EP3668663A1

EP3668663A1 - Deep drawing tool for deep drawing blanks

Info

Publication number: EP3668663A1
Application number: EP18746678.4A
Authority: EP
Inventors: Marcus Naroska
Original assignee: Neoform Flensburg & Co KG GmbH
Current assignee: Neoform Flensburg & Co KG GmbH
Priority date: 2017-08-15
Filing date: 2018-07-26
Publication date: 2020-06-24
Anticipated expiration: 2038-07-26
Also published as: DE102017118559A1; WO2019034386A1; ES2963928T3; EP3668663B1

Abstract

The invention relates to a deep drawing tool (100) for deep drawing blanks (106) from sheet material to form moulded blanks, comprising a drawing core (102) and a drawing bell (104), which are movable linearly relative to each other, and a blank holder (110) as an abutment for at least one part of the lower edge region of the drawing bell (104), wherein the drawing bell (104) has a radially outer part (124) and at least one radially inner part (126), which is movable relative to the outer part (124). The invention further relates to a corresponding method.

Description

DEEP DEVICE AND METHOD OF DEFLECTING ROHLINGEN

The present invention relates to a deep-drawing tool for deep drawing of blanks of sheet material to moldings, according to the preamble of claim 1, and to a corresponding method.

Such thermoforming tools are used in particular for the production of metal packaging such as container lids or cans. The blanks are punched out of metal sheets and deep-drawn in a deep-drawing tool, so that they receive an approximately cup-shaped form. The deep drawing tool comprises a pulling core and a drawing bell, which are linearly movable relative to each other, such that the pulling bell and the pulling core can be moved towards each other and inserted into each other. This movement will be referred to as "deep drawing motion." In a known and conventional arrangement, the drawing bell is approximated from a stroke position away from the pull core and passed over the pull core, which may be a downward movement of the pull bell In addition, the drawing core may be arranged stationary, but this need not necessarily be the case, but rather the drawing core may be moved towards a stationary drawing bell, in this respect there are different variants a relative movement between the drawing bell and the drawing core possible to perform the deep drawing process.

As an abutment for at least part of the lower edge region of the drawing bell is a so-called fold holder. This may, for example, be arranged annularly around the drawing core and be resiliently mounted so that it exerts a counterforce in the direction of the drawing bell during the deep drawing movement. As a result, the edge region of the blank between the drawing bell and the fold holder is clamped. This prevents the formation of wrinkles due to the material compression at the edge of the molded article. The clamping, however, on the other hand, leads to the problem that so-called material laces and / or lacquered material so-called paint hairs can form on the molding when leaving the clamp, that is hair-like structures and material particles that can contaminate the tool and subsequent machines. To reduce the formation of such paint hairs, material tabs and particles exist various approaches. For example, EP 2 125 264 B1 shows a deep-drawing tool, in which the fold holder is pressed by a pneumatic spring, a so-called die cushion, in the direction of the drawing bell. The removal of the clamping by the die cushion is achieved by a sudden venting of the die cushion, so that the counterforce is set to zero.

The use of such a pneumatic die cushion, however, involves various disadvantages which are avoided by the solution shown in DE 10 2015 113 267 AI of the applicant. Instead of a pneumatic die cushion here are force transmission means which apply a spring force to the fold holder, driven during the deep drawing movement to a movement that leads the drawing bell. By this anticipatory movement of the fold holder is removed from the drawing bell, and the clamping action of the fold holder is released. As a result, the edge of the molding is released, so that the Lackhaar- and Materialzipfelbildung is prevented.

These solutions known in the prior art have in common that the abutment force exerted by the fold holder in the direction of the drawing bell must be completely overcome in order to release the clamping. In addition, in cases in which moldings are drawn very deep with or without residual flange, the problem of deliberately reducing the initial high counter-counterforce and metering such that on the one hand still a clamping is exerted on the residual flange, which prevents wrinkling However, on the other hand, this is kept so low that the material of the blank is not tapered or torn by stretching. For this purpose, a control of the abutment force is necessary, which can not be performed in the prior art described above.

It is therefore an object of the present invention to develop a thermoforming tool of the generic type such that the counter-bearing force acting against the drawing bell or the residual flange of the molding during the deep drawing movement can be controlled and metered more targeted and efficient than it was in the state of Technique is the case.

This object is achieved by a thermoforming tool with the features of claim 1. According to the invention, the pulling bell of the deep-drawing tool has a radially outer part and at least one radially inner part. The drawing bell is thus divided. The radially inner part is movable relative to the outer part. This has the consequence that in a position of the drawing bell, in which the counter-bearing force of the folding holder acts as a clamping force against the radially outer part of the drawing bell, the radially inner part of this abutment force can escape and removed from the fold holder in the relative movement with respect to the radially outer part , This can be done by releasing a coupling between the radially outer part and the radially inner part, after both parts have first been moved in parts together and after lifting this coupling, the inner part relative to the outer part is free to move. However, it is also conceivable a guided movement of the inner part such that it can be moved under control, for example by a drive provided for this purpose to carry out the relative movement.

The abutment force is thus reduced only on a part of the drawing bell, namely on the radially inner part. To reduce the abutment force thus no or only a very small amount of energy is necessary. This energy consumption can be kept lower in any case, as is the case in the prior art.

To avoid the problems occurring in the prior art, it is sufficient during the deep drawing movement to reduce the clamping of the residual flange of the blank only at the radially inner region of the drawing bell. This reduction can take place at a point of the deep-drawing movement, at which the blank is stretched so far that only a relatively narrow residual finger rests between the inner part of the drawing bell and the fold holder. In this way, the desired goal of avoiding Lackhaaren can be achieved with relatively little effort. Alternatively, a very deep drawing of blanks with or without Restfiansch by a new dosage of clamping on the inner edge of the drawing bell is possible.

According to a preferred embodiment of the present invention, the thermoforming tool has deep drawing movement driving means in which the drawing bell and the drawing core are moved toward each other and inserted into each other.

Preferably, the deep-drawing tool according to the invention comprises coupling means, through which the outer part and the inner part of the drawing bell during the deep-drawing movement are coupled and which are intended to cancel this coupling upon reaching a predetermined point of the deep drawing movement. The coupling means may thus in this case be provided to couple the inner part and the outer part of the drawing bell during a part of the path of movement of the deep drawing movement in such a way that they carry out an identical or synchronous movement. After canceling this coupling, the outer part and the inner part can be moved relative to each other, such that the above-described cancellation of the clamping on the inner part of the drawing bell is possible, or the inner part is freely and without drive movable, while the relative movement between the outer Part of the bell and the pull core is continued.

Further preferably, the coupling means comprise means for positive engagement of the outer part and the inner part of the drawing bell into each other. These means may comprise, for example, dogs or stops which are provided on the outer part and on the inner part of the drawing bell and mesh during the deep drawing movement or abut each other, this engagement or stop being canceled upon reaching the predetermined point of the deep drawing movement, so that the decoupling is reached.

More preferably, the coupling means comprise means for exerting a holding force on the inner part of the drawing bell for holding it in a fixed position relative to the outer part.

According to a particular embodiment of the present invention, these means for exerting a holding force comprise at least one spring, by means of which the inner part of the drawing bell is pressed into a fixed position relative to the outer part. This fixed position can for example be defined by a stop on the outer part, against which the inner part is pressed by the spring.

Preferably, this spring is a mechanical spring.

According to an alternative embodiment, this spring is a pneumatic spring. According to another preferred embodiment of the present invention, the thermoforming tool comprises means for canceling or reducing the holding force on the inner part of the drawing bell. This makes it possible to completely neutralize or re-dose the clamping force between the fold holder and the drawing bell at the inner part.

Preferably, in this case, the spring is a compression spring biased between the inner part of the pulling bell and an abutment and the means for canceling or reducing the holding force comprise a drive for moving the anvil in a direction to relax the compression spring. As a result, the pressure exerted by the compression spring on the inner part of the drawing bell pressure is reduced. The compression spring may for example be a mechanical compression spring, in which case the abutment may be formed by a spring holder. Further, it is possible that the compression spring does not act directly, but via coupling elements on the inner part of the drawing bell, so that the pressure of the compression spring is transmitted via such elements. In particular, however, the compression spring may also be a pneumatic compression spring, and the abutment is formed by a piston which is moved by the drive so that the pneumatic compression spring is relaxed. For example, the piston may define a pressure chamber whose volume is increased by the movement of the piston.

