Transport vehicle

Abstract

To provide a carrying vehicle capable of easily lowering the vehicle height in a short time at the time of abnormality.SOLUTION: Normally, by closing the manual opening / closing unit 90, the expansion and contraction of the expansion / contraction devices 7a to 7j are controlled by the pressure control circuit 20304050, and the vehicle height of the transport vehicle 1 can be raised and lowered as before. On the other hand, at the time of abnormality such as stop of the pressure control circuit 20304050, the manual opening / closing unit 90 is opened to release the pressure inside the expansion / contraction devices 7a to 7j via the fixed branch passages 81 to 84 and the variable branch passage 8586, so that the expansion / contraction devices 7a to 7j contract by their own weight, and the vehicle height of the transport vehicle 1 can be lowered easily and in a short time.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a transport vehicle, and more particularly to a transport vehicle that can easily and quickly lower its vehicle height in the event of an emergency. [Background technology]

[0002] For example, Patent Document 1 describes a transport vehicle that lowers the vehicle height by retracting the hydraulic cylinders of multiple traveling devices, moves under a gate-shaped pallet, and then lifts the pallet by extending the hydraulic cylinders. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-93778 Summary of the Invention [Problem to be solved by the invention]

[0004] In the transport vehicle of Patent Document 1, if an abnormality occurs, such as a power outage while the pallet is raised, a worker with specialized knowledge can connect each part of the transport vehicle to an external hydraulic power source or power source, thereby retracting the hydraulic cylinder and lowering the vehicle height, and then lowering the pallet to the site. However, there are problems in that it takes time to prepare the hydraulic power source or power source, which means that it takes time to lower the vehicle height after the abnormality occurs, and it is difficult for a worker without specialized knowledge to deal with the problem.

[0005] The present invention has been made to solve the above-mentioned problems, and has as its object to provide a transport vehicle that can easily and quickly lower its vehicle height in the event of an abnormality. [Means for solving the problem]

[0006] In order to achieve this object, the transport vehicle of the present invention comprises a platform, a plurality of running devices that support the platform from below, and a fluid circuit that drives the plurality of running devices with a fluid, wherein each of the running devices comprises a wheel and an extension device that extends and retracts to change the distance from the wheel to the platform, and the fluid circuit comprises a main flow path connected to the extension device, a pressure control circuit that pressurizes or depressurizes the inside of the extension device via the main flow path and extends and retracts the extension device, branch flow paths branching off from the main flow path, and manual opening and closing means that is provided on the branch flow path and can be opened and closed manually, wherein the manual opening and closing means releases pressure inside the extension device via the branch flow path when opened, and blocks the branch flow path when closed. [Effects of the Invention]

[0007] According to the transport vehicle described in claim 1, by keeping the manual opening / closing means closed under normal circumstances, the expansion and contraction of the expansion device is controlled by the pressure control circuit, allowing the vehicle height to be raised and lowered as usual. On the other hand, in the event of an abnormality, such as a stoppage of the pressure control circuit, the pressure inside the expansion device is released through the branch flow path by opening the manual opening / closing means, causing the expansion device to contract under its own weight, lowering the vehicle height. In this way, a transport vehicle equipped with a manual opening / closing means can easily and quickly lower its vehicle height in the event of an abnormality.

[0008] The transport vehicle of claim 2 achieves the following effects in addition to those of claim 1. A plurality of pressure control circuits are provided, and a plurality of extension devices are divided into a plurality of groups. These groups include the same number of fixed groups as the plurality of pressure control circuits. A plurality of fixed-side flow paths of the main flow path individually connect the plurality of fixed groups to the plurality of pressure control circuits, and the branch flow path includes a plurality of fixed branch paths individually branching off from these fixed-side flow paths. The manual opening / closing means includes a plurality of individual valves individually provided in the fixed branch paths and manually opened / closed. Therefore, in the event of an abnormality, opening all the individual valves retracts each extension device, allowing the vehicle height to be lowered easily and quickly. Furthermore, during maintenance of the transport vehicle without driving the pressure control circuits, opening only some of the individual valves facilitates maintenance of the traveling device having the corresponding extension device (e.g., wheel replacement).

