Falling prevention tool

Abstract

To provide a falling prevention tool which can be attached / detached to / from a bolt and a nut with manual operation without using a tool to prevent the deviation of a mounting position.SOLUTION: A bolt holding part 7 of a falling prevention tool 5 has a coil spring type tilting support part 73 for connecting the base end side of a fixed arm 71 to the base end side of a movable arm 72. The tilting support part 73 has a torsion resistance for holding the state of isolating both arms 71, 72 from each other in a natural state, while allowing torsion operation against the torsion resistance to tilt both arms 71, 72 to come close to each other. At the finishing end of a first operation part 74 of the fixed arm 71 and at the finishing end of a second operation part 75 of the movable arm 72, a catch 77 and a hook 76 are provided in a divided manner, respectively, which are locked to hold the state that both arms 71, 72 come close to each other to sandwich a shaft part 11.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a fall-off prevention device that is attached to a bolt to which a nut having a polygonal outer periphery is attached, thereby preventing the nut from falling off. [Background technology]

[0002] For example, Patent Documents 1 and 2 disclose a device for preventing a hexagonal nut attached to a bolt from loosening.

[0003] The anti-fall-off device of Patent Document 1 comprises a first coil spring portion that is wound around the leg (shaft) of the bolt, a second coil spring portion that is rotated with a socket wrench in the direction of tightening the anti-fall-off device, a third coil spring portion that abuts against the upper surface of the nut, a fourth coil spring portion that is fitted into the outer peripheral surface of the nut, and an extension portion that is hooked onto one side of the hexagonal nut.

[0004] For example, the anti-fall-off device in Patent Document 2 comprises a first coil spring portion that is fitted onto the outer peripheral surface of a nut, a second coil spring portion that is wound around the leg of a bolt, and first and second arm portions for manually expanding the inner diameter of the second coil spring portion, and the first coil spring portion is provided with an apex that abuts against a corner of the nut. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-12545 A [Patent Document 2] Patent Publication No. 2021-32389 Summary of the Invention [Problem to be solved by the invention]

[0006] In the above-mentioned Patent Document 1, as described in paragraph 0047, when the fall-off prevention device is attached to the bolt and the nut and when it is removed from the bolt and the nut, it is necessary to use a tool such as the socket wrench. Therefore, without the tool, the fall-off prevention device cannot be attached or removed.

[0007] In Patent Document 2, the anti-fall-off device can be attached to the bolt and the nut by manually moving the first and second arm portions closer together. However, if the first and second arm portions are pushed in a direction in which they approach each other, the inner diameter of the second coil spring portion expands, which may cause the second coil spring portion to shift from its attachment position relative to the leg of the bolt, thereby weakening the anti-fall-off effect.

[0008] In view of the above circumstances, the present invention aims to provide a fall-off prevention device that can be attached to and detached from bolts and nuts manually without using tools and that can prevent the attachment position from shifting. [Means for solving the problem]

[0009] The present invention provides a fall-off prevention device that is attached to a bolt having a polygonal periphery to prevent the nut from falling off, the device comprising a nut holding part that is wrapped around the outer periphery of the nut so as not to rotate relative to the nut, and a bolt holding part that holds the shank of the bolt from the outer diameter side, the nut holding part and the bolt holding part being formed by bending a single metal wire, the bolt holding part being formed by bending a single metal wire, a fixed arm and a movable arm that can be tilted between a state in which they approach each other so as to hold the shank of the bolt from the outer diameter side and a state in which they are separated from the shank, and a base end side of the fixed arm and a base end side of the movable arm that are connected to each other and naturally rotate. and a coil spring-like tilting fulcrum portion that has a torsional resistance for maintaining the arms apart in a fixed state, while allowing a twisting operation against the torsional resistance to tilt the arms toward each other, and a first operating portion and a second operating portion are connected to the free end side of the fixed arm and the free end side of the movable arm for manually bringing the arms closer together, and a catch and a hook are provided at each end of the first operating portion and the second operating portion to engage and maintain the arms close together so as to sandwich the shaft portion.

