Lifting device

Abstract

To provide a lift device that can be used in various situations by avoiding interference with pallets placed on the floor, cargo, etc., and that is excellent in operability during transportation. [Solution] The lift device 1 comprises a base 2 that is movable on the floor surface, a sliding body 3 that can slide relatively back and forth on the base 2, a mast 4 erected on the sliding body 3, a carriage 5 supported on the mast 4 so that it can be raised and lowered, a pair of forks 6, 6 whose base ends are supported on the carriage 5 and extended forward, a carriage lifting mechanism 7 that raises and lowers the carriage 5 along the mast 4, a pair of fork wheels 61, 61 that support the pair of forks 6, 6 against the ground surface and allow them to move on the ground surface, and a pair of fork wheel displacement mechanisms 83, 83 that are provided between the pair of fork wheels 61, 61 and the pair of forks 6, 6 and that can displace the pair of fork wheels 61, 61 between a stored position and an deployed position.

Description

[Technical Field]

[0001] The present invention relates to a lift device. [Background technology]

[0002] BACKGROUND ART Lift devices known as hand lifters or traverse lifts have been proposed in the past that are capable of lifting, lowering, and transporting cargo in factories, warehouses, and the like (see, for example, Patent Documents 1 and 2).

[0003] These conventional lift devices are configured with a base with casters at the front and rear, a mast erected on the base, and a fork serving as a loading platform supported in front of the mast so that it can be raised and lowered. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-302409 [Patent Document 2] Utility Model Registration No. 3216452 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the prior art disclosed in Patent Document 1, the base is configured to extend forward to a position roughly the same as the front ends of the forks, so when a pallet is placed on the floor, the front ends of the base interfere with the pallet, making it impossible to insert the forks into the pallet. In other words, the lift device of this prior art has a usage restriction in that it cannot be used with pallets placed on the floor.

[0006] On the other hand, in the prior art described in Patent Document 2, the base barely extends forward of the mast and has front wheels on both sides, so even when the pallet is placed on the floor, the forks can be inserted into the pallet without the front end of the base interfering with the pallet, making it possible to use it with floor-mounted pallets. However, this prior art requires a counterweight on the base to balance the load on the forks that rise and fall at the front of the mast, which increases the lift's own weight. This results in a problem of reduced operability when pushing or pulling the lift body during load transport.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a lift device that can be used in a variety of situations by avoiding interference with floor-mounted pallets, luggage, etc., and that is easy to operate during transportation. [Means for solving the problem]

[0008] The lift device of the present invention comprises a base that can be moved freely on the floor surface, a slide body that can slide relatively back and forth on the base, a mast erected on the slide body, a carriage supported on the mast so that it can be raised and lowered, a load receiving member whose base end is supported on the carriage and extended forward, a carriage lifting mechanism that raises and lowers the carriage along the mast, a support moving member that supports the load receiving member against the ground surface and allows it to move on the ground surface, and a support moving member displacement mechanism that is provided between the support moving member and the load receiving member and is capable of displacing the support moving member between a stored position at approximately the same height as the load receiving member and an deployed position in which it protrudes downward from the load receiving member.

[0009] According to this configuration, the load receiving member can be advanced via the slide body formed by the upright mast. This avoids interference between the front end of the base and a floor-mounted pallet or load, allowing the load receiving member to receive a floor-mounted pallet or a pallet on a shelf when floor-mounted load is present. Furthermore, with the load receiving member advanced, the support / movement member displacement mechanism displaces the support / movement member from the retracted position to the deployed position, allowing the load receiving member to contact a ground surface such as a floor or shelf, thereby supporting the load receiving member. This prevents the lift device from tipping forward without requiring a counterweight. Furthermore, since a counterweight is not required, the overall weight can be reduced, allowing for easy operability during load transport. Furthermore, when the load receiving member is retracted via the slide body and positioned directly above the base, the load receiving member with the load placed on it can be safely raised and lowered along the mast via the carriage by the carriage lifting mechanism. This provides the advantage of providing a lift device that can be used in a variety of situations, avoiding interference with floor-mounted pallets, loads, etc., and that is also easy to operate during transport.

[0010] The lift device also includes a load receiving member relative lifting mechanism that is provided between the carriage and the load receiving member and that moves the load receiving member up and down relative to the carriage between a first relative height and a second relative height that is relatively higher than the first relative height, and the support moving member displacement mechanism displaces the support moving member in conjunction with the relative lifting and lowering movement of the load receiving member relative lifting mechanism so that when the load receiving member is at the first relative height, the support moving member is at the stored position, and when the load receiving member is at the second relative height, the support moving member is at the deployed position.

[0011] According to this configuration, the receiving member relative lifting mechanism lifts and lowers the receiving member relative to the carriage between a first relative height and a second relative height that is relatively higher than the first relative height, and the support and moving member displacement mechanism performs a displacement operation in conjunction with the relative lifting and lowering operation of the receiving member relative lifting mechanism, so that the support and moving member can be placed in the stored position when the receiving member is at the first relative height and in the deployed position when the receiving member is at the second relative height. Thus, a structure can be realized in which the support and moving member can be displaced between the stored position and the deployed position.

[0012] In addition, the lift device further includes a cancellation control unit that performs cancellation control to cause the carriage lifting mechanism to lift the carriage by the same distance in the opposite direction to the relative lifting operation when the cargo receiving member relative lifting mechanism lifts the cargo receiving member relative to the carriage.

[0013] According to this configuration, when the support moving member displacement mechanism displaces the support moving member in conjunction with the relative lifting and lowering operation of the cargo receiving member relative lifting and lowering mechanism to place the support moving member in a stored position when the cargo receiving member is at a first relative height and to a deployed position when the cargo receiving member is at a second relative height, the cancel control unit performs cancel control to cause the carriage lifting and lowering mechanism to lift the carriage the same distance in the opposite direction to the relative lifting and lowering operation, so that the support moving member can be displaced between the stored position and the deployed position while maintaining the height of the cargo receiving member from the ground surface.

[0014] The lift device also includes a ground contact detection unit that detects when the support and movement member touches the ground surface.

[0015] According to this configuration, the ground detection unit detects that the support and moving member has displaced from the stored position to the deployed position and made contact with the ground surface. Therefore, by firmly grounding the support and moving member to the ground surface to support the cargo receiving member, the sliding body can be slid back and forth to safely move the cargo receiving member on the ground surface while preventing the device from tipping forward.

[0016] The lift device also includes a lifting operation unit that inputs lifting and lowering operations through operation by an operator, and a switching control unit that automatically switches between the relative lifting and lowering operation of the cargo receiving member relative to the carriage by the cargo receiving member relative lifting mechanism and the lifting and lowering operation of the carriage by the carriage lifting and lowering mechanism when a lifting and lowering operation is input by the lifting operation unit.

[0017] According to this configuration, the switching control unit automatically switches between the relative lifting and lowering operation of the cargo receiving member relative to the carriage by the cargo receiving member relative lifting mechanism and the lifting and lowering operation of the carriage by the carriage lifting mechanism, so that the operator can easily achieve appropriate lifting and lowering operation simply by operating the lifting operation unit without having to be aware of the positional relationship between the cargo receiving member and the pallet, etc.

[0018] The lift device also includes a slide lock mechanism that releasably locks the slide of the sliding body to the base, and an unlock control unit that allows the slide lock mechanism to be unlocked when predetermined slide permission conditions are met, and prohibits the slide lock mechanism from being unlocked otherwise.