[0009] The transport vehicle of claim 3 achieves the following effect in addition to the effect achieved by the transport vehicle of claim 2. The multiple groups into which the multiple extension devices are divided include one or more variable groups in addition to the fixed group. The main flow path has one or more variable side flow paths individually connected to the variable groups, and the fixed side flow path connected to the variable side flow path is switched by a switching block of the fluid circuit. The branch flow path has one or more variable branch paths individually branching off from the variable side flow path, and these variable branch paths are also individually provided with multiple individual valves that can be opened and closed manually. As a result, even in the event of an abnormality in which communication between the variable side flow path and the fixed side flow path via the switching block is cut off, opening all the individual valves will retract each extension device, allowing the vehicle height to be lowered easily and quickly.

[0010] The transport vehicle of claim 4 achieves the following effect in addition to the effect of the transport vehicle of claim 3. The branch flow path comprises a single merging flow path where multiple fixed branch paths and one or more variable branch paths merge, and the manual opening / closing means comprises a merging valve that is provided in this merging flow path and can be opened and closed manually. By opening all the individual valves and then opening the merging valve, multiple extension devices can be retracted at once. In other words, it is possible to prevent the pressure of some extension devices from being released first, thereby preventing an unbalanced load from being applied to the extension devices before release.

[0011] The transport vehicle described in claim 5 achieves the following effect in addition to the effect achieved by the transport vehicle described in claim 2 or 3. Because the individual valves are needle valves that facilitate precise flow rate adjustment, it is possible to open multiple individual valves little by little and approximately evenly, making it easy to synchronize the pressure fluctuation speed and contraction speed of multiple expansion devices. As a result, even if pressure is released on the side of the branch flow path opposite the expansion device with respect to the individual valve (even if there is no merging valve opening and closing the branch flow path on that side), it is possible to prevent unbalanced loads from being applied to some of the expansion devices.

[0012] The transport vehicle described in claim 6 achieves the following effects in addition to those achieved by the transport vehicle described in claim 1. A plurality of pressure control circuits are provided, and a plurality of expansion devices are divided into a plurality of groups. The plurality of groups includes the same number of fixed groups as the plurality of pressure control circuits. A plurality of fixed-side flow paths of the main flow path individually connect the plurality of fixed groups to the plurality of pressure control circuits. The branch flow path includes a plurality of fixed branch paths individually branching off from the fixed-side flow paths and a single merging flow path where the plurality of fixed branch paths merge. The manual opening / closing means includes a merging valve provided in the merging flow path and manually opened / closed, and a plurality of check valves provided individually in the fixed branch paths to prevent backflow from the merging flow path. By keeping the merging valve closed under normal conditions, the internal pressure of the expansion devices is not released through the merging flow path. The check valves prevent the internal pressure of the expansion devices from being synchronized between the plurality of fixed groups through the merging flow path, allowing the transport vehicle to be raised or lowered as usual. Meanwhile, in the event of an abnormality, such as a pressure control circuit failure, the merging valve can be opened to simultaneously retract the plurality of expansion devices, thereby preventing unbalanced loads from being applied to some of the expansion devices.

[0013] The transport vehicle of claim 7 achieves the following effect in addition to the effect of the transport vehicle of claim 6. The multiple groups into which the multiple expansion devices are divided include one or more variable groups in addition to the fixed group. The main flow path has one or more variable side flow paths individually connected to the variable groups, and the fixed side flow path connected to the variable side flow path is switched by a switching block of the fluid circuit. The branch flow path has one or more variable branch paths that individually branch off from the variable side flow path and merge into the merging flow path, and these variable branch paths are also individually provided with check valves to prevent backflow from the merging flow path. As a result, by keeping the merging valves closed under normal circumstances, the check valves can prevent the internal pressures of the expansion devices between each group from being synchronized via the merging flow path. Meanwhile, even in an abnormal situation where communication between the variable side flow path and the fixed side flow path via the switching block is cut off, the multiple expansion devices can be retracted at once by opening the merging valve, thereby preventing unbalanced loads from being applied to some of the expansion devices. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1(a) is a side view of a transport vehicle in a first embodiment of the present invention, and FIG. 1(b) is a top view of the transport vehicle. [Figure 2] 1A is a front view of the transport vehicle with the pallet and the article unloaded, and FIG. 1B is a front view of the transport vehicle with the pallet and the article lifted. [Figure 3] FIG. 2 is a schematic diagram showing a hydraulic circuit of the transport vehicle. [Figure 4] FIG. 10 is a schematic diagram showing a hydraulic circuit of a transport vehicle in a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1(a) is a side view of a transport vehicle 1 in a first embodiment of the present invention. Fig. 1(b) is a top view of the transport vehicle 1. Note that arrows U, D, L, R, F, and B in each drawing indicate the upward, downward, leftward, rightward, forward, and backward directions of the transport vehicle 1, respectively. Fig. 1(b) also shows a partial perspective view of a loading platform 2.

