Parent hook miswinding prevention device

Abstract

To provide a device for preventing erroneous winding of a main hook, which mechanically and safely stops the winding up of a main hoisting rope even if the operator of a crane winds up the rope by mistake when the main hook is lowered to the bottom of the crane and fixed. [Solution] This device A has a pair of arms 3 with length adjustment means, and by adjusting the length of each arm, the wire rope 6 between each arm is positioned between the boom 1 and the main hoisting rope 11, at an appropriate distance close to the main hoisting rope 11.When the main hoisting rope 11 begins to be wound up, the wire rope 6 receives the pull of the main hoisting rope 11 toward the boom 1, and a limit switch detects the tensile force from this wire rope 6 and sends a control signal to a controller, which then stops the winding of the main hoisting rope 11 by the main hoisting winch.

Description

[Technical Field]

[0001] This device relates to a device for preventing mis-hoisting of a main hook, which can be used on a crane truck or other types of crane, and which allows safe lifting operations by the crane. [Background technology]

[0002] A typical crane used in construction and civil engineering work is disclosed in Patent Document 1, and an example is shown in FIG.

[0003] The crane C in Figure 11 is a mobile crane mounted on a swivel base rotatably installed on the top of a crawler-type vehicle, forming a so-called crane truck. In this crane C, a boom 1 is supported on the swivel base of the vehicle via a boom support bracket for elevation and is driven by a boom hoist winch, boom hoist rope, and guy cables installed on the swivel base. In this crane C, the boom 1 includes a main boom M1 and an upper boom S1 extending from the tip of the main boom M1. Boom point sheaves 101 and 102 are provided at the tip of the main boom M1 and the tip of the upper boom S1, respectively. Main and auxiliary winches are also installed on the swivel base. A main hoisting rope 11 and an auxiliary hoisting rope 12 are reeled out from the main and auxiliary winches, respectively, and wound around the boom point sheaves 101 and 102 at the tip of the main boom M1 and the tip of the upper boom S1, respectively. The main hoisting rope 11 is looped between the boom point sheave 101 and the hook sheave provided on the main hook 13, and its tip is connected to an end pin provided within the tip of the main boom M1.The main hook 13 is suspended from the tip of the main boom M1 by this main hoisting rope 11, and the secondary hook 14 is connected to the tip of the auxiliary hoisting rope 12 and suspended from the tip of the upper boom S1. The upper boom (S1) shown in FIG. 11 is also called an auxiliary boom, and is called an auxiliary sheave by those skilled in the art (the same applies to the upper boom (S1) shown in FIG. 12).

[0004] In this way, the main hook 13 and the sub hook 14 are raised and lowered by separately letting out and reeling in the main hoisting rope 11 and the auxiliary hoisting rope 12 from the main hoisting and auxiliary hoisting winches.

[0005] This crane C has such a configuration, and in various construction and civil engineering works, the main hook 13 is mainly used for low-speed lifting of heavy loads, and the sub hook 14 is mainly used for high-speed lifting of small (light) loads.

[0006] Furthermore, this type of crane C is provided with an overwinding prevention device for the main hoisting rope and the auxiliary hoisting rope to prevent wire cutting accidents and the boom tipping backward due to overwinding of the main hoisting rope used to raise and lower the main hook and the auxiliary hoisting rope used to raise and lower the sub hook. This type of overwinding prevention device is disclosed in Patent Document 2, etc.

[0007] The overwinding prevention devices for the main hoisting rope and the auxiliary hoisting rope each consist of a limit switch attached to the boom, a wire rope suspended from the limit switch's switch arm, and a weight. In this case, the weight has a through hole through which the main hoisting rope and the auxiliary hoisting rope pass. The weight can move up and down along the main hoisting rope and the auxiliary hoisting rope, and the weight pulls down the limit switch's switch arm, turning it off. From this state, when the main hoisting rope and the auxiliary hoisting rope are wound and are about to reach an overwinding state, the upper ends of the main hook and the auxiliary hook push up the weight, slackening the wire rope. This causes the limit switch's switch arm to move up and turn on, detecting that the rope is about to overwind. The limit switch then sends a detection signal to the winch's control unit, stopping the winch from winding the main hoisting rope and the auxiliary hoisting rope. In this way, overwinding of the main hoisting rope and auxiliary hoisting rope is prevented.

[0008] During crane-based lifting operations in construction and civil engineering projects, while one of the main or sub-hooks is in use, the other is left suspended in midair. For example, as shown in Figure 11, when a pile is hoisted by the sub-hook 14 and inserted into a hole drilled in the ground, the unused main hook 13 is reeled up and suspended above the crane C body. When the sub-hook 14 moves up and down to lift and lower the pile during operation, frictional resistance places a heavy load on the crane, causing the main body and boom to swing. This exacerbates the load, causing the unused main hook 13 to swing back and forth, potentially crashing into the boom 1 and damaging the boom frame and lattice. If the boom 1 is damaged or deformed in this way, the damaged portion of the boom 1 must be replaced with a sound one, and an inspection by the government (Labor Standards Inspection Office) is required. In this case, construction work will be halted for at least three days, resulting in a corresponding delay.

[0009] Therefore, in order to avoid such construction delays and to prevent the unused main hook 13 from swinging back and forth, the construction company handles this by lowering the main hook 13 below the crane C, attaching a wire W to the crane C, hanging this wire W on the main hook 13, tensioning it appropriately, and fixing the main hook 13, as shown in Figure 12.

[0010] However, even if this is done, if the operator of crane C mistakenly operates the main hoisting winch and winds up the main hoisting rope 11, the over-winding prevention device equipped on crane C will not function and there will be no mechanical detection, so the main hoisting rope 11 will continue to be wound up unless the main hoisting winch stops winding it. As a result, naturally, the wire W will break due to excessive winding of the lower part of the main hoisting rope 11. If the wire W breaks, the main hook 13 will act like a pendulum and swing back and forth, potentially colliding with and destroying anything close to crane C. In this case, the lower the boom 1 hoisting angle, the greater the swing range and force of the main hook 13. Since the main hook 13 typically weighs between 500 kg and 1,000 kg, it is easy to imagine that the force and destructive power will be considerable.

[0011] In order to avoid such wire breakage, it is possible to reinforce the wire by splitting it into two, or to stretch one of the two wires to a moderate level and make the other slack by making it several tens of centimeters longer so that even if one wire breaks, the other will still hold the main hook.However, even with these measures, if the operator does not immediately stop winding the main hoisting rope when the first wire breaks due to winding up the main hoisting rope, the second wire will also break, and the result will be the same.

[0012] Therefore, in order to solve these conventional problems, the applicant of the present application proposed in Patent Document 3 a main hook miswinding prevention device with the aim of mechanically stopping the winding of the main hoisting rope reliably and safely even if the crane operator erroneously operates the main hoisting winch and winds up the main hoisting rope when the main hook is lowered and fixed below the crane to prevent the unused main hook from swinging back and forth during lifting work using this type of crane.

[0013] This main hook mis-hoisting prevention device is for a crane of this type, namely, a boom having at least a main boom point sheave and an auxiliary boom point sheave at the tip end, the base end of which is supported on a base so as to be able to be raised and lowered, and which is driven by a drive unit installed on the base, a main hoisting rope that is let out from either the main hoisting winch or the auxiliary hoisting winch installed on the base and wound around the main boom point sheave at the tip end of the boom, an auxiliary hoisting rope that is let out from the other winch and wound around the auxiliary boom point sheave, and The device comprises a main hook connected to the tip of the hoisting rope and suspended from the tip side of the boom, a sub hook connected to the tip of the auxiliary hoisting rope and suspended from the tip side of the boom, and a controller that controls the operation of the drive unit, the main hoisting winch, and the auxiliary hoisting winch, and is equipped on a crane that raises and lowers the main hook and sub hook by letting out and taking up the main hoisting rope with either the main hoisting winch or the auxiliary hoisting winch, and prevents incorrect winding of the main hook. This main hook miswinding prevention device comprises a pair of arms arranged in parallel in the width direction and protruding from the front of the lower side of the boom facing the main hoisting rope, a rope stretched between the pair of arms, a tension spring attached to one of the pair of arms and connected to one end of the rope for pulling the rope, and a tension detector attached to the other arm, operatively connected to the other end of the rope and electrically connected to the controller via a signal line, which detects the tensile force of the rope and sends a control signal to the controller to stop winding of the main hoisting rope by the main hoisting winch or auxiliary hoisting winch. With this configuration, when performing lifting operations using the auxiliary hoisting rope and secondary hook, the boom and main hoisting rope are lowered and the primary hook is lowered to below the crane and fixed, and the rope between each arm is positioned between the boom and the main hoisting rope.If the main hoisting rope is wound up by the main hoisting winch or auxiliary hoisting winch during lifting operations, the rope elastically absorbs and holds down the main hoisting rope as it is pulled toward the boom, and the tension detector detects the tensile force from the rope pulled by the main hoisting rope being pulled toward the boom, and sends a control signal that causes the controller to stop the winding of the main hoisting rope by the main hoisting winch or auxiliary hoisting winch.

