Method for operating hoisting machine with tong-type lifting tool

Abstract

The present invention achieves further improvement in workability of transfer work by combining a tong-type lifting tool and a balance-type hoisting machine. The tong-type lifting tool comprises a lock mechanism for holding a pantograph mechanism in a folded state. The lock mechanism alternately switches between locking and unlocking when the pantograph mechanism is fully folded. The hoisting machine operates in a float mode in which a motor outputs drive force that is the sum of drive force corresponding to a load due to the weight of the tong-type lifting tool and a lifted object, and drive force obtained by amplifying the operating force of a worker. When the unwinding length of a chain is a predetermined value or more and the tong-type lifting tool has been in a stationary state for a predetermined time, the hoisting machine unwinds the chain by a fixed length by automatic control and immediately thereafter winds the chain having a required length equal to or more than the unwound length to cause the lock mechanism to switch between locking and unlocking.

Description

Method for operating a hoist equipped with a tongue-type lifting device

[0001] The present invention relates to a method of operating a hoist equipped with a tong-type lifting device that clamps and lifts an object to be transported.

[0002] Various hoists have been proposed for clamping and lifting an object. For example, one such hoist, such as the tire hoist described in Patent Document 1, clamps the object by operating a diamond-shaped link mechanism (pantograph mechanism). However, in order to clamp the object, an operator must lift the handle 34 of the contraction stopper 30 to release the engagement of the connecting shaft R2 with the locking portion 32b, which is time-consuming and inefficient.

[0003] One example of a device that automatically locks and unlocks a hoisting device in a released state using the weight of the hoisting device with a pantograph mechanism is the clamping device described in Patent Document 2. However, in order to land the lifted workpiece at its destination and then re-engage and lock the engaging claw 125 of the locking member 121 into the engaging recess 126 of the cam member 123, the alignment of these elements is required, and it is not possible to completely rely on the weight of the hoisting device to slacken the chain of the device (hoisting machine), so skill is required to operate the device.

[0004] Patent Application No. 2023-179249 Utility Model Registration No. 3219038

[0005] In order to solve the above problems, the applicant of the present application is currently developing a tong-type lifting device that employs a so-called "one-touch stay" instead of the contraction stopper of Patent Document 1. This is a device that combines a ratchet mechanism with a set of square pipes that can be extended and slid telescopically. This allows the square pipes to be locked in an extended state with little overlap and a long overall length, maintaining that overall length, and then can be extended a predetermined length from that extended state to reach its maximum length, which releases the lock and allows the square pipes to retract into a contracted state with a large overlap and a short overall length. This operation can be repeated.

[0006] This tong-type hoist operates as follows: First, the one-touch stay of the tong-type hoist attached to the hoist is locked in an extended position (the tong-type hoist is in an open position). In this state, the hoist is lowered, bringing the tong-type hoist into contact with a transported object, such as a cardboard box, from above. When the load chain (or wire rope) of the hoist is no longer subjected to the load of the tong-type hoist itself and some slack develops in the load chain, the tong-type hoist's own weight causes the vertical length to shrink, folding the pantograph mechanism. At the same time, the one-touch stay is further extended from the extended state by a predetermined length (e.g., about 2 cm) to its maximum length. This causes the switching pawl (ratchet pawl) of the locking mechanism to rotate half a turn, releasing the lock. Then, when the hoist is reeled in, the vertical length of the pantograph mechanism of the tong-type hoist increases, and at the same time, the holding member at the bottom of the tong-type hoist clamps and lifts the transported object. The lifted load is manually moved directly above the target location using a crane equipped with a hoist that can travel and move laterally, and the hoist is then lowered to land the load. By further lowering the hoist from there, the tong-type lifting device reduces the vertical length of the pantograph mechanism under its own weight, releasing the load from its grip. When the load chain is further lowered until there is some slack, the one-touch stay extends to its maximum length. When the one-touch stay extends to its maximum length, the switching claw of the ratchet mechanism rotates half a turn to lock, and the one-touch stay remains extended, shortened by a predetermined length (e.g., about 2 cm) from its maximum length.

