Patent Description:
There has conventionally been known a mobile crane provided with a swivel base turnable by a hydraulic motor or the like on the frame of a vehicle and with a crane apparatus made up of a telescoping boom, a main winch, a sub-winch, a cabin, and the like on the swivel base. For some cranes, during travelling on a public road, the telescoping boom and like components need to be detached from the swivel base according to a weight limitation or the like. In a hydraulic circuit of a crane with a detachable telescoping boom, the associated hydraulic actuator is also configured to be detachable in addition to the telescoping boom, and thus hydraulic piping connected to the actuator and hydraulic piping connected to a hydraulic pump provided in the vehicle are connected to each other through a joint. In this way, for the crane, a given hydraulic actuator can easily be detached from the hydraulic circuit together with the telescoping boom.

In the hydraulic circuit of the crane with such a configuration, when hydraulic fluid is supplied from a supply-side oil passage while a joint of a return-side oil passage is disconnected, the hydraulic fluid supplied to the hydraulic actuator cannot return from the hydraulic actuator to a hydraulic tank. Consequently, the hydraulic pressure increases with supply of hydraulic fluid in the hydraulic circuit; thus, precaution is made to avoid breakage and oil leakage in the hydraulic actuator by providing a relief valve for releasing hydraulic pressure at a predetermined pressure (relief pressure). However, when the allowable hydraulic pressure of the hydraulic actuator is lower than such a predetermined pressure, even if the relief valve releases hydraulic fluid at the predetermined pressure, the hydraulic actuator is subjected to a hydraulic pressure higher than the allowable hydraulic pressure. For this reason, a known hydraulic circuit is provided with a multi-stage relief valve to change the relief pressure between a low pressure and a high pressure depending on the discharge pressure of the hydraulic pump. An example is described in PTL <NUM>.

The hydraulic circuit described in PTL <NUM> is configured to determine that the return-side joint is connected when the discharge pressure of the hydraulic pump is below a predetermined value while the operating oil is circulated, and to switch the relief pressure of the multi-stage relief valve from the low pressure to the high pressure. Thus, a hydraulic pressure higher than the relief pressure of the low pressure is not applied to the hydraulic circuit until the return-side joint is determined to be connected. However, in the technique described in PTL <NUM>, the hydraulic pressure of the hydraulic circuit goes higher than the predetermined pressure of the relief valve when the discharge of the hydraulic pump exceeds the allowable relief flow rate of the relief valve. Moreover, when the hydraulic actuator is a hydraulic cylinder, because of the structure, the hydraulic pressure in a rod side oil chamber is amplified due to the hydraulic pressure in a head side oil chamber. In other words, in the hydraulic circuit described in PTL <NUM>, when control is made for maximizing the operating speed of the hydraulic actuator, the flow rate of the hydraulic fluid exceeds the allowable relief flow rate of the relief valve, so that the pressure of the head side oil chamber of the hydraulic cylinder may rise and the amplified hydraulic pressure may be applied to the rod side oil chamber.

An object of the present invention is to provide a crane capable of suppressing the supply of hydraulic fluid while in poor connection with a hydraulic circuit to protect the hydraulic cylinder.

According to a first aspect, the present invention provides a crane according to independent claim <NUM>. Further aspects of the present invention are set forth in the dependent claims, the drawings and the following description.

In the crane of the present invention, the connection state of a return side joint providing a connection between the rod side oil chamber and the control valve is determined according to the states of the hydraulic pressures of the rod side oil chamber and head side oil chamber of the hydraulic cylinder. Thus, the actuation of the hydraulic cylinder in poor connection with the hydraulic circuit is suppressed, thereby protecting the hydraulic cylinder.

In the crane of the present invention, the increase rates of the hydraulic pressures of the rod side oil chamber and head side oil chamber in the hydraulic cylinder are suppressed, thereby preventing the application of an excessive hydraulic pressure to the hydraulic cylinder due to the operation by the operator. Thus, the actuation of the hydraulic cylinder in poor connection with the hydraulic circuit is suppressed, thereby protecting the hydraulic cylinder.

In the crane of the present invention, the operator is made recognize a poor connection of the hydraulic cylinder with the hydraulic circuit. Thus, the actuation of the hydraulic cylinder in poor connection with the hydraulic circuit is suppressed, thereby protecting the hydraulic cylinder.

In the crane of the present invention, regardless of whether the operator recognizes a poor connection of the hydraulic cylinder with the hydraulic circuit, supply of hydraulic fluid to the hydraulic cylinder is forcibly stopped. Thus, the supply of hydraulic fluid in poor connection with the hydraulic circuit is suppressed, thereby protecting the hydraulic cylinder.

Crane <NUM> according to one embodiment of a crane will now be described with reference to <FIG>.