According to a further embodiment of the invention, the spring is a compression spring, which is biased between the outer part of the drawing bell and an abutment, via which the spring pressure is transferable to the inner part of the drawing bell. Also in this case, the compression spring may optionally be a mechanical spring or a pneumatic spring. In the latter case, the counter bearing can in turn be formed by a piston of the pneumatic spring, which acts directly or indirectly on the inner part of the drawing bell.

Preferably, in this case, the means for canceling or reducing the holding force comprise a drive for moving the anvil in a direction to tension the compression spring. For example, in the case of a mechanical spring, the drive may move a spring retainer which forms the anvil and to which one end of a mechanical spring is connected. For example, in the case of a pneumatic spring, the drive may be a piston that forms the anvil in a direction to reduce the volume of a pressure chamber are moved, which forms a pneumatic spring cushion, so that the voltage of the pneumatic compression spring is increased.

According to a further preferred embodiment, the means for canceling or reducing the holding force comprise a stop which is arranged to be engaged by the counter-bearing during the deep-drawing movement and, when touched, pushes the counter-bearing in a direction in which the compression spring is either tensioned, when it is biased between the outer part of the drawing bell and the anvil, or is relaxed when it is biased between the inner part of the drawing bell and the anvil. This stop can for example be arranged radially on the peripheral region of the outer part of the drawing bell, so that a catch mounted on the abutment detects the stop during a movement of the drawing bell. However, other arrangements of this stop are also possible, for example in the area radially inside the outer part of the pulling bell.

Further preferably, the spring comprises a pneumatic spring pillow having a first pressure chamber and means for transmitting the pneumatic pressure in the first pressure chamber to the inner part of the puller bell, the means for canceling or reducing the holding force means for controlling the pneumatic pressure in the first pressure chamber include.

Preferably, in this case, the means for controlling the pneumatic pressure in the first pressure chamber comprise a venting device. By venting the first pressure chamber, the spring pressure on the inner part of the drawing bell decreases.

Further preferably, the means for controlling the pneumatic pressure in the first pressure chamber comprises a piston which limits the first pressure chamber and is movably arranged to change the volume of the first pressure chamber. If the piston is moved to increase the volume of the first pressure chamber, the pneumatic pressure is reduced.

According to a further preferred embodiment, the deep-drawing tool according to the invention comprises a second pressure chamber, which is separated from the first pressure chamber by the piston. According to a further preferred embodiment of the present invention, the coupling means comprise a driver for the inner part of the drawing bell, which is held on the outer part of the drawing bell by magnetic force in a magnetic holder with switchable polarity, such that in a first switching position, a first axial position occupies and assumes a second axial position in a second switching position, which is linearly offset from the first axial position.

According to a further preferred embodiment, the coupling means comprise a driver for the inner part of the drawing bell, which is arranged radially displaceable on the outer part of the drawing bell and until reaching the predetermined point of deep drawing movement by a relative to the drawing bell stationarily arranged or mitbeweg with the pulling core curved path in an engagement position is held with the inner part of the drawing bell and is released upon reaching the predetermined point to a radial displacement, by which the inner part of the drawing bell is disengaged from the engagement.

Further preferably, the drawing bell comprises a first radially inner part and a second radially inner part, which first inner part is arranged between the outer part and the second inner part, wherein the deep drawing tool comprises further coupling means, through which the first inner part and the second inner part Part are coupled during the thermoforming movement and which are intended to cancel this coupling on reaching another predetermined point of the deep drawing movement. This makes it possible, for example, to move the two radially inner parts and also the outer part coupled to each other during the deep-drawing movement, at a certain point of the deep-drawing movement first to release the coupling with the outer part, so that only the two radially inner parts are still coupled , And finally to suspend the coupling of the two radially inner parts to a later state. As a result, a further possibility for gradual control of the clamping force is created on different radial parts of the drawing bell. In the context of the present invention, it is not excluded that also other parts of the drawing bell are present, that is, a third radially inner part, etc., which are movable relative to the other parts or with these bewegungsoppelbar. Preferably, in this case, the further coupling means are provided to cancel the coupling of the first inner part and the second inner part after reaching the predetermined point of the deep drawing movement, in which the outer part and the inner part of the drawing bell are decoupled.

The present invention further relates to a method for deep-drawing sheet metal to preform blanks using a deep-drawing tool of the type according to the invention as described above, comprising the following steps: a) providing the drawing bell and the drawing core in a stroke position in which between the underside of the Pulling bell and the drawing core remains a free space, the lower sides of the radially outer part and the radially inner part of the drawing bell substantially flush with each other;

b) positioning a blank in the free space;

c) performing a thermoforming movement by which the drawing bell and the drawing core are moved towards each other, such that the edge of the blank projecting radially beyond the drawing core is clamped between the underside of the drawing bell and the fold holder and pulled over the drawing core;

d) continuing the thermoforming movement until the outer edge of the deep-drawn edge of the blank is clamped between the underside of the radially inner portion of the drawing bell and the fold holder;

e) canceling the coupling between the radially outer part and the radially inner part of the drawing bell, wherein the radially inner part is freely movable relative to the radially outer part or is driven to such a movement relative to the outer part;

f) Further continuation of the deep drawing movement with contact between the fold holder and the outer part of the drawing bell.

It is possible that in step e) or the subsequent step f), the cancellation of the coupling between the radially outer part and the radially inner part of the drawing bell is revised again, ie there is a renewed coupling of the two Ziehglockenteile with each other. Further preferably, during step f), the drawing core is further introduced into the radially inner part of the drawing bell, such that the blank is further deep-drawn and the residual flange is further reduced or the deep-drawn edge of the blank is completely stretched.

In the following preferred embodiments of the present invention will be explained in more detail with reference to the drawing.

Fig. La and lb are schematic sectional views of a first embodiment of the deep drawing tool according to the invention;

FIGS. 2 a, 2 b and 2 c are schematic representations of the relationships of forces at the in

Fig. La and lb illustrated deep drawing tool;

3a and 3b are schematic sectional views of another embodiment of the deep-drawing tool according to the invention in different positions of the deep-drawing movement;

4a and 4b are schematic sectional views of another embodiment of the deep drawing tool according to the invention in different positions of the deep drawing movement;

5a and 5b are schematic sectional views of another embodiment of the deep drawing tool according to the invention in different positions of the deep drawing movement;

6a and 6b are schematic sectional views of another embodiment of the deep drawing tool according to the invention in different positions of the deep drawing movement;

Figures 7a and 7b are sectional views of another embodiment of the deep drawing tool according to the invention in different positions of the deep drawing movement; 8a and 8b are various sectional views of another embodiment of the deep drawing tool according to the invention in different positions of the deep drawing movement;

9a and 9b are various sectional views of another embodiment of the deep drawing tool according to the invention in different positions of the deep drawing movement;

10a and 10b are various sectional views of another embodiment of the deep drawing tool according to the invention in different positions of the deep drawing movement;

11a, 11b and 11c are various sectional views of a further embodiment of the deep drawing tool according to the invention in different positions of the deep drawing movement

Figures 12a, 12b and 12c are various sectional views of another embodiment of the deep drawing tool according to the invention in different positions of the deep drawing movement; and

Fig. 13 sectional view of another embodiment

Deep-drawing tool according to the invention.

1a and 1b show a first embodiment of a deep-drawing tool 100 according to the invention for deep-drawing blanks of sheet metal material into blanks. The deep-drawing tool 100 includes a pulling core 102 and a pulling bell 104, which are linearly movable relative to each other. During this linear movement, the drawing bell 104 can be moved onto the drawing core 102, such that the drawing bell 104 and the drawing core 102 are inserted into each other, as shown in FIGS. 1a and 1b. In the presently illustrated embodiment, the pulling core 102 is stationary and the pulling bell 104 is lowered onto the pulling core 102 in a linear lowering motion until it at least partially encloses the pulling core 102. However, the present invention is not limited to embodiments with a stationary holding core 102. Rather, the drawing bell 104 may be arranged stationary, and the pulling core 102 is in Direction of the drawing bell 104 raised. Furthermore, embodiments are conceivable in which the pulling bell 104 is located at the bottom and the pulling core 102 is arranged above it. Moreover, the above-described relative movement of the approach of the drawing bell 104 and the pulling core 102 is reversible, so that they can be separated and separated again from each other.

