JPH0424192Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a hydraulic shock absorber that absorbs the load acting on a piston rod by the hydraulic fluid in the hydraulic cylinder body.

"Prior art and its problems" FIGS. 2 and 3 each show a conventional example. The hydraulic shock absorber shown in FIG. 2 has a piston 3 slidably fitted into an inner tube 2 of a hydraulic cylinder body 1 to divide the inner tube 2 into a front chamber 4 and a rear chamber 5. An accumulator 8 is provided in a gap 7 between the inner tube 2 and the outer tube 6. A plurality of orifices 9 are bored in the peripheral wall of the inner tube 2, and a recess 10a and a communication hole 10 are formed in the piston 3.
A ball 11, which together with the valve seat forms a check valve, is disposed within the recess 10a. Furthermore, a rod packing 13 for scraping off the hydraulic oil in the hydraulic cylinder body 1 and a dust wiper 14 for preventing dust from entering from the outside are disposed on the sliding portion of the piston rod 12. The accumulator 8 is for absorbing the difference in volume of outflow or inflow between the front chamber 4 and the rear chamber 5, and has numerous independent air chambers partitioned by rubber membranes.
The piston 3 is connected to a return spring 15 disposed within the rear chamber 5.
It is restored by The cap side end of the inner tube 2 is closed by a bolt-shaped cap 16.

However, with this shock absorber, if fluid such as oil adheres to the protruding portion of the piston rod 12 from the outside, the scraping ability of the rod packing 13 is greater than that of the dust wiper 14. The fluid is gradually drawn into the hydraulic cylinder body 1. As a result, the accumulator 8 shrinks and loses its function, the piston 3 becomes unable to slide, and when a large load is applied to the piston rod 12, the shock absorber is damaged.

In the shock absorber shown in FIG. 3, rod packings 13a and 13b having different scraping directions are disposed facing each other in the sliding portion of the piston rod 12 in order to eliminate such drawbacks. However, although this shock absorber is superior in durability to the shock absorber shown in Figure 2,
If there is a difference in scraping ability between the two rod packings 13a and 13b, there is a problem that external fluid may be drawn in or internal hydraulic oil may leak.

This invention solves the above-mentioned problems by automatically discharging excess hydraulic fluid to the outside when fluid such as oil from outside enters the hydraulic cylinder and the internal hydraulic pressure rises above a predetermined level. The purpose of the present invention is to make it possible to easily add a relief valve for such discharge, and to make it easy to adjust the relief valve.

"Means for Solving Problems" In the present invention, the hydraulic cylinder main body 1 has a double cylindrical structure with an inner tube 2 having a plurality of orifices and an outer tube 6, and the piston is slid inside the inner tube 2. The interior of the inner tube 2 is divided into a front chamber and a rear chamber by being fitted freely, and a return spring for returning the piston forward is disposed in the rear chamber, and a return spring is disposed between the inner tube 2 and the outer tube 6. This hydraulic shock absorber is characterized in that an accumulator 8 is provided in the gap chamber and the cap side end of the inner tube 2 is closed with a bolt-shaped cap 16, and has the following structure.

That is, a screw hole 25 communicating with the rear chamber 5 of the inner tube 2 is provided in the center of the cap 16,
By screwing into the threaded hole 25 the male threaded cylindrical connecting protrusion 24 protruding from the base end of the cylindrical valve body 18 of the relief valve 17, the relief valve 17
is directly connected to the outside of the inner tube 2 to communicate the rear chamber 5 of the inner tube 2 and the inside of the valve body 18. A relief pressure adjustment bolt 22 having a discharge hole 22a is screwed onto the tip of the valve body 18, and a ball valve body 20 is inserted into the valve body 18, and the relief pressure adjustment bolt 22 is inserted into the spring seat. A spring 2 that presses the ball valve body 20 against the valve seat 19 as
1 is arranged.

``Function'' Therefore, when oil or the like enters into the hydraulic cylinder body 1 from the outside and the internal oil pressure rises above the set value, the increased hydraulic oil passes through the relief valve 17 and exits from the discharge hole 22a. It is discharged to the outside. The pressure for the discharge is determined by the relief pressure adjustment bolt 22.
It can be arbitrarily adjusted from the outside. relief valve 1
7 is a cylindrical connecting protrusion 24 at the base end of the valve body 18;
It can be easily added to the hydraulic cylinder body 1 by simply screwing it into the screw hole 25 provided in the cap 16 of the inner tube 2 without changing the hydraulic cylinder body 1 side.

