CN112157161B

CN112157161B - Inner high-pressure forming push head

Info

Publication number: CN112157161B
Application number: CN202010992589.3A
Authority: CN
Inventors: 王立虎; 王保平; 管志光; 孙芹; 李作丽; 段益东; 高禹; 杜道中
Original assignee: Shandong Jiaotong University
Current assignee: Shandong Jiaotong University
Filing date: 2020-09-21
Publication date: 2024-06-21
Anticipated expiration: 2040-09-21

Abstract

The invention discloses an internal high-pressure forming push head, which comprises: the front column head is a cylinder and is inserted into the pipe orifice of the pipe body to be formed, and a gap is reserved between the front column head and the pipe orifice; the sealing column is connected to the tail end of the front column head through a necking and is coaxial with the front column head; the diameter of the necking is smaller than that of the front column head, and an annulus is formed between the necking and the pipe orifice; the sealing column is a cylinder with the diameter larger than the front column head and smaller than the diameter of the pipe orifice and provided with a ring groove, and the ring groove is communicated with the annulus through an oil hole; the O-shaped sealing bag is embedded into the annular groove, and the inner cavity of the O-shaped sealing bag is communicated with the annular space through the oil hole; and the pressing column is connected to the tail end of the sealing column, the diameter of the pressing column is equal to the outer diameter of the pipe body to be formed, and the pressing column provides a pressure-bearing end face so as to prop the pipe end of the pipe body to be formed. The inner high-pressure forming push head provided by the invention has relatively good sealing performance, and the die stripping is not influenced.

Description

Inner high-pressure forming push head

Technical Field

The invention relates to an internal high-pressure forming push head.

Background

Internal high pressure forming, also known as hydroforming or hydroforming, is a material forming process that utilizes a liquid as a forming medium to achieve the purpose of forming hollow parts by controlling the internal pressure and material flow.

The internal high-pressure forming device mainly is used for forming pipe fittings (round pipes, square pipes, special pipes and the like), and the corresponding internal high-pressure forming device comprises a die, a pushing device and a hydraulic device, wherein the die generally comprises an upper die and a lower die, and a die cavity is formed after the parting surfaces are jointed. During processing, the pipe blank is placed in the cavity portion of the lower die, and then the upper die is lowered to restrain the pipe blank in the cavity. One pusher head at each end of the tube blank then bears against the corresponding end of the tube blank, providing an axial force to the tube blank for feeding by relatively pushing the tube body for hydraulic bulging.

One or both of the pusher heads has a hydraulic inlet for filling the tube blank with a liquid for bulging the tube blank, so that the upper part of the feed material is fed in order to obtain a uniform wall thickness.

It will be appreciated that the hydraulic force is sufficient to deform the tube blank, indicating the very high pressure of the liquid providing the hydraulic bulging, and that the pusher is therefore not only intended to provide the tube blank with an axial force, but also to ensure that it maintains a relatively high level of sealing with the tube opening of the tube blank, which is greater than or equal to the level of sealing allowed by the liquid pressure. If the sealing level is insufficient, the forming medium is decompressed, so that the defects of insufficient forming, wrinkling and the like of the tube blank are caused, or the quality of the finished product is unqualified.

The conventional push head used for internal high pressure forming mainly relies on the cooperation of the push head and the profile of the tube blank to realize sealing, typically, as in chinese patent document CN202387815U, the portion of the feed shaft which is in butt joint with the tube blank is provided with a section of part which is inserted into the tube opening of the tube blank, and a shoulder which blocks the periphery of the tube opening to provide axial force. The part of the pipe orifice penetrating into the pipe blank is matched with the inner wall of the pipe orifice to realize sealing with a small gap, and the sealing interface in the sealing mode has very high rigidity, but in order to realize jacking and material returning, the reserved gap can generate a certain amount of forming medium to flow out under the condition of very high liquid pressure, so that the pressure loss is caused.

