INTERNAL EXPANDED FLUID FORMING METHOD

Description

CROSS-REFERENCE TO THE RELATED APPLICATIONS

This application is based upon and claims priority to Chinese Patent Application No. 202411778210.3, filed on Dec. 5, 2024, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention belongs to the field of hydraulic bulging technology, particularly relates to an internal expanded fluid forming method.

BACKGROUND

At present, the commonly used forming method for sheet metal curved parts of hydraulic fluid expansion forming is to press the edge of the sheet metal on a sealed container that can withstand high pressure to introduce fluid into the container, and the upper surface of the sheet metal is pressed downward with a punch to force while forcing the fluid to flow out of the container, thereby forming the required curved surface shape, wherein the fluid action is auxiliary support; another fluid expansion forming method is to increase the fluid pressure and fluid volume in a closed container, the sheet metal is forced to expand outward and gradually form the desired shape. However, the above two forming methods all need to change the fluid volume. The Chinese invention patent with the Publication No. CN115634993B proposed the use of a floating blank holder hydraulic bidirectional single-mode deep drawing forming device and forming method, in this method, the piston of the blank holder is used to drive the sheet metal to be reversely stretched during the deep drawing process, and the biggest feature of this technology is that it does not change the fluid volume in the closed cavity but changes its flow shape to realize the deformation of the sheet metal, which saves half of the moving displacement compared with the conventional deep drawing.

However, the patent still has shortcomings, the floating technology of the blank holder will leak the liquid with the thinning of the sheet metal, and because the downward pressing of the punch is adopted, the forming part enters the piston hole, and it is difficult to pick up the part, and the size of the hole limits the diversity of the shape of the forming part, so an internal expanded fluid forming method is proposed.

SUMMARY

An objective of the present invention is to provide an internal expanded fluid forming method, which aims to solve the problems raised in the above background technology.

In order to achieve the above objective, the present invention provides the following technical scheme:

• • an internal expanded fluid forming device, the device includes a cylinder, a piston, an outer sealing ring, a downward-pressing cavity and a connecting mechanism; an interior of the cylinder is filled with a fluid medium, and a plurality of outer sealing rings are assembled between the cylinder and the piston; the piston is processed with a central through hole; the center of the downward-pressing cavity is processed with a cavity, and a mold is mounted in the cavity; the connecting mechanism is arranged between the piston and the downward-pressing cavity.

Further, the connecting mechanism includes an empty groove with a step and a column with a step, the empty groove with a step is arranged on the downward-pressing cavity, and the column with a step is fixed on the piston.

Further, the central through hole is assembled with a pressed piston, and a plurality of inner seal rings are assembled between the central through hole and the pressed piston.

Further, a top of the pressed piston is processed with a shape that matches the mold.

A sheet metal forming method using the internal expanded fluid forming device as described above, the method includes the following steps when the central through hole is not assembled with the pressed piston:

• • S1. assembly: assembling the sheet metal to be formed between a top of the piston and a lower end of the downward-pressing cavity;
  • S2. filling with fluid: pushing the downward-pressing cavity downwards by an external force, and pushing the piston to move downwards by the downward-pressing cavity, so as to increase pressure of the fluid medium in the cylinder, and as the pressure increases, flowing upwards the fluid medium through the central through hole and pressing the sheet metal;
  • S3. expanding: continuing to increase the external force, when the pressure of the fluid medium exceeds the strength of plastic deformation of the sheet metal, deforming the sheet metal and entering into the mold until completely fitted with the cavity of the mold, so as to obtain a sheet metal formed part;
  • S4. pick-up: lifting the downward-pressing cavity, and overlapping the empty groove with a step through the column with a step of the connecting mechanism to drive the piston to lift at the same time, decreasing the pressure in the cylinder, and flowing back the fluid medium into the cylinder from the central through hole of the piston; at this time, rotating the downward-pressing cavity to separate the column with a step and the empty groove with a step, so as to disengage the piston, and further lifting the downward-pressing cavity to take out the sheet metal formed part from the mold of the downward-pressing cavity.

