45, which constitutes "control switching means" set forth in the appended claims, in cooperation with an after-mentioned control selector switch 32, is operative to fundamentally switch the boom telescoping control by the control unit 40 to the selected one from the automatic telescoping control and the individual telescoping control by the control selector switch 32.
The switching-prohibition section 43 is operative to make a prohibition against switching from the individual telescoping control to the automatic telescoping control, irrespective of the selection by the selector switch 32, on condition that the movable boom members of the telescopic boom 10 have been operated in a sequence different from the regular boom-telescoping sequence when the control selected by the selector switch 32 is switched from the individual telescoping control to the automatic telescoping control.
The switching-prohibition release section 44 is operative to release the prohibition by the control switching prohibition section 43 at the time when the entire telescopic boom has been brought into a state of maximal retraction or maximal extension.
FIG. 2 is a block diagram showing a signal to be input into the control unit 40 and a signal to be output from the control unit 40.
The crane provided with the control unit 40 comprises a boom-telescoping manual operating device 31, a telescoping-control selector switch 32, a telescoping-target switching permission switch 33, telescopic-boom-length detection means 36, load detection means 37 and a moment limiting device 38, each of which is connected to the control unit 40.
The boom-telescoping manual operating device 31 inputs a telescoping command signal for commanding to extend or retract the telescopic boom 10 (see FIG. 1), into the control unit 40. The boom-telescoping manual operating device 31 has a control lever and a circuit for generating a command signal depending on an operation direction of the control lever, being operative to input a boom-extension command signal 31 a into the control unit 40 corresponding to the operation of the control lever in an extension direction and input a boom-retraction command signal 31b into the control unit 40 corresponding to the operation of the control lever in a retraction direction. The control unit 40 is operative to input a switching signal 21 for telescoping of the telescopic boom 10 into the extension/retraction selector valve 21 to operate the extension/retraction selector valve 21, based on the command signal input from the boom-telescoping manual operating device 31.
The control selector switch 32, which is provided in a crane cab (not shown), is to be manually operated to select a boom telescoping control to be executed by the control unit 40 from the automatic telescoping control performed by the automatic telescoping control section 41 and the individual telescoping control performed by the individual telescoping control section 42.
The control selector switch 32 is operated by an operator for manually selecting one from five items: "automatic telescoping", "2nd boom member", "3rd boom member", "4th boom member" and "5th boom member". Furthermore, the control selector switch 32 inputs an automatic-telescoping-control selection signal 32a into the control unit 40 when the "automatic telescoping" is selected while inputs an individual-telescoping-control selection signal 32b, upon selection of the "n th boom member (where n is an integer of 2 to 5)", for imparting a telescopic motion to only the selected boom member (movable boom member) into the control unit 40.
The telescoping-target switching permission switch 33 is manually operated by an operator to permit, following the finish of a telescopic motion of one of the movable boom members of the movable boom member assembly 12 during the automatic telescoping control, the next one of the boom members to start its telescopic motion. The telescoping-target switching permission switch 33 is provided, for example, to a top (not shown) of the control lever of the boom-telescoping manual operating device 31, so as to allow an operator to push it while manually operating the control lever, and input a permission signal 33a into the control unit 40 in response to the pushing operation.
Thus, the automatic telescoping control in this embodiment is not a full-automatic control of automatically moving all of the movable boom members in a continuous manner, irrespective of operator's intention, but a so-called semi-automatic control of waiting the finish of the telescopic motion of each of the movable boom members and the input of the permission signal 33a, thereafter, for permitting the telescopic motion of the next movable boom member and starting telescopically moving it following the input of the permission signal 33a. Meanwhile, the present invention includes another embodiment with the full-automatic telescoping control. In this embodiment, the telescoping-target switching permission switch 33 can be omitted, and each of the movable boom members are automatically and telescopically moved in a continuous manner based on only the manual operation of the control lever of the boom-telescoping manual operating device.
The telescopic-boom-length detection means 36 detects an actual overall length of the telescopic boom 10 shown in FIG. 1 (the overall length will hereinafter be called simply "telescopic boom length"), specifically, to input a telescopic-boom-length detection signal 36a corresponding to a detected telescopic boom length into the control unit 40. The load detection means 37 detects a hoisting load applied to the boom point of the telescopic boom 10 and inputs a load detection signal 37a corresponding to a detected hoisting load into the control unit 40.
The moment limiting device 38, which is designed to limit a tipping moment of the crane so as to prevent actual tipping, overloading or the like, sets an allowable value of the hoisting load, based on values detected by the telescopic-boom-length detection means 36, the load detection means 37, a boom-angle detector (not shown), etc., respectively. The allowable value is set on an assumption that the actual extension amounts of the respective boom members 12b to 12e of the movable boom member assembly 12 are equal to their respective regular extension amounts. The allowable value, however, may be limited, when a given condition is satisfied, by the control unit 40 (see an after-mentioned third embodiment).
When a value detected by the load detection means 37 is greater than the allowable value, the moment limiting device 38 inputs a stop command signal 38a into the control unit 40 to stop a hoisting operation. It is also possible that each of the telescopic-boom-length detection means 36 and the load detection means 37 is connected to the control unit 40 via the moment limiting device 38.
The control unit 40 may control various other operations, in addition to the telescoping operation of the telescopic boom 10, such as hoisting or lowering of the telescopic boom 10, slewing of a slewing upper structure (not shown), and hoisting.
Next will be described a specific telescoping control operation to be performed by the control unit 40 with reference to the flowcharts shown in FIGS. 3 and 4. The control includes the following routines, which are repeated every a given short period of time.

