Aerial work platform

Abstract

To provide an aerial work platform that allows for easy vertical raising and lowering of the work platform, and is also capable of horizontal movement of the work platform. [Solution] The vehicle comprises a vehicle body 2, a lower parallel link section 10a, an upper parallel link section 10b, a lower hydraulic cylinder 18 for raising and lowering the lower parallel link section 10a, an upper hydraulic cylinder 19 for raising and lowering the upper parallel link section 10b, and a controller 50 for driving and controlling the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19. It is possible to switch between a vertical operation mode in which the lower parallel link section 10a and the upper parallel link section 10b are raised and lowered simultaneously and at the same speed, and an individual operation mode in which the lower parallel link section 10a and the upper parallel link section 10b are raised and lowered individually.

Description

Technical Field

[0001] The present invention relates to an aerial work platform equipped with a folding lifting device including two parallel links on the vehicle body.

Background Art

[0002] Conventionally, there is an aerial work platform that raises and lowers a work table by a lifting device combining two parallel links. For example, the articulated parallelogram assembly of the aerial work platform described in Patent Document 1 arranges the lower extension arm upward and the lower compression arm downward in parallel, and axially fixes the proximal ends of the lower extension arm and the lower compression arm to a support frame provided on the vehicle body via a turntable, and axially fixes the distal ends of the lower extension arm and the lower compression arm to a floating frame, thereby constituting a lower parallel link. Further, the upper compression arm is arranged upward and the upper extension arm is arranged downward in parallel, and the proximal ends of the upper extension arm and the upper compression arm are axially fixed to the floating frame described above, and the distal ends of the upper extension arm and the upper compression arm are axially fixed to the lifting device, thereby constituting an upper parallel link. The upper parallel link is provided so as to be folded in a "く" shape from the floating frame to the lower parallel link side. Further, an extension link of a rod-shaped member is straddled between the floating frame and the upper extension arm. More specifically, one end of the extension link is axially fixed to the floating frame, and the other end of the extension link is axially fixed to the upper extension arm.

[0003] For such a parallel link mechanism, one hydraulic cylinder is straddled between the lower compression arm and the upper extension arm. Specifically, the cylinder tube of the hydraulic cylinder is axially fixed to the lower compression arm, and the tip of the piston rod of the hydraulic cylinder is axially fixed to the upper extension arm. When the above-described hydraulic cylinder extends when the lifting device is in the retracted state, as the angle formed by the upper parallel link and the lower parallel link expands, the lower parallel link is tilted upward by the extension link. As a result, the work table attached to the lifting device constituting the upper parallel link rises while maintaining a horizontal position.

[0004] Furthermore, the lifting device for the aerial work platform described in Patent Document 2 is composed of a first parallel link and a second parallel link. One end of the first parallel link is pivotally supported on a bracket fixed to the upper surface of the vehicle body, and the other end of the first parallel link is pivotally supported on one side of a connecting member. One end of the second parallel link is pivotally supported on the other side of the connecting member, and the other end of the second parallel link is pivotally supported on a base. A rotatable turntable is provided on the upper surface of the base, and a lower boom and an upper boom, with a work platform balanced at its tip, are sequentially pivotally connected to the turntable. The ends of the first hydraulic cylinder are pivotally supported coaxially at diagonal pivot positions of the first parallel link, and the ends of the second hydraulic cylinder are pivotally supported coaxially at diagonal pivot positions of the second parallel link. Then, the first and second hydraulic cylinders extend and retract simultaneously by the flow divider valve, and when the first and second hydraulic cylinders are fully retracted, the first and second parallel links become parallel, resulting in the stored state. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-258993 [Patent Document 2] Public Office No. 59-035514 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The aerial work platform described in Patent Document 1 has the advantage that the work platform can be raised and lowered by extending and retracting a single hydraulic cylinder, making the operation of raising and lowering the work platform easy, and that the work platform can be raised and lowered vertically in place without shifting in the front, back, left, or right directions. Similarly, the aerial work platform described in Patent Document 2 also has the advantage that the work platform can be raised and lowered vertically in place because the first and second hydraulic cylinders are extended and retracted simultaneously by a flow divider valve. However, depending on the work situation, it may be necessary to move the work platform horizontally in a manner other than by operating the boom, in which case the aerial work platform must be moved, which may lead to an increase in workload and a decrease in work efficiency.