[0014] In this way, when performing lifting work using a crane as described above, if the unused main hook is lowered and fixed below the crane to prevent it from swaying back and forth, even if the crane operator mistakenly operates the main hoisting winch or auxiliary hoisting winch and winds up the main hoisting rope, the winding of the main hoisting rope can be stopped mechanically, reliably, and safely. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Japanese Patent Application Publication No. 10-36081 [Patent Document 2] Japanese Patent Publication No. 2000-1293 [Patent Document 3] Japanese Patent Application Publication No. 2023-112808 Summary of the Invention [Problem to be solved by the invention]

[0016] The applicant of the present application has developed such a device for preventing mis-winding of a main hook into a practical machine and is using it at an actual construction site, where it has demonstrated its expected effectiveness and is enabling safe lifting work using a crane. However, construction sites where cranes are used have a variety of working environments, with different conditions at each site, different working conditions depending on the type of work, and different crane operating (operation) senses depending on the crane operator, etc. Therefore, the applicant of the present application has been diligently researching and developing this main hook mis-hoisting prevention device so that it can be adapted to the various working environments that differ at each construction site, and has now discovered improvements.

[0017] The present invention is an improvement to the parent hook mis-winding prevention device proposed by the applicant in Patent Document 3, and aims to make it more adaptable to the various working environments that vary at each construction site where a crane is used. [Means for solving the problem]

[0018] In order to achieve the above object, the present invention A boom has at least a main boom point sheave and an auxiliary boom point sheave at its tip end, its base end is supported on a base so as to be able to be raised and lowered, and is driven by a drive unit installed on the base; a main hoisting rope is let out from one of the main hoisting winch or the auxiliary hoisting winch installed on the base and wound around the main boom point sheave at the tip end of the boom; an auxiliary hoisting rope is let out from the other winch and wound around the auxiliary boom point sheave; and a boom is connected to the tip of the main hoisting rope. a main hook suspended at the tip of the boom and a sub hook connected to the tip of the auxiliary hoisting rope and suspended at the tip of the boom; and a controller for controlling the operation of the drive unit, the main winch, and the auxiliary winch, the main hook being equipped to a crane that raises and lowers the main hook and sub hook by letting out and taking up the main hoisting rope with one of the main winch and the auxiliary winch, and letting out and taking up the auxiliary hoisting rope with the other, and preventing erroneous winding of the main hook, a pair of arms attached to a lower side of the boom in parallel in the width direction of the boom and projecting from the boom; a rope stretched between the pair of arms; a tension spring attached to one of the pair of arms and connected to one end of the rope for pulling the rope; and a tension detector attached to the other arm, operatively connected to the other end of the rope and electrically connected to the controller via a signal line, for detecting the tensile force of the rope and transmitting a control signal to the controller to stop winding of the main hoisting rope by the main hoisting winch or the auxiliary hoisting winch. Equipped with The pair of arms have length adjustment means that can adjust the length of projection from the boom, During the lifting operation using the auxiliary hoisting rope and the secondary hook, the distance between the rope between each arm and the main hoisting rope that has been lowered and the primary hook that has been lowered to below the crane and fixed is adjusted, and the rope between each arm is positioned between the boom and the main hoisting rope that has been lowered and the primary hook that has been lowered to below the crane and fixed, When the main hoisting rope is wound up by the main hoisting winch or the auxiliary hoisting winch during the lifting operation, the pulling of the main hoisting rope toward the boom side is elastically received by the cord and held down, and the tension detector detects the tensile force from the cord pulled by the pulling of the main hoisting rope toward the boom side and transmits a control signal, and the controller stops the winding of the main hoisting rope by the main hoisting winch or the auxiliary hoisting winch based on the control signal. The gist of this is as follows.

[0019] It is also preferable that the main hook miswinding prevention device has the following configurations in each section. (1) The length adjusting means for the pair of arms is configured so that each arm is made of a double pipe, one side of the double pipe can be advanced and retreated from the other side, and can be fixed at the advanced and retreated position. (2) Each of the pair of arms is rotatably attached to the boom between an extended position in which it extends forward from the boom and a stored position in which it is folded along or adjacent to the boom. (3) The crane is equipped with an over-winding prevention device for the main hoisting rope and the auxiliary hoisting rope, and each of the over-winding prevention devices is electrically connected to the controller via a signal line. The tension detector is connected to the controller by connecting the signal line of the tension detector to the signal line between each of the over-winding prevention devices and the controller using a branch wiring method at any position of the boom, including the base at the base end of the boom or the boom top at the tip of the boom. [Effects of the Invention]

[0020] According to the main hook mis-winding prevention device of the present invention, the above-mentioned configuration allows for the device to be more adapted to the various working environments that vary at each construction site where a crane is used, when the main hook is lowered and fixed below the crane to prevent the unused main hook from swaying back and forth during lifting work using a crane, and provides the unique and exceptional effect of being able to mechanically stop the winding of the main hoisting rope reliably and safely, even if the crane operator mistakenly operates the main hoisting winch or auxiliary hoisting winch and winds up the main hoisting rope. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram showing an outline of a parent hook miswinding prevention device according to one embodiment of the present invention. [Figure 2] (a) A view of the device in use from the tip of the crane boom when the boom is lowered. (b) A view of the device in use from the base of the crane boom when the boom is lowered. [Figure 3] (a) A view of the device in use from above the crane boom when it is lowered. (b) A view of the device in use from below the crane boom when it is lowered. [Figure 4] (a) A view of the device in use from the right side of the crane boom when the boom is lowered. (b) A view of the device in use from the left side of the crane boom when the boom is lowered. [Figure 5] (a) A view of the device in use, seen from the left side of the crane boom when the boom is lowered. (b) A view of the device in use, seen from above the crane boom when the boom is lowered. [Figure 6] (a) A view of the device when folded and stored, seen from the left side of the crane boom with the boom lowered. (b) A view of the device when folded and stored, seen from above the crane boom with the boom lowered. [Figure 7]A diagram showing the main parts of the device (the signal line of the device and the signal line of the over-hoisting prevention device are connected at the base of the boom). [Figure 8] A diagram showing the main parts of the device (the signal line of the device and the signal line of the over-hoisting prevention device are connected at the boom top of the boom). [Figure 9] An enlarged view of the main part of the device (overwinding prevention device) [Figure 10] A diagram showing an example of how the device is used [Figure 11] A diagram showing a conventional crane and problems that arise when using it. [Figure 12] A diagram showing the conventional crane (Fig. 11) and the solutions to problems encountered when using it, as well as the problems associated with these solutions. DETAILED DESCRIPTION OF THE INVENTION

[0022] Next, an embodiment of the present invention will be described with reference to the drawings. Figure 1 shows a schematic diagram of a main hook mis-hoisting prevention device installed on a crane. Figures 2 to 9 show the configuration of each part of the main hook mis-hoisting prevention device.

