JPH0134920B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a lifting device used for lifting workers or materials for work at high places, and lowering unnecessary parts from high places. In particular, regarding a lifting device in which a pair of middle booms are pivoted in an X-shape, and an upper boom and a lower boom that extend and retract in the axial direction are inserted into each middle boom, the connecting oil passages of a pair of hydraulic cylinders connected in series are The present invention relates to a hydraulic correction mechanism for a lifting device that is capable of operating both hydraulic cylinders in synchrony by constantly maintaining hydraulic pressure at a specific pressure.

[Conventional technology]

Assembly at high places such as highways and building construction,
For painting and repair work, a lifting device was used to raise and lower a lifting platform, and workers and materials were placed on this lifting platform to be lifted, and unnecessary parts were lowered.
In this conventional elevating device, a pantograph type telescopic mechanism is used in which a pair of arms are pivoted at the center to form a set of link elements, and a plurality of sets of link elements are connected in the vertical direction. With this pantograph-type telescoping mechanism, in order to increase the maximum lifting height of the platform, it is necessary to increase the length of each arm.
It was necessary to increase the number of sets of link elements to be connected.

For this reason, if a design is intended to increase the lifting height, the height of the lifting device will be high when the telescoping mechanism is folded, making it cumbersome for workers to get on and off the platform and to load and unload materials. Ta. For this reason, an elevating mechanism has been devised in which multiple booms are telescopically inserted into the inside of the arm so that one arm can extend in its length direction (for example, No. 134487, Patent Application No. 191065 of 1982, etc.).

The outline of this newly proposed elevating mechanism is explained with reference to Fig. 1.The middle boom A, which is hollow inside,
B is rotatably connected at its center in an X-shape by an axis C, and upper booms D and E and lower booms F and G are inserted into the end faces of middle booms A and B, respectively, so that they can appear and retract. A lifting platform I is connected to the tips of the upper booms D and E, and a base H is connected to the tips of the lower booms F and G. A pair of hydraulic cylinders J and K are interposed between the base H and the axis C so as to form an isosceles triangle.

In order to raise the lifting platform I in this configuration,
First, when the shaft C is raised by hydraulic cylinders J and K, the upper booms D and E and the lower booms F and G are pulled out from the open ends of the middle booms A and B, and the lifting platform I
moves away from the base H and rises upward. Here, in order for the lifting platform I to rise vertically with respect to the base H, the upper booms D, E, the lower boom F,
The amount of movement l by which G is pulled out from the open ends of the middle booms A and B must always be the same, and for this reason, the synchronization that regulates the amount of movement of each of the upper booms D and E and the lower booms F and G is required. A mechanism is required.

Here, it is extremely easy to synchronize the movement amounts of the upper boom D and the lower boom F, or the upper boom E and the lower boom G, but the upper boom D,
In order to synchronize E with each other, since the shaft C is rotatable, the structure for synchronization becomes complicated and the mechanism has to be large. For this reason, it has also been proposed to connect both hydraulic cylinders J and K in series so that the hydraulic pressure discharged from one hydraulic cylinder J is supplied to the injection side of hydraulic cylinder K, and to synchronize the amount of expansion and contraction. However, in the closed circuit formed by arranging the two hydraulic cylinders J and K in series, there is a phenomenon in which pressure oil leaks slightly due to packing, cylinders, etc. Due to the accumulation of this leaked pressure oil, the expansion and contraction amounts of both hydraulic cylinders J and K are not synchronized, and the shaft C
The lifting direction of the lifting table I was not perpendicular to the base H, but the lifting table I was raised at an angle, which was inconvenient for raising the lifting table I vertically.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above-mentioned drawbacks. A pressurizing circuit is connected to the connecting oil passages of the closed circuits connected in series, and hydraulic pressure is applied to the closed circuit before the lifting platform is raised to supply pressure oil. The present invention provides a hydraulic correction mechanism for an elevating device that corrects leaked pressure oil by supplying the hydraulic oil and constantly synchronizes the amount of expansion and contraction of a pair of hydraulic cylinders.

