EP1073534B1 - Method and apparatus for hot pressing workpieces - Google Patents

Description

The present invention relates to a method for hot pressing workpieces and a hot forming machine to carry out this procedure as described in the preambles of independent claims 1 and 4 defined (see e.g. US-A-3 120 769).

a) Das Werkstück mit Zunder wird in die erste bzw. einzige Matrize einer Warmumformmaschine eingeführt und der Zunder dort während des Formpressens mit Hilfe eines Pressstempels vom Werkstück abgebrochen.

b) Das Werkstück mit Zunder wird in einer ersten Umformstation ausserhalb einer Matrize vorgestaucht und entzundert und in einer zweiten Umformstation in die erste bzw. einzige Matrize der Warmumformmaschine eingeführt und dort formgepresst.

In hot pressing, a cylindrical workpiece is usually first sheared off from a metal rod heated to the forging temperature. Due to the heating, the workpiece is surrounded by a scale coating, ie an oxide layer, which flakes off when the workpiece is formed. There are basically two options for descaling:

a) The workpiece with scale is inserted into the first or only die of a hot-forming machine, and the scale is broken off from the workpiece there during the compression molding with the aid of a press ram.

b) The workpiece with scale is pre-compressed and descaled outside a die in a first forming station and inserted into the first or only die of the hot-forming machine in a second forming station and compression-molded there.

A multi-stage hot forming machine, in which the scale in the die of the first forming station is broken off from the workpiece is in Japanese Utility Model No. 2521909 described. The flaking of the scale inside the die has the disadvantage that the tinder for the most part again is pressed into the workpiece. This has a worse one Surface quality resulted in what a more extensive Machining post-processing and more machining allowance required makes what the material requirement and thus the Cost per workpiece can be increased.

These disadvantages are avoided by hot forming machines, where descaling takes place in a separate first forming station he follows. Such a hot forging press is in CH 594 454 described, in which the workpieces outside be pre-compressed by a die, which is also called free diving, the tinder breaks off and falls off the workpieces. That descaled and pre-compressed workpiece is then with a pair of pliers transported to the second forming station and into the die introduced there, in which it is molded.

In this way it is guaranteed that the chipped Tinder is not pressed back into the workpiece, however an additional forming stage is required for this. Furthermore the outer diameter of the pre-compressed varies Workpiece, since the compressive force is already at an empty neighboring one Forming station, for example, after a usual drop of metal rod ends in normal Operation may occur, is greater than with full neighboring ones Forming stations. For the transport of the workpiece a self-centering transport tongs is therefore practical essential.

JP-A-60030545 is a vertical forming machine for the forming of a workpiece in a closed die known. A lowering sled presses first an upper outer stamp in a die against the previous one inserted workpiece. After that, become an upper inner Stamp and a lower inner stamp pressure monitored by pressed into the workpiece at the top or bottom. Ejecting the formed workpiece is finally done by means of of a lower outer stamp. An upsetting of the Workpieces outside the die are not intended.

Given the disadvantages of the previously known, described above Descaling is the invention of the based on the following task. A procedure has to be created for hot pressing workpieces of the type mentioned at the beginning, in which descaling of the workpieces outside of one Die is made without an additional forming station is needed.

This object is achieved by the hot pressing process according to the invention solved as in independent claim 1 is defined. Claim 4 relates to an inventive Hot forming machine for carrying out the Process. Preferred design variants result from the dependent claims.

The essence of the invention is that in a method for hot pressing of workpieces, in which a Forging temperature of a heated workpiece outside a die descaled by pre-compression using a stamp and then into one or more matrices in the desired shape is pressed, pre-upsetting and that Molding in the first or only die through the same Press stamp in the same movement cycle of the press stamp he follows.

Thanks to the invention, a workpiece to be pressed in a single forming station with a single press ram in a movement cycle, first outside one Matrix pre-compressed and descaled and then in a matrix be compression molded. Because the descaling outside a matrix, i.e. detached, is done, the chipped Tinder not pressed back into the workpiece, like this that its surface quality is not affected. In addition, compared to that described in CH 594 454 Hot forming machine saved a forming station and also a self-centering tongs is not necessary as the transport to the next one Forming station only after pressing in the die takes place, after which the workpieces have a defined outer contour have. The hot pressing process according to the invention thus combines the advantages of the two known, described above Descaling processes without their disadvantages exhibit.

A preferred embodiment of a hot forming machine for carrying out the method according to the invention at least one die, a corresponding off and retractable ejector and a forward and backward movable Press temple. According to the invention, means are available with which the retraction of the extended ejector through the forward moving ram about Workpiece arranged between ejector and ram is so delayed that the workpiece is outside the die is pre-compressible.

