JPH0342282Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a hydraulic switching valve having a spool, and in particular prevents water from entering into a cap provided to protect both ends of the spool. The present invention also relates to a hydraulic switching valve that allows smooth movement of the spool.

(Prior Art) For example, in a dump truck, a hydraulic pump connected to the output shaft of the engine via a power take-off shaft and a hydraulic actuator for tilting a cargo box are connected to each other in an axially movable manner. A hydraulic switching valve having a spool is installed, and this hydraulic switching valve switches and controls the pressure oil supplied from the hydraulic pump to the hydraulic actuator (hydraulic cylinder).
It is designed to extend and retract and tilt the cargo box. On both sides of this hydraulic switching valve body,
Protective caps were provided for protecting both ends of the spool, which protruded from the hydraulic switching valve when moved in the axial direction, so that they could be easily operated from the outside for safe operation.

However, since the inside of this protective cap is completely sealed, as the volume inside the protective cap changes as the spool moves, the pressure inside this protective cap changes slightly, causing the operating force to move the spool to become heavier. There was a problem that if the spool seal broke and hydraulic oil flowed into the protective cap and filled it, it would cause cylinder action.
Conventionally, in order to solve the above-mentioned problem, an air hole was provided below the protective cap, which also served as an oil vent. If this air hole is too large, water will easily enter from the outside, and if it is too small, it will cause problems such as dirt clogging, so approximately φ3
It was formed into an air hole about mm in size.

(Problem that the invention seeks to solve) However, when washing dump trucks, especially when high-pressure washing, water enters through the air holes in the protective cap, and once the water has entered the protective cap, it is Since it is small, it remains inside due to surface tension, etc. Here, the protective cap is formed as small as possible in order to reduce the size and weight of the entire device, and the gap between the outer peripheral surface of the spool and the protective cap is very small, about 1 to 2 mm. Therefore, water that has entered the protective cap accumulates in the gap between the protective cap and the spool, and in cold regions, this water freezes and causes a problem that the spool does not operate.

(Means for solving the problem) The hydraulic switching valve of the present invention has a spool that is movable in the axial direction, and the power extraction device is operated by remotely controlling the spool with an operating cable connected to the spool. In a hydraulic switching valve that switches and controls pressure oil supplied to a hydraulic actuator from a hydraulic pump driven through the hydraulic switching valve, protective caps are attached to both sides of the hydraulic switching valve body to protect both ends of the spool,
These caps are communicated with each other by a communication means.

(Function) The two protective caps attached to both sides of the hydraulic switching valve body are connected by a communication means, so that even if the volume inside both caps changes as the spool moves, the inside of these protective caps remains unchanged. pressure is kept uniform. Therefore, there is no need to form an air vent hole in the protective cap as in the conventional case, and the inside of the protective cap is always sealed, so that cleaning water does not enter the protective cap during high-pressure cleaning or the like.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a hydraulic switching valve according to the present invention applied to a hydraulic device for tilting a cargo box of a dump truck.

In the figure, reference numeral 1 denotes a hydraulic cylinder for tilting the cargo box 2. This hydraulic cylinder 1 expands and contracts by switching the pressure oil from the hydraulic pump 3 with the hydraulic switching valve 5, and tilts the cargo box 2. let The hydraulic pump 3 has a drive shaft 3a connected to an output shaft of an engine (not shown) via a power extraction device 6,
Pressure oil is supplied to the hydraulic cylinder 1 by driving the drive shaft 3a. The hydraulic switching valve 5 has a spool 7 that is movable in the axial direction, and by moving the spool 7 in the axial direction and switching the oil path, the hydraulic pressure oil from the hydraulic pump 3 is controlled and the hydraulic cylinder 1 is extended or contracted. The loading box 2 is tilted. Both ends of the spool 7 protrude from the hydraulic switching valve main body 5a, and these ends are protected by protective caps 10, 10 provided on both sides of the hydraulic switching valve main body 5a.

These protective caps 10, 10 have through holes 11.
are formed respectively, and these through holes 11,
Both ends of a communication pipe 12 (communication means) are connected to the communication pipe 11, respectively. The insides of the two protective caps 10, 10 are communicated through this communication pipe 12. Therefore, even if the spool 7 moves and the volume inside the protective cap 10 changes, these protective caps 10,
Since the air inside the protective caps 10 is communicated through the communication pipe 12, the internal pressures of the protective caps 10, 10 are kept equal. In addition, the protective cap 10 is connected to the communication pipe 12.
Simply connect one end of this protective cap 10
No other holes such as air holes are formed in the. Therefore, when cleaning the dump truck, especially when performing high-pressure cleaning, cleaning water will not enter into the protective cap 10.

Also, a wire (operating cable) is attached to one end of the spool 7.
One end of the wire 8 is connected to the other end of the wire 8, and the other end of the wire 8 is connected to an operating section (not shown) provided, for example, in the driver's seat.By operating the wire 8 with the operating section, the position of the spool 7 can be controlled. It is configured to switch.

FIG. 2 shows another embodiment of the hydraulic switching valve according to the present invention, in which the spool 7 is used as the communication means.
A communication hole 15 is formed in the axial direction of the
The protective caps 10, 10 are communicated through the protective caps 10, 10. Note that other members are the same as those in the previous embodiment, and the same members are given the same reference numerals.

[Effect of idea]

As described above, according to the present invention, the insides of the two protective caps that protect both ends of the spool are communicated by the communication means, so that when the spool moves, the volume inside these protective caps changes. However, the pressure inside these protective caps is maintained evenly, allowing smooth movement of the spool. Also,
There is no need to form air holes in the protective cap like in the past, and the inside of the protective cap is sealed, so when cleaning dump trucks, especially when high-pressure washing, for example, there is no possibility that cleaning water will infiltrate into the protective cap. This eliminates harmful effects such as freezing of the spool caused by water entering the protective cap.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the schematic structure of a hydraulic switching valve according to the present invention mounted on a dump truck, and Fig. 2 is a sectional view showing the schematic structure of a hydraulic window switching valve according to another embodiment of the invention. be. 1...Hydraulic cylinder, 3...Hydraulic pump, 3...
... Hydraulic switching valve, 6 ... Power take-off device, 7 ... Spool, 10 ... Protection cap, 12 ... Communication pipe,
15...Spool communication hole.

Claims (1)

[Claim for Utility Model Registration] It has a spool that is movable in the axial direction, and by remotely controlling the spool with an operating cable connected to the spool, a hydraulic actuator can be connected to a hydraulic pump driven via a power take-off device. In a hydraulic switching valve that switches and controls supplied pressure oil, protective caps are attached to both sides of the hydraulic switching valve body to protect both ends of the spool, and these caps are communicated with each other by a communication means. A hydraulic switching valve featuring: