JPS6239033Y2 - - Google Patents

Description

[Detailed explanation of the invention] The invention relates to a multi-stage jack.
This invention relates to a multi-stage jack in which a plurality of rods are inserted in multiple stages and each rod is sequentially expanded or compressed in multiple stages using a pressure medium.

As a conventional multi-stage jack of this kind, for example, the one shown in FIGS. 1 and 2 disclosed in Japanese Patent Publication No. 53-45879 is known.

In the multi-stage jack shown in FIG. 1, a second cylinder 2 is slidably inserted into a cylinder 1.
A third cylinder 3 is slidably inserted into the third cylinder 3, and a piston 4 is slidably inserted into the third cylinder 3, and when pressure oil is introduced into the chamber 5, the second cylinder 2 expands. The pressure oil in the chamber 6 is led to the chamber 7 to extend the third cylinder 3, and at this time, the pressure oil in the chamber 8 is introduced to the chamber 9 to extend the piston 4, and conversely, the pressure oil is introduced into the chamber 11 from the pipe 10. When guided, each cylinder and piston compress. By making the cross-sectional areas of chambers 6 and 7 and chambers 8 and 9 the same, each cylinder and piston can expand and contract at the same speed.

However, the first problem with such a multi-stage jack is that the stroke is small relative to the basic length of the jack because the piping 10 is disposed on the upper end side of the cylinder 3 during the contraction operation.

Also, check valves 1 are installed in the piston 17 of the second cylinder 2 and the piston 18 of the third cylinder 3, respectively.
9 and 20 are provided so as to be openable and closable, while the first cylinder 1
Valves 21 and 22 are provided at the upper end and the upper end of the piston 4, respectively. When the valves 21 and 22 are opened and the pressure medium is introduced into the chamber 5, this pressure medium flows into the chambers 6 and 9, and the pressure medium flows into the chambers 6 and 9. The air is supplied by valve 21,
22 is opened to the outside. Therefore, when the valves 21 and 22 are closed and the pressure medium is guided into the chamber 5, the pressure medium in the chamber 5 passes through the check valve 19 before reaching the second cylinder 2, which has a large diameter and high sliding resistance. , 20 open and flow into chambers 7 and 9,
There is a possibility that the third cylinder 3 or the piston 4 will be extended first, and even if the jack is extended to the maximum, the second cylinder 2 will only extend halfway and will not reach the desired stroke, and at the time of maximum compression, the third cylinder 3 There is a second problem in that it stops before reaching the lowest position and does not descend to the desired height. This is because, for example, the third cylinder 3 expands first,
When the second cylinder 2 is then extended, the pressure medium in the chamber 7 is already filled, and almost no pressure medium in the chamber 6 is introduced into the chamber 7. On the other hand, when the second cylinder 2 is compressed, the chamber 7 is filled with excess pressure medium and minute 3rd cylinder 3
This is because it will not be possible to descend.

Furthermore, in the jack of FIG. 2, the second cylinder 13 is slidably inserted into the first cylinder 12, the third cylinder 14 is slidably inserted into the second cylinder 13, and the third cylinder 14 is also slidably inserted into the third cylinder 14. piston 1
5 is slidably inserted, and a spring 16 is interposed between the piston 15 and the cylinder 14, the piston 15 is of a spring return type, and the spring 16 is compressed to contract each cylinder. In this case, if the jack is large, the resistance of the seal etc. in the sliding part is large, and the return spring 16 needs to have a large spring constant, and therefore the resistance when the jack is extended is large, and the pressure on the extension side is also large. There is a third problem in that high pressure is required.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a multi-stage jack which can reliably operate each cylinder in sequence in order to overcome the second of the above-mentioned drawbacks.

In order to achieve this objective, the present invention provides a low pressure relief valve in the middle of the passage connecting the oil chamber that acts on the top cylinder and the tank, so that the back pressure set by this relief valve is always applied to the oil chamber. It is characterized by the fact that it appears to be present.

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

A cylinder 31 stands up on a base 30, and a rod 35 is slidably inserted into the cylinder 31 via a piston 32 and seals 33, 34, and a piston 36 and seals 37, 38 are inserted into the first rod 35. A second rod 39 is slidably inserted through the second rod 39, and a piston 40, a seal 41,
A third rod is slidably inserted through 42.

