CN112157161A

CN112157161A - Internal high pressure forming push head

Info

Publication number: CN112157161A
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
Priority date: 2020-09-21
Filing date: 2020-09-21
Publication date: 2021-01-01

Abstract

The invention discloses an internal high-pressure forming push head, which comprises: the front column cap is a cylinder, extends into the pipe orifice of the pipe body to be formed, and a gap is reserved between the front column cap and the pipe orifice; the sealing column is connected with 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 annular space is formed between the necking and the tube orifice; the sealing column is a cylinder with a 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 an oil hole; and the compression column is connected at the tail end of the sealing column, the diameter of the compression column is equal to the outer diameter of the pipe body to be formed, and the compression column provides a pressure-bearing end face to support the pipe end of the pipe body to be formed. The internal high-pressure forming push head has relatively good sealing performance and does not influence the die stripping.

Description

Internal high pressure forming push head

Technical Field

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

Background

Internal high pressure forming, also called hydroforming or hydroforming, is a material forming process that uses 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 is mainly used for forming pipe fittings (round pipes, square pipes, special pipes and the like), the corresponding internal high-pressure forming equipment comprises a die, a pushing device and a hydraulic device, the die generally comprises an upper die and a lower die, and a die cavity is formed after the die cavity is jointed at a parting surface. During processing, the tube blank is placed into the cavity part of the lower die, and then the upper die is placed downwards, so that the tube blank is restrained in the cavity. Then, each push head at two ends of the tube blank is pushed against the corresponding end of the tube blank to provide axial force for the tube blank, and the axial force is used for supplementing materials for hydraulic bulging by relatively pushing the tube body.

One or both of the pushing heads has a hydraulic input pipe for filling the tube blank with a liquid for bulging the tube blank, and the above-mentioned supplementary material is only used to obtain a uniform wall thickness.

It is understood that the hydraulic force is sufficient to deform the tube blank, indicating a very high pressure of the liquid providing the hydroforming, and therefore the pusher head is not only used to provide the tube blank with an axial force, but also should ensure a relatively high level of sealing with the tube opening, the level of sealing being greater than or equal to the level of sealing permitted by the liquid pressure. If the sealing grade is not enough, the pressure of a forming medium is lost, so that the defects of insufficient forming, wrinkling and the like of the tube blank are caused, or the quality of a finished product is unqualified.

The traditional push head used in internal high pressure forming mainly relies on the push head to match the profile of the tube blank to realize sealing, typically, as in chinese patent document CN202387815U, the portion of the feed shaft provided to be butted with the tube blank has a section of portion protruding into the tube opening of the tube blank, and a shaft shoulder blocking the periphery of the tube opening to provide axial force. The part of the tube blank extending into the tube mouth is matched with the inner wall of the tube mouth, and sealing is realized by a small gap, although the sealing interface of the sealing mode has very high rigidity, the reserved gap can generate a certain amount of molding medium to flow out under the condition of very high liquid pressure so as to cause pressure loss in order to realize propping and material returning.

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

In some implementations, the screw thread is machined on the part extending into the pipe mouth of the pipe blank, namely, the screw seal is formed, so that the sealing capability is improved, but the strength of the feed shaft is affected. Meanwhile, the spiral seal belongs to the deformation of labyrinth seal, and the sealing capability is relatively low.

The pusher used in chinese patent document CN100409966C can be seen in fig. 4, and has a front end of the punch (corresponding to the end of the pusher) which is a conical head, so that the front end of the pusher can cooperate with the conical surface formed at the end of the pipe to form a sealing structure with a certain engaging pressure. The structure has a certain joint pressure, so the sealing capability is relatively good, but because the structure needs to process a conical surface at the pipe mouth of the pipe blank in advance, on one hand, the conical surface is not necessarily required by the pipe, and therefore, the conical surface needs to be cut off after processing, so the waste of the pipe and the waste of the process are caused, and on the other hand, because the conical surface of the pipe mouth generates a certain deformation due to the radial component force of the conical surface, the demoulding 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 the die stripping.

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

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

the sealing column is connected with 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 annular space is formed between the necking and the tube orifice; the sealing column is a cylinder with a 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 an oil hole;

and the compression column is connected at the tail end of the sealing column, the diameter of the compression column is equal to the outer diameter of the pipe body to be formed, and the compression column provides a pressure-bearing end face to support the pipe end of the pipe body to be formed.

Optionally, two oil holes are formed in the sealing column, and the two oil holes are symmetrical with respect to the axis of the sealing column.

Optionally, a check valve is arranged in the oil hole;

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

Optionally, the O-ring seal is configured to:

providing a capsule 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 connecting portion is coplanar with the outer cylindrical surface of the sealing post.

Optionally, the front stub front end has a chamfer or radius;

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

Optionally, the length of the front column cap 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 sealing column and the conical part is 3-7 degrees of an axis.

The conical part extends to the position which is more than or equal to 1mm at the front side of the ring groove.

Optionally, the front end of the compression leg has a radius or chamfer.