[0007] The applicant of the present application manufactures and sells a balancing hoist (Chain Balancer (registered trademark)) that uses a load sensor to measure the load suspended from the hoist or the load from an external force, and balances the load by outputting a driving force corresponding to the measured load from the motor. This balancing hoist can be used in two modes: a switch operation mode in which the hoist is hoisted up or down by pushing a button, and a float mode in which the user can raise or lower a heavy load by placing their hands on the load or hoisting equipment and applying a slight force, as if they were lightly lifting or lowering the load with their own hands.

[0008] The present invention aims to provide a method for operating a hoist equipped with a tong-type hoist, which combines a tong-type hoist that automatically opens and closes by locking and unlocking the pantograph mechanism with the float mode of a balance-type hoist, thereby further improving the operability of transport work without requiring skilled operation of the hoist.

[0009] [1] In order to achieve the above object, according to a first aspect of the present invention, there is provided a method for operating a hoist equipped with a tong-type hoisting device that clamps a transported object with a pantograph mechanism, wherein the tong-type hoisting device has a locking mechanism for holding the pantograph mechanism in a folded state, and the locking mechanism alternately switches between lock and unlock when the pantograph mechanism is sufficiently folded, the hoist has a float mode in which the motor outputs a driving force that is the sum of a driving force corresponding to the load caused by the tong-type hoisting device and the weight of the load to be suspended and a driving force that amplifies the operating force of the operator, and when the unwound length of the chain is equal to or greater than a predetermined value and the tong-type hoisting device has been in a state of being at or below a predetermined speed for a predetermined time or is in a stationary state, the hoist automatically controls the hoist to unwind the chain by a certain length, and then immediately retracts the chain to switch between locking and unlocking by the locking mechanism.

[0010] In the above, "chain" includes not only chains but also ropes. Also, "load due to the weight of the suspended load" refers to the load acting statically on the hoist body, such as the weight of the unwound chain and the lower hook.

[0011] [2] According to a second aspect of the present invention, there is provided a method for operating a hoist equipped with a tong-type hoisting device that clamps a transported object with a pantograph mechanism, wherein the tong-type hoisting device has a locking mechanism for holding the pantograph mechanism in a folded state, and the locking mechanism alternately switches between lock and unlock when the pantograph mechanism is sufficiently folded, the hoist has a float mode in which the motor outputs a driving force that is the sum of a driving force corresponding to the load caused by the tong-type hoisting device and the weight of the load to be suspended and a driving force obtained by amplifying the operating force of the operator, and when the unwound length of the chain is equal to or greater than a predetermined value and the tong-type hoisting device has been in a state of being at or below a predetermined speed or in a stationary state for a predetermined time, the hoist automatically controls to unwind the chain until the weight of the tong-type hoisting device no longer acts on the hoist, and then immediately retracts the chain to switch between locking and unlocking by the locking mechanism.

[0012] [3] Furthermore, in another aspect of the present invention, in the invention described in [1] or [2] above, it is preferable that the hoist puts the automatic control into an executable state when the unwinding length of the chain becomes equal to or greater than the predetermined value, then falls below the predetermined value, and then becomes equal to or greater than the predetermined value again.

[0013] [4] Furthermore, in another aspect of the present invention, in the invention described in [1] or [2] above, it is preferable that the hoist that has started the automatic control performs the chain winding / unwinding operation only once.

[0014] [5] Furthermore, in another aspect of the present invention, in the invention described in [1] or [2] above, it is preferable that the hoist that has started the automatic control automatically unwinds the chain by a certain length, and then immediately winds up the chain to a required length that is greater than or equal to the unwound length.

[0015] [6] In another aspect of the present invention, in the invention described in either [1] or [5] above, when the automatic control is completed, it is preferable to switch back to the float mode and perform initial settings required for that operation mode.

[0016] According to the present invention, by combining a tong-type lifting device that automatically opens and closes by locking and unlocking the pantograph mechanism with the float mode of a balance-type hoist, it is possible to further improve the workability of transport operations without requiring skilled operation of the hoist.

