Title of Invention

PROCESS AND APPARATUS FOR PRODUCING A HONEYCOMB BODY

Abstract

There is proposed a process for producing a honeycomb body having a plurality of passages through which a fluid can pass comprising a plurality of at least partially structured sheets wherein at least one stack is formed in layered relationship from a plurality of at least partially structured sheets. The stack is introduced into a mould and held therein by a wrapping device in the central region of the stack. The stack is then subjected to a wrapping procedure until a predetermined degree of wrapping of the stack is attained. A structural configuration formed in a central region with structures which are disposed relative to each other of the structured sheets of the stack is maintained at least during the wrapping procedure.

Full Text

Process and apparatus for producing a honeycomb body The present invention concerns a process for producing a honeycomb body, in particular a catalytic converter carrier body, comprising at least one stack of a plurality of at least partially structured metal sheets, and an apparatus for producing such a honeycomb body. Carrier bodies for catalytic converters which provide for a reduction in the amount of pollutants in exhaust gases, in particular exhaust gases of an engine, can be in the form of a metallic honeycomb body. Such honeycomb bodies include a stack comprising a plurality of at least partially structured metal sheets US-A-4 923 109 describes a honeycomb body which has a stack of at least partially structured metal sheets, the stack being twisted in opposite directions around itself and around a central region. DE 195 21 685 discloses a process for producing such a honeycomb body. In accordance with that process it is proposed that initially a stack is formed from a plurality of at least partially structured sheet metal layers, the stack is thereafter introduced into an open mould formed from mould segments corresponding to the outside shape of the honeycomb body to be produced, and the stack is held by a twisting device in a central region. Thereupon the stack is wound or wrapped around in a direction of rotation and the mould is closed by pivoting the mould segments in the opposite direction to the direction of rotation of the wrapping device when a predetermined degree of wrapping is attained DE 195 22 327 discloses a process for producing a honeycomb body having a plurality of passages through which a fluid can flow, comprising a plurality of at least partially structured sheet metal layers This process is suitable in particular for producing a honeycomb body as is known from WO 90/03220. Such a honeycomb body has at least three stacks of metal sheets, wherein at least three of the stacks are folded around a respective associated bend line in the central region of the honeycomb body and twisted in the folded 2 condition in the same direction around each other and around the central region with the bend lines. Production of such a honeycomb body is effected in accordance with DE 195 22 327 Al by virtue of each stack being folded about a respective bend line. The stacks when folded in that way are introduced into a mould. Each stack is held by a twisting device in a central region. The twisting device has winding bars which engage into the bent stack in the region of each bend line. The individual stacks are twisted in the same direction by rotation of the winding bars about a central axis. WO 94/01661 discloses a honeycomb body which is made up of only a small number of metal sheets and the structure of which is suitable for at least one elongate electrical conductor to be integrated into at least one of the sheet metal layers or for one of the sheet metal layers itself to be in the form of an elongate insulated electrical conductor. For the production of such a metallic honeycomb body consisting of at least partially structured sheet metal layers, WO 94/01661 proposes that a hollow cone is produced from a small number of at least partially structured sheet metal strips. That hollow cone or circular ring is deformed from the outside inwardly at at least three lines so that a corresponding number of reversal lines are formed both in an outer region of the ring and also in an inner region thereof. The resulting star-like or rosette-like structure which has loop configurations is twisted by rotational twisting in the same direction of the loop configurations which extend between the inner reversal lines and the outer reversal lines, about the inner reversal lines. It has been established that defects which adversely affect the quality of the honeycomb body occur in a region-wise manner in the macrostructure of the finished honeycomb body. Such defects occur in an irregular fashion in successive production of a plurality of honeycomb bodies which are manufactured using the same apparatuses. This results in particular measures in the area of quality control in relation to the honeycomb bodies produced. On that basis the object of the present invention is to provide a process by which the quality of the honeycomb body produced is improved. A further aim of the invention is to provide a process for producing a plurality of honeycomb bodies, by means of which quality assurance can be simplified. A