US20070137280A1

US20070137280A1 - Apparatus for forming production parts under internal high-pressure conditions

Info

Publication number: US20070137280A1
Application number: US10/545,664
Authority: US
Inventors: Thoralf Nehls; Heinz-Ruediger Otte
Original assignee: DaimlerChrysler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2003-02-14
Filing date: 2004-01-20
Publication date: 2007-06-21
Also published as: DE10306161B4; EP1592525A1; CA2516115A1; WO2004071689A1; DE10306161A1

Abstract

An apparatus for forming production parts under internal high-pressure conditions, has an internal high-pressure forming tool which includes a top and a bottom die half and also can produce a fluidic internal high pressure inside the closed die. A support plate is movable in a reciprocating manner relative to a head plate, and a supporting means is pushed into the intermediate space produced in the closed state of the die between the lowered support plate and the head plate (9) and supports the two plates against one another during the forming operation while maintaining the distance between them.

Description

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for forming production parts under internal high-pressure conditions. More particularly, the present invention relates to an apparatus having an internal high-pressure forming tool which includes a top and a bottom die half and also means for producing a fluidic internal high pressure inside the closed die, and having a device for applying the locking force for the internal high-pressure forming tool, which device includes tie rods, via which, during the forming operation, the force flow circuit consisting of an internal high pressure having an opening effect and an opposing closing force inside the forming tool is closed, the tie rods being connected at one end to a head plate, to which a support plate supporting the top die half is attached, and being fastened at the other end to a base plate, to which the bottom die half is fastened, and which device has a high-pressure source, via the high pressure of which the halves of the closed die can be pressed against one another during the internal high-pressure forming operation.
DE 196 14 243 C1 discloses an apparatus in which a head plate and a base plate are connected to one another by guide columns. Whereas the bottom end of the columns are anchored in the base plate, their top end passes through the head plate in such a way that the latter is vertically displaceable on the guide rods. Furthermore, lifting cylinders are arranged on the underside of the base plate, by way of which lifting cylinders the head plate can be driven vertically via push rods fastened to the latter. The guide columns are intended to cause the lifting or lowering movement of the head plate during the opening and closing of the forming tool to be effected purely in the vertical direction, so that no transverse forces act on the lifting cylinders. Piston rods serving as tie rods pass through the internal high-pressure forming tool, at which the top die half constitutes one part, and these piston rods can be driven by means of hydraulic cylinders, with a tensile force being formed.
In the known apparatus, a high pressure corresponding to the internal high pressure prevailing inside the internal high-pressure forming tool can be applied, so that the two die halves remain pressed against one another against the spreading effect of the internal high pressure. A complicated press, as was normal in the case of hitherto known devices for internal high-pressure forming, is dispensed with in this case. However, the hydraulic cylinders of the actively working tie rods mentioned require a high volumetric flow during the opening of the forming tool. Furthermore, the closing movement is very complex on account of the displacement of a closing plate. In addition the grooves through which the piston rods of the tie rods pass do not allow uniform pressure against the top die half over the full surface area. The absolutely necessary manipulation of the closing plate, also produces longer process times, which make the forming method uneconomical. Furthermore, the resetting of the forming tool is difficult because the piston rods pass through the tool. In addition, different piston rods are also to be produced for different tools, which leads to a considerable construction cost and investment.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved apparatus which uses an economical internal high-pressure forming process and is implementable in a simple manner.
This object has been achieved according to the present invention by characterized in that the support plate is movable in a reciprocating manner relative to the head plate, and in that the device has a supporting means which can be pushed into the intermediate space produced in the closed state of the die between the lowered support plate and the head plate and supports the two plates against one another during the forming operation while maintaining the distance between them.
As a result, actively working tie rods with hydraulic cylinders and piston rods as well as the closing plate are dispensed with. Because the fact that the support plate is movable in a reciprocating manner relative to the head plate, only one supporting device is required, which, in the closed position of the forming tool. (i.e., when the top die half comes to lie on the bottom die half,) is pushed into the intermediate space between the top side of the support plate and the head plate and bridges the distance between support plate and head plate in the process. In this event, of course, the distance must not change, because otherwise the forming tool opens as a result of the internal high pressure and spreads it apart. The support must therefore inevitably be configured such that it counteracts the internal high pressure in an unyielding manner during the entire forming process, as a result of which the distance produced in the closed position is maintained. In the supporting position, it is necessary for the support to act as far as possible over the full surface area on the surface, covering the forming tool, of the support plate in order to achieve sufficiently good pressure of the support plate against the top die half and thus of the two die halves against one another.
Inasmuch as the tie rods no longer have to pass through the forming tool, but need only surround the forming tool, both the configuration of the tie rods and of the forming tool have been simplified and are independent of one another. The forming tool can, therefore, be reset or even repaired without a corresponding adaptation of the configuration of the tie rods also being necessary. The omission of the closing plate and of a pressure control and fluid feed required in the case of actively operating tie rods simplifies not only the apparatus but also the kinematics of the apparatus parts to be moved during the opening and closing of the forming tool. Thereby, the process times are shortened and the outlay in terms of equipment and the financial input for the internal high-pressure forming process are considerably reduced, resulting in a high efficiency for all types of production parts.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
FIG. 1 is a perspective view of an apparatus according to the present invention in the open position of the forming tool; and
FIG. 2 is a perspective view of the apparatus FIG. 1 in the closed position of the forming tool.

