Forklift

Abstract

To provide a forklift capable of preventing damage of a stopper mechanism due to elongation of a lift chain in a full-free three-stage mast.SOLUTION: A forklift 10 includes an outer mast 19, a middle mast 20 capable of moving up and down with respect to the outer mast 19, an inner mast 21 capable of moving up and down with respect to the middle mast 20, a lift bracket 23 capable of moving up and down with respect to the inner mast 21, a rear lift cylinder 36 raising / lowering the middle mast 20 with respect to the outer mast 19, a lift chain 32 being connected to the outer mast 19 and the inner mast 21 and raising / lowering the inner mast 21 by the expansion or contraction of the rear lift cylinder 36, and a stopper mechanism 50 for locking the inner mast 21 to the middle mast 20. The stopper mechanism 50 includes a stopper part, a stopped part to which the stopper part is locked, and a stopper detector for detecting a locking state between the stopper part and the stopped part.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] This invention relates to a forklift.

Background Art

[0002] There are known forklifts equipped with a cargo handling device having a full-free three-stage mast. This full-free three-stage mast has an outer mast, a middle mast, an inner mast, a rear lift cylinder for raising and lowering the middle mast, and a front lift cylinder for raising and lowering a lift bracket. Further, the full-free three-stage mast has a rear lift chain connected to the outer mast and the inner mast, and a front lift chain connected to the inner mast and the lift bracket. There may be provided a stopper mechanism having a stopper portion provided on the inner mast and a stopper-receiving portion provided on the middle mast for locking the stopper portion. The stopper mechanism is provided to prevent the inner mast from falling out of the middle mast even if the rear lift chain stretches due to long-term use.

[0003] By the way, there is known a technique for preventing the free fall of the fork due to loosening of the lift chain and preventing damage to the equipment due to impact (see, for example, Patent Document 1). In the forklift disclosed in Patent Document 1, a mast device in which a load support moves up and down is erected in front of the vehicle body of the forklift. The mast device is composed of a pair of fixed masts and a lifting mast. A hole is formed in a chain mounting bracket fixed to the fixed mast, and an anchor bolt for connecting one end of the lift chain is inserted through the hole. A coil spring is inserted around the outer periphery of the anchor bolt between a lower plate member inserted and fixed to the lower end of the anchor bolt protruding downward from the lower surface of the chain mounting bracket and an upper plate member inserted in the vicinity of the bracket of the anchor bolt. Both ends of the lift chain are fixed to the bracket and the cargo handling support.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a conventional forklift equipped with a full-free three-stage mast, even if the lift chain extends, the stopper portion and the stopper-receiving portion are engaged, and the inner mast does not fall out of the middle mast. However, if the forklift is continuously operated even when the stopper portion and the stopper-receiving portion are engaged, the stopper portion may be damaged by fatigue. On the other hand, the technique disclosed in Patent Document 1 is merely a technique for simply mitigating the impact caused by the loosening of the lift chain using a coil spring.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide a forklift capable of preventing damage to a stopper mechanism due to the extension of a lift chain in a full-free three-stage mast.

Means for Solving the Problems

[0007] In order to solve the above problems, the present invention provides a forklift having a pair of outer masts, a pair of middle masts that can move up and down with respect to the pair of outer masts, a pair of inner masts that can move up and down with respect to the pair of middle masts, a lift bracket that can move up and down with respect to the pair of inner masts, a rear lift cylinder that moves the pair of middle masts up and down with respect to the pair of outer masts, a lift chain that is connected to the pair of outer masts and the pair of inner masts via the pair of middle masts and moves the pair of inner masts up and down by the expansion and contraction of the rear lift cylinder, and a stopper mechanism that locks the pair of inner masts with respect to the pair of middle masts. A middle lower beam that connects the lower portions of the pair of middle masts, an inner lower beam that connects the lower portions of the pair of inner masts, and a chain anchor bolt that fixes the lift chain to the outer mast, The stopper mechanism includes provided on the inner lower beam a stopper portion and provided on the middle lower beam, a stopper-receiving portion where the stopper portion is engaged andcomprising a stopper detector for detecting the locked state between the stopper portion and the portion to be stopped and the stopper detector is a strain detection sensor that detects the strain of the chain anchor bolt It is characterized by that.