[0007] This invention has been made in view of the above problems, and aims to provide an aerial work platform that can be raised and lowered vertically with easy operation, and can also move the work platform horizontally in addition to operating the boom. [Means for solving the problem]

[0008] To solve the above problems, the aerial work platform according to the present invention comprises a vehicle body, a lower parallel link formed by rotatably attaching the base ends of parallel-arranged lower arms and lower rods to a base bracket provided on the vehicle body, and rotatably attaching the tips of the lower arms and lower rods to an intermediate bracket, an upper parallel link formed by rotatably attaching the base ends of parallel-arranged upper arms and upper rods to the intermediate bracket, and rotatably attaching the tips of the upper arms and upper rods to an end bracket, a work platform attached to the end bracket, a lower actuator (for example, a lower hydraulic cylinder 18 in the embodiment) for raising and lowering the lower parallel link, and an upper actuator (for example, an upper hydraulic cylinder in the embodiment) for raising and lowering the upper parallel link. The apparatus comprises a Linda 19) and a control device (for example, a controller 50 in the embodiment) for driving and controlling the lower actuator and the upper actuator, wherein the upper parallel link is provided so as to fold back toward the lower parallel link side, and is capable of raising and lowering upward from the lower parallel link side and lowering toward the lower parallel link side from the raised state, and the control device is capable of switching between a vertical operation mode in which the lower actuator and the upper actuator are driven and controlled to raise and lower the lower actuator and the upper actuator so that the workbench is raised and lowered vertically by raising and lowering the lower parallel link and the upper parallel link simultaneously and at the same speed, and an independent operation mode in which the lower actuator and the upper actuator are driven and controlled so that the lower actuator and the upper actuator are raised and lowered individually.

[0009] Furthermore, in the above-mentioned aerial work platform, it is preferable that the control device stops driving the lower actuator and the upper actuator when the control device is driving and controlling the lower actuator and the upper actuator in the independent operation mode, and the calculation result based on the elevation angle of the lower parallel link and the elevation angle of the upper parallel link falls outside a predetermined allowable range.

[0010] Furthermore, in the above-mentioned aerial work platform, it is preferable that the length of the lower arm and the lower rod be approximately the same as the length of the upper arm and the upper rod.

[0011] Furthermore, the above-mentioned aerial work platform is preferably equipped with a lower parallel link operating lever for operating the elevation of the lower parallel link, an upper parallel link operating lever for operating the elevation of the upper parallel link, and a mode switching switch for switching between the vertical operation mode and the standalone operation mode. When the mode switching switch is switched to the standalone operation mode, the control unit drives the lower actuator based on the operation of the lower parallel link operating lever and drives the upper actuator based on the operation of the upper parallel link operating lever. When the mode switching switch is switched to the vertical operation mode, the control unit drives the lower actuator and the upper actuator based on the operation of one of the lower parallel link operating levers, which is predetermined, and disables the operation of the other operating lever.

[0012] Furthermore, in any of the above-mentioned aerial work platforms, it is preferable that the platform is attached to the tip bracket and is capable of swiveling horizontally, and that it is attached to the swivel and is capable of raising, lowering and extending relative to the swivel, and that the work platform is attached to the tip of the boom, thereby being attached to the tip bracket via the swivel and the boom. [Effects of the Invention]

[0013] According to the aerial work platform of the present invention, the control device can switch between a vertical operation mode, in which the lower actuator and upper actuator are driven and controlled to raise and lower the work platform vertically by simultaneously and at the same speed raising and lowering the lower parallel link and upper parallel link, and a standalone operation mode, in which the lower actuator and upper actuator are driven and controlled to raise and lower the lower parallel link and upper parallel link individually. In the vertical operation mode, the work platform can be raised and lowered vertically with easy operation, and in the standalone operation mode, it is also possible to move the work platform horizontally. Therefore, by switching between the vertical operation mode and the standalone operation mode according to the work situation, the operability for raising and lowering the work platform and the working range of the work platform can be flexibly switched.

[0014] Furthermore, in an aerial work platform having the above configuration, preferably, when the control device is driving and controlling the lower actuator and the upper actuator in independent operation mode, if the calculation result based on the elevation angle of the lower parallel link and the elevation angle of the upper parallel link falls outside a predetermined allowable range, the drive of the lower actuator and the upper actuator is stopped, thereby enabling safe raising and lowering even when the work platform moves horizontally in independent operation mode.

[0015] Furthermore, in an aerial work platform having the above configuration, preferably, by making the length of the lower arm and lower rod approximately the same as the length of the upper arm and upper rod, the work platform can be raised and lowered vertically while maintaining its horizontal position in the vertical operation mode.

[0016] Furthermore, in an aerial work platform having the above configuration, preferably, when the mode switching switch is switched to the standalone operation mode, the control device individually drives and controls the lower actuator and the upper actuator based on the operation of the lower parallel link operating lever and the upper parallel link operating lever, and when switched to the vertical operation mode, it drives and controls the lower actuator and the upper actuator based on the operation of one of the lower parallel link operating levers, which is predetermined, and disables the operation of the other operating lever, thereby allowing the lower parallel link operating lever and the upper parallel link operating lever to be used interchangeably in the standalone operation mode and the vertical operation mode.