Further, the method includes the following steps when the central through hole is assembled with the pressed piston:

• • S1. assembly: assembling the sheet metal to be formed between a top of the piston and a lower end of the downward-pressing cavity;
  • S2. filling with fluid: pushing the downward-pressing cavity downwards by an external force, and pushing the piston to move downwards by the downward-pressing cavity, so as to increase the pressure of the fluid medium in the cylinder, and as the pressure increases, pushing the pressed piston by the fluid medium to move upward along the central through hole, and starting to press the sheet metal by the pressed piston;
  • S3. expanding: continuing to increase the external force to make the pressed piston continue to move upwards, forcing the sheet metal to deform and gradually fit into the cavity of the mold until completely fitted with the cavity of the mold, so as to obtain a sheet metal formed part;
  • S4. pick-up: lifting the downward-pressing cavity, and overlapping the empty groove with a step through the column with a step of the connecting mechanism to drive the piston to lift at the same time, so that decreasing the pressure of the fluid medium in the cylinder, and moving down the pressed piston by itself under the gravity of the pressed piston, at this time, rotating the downward-pressing cavity to separate the column with a step and the empty groove with a step, so as to disengage the piston, and further lifting the downward-pressing cavity to take out the sheet metal formed part from the mold of the downward-pressing cavity.

Further, the fluid medium is a mixture of one or more components in hydraulic oil, pure water, brine water and an acid solution or alkali solution.

Further, the sheet metal is one or a composite of metal and polymer materials, the metal is one or more of steel, copper, aluminum alloy and magnesium alloy, and the polymer material is one or more of polycarbonate (PC), and polyethylene (PE).

In comparison with the existing technology, the beneficial effects of the present invention are:

• • 1. in the present invention, it is ensured that the sheet metal will not cause fluid leakage even if it is thinned during the forming process by maintaining the edge of the sheet metal in the dynamic pressing state of the piston and the downward-pressing cavity.
  • 2. In the present invention, the internal expanded fluid forming process is adopted, which can realize the diversification of sheet metal forming shape.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural schematic diagram of an internal expanded fluid forming device.

FIG. 2 is a structural schematic diagram of an internal expanded fluid forming device is assembled with a pressed piston.

FIGS. 3A-3C show an action schematic diagram of sheet metal forming when an internal expanded fluid forming device is not assembled with a pressed piston; wherein FIG. 3A is a schematic diagram of the fluid medium starting to press the sheet metal when the device is not assembled with the pressed piston; FIG. 3B is a schematic diagram of the sheet metal deformed and entered into the mold when the device is not assembled with the pressed piston; FIG. 3C is a schematic diagram of the deformed sheet metal is completely fitted to a cavity of the mold when the device is not assembled with the pressed piston.

FIGS. 4A-4C show the action schematic diagram of sheet metal forming when an internal expanded fluid forming device is assembled with a pressed piston; wherein FIG. 4A is a schematic diagram of the fluid medium starting to press the sheet metal when the device is assembled with the pressed piston; FIG. 4B is a schematic diagram of the sheet metal deformed and entered into the mold when the device is assembled with the pressed piston; FIG. 4C is a schematic diagram of the deformed sheet metal is completely fitted to a cavity of the mold when the device is assembled with the pressed piston.

FIGS. 5A-5B show a schematic diagram of the connection and disconnection between a downward-pressing cavity and a piston through rotating a connecting mechanism, wherein FIG. 5A is a schematic diagram of a state of connection; FIG. 5B is a schematic diagram of a state of disengagement.

FIGS. 6A-6B show a flow chart of a sheet metal forming method realized by an internal expanded fluid forming device; wherein FIG. 6A is a flow chart of the sheet metal forming method realized by the internal expanded fluid forming device without a pressed piston; FIG. 6B is a flow chart of the sheet metal forming method realized by the internal expanded fluid forming device with a pressed piston.