The control switching section 45 of the control unit 40 detects a control selected through the manual operation of the control selector switch 32 (Step S1), and fundamentally switches an actual control subroutine to the selected control. Specifically, when the "individual telescoping control" is selected (NO in the Step S1), the control switching section 45 switches the control to be performed by the control unit 40 to the individual telescoping control based on the individual telescoping control section 42 (Step S20). On the other hand, when the "automatic telescoping control" is selected (YES in Step S1), the control switching section 45 switches the control to the automatic telescoping control (Step S10) by the automatic telescoping control section 41 on condition that an after-mentioned automatic-telescoping-control switching prohibition flag F1 is OFF (YES in Step S2), while the control switching section 45 does not switch to the automatic telescoping control irrespective of the selection by the control selector switch 32 on condition that the flag F1 is ON (NO in the Step S2). The automatic-telescoping-control switching prohibition flag F1 is selectively set to ON or OFF by the automatic-telescoping-control switching prohibition section 43 and the switching-prohibition release section 44, as described in detail later. Upon the finish of the performance of the individual telescoping control, an automatic- telescoping-control flag F2 is set to OFF (Step S21).

The automatic telescoping control section 41 performs an automatic telescoping control for automatically imparting a telescopic motion to each of the movable boom members (2nd to 5th boom members 12b to 12e) according to the regular boom-telescoping sequence. The automatic telescoping control is used during a normal crane operation.
FIG. 4 shows a subroutine for the automatic telescoping control. Immediately after switching from the individual telescoping control to the automatic telescoping control, the automatic-telescoping-control flag F2 is OFF (Step S21 in FIG. 3 ; NO in Step S11); therefore, after only determining a movable boom member to be moved (hereinafter referred to as "target boom member") based on a current telescopic boom length (Step S12), the control unit 40 changes the automatic-telescoping-control flag F2 to ON (Step S13). In summary, the automatic-telescoping-control flag F2 is set to OFF (1) in its initial state, (2) during the performance of the individual telescoping control (Step S20) , and (3) immediately after switching from the individual telescoping control to the automatic telescoping control, while it is set to ON upon the routine for the automatic telescoping control (the Step S 10) shown in FIG. 4 has been performed continuously two times or more (Step S13), and subsequently will be kept ON during the performance of the automatic telescoping control.

In the Step 12, the automatic telescoping control section 41 determines a target boom member to be telescopically moved from the movable boom member assembly 12, based on the current telescopic boom length, i.e., based on the telescopic-boom-length detection signal 36a. Specifically, it makes judgment on which condition of the following conditions A to D the current telescopic boom length meets, and selects an n th boom member (where n is an integer of 2 to 5; the same applies to the following description) corresponding to the met condition, as a target boom member.