[0016] The transport vehicle 1 is a vehicle for transporting an object W (see FIG. 2(a)). The transport vehicle 1 includes a platform 2 on the upper surface of which the object W can be placed, ten traveling devices 3a to 3j that support the platform 2 from below and allow the transport vehicle 1 to travel, and a driver's cab 2a and a control unit 10 that are suspended and fixed to the underside of the platform 2.

[0017] The loading platform 2 is formed in a rectangular shape elongated in the front-to-rear direction when viewed from above. An operator's cab 2a is provided at each of the front and rear ends of the loading platform 2. Each part of the transport vehicle 1 is operated by an operator in the operator's cab 2a. The control unit 10 is provided with a power source and part of a hydraulic circuit 11 (see FIG. 3) for controlling the operation of the traveling devices 3a to 3j etc. in response to the operation.

[0018] The traveling devices 3a to 3j are each attached to the underside of the loading platform 2. Specifically, the traveling devices 3a, 3c, 3e, 3g, and 3i are attached to the left side of the loading platform 2 in order from the front, and the traveling devices 3b, 3d, 3f, 3h, and 3j are attached to the right side of the loading platform 2 in order from the front.

[0019] Each of the traveling devices 3a to 3j includes a pair of wheels 4 that roll on the road surface S, a link member 5 that rotatably supports the wheels 4 and connects them to the platform 2, a steering unit (not shown) that steers and drives the wheels 4, and a drive motor (not shown) that rotates and drives the wheels 4. Note that a drive motor does not necessarily have to be provided on all of the traveling devices 3a to 3j. Furthermore, the traveling devices 3a to 3j are each provided with extension devices 7a to 7j in order (for example, the traveling device 3a is provided with the extension device 7a, and the traveling device 3c is provided with the extension device 7c).

[0020] The link member 5 is formed in a dogleg shape when viewed from the axle direction of the wheel 4, and the angle of the dogleg portion is configured to be freely changeable. The extension devices 7a to 7j are hydraulic cylinders that extend and contract to change the angle of this link member 5 and change the distance from the wheel 4 to the platform 2. By extending the multiple extension devices 7a to 7j, the vehicle height of the transport vehicle 1 (the upper surface of the platform 2) increases, and by retracting the multiple extension devices 7a to 7j, the vehicle height of the transport vehicle 1 decreases.

[0021] Fig. 2(a) is a front view of the transport vehicle 1 with the pallet P and the transported object W unloaded. Fig. 2(b) is a front view of the transport vehicle 1 with the pallet P and the transported object W lifted up. The pallet P is formed in a gate shape when viewed from the front to back, and extends in the front to back direction. The transported object W is placed on the top surface of the pallet P.

[0022] To transport an object W using the transport vehicle 1, as shown in FIG. 2(a), first, the transport vehicle 1 is driven with the extension devices 7a to 7j retracted to lower the vehicle height, and the transport vehicle 1 is driven to slide under a pallet P placed on the road surface S. Next, as shown in FIG. 2(b), the extension devices 7a to 7j are extended to increase the vehicle height, and the pallet P and the object W are placed on the top surface of the loading platform 2, and as the vehicle height is increased further, the pallet P and the object W are lifted and the pallet P is removed from the road surface S. When the transport vehicle 1 is driven in this state and arrives at the destination, the extension devices 7a to 7j are retracted again to lower the vehicle height, as shown in FIG. 2(a), and the pallet P is placed on the road surface S.

[0023] FIG. 3 is a schematic diagram showing the hydraulic circuit 11 of the transport vehicle 1. The hydraulic circuit 11 in FIG. 3 mainly shows the circuit for extending and retracting the extension devices 7a to 7j, and does not include the circuit for driving the steering unit and other components. The extension devices 7a to 7j are configured to extend when hydraulic oil is supplied to the interior of the head side and pressurized, and to contract when hydraulic oil is discharged from the interior of the head side and reduced in pressure. Note that normally open manual valves 8a to 8j are provided on the head side of the extension devices 7a to 7j, respectively. An operator can close these manual valves 8a to 8j to prevent the extension and retraction of the extension devices 7a to 7j.

