JPS6123683Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a shock absorber for a lift cylinder, which decelerates the piston a little before the piston's rising end to reduce the impact at the rising end, and further stabilizes the impact quickly when descending from the rising end. The object is to provide a shock absorber that can reach a descending speed.

Hereinafter, an embodiment in which the present invention is applied to a three-stage mast with a full free will be explained based on FIGS. 1 to 3. A first lift cylinder 5 with a large diameter, which is movable up and down, has a built-in piston 4, expands first, and then shortens; and a second lift cylinder with a small diameter, which has a built-in piston 6, expands later, and shortens first. 7, and a hydraulic pump 8 for both cylinders 5 and 7.
A supply/discharge pipe 9 common to both cylinders is provided for supplying and discharging pressure oil from the first lift cylinder 5, and a first buffer device 10 is provided for creating a hydraulic buffer state slightly before the rising end of the piston 4 of the first lift cylinder 5. The second lift cylinder 7 is provided with a second shock absorber 11 for creating a hydraulic shock absorbing state a little before the descending end of the piston 6.

The first shock absorber 10 includes a cylinder cap 13 fixed to the upper end of the first lift cylinder 5 and having a piston rod sliding portion 12;
A large-diameter L-shaped communication hole 15 is bored in the piston rod 14 to communicate the lower chamber A on the lower side of the piston 4 with the upper chamber B on the upper side of the piston 4, and a large diameter L-shaped communication hole 15 is provided in the piston rod 14 to communicate the lower chamber A on the lower side of the piston 4 with the upper chamber B on the upper side of the piston 4. The piston includes a plurality of vertical holes 16 bored in the piston so as to communicate with the lower chamber A, and the upper chamber side outlet 17 of the communication hole is connected to the piston 4.
A spherical valve 18 is inserted into the vertical hole 16 and closes the hole when the piston rises and opens when the piston descends. .

The valve element 18 is removably fitted into a valve seat 19 at the upper part of the vertical hole 16, and the notch 20 formed in the piston joint part of the piston rod 14 and the upper end of the hole wall of the vertical hole 16. It cannot be pulled out from between the edge 16a. Further, the sliding portion 12
Oil seals 21, 22 and a bush 23 are fitted therein. The communication hole 15 includes a large-diameter vertical hole portion 15a that communicates with the lower chamber A, and large-diameter, medium-diameter, and small-diameter horizontal hole portions 15b, 15c that communicate with the vertical hole and are arranged in order from the top. 15d. A slipper 24 and a packing 25 are fitted onto the piston 4, and an oil reservoir 13a is formed on the inner wall of the cap 13 on which the piston rises. Further, the supply/discharge pipe 9 is connected to the lower end of the first lift cylinder 5.

On the other hand, the second shock absorber 11 includes a cylindrical cylinder cap 26 fixed to the lower end of the second lift cylinder 7 and pressure from a supply/discharge port 27 of the cap 26 connected to the supply/discharge pipe 9. A fixed cylinder 30 having large, medium and small diameter inflow holes 28a, 28b and 28c formed in the center for oil to flow into the cylinder chamber D and fitted into the central hole 26a of the cap 26; A movable cylinder 32 with an upper cover 31 is fitted in the cylinder so as to be movable up and down and arranged to collide with the piston 6 slightly before the descending end of the piston 6, and the central hole 32a of the cylinder is always in communication with the cylinder chamber D. A large diameter communication hole 33 is bored in the side surface of the cylinder 32 so as to
and a buffer spring 34 that urges the movable cylinder 32 upward.
, a small diameter throttle hole 35 bored in the lower part of the fixed cylinder 30 so as to communicate between the center hole 32a of the movable cylinder 32 and the supply/discharge port 27, and the supply/discharge port 27 of the cap 26 and the cylinder chamber. A check valve 36 opens the passage 29 communicating with D only to the flow of pressure oil in the upward direction of the piston.