Condition A: (Telescopic boom length) < (2nd length + a)
		→ Select the 2nd boom member 12b
Condition B: (2nd length + α) ≤ (Telescopic boom length) < (3rd length + a)
	→ Select the 3rd boom member 12c
Condition C: (3rd length + a) ≤ (Telescopic boom length) < (4th length + a)
	→ Select the 4th boom member 12d
Condition D: (4th length + α) ≤ (Telescopic boom length)
		→ Select the 5th boom member 12e

Herein, the term "n th length" means an actual overall length of the telescopic boom 10 under a condition that, in FIG. 1, each of the n th boom member and any of the movable boom members located on the side of the base end with respect to the n th boom member is maximally extended, and any of the movable boom members located on the side of the boom point with respect to the n th boom member is maximally retracted. Besides, "a" is a constant (e.g., 0.5 m) for letting a parameter in each of the conditions A to D correspond to the target boom member (the boom member to be selected).
The automatic telescoping control section 41, after setting the automatic-telescoping-control flag F2 to ON (the Step S13), inputs a control signal for imparting a telescopic motion to the selected target boom member into each valve of the hydraulic circuit 20 (Step S 17). Subsequently, performed is a process of judgment on switching the target boom member (Steps S 14 to S16).
This judgment is based on the permission signal 33a of the telescoping-target switching permission switch 33. Specifically, when the permission signal 33a is OFF (NO in Step S14), the selection of the currently target boom member is continued, regardless of the actual telescopic boom length (Step S16). For example, during the extension operation of the telescopic boom 10, even if the 2nd boom member 12b is selected as the target boom member and the extension operation of the 2nd boom member 12b has been completed, an extension operation of the 3rd boom member 12c is not started during the period in which the permission signal 33a is OFF.
When the telescoping-target switching permission switch 33 is operated to change the permission signal 33a from OFF to ON (YES in the Step S14), the next target boom member is allowed to be determined based on the current telescopic boom length (Step S15). In other words, upon the finish of the extension or retraction of the currently selected target member, the movable boom member to be selected as the target boom member is automatically switched to the next movable boom member.
In this way, the automatic telescoping control section 41 in this embodiment switches the target boom member to a next movable boom member only after the manual operation of the telescoping-target switching permission switch 33 (the rise of the permission signal 33a), thus allowing the semi-automatic control, which complies with the regular boom-telescoping sequence while taking the operator's intention into consideration, to be achieved.
Furthermore, the telescoping-target switching permission switch 33, provided on the control lever of the boom-telescoping manual operating device 31 as mentioned above, allows an operator to manually operate both of the telescoping-target switching permission switch 33 and the control lever at the same time, which prevents the efficiency of the operation by the operator from being lowered and inhibits the burden on the operator from being increased.

In this embodiment, the determination of the target boom member in the Step S15 is performed by the judgment on which condition of the following conditions A to G a current telescopic boom length meets. Specifically, the judgment on whether the current telescopic boom length meets each of the conditions A to G is sequentially carried out in this order, and the movable boom member (n th boom member) corresponding to the met condition is selected as the target boom member.

Condition A: (Telescopic boom length) < (2nd length - a)
		→ Select the 2nd boom member 12b
Condition B: (2nd length - a) ≤ (Telescopic boom length) < (2nd length + a)
	→ Switch between the 2nd and 3rd boom members 12b and 12c
Condition C: (2nd length + α) ≤ (Telescopic boom length) < (3rd length - a)
		→ Select the 3rd boom member 12c
Condition D: (3rd length - α) ≤ (Telescopic boom length) < (3rd length + a)
	→ Switch between the 3rd and 4th boom members 12c and 12d
Condition E: (3rd length + a) ≤ (Telescopic boom length) < (4th length - a)
		→ Select the 4th boom member 12d
Condition F: (4th length - a) ≤ (Telescopic boom length) < (4th length + a)
→ Switch between the 4th and the 5th boom member 12d and 12e
Condition G: (4th length + a) ≤ (Telescopic boom length)
		→ Select the 5th boom member 12e

