Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D26/00—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces
  • B21D26/02—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure
  • B21D26/033—Deforming tubular bodies
  • B21D26/041—Means for controlling fluid parameters, e.g. pressure or temperature

Definitions

• the invention relates to a method for the hydrostatic shaping of hollow bodies made of cold-formable metal within a mold cavity of a die, pressure fluid being fed into the hollow body from the outside and the hollow body wall being pressed onto the engraving thereof with relative movement to the mold cavity.
• tubular hollow parts made of cold-formable metal e.g. made of 16 MnCr 5
• tubular hollow parts made of cold-formable metal e.g. made of 16 MnCr 5
• high hydrostatic internal pressure there is an additional axial pressure that acts on the pipe end faces. That axial pressure and the simultaneous effect of the internal pressure result in the hollow body wall engaging with the engraving of the mold or die.
• hollow parts produced in this way is, on the one hand, that - e.g. in permanent mold casting - undercut internal cavities can be created, which can either not be machined or can only be produced with complicated tools (e.g. by spark erosion).
• the known hollow parts - in contrast to the hollow parts produced by machining - are relatively light and, as a result of the work hardening associated with the forming, are very resistant with a favorable fiber course, which is similar to that of a forged fiber.
• the known internal high-pressure forming process is perceived as disadvantageous because the hollow body wall cannot fall below a certain minimum thickness. This is essentially due to the fact that the tubular body to be deformed must be designed to be dimensionally stable in order to accommodate the relatively high axial pressure acting on its end faces, which can only be achieved by way of a sufficient wall thickness.
• the known internal high-pressure forming process is always limited to parts in which the force action lines for introducing the axial forces, that is to say the ram and the longitudinal central axis of the tube, coincide exactly. In this way, at most lateral sectoral protuberances can be produced for the production of cross pieces or T pieces, for example.
• the longitudinal axis of the protuberance which is produced sectorally in accordance with the die engraving, runs transversely to the force line of the press ram and the tube (see “Industrial Indicator” loc. Cit., P. 4 and 8).
• the known method is perceived as complex and cumbersome because it requires additional method steps which are caused by the use of the above-described press rams for introducing separate axial forces.
• This invention is based on the object to create the conditions for the known method to be operated more simply and particularly effectively.
• this object is achieved in that the hollow body is kept floating outside its deformation region essentially free of axial force and is only reshaped by the pressure fluid, which initially increases during a filling phase with increasing filling pressure and then in immediate succession is fed into the hollow body during a forming phase with increasing forming pressure, the maximum forming pressure being a multiple of the maximum filling pressure and, during the filling phase, the quantity of hydraulic fluid fed in per unit of time being a multiple of the quantity of hydraulic fluid fed in during the forming phase per unit of time is.
• the method according to the invention is initially very simple because the method steps associated with the use of separate external axial forces can be omitted. Because when separate axial forces are switched off, only the hydraulic fluid takes over the forming work.
• the hollow body is kept floating outside of its deformation area essentially free of axial force.
• material can, so to speak, from that area of the hollow body can be retightened, in which it is only kept floating without axial force.
• stretching deformation of the hollow body is therefore carried out with the exclusion of external axial compressive forces.
• a special feature of the method according to the invention is that it allows rapid operation when a hollow body is formed.
• the entire forming process is divided into two phases, namely a filling phase and the actual forming phase.
• the hollow body to be reshaped in the die is quickly filled with pressure fluid.
• a suitable hydraulic fluid in particular an emulsion intended for hydraulic purposes, can be used as the pressure fluid.
• the forming phase follows in immediate succession with increasing forming pressure.
• the volume displacement of hydraulic fluid is very small in relation to the filling phase.
• the immediate chronological sequence of the filling phase and the forming phase may not only be important because of the rapid process flow. Much more could end up with more easily formable metals A plastic deformation has already occurred in the filling phase, which, if the deformation were interrupted, would lead to a cold work hardening preventing further deformation, which could only be eliminated again by normalizing (normalizing).
• Essential features of the method according to the invention consist in that the air previously located in the hollow body during the shaping is compressed by the pressure fluid fed in, that after the shaping has been completed, the pressure supply for the pressure fluid is switched off, whereupon the compressed Air relaxes and the hydraulic fluid is forced out of the hollow body.
• This measure according to the invention contributes to a rapid operational sequence and, moreover, does not require any complex device means for implementing the method. It is also essential in this connection that the return stroke of the high-pressure displacement piston is accelerated by the relaxing air.
• Another object of the invention is to provide a device for carrying out the method. According to the invention, this object is achieved by a filling pressure generator which is functionally connected to a high pressure generator for the forming pressure and which switches on the high pressure generator when a certain filling pressure is reached.