[0019] According to this configuration, when predetermined slide permission conditions are met, the slide lock mechanism is permitted to be unlocked, so that the slider can be slid on the base to insert or remove the load receiving member into or from a pallet, etc. On the other hand, when the predetermined slide permission conditions are not met, the unlock control unit prohibits the slide lock mechanism from being unlocked, so that accidental unlocking of the slide lock mechanism due to an operator's incorrect operation can be reliably prevented, thereby ensuring safety. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a perspective view of a lift device according to an embodiment of the present invention, seen from diagonally front and above. [Figure 2] FIG. 2 is a perspective view of the lift device as seen from diagonally front and below. [Figure 3]FIG. 2 is a perspective view of the lift device as seen obliquely from the rear and above. [Figure 4] 2 is a perspective view of the lift device of FIG. 1, seen from diagonally front and above, with the mast moved forward via a slide body and the pair of fork wheels in the deployed position. FIG. [Figure 5] 2 is a perspective view of the lift device of FIG. 1 with a carriage raised, as seen obliquely from the front and above. FIG. [Figure 6] 2 is a perspective view of the lift device of FIG. 1, showing a state in which the mast is advanced and the carriage is raised via a slide body, as viewed obliquely from the front and from above. FIG. [Figure 7] FIG. 2 is a partially enlarged rear view showing the lower rear portion of the lift device. [Figure 8] 10 is a partially enlarged side view showing a state in which a part of a side plate of the slider is broken away and a plurality of rollers engage with a rail portion of the support arm. FIG. [Figure 9] FIG. 2 is a side view of the inside of the fork, showing the arrangement of the fork moving mechanism (fork relative lifting mechanism, fork wheel displacement mechanism) and each sensor. [Figure 10] 10 is an explanatory diagram illustrating the operation of the fork relative lifting / lowering mechanism and the fork wheel displacement mechanism (fork: first relative height, fork wheel: stored position). FIG. [Figure 11] 10 is an explanatory diagram illustrating the operation of the fork relative lifting / lowering mechanism and the fork wheel displacement mechanism (fork: midway between the first relative height and the second relative height, fork wheel: midway between the stored position and the deployed position). FIG. [Figure 12] 10 is an explanatory diagram illustrating the operation of the fork relative lifting / lowering mechanism and the fork wheel displacement mechanism (fork: second relative height, fork wheel: deployed position). FIG. [Figure 13] FIG. 2 is a block diagram showing the electrical configuration of the lift device. [Figure 14] 10 is a first half of a flowchart showing a main control flow of the lift device. [Figure 15] 10 is a flowchart showing the second half of the main control flow of the lift device. [Figure 16]10 is a flowchart showing a flow of a sensor processing routine. [Figure 17] This is an explanatory diagram for explaining steps [1] and

[13] in an example of a luggage shelving operation using a lifting device. [Figure 18] FIG. 10 is an explanatory diagram for explaining step [2]. [Figure 19] FIG. 10 is an explanatory diagram for explaining step [3]. [Figure 20] This is an explanatory diagram for explaining step [4]. [Figure 21] This is an explanatory diagram for explaining step [5]. [Figure 22] This is an explanatory diagram for explaining step [6]. [Figure 23] This is an explanatory diagram for explaining step [7]. [Figure 24] This is an explanatory diagram for explaining step [8]. [Figure 25] This is an explanatory diagram for explaining step [9]. [Figure 26] This is an explanatory diagram for explaining steps

[10] and

[11] . [Figure 27] This is an explanatory diagram for explaining step

[12] . DETAILED DESCRIPTION OF THE INVENTION

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A lift device according to an embodiment of the present invention will now be described with reference to the drawings.

[0022] <Configuration of lift device 1> First, the mechanical configuration of a lift device 1 according to an embodiment of the present invention will be described with reference to FIGS.

[0023] Fig. 1 is a perspective view of the lift device 1 as seen from diagonally front and above, Fig. 2 is a perspective view as seen from diagonally front and below, and Fig. 3 is a perspective view as seen from diagonally rear and above. Fig. 4 is a perspective view as seen from diagonally front and above of the lift device 1 of Fig. 1 with the mast 4 advanced via the slide body 3 and the pair of fork wheels 61, 61 in the extended position, Fig. 5 is a perspective view as seen from diagonally front and above of the carriage 5 raised, and Fig. 6 is a perspective view as seen from diagonally front and above of the mast 4 advanced via the slide body 3 and the carriage 5 raised.

[0024] FIG. 7 is a partially enlarged rear view showing the lower rear portion of the lift device 1. FIG. 8 is a partially enlarged side view showing the state in which the side plate 31 of the slide body 3 is partially broken away to show the engagement of the rollers 32 with the rail portion 21a of the support arm 21. FIG. 9 is a side view of the interior of the fork 6, showing the fork moving mechanism 8 (fork relative lifting mechanism 82, fork wheel displacement mechanism 83) and the arrangement of each sensor. FIG. 10 is an explanatory diagram explaining the operation of the fork relative lifting mechanism 82 and fork wheel displacement mechanism 83 (fork 6: first relative height, fork wheel 61: stored position), FIG. 11 is an explanatory diagram of the same (fork 6: intermediate between the first relative height and the second relative height, fork wheel 61: in the middle of displacement between the stored position and the deployed position), and FIG. 12 is an explanatory diagram of the same (fork 6: second relative height, fork wheel 61: deployed position). Note that the control device 9 is not shown in FIG. 7.

[0025] The lift device 1 is a lift device that can move freely on the floor surface in a factory, warehouse, or the like and is used to supply pallets or skids on which cargo is placed to a shelf or to retrieve them from the shelf.

[0026] As shown in FIG. 1 etc., the lift device 1 includes a base 2, a slide body 3, a mast 4, a carriage 5, a pair of forks 6, 6, a carriage lifting mechanism 7, a fork moving mechanism 8, and a control device 9.

[0027] The base 2 is a steel member that forms the base of the lift device 1, and is equipped with a pair of support arms 21, 21, a connecting rod 22, a pair of rear wheel support members 23, 23, and a floor lock mechanism 26, and is formed into an overall H-shaped shape when viewed from above.

[0028] The pair of support arms 21, 21 are linear members extending in the front-rear direction and arranged parallel to each other with a gap between them on the left and right. Each support arm 21 has a rail portion 21a formed on the side opposite the opposing surface thereof, the rail portion 21a having a generally C-shaped cross section that opens over the entire length. A plurality of rollers 32 (described later) of the slide body 3 are rotatably engaged with each rail portion 21a. Front wheels 24, 24 are provided at the front ends of the pair of support arms 21, 21.

[0029] The connecting rod 22 is a square rod-shaped member made of steel, and connects the pair of support arms 21, 21 together at a predetermined position near the rear.

[0030] The pair of rear wheel support members 23, 23 are formed at the rear ends of the pair of support arms 21, 21 in a downward L-shape when viewed from the side. A rear wheel 25 is provided at the rear end of each rear wheel support member 23 so as to be horizontally rotatable. Therefore, the base 2 is provided with front wheels 24, 24 and rear wheels 25, 25 as casters, allowing it to be freely moved on the floor.

[0031] The floor lock mechanism 26 is a mechanism for releasably locking (immobilizing) the base 2 to the floor. As shown in FIG. 7, the floor lock mechanism 26 is configured to include a floor lock main body 26a, a lock pedal 26b, a lock release lever 26c, and a floor lock switch 984.