[0017] Furthermore, in an aerial work platform having any of the above configurations, preferably, it comprises a slewing platform attached to a tip bracket and capable of swiveling horizontally, and a boom attached to the slewing platform and capable of luffing and extending relative to the slewing platform, and the work platform can be attached to the tip of the boom and then attached to the tip bracket via the slewing platform and boom, thereby extending the range of movement of the work platform without moving the aerial work platform. [Brief explanation of the drawing]

[0018] [Figure 1] This is a side view showing the external appearance of an aerial work platform according to an embodiment of the present invention. [Figure 2] This is a perspective view showing the exterior of the above-mentioned aerial work platform. [Figure 3] This is a front view showing a part of the operating device of the above-mentioned aerial work platform. [Figure 4] This block diagram schematically shows the configuration of the control system that controls each part of the above-mentioned aerial work platform. [Figure 5] This is an explanatory diagram illustrating the operation of the lifting device of the above-mentioned aerial work platform in vertical operation mode. [Figure 6] This is an explanatory diagram illustrating the operation of the lifting device of the above-mentioned aerial work platform in standalone mode. [Figure 7]This is an explanatory diagram for explaining another state in which the lifting device of the above-mentioned aerial work vehicle operates in the independent operation mode.

Embodiments for Carrying out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the overall configuration of the aerial work vehicle 1 according to the present invention will be described while referring to the side view shown in FIG. 1 and the perspective view shown in FIG. 2. In the following description, the front-rear direction, left-right direction, and up-down direction follow the directions indicated by the arrows in FIGS. 1 and 2. The aerial work vehicle 1 has a vehicle body 2 of a truck-type vehicle, tire wheels 3 are provided at the front and rear of the vehicle body 2, and driving operation is possible from a driver's cab 4 provided at the front of the vehicle body 2. In FIG. 1, only the left front wheel 3FL and the left rear wheel 3RL are shown, and the illustration of the right front wheel and the right rear wheel is omitted. Also, in FIG. 2, only the left front wheel 3FL, the left rear wheel 3RL, and the right rear wheel 3RR are shown, and the illustration of the right front wheel is omitted.

[0020] Outrigger jacks 5, which can extend and retract vertically, are provided on the front, rear, left, and right sides of the vehicle body 2. The outrigger jacks 5 can be expanded and contracted and extended and retracted by the jack cylinders 7 (see Figure 4) and outrigger cylinders 8 (see Figure 4) in response to the operation of the outrigger operating device 6. In Figure 1, only the left front jack 5FL and the left rear jack 5RL are shown, and the right front jack and right rear jack are not shown. Similarly, in Figure 2, only the left front jack 5FL, the left rear jack 5RL, and the right rear jack 5RR are shown, and the right front jack is not shown. Each of these jacks is equipped with a jack cylinder 7 and an outrigger cylinder 8, and the outrigger operating device 6 is equipped with operating levers for individually extending and retracting each jack cylinder 7 and outrigger cylinder 8. When a worker is on the work platform 40 (described later) to perform work at height, the worker tilts the operating lever of the outrigger operating device 6 according to the relative positional relationship with surrounding obstacles, thereby widening and extending the left and right outrigger jacks 5 in the vehicle width direction and extending them downward to lift and support the vehicle body 2, thereby ensuring a stable posture.

[0021] The area behind the driver's cabin 4 is the bodywork section of the vehicle body 2, and a base bracket 11 is attached to the front end of this bodywork section. One end (base end) of each long rod-shaped lower arm 12 and lower rod 13 is rotatably fixed to the base bracket 11. The other end (tip) of each lower arm 12 and lower rod 13 is rotatably fixed to an intermediate bracket 14. The lower arm 12 is positioned above the lower rod 13, and the lower arm 12 and lower rod 13 are rotatably fixed to the base bracket 11 and the intermediate bracket 14 so that they are parallel to each other. In this way, the base bracket 11, lower arm 12, lower rod 13 and intermediate bracket 14 constitute the lower parallel link section 10a (see Figure 2). The lower parallel link section 10a is provided so as to extend from the base bracket 11 toward the rear end of the mounting section of the vehicle body 2, and is capable of raising and lowering within a range from a horizontally tilted state (elevation angle 0°) to a vertically raised state (elevation angle 90°) with the base bracket 11 as the pivot point.

[0022] The intermediate bracket 14 is pivotally attached to one end (base end) of each long, rod-shaped upper arm 15 and upper rod 16. The other end (tip) of each upper arm 15 and upper rod 16 is pivotally attached to the tip bracket 17. The upper arm 15 is positioned below the upper rod 16 and is pivotally attached to the intermediate bracket 14 and tip bracket 17 so that the upper arm 15 and upper rod 16 are parallel to each other. Thus, the intermediate bracket 14, upper arm 15, upper rod 16 and tip bracket 17 constitute the upper parallel link section 10b (see Figure 2). The upper parallel link section 10b is provided so as to extend from the intermediate bracket 14 toward the front end of the mounting section of the vehicle body 2, and can move up and down within a range from a horizontally tilted state (elevation angle 0°) to a vertically raised state (elevation angle 90°) with the intermediate bracket 14 as the pivot point.