In some implementations, the sealing ability is improved by extending the length of the portion that is brought into the mouth of the tube blank, however this approach inevitably increases the idle stroke of the feed shaft.

In some implementations, the threading is performed on the portion extending into the tube orifice, i.e., the manner in which the screw seal is formed, improves the sealing ability, but affects the strength of the feed shaft. At the same time, the spiral seal belongs to the deformation of the labyrinth seal, and the sealing capacity is relatively low.

A pusher as used in chinese patent CN100409966C is shown in fig. 4, and has a front end (corresponding to the end of the pusher) of the punch, and the front end of the pusher is a conical head, so that the front end of the pusher can be matched with a conical surface formed by the end of the pipe to form a sealing structure with a certain joint pressure. The structure has certain joint pressure, so the sealing capability is relatively good, but because the structure needs to process a conical surface at the pipe orifice of the pipe blank end in advance, on one hand, the conical surface is not necessarily required by a pipe fitting, therefore, the pipe fitting needs to be cut off after processing, waste of the pipe fitting and waste in the process are caused, and on the other hand, the conical surface of the pipe orifice can generate certain deformation due to the radial component force of the conical surface, so the demolding is influenced.

Disclosure of Invention

The invention aims to provide an internal high-pressure forming push head which has relatively good sealing performance and does not influence die withdrawal.

In an embodiment of the present invention, there is provided an internal high pressure molded pusher head comprising:

The front column head is a cylinder and is inserted into the pipe orifice of the pipe body to be formed, and a gap is reserved between the front column head and the pipe orifice;

The sealing column is connected to the tail end of the front column head through a necking and is coaxial with the front column head; the diameter of the necking is smaller than that of the front column head, and an annulus is formed between the necking and the pipe orifice; the sealing column is a cylinder with the diameter larger than the front column head and smaller than the diameter of the pipe orifice and provided with a ring groove, and the ring groove is communicated with the annulus through an oil hole;

The O-shaped sealing bag is embedded into the annular groove, and the inner cavity of the O-shaped sealing bag is communicated with the annular space through the oil hole;

And the pressing column is connected to the tail end of the sealing column, the diameter of the pressing column is equal to the outer diameter of the pipe body to be formed, and the pressing column provides a pressure-bearing end face so as to prop the pipe end of the pipe body to be formed.

Optionally, two oil holes are arranged, and the two oil holes are symmetrical relative to the axis of the sealing column.

Optionally, a one-way valve is arranged in the oil hole;

the valve core of the one-way valve is provided with a damping hole which is communicated with the O-shaped sealing bag and the annular space so as to provide oil return damping.

Optionally, the O-ring bladder is configured to:

Providing a bag skin with an arc-shaped cross section and connecting parts at two ends of the arc;

The connecting part is sealed with the corresponding side wall surface of the ring groove.

Optionally, the outer surface of the connection portion is coplanar with the outer cylindrical surface of the sealing post.

Optionally, the front end of the front column head is provided with a chamfer or a rounding;

The gap is 0.1-0.3 mm and is positively related to the length of the front column head.

Optionally, the length of the front column head is 1.2-1.4D, and D is the inner diameter of the pipe body to be formed.

Optionally, the front end of the sealing column is a conical part, and an included angle between the front end of the sealing column and the sealing column is 3-7 degrees.

The conical part extends to the front side of the ring groove by more than or equal to 1 mm.

Optionally, the front end of the press stud has a rounded or chamfered shape.

Optionally, the structure body for connecting the compression column and the sealing column is a small cylinder or a cylinder;

the small cylinder is a connecting cylinder with the diameter smaller than that of the sealing cylinder, and a space is reserved between the pressing cylinder and the sealing cylinder.