further aim of the invention is to provide an apparatus for producing a honeycomb body, by means of which honeycomb bodies of improved quality can be produced In accordance with the invention, to attain that object there is proposed a process for producing a honeycomb body having a plurality of passages through which a fluid can flow comprising a plurality of at least partially structured metal sheets wherein at least one stack is formed from a plurality of at least partially structured metal sheets. The stack is introduced into 3 a mould and is held therein by a wrapping device rotatable about an axis in the central region of the stack. The stack which has been introduced into the mould is then subjected to a wrapping procedure until the stack has reached a predetermined degree of wrapping, wherein at least during the wrapping procedure a structural configuration formed in a central region with structures which are disposed relative to each other of the metal sheets is maintained. That configuration of the process ensures that no relative movement of the structures occurs in a central region of the stack, whereby it is possible to produce honeycomb bodies which are of consistent quality. Maintaining the structural configuration with structures of the metal sheets, which are disposed relative to each other, in the central region of the stack is preferably effected as from formation of the structural configuration in the central region. In the case of honeycomb bodies as are known for example from DE 195 21 685 Al the structural configuration is preferably maintained for the further steps in the process with the termination of the operation of forming the stack of metal sheets In the case of honeycomb bodies in which the stack is bent about a bend line, the macrostructure of the stack in the central region, that is to say in the region of the bend line is considered as the structural configuration. Preferably the structural configuration is predetermined in the central region of a stack. It is also possible on the basis of empirical investigations to determine a structural configuration in the central region of a stack, which results in honeycomb bodies which are particularly advantageous in qualitative terms It has already been stated hereinbefore that honeycomb bodies may have defects in their macrostructure. Those defects involve deformation of passage walls which are formed by the at least partially structured metal sheets. Such deformation phenomena adjoin in particular regions in which the honeycomb body has a relatively stiff structure. To avoid deformation of the passage walls in the region of such stiff structures, it is proposed that a stack is formed from alternately structured metal sheets which have corrugation crests and troughs, with smooth metal sheets, wherein the layering of the stack is effected in such a way that a corrugation crest of a structured metal sheet is disposed substantially between two corrugation troughs of an adjacent structured metal sheet. Such a stack involves a relatively low level of stiffness. Relative displacement of the structures of adjacent metal sheets occurs due to the operation of wrapping the stack or stacks. As a result, the cross-section of the honeycomb body has regions which can have a higher level of stiffness than the central region. Those stiffer regions however are not so pronounced or stiff that in adjacent areas of those regions the assembly suffers from deformation of the structures which form the passage walls. 4 Forming a stack with a relatively soft central region is particularly suitable for the production of honeycomb bodies of a small diameter or a small degree of wrapping. To avoid relatively stiff regions in the cross-section of the honeycomb body it is sufficient if the structural configuration in the central region of a stack is relatively soft. It is also possible to construct a stack in such a way that the stiffness of the stack is everywhere the same transversely with respect to the longitudinal direction of the structures. For that purpose it is proposed that the structured metal sheets have corrugation crests and troughs which are repeated with a constant corrugation or wave length. With such a configuration in respect of the structured sheets it is proposed that the metal sheets, prior to the stacking operation, are severed from a metal sheet strip, wherein the sheets are of a length which corresponds to an integral multiple of the corrugation length. That operation of cutting the metal sheets to length provides that, when the structured metal sheets are put into a layered assembly to form a stack a corrugation crest of a structured metal sheet is disposed substantially between two corrugation troughs of an adjacent structured sheet. As an alternative to a stack which has a structural configuration in the central region which is of a low level of stiffness, it is proposed that the structural configuration in the central region of the stack has a relatively high level of stiffness A relatively high level of stiffness is imparted to the structural configuration in the central region of the stack by virtue of the structured metal sheets with corrugation crests and troughs and the smooth metal sheets being arranged in a layer assembly alternately