Patent Number: 055703992
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to the FIGS. 1 to 9. The same reference numerals are attached to the same parts and equivalent parts in FIGS. 1 to 9. FIG. 1 is a schematic vertical sectional view showing a control rod and fuel supporting member gripping apparatus according to the first embodiment of the present invention which is hoisted in a reactor pressure vessel. FIGS. 2 to 8 show the details of respective sections thereof. The CR (control rod) 4 is detachably connected to the CRD (control rod driving mechanism) 8 by means of a bayonet coupling 14 designated by a reference numeral 15. A control rod and fuel supporting metal gripping apparatus 20 which is the first embodiment of the present invention is hoisted and carried into the reactor pressure vessel 1 at the time of the periodic inspection of a boiling water reactor (BWR). The CR 4 and the FS (fuel supporting member) 6 which are mounted in the core are removed and hoisted to be carried out of the reactor pressure vessel 1. The control rod and fuel supporting member gripping apparatus 20 is used for reinstalling the CR 4 and the FS 6 and comprises an upper plate 30 which is tied with a hoisting rope or the like of an auxiliary hoist of a fuel exchanging device, not shown, a CR gripping device 40 which is hoisted by the upper plate 30 so that the device is axially rotatable and an FS gripping device 50 which is mounted on the CR gripping device 40 so that the FS gripping device can be lifted up and down. The upper plate 30 is hoisted on a given lattice of the upper lattice plate 5 as shown in FIGS. 1 and 2 so that the entire weight of the control rod and fuel supporting member gripping apparatus 20 is loaded on the upper lattice plate 30 and the supporting member gripping apparatus 20 is prevented from rotating. An upper plate settling detection lever 30a is disposed on the bottom of the square corner of the upper plate 30 so that the detection lever can be swung freely. When the upper plate 30 is settled on the upper lattice plate 5, the swing end of the upper plate settling detection lever 30a swings and then the upper plate settling detection lever 30a turns "ON" the upper plate settling detection limit switch 30b in order to output an upper plate settling detection signal to the fuel exchanging device or the like through a cable, not shown. A square supporting cylinder 31 is fastened to the upper plate 30 so that the cylinder 31 goes vertically through the center of the upper plate 30 and a square stud 32 is provided on the top center of the supporting cylinder by means of a pin 32a so that the stud 32 can be swung. Thus, it is not possible to easily change the state of the long control rod and fuel supporting metal gripping device 20 from its storage condition in which the gripping device is laid to the state in which the gripping device 20 is vertically hoisted. The square stud 32 has a screw hole 32b formed on the top end as shown in FIGS. 2 and 5. A bolt which is provided on the front end of a wire rope such as a torqueless wire is screwed into the screw hole 32b in order to prevent the auxiliary hoist of the fuel exchanging device from rotating. Thus, it is possible to hoist entirely the control rod and fuel supporting member gripping apparatus 20 freely so that the gripping device is not rotated. The supporting cylinder 31 contains a CR gripping device 40. The CR gripping device 40 contains double internal and external cylinders 41 and 42 which are located coaxially in the supporting cylinder 31. The external cylinder 42 is fastened to the supporting cylinder 31 and the internal rotating cylinder 41 is mounted on the external cylinder by means of a thrust bearing 43a and a radial bearing 43b so that the internal cylinder 41 is axially rotatable. The rotating cylinder 41 has a hook 44 provided on the bottom end thereof which grips and releases the handle 4d as shown in FIGS. 1 and 4. As shown in FIGS. 2 and 6, the rotating cylinder 41 is axially rotatable clockwise and counterclockwise by means of a CR rotating mechanism 45. The CR rotating mechanism 45 contains a rotating gear 45a which is provided on the side in the middle of the rotating cylinder along the length thereof, the rotating gear 45a being interlocked with the rotating cylinder 41. Both ends of the wire 45b which is wound around the rotating gear 45a are wound around pulleys 45c and 45d and connected to both the top and bottom ends of piston rods 45g of a pair of right and left air cylinders 45e and 45d for rotation driving. When the piston rods 45g reciprocate, the rotating cylinder 41 is rotated axially clockwise and counterclockwise. The rotating cylinder 41 is lifted up and down by means of a CR lifting air cylinder 46. When low pressure air is supplied to the lift-up chamber, i.e. lower chamber, in the air cylinder 46, the hook 44 which grips the handle 4d of the CR 4 is lifted up slightly and then the hook 