[0023] As shown in FIG. 1, the crane C has at least a boom point sheave 101 for main hoisting and a boom point sheave 102 for auxiliary hoisting at the tip end, and the base end is supported on a base 10 so as to be able to be raised and lowered. The boom 1 is driven by a drive unit (not shown) installed on the base 10, and a main hoisting rope 11 is let out from either a main hoisting winch (not shown) or an auxiliary hoisting winch (not shown) installed on the base 10 and wound around the boom point sheave 101 for main hoisting at the tip end of the boom 1, and is let out from the other winch and wound around the auxiliary hoisting winch. The boom 1 is equipped with an auxiliary hoisting rope 12 that is wound around the boom point sheave 102, a main hook 13 and a secondary hook 14 that are connected to the ends of the main hoisting rope 11 and the auxiliary hoisting rope 12 and suspended at the tip side of the boom 1, and a controller (not shown) that controls the operation of the drive unit, main hoisting winch, and auxiliary hoisting winch.The main hook 13 and secondary hook 14 are raised and lowered by letting out and reeling in the main hoisting rope 11 using either the main hoisting winch or the auxiliary hoisting winch, and letting out and reeling in the auxiliary hoisting rope 12 using the other. In this case, the main hook 13 is raised and lowered by letting out and reeling in the main hoisting rope 11 using the main hoisting winch, and the sub hook 14 is raised and lowered by letting out and reeling in the auxiliary hoisting rope 12 using the auxiliary hoisting winch. In this case, the boom 1 comprises a main boom M1 and an upper boom S1 extending from the tip of the main boom M1. The tip of the boom 1 refers to the tip of the main boom M1 and the tip of the upper boom S1. Boom point sheaves 101, 102 are rotatably disposed at the tip of the main boom M1 and the tip of the upper boom S1, respectively. Here, as mentioned above, the upper boom (S1) is also referred to as an auxiliary boom, and those skilled in the art refer to it as an auxiliary sheave. The main hoisting rope 11 is routed between the boom point sheave 101 and a hook sheave (not shown) provided on the main hook 13, and its tip is connected to an end pin (not shown) provided in the tip of the main boom M1. The main hook 13 is connected to the tip of the main hoisting rope 11 and suspended from the tip of the main boom M1. The secondary hook 14 is connected to the tip of the auxiliary hoisting rope 12 and suspended from the tip of the upper boom S1. Furthermore, in this case, the crane C is mounted on a swivel base that is rotatably installed on the top of a crawler vehicle as a base 10, and is configured as a so-called crane vehicle.

[0024] Furthermore, as in the conventional case, this crane C is provided with overwinding prevention devices for the main hoisting rope and the auxiliary hoisting rope to prevent wire cutting accidents and rearward tipping of the boom 1 due to overwinding of the main hoisting rope 11 used to raise and lower the main hook 13 and the auxiliary hoisting rope 12 used to raise and lower the secondary hook 14. Since the overwinding prevention devices for the main hoisting rope and the auxiliary hoisting rope basically have the same configuration, only the main hoisting rope overwinding prevention device B will be shown and explained in Figure 9, and the illustration and explanation of the auxiliary hoisting rope overwinding prevention device will be omitted.

[0025] As shown in FIG. 9, overwinding prevention device B is a standard, i.e., general, device composed of an overwinding detector 21, a weight hanging rope 22, and a weight 23. The overwinding detector 21 is a known limit switch (hereinafter referred to as limit switch 21) that transmits a control signal when an operating pin that detects tension from the weight hanging rope 22 is activated. In this case, the operating pin is disposed within the body case of limit switch 21 via a coil spring. The coil spring's urging force normally urges the operating pin upward to an ON state, and the weight of weight 23, which is connected to this operating pin via weight hanging rope 22, pulls it downward to an OFF state. The weight hanging rope 22 is a wire rope (hereinafter referred to as wire rope 22), and is connected to the lower end of the operating pin of limit switch 21 and hangs below the operating pin. The weight 23 has a through-hole (not shown) in its center for passing the main hoisting rope 11 through, and is connected to the lower end of wire rope 22. The position of this weight 23, in other words, the length of the wire rope 22, is set so that the main hook 13 can push up the weight 23 when it is moved up to a position just before it becomes difficult to maintain a specified safety distance (a distance at which the main hook 13 will not come into contact with the tip side of the boom 1) from below the tip side of the boom 1.

[0026] The over-hoisting prevention device B has the above-mentioned configuration, with the limit switch 21 attached to a predetermined position on the side of the tip of the boom 1, the main hoisting rope 11 passed through the hole in the weight 23, and the weight 23 being positioned so that it can move up and down on the main hoisting rope 11 between the tip of the boom 1 and the main hook 13. In this way, the limit switch 21 is used as a return detection type.

[0027] In addition, the over-hoisting prevention device B is operatively connected to the controller, with the limit switch 21 and the controller of the main winch electrically connected via a signal line 24. In this case, the signal line 24 (see Figure 1) connected to the limit switch 21 is routed along the main boom M1, extended towards the controller via the cord reel 15 at the base end of the main boom M1, and connected to the controller.

[0028] In this way, in the overwinding prevention device B, the wire rope 22 is subjected to the gravity of the weight 23 and hangs down from the lower end of the operating pin of the limit switch 21. In this state, the gravity of the weight 23 acts on the operating pin of the limit switch 21, pulling the operating pin downward and causing the limit switch 21 to assume the OFF state. In the OFF state, no control signal is sent from the limit switch 21. Then, from this OFF state, the main hoisting winch reels in the main hoisting rope 11, moving the main hook 13 upward. When the upper part of the main hook 13 abuts against and pushes up the weight 23, the wire rope 22 slackens and the operating pin of the limit switch 21 is released from the weight of the weight 23. The operating pin of the limit switch 21 moves upward due to the biasing force of the coil spring, causing the limit switch 21 to assume the ON state. In this ON state, the limit switch 21 sends a control signal to the controller of the main hoisting winch, causing the controller to stop the main hoisting winch from reeling in the main hoisting rope 11. Thus, excessive winding of the main hoisting rope 11 is prevented, and collision between the main hook 13 and the boom 1, and further tipping of the boom 1 backward, are prevented in advance.

[0029] As shown in Figure 1, the main hook miswinding prevention device A is installed on the front side facing the main hoisting rope 11 at the bottom of the boom 1, and prevents the main hoisting rope 11 from being wound up incorrectly.

[0030] As shown in FIGS. 2 to 4, this main hook erroneous winding prevention device A (hereinafter referred to as the device A) comprises a pair of arms 3, a tension spring 4, a tension detector 5, and a cord 6.

[0031] The pair of arms 3 are attached in parallel in the width direction of the boom 1 on both the left and right sides of the front of the boom 1 facing the main hoisting rope 11 at the lower side of the vertically intermediate portion of the boom 1, and protrude from the boom 1 toward the front of the boom 1. The pair of arms 3 have length adjustment means 3L that allows the length of protrusion from the boom 1 to be adjusted by extension or retraction.

[0032] Each of the pair of arms 3 is made of steel, such as steel pipes, steel bars, or steel plates, and has a predetermined overall length (total length) extending from the attachment position of each arm 3 on the boom 1 to just before the position of the main hoisting rope 11 suspended from the tip of the main boom M1. Here, the pair of arms 3 are formed from steel to a predetermined length that is assumed to be an appropriate length from the front side of the main boom M1, where each arm 3 is attached, to a position slightly before the position of the main hoisting rope 11. Furthermore, the pair of arms 3 are particularly designed with a length adjustment means 3L that allows the length to be adjusted to suit various working environments, such as the situation at each site, which differs depending on the type of work, the working conditions, which differ depending on the type of work, and the driving (operating) feel of each crane operator.