[0032] The floor lock body 26a is a cylindrical, extendable member and is attached to the connecting rod 22 of the base 2. The lock pedal 26b is a plate-shaped operating member that the operator steps on with their foot and is attached to the bottom of the floor lock body 26a. When the lock pedal 26b is pressed while the floor lock mechanism 26 is in the unlocked state, the floor lock body 26a extends and its lower end abuts the floor surface, thereby entering the floor locked state. The lock release lever 26c is a lever-shaped operating member and is attached to the top of the floor lock body 26a. When the lock release lever 26c is pushed up while the floor lock mechanism 26 is in the floor locked state, the floor lock body 26a contracts and moves away from the floor surface, thereby releasing the floor locked state. The floor lock switch 984 is a known limit switch with a contact and is located near the floor lock body 26a. It outputs an ON signal when the contact is pressed as the floor lock body 26a extends or retracts, and outputs an OFF signal when the floor is in the unlocked state.

[0033] The sliding body 3 is a steel member mounted between a pair of support arms 21, 21 and slidable relatively in the front-to-rear direction on the base 2, with a mast 4 erected on its upper surface. The sliding body 3 has side plates 31, 31 that are triangular in side view on both left and right sides, and as shown in FIG. 8, a plurality of rollers 32 are rotatably mounted on each side plate 31. Each roller 32 engages with a respective rail portion 21a provided on the side surface of the left and right support arms 21. The rollers 32 roll on the respective rail portions 21a, allowing the sliding body 3 to slide in the front-to-rear direction along the pair of support arms 21, 21. Note that FIGS. 1 to 3 and 5 show the sliding body 3 in the retracted position, and FIGS. 4 and 6 show the sliding body 3 in the advanced position.

[0034] 7, a slide lock mechanism 33 for locking the sliding of the slide body 3 relative to the base 2 is provided between the slide body 3 and the base 2. The slide lock mechanism 33 is configured to include a lock pin 33a, a wire 33b, an engaged member 33c, and a slide lock switch 983.

[0035] The lock pin 33a is a pin-shaped member supported on the slider 3 so as to be movable up and down. One end of the wire 33b is connected to the lock pin 33a, and the other end extends toward the right handle 41 and is connected to a slide lock release lever 42 (described later). The engaged member 33c is a cylindrical member with a diameter slightly larger than that of the lock pin 33a. It is fixed to the connecting rod 22 of the base 2 and faces the lock pin 33a from below when the slider 3 is retracted. When the lock pin 33a descends in the retracted position of the slider 3, it engages with the engaged member 33c, establishing a slide lock state. When the lock pin 33a ascends, it disengages from the engaged member 33c, establishing a slide lock release state. The slide lock switch 983 is a known limit switch with a contact and is located near the lock pin 33a of the slider 3. In the slide lock state where the lock pin 33a is engaged with the engaged member 33c, the contact of the slide lock switch 983 is pressed and outputs an ON signal, and in the slide lock release state where the lock pin 33a is not engaged with the engaged member 33c, the contact is not pressed and outputs an OFF signal.

[0036] Furthermore, the slide body 3 is equipped with hydraulic equipment commonly used for the carriage cylinder 71 and the fork cylinder 81 described later, including a motor 35, a hydraulic pump 36 operated by the motor 35, and a switching valve 37 that receives pressurized oil supplied from the hydraulic pump 36 and switches it to the output oil path of the carriage cylinder 71 or the fork cylinder 81 (see Figure 13).

[0037] The mast 4 is a support structure erected on the sliding body 3 and includes a pair of left and right support columns 4a, 4a erected on the left and right, and connecting plates 4b connecting the pair of support columns 4a, 4a at multiple locations in the vertical direction. The mast 4 supports the carriage 5 so that it can be raised and lowered. Frame-shaped handles 41, 41 are provided on the left and right sides of the rear of the pair of support columns 4a, 4a, facing backward. The right handle 41 further includes a slide lock release lever 42 that can be gripped by hand. A docking switch 985 is disposed on the lower side of one of the support columns 4a. The docking switch 985 is a known limit switch with a contact. When the sliding body 3 is in the retracted position, the contact is pressed by a member on the base 2 side (specifically, the rear wheel support member 23) to output an ON signal; otherwise (when the sliding body 3 is sliding forward from the retracted position), the docking switch 985 outputs an OFF signal.

[0038] A lifting distance encoder 989 is provided between the slider 3 and the mast 4 to detect the lifting distance of the pair of forks 6, 6. The lifting distance encoder 989 includes an encoder belt 989a and an encoder sensor 989b. The encoder belt 989a is an endless belt with multiple slits formed along the conveyance direction. It is suspended vertically between an upper pulley provided on the connecting plate 4b at the upper end of the mast 4 and a lower pulley provided on the slider 3. The encoder belt 989a is connected to the pair of forks 6, 6 at one point between the upper and lower ends via a fork relative lifting mechanism 82, and is conveyed between the upper and lower pulleys as the pair of forks 6, 6 move up and down. The encoder sensor 989b is disposed on the slider 3 facing the encoder belt 989a. As the encoder belt 989a is conveyed, the encoder sensor 989b optically detects each slit in sequence.

[0039] The carriage 5 is an elevator body supported between a pair of support posts 4a, 4a on the mast 4 so as to be able to move up and down. The carriage 5 is driven to move up and down by a carriage elevator mechanism 7. A pair of forks 6, 6 are provided on the carriage 5 and extend forward.

[0040] The pair of forks 6, 6 are supported at their base ends by the carriage 5 via the fork relative lifting mechanism 82. They extend forward in a fork-like fashion and are a pair of left and right load-receiving members that are inserted into the insertion openings of a pallet or skid. Fork wheels 61, 61 are attached to the front ends of the pair of forks 6, 6 so that they can freely extend and retract downward. A fork under-ground surface sensor 987 is disposed facing downward at a predetermined position a predetermined distance behind the front end of at least one of the forks 6. The fork under-ground surface sensor 987 is a photoelectric sensor that outputs an ON signal when a ground surface (such as a floor or shelf) is present within a predetermined distance below it, and outputs an OFF signal when no ground surface is present within the predetermined distance below it. The predetermined distance, which is the condition for outputting an ON signal, is the distance between the fork under-ground surface sensor 987 and the ground surface that allows the fork wheels 61, 61 to reliably contact the ground surface when in the extended position. This distance is set to, for example, several centimeters.

[0041] The carriage lifting mechanism 7 includes a carriage cylinder 71 , a sprocket 72 , and a chain 73 .

[0042] The carriage cylinder 71 is a hydraulic cylinder that includes a cylinder body 71a and a cylinder rod 71b, and is disposed on the slide body 3 with the cylinder rod 71b facing upward. When pressurized oil is supplied from the hydraulic pump 36 by driving the motor 35, and the pressurized oil is supplied to the cylinder body 71a via the switching valve 37, the cylinder rod 71b moves up and down, thereby extending and contracting the carriage cylinder 71.

[0043] The sprocket 72 is supported on the upper end of the cylinder rod 71b of the carriage cylinder 71 so as to be rotatable about its axis.

[0044] The chain 73 is made up of multiple chain elements connected together, with one end connected and fixed to the connecting plate 4b of the mast 4 and the other end connected and fixed to the carriage 5, and the middle part being stretched over the sprocket 72 at the upper end of the cylinder rod 71b.

