Fall prevention device and lifting cart

Abstract

To provide a fall prevention device capable of dispensing with a power supply, and achieving miniaturization and weight reduction as well as low-cost introduction and excellent operability of reliable and stable operation, and to provide a lifting carriage excellent in safety capable of surely preventing the fall by having the fall prevention device when ascending and descending a step such as a staircase.SOLUTION: A fall prevention device 10 mounted on a lifting carriage ascending and descending a step by a pair of left and right crawlers includes: a frame body 18 installed between the left and right crawlers; an oscillation supporting part 19 provided inside the frame body 18; an engaging claw 20 having a proximal end side in a longitudinal direction journaled to the oscillation supporting part 19 and capable of oscillating in a vertical direction; and a lock mechanism 22 mounted on the frame body 18, fixing the engaging claw 20 at a standby position so that a tip side of the engaging claw 20 does not protrude downward more than a ground surface 21 of the crawler in a normal state, and oscillating the engaging claw 20 up to such an operating position that the tip side of the engaging claw 20 protrudes more downward than the ground surface 21 of the crawler by an operation of a worker in an emergency case.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a fall prevention device that is attached to a lifting cart that ascends and descends steps and other uneven surfaces, and to a lifting cart that is equipped with the fall prevention device so that the lifting cart can ascend and descend steps and other uneven surfaces safely. [Background technology]

[0002] Conventionally, there is known a lifting cart that includes a platform on which a load is placed, wheels used for moving on flat roads, and a pair of crawlers driven by a drive source for ascending and descending steps such as stairs. With such a lifting cart, an operator holds a handle with his or her hand to carry out a transport (lifting) operation, but if the weight balance is lost and the platform tilts, or if the contact surface of the crawler becomes wet and slips, the operator's hand may come off the handle and the lifting cart may fall. Therefore, for example, Patent Document 1 and Patent Document 2 propose a fall prevention device for a lifting cart (crawler device). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-23211 A [Patent Document 2] JP 2014-54948 A Summary of the Invention [Problem to be solved by the invention]

[0004] The fall prevention device in Patent Document 1 is provided with a fixing mechanism that fixes the lifting cart to a wire member arranged on a ramp along which the lifting cart ascends and descends when the worker's hands leave the handle and the operation of the operating unit operated to activate the drive source is no longer performed. For this reason, when using the lifting cart, the wire member must be installed in advance along the ramp (the movement path of the lifting cart) and the wire member must be collected after the work (transportation) is completed, which poses the problem of cumbersome handling and poor workability. In addition, the fall prevention device of Patent Document 2 includes an acceleration sensor that detects a fall from the acceleration of the crawler device and outputs an abnormality signal to a braking mechanism, and when an abnormality signal is detected, the braking mechanism brakes the rotation of the flipper and fixes it in a standby position, thereby making the flipper function as a stopper (stop bar) and preventing the crawler device from falling. Therefore, the fall prevention device of Patent Document 2 has a problem that it may not function due to various factors such as a loss of power or a malfunction (malfunction) or failure of the acceleration sensor or the braking mechanism, and therefore lacks reliability and stability of operation. In addition, since it requires a motor for rotating the flipper and a power source for supplying power to the acceleration sensor and the motor, etc., it is costly, the device is easily enlarged and heavy, and there is also a problem that it is difficult to handle. In particular, there is a problem that the width is increased by attaching the flippers to both outer sides of the crawler device, which limits the operating (movable) range of the crawler device and reduces mobility. The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a fall prevention device that does not require a power source, can be made small and lightweight, can be introduced at low cost, and has excellent operability as it operates reliably and stably, and a lifting cart that is equipped with this fall prevention device and is therefore highly safe and can reliably prevent falls when going up or down steps or other uneven surfaces. [Means for solving the problem]

[0005] A fall prevention device according to a first aspect of the present invention that meets the above-mentioned objective is a fall prevention device that is attached to a lifting cart that ascends and descends steps using a pair of left and right crawlers, The device comprises a frame body installed between the left and right crawlers, a swinging support part provided inside the frame body, a locking claw whose base side in the longitudinal direction is journalled on the swinging support part and which can swing up and down, and a locking mechanism attached to the frame body and which fixes the locking claw in a standby position so that the tip of the locking claw does not protrude below the ground contact surface of the crawler under normal conditions, and which, in an emergency, can be operated by an operator to swing the locking claw to an operating position in which the tip of the locking claw protrudes below the ground contact surface of the crawler.