[0023] The longitudinal lengths of the lower parallel link section 10a and the upper parallel link section 10b are approximately the same. Furthermore, the upper parallel link section 10b is positioned to bend in a "V" shape relative to the lower parallel link section 10a (folding back towards the front of the vehicle body 2). The lower parallel link section 10a and the upper parallel link section 10b constitute the parallel link mechanism 10.

[0024] As actuators for operating the parallel link mechanism 10, a lower hydraulic cylinder 18 is provided to raise and lower the lower parallel link section 10a, and an upper hydraulic cylinder 19 is provided to raise and lower the upper parallel link section 10b. The cylinder tube of the lower hydraulic cylinder 18 is rotatably fixed to a base-side fixing member 20 formed inside the base bracket 11, and the piston rod of the lower hydraulic cylinder 18 is rotatably fixed to a lower fixing part 12a formed on the lower arm 12. The cylinder tube of the upper hydraulic cylinder 19 is rotatably fixed to a tip-side fixing member 21 formed inside the tip bracket 17, and the piston rod of the upper hydraulic cylinder 19 is rotatably fixed to an upper fixing part 15a formed on the upper arm 15.

[0025] The upper surface of the tip bracket 17 is horizontal, and a slewing platform 31 that can rotate horizontally by a slewing motor 30 (see Figure 4) is provided on this upper surface. A boom support member 33 that pivotally supports the base end of the boom 32 so that it can be raised and lowered is fixed to the upper part of the slewing platform 31. A luffing cylinder 34 for raising and lowering the boom 32 is mounted between the boom 32 and the boom support member 33, and the boom 32 is raised and lowered by the extension and retraction of the luffing cylinder 34. Furthermore, the boom 32 is constructed by assembling multiple booms in a nested manner, and the entire boom 32 is able to extend and lower as the multiple booms slide relative to each other in accordance with the extension and retraction of a telescopic cylinder 35 (see Figure 4) provided inside the boom 32. A vertical post (not shown) is pivotally supported at the tip of the boom 32 so that it can swing up and down. This vertical post is configured to maintain a vertical position in response to the luffing motion of the boom 32 by a leveling device consisting of a main leveling cylinder 36 provided at the base end of the boom 32 and a secondary leveling cylinder (not shown) provided inside the tip of the boom 32.

[0026] A work platform 40, on which an operator sits, is attached to the aforementioned vertical post via a work platform bracket (not shown). A swivel motor 41 (see Figure 4) is provided inside this work platform bracket, and by driving and controlling the swivel motor 41, the entire work platform 40 can be made to swivel (rotate horizontally) around the vertical post. Furthermore, as described above, the vertical post is kept in a vertical position at all times by a leveling device, so the floor surface of the work platform 40 is kept horizontal at all times regardless of the elevation angle of the boom 32.

[0027] The work platform 40 is equipped with an upper operating device 42 that includes various operating means such as operating levers and operating switches for operation by an operator riding on it. By operating the upper operating device 42, an operator riding on the work platform 40 can perform various operations such as luffing the lower parallel link section 10a and the upper parallel link section 10b (extension and retraction of the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19), slewing the turntable 31 (forward or reverse rotation of the slewing motor 30), luffing the boom 32 (extension and retraction of the luffing cylinder 34), extending and retracting the boom 32 (extension and retraction of the extension cylinder 35), and swiveling the work platform 40 (rotation of the slewing motor 41). In the aerial work platform 1 with the above configuration, the configuration from the parallel link mechanism 10 to the work platform 40 constitutes the lifting device. Although not shown in the figures, the vehicle body 2 is equipped with a lower operating device, which allows an operator on the ground or on the vehicle body 2 to perform operations similar to those of the upper operating device 42.

[0028] As shown in Figure 3, the upper operating device 42 is equipped with a mode selector switch 43, a lower parallel link operating lever 44, and an upper parallel link operating lever 45 for operating the parallel link mechanism 10. The mode selector switch 43 is a two-position toggle switch used to switch the operating mode of the parallel link mechanism 10 between vertical operation mode and standalone operation mode. The lower parallel link operating lever 44 and the upper parallel link operating lever 45 can each be tilted vertically from a neutral position and are used to operate the extension and retraction of the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19. The lower parallel link operating lever 44 and the upper parallel link operating lever 45 are designed to return to the neutral position when the hands are released from the state in which they are tilted upward or downward. Note that toggle switches may be used instead of levers that can be tilted vertically as the lower parallel link operating lever 44 and the upper parallel link operating lever 45.