[Means for solving problems]

The present invention includes a movable vehicle body, a lifting platform located above the vehicle body that can be raised and lowered vertically, a pair of middle booms rotatably supported in the center and combined in an X shape, and a longitudinal direction of each middle boom. a lower boom whose lower ends are connected to the vehicle body; an upper boom which moves in the length direction of each intermediate boom and whose upper ends are connected to a lifting platform;
In order to make the amount of movement of the lower boom and upper boom the same with respect to the middle boom,
In an elevating device that has a flexible connecting means that connects a lower boom and an upper boom to regulate the amount of movement of both, the connecting portion of a pair of middle booms is connected to two points spaced apart on a base. A pair of hydraulic cylinders arranged in an inverted V shape between them, a hydraulic pressure generation source connected to the injection side of one hydraulic cylinder, and communication between the discharge side of one hydraulic cylinder and the injection side of the other hydraulic cylinder. A lifting device characterized by comprising: a connecting oil passage for causing the lifting platform to move; an initial oil pressure supply mechanism that supplies pressure oil to the connecting oil passage; and a control mechanism that operates the initial oil pressure supply mechanism before the lifting operation of the lifting platform. It provides a hydraulic correction mechanism for the device.

[Effect]

In the present invention, when starting the elevating mechanism to raise the elevating platform, first, pressure oil is supplied to the connecting oil passage by the initial oil pressure supply mechanism to increase the pressure in the connecting oil passage. Therefore, it is possible to replenish the decrease in pressure oil in the connecting oil passage due to leakage, etc., and correct the synchronization between the pair of hydraulic cylinders. Therefore, the amount of expansion and contraction of both hydraulic cylinders will be the same, and the lifting platform will rise in the vertical direction.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

The reference numeral 1 in the figure is a truck body.A front wheel 2 and a rear wheel 3 are pivotally supported on the front, rear, left, and right sides of the vehicle body 1, respectively.A driver's cab 4 is provided above the front wheels 2. Outriggers 5 are fixed to the center and left and right sides of the rear end, respectively. An elevating mechanism 6 is placed on the upper surface of the vehicle body 1. A elevating table 7 is fixed to the upper part of the elevating mechanism 6, and a handrail 8 is provided around the elevating table 7.

This lifting mechanism 6 consists of four telescopic booms,
Each telescoping boom has a middle boom 1
0, a lower boom 11, and an upper boom 12. The center of each of the two middle booms 10 is connected by a connecting shaft 13 so as to be rotatable in an X-shape, and a connecting piece 14 is provided at each tip of the lower boom 11 and the upper boom 12. , 15 are fixed to each other. This connecting piece 14 is rotatably connected to a fixed piece 16 fixed on the vehicle body 1 by a pin, and the connecting piece 15 is rotatably connected to a fixed piece 17 fixed to the lower surface of the elevator platform 7 by a pin. There is.

The intervals between the fixed pieces 16 and the fixed pieces 17 are the same, and the vehicle body 1 and the lifting platform 7 are configured to be parallel even if the telescopic boom is extended in an X-shape. The two sets of middle stage booms 10 are arranged in parallel with an interval between them, and the middle stage booms 10 inside each set are connected at the center by an operating shaft 18. Inside middle boom 1 of each set
0 are connected at the center by an operating shaft 18, and the axes of the operating shaft 18 and the connecting shaft 13 are arranged in a straight line. Hydraulic cylinders 19 and 20 are respectively arranged between two positions close to the fixed piece 16 of the vehicle body 1 and the operating shaft 18, and both hydraulic cylinders 19 and 20 form an isosceles triangle with the operating shaft 18 as the apex. It is arranged so that

Next, FIGS. 5 and 6 show the internal structure of the above-mentioned telescopic boom, that is, the middle boom 10. The middle boom 10 has a structure in which a thin steel plate is bent and the cross section is hollow in the longitudinal direction. A lower boom 11 is slidably inserted through one end of the middle boom 10. The lower boom 11 has a hollow rectangular cross section made by bending a thin steel plate, and the upper boom 12 inserted from the other open end of the middle boom 10 is slidably inserted into the lower boom 11. be.

