Pressing tool for the production of multilayer formed plates

A compression molding tool comprises an upper part (3) and a lower part (2) connected by guides (4). A die (5) arranged in the lower part (3) of the tool cooperates with a force plug (6) arranged on the upper part (2) of the tool. The die (5) contains a mold cavity (7) the side walls of which are formed by two regions (12, 13). The outer region (13) of the side walls is inclined outward, i.e., divergent. A frame (14) guided on the columns (4) can be connected to the force plug (6) via a coupling device (15). Mounted on the frame (14) are spring-loaded elements (16) the free ends (17) of which cooperate with the inclined region (13) of the side walls of the mold cavity (7) in the die (5). The spring-loaded elements serve to produce a circular folded seam around the multilayer molded plates.

TECHNICAL FIELD 
The invention relates to a pressing tool for the production of multilayer 
formed plates with at least two outer layers. The pressing tool includes a 
tool lower part, a tool upper part, guide columns and a coupling device 
for driving the press. The lower part of the tool has a die with a forming 
hollow corresponding to the formed plate. The upper part of the tool has a 
pressing stamp fitting the forming hollow. The invention also relates to a 
process for the operation of such a pressing tool. 
BACKGROUND ART 
Pressing tools of this kind are generally known and are used, for example, 
in areas of sheet metal working, especially in the vehicle industry. The 
flat objects formed with these tools may include flat, curved or any 
desired combination of flat and curved surfaces. Multilayer formed plates 
which include, for example, two outer layers of sheet metal and an 
intermediate layer of insulation material, must be produced with several 
tools and in several work steps. The production of such multilayer formed 
plates is known in which a metal sheet, a covering foil, and the 
intermediate layer of insulation material are cut to the desired outer 
form. Each is prepared in separate work steps into a flat surface. These 
cut pieces are laid, in the desired construction order, into the forming 
hollow of a pressing tool and pressed into the desired form. Both outer 
layers of metal are cut larger than the insulation layer to produce a 
perfect joining in the rim portion of the formed plate between the 
individual layers of the formed plate. A metal cover foil overlaps the 
outer layer lying opposite. After the end of the form process, the metal 
cover foil must be laid manually around the outer layer lying opposite and 
pressed against the latter. Formed plates of this kind are used, for 
example in vehicle construction, as motor or exhaust pipe coverings. The 
production process described which requires, on the one hand, several 
tools, and on the other hand, a final manual finishing, is extremely 
costly and time-consuming. The use of automatic finishing instead of 
manual finishing of the rims is only possible to a limited extent, namely, 
only where a large enough number of pieces are needed. This is because 
multilayer formed plates of this kind have rim portions which are bent or 
curved in all spatial directions. 
SUMMARY OF THE INVENTION 
The invention addresses the problem of providing a pressing tool with which 
the layers of the formed plate may be formed, the edge portions of the 
outer layers trimmed as necessary, and with the same tool, the rim portion 
of one outer layer laid around the rim portion of the other outer layer, 
and the rim portions pressed together. The tool should make possible the 
production of multilayer formed plates without manual finishing and should 
be simple and economical to produce. 
This problem is solved, according to the invention, by the fact the rim 
around the forming hollow includes side walls having two portions with 
different inclination toward the forming surface of the forming hollow. 
The first side wall portion abuts directly against the forming surface and 
is perpendicular to this forming surface. The second upper side wall 
portion diverges outward. The upper part of the tool has a frame, movable 
along and arranged coaxially around the pressing stamp. A coupling device 
is arranged between this frame and the pressing stamp. Springs elastic 
elements are fastened to the Frame. The free ends of these spring elastic 
elements cooperate with the second diverging side wall portion of the 
forming hollow. 
In another embodiment of the invention, the two side wall portions of the 
forming hollow run parallel to the curvature of the rim line of the 
forming surface. The free ends of the spring elastic elements form a line 
running parallel to the second upper side wall portion. 
To allow the cutting of the rim portion of the outer layer of the formed 
plate, according to another embodiment of the invention, the lower part of 
the tool has the cutting plate arranged around the forming hollow. On the 
upper part of the tool is arranged a cutting stamp around the pressing 
stamp. The frame with the spring elastic elements is conducted between the 
pressing stamp and the cutting stamp. One preferred execution of the 
invention is distinguished by the fact that the cutting plate and the 
cutting stamp, in the zone of the cutting line, include a plurality of 
individual cylindrical cutting elements of polygonal cross-section. One 
cutting element each of the cutting plate and the cutting stamp form a 
pair, with cutting edges directed toward each other. In a further 
embodiment of the invention, the spring elastic elements are arranged 
against the cutting elements of the cutting stamp, and the frame and the 
cutting stamp form one construction unit. Another preferred embodiment of 
the invention is distinguished by the fact that the frame is connected 
with springs, and these springs press the frame against the upper part of 
the tool. In a further embodiment, the opening distance of the frame is 
limited by stops. At the upper dead point of the pressing stamp, the free 
ends of the spring elastic elements project beyond the end surface of the 
pressing stamp. In this position, the coupling device connects the frame 
with the pressing stamp. 