• filling pressure generators and high pressure generators each represent a piston and cylinder having a displacer, namely a filling pressure displacer and a high pressure displacer, which each generate the filling pressure or the forming pressure with at least one stroke.
• the invention provides that the cylinders of the filling pressure and high pressure displacers each have at least one control slot which is released when the piston is in the bottom dead center position and which is to be passed over in the direction of the top dead center as an inlet opening for the pressure fluid, each cylinder adjacent to the top dead center position of the piston has a line connection for the pressure fluid.
• the cylinders of filling pressure and high pressure displacers therefore do not require any valves that are particularly sensitive to metal particles, but rather have control slots as inlet openings for the pressure fluid, such as are used, for example, in a different context than overflow channels of two-stroke actuators - Internal combustion engines are known.
• a special embodiment of the invention which allows the already mentioned transition from the filling phase to the forming phase in a particularly simple manner with little expenditure on the device, consists in that the control slot of the high-pressure displacer and the line connection of the filling-pressure displacer are connected via a pressure medium line are, while a feed line leads to the die from the line connection of the high-pressure displacer.
• the liquid required for filling the hollow body to be formed is fed from the filling pressure displacer through the cylinder of the high pressure displacer via its line connection and the feed line to the die. If the maximum filling pressure is now reached and a corresponding signal is passed on to the drive of the high-pressure displacer, the high-pressure displacer immediately comes into operation and cuts off the filling-pressure displacer from the feed line leading to the die by the fact that it passes over its control slot connected to the line connection of the filling pressure displacer. When the control slot is passed over, the piston of the high-pressure displacer simultaneously builds up the increasing forming pressure, from which it also separates the filling-pressure displacer without a valve and thus relieves the pressure.
• a very compact filling pressure displacer is achieved in accordance with further features of the invention in that the full pressure displacer with a control slot open on the cylinder side inside a storage container for the pressure fluid is arranged below the liquid level.
• the control slot of the filling pressure displacer is expediently arranged on the region of the cylinder which points away from the bottom of the storage container.
• a particularly inexpensive, easy-to-control and fast-acting drive results from the fact that the filling-pressure displacer and high-pressure displacer are each driven by means of a compressed-air piston-cylinder unit.
• a hydraulic drive optionally also in combination with a pneumatic drive, can be used.
• FIG. 1 shows a more schematic overview of a device for the hydrostatic shaping of hollow bodies made of cold-formable metal, with a filling pressure displacer, a high pressure displacer and with a die;
• Fig. 1 also shows an electro-pneumatic circuit diagram;
• FIG. 2 shows an arrangement of the filling pressure displacer and high pressure displacer according to FIG. 1 in isolation on completion of the filling phase
• FIG. 3 shows the arrangement according to FIG. 2, but the high-pressure displacer is shown at the end of the shaping phase, while the filling pressure displacer is again ready for a new filling stroke
• Fig. 4 is a diagram with the entire pressure curve during the forming of a hollow body
• Fig. 5 is an enlarged detail corresponding to the encirclement designated V in Fig. 4.
• the entire device for the hydrostatic forming of hollow bodies made of cold-formable metal is designated by the reference number 10.
• a die 11 has an upper die 12 and a lower die 13, which between them represent a shape division plane E, indicated by dashed lines.
• the lower die 13 is arranged fixed in space on a press table 14, while the upper die 12 is fixed in a uniform manner with a press upper part 15, ie is arranged to move up and down in accordance with the double arrow denoted by y. Between them, upper die 12 and lower die 13 form a mold cavity 16, in which, as shown in FIG. 1, there is an as yet undeformed tubular hollow body 17 which is held at one end in a feed sleeve 18, which in its position shown in FIG. 1 lung along its horizontal direction of movement x is blocked. Specifically, the hollow body 17 is held on a holding area 19 that does not participate in the deformation and is free of axial force and floating.
• a high-pressure pipeline 20 leads from the feed sleeve 18 to the high-pressure cylinder 21 of a high-pressure displacer 22.
• the interior 23 of the high pressure cylinder 21 ends adjacent to the top dead center position of the displacer 24 with a line connection 25 which merges into the high pressure line 20.
• the high-pressure cylinder 21 Adjacent to the bottom dead center position of the displacer piston 24, the high-pressure cylinder 21 has, as an inlet opening, a control slot 26 which represents an annular expansion of the interior 23 of the high-pressure cylinder 21.
• the filling line 27 of the filling pressure displacer 28 is connected directly to the control slot 26.
• the filling pressure displacer 28 has a storage container 29, in the interior of which the filling line 27 leads there, which is connected to a line connection 30, which leads adjacent to the top dead center position into the cylinder interior 31 of the cylinder head 32 of the filling pressure displacer 28.