As shown in <FIG>, crane <NUM> is a mobile crane relocatable to an unspecified location. Crane <NUM> includes vehicle <NUM> and crane apparatus <NUM>.

Vehicle <NUM> carries crane apparatus <NUM>. Vehicle <NUM> has operator's cab 2A and a plurality of wheels <NUM> and is mounted with engine <NUM> which serves as a power source (see <FIG>). Vehicle <NUM> is configured to transmit the driving force of engine <NUM> to the plurality of wheels <NUM> according to the operation from operator's cab 2A to travel. Vehicle <NUM> is provided with outrigger <NUM>. Outrigger <NUM> is made up of an overhang beam which can be extended by hydraulic pressure in the width direction of vehicle <NUM> toward both sides and hydraulic jack cylinders which can be extended in a direction perpendicular to the ground. In vehicle <NUM>, outrigger <NUM> can be extended in the width direction of vehicle <NUM> and the workable range of crane <NUM> can be extended by grounding the jack cylinders.

Crane apparatus <NUM> lifts an object to be carried, with a wire rope. Crane apparatus <NUM> includes swivel base <NUM>, telescoping boom <NUM>, main hook block <NUM>, sub-hook block <NUM>, derricking cylinder <NUM>, main winch <NUM>, sub-winch <NUM>, main wire rope <NUM>, sub-wire rope <NUM>, cabin <NUM>, and safety apparatus <NUM>.

Swivel base <NUM> makes crane apparatus <NUM> rotatable. Swivel base <NUM> is provided on the frame of vehicle <NUM> through an annular bearing. The annular bearing is disposed such that its rotation axis can be perpendicular to the installation surface of vehicle <NUM>. Swivel base <NUM> is configured to be rotatable about a rotation axis that passes the center of the annular bearing. Moreover, swivel base <NUM> is configured to be rotated through a hydraulic rotation motor which is not shown in the drawing.

Telescoping boom <NUM> serving as a boom supports a wire rope so that an object to be carried can be lifted. Telescoping boom <NUM> is made up of a plurality of boom members: base boom member 8A, second boom member 8B, third boom member 8C, fourth boom member 8D, fifth boom member 8E, and top boom member 8F. The boom members are hollow cylinders with polygonal cross-sections similar to each other. The boom members have such sizes that they can be inserted in one another in descending order of cross sectional area. In other words, top boom member 8F with the smallest cross sectional area has such a size that it can be inserted in fifth boom member 8E with a cross sectional area following that of top boom member 8F. Fifth boom member 8E has such a size that it can be inserted in fourth boom member 8D with a cross sectional area following that of fifth boom member 8E. In this manner, in telescoping boom <NUM>, second boom member 8B, third boom member 8C, fourth boom member 8D, fifth boom member 8E, and top boom member 8F are nested in base boom member 8A, which has the largest cross sectional area, in descending order of cross sectional area.

Moreover, in telescoping boom <NUM>, second boom member 8B, third boom member 8C, fourth boom member 8D, fifth boom member 8E, and top boom member 8F are configured to be movable in the axial direction of telescoping boom <NUM> with respect to base boom member 8A. In other words, telescoping boom <NUM> is configured to be telescopic by moving each boom member with a telescoping cylinder or the like not shown in the drawing. In telescoping boom <NUM>, the base end of base boom member 8A is provided on swivel base <NUM> so that it is swingable. Thus, telescoping boom <NUM> is configured to be horizontally rotatable on the frame of vehicle <NUM>. Further, telescoping boom <NUM> is configured to be swingable about the base end of base boom member 8A with respect to swivel base <NUM>.

The distal end of top boom member 8F of telescoping boom <NUM> is provided with main guide sheave <NUM>, sub-guide sheave <NUM>, main sheave <NUM>, and sub-sheave <NUM>. Main guide sheave <NUM> around which main wire rope <NUM> is wound and sub-guide sheave <NUM> around which sub-wire rope <NUM> is wound are rotatably provided to the back surface of the distal end of top boom member 8F (the side surface of standing telescoping boom <NUM> in the swinging direction). Sub-sheave <NUM> around which sub-wire rope <NUM> is wound and a plurality of main sheaves <NUM> around which main wire rope <NUM> is wound are rotatably provided, in this order from the distal end side, to the ventral surface of the distal end of top boom member 8F (the side surface of standing telescoping boom <NUM> in the direction opposite to the swinging direction). Moreover, jib support unit <NUM> is provided at the distal end of top boom member 8F.

An object to be carried is suspended on main hook block <NUM>. A plurality of hook sheaves 13A around which main wire rope <NUM> is wound, and main hook 13B which suspends an object to be carried are provided to main hook block <NUM>. An object to be carried is suspended on sub-hook block <NUM>. Sub-hook block <NUM> is provided with sub-hook 14A on which an object to be carried is suspended.

