JPH02175100A - Die spring - Google Patents

Abstract

PURPOSE:To suppress a leakage from a sliding part in a small quantity by providing a liquid chamber filled with a liquid in the inside of a cylinder partitioned by a bellows, and providing an air chamber in which compressed gas exceeding the atmospheric pressure is filled on the side where a sealing means is not provided. CONSTITUTION:Gas in an air chamber 65 is partitioned from oil in a liquid chamber 60 by a metallic bellows 45. In the air chamber 65, a sliding part which communicates with the atmospheric side does not exist, therefore, even if a reciprocating motion of a rod 22 is repeated at a high speed, it does not occur that gas in the air chamber 65 escapes through the sliding part of the rod 22. A die spring 20 is provided with a self-sealing means for confining oil in the inside surface of a bellows body 46, when a deflection of the bellows 45 exceeds a prescribed stroke. By this oil, the bellows body 46 is supported equally from the inside surface side, it is prevented that the bellows body 46 is bent excessively, and the set load is maintained in the same state for a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a gas-filled die spring used in a press machine or the like.

[Prior Art] There are various types of press working, and for example, taking the well-known deep drawing as an example, pressing is performed through steps a to e as shown in FIG. That is, in step a, 1A
N (blank) 1 is placed on a die 2, and a creasing pad 3 and a punch 4 are arranged on the upper surface side of the die 2 in the drawing. In the process, as the wrinkle presser pad 3 descends,
The peripheral edge of the blank plate 1 is pressed. Punch 4 in process C
By descending, the product 1' is squeezed to the desired depth.
is ignored. Thereafter, the pad 3 and the punch 4 are raised in step d, and the product 1' is taken out from the die 2 by the knockout member 5 in step e.

If the load applied to the wrinkle pressing pad 3 is too weak, wrinkles will occur in the processed product 1'. On the other hand, if the load is too strong,
Since defects such as breakage of the blank plate 1 occur during processing, it is necessary to apply an appropriate wrinkle pressing force to obtain a perfect product 1'.

As a mechanism for generating this wrinkle-pressing force, large-scale press machines are known to use hydraulic pressure to generate the wrinkle-pressing force, such as opposed hydraulic presses, but in normal press processing, a die spring is used. It is being said. A coil spring is generally used as the die spring, or if a particularly heavy load is required, an elastic block made of hard urethane or the like may be used. However, it is practically impossible to use hard urethane with a small deflection stroke, especially in a press machine with a large processing stroke such as deep drawing. Furthermore, when a coiled spring is used, there are drawbacks such as increased dimensions. In addition, in the case of both hard urethane and coiled springs, the spring constant becomes large, and the wrinkle holding force during press forming inevitably changes greatly, so there is a high possibility of causing prime number 1 breakage. .

In order to solve these drawbacks of the conventional die spring, a gas spring type die spring 6 illustrated in FIG. 4 is provided. This die spring 6 has a cylinder 7 filled with high-pressure nitrogen gas of several tens of atmospheres or more, and a rod 8 movably inserted into the cylinder 7. The pressure of the gas within the cylinder 7 acts in a direction to push out the rod 8. A seal portion 9 is provided at the sliding portion between the cylinder 7 and the rod 8.

In this gas spring type die spring 6, the wrinkle pressing force at the initial stage of press working can be set to a value according to the gas filling pressure inside the cylinder 7, and the spring constant can be increased by increasing the internal volume of the cylinder 7. It is possible to set it low.

Therefore, compared to the case where a coiled spring or the like is used, there is an advantage that the change in the wrinkle pressing force during pressing can be reduced.

[Problems to be Solved by the Invention] However, in the case of the die spring 6 shown in FIG. It is inevitable that gas will leak from this seal portion 9. Therefore, there is a drawback that the wrinkle pressing force (set load) decreases in a relatively short period of time.

Gases have lower viscosity than liquids, so it is more difficult to seal gases than liquids. Particularly, when the rod 8 is reciprocated at one speed as in the case of the die spring 6 and high pressure gas is sealed inside the cylinder 7, the gas inevitably leaks from the general seal portion 9.

Therefore, by providing a free piston 10 inside the cylinder 7 as shown in FIG. 5, the inside of the cylinder 7 is partitioned into an air chamber 11 and a liquid chamber 12, and the seal portion 9 is located on the liquid chamber 12 side. As shown in FIG.
It has been considered to partition the liquid chamber 12 and position the seal portion 9 on the liquid chamber 12 side. For example, an elastic polymer such as urethane elastomer is used as the material for the material [;IJM, 13]. According to these structures, since the seal portion 9 only needs to seal liquid, the seal should be more effective than when sealing gas.

However, these methods also have room for improvement in the following points.