• a displacement piston 33 of the filling pressure displacer 28 can be moved up and down within the cylinder interior 31. 1, the displacer 33 is in its top dead center position, in which the inlet openings formed by control slots 34 are passed over.
• the displacer pistons 24 and 33 are driven by compressed air drives (piston-cylinder units) 35 and 36, respectively.
• the compressed air drives 35, 36 cause one
• Pressure translation i.e. an increase in one
• Compressed air source 37 with an air pressure of 10 bar up to a possible hydrostatic forming pressure (the pressure fluid F) up to 3000 bar and more.
• the pneumatic control lines are drawn through in the circuit diagram according to FIG. 1 and the electrical ones are shown in dashed lines.
• top dead center and bottom dead center are of course independent of the spatial position of a cylinder arrangement. In its top dead center, the respective piston has reduced the cylinder interior space as much as possible during its working stroke, while in its bottom dead center it releases the entire displacement.
• FIG. 2 shows in another context the starting position of the displacer 33 in the position of its bottom dead center.
• Fig. 3 shows the piston 33 in the position of its top dead center.
• the displacement piston 33 which is initially in a guide bush 72, thus first passes over the control slots 34 on its way to the top dead center and then displaces the pressure fluid F via the line connection 30, the fill line 27, the interior 23 of the high pressure cylinder 21 and finally via the High-pressure line 20 and via the feed sleeve 18 into the interior of the hollow body 17.
• a contactor 43 transmits a switching signal to the 4/2-way valve 45 via the 74H line 44, which in turn is switched through from its switching position D shown to its switching position C, so that the air cylinder 46 of the compressed air drive 35 receives compressed air via the connections 47, 48.
• the compressed air is supplied via an adjustable throttle 60, so that the reaction speed of the compressed air drive 35 can be adjusted to generate the forming pressure.
• the throttle valve 60 also allows the optimum forming speed to be set, so to speak, from a soft to an abrupt course of the forming.
• the compressed air drive 35 is designed as a tandem cylinder, i.e. the air cylinder 46 has an intermediate floor 49 which divides the cylinder interior into an upper cylinder interior 50 and into a lower cylinder interior 51.
• the piston rod 52 carries two individual pistons 53, 54, so that the total effective piston area of the drive 35 is very large with a compact design.
• the ineffective areas of the cylinder subspaces 50, 51 are vented via the conduit paths 59, 63, 62, 57, 58, which is not the case with regard to subspace 51 individual is shown.
• the piston rod 52 carries a displacement piston 24 with a small cross-section in order to generate the hydrostatic forming pressure.
• the displacement piston 24 passes over the control slot 26 and at the same time separates the Ful effet 27 from the high pressure area.
• the hydrostatic forming pressure rises relatively quickly and is interrupted abruptly by means of a high-pressure switch 55 as soon as the forming has ended.
• the high pressure switch 55 allows a desired pressure maximum P "max" to be set in a manner not shown in detail.
• FIG. 2 is only an enlarged detailed illustration from FIG. 1, with omission of details, FIG. 3 shows the drive 35 with associated high-pressure displacer 22 in the fully extended position (in the top dead center position) of the compressed air pistons 53, 54 and hydrostatic high pressure displacer 24 at maximum pressure.
• the 4/2-way valve 45 receives a switching signal and switches to the switching position D shown in FIG. 1, which means that the previously compressed working compressed air can escape very quickly into the free atmosphere via the connections 47, 48, the air lines 56 and 57 via a silencer 58.
• an electrical signal is simultaneously sent to the press control 39 via the switching line 64, so that the press upper part 15 can start up, while the pressure fluid F has previously been subjected to the compressed residual air inside the hollow body 17 via the line paths 20 , 23 and 27, 30 are given back into the cylinder interior 31 of the filling pressure displacer 28.
• the filling pressure displacer 28 is also made available at its bottom dead center due to an electrical signal coming from the 4/2-way valve 45 to the 4/2-way valve 40 via line 44 (see FIG. 3) set back.
• the compressed air cylinder 41 can even receive the maximum air pressure (approximately 10 bar) from the compressed air source 34 through the lines 64 and 65, specifically via the 4/2-way valve 40 in its switching position B according to FIG 1.
• the cylinder 41 is vented via the lines 42, 66 and the silencer 67.
• Hollow body 17 developed.
• the filling phase ends at nem filling pressure P F of about 65 bar.
• the development of the actual forming pressure of the forming phase begins without interruption, which in the pressure maximum P max at 1500 bar is interrupted practically abruptly with a small amount of time by switching off the compressed air drive.
• the entire pressure development or the entire forming process takes about 0.5-3 s in the example shown.
• the coupling of the piston rod 73 of the air cylinder 41 to the displacement piston 33 takes place by means of a union nut 71.
• the piston rod 52 of the compressed air drive 35 is coupled to the displacement piston 24 by means of a union nut 74.
• the union nuts 71, 74 each allow their displacement pistons 33 and 24 a certain lateral (radial) play, which ensures a tilt-free coupling.

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• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Shaping Metal By Deep-Drawing, Or The Like (AREA)
• Control Of Presses (AREA)

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Citations (3)

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• 1991
  • 1991-02-01 DE DE19914103081 patent/DE4103081A1/de active Granted
• 1992
  • 1992-01-31 WO PCT/DE1992/000062 patent/WO1992013654A1/de unknown

Patent Citations (3)

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