[0010] According to this configuration, the nut holding portion is wrapped around the nut, and the tilting fulcrum portion is twisted to bring the first operating portion and the second operating portion closer together so that the fixed arm and the movable arm are clamped to the shaft portion of the bolt, and then the hook is engaged with the catch, thereby maintaining the anti-fall-off device attached to the bolt and the nut.

[0011] In this state, even if an external force acts on the fixed arm and the movable arm such that they approach each other, the fixed arm and the movable arm are prevented from moving away from the shaft of the bolt, and the nut is prevented from loosening.

[0012] Then, when the hook is removed from the catch and the tilting fulcrum portion is twisted to bring the fixed arm and the movable arm closer together, the fixed arm and the movable arm are separated from the shaft portion of the bolt, and the anti-fall-out device can be removed from the bolt and the nut.

[0013] In this way, by manually moving the fixed arm and the movable arm closer together and manually engaging and disengaging the catch and the hook, it is possible to maintain the anti-fall-off device attached to the bolt and the nut, or to make the anti-fall-off device removable from the bolt and the nut.

[0014] In the above-mentioned anti-fall-out device, the nut holding portion includes a winding ring that is wound in a polygonal shape starting from one end of the metal wire to correspond to the outer peripheral shape of the nut, and a tightening ring that is wound in a circular shape starting from the end of the winding direction of the winding ring so that its inner circumference is circumscribed by the winding ring, and the end of the winding direction of the tightening ring can be configured to be connected to the catch.

[0015] In this configuration, the configuration of the nut holding portion is specified, and it becomes clear that this specification enables the nut holding portion to be easily attached to and detached from the nut.

[0016] Furthermore, in the above-mentioned anti-fall-off device, the second operating part is formed in a straight rod shape from a midpoint closer to the movable arm to a part closer to the hook, and this straight rod-shaped part is inclined with respect to an imaginary line seen from the side of the central axis of the movable arm so that the end side closer to the hook is closer to the nut holding part than the end side closer to the movable arm, in side view; the catch is formed in a straight rod shape and is inclined with respect to the central axis of the tightening ring so that the end side closer to the tightening ring is positioned radially inward than the end side closer to the first operating part, in side view; and the hook can be formed in a shape that allows it to engage with the catch from the radially inside.

[0017] According to this configuration, the operation of engaging the hook with the catch can be performed relatively easily, and the hook is less likely to come off the catch.

[0018] Furthermore, in the above-mentioned fall-off prevention device, a marker may be attached to the tilting fulcrum portion to facilitate visual recognition of the position of the tilting fulcrum portion.

[0019] According to this configuration, the position of the tilt fulcrum part can be easily recognized by visually checking the marker attached to the tilt fulcrum part.

[0020] As a result, for example, in the event that the nut becomes loose while the fall-off prevention device is attached to the bolt and the nut, the positions of the tilting fulcrum and the marker are displaced by a predetermined angle toward the loosening side from the initial positions of the fall-off prevention device when it is attached. Therefore, when an operator or the like visually checks the position of the marker attached to the tilting fulcrum, he or she can recognize that the nut is loose. Effect of the Invention

[0021] According to the present invention, it is possible to provide a fall-off prevention device that can be attached to and detached from a bolt and a nut by hand without using tools and that can prevent the attachment position from shifting. [Brief description of the drawings]