[0008] In the present invention, when the stopper portion is about to be locked or unlocked to the portion to be stopped due to the elongation of the lift chain, the stopper detector detects the locked state between the stopper portion and the portion to be stopped. Therefore, the forklift operator can grasp that the locked state between the stopper portion and the portion to be stopped is detected by the detection of the stopper detector. Note that the locked state between the stopper portion and the portion to be stopped includes not only the state where the stopper portion is locked to the portion to be stopped but also the state where the stopper portion is likely to be locked to the portion to be stopped.

[0009] Also , s In a state where the top portion is not locked to the portion to be stopped, since at least the weight of the inner mast and the front cylinder is reflected in the tension of the lift chain, the strain gauge or the load cell indicates a large value of the strain of the chain anchor bolt. On the other hand, when the stopper portion is locked to the portion to be stopped, the weights of the inner mast and the front cylinder are no longer reflected in the tension of the lift chain. For this reason, the value indicated by the strain gauge or the load cell becomes small, and the locked state where the stopper portion is locked to the portion to be stopped can be detected. That is, the operator can indirectly grasp that the stopper portion is locked to the portion to be stopped by the strain of the chain anchor bolt.

[0011] Also , s Since the top portion is provided on the inner lower beam and the portion to be stopped is provided on the middle lower beam, it becomes easy to provide the stopper mechanism.

[0012] Further, in the above forklift, when the stopper detector detects the locked state between the stopper portion and the portion to be stopped, it may be configured to include a controller that controls to generate a warning. In this case, when the stopper detector detects that the stopper is locked to the stopped part, the controller either generates a warning or stops the rear lift cylinder. Therefore, the operator can surely recognize that the stopper part is locked to the stopped part due to the generation of the warning.

[0013] Further, in the forklift described above, it may be provided with a lift height sensor for detecting the lift height of the pair of middle masts, and the controller may be configured to determine the expansion and contraction state of the rear lift cylinder based on the detection of the lift height sensor. In this case, when the lift height sensor detects the lift height of the middle mast, the controller determines the expansion and contraction state of the rear lift cylinder. Therefore, the controller can determine the locking between the stopper part and the stopped part in a state where the rear lift cylinder is not extended.

Effect of the Invention

[0014] According to the present invention, it is possible to provide a forklift that can prevent damage to the stopper mechanism due to the elongation of the lift chain in a full-free three-stage mast.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Best Mode for Carrying Out the Invention

[0016] (First Embodiment) Hereinafter, a forklift according to the first embodiment will be described with reference to the drawings. The forklift of this embodiment is a forklift equipped with a full-free three-stage mast. Regarding "front and rear", "left and right", and "up and down" for specifying directions, it is shown based on the state where the operator of the forklift is seated on the driver's seat of the driver's cab and facing the forward side of the forklift.

[0017] As shown in FIG. 1, the forklift 10 includes a cargo handling device 12 at the front part of the vehicle body 11. A driver's cab 13 is provided near the center of the vehicle body 11. Drive wheels 14 as front wheels are provided at the front part of the vehicle body 11, and steering wheels 15 as rear wheels are provided at the rear part of the vehicle body 11. A counterweight 16 is provided at the rear part of the vehicle body 11, and the counterweight 16 is for adjusting the vehicle weight and achieving weight balance in the vehicle body 11. The forklift 10 of this embodiment is an engine forklift.

[0018] A head guard 17 that covers the upper part of the driver's cab 13 is provided on the vehicle body 11. A tilt cylinder 18 that operates with hydraulic oil is installed between the vehicle body 11 and the cargo handling device 12. The cargo handling device 12 tilts in the front-rear direction with the lower end of the cargo handling device 12 as a fulcrum by the operation of the tilt cylinder 18.

[0019] As shown in FIG. 2, the cargo handling device 12 includes a full-free three-stage mast 22 having an outer mast 19, a middle mast 20, and an inner mast 21. A pair of left and right middle masts 20 that can be lifted and lowered inside the outer mast 19 are provided on a pair of left and right outer masts 19. An inner mast 21 that can be lifted and lowered inside the middle mast 20 is provided on the middle mast 20. The cargo handling device 12 includes a lift bracket 23 that moves up and down along the inner mast 21, and the lift bracket 23 enables the attachment and detachment of various attachments.

[0020] As shown in FIGS. 2 and 3, the upper end of the outer mast 19 is connected by an upper beam 24. The lower part of the outer mast 19 is connected by an outer lower beam 25. The upper end of the middle mast 20 is connected by an upper beam 26. The lower part of the middle mast 20 is connected by a middle lower beam 27. The upper end of the inner mast 21 is connected by an upper beam 28. The lower part of the inner mast 21 is connected by an inner lower beam 29. The lift bracket 23 is provided with a pair of left and right forks 30 and a backrest 31. The left and right forks 30 lift and support the load. The backrest 31 supports the rear surface of the load supported by the pair of left and right forks 30.