Another preferred form of execution is distinguished by the fact that the 
spring elastic elements includes a plurality of rod-form strips arranged 
side-by-side. The spring elastic elements are made of metal or plastic. In 
the choice of material for the spring elastic elements, their elasticity 
and their material quality and the strength of the outer layer of the 
formed plate to be folded over should be considered. If the outer layer to 
be folded over is of aluminum foil, then spring elastic elements arranged 
tightly side-by-side and made of plastic are especially suitable. If an 
aluminum plate is used for the outer layer of the formed plate to be 
folded over, then the spring elastic elements are more suitably of spring 
steel. In accordance with the combination of materials, still other spring 
elastic materials may be used. 
One advantageous process for operation of the pressing tool, according to 
the invention, for multilayer formed plates includes laying the individual 
layers of the formed plate between the upper and lower parts of the tool 
and then, by pressing the two parts of the tool together, forming the 
formed plate. The distinction is that, simultaneously with the forming of 
the plate, the overlapping edge of an outer layer is at least partly laid 
around the edge of the second outer layer. The tool is completely opened 
again, and the frame is solidly joined with the pressing stamp by means of 
the coupling device. Then the two parts of the tool are moved together 
again, while the elastic elements are turned inward against the diverging 
portions of the side walls of the forming hollow, and the edge of the 
first outer layer is completely laid around the edge of the second outer 
layer by means of the elastic elements. Then the tool is opened again, and 
the frame is uncoupled from the pressing stamp. In another execution, the 
process is distinguished by the fact that before the end of the forming 
process of the plate, the edge of the first outer layer is trimmed in the 
same work step. Preferably, after the complete folding over of the edge of 
the first outer layer, the pressing tool is closed again and the formed 
plate and its edge are completely pressed. 
The advantages attainable with the invention include, in particular, the 
fact that multilayer formed plates, after laying the individual layers 
into the pressing tool, can remain in the same tool for complete finishing 
and production, and that all the necessary work steps can be carried out 
with this tool. With this, the formed plates have a good form stability 
and a good clamping connection of the edge portion of the outer layers. 
Unlike manual laying of the outer layer around the edge portion thicker 
sheet metal may also be used as outer layers and folded over because of 
the high tool forces possible. The multilayer formed plates can be 
produced much faster and more economically than with methods and tools 
known heretofore. By the use of a plurality of individual cutting elements 
for the production of cut edges, even very complicated outer forms can be 
produced more simply and economically. For this purpose, these individual 
cutting elements are simply arranged along the desired outer contour of 
the formed plate, and are joined with the cutting plate or cutting stamp 
by casting, gluing or other known joining methods. With this arrangement, 
no expensive and complicated cutting rings are needed. This leads to a 
further cost advantage.

DESCRIPTION OF A PREFERRED EMBODIMENT 
The pressing tool according to FIG. 1 includes a tool lower part 2 and a 
tool upper part 3 connected with each other by several guide columns 4. As 
a rule, the guide columns 4 are anchored in the lower part 2 of the tool, 
and the upper part 3 of the tool is movable in the direction of the 
longitudinal axis of the guide columns 4. For this purpose, guide bushings 
21 are fastened in the upper part 3 of the tool and enclose the guide 
columns 4. The upper part 3 of the tool is joined by couplings and 
movement devices for the driving of the press (not shown), and has other 
devices (also not shown) for the stop limitation and holding of auxiliary 
means. The total structure of the tool may be varied in the known way from 
the partial section in FIG. 1. The size of the tool depends on the total 
extent of the plate 1 to be formed. The section shown in FIG. 1 extends 
through the edge portion around the circumference of the whole tool. 
The multilayer formed plate shown in FIG. 1 is a heat-insulation plate for 
covering exhaust pipe parts of combustion engines. The formed plate 1 
includes a first outer layer 8 of aluminum sheet metal, a mat 10 of 
insulation material, and a second outer layer 9 of a thin aluminum foil. 
