JPS628400B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a boom extension/retraction device used in a crane or the like.

In the conventional boom extension/retraction device, a hose reel or the like is used as a means for feeding oil to the extension side oil chamber of the second cylinder device on the upper stage side. However, this sometimes causes unforeseen situations such as pressure oil leakage due to deterioration of the hose and damage to the hose fittings due to long-term use. Therefore, the present invention aims to eliminate the above-mentioned problems by using a hollow pipe material as an oil feeding means to provide rigidity, and to provide a boom device that sequentially expands and contracts each cylinder device using this pipe material. It is something.

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

FIG. 1 shows the boom telescoping device of the present invention at full extension, where 1 is the base boom, and 2 is the base boom 1.
3 is a tip boom that is slidably inserted into the intermediate boom 2; 4 is a first cylinder device that is inverted between the base boom 1 and the intermediate boom 2; , 5 and 6 are their pivot pins, 7 is a second cylinder device disposed between the intermediate boom 2 and the tip boom 3, and 8 and 9 are their pivot pins. Reference numeral 10 denotes a switching valve 11 pivotally mounted on the base of the base boom 1, and 12 a spool for switching the oil passage of this switching valve, one side of which is slidably and tightly fitted into the second cylinder device 7, as will be described later.

The details of these cylinder devices and their operations will be explained below in FIG. 2A by taking out only the cylinder device from the boom telescoping device according to the present invention.

FIG. 2A shows each cylinder device in its fully retracted condition (and thus in its fully retracted boom condition).

In FIG. 2A, the first cylinder device 4 is a cylinder device with a conventionally known configuration, and a piston rod 4
Ports 13 and 14 are provided at the tip of the piston rod, and the ports 13 and 14 are connected to the expansion and contraction side oil chambers 1 through oil passages 15 and 16 provided inside the piston rod.
It is connected to 7 and 18. Second cylinder device 7
The inside of the piston rod 7b is made hollow 19 and the extension side oil chamber 20 side is opened, and the hollow part 1
9 is configured such that the spool 12 of the switching valve 10 can be inserted therein as described above. Further, an actuating member 22 is provided on the base side of the cylinder device 7, and is always biased in the extension direction by a spring 21, and this actuating member 22 is pushed and restrained by a piston 23 at the end of contraction of the second cylinder device 7. However, when this cylinder device starts to extend, its restraint is released and it is pushed by the spring 21 and is configured to move a certain distance in the direction of the extension operation. Furthermore, an engaging portion 22a that engages with the stepped portion 12a provided at the end of the spool 12 described above is provided inside the actuating member 22.

Next, the configuration of the switching valve 10 is shown in FIG. 2B. This FIG. 2B shows the valve configuration in FIG. 2A. This switching valve 10 includes a valve body 25 and a valve body 25.
The spring 26 is inserted tightly into the
The port P provided in the valve body 25 is made up of a spool 12 biased to the left by the spool 12, which moves to the right against the spring 26.
Oil passage 27 provided in B, T or spool 12
The structure is such that the oil passages leading to each of the two can be switched.
Note that the oil passage 27 in the spool 12 is opened at its tip side so as to communicate with the extension side oil chamber 20 of the second cylinder device 7. Further, 28 is a balance circuit for preventing this spool 12 from being affected by the pressure oil on the extension side oil chamber 20 side of the second cylinder device 7, and 29 is a balance circuit for preventing the flow from the oil path 27 side to the port P side. This is a check valve that allows backflow but prevents backflow, and the reason for its installation will be explained later.

Next, in FIG. 2A again, 30 is a pump;
1 is a tank, 32 is a directional control valve, and the output port of this directional control valve is connected to the P port of the control valve 10 and the port 1 of the first cylinder device 4 via pipes 33 and 34.
4 respectively. In addition, the B port of the switching valve 10 and the port 13 of the first cylinder device 4 are connected to the pipe line 3.
Connect with 5. Further, the T port of the switching valve 10 is connected to the tank 31. Further, the contraction side oil chamber 18 of the first cylinder device 4 and the contraction side oil chamber 24 of the second cylinder device 7 are connected by a pipe line 36.

The operation of the cylinder device constructed in this way will be explained.

First, in FIG. 2A, the directional control valve 32 is
When the pressure oil is switched to the position shown in FIG.
5, the port 13, and the oil passage 15 into the extension-side oil chamber 17 of the first cylinder device 4, so that the first cylinder device 4 is extended. As a result, the intermediate boom 2 is extended from the base boom 1, but since the base of the second cylinder device 7 is pivotally connected to the intermediate boom 2, the second cylinder device 7 also moves together with the intermediate boom 2, and the second cylinder device 7 also moves with the intermediate boom 2. The spool 12 of the switching valve 10 is then pulled out from the base side of the second cylinder device 7. At this time, the extension side oil chamber 20 of the second cylinder device 7 becomes empty by the amount that the spool 12 is pulled out, but the pressure there becomes negative, and oil is sucked up from the port T of the switching valve 10 through the oil passage 27. It will flow into that area. When this state continues and the first cylinder device approaches the end of extension, the stepped portion 12a of the spool 12 engages with the engaging portion 22a of the actuating member 22, and the spool 12 begins to move to the right, causing the first cylinder device to extend. Travel distance B of spool 12 at the end
becomes B=l ₁ −l ₂ (l ₁ 7l ₂ ). where l ₁ is the extension stroke of the first cylinder device, l ₂ is the intermediate boom 2
This is the distance between the stepped portion 12a of the spool 12 and the engaging portion 22a of the actuating member 22 in the retracted position (therefore, the first cylinder device 4 is in the most contracted state) (see FIG. 2A).