When either of the conditions B, D, F is met, the target boom member is switched to the distal end-side one of the two movable boom members during the extension operation, whereas the target boom member is switched to a base-end-side one (a boom-foot-side one) of the two movable boom members during the extraction operation. For example, in the case where the condition B is met during the extension operation, the target boom member is switched from the 2nd boom member 12b to the 3rd boom member 12c; in the case where the condition B is met during the retraction operation, the target boom member is switched from the 3rd boom member 12c to the 2nd boom member 12b. In the above conditions, "a" is a constant (e.g., 0.5 m) for letting a parameter in each of the conditions A to D correspond to the target boom member (boom member to be selected).
The automatic telescoping control section 41 inputs the control signals 21 s, 22s, 26s and 28s (FIG. 2) for moving the thus determined target boom member into each of the valves 21, 22, 26 and 28 in the hydraulic circuit 20 (the Step S17).

The individual telescoping control section 42 performs an individual telescoping control for making only a manually selected one of the movable boom members be moved individually in the telescoping direction of the telescopic boom. This individual telescoping control is used, for example, during maintenance (or repair, inspection, etc.) of the telescopic boom 10.
The individual telescoping control is not only performed in a first case that the individual telescoping control is selected by the control selector switch 32 but also continued in a second case that the automatic telescoping control is selected while the automatic-telescoping-control switching prohibition section 43 prohibits switching from the individual telescoping control to the automatic telescoping control. Specifically, the individual telescoping control section 42, in the first case, selects a movable boom member (one of the n th boom members 12b to 12e) which is manually selected by an operator using the control selector switch 32, i.e., which is specified by the individual-telescoping-control selection signal 32b, as the target boom member, and then inputs the control signals 21 s, 22s, 26s and 28s into the valves 21, 22, 26 and 28 of the hydraulic circuit 20 respectively to make the selected target boom member be moved. In the second case where, in spite of the selection of the automatic telescoping control by the control selector switch 32, the individual telescoping control is continued due to the automatic-telescoping-control switching prohibition flag F1 of ON, the individual telescoping control section 42 does not output the control signals, that is, keep the telescopic boom 10 in a current state.
On the other hand, upon the finish of the performance of the individual telescoping control, the automatic- telescoping-control flag F2 is set to OFF (Step S21).

< Prohibition against Switching to Automatic Telescoping Control (Steps S31 and S32)>

The automatic-telescoping-control switching prohibition section 43, when the telescoping operation of the telescopic boom 10 fulfils a specific condition (Step S31), sets the automatic-telescoping-control switching prohibition flag F1, which is one for switching the control selected by the control selector switch 32 from the individual telescoping control to the automatic telescoping control, to ON (Step S32).
Specifically, in the Step S31, a judgment is performed on whether the movable booms of the movable boom assembly 12 are operated in a sequence different from the regular boom-telescoping sequence or not. If operated in a sequence different from the regular boom-telescoping sequence (YES in the Step S31), the automatic-telescoping-control switching prohibition flag F1 is set to ON (the Step S32). This produces a prohibition against switching to the automatic telescoping control. If operated in the regular boom-telescoping sequence (NO in the Step S31), the current automatic-telescoping- control switching prohibition flag F1 is maintained.
According to the first embodiment, whether the sequence of the operations of the respective movable boom members conforms to the regular boom-telescoping sequence is judged based on the reference of the telescopic boom length and the target boom member manually selected by the control selector switch 32. Specifically, if the target boom member to be selected in the Step S12 (see FIG. 4) of the automatic telescoping control is different from the actually manually selected target boom member, the telescopic boom is judged as being in an irregularly selected state (YES in the Step S31). The control unit 40 according to the first embodiment further comprises a operation limitation section operative to fundamentally input the stop command signal 38a into the moment limiting device 38 to automatically stop the telescoping operation of the telescopic boom 10, in the case of the judgment of the telescopic boom as being in an irregularly selected state, in addition to the prohibition against switching to the automatic telescoping control switching prohibition. However, upon switching operation of an automatic stop release switch (not shown) provided in the moment limiting device 38 to a "release" position, the telescoping operation of the movable boom members comprised in the movable boom member assembly 12 is permitted in spite of the irregularly selected state.