At the upper end of the cylinder 31 is a seal 44 and a bolt 4.
A guide 46 is fixed via 5, and this guide 4
The first rod 35 is in sliding contact with the inner periphery of the rod 6 through seals 47 and 48, and a guide 49 is formed at the upper end of the first rod 35. Rod 39 makes sliding contact,
Similarly, the third rod 43 comes into sliding contact within a guide 52 provided on the second rod 39 via seals 53 and 54.

A liquid chamber 55 is defined between the base 30 of the cylinder 31 and the piston 32 of the first rod.
is connected to the pump P or tank T via a port 56 provided in the cylinder 31.

A chamber 57 is defined between the cylinder 31 and the first rod 35, and the piston rod 3 of the first rod 35
A liquid chamber 58 is defined between the piston rod 36 of the first rod 2 and the second rod 39, and this liquid chamber 58 has the same cross-sectional area as the chamber 57 and communicates with the chamber 57 through a passage 59 provided in the first rod 58. are doing.

There is a chamber 60 between the first rod 35 and the second rod 39.
is formed, while the piston 36 of the second rod 39
A liquid chamber 61 is defined between the second rod 39 and the piston 40 of the third rod 43, and this liquid chamber 61 has the same cross-sectional area as the chamber 60 and communicates with the chamber 60 through a passage 62 provided in the second rod 39. There is.

A chamber 63 is located between the second rod 39 and the third rod 43.
This chamber 63 is connected to a passage 64 provided in the third rod 43 to selectively communicate with the pump P or the tank T.

A space 65 is formed in the center of the third rod 43, and this space 65 communicates with the passage 64 through a passage 66 provided in the third rod 43.

Inside the space 65 are a first pipe 67 and a second pipe 6.
8 and a third pipe 69 are inserted.

The upper end piston 70 of the third pipe 69 has a seal 7
The bracket 72 at the upper end is held by the piston 36 of the second rod 39. That is, the bracket 72 is welded to the third pipe 69, and the outer periphery of the bracket 72 comes into contact with the piston 36 in a freely floating manner through a seal 73 and a gap 74, and by screwing a nut 75 from below, the flange 76 is fixed. The third pipe 69 is hooked onto the piston 36, so that the third pipe 69 stands up while being held in a floating manner by the piston 36, and the inner passage 77 of the third pipe 69 communicates with the liquid chamber 58.

The second pipe 68 is inserted into the third pipe 69, the piston 77 at the upper end is in sliding contact with the third pipe 69 through seals 78, 78, and the bracket 79 at the lower end is inserted into the first rod through a seal 80 and a gap 81. The bracket 79 is connected to the piston 32 of No. 35 in a freely floating manner, and the bracket 79 is held on the piston 32 side by screwing a nut 82 from above.

A passage 88 within the second pipe 68 communicates with the liquid chamber 55 .

The first pipe 67 is inserted into the second pipe 68, the piston 83 at the upper end is in sliding contact with the second pipe 68 via seals 84, 84, and the lower end is screwed into the base 30 side via a screw 85, A seal 86' is also provided between the nut 86 and the nut 86 screwed onto the base 30 from above.
A gap 87 is interposed therebetween, and the gap 87 allows the first pipe 67 to float relative to the base.

The central passage 89 of the first pipe 67 opens to the passage 66 through the space 65 at the upper end, and the lower part of the passage 89 is selectively connected to the pump P or the tank T through the passage 96 provided in the base 30. I'm starting to understand.

By allowing the first pipe 67, second pipe 68, and third pipe 69 to float through the gaps 87, 80, and 74, even if concentricity cannot be achieved due to design errors, they can be easily assembled or operated. This is corrected from time to time to prevent galling of each pipe.

The guide 46 of the cylinder 31 is provided with a passage 90 and an air bleed valve 91, the guide 49 of the first rod 35 is similarly provided with a passage 92 and an air bleed valve 93, and the guide 52 of the second rod 39 is provided with a passage 94.
and an air bleed valve 95 are provided.

Port 56 of cylinder 31 and passage 9 of base 30
6 is selectively connected to a pump P or a tank T via circuits 97, 98 and a switching valve 99, respectively, and a low pressure relief valve 100 is provided between the switching valve 99 and the tank T. Further, a relief valve 101 is provided in parallel with the pump P.

The low pressure relief valve 100 is this relief valve 100.
By constantly maintaining the pressure set in the chamber 63, the first rod 35, second rod 39, and third rod 43 are extended at the same time and at the same speed.