[0033] In this case, each of the pair of arms 3 is made of a double pipe so that it can be advanced and retracted from one side to the other and fixed in an advanced and retracted position, so that the arm 3 also has a length adjustment means 3L. Here, each arm 3 includes a fixed arm 301 made of a square or round pipe with a large cross section that protrudes forward from the boom 1, and a movable arm 302 made of a square or round pipe with a small cross section that can be slidably arranged within the fixed arm 301. Note that in this embodiment, a square pipe is used as an example. Each fixed arm 301 has a predetermined length that is shorter than the reference length assumed as an appropriate length from the attachment positions of the frames M11 on both the left and right sides of the front of the main boom M1 to a position slightly forward of the position of the main hoisting rope 11. Furthermore, a plurality of bolt insertion holes 3010 are drilled in the opposing peripheral surfaces of each fixed arm 301, i.e., the upper and lower surfaces in this case, facing each other and arranged in series in the axial direction of the pipe. Each movable arm 302 only needs to have a length that allows it to be inserted into and advanced / retracted from each fixed arm 301, and may be the same length as each fixed arm 301, or may be longer or shorter than each fixed arm 301. Here, each movable arm 302 is the same length as or slightly longer than each fixed arm 301. A plurality of bolt insertion holes (not shown) are drilled in mutually opposing peripheral surfaces of each movable arm 302, i.e., the upper and lower surfaces in this example, so as to face each other in series in the axial direction of the pipe and to be able to communicate with the bolt insertion holes 3010 of each fixed arm 301. In this way, each movable arm 302 is inserted into each fixed arm 301, and with the tip of each movable arm 302 slightly protruding from each fixed arm 301, a plurality of bolt insertion holes are formed in each fixed arm 301 and each movable arm 302 so that the bolt insertion holes of each movable arm 302 and the bolt insertion holes of each fixed arm 301 can face each other in whole or in part.Thus, by projecting each movable arm 302 from each fixed arm 301 to a predetermined length that is shorter than the reference length, the bolt insertion holes, for example, at the base ends between each fixed arm 301 and each movable arm 302 are aligned, and by projecting each movable arm 302 from each fixed arm 301 to the reference length, the bolt insertion holes, for example, intermediate between the base end and the tip end between each fixed arm 301 and each movable arm 302 are aligned, thereby enabling communication between the bolt insertion holes at predetermined positions between each fixed arm 301 and each movable arm 302. Note that multiple bolt insertion holes may be formed in one of each fixed arm 301 or each movable arm 302, and only one bolt insertion hole or a number fewer than the multiple belt insertion holes on one side may be formed. In other words, it is sufficient that each movable arm 302 can be advanced and retracted from each fixed arm 301 and can be fixed in an advanced and retracted position. As a result, each movable arm 302 is incorporated into each fixed arm 301 so that it can be advanced and retreated from each fixed arm 301, and when each movable arm 302 advances and retreats from each fixed arm 301, the bolt insertion holes of each fixed arm 301 and each movable arm 302 are aligned, and a bolt 303 is passed between these bolt insertion holes and a nut 304 is tightened, thereby fixing each movable arm 302 to each fixed arm 301.

[0034] A pulley 30 for passing the cord 6 is attached to the tip of each movable arm 302 of each arm 3. In this case, these pulleys 30 are attached to the tip of each movable arm 302 so as to be rotatable in the direction in which the cord 6 is stretched between the arms 3.

[0035] Furthermore, as shown in Figures 5 and 6, each arm 3 of this pair of arms 3 is rotatably attached to the boom 1 via a mounting bracket 31 between a protruding position in which it protrudes forward from the boom 1 and a stored position in which it is folded along the boom 1.

[0036] The mounting bracket 31 comprises a boom-side mounting bracket 31A and an arm-side mounting bracket 31B.

[0037] The mounting bracket 31A on the boom side has a mounting body 311 and a rotation guide 312.

[0038] The mounting body 311 consists of a receiving bracket 3111 having an approximately U-shaped cross section (in this case, an approximately semicircular cross section) that can be attached to a columnar frame M11 that extends vertically on both the left and right sides of the front of the main boom M1, and a flat tightening bracket 3112 (in this case, the inner surface of which has an approximately semicircular cross section) that is fixed and connected between both ends of this receiving bracket 3111 using a plurality of bolts and nuts.

[0039] The rotation guide 312 has a protrusion position guide 312A for guiding and fixing the arm 3 to a protrusion position when in use, and a storage position guide 312B for guiding and fixing the arm 3 to a storage position when not in use. A shaft insertion portion 313 for a rotation shaft 314 for rotatably supporting the arm 3 is provided between the protrusion position guide 312A and the storage position guide 312B. In this case, the rotation guide 312 is an L-shaped plate. The vertical plate portion of the L-shaped plate is the protrusion position guide 312A, and a bolt insertion hole 3121 is formed at the vertical tip thereof as a fixing portion for the arm 3 in the protrusion state when in use. The horizontal plate portion of the L-shaped plate is the storage position guide 312B, and a bolt insertion hole 3122 is formed at the horizontal tip thereof as a fixing portion for the arm 3 in the storage state when not in use. A fixing bolt 315 is inserted into the bolt insertion portions 3121 and 3122, and a nut 316 is fastened. A shaft insertion portion 313 is formed at an end (middle portion) common to both the vertical and horizontal directions of this L-shaped plate. A rotation shaft 314 is inserted into this shaft insertion portion 313. This rotation guide 312 is fixed to one side (the side that faces outward when attached) of the fastening metal fitting 3112 of the mounting body 311, with the protrusion position guide 312A facing the rear frame at a right angle to the front frame M11 of the main boom M1, and the retracted position guide 312B facing the tip of the front frame M11 and parallel to the front frame M11 of the main boom M1.

[0040] The arm-side mounting bracket 31B is formed as a rotation guide that can engage with the protruding position guide 312A and the retracted position guide 312B of the boom-side rotation guide 312, and has at its base end a shaft insertion portion 3140 for a rotation shaft 314 that communicates with a shaft insertion portion 313 at the middle portion of the boom-side rotation guide 312 and rotatably supports the arm 3. In this case, the arm-side mounting bracket (rotation guide) 31B is made of a long, thin plate that corresponds to the protruding position guide 312A or the retracted position guide 312B of the rotation guide 312 of the boom-side mounting bracket 31A. A bolt insertion hole 3150 is formed at the tip of this plate as a fixing portion for the arm 3 in the protruding state when in use or in the retracted state when not in use. A fixing bolt 315 is inserted through the bolt insertion holes 3121, 3122 of the boom-side rotation guide 312 into this bolt insertion hole 3150, and a nut 316 is fastened. A shaft insertion portion 3140 is formed at the base end of this plate. A rotating shaft 314 is inserted from the shaft insertion portion 313 of the boom-side turning guide 312 into this shaft insertion portion 3140. This arm-side mounting bracket 31B is fixed to the base end of the arm 3, positioned on an extension of the base end of the arm 3 with their base ends facing each other.

[0041] In addition, in the rotation method of this pair of arms 3, the example is shown in which the tip of each arm 3 is rotatable between a protruding position where it protrudes forward from the boom 1 and a retracted position where it is retracted toward the base end of the boom 1, but conversely, the tip of each arm 3 may be rotated between a protruding position where it protrudes forward from the boom 1 and a retracted position where it is retracted toward the tip of the boom 1. In other words, each arm 3 may be rotatable downward or upward from the protruding position where it protrudes forward from the boom 1.

[0042] Furthermore, in this case, an inter-arm holding member 33 is also provided between the pair of arms 3 to prevent the arms 3 from being drawn together due to the tension of the cord-like member 6 described below. The inter-arm holding member 33 is made of a steel material such as a steel pipe, steel rod or steel plate, and is arranged and fixed between the arms 3. In this case, the inter-arm holding member 33 is made of a steel rod, arranged between the fixed arms 301, and directly fixed to each fixed arm 3. Note that this inter-arm holding member 33 may be bridged between the mounting brackets 31A on each arm side and fixed to each mounting bracket 31A.

[0043] The tension spring 4 is provided on one of the pair of arms 3 and tensions the cord 6 stretched between the arms 3. In this case, the tension spring 4 is a tension coil spring (hereinafter referred to as the tension coil spring 4). This tension coil spring 4 is attached to a mounting part 32 provided on the outward-facing side of the right arm 3 in the middle of its length (the side opposite the side facing the other (left) arm 3). In this case, the mounting part 32 is made up of a protruding part 321 having a bolt insertion hole protruding from the side of one of the arms 3, a bolt 322 that is passed through the bolt insertion hole of this protruding part 321, and a nut 323 that is screwed onto this bolt 322. One end of the tension coil spring 4 is connected to the tip of the bolt 322 of this mounting part 32, and the other end is directed toward the tip of one of the arms 3, and is disposed parallel to the one of the right arm 3.