< Release of Prohibition against Switching to Automatic Telescoping Control (Steps S41 and S42)>

The switching-prohibition release section 44, when the telescoping state of the telescopic boom 10 satisfies a specific condition (YES in Step S41), releases the prohibition against switching to the automatic telescoping control (Step S42). Specifically, the switching-prohibition release section 44, in the Step S41, makes a judgment on whether the state of the telescopic boom 10 satisfies a prohibition release condition that the telescopic boom 10 is brought into a maximally shorten state where the telescopic boom length is equal to a basic length, or into a maximally extended state (longest state), by the individual telescoping control. The switching-prohibition release section 44, only in the case that the prohibition release condition is satisfied (YES in the Step S41), set the automatic-telescoping-control switching prohibition flag F1 to OFF (the Step S42), whereas, in the case of not satisfied (NO in the Step S41), it maintains the automatic-telescoping-control switching prohibition flag F1 in a current state. As described above, the control unit 40 according to the first embodiment has a feature of comprising the automatic-telescoping-control switching prohibition section 43, and the switching-prohibition release section 44, as shown in FIG. 3. The automatic-telescoping-control switching prohibition section 43 makes a prohibition against switching from the individual telescoping control to the automatic telescoping control in the case that the movable boom members are telescopically moved in a sequence different from the regular boom-telescoping sequence during the individual telescoping control (the Step S32), because, in this case, the telescopic boom 10 can be placed in an irregular telescope state where the movable boom members have respective actual extension amounts different from their respective regular extension amounts. Furthermore, the switching-prohibition release section 44, when the telescopic boom 10 has been brought into the maximally retracted or maximally extended state by the manual operation in the individual telescoping control, releases the prohibition against switching to the automatic telescoping control (the Step S42), because the maximal extension or retraction of the telescopic boom 10 always makes an actual extension amount of each of the movable boom members be equal to the regular extension amount.
The above prohibition against switching to the automatic telescoping control is effective in enhancing safety in a crane operation. Since operators, in general, select the automatic telescoping control for performing a crane operation so as to rely on a machine, the prohibition against switching to the automatic telescoping control can allow the operators to know that the telescopic boom 10 is in the irregular telescope state where the actual extension amounts of the movable boom members are different from their respective regular extension amounts, thereby inhibiting the operators from wrongly performing a crane operation based on the automatic telescoping control in the irregular telescope state.
Next will be described a second embodiment according to the present invention with reference to the flowchart shown in FIG. 5 corresponding to the flowchart in FIG. 3. The second embodiment is the same as the first embodiment except a difference in the following points a to c.

a. The control unit further comprises an extension-amount storage section 46 operative to store respective actual extension amounts of the movable boom members of the movable boom member assembly 12 shown in FIG. 1 (Step S25).
b. The control unit further comprises an extension-amount correction section 47 operative to correct the stored actual extension amounts (Steps S71 and S72).
c. The switching-prohibition release section 44 has a function of removing, when the telescoped state of the telescopic boom 10 is different from the irregular telescope state (YES in Step 43), the prohibition against switching to the automatic telescoping control (Step S42).