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

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

In the embodiment of the invention, the provided internal high-pressure forming push head is provided with a plurality of sections, namely, multi-stage sealing is provided, wherein a gap seal is formed between the front column head part and the pipe orifice of the pipe body to be formed, the traditional sealing is realized, and the main principle is that the front column head penetrates into the pipe orifice and keeps a small gap with the inner wall of the pipe orifice, so that the sealing can be formed based on boundary friction. This seal is formed by boundary friction and when the pressure is high, there is still leakage of hydraulic oil. Furthermore, the sealing column provides contact sealing, the contact sealing is formed by a sealing assembly positioned on the sealing column, an annular space is formed between the necking section between the sealing column and the front column head and the pipe orifice, hydraulic oil leaked from the gap sealing can freely enter the annular space, and after the sealing column is filled 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 and is in contact with the inner wall of the pipe body to form the contact sealing. With further filling of the annulus with hydraulic oil, the sealing ability of the contact seal is reduced. However, leakage often occurs in the early stages of molding, and the subsequent reduction in sealing ability has less effect on the progress of the process. And for the compression column, a third-stage seal is formed by matching the end face of the compression column with the end face of the pipe orifice. The effect of tertiary sealed on the whole is relatively better, and all do not have the sealed that the cooperation of toper interface formed at tertiary sealed, can not produce consequently that the mouth of pipe bulging for example produces the problem of demolding difficulty.

Drawings

Fig. 1 is a schematic view of an operating state of an internal high pressure forming pushing head in one embodiment.

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

In the figure: 1. the device comprises an upper die, a pipe to be formed, a lower die, a front column head, a gap, a neck, a ring space, a sealing assembly, a sealing column, a conical part, a pressing column, a liquid guide pipeline, a push rod, a cylinder, a sealing bag, an O-shaped sealing bag, a ring groove and a valve, wherein the upper die comprises 2 a pipe to be formed, 3 a lower die, 4 a front column head, 5 a gap, 6 a neck, 7 an annular space, 8 a sealing assembly, 9 a sealing column, 10.

Detailed Description

In general, as for the push head, the direction in which it applies pressure to act on the pipe 2 to be formed is the forward direction, and is also the working direction, and the side where the push head is forward is the front side; correspondingly, the front end of the pushing head is arranged. The other end of the pushing head opposite to the front end is the tail end, which can also be called as the back end.

Referring to the accompanying drawing 1 of the specification, in which an upper die 1 and a lower die 3 are portions for forming a cavity, the upper die 1 and the lower die are separable from each other, and the upper die 1 is generally lifted upward and lifted by using, for example, a press machine or a separate lifting mechanism in an internal high-pressure molding machine. The upper mold 1 and the lower mold 3, if viewed in a split configuration, each have a half cavity, and form a complete cavity after being closed.

After the upper die 1 rises, the tube blank is placed in a cavity on the lower die 3, then the upper die 1 is put down in place, and high-pressure forming push heads are arranged at two opposite ends of the cavity.

As can be seen from the right part of fig. 1, the inner high-pressure forming ram used in the embodiment of the present invention is a ram of a multi-segment structure, and the parts which protrude into the opening of the pipe 2 to be formed are mainly the front column head 4 and the sealing column 9, and the constriction 6 for connecting the front column head 4 and the sealing column 9. In some embodiments, the portion that protrudes into the spout further comprises a taper 10 as shown in fig. 1. The inner high-pressure forming pusher also has a pressing column 11 at its rear end, the pressing column 11 providing a pushing force which is exerted by a cylinder 14 shown in the figure.

The front column head 4 provides a first-stage seal, the body of the front column head is a cylinder, the front column head 4 extends into the pipe orifice of the pipe 2 to be formed, is coaxial with the pipe orifice and has a gap with the pipe orifice. The sealing between the front cap 4 and the nozzle is conventionally provided in a sealing manner, which has a certain sealing capability while ensuring that the pusher is smoothly and partially inserted into the nozzle, and the sealing principle is stated in the foregoing, mainly by using boundary friction.

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

In the 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 from this that a simple clearance seal requires a higher sealing capacity and a very low leakage. In embodiments of the invention, however, a relatively high sealing capacity of the gap seal is not required, so that the front post head 4 can be of a slightly shorter length to accommodate a greater volume of liquid filling the annulus 7 during the initial stages of thrust.

It is to be understood that a small amount of leakage during the initial stage does not result in insufficient bulging of the product.

The gap seal mainly plays a role in 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 tail end of the front post head 4 by the constriction 6 and is coaxial with the front post head 4. The constriction 6 therein corresponds to a small cylinder having a smaller diameter than the front head 4 and the sealing cylinder 9, so that a larger space, called annulus 7, is left between the nozzle for the formation of a cavity for the further formation of a channel.

Accordingly, the diameter of the constriction 6 is smaller than the diameter of the front post head 4; the sealing post 9 is a cylinder with a diameter greater than the front post head 4 and smaller than the diameter of the spout and with a circumferential groove 16, it being clear 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 the 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 small, the resistance is large, and the liquid is filled into the O-shaped sealing bag 15 firstly, so that good contact sealing can be kept at the initial stage.