[0017] FIG. 1 is a perspective view of a tong-type hoisting device, partially seen through; FIG. 2 is a front view of the tong-type hoisting device, partially seen through; FIG. 3 is a rear view of the tong-type hoisting device; FIG. 4 is a diagram showing the control configuration of a hoisting machine; and FIG. 5 is a diagram showing the operating procedure of the tong-type hoisting device and the operating method of the hoisting machine in the present invention.

[0018] An embodiment of a tong-type sling used in the present invention will now be described with reference to the drawings. Fig. 1 is a perspective view of a tong-type sling 10, and Fig. 2 is a front view thereof, showing upper links 12 and 13, lower links 14 and 15, a portion of a rail member 64, and a portion of brackets 52 of clamps 16 and 17 on the front side, as will be described later, in a see-through manner. Fig. 3 is a rear view of the tong-type sling 10.

[0019] The tong-type lifting device 10 has a pair of opposing clamp sections 16, 17 that clamp the cardboard box, which is the item being transported, and these clamp sections 16, 17 move closer to and away from each other without changing their opposing angle due to the opening and closing movement of the lower links 14, 15 caused by the expansion and contraction of the pantograph mechanism A of the tong-type lifting device 10, which will be described later.

[0020] 1 to 3, the tongue-type sling 10 includes a connecting fitting 11, a set of upper links 12, 13, a set of lower links 14, 15, a rail member 64, a clamp moving member 70, and a pair of opposing clamps 16, 17. The upper links 12, 13 and lower links 14, 15 form a pantograph mechanism A. The tongue-type sling 10 also includes a one-touch stay 30 that regulates the extension and retraction of the pantograph mechanism A, and a guide member 80 provided with a handle 81 that facilitates handling of the tongue-type sling 10 and a holder 82 for attaching a wireless remote control (not shown) that transmits operation signals to the hoist.

[0021] The connecting fitting 11 is a component connected to a hoist, which is a transport device. An insertion hole is provided at the upper end of the connecting fitting 11, through which a lower hook of the hoist is inserted. The upper links 12 and 13 are connected to the lower end of the connecting fitting 11 by a pivot pin 21, with the upper end of the upper link 12 positioned on the front side of the connecting fitting 11 and the upper end of the upper link 13 positioned on the rear side of the connecting fitting 11, for example.

[0022] Each set of upper links 12, 13 is made of a substantially elongated plate member having the same length in the extension direction. The two sets of upper links 12, 13 are connected to each other at a predetermined distance by a pivot pin 21 that also serves as a spacer. As described above, the upper ends of the upper links 12, 13 are connected to the connecting fitting 11 by the pivot pin 21. This allows the upper links 12, 13 to rotate individually around the pivot pin 21.

[0023] Each set of lower links 14, 15 is composed of a plate member with a slightly bent L-shaped central portion. The two sets of lower links 14, 15 are connected at the bent portions by pivot pins 24, which also serve as spacers, spaced a predetermined distance apart so that they are symmetrical about a line passing through the center of the pivot pin 21 (hereinafter referred to as the center line) in a plan view of the tong-type lifting device 10. Therefore, the lower links 14, 15 can also rotate individually around the pivot pin 24. The upper ends of the lower links 14, 15 are connected to the lower end of the upper link 13 by pivot pins 22, 23, which also serve as spacers. Connecting the upper links 12, 13 to the lower links 14, 15 using the pivot pins 22, 23 in this manner constitutes a pantograph mechanism A.

[0024] The clamps 16 and 17 are, for example, substantially L-shaped members formed by bending one end of a flat plate downward by 90°. The clamps 16 and 17 have the same configuration as each other and the same configuration for attaching the clamps 16 and 17 to a rail member 64 (described later).