in such a way that corrugation crests and troughs of adjacent structured metal sheets are aligned in mutually superposed relationship substantially transversely with respect to the longitudinal extent of the corrugation crests or troughs respectively. If the structured metal sheets are of such a nature that the corrugation crests and troughs involve a repeating corrugation or wave length, the layering array produces a stack which has a relatively high level of stiffness. The operation of wrapping around the stack causes relative displacement of the corrugation crests and troughs of the adjacent metal sheets. As a result the corrugation crests are no longer disposed in alignment with respect to the corrugation troughs of adjacent metal sheets, whereby imparted to the finished honeycomb body, outside the central region, is a structure which as viewed in the radial direction involves a lower level of stiffness than the central region. The central region of the finished honeycomb body can be considered as a relatively hard core and the region outside the core can be considered as a relatively soft shell. This form of the process also provides for the production of a honeycomb body in which the 5 formation of pronounced regions with a high level of strength in the shell is avoided. If structured sheets which have corrugation crests and troughs that are repeated with a corrugation or wave length ? are used to form the honeycomb body, it is proposed that the sheets, prior to the stacking operation, are severed from a sheet metal strip in a length corresponding to the relationship L = n?+05 ? wherein n is an element from the group of natural numbers. That ensures that in the operation of stacking the structured metal sheets corrugation crests and troughs of adjacent structured metal sheets are substantially aligned with each other. In the production of a honeycomb body the length of the structured metal sheets cannot always be freely selected as the finished honeycomb body, as a catalytic converter carrier body, must involve certain geometrical properties, for example a given number of passages in relation to the cross-section. To form a defined structural configuration in the central region of the stack it is therefore proposed that positioning elements are introduced into the passages in the central region after an operation of forming a stack. A suitable configuration and arrangement of the positioning elements with respect to each other makes it possible to produce a structural configuration in the central region of the stack, which has a relatively low or a relatively high level of stiffness. It is also possible to achieve suitable levels of stiffness of the stack in the central region, in which respect the positioning elements are suitably adapted to the required structural configuration of the central region. In accordance with another concept of the invention there is proposed a process for producing honeycomb bodies, wherein each honeycomb body has a plurality of passages through which a fluid can flow, comprising a plurality of at least partially structured metal sheets, by means of which process honeycomb bodies of improved quality can be produced In accordance with this process for the production of honeycomb bodies it is proposed that at least one stack is formed from a plurality of at least partially structured metal sheets. The layered stack is introduced into a mould and held therein by a wrapping device rotatable about an axis in the central region of the stack. The stack is subjected to a wrapping procedure until a predetermined degree of wrapping of the stack is achieved. The stack when wrapped in that way is removed from the mould, possibly after a fixing operation, for example by means of a tubular casing Those process steps are repeated for each stack of a further honeycomb body. Each stack is formed with a structural configuration which is always the same in a central region. The structural configuration has structures, which are arranged relative to each other, of the metal sheets. That structural configuration is maintained 6 at least during the wrapping procedure for each stack. The fact that the structural configuration of the structures of the metal sheets, which are arranged relative to each other, in the central region of the stack is the same in the case of each honeycomb body ensures that the distribution of the passages over the cross-section of the honeycomb body is almost the same in relation to a plurality of honeycomb bodies. Preferably the structural configuration in the central region of a stack is predetermined for a first honeycomb body of a plurality of honeycomb bodies. The predetermined structural configuration in the central region is preferably so selected that within the cross-section of the honeycomb body there are no pronounced regions involving a high level of stiffness, in the proximity of which deformed structures are produced. A further development of the process according to the invention provides that a stack for a first honeycomb body of a plurality of honeycomb bodies is formed in a layered arrangement and the structural configuration in the central region of the stack is determined for the first honeycomb body. That structural configuration of the first stack in