That is, in the die spring shown in FIG. 5, the high-pressure gas in the air chamber 11 gradually melts into the well in the liquid chamber 12 through the seal portion 14 provided at the sliding portion of the free piston 10. Furthermore, the gas that has entered the liquid chamber 12 flows out of the cylinder 7 through the seal portion 9. Therefore, the gas in the air chamber 11 will eventually escape to the atmosphere.

On the other hand, in the case of the die spring shown in FIG.
The high-pressure gas in the chamber 1 passes through the partition membrane 13 made of an elastic polymer and gradually dissolves into the oil in the liquid chamber 12, and the gas that dissolves in the chamber 12 eventually enters the atmosphere through the seal part 9. I run away to

Therefore, an object of the present invention is to provide a die spring that can completely prevent the gas inside the cylinder from escaping into the atmosphere and has a long life.

[Means for Solving the Problems] The die spring of the present invention developed to achieve the above object includes a hollow cylinder, a rod inserted into the cylinder so as to be movable in the axial direction, and a die spring with respect to the cylinder. It has a sealing means arranged on the inner periphery of the part where the rod penetrates and seals the sliding part with respect to the rod, and a metal bellows body housed inside the cylinder and expandable and retractable in the axial direction of the cylinder. a liquid chamber filled with liquid on the side where the sealing means is provided of the space inside the cylinder partitioned by the bellows, and a space inside the cylinder partitioned by the bellows that is sealed. An air chamber is provided on the side where the means is not provided and is filled with gas at a pressure equal to or higher than atmospheric pressure.

[Operation] The pressure of the gas sealed in the air chamber in the cylinder acts on the liquid in the liquid chamber via the metal bellows, so the rod receives a load in the direction of being pushed out of the cylinder. This load is used to straighten the wrinkles of the blank plate during press working. When the rod moves in the direction of being pushed into the cylinder due to the descent of the die during press working, the air chamber is further compressed as the amount of pushing of the rod into the cylinder increases, causing the bellows to move in the axial direction. bend to This increases the repulsive force of the gas within the air chamber. When the mold is in the oven,
When the rod moves in the direction of removal from the cylinder, the volume of the air chamber expands as the rod moves, causing the bellows to bend in the opposite direction.

Since the gas pressure in the air chamber also acts on the liquid chamber, the gas pressure acts on the sliding portion between the cylinder and the rod via the liquid. Since the sealing means provided on this sliding portion only needs to seal the liquid in the liquid chamber, it is possible to seal more reliably than when directly sealing high pressure gas. Since the air chamber and liquid chamber are completely separated by a metal bellows, there is no possibility of high-pressure gas in the air chamber leaking into the liquid in the liquid chamber.

[Example] An example of the present invention will be described below with reference to FIGS. 1 and 2. The die spring shown in Figure 1 is 2
0 is equipped with a hollow cylinder 21, a mouth, and a throat 22. Inside the cylinder 21, an inner cylinder part 23 is provided concentrically with the cylinder 21. A communication port 25 is opened in an end member 24 located at the lower end of the inner cylinder portion 23 in the drawing.

The rod 22 is inserted into the cylinder 21 so as to be movable in its axial direction, and a piston-shaped portion 30 is provided at the inner end of the mouth/rad 22 .

This piston portion 30 comes into sliding contact with the inner circumferential surface of the inner cylinder portion 23 via a sliding bearing 31 .

At the illustrated upper end of the cylinder 21, a sliding bearing 34 and a sealing means 35 for sealing the sliding portion with respect to the rod 22 are provided on the inner circumference of the portion through which the mouth and the rod 22 pass. This sealing means 35 includes a high pressure sealing member 36
, a low-pressure seal part 37 provided on the lower pressure side, that is, the atmosphere side, than this seal part month 36, and a dust seal part 37.
It consists of 8 etc. The rebound stopper 39 is made of an elastic material such as urethane elastomer. This stopper 3
9 defines the end of the stroke in this direction when the rod 22 moves in the direction in which it protrudes from the cylinder 21 .

A metal bellows 45 is housed inside the cylinder 21 . The bellows 45 includes a bellows body 46 that is expandable and retractable in the axial direction of the cylinder 21, and a bellows cap 47 that closes one end of the bellows body 46. The bellows body 46 has a thickness of 0.1 to 0.3.
It is made of a stainless steel plate of around 1.2 mm in diameter. However, metals other than stainless steel may be used. Bellows body 46
The other end 48 is fixed to an end wall 49 of the cylinder 21.

A valve body 50 is provided on the inner surface of the bellows cap 47. The valve body 50 is made of a rubber-like elastic material such as urethane elastomer or silicone resin, and faces the annular valve seat 51 formed around the above-mentioned flow port 25. These valve body 50 and valve seat 51 are connected to the inner cylindrical portion 23 when the bellows 45 is contracted by a predetermined amount or more, as will be described later.
A self-sealing means 52 is configured between the bellows body 46 and the bellows body 46 to confine the ura.