Derricking cylinder <NUM> (gray portion) makes telescoping boom <NUM> stand and lie down and holds the attitude of telescoping boom <NUM>. Derricking cylinder <NUM> is composed of a hydraulic cylinder which is made up of cylinder unit 15A and rod unit 15B. In derricking cylinder <NUM>, an end of cylinder unit 15A is swingably coupled to swivel base <NUM> through cylinder-side swinging shaft 15C, and an end of rod unit 15B is swingably coupled to base boom member 8A of telescoping boom <NUM> through rod-side swinging shaft 15D. In derricking cylinder <NUM>, head side oil chamber 15E (see <FIG>) is connected to derricking direct-acting selector valve <NUM> (see <FIG>) of derricking hydraulic circuit <NUM> (see <FIG>) through derricking one side oil passage <NUM> (see <FIG>), and rod side oil chamber 15F (see <FIG>) is connected to derricking direct-acting selector valve <NUM> through derricking other side oil passage <NUM> (see <FIG>). Moreover, derricking cylinder <NUM> includes head side hydraulic sensor <NUM> which is a head side hydraulic detecting section for detecting the value of hydraulic pressure Ph which is the head side hydraulic pressure of head side oil chamber 15E, and rod side hydraulic sensor <NUM> which is a rod side hydraulic detecting section for detecting the value of hydraulic pressure Pr which is the rod side hydraulic pressure of rod side oil chamber 15F. Head side hydraulic sensor <NUM> and rod side hydraulic sensor <NUM> are connected to control apparatus <NUM> which will be described below (see <FIG> and <FIG>).

In derricking cylinder <NUM>, the direction of movement of rod unit 15B is changed by selective supply of hydraulic fluid to head side oil chamber 15E and rod side oil chamber 15F through derricking direct-acting selector valve <NUM>. Thus, in derricking cylinder <NUM>, hydraulic fluid is supplied to head side oil chamber 15E in such a manner that rod unit 15B is pushed out from cylinder unit 15A so that base boom member 8A stands, and hydraulic fluid is supplied to rod side oil chamber 15F in such a manner that rod unit 15B is pushed back to cylinder unit 15A so that base boom member 8A lies down.

As shown in <FIG>, one side joint 16A, which divides derricking one side oil passage <NUM> into a cylinder side part and a switching valve side part, is provided in the middle of derricking one side oil passage <NUM> for connection between head side oil chamber 15E of derricking cylinder <NUM> (gray portion) and derricking direct-acting selector valve <NUM>. Similarly, other side joint 16B, which divides derricking other side oil passage <NUM> into a cylinder side part and a switching valve side part, is provided in the middle of derricking other side oil passage <NUM> for connection between rod side oil chamber 15F of derricking cylinder <NUM> and derricking direct-acting selector valve <NUM>. One side joint 16A and other side joint 16B are configured to close the ends of separated oil passages. Such a configuration prevents hydraulic fluid from flowing out from separated derricking one side oil passage <NUM> and derricking other side oil passage <NUM>. Further, in the middle of a communication line for connection between head side hydraulic sensor <NUM> and control apparatus <NUM>, and between rod side hydraulic sensor <NUM> and control apparatus <NUM>, connector 16C (see <FIG> and <FIG>), which divides the communication line into a sensor side part and a control apparatus <NUM> side part, is provided.

Derricking cylinder <NUM> is separated from swivel base <NUM> and telescoping boom <NUM> upon detachment of cylinder-side swinging shaft 15C and rod-side swinging shaft 15D. Derricking cylinder <NUM> is separated from derricking hydraulic circuit <NUM> (see <FIG>) upon separation of one side joint 16A and other side joint 16B. Further, as for derricking cylinder <NUM>, separation of connector 16C allows head side hydraulic sensor <NUM> and rod side hydraulic sensor <NUM> to be separated from control apparatus <NUM> (see <FIG> and <FIG>). Thus, derricking cylinder <NUM> is configured to be separable from swivel base <NUM>, telescoping boom <NUM>, derricking hydraulic circuit <NUM>, and control apparatus <NUM>.