[0021] As shown in FIGS. 4 and 5, one end of a lift chain 32 is fixed to the upper part of the outer mast 19. A lift chain anchor bracket 33 is attached to the outer mast 19, and a chain anchor bolt 34 is fixed to the lift chain anchor bracket 33. One end of the lift chain 32 is connected to the upper end of the chain anchor bolt 34.

[0022] A chain wheel 35 around which the lift chain 32 is hung is provided at the upper part of the middle mast 20. The lift chain 32 is hung on the chain wheel 35, and the other end of the lift chain 32 is fixed to the lower part of the inner mast 21. Therefore, the lift chain 32 is connected to the outer mast 19 and the inner mast 21 via the middle mast 20. A rear lift cylinder 36 that operates by supplying and discharging hydraulic oil is provided in the outer mast 19. By the operation of the rear lift cylinder 36, the middle mast 20 moves up and down inside the outer mast 19, and the inner mast 21 moves up and down inside the middle mast 20.

[0023] As shown in FIG. 4, the rear lift cylinder 36 includes a cylinder body 37, a piston 38 that slides inside the cylinder body 37, and a piston rod 39 that is connected to the piston 38 and expands and contracts with respect to the cylinder body 37. Below the piston 38 in the cylinder body 37, an oil chamber 40 is formed as a lift cylinder hydraulic oil chamber. When hydraulic oil is supplied to the oil chamber 40, the piston 38 rises in the cylinder body 37 and the piston rod 39 extends. When the hydraulic oil in the oil chamber 40 is discharged, the piston 38 descends in the cylinder body 37 and the piston rod 39 contracts. The upper end of the piston rod 39 is connected to the middle mast 20.

[0024] As shown in FIG. 4, a front lift cylinder 41 is erected on the inner lower beam 29 of the inner mast 21. The front lift cylinder 41 is a hydraulic cylinder for raising and lowering the lift bracket 23 with respect to the inner mast 21. As shown in FIG. 4, the front lift cylinder 41 includes a cylinder body 42, a piston 43 that slides inside the cylinder body 42, and a piston rod 44 that is connected to the piston 43 and expands and contracts with respect to the cylinder body 42. Below the piston 43 in the cylinder body 42, an oil chamber 45 is formed as a full-free cylinder hydraulic oil chamber. When the hydraulic oil in the oil chamber 45 is discharged, the piston 43 descends in the cylinder body 42 and the piston rod 44 contracts. The pressure receiving area of the oil chamber 45 is set larger than that of the oil chamber 40 of the rear lift cylinder 36.

[0025] As shown in Fig. 2, a pair of left and right chain wheels 46 are provided at the upper end of the piston rod 44. A lift chain 47 that connects the inner mast 21 and the lift bracket 23 is hung on the chain wheel 46. One end of the lift chain 47 is connected to the upper part of the cylinder body 42, and the other end of the lift chain 47 is connected to the lower part of the lift bracket 23. Therefore, when the piston rod 44 of the front lift cylinder 41 rises, the lift bracket 23 rises without the inner mast 21 and the middle mast 20 rising. Note that the outer mast 19 is provided with a lift sensor 48 for detecting whether the middle mast 20 rises (see Fig. 4). The lift sensor 48 is provided for detecting the expansion and contraction state of the rear lift cylinder 36, and any sensor that emits an ON signal when the middle mast 20 rises may be used.

[0026] Incidentally, as shown in Figs. 3 and 4, the cargo handling device 12 of the present embodiment is provided with a stopper mechanism 50. The stopper mechanism 50 is a mechanism for preventing the inner mast 21 from coming out of the middle mast 20 due to elongation of the lift chain 32 due to aging or the like. The stopper mechanism 50 includes a stopper body 51 as a stopper portion provided on the inner lower beam 29 of the inner mast 21, and a middle lower beam 27 of the middle mast 20 as a stopper portion to which the stopper body 51 is locked.

[0027] The stopper body 51 is fixed to the upper end of the inner lower beam 29 of the inner mast 21 and protrudes from the rear surface of the inner lower beam 29 so as to protrude toward the middle lower beam 27 side of the middle mast 20. Therefore, even if the lift chain 32 elongates, the stopper body 51 is locked to the upper end of the middle lower beam 27, preventing the inner mast 21 from coming out. In a state where the lift chain 32 has not elongated, even when the rear lift cylinder 36 is most contracted and the inner mast 21 is in the lowest position, a gap is generated between the stopper body 51 and the middle lower beam 27.