[0006] In the fall prevention device of the first invention, the locking mechanism comprises a sliding member slidably attached along the longitudinal direction of the locking claw, and an operating rod whose tip side is connected to the sliding member and whose base side penetrates the frame body, protruding outward from the high position side of the crawler when ascending or descending a step, and the sliding member has an engagement portion whose base side in the longitudinal direction is held by the sliding member and whose tip side engages with the underside of the tip side of the locking claw to hold the locking claw in the standby position in the normal state, and in the emergency, the base side of the operating rod is pushed toward the frame body by the operation of the operator, causing the sliding member to slide toward the low position side of the crawler when ascending or descending a step, and the engagement portion moves away from the tip side of the locking claw, thereby releasing the fixation of the locking claw, and the locking claw swings from the standby position to the operating position.

[0007] In the fall prevention device of the first invention, the locking mechanism may include a spring that connects the frame body and the locking claw and moves the locking claw from the standby position to the operating position when the locking claw is released.

[0008] In the fall prevention device of the first invention, the engagement portion is held by the sliding member in a tiltable manner, and after the fixation of the locking claw is released, the base side of the operating rod is pulled out from the frame body to the high position side of the crawler when ascending or descending a step by operation of the operator, and while the sliding member slides to the base side of the locking claw in the longitudinal direction, the engagement portion is pushed by the locking claw in the operating position and passes along the side of the locking claw in a tilted state, and after passing the locking claw, it returns to its initial position before tilting, and while the base side of the operating rod is pushed toward the frame body again and the sliding member slides to the tip side of the locking claw in the longitudinal direction, the locking claw that was in the operating position is lifted by the engagement portion that has returned to its initial position and moves to the standby position, and the locking mechanism is reset to the normal state.

[0009] In the fall prevention device of the first invention, the locking mechanism can include a tilting support axis that is arranged on the sliding member perpendicular to the contact surface and supports the engaging portion so that the engaging portion can be tilted midway in the longitudinal direction, and a fixed spring that connects the sliding member and the base side of the engaging portion in the longitudinal direction and holds the engaging portion in the initial position.

[0010] In the fall prevention device of the first invention, the locking mechanism comprises two left and right pressed parts provided on the sliding member, and an oscillating hammer attached to the frame body so as to be swingable in the left-right direction at the low position of the crawler when ascending or descending a step, and positioned in the middle of the two pressed parts in the normal state, and when the lifting cart tilts by a predetermined angle or more in a direction in which the positions of the left and right crawlers shift forward and backward or up and down when ascending or descending the step, the oscillating hammer swings to press either the left or right pressed part, and the sliding member slides toward the low position of the crawler when ascending or descending the step, and the engagement part moves away from the tip side of the locking claw, thereby releasing the fixation of the locking claw, and the locking claw swings from the standby position to the operating position.

[0011] A lifting cart according to a second invention that meets the above-mentioned object is a lifting cart that ascends and descends steps using a pair of left and right crawlers, A fall prevention device according to the first aspect of the present invention is attached between the left and right crawlers. Effect of the Invention

[0012] The fall prevention device according to the first invention is integrated with a frame body and installed between the left and right crawlers, so that it is easy to attach to the lifting cart and does not increase the width of the lifting cart, and is highly practical. In addition, in an emergency (for example, when the lifting cart is about to fall down a step due to loss of balance while ascending or descending a step), the tip side of the locking claw held swivelably on the frame body can be protruded below the ground surface of the crawler and hooked onto the step to prevent the fall, and is therefore highly safe. In addition, since the locking mechanism does not require a power source and is operated by the operator, the device is small, lightweight, and low-cost, yet has excellent reliability and stability of operation.