As shown in <FIG>, main winch <NUM> draws in (winds up) and draws out (winds down) main wire rope <NUM>. Main winch <NUM> is configured such that main drum 17B around which main wire rope <NUM> is wound can be rotated through main hydraulic motor 17A. Main winch <NUM> is provided to swivel base <NUM> so that the rotation shaft of main drum 17B can be orthogonal to the telescoping direction of telescoping boom <NUM>. As for main hydraulic motor 17A, the rotation direction is changed between one direction and the other direction by selective supply of hydraulic fluid to a draw-in side plunger (hereinafter simply referred to as "draw-in side part") and a draw-out side plunger (hereinafter simply referred to as "draw-out side part"). Thus, in main winch <NUM>, hydraulic fluid is supplied such that main hydraulic motor 17A can rotate in one direction and main wire rope <NUM> wound around main drum 17B can thus be drawn out, and hydraulic fluid is supplied such that main hydraulic motor 17A can rotate in the other direction and main wire rope <NUM> can thus be drawn in while being wound around main drum 17B.

Sub-winch <NUM> draws in (winds up) and draws out (winds down) sub-wire rope <NUM>. Sub-winch <NUM> is configured such that sub-drum 18B around which sub-wire rope <NUM> is wound is rotated through sub hydraulic motor 18A. Sub-winch <NUM> is provided to swivel base <NUM> so that the rotation shaft of sub-drum 18B can be orthogonal to the telescoping direction of telescoping boom <NUM>. As for sub hydraulic motor 18A of sub-winch <NUM>, the rotation direction is changed between one direction and the other direction by selective supply of hydraulic fluid to the draw-in side part and the draw-out side part. Thus, in sub-winch <NUM>, hydraulic fluid is supplied such that sub hydraulic motor 18A can rotate in one direction and sub-wire rope <NUM> wound around sub-drum 18B can thus be drawn out, and hydraulic fluid is supplied such that sub hydraulic motor 18A can rotate in the other direction and sub-wire rope <NUM> can thus be drawn in while being wound around sub-drum 18B.

Main wire rope <NUM> is passed from main winch <NUM> to a plurality of main sheaves <NUM> and a plurality of hook sheaves 13A through main guide sheave <NUM> and wound around them. An end of main wire rope <NUM> is fixed to top boom member 8F. Further, sub-wire rope <NUM> from sub-winch <NUM> is connected to sub-hook block <NUM> through sub-guide sheave <NUM> and sub-sheave <NUM>.

Cabin <NUM> covers operator's seat <NUM> (see <FIG>). Cabin <NUM> is provided on a side of swivel base <NUM> adjacent to telescoping boom <NUM>. Operator's seat <NUM> is provided in cabin <NUM>.

As shown in <FIG>, operator's seat <NUM> is provided with rotation telescoping operation tool 22A for performing rotation operation for swivel base <NUM> and telescoping operation for telescoping boom <NUM>, derricking operation tool 22B for performing draw-in and draw-out operation for main winch <NUM> and derricking operation for telescoping boom <NUM>, alarm apparatus 22C serving as an informing section, safety apparatus <NUM> for inputting the work content or the like of crane <NUM>, and power switch <NUM> for crane <NUM>, for example.

Safety apparatus <NUM> is used to set the type of work showing the mode of use of telescoping boom <NUM>, and the number of turns. Safety apparatus <NUM> is made up of a display monitor such as a touch panel. The safety apparatus <NUM> allows various settings to be made from the display screen of the display monitor and serves as an informing section informing the operator of a warning or an alarm.

In crane <NUM> with such a configuration, crane apparatus <NUM> can be moved to an arbitrary position by running vehicle <NUM>. Moreover, in crane <NUM>, the lifting height and operating radius of crane apparatus <NUM> can be increased by making telescoping boom <NUM> stand at an arbitrary derricking angle with derricking cylinder <NUM> and making telescoping boom <NUM> telescope to an arbitrary boom length or connecting a jib. Further, for crane <NUM>, selection can be made between use of main winch <NUM> or use of sub-winch <NUM> according to the weight and the desired lifting rate of the object to be carried. Meanwhile, for crane <NUM>, the allowable lifting load can be changed by changing the number of turns of main wire rope <NUM> according to the weight of the object to be carried.

Derricking hydraulic circuit <NUM> related to derricking cylinder <NUM> in crane <NUM> will be now described with reference to <FIG>.

As shown in <FIG>, derricking hydraulic circuit <NUM> actuates derricking cylinder <NUM>. Derricking hydraulic circuit <NUM> includes derricking cylinder <NUM>, one side joint 16A, other side joint 16B, derricking operation tool 22B, which is an operation tool for hydraulic cylinder, hydraulic pump <NUM>, derricking direct-acting selector valve <NUM>, derricking counter balance valve <NUM>, head side hydraulic sensor <NUM>, rod side hydraulic sensor <NUM>, and control apparatus <NUM>.