Furthermore, a liquid chamber 55 is provided in the piston 32 of the first rod 35.
A check valve 102 for opening and closing 58 and 58 is provided.
Similarly, the piston 36 of the second rod 39 also has a liquid chamber 5.
A check valve 103 for opening and closing valves 8 and 61 is provided.

Next, we will discuss the operation.

First, when the air bleed valves 91, 93, and 95 are opened and pressure oil is supplied from the port 56, the liquid chamber 55
The air enters the liquid chambers 58, 61 through the check valves 102, 103, and is further led to the chambers 57, 60 through the passages 59, 62. is discharged.

Similarly, when pressure oil is supplied to the passage 96 and introduced into the chamber 63, air is released from the air release valve 95 to the outside.

Regarding the extension operation, when the switching valve 99 is switched to the left position, the port 56 is connected to the pump P.
On the side, a passage 96 is connected to the tank T.

When the pump-side pressure oil is introduced into the liquid chamber 55 through the port 56, the first rod 35 rises and compresses the chamber 57. When the chamber 59 is compressed, the discharged oil flows through the passage 5.
9 to the liquid chamber 58, and the pressure of the liquid chamber 58 causes the second rod 39 to expand. As the second rod 39 expands, the pressure oil in the chamber 60 is guided to the liquid chamber 61 through the passage 62, and the third rod 43 is raised by the pressure oil in the liquid chamber 61. In this case, by making the cross-sectional areas of the chamber 57 and the liquid chamber 58, and the cross-sectional areas of the chamber 60 and the liquid chamber 61 equal, the first, second and third rods are extended simultaneously. When the third rod 43 extends, the pressure oil in the chamber 63 is discharged into the tank T via the passage 64, the passage 66, the space 65, the passage 89 in the first pipe 67, and the passage 96.

By the way, a low-pressure relief valve 100 is interposed in the middle of the discharge passage to the tank, and the pressure set by this relief valve 100 is always applied to the chamber 63 as back pressure. In this case, the second rod 39 and the third rod 43 are connected to the first rod.
Elongation ahead of the rod 35 is prevented.

In addition, the oil discharged from the chamber 63 is drained through a passage 6 provided in the jack.
4. Since it is returned to the tank through the first pipe 67, there is no need to install any external piping that would get in the way.
This allows each rod to extend its desired stroke relative to its basic length without hitting any obstacles.

Also, in order to form the central passage, the first pipe 6
7. The second pipe 68 and the third pipe 69 are connected in a floating manner with a gap at the bottom, so even if the concentricity of the sliding part is poor due to machining errors, this can be corrected automatically. It is possible.

Next, for compression operation, the switching valve 99 is switched to the right position. At this time, the pressure oil is in the passage 96.
furthermore, passage 89 - space 65 - passage 66 -
The third rod 43 is guided into the chamber 63 through the passage 64.
At the same time, the pressure oil in the liquid chamber 61 is guided to the chamber 60 via the passage 62 to lower the second rod 39, and furthermore, the pressure oil in the liquid chamber 58 is introduced to the chamber 5 through the passage 59.
7, the first rod 35 descends. As the first rod 35 descends, the pressure oil in the liquid chamber 55 is returned to the tank T through the port 56.

In the above case, each rod is lowered simultaneously using pressure oil, so there is no need for a return spring, and because the resistance when the jack is extended is small, there is no need for such a high pressure on the extension side.

As described above, the present invention provides a low pressure relief valve in the middle of the passage that connects the chamber that acts on the third rod with the tank during expansion, so that back pressure is always built up in the chamber, and the second rod , the third rod is the first
This prevents the rod from elongating before the rod, and ensures sequential operation.

[Brief explanation of the drawing]

1 and 2 are longitudinal sectional front views of a conventional multi-stage jack, FIG. 3 is a partial longitudinal sectional front view of a multi-stage jack according to an embodiment of the present invention, and FIG. It is an enlarged sectional view. 31... Cylinder, 35, 39, 43... Rod, 63... Oil chamber, 100... Low pressure relief valve,
T...Tank.

Claims (1)

[Scope of utility model registration request] In a jack in which multiple rods are inserted in multiple stages in a cylinder, a low-pressure relief valve is installed in the middle of the passage connecting the tank and the oil chamber that acts on the uppermost rod, and the low-pressure relief valve is set when the rod is extended. A multi-stage jack in which back pressure is applied to the oil chamber.