The insulation material 10 is smaller in the edge portion than the 2 outer 
layers 8, 9, while in the example shown, the outer layer 8 of sheet 
aluminum is smaller, in turn, than the outer layer 9 of aluminum foil. In 
the formed condition of the formed plate 1, the two outer layers 8, 9 are 
pressed against each other in the outer portion, and the edge of the outer 
layer 9 is folded or turned around the edge portion of the outer layer 8. 
The strength of the outer layer 9 of aluminum foil is so chosen that the 
folding of the outer portion provides a perfect connection of the 
individual layers of the formed plate 1, and that the outer layer 9 also 
retains the curvatures of the formed plate 1 after the forming. 
The lower part 2 of the tool has a die 5 with a forming hollow 7. As 
counterpart to the forming hollow 7, a pressing stamp 6 is arranged on the 
upper part 3 of the tool. The pressing stamp 6 has an end surface 32 
corresponding in form to the forming hollow 7. The spatial dimensions of 
the forming hollow 7 are defined by the forming surface 11 which 
determines the spatial form of the formed plate 1. The border includes 
side wall portions 12, 13. The first side wall portion 12 abuts directly 
against the edge line 31 of the formed surface 11 and is perpendicular to 
the formed surface 11. The height of the side wall portion 12 corresponds 
to the thickness of the folded edge portion of the two outer layers 8, 9. 
The first side wall portion 12 is adjoined by a second side wall portion 
13 which is inclined outward and forms a divergent opening of the forming 
hollow 7. In the example shown, the side wall portion 13 has an 
inclination of 45.degree. from the axis of movement of the upper part 2 of 
the tool. The two side wall portions 12, 13 run parallel to the edge line 
31 of the forming surface 11. During the pressing of the formed plate 1, 
the outer layer 9 is drawn over the oblique side wall portion 13, and at 
the end of the pressing process, is erected between the first 
perpendicular side wall portion 12 and the wall surface 33 of the pressing 
stamp 6. The pressing stamp 6 and the forming hollow 7 are arranged with 
suitable play between them. 
A frame 14 is arranged around the pressing stamp 6 and can be moved along 
in relation to the upper part 3 of the tool. For this purpose, the frame 
14 is supported by guide bushings 21, 22 sliding on the guide columns 4. 
Spring elastic elements 16 are fastened to the lower surface 28 of this 
frame 14 in the zone of the wall surface 33 of the pressing stamp 6. The 
spring elastic elements 16 form a plurality of rod-form strips which are 
arranged closely side-by-side and which have free ends 17. The free ends 
17 of the spring elastic elements 16 form a line running parallel to the 
second upper side wall portion 13 of the forming hollow 7. A spring 20 
presses the frame 14 against the upper part 3 of the tool and prevents the 
spring elastic elements 16 from cooperating with the die during the 
pressing process. A coupling device 15 makes possible, in definite work 
steps, the form-fitting connection of the frame 14 with the upper part 3 
of the tool. The coupling device 15 includes a known piston-cylinder unit 
24 with pressure medium feeds and control elements, not shown. A coupling 
pin 25 is guided in a bearing bushing 27 of the frame 14, and is in the 
starting position during the pressing process. In the guide bushing 21, a 
coupling bore 26 is solidly connected with the upper part 3 of the tool. 
The bore 26 is arranged in the lower portion of the guide bushing 21 and 
has the same dimensions as the coupling pin 25 of the coupling device 15. 
In FIG. 2, the tool according to FIG. 1 is shown in opened position after 
the end of the pressing process of the formed plate 1. Here, the upper 
part 3 of the tool is in the upper dead point. Above the upper part 3 of 
the tool is an opposite plate 23 into which stops 19 are fastened. 
Passages 30 for the stops 19 are arranged in the upper part 3 of the tool. 
In this position of the upper part 3 of the tool, an upper surface 29 of 
the frame 14 is pressed by the spring 20 against the stop 19. The stop 19 
and the upper dead point position of the upper part 3 of the tool are so 
in accord with each other that the axis of the coupling pin 25 coincides 
with the axis of the coupling bore 26. In this way, the frame 14 is 
connected form-fitting with the upper part 3 of the tool and now follows 
every movement of the upper part 3 of the tool. The upper part of the tool 
is now run toward the lower part of the tool again until the free ends 17 
of the spring elastic elements 16 arrive at the second side wall portion 
13 of the forming hollow 7. Here the free ends 17 are turned against the 
erected rim portion of the second outer layer 9 of the formed plate 1. The 
erected edge portion lays over the edge portion of the first outer layer 
8. This movement process is continued until the lower surface 28 of the 
frame 14 arrives at the stop 18, and thus the folding process is 
concluded. This end position of the spring elastic elements 16 is shown in 
FIG. 3. The stop 18 is not shown in FIG. 3, but is present there. The 
upper part 3 of the tool is now drawn back to the upper dead point, the 
piston-cylinder unit 24 is actuated again, and the coupling pin 25 is 
drawn out of the coupling bore 26 and returned to its starting position. 