[0013] In the fall prevention device of the first invention, the locking mechanism comprises a sliding member slidably attached along the longitudinal direction of the locking claw, and an operating rod connected to the sliding member and having a base side penetrating the frame body and protruding outward from the high side of the crawler, and the sliding member has an engagement portion whose base side in the longitudinal direction is held by the sliding member and whose tip side engages with the underside of the tip side of the locking claw in a normal state to hold the locking claw in a standby position, and in an emergency, the base side of the operating rod is pushed toward the frame body by the operator's operation, causing the sliding member to slide toward the low position side of the crawler when ascending or descending a step, and the engagement portion moves away from the tip side of the locking claw, releasing the locking claw, and when the locking claw swings from the standby position to the operating position, the operator can immediately activate the locking mechanism in an emergency at his discretion.

[0014] In the fall prevention device of the first invention, if the locking mechanism connects the frame body and the locking claw and has a spring that moves the locking claw from a standby position to an operating position when the locking claw is released, the locking claw can be quickly and reliably moved to the operating position in the event of an emergency.

[0015] In the fall prevention device according to the first aspect of the invention, the engagement portion is held by the sliding member so as to be tiltable, and after the locking claw is released, the base side of the operating rod is pulled out from the frame body toward the high position side of the crawler when ascending or descending a step by the operation of the operator, and while the sliding member slides to the base side in the longitudinal direction of the locking claw, the engagement portion passes beside the locking claw in a tilted state by being pushed by the locking claw in the operating position, and after passing the locking claw, it returns to its initial position before tilting, and the base side of the operating rod is again pulled out of the frame body When the sliding member is pushed toward the side and slides toward the longitudinal tip of the locking claw, the locking claw, which was in the operating position, is lifted up by the engagement portion which has returned to its initial posture and moves to the standby position, and the locking mechanism is reset to the normal state. After adjusting the balance (posture) of the lifting cart, the operator can simply pull the operating lever out from the frame body toward the high position of the crawler when ascending or descending a step and then push it back toward the frame body, thereby moving the locking claw to the standby position and fixing it with the engagement portion, resulting in excellent operability.

[0016] In the fall prevention device of the first invention, when the locking mechanism includes a tilting support shaft that is attached to the sliding member perpendicular to the contact surface and supports the engaging part so that it can be tilted midway in the longitudinal direction of the engaging part, and a fixed spring that connects the sliding member and the base side of the engaging part in the longitudinal direction and holds the engaging part in its initial position, when the locking mechanism is reset, the engaging part can be reliably tilted using the fixed spring, resulting in excellent reliability and stability of operation.

[0017] In the fall prevention device of the first invention, the locking mechanism comprises two left and right pressed parts provided on the sliding member, and an oscillating hammer that is attached to the frame body on the low side of the crawler so that it can swing left and right, and in a normal state is positioned in the middle of the two pressed parts.When the lifting cart tilts by a predetermined angle or more in a direction that shifts the positions of the left and right crawlers back and forth or up and down when going up or down a step, the oscillating hammer swings and presses either the left or right pressed part, and the sliding member slides toward the low side of the crawler, causing the engagement part to move away from the tip side of the locking claw, thereby releasing the locking claw from its locked position and allowing the locking claw to swing from the standby position to the operating position.When the balance is suddenly lost and the lifting cart is about to fall, the locking claw is automatically released without the operator having to operate it, and the lifting cart can be prevented from falling.

[0018] The lifting cart of the second invention has the fall prevention device of the first invention attached between the left and right crawlers, so that while it is compact and lightweight, it can reliably prevent falls when going up and down steps or other uneven surfaces, making it highly safe. [Brief description of the drawings]