[0029] Next, the general configuration of each part that controls the operation of the aerial work platform 1 will be described with reference to the block diagram shown in Figure 4. In this figure, the same reference numerals are used for components that are the same as those shown in Figures 1 to 3, and their detailed explanations are omitted. The aerial work platform 1 is equipped with a hydraulic unit for operating the hydraulic actuators, such as the various hydraulic cylinders mentioned above. This hydraulic unit includes a hydraulic pump 60 that discharges hydraulic fluid and a group of control valves 61 that control the supply direction and amount of hydraulic fluid supplied from the hydraulic pump 60 to each hydraulic actuator. The hydraulic pump 60 is operated by power taken from the engine of the aerial work platform 1 via a PTO mechanism (not shown). The control valve group 61 includes an electromagnetic proportional control valve V1 that controls the hydraulic fluid supplied to the jack cylinder 7, an electromagnetic proportional control valve V2 that controls the hydraulic fluid supplied to the outrigger cylinder 8, an electromagnetic proportional control valve V3 that controls the hydraulic fluid supplied to the swing motor 30, an electromagnetic proportional control valve V4 that controls the hydraulic fluid supplied to the luffing cylinder 34, an electromagnetic proportional control valve V5 that controls the hydraulic fluid supplied to the telescopic cylinder 35, an electromagnetic proportional control valve V6 that controls the hydraulic fluid supplied to the swivel motor 41, an electromagnetic proportional control valve V7 that controls the hydraulic fluid supplied to the lower hydraulic cylinder 18, and an electromagnetic proportional control valve V8 that controls the hydraulic fluid supplied to the upper hydraulic cylinder 19.

[0030] The controller 50 controls the direction and amount of hydraulic fluid supplied to the jack cylinder 7 and outrigger cylinder 8 by electromagnetically driving the spools of electromagnetic proportional control valves V1 and V2 in response to the operation of various operating levers provided on the outrigger operating device 6, thereby causing these cylinders to extend and retract. The controller 50 also controls the direction and amount of hydraulic fluid supplied to the slewing motor 30, luffing cylinder 34, telescopic cylinder 35, and swivel motor 41 by electromagnetically driving the spools of electromagnetic proportional control valves V3 to V6 in response to various operating levers provided on the upper operating device 42 or the lower operating device. This causes the slewing motor 30 and swivel motor 41 to rotate in the forward or reverse direction, and the luffing cylinder 34 and telescopic cylinder 35 to extend and retract. Furthermore, the controller 50 controls the direction and amount of hydraulic fluid supplied to the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 by electromagnetically driving the spools of the electromagnetic proportional control valves V7 and V8 in response to the operation of the mode switching switch 43 of the upper operating device 42, the lower parallel link operating lever 44, and the upper parallel link operating lever 45, thereby causing each cylinder to extend and retract.

[0031] The controller 50 receives elevation angle detection signals output from the lower parallel link elevation angle sensor 70 and the upper parallel link elevation angle sensor 71. The lower parallel link elevation angle sensor 70 outputs angle information to the controller 50 corresponding to the elevation angle θa of the lower parallel link 10a relative to the horizontal. The upper parallel link elevation angle sensor 71 outputs angle information to the controller 50 corresponding to the elevation angle θb of the upper parallel link 10b relative to the horizontal. Based on the elevation angle detection signals output from the lower parallel link elevation angle sensor 70 and the upper parallel link elevation angle sensor 71, the controller 50 controls the elevation movement of the lower parallel link 10a and the upper parallel link 10b so as not to compromise the safety of the lifting device.

[0032] Next, the vertical operation mode and the standalone operation mode, which can be switched using the mode selector switch 43, will be explained. As will be explained below, the extension and retraction movements of the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 in response to the tilting operation of the lower parallel link operating lever 44 and the upper parallel link operating lever 45 are different in the vertical operation mode and the standalone operation mode. (Vertical operation mode) When the mode selector switch 43 is tilted upward (towards vertical operation), the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 extend and retract in vertical operation mode. In vertical operation mode, when the lower parallel link operating lever 44 is tilted upward, the controller 50 extends the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 simultaneously and at the same speed. As a result, the lower parallel link section 10a and the upper parallel link section 10b are raised and lowered until the elevation angles θa and θb are both 90°, and the work platform 40, which is attached to the tip bracket 17 via the turntable 31 and boom 32, rises vertically in place without moving in the forward, backward, left, or right directions. Conversely, when the lower parallel link operating lever 44 is tilted downward, the controller 50 retracts the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 simultaneously and at the same speed. As a result, the lower parallel link section 10a and the upper parallel link section 10b are lowered until the elevation angles θa and θb are both 0° (horizontal), and the work platform 40, which is attached to the tip bracket 17 via the slewing platform 31 and boom 32, descends vertically in place without moving in the forward, backward, left, or right directions. Even if the upper parallel link operating lever 45 is tilted during vertical operation mode, the controller 50 disables the tilting operation of the upper parallel link operating lever 45 and prevents the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 from extending or retracting.