Fan-shaped shaft support pieces 21 and 22 are fixed to both ends of the middle boom 10, respectively, and a pair of guide rollers 23 and 24 are rotatably supported on the shaft support pieces 21 and 22, respectively. The guide rollers 23 are in contact with both sides of the lower boom 11, and the guide rollers 24 are in contact with both sides of the upper boom 12. Furthermore, a gear box 25 is located at the end of the middle boom 10 that is close to the shaft support piece 22.
is fixedly fixed thereto, and two sprocket wheels 26 and 27 are pivotally supported within this gear box 25. The tip of the lower boom 11 (middle boom 1
0 is the deepest position) and the tip of the upper boom 12 are connected by a chain 28, which is wound around the outer periphery of the sprocket wheels 26 and 27 in an S-shape. . By this chain 28, the amount of expansion and contraction of the lower boom 11 and the upper boom 12 is synchronized, and the lower boom 11 and the upper boom 12 extending from the middle boom 10
will appear and disappear depending on the same amount of expansion and contraction.

Further, FIG. 6 shows a cross section of the center of the middle boom 10, and a band-shaped holder 29 is wrapped around and fixed to the outer periphery of the center of the middle boom 10, and the side surface of one holder 29 is A cylindrical connecting shaft 13 is fixed, and an engaging piece 31 fixed with a screw 30 is fixed to the other holder 29.
The engaging piece 31 is fitted into an engaging groove 32 formed on the outer periphery of the connecting shaft 13. With this configuration, the two middle booms 10 are connected in an X-shape, and their rotation is maintained freely. The connecting shaft 1 of the holder 29 is fixed to one middle boom 10.
A support shaft 33 is projected at a position opposite to 3, and the operating shaft 18 is connected to this support shaft 33.

Next, FIG. 7 shows a hydraulic circuit according to an embodiment of the present invention, in which the output of the engine 51 is
2, and the pump 52
The suction side of the pump 52 is connected to a tank 53 filled with pressure oil, and the discharge side of the pump 52 is connected to a switching valve 54 and a pressure regulating valve 56 in a pressure regulating section 55. This switching valve 54 is a three-way switching solenoid valve, and this switching valve 54 has two oil passages 57,
The oil passage 57 is connected to the working side of the hydraulic cylinder 19, and the discharge side of the hydraulic cylinder 19 and the working side of the hydraulic cylinder 20 are connected to each other via a check valve 59 and a control valve 60. They are connected by a connecting oil line. A check valve 61 and a control valve 62 are connected in parallel between the discharge side of the hydraulic cylinder 20 and the oil passage 58.

The output of the aforementioned pressure regulating valve 56 is connected to a switching valve 64 in the correction section 63, and one output of the switching valve 64 is connected between the control valve 60 and the hydraulic cylinder 20 via a check valve 65. A relief valve 66 is provided between the switching valve 64 and the oil passage 58. This control valve 64 is a solenoid valve that can be switched between forward and reverse directions, and is normally positioned in the forward direction.

Further, reference numeral 67 is a control unit provided in the lifting platform 7, and this control unit 67 is provided with a rising switch 68 and a descending switch 69, and a timer circuit 70 and an AND circuit 71 are connected to the switch 68. The switching valve 64 is connected to the output of the timer circuit 70 via a drive circuit 72. The output of this timer circuit 70 is connected to an AND circuit 71 via an inverting circuit 73, and the output of the AND circuit 71 is connected to the rising side coil of the switching valve 54 via a drive circuit 74. The switch 69 is connected to the descending coil of the switching valve 54 via a drive circuit 75.

Next, the operation of this embodiment will be explained.