[0024] The hydraulic circuit 11 includes a tank 12 for storing hydraulic oil, pressure control circuits 20, 30, 40, and 50 for controlling the direction and flow rate of hydraulic oil supplied to the extension devices 7a to 7j, a switching block 60 for switching the interlocking relationship of the extension devices 7e and 7f, a manual opening / closing device 90 for forcibly retracting the extension devices 7a to 7j, and multiple pipes for sending hydraulic oil between them.The multiple pipes include a supply path 15, a discharge path 16, fixed-side flow paths 21, 31, 41, and 51, switching branch paths 22, 32, 42, and 52, variable-side flow paths 65 and 66, a connecting path 71, fixed branch paths 81 to 84, variable branch paths 85 and 86, and a merging path 87.

[0025] The tank 12 is connected to the pressure control circuits 20, 30, 40, and 50 by a supply path 15 and a discharge path 16. A pump 14 is provided in the supply path 15 to supply hydraulic oil from the tank 12 to the pressure control circuits 20, 30, 40, and 50. The pump 14 is driven by the engine 13 of the transport vehicle 1. The discharge path 16 is a section for discharging hydraulic oil from the pressure control circuits 20, 30, 40, and 50 to the tank 12. In other words, hydraulic pressure is released in the discharge path 16.

[0026] The expansion devices 7a and 7c are connected to the pressure control circuit 20 via a fixed-side flow path 21. A solenoid switching valve is built into the pressure control circuit 20, which separates the fixed-side flow path 21 from both the supply path 15 and the discharge path 16 when not energized, and connects the fixed-side flow path 21 to either the supply path 15 or the discharge path 16 when energized.

[0027] When the supply path 15 is connected, hydraulic oil is supplied via the fixed-side flow path 21, causing the extension devices 7a and 7c to extend. On the other hand, when the fixed-side flow path 21 is connected to the discharge path 16, hydraulic oil is discharged via the fixed-side flow path 21, causing the extension devices 7a and 7c to retract. Furthermore, when the pressure control circuit 20 is not energized, the hydraulic pressure inside the extension devices 7a and 7c basically does not fluctuate, and the lengths of the extension devices 7a and 7c are maintained. In this way, the left front extension devices 7a and 7c, whose extension and retraction are synchronized, are called the fixed group GA1.

[0028] Similarly, the pressure control circuit 30 is connected to the expansion devices 7b and 7d via the fixed-side flow path 31. The pressure control circuit 40 is connected to the expansion devices 7g and 7i via the fixed-side flow path 41. The pressure control circuit 50 is connected to the expansion devices 7h and 7j via the fixed-side flow path 51. The pressure control circuits 30, 40, and 50 are configured identically to the pressure control circuit 20, except for the connected parts.

[0029] The right front extension devices 7b and 7d, whose extension and contraction are synchronized by the pressure control circuit 30, are designated as fixed group GA2. The left rear extension devices 7g and 7i, whose extension and contraction are synchronized by the pressure control circuit 40, are designated as fixed group GA3. The right rear extension devices 7h and 7j, whose extension and contraction are synchronized by the pressure control circuit 50, are designated as fixed group GA4.

[0030] The switching block 60 is equipped with four solenoid switching valves 61 to 64. The solenoid switching valve 61 is connected between a switching branch path 22 branching off from the fixed-side flow path 21 and a variable-side flow path 65 connected to the expansion device 7e. The solenoid switching valve 62 is connected between a switching branch path 42 branching off from the fixed-side flow path 41 and the variable-side flow path 65. The solenoid switching valve 63 is connected between a switching branch path 32 branching off from the fixed-side flow path 31 and a variable-side flow path 66 connected to the expansion device 7f. The solenoid switching valve 64 is connected between a switching branch path 52 branching off from the fixed-side flow path 51 and the variable-side flow path 66.

[0031] The switching block 60 is controlled to energize one of the solenoid directional control valves 61, 62 and de-energize the other. When the solenoid directional control valve 61 is energized and the solenoid directional control valve 62 is de-energized, the variable-side flow path 65 is connected to the fixed-side flow path 21 and is cut off from the fixed-side flow path 41, and the expansion and contraction of the expansion devices 7a, 7c and the expansion device 7e of the fixed group GA1 are synchronized. In contrast, when the solenoid directional control valve 61 is de-energized and the solenoid directional control valve 62 is energized, the variable-side flow path 65 is connected to the fixed-side flow path 41 and is cut off from the fixed-side flow path 21, and the expansion and contraction of the expansion devices 7g, 7i and the expansion device 7e of the fixed group GA3 are synchronized. In this way, the left-side expansion device 7e that is synchronized with either of the left-side fixed groups GA1 or GA3 is designated as the variable group GB1.