[0033] (Standalone operation mode) When the mode selector switch 43 is tilted downward (to the independent operation side), the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 extend and retract in independent operation mode. In independent operation mode, the lower parallel link section 10a and the upper parallel link section 10b each move up and down independently. That is, when the lower parallel link operation lever 44 is tilted upward, the controller 50 extends the lower hydraulic cylinder 18 at a predetermined speed. As a result, the lower parallel link section 10a is raised until the elevation angle θa is 90°, and the workbench 40 rises in an arc. Also, when the lower parallel link operation lever 44 is tilted downward, the controller 50 retracts the lower hydraulic cylinder 18 at a predetermined speed. As a result, the lower parallel link section 10a is lowered until the elevation angle θa is 0°, and the workbench 40 descends in an arc.

[0034] When the upper parallel link operating lever 45 is tilted upward, the controller 50 extends the upper hydraulic cylinder 19 at a predetermined speed. As a result, the upper parallel link section 10b is raised until the elevation angle θb is 90°, and the workbench 40 rises in an arc. Conversely, when the upper parallel link operating lever 45 is tilted downward, the controller 50 retracts the upper hydraulic cylinder 19 at a predetermined speed. As a result, the upper parallel link section 10b is lowered until the elevation angle θb is 0°, and the workbench 40 descends in an arc.

[0035] In this embodiment, while the lower parallel link operating lever 44 and the upper parallel link operating lever 45 are tilted, the lower parallel link section 10a and the upper parallel link section 10b are raised and lowered according to the operating mode and tilting direction at that time. When the operator releases their hands from the operating levers and returns to the neutral position, the system is configured to maintain the raised and lowered angle at that time. Furthermore, in both the vertical operation mode and the standalone operation mode, the work platform 40 is raised and lowered by the raised and lowered movement of the lower parallel link section 10a and the upper parallel link section 10b, so the floor surface of the work platform 40 is always kept horizontal.

[0036] Next, with reference to Figure 5, the movement of the lower parallel link section 10a and the upper parallel link section 10b in vertical operation mode will be explained. First, Figure 5(a) shows the retracted state of the lifting device (configuration from the parallel link mechanism 10 to the work platform 40) provided on the aerial work platform 1. Here, the retracted state means that the elevation angle of the lower parallel link section 10a and the upper parallel link section 10b is 0° (horizontal state), and the boom 32 is in its maximum reclined state. When the lifting device is in the retracted state, the boom 32 is supported by the support base 37 (see Figures 1 and 2) provided on the mounting part of the vehicle body 2. In this state, when the mode switching switch 43 shown in Figure 3 is switched to the vertical operation mode side, and the lower parallel link operation lever 44 is tilted upward from the neutral position, the controller 50 extends the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 at the same speed. As a result, the lower parallel link section 10a and the upper parallel link section 10b rise and fall at the same speed and angle, and the parallel link mechanism 10 rises up in a "V" shape as shown in Figure 5(b). Consequently, the work platform 40 rises vertically in place without moving in the forward, backward, left, or right directions.

[0037] Then, as shown in Figure 5(c), when the elevation angles (θa and θb) of the lower parallel link section 10a and the upper parallel link section 10b both reach 90°, the parallel link mechanism 10 becomes upright from the lower parallel link section 10a to the upper parallel link section 10b, and the controller 50 stops the extension movement of the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 to maintain this state. Furthermore, when the lower parallel link operating lever 44 is tilted downward from the neutral position from this state, the controller 50 causes the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 to retract at the same speed. As a result, the lower parallel link section 10a and the upper parallel link section 10b collapse at the same speed and elevation angle, and the parallel link mechanism 10 folds into a "V" shape. Consequently, the work platform 40 descends vertically in place without moving in the forward, backward, left, or right directions.

[0038] In the vertical operation mode described above, low-lift work is performed with the parallel link mechanism 10 folded, and when high-lift work is required, the work platform 40 can be easily raised vertically by operating only the lower parallel link operating lever 44. Furthermore, since the work platform 40 is raised and lowered vertically without changing its position in the front, rear, left, or right directions, there is the advantage that the movement of the work platform 40 accompanying the raising and lowering is easy to predict. Moreover, in the case of an aerial work platform with a slewing platform and boom directly attached to the vehicle body, if the boom is controlled to move vertically and horizontally automatically in response to the operation of a single operating lever (so-called HV control), the work platform cannot be raised or lowered vertically if it exceeds the range of motion of the boom's luffing cylinder or telescopic cylinder. However, in the aerial work platform 1 of this embodiment, by providing the parallel link mechanism 10, the work platform 40 can be raised and lowered vertically regardless of the range of motion of the boom 32's luffing cylinder 34 or telescopic cylinder 35.

