FR2618515A1 - IMPROVED SEAL SEAL HAVING SEVERAL REGIONS OF DIFFERENT DENSITY AND THICKNESS AND PROCESS FOR MANUFACTURING THE SAME - Google Patents

Abstract

Disclosed is a gasket having a plurality of regions of different densities as well as a process for the manufacture thereof. This gasket essentially comprises a unitary layer of gasket material having a uniform thickness throughout, this layer of gasket material having a region of first density 17d and a region of first density. second density 17different from the aforementioned first density region. Essentially, the process involves providing first and second sheets of gasket material and then arranging them in a partial overlap between die elements which are then moved towards each other to form a seal. sealing comprising regions of first and second density defined by the parts covered or not of the sheets. This invention applies for example to any type of flat seal fitted to the driving elements of a vehicle.

Description

The present invention relates generally to seals and

  to seal manufacturing processes and in particular to an improved seal having a plurality of regions of different densities and thicknesses and to a method for

the manufacture of it.

  Seals are often used as a shutter between mechanical parts of

  junction to prevent fluid leakage between them.

  A common application for such seals is inside an internal combustion engine for a vehicle. Carburetors, manifolds, and cylinder head heads are only a few of the members that are sealingly protected on an engine block within such internal combustion engines by seal means. In order to operate reliably within an internal combustion engine, the seals must be resistant to wear resulting from corrosion, heat and mechanical stress. In some cases, the seals include a metal core so as to increase their strength. In other cases, the seals are formed of materials that are highly compressed in certain regions in order to increase the density and consequently the rigidity and durability thereof. In still other cases, the seals are formed having in certain regions of varying thicknesses, depending on the nature of the required sealing to be performed in these regions. It is known to form a seal having distinct regions which vary from one another in both density and thickness. Be that as it may, in the past, it has been difficult and expensive to form such seals. Since seals are relatively expensive products, there is a continuing need to improve manufacturing processes thereof to reduce costs. Such a need is amplified with respect to seals having multiple densities and thicknesses, where complex structural patterns may be required. The present invention relates to an improved seal having a plurality of regions of different densities and thicknesses and to a method of manufacturing the same. First and second squeeze sheets or compressible seal gaskets may be used to form a finished seal or a seal blank having two regions of different densities. The first sheet has a shape that corresponds to the overall shape of the seal. The second sheet has a shape that corresponds only to those regions of the seal for which a higher density is desired. The first and second sheets are centered with each other in a plan overlap ratio and pressed together by a die having opposed flat surfaces. When so pressed, the second sheet is compressed into, and combined with, the first sheet to form a unitary seal having flat surfaces facing each other and two regions of different densities. The region of higher density is defined by that portion of the first sheet of material that has been covered by the second sheet during the pressing process, while the region of lower density is defined by the uncoated portion of the first sheet. Several sidewall flaps or seal gaskets having different shapes can be used in this way to form gaskets or seal blanks having additional regions of different densities. In alternative embodiments of the present invention, the flat surfaces of the die may be provided with recessed grooves or profiled bosses in certain regions. When the sidewall flaps or seal gaskets are pressed together as discussed above, portions thereof engaged in the grooves or bosses are compressed differently from other portions engaged on the flat surfaces of the die. These differently compressed parts of the finished seal or seal blank do not only have a different density than the other parts of the seal, but also a different thickness.

  other parts of the seal.

  An object of the present invention is to provide an improved method for forming a seal having a plurality of density regions and

of different thicknesses.

  Another object of the present invention is to

  provide a process that is simple and economical.