In embodiments of the present invention, an internal high pressure forming pusher is provided having a plurality of segments, equivalent to providing a multi-stage seal, wherein the front post portion forms a gap seal with the nozzle of the tubular body to be formed, which is a conventional seal, the main principle being that the front post extends into the nozzle and maintains a small gap with the inner wall of the nozzle, enabling the formation of a seal based on boundary friction. Such a seal is formed by means of boundary friction, and when the pressure is high, hydraulic oil still leaks out. Furthermore, the sealing column provides contact sealing, the contact sealing is formed by a sealing assembly positioned on the sealing column, an annulus is formed between a necking between the sealing column and the front column head and a pipe orifice, hydraulic oil leaked from the gap sealing can freely enter the annulus, and after filling to a certain degree, the hydraulic oil can firstly enter the O-shaped sealing bag through the oil hole, and the O-shaped sealing bag is opened to be in contact with the inner wall of the pipe body to form contact sealing. With further filling of the annulus with hydraulic oil, the sealing capacity of the contact seal may be reduced. However, leakage occurs more in the early stages of forming, after which the sealing ability is reduced with less impact on the process. For the compression column, a third-stage seal is formed by the cooperation of the end face of the compression column and the end face of the pipe orifice. The effect of the three-stage seal is relatively good on the whole, and the three-stage seal is not provided with a seal formed by conical interface fit, so that the problem that the die is difficult to withdraw due to bulging of a pipe orifice is avoided.

Drawings

FIG. 1 is a schematic diagram illustrating an operation state of an inner high pressure forming pusher in an embodiment.

FIG. 2 is a schematic diagram of an embodiment of a seal assembly configuration.

In the figure: 1. the pipe forming device comprises an upper die, a pipe to be formed, a lower die, a front column head, a gap, a neck, an annular space, a sealing assembly, a sealing column, a conical part, a pressing column, a liquid guiding pipe, a push rod, an oil cylinder, a 15O-shaped sealing bag, a ring groove and a valve.

Detailed Description

In general, for the pusher, the direction in which it applies pressure so as to act on the tube 2 to be formed is the forward direction, also the working direction, the side on which the pusher is forward is the front side; correspondingly, the front end of the push head is provided. The other end of the push head, opposite to the front end, is the tail end, which may also be referred to as the rear end.

Referring to fig. 1 of the drawings, an upper die 1 and a lower die 3 are portions for constructing a cavity, and can be separated from each other, and generally the upper die 1 can be lifted upward, for example, by a press, or by a separate lifting mechanism in an internal high-pressure molding machine. The upper die 1 and the lower die 3 have half cavities respectively in terms of split structure, and form complete cavities after being combined.

After the upper die 1 is lifted, the tube blank is placed in a cavity positioned on the lower die 3, then the upper die 1 is put down in place, and push heads are formed at two opposite ends of the cavity in an inner high-pressure mode.

As can be seen from the right part of fig. 1, the inner high pressure forming push head used in the embodiment of the present invention is a push head of a multi-segment structure, the parts which are inserted into the mouth of the pipe 2 to be formed are mainly the front pillar head 4 and the sealing pillar 9, and the neck 6 for connecting the front pillar head 4 and the sealing pillar 9. In some embodiments, the portion that is advanced into the nozzle also includes the taper 10 shown in FIG. 1. The inner high pressure forming ram also has a ram 11 at its trailing end, the ram 11 providing a jacking force which is exerted by a ram 14 shown in the figures.

The front column head 4 provides a first-stage seal, the body of the front column head 4 is a cylinder, the front column head 4 extends into the pipe orifice of the pipe 2 to be formed, the front column head is coaxial with the pipe orifice, and a gap is reserved between the front column head and the pipe orifice. The sealing between the front column head 4 and the pipe orifice is conventionally provided in a sealing mode, and certain sealing capability is provided under the condition that the pushing head is ensured to be smoothly and partially inserted into the pipe orifice, and the sealing principle is mainly utilized by boundary friction as already stated in the foregoing.

It will be appreciated that the smaller the gap, the better the gap seal, and the longer the gap is in the direction of the blockage. The front head 4 needs to have a certain length in order to obtain a good gap seal.