[0032] The switching block 60 is similarly controlled to energize one of the solenoid directional control valves 63, 64 and de-energize the other. When the solenoid directional control valve 63 is energized and the solenoid directional control valve 64 is de-energized, the variable-side flow path 66 is connected to the fixed-side flow path 31 and is cut off from the fixed-side flow path 51, and the expansion and contraction of the expansion devices 7b, 7d and 7f of the fixed group GA2 are synchronized. In contrast, when the solenoid directional control valve 63 is de-energized and the solenoid directional control valve 64 is energized, the variable-side flow path 66 is connected to the fixed-side flow path 51 and is cut off from the fixed-side flow path 31, and the expansion and contraction of the expansion devices 7h, 7j and 7f of the fixed group GA4 are synchronized. The right-side expansion device 7f that is synchronized with either of the right-side fixed groups GA2 or GA4 is designated as the variable group GB2.

[0033] As described above, in the transport vehicle 1, the multiple extension devices 7a-7j are divided into six groups (fixed groups GA1-GA4 and variable groups GB1 and GB2), and the switching block 60 synchronizes the extension and retraction of the extension devices 7a-7j for each of the four groups. This makes it possible to control the amount of extension and retraction for each of the four groups (front left, front right, rear left, and rear right) depending on the traveling situation of the transport vehicle 1 and the condition of the road surface on which the transport vehicle 1 is traveling, allowing the loading platform 2 (transport vehicle 1) to travel stably with four-point support. As a result, the transport vehicle 1 can transport the pallet P and the transported object W stably.

[0034] Furthermore, by switching between the fixed groups GA1 to GA4 synchronized with the variable groups GB1 and GB2 using the switching block 60 depending on the traveling conditions of the transport vehicle 1, the platform 2 can exhibit the supporting performance suited to the traveling conditions, etc. As a result, the transport vehicle 1 can transport the pallet P and the transported object W more stably.

[0035] Furthermore, in the transport vehicle 1, the fixed-side flow path 41 and the fixed-side flow path 51 are connected by a connecting path 71, and an electromagnetic switching valve 73 is provided in this connecting path 71. The electromagnetic switching valve 73 cuts off the connecting path 71 when not energized, and connects the fixed-side flow path 41 and the fixed-side flow path 51 via the connecting path 71 when energized. When this electromagnetic switching valve 73 is energized, the amount of extension and contraction of the extension devices 7a to 7j is controlled for each of three groups: left front, right front, and rear, allowing the loading platform 2 (transport vehicle 1) to travel stably with three-point support. Therefore, by switching between three-point support and four-point support depending on the traveling conditions of the transport vehicle 1, the transport vehicle 1 can transport the pallet P and the transported object W more stably.

[0036] In the transport vehicle 1, if an abnormality occurs in which the power supply is stopped due to, for example, a malfunction in the engine 13, and the piping is cut off on both sides of the pressure control circuits 20, 30, 40, 50 and the switching block 60, the states of the extension devices 7a-7j are maintained. Specifically, if the extension devices 7a-7j were in an extended state, they will remain in the extended state, and if the extension devices 7a-7j were in a retracted state, they will remain in the retracted state. If the extension devices 7a-7j cannot be retracted, the pallet P and the transported article W being transported cannot be lowered to the site and transported by another transport vehicle. Note that in the event of an abnormality in which the pallet P cannot be lowered, in addition to an interruption in the power supply, a malfunction of the pressure control circuits 20, 30, 40, 50, for example, may be the cause.

[0037] However, the transport vehicle 1 is provided with a manual opening / closing means 90 for retracting the extension devices 7a to 7j in the event of an emergency to lower the pallet P, etc. The manual opening / closing means 90 includes six individual valves 91 to 96 and one merging valve 97.

[0038] The individual valve 91 is provided in a fixed branch path 81 branching off from the fixed side flow path 21. The individual valve 92 is provided in a fixed branch path 82 branching off from the fixed side flow path 31. The individual valve 93 is provided in a fixed branch path 83 branching off from the fixed side flow path 41. The individual valve 94 is provided in a fixed branch path 84 branching off from the fixed side flow path 51. The individual valve 95 is provided in a variable branch path 85 branching off from the variable side flow path 65. The individual valve 96 is provided in a variable branch path 86 branching off from the variable side flow path 66.