  But other features and benefits of

  the invention will appear better in the description

  FIG. 1 is an exploded perspective view schematically illustrating a plurality of sheets of sealant material before being pressed together between opposite flat surfaces of a pair of die elements; Figure 2 is a top view of a multi-density seal blank formed by the method illustrated in Figure 1; - Figure 3 is an elevational view in section taken along the line 3-3 of Figure 2; - Figure 4 is an exploded perspective view similar to the. FIG. 1, illustrating a first alternative embodiment of the present invention, in which the flat surfaces of the matrix elements are provided with profiled bosses in certain regions; FIG. 5 is a top view of a multi-density and thickness seal blank formed by the method illustrated in FIG. 4; FIG. 6 is a sectional and elevational view taken along line 6-6 of FIG. 5; Figure 7 is a sectional and elevational view taken along line 7-7 of Figure 5; FIG. 8 is an exploded perspective view similar to FIG. 1 illustrating a second alternative embodiment of the present invention, in which the flat surfaces of the elements of the matrix are provided with recessed grooves in certain regions; FIG. 9 is a top view of a multi-density and thickness joint blank formed by the method illustrated in FIG. 8; Fig. 10 is a sectional and elevational view taken along line 10-10 of Fig. 9, and Fig. 11 is a sectional view showing

  elevation taken along line 11-11 of Figure 9.

  Referring now to the drawings, there is illustrated in FIG. 1 a device for forming a multi-density seal or seal blank according to the method of the present invention. For the sake of simplicity, the present invention will be described and illustrated in the context of forming a gasket blank. In any case, as will become apparent below, the present invention can also be used to form a finished seal. As shown in FIG. 1, opposite upper and lower die members 11 and 12, respectively, are provided having flat parallel surfaces 11a and 12a respectively facing each other. The die members 11 and 12 include locating means disposed on the facing flat surfaces 11a and 12a, respectively. In the illustrated embodiment, the positioning means comprises a plurality of cylindrical positioners 12b formed on the flat surface 12a of the lower die member 12 and a plurality of corresponding cylindrical recesses (not shown) formed in the flat surface 11a. of the upper die member 11. The cylindrical positioners 12b are adapted to be received in the recesses when the upper and lower die members 11 and 12, respectively, are moved toward each other so that the flat surfaces opposites lla and 12a can lead to one another. The function of the means of

  positioning will be explained in more detail below.

  Between the upper and lower die members 11 and 12, a plurality of sheets of sealing materials are disposed. In the illustrated embodiment, such leaflets include a central core 13, respective first sidewall flaps or seal gaskets 15 disposed between each side of the core 13 and the corresponding die element 11 or 12, and second flaps 16 of flanks or respective seal gaskets disposed between each side of the core 13 and each of the corresponding first leaflets 15. The core structure 13 is conventional in the art and may consist of a perforated metal sheet having a plurality of claws 13b (see Figs. 2 and 3) extending normally therefrom on both sides. The first and second flaps of the seals or gaskets and 16, respectively, may be formed of any conventional compressible sealing material, such as expanded graphite or the like. The first flaps 15 of the gasket flanks or gaskets are each shaped to correspond to the overall shape of the multi-density finished gasket or gasket blank. The second flaps 16 of the gasket flanks or gaskets are each shaped to correspond only to those portions of the multi-density finished gasket or gasket blank for which regions of higher densities are required. large are desired. Each core 13, the first leaflets 15 and the second leaflets 16 have respective openings 13a, 15a and 16a formed therethrough. The openings 13a, 15a and 16a correspond to the combustion ports of the seal or seal blank to be formed and are adapted to receive the positioners 12b therethrough. As a result, the core 13, the first leaflets 15, and the second leaflets 16 can be arranged and held in relative positions relative to each other on the lower die member 12 prior to the formation of the seal. sealing at several densities finished or the seal blank. Thus, the positioning means are provided to initially orient the various leaflets used to form the multi-density seal or the seal blank relatively to each other. It will be appreciated that the positioning means of the present invention can be made like any other conventional structure than that illustrated in Figure 1 which performs the same positioning function. To form the finished multi-density seal or the seal blank, the core 13, the first leaflets 15 and the second leaflets 16 are inserted on the positioners 12b in the order illustrated in FIG. extend on the flat surface 12a of the lower die member 12. Once thus arranged, the upper and lower die members 11 and 12, respectively, are moved toward each other using any what a classic way. A predetermined level of force is exerted by the die members 11 and 12 to press the core 13, the first leaflets 15, and the second leaflets 16 together. During this pressing operation, the pairs of first and second sheets 15 and 16, respectively, on each side of the core 13 are pressed together to combine each pair-in a unit sheet disposed on each side of the core 13. Simultaneously, the pairs of first and second sheets 15 and 16, respectively, on each side of the core 13 are pressed in engagement with the projecting claws 13b formed on each side of the core 13. As is well known in the art, such claws 13b can be used to mechanically rivet the flanks or gaskets or gasket or metal core 13. Once the pairs of the first and second leaflets 15 and 16, respectively, have been pierced by the claws 13b of the core 13, additional pressing by the elements of die 11 and 12 leads the claws 13b to bend inwards towards the core 13 as illustrated in FIG. 3, thus preventing the sheets 15 and 16 to be detached from the core 13. In this mechanical riveting step, the pressing operation is interrupted to move the upper and lower die elements 11 and 12,

  respectively, away from each other.