For complete smoothing of the fold in the edge portions of the outer 
layers 8, 9 of the formed plate 1, the upper part 3 of the tool is closed 
again and the formed plate 1 completely pressed. 
FIG. 3 shows a schematic arrangement of the edge portions of a pressing 
tool in the same work process in which the outer layer of the formed plate 
1 to be folded over is cut. A cutting plate 34 with a cutting edge 41 is 
arranged around the die 5 with the forming hollow 7. On the upper part 3 
of the tool is fastened a cutting stamp 35 which has a second cutting edge 
42. The cutting plate 34 and the cutting stamp 35 are, in the example 
shown, arranged in ring form around the die 5 and the pressing stamp 6, 
respectively. Between the cutting stamp 35 and the pressing stamp 6 is the 
frame 36 to which are fastened the spring elastic elements 16. On the 
upper side of the frame 36 are arranged stops 37 with springs 38. In this 
arrangement, the springs 38 pull the frame 36 upward toward the upper part 
3 of the tool with the coupling device 15 not engaged. Above the upper 
part 3 of the tool, there is also arranged a solid plate (not shown) with 
stops which cooperate with the stops 37. In FIG. 3, the upper part 3 of 
the tool with the pressing stamp 6 is in the end position after the ending 
of folding process. The outer layer nine of the formed plate is completely 
laid over. With this, the coupling pin 25 is engaged in a coupling bore 40 
on the frame 36, and is guided in a bearing bushing 39 in the cutting 
stamp 35. The moving in and out of the coupling pin 25 takes place again 
through the piston-cylinder unit 24 and pressure medium feed lines and 
controls (not shown). In the tool arrangement shown, the individual layers 
of the formed plate 1 are laid, at the beginning of the work process, into 
the forming hollow 7. The second outer layer 9 again includes an aluminum 
foil and its edge projecting beyond the cut edge 41. Simultaneously with 
the pressing and forming of the formed plate 1, the edge portion of the 
second outer layer 9 is cut between the two cutting edges 41, 42. The 
cutting stamp 35 is moved, at the same time with the pressing stamp 6, 
toward the lower part 2 of the tool. Into the cutting plate 34 is laid an 
elastic support 43 which assures that the pressing stamp 6 can carry out 
the pressing movement with the necessary pressing force and without this 
movement being hindered by the cutting stamp 35. After the forming and 
cutting of the individual layers of the formed plate 1, the tool is 
completely opened as described in the arrangement according to FIGS. 1 and 
2 until the upper part 3 of the tool is in the upper dead point. With 
this, the stops 37 strike against the limiting stops (not shown), and hold 
the frame 36 in a position at which the free ends 17 of the spring elastic 
elements 16 project above the end surfaces 32 of the pressing stamp 6. In 
this position, the coupling device 15 and its coupling pin 25 engage in 
the frame 36 and its coupling bore 40, respectively. Since the cutting 
stamp 35 is connected with the upper part 3 of the tool and thus with the 
pressing stamp 6, there is provided here again a form-fitting connection, 
and the frame 36 is moved downward by the upper part 3 of the tool or the 
pressing stamp 6. With this, the free ends 17 of the spring elastic 
elements 16 strike against the second side wall portion 13 of the forming 
hollow 7, lay the edge portion of the second outer layer 9 around the 
first outer layer 8, and produce an edge fold. To limit the movement of 
the upper part 3 of the tool, stops (not shown) are again built in here. 
In FIG. 4, the frame 14 and the cutting stamp 35 shown in FIGS. 1 and 3 
also form a frame-form construction unit 50. The cutting plate and the 
cutting stamp are formed in the zone of the cutting line and include a 
plurality of cutting elements 44, 45 lined up one after the other. The 
cutting elements 44, 45, have a polygonal cross-section, and in the 
example shown, a hexagonal cross-section. The cutting elements 44, 45 have 
cutting edges 41, 42 which are formed by the placing of step-form offsets. 