[0039] The individual valves 91-96 are known needle valves that are manually opened and closed, and when open, they connect the fixed branch paths 81-84 and the variable branch paths 85, 86 provided therein, and when closed, they block them. A needle valve is a valve with a needle-shaped valve body that makes it easy to precisely adjust the flow rate when open.

[0040] A plurality of fixed branch paths 81 to 84 and variable branch paths 85, 86 merge into one merging path 87, and the merging path 87 is connected to the tank 12 via the discharge path 16. A merging valve 97 is provided in this merging path 87. The merging valve 97 is a valve that is manually opened and closed, and when opened, it connects the merging path 87, and when closed, it blocks the merging path 87.

[0041] During normal times, such as when the pallet P and the transported object W are being transported by the transport vehicle 1, the individual valves 91-96 of the manual opening / closing means 90 are all closed, and the expansion and contraction of the extension devices 7a-7j are controlled by the pressure control circuits 20, 30, 40, and 50. This allows the vehicle height of the transport vehicle 1 to be raised and lowered as in the conventional case, and the pallet P and the transported object W to be transported.

[0042] On the other hand, in the event of an abnormality, by opening all of the individual valves 91-96 and the junction valve 97 of the manual opening / closing means 90, the hydraulic pressure inside the extension devices 7a-7j is released via the fixed branch paths 81-84, the variable branch paths 85, 86, the junction path 87, etc. (the hydraulic oil returns to the tank 12). As a result, the extension devices 7a-7j contract due to the weight of the platform 2, pallet P, and transported object W, lowering the vehicle height of the transport vehicle 1. In this way, the transport vehicle 1 having the manual opening / closing means 90 can easily and quickly lower its vehicle height in the event of an abnormality, and the pallet P, etc. being transported can be lowered to the site.

[0043] Furthermore, in the event of an abnormality, by opening all of the individual valves 91-96 so that the flow rates are approximately the same, and then opening the merging valve 97, it is possible to contract the multiple expansion devices 7a-7j approximately evenly at once. In other words, it is possible to prevent the pressure of some of the expansion devices 7a-7j from being released first, thereby preventing an unbalanced load from being applied to the expansion devices 7a-7j before they are released.

[0044] Furthermore, during maintenance of the transport vehicle 1, which is performed without applying electricity, the corresponding extension devices 7a to 7j can be made extendable and retractable by opening only some of the individual valves 91 to 96 while opening the junction valve 97. This makes it easy to perform maintenance, such as replacing the wheels 4, on the traveling devices 3a to 3j that have the extendable extension devices 7a to 7j.

[0045] Note that maintenance of the traveling devices 3a to 3j can also be performed by opening the manual valves 8a to 8j. However, because the manual valves 8a to 8j are installed in complicated locations, such as near the traveling devices 3a to 3j, it is difficult for workers to open and close them. In contrast, the individual valves 91 to 96 and the junction valve 97 can be installed in locations that make opening and closing them easy, depending on how the piping is installed. Furthermore, in this embodiment, the individual valves 91 to 96 and the junction valve 97 are installed in close proximity to each other, so that the individual valves 91 to 96 and the junction valve 97 can be easily opened and closed without the worker having to move to multiple locations.

[0046] In this embodiment, as shown in Fig. 1(a), the manual opening / closing means 90 (individual valves 91 to 96 and merging valve 97) is provided on the left side of the control unit 10, i.e., on the side of the transport vehicle 1. This makes it easy for an operator to open and close the manual opening / closing means 90. Furthermore, the operator can open and close the manual opening / closing means 90 without having to crawl under the loading platform 2, which descends when the platform is opened, ensuring the safety of the operator.

[0047] Next, a second embodiment will be described with reference to Fig. 4. In the first embodiment, a manual opening and closing means 90 including six individual valves 91 to 96 and one merging valve 97 will be described. In contrast, in the second embodiment, a manual opening and closing means 110 including six check valves 111 to 116 and one merging valve 117 will be described. Note that the same parts as in the first embodiment are given the same reference numerals, and the following description will be omitted. Fig. 4 is a schematic diagram showing a hydraulic circuit 100 of a transport vehicle in the second embodiment.

[0048] The hydraulic circuit 100 of the second embodiment has the same configuration as the hydraulic circuit 11 of the first embodiment except for the manual opening and closing means 110. The manual opening and closing means 110 includes six check valves 111 to 116 and one merging valve 117. The merging valve 117 has the same configuration as the merging valve 97 in the first embodiment.