[0039] Next, the movement of the lower parallel link section 10a and the upper parallel link section 10b in the standalone operation mode will be explained with reference to Figures 6 and 7. First, Figure 6(a), like Figure 5(a), shows the retracted state of the lifting device provided by the aerial work platform 1. In this state, if the mode selector switch 43 shown in Figure 3 is switched to the standalone operation mode, and for example the upper parallel link operation lever 45 is tilted upward from the neutral position, the controller 50 extends the upper hydraulic cylinder 19. As a result, the upper parallel link section 10b is raised and lowered at a predetermined speed, and the work platform 40 moves upward and towards the rear of the vehicle body 2 in an arc, as shown in Figure 6(b). During this time, the upper parallel link section 10b maintains the horizontal state of the floor surfaces of the turntable 31 and the work platform 40. Then, as shown in Figure 6(c), when the elevation angle θb of the upper parallel link section 10b reaches 90°, the controller 50 stops the extension of the upper hydraulic cylinder 19 and stops the raising and lowering of the upper parallel link section 10b. Comparing Figure 6(a) and Figure 6(c), the position of the workbench 40 rises by the length of the upper parallel link section 10b and also moves to the rear of the vehicle body 2.

[0040] If, for example, the lower parallel link operating lever 44 is tilted upward from the neutral position, the controller 50 extends the lower hydraulic cylinder 18. As a result, the lower parallel link section 10a is raised and lowered at a predetermined speed, and the work platform 40 moves upward and forward of the vehicle body 2 in an arc, as shown in Figure 7(a). During this time, the lower parallel link section 10a maintains the horizontal position of the floor surfaces of the turntable 31 and the work platform 40. Then, as shown in Figure 7(b), when the elevation angle θa of the lower parallel link section 10a reaches 90°, the controller 50 stops the extension of the lower hydraulic cylinder 18 and stops the raising and lowering of the lower parallel link section 10a. Comparing Figure 6(c) and Figure 7(b), the position of the work platform 40 rises further by the length of the lower parallel link section 10a and also moves forward of the vehicle body 2, returning to the same position as the stored state (see Figure 6(a)) in the front-rear direction of the vehicle body 2. Furthermore, when the lower parallel link operating lever 44 or the upper parallel link operating lever 45 is tilted downward from the neutral position from the state shown in Figure 7(b), the controller 50 retracts the lower hydraulic cylinder 18 or the upper hydraulic cylinder 19 in accordance with the operation of each operating lever. As a result, the lower parallel link section 10a or the upper parallel link section 10b tilts down at a predetermined speed, and the work platform 40 descends in an arc.

[0041] In standalone operation mode, the controller 50 controls the extension and retraction of the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 based on the elevation angle detection signals output from the lower parallel link elevation angle sensor 70 and the upper parallel link elevation angle sensor 71, respectively. Specifically, while the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 are being driven, the controller 50 subtracts the elevation angle θa from the elevation angle θb. If the result of this subtraction is 0° or greater, the controller 50 drives the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 in response to the operation of the lower parallel link operating lever 44 and the upper parallel link operating lever 45. On the other hand, if the result of the subtraction becomes less than 0°, the controller 50 stops driving the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19. In this state, if the lower parallel link operating lever 44 or the upper parallel link operating lever 45 is operated in a direction that increases the value obtained by subtracting the elevation angle θa from the elevation angle θb, the controller 50 drives the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 in response to that operation.

[0042] Thus, in the standalone operation mode, the controller 50 controls the extension and retraction of the lower hydraulic cylinder 18 and the upper hydraulic cylinder 19 based on the elevation angles of the lower parallel link section 10a and the upper parallel link section 10b. Therefore, even if the vehicle body 2 moves in the front-rear direction as the work platform 40 is raised or lowered, the lifting device can be safely raised and lowered.

[0043] In the aforementioned vertical operation mode, the pivot center position of the turntable 31 remains constant, resulting in a constant working radius. However, in the aforementioned standalone operation mode, the pivot center position of the turntable 31 can be appropriately changed by adjusting the elevation angles of the lower parallel link section 10a and the upper parallel link section 10b. Therefore, by raising and lowering the parallel link mechanism 10, the position of the work platform 40 in the front-rear direction of the vehicle body 2 can be moved, thus expanding the working radius without moving the vehicle body 2. On the other hand, in the vertical operation mode, since the pivot center position remains constant, the direction in which the boom 32 approaches the work object cannot be significantly changed. Therefore, if the direction in which the boom 32 approaches needs to be changed, the vehicle body 2 must be moved. In contrast, in standalone operation mode, by adjusting the elevation angles of the lower parallel link section 10a and the upper parallel link section 10b, the boom 32 can approach the work object from a different angle without moving the vehicle body 2, thereby improving work efficiency.

[0044] In this way, the aerial work platform 1 can take advantage of the benefits of both the vertical operation mode and the standalone operation mode depending on the work situation by appropriately switching between the vertical operation mode and the standalone operation mode. For example, by raising the work platform 40 vertically in the vertical operation mode, the work can be approached from the front of the work object, and after performing the work there, the system can be switched to the standalone operation mode to raise only the upper parallel link section 10b and approach the work object from a different direction to perform the work.