Reference numerals in figures: a cylinder 1; a piston 2; an outer sealing ring 3; a downward-pressing cavity 4; a central through hole 201; a fluid medium 5; a cavity 401; a mold 402; a sheet metal 6; an inner seal ring 7; a pressed piston 8; an empty groove with a step 901; a column with a step 902.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In order to make the objective, technical solution and advantages of the present invention clearer and more specific, the present invention will be further described in detail below with reference to accompanying drawings and examples. It should be understood that the specific examples described herein are merely illustrative of the present invention and are not intended to limit the present invention.

As shown in FIG. 1 and FIGS. 5A-5B, an internal expanded fluid forming device is provided for the embodiment of the present invention, the device includes a cylinder 1, a piston 2, an outer sealing ring 3, a downward-pressing cavity 4 and a connecting mechanism; an interior of the cylinder 1 is filled with a fluid medium 5, and a plurality of outer sealing rings 3 are assembled between the cylinder 1 and the piston 2; the piston 2 is processed with a central through hole 201; the center of the downward-pressing cavity 4 is processed with a cavity 401, and a mold 402 is mounted in the cavity 401; the connecting mechanism is arranged between the piston 2 and the downward-pressing cavity 4.

Further, the connecting mechanism includes an empty groove with a step 901 and a column with a step 902, the empty groove with a step 901 is arranged on the downward-pressing cavity 4, and the column with a step 902 is fixed on the piston 2.

In the embodiment of the present invention, the assembly of the sheet 6 will not be affected by the arrangement of the connecting mechanism, and the edge diameter of the sheet metal 6 can be reduced or slotted at the contact area with the connecting mechanism to avoid the column with a step 902.

The downward-pressing cavity 4 is pushed downwards by an external force, and the piston 2 is pushed to move downwards by the downward-pressing cavity 4, so as to increase pressure of the fluid medium 5 in the cylinder, and as the pressure of the cylinder 1 increases, the fluid medium 5 flows upwards through the central through hole 201 and starts to press the sheet metal 6. When further increase the external force of the downward-pressing cavity 4, the pressure of the fluid medium 5 exceeds the strength of plastic deformation of the sheet metal 6, the sheet metal deforms and enters into the mold 402, the external force is further increased until the deformed sheet metal 6 is completely fitted with the cavity of the mold 402, so as to obtain a sheet metal formed part.

As shown in FIG. 1 and FIG. 2, as a preferred embodiment of the present invention, the central through hole 201 is assembled with a pressed piston 8, and a plurality of inner seal rings 7 are assembled between the central through hole 201 and the pressed piston 8, a top of the pressed piston 8 is processed with a shape that matches the mold 402 to form a mold-like nested mold punch.

In the embodiment of the present invention, the downward-pressing cavity 4 is pushed downwards by an external force, and the piston 2 is pushed to move downwards by the downward-pressing cavity, so as to increase the pressure of the fluid medium 5 in the cylinder 1, and as the pressure increases, the pressed piston 8 is pushed by the fluid medium 5 to move upward along the central through hole 201, and the sheet metal 6 starts to be pressed by the pressed piston 8. With further increase of the external force, the pressed piston 8 continues to move upwards, the sheet metal 6 is forced to deform and gradually fitted into the cavity of the mold 402 until the deformed sheet metal 6 is completely fitted with the cavity of the mold 402, so as to obtain a sheet metal formed part.