In an embodiment of the invention, however, a certain amount of leakage is allowed, whereby the leaked liquid will flow into the annulus 7 shown in fig. 1, gradually filling the annulus 7. It can also be seen here that a simple gap seal requires a higher sealing capacity with very little leakage. In the embodiment of the invention, however, a relatively high sealing capacity of the gap seal is not required, so that the length of the front head 4 can be somewhat shorter to meet the requirement that a larger amount of liquid fills the annulus 7 at the beginning of the pushing.

It is known that a small amount of leakage in the initial stage does not lead to insufficient bulging of the product.

The gap seal mainly plays a role of increasing flow resistance in the embodiment of the invention, and the multi-stage seal also forms a contact type labyrinth seal as a whole, and has higher sealing capability as a whole.

In fig. 1, the sealing post 9 is also a cylinder which is connected to the rear end of the front post 4 by a constriction 6 and is coaxial with the front post 4. The constriction 6 corresponds to a small cylinder with a smaller diameter than the front head 4 and the sealing post 9, leaving a larger space between the orifice, called annulus 7, for the construction of the chamber and thus the passage.

Correspondingly, the diameter of the necking 6 is smaller than the diameter of the front column head 4; the sealing post 9 is a cylinder with a diameter greater than the front post head 4 and less than the diameter of the orifice and with a ring groove 16, it being evident that the diameter of the sealing post 9 is also greater than the diameter of the constriction 6.

The annular groove 16 is communicated with the annular space 7 through an oil hole, when the annular space 7 is filled with liquid, the gap between the sealing column 9 and the inner wall of the pipe orifice is smaller, the resistance is larger, and the liquid is filled into the O-shaped sealing bag 15 first, so that good contact sealing can be kept in the initial stage.

It is evident that the ring groove 16 is mainly intended to receive the O-ring 15 and accordingly that the axis of the ring groove 16 must be collinear with the axis of the sealing post 9.

The O-shaped sealing bag 15 is made of rubber capsule, and is assembled in a similar way to a common O-shaped ring, and is sleeved in a corresponding annular groove 16 by utilizing the elasticity of the O-shaped ring.

Accordingly, the inner cavity of the O-ring 15 communicates with the annulus 7 via oil holes.

For the press column 11, it provides a pushing force for pressing the nozzle, which is mounted on the cylinder 14 by the push rod 13 and is connected to the tail end of the seal column 9. The diameter of the press stud 11 is equal to the outer diameter of the pipe 2 to be formed, and the press stud 11 provides a pressure-bearing end face to press against the pipe end of the pipe 2 to be formed.

In addition, the liquid guide oil passage 12 shown in fig. 1 is an inherent configuration of the push head, and will not be described here.

In order to ensure a rapid filling of the O-ring 15, two oil openings are provided, which are symmetrical with respect to the axis of the sealing post 11.

As mentioned above, the seal column 9 mainly provides an initial contact seal, and impact pressure is generated in the initial stage, and is larger than later static pressure, and the O-ring seal 15 is directly connected with the annulus 7, so that normal use can be satisfied.

In the preferred embodiment, the oil hole is internally provided with a one-way valve, so that the O-shaped sealing bag 15 can be better filled with liquid at the initial stage, and even if the liquid intervenes on the outer side of the sealing column 9, the O-shaped sealing bag 15 can still keep a better shape, thereby having a better contact sealing effect.

In order to facilitate the die stripping, the valve core of the one-way valve is provided with a damping hole for communicating the O-shaped sealing bag 15 with the annular space 7 so as to provide oil return damping. The damping hole is understood to be a hole having a very small diameter, in other words, a relatively slow oil discharge speed, and can satisfy the die sinking requirement even when the initial seal is satisfied.

In the embodiment of the present invention, the aperture of the orifice is positively correlated with the capacity of the O-ring 15 in the filled state, and it is generally sufficient that no leakage from the press post 11 side occurs during the tube blank forming process.