The movement of the drawing bell 104 and the drawing core 102 toward and into one another is to be referred to below as a deep drawing movement. It serves to deep-draw a blank from the blank 106. The blank 106 is arranged for this purpose on the side of the pulling core 102, which faces the pulling bell 104. By the deep drawing movement of the radially outer edge of the blank 106 is detected by the lower edge portion 108 of the drawing bell 104 and deep drawn on the drawing bell 104. In this case, it is necessary to clamp the outer edge of the blank 106. This is done by a fold holder 110, which is arranged as an abutment for the lower edge region 108 of the drawing bell 104 below the same. The pleat holder 110 is pushed upwards by a pin 112 in the direction of the pulling bell 104. For this purpose, the pin 112 is pressurized on its underside by means of a spring 114 with pressure. In this way, the radially outer edge of the blank 106 is clamped between the edge region 108 of the drawing bell 104 and the top of the fold holder 110.

Radially outside the pleat holder 110, a cutting ring 116 is further arranged, on which a radially outermost edge 118 of the blank 106 rests flat. When lowering the pulling bell 104, this outermost edge 118 is sheared off by a radially further inner edge region of the blank 106.

The drawing bell 104 is shown in FIGS. 1a and 1b as well as in the following figures in longitudinal section, wherein the cutting plane lies in the axis of movement of the linear deep drawing movement. In the horizontal cross section (perpendicular to the plane of the drawing), the drawing bell 104 has a cross section which is adapted to the desired shape of the blank, eg circular, rectangular or oval, as well as the pulling core 102. The pleat holder 110 is disposed in and around the pulling core 102 in the corresponding shape. The drawing bell 104 has an upper part 120, the upper side of which is closed by a flat ceiling area 122, a radially outer part 124, which is arranged below the upper part 120 and adjoins it, and a radially inner part 126, which is radial is disposed within the radially outer portion 124. For the sake of simplicity, the radially outer part 124 will be referred to hereinafter as the outer part 124 of the drawing bell 104 and correspondingly the radially inner part 126 as the inner part 126.

The inner part 126 is movable relative to the outer part 124. In the present embodiment, the inner portion 126, which is approximately cylindrically shaped, can be displaced along its cylinder axis relative to the outer portion 124. In Fig la, the inner portion 126 assumes a lower stop position in which an annular stop 128 rests on the radially outer side of the inner portion 126 on a corresponding stop 130, which is formed by an inner step of the outer portion 124. In this lower stop position, the undersides of the inner part 126 and the outer part 124 close to each other.

From this stop position in Fig. La, the inner part 126 can move upwards into an upper stop position, in which the annular stop 128 can be moved to an upper stop 132 at the inner lower edge of the upper part 120. The stops 130 and 132 thus limit an axial displacement of the inner part 126. In the upper stop position shown in Fig. Lb, the bottom 134 of the inner part 126 is raised relative to the lower side 136 of the outer part 124.

The stops 130 and 132 on the outer part 124 and the annular stop 128 on the inner part 126 constitute coupling means by which the outer part 124 and the inner part 126 of the drawing bell 104 are coupled during a portion of the deep drawing movement. This means in the present case that the outer part 124 and the inner part 126 are integrally connected by this coupling and perform the same movement. This thermoforming movement (in the present embodiment, the drawing bell 104 down) takes place against the abutment force of the folding holder 1 10 from below, which is generated by the spring 114. The coupling means further comprise means for exerting a holding force on the inner part 126 by which it is pressed down against the lower stop 130 of the outer part 124. These means for exerting a holding force are not shown in FIGS. 1a and 1b, but will be described later on the basis of further examples Embodiments explained. In particular, these means may comprise a further spring through which the inner part 126 is pressed down against the stop 130 of the outer part 124.

At a predetermined point of the deep drawing movement, the coupling is canceled by the coupling means. This means that the outer part 124 and the inner part 126 are no longer moved together, but the inner part 126 can perform a relative movement to the outer part 124. This is in particular an upward movement, as shown in Fig. Lb, through which the annular stop 128 of the inner part of the stop 130 of the outer part 124 dissolves. At the same time, the underside 134 of the inner part 126 is raised relative to the lower side 136 of the outer part 124. This release of the coupling of the inner member 126 to the outer member 124 may be effected by means for canceling or reducing the holding force on the inner member 126. These means may include a drive to move the inner part 126 relative to the outer part 124, in the present embodiment upwards, or they may cause the inner part 126 to move completely freely with respect to the outer part 124 and thus one from below acting force can move axially upward.

Preferably, the coupling between the inner member 126 and the outer member 124 is canceled at a point of the deep drawing movement, at which the blank 106 is deep drawn so that only a residual flange 138 between the bottom 134 of the inner member 126 and the fold holder 110 rests. When the coupling is removed, the underside 136 of the outer part 124 can thus abut directly on the fold holder 10 and press it further against the force of the spring 114. Meanwhile, due to the cancellation of the coupling, the clamping between the lower surface 134 of the inner member 126 and the fold holder 110, through which the residual flange 138 is held, is either completely canceled or its clamping force is greatly reduced. If the thermoforming movement is then continued, the residual flange 138 can be completely stretched between the inner wall of the outer part 126 and the outer cylindrical wall of the pulling core 102, without lacquer hairs forming on the remaining residual flange 138.

According to the invention, therefore, only the holding force on the inner part 126 of the drawing bell 104 has to be reduced in order to avoid the counter bearing force by the fold holder 110. This is a significant advantage over the known from the prior art thermoforming tools, in which the abutment force must be completely eliminated.

The balance of power should be explained in more detail with reference to the schematic diagrams in FIGS. 2a, 2b and 2c.

These figures each include an enlarged view of the skirt portion 108 of the die 104, including the bottoms 136, 134 of the inner portion 126 and outer portion 124 of the die 104, the upper portion of the pleat holder 110, and the upper portions of the die core 102 and outer die Cutting rings 116. Shown is also the blank 106 in various positions during the deep drawing movement.

In Fig. 2a, the residual flange 138 of the blank 106 is clamped between the flush bottom surfaces 134, 136 of the inner portion 126 and the outer portion 124. The force exerted from above by the outer part 124 is denoted by F2, and the force exerted by the inner part 126 in the same direction by F4. From below acts on the fold holder 110 in the radially outer portion which is axially opposite the outer portion 124 of the drawing bell 104, the counterforce force Fl, and optionally a parallel additional force component Fla in a region in which the fold holder 110 an axial pressure on the inner part 126 can exercise. In addition, a force F3v acts as a vertical component of a force F3 acting on a rounded inner edge region 140 of the inner part 126 due to the counterforce of the material of the blank 106. Fla can become very small or equal to zero if this rounded edge portion 140 extends radially outwardly to the outer portion 124 so far that no counterforce force is exerted directly above the fold holder 110 upwardly on the inner portion 126.

This results in:

F4 = F3v + Fla, where Fla = 0. The holding force F4 on the inner part 126 must therefore be used to release the clamping at the radially inner region of the drawing bell 104. It is much smaller than a total force F5, which would be used to counteract the full counterforce from below and which is equivalent to

F5 = F1 + Fla, where Fla = 0.

In Fig. 2b and 2c is shown how the force F4 greatly reduced or completely eliminated to cancel the clamping. This is preferably done in the deep-drawing process in a situation in which the residual flange 138 is shortened so far radially inward, that it only rests between the radially inner portion 126 and the radially inner lower edge of the fold holder 110. On the other hand, the outer part 124 abuts directly on the upper side of the fold holder 110, so that the fold holder 110 can be pressed further downwards. By reducing or canceling the force F4 through the inner portion 126, the residual flange 138 is released and is no longer clamped. If, from the position in FIG. 2b, the deep-drawing movement is continued with renewed coupling of the inner and outer part (FIG. 2c), the residual flange 138 can be completely stretched. The formation of enamel hairs on the residual flange 138 is avoided.

3a and 3b show an embodiment of the deep-drawing tool 200 according to the invention, in which the pulling bell 204 is formed similar to the previous embodiment of the deep-drawing tool 100. Accordingly, the pulling bell 204 comprises an upper part 220, an axially subsequent outer part 224 and a radially inner part 226.