[0022] [Figure 1] 1 is a perspective view showing one embodiment of a fall-off prevention device according to the present invention, illustrating a state in which a hook is engaged with a catch. FIG. [Diagram 2] FIG. 2 is a front view of the fall-off prevention device, showing the natural state in which the hook is not engaged with the catch. [Diagram 3] 3 is a front view of the fall-prevention device, showing a state in which the hook has passed before the catch in preparation for attaching the fall-prevention device to a bolt or nut from the natural state of FIG. 2. [Figure 4] This is a front view of the fall-prevention device, showing the state in which the fall-prevention device has been attached to the bolt and nut from the state in Figure 3 and the hook has been engaged with the catch. [Diagram 5] 2. FIG. [Figure 6] This is a view seen from the direction of the arrow (6) in FIG. [Figure 7] This is a view seen from the direction of the arrow (7) in FIG. [Figure 8] 1 is a side view showing the state in which the fall-off prevention device is attached to a bolt and a nut. FIG. [Figure 9] FIG. 11 is a front view showing another embodiment of the fall-off prevention device according to the present invention, showing the state in which the fixed arm and the movable arm are close to each other but the hook is not engaged with the catch. [Figure 10] This is a view seen from the direction of the arrow (10) in FIG. [Figure 11] 5 is a front view showing another embodiment of the fall-off prevention device according to the present invention, illustrating a state in which a marker is attached to the tilting fulcrum portion in FIG. 4. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings.

[0024] One embodiment of the present invention is shown in Figures 1 to 8. A fall prevention device 5 is attached to a bolt 1 to which a nut 2 having a polygonal outer periphery is attached, thereby preventing the hexagonal nut 2 from falling off. The bolt 1 and the nut 2 are intended to be mounted on, for example, large freight vehicles, ordinary automobiles, or various types of mechanical equipment.

[0025] The fall-off prevention device 5 includes a nut holding portion 6 and a bolt holding portion 7, and the nut holding portion 6 and the bolt holding portion 7 are formed by bending a single metal wire.

[0026] The nut holding portion 6 is wrapped around the outer periphery of the nut 2 so as to be non-rotatable relative to the nut 2, and includes a wrapping ring 61 and a tightening ring 62.

[0027] The winding ring 61 is wound hexagonally to correspond to the outer peripheral shape of the nut 2 , and each of its six straight rod portions is close to or in contact with six faces of the hexagonal nut 2 .

[0028] The tightening ring 62 is wound in a circular shape, and its inner circumference is set to a size such that it is circumscribed by the winding ring 61 .

[0029] Here, in the hexagonal winding ring 61, one end is referred to as the "starting end in the winding direction" and the other end is referred to as the "terminal end in the winding direction." In addition, in the circular tightening ring 62, one end is referred to as the "starting end in the winding direction" and the other end is referred to as the "terminal end in the winding direction." However, hereinafter, the starting end in the winding direction is abbreviated to the "winding starting end" and the terminal end in the winding direction is abbreviated to the "winding terminal end."

[0030] The winding starting end of the tightening ring 62 is connected to the winding end of the winding ring 61, the winding starting end of the tightening ring 62 is connected to the winding end of the first operating portion 74 of the fixed arm 71 described below, and the winding starting end of the winding ring 61 is connected to the winding starting end of the second operating portion 75 of the movable arm 72 described below.

[0031] The bolt holding portion 7 clamps the shaft portion 11 of the bolt 1 from the outer diameter side, and includes a fixed arm 71 , a movable arm 72 , a tilt fulcrum portion 73 , a hook 76 , and a catch 77 .

[0032] The fixed arm 71 and the movable arm 72 are tiltable between a state in which they approach each other so as to sandwich the shaft portion 11 of the bolt 1 from the outer diameter side, and a state in which they are separated from the shaft portion.

[0033] The fixed arm 71 and the movable arm 72 are provided at their free ends with curved portions 71a and 72a that are curved in a semicircular ring shape.

[0034] The curved portion 71 a of the fixed arm 71 and the curved portion 72 a of the movable arm 72 form an annular space that can be fitted onto the shank 11 of the bolt 1 by bringing the two arms 71 , 72 close to each other.

[0035] A first operating part 74 is connected to the curved part 71 a of the fixed arm 71 , and a second operating part 75 is connected to the curved part 72 a of the movable arm 72 .