[0025] The tips (lower ends in FIG. 1 ) of the bent portions of the clamping units 16 and 17 are provided with anti-slip members 51 to prevent slippage of the clamped transported object. The clamping units 16 and 17 are also fitted with brackets 52 for connection to a clamping unit moving member 70 (described later) and a rail member 64. The opposing, generally L-shaped, bent plates constituting each bracket 52 are fixed to the upper surfaces of the clamping units 16 and 17 via spacer rollers 53 provided at two upper and one lower locations, at a distance slightly greater than the thickness of the rail member 64. The rail member 64 is disposed between the spacer rollers 53 of the bracket 52, and three horizontally arranged circular pin holes 54 are formed through the center of each bracket 52 and 53 to allow the clamping units 16 and 17 to move smoothly along the rail member 64. A rail pin (not shown) is selectively inserted into these pin holes.

[0026] The clamp portion moving member 70 is a thick, substantially rectangular plate member in which a plurality of round holes 71 having the same diameter as the pin holes 54 are formed at regular intervals.

[0027] The rail member 64 is made up of two rectangular long plate members fixed facing each other with spacers sandwiched between them at both ends and the center, allowing the clamp movement member 70 to slide within the space between them. In addition, the two long plate members are formed with long holes 61 extending in the longitudinal direction at regular intervals at symmetrical positions on the left and right sides of the rail member 64.

[0028] The long holes 61 of the rail member 64, the round holes 71 of the clamp unit moving member 70, and the pin holes 54 of the bracket 52 can be aligned so as to communicate with each other, and by selecting an appropriate one from the long holes 61 of the rail member 64, the round holes 71 of the clamp unit moving member 70, and the pin holes 54 of the bracket 52 and inserting a rail pin (not shown) through it, the spacing between the opposing clamp units 16, 17 can be changed according to the width of the transported object. In addition, connecting pins 62 that connect the lower ends of the two sets of lower links 14, 15 are inserted into the two long holes 61 on the central side of the rail member 64 and into the round hole 71 at one end of the clamp unit moving member 70.

[0029] The one-touch stay 30 is a set of telescopic rod-shaped square pipes that slide nested between the outer and inner pipe members, combined with a ratchet (locking mechanism). The telescopic stay 30 is restricted to a predetermined length range, and each time the one-touch stay 30 extends to its maximum length, a switching pawl (ratchet pawl) (not shown) of the locking mechanism rotates half a turn, alternately locking and unlocking. One end of the one-touch stay 30 (the outer pipe member side) is connected to one upper link 13, and the other end (the inner pipe member side) is connected to the other upper link 12 via a rotating pin 35. The one-touch stay 30 extends and contracts as the pantograph mechanism A extends and contracts, and the locking mechanism locks, maintaining the extended state and holding the pantograph mechanism A in its folded state. This maintains the open state of the tong-type sling device 10. Furthermore, the one-touch stay 30 can be unlocked by extending it a predetermined length from the locked extended state to its maximum length, and can enter a contracted state in which the outer pipe member and the inner pipe member overlap to a large extent and the overall length is short, allowing the tong-type suspension device 10 to transition to a closed state.

[0030] The guide member 80 is a long, plate-like rod arranged parallel to the one-touch stay 30 without interfering with it, and has a handle 81 attached to one end to make it easier for an operator to handle the tong-type lifting device 10, and a holder 82 attached to the other end for attaching a wireless remote control that transmits operation signals to the hoist. One end of the guide member 80 is connected to a pivot pin 22 that connects the upper link 13 and the lower link 15. The other end of the guide member 80 is provided with an elongated hole 41 that extends in the extension direction of the guide member 80. The pivot pin 23 that connects the upper link 12 and the lower link 14 is inserted into the elongated hole 41.

[0031] With the tong-type hoisting device 10 having the pantograph mechanism A configured as described above, even when the weight of the hoisting device is completely loaded onto the transported object or the like and the chain or the like of the hoist is slackened, the locking and unlocking of the released state can be performed reliably and automatically.

[0032] [Regarding the hoist (chain balancer)] Figure 4 is a diagram showing the control configuration of the hoist 130. As shown in the figure, the hoist 130 mainly comprises a hoist main body 131, an upper hook 132, a cylindrical grip 133, a chain bucket 134 that holds the wound-up load chain C1, and a lower hook 136. The hoist main body 131 is suspended from a crane (not shown) via the upper hook 132 and a pulley, and can be manually pulled to move horizontally along the crane's traverse rails and traveling rails.