The extension-amount storage section 46 stores therein respective actual extension amounts of the movable boom members, i.e., the 2nd to 5th boom members 12b to 12e. Each of the actual extension amounts is calculated based on a change in the telescopic boom length (based on change in the telescopic-boom-length detection signal 36a) and the selection of the target boom member. The storage of the actual extension amounts is performed even during the performance of the automatic telescoping control which cannot cause the irregular telescope state. During the performance of the automatic telescoping control, the actual extension amount can be calculated also by subtracting a sum of respective lengths of the movable boom members on the side of the boom foot with respect to the target boom member from an actual overall length of the telescopic boom 10.
Following the storage of the actual extension amounts, the extension-amount correction section 47, if the telescopic boom 10 is in the maximally retracted or extended state (YES in the Step S71), corrects the actual extension amounts stored in the extension-amount storage section 46 (the Step S72). Specifically, the extension-amount correction section 47 corrects the actual extension amounts of the movable boom members to 100% of their respective length when the telescopic boom 10 is maximally extended, while it corrects the actual extension amounts of the movable boom members to 0% of their respective length when the telescopic boom 10 is maximally retracted.
Following the correction, the switching-prohibition release section 44 makes a judgment on whether the telescopic boom 10 is in the irregular telescope state (the Step S43), that is, a judgment whether there is a difference between an actual extension amount of at least one of the movable boom members stored in the extension-amount storage section 46 and the regular extension amount corresponding to the stored extension amount. More specifically, the switching-prohibition release section 44 checks each of the extension amounts of the movable boom members stored in the extension-amount storage section 46, in order from one thereof closest to the boom foot to one thereof closest to the boom point, and determines that the telescopic boom is in the irregular telescope state, if a boom member having an actual extension amount greater than a given value (e.g., 0.5 m) exists on the side of the boom point with respect to a boom member having an actual extension amount of less than the 100% length (± a (e.g., a = 0.5 m)).
When it is determined that the telescopic boom is not in the irregular telescope state (YES in the Step S43), the switching-prohibition release section 44 sets the automatic-telescoping- control switching prohibition flag F1 to OFF to release the prohibition against switching to the automatic telescoping control. If the automatic-telescoping-control switching prohibition flag F1 has been already set to OFF, this is maintained. Meanwhile, the irregular telescope state is ascertained (NO in the Step S43), the switching-prohibition release section 44 keeps the automatic-telescoping-control switching prohibition flag F1 in the current state.
The switching-prohibition release section 44 of the control unit 40 according to the second embodiment releases the prohibition against switching to the automatic telescoping control (the Step S42) on a condition that the actual extension amounts of all of the movable members are equal to their respective regular extension amounts (the Step S43) even if the telescopic boom 10 is not maximally retracted or extended. This enables the prohibition to be adequately released more in a shorter period of time, as compared with the cases where the prohibition against switching to the automatic telescoping control is released only on the condition that the telescopic boom 10 is placed in the maximally retracted or extended state.
There will be described a third embodiment of the present invention with reference to FIG. 6 corresponding to the flowchart in FIG. 3. The third embodiment is the same as the second embodiment except that the third embodiment further includes a crane-capacity limiting section 48 to limit a crane capacity when the telescopic boom is in the irregular telescope state (NO in Step S43).
Specifically, the crane-capacity limiting section 48 is operative to make the moment limiting device 38 set the allowable value of the hoisting load to a lower value when the switching-prohibition release section 44 ascertains the irregular telescope state (NO in the Step S43) than a value when the switching to the automatic telescoping control is permitted, i.e., when the telescopic boom is not in the irregular telescope state. In the third embodiment, the crane-capacity limiting section 48 is configured to input an allowable-value limiting command signal 38b (FIG. 2) for limiting the allowable value to a given value or less into the moment limiting device 38 (Step S81), thereby limiting the crane capacity as compared with a normal state. The allowable value of the hoisting load may be limited to 0 (zero) t, which results in a full prohibition of a crane operation of hoisting a load while permitting only a movement of the telescopic boom 10. Alternatively, the allowable value of the hoisting load may be set to a give value (> 0) enough to reliably avoid damage of the telescopic boom 10. On the other hand, when the telescopic boom is not in the irregular telescope state (YES in the Step S43), the crane-capacity limiting section 48 returns the allowable value of the hoisting load to be set by the moment limiting device 38 to a normal value (Step S82).
In the control unit according to the third embodiment, the crane-capacity limiting section 48 limits the crane capacity when the prohibition against switching to the automatic telescoping control is performed, i.e., the telescopic boom is in the irregular telescope state where an actual extension amount of at least one of the movable boom members is not equal to its regular extension amount, to thus preventing an operator from performing a crane operation of hoisting a load in the irregular telescope state without noticing, thereby further enhancing the safety of the crane operation.