[0019] [Figure 1] 1 is a perspective view showing a state in which a lifting cart having a fall prevention device according to an embodiment of the present invention is used; [Diagram 2] FIG. 2 is a bottom perspective view of the fall prevention device. [Diagram 3] FIG. [Figure 4] 1A is a bottom view showing the fall prevention device in its normal state, and FIG. 1B is a cross-sectional view taken along line AA of FIG. [Diagram 5] 1A is a bottom view showing the state in which the locking claw of the fall prevention device has been released, and FIG. 1B is a cross-sectional view taken along line BB in FIG. [Figure 6] 1A is a bottom view of the main part showing the operation of the oscillating hammer of the fall prevention device, and FIG. 1B is a cross-sectional view taken along line CC in FIG. [Figure 7] 1A is a bottom view showing the operation of the fall prevention device during a reset operation, and FIG. 1B is a cross-sectional view taken along line DD in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Next, with reference to the attached drawings, an embodiment of the present invention will be described for better understanding of the present invention. As shown in FIG. 1, a fall prevention device 10 according to an embodiment of the present invention is attached to a lifting cart 13 that ascends and descends a step 12 such as a staircase by a pair of left and right crawlers 11a, 11b, and prevents the lifting cart 13 from falling. With a load (not shown) placed on a loading platform 15, the lifting cart 13 is tilted backward (toward the handle 14) and the crawlers 11a, 11b are grounded on the surface of the step 12 and driven, so that the lifting cart 13 ascends and descends the step 12. At this time, the front side of the lifting cart 13 becomes the low position side of the crawlers 11a, 11b, and the rear side of the lifting cart 13 becomes the high position side of the crawlers 11a, 11b. Wheels 16 for moving on flat ground are attached to key points on the bottom of the loading platform 15. In this embodiment, the crawlers 11a, 11b are arranged behind (on the back side of) the handle 14 that is held by the worker, but the crawlers may also be arranged below (on the bottom side of) the platform 15.

[0021] The fall prevention device 10 will be described in detail below. As shown in Figs. 2 to 7, the fall prevention device 10 has a frame 18 installed between the left and right crawlers 11a and 11b. Four swing support parts 19 are provided inside the frame 18, and each swing support part 19 holds a locking claw 20 pivotally supported at its base side in the longitudinal direction so that it can swing up and down. A locking mechanism 22 is attached to the frame 18. The locking mechanism 22 fixes the locking claw 20 to a standby position in a normal state so that the tip of the locking claw 20 does not protrude below the ground surface 21 of the crawlers 11a and 11b as shown in Fig. 4(B), and in an emergency, the locking claw 20 is swung by an operator to an operating position in which the tip of the locking claw 20 protrudes below the ground surface 21 of the crawlers 11a and 11b as shown in Fig. 5(B). In this embodiment, two locking claws 20 are arranged at two locations, one on the left and one on the front, for a total of four locking claws 20; however, the number and arrangement of the locking claws can be appropriately selected depending on the size and aspect ratio of the cargo bed, etc.

[0022] Next, the specific structure and operation of the lock mechanism 22 will be described. The lock mechanism 22 includes two front and rear sliding members 24a, 24b slidably attached along the longitudinal direction of the locking claw 20 (which coincides with the longitudinal direction of the crawlers 11a, 11b and the longitudinal direction of the frame 18), and an operating rod 25 whose tip side is connected to each of the sliding members 24a, 24b and whose base side penetrates the frame 18 and protrudes outward from the high position side (lower side in Figs. 4 and 5) of the crawlers 11a, 11b when ascending or descending a step. In a normal state, as shown in Fig. 4, the base side in the longitudinal direction is connected to each of the sliding members 24a, 24b, and the tip sides of a total of four cylindrical engagement parts 26, two on each side of the sliding members 24a, 24b, engage with the tip side of the lower surface 27 of each corresponding one of the locking claws 20, thereby holding each of the locking claws 20 in the standby position. Therefore, in a normal state, the locking claws 20 do not get caught on the surface of the step 12, and the step 12 can be ascended and descended by the crawlers 11a, 11b. In an emergency, the base side of the operating rod 25 is pushed toward the frame 18 from the state shown in Figs. 4(A) and (B) by the operator, and as shown in Figs. 5(A) and (B), the sliding members 24a and 24b slide toward the lower position side of the crawlers 11a and 11b (upper side in Figs. 5(A) and (B)). Then, the engagement portions 26 move away from the tip side of the locking claws 20, and the locking claws 20 are released from the fixed state, and the locking claws 20 swing from the standby position to the operating position. Therefore, the locking claws 20 are hooked onto the surface of the step 12, and the lifting cart 13 can be prevented from falling. Furthermore, since the base side of the operating rod 25 protrudes from the high position side of the crawlers 11a, 11b (the handle 14 side of the lifting cart 13), an operator holding the handle 14 with his or her hand can easily and quickly operate the locking mechanism 22 by pushing the base side of the operating rod 25 with his or her foot in the event of an emergency.