The cutting edges 41, 42 run from one angle of the hexagonal 
cross-section, through the center, to the angle of the hexagon lying 
opposite. The cutting elements 44, 45 formed in this way are lined up 
edge-to-edge, through which, in a simple way curved cutting lines can be 
formed. In the example shown, the die 5 with the integrated cutting 
elements 44, as well as the construction unit 50, consist of plastic. The 
cutting elements 44, 45 are cast into this plastic and thus form a 
form-fitting unit. With the cutting elements 45 are integrated fastened 
the spring elastic elements 46 with the free ends 47. By suitable working 
of the cutting elements 45, the spring elastic elements 46 might be made 
in one piece from the same material. The elements 44, 45 consist, in the 
example shown, of hardened spring steel. 
The detail of the pressing tool in FIG. 4 shows the lower part 2 and the 
upper part 3 of the tool in the starting position before the beginning of 
the pressing process. Here, the multilayer plates 1 to be formed or their 
individual layers 8, 9, 10 are laid in as flat surfaces above the forming 
hollow 7. In the example shown, an aluminum plate 8 forms the outer layer 
which is to be folded over. This has the advantage that the aluminum foil 
9 which forms the second outer layer is clamped fast between the aluminum 
plate 8. Thus, a very good joining results between the outer layers 8, 9. 
The exact outer contour of the outer layer 8 needed for this kind of 
production is produced by the fact that before the end of the forming 
process of the rim portion, the outer layer 8 is cut between the cutting 
edges 41, 42 of the cutting elements 44, 45. This is done during the 
pressing of the formed plate, while the tool still has the holding-down 
devices (not shown) for the outer layer 8. After the pressing and cutting 
of the formed plate 1, the upper part 3 of the tool is run into its upper 
dead point. During this movement cycle, the upper surface 49 of the 
construction unit 50 strikes against the stop 19 and is fixed in a 
position in which at the upper dead point of the upper part 3 of the tool, 
the coupling pin 25 can be engaged in the coupling bore 26. In this 
position, the free ends 47 of the spring elastic elements 46 stand above 
the end surfaces 32 of the pressing stamp 6. If the upper part 3 of the 
tool is run toward the lower part 2 of the tool again, the free ends 47 
arrive at the second side wall portion 13, are turned at this surface 
toward the edge zone of the outer layer 8, set in the first work step 
during the pressing process against the first side wall portion 12, and 
lay this around the edge portion of the outer layer 9 to an edge fold. 
Since the spring elastic elements 46 in this form of execution include 
spring steel, aluminum plate can be worked directly with no problem. Here 
also, in another work step, after the uncoupling of the construction unit 
50 from the upper part 3 of the tool, the edge zone of the formed plate 1 
may be pressed completely. 
The process for the operation of the pressing tool shown in FIGS. 1 to 4 
includes a first work step in which the individual layers of plate to be 
formed are laid into the open tool between the lower part 2 and the upper 
part 3 of the tool. In the form of execution according to FIGS. 1 and 2, 
all layers are pre-cut to the right form. In the form of execution 
according to FIGS. 3 and 4, the outer layer, which is folded over, is cut 
in the tool driving the next work step, and may thus have a rather inexact 
outer form. In the next work step, the upper part of the tool is run 
toward the lower part 2 of the tool. By the pressing stamp 6, the 
individual layers 8, 9, 10 of the plate 1 to be formed, are pressed and 
formed in the forming hollow 7. Simultaneously with this pressing and 
forming process, the outer layer 8, 9 which is to form the fold, is drawn 
over the oblique side portion surface 13 of the forming hollow 7, and is 
set up between the side wall zone 12 and the wall surface 33 on the 
pressing stamp 6 perpendicular to the forming surface 11 of the forming 
hollow 7. The upper part 3 of the tool is now moved away from the lower 
part 2 of the tool and into its upper dead point. In the next work step by 
means of the coupling device 15, the frame 14, 36, 50 is joined with the 
upper part 3 of the tool and the pressing stamp 6, respectively. Then the 
two parts of the tool, 2, 3 are run together again, while the spring 
elastic elements 16, 46 are turned at the diverging zones of the forming 
hollow 7, or the side wall zone 13, and the edge of the one outer layer is 
laid, by the elastic elements 16, 46, completely around the edge of the 
other outer layer 8 or 9. The tool is now completely opened again, the 
frame 14, 36, 50 is uncoupled from the upper part 3 of the tool, and the 
tool is closed once more for a cleaner pressing of the edge portion of the 
formed plate 1. After opening the tool again, the formed plate 1 
completely formed and folded in the edge portion can be removed, and 
without further finishing, sent on for use.