First, the engine 51 attached to the vehicle body 1 is operated, and the engine 51 makes full use of the pump 52 to generate oil pressure. This oil pressure is transmitted to the switching valve 54, and is also reduced by the pressure regulating valve 56 and transmitted to the switching valve 64. However, when the switching valve 64 is in a stationary state (the position shown in FIG. 7), the oil pressure is transferred to the correction section. 63, goes around inside the pressure regulating section 55, and is collected into the oil tank 53 through a return path.

When the lifting platform 7 is to be raised, the lifting switch 68 is pressed and a signal is transmitted to the timer circuit 70 and the AND circuit 71. The timer circuit 70 outputs a signal to the drive circuit 72 for a predetermined period of time (several seconds to several tens of seconds) after the control signal is input.
, the switching valve 64 is switched, the hydraulic pressure from the pressure regulating valve 56 is transmitted to the check valve 65 direction, and the hydraulic cylinder 1
Apply hydraulic pressure to the connecting oil path to which 9 and 20 are directly connected, and add hydraulic pressure to compensate for the leaked pressure oil.
The space between both hydraulic cylinders 19 and 20 is filled with pressure oil. Excess hydraulic pressure is transferred from the relief valve 66 to the oil path 58.
The oil enters the oil tank 53 and is collected in the oil tank 53.

While this timer circuit 70 is operating, a high-level signal is input to the inversion circuit 73, so its output is low, and the AND circuit 71 does not output a signal, but after a predetermined period of time, the timer circuit 70 outputs a signal. When the signal is no longer output, the inverting circuit 73 outputs a high level signal. Based on the signal from the reversing circuit 73 and the signal from the lift switch 68, the AND circuit 71 outputs a signal and stops the operation of the switching valve 64. At the same time, the drive circuit 74 operates the switching valve 54 to correct the valve. Switch to the position of the direction. Therefore, pressure oil is supplied to the hydraulic cylinder 19 and the hydraulic cylinder 19 expands, and at the same time, the discharged pressure oil is transmitted to the hydraulic cylinder 20 from the control valve 60, and the hydraulic cylinder 20 expands in synchronization with the hydraulic cylinder 19. do. Pressure oil discharged from the hydraulic cylinder 20 is collected into the oil tank 53 through the control valve 62.

When the hydraulic cylinders 19 and 20 are operated and their cylinder rods are extended, the middle boom 10 is lifted upward, and the lower boom 11 and the upper boom 12 are moved upward.
It will be extracted from 0. At this time, the lower boom 11 and the upper boom 12 are connected by a chain 28, so when the lower boom 11 comes out of the middle boom 10, the chain 28 fixed to the tip of the lower boom 11 connects to the sprocket wheel 2.
The lower end of the upper boom 12 is pulled by the movement of the chain 28, and the upper boom 12 is pulled out from the upper end opening of the middle boom 10. Moreover, since the chain 28 does not extend, the amount by which the lower boom 11 and the upper boom 12 come out is the same, and the lower boom 11 and the upper boom 12 are combined into a pair.
The extension amount of the middle boom 10 is the same as that of the connecting shaft 13.
Lift the platform 7 by rotating it in an X-shape around the center. When the middle boom 10 is pushed up by the hydraulic cylinders 19 and 20, since the hydraulic cylinders 19 and 20 are both arranged in an isosceles triangle shape with the connecting shaft 13 as the center, the amount of extension of each cylinder rod is the same. If so, connection shaft 1
3 will rise in a direction perpendicular to the vehicle body 1.

As mentioned above, since the hydraulic oil discharged from the hydraulic cylinder 19 is injected into the working side of the hydraulic cylinder 20, both hydraulic cylinders 19 and 20 are synchronized so that the amount of extension thereof is the same. Therefore, the elongation of the cylinder rod is the same at any point in time.

To explain the relationship between the amounts of movement with reference to FIG. 8, the amount of extension W of both hydraulic cylinders 19 and 20 is the same, the connecting shaft 13 is raised in a straight line, and the lower boom 11, the upper boom 12 The extrusion amount Z is the same for all booms 11,
12 will be synchronized with the amount of movement.