44 is lifted up so as to eliminate a play of the handle 4d thereby making the hook 44 fit to the handle 4d. This mechanism relaxes a shock which occurs when the hook 44 is lifted up all at once. When the supplied air pressure is high, the CR lifting air cylinder 46 lifts the handle 4d higher than a time when a low pressure is supplied, for example, by several tens mm. As shown in FIG. 4, the rotating cylinder 41 incorporates the CR gripping mechanism 47 which is provided on the bottom end of the rotating cylinder 41. The CR gripping mechanism 47 makes the piston rod 47b of the hook opening/closing air cylinder 47a communicate with the swing end of the hook 44 through a link mechanism 47c to change the supply of air to the hook opening/closing air cylinder 47a to the top chamber or the bottom chamber thereby opening or closing the hook 44. Consequently, the handle 4d of the CR 4 is gripped or released. The CR gripping mechanism 47 comprises a hook open detecting limit switch 47d for detecting that the hook 44 is opened, a hook detecting limit switch 47e for detecting that the hook 44 is closed, and a CR settling detection limit switch 47f for detecting that the hook 44 is settled on the handle 4d of the CR 4. The rotating cylinder 41 has a guide protrusion 47g which is provided on the bottom thereof. The guide protrusion 47g has a guide groove which fits to the cross shaped center of the cross shaped handle 4d, the guide groove being provided on the bottom thereof. If the hook 44 is lifted down to the CR 4, the handle 4d gradually fits to the cross shaped guide groove so as to guide the hook 44 to an optimum position of the handle 4d. Further, the hook opening/closing air cylinder 47a includes a holding spring 47i which urges the piston rod 47b to the gripping position as a means for corresponding to a trouble of the hook opening/closing air cylinder 47a, so as to hold the gripping action when the supply of air to the air cylinder 47a is interrupted due to a rupture of the air hose. A releasing wire 47h is connected to the piston rod 47b and when the wire 47h is pulled up to resist the force of the holding spring 47i, the hook opening/closing air cylinder 47a is forcibly released. On the other hand, in the FS gripping device 50, as shown in FIG. 3, the lower half portions of a square shaped supporting cylinder 31 and a rotating cylinder 41 are inserted into a lifting square cylinder 51 having a diameter larger than that of the supporting cylinder 31, and as shown in FIGS. 7A and 7B, the lifting square cylinder 51 is mounted so as to be lifted up and down so that the lifting square cylinder 51 is axially deviated by 45.degree. with respect to the internal supporting cylinder 31. That is, an FS lifting air cylinder 52 is fixed on the external side face in the middle along the length of the square supporting cylinder 31 and the lifting square cylinder 51 is held by a piston rod 52a which goes up and down within the FS lifting air cylinder 52 so that the lifting square cylinder can be lifted freely. As shown in FIG. 8, a plurality of guide rollers 53, 53,--which move on the external faces of the respective corners of the external side face of the square supporting cylinder 31 are provided inside the lifting square cylinder 51. On the other hand, as shown in FIG. 4, the lifting square cylinder 51 has a cross shaped insertion hole 51b which allows the cross shaped handle 4d of the CR 4 to pass therethrough, the hole being provided on the bottom of the lifting square cylinder 51. As shown in FIG. 8, the lifting square cylinder 51 has corner pins 54 which protrude vertically downward and which are in contact with the guide pins of the core supporting plate 7, the core supporting plate 7 being provided on the external faces of the respective corners of the bottom 51a. Further, as shown in FIG. 4, the bottom face 51a of the lifting square cylinder 51 has a pair of sheet-shaped guides 55, 55 which are disposed on a pair of corners which diagonally corresponds to each other. The sheet-shaped guides 55, 55 are inserted into a pair of fuel supporting engagement holes 6b and 6d which face each other with respect of the diameter of the FS 6 shown in FIG. 16 so as to guide the hook 44 to the handle 44d of the CR 4. The lifting square cylinder 51 has a pair of right and left FS gripping mechanisms 56, an FS gripping lock mechanism 57 and an FS settling detection device 58, these mechanisms and device being disposed on the bottom end thereof. FIG. 4 shows only one of a pair of right and left FS gripping mechanisms 56 and the representation of the other side is omitted. Each FS gripping mechanism 56 comprises an air cylinder 56c which advances or retracts a pair of plungers 56 through a link mechanism 56b, the plungers being protruded through a pair of orifices which face each other with respect to the diameter of the FS 6, for example, 6f, 6h, in order to grip the FS 6, an FS gripping detection limit