[0049] Check valve 111 is provided in fixed branch path 81, check valve 112 in fixed branch path 82, check valve 113 in fixed branch path 83, and check valve 114 in fixed branch path 84. Check valve 115 is provided in variable branch path 85, and check valve 116 in variable branch path 86. Check valves 111 to 116 are valves that allow hydraulic oil to flow from the expansion devices 7a to 7j side to the junction path 87 side, and prevent backflow from the junction path 87 side to the expansion devices 7a to 7j side.

[0050] Normally, by keeping the junction valve 117 of the manual opening / closing means 110 closed, the hydraulic pressure inside the extension devices 7a to 7j is not released through the junction path 87. In addition, the check valves 111 to 116 can prevent the hydraulic pressure inside the extension devices 7a to 7j from being synchronized through the junction path 87 between the multiple fixed groups GA1 to GA4 and the floating groups GB1 and GB2, so the vehicle height of the transport vehicle of the second embodiment can be raised and lowered as in the conventional case.

[0051] On the other hand, in the event of an abnormality such as a stoppage of the pressure control circuits 20, 30, 40, 50 or the switching block 60, the multiple extension devices 7a to 7j can be retracted at once by opening the confluence valve 117, so that the vehicle height of the transport vehicle of the second embodiment can be lowered easily and in a short time, and uneven loads on some of the extension devices 7a to 7j can be prevented.

[0052] The present invention has been described above based on the above embodiment, but the present invention is not limited to the above form in any way, and it can be easily inferred that various modifications and improvements are possible within the scope that does not deviate from the spirit of the present invention.

[0053] In the above embodiment, the fluid circuit that supplies and discharges fluid to control each part is the hydraulic circuit 11, 100 that supplies and discharges hydraulic oil to control each part, and the telescopic devices 7a to 7j are hydraulic cylinders. However, the type of fluid may be changed as appropriate. For example, the fluid circuit may be configured by a pneumatic circuit that uses air as the fluid, and the telescopic devices 7a to 7j may be configured by pneumatic cylinders. In this case, the tank 12 may be omitted, and air may be supplied from the atmosphere to the supply path 15 by the pump 14, or the discharge path 16 and the junction path 87 may be configured to be open to the atmosphere. Furthermore, the telescopic devices 7a to 7j may be configured to expand when their internal pressure is reduced and contract when their internal pressure is increased.

[0054] In the above embodiment, the case where ten traveling devices 3a to 3j are provided on the transport vehicle 1 has been described, but this is not necessarily limited to this. The number of traveling devices 3a to 3j may be nine or less, or eleven or more.

[0055] In the above embodiment, the case where the multiple traveling devices 3a to 3j are divided into four fixed groups GA1 to GA4 and two variable groups GB1 and GB2 has been described, but this is not necessarily limited to this. The number of fixed groups GA1 to GA4 may be three or less or five or more, and the number of variable groups GB1 and GB2 may be one or three or more.

[0056] It is sufficient to provide pressure control circuits 20, 30, 40, 50, fixed-side flow paths 21, 31, 41, 51, switching branch paths 22, 32, 42, 52, fixed branch paths 81-84, and individual valves 91-94 or check valves 111-114 individually according to the number of fixed groups GA1-GA4. Also, it is sufficient to provide variable-side flow paths 65, 66, variable branch paths 85, 86, and individual valves 95, 96 or check valves 115, 116 individually according to the number of variable groups GB1, GB2, and change the configuration of the switching block 60 according to the number.

[0057] Furthermore, the number of traveling devices 3a to 3j in each of the fixed groups GA1 to GA4 is not limited to two, but may be one or three or more. The number of traveling devices 3a to 3j in each of the variable groups GB1 and GB2 is not limited to one, but may be two or more.

[0058] Some of the configurations in the above embodiment may be omitted. For example, the variable groups GB1 and GB2 may be omitted, and the corresponding variable side flow paths 65 and 66, variable branch paths 85 and 86, individual valves 95 and 96 or check valves 115 and 116, and switching block 60 may be omitted. In this case, for example, the expansion devices 7e and 7f may be included in any of the fixed groups GA1 to GA4.