[0045] When the cylinder rod 71b moves up and down due to the pressurized oil supplied from the hydraulic pump 36, the carriage lifting mechanism 7 raises and lowers the other end of the chain 73 via the sprocket 72 at the upper end, thereby raising and lowering the carriage 5.

[0046] The fork moving mechanism 8 is configured to include a fork cylinder 81, a fork relative lifting mechanism 82, and a pair of fork wheel displacement mechanisms 83, 83.

[0047] 9 to 12, the fork cylinder 81 is a hydraulic cylinder that includes a cylinder body 81a and a cylinder rod 81b, and is attached to the carriage 5 via a mounting member 5a with the cylinder rod 81b facing upward. When pressure oil is supplied from the hydraulic pump 36 by driving the motor 35, and the pressure oil is supplied to the cylinder body 81a via the switching valve 37, the fork cylinder 81 moves up and down, thereby extending and contracting.

[0048] The fork relative lifting mechanism 82 is a mechanism for lifting and lowering the pair of forks 6, 6 relative to the carriage 5, and is configured to include a first link 82a, a second link 82b, and a third link 82c.

[0049] The first link 82a is a link member that is bent in a V-shape, with one end pivotally attached to the top of the carriage 5 and the other end pivotally attached to the upper end of the second link 82b. A fork upper limit switch 981 is located near the first link 82a. The fork upper limit switch 981 is a known limit switch with a contactor, and when the fork 6 is at the upper limit position, the contactor is pressed to output an ON signal, and otherwise the switch outputs an OFF signal.

[0050] The second link 82b is disposed vertically, with its lower end fixed to the base end of the fork 6 to support the fork 6, and its upper portion pivotally connected to the first link 82a and its lower portion pivotally connected to the third link 82c. A cargo sensor 988 is disposed facing forward at the bottom of the second link 82b. The cargo sensor 988 is constituted by a photoelectric sensor, and outputs an ON signal when a cargo (including a pallet or skid) is placed on the fork 6 in front of the sensor, and outputs an OFF signal when no cargo is placed thereon.

[0051] The third link 82c is a link member that is bent in a V-shape similar to the first link 82a and is arranged parallel to the first link 82a, with one end pivotally attached to the bottom of the second link 82b and the other end pivotally attached to the bottom of the carriage 5. A fork lower limit switch 982 is arranged near the third link 82c. The fork lower limit switch 982 is a known limit switch with a contactor, and when the fork 6 is at the lowest position, the contactor is pressed to output an ON signal, and otherwise the switch outputs an OFF signal.

[0052] The fork wheel displacement mechanism 83 is a mechanism for displacing the fork wheel 61 between a storage position at approximately the same height as the fork 6 and a deployed position in which it protrudes below the fork 6, and is composed of an interlocking link 83a, a forward / backward rod 83b, a wheel support link 83c, and a pivot shaft 83d.

[0053] One end of the interlocking link 83a is pivotally attached coaxially with the lower end of the second link 82b and the third link 82c of the fork relative lifting and lowering mechanism 82, and the other end is pivotally attached to the rear end of the advancing and retracting rod 83b. The advancing and retracting rod 83b is a rod-shaped member that is arranged horizontally inside the lower side of the fork 6 and extends in the front-to-rear direction. The rear end of the advancing and retracting rod 83b is pivotally attached to the interlocking link 83a, and the front end is pivotally attached to one end of the wheel support link 83c. One end of the wheel support link 83c is pivotally attached to the front end of the advancing and retracting rod 83b, the other end rotatably supports the fork wheel 61, and the middle portion is rotatably supported near the front end of the fork 6 via a pivot shaft 83d.

[0054] Specifically, the retractable rod 83b is split into two longitudinally, with a gap between the two components. When the fork wheel 61 is not in contact with the ground, the front end of the retractable rod 83b drops due to gravity, increasing the gap to a predetermined value or greater. When the fork wheel 61 is in contact with the ground, the front end becomes substantially horizontal, reducing the gap to less than the predetermined value. A fork wheel grounding sensor 986 is provided on the retractable rod 83b, facing the gap. The fork wheel grounding sensor 986 is a known proximity switch that outputs an ON signal when the gap is less than the predetermined distance (i.e., when the fork wheel 61 is in contact with the ground), and outputs an OFF signal otherwise (i.e., when the fork wheel 61 is not in contact with the ground).

[0055] When the fork cylinder 81 is retracted, the fork 6 is positioned at a first relative height with respect to the carriage 5, as shown in Fig. 10. In Fig. 10, the first relative height h1, which is the relative height of the upper ends of the pair of forks 6, 6 based on the height h0 of the lower end of the carriage 5, is expressed as h1 = h0 - Δh1, where the difference in height is -Δh1.

[0056] When the rod 81c rises and the fork cylinder 81 extends, the first link 82a and the third link 82c of the fork relative lifting mechanism 82 rotate upward, and the fork 6 supported by the second link 82b rises relative to the carriage 5, eventually reaching the state shown in FIG. 11 and finally reaching a second relative height that is relatively higher than the first relative height, as shown in FIG. 12. In FIG. 12, the second relative height h2, which is the relative height of the upper ends of the forks 6 based on the height h0 of the lower ends of the carriage 5, is expressed as h2 = h0 + Δh2, where Δh2 is the difference in height. In other words, the second relative height h2 is greater than the first relative height h1.

[0057] When the fork relative lifting mechanism 82 sets the pair of forks 6, 6 to a first relative height, the advancing / retracting rod 83b retreats, the wheel support link 83c assumes a horizontal position, and the fork wheels 61, 61 are in the retracted position. On the other hand, when the fork relative lifting mechanism 82 sets the pair of forks 6, 6 to a second relative height, the advancing / retracting rod 83b is pushed forward by the interlocking link 83a, and the rear end of the wheel support link 83c is pushed forward by the advancing / retracting rod 83b. As a result, the wheel support link 83c rotates forward around the pivot shaft 83d, and the fork wheels 61, 61 supported on the other end of the wheel support link 83c move downward to the deployed position.

[0058] The control device 9 is a device that electrically controls the carriage cylinder 71, the fork cylinder 81, and the slide lock release lever 42, and is electrically connected to the battery BT, the motor 35, the lifting operation unit 97, and each sensor that makes up the sensor group 98. The electrical configuration of the control device 9 will be described in detail later in <2. Electrical configuration of the lift device 1>.

[0059] The lift operation unit 97 is a lever-type operation input device for inputting a lift command to the control device 9. When the lever of the lift operation unit 97 is tilted further back (forward) from the neutral position, a signal indicating a lowering command is input to the control device 9, and when the lever is pulled forward (rearward) from the neutral position, a signal indicating an raising command is input to the control device 9. Note that the lift operation unit 97 is not limited to the lever type, and for example, a push-button type operation input device or other types of input devices may be used.

[0060] <2. Electrical configuration of the lift device 1> Next, the electrical configuration of the lift device 1 will be described with reference to Fig. 13. Fig. 13 is a hardware block diagram showing the electrical configuration of the lift device 1. The electrical configuration of the lift device 1 is configured to include a battery BT, a control device 9, a motor 35, a lifting operation unit 97, and a group of sensors 98. Since each component other than the control device 9 has already been described, the following description will focus on the configuration of the control device 9.