switch 56d for detecting the gripping action of the FS 6 by means of the FS gripping air cylinder 56c and an FS releasing detection limit switch 56e for detecting the releasing action of the FS 6. The FS gripping air cylinder 56c contains a gripping holding spring 56g which urges the piston rod 56f in the direction in which the gripping action is held, as a means for treating a trouble of the FS gripping air cylinder 56c, if the supply of air to the FS gripping air cylinder 56c is interrupted due to a breakage of an air hose when the FS 6 is gripped by means of the FS gripping air cylinder 56c. A wire rope 56h for the releasing operation is connected to the FS gripping air cylinder 56c. By pulling the wire rope 56h so as to resist the force of the gripping holding spring 56g, the gripping action of the FS gripping air cylinder 56c is forcibly changed to releasing action so as to retract a pair of the plungers 56a, 56a from a pair of the orifices 6f and 6h of the FS 6 backward, that is, to the inside, thereby forcibly releasing the FS 6. The FS gripping lock mechanism 57 has a lock lever 57a which is provided so as to be able to swing freely on the bottom face 51b of the lifting square cylinder 51. The lock lever 57a is urged always to be engaged with an engagement hole 56i in a communicating rod 56f of the link mechanism 56b of the FS gripping mechanism 56 in order to hold the communicating rod 56f. When the bottom face 51a of the lifting square cylinder 51 is settled on the top face of the FS 6, the lock lever 57a is swung and disengaged from the engagement hole 56i of the communicating rod 56f of the lifting square cylinder 51. Consequently, the communicating rod 56f is released to allow the link mechanism to operate. When the bottom face 51a of the lifting square cylinder 51 is separated from the top face of the FS 6, the lock lever 57a is swung to be engaged with the engagement hole 56i of the communicating rod 56f. Consequently, the action of releasing the communicating rod 56f is held to lock the gripping action of the FS 6. The FS settling detection device 58 has a settling detection lever 58a which is provided so as to be swung freely on the bottom face 51a of the lifting square cylinder 51. When the settling detection lever 58a is settled on the top face of the FS 6, an FS settling detection limit switch 58 is turned on/off by the swing end thereof in order to output or stop an FS settling signal. As shown in FIGS. 1 and 3, a cable absorbing mechanism 59 is provided on the internal face of the top of the lifting square cylinder 51. This mechanism absorbs ropes 60 such as air hoses, cables connected to respective air cylinders 45e, 45f, 46, 47a, 52, 56c and operating wires 45h, 47h, 56h by means of pulleys 59a, 59b and a spring 59c in order to prevent a trouble due to the looseness of the ropes 60. Next, a case in which the CR 4 and the FS 6 are lifted up from a water filled reactor pressure vessel 1 by using the control rod and fuel supporting member gripping apparatus 20 having the aforementioned construction at the time of the periodic inspection of the BWR will be described below. As shown in FIG. 9A, the CR 4 is inserted fully into the core to maintain the subcriticality of four fuel assemblies 3, 3, 3, 3 which are placed in a lattice and two fuel assemblies 3, 3 which are placed diagonally are pulled out of the core by means of a fuel exchanging device or the like. As shown in FIG. 9B, a blade guide (control rod guiding device) 61 in which a pair of dummy channels 61a, 61b are connected diagonally by the handle 61c is inserted into positions from which two fuel assemblies 3, 3 are removed. After that, the remaining two fuel assemblies 3, 3 are pulled out of the core, as shown in FIG. 9C. As shown in FIG. 9D, the CR 4 is guided by means of the blade guide 61 and moved downward of the core by means of the CRD 8 so that the CR 4 is completely pulled out. Further, as shown in FIG. 9E, the blade guide 61 is pulled out of the core. After these operations, the bolt of the wire rope of the auxiliary hoist of a fuel exchanging device, not shown, is screwed into the screw hole 32b of the square stand of the control rod and fuel supporting metal gripping device 20 according to the present invention, and then the fuel assembly is lowered into the reactor pressure vessel 1. Thereafter, as shown in FIG. 1, the upper plate 30 of the control rod and fuel supporting metal gripping device 20 is settled on the upper lattice plate 5 to transfer the total weight of the control rod and fuel supporting member gripping apparatus 20 from the wire rope to the upper lattice plate 5. When the upper plate 30 is settled on the top face of the upper lattice plate 5, the upper plate settling detection lever 30a comes into contact with the top face of the upper lattice plate 5 to turn on the upper plate settling detection limit switch 30b. Then, an upper plate settling detection signal is output to the fuel