Therefore, the pressure oil from the P port starts to flow in the direction of the oil passage 27 as well as the B port, and the pressure oil flowing through this oil passage 27 flows into the extension side oil chamber 20 of the second cylinder device 7, and the pressure oil flows into the extension side oil chamber 20 of the second cylinder device 7. The device begins to extend.
As a result, the actuating member 22, which was restrained by the piston 23, is released from its restraint and begins to move to the right by the force of the spring 21. As a result, the spool 12 is also pulled by the actuating member 22 and moves to the right, so that the switching valve 10 assumes the configuration shown in FIG. 4B (see FIGS. 4A and 4B). That is, the pressure oil from the port P only flows to the oil passage 27, and only the second cylinder device is extended. Of course, in this state, the first cylinder device 4 is already in the most extended state. Note that the moving distance C of the spool 12 in this state is C=B+ _l3 . here
l ₃ is the moving distance of the actuating member 22.

Note that when the first and second cylinder devices are extended, the oil in these contraction side oil chambers 18, 24 returns to the tank via the oil passage 16 and port 14 in the piston rod 4b of the first cylinder device 4.

Through the above operations, the three-stage boom becomes fully extended.

When retracting the boom from this state, when the direction switching valve 32c is switched to the position, the pressure oil is transferred to the retraction side oil chamber 1 of the first cylinder device and the second cylinder device.
8 and 24. However, since the valve mode of the switching valve 10 is in the position shown in FIG. 4B, the first
The oil in the extension side oil chamber 17 of the cylinder device is supplied to the switching valve 10.
is blocked at port B, so the first cylinder device does not retract. In the extension-side oil chamber 20 of the second cylinder device, the port P of the switching valve 10 communicates with the tank 31 side, so the oil in this extension-side oil chamber 20 flows to the tank 31 side via the oil path 27. The cylinder device 7 is retracted.

When this state continues and the second cylinder device approaches the end of its contraction, the piston 23 of the second cylinder device 7 comes into contact with the actuating member 22, and further moves the actuating member 22 to the left against the spring 21. Accordingly, the spool 12 of the switching valve 10 also has a spring 2.
6 and begins to move to the left, and at the end of the contraction of the second cylinder device 7, the switching valve 10 assumes the valve mode shown in FIG. 3B (see FIGS. 3A and 3B), and
The port will also lead to the tank side. Therefore, the first cylinder device 4 will also be reduced in size.

When the first cylinder device 4 starts to contract, the second cylinder device also moves to the left together with the intermediate boom 2, so that the engagement portion 22a of the actuating member 22 in the second cylinder device 7 and the right end of the spool of the switching valve 10 are connected to each other. Stepped portion 12
a is disengaged, and the spool 12 is further moved to the left by the force of the spring 26. By doing so, the valve mode of the switching valve 10 becomes the mode shown in FIG. 2B, and only the first cylinder device is reduced. At this time, due to the contraction of the first cylinder device, the spool 12 will be pushed into the second cylinder device, but the oil in the extension side oil chamber 20 will be transferred to the switching valve 1 by that amount.
It will be discharged from port T of 0.

In addition, when the mode of the switching valve changes from Fig. 3B to Fig. 2B, when the discharge oil of the extension side oil chamber 20 of the second cylinder device 7 changes from the P port to the T port, the transient Surge pressure may occur. Therefore, in the present invention, a check valve 29 is provided between the oil passage 27 and the port P in order to discharge the oil in the extension side oil chamber 20 of the second cylinder device in a free flow regardless of this switching.

As described above, the present invention is configured so that the means for supplying oil to the second cylinder device on the upper stage side can be used as a means for detecting and switching the sequential expansion and contraction of this boom telescoping device, thereby simplifying the device itself. . In addition, the oil passage switching valve as the switching means can be switched to three directional positions, and the oil passage at the intermediate position is configured so that oil can be supplied (or drained) in both directions.
The oil passages could be switched continuously from one side to the other, and each cylinder device could be expanded and contracted completely sequentially.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing the fully extended state of the boom telescoping device according to the present invention, Fig. 2A, 2B, 3A, 3B,
4A and 4B are explanatory views of the operation of each cylinder device and the oil passage switching valve 10 that switches the oil passage to this cylinder device. DESCRIPTION OF SYMBOLS 1... Base boom, 2... Intermediate boom, 3... Tip boom, 4... First cylinder device, 7... Second cylinder device, 10... Oil path switching valve, 12... Spool, 12
a... Step portion, 22... Actuation member.

Claims (1)

[Claims] 1 A boom in which a base boom, an intermediate boom, and a tip boom are slidably inserted in order, and a first cylinder device is provided between the base boom and the intermediate boom, and a second cylinder device is provided between the intermediate boom and the tip boom. In the telescopic device, a switching valve is provided at the base of the base boom for switching the oil passage of the supply/discharge circuit to the extension side oil chamber of each cylinder device, and a spool for switching the switching valve is slidably and tightly penetrated into the second cylinder device. At the same time, a stepped portion is provided at the end of the spool, and an oil passage is provided inside the spool, and this oil passage is configured to serve as a supply/discharge circuit from the switching valve to the extension side oil chamber of the second cylinder device. , on the other hand, the second cylinder device has an engaging portion that engages with the stepped portion of the spool, and is always biased in the direction of extension of the cylinder device and moves in the direction of extension when the second cylinder device starts to extend. The switching valve switches the oil passage by engagement of the step portion and the operating member at the end of extension position of the first cylinder device and the start position of extension of the second cylinder device, and A boom extension/retraction device characterized in that the device is configured to extend and contract in sequence.