DETAILED DESCRIPTION OF THE DRAWINGS

The apparatus 1 for forming production parts under internal high-pressure conditions shown in FIG. 1 has an internal high-pressure forming tool 2 which includes a top die half 3 and a bottom die half 4, the cavities 5 of which form the common impression. The forming tool 2 has structure for producing a fluidic internal high pressure inside the closed die and also axial rams 7, which are movable by hydraulic cylinders 6, by way of which the inserted production part is sealed off and, if need be, hollow profile material is subsequently pushed from the hollow profile ends into the impression during the forming. Here, the rams 7 are arranged so as to point obliquely upward.
Furthermore, the apparatus 1 includes a device for applying the locking force for the internal high-pressure forming tool 2. This device has column-like tie rods 8, via which, during the forming operation, the force flow circuit consisting of an internal high pressure having an opening effect and an opposing closing force within the forming tool 2 is closed. The tie rods 8 are firmly connected at one end to a head plate 9 of the device and are fastened at the other end to a base plate 10 to which the bottom die half 4 is attached. The tie rods 8 are therefore arranged in a fixed position and the head plate 9 is firmly positioned.
As a variant of the foregoing, the tie rod ends may be mounted in the head plate 9 and the base plate 10 in a floating manner, so that no bending forces which could impair the durability of the tie rods 8 occur in the latter. This simplifies the construction and the control of the apparatus 1 and minimizes the wear of the device compared with a variant in which the tie rods 8 and the head plate 9 move in a reciprocating direction. Furthermore, the absorption of tension during the internal high-pressure forming by the rigid or floating construction of the tie rods 8 and of the head plate 9 is simple and controlled. In this event, the tie rods 8 surround the forming tool 2, so that, due to the generous intervention space produced, especially good accessibility of the tool 2, is achieved, in particular for unhindered handling of the production part during insertion into or removal from the impression of the tool 2.
Arranged below the head plate 9 is a support plate 11 having marginal through-holes (i.e., at the marginal area), through which the tie rods 8 project with slight clearance, as a result of which the support plate 11 is guided in a reciprocating manner along the tie rods 8. The die half 3 of the forming tool 2 is fastened to the underside 12 of the support plate 11. The support plate 11 is therefore movable in a reciprocating manner relative to the head plate 9. Although the support plate 11 can be lifted and lowered by A, for example, a crane-like, manipulator arranged outside the device for applying the locking force or by an external hydraulic cylinder, connected via guide rods, it is particularly advantageous with regard to the saving of construction space if the lifting and lowering of the support plate 11 is effected from the device itself. To this end, the apparatus 1 includes a first hydraulic cylinder 13 which is fastened centrally to the top side 14 of the circular head plate 9 and in which a piston rod 15 is guided. That end 16 of the piston rod 15 which projects from the cylinder is connected to the support plate 11 via guide rods 17 fastened to the latter at the margin, so that said support plate 11 is movable in a reciprocating manner.
For the uniform loading of the hydraulic cylinder 13 and in order to avoid canting during the reciprocating movement, a plurality of horizontally projecting supporting arms 18, as illustrated three supporting arms 18, are arranged on the end 16 of the piston rod 15. The supporting arms 18 are offset symmetrically to one another (again as illustrated by 120°) in the circumferential direction relative to the center piston rod end 16 and carry the vertically running guide rods 17 at their free ends 19. Instead of the supporting arms 18, cable controls and the like can perform the same function.
Furthermore, the device is coupled to a high-pressure source by which high pressure causes the halves 3, 4 of the closed die to be pressed against one another during the internal high-pressure forming operation and without the effect of which the die halves 3, 4 would drift apart in the closed position without a counteraction. According to the present invention, the device has a supporting feature which can be pushed into the intermediate space 20 produced in the closed state of the die (FIG. 2) between the lowered support plate 11 and the head plate 9 to support the two plates 11 and 9 against one another during the forming operation while maintaining the distance between them. The supporting structure is formed in a simple manner by a second hydraulic cylinder 21 which works according to the plunger principle and is connected to the high-pressure source.
For simple manipulation of the hydraulic cylinder 21, a handling device 22 is integrated in the apparatus 1 and is positioned outside the device for applying the locking force and outside the forming tool 2. The supporting structure, i.e., the hydraulic cylinder 21, is held on the handling device 22 in a vertically movable manner and, via a guide arm 23, in a horizontally movable manner according to the double arrows shown in FIGS. 1 and 2. For changing position, the handling device 22 is equipped with travel apparatus 24, which may be rollers or skids. The handling device 22 can thus be transported either in a variable manner via rollers or in a positively driven manner by way of the skids in interaction with a rail system, so that the device can be used together with the second hydraulic cylinder 21 at different work stations. Apart from that, the handling device 22 may also have a plurality of guide arms 23 for manipulating two or more hydraulic cylinders 21, so that a single device 22 can be used simultaneously at a plurality of surrounding work stations which each comprise an internal high-pressure forming tool 2 and a device for applying the locking force. It may also be necessary to push more than one hydraulic cylinder 21 into the intermediate space 20 between the two plates 11 and 9.
After the support plate 11 has been lowered, the hydraulic cylinder 21 is thus pushed with clearance into the intermediate space 20, after which a fluid pressure is applied to the hydraulic cylinder 21 from inside in its pushed-in position. As a result, a plunger of the cylinder 21 is extended and bridges the clearance still present until then. At the same time, the production part inserted into the forming tool 2 is put under internal high pressure, with the fluid pressure on the plunger accordingly increasing at the same time in order to prevent undesirable opening of the forming tool 2 diverging under the internal high pressure. In the process, the hydraulic cylinder 21, as supporting structure, forms the link in the force flow circuit, open until the pushed position is assumed, of force exertion and force absorption. After the forming of the production part has been completed and the internal high pressure has been relieved, the pressure of the second hydraulic cylinder 21 is also relieved, after which its plunger retracts into its inactive position. The hydraulic cylinder 21 is then pulled out of the intermediate space 20 by way of the handling device 22 and the support plate 11 is raised by the first hydraulic cylinder 13, so that the finish-formed production part can be removed and a next blank of a production part can be assigned to the impression of the forming tool 2. This sequence of the working steps of the apparatus 1 can take place very quickly due to its simplicity, which leads to very short cycle times of the entire manufacturing process without losses of quality at the finished production part.
The high-pressure source may be arranged separately from the apparatus for producing the internal high pressure, with the pressure exerted by the source being greater than the internal high pressure, so that the tool halves 3, 4 remain pressed against one another during the forming.
Furthermore, an economically favorable of the method results if the high-pressure source of the second hydraulic cylinder 21 also at the same time forms the way for producing the fluidic internal high pressure, thereby additionally dispensing with a separate pressure control for the hydraulic cylinder 21 while simplifying the equipment. In this embodiment, the internal high pressure corresponds to the closure pressure applied by the supporting effective area is greater than the projected component area of the production part to be deformed. This also ensures that the tool halves 3, 4 bear against one another during the forming operation.