  A multi-density seal blank 17 formed according to the method described above

  is illustrated in detail in Figures 2 and 3.

  The seal blank 17 may be cut or otherwise machined in any known manner to provide a finished seal structure at a plurality of desired densities. As mentioned above, a finished multi-density seal formed in accordance with the present invention has not been illustrated for the sake of simplicity. In any event, it will be apparent to anyone skilled in the art that the core 13, the first leaflets 15 and the second leaflets 16 may initially be shaped in accordance with the desired final shape of the multi-seal. Finished densities so that the pressing operation described above results in a finished seal structure requiring little or no additional machining. As a result, the terms "gasket" and "gasket blank" used herein are used in a switchable manner and the illustrated gasket blanks 17 can be viewed as finished seals. The seal blank 17 has top and bottom faces 17a and 17b, respectively, having a plurality of openings 17c formed therethrough. The top and bottom faces 17a and 17b, respectively, of the seal blank 17 are flat because the facing surfaces 11a and 12a of the upper and lower die members 11 and 12, respectively, engage and compress. these parts of the seal blank 17 are likewise flat. The openings 17c correspond to the openings 13a, 15a and 16a described above. Regions of first and second densities 17d and 17e, respectively, are formed within the seal blank 17 as a result of the size difference of the sheets 15 and 16. The first density region 17d is extends from one end to the other of this part of the seal blank 17 where the first leaflets 15 have not been covered by the second leaflets 16 during the pressing operation, as illustrated in FIG. 2. The second density region 17e extends from one end to the other of this portion of the seal blank 17 or the first sheets 15 were covered by the second sheets 16 during the pressing operation also, as shown in Fig. 2. Also, the first density region 17d consists only of the compressed portions of the first leaflets 15, while the second density region 17e consists of the compressed portions of the first and second halves. d sheets 15 and 16, respectively. As a result, the density of the first density region 17d is lower than the density of the second density region 17e, although the upper and lower faces 17a and 17b, respectively, are flat over the entire extent. of the gasket blank 17. The structure of the gasket blank 17 is unique because the regions of different densities 17d and 17e are formed by the compression of different levels of the sealing material in a uniform thickness. As best illustrated in FIG. 3, the overall thickness of the seal blank 17 is constant, as is the thickness of each of the riveted combined sealing materials of each side of the core 13, from one end to the other of the two density regions

17d and 17th.

  The method described above illustrates a method of forming a seal blank 17 having distinct low and high density regions 17d and 17e, respectively, while a uniform thickness from one end to the other. the other of the seal 17 is maintained. The number of leaflets 15 and 16 of the flanks or

  Seal gaskets may vary as desired.

  For example, in some applications it may be desired to form the seal at only a few densities of a single first sheet and a second single sheet 16, thus omitting the core 13 and the other first and second sheets. 15 and 16, respectively. Conversely, additional flaps or seal gaskets having different shapes may be used to create a multi-density seal having more than two regions of different densities. For example, if three sidewall flaps or seal gaskets were used, each having a different shape, three different regions having different densities could be formed by the method according to the invention. Further, if each of the three sidewall flaps or gasket liners differ from one another in thickness, a greater number of regions of distinct densities could be formed using the method of the invention, although the thickness of the finished seal or seal blank would be

uniform as described above.

  Alternatively, it may be desirable to replace the central core 13 with one or more outer cores to create a structure where one or both of the first leaflets would be replaced by a perforated metal core having claws formed on only one face, while the Central core 13 would be replaced by one or more sidewall flaps or seal gaskets. Thus, it will be appreciated that the method of the present invention can be used to quickly and easily form a multi-density seal having virtually any model of

densities located on it.