the central region is repeated by suitably arranging metal sheets in layers to form stacks for each further honeycomb body if the honeycomb body produced from the first stack satisfies predetermined quality criteria. In accordance with a further concept of the invention there is proposed an apparatus for producing at least one honeycomb body, in particular a catalytic converter honeycomb body, comprising at least one stack comprising a plurality of at least partially structured metal sheets which form a plurality of passages through which a fluid can flow. The apparatus includes a mould, the internal configuration of which substantially corresponds to an external shape of a honeycomb body to be produced. The apparatus also includes a wrapping device by which each stack is held in its central region at least during a wrapping procedure. The wrapping device has a holding device by which each stack is held in the central region of the stack in such a way that a structural configuration produced in a central region with structures, which are disposed relative to each other, of the metal sheets. is maintained at least during the wrapping procedure Advantageously the holding device has positioning elements which can be at least partially introduced into the passages of the structural configuration in a central region of each stack. The configuration of the positioning elements substantially corresponds to the shape of the passages Preferably the positioning elements are of a bar-like configuration The width of the holding device is preferably such that it corresponds to the thickness of a stack. Further details of the process and the apparatus are described by means 7 of the embodiments illustrated in the drawing accompaning in which. Figure 1 diagrammatically shows a procedure for forming a first embodiment of a stack. Figure 2 diagrammatically shows a procedure for forming a second embodiment of a stack. Figure 3 is a diagrammatic plan view of an embodiment of an apparatus with a stack, Figure 4 shows a first embodiment of a wrapping device, Figure 5 shows a second embodiment of a wrapping device, Figure 6 shows a sectional view of the wrapping device shown in Figure 5. Figure 1 shows a procedure for forming a stack 1. - The stack 1 includes a plurality of at least partially structured metal sheets 2. Smooth metal sheets 3 are arranged between the structured metal sheets 2 which are disposed in superposed relationship. Passages 4 are formed in the stack 1 by the structured sheets 2 and the smooth sheets 3. The individual structured sheets 2 are cut off a sheet metal strip 5 at a suitable length by a cutting device 6. The structured sheets 2 have corrugation crests 7 and corrugation troughs 8. The structured sheets 2 are arranged in a layered relationship alternately in such a way that corrugation crests 7 and corrugation troughs 8 of adjacent structured sheets are substantially aligned with each other. The structured sheets 2 have corrugation crests 7 and corrugation troughs 8 which are repeated with a corrugation or wave length ?. Prior to the stacking operation the sheets 2 are severed from a sheet metal strip 5 at a length L corresponding to the relationship L = n? + 0 5 ?, wherein n is an element from the group of natural numbers. By virtue of that configuration and arrangement of the stack it involves a relatively high level of stiffness. Figure 2 shows a further possible layer arrangement of structured metal sheets 2 and smooth metal sheets 3. The stack 9 shown in Figure 2 has an arrangement of structured sheets 2 and smooth sheets 3 in which the corrugation crests 7 of a structured sheet 2 are disposed between two corrugation troughs 8 of an adjacent structured sheet 2. The structured sheets 2 have a corrugation crest and trough structure which is repeated with a corrugation or wave length ?. The structured sheets 2 are severed prior to the stacking operation from a sheet metal strip 5 of a length L which corresponds to an integral multiple of the length X. The stack 9 is of a lower level of stiffness than the stack 1 as the corrugation crests 7 of a structured sheet 2 are so positioned that they are always between two corrugation troughs 8 of an adjacent structured sheet 2. Figure 3 shows an apparatus for producing a honeycomb body. This involves an illustration by way of example of an apparatus for the production of a 8 honeycomb body. Such an apparatus is known from DE 195 21 685 Al. The apparatus has a mould 12 comprising two mould segments 10, 11. Each mould segment 10, 11 is pivotable about a respective pivot axis 13, 14. In the pivoted condition of the mould segments 10, 11 they embrace a honeycomb body formed by a wrapping device 15. The envelope of the honeycomb body is identified by reference numeral 16. The wrapping device 15 is pivotable about a central axis 17. The wrapping' device 15 holds the stack 1 together in a central region. Figure 4 diagrammatically illustrates the wrapping device 15. The wrapping device 15 has a carrier 19. Arranged at each end of the carrier 19 is a respective winding mandrel or bar 20 and 21 respectively which each engage a respective outside surface 22, 23 of the stack 1. Disposed between the winding bars 20, 21 are positioning elements 22 which extend substantially parallel