[0033] The hoist main body 131 accommodates various components inside its housing 135. Specifically, the housing 135 is provided with a motor 140, a speed reduction mechanism 141, a brake mechanism 142, a load sheave 143 that winds up the load chain C1, a load sensor 144, a hoist control unit 145, and a driver 146.

[0034] It should be noted that a hoist body consisting of a rope and a take-up drum (not shown) can be used instead of the load chain C1 and the load sheave 143. In this case, the taken-up rope is held by the take-up drum, making the chain bucket 134 unnecessary.

[0035] The motor 140 is a power source that provides the driving force to drive the load sheave 143. In this embodiment, the motor 140 is a servomotor equipped with a detector (encoder 140a) for detecting the position (the rotational position of the rotor, not shown), and is preferably an AC servomotor. Note that a synchronous motor is preferable as the AC servomotor, but an induction motor may also be used.

[0036] The speed reduction mechanism 141 is a part that reduces the speed of the rotation of the motor 140 and transmits it to the load sheave 143. The brake mechanism 142 is a part that can release the braking force by electromagnetic force when the motor 140 is operating, but is also a part that generates braking force to prevent the load from dropping even when the motor 140 is not operating.

[0037] The load sheave 143 is a part that winds up and down the load chain C1, and is provided with a plurality of chain pockets along its outer periphery into which the metal rings of the load chain C1 fit.

[0038] The load sensor 144 is a sensor that measures the load applied to the upper hook 132. That is, the load sensor 144 measures and detects the total load of the load on the hoisting machine main body 131, the load on the load chain C1 (the portion not touching the floor, etc.), the load of the load (including the tong-type lifting device), and the vertical operating force from the operator's hand. By subtracting the weight of the main body, etc. from the total load measured and detected using this load sensor 144, it is possible to detect (calculate) the load applied to the load sheave 143 via the load chain C1. The load sensor 144 is attached, for example, to a mounting shaft that attaches the upper hook 132 to the hoisting machine main body 131.

[0039] A load cell equipped with a strain gauge can be used as the load sensor 144. The load sensor 144 may be disposed at any position where it can detect and measure the load applied to the load sheave 143 by the load chain C1 that suspends the load, such as between the upper hook 132 and a pulley (not shown), between the lower hook 36 and the load, or between the end of the load chain C1 and the lower hook 136. In addition to a load cell, a crane scale or the like can also be used as the load sensor 144, but it is necessary that the sensor have the accuracy and responsiveness suitable for use in balancing control of the hoist.

[0040] The hoist control unit 145 is capable of controlling the driver 146 according to the control mode (switch operation mode, float mode), and is a part that gives command values ​​for position (height), speed, torque, etc. in each control mode. The hoist control unit 145 may be, for example, a computer or integrated circuit equipped with a CPU (Central Processing Unit), memory (RAM (Random Access Memory), ROM (Read Only Memory), internal storage, external storage device, etc.), input / output interface, etc.

[0041] In addition, the driver 146 is a part that controls the power source supplied from the outside to an appropriate level of power based on the current value of the motor 140, the output of the encoder 140a, and command values ​​for motor drive control given by the hoist control unit 145, and supplies that power to the motor 140 to rotate it.

[0042] The cylindrical handle 133, which is a portion that an operator holds in his / her hand to operate the load chain C1, is connected to the lower end of the load chain C1. The cylindrical handle 133 is also provided with a lower hook 136 for hanging the tong-type hoist 10. Although not shown in the drawings, the cylindrical handle 133 has multiple disc springs stacked inside it, and the shaft to which the lower hook 136 is attached is supported by the disc springs inside the cylindrical handle like a piston, thereby also functioning as a damper to absorb vibrations. In this embodiment, switching of the control modes (switch operation mode, float mode) and hoisting / lowering operations in the switch operation mode are performed by a wireless remote control attached to the holder 82 of the guide member 80 of the tong-type hoist. However, the cylindrical handle 133 itself may be provided with various switches to provide a wireless remote control, or a pendant switch suspended from the hoisting machine main body 131 may be used to switch the control mode.