When operating such a hot forming machine is by the moving die in the same movement cycle the workpiece is pre-compressed outside the die, pushed into the die, pressed there and finally pushed out of the die by the ejector. With a multi-stage hot forming machine, that will be The workpiece is then transferred to the next forming station in a known manner transferred.

The means of delaying the ejector rebound and the insertion of the workpiece into the die for example hydraulic, pneumatic, mechanical or electromechanical means.

Hydraulic or pneumatic delay means include in a preferred embodiment, one in one Pressure chamber arranged, directly or indirectly with the ejector connected control piston and means for feeding and discharging liquid or gas into or out of the Pressure chamber. The liquid or gas laxatives are formed such that the liquid or gas discharge partially delayed from the pressure chamber and the repulsion of the control piston and the ejector is delayed. They advantageously comprise a liquid or Gas discharge line, in which a throttle or a pressure relief valve is arranged, which is only at one certain liquid or gas pressure opens, or with a control pin is opened and closed.

An advantageous hot forming machine according to the invention with mechanical delay means includes a rotatable Curve for controlling the extension and retraction of the ejector, which are shaped and their rotation with the forward and backward movement of the press stamp is coordinated that the The retracted ejector is pushed back with a delay.

Fig. 1 -

eine Schnittansicht eines Teils eines ersten Ausführungsbeispiels einer erfindungsgemässen Warmumformmaschine mit hydraulischen Verzögerungsmitteln mit einer Drossel während des Vorstauchens;

Fig. 2 -

eine Schnittansicht eines Teils eines zweiten Ausführungsbeispiels einer erfindungsgemässen Warmumformmaschine mit hydraulischen Verzögerungsmitteln mit einem Druckbegrenzungsventil anstelle der Drossel am Ende des Formpressens;

Fig. 3 -

eine Schnittansicht eines Teils eines dritten Ausführungsbeispiels einer erfindungsgemässen Warmumformmaschine mit hydraulischen Verzögerungsmitteln mit einem Steuerstift während des Vorstauchens und

Fig. 4 -

eine Schnittansicht eines Teils eines vierten Ausführungsbeispiels einer erfindungsgemässen Warmumformmaschine mit mechanischen Verzögerungsmitteln.

The method according to the invention for hot pressing workpieces and the hot forming machine according to the invention for carrying out the method are described in more detail below with reference to the accompanying drawings and using exemplary embodiments. Show it:

Fig. 1 -

a sectional view of part of a first embodiment of a hot-forming machine according to the invention with hydraulic delay means with a throttle during pre-upsetting;

Fig. 2 -

a sectional view of part of a second embodiment of a hot-forming machine according to the invention with hydraulic delay means with a pressure relief valve instead of the throttle at the end of the compression molding;

Fig. 3 -

a sectional view of part of a third embodiment of a hot-forming machine according to the invention with hydraulic delay means with a control pin during pre-upsetting and

Fig. 4 -

a sectional view of part of a fourth embodiment of a hot-forming machine according to the invention with mechanical delay means.

Figure 1

The illustrated first embodiment of an inventive Hot-forming machine comprises one by means of a Die holder 6 between an anvil 15 and an anvil cover 18 arranged die 5, which for receiving and Compression molding of a workpiece 4 is used. The bottom of the die 5 has a hole for an extendable and retractable Ejector 7 on, during the pre-upsetting as a pressing resistor for the adjacent workpiece 4, during compression molding as a shaping part for the workpiece 4 and after the compression molding for pushing out the formed workpiece from the die 5 is used. The ejector 7 is with one slidably arranged in a pressure chamber 28 Control piston 8 connected to a pressure ring 12 for Adjustment of the ejector position is provided. The pressure chamber 28 is formed in a clamping ring 13 to which the Die holder 6 screwed on a position wedge 19 is.

At the opposite end of the ejector 7 Control piston 8 with an ejector pin 9 and this with an ejector rod 17 connected in a known manner indirectly by means of a curve, not shown, in the direction Die 5 is slidable. The ejector pin 9 is in a deposit 14 performed, which also for receiving Serves pressing forces and abuts a pressure plate 16. In the backing 14 is a cooling channel 141 and in the ejector pin 9, a cooling channel 91 is arranged, over which one axially extending in the control piston 8 and ejector 7 die hole 10 coolant can be supplied. For cooling and rinsing cleaning of the die 5 are in the ejector 7 Outlet openings 11 are provided. To prevent a Pumping action of the control piston 8 on the side of the ejector 7 while pushing out the formed workpiece 4 from the die 5 is the clamping ring 13 with a Coolant relief opening 159 provided by leads the anvil 15.

The clamping ring 13 and the anvil cover 18 are dashed with a shown liquid inlet bore 21 and a liquid outlet bore, also shown in dashed lines 24 provided. At the liquid inlet hole 21 a liquid supply line 20 is connected, in which a check valve 22 is arranged. To the Liquid outlet bore 24 is a liquid discharge line 23 connected in the one to one Pressure of 350 bar insertable throttle 25 for deceleration the liquid outflow from the pressure chamber 28 is arranged is.