In derricking cylinder <NUM>, head side oil chamber 15E (dark gray portion) is connected to one port of derricking direct-acting selector valve <NUM> through derricking one side oil passage <NUM>. Further, in derricking cylinder <NUM>, rod side oil chamber 15F (light gray portion) is connected to the other port of derricking direct-acting selector valve <NUM> through derricking other side oil passage <NUM>. In this case, derricking cylinder <NUM> is configured to be detachable from derricking direct-acting selector valve <NUM> through one side joint 16A. Similarly, derricking cylinder <NUM> is detachable from derricking direct-acting selector valve <NUM> through other side joint 16B. One side joint 16A and other side joint 16B are configured to block the passage of hydraulic fluid when derricking cylinder <NUM> is separated from derricking direct-acting selector valve <NUM>. Such a configuration prevents hydraulic fluid from flowing out from derricking one side oil passage <NUM> and derricking other side oil passage <NUM> from which derricking cylinder <NUM> is separated.

Derricking operation tool 22B controls the behavior of derricking cylinder <NUM>. Derricking operation tool 22B is configured to transmit a pump signal from the electromagnet of derricking direct-acting selector valve <NUM> to control apparatus <NUM>. When located in neutral position S through operation, derricking operation tool 22B transmits a signal that instructs not to excite the electromagnet of derricking direct-acting selector valve <NUM>. When located in standing position U through operation, derricking operation tool 22B transmits a signal that instructs to excite the electromagnet that opens one port of derricking direct-acting selector valve <NUM>, to control apparatus <NUM>. When located in lying position D through operation, derricking operation tool 22B transmits a signal that instructs to excite the electromagnet that opens the other port of derricking direct-acting selector valve <NUM>, to control apparatus <NUM>.

Hydraulic pump <NUM> discharges hydraulic fluid. Hydraulic pump <NUM> is driven by engine <NUM>. Hydraulic fluid discharged from hydraulic pump <NUM> is supplied to derricking direct-acting selector valve <NUM>. Discharged oil passage <NUM> of hydraulic pump <NUM> is provided with relief valve <NUM>.

Derricking direct-acting selector valve <NUM> serving as a control valve switches the direction of hydraulic fluid supplied to derricking cylinder <NUM>. The supply port of derricking direct-acting selector valve <NUM> is connected to hydraulic pump <NUM> through discharged oil passage <NUM>. One port of derricking direct-acting selector valve <NUM> is connected to head side oil chamber 15E of derricking cylinder <NUM> through derricking one side oil passage <NUM>. The other port of derricking direct-acting selector valve <NUM> is connected to rod side oil chamber 15F of derricking cylinder <NUM> through derricking other side oil passage <NUM>. Further, derricking direct-acting selector valve <NUM> is connected to control apparatus <NUM>.

In derricking direct-acting selector valve <NUM>, when the electromagnet is not excited (derricking operation tool 22B is located in neutral position S through operation), derricking one side oil passage <NUM> and derricking other side oil passage <NUM> are closed. This keeps the position of rod unit 15B of derricking cylinder <NUM>. In derricking direct-acting selector valve <NUM>, when the electromagnet is excited such that one port can be opened (when derricking operation tool 22B is located in standing position U through operation), hydraulic fluid from hydraulic pump <NUM> is supplied to head side oil chamber 15E of derricking cylinder <NUM> through derricking one side oil passage <NUM>. Thus, in derricking cylinder <NUM>, rod unit 15B is pushed out from cylinder unit 15A so that telescoping boom <NUM> can stand. In derricking direct-acting selector valve <NUM>, when the electromagnet is excited such that the other port can be opened (when derricking operation tool 22B is located in lying position D through operation), hydraulic fluid from hydraulic pump <NUM> is supplied to rod side oil chamber 15F of derricking cylinder <NUM> through derricking other side oil passage <NUM>. Thus, in derricking cylinder <NUM>, rod unit 15B is pushed back to cylinder unit 15A so that telescoping boom <NUM> can lie down. Although derricking direct-acting selector valve <NUM> is a control valve for controlling the flow rate of hydraulic fluid in this embodiment, this is not necessarily the case and it may be a pressure control valve for controlling the supply pressure.

Derricking counter balance valve <NUM> prevents rod unit 15B of derricking cylinder <NUM> from being pushed back by the load on telescoping boom <NUM>. Derricking counter balance valve <NUM> is provided to derricking one side oil passage <NUM>. Further, derricking counter balance valve <NUM> is configured such that the hydraulic pressure in derricking other side oil passage <NUM> is applied as pilot pressure. Derricking counter balance valve <NUM> always permits hydraulic fluid to flow into head side oil chamber 15E of derricking cylinder <NUM>. On the other hand, derricking counter balance valve <NUM> permits the flow of hydraulic fluid to be discharged from head side oil chamber 15E of derricking cylinder <NUM> only when rod side oil chamber 15F of derricking cylinder <NUM> is supplied with hydraulic fluid.