[0061] As shown in the block diagram of FIG. 13, the control device 9 includes a calculation unit 91, a motor driver 92, and a valve control unit 93.

[0062] The calculation unit 91 is a known microcomputer that includes a CPU as a central calculation unit and a ROM, RAM, etc. as storage units. A program describing the control processing described below is stored in the ROM, and is executed by the CPU to perform the control processing.

[0063] The motor driver 92 is a motor drive circuit that converts motor rotation control information from the calculation unit 91 into power to be supplied to the motor 35. The motor rotation control information is generated by the calculation unit 91 based on an elevation command from an elevation operation unit 97. The motor 35 is rotationally driven by the power supplied from the motor driver 92, and operates the hydraulic pump 36.

[0064] The valve control unit 93 performs control to switch the output oil passage of the switching valve 37 between the carriage cylinder 71 side and the fork cylinder 81 side in response to a command from the calculation unit 91 .

[0065] The battery BT is a DC power supply made up of a known secondary battery, and supplies power to the control device 9. The battery BT is charged from an external AC power supply by a charger (not shown).

[0066] The sensor group 98 is a collective term for various sensors provided in the lift device 1, and consists of a fork upper limit switch 981, a fork lower limit switch 982, a slide lock switch 983, a floor lock switch 984, a docking switch 985, a fork wheel ground contact sensor 986, a fork lower ground contact sensor 987, a luggage sensor 988, and a lifting distance encoder 989, and the output of each sensor is input to the calculation unit 91.

[0067] <3. Flow of control process in lift device 1> Next, the flow of control processing of the lift device 1 will be described with reference to Figures 14 to 16. Figure 14 is the first half of a flowchart showing the flow of main control of the lift device 1, and Figure 15 is the second half of the flowchart showing the flow of the main control. Figure 16 is a flowchart showing the flow of a sensor processing routine.

[0068] When the power supply to the lift device 1 is turned on, the calculation unit 91 (CPU) executes the main control processing shown in Figures 14 and 15, and first performs initialization processing / sensor processing in S1 ("S" represents a step; the same applies to the other steps).

[0069] In the initialization process / sensor process S1, the device is initialized, including processes for setting various variables to their initial states, and the sensor process routine shown in Fig. 16 is executed. Note that the sensor process routine is repeatedly executed at predetermined time intervals after S1 while the main control is being executed.

[0070] The flow of the sensor processing routine will now be described with reference to Figure 16. In the sensor processing routine, reading of the sensors 98 is executed. That is, the fork upper limit switch 981 is read in S51, the fork lower limit switch 982 is read in S52, the slide lock switch 983 is read in S53, the floor lock switch 984 is read in S54, the docking switch 985 is read in S55, the fork wheel ground contact sensor 986 is read in S56, the fork lower ground contact sensor 987 is read in S57, the baggage sensor 988 is read in S58, and the lifting distance encoder 989 is read in S59.

[0071] Next, in S60, it is determined whether a slide permission condition is met. The slide permission condition is "baggage sensor 988: off, floor lock switch 984: on" or "baggage sensor 988: on, fork wheel grounding sensor 986: on, floor lock switch 984: on."

[0072] If the slide permission condition is met (S60: Yes), an unlock permission process is executed in S61. In the unlock permission process S61, the solenoid of the slide lock release lever 42 is energized to displace a locking piece (not shown) from a locking position relative to the slide lock release lever 42 to a non-locking position. This allows the operator to grasp the slide lock release lever 42 and activate the slide lock mechanism 33, thereby enabling the slide lock of the sliding body 3 to be released.

[0073] If the slide permission condition is not satisfied (S60: No), an unlocking prohibition process is executed in S62. In the unlocking prohibition process S62, the solenoid of the slide lock release lever 42 is not energized, and a locking piece (not shown) is set to a locking position relative to the slide lock release lever 42. As a result, even if the operator tries to grip the slide lock release lever 42, the lever does not move, and the slide lock mechanism 33 does not operate, thereby prohibiting the slide lock of the sliding body 3 from being released.

[0074] Next, in S2, it is determined whether or not an operation input has been made. If no operation input has been made (S2: No), S2 is repeated, and the input standby state continues until an operation input is made.

[0075] If an operation input is made in S2 (S2: Yes), it is determined in S3 whether or not the operation input is an up operation input.

[0076] If an upward operation is input in S3 (S3: Yes), it is determined in S4 whether a wheel deployment sensor condition is met. The wheel deployment sensor condition is the output status of the sensor group 98 corresponding to the state in which the pair of fork wheels 61, 61 is deployed, and specifically, "docking switch 985: off, floor lock switch 984: on, fork upper limit switch 981: off."

[0077] If the wheel deployment sensor condition is met in S4 (S4: Yes), the ascending wheel deployment control is executed in S5 to S7. Specifically, first, the extension operation of the fork cylinder 81 is executed in S5.

[0078] Next, in S6, it is determined whether the wheel grounding is on (whether the fork wheel grounding sensor 986 is on). If the wheel grounding is not on in S6 (fork wheel grounding sensor 986: off, S6: No), in S7, the carriage cylinder 71 is retracted. In the retraction operation of the carriage cylinder 71 in S7, the count output of the lift distance encoder 989 is referenced, and cancellation control is performed to lower the carriage 5 by the relative lift distance of the pair of forks 6, 6 due to the extension operation of the fork cylinder 81 in S5, thereby maintaining the height of the pair of forks 6, 6 from the ground surface. After S7 is executed, the process returns to S2.

[0079] On the other hand, if the wheel grounding is on in S6 (fork wheel grounding sensor 986: on, S6: Yes), the process returns to S2 without executing S7. Therefore, when the pair of fork wheels 61, 61 touches the ground surface, the above-mentioned cancellation control for lowering the carriage 5 is not performed, and only the relative lifting operation of the pair of fork wheels 61, 61 is performed until the fork upper limit switch 981 is turned on.

[0080] If the wheel unfolding sensor condition is not met in S4 (S4: No), it is determined in S8 whether the wheel retracting sensor condition is met. The wheel retracting sensor condition is the output status of the sensor group 98 corresponding to the state in which the wheel retracting operation is performed, and specifically, "docking switch 985: ON, floor lock switch 984: OFF."

[0081] If the wheel storage sensor condition is met in S8 (S8: Yes), wheel storage control during ascent is executed in S9 to S10. Specifically, the fork cylinder 81 is retracted in S9, and then the carriage cylinder 71 is extended in S10. In the extension operation of the carriage cylinder 71 in S10, the count output of the lift distance encoder 989 is referenced, and cancellation control is performed to raise the carriage 5 by the relative lowering distance of the pair of forks 6, 6 due to the retraction operation of the fork cylinder 81 in S9, thereby maintaining the height of the pair of forks 6, 6 from the ground surface. After executing S10, the process returns to S2.

[0082] If the wheel storage sensor condition is not met in S8 (S8: No), then in S11 it is determined whether the carriage lift sensor condition is met. The carriage lift sensor condition is a condition of the sensor group 98 that corresponds to the state in which the carriage 5 is lifted, and specifically, "docking switch 985: ON, floor lock switch 984: OFF."

[0083] If the carriage lift sensor condition is met in S11 (S11: Yes), carriage lift control is executed in S12. Specifically, in S12, the extension operation of the carriage cylinder 71 is executed. After S12 is executed, the process returns to S2.