In some embodiments, the O-ring 15 may be formed from a tubular body joined end to end with an annular cavity, then side vented and tubing configured to communicate with the annulus 7.

In other embodiments, the O-ring 15 is configured to:

The connection portion is sealed with the corresponding side wall surface of the ring groove 16. Such sealing is typically performed by using a metal paste adhesive to ensure the structural reliability of the O-ring 15.

Preferably, the outer surface of the connection portion is coplanar with the outer cylindrical surface of the sealing post 9, corresponding to the connection portion being directly supported on the inner wall of the nozzle, the hydraulic force has a weak effect on the connection between the connection portion and the wall surface of the annular groove 16.

Accordingly, the sealing post 9 and the nozzle adopt a clearance fit manner, wherein the clearance fit is a term based on tolerance, in other words, the sealing post 9 and the inner wall of the nozzle are in macroscopic contact, so that when the O-shaped sealing bag 15 is constructed by the bag skin fit ring groove 16, the connecting part can be supported on the inner wall of the nozzle, and thus, good structural reliability is still provided.

Because of the relatively tight fit, in order to facilitate the insertion of the front column head 4 into the orifice, the front end of the front column head 4 is provided with a chamfer or a rounding;

the gap is 0.1-0.3 mm and is positively correlated with the length of the front column head 4.

Further, the length of the front column head 4 is 1.2-1.4D, and D is the inner diameter of the pipe body pipe 2 to be formed.

As the sealing column 9 and the inner wall of the pipe mouth are in clearance fit, the sealing column is in tight fit, the front end of the sealing column 9 is a conical part, and the included angle A between the front end of the sealing column and the axis of the sealing column is 3-7 degrees for facilitating penetration.

In the preferred embodiment, the taper extends to 1mm or more in front of the groove 16 to ensure that liquid does not enter the groove 16 from the outside quickly, affecting the proper operation of the O-ring 15.

As mentioned above, the diameter of the press stud 11 is equal to the outer diameter of the nozzle, and the pusher needs to be pushed in, for which purpose the front end of the press stud 11 has a rounded or chamfered shape to facilitate insertion of the pusher into the cavity.

In some embodiments, the structure for connecting the compression column 11 with the sealing column 9 is a small cylinder or cone;

Claims

1. An internal high pressure forming pusher, comprising:

the pressing column is connected to the tail end of the sealing column, the diameter of the pressing column is equal to the outer diameter of the pipe body to be formed, and the pressing column provides a pressure-bearing end face to prop against the pipe end of the pipe body to be formed;

a one-way valve is arranged in the oil hole;

The valve core of the one-way valve is provided with a damping hole which is communicated with the O-shaped sealing bag and the annular space so as to provide oil return damping;

The O-shaped sealing bag is configured as follows:

2. The inner high pressure molding plug according to claim 1, wherein two oil holes are provided, and the two oil holes are symmetrical with respect to the axis of the seal post.

3. The inner high pressure molded pusher of claim 1, wherein the outer surface of the connecting portion is coplanar with the outer cylindrical surface of the sealing post.

4. The inner high pressure forming pusher of claim 1, wherein the front end of the front column head has a chamfer or a radius;

5. The inner high pressure forming push head of claim 4, wherein the length of the front column head is 1.2-1.4 d, and d is the inner diameter of the pipe body to be formed.

6. The inner high-pressure forming push head according to claim 1, wherein the front end of the sealing column is a conical part, and an included angle between the front end of the sealing column and the axis of the sealing column is 3-7 degrees; the conical part extends to the front side of the ring groove by more than or equal to 1 mm.

7. The inner high pressure forming pusher of claim 1, wherein the front end of the press stud has a rounded or chamfered shape.

8. The inner high pressure forming pusher of claim 1, wherein the structure for connecting the press stud to the seal stud is a small cylinder or cone;