[0036] The first operating part 74 is formed in a straight rod shape so as to extend radially outward from the curved part 72a of the movable arm 72. In this first operating part 74, the end part closer to the fixed arm 71 is referred to as the "starting end" and the end part closer to the catch 77 is referred to as the "ending end".

[0037] The second operating portion 75 is formed in a U-shaped rod shape that extends radially outward from the curved portion 71a of the fixed arm 71 and then makes a U-turn.

[0038] In the long straight portion 75a of the second operating part 75, the end portion closer to the movable arm 72 is referred to as the "starting end" and the end portion closer to the hook 76 is referred to as the "terminal end." As shown in Fig. 7, the long straight portion 75a of the second operating part 75 is inclined at a predetermined angle α with respect to an imaginary straight line 100 (see dashed line) which is a view of the central axis of the movable arm 72 from the side, so that the terminal end side is closer to the nut holding part 6 than the starting end side in a side view.

[0039] The tilting fulcrum part 73 is formed in a coil spring shape. One end of the tilting fulcrum part 73 in the winding direction is connected to the base end side of the fixed arm 71, and the other end of the tilting fulcrum part 73 in the winding direction is connected to the base end side of the movable arm 72.

[0040] This tilting fulcrum portion 73 has a torsional resistance to keep the fixed arm 71 and the movable arm 72 separated in the natural state, while allowing a twisting operation that resists the torsional resistance to tilt the fixed arm 71 and the movable arm 72 toward each other.

[0041] When the coil spring-like tilt fulcrum portion 73 is twisted, a reaction force to the twisting operation, that is, an elastic restoring force that returns the twisting, is stored in the tilt fulcrum portion 73 .

[0042] 5 to 7, the catch 77 is formed in a straight rod shape and connects the end of the first operating part 74 of the fixed arm 71 to the winding end of the tightening ring 62. The end of the first operating part 74 refers to the end portion closer to the catch 77 and the tightening ring 62.

[0043] In this straight rod-shaped catch 77, the end closer to the first operating part 74 is referred to as the starting end, and the end closer to the fastening ring 62 is referred to as the terminal end. As shown in Fig. 7, the catch 77 is inclined at a predetermined angle β with respect to the central axis 200 (see dashed line) of the fastening ring 62 so that the terminal end side is positioned radially inward relative to the starting end side in a side view.

[0044] The hook 76 is provided at the terminal end of the second operating portion 75 of the movable arm 72. The terminal end of the second operating portion 75 is the end portion away from the curved portion 72a, that is, the terminal end of the long straight portion 75a.

[0045] The hook 76 is formed in a wave shape as shown in Figures 2 and 4. More specifically, the hook 76 is bent inwardly in the radial direction from the end of the second operating part 75 in a direction perpendicular to the end of the second operating part 75 in the natural state shown in Figure 2, then bent into an inverted V shape, and is further bent into a V shape to form a wave shape.

[0046] The valleys of the inverted V-shaped bent portions of the wavy hooks 76 are engaged with the straight rod-shaped catches 77 from the radially inner side.

[0047] When the hook 76 is engaged with the catch 77 , they protrude slightly toward the outer diameter side beyond the fastening ring 62 of the nut holding portion 6 .

[0048] When the hook 76 is engaged with the catch 77, the fixed arm 71 and the movable arm 72 are held in a state in which they are close to each other so as to sandwich them. On the other hand, when the hook 76 is released from the catch 77, the worker can manually move the fixed arm 71 and the movable arm 72 apart in order to release the fall-off prevention device 5 from the bolt 1 and the nut 2.

[0049] Next, the procedure and operation for attaching the fall-off prevention device 5 to the bolt 1 and the nut 2 will be described with reference to Figs.