Fig. 3a shows a coupling position in which the inner part 226 is coupled to the outer part 224 so that they can perform together with the upper part 220, the deep drawing movement of the pulling bell 204 down. These coupling means comprise the annular stop 228 on the radially outer side of the inner part 226 and a stepped stop 230 on the inside of the outer part, comparable to the stop 130 in Fig. La and Fig. Ib. The stop 228 of the inner part 226 is pressed down against the stop 230 of the outer part 224 by a compression spring 250, which rests between the upper edge 252 of the inner part 226 and a spring holder 254. The upper edge 252 forms a first stop 252 for the compression spring 250, while the spring holder 254 forms an abutment. In the coupled position in Fig. 3a, the compression spring 250 presses the radially inner portion 126 down, so that the stop 228 abuts the stop 230.

In order to decouple the inner part 226 and the outer part 224, the abutment 254 formed by the spring holder is moved upwards by a drive (not shown in more detail), ie away from the first stop 252. This has the consequence that the compression spring 250 is relaxed and the pressure force, which presses the inner part 126 down, is reduced. In the embodiment shown here, the spring holder 254 is moved so far by the drive that the inner part 226 abuts with its stop 228 at an upper stop 232 at the lower inner edge of the upper part 220. By the drive for moving the spring holder 254 upwards thus the holding force which presses the inner part 226 in a fixed position relative to the outer part 224, repealed. In the position in Fig. 3b, a re-coupling between the inner part 226 and the outer part 224 takes place, with which the deep drawing movement can be continued.

The arrangement of the compression spring 250 and the spring retainer 254 as a means for holding the inner part 226 in the coupling position and a drive for lifting the spring retainer 254 to cancel or reduce the holding force, with the embodiment in the thermoforming tool 100 in Figs and lb combinable. Furthermore, this embodiment can also be operated with a pneumatic compression spring which replaces the mechanical compression spring 250 shown here. The spring holder 254 is replaced in this case by a piston which limits the volume of the pneumatic compression spring. The piston thus acts here as an abutment of the pneumatic compression spring. When the piston is lifted by the drive, the pneumatic compression spring is released.

An alternative embodiment of a deep drawing tool 300 provided with means for holding the inner part 226 in the coupling position and means for canceling or reducing the holding force is shown in Figs. 4a and 4b. The training of individual parts of the drawing bell including its upper part 320, the underlying radially outer part 324 and the radially inner part 326 corresponds to the drawing bell 204 in Fig. 3a and 3b, as well as the annular outer stop 328, the stepped stop 330 on the outer part 324th and the stopper 332 at the upper part 320, between which the stopper 328 is movable up and down.

Within the upper portion 320 is a compression spring 350 between the flat ceiling portion 322, which closes the drawing bell 304 at the top, and a spring holder 354 arranged underneath. This spring holder 354 is here directly (alternatively also indirectly) on the upper edge of the inner part 326 and forms an abutment for the compression spring 350. This upper edge forms a third stop 352, via which the pressure of the compression spring 350 via the spring holder 354 on the inner Part 326 is transferable and thus exerts a force for holding the inner part 326 in the coupling position. The ceiling portion 322, however, forms a second stop 356 for the compression spring 350, which is coupled to the outer part 324 motion.

In Fig. 4a is the spring posture 354 in a lower position, in which the inner part 326 is coupled to the outer part 324, since the annular stop 328 abuts against the stop 330. This coupling can be canceled by a non-illustrated drive the spring retainer 354 moves upward and the compression spring 350 compresses. In the position in FIG. 4 b, a renewed coupling between the inner part 326 and the outer part 324 is achieved by abutting the stop 328 on the stop 332. Between these positions, the inner part 326 and the outer part 324 are decoupled from each other.

The means for canceling or reducing the holding force of the compression spring 350 thus include here the drive, which moves the spring holder 354 up and relieves the inner part 326 of the pressure of the compression spring 350. Analogous to the previous embodiment in FIGS. 3 a and 3 b, a pneumatic compression spring may also be used instead of a mechanical compression spring 350, wherein the spring support 354 is to be replaced by a piston as an abutment. The piston exerts a pressure on the inner part 326. When the piston is lifted by a drive, the volume in the pressure chamber of the pneumatic compression spring is compressed and the pneumatic compression spring is tensioned, while the inner part 326 is relieved. 5a and 5b show a further embodiment of a deep-drawing tool 400 with a deep-drawn bell 402, which comprises an upper part 404, a lower radially outer part 424 and a radially inner part 426. An annular outer stop 428 on the inner part 426 abuts between a lower stop 430 on the inside of the outer part 424, corresponding to the stop 330 of the previous embodiment of the deep drawing tool 300, and an upper stop 432 is on the radially inner corresponding to the position of the stop 332 arranged lower edge of the upper part 420. As in the previous embodiment of the deep drawing tool 300, a compression spring 450 is disposed between a second stop 456 on the underside of the flat ceiling portion 422 and a spring retainer 454 resting on a third stop 452 formed by the top edge of the inner portion 426. The spring retainer 454 is thus urged downwardly on the radially inner portion 426 by the compression spring 450, so that a holding force is applied to the inner portion 426 for holding it in a fixed position relative to the outer portion 424, in which the stopper 428 against the Stop 430 is held. Analogous to the previous embodiment in FIGS. 4 a and 4 b, the spring holder 454 forms an abutment for the compression spring 450.

In the present embodiment, the spring retainer 454 has a radially outwardly projecting cam 458 which extends through the cylindrical wall of the upper portion 420 of the pulling bell 404. A fourth stop 460 is statically disposed outside of the pulling bell 404, in a position in the path of travel of the driver 458 during a downward movement of the pulling bell 404.

During the deep drawing movement, the driver 458 of the spring holder 454 detects the fourth stop 460. As a result, the spring holder 454 is pushed upwards, ie in the direction of the second stop 456 on the ceiling region 422, so that the inner part 426 is relieved of the holding force. This situation is shown in Fig. 5b. As a result, the stop 428 detaches from the stop 430 so that the inner part 426 is released and its coupling with the outer part 424 is released. Analogous to FIGS. 4 a and 4 b, the mechanical compression spring 450 can be replaced by a pneumatic compression spring, and a piston acts as an abutment instead of the spring retainer 454, which, like the spring retainer 454 described above, is equipped with a driver 458. A lifting of the piston thus also causes a compression of the pneumatic compression spring. 6a and 6b show an embodiment of the deep-drawing tool 500 with a pulling bell 504, the construction of which is comparable to the pulling bell 404 of the deep-drawing tool 400 and thus comprises an upper part 502, a radially outer part 524 arranged underneath and a radially inner part 526. The arrangement of the stop 528 on the radially inner part 526 and the stops 530 and 532 on the radially outer part to limit the movement of the stop 528 correspond to the embodiment of the deep-drawing tool 400. Also agrees is the arrangement of a spring support 554 as an abutment, which is arranged by an above Compression spring 550, which is supported up against a second stop 556 on the ceiling portion 522 of the upper part 520, is pressed down against the upper edge of the inner part 526, which forms a third stop 552. The spring holder 554 here also has a driver 558 projecting through the cylindrical outer wall of the upper part 520, which strikes against a fourth stop 560 during the deep-drawing movement.

The fourth stop 560 is in the present embodiment, however, not static, but arranged on a vertically movable scraper 564 and connected via a further compression spring 562 with a radially outwardly projecting portion of the upper part 520 of the pulling bell 504. In the coupling position of the inner part 526 on the outer part 524 shown in FIG. 6 a, the catch 558 is at a distance from the fourth stop 560, which is maintained by the compression spring 562.

Fig. 6a shows a position of the deep drawing movement, in which the scraper 564 already abuts a stop and can not be moved further. As a result of the further axial deep-drawing movement of the pulling bell 504, it moves downwards relative to the scraper 564, and the catch 558 of the spring holder 554 engages the fourth stop 560 and is pushed upwards, as shown in FIG. 6b. As a result, the force of the compression spring 550 on the inner part 526 is reduced or canceled, so that the holding force for holding the inner part 526 in the coupling position on the outer part 524 is reduced or canceled.

As in the previous embodiments, also in the embodiment in Figs. 6a and 6b, the compression spring 550 and also the compression spring 562 can be selectively formed by mechanical springs or pneumatic springs. The spring holder 554 is replaced in this case by a piston as an abutment. Corresponding piston surfaces are to be provided on the upper and lower stop surfaces of the pressure spring 562, which delimit a corresponding pressure chamber.