[0028] Further, the forklift 10 of the present embodiment includes a stopper detector that detects the locked state between the stopper body 51 and the middle lower beam 27 of the middle mast 20, which is the stoppered portion. As shown in FIG. 5, the stopper detector is a strain detection sensor 52 attached to the upper end of the chain anchor bolt 34. The strain detection sensor 52 is a strain gauge or a load cell that detects the axial strain of the chain anchor bolt 34. The strain detection sensor 52 is connected to a controller 53 mounted on the forklift 10, and the signal detected by the strain detection sensor 52 is transmitted to the controller 53.

[0029] In addition to controlling each part of the forklift 10, the controller 53 receives the transmission of signals from each sensor including the strain detection sensor 52. The controller 53 includes a CPU and a storage unit composed of a RAM or the like, although not shown. The controller 53 may include dedicated hardware for executing at least some of various processes, for example, an application-specific integrated circuit (ASIC). The controller 53 can be configured as a circuit including one or more processors that operate according to a computer program, one or more dedicated hardware circuits such as an ASIC, or a combination thereof. The storage unit stores program codes or instructions configured to cause the CPU to execute processes. Various programs for controlling the forklift 10 are stored in the storage unit. The storage unit, that is, the computer-readable medium, includes anything accessible by a general-purpose or dedicated computer. Note that the controller 53 is connected to a warning device (not shown) provided in the driver's seat 13, and the warning device warns the operator by visual display or generation of a warning sound.

[0030] When the lift chain 32 is not extended, at least a load based on the weights of the inner mast 21, the front lift cylinder 41, and the lift chain 32 acts on the lift chain 32. For example, when the fork 30 touches the road surface, the weights of the inner mast 21, the front lift cylinder 41, and the lift chain 32 act on the lift chain 32. Also, for example, when the fork 30 does not touch the road surface, in addition to the inner mast 21, the front lift cylinder 41, and the lift chain 32, the weights of the lift bracket 23, the fork 30, etc. act on the lift chain 32.

[0031] When the lift chain 32 is not extended, a tensile load always occurs in the lift chain 32. The tensile load tries to pull up the chain anchor bolt 34, causing an axially extending strain in the chain anchor bolt 34. Therefore, the strain detection sensor 52 detects the strain and transmits a signal to the controller 53. The controller 53 can recognize that a load is acting on the lift chain 32. On the other hand, when the stopper body 51 provided on the inner mast 21 is locked to the middle lower beam 27 of the middle mast 20 while the lift chain 32 is extended, the load acting on the lift chain 32 is almost eliminated, and the strain that occurred in the chain anchor bolt 34 is also almost eliminated. Therefore, the strain detection sensor 52 hardly detects the strain. In the controller 53, when the strain gauge hardly detects the strain, it can be determined that the stopper body 51 is locked to the middle lower beam 27 of the middle mast 20.

[0032] Figure 6 is a flowchart for the controller 53 to determine whether the stopper body 51 is locked to the middle lower beam 27 of the middle mast 20. The controller 53 determines whether the elevation sensor 48 is OFF (step S01). When the elevation sensor 48 is OFF, the middle mast 20 is at the lowest position (step S02). In step S01, when the elevation sensor 48 is ON, since the rear lift cylinder 36 is operating (step S07) and the middle mast 20 is rising, the process returns to step S01.

[0033] When the middle mast 20 is in the lowest position, next, strain detection is performed by the strain detection sensor 52 (step S03). The controller 53 determines whether or not the strain detected by the strain detection sensor 52 is equal to or less than the threshold value (see step S04). If the strain detected by the strain detection sensor 52 is equal to or less than the threshold value, the stopper body 51 is locked to the middle lower beam 27 (step S05). For this reason, the controller 53 gives a warning by the warning device (step S06). In steps S03 and S04, if the strain detected by the strain detection sensor 52 exceeds the threshold value, the stopper body 51 is not locked to the middle lower beam 27 (step S08). In this case, the process returns to step S01. Note that the strain threshold value is stored in the controller 53 in advance.