[0044] The tension detector 5 is provided on the other of the pair of arms 3 and is electrically connected to the controller via a signal line L5. It is configured to detect the tension force of the rope 6 and send a control signal to the controller to stop the winding of the main hoisting rope 11 by the main winch or the auxiliary winch, in this case the former.

[0045] In this case, the tension detector 5 is a limit switch (hereinafter referred to as limit switch 5). This limit switch 5 is the same as the limit switch 21 used in the overwinding prevention device B described above, and can be selected as either a return-sensing type or a tension-sensing type depending on the wiring method of the device. In the overwinding prevention device B, the limit switch 21 is used as a return-sensing type, whereas in this tension detector 5, the limit switch 5 is used as a tension-sensing type. That is, this limit switch 5 is configured so that the operating pin is normally urged upward by the urging force of the coil spring to take the OFF state, and is switched to the ON state when the operating pin is pulled downward by an external force (in this case, the tensile force from the cord 6). This limit switch 5 is fixed to the side of the main case facing outward at the middle of the length of the left arm 3 (the side opposite the side facing one (right) arm 3), and is positioned parallel to the other left arm 3 with the tip of the operating pin inside the main case facing the tip of the other arm 3. Thus, this limit switch 5 is used as a tension-sensing type.

[0046] Also, in this case, signal wire L5 of limit switch 5 may be routed along boom 1 (main boom M1) and connected directly to the controller of the main hoisting winch, but in this device A, as already mentioned, crane C is equipped with over-hoisting prevention devices for the main hoisting rope and the auxiliary hoisting rope, and each over-hoisting prevention device is electrically connected to the controller via signal wire 24, so signal wire L5 of limit switch 5 is connected by a branch wiring method to signal wire 24 between each over-hoisting prevention device and the controller at any position on boom 1, including base 10 at the base end of boom 1 or boom top 16 at the tip of boom 1, and is then electrically connected to the controller. In other words, signal wire L5 is incorporated into the circuit between the over-hoisting prevention device and the controller and is connected to the controller.

[0047] Therefore, in this case, using the signal line 24 connected between these over-winding prevention devices and the controller, the limit switch 5 is connected to the controller by connecting the signal line L5 of this limit switch 5 to the signal line 24 between each over-winding prevention device and the controller via a branch wiring type connector J at the base 10 at the base end of the boom 1 or the boom top 16 at the tip of the boom 1.

[0048] Figure 7 shows an example of the former. In the former case, the signal line 24 connecting the over-hoist prevention device and the controller is connected via a relay panel 7 at the base 10 at the base end of the main boom M1. The limit switch 5, which functions as a tension detector, is branched to this relay panel 7 via a branch connection connector J, and the limit switch 5 is located in the circuit between the over-hoist prevention device and the controller. In this case, the base 10 at the base end of the main boom M1 is a rotating frame, which is mounted on crawlers parallel to the vehicle's cab and rotatably installed. The rotating frame is composed of four-sided frames P, with left and right frames P1 and P2 rising to correspond to the left and right sides of the cab, and front and rear frames P3 and P4 rising to correspond to the front and rear of the cab. The relay panel 7, consisting of two terminals attached to the center of a U-shaped panel, is attached to the outer surface of the front frame P3 of this four-sided frame P. The branch connection connector J is added to the back of the relay panel 7 on the front frame P3. In this way, signal wire L5 of limit switch 5 is connected via connector J for branch connection on the back side of relay panel 7 of four-sided frame P at the base end of the main boom M1. By doing this, signal wire L5 of limit switch 5 can be short and can be routed along signal wire 24 between the over-hoist prevention device and controller, so this signal wire L5 does not get in the way. In addition, because connector J for branch connection is attached to the back side of relay panel 7 of four-sided frame P at the base end of the main boom M1, this is preferable considering the waterproof properties of this connector J.

[0049] Figure 8 shows an example of the latter. In the latter case, the signal line 24 connecting the over-hoist prevention device and the controller is connected via a junction box 8 at the boom top 16 at the tip of the main boom M1. The signal line L5 of the limit switch 5, which serves as a tension detector, is branched to this junction box 8 via a branch connection connector J, and the limit switch 5 is located in the circuit between the over-hoist prevention device and the controller. In this case, the boom top 16 at the tip of the main boom M1 is composed of a pair of side plates 161 arranged in parallel on both the left and right sides of the tip of the main boom M1, and an intermediate plate 162 with an inverted L-shaped cross section located at the base end between these side plates 161. A junction box 8 with two terminals attached is attached to the surface of one of the intermediate plates 162 of the boom top 16, facing the base end of the boom. The branch connection connector J is additionally installed on the back side of the junction box 8 on the intermediate plate 162. In this way, the signal line L5 of the limit switch 5 is connected via the branch connection connector J on the back side of the relay box 8 on the intermediate plate 162 of the boom top 16. By doing this, the signal line L5 of the limit switch 5 can be routed along the signal line 24 between the over-hoist prevention device and the controller, and this signal line L5 does not get in the way. In addition, since the branch connection connector J is attached to the back side of the relay box 8 on the intermediate plate of the boom top 16 of the main boom M1, this is more preferable in consideration of the waterproofness of this connector J.

[0050] The cord 6 has one end connected to the tension coil spring 4 and the other end operatively connected to the limit switch 5, and is elastically stretched between the pair of arms 3. In this case, the cord 6 is made of a wire rope (hereinafter referred to as the wire rope 6), and has a length that is the length between the pair of arms 3 plus the length required to connect one end to the tension coil spring 4 and the other end to the operating pin of the limit switch 5. The wire rope 6 is stretched between the tips of the arms 3 via pulleys 30, with its right end connected to the tip of the tension coil spring 4 on the side of the right arm 3 and its left end connected to the operating pin of the limit switch 5 on the side of the left arm 3 via a wire clip on the wire rope 6 side and a shackle on the operating pin side. The tension of the wire rope 6 between the pair of arms 3 can be adjusted by moving a bolt 322 forward and backward relative to a nut 323 at the mounting portion 32 of the tension coil spring 4 on the right arm 3.

[0051] In this way, in this device A (see Figure 1), during lifting work using the auxiliary hoisting rope 12 and sub hook 14 of the crane C, the distance between the rope 6 between each arm 3 and the main hoisting rope 11 is adjusted so that the rope 6 between each arm 3 is positioned between the boom 1 and the main hoisting rope 11 in a state where the main hoisting rope 11 has been lowered and the main hook 13 has been lowered to below the crane C and secured thereto. That is, in this case, the wire rope 6 between each arm 3 can be positioned between the boom 1 and the main hoisting rope 11 in a state where the main hoisting rope 11 has been lowered and the main hook 13 has been lowered to below the crane C and secured thereto by adjusting the distance between the wire rope 6 and the main hoisting rope 11.

[0052] In this way, when the main hoisting rope 11 is wound up by the main winch or auxiliary winch (in this case the former) during lifting operations, the slack in the main hoisting rope 11 decreases and the main hoisting rope 11 is pulled toward the boom 1. The wire rope 6 elastically receives and holds down the pulling force of the main hoisting rope 11, and the limit switch 5 detects the tensile force from the wire rope 6 pulled by the pulling of the main hoisting rope 11 toward the boom 1, and based on the control signal sent, the controller stops the winding of the main hoisting winch or auxiliary winch (in this case the former) by the main hoisting rope 11.

[0053] Figure 10 shows an example of how to use this device A. Note that here, the crane work shown is an example of suspending a pile with a secondary hook 14 and inserting it into a hole drilled in the ground. In this case, when the pile is moved up and down by the vertical movement of the secondary hook 14, the unused primary hook 13 does not swing back and forth and crash into the boom 1, damaging the boom frame or lattice. To prevent this, the primary hook 13 is lowered below the crane C, and a wire W is attached to the base 10, such as the swivel of the crane C, and this wire W is hung on the primary hook 13 and tensioned appropriately to secure the primary hook 13, thereby preventing the primary hook 13 from swinging back and forth.