7a and 7b show a further embodiment of the deep-drawing tool 600 according to the invention with a scraper 664, the upper edge of which forms a fourth stop 660, which is comparable to the fourth stop 560 of the previous embodiment of the deep-drawing tool 500, but is arranged inside the pulling bell 604. The puller bell 604 is similar in construction to the puller bell 504 in FIGS. 6a and 6b, and includes an upper portion 620, an outer portion 624 disposed thereunder, and an inner portion 626 that interposes between the outer portion 624 and the wiper 664. The location of the outer stop 628 on the inner portion 626 corresponds to that of the stop 528 in Figs. 6a and 6b, i. the stop 628 is disposed between upper and lower inner stops 630 and 632 of the outer part 624 so that the inner part 626 is movable up and down between the stops 630 and 632.

The spring retainer 654 is urged downward by a compression spring 650 onto the top edge of the inner portion 626 so that the inner portion 626 is retained in its coupling position on the outer portion 624. The arrangement of the compression spring 650 between the second stop 656 on the ceiling portion 622 of the upper part 620 and the spring support 654 corresponds to Fig. 5a and Fig. 5b, such that the spring support 654 is pressed onto the upper edge of the inner part 626 as a third stop 652 and thus, a holding force is exerted downward for holding the inner part 626 in the coupling position on the outer part 624, in which the abutment 628 abuts against the stop 630.

While a radially outwardly projecting portion 670 of the spring retainer 654 extends into and is guided within an opening 672 within the cylindrical wall of the upper portion 620, a radially inwardly projecting portion 674 of the spring retainer 654 projects beyond the fourth stop 660 on the wiper 664. A compression spring 662, in the position in Fig. 7a, maintains the fourth stop 660 spaced from the inwardly projecting portion 674 of the spring retainer 654. During the retracting movement, the wiper 664 reaches a fixed stop position and approaches the cantilever portion 674 of the spring retainer 654. whereupon the spring holder 654 during the further deep drawing movement detects the fourth stop 660 and is pushed upwards, ie in the direction of the second stop 656. As a result, similar to the embodiment of the thermoforming tool 500 in FIGS. 6a and 6b, the coupling between the inner part 426 and the outer part 624 is canceled. The main difference with respect to the deep-drawing tool 500 is that the fourth stop 660 arranged on the wiper 664 is not arranged outside, but inside the pulling bell 604.

As in the previous embodiment, the compression springs 650 and 662 may each be formed by pneumatic springs. While in the above-described illustration, the spring retainer 654 forms an abutment for the compression spring 650, in the case of using a pneumatic spring, this abutment may be constituted by a piston which is used in place of the spring retainer 654.

8a and 8b show a further embodiment of the deep-drawing tool 700 according to the invention, the pulling bell 704 of which in turn has a substantially cylindrical upper part 770 with a ceiling region 722 closing up the interior of the pulling bell 704, and a lower outer part 724 and an inner part 726 , which are constructed like the outer and inner parts 624, 626 of the deep drawing tool 600 in Figs. 7a and 7b, including the outer stop 728 on the inner part 726, between the lower stop 730 on the outer part 724 and an overlying further stop 732 on the upper part 720 is movable. Also in the present embodiment, the inner part 726 is pressed down against the stopper 730 by a holding force so that the inner part 726 can assume a fixed coupling position relative to the outer part 724 during the deep drawing movement. In the present case, the means for exerting such holding force comprise a pneumatic spring 750 comprising a piston 752 which is movable up and down as an abutment within the drawing bell 704 between the upper edge 754 of the inner part 726 and the ceiling area 722. To the cylindrical inner wall of the upper part 720, the piston 752 is sealed by an O-ring 756.

Above the piston 752 is located within the pulling bell 704, a space 758 which is opened by a radial opening 760 in the cylindrical outer wall of the upper part 720 to the outside and via a valve (not shown) can be acted upon with compressed air. By this compressed air, the piston 752 is down directly or indirectly (ie For example, via a coupling element, not shown here) against the upper edge 754 of the inner part 726 driven.

On the one hand, the interior 758 can be pressurized via the valve but, on the other hand, vented in order to reduce or remove the holding force on the inner part 726 against the stop 730. The valve thus provides a means for canceling or reducing the holding force by which outer and inner parts 624, 626 are held in their coupling position.

The deep-drawing tool 800 in FIG. 8 b likewise comprises a pneumatic spring cushion 850 with a piston 852 which is constructed like the piston 752 in FIG. 8 a and arranged as an abutment, in which case the space 858 between the upper side of the piston 852 and the ceiling region 822 of the upper part 820 can be pressurized or vented through a radial opening 860. The arrangement of the inner part 824 and the outer part 826 corresponds to that of the inner part 724 and the outer part 726 in Fig. 8a.

However, unlike the previous embodiment of FIG. 8a, the piston acts on a pin 864 that extends vertically downwardly through an opening 866 in a bottom 867 of the upper part 820 of the pulling bell 804. The pin 864 in turn pushes the upper edge 854 of the inner part 826 of the pulling bell 804 down so that a radially outer stop 828 abuts the inner part 826 against a stop 830 on the inside of the outer part 824. An upper stop 832 on the inner lower edge of the upper part 820 limits the movement of the stop 828 upwards.

Fig. 8b shows a sectional view in which only a single pin 864 can be seen. Preferably, a plurality of pins may be disposed along the annular top edge 854.

A difference from the deep-drawing tool 700 in FIG. 8a is that the piston 852 does not act directly on the inner part 826 and pushes it downwards, as is the case in FIG. 8a, so that the holding force is exerted via the pin 864 becomes.

9a and 9b show a further embodiment of a deep drawing tool 900 according to the invention with a pulling bell 904 which, like the pulling bell 804, has an upper part 920, an outer part 924 arranged underneath and an inner part 926, which is arranged axially displaceable relative to the outer part 924. In the manner already described, the inner part 926 can be coupled via a radially outer stop 928 to the outer part 924, which has an inner stop 930 against which the stop 928 can abut.

To exert a holding force which presses the inner part 926 down against the stop 930 of the outer part 924, in the present case, a driver 950, which is held vertically displaceable within an opening 952 in the cylindrical outer wall of the upper part 920. The driver 950 is located with its inner end on the upper edge 954 of the inner part 926, so that in a lower position of the driver, the inner part 926 is held in the coupling position with the outer part 924 in which the stops 928 and 930 lie on each other ,

In this position, which is shown in Fig. 9a, the driver 950 is held by magnetic force. The opening 952 is in fact designed as an electromagnetic holder with switchable polarity. The position in FIG. 9a corresponds to a first switching position in which driver 950 is attracted magnetically from the underside 956 of the opening 952. By switching the shift position, the cam 950 is repelled from this lower end 956 and moves toward the upper end 958, as shown in Fig. 9b. As a result, the holding force is released, which presses the inner part 926 down against the stop 930. The inner part 926 is then decoupled from the outer part 924 and can move upwards. In the position in Fig. 9a, the cam 950 is attracted to the magnetic holder upper end 958 and assumes a second axial position, which is linearly offset upwardly from the first axial position in Fig. 9a. Correspondingly, the inner part 926 bears against an upper stop 932 on the inner lower edge of the upper part 920 of the pulling bell 904.

The driver 950 thus represents an embodiment of the coupling means by which the inner part 926 can be coupled to the outer part 924 of the pulling bell 904. The switching of the polarity of the magnetic holder from the first switching position in Fig. 9a to the second switching position in Fig. 9b may take place upon reaching the predetermined point of the deep drawing movement, in which the inner part 926 is to be released. 10a and 10b show a further embodiment of a deep-drawing tool 1000 according to the invention with a pulling bell 1004 which, like the preceding embodiments, has a substantially cylindrical upper part 1020, a radially outer part 1024 arranged underneath and a radially inner part 1026. The inner part 1026 is axially displaceable with respect to the outer part 1024, with an outer stop 1028 on the radially inner part 1026 being provided to abut against an inner stop 1030 of the radially outer part 1024, so that the outer part 1024 and the inner part 1026 coupled together as shown in Fig. 10a.

In this coupling position, the inner part 1026 is held by a driver 1050 which extends radially through an opening 1052 in the cylindrical wall of the upper part 1020 and is radially displaceable outwardly and inwardly. A beveled abutment surface 1054 at the radially inner end of the driver 1050 rests on a corresponding upper abutment surface 1056 of the inner part 1026. If the driver 1050 is in the pushed-in position in FIG. 10a, its beveled abutment surface 1054 pushes the inner part 1026 downwards and thus the stop 1028 against the stop 1030, so that the coupling between the inner part 1026 and the outer part 1024 is reached.