As shown in the flowcharts of FIGS. 7 and 8, which correspond to FIGS. 3 and 4 respectively and discloses an embodiment not included in the present invention, only the crane capacity may be limited without inhibiting the switching to the automatic telescoping control. In FIG. 7, when the automatic telescoping control is selected by the control selector switch 32 (YES in Step S1), the boom telescoping control routine is unconditionally switched to an automatic telescoping control subroutine (Step S410), and the automatic-telescoping-control flag F2 is set to ON (Step S44) when the telescopic boom is not in the irregular telescope state (YES in Step S43).
On the other hand, in the automatic telescoping control (the Step S410), the target boom member is determined, irrespective of the telescopic boom length (Steps S418, S419a and S419b), as shown in FIG. 8, when the telescopic boom is in the irregular telescope state (NO in Step S 11); , the target boom member is set based on the telescopic boom length (Steps S 14 to S16) when the telescopic boom is not in the irregular telescope state (YES in Step S 11), the target boom member is set based on the telescopic boom length (Steps S 14 to S16).
In the Steps 418, there is made a judgment on whether the telescoping operation is an extension operation or a retraction operation. In the case of not extension operation (NO in the Step S418), the target boom member is selected from the movable boom members in order from one thereof closest to the boom point, irrespective of the telescopic boom length. Then, following the finish of the retraction operation of the selected target boom member, an adjacent one of the movable boom members on the side of boom foot is newly selected as a next target boom member. More specifically, for example in FIG. 1, the 5th boom member 12e as a movable boom member closest to the boom point is firstly retracted. Then, following the finish of the retraction operation of the 5th boom member 12e (for example, after a given time from the time at which a change in the telescopic boom length has been stopped), an retraction operation of the adjacent 4th boom member 12d is started. Switching will be thus sequentially performed in the order from the boom point to the boom foot.
On the other hand, in the case of the extension operation of the telescopic boom 10 (YES in the Step S418), the target boom member is selected from the movable boom members in order from one thereof closest to the boom foot (from the 2nd boom member 12b, regardless of a length of the telescopic boom 10 (see FIG. 1). Then, following the finish of the extension operation of the selected target boom member, an adjacent (boom-point-side) one of the movable boom members is selected as a next target boom member. In other words, performed is an operation reverse to the Step S419a.
The present invention is not limited to the above embodiments. For example, the control unit 40 may additionally have a function of controlling an indicator adapted to indicate an occurrence of the irregular telescope state where an actual extension amount of each of the movable boom members is not equal to a regular extension amount thereof, and/or a settlement of the irregular telescope state, within a crane cab. The indication lets an operator know the present or absence of the irregular telescope state, thereby more effectively preventing a normal crane operation from being continuously performed in the irregular telescope state.
The number of boom members of the telescopic boom 10 shown in FIG. 1 can be changed. Means for driving the movable boom members is not limited to the telescopic cylinder; for example, in place of or in addition to the telescopic cylinder, there may be employed a wire rope for telescopically driving the movable boom members. For example, there may be a 6th boom member and a 7th boom member to be attached to the side of a distal end of the 5th boom member 12e so as to be telescopically and simultaneously driven by the wire rope. In this case, the above telescoping control may be performed for the 2nd to 5th boom members 12b to 12e.
Provided is a boom telescoping control unit (40) for controlling a telescoping operation of a telescopic boom (10) having a plurality of movable boom members (12b to 12e). The boom telescoping control unit (40) comprises automatic telescoping control means (41) to perform an automatic telescoping control for sequentially moving the movable boom members (12b to 12e) according to a regular boom-telescoping sequence; individual telescoping control means (42) to perform an individual telescoping control for moving only a manually selected one of the movable boom members individually; control switching means (45) including a selector switch_(32) for selecting between the automatic telescoping control and the individual telescoping control, wherein the control switching means switches, based on the selection by the selector switch, between the two telescoping controls; automatic-telescoping-control switching prohibition means (43) operative to make a prohibition against switching from the individual telescoping control to the automatic telescoping control, irrespective of the selection by the selector switch (32), under a condition that, when the telescopic control selected by the selector switch (32) is switched from the individual telescoping control to the automatic telescoping control, the movable boom members (12b to 12e) have been moved in a sequence different from the regular boom-telescoping sequence; and switching-prohibition release means (44) to release the prohibition when the entire telescopic boom (10) has been brought into a maximally retracted or extended state.