to the winding bars 20, 21. The positioning elements 22 are substantially of a bar-like configuration and they at least partially engage into the passages 4 of the stack 1, whereby the structural configuration of the stack in the central region 18 is maintained. The wrapping device 15 may have a plurality of rows of positioning elements 22. They may also be arranged in displaced relationship relative to each other. The arrangement of the positioning elements 22 substantially depends on the desired structural configuration in the central region 18 of a stack. In this connection, the positioning elements 22 and the carrier 19 form a holding device 23 by which each stack 1 is held in the central region 18 thereof in such a way that, at least during the wrapping procedure, a structural configuration provided in the central region 18, having structures which are disposed relative to each other, in particular corrugation crests 7 and corrugation troughs 8. of the structured sheets 2, is maintained Figures 5 and 6 show a further embodiment of a wrapping device 15. The wrapping device 15 is intended in particular for producing a honeycomb body having a plurality of passages through which a fluid can flow, comprising a plurality of at least partially structured metal sheets, wherein a plurality of stacks is formed in a layered arrangement from a plurality of at least partially structured metal sheets 2, with each stack being folded about a respective bend line. The stacks are introduced into an open mould which is formed from mould segments corresponding to the external shape of the honeycomb body to be produced, and held in the mould by the wrapping device 15. The stacks which are not shown are twisted or wound around each other in one direction of rotation. The production of a honeycomb body of that kind is described for example in DE 195 22 327 Al and DE 195 21 685 Al. The content of those publications is deemed to be content of the present patent application. 9 The wrapping device 15. as is illustrated in Figure 5. has three carriers 19, 24. 25 which extend away from a common centre 26. Provided at the centre 26 is a drive shaft 27 by which the wrapping device 15 is pivotable about the axis 17 Each carrier 19. 24. 25 is of the same configuration. An angle of about 120° is formed between each carrier 19. 24, 25. Provided at the free ends of each of the carriers 19. 24. 25 are respective winding bars 20 which can be brought into engagement with the stack or stacks. The winding bars 20 engage substantially into the region of the bend line of a stack. Rotating the winding bars 20 about the axis 17 in one direction causes the individual stacks which are not shown to be twisted in the same direction. In order to ensure that the structural configuration of the stack in the central region is maintained at least during the wrapping procedure, each carrier 19. 24. 25 has positioning elements 22 which can be at least partially introduced into passages 4 in each stack. It is not necessary for the arrangement of the positioning elements 22 on each carrier 19.24. 25 of the holding device 23 to be the same. It is also possible to provide for different arrangements of the positioning elements 22. 10 List of references 2 structured sheet 3 smooth sheet 4 passage 5 sheet strip 6 cutting device 7 corrugation crest 8 corrugation trough 9 stack 10. 11 mould segment 12 mould 13, 14 pivot axis 15 wrapping device 16 envelope 17 axis 18 central region 19 carrier 20, 21 winding bar 22 positioning element 23 holding device 24, 25 carrier 26 centre 11 1. A process for producing a honeycomb body having a plurality of passages ,(4) through which exhaust gases of an engine can pass comprising a plurality of at least partially known material structured sheets (2), in which a) at least one stack (1) is formed in layered relationship from a plurality of at least partially structured sheets (2), b) the stack (1, 9) is introduced into a mould (12) and is held therein by a wrapping device (15) in the central region (18) of the stack (1. 9). and c) the stack (1, 9) is subjected to a wrapping procedure until a predetermined degree of wrapping of the stack (1, 9) is attained and a structural configuration provided in a central region (18) and having structures (7. 8). which are disposed relative to each other, of the sheets (2) is maintained at least during the wrapping procedure. 2. A process for producing honeycomb bodies wherein each honeycomb body has a plurality of passages through which a fluid can pass, comprising a plurality of at least partially structured sheets (2), in which a) at least one stack (1) is formed in layered relationship from a plurality of at least partially structured sheets (2). b) the stack (1. 9) is introduced into a mould (12) and is held therein by a wrapping device (15) in the central region (18) of the stack (1. 9), c) the stack (1, 9) is subjected to a wrapping procedure until a predetermined degree of wrapping of the stack (1, 9) is attained, d) the stack (1, 9) is removed in the wrapped condition from the mould (12). and e) process steps a) to d) are repeated for each stack (1, 9) of a further honeycomb body and each stack (1, 9) is formed with a structural configuration, that is always the same in a central region (18). of the structures (7, 8), which are arranged relative to each other, of the sheets (2). and the structural configuration of the structures (7. 