[0084] If the input is not an up operation in S3 (S3: No), it is determined in S13 whether or not the input is a down operation. If the input is not a down operation in S13 (S13: No), the process returns to S2.

[0085] If a lowering operation is input in S13 (S13: Yes), it is determined in S14 whether or not a wheel deployment sensor condition is met. The wheel deployment sensor condition is the output status of the sensor group 98 corresponding to the state in which the pair of fork wheels 61, 61 is deployed, and specifically, "docking switch 985: on, floor lock switch 984: on, fork lower ground contact surface sensor 987: on, fork upper limit switch 981: off."

[0086] If the wheel deployment sensor condition is met in S14 (S14: Yes), then in S15 to S17, the wheel deployment control during descent is executed. Specifically, first, in S15, it is determined whether the wheel ground contact is on (whether the fork wheel ground contact sensor 986 is on). If the wheel ground contact is not on in S15 (fork wheel ground contact sensor 986: off, S15: No), then in S16, the fork cylinder 81 is extended.

[0087] After S16 is executed, in S17, the carriage cylinder 71 is retracted. In the retraction operation of the carriage cylinder 71 in S7, the count output of the lift distance encoder 989 is referenced, and cancellation control is performed to lower the carriage 5 by the relative lift distance of the pair of forks 6, 6 due to the extension operation of the fork cylinder 81 in S16, thereby maintaining the height of the pair of forks 6, 6 from the ground surface. After S17 is executed, the process returns to S2. On the other hand, if the wheel ground contact is on in S15 (fork wheel ground contact sensor 986: on, S15: Yes), the process returns to S2.

[0088] If the wheel unfolding sensor condition is not satisfied in S14 (S14: No), it is determined in S18 whether or not the wheel retracting sensor condition is satisfied. The wheel retracting sensor condition is the output status of the sensor group 98 corresponding to a state in which the retracting operation of the pair of fork wheels 61, 61 is being performed, and specifically, is "docking switch 985: off, floor lock switch 984: on, fork wheel grounding sensor 986: on" or "docking switch 985: on, floor lock switch 984: off, slide lock switch 983: on."

[0089] If the wheel storage sensor condition is met in S18 (S18: Yes), wheel storage control during descent is executed in S19 to S20. Specifically, in odd-numbered iterations of wheel storage control during descent, the fork cylinder 81 is retracted in S19. After S19 is executed, the process returns to S2. In even-numbered iterations of wheel storage control during descent, the fork cylinder 81 is retracted in S19, and then the carriage cylinder 71 is extended in S20. In the extension operation of the carriage cylinder 71 in S20, the count output of the lift distance encoder 989 is referenced, and cancellation control is performed to raise the carriage 5 by the relative lowering distance of the pair of forks 6, 6 due to the retraction operation of the fork cylinder 81 in S16, thereby maintaining the height of the pair of forks 6, 6 from the ground surface. After S20 is executed, the process returns to S2. The reason why the cancellation control is performed only on even-numbered lowering wheel storage control is to allow the operator to visually confirm the height at which the pair of forks 6, 6 can be pulled out from the pallet, and to store the pair of fork wheels 61, 61 while maintaining that height.

[0090] If the wheel storage sensor condition is not met in S18 (S18: No), it is determined in S21 whether the carriage lowering sensor condition is met in S18. The carriage lowering sensor condition is the output status of the sensor group 98 corresponding to the state in which the carriage 5 is lowered, and specifically, "docking switch 985: ON, floor lock switch 984: OFF, slide lock switch 983: ON."

[0091] If the carriage lowering sensor condition is met in S21 (S21: Yes), carriage lowering control is executed in S22. Specifically, in S22, the carriage cylinder 71 is contracted. After S22 is executed, the process returns to S2.

[0092] After returning from the control processing of each step to S2, the flow of each control processing from S2 onwards is repeatedly executed.

[0093] <4. Procedures for lifting luggage and operation of each part> Next, the procedures and operation of each part in an example of a luggage shelving operation using the lift device 1 will be described with reference to Figures 17 to 27. In the following example, a task will be performed in which a pallet placed on the floor is supplied onto a shelf. Figure 17 is an explanatory diagram for explaining steps [1] and

[13] in an example of a luggage shelving operation using the lift device 1, Figures 18 to 25 are explanatory diagrams for explaining steps [2] to [9], Figure 26 is explanatory diagrams for explaining steps

[10] and

[11] , and Figure 27 is explanatory diagram for explaining step

[12] , and each figure shows the lift device 1 from a side view.

[0094] In step [1], the lift device 1 is set to the initial state shown in Fig. 17. In the initial state, the slide body 3 is in the retracted position, the carriage 5 is in the lowest position, the pair of fork wheels 61, 61 are in the stored position, the slide lock release lever 42 is in the non-gripped state, and the floor lock mechanism 26 is in the unlocked state.

[0095] In step [2], as shown in Figure 18, an upward operation is input using the lifting operation unit 97 to raise the carriage 5 by a short distance (several centimeters) (Figure 14: S11, S12), and the lift device 1 together with the base 2 is moved to the vicinity of the pallet, after which the floor lock mechanism 26 is set to the locked state. In step [2], the floor lock switch 984 changes from OFF to ON. At this time, only the tip portions of the pair of forks 6, 6 are inserted into the insertion openings of the pallet, and the pair of support arms 21, 21 are positioned in front of the pallet.

[0096] In step [3], as shown in Fig. 19, the operator grasps the slide lock release lever 42 to unlock the slide lock mechanism 33 (Fig. 16: S60, S61), and slides the slider 3 forward to insert the pair of forks 6, 6 deep into the pallet. In step [3], the output of the baggage sensor 988 changes from off to on.

[0097] In step [4], as shown in Fig. 20, the operator again inputs an upward operation using the lift operation unit 97 to displace the pair of fork wheels 61, 61 to the deployed position (Fig. 14: wheel deployment control during ascent S5 to S7). At this time, a cancel control is executed to lower the carriage 5 by the amount of lift of the pair of fork wheels 61, 61 until wheel ground contact is detected (i.e., the fork wheel ground contact sensor 986 changes from off to on) (Fig. 14: S7). By step [4], the pair of forks 6, 6 pick up the pallet (lift it slightly), and the pallet is supported by the pair of fork wheels 61, 61 contacting the floor surface.

[0098] In step [5], as shown in Figure 21, the operator grasps the handles 41, 41 with their hands and pulls the sliding body 3 backward to the retracted position. At this time, the pair of fork wheels 61, 61 supporting the pair of forks 6, 6 that receive the pallet roll on the floor surface, allowing the sliding body 3 to be smoothly retracted.

[0099] Next, in step [6], as shown in Fig. 22, the operator inputs an upward operation using the lifting operation unit 97 to displace the pair of fork wheels 61, 61 to the storage position (Fig. 14: wheel storage control during ascent S9 to S10). At this time, a cancel control is executed to lower the carriage 5 by the amount of elevation of the pair of fork wheels 61, 61 (Fig. 14: S10). After the pair of fork wheels 61, 61 are displaced to the storage position, the carriage 5 is raised to an arbitrary height (S12).

[0100] In step [7], as shown in Figure 23, the operator pushes the lift device 1 to move it to the front of the shelf to which the pallet is to be moved, and then inputs an upward operation on the lifting operation unit 97 to raise the carriage 5 to a height slightly above the shelf surface (Figure 14: S12).