[0023] Here, the lock mechanism 22 includes a biasing spring 28 which connects the frame body 18 and each of the locking claws 20 and moves each of the locking claws 20 from a standby position to an actuated position when the locking claws 20 are released. In this embodiment, one end of each of the biasing springs 28 is connected to a connector 29 attached to the frame body 18 at the tip side of each of the locking claws 20, and the other end of each of the biasing springs 28 is connected to a connector 30 attached to the upper surface of each of the locking claws 20 on the base side from the position of each of the swing support parts 19. In the normal state, each of the biasing springs 28 is pulled (stretched) by lifting the tip side of each of the locking claws 20 upward at each of the engagement parts 26, and each of the locking claws 20 is rotated to the standby position and fixed. Therefore, when the fixation of each locking claw 20 by each engagement portion 26 is released, each biasing spring 28 can be contracted (restored), and each locking claw 20 can be reliably (forcibly) swung to the operating position. In this way, by forcibly swinging the locking claw 20 with the biasing spring 28, it is not necessary to rely on the locking claw 20 swinging due to its own weight, and the locking claw 20 can be made lighter. In addition, the biasing spring only needs to be able to move each of the locking claws from the standby position to the operating position by contraction or expansion when the fixation of each of the locking claws is released, and the expansion / contraction state at the attachment position and standby position can be appropriately selected. For example, if one end of the biasing spring is connected to a connector attached to the frame body above the tip side of the locking claws and the other end of the biasing spring is connected to the upper surface of the tip side of each of the locking claws, and in the normal state, the tip side of each of the locking claws is lifted upward by each of the engagement parts to compress (contract) each of the biasing springs, and each of the locking claws is rotated to the standby position and fixed, then when the fixation of the locking claws by each of the engagement parts is released, each biasing spring can be expanded (restored), and each of the locking claws can be swung to move to the operating position. However, by appropriately selecting the weight of the locking pawl, the position of the center of gravity, and the position of the swing support part relative to the overall length of the locking pawl, it is possible to swing the locking pawl from the standby position to the operating position by its own weight when the locking pawl is released, in which case the biasing spring may be omitted. Also, the number and arrangement of the sliding members and engaging parts are appropriately selected according to the number and arrangement of the locking pawls.

[0024] Next, as shown in Figures 3, 4(A), (B), 5(A) and (B), the lock mechanism 22 includes two cylindrical pressed parts 32, one on the left and one on the right, provided on the sliding member 24a, and a swinging hammer 33 attached to the center of the width of the frame 18 so as to be swingable in the left-right direction on the lower side of the crawlers 11a, 11b when ascending or descending the step. The swinging hammer 33 is normally disposed in the middle position between the two pressed parts 32, and swings when the lifting cart 13 tilts in a direction that shifts the positions of the left and right crawlers 11a, 11b back and forth or up and down when ascending or descending the step 12, and presses either the left or right pressed part 32 when the tilt reaches a predetermined angle or more. As a result, as shown in Figures 6(A) and (B), the sliding member 24a slides toward the lower position of the crawlers 11a and 11b when ascending or descending the step, the engaging portions 26 move away from the tips of the locking claws 20, the locking claws 20 are released, and the locking claws 20 swing from the standby position to the operating position. At this time, the sliding member 24b connected to the sliding member 24a by the operating rod 25 also slides toward the lower position of the crawlers 11a and 11b when ascending or descending the step, the engaging portions 26 move away from the tips of the locking claws 20, the locking claws 20 are released, and the locking claws 20 swing from the standby position to the operating position (see Figures 5(A) and (B)). Therefore, in an emergency, not only when an operator operates the lifting cart 13, but also when the balance is lost and the lifting cart 13 is greatly tilted, the locking mechanism 22 automatically functions to prevent the lifting cart 13 from falling.