Head side hydraulic sensor <NUM> and rod side hydraulic sensor <NUM> detect values of hydraulic pressure. Head side hydraulic sensor <NUM> is provided in head side oil chamber 15E of derricking cylinder <NUM>, and is configured to detect hydraulic pressure Ph in head side oil chamber 15E. Rod side hydraulic sensor <NUM> is provided in rod side oil chamber 15F of derricking cylinder <NUM>, and is configured to detect hydraulic pressure Pr in rod side oil chamber 15F. Head side hydraulic sensor <NUM> and rod side hydraulic sensor <NUM> are connected to control apparatus <NUM> through connector 16C. In other words, head side hydraulic sensor <NUM> and rod side hydraulic sensor <NUM> are configured to be detachable from control apparatus <NUM> through connector 16C. Further, head side hydraulic sensor <NUM> and rod side hydraulic sensor <NUM> are supplied with electric power from control apparatus <NUM>.

Crane <NUM> including derricking hydraulic circuit <NUM> with such a configuration controls derricking direct-acting selector valve <NUM> according to a signal from derricking operation tool 22B, thereby changing the flow of hydraulic fluid supplied to derricking cylinder <NUM>. Thus, for crane <NUM>, telescoping boom <NUM> can be freely made stand and lie down with derricking cylinder <NUM> by the operation of derricking operation tool 22B.

Next, with reference to <FIG>, the configuration of control apparatus <NUM> of crane <NUM> with the above-described configuration, determination of a poor connection of derricking cylinder <NUM> through control apparatus <NUM>, and protection control of derricking cylinder <NUM> will be described.

As shown in <FIG>, control apparatus <NUM> controls the operation of derricking cylinder <NUM>. Substantively, control apparatus <NUM> may have a configuration in which a CPU, a ROM, a RAM, and an HDD, for example, are connected through a bus, or may include a one-chip LSI, or the like. Control apparatus <NUM> stores various programs or data for controlling the operation of derricking cylinder <NUM>.

Control apparatus <NUM> is connected to derricking operation tool 22B and can obtain a signal indicating an operational position from derricking operation tool 22B.

Control apparatus <NUM> is connected to alarm apparatus 22C and can issue an alarm through alarm apparatus 22C.

Control apparatus <NUM> is connected to safety apparatus <NUM> and can obtain information such as the type of work input from safety apparatus <NUM> and allows safety apparatus <NUM> to display various information, an alarm, and the like on the screen.

Control apparatus <NUM> is connected to derricking direct-acting selector valve <NUM> and can selectively excite the electromagnet of derricking direct-acting selector valve <NUM> based on the derricking signal obtained from derricking operation tool 22B, thereby switching the position of the spool of derricking direct-acting selector valve <NUM>.

Control apparatus <NUM> is connected to head side hydraulic sensor <NUM> and rod side hydraulic sensor <NUM> and can obtain hydraulic pressure Ph value of head side oil chamber 15E of derricking cylinder <NUM> from head side hydraulic sensor <NUM>, and hydraulic pressure Pr value of rod side oil chamber 15F of derricking cylinder <NUM> from rod side hydraulic sensor <NUM>. Further, control apparatus <NUM> is connected to head side hydraulic sensor <NUM> and rod side hydraulic sensor <NUM> through connector 16C.

Control apparatus <NUM> is connected to battery <NUM> via power switch <NUM> of crane <NUM> and can be supplied with electric power from battery <NUM> by turning on power switch <NUM> while electric power is supplied to head side hydraulic sensor <NUM> and rod side hydraulic sensor <NUM>.

With reference to <FIG>, determination control of a poor connection of derricking cylinder <NUM> of crane <NUM> with the above-described configuration, and protection control of derricking cylinder <NUM> will now be described. In this embodiment, in crane <NUM>, derricking cylinder <NUM> is assembled to swivel base <NUM> and telescoping boom <NUM>.

As shown in <FIG>, control apparatus <NUM> of crane <NUM> is supplied with electric power from battery <NUM> by turning on power switch <NUM>. When power is supplied from battery <NUM>, control apparatus <NUM> starts to supply electric power to head side hydraulic sensor <NUM> and rod side hydraulic sensor <NUM>. In other words, control apparatus <NUM> obtains hydraulic pressure Ph of head side oil chamber 15E at a predetermined interval from head side hydraulic sensor <NUM> and obtains hydraulic pressure Pr of rod side oil chamber 15F at a predetermined interval from rod side hydraulic sensor <NUM>. Receiving a derricking signal (a control signal for derricking direct-acting selector valve <NUM>) from derricking operation tool 22B for the first time after the initiation of supply of electric power to head side hydraulic sensor <NUM> and rod side hydraulic sensor <NUM>, control apparatus <NUM> controls derricking direct-acting selector valve <NUM> so that the amount of hydraulic fluid supplied to derricking cylinder <NUM> can be less than or equal to predetermined value F regardless of the amount of operation of derricking operation tool 22B.