[0050] First, with the fixed arm 71 and the movable arm 72 spaced apart as shown in FIG. 2, the operator places the thumb of one hand on the starting end of the long straight portion 75a of the second operating part 75 while placing the middle finger or index finger of one hand on the terminal portion of the first operating part 74 and operates them to draw them closer to each other, thereby bringing the fixed arm 71 and the movable arm 72 closer together and creating a circular space between the curved portion 71a of the fixed arm 71 and the curved portion 72a of the movable arm 72, and causing the hook 76 of the movable arm 72 to pass beyond the catch 77 of the fixed arm 71, as shown in FIG. 3.

[0051] The pulling operation is a twisting operation that resists the torsional resistance of the tilt fulcrum portion 73 and the tightening ring 62. When the tilt fulcrum portion 73 is twisted in this manner, a reaction force of the twisting operation (an elastic restoring force that returns the twisting) is stored in the tilt fulcrum portion 73 and the tightening ring 62.

[0052] After this, the operator again manually operates the second operating part 75 to draw the starting end portion of the long straight portion 75a and the terminal end portion of the first operating part 74 together to expand the diameter of the annular space, and while fitting the space onto the shank 11 of the bolt 1, the wrapping ring 61 of the nut holding part 6 is fitted so as to wrap around the nut 2, and then the operator releases his / her fingers from the second operating part 75 and the first operating part 74.

[0053] As a result, the reaction force of the twisting operation of the tilting fulcrum portion 73 presses the curved portion 71a of the fixed arm 71 and the curved portion 72a of the movable arm 72 into the threaded groove of the shaft portion 11 of the bolt 1, and further, the reaction force of the twisting operation of the tightening ring 62 causes the hexagonal wrapping ring 61 to tighten the nut 2.

[0054] 4, the worker uses one or both hands to engage the hook 76 of the movable arm 72 with the catch 77 of the fixed arm 71. This keeps the fall-off prevention device 5 attached to the bolt 1 and nut 2, so they are locked and cannot be separated.

[0055] In this state where the hook 76 is engaged with the catch 77, the short straight portion 75b of the second operating part 75 is pressed radially inward, but the reaction force (see arrow F1 in Fig. 4) causes the long straight portion 75a of the second operating part 75 to be pushed in the directions of the arrows F2 and F3 in Fig. 4. Because loads (F2 and F3) are generated due to this pushing, the hook 76 becomes difficult to disengage from the catch 77.

[0056] Furthermore, if vibration or the like is input to the bolt 1 and the nut 2, a load is generated in a direction that causes the bolt retaining portion 7 to come out of the shank 11 of the bolt 1 (see the direction of arrow F4 in Figure 8). However, this load (F4) is reduced by the loads (F2, F3) associated with the tensioning, and therefore the bolt retaining portion 7 can be prevented from coming out of the shank 11 of the bolt 1.

[0057] In this manner, the fall-off prevention device 5 according to this embodiment can prevent the nut 2 from loosening or falling off.

[0058] 2 to 4, the procedure and operation for detaching the fall-off prevention device 5 from the bolt 1 and the nut 2 will be described.

[0059] With the hook 76 engaged with the catch 77 as shown in FIG. 4, an operator manually removes the hook 76 from the catch 77.

[0060] Thereafter, the worker manually operates the second operating part 75 to pull together the starting end portion of the long straight part 75a and the terminal end portion of the first operating part 74, thereby separating the curved part 71a of the fixed arm 71 and the curved part 72a of the movable arm 72 from the shaft part 11 of the bolt 1, and removes the bolt holding part 7 from the shaft part 11, and also removes the wrapping ring 61 and the tightening ring 62 from the nut 2. This allows the fall-off prevention device 5 to be removed from the bolt 1 and the nut 2.

[0061] After removing the anti-fall-off device 5 in this manner, when the operator releases his / her fingers from the second operating part 75 and the first operating part 74, the reaction force of the twisting operation of the tilting fulcrum part 73 causes the fixed arm 71 and the movable arm 72 to return to their natural state in which they are separated from each other, as shown in Figure 2.