[0101] In step [8], as shown in FIG. 24, the operator confirms that the tips of the pair of forks 6, 6 overlap the shelf surface in a side view, and then steps on the lock pedal 26b with his / her foot to place the floor lock mechanism 26 in the floor lock state. Next, a lowering operation input is performed with the lifting / lowering operation unit 97 to displace the pair of fork wheels 61, 61 to the deployed position (FIG. 15: wheel deployment control during descent S15 to S17). At this time, a cancel control is executed to lower the carriage 5 by the amount of lift of the pair of fork wheels 61, 61 until wheel ground contact is detected (i.e., the fork wheel ground contact sensor 986 changes from off to on) (FIG. 15: S17). Through step [8], the pair of forks 6, 6 are supported by the pair of fork wheels 61, 61 contacting the floor surface.

[0102] In step [9], as shown in Figure 25, the operator grasps the slide lock release lever 42 to release the slide lock, and then pushes the slider 3 to slide it forward, thereby inserting the pair of forks 6, 6 into the back of the shelf. At this time, the pair of fork wheels 61, 61 supporting the pair of forks 6, 6 that receive the pallet roll on the shelf surface, allowing the slider 3 to move forward smoothly.

[0103] Next, in step

[10] , as shown in Figure 26, the operator inputs a lowering operation using the lifting operation unit 97, and while the pair of fork wheels 61, 61 are moving from the deployed position to the stored position, the operator visually confirms that the pallet has been placed on the shelf surface and interrupts the lowering operation input. Since this lowering operation input corresponds to an odd-numbered cycle of the wheel position control during descent, only the retraction of the fork cylinder 81 is executed (Figure 15: S19).

[0104] Next, in step

[11] , the operator resumes inputting the lowering operation using the lifting operation unit 97, displacing the pair of fork wheels 61, 61 to the storage position. This lowering operation input corresponds to the even-numbered cycle of the wheel position control during descent, so following contraction of the fork cylinder 81 (FIG. 15: S19), a cancel control is executed to raise the carriage 5 by the amount of relative descent of the pair of forks 6, 6 (FIG. 15: S20). Step

[11] makes it possible to pull out the pair of forks 6, 6 from the pallet.

[0105] Next, in step

[12] , as shown in Figure 27, the operator grasps the slide lock release lever 42 to release the slide lock, and then slides the slide body 3 backward to pull out the pair of forks 6, 6 from the pallet and move the slide body 3 back to the retracted position.

[0106] Finally, in step

[13] , as shown in Figure 17, the operator moves the lift device 1 to the waiting location and inputs a lowering operation on the lifting operation unit 97 to lower the carriage 5 to its lowest limit and return to the initial state (Figure 15: S22).

[0107] <Summary of the embodiment> As is clear from the above detailed description, the lift device 1 of this embodiment comprises a base 2 that can move freely on the floor surface, a sliding body 3 that can slide relatively back and forth on the base 2, a mast 4 erected on the sliding body 3, a carriage 5 supported on the mast 4 so that it can be raised and lowered, a pair of forks 6, 6 as load-receiving members whose base ends are supported on the carriage 5 and extended forward, a carriage lifting mechanism 7 that raises and lowers the carriage 5 along the mast 4, a pair of fork wheels 61, 61 as support and moving members that support the pair of forks 6, 6 against the ground surface and allow them to move on the ground surface, and a pair of fork wheel displacement mechanisms 83, 83 that are provided between the pair of fork wheels 61, 61 and the pair of forks 6, 6 and serve as support and moving member displacement mechanisms that can displace the pair of fork wheels 61, 61 between a stored position at approximately the same height as the pair of forks 6, 6 and an deployed position protruding downward from the pair of forks 6, 6.

[0108] According to this configuration, the pair of forks 6, 6 can be advanced via the slide body 3 on which the mast 4 is erected. This avoids interference between the front end of the base 2 and a pallet or cargo placed on the floor. This allows the pair of forks 6, 6 to support a pallet placed on the floor, or a pallet on a shelf when there is cargo placed on the floor. Furthermore, with the pair of forks 6, 6 advanced, the pair of fork wheel displacement mechanisms 83 displace the pair of fork wheels 61, 61 from the retracted position to the extended position, allowing the pair of forks 6, 6 to contact a ground surface such as a floor or shelf. This prevents the lift device 1 from tipping forward without requiring a counterweight. Furthermore, since a counterweight is not required, the overall weight can be reduced, enabling agile operability during cargo transport. Furthermore, when the pair of forks 6, 6 are retracted via the slide body 3 and positioned directly above the base 2, the pair of forks 6, 6 carrying cargo can be safely raised and lowered along the mast 4 via the carriage 5 by the carriage lifting mechanism 7. Therefore, it is possible to provide a lift device 1 that can be used in various situations by avoiding interference with pallets or cargo placed on the floor, and that is easy to operate during transportation.

[0109] The lift device 1 also includes a fork relative lifting mechanism 82 as a load receiving member relative lifting mechanism that is provided between the carriage 5 and the pair of forks 6, 6 and moves the pair of forks 6, 6 relatively up and down relative to the carriage 5 between a first relative height and a second relative height that is relatively higher than the first relative height, and the pair of fork wheel displacement mechanisms 83, 83 move in conjunction with the relative lifting and lowering movement of the fork relative lifting mechanism 82 to move the pair of fork wheels 61, 61 to a stored position when the pair of forks 6, 6 are at the first relative height, and move the pair of fork wheels 61, 61 to an extended position when the pair of forks 6, 6 are at the second relative height.

[0110] According to this configuration, the fork relative lifting and lowering mechanism 82 raises and lowers the pair of forks 6, 6 relative to the carriage 5 between a first relative height and a second relative height that is relatively higher than the first relative height, and the pair of fork wheel displacement mechanisms 83, 83 perform displacement operations in conjunction with the relative lifting and lowering operation of the fork relative lifting and lowering mechanism 82, so that when the pair of forks 6, 6 are at the first relative height, the pair of fork wheels 61, 61 can be placed in the stored position, and when the pair of forks 6, 6 are at the second relative height, the pair of fork wheels 61, 61 can be placed in the deployed position. Thus, a structure can be realized that allows the pair of fork wheels 61, 61 to be displaced between the stored position and the deployed position.

[0111] In addition, the lift device 1 further includes control steps S7, S17, and S20 as a cancellation control unit that performs cancellation control by causing the carriage lifting mechanism 7 to lift the carriage 5 by the same distance in the opposite direction to the relative lifting operation when the fork relative lifting mechanism 82 lifts and lowers the pair of forks 6, 6 relative to the carriage 5.

[0112] According to this configuration, when the pair of fork wheel displacement mechanisms 83, 83 perform a displacement operation in conjunction with the relative lifting and lowering operation of the fork relative lifting and lowering mechanism 82 to move the pair of fork wheels 61, 61 to a stored position when the pair of forks 6, 6 are at a first relative height, and to move the pair of fork wheels 61, 61 to an extended position when the pair of forks 6, 6 are at a second relative height, the control steps S7, S17, and S20 perform cancellation control to cause the carriage lifting and lowering mechanism 7 to lift the carriage 5 by the same distance in the opposite direction to the relative lifting and lowering operation, so that the pair of forks 6, 6 can be displaced between the stored position and the extended position while maintaining the height of the pair of forks 6, 6 from the ground surface.

[0113] The lift device 1 also includes a fork wheel ground contact sensor 986 as a ground contact detection unit that detects when the pair of fork wheels 61, 61 touches the ground surface.