[0034] Next, the operation of the forklift 10 according to the present embodiment will be described. In a state where the lift chain 32 is not extended, even when the rear lift cylinder 36 is most contracted, the stopper body 51 of the inner mast 21 is located above the middle lower beam 27 of the middle mast 20 and is not locked to the middle lower beam 27. For this reason, a load based on at least the weights of the inner mast 21, the front lift cylinder 41, and the lift chain 32 acts on the lift chain 32. As a result, the strain detection sensor 52 detects the strain of the chain anchor bolt 34 according to the load based on the weights of the inner mast 21, the front lift cylinder 41, and the lift chain 32. Since the strain detected by the strain detection sensor 52 exceeds the threshold value, the controller 53 determines that the stopper body 51 is not locked to the middle lower beam 27.

[0035] When the lift chain 32 extends and the rear lift cylinder 36 contracts the most so that the stopper body 51 is locked to the middle lower beam 27, there is almost no tension in the lift chain 32. This is because the load based on the weights of the inner mast 21, the front lift cylinder 41, and the lift chain 32 acts on the middle lower beam 27 of the middle mast 20 through the stopper body 51. When the stopper body 51 is locked to the middle lower beam 27, the strain detected by the strain detection sensor 52 becomes equal to or less than the threshold value. The controller 53 determines that the stopper body 51 is locked to the middle lower beam 27 and activates the warning device.

[0036] When the rear lift cylinder 36 is not in the lowest position, the controller 53 does not determine whether the strain detected by the strain detection sensor 52 is equal to or less than the threshold value.

[0037] The forklift 10 of the present embodiment has the following effects. (1) When the stopper body 51 as a stopper portion is locked to the middle lower beam 27 which is the stoppered portion due to the extension of the lift chain 32, the stopper detector detects that the stopper body 51 is locked to the middle lower beam 27. Then, the controller 53 activates the warning device. Therefore, the operator of the forklift 10 can recognize that the stopper body 51 is locked to the middle lower beam 27 by the activation of the warning device due to the detection by the stopper detector.

[0038] (2) It is provided with a chain anchor bolt 34 for fixing the lift chain 32 to the outer mast 19, and the stopper detector is a strain detection sensor 52 for detecting the strain of the chain anchor bolt 34. Therefore, when the stopper body 51 is not locked to the middle lower beam 27, at least the weights of the inner mast 21 and the front lift cylinder 41 are reflected in the tension of the lift chain 32, so the strain detection sensor 52 indicates a large value of the strain of the chain anchor bolt 34. On the other hand, when the stopper body 51 is locked to the middle lower beam 27, the weights of the inner mast 21 and the front lift cylinder 41 are no longer reflected in the tension of the lift chain 32. For this reason, the value indicated by the strain detection sensor 52 becomes small, and it is possible to indirectly detect that the stopper body 51 is locked to the middle lower beam 27 based on the strain of the chain anchor bolt 34. That is, the operator can indirectly grasp that the stopper body 51 is locked to the middle lower beam 27 due to the strain of the chain anchor bolt 34.

[0039] (3) It has a middle lower beam 27 connecting the lower parts of the pair of middle masts 20 and an inner lower beam 29 connecting the lower parts of the pair of inner masts 21, and the stopper body 51 is provided on the inner lower beam 29 and also on the middle lower beam 27. For this reason, it becomes easy to provide the stopper mechanism 50.

[0040] (4) It is provided with a controller 53 that controls to generate a warning when the strain detection sensor 52 detects that the stopper body 51 is locked to the middle lower beam 27. For this reason, when it is detected by the strain detection sensor 52 that the stopper body 51 is locked to the middle lower beam 27, the controller 53 operates the warning device to generate a warning. Therefore, the operator can surely grasp that the stopper body 51 is locked to the middle lower beam 27 due to the occurrence of the warning.

[0041] (5) The strain detection sensor 52 is attached to the chain anchor bolt 34. Therefore, the work of routing the wiring drawn from the strain detection sensor 52 and connected to the controller 53 mounted on the vehicle body 11 is easier than the case where the strain detection sensor 52 is provided on the inner mast 21 or the middle mast 20.

[0042] (Second Embodiment) Next, the forklift according to the second embodiment will be described. In this embodiment, the configuration of the stopper detector is different from that of the first embodiment. For the same configurations as those in the first embodiment in this embodiment, the description in the first embodiment is incorporated and common reference numerals are used.

[0043] As shown in FIG. 7, in the forklift 60 of this embodiment, the stopper detector is a limit switch 61 that physically detects the engagement between the stopper body 51, which is a stopper portion, and the middle lower beam 27 of the middle mast 20, which is a stoppered portion. The limit switch 61 is provided on the middle lower beam 27 of the middle mast 20 and is connected to the controller 53. When the lift chain 32 extends and the stopper body 51 comes into contact with the limit switch 61 when the stopper body 51 is engaged with the middle lower beam 27, it turns ON and transmits a signal to the controller 53. That is, the stopper body 51 functions as a contact that comes into contact with the limit switch 61.