The movable cylinder 32 is composed of a small-diameter upper cylinder part 32b and a large-diameter lower cylinder part 32c, and the lower cylinder part is vertically slidable along the inner wall of the fixed cylinder 30, and the upper cylinder part 32b has a certain gap E with the inner wall of the fixed cylinder 30, and has a plurality of communication holes 33 in the upper cylinder part.
will be arranged. Further, the check valve 36 has a cylindrical valve element 37 fitted into the lower end of the fixed cylinder 30, and receives pressure oil passing through the passage 29 formed at the lower end of the fixed cylinder 30. An inclined surface 38 is formed on the outer periphery of the valve element 37 so that the valve element 37 can rise upward. The spring 3 is placed between the valve element 37 and the movable cylinder 32.
4 is interposed, and the movable cylinder 32 is in a free state with its upper cover 31 positioned above the descending end of the piston 6 to open the inflow holes 28a, 28b, and 28c, and the movable cylinder 32 is pushed down by the piston 6. The inlet holes 28a, 28b, and 28c are closed in the recessed state to open the throttle hole 3.
It is positioned to open only 5.

Note that 39 is an elevation switching valve provided in the pressure oil supply/discharge pipe 9, and 40 is a hydraulic tank.

In the above configuration, when pressure oil is supplied to the first and second lift cylinders 5 and 7 via the supply/discharge pipe 9, the first lift cylinder 5 with a larger cylinder diameter first raises the piston 4 and expands. The fork 41 moves the piston 4 against the first lifting mast 2.
rises at twice the rate of rise. And Figure 2b
When the piston 4 reaches just before its rising end, the outlet 17 of the communication hole 15 begins to enter the sliding portion 12. Therefore, the flow of oil from the communication hole 15 into the upper chamber B gradually stops. Then, the piston 4 further rises, causing oil to escape from the upper chamber B to the lower chamber A through a small gap F on the outer periphery of the piston 4, creating a hydraulic buffer state, and rising very slowly. Therefore, even when the piston 4 reaches the rising end and comes into contact with the cylinder cap 13 as shown in FIG. 2a, almost no impact noise is generated.

When the piston 4 of the first lift cylinder 5 reaches the rising end, the oil pressure on the side of the supply/discharge port 27 of the second lift cylinder 7 rises rapidly, and the pressure oil is transferred to the cap 26.
The valve element 37 of the check valve 36 is pushed up through the supply/discharge port 27 of the valve element 37 to the passage 29, and the flow flows from the central hole 37a of the valve element 37 through the central hole 32a of the movable cylinder 32 and from the communication hole 33 to the cylinder chamber D, and the piston Push up 6. As the piston 6 rises, the second elevating mast 3 rises, and the fork 41 and the first elevating mast 2 together rise at twice the speed of the piston 6 relative to the fixed mast 1, reaching the maximum lifting height. reach At this time, the movable cylinder 32 of the second lift cylinder 7 is pushed by the spring 34 as the piston 6 rises, as shown in FIG. 3B, and rises to a free state.

Next, switch the switching valve 39 from the highest lifting height and
When this is communicated to the tank 40, pressure oil first flows out from the second lift cylinder 7, which has a high oil pressure, and the piston 6 begins to descend. That is, the pressure oil flows out from the cylinder chamber D through the communication hole 33, through the inflow holes 28a, 28b, and 28c, and from the supply/discharge port 27. When the piston 6 reaches the lower end, it collides with the upper cover 31 of the movable cylinder 32, pushing it down against the spring 34, as shown in FIG.
8c is sequentially closed, the pressure oil flows out to the supply/discharge port 27 through the throttle hole 35, creating a hydraulic buffer state and causing the piston 6 to descend extremely gently.
Therefore, even if it comes into contact with the cylinder cap at the lower end, almost no impact noise is generated. At this time, since the cylinder chamber D and the central hole 32a of the movable cylinder 32 are always communicated through the communication hole 33, there is almost no pressure difference between them, and the piston 6 and the movable cylinder 32 lower together.