As shown in <FIG>, when hydraulic pressure Pr of rod side oil chamber 15F obtained by the time when predetermined time T elapses is greater than or equal to hydraulic pressure Ph of head side oil chamber 15E (e.g., hydraulic pressure Pr1 or hydraulic pressure Pr2 in <FIG>), control apparatus <NUM> determines that rod side oil chamber 15F (light gray portion) of derricking cylinder <NUM> and derricking direct-acting selector valve <NUM> are not properly connected to each other through other side joint 16B. Control apparatus <NUM> displays a warning on safety apparatus <NUM>, which is a joint informing section, and issues an alarm from alarm apparatus 22C. Further, control apparatus <NUM> controls derricking direct-acting selector valve <NUM> so that the supply of hydraulic fluid to derricking cylinder <NUM> is stopped.

Next, with reference to <FIG>, determination control of a poor connection of derricking cylinder <NUM> and protection control of derricking cylinder <NUM> through control apparatus <NUM> of crane <NUM> will be described. In this embodiment, it is assumed that control apparatus <NUM> of crane <NUM> starts to be supplied with electric power from battery <NUM> by operation of power switch <NUM> after assembling derricking cylinder <NUM>.

As shown in <FIG>, in Step S110, control apparatus <NUM> determines whether or not the control signal of derricking direct-acting selector valve <NUM> has been received from derricking operation tool 22B.

Consequently, if the control signal of derricking direct-acting selector valve <NUM> has been received from derricking operation tool 22B, control apparatus <NUM> advances the process to Step S120.

In contrast, if the control signal of derricking direct-acting selector valve <NUM> has not been received from derricking operation tool 22B, control apparatus <NUM> advances the process to Step S110.

In Step S120, control apparatus <NUM> determines whether or not the control signal of derricking direct-acting selector valve <NUM> has been received from derricking operation tool 22B for the first time after receiving electric power from battery <NUM>.

Consequently, if the control signal of derricking direct-acting selector valve <NUM> has been received from derricking operation tool 22B for the first time after receiving electric power from battery <NUM>, control apparatus <NUM> advances the process to Step S130.

In contrast, if the control signal of derricking direct-acting selector valve <NUM> has already been received from derricking operation tool 22B after receiving electric power from battery <NUM>, control apparatus <NUM> advances the process to Step S170.

In Step S130, control apparatus <NUM> controls derricking direct-acting selector valve <NUM> so that the amount of hydraulic fluid supplied to derricking cylinder <NUM> is less than or equal to predetermined value F, and advances the process to Step S140.

In Step S140, control apparatus <NUM> obtains hydraulic pressure Ph of head side oil chamber 15E and hydraulic pressure Pr of rod side oil chamber 15F and advances the process to Step S150.

In Step S150, control apparatus <NUM> determines whether or not obtained hydraulic pressure Ph of head side oil chamber 15E is greater than hydraulic pressure Pr of rod side oil chamber 15F.

Consequently, if obtained hydraulic pressure Ph of head side oil chamber 15E is determined to be greater than hydraulic pressure Pr of rod side oil chamber 15F, control apparatus <NUM> advances the process to Step S160.

In contrast, if obtained hydraulic pressure Ph of head side oil chamber 15E is determined to be not greater than hydraulic pressure Pr of rod side oil chamber 15F, that is, if hydraulic pressure Pr of rod side oil chamber 15F is greater than or equal to hydraulic pressure Ph of head side oil chamber 15E, control apparatus <NUM> advances the process to Step S180.

In Step S160, control apparatus <NUM> determines whether or not predetermined time T has elapsed after the initiation of control of derricking direct-acting selector valve <NUM> so that the amount of hydraulic fluid supplied to derricking cylinder <NUM> is less than or equal to predetermined value F.

Consequently, if it is determined that predetermined time T has elapsed after the initiation of control of derricking direct-acting selector valve <NUM> so that the amount of hydraulic fluid supplied to derricking cylinder <NUM> is less than or equal to predetermined value F, control apparatus <NUM> advances the process to Step S170.

In contrast, if it is determined that predetermined time T has not elapsed after the initiation of control of derricking direct-acting selector valve <NUM> so that the amount of hydraulic fluid supplied to derricking cylinder <NUM> is less than or equal to predetermined value F, control apparatus <NUM> advances the process to Step S140.