[0044] Therefore, since the limit switch 61 can physically detect the locking of the stopper body 51 and the middle lower beam 27, the operator can surely grasp that the stopper body 51 is locked to the middle lower beam 27. Note that by providing a contactor that abuts against the limit switch 61 separately instead of the stopper body 51, it is possible to transmit an ON signal even when the lift chain 32 is extended immediately before the stopper body 51 is locked to the middle lower beam 27. That is, even when the stopper body 51 is not locked to the middle lower beam 27, the controller 53 can issue a warning. The state immediately before the stopper body 51 is locked to the middle lower beam 27 is a state where the stopper portion is likely to be locked to the stoppered portion, and is a form of the locking state between the stopper body 51 and the middle lower beam 27.

[0045] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the invention. For example, the following modifications may be made.

[0046] ○ In the above-described first and second embodiments, the stopper portion is provided on the inner lower beam of the inner mast, and the stoppered portion is provided on the middle lower beam of the middle mast. However, the present invention is not limited to this. For example, the stopper portion may be provided on the middle lower beam of the middle mast, and the stoppered portion may be provided on the inner lower beam of the inner mast. ○ In the above-described first embodiment, the stopper detector detects the distortion of the chain anchor bolt connected to the outer mast. However, the present invention is not limited to this. The stopper detector may detect the distortion of the chain anchor bolt connected to the inner mast. Further, the threshold value of the distortion may be changed so that the stopper detector detects a state where the stopper portion is likely to be locked to the stoppered portion. ○ In the above-described second embodiment, a limit switch is exemplified and described as the stopper detector. However, the present invention is not limited to this. Instead of the limit switch, the stopper detector may use, for example, a pressure-sensitive element. In this case, when the stopper body presses the pressure-sensitive element, the locking of the stopper portion and the stoppered portion can be physically detected. 〇 In the above-described embodiment, an engine forklift as a forklift has been exemplified and described, but the present invention is not limited thereto. The forklift may be an electric forklift. Further, the forklift may be not only a forklift equipped with a counterweight but also a reach forklift.

Explanation of Signs

[0047] 10, 60 Forklift 11 Vehicle body 12 Cargo handling device 13 Driver's seat 19 Outer mast 20 Middle mast 21 Inner mast 22 Mast 23 Lift bracket 27 Middle lower beam (stopped part) 29 Inner lower beam 30 Fork 32, 47 Lift chain 33 Lift chain anchor bracket 34 Chain anchor bolt 36 Rear lift cylinder 41 Front lift cylinder 48 Lifting sensor 50 Stopper mechanism 51 Stopper body (stopped part) 52 Strain detection sensor (stopper detector) 53 Controller 61 Limit switch (stopper detector)

Claims

1. A pair of outer masts, A pair of middle masts that can move up and down relative to the pair of outer masts, A pair of inner masts that can move up and down relative to the pair of middle masts, A lift bracket that can move up and down relative to the pair of inner masts, A rear lift cylinder that raises and lowers the pair of middle masts relative to the pair of outer masts, A lift chain that is connected to the pair of outer masts and the pair of inner masts via the pair of middle masts, and raises and lowers the pair of inner masts by the expansion and contraction of the rear lift cylinder, In a forklift having a stopper mechanism for locking the pair of inner masts relative to the pair of middle masts, A middle lower beam connecting the lower parts of the pair of middle masts, An inner lower beam connecting the lower parts of the pair of inner masts, And a chain anchor bolt for fixing the lift chain to the outer mast, The stopper mechanism, A stopper portion provided on the inner lower beam, And a stoppered portion provided on the middle lower beam, to which the stopper portion is locked, It has a stopper detector for detecting the locked state between the stopper portion and the stoppered portion, The forklift, wherein the stopper detector is a strain detection sensor for detecting the strain of the chain anchor bolt.

2. The forklift according to claim 1, further comprising a controller that controls to generate a warning when the stopper detector detects the locked state between the stopper portion and the stoppered portion.

3. It is provided with a lift height sensor for detecting the lift height of the pair of middle masts, The forklift according to claim 2, wherein the controller determines the expansion and contraction state of the rear lift cylinder based on the detection of the lift height sensor.

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