Claims

A boom telescoping control unit (40) for controlling a telescoping motion of a telescopic boom (10) having a plurality of movable boom members (12b to 12e) capable of relative displacement to each other to telescopically move the entire telescopic boom, the boom telescoping control unit (40) comprising:
automatic telescoping control means (41) operative to sequentially make the movable boom members (12b to 12e) be moved in a telescoping direction of the telescopic boom (10) according to a predetermined regular boom-telescoping sequence to automatically telescopically move the telescopic boom (10);

individual telescoping control means (42) operative to make only a manually selected one of the movable boom members (12b to 12e) be moved, individually, in the telescoping direction of the telescopic boom (10);

control switching means (32, 45) including a selector switch (32) for selecting between an automatic telescoping control performed by the automatic telescoping control means (41) and an individual telescoping control performed by the individual telescoping control means (42), the control switching means (32, 45) being operative to switch between the automatic telescoping control and the individual telescoping control, based on the selection by the selector switch (32);

automatic-telescoping-control switching prohibition means (43) operative to make a prohibition against switching from the individual telescoping control to the automatic telescoping control irrespective of the selection by the selector switch (32), on condition that the movable boom members (12b to 12e) have been moved in a sequence different from the regular boom-telescoping sequence when the telescoping control selected by the selector switch (32) is switched from the individual telescoping control to the automatic telescoping control; and

switching-prohibition release means (44) operative to release the prohibition by the control switching prohibition means (43) , when the entire telescopic boom (10) has been brought into a maximally retracted state or a maximally
The boom telescoping control unit (40) as defined in claim 1, wherein the regular boom-telescoping sequence is a sequence in which the movable boom members (12b to 12e) are moved in an extending direction in order from the movable boom member closest to a base end of the telescopic boom to the movable boom member closest one to a distal end of the telescopic boom for extending the telescopic boom (10) while the movable boom members (12b to 12e) are moved in a retracting direction in order from the movable boom member closest to the distal end to the movable boom member closest to the base end for retracting the telescopic boom (10).
The boom telescoping control unit (40) as defined in claim 1 or 2, which further comprises extension-amount storage means (46) operative to store therein respective actual extension amounts of the movable boom members (12b to 12e), wherein the switching-prohibition release means (44) is operative to release the prohibition, on condition that the actual extension amounts stored in the extension-amount storage means (46) become equal to their respective regular extension amounts which are assumed extension amounts of the respective movable boom members (12b to 12e) when the movable boom members (12b to 12e) have been telescopically moved in the regular boom-telescoping sequence.
The boom telescoping control unit (40) as defined in any one of claims 1 to 3, which is designed to be used in a crane comprising a moment limiting device (38) to set an allowable value of a hoisting load of the telescopic boom (10) so as to limit a tipping moment produced by a weight of the telescopic boom (10) itself and the hoisting load, wherein the boom telescoping control unit (40) further comprises crane-capacity limiting means (48) operative to make the moment limiting device (38) set the allowable value of the hoisting load to a lower level, when the prohibition against switching to the automatic telescoping control is made by the automatic- telescoping-control switching prohibition means (43), than a level of the hoisting load when the prohibition is not made.
A crane equipped with a telescopic boom (10), comprising:
a hydraulic circuit (20) for driving the telescopic boom (10);

a moment limiting device (38) adapted to set an allowable value of a hoisting load for the telescopic boom (10) so as to limit an tipping moment produced by a weight of the telescopic boom (10) itself and the hoisting load; and

a boom telescoping control unit adapted to input a control signal into the hydraulic circuit (20), wherein the boom telescoping control unit is formed of the boom telescoping control unit (40) as defined in claim 4,

and wherein the crane-capacity limiting means (48) of the boom telescoping control unit (40) is operative to make the moment limiting device (38) set the allowable value of the hoisting load to a lower level, when the prohibition against switching to the automatic telescoping control is made by the automatic-telescoping-control switching prohibition means (43), than a level of the hoisting load when the prohibition is not made.