If the seventh lift rises to a predetermined height,
The rising can be stopped by pushing the switch 68. By turning off the switch 68, the drive circuit 74 stops outputting the control signal, and the switching valve 5
4 returns to the neutral position, and each hydraulic cylinder 1
9 and 20 remain in their extended state, the hydraulic circuit is closed, and they are held in that position, so that the lifting platform 7 does not descend.

Next, when the elevator platform 7 is to be lowered, when the lowering switch 69 is turned on, the drive circuit 75 switches the switching valve 54 in the opposite direction, and the pump 5
The pressure oil from the hydraulic cylinder 2 is injected into the hydraulic cylinder 20 through the oil passage 58 and the check valve 61, and
0 reduces. The hydraulic oil discharged from the hydraulic cylinder 20 passes through the check valve 59 to the hydraulic cylinder 1.
9 and causes the hydraulic cylinder 19 to contract. Pressure oil discharged from the hydraulic cylinder 19 returns to the oil tank 53 through the oil path 58. Even when both cylinders 19 and 20 are contracted, both hydraulic cylinders 1
The reduction amounts of 9 and 20 are synchronized, and the connecting shaft 13 of the middle boom 10 descends perpendicularly to the vehicle body 3.

〔Effect of the invention〕

Since the present invention is configured as described above, by connecting a pair of hydraulic cylinders in series, the amount of extension can be synchronized, and furthermore, the connection oil passage connecting both hydraulic cylinders is equipped with an initial hydraulic pressure supply mechanism. Since hydraulic pressure is applied before the lifting platform is raised, it is possible to correct leakage of pressure oil in this connecting oil passage and always operate both hydraulic cylinders in synchronization. Therefore, the platform can always rise and fall vertically above the vehicle body without tilting in any particular direction.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the outline of a newly proposed elevating device, Fig. 2 is a side view showing a state in which the elevating mechanism of the elevating device according to an embodiment of the present invention is lowered to the lowest position, and Fig. 3 The figure is a side view showing the elevating mechanism as above extended to its maximum extent, Fig. 4 is a rear view of the state shown in Fig. 3, Fig. 5 is a side sectional view showing the inside of the middle boom, and Fig. 6 is FIG. 7 is a circuit diagram showing the oil path circuit of the hydraulic mechanism, and FIG. 8 is a schematic diagram showing the relationship between the lifting mechanism and the hydraulic expansion/contraction mechanism. 1... Vehicle body, 6... Lifting mechanism, 7... Lifting platform,
10...middle boom, 11...lower boom, 12
... Upper boom, 19, 20 ... Hydraulic cylinder, 63 ... Correction section, 64 ... Switching valve, 67 ...
control unit.

Claims (1)

[Claims] 1. A movable vehicle body, a lifting platform located above the vehicle body that can be raised and lowered, a pair of middle booms that are rotatably supported in the center and combined in an X shape, and each middle boom A lower boom that slides and whose lower end is connected to the vehicle body, an upper boom that moves along the length of each middle boom and whose upper end is connected to a lifting platform, and a lower boom that moves with respect to the middle boom. In order to make the amount of movement of the boom and the upper boom the same, a pair of lifting devices have a flexible linking means that connects the lower boom and the upper boom to regulate the amount of movement of both. A pair of hydraulic cylinders arranged in an inverted V-shape between the connecting part of the middle boom and two points spaced apart on the base, and a hydraulic power source connected to the injection side of one of the hydraulic cylinders. , a connecting oil passage that communicates the discharge side of one hydraulic cylinder with the injection side of the other hydraulic cylinder, an initial hydraulic pressure supply mechanism that supplies pressure oil to this connecting oil passage, and an initial hydraulic pressure supply mechanism that connects the 1. A hydraulic correction mechanism for a lifting device, comprising a control mechanism that is activated before a lifting operation.