JPH0120394Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a hydraulic jack, and more particularly to a portable hydraulic jack that can also cause the ram to move back by hydraulic action.

[Prior art]

A conventional portable hydraulic jack is shown in Figs. 1-3. This jack has cylinder 12 on base 10.
The ram 14 is inserted into the ram 14 in an upright manner so as to be removable and removable, and the ram 14 is moved upward by supplying hydraulic oil to a hydraulic chamber provided on the lower surface of the ram 14 to perform a jack up action. The hydraulic oil is stored in a tank chamber 2 formed by a casing 16 surrounding the outer periphery of the cylinder 12 and a top nut 18 at the upper end.
Contained within 0. The hydraulic oil in the tank chamber 20 is
It is sent from a suction passage 22 drilled in the base 10 and opening into the tank chamber 20, through a suction valve 24, to a supply passage 26 opening into a hydraulic chamber at the bottom of the cylinder 12, thereby moving the ram 14 upward. Hydraulic oil is supplied by pump means 28 interposed between the passages 22 and 26. The pump means 28 includes a pump housing 32 in which a plunger 30 is inserted into a base 10, and the passages 22 and 26 are commonly opened in the housing 32. The plunger 30 is reciprocated by a lever 34 and works together with the suction valve 24 to perform a pumping action. On the other hand, when the jack-up work is completed, it is necessary to drain the hydraulic fluid in the hydraulic chamber and lower the ram 14, which is in an extended state. For this reason, the passages 22, 26
Separately, a discharge passage 36 connecting the hydraulic chamber and the tank chamber 20 is provided. This passage 36 has a shutoff valve 3.
8 is installed and is opened only when the ram is lowered.

However, in the conventional hydraulic jack described above, when the ram 14 is lowered, when the ram 14 is under load, the hydraulic fluid in the hydraulic chamber can be returned to the tank chamber 20 by the action of the load, but when the ram 14 is under load, the hydraulic oil in the hydraulic chamber can be returned to the tank chamber 20. Sometimes there is a problem that the ram 14 cannot be lowered. Similar problems also occur when the jack is used horizontally. Therefore, conventionally,
When retracting the jack, the receiver at the tip of the ram had to be held down by hand, resulting in extremely poor workability. Particularly large nominal load (50ton)
(above) With jacks, the falling resistance becomes large due to the sliding resistance of the packing, resistance to pressure loss in the pipeline, etc., and it is not easy to shrink the jacks manually.

Although it is conceivable to provide a return device such as a spring on the outside of the jack, there are problems such as limitations on stroke length and fatigue deterioration, and there are disadvantages in that sufficient effects cannot be achieved.

[Purpose of invention]

The present invention has focused on the above-mentioned conventional problems, and an object of the present invention is to provide a hydraulic jack that has a simple structure and can lower the ram even under no load by hydraulic action.

[Structure of the idea]

In order to achieve the above object, the hydraulic jack according to the present invention inserts a ram into a cylinder set upright on a base, and extends the ram by supplying hydraulic oil to a first hydraulic chamber defined by the upper surface of the ram. In the hydraulic jack, a second hydraulic chamber having a smaller cross-sectional area than the first hydraulic chamber is formed by using an upper portion of the sliding portion on the insertion end side of the ram as a small diameter portion, and in this second hydraulic chamber,
An oil feed passage is communicated with the first hydraulic chamber via a low pressure relief valve, and an oil drain passage is formed in the first hydraulic chamber via a cutoff valve.

With the above configuration, when the shutoff valve is closed and hydraulic oil is sent, it is simultaneously supplied to both the first and second hydraulic chambers, and hydraulic pressure acts based on the difference in cross-sectional area between the two hydraulic chambers, causing the ram to extend. is planned. Conversely, when the shutoff valve is opened and oil is pumped, the pressure in the first hydraulic chamber becomes low, the relief valve closes the oil passage to the first hydraulic chamber, and only the oil is supplied to the second hydraulic chamber. Supplied. Since this supplied hydraulic oil acts in a direction to push down the ram, the ram is lowered while discharging the hydraulic oil in the first hydraulic chamber into the tank.

[Example of idea]

Hereinafter, specific embodiments of the hydraulic jack according to the present invention will be described in detail with reference to the drawings.

FIG. 4 is a hydraulic circuit diagram of the hydraulic jack according to this embodiment, and FIGS. 5 to 8 are actual structural diagrams.