[0114] According to this configuration, the fork wheel ground contact sensor 986 detects that the pair of fork wheels 61, 61 have been displaced from the stored position to the deployed position and have come into contact with the ground surface. Therefore, by supporting the pair of forks 6, 6 by reliably bringing the pair of fork wheels 61, 61 into contact with the ground surface, the slide body 3 can be slid back and forth to safely move the pair of forks 6, 6 on the ground surface while preventing the lift device 1 from tipping forward.

[0115] The lift device 1 also includes a lifting operation unit 97 that inputs lifting and lowering operations through operation by the operator, and a control step S4 that functions as a switching control unit that automatically switches between the relative lifting and lowering operation of the pair of forks 6, 6 relative to the carriage 5 by the fork relative lifting and lowering mechanism 82 and the lifting and lowering operation of the carriage 5 by the carriage lifting and lowering mechanism 7 when a lifting and lowering operation is input by the lifting and lowering operation unit 97.

[0116] According to this configuration, the control step S4 automatically switches between the relative lifting and lowering operation of the pair of forks 6, 6 relative to the carriage 5 by the fork relative lifting and lowering mechanism 82 and the lifting and lowering operation of the carriage 5 by the carriage lifting and lowering mechanism 7, so that the operator can easily achieve appropriate lifting and lowering operation by simply operating the lifting and lowering operation unit 97 without being aware of the positional relationship between the pair of forks 6, 6 and the pallet, etc.

[0117] The lift device 1 also includes a slide lock mechanism 33 that releasably locks the sliding of the sliding body 3 to the base 2, and control steps S60 to S62 as an unlock control unit that allows the slide lock mechanism 33 to be unlocked when predetermined slide permission conditions are met, and prohibits the slide lock mechanism 33 from being unlocked otherwise.

[0118] According to this configuration, if predetermined slide permission conditions are met (S60: Yes), the control step of S61 permits unlocking of the slide lock mechanism 33, so that the pair of forks 6, 6 can be inserted into or pulled out of a pallet or the like by sliding the slider 3 on the base 2. On the other hand, if predetermined slide permission conditions are not met (S60: No), the control step of S62 prohibits unlocking of the slide lock mechanism 33, so that accidental unlocking of the slide lock mechanism 33 due to an operator's incorrect operation can be reliably prevented, thereby ensuring safety.

[0119] <Modification> The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, wheels (fork wheels 61) are provided as support and movement members that support the fork 6 on the ground surface and enable it to move on the ground surface, but this is not limiting. For example, the support and movement members may be ball rollers or crawlers instead of wheels.

[0120] In the above embodiment, the carriage cylinder 71 and the fork cylinder 81 are configured as electric hydraulic cylinders, but this is not limiting. For example, each cylinder may be configured as a mechanical electric cylinder, i.e., a cylinder device in which a motor rotates a ball screw around its axis to move a ball screw nut, and the movement of the ball screw nut moves the rod forward and backward. Alternatively, each of these cylinders may be configured as a manual hydraulic cylinder or other type of actuator.

[0121] In the above embodiment, the slider 3 is configured to slide back and forth while the base 2 is locked to the floor surface, but the slider 3 may be configured to slide back and forth while the base 2 is locked to the floor surface. In short, it is sufficient that the slider 3 is configured to be able to slide back and forth relatively on the base 2.

[0122] In the above embodiment, a pair of forks 6, 6 is provided as the cargo receiving member, but this is not limiting. For example, a table-shaped cargo receiving plate may be provided as the cargo receiving member. In the above embodiment, a photoelectric sensor is used as the cargo sensor 988 to optically detect cargo, but the presence or absence of cargo may be detected by detecting the load using a load sensor.

[0123] Furthermore, in the above embodiment, an example of a luggage shelving operation shown in Figures 17 to 27 is an example of transporting an empty pallet, but even if a heavy object within the loading capacity range is loaded on the pallet, the pair of fork wheels 61, 61 will be displaced to the extended position at the appropriate time to support the pair of forks 6, 6 against the floor or shelf surface, so it goes without saying that the lift device 1 can be reliably prevented from tipping forward.

[0124] In addition, in the above embodiment, an example has been shown in which the base 2 is configured to be manually movable on the floor surface, but this is not limiting. For example, the base 2 may be configured to be movable on the floor surface using an electric travel function. In addition, in the above embodiment, the height of the mast 4 is fixed, but the height of the mast 4 may be adjustable using a multi-stage telescopic structure with two or more stages, allowing work to be done at higher altitudes. [Explanation of symbols]

[0125] 1 Lifting device 2 bases 3 Slide body 4 Mast 5 Carriage 6 Fork (load receiving member) 7 Carriage lifting mechanism 8 Fork moving mechanism (load receiving member relative lifting mechanism, support moving member displacement mechanism) 33 Slide lock mechanism 61 Fork wheels (supporting and moving members) 82 Fork relative lifting mechanism (load receiving member relative lifting mechanism) 83 Fork wheel displacement mechanism (support moving member displacement mechanism) 97 Lifting control unit 986 Fork wheel ground sensor (ground detection part) S4, S8, S14, S18 switching control section S7, S10, S17, S20 Cancel control section S60~S62 Unlock control section

Claims

1. A base that can be moved freely on the floor, a slider that can slide relatively back and forth on the base; a mast erected on the slide body; a carriage supported on the mast so as to be able to rise and fall; a load receiving member whose base end is supported by the carriage and extends forward; a carriage lifting mechanism that raises and lowers the carriage along the mast; a support and movement member that supports the load receiving member on a ground surface and allows the load receiving member to move on the ground surface; a support / movement member displacement mechanism provided between the support / movement member and the load receiving member, capable of displacing the support / movement member between a stored position at substantially the same height as the load receiving member and an deployed position in which the support / movement member protrudes downward from the load receiving member; A lift device comprising:

2. a load receiving member relative lifting mechanism provided between the carriage and the load receiving member for lifting and lowering the load receiving member relative to the carriage between a first relative height and a second relative height that is higher than the first relative height; The lift device described in claim 1, wherein the support and moving member displacement mechanism displaces the support and moving member to the stored position when the load receiving member is at the first relative height, and to the deployed position when the load receiving member is at the second relative height, in conjunction with the relative lifting and lowering operation of the load receiving member relative lifting mechanism.

3. The lift device further comprises:

3. The lift device according to claim 2, further comprising a cancellation control unit that performs cancellation control in the carriage lifting mechanism to raise and lower the carriage by the same distance in the opposite direction to the relative lifting movement when the load receiving member relative lifting mechanism raises and lowers the load receiving member relative to the carriage.

4. The lift device according to claim 1 , further comprising a ground contact detector that detects when the support and movement member touches the ground surface.

5. a lifting operation unit for inputting lifting operation by an operator; a switching control unit that automatically switches between a lifting operation of the receiving member relative to the carriage by the receiving member relative lifting mechanism and a lifting operation of the carriage by the carriage lifting mechanism when a lifting operation is input by the lifting operation unit; The lifting device of claim 2 , comprising:

6. a slide lock mechanism that releasably locks the slide of the slider to the base; an unlock control unit that allows the slide lock mechanism to be unlocked when a predetermined slide permission condition is satisfied, and prohibits the slide lock mechanism from being unlocked otherwise; The lifting device of claim 1 , comprising:

Images