As shown in FIGS. 3A-3C, FIGS. 5A-5B and FIG. 6A, a sheet metal forming method using the internal expanded fluid forming device as described above in an embodiment of the present invention, the method includes the following steps when the central through hole 201 is not assembled with the pressed piston 8:

• • S1. assembly: the sheet metal 6 to be formed is assembled between the top of the piston 2 and the lower end of the downward-pressing cavity 4;
  • S2. filling with fluid: the downward-pressing cavity 4 is pushed downwards by an external force, and the piston 2 is pushed to move downwards by the downward-pressing cavity 4, so as to increase the pressure of the fluid medium 5 in the cylinder, and as the pressure of the cylinder 1 increases, the fluid medium 5 flows upwards through the central through hole 201 and starts to press the sheet metal 6 (refer to FIG. 3A);
  • S3. expanding: when further increasing the external force of the downward-pressing cavity 4, the pressure of the fluid medium 5 exceeds the strength of plastic deformation of the sheet metal 6, the sheet metal 6 deforms and enters into the mold 402 (refer to FIG. 3B), further increase the external force until the deformed sheet metal 6 is completely fitted with the cavity of the mold 402 (refer to FIG. 3C), so as to obtain a sheet metal formed part;
  • S4. pick-up: the downward-pressing cavity 4 is lifted, and overlaps the empty groove with a step 901 through the column with a step 902 of the connecting mechanism to drive the piston 2 to lift at the same time, the pressure in the cylinder 1 is decreased, and the fluid medium 5 flows back into the cylinder 1 from the central through hole 201 of the piston 2, at this time, the downward-pressing cavity 4 is rotated to separate the column with a step 902 and the empty groove with a step 901, so as to disengage the piston 2, and the downward-pressing cavity 4 is further lifted to take out the sheet metal formed part from the mold 402 of the downward-pressing cavity.

As shown in FIGS. 4A-4C, FIGS. 5A-5B and FIG. 6B, as a preferred embodiment of the present invention, the method includes the following steps when the central through hole 201 is assembled with the pressed piston 8:

• • S1. assembly: the sheet metal 6 to be formed is assembled between the top of the piston 2 and the lower end of the downward-pressing cavity 4;
  • S2. filling with fluid: the downward-pressing cavity 4 is pushed downwards by an external force, and the piston 2 is pushed to move downwards by the downward-pressing cavity, so as to increase the pressure of the fluid medium 5 in the cylinder 1, and as the pressure increases, the pressed piston 8 is pushed by the fluid medium 5 to move upward along the central through hole 201, and the sheet metal 6 starts to be pressed by the pressed piston 8 (refer to FIG. 4A);
  • S3. expanding: with further increase of the external force, the pressed piston 8 continues to move upwards, the sheet metal 6 is forced to deform and gradually fitted into the cavity of the mold 402 (refer to FIG. 4B), until the deformed sheet metal 6 is completely fitted with the cavity of the mold 402 (refer to FIG. 4C), so as to obtain a sheet metal formed part;
  • S4. pick-up: the downward-pressing cavity 4 is lifted, and overlaps the empty groove with a step 901 through the column with a step 902 of the connecting mechanism to drive the piston 2 to lift at the same time, so that the pressure of the fluid medium 5 in the cylinder 1 is decreased, and the pressed piston 8 is moved down by itself under the gravity of the pressed piston, at this time, the downward-pressing cavity 4 is rotated to separate the column with a step 902 and the empty groove with a step 902, so as to disengage the piston 2, and the downward-pressing cavity 4 is further lifted to take out the sheet metal formed part from the mold 402 of the downward-pressing cavity 4.

As shown in FIG. 1, as a preferred embodiment of the present invention, the fluid medium 5 is a mixture of one or more components in hydraulic oil, pure water, brine water and an acid solution or alkali solution.

As shown in FIG. 1, as a preferred embodiment of the present invention, the sheet metal 6 is one or a composite of metal and polymer materials, the metal is one or more of steel, copper, aluminum alloy and magnesium alloy, and the polymer material is one or more of the PC, and PE.

In the embodiment of the present invention, the above-mentioned materials are the only preferred materials, the metal materials are not limited to steel, copper, aluminum alloy and magnesium alloy, and the polymer materials are not limited to PC and PE.

The above is only a preferred embodiment of the present invention, it should be noted that for technicians in this field, some deformations and improvements can be made without deviating from the concept of the present invention. These should also be regarded as the scope of protection of the present invention. These will not affect the effectiveness of the embodiment of the present invention and the practicality of the patent.