In Step S170, control apparatus <NUM> controls derricking direct-acting selector valve <NUM> so that hydraulic fluid supplied to derricking cylinder <NUM> is supplied according to the amount of operation of derricking operation tool 22B, and advances the process to Step S110.

In Step S180, control apparatus <NUM> determines that other side joint 16B has a poor connection, and advances the process to Step S190.

In Step S190, control apparatus <NUM> controls derricking direct-acting selector valve <NUM> so that supply of hydraulic fluid to derricking cylinder <NUM> stops, and advances the process to Step S200.

In Step S200, control apparatus <NUM> informs the operator of an alarm saying that other side joint 16B has a poor connection through safety apparatus <NUM>, which is an informing section, and further informs the operator through alarm apparatus 22C, and advances the process to Step S110.

With this configuration, in crane <NUM>, when electric power is supplied to head side hydraulic sensor <NUM> and rod side hydraulic sensor <NUM> through the operation of power switch <NUM>, it is determined that derricking cylinder <NUM> is assembled to swivel base <NUM> and derricking cylinder <NUM>'s poor connection determination control and protection control are started. In crane <NUM>, the connection state of other side joint 16B, which provides a connection between rod side oil chamber 15F and derricking direct-acting selector valve <NUM>, is determined according to the states of hydraulic pressure Pr of rod side oil chamber 15F and hydraulic pressure Ph of head side oil chamber 15E in derricking cylinder <NUM>. In this case, in crane <NUM>, derricking direct-acting selector valve <NUM> is controlled such that hydraulic fluid supplied to derricking cylinder <NUM> is less than or equal to predetermined value F. The increase rates of hydraulic pressure Pr of rod side oil chamber 15F and hydraulic pressure Ph of head side oil chamber 15E in derricking cylinder <NUM> are suppressed, thereby preventing the application of an excessive hydraulic pressure to derricking cylinder <NUM> due to the operation by the operator. In crane <NUM>, when it is determined that other side joint 16B providing a connection between rod side oil chamber 15F of derricking cylinder <NUM> and derricking direct-acting selector valve <NUM> is not properly connected, derricking direct-acting selector valve <NUM> is controlled such that the supply of hydraulic fluid to derricking cylinder <NUM> is forcibly stopped. Further, in crane <NUM>, the operator is informed of the fact that derricking direct-acting selector valve <NUM> between derricking cylinder <NUM> and derricking hydraulic circuit <NUM> is not properly connected. Thus, the actuation of derricking cylinder <NUM> in poor connection with derricking hydraulic circuit <NUM> is suppressed, thereby properly protecting derricking cylinder <NUM>.

Although the above-described crane <NUM>, which is one embodiment of crane <NUM>, has a configuration including main winch <NUM> and sub-winch <NUM>, this is not necessarily the case, and it is only required that derricking cylinder <NUM> is configured to be detachable from vehicle <NUM>. Further, it is applicable to any hydraulic cylinder that is configured to be detachable from crane <NUM>. The above-described embodiment is mere illustration of a representative mode, and various modifications can be implemented without departing from the scope of the invention.

It is natural that it can be implemented in various other modes, the scope of the present invention is defined by the appended claims.

Claim 1:
A crane (<NUM>), comprising:
- a detachable hydraulic cylinder (<NUM>);
- a control valve (<NUM>);
- a head side joint (16A), a rod side joint (16B);
- a control apparatus (<NUM>);
the detachable hydraulic cylinder (<NUM>) including a head side oil chamber (15E) and a rod side oil chamber (15F), the head side oil chamber (15E) being detachably connectable to the control valve (<NUM>) through the head side joint (16A), the rod side oil chamber (15F) being detachably connectable to the control valve (<NUM>) through the rod side joint (16B)
characterized in that a head side hydraulic detecting section (<NUM>) is provided in the head side oil chamber (15E) of the hydraulic cylinder (<NUM>) to detect the hydraulic pressure in the head side oil chamber (15E) and a rod side hydraulic detecting section (<NUM>) is provided in the rod side oil chamber (15F) of the hydraulic cylinder (<NUM>) to detect the hydraulic pressure in the rod side oil chamber (15F)
and the control apparatus (<NUM>) is configured to determine that the rod side oil chamber (15F) and the control valve (<NUM>) are not connected to each other through the rod side joint (16B) when a rod side hydraulic pressure (Pr) measured by the rod side detecting section (<NUM>) becomes greater than or equal to a head side hydraulic pressure (Ph) measured by the head side detecting section (<NUM>) by the time when a predetermined time elapses after supply of electric power to the head side hydraulic detecting section (<NUM>) and the rod side hydraulic detecting section (<NUM>) is started and an operation tool (22B) for operating the hydraulic cylinder switches the control valve (<NUM>) to a state of supplying hydraulic fluid to the head side oil chamber (15E).