[0062] As described above, according to the embodiment of the fall-off prevention device 5 to which the present invention is applied, the fall-off prevention device 5 can be attached to or removed from the bolt 1 and nut 2 easily by hand, without using tools as in the conventional example.

[0063] Furthermore, when the fall prevention device 5 is attached to the bolt 1 and the nut 2 and the hook 76 is engaged with the catch 77, the locking action between the hook 76 and the catch 77 maintains the fastening action of the nut 2, thereby preventing the nut 2 from easily loosening or falling off.

[0064] Furthermore, since the long straight portion 75a of the second operating part 75 is inclined at a predetermined angle α with respect to the imaginary straight line 100 and the catch 77 is inclined at a predetermined angle β with respect to the central axis 200, the engagement state of the hook 76 with the catch 77 is strengthened and the hook 76 is less likely to come off the catch 77.

[0065] Furthermore, since the fall-off prevention device 5 of this embodiment is formed by bending a single metal wire, it is advantageous in terms of reducing manufacturing costs compared to a configuration in which a large number of individual parts are combined.

[0066] Furthermore, when the fall prevention device 5 of this embodiment is attached to the bolt 1 and nut 2, the amount by which the tilting fulcrum portion 73, hook 76 and catch 77 protrude toward the outer diameter side of the circular tightening ring 62 is made as small as possible, making it less likely that the hands or feet of an operator will hit the hook 76 and catch 77, and making it relatively easy to attach and detach the device to and from the bolt 1 and nut 2 installed in a narrow space.

[0067] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the claims and a range equivalent to the claims.

[0068] (1) For example, Figures 9 and 10 show another embodiment of the present invention. This embodiment is a modification of the embodiment shown in Figure 1. In this embodiment, the shapes of the hook 76 and the catch 77 are different from those of the above embodiment. The other configurations are basically the same as those of the embodiment shown in Figure 1.

[0069] The hook 76 is formed in a V-shape. Specifically, as shown in Fig. 9, the hook 76 is bent from the end of the second operating part 75 so as to be perpendicular to the counterclockwise direction, and then further bent from the perpendicular state by a predetermined angle (for example, 90 to 170 degrees, preferably 110 to 150 degrees, and more preferably 130 degrees) in the clockwise direction. As a result, the interior angle of the V-shaped hook 76 is set to, for example, 10 to 90 degrees, preferably 30 to 70 degrees, and more preferably 50 degrees. In addition, the straight rod-shaped catch 77 is parallel to the central axis 200 of the tightening ring 62 in a side view as shown in Fig. 10.

[0070] Since the end edge of the hook 76 having this shape faces radially outward, when engaging the hook 76 with the catch 77, the end of the hook 76 needs to be significantly bent so as to move toward the inner diameter side from the position of the catch 77; however, once engaged, the hook 76 is difficult to come off the catch 77.

[0071] (2) For example, Fig. 11 shows another embodiment of the present invention. This embodiment is a modification of the embodiment shown in Fig. 1. In this embodiment, a marker 8 for an indicator is attached to the tilt fulcrum part 73.

[0072] The marker 8 is an optional accessory that can be selected as needed for the fall-off prevention device 5. The marker 8 is colored in a conspicuous color, such as orange, so that it can be easily recognized by visual inspection.

[0073] After the fall-off prevention device 5 is attached to the bolt 1 and the nut 2, the marker 8 is fitted, for example by press fitting, into the inner diameter side of the coil spring-shaped tilt fulcrum portion 73.

[0074] Furthermore, when the anti-fall-off device 5 is attached to the bolt 1 and nut 2, the inner diameter of the coil spring-shaped tilt fulcrum portion 73 is reduced, so that if the marker 8 is pressed into the tilt fulcrum portion 73 in this state, the marker 8 will not easily come out.