exchanging device or the like through a cable, not shown. At this time, the bottom face 51a of the lifting square cylinder 51 is settled on the top face of the FS 6 and the top face of the handle 4d of the CR 4 at the same time, and both the CR settling detection limit switch 47f and the FS settling limit switch 58b output settling signals. Further, the lock lever 57a is disengaged from the engagement hole 56i of the communicating rod 56f in order to release the locking condition of the lock mechanism 57. Next, when air is supplied to the FS gripping air cylinder 56c, a pair of right and left plungers 56a, 56a are protruded into a pair of orifices 6f, 6h of the FS 6 through the link mechanism 56b which is unlocked, in order to hold the FS 6. At this time, the FS gripping detection limit switch 56d outputs a gripping signal for detecting the gripping condition of the FS 6. When air is supplied to the gripping side of the hook opening/closing air cylinder 47a, the hook 44 is closed while gripping the handle 4d with a slight vertical play, thereby gripping the CR 4. At this time, the hook close detection limit switch 47e outputs a hook close signal. Then, when low pressure air is supplied to the CR lifting air cylinder 46, the rotating cylinder 41 rises slightly so that the hook 44 comes into contact with the bottom face of the handle 4d. That is, because the pressure of air supplied to the CR lifting air cylinder 46 is low, the rotating cylinder 41 rises by only a gap, i.e. play, between the hook 44 and the handle 4a of the CR 4 so as to make the hook 44 contact the handle 4d firmly. When air is supplied to the lift-up chamber, i.e. lower chamber, of the FS lifting air cylinder 52, the lifting square cylinder 51 rises. Thus, the FS 6 which is held by means of the FS gripping mechanism 56 is pulled slightly upward to remove the FS 6 from the core supporting plate 7. The FS 6 is raised slightly higher than the top face of the handle 4d of the CR 4 and the FS 6 is maintained at that height. When the lifting square cylinder 51 is lifted up, a plurality of guide rollers 53, 53,--which are provided inside thereof rotate on the external face of the supporting cylinder 31 in order to prevent the FS 6 which is held by means of the lifting cylinder 51 and the FS gripping mechanism 56 from rotating axially. Thus, it is possible to prevent the FS 6 from colliding with the fuel assembly 3 loaded within the lattice. After this operation, high pressure air is supplied to the lift-up chamber, i.e. lower chamber, of the CR lifting air cylinder 46 in order to raise the CR gripping mechanism 47 by several tens mm and rotate the CR 4. Consequently, all the weight of the CR 4 and the members which are connected with the bayonet coupling 14 of the CR 8 are received from the control rod and fuel supporting member gripping apparatus 20 and the weight is loaded and supported by the upper lattice plate 5. When air is supplied to one of the CR rotating air cylinders 45e, 45f, for example, 45e, while hoisting the CR 4 as described above, the rotating gear 45a is turned clockwise. By turning the rotating cylinder 41 by 45.degree. for example, by means of the rotating gear 45a, it is possible to release connection between the CR 4 and the CRD 8 by the bayonet coupling 14. If air is supplied to the other CR rotating air cylinder 45f to turn the rotating cylinder 41 by 45.degree., the CR 4 is connected with the CRD 8 by the bayonet coupling 14. After the CR 4 is removed from the CRD 8, the CR 4 and the FS 6 are hoisted to the top portion of the core by winding the wire rope of the auxiliary hoist or the like of the fuel exchanging device. The CR 4 and the FS 6 are lifted through the upper lattice plate 5 from the inside of the reactor pressure vessel to a reactor well located above the reactor pressure vessel and then moved to a fuel storage pool which communicates with the reactor well while keeping the CR 4 and the FS 6 in water. Thereafter, the CR and FS gripping mechanisms 47 and 56 are actuated to release the CR 4 and the FS 6 at a predetermined position. Then, the CR 4 and the FS 6 are released and stored to terminate the operation. However, if these gripping mechanisms 47 and 56 are not capable of releasing the CR 4 and the FS 6 for some reason, the releasing operation wires 47h and 56h are pulled strongly. Consequently, it becomes possible to forcibly release the CR 4 and the FS 6. If the CR 4 and the FS 6 are gripped by means of both the CR gripping mechanism 47 and the FS gripping mechanism 56, the gripping action is maintained by the holding springs 47g and 56g and the locking mechanism 57. Thus, it is possible to prevent an unexpected accident which may occur when the CR 4 and the FS 6 are accidently released if the CR 4 and the FS 6 are being gripped and transferred. According to the described embodiment of the present invention, it is possible to grip and remove the CR 4 and the FS 6 by means of the