[0043] The chain bucket 134 is a portion for storing the unloaded (already wound) load chain C1 located on the opposite side of the load sheave 143 from the lower hook 136.

[0044] In the hoist 130 (chain balancer) configured as described above, in float mode, regardless of whether a load is suspended from the tong-type hoisting device 10 hooked on the lower hook 136, when no operational force is being applied by the operator, the hoist control unit 45 controls the motor 140 based on the load X measured by the load sensor 44 to drive the motor 140 so that the tong-type hoisting device 10 remains in the air without being hoisted up or lowered. On the other hand, when an operational force is being applied by the operator, the motor 140 outputs a driving force corresponding to the applied load and a driving force obtained by amplifying the measured operational force of the operator (the difference from the applied load X). This allows the operator to lift and lower a heavy load with the feeling that they are lifting and lowering it lightly with their own hands.

[0045] [Regarding the operating procedure of the tong-type hoisting device and the operation method of the hoist equipped with the tong-type hoisting device] Next, a description will be given of the operating method of the hoisting device equipped with the tong-type hoisting device, etc. Figure 5 is a diagram showing the operating procedure of the tong-type hoisting device 10 and the operation flow of the hoisting device 130 when the tong-type hoisting device 10 is used to lift, lower, and transport a load (a cubic cardboard box) as a transport object.

[0046] First, the worker aligns the pin holes 54 of the brackets 52 of the clamping sections 16 and 17 with the appropriate long holes 61 of the rail members 60 and the round holes 71 of the clamping section moving members 70 to match the width of the cardboard box, and then inserts and connects the rail pins (not shown) to adjust the width of the clamping sections 16 and 17 (S1).

[0047] Next, the worker locks the locking mechanism of the one-touch stay 30 to maintain the extended state so that the pantograph mechanism A of the tongue-type hoisting device 10 suspended from the hoist is kept in the folded state, and holds the lower links 14, 15 (the tongue-type hoisting device 10) in the open state (S2).

[0048] Next, the hoisting machine 130 is shifted to the float mode by operating the wireless remote control attached to the holder 82 of the guide member 80 of the tongue-type hoisting device 10 (S3).

[0049] The operator then grasps the handle 81 or cylindrical grip 133 of the tong-type lifting device 10 and pushes down until the length of the chain C1 unwound from the hoist 130 reaches a predetermined value (for example, a length that results in a distance of approximately 1 meter from the floor to the lower hook), and then pushes up again until the unwound length falls below the predetermined value. This operation triggers the hoist 130 to enter a state in which automatic control can be executed (S4). At this point, it is preferable that the hoist 130 notify the operator of this state by sounding an alarm. Note that if automatic control is always enabled in float mode, such an operation for triggering the operation is unnecessary, but which is preferable depends on the work environment and can be freely selected.

[0050] The worker then grasps the handle 82 or cylindrical grip 133 of the tong-type lifting device 10 and pulls it horizontally, manually moving the hoist 130 and the tong-type lifting device 10 up to above the cardboard box being transported. Then, by applying a downward operating force, the hoist 130 in float mode will lower in response to the operating force (S5).

[0051] The worker then positions the tips of the bent portions of the clamps 16 and 17 of the tong-type lifting device 10 on the left and right sides of the cardboard box, respectively, so that they straddle the cardboard box. In this state, the worker releases his or her hands (S6). At this time, the distance between the top of the cardboard box and the clamps 16 and 17 facing it is approximately 1 to 3 cm. Even if multiple cardboard boxes are lined up with only a small gap between them, there is no problem as long as the bent portions of the clamps 16 and 17 can be inserted into the gap. Up to this point, the worker performs the operation; the operation of clamping and lifting the next cardboard box is performed automatically by the hoist 130.

[0052] If the hoist 130 determines that the length of the chain C1 unwound from the hoist 130 is equal to or greater than a predetermined value (e.g., a length such that the distance from the floor to the lower hook is approximately 1 meter) and that the tong-type hoist 10 has been stationary (or moving at or below a predetermined speed) for a predetermined time (e.g., 0.5 seconds), the hoist 130 automatically unwinds the chain C1 by a certain length (e.g., 10 cm) (S7). At this time, the pantograph mechanism A of the tong-type hoist 10 rests on the top surface of the cardboard box and is further folded under its own weight, thereby extending the one-touch stay 30 to its maximum length. This releases the locking mechanism, allowing the one-touch stay 30 to transition from an extended state to a retracted state.