[0025] Next, the reset operation of the lock mechanism 22 will be described. As shown in Figures 4(A), (B), 5(A) and (B), the locking mechanism 22 includes a total of four tilting support shafts 34, two of which are provided on each of the sliding members 24a, 24b perpendicular to the contact surface 21 and which support each of the engaging portions 26 in a tiltable manner midway along the longitudinal direction of the engaging portions 26, and a total of four fixed springs 35 that connect the longitudinal base sides of each of the engaging portions 26 provided on each of the sliding members 24a, 24b to each of the sliding members 24a, 24b and hold each of the engaging portions 26 in an initial position. In this embodiment, one end of each fixed spring 35 is connected to a first connecting device 36 attached to a lower position of the crawlers 11a, 11b than each tilting support shaft 34 of each sliding member 24a, 24b when ascending or descending a step, and the other end of each fixed spring 35 is connected in a neutral state to a second connecting device 37 attached to the base side of the longitudinal direction of each engaging portion 26, but the method of connecting the fixed springs can be selected as appropriate.

[0026] With the above configuration, each of the engagement parts 26 is held by each of the sliding members 24a, 24b so as to be tiltable. Therefore, after the locking claws 20 are released, the base side of the operating rod 25 is pulled out from the frame 18 toward the high position side of the crawlers 11a, 11b by the operator's operation as shown in Fig. 7, and while each of the sliding members 24a, 24b slides toward the base side in the longitudinal direction of the locking claws 20, each of the engagement parts 26 is pushed by each of the locking claws 20 in the operating position and tilts as shown by the imaginary line. Then, each of the engagement parts 26 passes by the side of each of the locking claws 20 while each of the fixing springs 35 is in a tensioned state, and after passing each of the locking claws 20, each of the fixing springs 35 contracts (returns to a neutral state), thereby returning to the initial position before tilting. Thereafter, by the operator's operation, the base side of the operating rod 25 is again pushed toward the frame body 18 (the lower position side of the crawlers 11a, 11b when ascending and descending steps) and each sliding member 24a, 24b slides toward the longitudinal tip side of each locking claw 20, while each locking claw 20, which was in the operating position, is lifted by each engagement portion 26 (see Figures 7(A) and (B)), which has returned to its initial posture, and moves to the standby position, and the locking mechanism 22 is reset to the normal state shown in Figures 4(A) and (B). In this way, the locking mechanism 22 can be reset to the normal state by a simple operation of pulling the operating rod 25 out once to the high position of the crawlers 11a, 11b when ascending or descending a step, and then pushing it back to the low position. This eliminates the need for the operator to directly and manually move each of the locking claws 20 or each of the sliding members 24a, 24b, etc., providing excellent operability. In this embodiment, as shown in FIG. 3, a guide member 39 is provided in the widthwise center of the frame body 18 along the longitudinal direction of the frame body 18, and long guide holes 40a, 40b are formed in two locations, one at the front and one at the rear, penetrating the guide member 39 in the widthwise direction. The guide shafts 41a, 41b provided on each of the sliding members 24a, 24b are loosely fitted into the guide holes 40a, 40b, respectively, to enable each of the sliding members 24a, 24b to slide smoothly. However, the structure of the guide member and the method of guiding each of the sliding members are not limited to this and may be selected as appropriate.