In this position, the cam 1050 is held by a cam track 1058 that is stationarily located outside the puller bell 1004. During the deep drawing movement, the pulling bell 1004 moves along this cam track 1058 such that the cam 1050 is pressed radially inwardly by an inner surface 1060 of the cam track 1058 facing the bell jig 1004. The radially outer end 1062 of the driver 1050 then slides on this inner surface 1060 of the cam track 1058.

At a predetermined point of the deep drawing movement, the outer end 1062 of the follower 1050 reaches a lower end 1064 of that face 1060 and is released for outward movement, as shown in Fig. 10b. As a result of the displacement of the driver 1050 outwardly there, its abutment surface 1054 is likewise moved outward and releases the inner part 1026 for upward movement, so that the coupling between the inner part 1026 and the outer part 1024 is released. The inner part 1026 can then move up to an upper inner stop 1032 at the lower inner edge of the upper part 1020 of the pulling bell 1004, so that a renewed Coupling of the inner part 1026 is achieved with the outer part 1024 in a position in which the inner part 1026 is displaced upwards relative to the outer part 1024.

11a, 11b and 11c show an embodiment of the deep-drawing tool 1100 according to the invention, in which the pulling bell 1104 has a first radially inner part 1126 and a second radially inner part 1128, in addition to the upper part 1120 and the outer part 1124 arranged underneath the first inner part 1126 is disposed between the outer part 1124 and the second inner part 1128. The arrangement of the first inner part 1126 relative to the outer part 1124 corresponds to that of the outer part 224 and the inner part 226 of the deep-drawing tool 200 in Figs. 3a and 3b, also with respect to the means for exerting a holding force on the first inner part 1126 for holding it in a fixed coupling position relative to the outer part 1124. A radially outer stop 1130 on the first inner part 1126 is linearly displaceable between an inner lower stop 1132 and an upper stop 1134 on the upper part 1120 of the pulling bell 1104. The stopper 1130 is pressed down against the stop 1132 by a compression spring 1150 biased between a first stop 1152 formed by the upper edge of the first inner part 1126 and a spring retainer 1154. The action of the compression spring 1150 and the spring support 1154 is the same as that of the compression spring 250 in the spring retainer 254 of the deep drawing tool 200, ie, the spring retainer 1154 can be moved upward as an abutment of the compression spring 1250 to increase the holding force on the first inner part 1126 reduce or cancel.

The second inner part 1128 is coupled to the first inner part 1126 by a driver 1156 which is radially slidable in the first inner part 1126 between an inwardly pushed position as shown in FIG. 11a and an outward pushed position (FIG. Fig. 11c) is displaceable. In the pushed inward position of the driver 1156 forms on its underside a stop for the second inner part 1128 so that it abuts on the driver 1156 from below and can not be moved even further relative to the first inner part 1126 upwards. The first inner part 1126 and the second inner part 1128 are thus coupled together. Thus, by the compression spring 1150, the first inner part 1126 and the second inner part 1128 are slid downwardly as a unit into the coupling position defined by the stopper 1132 and held therein. Upon reaching a predetermined point of the thermoforming movement, the coupling between the first inner part 126 and the outer part 1124 can first be canceled by the drive moving the spring holder 1154 upwards. This situation is shown in Fig. 1 lb. The position of the follower 1156 remains unchanged so that the coupling of the first inner part 1126 and the second inner part 1128 and their relative position to each other is maintained.

At a later later point of the deep drawing movement, the coupling between the first inner part 1126 and the second inner part 1128 can then be canceled by the driver 1156 being pushed outward, that is to say into the first inner part 1126. As a result, the second inner part 1128 can be moved upwards. Optionally, this results in a further stop position 1157 in the form of an inner step on the inner upper edge of the second inner part 1128 and thus a coupling of the first inner part 1 126 and the second inner part 1128 in a further coupling position reaches, in which the second inner part 1128 is raised relative to the first inner part 1126.

As in the previous embodiments, in particular as in the arrangement of the embodiment in Fig. 3a and 3b, here too, the compression spring 1150 can be replaced by a pneumatic spring or the like. While in the above-described arrangement with a mechanical compression spring, the spring support 1154 forms the thrust bearing for the compression spring, 1154 can be replaced by a piston as an abutment when using a pneumatic compression spring, the pressure of the compression spring 1150 are changed by its upward and downward movement can.

12a, 12b and 12c show a further embodiment of a deep drawing tool according to the invention with a pulling bell 1204, which has an outer part 1224, a first inner part 1226 and a second inner part 1228. As with the previous embodiments, the first inner part 1226 is movable up and down with respect to the outer part 1224, and these two parts 1224 and 1226 can be coupled to each other up to a predetermined point of the deep drawing movement. Between the upper edge 1252 of the first inner part 1226 and a spring holder 1254 disposed above a compression spring 1250 is arranged, and between the spring holder 1254 and an overhead ceiling portion 1222 of the pulling bell 1204, a further compression spring 1256 is arranged. The spring holder 1254 can thus be raised against the pressure of the compression spring 1256 upwards, whereby the pressure of the compression spring 1250 is reduced to the underlying inner part 1226 below.

The second inner part 1228 is coupled to the first inner part 1226 via a stopper ring 1231. Specifically, the second inner portion 1228 has an inner step which forms a lower stop 1230 upon which the lower surface of the stopper ring 1231 rests in the position of FIG. 12a. At the lower end of the stop ring 1231, a radially outer step 1232 is further provided, on which a radially inwardly facing step 1234 of the first inner part 1226 rests. Thus, the second inner part 1228 can only be pushed upwards until its abutment 1230 on the underside of the stop ring 1231 and its step 1232 again abuts against the stop 1234 of the first inner part. A displacement of the second inner part 1228 with respect to the first inner part 1226 is thus limited upwards.

In this coupling position of the second inner part 1228 with the first inner part 1226, their lower sides 1236 and 1240 are flush with each other. In the position in FIG. 12a, these also terminate flush with the bottom 1242 of the outer part 1224. As a result, a uniform lower side of the pulling bell 1204 is formed, which presses the remaining flange 1244 of the blank 1246 down against the fold holder 1248.

In Fig. 12b, the thermoforming movement has progressed further, and the residual flange 1244 is located only between the first inner part 1226 and the second inner part 1228, while the lower side 1242 of the outer part 1224 presses directly on the fold holder 1248. At this point of the pulling movement, the coupling of the first inner part 1226 to the outer part 1224 may be canceled by lifting the spring holder 1254 against the pressure of the compression spring 1256. As soon as the force of the compression spring 1250 falls below the holding force of the pleat holder 1248 (see FIG. 2b, F4 <Fl + Fla), the pleat holder 1248 strikes the outer part 1224. In this position, a new coupling takes place between the first inner part 1226 and the outer part 1224, in a position axially offset by the material thickness of the residual flange 1244. The Clamping the Restfiansches 1244 now takes place with newly metered, reduced clamping force by the elongated compression spring 1250th This new clamping force can be transmitted via the gradation 1234 and the stop 1232 on the second inner part 1228th That is, after the suspension and restoration of the coupling between the first inner portion 1226 and the outer portion 1224, the first inner portion 1226 and the second inner portion 1228 are still relatively coupled, with their lower surfaces 1236 and 1240 still flush with each other to lock.

Up to this point, the thermoforming movement was carried out similarly to the embodiment of FIG. 3b: the compression spring 1250 (250 in FIG. 3b) was elongated, decoupling of the inner part 1226 (226 in FIG. 3b) was done and also a re-coupling of the inner part 1226 (226 in Fig. 3b) in an axially offset position, but here in Fig. 12b frictionally by pressing on the residual flange 1244 and not form-fitting as in Fig. 3b by the stop 232. Fig. 12a and 12b thus show a Deep-drawing process of blanks with Restfiansch, the initial clamping force on the Restfiansch 1244 could be reduced by decoupling and re-coupling an inner Ziehglockenteils and re-dosed for the smaller become residual fischsch.