[0045] When switching from vertical operation mode to standalone operation mode, the switch may be made regardless of the elevation angles of the lower parallel link section 10a and the upper parallel link section 10b. However, when switching from standalone operation mode to vertical operation mode, it is necessary to control the system so that the elevation angles of the lower parallel link section 10a and the upper parallel link section 10b match before switching the operation mode. In this case, the controller 50 may automatically extend or retract the lower hydraulic cylinder 18 or the upper hydraulic cylinder 19 until the elevation angles of the lower parallel link section 10a and the upper parallel link section 10b match.

[0046] Furthermore, in the above-described aerial work platform 1, the work platform 40 was attached to the tip bracket 17 via a slewing platform 31, boom support member 33, boom 32, etc., but the work platform 40 may be attached directly to the tip bracket 17. Also, in the standalone operation mode, the control of the lower hydraulic cylinder 18 and upper hydraulic cylinder 19 based on the elevation angle of the lower parallel link section 10a and the upper parallel link section 10b may be omitted. In addition, in the parallel link mechanism 10, the longitudinal lengths of the lower parallel link section 10a and the upper parallel link section 10b were approximately the same, but the lengths of the two parallel links may be different. Furthermore, in the vertical operation mode, the lower parallel link section 10a and the upper parallel link section 10b were raised and lowered in response to the operation of the lower parallel link operation lever 44, but a dedicated operation lever that is only effective in the vertical operation mode may be provided. [Explanation of Symbols]

[0047] 1. Aerial work platform 2 car bodies 10 Parallel link mechanism 10a Lower parallel link section 10b Upper parallel link section 11 Base bracket 12 Lower arm 13 Lower rod 14 Intermediate bracket 15 Upper Arm 16 Upper rod 17. Tip bracket 18 Lower hydraulic cylinder 19 Upper hydraulic cylinder 31 Turntable 32 Boom 33 Boom support member 40 workbenches 43 Mode selector switch 44 Lower parallel link operating lever 45 Upper parallel link operating lever 50 Controllers 70 Lower arm elevation angle sensor 71 Upper arm elevation angle sensor

Claims

1. The car body and, A lower parallel link is formed by rotatably attaching the base ends of the parallel-arranged lower arms and lower rods to a base bracket provided on the vehicle body, and rotatably attaching the tips of the lower arms and lower rods to an intermediate bracket, An upper parallel link is formed by rotatably attaching the base ends of the upper arms and upper rods, which are arranged in parallel, to the intermediate bracket, and rotatably attaching the tips of the upper arms and upper rods to the tip bracket, A workbench attached to the aforementioned tip bracket, A lower actuator that causes the lower parallel link to move up and down, An upper actuator that causes the upper parallel link to move up and down, The system comprises a control device for driving and controlling the lower actuator and the upper actuator, The upper parallel link is provided so as to fold back toward the lower parallel link, and is capable of raising and lowering upward from the lower parallel link side, and then lowering toward the lower parallel link side from the raised state. The aerial work platform is characterized in that the control device can switch between a vertical operation mode, in which the lower actuator and the upper actuator are driven and controlled to raise and lower the lower parallel link and the upper parallel link simultaneously and at the same speed so that the work platform moves up and down vertically, and an independent operation mode, in which the lower actuator and the upper actuator are driven and controlled so that the lower parallel link and the upper parallel link move up and down individually.

2. The aerial work platform according to claim 1, characterized in that when the control device is driving the lower actuator and the upper actuator in the independent operation mode, if the calculation result based on the elevation angle of the lower parallel link and the elevation angle of the upper parallel link falls outside a predetermined allowable range, the drive of the lower actuator and the upper actuator is stopped.

3. The aerial work platform according to claim 2, characterized in that the length of the lower arm and the lower rod is approximately the same as the length of the upper arm and the upper rod.

4. A lower parallel link operating lever for operating the elevation movement of the lower parallel link, An upper parallel link operating lever for operating the elevation movement of the upper parallel link, The system includes a mode selector switch that switches to either the vertical operation mode or the standalone operation mode, The control device is When the mode selector switch is switched to the standalone operation mode, the lower actuator is driven and controlled based on the operation of the lower parallel link operating lever, and the upper actuator is driven and controlled based on the operation of the upper parallel link operating lever. The aerial work platform according to claim 3, characterized in that when the mode switching switch is switched to the vertical operation mode, the lower actuator and the upper actuator are driven and controlled based on the operation of one of the lower parallel link operating levers and the upper parallel link operating lever, and the operation of the other operating lever is disabled.

5. A swivel platform attached to the aforementioned tip bracket and capable of rotating horizontally, The system includes a boom attached to the aforementioned slewing platform, which is capable of raising and lowering and extending relative to the slewing platform, The aerial work platform according to any one of claims 1 to 4, characterized in that the work platform is attached to the tip of the boom, and thereby attached to the tip bracket via the slewing platform and the boom.

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