As shown in the figure, this hydraulic jack has a cylinder 12 erected on a base 10, and a tank chamber 20 is formed around the outer periphery of the cylinder 12 by two casings 16 and a snap nut 18. Said cylinder 1
An improved ram 40 is removably inserted into 2. The ram 40 has an outer circumferential surface of a sliding portion 42 provided at the insertion tip that is in close contact with the inner wall surface of the cylinder 12 to partition the inside, and the lower surface of the ram 40 and the base 1
0, a first hydraulic chamber 44 is formed between the two. Further, an upper portion of the sliding portion 42 is a small diameter portion 46 having an outer diameter smaller than the inner diameter of the cylinder 12, and forms a second hydraulic chamber 48 between the sliding portion 42 and the cylinder 12. Therefore, when hydraulic oil is supplied to the first hydraulic chamber 44, the lower surface of the ram 40 becomes a pressure receiving surface, and the ram 40
When the oil is expanded and supplied to the second hydraulic chamber 48, the stepped portion of the ram 40 becomes a pressure receiving surface and the ram 40 is lowered.

Further, a circular tube 50 concentric with the cylinder 12 is located at a position corresponding to the center axis of the ram 40 on the base 10.
It is erected in The circular tube 50 has a height similar to that of the cylinder 12 and has an open upper end. Corresponding to the circular tube 50, a circular tube insertion hole 52 with an open lower end is formed in the ram 40. The circular tube 50 has a slightly smaller diameter than the circular tube insertion hole 52 to form a gap 54 between the wall surfaces, and this gap 54 communicates with the second hydraulic chamber 48 through a communication hole 56 bored in the side wall of the small diameter portion 46 of the ram 40. ing. Further, it is separated from the first hydraulic chamber 44 by the inner wall surface of the sliding portion 42 being in close contact with the outer wall surface of the circular tube 50 in a slidable state.

For this reason, although the ram 40 moves up and down in the space between the cylinder 12 and the circular pipe 50, the cross-sectional area of the first hydraulic chamber 44 is formed larger than that of the second hydraulic chamber 48. There is. That is, the pressure receiving part of the first hydraulic chamber 44 is connected to the cylinder 12 and the circular pipe 50.
The pressure receiving portion of the second hydraulic chamber 48 is the stepped portion surface of the sliding portion 42 surrounded by the cylinder 12 and the ram small diameter portion 46.
Therefore, when hydraulic oil at a constant pressure is simultaneously supplied to both hydraulic chambers 44 and 48, an action is exerted on the ram 40 based on the difference in cross-sectional area (pressure-receiving area).

Next, the hydraulic oil supply and discharge passages for the first and second hydraulic chambers 44 and 48 are configured as follows. That is, as shown in FIG. 8, the base 10 has a suction passage 22 that opens into the tank chamber 20 and a first hydraulic chamber 44.
a first supply passage 58 that is open to the passages 22 and 58, and a first supply passage 58 that is located between the passages 22 and 58 and communicates therewith, and that opens in the circular pipe 50 and communicates with the second hydraulic chamber 48 through a gap 54 and a communication hole 56; Two supply passages 60 are each drilled therein. first and second supply passages 58,
60 are connected to each other, so that the first hydraulic chamber 4
4 and the second hydraulic chamber 48.
The suction passage 22 is provided with a suction valve 24 and a discharge valve 62, each of which is a pair of one-way valves.
A pump means 28 is provided between the tank chamber 20 and the tank chamber 20 to supply the hydraulic oil to the connecting passage between the first and second supply passages 58 and 60.

Here, a low pressure relief valve 64 is provided in one of the first supply passages 58 that connects the first and second hydraulic chambers 44 and 48. The relief valve 64 has a poppet 68 pressed against the valve seat by a set pressure of a spring 66, which isolates the first and second supply passages 58, 60 from each other. Then, when the pressure on the second supply passage 60 side becomes equal to or higher than the set pressure, both supply passages 5
8 and 60 are communicated. Further, the poppet 68 of the relief valve 64 supports the valve body of the discharge valve 62 by a spring, and when the discharge valve 62 is opened by pump pressure, the valve body contacts and presses the poppet 68. The relief valve 64 is also formed to be opened. In addition, the relief valve 6
The set pressure of 4 is the jack lowering force, that is, the ram 4
The pressure is set to overcome the descending force of 0.