A bellows guide member 5 is attached to the outer periphery of the bellows body 46.
5.56 is provided. These guide members 55.
56 is for securing a predetermined clearance between the bellows body 46 and the cylinder 21, and for ensuring a predetermined clearance between the bellows body 46 and the cylinder 21.
It is used to reduce the It1 dynamic resistance between the cylinder 21 and the cylinder 21.

Of the internal space of the cylinder 21 partitioned by the bellows 45, the side where the sealing means 35 is provided;
That is, a liquid chamber 60 is defined on the inner surface side of the bellows 45. This liquid chamber 60 is filled with oil as an example of liquid. A hole 63 that can be closed by a ball 61 and a screw 62 is provided in the upper part of the liquid chamber 60 .

An air chamber 65 is provided in the internal space of the cylinder 21 on the side where the sealing means 35 is not provided, that is, on the side defined by the outer surface of the bellows 45 and the inner wall of the cylinder 21. This air chamber 65 is filled with an inert gas such as nitrogen. The pressure at which the gas is sealed is determined depending on the wrinkle pressing force required for the die spring 20, and the gas is sealed at a high pressure of, for example, several tens of kg/cd or more. The pressure of this gas acts in the direction of contracting the bellows 45, that is, in the direction of pushing the rod 22 out of the cylinder 21. A gas supply port 67 provided in the end wall 66 of the cylinder 21 can be closed with a plug 68 . In addition,
An air chamber 6 is placed at an appropriate position in the die spring 20 of this embodiment.
A safety valve is provided that opens when the pressure at No. 5 rises above a predetermined value.

The process of supplying gas to the air chamber 65 is as follows.

When supplying gas, the liquid chamber 60 is filled in advance. As shown in FIG. 2, a pressurized gas supply source 70 is connected to the gas 0 (supply port 67). A valve 71 is located between the supply source 70 and the supply port 67. Gas is supplied into the chamber 65. As the amount of gas in the air chamber 65 increases, the bellows body 46 contracts in the axial direction. Therefore, the oil in the liquid chamber 60 is discharged to the outside through the hole 63. be done.

When the bellows 45 is bent to a predetermined stroke, the valve body 50 of the self-sealing means 52 comes into close contact with the valve seat 51, thereby closing the flow port 25. For this reason, bellows body 4
6 no longer bends in the axial direction, and the inner cylinder part 2
Gap 7 between the outer peripheral surface of 3 and the inner surface of the bellows body 46
Oil is trapped in 2.

Since gas continues to be supplied to the air chamber 65 even after the valve body 50 comes into close contact with the valve seat 51, the pressure in the air chamber 65 gradually increases. Oil is substantially incompressible. Therefore, the entire inner surface of the bellows body 46 is evenly supported by the oil trapped in the gap 72. Therefore, even if gas is continuously supplied at high pressure, there is no risk that the bellows 45 will bend excessively. When the pressure in the air chamber 65 reaches a predetermined value, the gas supply is stopped and the supply port 67 is closed to the plug 68.
blocked by.

The die spring 20, whose air chamber 65 is filled with gas at a predetermined pressure as described above, is assembled at a position where it can suppress a wrinkle pressing pad of a press machine (not shown). Then, during pressing, the rod 22 moves in the direction in which it is pushed into the cylinder 21. At this time, the amount of insertion of the rod 22 into the cylinder 21 increases. Therefore, the air chamber 65 is compressed by the amount that the rod 22 has moved, the bellows 45 is expanded, and the pressure in the air chamber 65 is increased. When the press is finished and the die is opened, the rod 22 is moved against the cylinder 21.
move in the direction in which it protrudes. At this time, the volume of the air chamber 65 increases by the amount that the rod 22 has moved, so the bellows 45 returns to its original deflection. In this way, the bellows 45 repeatedly expands and contracts as the rod 22 moves relative to the cylinder 21, and oil flows in and out of the flow port 25 as the bellows 45 expands and contracts.

The gas in the air chamber 65 is transferred to the liquid chamber 6 by the metal bellows 45.
It is separated from Ura within 0. Even if the metal bellows 45 is thin, it exhibits extremely good gas barrier properties. Therefore, the gas in the air chamber 65 does not dissolve into the oil in the liquid chamber 60. Since the air chamber 65 does not have a sliding part that communicates with the atmosphere, even if the rod 22 reciprocates repeatedly at high speed, the gas in the air chamber 65 will not flow directly to the atmosphere through the sliding part of the rod 22. It's impossible to escape.

The sealing means 35 for sealing the sliding portion of the rod 22 is a liquid chamber 65.
Since the sealing means 35 is provided on the side, it is sufficient if the sealing means 35 can seal the ura. It is relatively easy to seal ura, which has a high viscosity compared to gas.