The workpiece 4 is pressed by means of a press ram 1, each in two different positions is shown in half. In the upper position it is still undeformed workpiece 4 between one by means of a Tension spring 3 biased towards the die 5 holding pin 2 and the ejector 7 held. The preload on the retaining pin 2 can alternatively also be done by means of air pressure.

The punch 1 has the workpiece in the lower position 4 pre-compressed and descaled and begins now to push this into the die 5.

The workpiece 4 is moved forward by the Press stamp 1 pre-compressed in that the ejector 7 due to the resistance of the throttle 25 to fluid drainage from the pressure chamber 28 through the control piston 8 is held in its extended position. On easy yielding, i.e. Retracting the ejector 7 during pre-upsetting has no negative impact the descaling and removal of the scale outside of the Die 5. After pre-upsetting the workpiece 4 the further moving die 1 in the Die 5 pushed, the resistance of the throttle 25th against a liquid drain through the increasing Pressure is overcome, and compression molded there. After The ejector 7 pushes the mold - driven by the Above-mentioned curve, not shown, over the ejector rod 17, the ejector pin 9 and the control piston 8 - the workpiece 4 out of the die 5 so that it for example, can be taken over by transport tongs can.

Figure 2

The illustrated second embodiment differs differs from the first in that in the liquid discharge line 23 instead of a throttle 25, a pressure relief valve 26 is arranged with a control line 27. It can for example a pressure relief valve for up to approx. 350 bar from Bieri, Bern. At the end of Pre-upsetting is caused by the forward-moving press ram 1 the pressure on the control piston 8 and thus in the Pressure chamber 28 and liquid discharge line 23 so strong increases that the previously closed pressure relief valve 26 is opened via the control line 27 and so liquid can drain off. As a result, the ejector 7 retracted and the workpiece 4 inserted into the die 5 and molded there. The workpiece 4 and the stamp 1 are shown here at the end of the compression molding.

The following is a description of the first exemplary embodiment directed.

Figure 3

In this third embodiment, there is a difference to the first two through the liquid discharge line 29 the clamping ring 13, the backing 14 and the anvil 15 out. The front part of one with the ejector rod 17 firmly connected control pin 30 is in a bore 31 in the deposit 14 movable back and forth, each depending closes the liquid discharge line 29 after position or leaves it completely or partially open.

As in Fig. 1, the pressing of the workpiece 4 is two shown at different times. In the upper half of the figure is the undeformed workpiece 4 between the biased retaining pin 2 and the ejector 7 held. The rear part of the control pin 30 lies on the ejector pin 9 on and its front part closes the liquid discharge line 29 so no liquid from the Pressure chamber 28 can flow away. The ejector rod 17 and the control pin 30 then begin to move backward and the workpiece 4 is then moved forward by the Press stamp 1 pre-compressed until finally the situation shown in the lower half of the figure is reached, i.e. the workpiece 4 pre-compressed and descaled and the control pin 30 is immediately in front of it, to open the liquid discharge line 29. Hereinafter the ejector rod 17 and the control pin 30 are still moved further backward so that through the liquid discharge line 29 Drain liquid from the pressure chamber 28 can, whereby the control piston 8 and the ejector 7th Direction ejector rod 17 and the workpiece 4 in the die 5 can be pushed. The length of the control pin 30 can be selected according to the desired pre-compression path become.

So that the ejector rod 17 and the associated control pin 30 in front of the ejector pin 9, the control piston 8 and the ejector 7 can be moved backwards on the one hand indirectly controlling the ejector rod 17 Curve be designed so that they have such a backward movement permits, and on the other hand funds must be provided that are responsible for this backward movement. In the illustrated Embodiment is the backward movement generated by a spring 32. But is conceivable, for example also, the ejector rod 17 articulated to one over the To couple curve controlled ejector levers so they not only pushed forward by it, but also backwards is pulled.

The following is a description of the first exemplary embodiment directed.

Figure 4

The fourth exemplary embodiment shown of an inventive one The hot forming machine comprises a machine body 130 and a tool block 100 in which a die 105 and an associated extendable and retractable ejector 107, which is essentially the ejector 7 of the first embodiment corresponds, are arranged. The ejector 107 is via an ejector pin 109 with an axially displaceable Ejector rod 117 connected. One around an axis 152 rotatable ejector lever 150 has a pressure pin 151 for the ejector rod 117 and a freely rotatable roller 153, which abuts a curve 160. The ejector lever 150 is biased by means of a tension spring 170, that the roller 153 is constantly on the curve 160.