[0054] When using this device A, it is attached to the boom 1 of the crane C. This attachment is performed by attaching the pair of arms 3 to the frames M11 on both the left and right sides of the front of the main boom M1 using mounting brackets 31, as shown in Figures 2 to 6.

[0055] In this case, first, the boom 1 of the crane C is lowered to a substantially horizontal position, and two boom-side mounting brackets 31A are attached to the frames M11 on both the left and right sides of the front of the main boom M1, slightly above the fixed position of the main hook 13, by wrapping a receiving bracket 3111 around the lowered boom 1 from below, and then fastening the fastening brackets 3112 to both ends of the receiving bracket 3111 with bolts and nuts from above the lowered boom 1. With this attachment, the protruding position guide 312A of the rotation guide 312 is oriented perpendicular to the frame M11 of the main boom M1, and the retracted position guide 312b is oriented parallel to the frame M11 of the main boom M1 and toward the tip of the frame M11. Next, the arm-side mounting bracket 31B is placed over the boom-side mounting bracket 31A, and a rotation shaft 314 is inserted between the shaft insertion portions 313, 3140, thereby rotatably attaching the pair of arms 3 to both the left and right sides of the front of the boom 1. Then, arm-side mounting bracket 31B, i.e., the pivot guide, is aligned longitudinally with protrusion position guide 312A of boom-side mounting bracket 31A, and bolts 315 are inserted between bolt insertion holes 3121, 3150 of both brackets, and nuts 316 are tightened to secure them together. This causes each arm 3 to protrude downward (forward) from each frame M11 on both sides of the front of the main boom M1 at a right angle to each frame M11. In this way, each arm 3 can be easily and quickly attached to the boom 1 by fastening them at two points, via rotation shaft 314 and bolt 315. The length of each arm 3 can then be adjusted in advance using arm-3 length adjustment means 3L to suit various work environments, such as on-site conditions that vary from job site to job site, working conditions that vary depending on the type of work, and the driving (operating) feel of each crane operator. Furthermore, if necessary, the tension state of the wire rope 6 between the pair of arms 3 can be adjusted by moving the bolt 322 forward or backward relative to the nut 323 at the mounting portion 32 of the tension coil spring 5 of one of the arms 3. At this time, the arms 3 are prevented from being pulled closer together due to the tension of the wire rope 6 by the inter-arm holding member 33.

[0056] After installing the device A in this manner, as shown in Figure 10, the main boom M1 of the crane C is raised, the device A is interposed between the main boom M1 and the main hoisting rope 11, and the wire rope 6 is positioned close to the main hoisting rope 11 using a pair of arms 3.In this state, work is performed using the crane C, in this case, the pile is hoisted by the sub-hook 14 and inserted into a hole drilled in the ground.

[0057] As shown in Figure 10, if an accident occurs during operation of crane C where the operator of crane C mistakenly operates the main hoisting winch and winds up the main hoisting rope 11, the main hoisting rope 11 is not over-wound at the time of winding, so the over-hoisting prevention device B equipped to crane C will not work and will not be able to mechanically detect the accident. For this reason, whereas conventionally the main hoisting rope 11 would continue to be wound up unless the operator stopped the winding of the main hoisting rope 11 by the main hoisting winch, the installation of device A in crane C mechanically stops the winding of the main hoisting rope 11 reliably and safely.

[0058] That is, as the main hoisting rope 11 fixed to the crane C is wound up, it gradually becomes taut, and is drawn toward the front of the main boom M1, approaching it. When the main hoisting rope 11 comes into contact with and presses against the wire rope 6 of this device A, the main hoisting rope 11 is elastically supported by the wire rope 6 due to the expansion and contraction action of the tension coil spring 4 at one end of the wire rope 6, and the push from the main hoisting rope 11 pulls the wire rope 6 in the direction of the main hoisting rope 11's swing, that is, toward the front of the main boom M11. This pulling force is detected by the limit switch 5 of this device A, and a control signal is sent from this limit switch 5 to the controller of the main hoisting winch. In this case, the control signal is sent from signal line L5 of limit switch 5 to the controller via a branch wiring connector J connected to the over-hoisting prevention device at the base 10 at the base end of the main boom M1 or the boom top 16 at the tip, in this case a branch wiring connector J added to the relay panel 7 or relay box 8, and then to the controller via signal line 24 between the controller and the over-hoisting prevention device. Then, based on this control signal, the controller controls the main hoisting winch to stop driving and stop winding of the main hoisting rope 11 by this winch. In this way, pulling of the main hoisting rope 11 toward the boom 1 is stopped, winding up of the main hoisting rope 11 is stopped, and miswinding of the main hook 13 is prevented.

[0059] Furthermore, both during and outside of this work, in this device A, the signal line L5 of the limit switch 5 is connected to the signal line 24 between the over-hoisting prevention device and the controller via a branch wiring type connector J that is added to the back of the relay panel 7 or relay box 8 at the base 10 or boom top 16 of the boom 1, thereby improving the waterproofness of the connection point and preventing breakdowns and malfunctions due to water seepage at the connection point.

[0060] In this way, it is possible to prevent the wire W from being cut due to excessive winding of the main hoisting rope 11, as in the past, and to prevent collisions with and destruction of objects close to the crane C due to the swinging back and forth of the main hook 13 caused by the breaking of the wire W. That is, in the past, when the pile was moved up and down by the up and down movement of the secondary hook 14, the unused suspended main hook 13 would swing back and forth, crashing into the boom 1 and damaging the boom frame or lattice, and in order to prevent this, the main hook 13 was lowered below the crane C, the wire W was attached to the crane C, the wire W was hung on the main hook 13, and the wire W was tensioned appropriately to secure the main hook 13, but this measure can be made more effective.

[0061] When dismantling and transporting the crane C, as shown in Figures 5 and 6, the device A can be folded onto the crane C and transported together with the crane C. To fold the device A, first, the boom 1 of the crane C is lowered to a substantially horizontal position, and the bolts 315 are removed from the mounting brackets 31 on each frame M11 on both the left and right front sides of the main boom M1, releasing the fixed state of each arm 3 to each mounting bracket 31 and making it rotatable. In this case, the bolts 315 between the extension position guides 312A of the boom-side mounting bracket 31A and the arm-side mounting bracket 31B are removed, releasing the fixed base ends of each arm 3. This makes each arm 3 rotatable. Then, the arm-side mounting brackets 31B are overlapped with the storage position guides 312B of the boom-side mounting brackets 31A, with their longitudinal directions aligned, and bolts 315 are inserted between the bolt insertion holes 3150 and 3122 of the two, and nuts 316 are tightened to secure them together. In this way, each arm 3 is folded and arranged parallel to each frame M11 in front of the main boom M1. As a result, device A is folded and mounted parallel to the main boom M1, does not protrude from the front of the main boom M1, and does not get in the way at all. Thus, device A can be transported by crane C as it moves. Furthermore, by doing this, device A can be kept on crane C without getting in the way, and device A can be used in the same way when crane C performs similar lifting operations.

[0062] As described above, the device A includes the pair of arms 3, the cord 6, the tension spring 4, and the tension detector 5. The pair of arms 3 have length adjustment means 3L. With this configuration, during lifting work using the auxiliary hoisting rope 12 and the secondary hook 14, the distance between the rope 6 between each arm 3 and the main hoisting rope 11, which has been lowered and the primary hook 13 lowered to below the crane C and fixed there, is adjusted, and the rope 6 between each arm 3 is positioned between the boom 1 and the main hoisting rope 11, which has been lowered and the primary hook 13 lowered to below the crane C and fixed there.If the main hoisting rope 11 is wound up by the main hoisting winch or the auxiliary hoisting winch during lifting work, the rope 6 elastically receives and holds down the pulling of the main hoisting rope 11 toward the boom, and the tension detector 5 detects the tensile force from the rope 6, which is pulled by the pulling of the main hoisting rope 11 toward the boom, and sends a control signal which is transmitted by the controller to stop the winding of the main hoisting rope 11 by the main hoisting winch or the auxiliary hoisting winch.