[0053] When a certain length of chain C1 has been unwound, the hoist 130 immediately reels in a required length of chain C1 (e.g., 25 cm, taking into account the vertical extension of the pantograph mechanism A) that is longer than the length that was unwound (S8). As a result, the clamps 16 and 17 of the tong-type hoist 10 clamp the cardboard box as it is being wound up, and the weight of the cardboard box causes the tong-type hoist 10 to firmly clamp and lift the cardboard box.

[0054] After clamping the cardboard box and completing automatic lifting control, the hoist 130 calculates the load of the cardboard box (at this time, the operating force from the operator's hand is 0) from the load X measured by the load sensor 144 as an initial setting for switching operation to float mode, and outputs a driving force from the motor 140 to maintain a balanced state (S9). Note that if the weight of the cardboard box is the same each time, this measurement can be omitted by setting in advance the driving force from the motor 140 to maintain this balanced state.

[0055] The worker then grasps the handle 82 or cylindrical grip 133 of the tong-type lifting device 10, or places his or her hand on the cardboard box, and manually pulls the cardboard box to the desired position. The load sensor 144 of the hoist 130 measures the vertical operating force (difference from the load X) due to the manual pulling operation, and the hoist control unit 145 outputs a driving force from the motor 140 that is a combination of a driving force for maintaining the above-mentioned balance state and a driving force obtained by amplifying the operating force, based on the measured value. The cardboard box is moved horizontally by the crane's traverse rails and running rails, and vertically by the lifting and lowering of the hoist 130, by the worker's manual pulling operation. After the box has been moved directly above the desired position, the worker lowers it and manually pulls it until the distance from the landing surface is approximately 1 to 10 cm, and then releases his or her hand (S10). Up to this point, the worker performs the operations; the hoist 130 automatically performs the operations of landing the next cardboard box, releasing the clamping of the cardboard box by the tong-type lifting device 10, and lifting only the tong-type lifting device 10.

[0056] When the hoist 130 determines that the unwound length of the chain C1 is equal to or greater than a predetermined value (e.g., a length such that the distance from the floor to the lower hook is approximately 1 m) and that the tong-type hoist 10 has been substantially stationary for a predetermined time (e.g., 0.5 seconds), it automatically unwinds a certain length of chain (e.g., 20 cm). At this time, the pantograph mechanism A of the tong-type hoist 10 rests on the top of the cardboard box and folds under its own weight, releasing the clamping of the cardboard box. Accordingly, the one-touch stay 30 extends to its maximum length. This locks the locking mechanism, and the one-touch stay 30 remains extended. Once the certain length of chain has been unwound, the hoist 130 immediately retracts a length of chain C1 (e.g., 25 cm) that is equal to or greater than the unwound length (S11). This completes the movement of the cardboard box to the target position, and the automatic control is completed, with only the tong-type hoist 10 suspended. Then, as an initial setting for switching the operation to float mode, the load on the tong-type lifting device 10, etc. (at this time, the operating force from the operator's hand is 0) is calculated from the load X measured by the load sensor 144, and a driving force is output from the motor 140 to maintain a balanced state (S12). This allows the operator to move on to transporting the next cardboard box with the hoist in float mode.

[0057] In this embodiment, the chain C1 is automatically unwound when it is determined that the tong-type sling device 10 has been (almost) stationary for a certain period of time, and then, as soon as the length of the unwound chain C1 reaches a certain length, a length of the chain C1 equal to or greater than the unwound length is immediately reeled in. In other words, the reeling operation is switched to based on the unwound length of the chain C1. However, in another embodiment, the reeling operation can be switched to based on the measurement value of the load sensor 144 rather than the unwound length, when the weight of the tong-type sling device 10 no longer acts on the hoist 130.