Claims

1-12. (canceled)

13. An apparatus for forming a production part under internal high-pressure conditions, comprising an internal high-pressure forming tool which includes a top and a bottom die half a source of fluidic internal high pressure inside the closed die, and a device for applying the locking force for the internal high-pressure forming tool, which device includes tie rods, via which, during a forming operation, a force flow circuit consisting of an internal high pressure having an opening effect and an opposing closing force inside the forming tool is closed, with the tie rods being connected at one end to a head plate, to which a support plate supporting the top die half is attached, and being fastened at another end to a base plate to which the bottom die half is fastened, and which device also has a high-pressure source, via the high pressure of which the halves of the closed die can be pressed against one another during the internal high-pressure forming operation, wherein the support plate is reciprocatingly movable relative to the head plate, and the device has a supporting feature which can be pushed into the intermediate space produced in a closed state of the die between the lowered support plate and the head plate and supports the plates against one another during the forming operation while maintaining a desired distance between them.

14. The apparatus as claimed in claim 13, wherein, the tie rods are arranged in a fixed position or are mounted in a floating manner while maintaining an axial position.

15. The apparatus as claimed in claim 13 wherein the head plate is fixedly positioned.

16. The apparatus as claimed in claims 13 wherein the apparatus further includes a first hydraulic cylinder connected to the support plate via guide rods to allow the support plate to be reciprocatingly moved.

17. The apparatus as claimed in claim 16, wherein the first hydraulic cylinder is fastened to a top side of the head plate.

18. The apparatus as claimed in claim 16, wherein the first hydraulic cylinder comprises a piston rod a plurality of horizontally projecting supporting arms at an end thereof projecting from the cylinder, the supporting arms being offset symmetrically to one another in a circumferential direction relative to a center piston rod end and carrying guide rods which are vertically operated.

19. The apparatus as claimed in claim 13, wherein the supporting feature is a second hydraulic cylinder operatively connected to the high-pressure source.

20. The apparatus as claimed in claim 19 wherein the high-pressure source is the source for producing the fluidic internal high pressure.

21. The apparatus as claimed in claim 20, wherein the internal high pressure corresponds to the closure pressure applied by the supporting feature which has an effective area greater than a projected component area of the production part to be deformed.

22. The apparatus as claimed in claim 19, wherein the high-pressure source is arranged separately from the source for producing the fluidic internal high pressure, and the pressure applied by the high-pressure source is greater than the internal high pressure.

23. The apparatus as claimed in claim 13, wherein the apparatus further includes a handling device positioned outside the device for applying the locking force and the forming tool, with the supporting feature being movably held on the handling device.

24. The apparatus as claimed in claim 23, wherein the handling device is equipped with travel structure for changing position thereof.