[0027] Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations described in the above embodiments, and also includes other embodiments and variations that can be considered within the scope of the matters described in the claims. The components of the fall prevention device are preferably made of metal such as stainless steel. [Explanation of symbols]

[0028] 10: fall prevention device, 11a, 11b: crawler, 12: step, 13: lifting cart, 14: handle, 15: loading platform, 16: wheels, 18: frame, 19: swing support part, 20: locking claw, 21: contact surface, 22: lock mechanism, 24a, 24b: sliding member, 25: operating rod, 26: engagement part, 27: lower surface, 28: biasing spring, 29: connector, 30: connector, 32: pressed part, 33: swing hammer, 34: tilt support shaft, 35: fixed spring, 36: first connector, 37: second connector, 39: guide member, 40a, 40b: guide hole, 41a, 41b: guide shaft

Claims

1. A fall prevention device that is attached to a lifting cart that ascends and descends steps using a pair of left and right crawlers, The locking mechanism includes a frame body installed between the left and right crawlers, a swing support part provided inside the frame body, a locking claw whose base side in the longitudinal direction is journaled on the swing support part and can swing up and down, and a locking mechanism attached to the frame body, which fixes the locking claw in a standby position so that the tip side of the locking claw does not protrude below the ground contact surface of the crawler in a normal state, and swings the locking claw by operation of an operator to an operating position in which the tip side of the locking claw protrudes below the ground contact surface of the crawler in an emergency, the locking mechanism including a sliding member attached slidably along the longitudinal direction of the locking claw, and a locking mechanism having a tip side connected to the sliding member and a base side penetrating the frame body, and an operating rod that protrudes outward from the high position side of the crawler when ascending or descending a step, wherein the sliding member has an engagement portion whose base side in the longitudinal direction is held by the sliding member and whose tip side engages with the underside of the tip side of the locking claw to hold the locking claw in the standby position in the normal state, and in the emergency, the base side of the operating rod is pushed toward the frame body by the operator, causing the sliding member to slide toward the low position side of the crawler when ascending or descending a step, and the engagement portion moves away from the tip side of the locking claw, releasing the locking claw and causing the locking claw to swing from the standby position to the operating position.

2. 2. A fall prevention device as described in claim 1, characterized in that the locking mechanism is provided with a spring that connects the frame body and the locking claw and moves the locking claw from the standby position to the operating position when the locking claw is released.

3. 3. A fall prevention device as claimed in claim 1 or 2, characterized in that the engagement portion is held by the sliding member in a tiltable manner, and after the locking claw is released, the base side of the operating rod is pulled out from the frame body to the high position side of the crawler when ascending or descending a step by the operation of the operator, and while the sliding member slides to the base side of the locking claw in the longitudinal direction, the engagement portion is pushed by the locking claw in the operating position and passes beside the locking claw in a tilted state, and after passing the locking claw, the engagement portion returns to its initial position before tilting, and while the base side of the operating rod is pushed towards the frame body again and the sliding member slides to the tip side of the locking claw in the longitudinal direction, the locking claw that was in the operating position is lifted by the engagement portion that has returned to its initial position and moves to the standby position, and the locking mechanism is reset to the normal state.

4. In the fall prevention device described in claim 3, the locking mechanism is characterized in that it comprises a tilting support shaft that is provided on the sliding member perpendicular to the ground contact surface and supports the engaging portion in a tiltable manner midway in the longitudinal direction of the engaging portion, and a fixed spring that connects the sliding member and the base side of the engaging portion in the longitudinal direction and holds the engaging portion in the initial position.

5. In a fall prevention device described in any one of claims 1 to 4, the locking mechanism comprises two pressed parts, left and right, provided on the sliding member, and an oscillating hammer attached to the frame body so as to be swingable in the left-right direction on the low position side of the crawler when ascending or descending a step, and positioned in the middle position of the two pressed parts in the normal state, wherein when ascending or descending the step, the lifting cart tilts at a predetermined angle or more in a direction in which the positions of the left and right crawlers shift forward and backward or up and down, the oscillating hammer swings to press either the left or right pressed part, and the sliding member slides toward the low position side of the crawler when ascending or descending the step, and the engagement part moves away from the tip side of the locking claw, thereby releasing the fixation of the locking claw, and the locking claw swings from the standby position to the operating position.

6. A lifting cart that ascends and descends steps using a pair of left and right crawlers, A lifting cart, comprising a fall prevention device according to any one of claims 1 to 5 attached between the left and right crawlers.

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