[0075] In the case where the marker 8 is attached to the tilting fulcrum part 73 in this way, in the unlikely event that the nut 2 to which the fall-off prevention device 5 is attached becomes loose, the positions of the tilting fulcrum part 73 and the marker 8 will be displaced by a predetermined angle toward the loosening side from the initial positions at which the fall-off prevention device was attached. Therefore, by visually checking the position of the marker 8 attached to the tilting fulcrum part 73, an operator or the like can recognize that the nut has loosened.

[0076] (3) In the above embodiment, an example was given in which the wrapping ring 61 of the nut holding portion 6 was hexagonal, but the present invention is not limited to this.

[0077] For example, although not shown, the nut holding portion 6 can be formed into various shapes (polygonal shapes) in accordance with the shape of the nut. In the case of such an embodiment, the same actions and effects as those of the above embodiment can be obtained. [Industrial Applicability]

[0078] INDUSTRIAL APPLICABILITY The present invention can be suitably used for a fall prevention device that is attached to a bolt to which a nut having a polygonal outer periphery is attached, thereby preventing the nut from falling off. [Explanation of symbols]

[0079] 1 Volt 11 Shaft 2 Nuts 5 Fall prevention device 6 Nut holder 61 Winding Ring 62 Clamping Ring 7 Bolt holder 71 Fixed Arm 71a Curved section 72 Movable Arm 72a Curved section 73 Tilting support part 74 1st operation section 75 2nd operation section 76 Hook 77 Catch 100 Imaginary straight line along the radial direction of the nut holding part 200 Central axis of the tightening ring

Claims

1. A fall prevention device that is attached to a bolt to which a polygonal nut is attached, thereby preventing the nut from falling off, A nut holding part is wound around the outer periphery of the nut so as not to rotate relative to the nut, and a bolt holding part is provided which holds the shaft part of the bolt from the outer diameter side. The nut holding portion and the bolt holding portion are formed by bending a single metal wire, the bolt holding portion includes a fixed arm and a movable arm that are tiltable between a state in which the bolt is brought close to the shaft portion of the bolt so as to sandwich the shaft portion from an outer diameter side and a state in which the bolt is separated from the shaft portion; a coil spring-like tilt fulcrum portion that connects a base end side of the fixed arm and a base end side of the movable arm and has a torsional resistance for maintaining a state in which the two arms are separated in a natural state, while allowing a torsional operation against the torsional resistance so as to tilt the two arms to a state in which they approach each other, A first operating unit and a second operating unit are connected to the free end side of the fixed arm and the free end side of the movable arm for manually moving the arms closer to each other, This anti-fall-off device is characterized in that a catch and a hook are provided at each end of the first operating part and the second operating part to engage and hold the arms close together so as to sandwich the shaft part.

2. The fall-off prevention device according to claim 1, The nut holding portion includes a winding ring that is wound in a polygonal shape with one end of the metal wire as a starting point in correspondence with the outer peripheral shape of the nut, and a tightening ring that is wound in a circular shape with an inner periphery circumscribed by the winding ring with an end of the winding direction of the winding ring as a starting point, A device for preventing a fall-off, characterized in that the end of the tightening ring in the winding direction is connected to the catch.

3. The fall-off prevention device according to claim 2, the second operating portion is formed in a straight rod shape from a middle portion closer to the movable arm to a portion closer to the hook, and the straight rod-shaped portion is inclined in side view with respect to a virtual straight line of a central axis of the movable arm as viewed from the side such that the end side closer to the hook is closer to the nut holding portion than the end side closer to the movable arm, the catch is formed in a straight rod shape, and is inclined with respect to a central axis of the fastening ring such that an end side closer to the fastening ring is positioned radially inward relative to an end side closer to the first operating portion in a side view, The hook is shaped to be engaged with the catch from the radially inner side.

4. The fall-off prevention device according to any one of claims 1 to 3, A fall-off prevention device characterized in that a marker is attached to the tilt fulcrum portion to make it easier to visually recognize the position of the tilt fulcrum portion.

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