[0063] By doing this, when the unused main hook 13 is lowered below the crane C and secured with a wire W to prevent it from being pulled toward the boom 1 during lifting work using the crane C as described above, the device A (particularly the rope 6) can be arranged to better suit the various working environments that differ at each construction site where the crane C is used, and even if the operator of the crane C mistakenly operates the main hoisting winch or auxiliary hoisting winch and winds up the main hoisting rope 11, the winding of the main hoisting rope 11 can be stopped mechanically, reliably, and safely. Therefore, with this device A, it is possible to reliably prevent the wire W from being cut due to over-winding of the main hoisting rope 11 at construction sites with various working environments, and to prevent collisions and destruction with objects close to the crane C due to the main hook 13 swinging back and forth caused by the wire W being cut.

[0064] Furthermore, the length adjustment means 3L of the pair of arms 3 is configured so that each arm 3 is made of a double tube, one of which can be moved forward and backward from the other and can be fixed at the forward and backward position, so that the length adjustment of each arm 3 is simplified and the device A can be manufactured easily and at low cost.

[0065] Furthermore, in device A, each of the pair of arms 3 is attached to the boom 1 so as to be rotatable between a protruding position where it protrudes forward from the boom 1 and a stored position where it is folded along the boom 1, so that by folding device A along the front of the boom 1, device A can be mounted on the boom 1 without protruding from the front of the boom 1 and getting in the way, and crane C can be dismantled and transported with device A still mounted on it. Furthermore, by doing so, device A can be kept on crane C without getting in the way, and device A can be used in the same way when crane C performs similar lifting work.

[0066] Furthermore, in Device A, crane C is equipped with over-winding prevention devices for the main hoisting rope and the auxiliary hoisting rope, and each over-winding prevention device is electrically connected to the controller via signal line 24, and tension detector 5 is connected to the controller by connecting signal line L5 of said tension detector 5 to signal line 24 between each over-winding prevention device and the controller via branch wiring connector J added to the back of relay panel 7 or relay box 8 at base 10 at the base end of boom 1 or boom top 16 at the tip of boom 1, so Device A has a simple overall structure and can be manufactured easily and at low cost. Another advantage of this case is that signal line 24 between each over-winding prevention device and the controller can be easily restored to its original state by simply removing branch wiring connector J and connecting a connector in the original wiring position.

[0067] Each part of the device A can be changed as follows.

[0068] In this embodiment, the pair of arms 3 are made of double pipes so that these arms 3 also have length adjustment means 3L, one of which is fixed arm 301 made of a pipe material with a large cross section that protrudes forward from boom 1, and the other is movable arm 302 made of a pipe material with a small cross section that can be slidably arranged within fixed arm 301, but on the other hand, one may be fixed arm made of a pipe material with a small cross section and the other movable arm made of a pipe material with a large cross section, with the movable arm being slidably arranged on the circumferential surface of the fixed arm. This can also achieve the same effects as the above embodiment.

[0069] Furthermore, this length adjustment means 3L may be configured such that each of the pair of arms is made of a single member, and each arm is provided on the boom so that it can be extended and retracted from the boom and fixed at any extended and retracted position, thereby adjusting the extension length of each arm. Even in this case, the same effects as those of the above embodiment can be achieved.

[0070] Furthermore, this length adjustment means 3L may be configured such that each of a pair of arms is made of a single member, and each arm is rotatably attached to the boom and can be fixed at any rotational position, thereby adjusting the protruding length of each arm. In this case, the rotation mechanism of each arm may use a rotation guide and bolts and nuts, as in the above embodiment, or a gear mechanism such as engagement between a gear and a latch may be used. This configuration also achieves the same effects as the above embodiment.

[0071] The length adjusting means 3L of the arm 3 and the rotation method may be driven and fixed using various types of power such as a motor or a cylinder.

[0072] In this embodiment, each of the pair of arms 3 is attached to the boom 1 so as to be rotatable between a protruding position where it protrudes forward from the boom 1 and a retracted position where it is folded along the boom 1, but each of the pair of arms 3 may also be attached to the boom 1 so as to be rotatable between a protruding position where it protrudes forward from the boom 1 and a retracted position where it is folded close to the boom 1. In this case, the same effects as those of the above embodiment can be achieved. Furthermore, each of the pair of arms 3 is attached to the boom 1 so as to be rotatable between a protruding position where it protrudes forward from the boom 1 and a retracted position where it is folded along or adjacent to the boom 1, but when the length adjustment means 3L is of a rotating type as described above, these may be configured as a single unit with the same rotating structure as a whole. In this way, the structure of the device A is simplified, and the device A can be manufactured easily and at low cost. Furthermore, each of the pair of arms 3 is rotatably attached to the boom 1 via a mounting bracket 31 between a protruding position where it protrudes forward from the boom 1 and a storage position where it is folded along the boom 1, but this mounting bracket can be changed as desired and may, for example, be replaced with the mounting bracket disclosed in Patent Document 3. That is, this mounting bracket has a frame mounting portion and an arm mounting portion. The frame mounting portion consists of a receiving bracket with a generally U-shaped cross section (in this case, a generally semicircular cross section) that can be attached to a columnar frame extending vertically on both the left and right sides of the front of the main boom, and a flat tightening bracket (in this case, the inner surface has a generally semicircular cross section) that is fixed and connected between both ends of the receiving bracket with a plurality of bolts and nuts. The arm mounting portion consists of a protruding direction mounting portion that is fixed to the side of the frame mounting portion, extends generally perpendicular to the tightening bracket (in other words, perpendicular to the frame), and is made of a pipe into which one end of the arm can fit, and a folding direction mounting portion that extends generally parallel to the tightening bracket (in other words, parallel to the frame), and is made of a pipe into which one end of the arm can fit. Threaded holes for bolts are formed on the periphery of each of the protruding direction mounting portion and the folding direction mounting portion. When using this device, the mounting brackets are attached to the frames on both the left and right sides of the front of the main boom by wrapping the receiving brackets around them and fastening the clamping brackets to both ends of the receiving brackets with bolts and nuts. One end of each arm is inserted into the protruding direction mounting portion of the arm mounting portion of each mounting bracket and secured by tightening bolts into the respective threaded holes of the protruding direction mounting portion, causing each arm to protrude perpendicularly from the respective frames in front of the main boom. To fold this device, loosen or remove the bolts from the respective threaded holes of the protruding direction mounting portion of the arm mounting portion of each mounting bracket, releasing the fastening of one end of each arm, and pull each arm out of the respective protruding direction mounting portion. One end of each arm is then inserted into the respective folding direction mounting portion and secured by tightening bolts into the respective threaded holes, allowing each arm to fold and position parallel to the respective frames in front of the main boom. For details, see Patent Document 3. This also provides the same effects as those of the above embodiment.

[0073] In this embodiment, the limit switch 5 is connected to the controller by connecting the signal line L5 of the limit switch 5 to the signal line 24 between each over-hoisting prevention device and the controller via a branch wiring type connector J at the base 10 at the base end of the boom 1 or the boom top 16 at the tip of the boom 1, but the signal line L5 of the limit switch 5 may also be connected by a branch wiring method to the signal line 24 between each over-hoisting prevention device and the controller at any position on the boom 1, in addition to the base 10 at the base end of the boom 1 or the boom top 16 at the tip. Even in this case, the same effects as those of the above embodiment can be achieved.

[0074] In this embodiment, the signal line L5 of the limit switch 5 is connected to the signal line 24 between each overwinding prevention device and the controller via a branch wiring type connector J, but the branch wiring type connector J can be replaced with various branch wiring methods. Examples of this type of branch wiring method include a connection method in which the signal line between each overwinding prevention device and controller is cut, the limit switch signal line is entangled with this signal line, and the line is reinforced and waterproofed with vinyl tape, and a wiring method in which the signal line between each overwinding prevention device and controller is cut, and this signal line is connected to the limit switch signal line with a crimp terminal, splice terminal, or simple tap.By using these methods, the signal line between each overwinding prevention device and controller and the limit switch signal line can be connected easily and at low cost.