control rod and fuel supporting member gripping apparatus 20 and further to hoist the CR 4 and the FS 6 and carry them out of the reactor pressure vessel 1 at the same time. Thus, a sequence of such operations can be performed simply, securely and rapidly, and the working efficiency of BWR's periodic inspection can be enhanced remarkably. FIG. 10 represents a second embodiment according to the present invention, and referring to FIG. 10, the gripping apparatus body 100 is hoisted down into the reactor pressure vessel by means of a wire rope 101 driven by a hoist, not shown. A hanging member 102 is secured to the upper portion of the gripping apparatus body 100 and the wire rope 101 is firmly engaged with the hanging member 102. A fuel supporting member gripping device 103 is mounted to a lower portion of the gripping apparatus body 100 to grip the fuel supporting member 6 mounted on a core supporting plate 7. Further, a control rod gripping device 106 for gripping a neck portion of a control rod 4 is supported by the gripping apparatus body 100 through a shaft member 107 and a support plate 108 supporting the shaft member 107 so that the shaft member 107 is attached to the support plate 108 to be movable up and down with respect to the support plate 108. A control rod rotating mechanism 109 for rotating the shaft member 107 with respect to the support plate 108 is mounted to a portion near the attaching portion of the shaft member 107 to the support plate 108. A stopper member 110 is provided for the upper end of the shaft member 107 for preventing the control rod gripping device 106 and the shaft member 107 from coming off from the support plate 108 at a time when the gripping apparatus body 100 is lifted upward. In FIG. 10, an upper lattice plate 5 is a plate for supporting the top end of a fuel assembly, not shown, in a horizontal plane and four fuel assemblies are charged, in a usual core running state, in one cell 113 in which the gripping apparatus body 100 is located. The gripping body 100 has a horizontal cross section of a square shape slightly smaller than that of the cell 113 so as to prevent the gripping body 100 from being rotated in the cell 113. Hereunder, a method for taking out, i.e. uncoupling, the control rod (CR) 4 and the fuel supporting member (FS) 6 will be described with reference to FIGS. 10 and 11. FIG. 11A shows a state before the uncoupling operation, in which the FS 6 is settled on a control rod guide tube 114 supported by the core supporting plate 7 and the FS 6 is prevented from rotation by a pin 115 secured to the core supporting plate 7. The CR 4 penetrates inside the FS 6 so that the top end thereof extends upward, as viewed, from the FS 6. From this state, the gripping apparatus body 100 is hoisted down from an upper portion on the FS 6 by means of the wire rope 101, and this state corresponds to the state shown in FIG. 10. Then, the fuel supporting member gripping device 103 is operated to grip the FS 6, and the control rod gripping device 106 is also operated to grip the CR 4. The wire rope 101 is thereafter lifted up to thereby lift up the gripping apparatus body 100. At this time, the FS 6 is also lifted up together with the gripping apparatus body 100, but the control rod gripping device 106 is not lifted up because of the sliding motion of the shaft member 107. FIG. 11B shows a state in which the FS 6 is lifted up. In the next step, the control rod rotating member 109 is driven to rotate the control rod gripping device 106 and the CR 4 by 45.degree. to thereby uncouple the CR 4 and the control rod driving mechanism. FIG. 11C shows a state before this rotation. Then, the CR 4 and the FS 6 are taken out of the core by hoisting up the gripping apparatus body 100. FIG. 11D shows a state before the lift-up of the CR 111. When the gripping apparatus body 100 is lifted up, the control rod gripping device 106 is not slid off because of the location of the stopper member 110 and the control rod 4 is lifted up together with the FS 6. As described hereinbefore with reference to two preferred embodiments, according to the present invention, the FS 6 is not rotated horizontally from the setting state of FIG. 12A to the state of FIG. 12B, and only the CR 4 is rotated to thereby uncouple the same. Accordingly, the CR 4 and the FS 6 can be taken out of the core simultaneously. FIG. 12C shows a state in which fuel assemblies are withdrawn for setting a television camera for monitoring the working state of the gripping apparatus body. The fuel assemblies are expected in future not to be withdrawn through the used reliance of the gripping apparatus. As described hereinbefore with reference to two preferred embodiments, according to the present invention, the fuel supporting member is not moved horizontally in the state shown in FIG. 12B from the state shown in FIG. 12A mentioned with reference to the conventional structure, and only the control rod is rotated to perform