[0058] Furthermore, the hoist 130 is configured to automatically unwind and retract the chain C1 only once when it determines that the tong-type lifting device 10 has been stationary for a certain period of time. This is to prevent the unwinding and retracting operations under automatic control from being repeated endlessly if the operator does not immediately begin manual operation after the chain C1 has been unwound and retracted under automatic control.

[0059] According to the above-described method of operating the hoist 130 equipped with the tong-type hoisting device 10, the workability of transport work can be further improved by combining the tong-type hoisting device 10 with the float mode of the balancing hoist. It is of course possible to regard the present invention as a system that operates as described above.

[0060] DESCRIPTION OF SYMBOLS 10...Tong-type lifting device 11...Connecting fitting 11 12, 13...Upper link 14, 15...Lower link 16, 17...Clamp section 21, 22, 23, 24...Pivoting pin 30...One-touch stay 35...Pivoting pin 41...Elongated hole 51...Anti-slip member 52...Bracket 53...Roller with spacer 54...Pin hole 64...Rail member 61...Elongated hole 62...Connecting pin 70...Clamp section moving member 71...Round hole 80...Guide member 81...Handle 82...Holder A...Pantograph mechanism 130...Hoisting machine 131...Hoisting machine main body 132...Upper hook 133...Cylindrical grip 134...Chain bucket 135...Housing 136...Lower hook 140...Motor 140a...Encoder 141...Reduction mechanism 142...Brake mechanism 143... Load sheave 144... Load sensor 145... Hoisting machine control unit 146... Driver

Claims

1. A method for operating a hoist equipped with a tong-type hoisting device that clamps a transported object with a pantograph mechanism, wherein the tong-type hoisting device has a locking mechanism for maintaining the pantograph mechanism in a folded state, and the locking mechanism alternately switches between lock and unlock when the pantograph mechanism is fully folded; the hoisting device has a float mode in which the motor outputs a driving force that is the sum of a driving force corresponding to the load caused by the tong-type hoisting device and the weight of the load to be suspended and a driving force that amplifies the operating force of the operator; and when the unwound length of the chain is equal to or greater than a predetermined value and the tong-type hoisting device has been moving at a predetermined speed or less for a predetermined time, the hoist automatically unwinds the chain by a certain length, and then immediately retracts the chain to switch between locking and unlocking using the locking mechanism.

2. A method for operating a hoist equipped with a tong-type hoisting device that clamps a transported object with a pantograph mechanism, wherein the tong-type hoisting device has a locking mechanism for holding the pantograph mechanism in a folded state, and the locking mechanism alternately switches between lock and unlock when the pantograph mechanism is fully folded; the hoist has a float mode in which the motor outputs a driving force that is the sum of a driving force corresponding to the load caused by the tong-type hoisting device and the weight of the load to be suspended and a driving force that amplifies the operating force of the operator; and when the unwound length of the chain is equal to or greater than a predetermined value and the tong-type hoisting device has been in a state of being at or below a predetermined speed or in a stationary state for a predetermined time, the hoist automatically controls to unwind the chain until the weight of the tong-type hoisting device no longer acts on the hoist, and then immediately retracts the chain to switch between lock and unlock using the locking mechanism.

3. A method of operating a hoist equipped with a tong-type lifting device as described in claim 1 or 2, characterized in that the hoist puts the automatic control into an executable state when the unwinding length of the chain becomes equal to or greater than the predetermined value, then falls below the predetermined value and then returns to above the predetermined value as a trigger.

4. The method of operating a hoist equipped with a tong-type lifting device according to claim 1 or 2, characterized in that the hoist that has started the automatic control performs the chain winding and unwinding operation only once.

5. A method of operating a hoist equipped with a tong-type lifting device as described in claim 1 or 2, characterized in that the hoist, having started the automatic control, automatically unwinds a certain length of chain, and then immediately rewinds a required length of chain that is longer than the unwound length.

6. A method for operating a hoist equipped with a tong-type lifting device according to any one of claims 1 to 5, characterized in that, when the automatic control is completed, the mode is switched back to the float mode and initial settings required for the operation mode are performed.

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