[0075] In this embodiment, the signal line L5 of the limit switch 5 is connected to the signal line 24 between each overwinding prevention device and the controller via a branch wiring type connector J added to the back of the relay panel 7 or relay box 8, and then connected to the controller, but if the relay panel or relay box has a connector for the relay cable for the overwinding prevention device and this connector is not in use, this connector may be used to connect the signal line L5 of the limit switch 5 to the controller. This also achieves the same effects as the above embodiment.

[0076] In this embodiment, the signal line L5 of the limit switch 5 is connected to the signal line 24 between each overwinding prevention device and the controller via a branch wiring type connector J added to the back of the relay panel 7 or relay box 8, and then connected to the controller, but it is also possible to add a connector for a relay cable in front of the relay panel or relay box and use this connector to connect the signal line of the limit switch 5 to the signal line between each overwinding prevention device and the controller. This also achieves the same effects as the above embodiment.

[0077] In addition to the above, it goes without saying that the signal line L5 of the limit switch 5 may be directly connected to the controller (computer).

[0078] In this embodiment, a main winch is used to hoist the main hook and an auxiliary winch is used to hoist the sub hook. However, the reverse is also true: an auxiliary winch is sometimes used to hoist the main hook and a main winch is used to hoist the sub hook. This type of winch usage is seen, for example, in underground obstacle removal work and bucket excavation work. Typically, the main winch, which bears the heavier load, is installed at the front near the boom, and the auxiliary winch is installed behind it. However, some operators have the control levers and brake pedals in the driver's seat arranged in a main winch and auxiliary winch from left to right, while others have a different arrangement. The current arrangement of the control levers and brake pedals varies depending on the manufacturer. Furthermore, the main and auxiliary ropes are usually hoisted and lowered by power operation, i.e., by winch. However, when a pile cannot be inserted by power operation, for example, the load weight is used to lower it, i.e., by gravity, or free fall. This type of operation is often used in underground obstacle removal work and clam drilling work. In this case, hoisting is performed with an operating lever, but lowering is performed by letting the load fall under gravity, and the brake pedal is used to slow or stop the fall. The brake pedal is operated by pressing the brake pedal with the driver's foot, so the position of the brake pedal is important for operation, including the driver's convenience, but the brake pedal position is fixed and cannot be changed. Therefore, depending on the brake pedal position, the main hoisting rope is switched to an auxiliary winch and the auxiliary rope is switched to a main hoisting winch, and the auxiliary winch is used to hoist the main hook and the main hoisting winch is used to hoist the sub hook. The main and auxiliary hoisting winches rotate at the same speed. However, whether it is a main hoisting winch or an auxiliary hoisting winch, if a main hook is installed, the number of wire ropes attached to the pulleys increases, which slows the up and down movement of the main hook accordingly. Even when an auxiliary winch is used to hoist the parent hook and a main winch is used to hoist the child hook, this device can be applied in the same manner as in the above embodiment and can achieve the same effects as in the above embodiment.

[0079] In this embodiment, a general limit switch is used as the tension detector, but any other detector or sensor that has roughly the same function as this limit switch may be selected and used as a suitable substitute.

[0080] In this embodiment, a tension coil spring is used as the tension spring, but any other spring member or spring mechanism that has the same function as this tension coil spring may be selected and used as appropriate.

[0081] In this embodiment, a wire rope is used in the form of a cord, but any other cord or wire material that has the same function as this wire rope may be selected and used as appropriate. [Explanation of symbols]

[0082] C Crane 1. Boom M1 main boom M11 frame S1 Upper Boom 10 base P 4-sided frame P1 left frame P2 Right Frame P3 Previous frame Frame after P4 101 Boom point sheave for main hoist 102 Boom point sheave for auxiliary hoist 11 Main winding rope 12 Auxiliary rope 13 Parent Hook 14 Child Hook 15 Cord reel 16 Boom Top 161 Side Plate 162 Intermediate plate W Wire B Overwinding prevention device 21 Overwinding detector (limit switch) 22 Weight lifting rope (wire rope) 23 weight 24 signal line A. Parent hook miswinding prevention device (this device) 3 Arm 3L Length adjustment means 301 Fixed Arm 3010 Bolt insertion hole 302 Movable Arm 303 volts 304 Nut 30 Pulley 31 Mounting bracket 31A Boom side mounting bracket 311 Mounting body 3111 Bracket 3112 Fastening hardware 312 Rotating guide 312A Protrusion Position Guide 312B Storage Position Guide 3121 Bolt insertion hole 3122 Bolt insertion hole 313 Shaft insertion part 314 Rotational Axis 315 volts 316 Nut 31B Arm side mounting bracket (rotating guide) 3140 Shaft insertion part 3150 Bolt insertion hole 33 Inter-arm holding member 4. Tension springs (tension coil springs) 5. Tensile detector (limit switch) L5 signal line 6. Wire rope 7 Relay Panel 8 Junction Box J Branch wiring connector

Claims

1. A boom has at least a main boom point sheave and an auxiliary boom point sheave at its tip end, its base end is supported on a base so as to be able to be raised and lowered, and is driven by a drive unit installed on the base; a main hoisting rope is let out from one of the main hoisting winch or the auxiliary hoisting winch installed on the base and wound around the main boom point sheave at the tip end of the boom; an auxiliary hoisting rope is let out from the other winch and wound around the auxiliary boom point sheave; and a boom is connected to the tip of the main hoisting rope. a main hook suspended at the tip of the boom and a sub hook connected to the tip of the auxiliary hoisting rope and suspended at the tip of the boom; and a controller for controlling the operation of the drive unit, the main winch, and the auxiliary winch, the main hook being equipped to a crane that raises and lowers the main hook and sub hook by letting out and taking up the main hoisting rope with one of the main winch and the auxiliary winch, and letting out and taking up the auxiliary hoisting rope with the other, and preventing erroneous winding of the main hook, a pair of arms attached to a lower side of the boom in parallel in the width direction of the boom and projecting from the boom; a rope stretched between the pair of arms; a tension spring attached to one of the pair of arms and connected to one end of the rope for pulling the rope; and a tension detector attached to the other arm, operatively connected to the other end of the rope and electrically connected to the controller via a signal line, for detecting the tensile force of the rope and transmitting a control signal to the controller to stop winding of the main hoisting rope by the main hoisting winch or the auxiliary hoisting winch. Equipped with The pair of arms have length adjustment means that can adjust the length of projection from the boom, During the lifting operation using the auxiliary hoisting rope and the secondary hook, the distance between the rope between each arm and the main hoisting rope that has been lowered and the primary hook that has been lowered to below the crane and fixed is adjusted, and the rope between each arm is positioned between the boom and the main hoisting rope that has been lowered and the primary hook that has been lowered to below the crane and fixed, When the main hoisting rope is wound up by the main hoisting winch or the auxiliary hoisting winch during the lifting operation, the pulling of the main hoisting rope toward the boom side is elastically received by the cord and held down, and the tension detector detects the tensile force from the cord pulled by the pulling of the main hoisting rope toward the boom side and transmits a control signal, and the controller stops the winding of the main hoisting rope by the main hoisting winch or the auxiliary hoisting winch based on the control signal. A device for preventing miswinding of a main hook.

2. 2. The device for preventing erroneous winding of a main hook according to claim 1, wherein the length adjustment means for the pair of arms comprises a double tube, one of which can be advanced and retreated from the other and can be fixed in the advanced and retreated position.

3. The main hook miswinding prevention device according to claim 1 or 2, wherein each of the pair of arms is rotatably attached to the boom between an extended position in which it extends forward from the boom and a stored position in which it is folded along or adjacent to the boom.

4. The crane is equipped with over-winding prevention devices for the main hoisting rope and the auxiliary hoisting rope, and each of the over-winding prevention devices is electrically connected to a controller via a signal line, and the tension detector is connected to the controller by connecting its signal line to the signal line between each over-winding prevention device and the controller using a branch wiring method at any position of the boom, including the base at the base end of the boom or the boom top at the tip of the boom.

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