the uncoupling thereof. Accordingly, the control rod and the fuel supporting member in the given fuel assembly can be withdrawn at the same time without moving or shifting the fuel assemblies disposed neighboring the given fuel assembly. With reference to FIG. 12C, the fuel assembly 116 is now withdrawn for disposing a television camera for monitoring the operation of the control rod and fuel supporting member gripping apparatus, but it will be expected in future not to remove such fuel assembly upon repeated confirmation of the performance of this gripping apparatus. As described above, according to the present invention, it is possible to grip and remove the control rod and the fuel supporting member which are located within the reactor pressure vessel and hoist the control rod and the fuel supporting member so as to be taken out of the reactor pressure vessel. Thus, as compared with the conventional case in which the control rod and the fuel supporting member are gripped separately by means of different gripping devices successively and conveyed out of the reactor pressure vessel after they are removed from the gripping devices, the present invention is capable of improving the working efficiency of hoisting operation markedly. Consequently, it is possible to improve the working efficiency of the BWR's periodic inspection. That is, for example, in the conventional technique, it is required to remove totally twenty fuel assemblies, but, according to the present invention, only the seven fuel assemblies have to be removed, and preferably four fuel assembly, in future. Thus, the working of the operator to remove the fuel assemblies can be extremely reduced, being advantageous. This advantage results in the reduction of a space of a pool in which the withdrawn control rods and the fuel supporting members are stored. Further, in the control rod rotating mechanism, the rotating members which rotate the rotating body which has the hook for gripping the handle of the control rod are connected to the clockwise/counterclockwise rotating air cylinder through a wire in order to turn the rotating body. Thus, it is possible to reduce the load of the rotating force. If the supply of a drive medium such as air to the control rod gripping driving source such as air cylinder is interrupted when the control rod is gripped by means of the hook which is actuated by the control rod gripping driving source, the gripping action of the control rod gripping driving source is maintained by the force of the spring. Thus, even if the supply of the drive medium to the control rod gripping air cylinder is interrupted due to a breakage of the air hose or the like when the control rod is gripped and hoisted by means of the hook, the hook does not release the control rod. Thus, the safety operation can be assured. When the control rod cannot be released due to a trouble in the control rod gripping driving source, it is possible to forcibly release the control rod by pulling the rope. A pair of plungers are protruded into a pair of the existing side holes of the fuel supporting metal to support the fuel supporting metal, it is not necessary to make devices for the fuel supporting metal for assuring the gripping operation. Further, because a pair of plungers are inserted into a pair of side holes which faces each other with respect to the diameter of the fuel supporting metal to support and hoist the fuel supporting metal, the fuel supporting metal can be supported and hoisted stably with a balance with respect to the diameter thereof. Thus, it is possible to increase the operational reliability and the safety of supporting and hoisting the fuel supporting member. When the fuel supporting member is gripped by means of the fuel supporting member gripping device and hoisted, the gripping state is locked by the locking mechanism. Thus, it is possible to prevent the fuel supporting member from dropping due to an action of releasing the fuel supporting member and damaging, thereby increasing the operational reliability and safety. If the supply of a drive medium such as air to the fuel supporting member gripping driving source such as air cylinder is interrupted due to a breakage of the drive line such as air hose when the fuel supporting member is held by means of the fuel supporting member gripping driving source, the gripping action of the fuel supporting member gripping driving source is maintained by the force of a spring. Thus, if the supply of the drive medium to the fuel supporting member gripping driving source is interrupted due to a breakage of the air hose when the fuel supporting metal is gripped and hoisted, the fuel supporting member is held, thereby securing the safety operation. When an action of releasing the fuel supporting member cannot be performed due to a trouble in the fuel supporting member gripping driving source, it is possible to forcibly release the fuel supporting member by pulling a rope.