Fig. 12c shows how this embodiment of the thermoforming tool can be used to prevent enameled hair when the residual flange 1244 is to be fully stretched, similar to the principle presented in Fig. 4b. As the remainder of the thermoforming movement continues, as residual scrap 1244 is reduced in size to contact only the underside of second inner portion 1240, the first inner portion 1226 of the die is decoupled to release the clamping force and second inner portion 1228 is recoupled with the outer part of the puller bell 1224 to strip the remainder of the flea completely without lacquer hair.

decoupling:

Since the spring mount 1254 is held stationary by reaching a stationary stop in the position in FIG. 12b during the further deep drawing movement to the position in FIG. 12c, a stop 1272 engages at the upper end of the stop ring 1231 on a radially inner stop 1274 on the spring element 1254 and also remains stationary during the further deep drawing movement. This ensures that the radially outer Step 1232 of the stop ring 1231 abuts against the radially inner stop 1234 of the first inner part 1226, whereby also the first inner part 1226 remains stationary. The stop ring 1231, on which the pressure spring 1250 acts indirectly, is similar in function and movement to the spring holder 354 in FIGS. 4a and 4b. The holding force on the second inner pull-block part 1228 is released by the contact of the spring element 1254 with the stop ring 1231.

Reconnection:

The opposing force acting on the drag core 1202 via the residual flange 1244 and its inner pull radius keeps the second inner part 1228 of the pull bell stationary as well as the first inner part 1226 until the second inner part 1228 retracts as the deep-drawing motion progresses via a stop 1270 at its upper end the outer part 1224 and its ceiling portion 1222 coupled.

A further continuation of the deep-drawing movement from the situation in FIG. 12c causes a complete stretching of the residual flange 1244 downwards over the pulling core 1202.

In the embodiment of Figs. 12a, 12b and 12c, each of the compression springs 1250 and 1256 disposed on either side of the spring retainer 1254 as an abutment for the respective springs is replaceable by a pneumatic compression spring. In particular, in this case, the spring retainer 1254 may be replaced by a piston which separates the respective pressure chambers of the pneumatic compression springs 1250 and 1256 from each other and is movable up and down.

FIG. 13 shows a further embodiment of the deep-drawing tool 1300 according to the invention, which is constructed similar to the deep-drawing tool 800 in FIG. 8b but comprises an extension thereof. More specifically, the deep-drawing tool 1300 also includes a pulling bell 1304 having an upper portion 1320, an outer portion 1324 located thereunder, and an inner portion 1326. The outer portion 1324 and inner portion 1326 of the pulling bell 1304 are constructed as the outer portion 824 and the outer portion, respectively inner part 826 of the deep drawing tool 800, including the outer stop 1328 on the inner part 1326, which corresponds to the stop 828, the stop 1330, corresponding to the stop 830, and the upper stop 1332 at the inner lower edge of the upper part 1320, wherein the stopper 1328 between the stops 1330 and 1332 is movable upwards and downwards.

Consistent with the deep drawing tool 800 is also the arrangement of a piston 1352 within the upper part 1320 and pins 1364 that extend vertically downwards through openings 1366 in the bottom 1367 of the upper part 1320 of the pulling bell 1304. The piston 1352 acts vertically downward on the upper ends of the pins 1364, and in turn presses on the upper edge of the inner part 1326.

A downward pressure on the piston 1352 is thus transmitted through the pins 1364 on the inner part 1326.

Above the piston 1352 is located within the pulling bell 1304, a space 1358 which is bounded at the top by the ceiling portion 1322 of the upper part 1320. Deviating from the embodiment of the deep drawing tool 800 in FIG. 8 b, the space is divided by a further piston 1370 into a first pressure chamber 1372 and a second pressure chamber 1374. The first pressure chamber 1372 is located below the further piston 1370 and is bounded by the underside thereof and the top of the piston 1352 described above. The second, overlying pressure chamber 1374 is bounded by the top of the further piston 1370 and the ceiling portion 1322. The further piston 1370 is movable up and down. By an upward movement increases the volume of the first pressure chamber 1372, and the volume of the second pressure chamber 1374 decreases accordingly. Conversely, the volume of the second pressure chamber 1374 increases by a downward movement of the other piston 1370, and the volume of the first pressure chamber 1372 is reduced.

Both pressure chambers 1372 and 1374 are each acted upon via radial openings 1376, 1378 which extend through cylindrical outer wall of the upper part 1320, with compressed air.

When the further piston 1370 is lowered and reduces the first pressure chamber 1372, the pressure within the first pressure chamber increases (with the opening 1376 closed). This pressure acts from above on the piston 1352, which presses down on the pins 1364 and thus passes the pressure to the inner part 1326 of the pulling bell 1304. hereby a holding force can be exercised. Conversely, if the further piston 1370 is raised and reduces the pressure within the pressure chamber 1372, the holding force is reduced. The movement of this further piston 1370 can be effected by a corresponding drive, by a driver on the piston 1370, which abuts against a stop during a movement of the pulling bell 1304, or the like. The second pressure chamber 1374 in this case serves to maintain a pressure that keeps the piston 1370 in balance.

The pressure chambers 1372 and 1374 thus form pneumatic spring cushions 1350 which can exert, for example, the function of the springs 1250 and 1256 of the deep drawing tool 1200 in FIGS. 12a, 12b and 12c and can replace them in a correspondingly constructed embodiment. The piston 1370 in this case forms the counter bearing for the two pneumatic compression springs and replaces the spring holder 1254.

In all illustrated embodiments, in which compression springs are used, alternatively mechanical compression springs, pneumatic compression springs or compression springs of another type can be used. The operation of the present invention is not bound to a particular type of compression spring, but the skilled person can select and adapt them according to the present needs. Counter bearing of the springs, such as mechanical springs, can be replaced for example by acted upon by the pressure of a pneumatic spring active surfaces of a piston of the respective pneumatic spring.

Claims

1. thermoforming tool (100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300) for deep-drawing blanks (106, 1246) of sheet material into blanks, with a drawing core (102, 1202) and a drawing bell (104, 204, 304, 404, 504, 604, 704, 804, 904, 1004, 1104, 1204, 1304), which are linearly movable relative to each other, and a folding holder (110, 1248) as an abutment for at least part of the lower edge region of the drawing bell (104, 204, 304, 404, 504, 604, 704, 804, 904, 1004, 1104, 1204, 1304), characterized in that the pulling bell (104, 204, 304, 404, 504, 604, 704, 804, 904, 1004, 1104, 1204, 1304) has a radially outer portion (124, 224, 324, 424, 524, 624, 724, 824, 924, 1024, 1124, 1224, 1324 ) and at least one radially inner part (126, 226, 326, 426, 526, 626, 726, 826, 926, 1026, 1126, 1226, 1326), which relative to the outer part (124, 224, 324, 424, 524, 624, 724, 824, 924, 1024, 1124, 1224, 1324) is movable.

2. thermoforming tool according to claim 1, characterized by drive means for a thermoforming movement, in which the drawing bell (104, 204, 304, 404, 504, 604, 704, 804, 904, 1004, 1104, 1204, 1304) and the drawing core (102 , 1202) are moved towards each other and inserted into each other.

3. thermoforming tool according to claim 1 or 2, characterized by coupling means through which the outer part (124, 224, 324, 424, 524, 624, 724, 824, 924, 1024, 1124, 1224, 1324) and the inner part ( 126, 226, 326, 426, 526, 626, 726, 826, 926, 1026, 1126, 1226, 1326) of the drawing bell (104, 204, 304, 404, 504, 604, 704, 804, 904, 1004, 1104 , 1204, 1304) are coupled during the deep drawing movement and which are intended to cancel this coupling when a predetermined point of the deep drawing movement is reached.

4. thermoforming tool according to claim 3, characterized in that the coupling means for means for positive engagement of the outer part (124, 224, 324, 424, 524, 624, 724, 824, 924, 1024, 1124, 1224, 1324) and the inner Part (126, 226, 326, 426, 526, 626, 726, 826, 926, 1026, 1126, 1226, 1326) of the drawing bell (104, 204, 304, 404, 504, 604, 704, 804, 904, 1004 , 1104, 1204, 1304).

5. thermoforming tool according to claim 3 or 4, characterized in that the coupling means comprises means for exerting a holding force on the inner part (126, 226, 326, 426, 526, 626, 726, 826, 926, 1026, 1126, 1226, 1326 ) of the pulling bell (104, 204, 304, 404, 504, 604, 704, 804, 904, 1004, 1104, 1204, 1304) for holding it in a fixed position relative to the outer part (124, 224, 324, 424, 524, 624, 724, 824, 924, 1024, 1124, 1224, 1324).