"Embodiments" Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

In FIG. 1, the shock absorber according to the present invention has an internal structure of a hydraulic cylinder body 1 that is substantially the same as the conventional one described above, and the illustrated parts are designated by the same reference numerals as in FIG. . In this shock absorber, a relief valve 17 is directly connected to the outside of the cap 16, and the relief valve 17 has a valve seat 19 formed in a cylindrical valve body 18, and a ball valve body 20 inserted thereinto. The ball valve body 20 is attached to the valve seat 1 by the spring 21.
9, and the relief pressure adjusting bolt 22 that receives this spring 21 is connected to the male thread 2 on the inner peripheral surface of the valve body 17.
3 is screwed into place. Relief pressure adjustment bolt 2
2 is provided with a discharge hole 22a. The relief valve 17 is attached to the cap 16 by screwing the cylindrical connecting protrusion 24 protruding from the base end of the valve body 18 into the screw hole 25 on the inner peripheral surface of the cap 16. Hydraulic cylinder body 1
It communicates with the inside.

Therefore, when the fluid adhering to the piston rod 12 from the outside is drawn into the hydraulic cylinder body 1, the amount of hydraulic oil in the hydraulic cylinder body 1 increases, and the internal pressure rises above a predetermined level, the ball valve body 20 opens. It separates from the valve seat 19 against the force of the spring 21, and the increased amount of hydraulic oil in the hydraulic cylinder 1 is released into the cap 16, the valve body 17, and the discharge hole 2 of the relief pressure adjustment bolt 22.
It is discharged to the outside through 2a. The relief pressure can be arbitrarily adjusted using the relief pressure adjustment bolt 22. The internal pressure of the hydraulic cylinder body 1 is proportional to the number of piston operations, and the following relationship holds true.

(Relief pressure) = (Relief valve setting pressure) ÷ {(π/4) d ² } However, d is the diameter of the valve seat 19.

``Effect of the invention'' As described above, according to the invention, when fluid such as oil from the outside enters the hydraulic cylinder and the internal oil pressure rises above a predetermined level, the excess hydraulic oil is automatically drained to the outside. Since it can be discharged, there are no problems such as the accumulator shrinking and losing its function, the piston becoming unable to slide, and the shock absorber being damaged when a large load is applied to the piston rod.

Further, the pressure when performing excess discharge can be arbitrarily adjusted from the outside using the relief pressure adjustment bolt of the relief valve.

Furthermore, the relief valve has an independent structure, and can be easily installed by simply screwing the cylindrical connecting protrusion at the base end of the valve body into the screw hole provided in the cap of the inner tube, without changing the hydraulic cylinder body. Since it can be expanded, it is suitable for small and narrow diameter shock absorbers. If a relief valve is not required, it can be used in the same way as a conventional shock absorber by simply removing the relief valve body from the screw hole in the inner tube cap and plugging the screw hole with a screw.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway side view of an embodiment of the present invention.
FIGS. 2 and 3 are partially cutaway side views of the conventional example. 1... Hydraulic cylinder body, 2... Inner tube, 3... Piston, 5... Rear chamber, 6... Outer tube, 8... Accumulator, 9...
Orifice, 15... Return spring, 16... Cap, 17... Relief valve, 18... Valve body, 19
... Valve seat, 20 ... Ball valve body, 21 ... Spring,
22... Relief pressure adjustment bolt, 22a... Discharge hole, 24... Cylindrical connection protrusion, 25... Screw hole.

Claims (1)

[Scope of utility model registration request] A hydraulic cylinder main body 1 has a double cylindrical structure with an inner tube 2 having a plurality of orifices and an outer tube 6, and a piston is slidably fitted into the inner tube 2 to form a front chamber inside the inner tube 2. and a rear chamber, and inside the rear chamber,
A return spring for returning the piston forward is arranged, an accumulator 8 is provided in the gap between the inner tube 2 and the outer tube 6, and the end of the inner tube 2 on the cap side is closed with a bolt-shaped cap 16. In the hydraulic shock absorber, a screw hole 25 is provided in the center of the cap 16 and communicates with the rear chamber 5 of the inner tube 2, and the base end of the cylindrical valve body 18 of the relief valve 17 is inserted into the screw hole 25. The relief valve 17 is directly connected to the outside of the inner tube 2 by screwing together the male-threaded cylindrical connection protrusion 24 protruding from the inner tube 2, and the rear chamber 5 of the inner tube 2 and the inside of the valve body 18 are communicated with each other. , a discharge hole 22a is provided at the tip of the valve body 18.
The ball valve body 20 is inserted into the valve body 18, and the ball valve body 20 is pressed against the valve seat 19 by using the relief pressure adjustment bolt 22 as a spring seat. A hydraulic shock absorber characterized in that a spring 21 is arranged.