On the other hand, the base 10 has the passages 22, 58,
A discharge passage 70 is provided separately from the discharge passage 60 . This passage 70 connects the tank chamber 20 and the first hydraulic chamber 44, and is provided with a shutoff valve 72 as a pressure relief valve. This shutoff valve 72 is manually operated, and is opened and closed by operating a handle 74 at the rear end.

The pump means 28 has a pump housing 32 erected on the base 10, and a plunger 3 is attached to the pump housing 32.
A lever is attached to a lever socket 76 connected to the plunger 30 to cause the plunger 30 to reciprocate and perform a pumping action. Lever socket 76 is connected to bracket 80 on base 10 by link 78. Further, a screw is carved into the upper end of the ram 40 so that a receiver that abuts against a load can be attached thereto.

The hydraulic jack configured as described above operates as follows.

First, when extending the jack, shut off valve 7.
Close 2 and operate the pump. With this operation, the suction valve 24 and the discharge valve 62 are opened, and the second supply passage 60 is opened.
from the circular pipe 50, the gap 54, and the communication hole 56 to the second
Hydraulic oil flows into the hydraulic chamber 48, but since the shutoff valve 72 is closed, the pressure on the second supply passage 60 side becomes higher than the set pressure, opening the relief valve 64, and simultaneously causing the first supply passage 58 to operate. Supply oil. The first and second hydraulic chambers 4 pass through both passages 58 and 60.
The hydraulic oil introduced into both chambers 44, 48
Based on the difference in cross-sectional area, the hydraulic fluid flows into the first hydraulic chamber 44 and causes the ram 40 to extend. Therefore, Ram 4
It is possible to carry out the jacking action while supporting the load with the mounting bracket attached to the tip of the 0.

Next, when lowering the jack, shut off valve 7
2 and operate the pump. Shutoff valve 72
When the first hydraulic chamber 44 is opened, the first hydraulic chamber 44 is opened to the tank chamber 20.
The pressure in the second hydraulic chamber 48 is reduced, the pressure in the second supply passage 60 becomes lower than the set pressure of the relief valve 64, and the first supply passage 58 is closed. The hydraulic oil pumped under pressure is supplied only to the second hydraulic chamber 48, and while the ram 40 is lowered, the oil in the first hydraulic chamber 44 is returned to the tank chamber 20, and the ram 40
can be reduced.

As described above, according to the hydraulic jack according to the present embodiment, the ram 40 is extended and retracted by the operation of the pump means 28, and the jack can be easily contracted by hydraulic action even in a no-load state. Further, there is no need to provide an external return device even when the jack is pushed sideways or used upside down.
Further, even if the jack has a large nominal load, it is possible to easily lower the jack. Furthermore, since it is not necessary to provide an external return device, the device can be made smaller and its external shape can be simplified.

[Effect of idea]

As described above, the hydraulic jack according to the present invention has an excellent effect in that the ram can also be lowered by hydraulic action.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a conventional hydraulic jack, Fig. 2 is a side view of the same, Fig. 3 is a sectional view of the same, Fig. 4 is a hydraulic circuit diagram of the hydraulic jack according to this embodiment, and Fig. 5 is a hydraulic jack of the same. The top view of the jacket, Figure 6 is the same side view, and Figure 7 is the same side view.
The figure is a sectional view of the same, and FIG. 8 is a layout diagram of the hydraulic passage. 10...Base, 12...Cylinder, 20...
Tank chamber, 22... Suction passage, 24... Suction valve,
28... Pump means, 40... Ram, 44, 48
... Hydraulic chamber, 58, 60 ... Supply passage, 64 ...
Low pressure relief valve, 70...Discharge passage, 72...Shutoff valve.

Claims (1)

[Scope of utility model registration request] Insert the ram into the cylinder set up on the base,
In a hydraulic jack that extends the ram by supplying hydraulic oil to a first hydraulic chamber defined by the upper surface of the ram, an upper part of the sliding part on the insertion end side of the ram is defined as a small diameter part smaller than the first hydraulic chamber. The second cross-sectional area
A hydraulic chamber is formed, and an oil feed passage is communicated with the second hydraulic chamber and the first hydraulic chamber via a low pressure relief valve, and an oil drain passage is communicated with the first hydraulic chamber via a cutoff valve. A hydraulic jack characterized by forming.