6. thermoforming tool according to claim 5, characterized in that the means for exerting a holding force comprise at least one spring (250, 350, 450, 550, 650, 750, 1150, 1250) through which the inner part (126, 226, 326 , 426, 526, 626, 726, 1126, 1226, 1326) of the drawing bell (104, 204, 304, 404, 504, 604, 704, 1104, 1204, 1304) into a fixed position relative to the outer part (124, 224 , 324, 424, 524, 624, 724, 1124, 1224, 1324).

7. thermoforming tool according to claim 6, characterized in that the spring is a mechanical spring (250, 350, 450, 550, 650, 1150, 1250).

8. thermoforming tool according to claim 6, characterized in that the spring is a pneumatic spring (750, 1372, 1374).

9. Deep-drawing tool according to one of claims 5 to 8, characterized by means for canceling or reducing the holding force on the inner part (126, 226, 326, 426, 526, 626, 726, 826, 926, 1026, 1126, 1226, 1326 ) of the pulling bell (104, 204, 304, 404, 504, 604, 704, 804, 904, 1004, 1104, 1204, 1304).

10. thermoforming tool according to claim 9, characterized in that the spring is a compression spring (250, 1150, 1250, 1372), between the inner part (226, 1126, 1226) of the drawing bell (204, 1104, 1304) and an abutment (254, 1154, 1254, 1370) is biased, and that the means for canceling or reducing the holding force comprises a drive for moving the anvil (254, 1154, 1254, 1370) in a direction to relax the compression spring (250, 1150, 1250 , 1372).

11. Deep-drawing tool according to claim 9, characterized in that the spring is a compression spring (350, 450, 550, 650, 750, 850, 1256, 1374), which between the outer part of the drawing bell (304, 404, 504, 604, 704, 804, 1204, 1304) and an abutment (354, 454, 554, 654, 752, 852, 1254, 1370), via which the spring pressure on the inner part (326, 426, 526, 626, 726, 826, 1226, 1326) of the drawing bell (304, 404, 504, 604, 704 , 804, 1204, 1304) is transferable.

12. thermoforming tool according to claim 11, characterized in that the means for canceling or reducing the holding force a drive for moving the thrust bearing (354, 454, 554, 654, 752, 852, 1254, 1370) in a direction to the tension of the compression spring ( 350, 450, 550, 650, 750, 850, 1256, 1374).

13. thermoforming tool according to claim 10 or 11, characterized in that the means for canceling or reducing the holding force comprise a stop (460, 560, 660), which is arranged, during the thermoforming movement of the abutment (454, 554, 654) detected to be touched and at the contact the abutment (454, 554, 654) in a direction to tension or relaxation of the compression spring (450, 550, 650) is pressed.

14. thermoforming tool according to one of claims 9 to 13, characterized in that the spring comprises a pneumatic spring cushion (750, 850, 1372, 1374), with a first pressure chamber (758, 858, 1372) and means for transmitting the pneumatic pressure in the first pressure chamber on the inner part (726, 826, 1326) of the drawing bell (704, 804, 1304), wherein the means for canceling or reducing the holding force comprise means for controlling the pneumatic pressure in the first pressure chamber.

15. thermoforming tool according to claim 14, characterized in that the means for controlling the pneumatic pressure in the first pressure chamber (758, 858, 1372) comprise a venting device.

A deep drawing tool according to claim 14 or 15, characterized in that the means for controlling the pneumatic pressure in the first pressure chamber (758, 858, 1372) comprise a piston (1370) delimiting the first pressure chamber (758, 858, 1372) and movably arranged to change the volume of the first pressure chamber (758, 858, 1372).

17. thermoforming tool according to claim 16, characterized by a second pressure chamber (1374) which is separated from the first pressure chamber (758, 858, 1372) by the piston (1370).

18. thermoforming tool according to claim 3, characterized in that the coupling means comprise a driver (950) for the inner part of the pulling bell (904) on the outer part (924) of the pulling bell (904) by magnetic force in a magnetic holder with switchable polarity is held such that it occupies a first axial position in a first switching position and assumes a second axial position in a second switching position, which is linearly offset from the first axial position.

19. thermoforming tool according to claim 3, characterized in that the coupling means comprise a driver (1050) for the inner part (1026) of the drawing bell (1004), which is arranged radially displaceably on the outer part (1024) of the drawing bell (1004) and is held in an engaged position with the inner part (1026) of the pulling bell (1004) to reach the predetermined point of the deep drawing motion by a cam (1024) stationarily arranged relative to or moving along with the pulling core, and upon reaching said predetermined point a radial displacement is released, by which the inner part (1026) of the pulling bell (1004) is released from engagement.

20. deep-drawing tool according to one of claims 3 to 19, characterized in that the drawing bell (1104, 1204) comprises a first radially inner part (1126, 1226) and a second radially inner part (1128, 1228), which first inner part ( 1126, 1226) is arranged between the outer part (1124, 1224) and the second inner part (1128, 1228), and by further coupling means, through which the first inner part (1126, 1226) and the second inner part (1128, 1228) are coupled during the deep drawing movement and which are intended to cancel this coupling upon reaching a further predetermined point of the deep drawing movement.

A deep-drawing tool according to claim 20, characterized in that the further coupling means are provided for coupling the first inner part (1126, 1226) and the second inner part (1128, 1228) after reaching the predetermined point Canceling thermoforming movement, at which the outer part (1124, 1224) and the first inner part (1124, 1224) of the drawing bell (1104, 1204) are decoupled.

22. A method for deep drawing of blanks from sheet material to moldings using a thermoforming tool according to one of the preceding claims, characterized by the following steps:

a) providing the pulling bell (104, 204, 304, 404, 504, 604, 704, 804, 904, 1004, 1104, 1204, 1304) and the pulling core in a lifting position, in between the underside of the pulling bell and the pulling core remaining free space, the lower surfaces of the radially outer portion (124, 224, 324, 424, 524, 624, 724, 824, 924, 1024, 1124, 1224, 1324) and the radially inner portion (126, 226, 326, 426, 526, 626, 726, 826, 926, 1026, 1126, 1226, 1326) of the drawing bell (104, 204, 304, 404, 504, 604, 704, 804, 904, 1004, 1104, 1204, 1304) in Substantially flush with each other;

b) positioning a blank in the free space;

c) performing a deep drawing movement, by which the drawing bell (104, 204, 304, 404, 504, 604, 704, 804, 904, 1004, 1104, 1204, 1304) and the drawing core are moved towards each other, such that the radial over the die core projecting edge of the blank between the bottom of the drawing bell (104, 204, 304, 404, 504, 604, 704, 804, 904, 1004, 1104, 1204, 1304) and the fold holder is clamped and pulled over the pulling core ;

d) continuing the deep drawing movement until the outer edge of the deep drawn edge of the blank between the underside of the inner part (126, 226, 326, 426, 526, 626, 726, 826, 926, 1026, 1126, 1226, 1326) of the drawing bell ( 104, 204, 304, 404, 504, 604, 704, 804, 904, 1004, 1104, 1204, 1304) and the fold holder is clamped;

e) cancellation of the coupling between the outer part (124, 224, 324, 424, 524, 624, 724, 824, 924, 1024, 1124, 1224, 1324) and the inner part (126, 226, 326, 426, 526 , 626, 726, 826, 926, 1026, 1126, 1226, 1326) of the drawing bell (104, 204, 304, 404, 504, 604, 704, 804, 904, 1004, 1104, 1204, 1304), wherein the inner Part (126, 226, 326, 426, 526, 626, 726, 826, 926, 1026, 1126, 1226, 1326) relative to the outer part (124, 224, 324, 424, 524, 624, 724, 824, 924 , 1024, 1124, 1224, 1324) is freely movable or is driven to move relative to the outer part (124, 224, 324, 424, 524, 624, 724, 824, 924, 1024, 1124, 1224, 1324); f) Continuing the deep drawing movement with contact between the pleat holder and the outer part (124, 224, 324, 424, 524, 624, 724, 824, 924, 1024, 1124, 1224, 1324) of the drawing bell (104, 204, 304 , 404, 504, 604, 704, 804, 904, 1004, 1104, 1204, 1304).

A method according to claim 22, characterized in that during step f) the pulling core is further into the inner part (126, 226, 326, 426, 526, 626, 726, 826, 926, 1026, 1126, 1226, 1326) of Pulling bell (104, 204, 304, 404, 504, 604, 704, 804, 904, 1004, 1104, 1204, 1304) is introduced, such that the blank further deep drawn and the residual flange is further reduced or the deep-drawn edge of the blank is completely stripped.