When the piston 6 of the second lift cylinder 7 reaches the lowering end, the pressure oil in the first lift cylinder 5, which has the next lowest oil pressure, is discharged, and the piston 4 begins to descend. When the piston 4 descends from the rising end, the upper surface 4a of the piston 4 and the cap 1 due to its own weight.
3, a pressure difference is generated between the lower chamber A and the upper chamber B, and this pressure difference pushes up the valve 18 and moves it from the lower chamber A to the upper chamber B. Pressure oil suddenly flows into the piston 4, and as shown in FIG.

In this way, when the masts 2 and 3 are raised, the first shock absorber 10 of the first lift cylinder 5 acts to smoothly raise the elevating masts 2 and 3, and when the masts are lowered, the second lift cylinder The second shock absorber 11 of No. 7 acts to smoothly lower the elevating masts 2 and 3 one after another.

As is clear from the above description, the present invention includes a cylinder cap that is fixed to the upper end of a lift cylinder containing a lifting piston and has a sliding portion for the piston rod, and a lower chamber on the lower side of the piston and an upper chamber on the upper side of the piston. an L-shaped communication hole bored in the piston rod to communicate with the upper chamber, and a vertical hole drilled in the piston separately from the communication hole to communicate the upper chamber with the lower chamber; The chamber side outlet is formed at a position slightly before the rising end of the piston and recessed into the sliding part, and the vertical hole is equipped with a valve that closes the hole when the piston rises and opens when the piston falls. It is.

Therefore, according to the present invention, a hydraulic buffer state is created just before the rising end of the piston, so that the piston can be raised very slowly, and the occurrence of impact noise when the piston abuts against the cylinder cap is prevented. In addition, when the piston descends from the rising end, the vertical hole opens due to a slight pressure difference between the upper and lower chambers, so that it is possible to prevent the loaded object from being damaged by impact. Due to the rapid inflow of pressure oil, the piston can quickly begin to descend and reach a constant descending speed, which is an excellent effect.

[Brief description of the drawings]

Fig. 1 is a schematic side view showing an embodiment of the present invention, Fig. 2a is a longitudinal cross-sectional view showing the operating state of the first shock absorber at the piston rising end, and Fig. 2b is a schematic side view showing the first shock absorber when the piston is rising. Fig. 2c is a vertical sectional view showing the operating state of the piston just before its rising end, Fig. 2c is a longitudinal sectional view showing the operating state of the piston when it is lowered, and Fig. 3a is the retracted state of the movable cylinder of the second shock absorber. Fig. 3b
FIG. 2 is a longitudinal cross-sectional view showing the movable cylinder in a free state. 4... Piston, 5... First lift cylinder,
6... Piston, 7... Second lift cylinder, 8
... Hydraulic pump, 9 ... Supply and discharge pipe, 10 ... First shock absorber, 11 ... Second shock absorber, 12 ... Sliding part, 13 ... Cylinder cap, 14 ... Piston rod, 15 ... Communication Hole, 16...Vertical hole, 17
...Upper chamber side exit, 18...Bentko, A...Lower chamber, B
…….

Claims (1)

[Scope of utility model registration request] a cylinder cap fixed to the upper end of a lift cylinder containing a lifting piston and having a sliding portion for the piston rod; and an L-shaped hole bored in the piston rod to communicate the lower chamber on the lower side of the piston to the upper chamber on the upper side of the piston. The piston includes a communicating hole and a vertical hole that is bored in the piston so as to communicate the upper chamber and the lower chamber separately from the communicating hole, and the upper chamber side outlet of the communicating hole is slightly before the rising end of the piston. A shock absorber for a lift cylinder, characterized in that a valve element is formed in the vertical hole so as to be recessed into the sliding part, and the valve element is interposed in the vertical hole so as to close the hole when the piston is ascending and open when the piston is descending.