[0059] Furthermore, the junction valve 97 in the first embodiment may be omitted, and further, the junction passage 87 may be omitted. In these cases, the hydraulic pressure is released on the opposite side (downstream side) of the expansion joints 7a-7j from the individual valves 91-96 of the fixed branch passages 81-84 and the variable branch passages 85, 86. Therefore, when an operator opens the individual valves 91-96 one by one, the hydraulic pressure of the corresponding expansion joints 7a-7j is released one by one. At this time, there is a risk of an unbalanced load being applied to the expansion joints 7a-7j before release. However, because the individual valves 91-96 are needle valves that allow for easy precise flow rate adjustment, an operator can easily synchronize the decompression and retraction speeds of the multiple expansion joints 7a-7j by gradually and approximately uniformly opening the multiple individual valves 91-96. As a result, even without the junction valve 97, it is possible to prevent an unbalanced load from being applied to some of the expansion joints 7a-7j. [Explanation of symbols]

[0060] 1 transport vehicle 2 Cargo bed 3a~3j Traveling device 4 wheels 7a~7j Expansion device 11,100 Hydraulic circuit (fluid circuit) 20, 30, 40, 50 Pressure control circuit 21,31,41,51 Fixed side flow path (main flow path) 60 Switching Block 65,66 Variable side channel (main channel) 81~84 Fixed branch (branch flow path) 85,86 Variable branch channel (branch channel) 87 Confluence road 90,110 Manual opening and closing means 91~96 Individual valves 97,117 Confluence valve 111~116 Check valve GA1~GA4 fixed group GB1, GB2 variable group

Claims

1. A transport vehicle including a loading platform, a plurality of traveling devices that support the loading platform from below, and a fluid circuit that drives the plurality of traveling devices by fluid, Each of the running devices includes a wheel and an extension and retraction device that extends and retracts to change the distance from the wheels to the loading platform, The fluid circuit includes a main flow path connected to the expansion device; a pressure control circuit that applies pressure or pressure to the inside of the expansion device through the main flow path to expand or contract the expansion device; a branch flow path branched from the main flow path; a manual opening / closing means provided in the branch flow path and manually opened and closed, The manual opening / closing means releases pressure inside the expansion device through the branch flow path when opened, and blocks the branch flow path when closed.

2. The pressure control circuit is provided in plurality, The plurality of expansion devices are divided into a plurality of groups, The plurality of groups includes the same number of fixed groups as the plurality of pressure control circuits; the main flow path includes a plurality of fixed-side flow paths that individually connect the plurality of fixed groups to the plurality of pressure control circuits, the branch flow path includes a plurality of fixed branch paths individually branched from the fixed-side flow path, 2. The transport vehicle according to claim 1, wherein the manual opening and closing means comprises a plurality of individual valves that are individually provided in the fixed branch path and that are manually opened and closed.

3. The plurality of groups includes one or more variable groups in addition to the fixed group, The main flow path includes one or more variable side flow paths individually connected to the variable group, the fluid circuit includes a switching block that switches the fixed-side flow path that is to be connected to the variable-side flow path, The branch flow path includes one or more variable branch paths individually branched from the variable side flow path, 3. The transport vehicle according to claim 2, wherein the plurality of individual valves that are manually opened and closed are also individually provided on the variable branch path.

4. the branch flow path includes one merging flow path formed by merging a plurality of the fixed branch paths and one or more of the variable branch paths, 4. The transport vehicle according to claim 3, wherein the manual opening / closing means comprises a merging valve that is provided in the merging passage and that is manually opened and closed.

5. the individual valves are needle valves; The transport vehicle according to claim 2 or 3, wherein pressure in the branch flow path is released on the side opposite to the expansion device with respect to the individual valve.

6. The pressure control circuit is provided in plurality, The plurality of expansion devices are divided into a plurality of groups, The plurality of groups includes the same number of fixed groups as the plurality of pressure control circuits; the main flow path includes a plurality of fixed-side flow paths that individually connect the plurality of fixed groups to the plurality of pressure control circuits, The branch flow path includes a plurality of fixed branch flow paths individually branched from the fixed-side flow path; a single merging path formed by merging a plurality of the fixed branch paths, The manual opening / closing means comprises a merging valve provided in the merging passage and manually opened and closed; 2. The transport vehicle according to claim 1, further comprising a plurality of check valves individually provided in the fixed branch paths to prevent backflow from the merging path side.

7. The plurality of groups includes one or more variable groups in addition to the fixed group, The main flow path includes one or more variable side flow paths individually connected to the variable group, the fluid circuit includes a switching block that switches the fixed-side flow path that is to be connected to the variable-side flow path, The branch flow path includes one or more variable branch paths that individually branch off from the variable side flow path and merge into the merging flow path, 7. The transport vehicle according to claim 6, wherein the check valve for preventing backflow from the junction is also individually provided in the variable branch path.

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