By turning curve 160 by means of an in operation in Rotating shaft 161 in the direction of the arrow becomes the ejector lever 150 swung back and forth, the movement at the lever position shown, the pressure pin is imminent 151 the ejector rod 117 in the direction of the die 105 pushes so that the ejector 107 is extended. The Curve 160 is shaped and its rotation so with the fore and aft Backward movement of the press ram not shown here coordinates that pushing back the extended Ejector 107 is delayed. Roll 153 is lying the ejector is located in area A on curve 160 107 in the extended position on hold. The Press stamp moves forward towards die 105, but does not yet press against between ejector 107 and Stamp arranged workpiece. While the role 153 by continuing to turn curve 160 in area B rolls, the ram moves forward and compresses the workpiece, causing the scale to flake off. After leaving area B, the ejector lever 150 swiveled back and the punch rams the ejector 107 and the pre-compressed workpiece in the Die 105, where the latter is compression molded. After that the workpiece is pushed out of the die 105 again and, for example with a pair of tongs into another forming station transferred. Start with a next workpiece then the whole thing all over again. For different heights Workpieces have the curve 160 with respect to the shaft 161 the same can be rotated, so that a time shift of pre-upsetting can be achieved.

To the processes and hot-forming machines described above for hot pressing workpieces are further variations realizable. It should be explicitly mentioned here that instead of the hydraulic shown in FIGS. 1 to 3 Devices also constructed similarly, with the necessary Pneumatic devices provided with seals are conceivable.

Claims (12)

1. Method for the hot-pressing of workpieces, in which a workpiece (4) heated to forging temperature is descaled outside a die (5; 105) by pre-upsetting by means of a press ram (1) and is thereafter pressed to the desired shape in one or more dies (5; 105), characterized in that the pre-upsetting and the compression moulding take place in the first or single die (5; 105) by the same press ram (1) in the same cycle of movement of the latter.
2. Method according to Claim 1, characterized in that, during pre-upsetting, the workpiece (4) is held by an extended ejector (7; 107) of the first or single die (5; 105) outside the latter and, after pre-upsetting, is conveyed by the pressure of the forwardly moving press ram (1) into the die (5; 105), where it is compression-moulded as a result of the further forward movement of the press ram (1).
3. Method according to Claim 2, characterized in that the workpiece (4) is already being moved towards the die (5; 105) during pre-upsetting, but the speed of movement is low, as compared with the speed of movement after pre-upsetting.
4. Hot-forming machine for carrying out the method according to Claim 1, 2 or 3, with at least one die (5; 105), an associated extendable and retractable ejector (7; 107) and a forwardly and backwardly movable press ram (1), characterized in that there are means by which the repulsion of the extended ejector (7; 107) by the forwardly moving press ram (1) via a workpiece (4) arranged between ejector (7; 107) and press ram (1) can be delayed in such a way that the workpiece (4) can thereby be pre-upset outside the die (5; 105).
5. Hot-forming machine according to Claim 4, characterized in that the said delay means comprise a control piston (8), arranged in a pressure chamber (28) and connected directly or indirectly to the ejector (7), and means for the supply and discharge of liquid or gas into and out of the pressure chamber (28), the liquid or gas discharge means being designed in such a way that the liquid or gas discharge from the pressure chamber (28) takes place partially with a delay and delays the repulsion of the control piston (8) and the ejector (7).
6. Hot-forming machine according to Claim 5, characterized in that the liquid or gas discharge means comprise a liquid or gas discharge line (23), in which is arranged a throttle (25).
7. Hot-forming machine according to Claim 5, characterized in that the liquid or gas discharge means comprise a liquid or gas discharge line (23), in which is arranged a pressure relief valve (26) opening only at a particular liquid or gas pressure.
8. Hot-forming machine according to Claim 5, characterized in that the liquid or gas discharge means comprise a liquid or gas discharge line (29) which is opened and closed by means of a control pin (30).
9. Hot-forming machine according to Claim 8, characterized in that the control pin (30) is connected to a forwardly and backwardly movable ejector rod (17) for extending the ejector (7), there being means (32) for moving the ejector rod (17) backwards before the retraction of the ejector (7).
10. Hot-forming machine according to Claim 4, characterized in that it comprises a rotatable cam (160) for controlling the extension and retraction of the ejector (107), the said cam being so shaped and its rotation so coordinated with the forward and backward movement of the press ram that the repulsion of the extended ejector (107) takes place with a delay.
11. Hot-forming machine according to Claim 10, characterized in that the position of the rotatable cam (160) relative to the position of the press ram is adjustable.
12. Hot-forming machine according to Claim 10 or 11, characterized in that an ejector lever (150) can be moved outwards and inwards by means of the cam (160), by means of which ejector lever the ejector (107) can be extended and retracted again via an ejector rod (117) and, if appropriate, an ejector bolt (109).

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