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

The O-ring sealing member 15 is a rubber member, and is assembled in a manner similar to a general O-ring, and is fitted into the corresponding ring groove 16 by elasticity of the O-ring.

Correspondingly, the inner cavity of the O-shaped sealing bag 15 is communicated with the annular space 7 through an oil hole.

The pressing column 11 provides pushing force for pressing the nozzle, is arranged on an oil cylinder 14 through a push rod 13, and is connected to the tail end of the sealing column 9. The diameter of the press stud 11 is equal to the outer diameter of the pipe 2 to be formed, the press stud 11 providing a pressure-bearing end surface for holding the end of the pipe 2 to be formed.

In addition, the oil guide passage 12 shown in fig. 1 is an inherent configuration of the plunger, and will not be described herein.

In order to ensure that the O-shaped sealing bag 15 is filled quickly, two oil holes are formed, and the two oil holes are symmetrical about the axis of the sealing column 11.

As mentioned above, the sealing column 9 mainly provides the initial contact sealing, and the impact pressure is larger than the later static pressure in the initial period, and the O-shaped sealing bag 15 is directly connected with the annular space 7 to meet the normal use.

In a preferred embodiment, the oil hole is provided with a one-way valve, liquid can better fill the O-shaped sealing bag 15 in the early stage, and even if liquid is introduced from the outer side of the sealing column 9, the O-shaped sealing bag 15 can still keep a better shape, so that a better contact sealing effect is achieved.

In order to facilitate the demolding, a 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 term "orifice" is understood to mean a hole having a very small diameter, i.e., a relatively slow oil discharge rate, which can satisfy the requirement of die stripping even when the initial seal is satisfied.

In the embodiment of the present invention, the diameter of the damping hole is positively correlated with the filling capacity of the O-ring seal 15, and it is generally sufficient that no leakage from the side of the pressure column 11 occurs during the tube blank forming process.

In some embodiments, the O-ring 15 may be a balloon with an annular cavity formed by the ends of the tube, then be perforated and provided with tubing to communicate with the annulus 7.

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

the connecting part is sealed with the corresponding side wall surface of the ring groove 16. The sealing is generally made of metal glue, so that the structural reliability of the O-shaped sealing bag 15 can be ensured.

Preferably, the outer surface of the connecting part is coplanar with the outer cylindrical surface of the sealing column 9, which means that the connecting part is directly supported on the inner wall of the pipe orifice, and the hydraulic pressure has a weak influence on the connection between the connecting part and the wall surface of the ring groove 16.

Accordingly, the sealing post 9 is in clearance fit with the nozzle, where the clearance fit is a term based on tolerance, in other words, the sealing post 9 is in contact with the inner wall of the nozzle in a macroscopic manner, so that when the O-ring type sealing bag 15 is constructed through the bag skin fitting ring groove 16, the connecting portion can be supported on the inner wall of the nozzle, and good structural reliability can still be achieved.

Because the matching is relatively tight, the front end of the front column head 4 is provided with a chamfer or a radius in order to facilitate the front column head 4 to be inserted into the pipe orifice;

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 2 to be formed.

Because as before, adopt clearance fit between sealed post 9 and the orificial inner wall, belong to comparatively inseparable cooperation, for the convenience of exploring into, sealed post 9 front end is the toper portion, and is 3~7 degrees with the contained angle A of sealed post axis.

In a preferred embodiment, the tapered portion extends to a distance of 1mm or more from the front side of the ring groove 16 to ensure that liquid does not rapidly enter the ring groove 16 from the outside and affect the normal operation of the O-ring seal 15.

As mentioned above, the diameter of the pressing column 11 is equal to the outer diameter of the pipe orifice, and the pushing head needs to be pushed, for which purpose, the front end of the pressing column 11 has a radius or chamfer to facilitate the insertion of the pushing head 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 pushing head, which is characterized by comprising:

2. The internal high pressure forming pushing head as claimed in claim 1, wherein there are two oil holes, and the two oil holes are symmetrical with respect to the axis of the sealing column.

3. The internal high pressure forming pushing head according to claim 1 or 2, wherein a one-way valve is arranged in the oil hole;

4. The internal high pressure forming pusher head of claim 1, wherein the O-ring seal pocket is configured to:

5. The internal high pressure forming pusher head of claim 4, wherein the outer surface of the connecting portion is coplanar with the outer cylindrical surface of the sealing post.

6. The internal high pressure forming pusher head according to claim 1, wherein the front end of the front cylinder head has a chamfer or radius;

7. The inner high pressure forming pushing head according to claim 6, wherein the length of the front column head is 1.2-1.4D, and D is the inner diameter of the tube body to be formed.

8. The internal high pressure forming pushing head according to claim 1, wherein the front end of the sealing post is a tapered portion, and the included angle between the front end of the sealing post and the axis of the sealing post is 3-7 degrees;

9. The internal high pressure forming pusher head of claim 1, wherein the front end of the plunger has a radius or chamfer.

10. The internal high pressure forming pushing head according to claim 1, wherein the structure for connecting the pressing column and the sealing column is a small cylinder or a cone;