A gas supply port 67 is present in the air chamber 65, but since this supply port 67 is not a location where sliding occurs, it can be easily sealed with a fixed sealing member 73 such as an ordinary O-ring. In order to further improve the sealing performance of the supply port 67, it is also effective to put a small amount of oil inside the air chamber 65.

In addition, the die spring 20 of this embodiment has the bellows body 4 when the deflection of the bellows 45 exceeds a predetermined stroke.
6 is provided with a self-sealing means 52 for trapping oil on the inner surface side. Therefore, even if the oil in the liquid chamber 60 escapes for some reason and the pressure of high-pressure gas acts in a direction that bends the bellows 50, the bellows will close until the valve body 50 is in close contact with the valve seat 51. 45 is bent, oil is trapped in the gap 72. This oil enables the bellows body 46 to be evenly supported from the inner surface side. Therefore, excessive bending of the bellows body 46 can be prevented, which is effective in protecting the bellows 45.

[Effects of the Invention] According to the present invention, the gas in the air chamber is prevented from escaping to the atmosphere side through the sliding portion between the cylinder and the rod, so that a so-called maintenance-free gas spring type die spring can be obtained. And since the sliding part between the cylinder and the rod only needs to be sealed with liquid, which is easier to seal than when sealing with gas, leakage from this sliding part can be kept to an extremely low level. The spring constant and set load can be maintained the same over a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of a die spring showing an embodiment of the present invention, Fig. 2 is a sectional view showing the die spring shown in Fig. 1 when gas is supplied, and Fig. 3 is a deep drawing. The process explanatory drawings and FIGS. 4 to 6 are longitudinal cross-sectional views showing conventional die springs, respectively. 20... Die spring, 21... Cylinder, 22
... Rod, 25 ... Communication port, 35 ... Sealing means, 45 ... Metal bellows, 46 ... Bellows body, 50 ... Valve body, 51 ... Valve seat, 52 ...・Self-sealing means, 60...liquid chamber, 65...air chamber, 67...
・Gas (JLI supply. Applicant's representative Patent attorney Takehiko Suzue Figure 5 Figure 6 Figure 1, Display of the case Japanese Patent Application No. 63-326177 2, Name of the invention Die Spring 3, Relationship with the person making the amendment case) Patent applicant (464) NHK Spring Co., Ltd. 4, Agent 3-7-2 Kasumigaseki, Chiyoda-ku, Tokyo 100 Telephone 03 (502) 3181 (Main representative) (5847) Patent attorney Takehiko Suzue 5, Voluntary amendment 7゜Amendment details (1) In the specification, from page 13, line 12 to line 18, the statement ``The bellows 45 is closed in a predetermined position.'' has been corrected to the following sentence. The gas is sealed in two stages. That is, the gas is initially supplied to the air chamber 65 at low pressure. When the bellows 45 is bent to a predetermined stroke, the valve body 50 of the self-sealing means 52 is closed. The flow port 25 is closed by coming into close contact with the valve seat 51. Therefore, the bellows body 4
6 can no longer be bent in the axial direction. In this way, the valve body 50
After the valve seat 51 comes into close contact with the valve seat 51, the hole 63 is closed by the ball 61 and the screw 62, thereby trapping oil in the gap 72 between the outer circumferential surface of the inner cylindrical portion 23 and the inner surface of the bellows body 46. Thereafter, high pressure gas is supplied to the air chamber 65. (2) In the drawings, Figure 2 will be corrected as shown in the attached sheet.

Claims (2)

[Claims] (1) A hollow cylinder, a rod inserted into the cylinder so as to be movable in the axial direction, and a sealing member placed on the inner periphery of the part where the rod penetrates the cylinder to seal the sliding part with respect to the rod. a sealing means; a bellows having a metal bellows body which is housed inside the cylinder and is expandable and retractable in the axial direction of the cylinder; and a space inside the cylinder partitioned by the bellows, in which the sealing means is provided. A liquid chamber is filled with liquid on the side where the bellows is installed, and a gas chamber is filled with gas at a pressure higher than atmospheric pressure on the side where the sealing means is not provided, of the space inside the cylinder partitioned by the bellows. A die spring characterized by being equipped with a chamber and. (2) Inside the cylinder, there is a communication port through which the liquid in the liquid chamber enters and exits when the bellows expands and contracts, and furthermore, the cylinder has a flow port that allows the bellows to bend in the axial direction beyond a predetermined stroke. Self-sealing means is provided that prevents the bellows from further deflecting when the end surfaces of the bellows abut against each other in the open state, and also confines a portion of the liquid between the bellows body and the bellows body by blocking the communication port. The die spring according to claim 1.