8), which are arranged relative to each other, of the sheets (2) of each stack (1, 9) is maintained at least during the wrapping procedure. 3. A process according to claim 1 or claim 2 wherein the structural configuration in the central region (18) of a stack (1. 9) is predetermined for the honeycomb body or for a first of a plurality of honeycomb bodies. 4. A process according to claim 2 wherein a stack (1. 9) for a first honeycomb body is formed in a layered relationship and the structural configuration in the central region (18) of the stack (1. 9) is determined for 12 the first honeycomb body, wherein said structural configuration is repeated by correspondingly arranging further sheets in layered relationship to form a respective stack (1, 9) for each further honeycomb body if the honeycomb body produced from the first stack (1. 9) satisfies predetermined quality criteria. 5 A process according to claim 1. claim 2 or claim 3 wherein structured sheets (2) with corrugation crests (7) and corrugation troughs (8) and smooth sheets (3) are arranged in layered relationship alternately to form a stack (9) in such a way that a corrugation crest (7) of a structured sheet (2) is disposed substantially between two corrugation troughs (8) of an adjacent structured sheet (2). 6. A process according to claim 5 wherein the structured sheets (2) have corrugation crests (7) and corrugation troughs (8) which are repeated with a corrugation length (?) and the sheets (2) are severed prior to the stacking operation from a sheet strip with a length CD which corresponds to an integral multiple of the corrugation length (?). 7. A process according to claim l. claim 2 or claim 3 wherein structured sheets (2) with corrugation crests (7) and corrugation troughs (8) and smooth sheets (3) are arranged in layered relationship alternately in such a way that corrugation crests (7) and corrugation troughs (8) of adjacent structured sheets (2) are substantially aligned with each other. 8. A process according to claim 7 wherein the structured sheets (2) have corrugation crests (7) and corrugation troughs (8) which are repeated with a corrugation length (?) and the sheets (2) are severed prior to the stacking operation from a sheet strip (5) with a length (L) corresponding to the relationship L = n ? + 0.5 ? wherein n is an element from the group of natural numbers. 9. A process according to one of claims 1 to 8 wherein positioning elements (22) are at least partially introduced into the passages (4) after an operation of forming a stack (1. 9) in layered relationship, in the central region (18). carrying out the process as claimd in Claim 1, for 10 Apparatus for producing at least one honeycomb body, in particular a catalytic converter carrier body, comprising at least one stack (1. 9) comprising a plurality of at least partially structured sheets (2) which form a plurality of passages (4) through which a fluid can pass, wherein the 13 apparatus has a mould (12) whose internal configuration substantially corresponds to an external shape of a honeycomb body to be produced, and a wrapping device (15) by which each stack (1. 9) is held in its central region (18) at least during a wrapping procedure characterised in that the wrapping device (15) has a holding device (23) by which each stack (1, 9) is so held in the central region (18) of the stack (1. 9) that a structural configuration formed in a central region (18) with structures (7, 8), which are disposed relative to each other of the structured sheets (2) is maintained at least during the wrapping procedure. 11. Apparatus according to claim 10 characterised in that the holding device (23) has positioning elements (22) which can be at least partially introduced into the passages (4) of the structural configuration in a central region (18) of each stack (1. 9). 12. Apparatus according to claim 11 characterised in that the positioning elements (22) are of a bar-like configuration. Dated this 28th day of JANUARY 1998. There is proposed a process for producing a honeycomb body having a plurality of passages through which a fluid can pass comprising a plurality of at least partially structured sheets wherein at least one stack is formed in layered relationship from a plurality of at least partially structured sheets. The stack is introduced into a mould and held therein by a wrapping device in the central region of the stack. The stack is then subjected to a wrapping procedure until a predetermined degree of wrapping of the stack is attained. A structural configuration formed in a central region with structures which are disposed relative to each other of the structured sheets of the stack is maintained at least during the wrapping procedure.

Documents:

00144-cal-1998-abstract.pdf

00144-cal-1998-claims.pdf

00144-cal-1998-correspondence-1.1.pdf

00144-cal-1998-correspondence.pdf

00144-cal-1998-description(complete).pdf

00144-cal-1998-drawings.pdf

00144-cal-1998-form-1.pdf

00144-cal-1998-form-2.pdf

00144-cal-1998-form-3.pdf

00144-cal-1998-form-5.pdf

00144-cal-1998-pa.pdf

00144-cal-1998-priority document(others).pdf

00144-cal-1998-priority document.pdf