  Referring now to FIG. 4, there is illustrated a device for forming a multi-density seal according to the first alternative embodiment of the method according to the present invention. The device illustrated in FIG. 4 is basically identical to the device illustrated in FIG. 1, and similar numerical references are there

  used to indicate the common elements of it.

  The lower die member 12 of the device illustrated in FIG. 4, however, is provided with a profiled boss 12c in certain regions of the lower flat surface 12a thereof, which boss 12c is not included in the lower die member 12 illustrated in FIG. 1. The upper die member 11 illustrated in FIG. 4 is also provided with a profiled boss (not shown) which is of the same extent as the; lower boss 12c. The device illustrated in FIG. 4 can be used as described above to form a modified seal blank 20, shown in detail in FIG. 5 in FIG.

  several regions of different densities and thicknesses.

  As illustrated therein, the seal blank 20 generally has faces

  upper and lower plates 20a and 20b, respectively

  with top and bottom surfaces

  lower 20c and 20d respectively formed thereon.

  The flat faces 20a and 20b of the seal blank 20 correspond to those portions of the leaflets 16 which were engaged on the flat surfaces 11a and 12a of the die members 11 and 12, respectively, during the pressing operation. . The recessed surfaces 20c and 20d of the seal blank 20 correspond to those portions of the leaflets 15 and 16 which were engaged on the boss 12c during the pressing operation. Thus, the bosses 12c are provided to generate regions of different thicknesses within the seal blank 20. The openings 20c

  correspond to the openings 17c described above.

  The seal blank 20 has a first density region 20f, a second density region 20g, a third density region 20h, and a fourth density region 20i. The first density region 20f extends from one end to the other of this portion of the seal blank 20 where the first leaflets 15 have not been covered by the second leaflets 16 during the operation. and the first sheets 15 were engaged on the flat surfaces 11a and 12a of the upper and lower die members 11 and 12, respectively. Thus, the region of first density 20f is composed only of the first compressed sheets 15 to the relatively largest thickness defined by the upper and lower flat faces 20a and 20b, respectively, of the seal blank 20. The region of second density 20g extends from one end to the other of this part of the seal blank 20 o the first sheets 15 were not covered by the second sheets 16 during the pressing operation and o the first sheets 15 were engaged on the bosses 12c. Thus, the second density region 20g is composed only of the first compressed sheets at the relatively lowest thickness defined by the surfaces.

  upper and lower recesses 20c and 20d respecti-

  The third density region 20h extends from one end to the other of this portion of the seal blank 20 where the first leaflets 15 were covered. by the second leaflets 16 during the pressing operation and where the first and second leaflets 15 and 16, respectively, were engaged on the upper and lower flat surfaces 11a and 12a of the elements.

  upper and lower die 11 and 12, respectively.

  Thus, the third density region 20h consists of the two first and second sheets 15 and 16, respectively, compressed to the relatively larger thickness defined by the upper and lower flat faces 20a and 20b, respectively, of the joint blank. Finally, the fourth density region 20i extends from one end to the other of this portion of the seal blank 20 where the first sheets 15 were covered by the second sheets 16 during the pressing operation and o the first and second sheets were engaged on the bosses 12c. Thus, the fourth density region 20i is composed of the first and second sheets 15 and 16, respectively, compressed to the relatively smallest thickness defined by the recessed surfaces 20c and 20d, respectively, of the seal blank. Sealing 20. From the above presentation of the present invention, several variations will occur to those skilled in the art. For example, additional bosses may be provided on the upper and lower die members 11 and 12, respectively, having different heights of the illustrated bosses 12c. Such a structure would produce a finished seal having more than two different thicknesses. Thus, by varying the number of different leaflets 15 and 16 used to form the seal blank, the shapes of the various leaflets 15 and 16 thus used, and the shapes and configurations of the bosses 12c of the die elements 11 and 12, the method according to the present invention can be used to form a seal blank 20 having virtually any configuration of regions of densities and thicknesses. Referring now to Figure 8, there is illustrated a device for forming a multi-density seal according to a second alternative embodiment of the method according to the present invention. The device illustrated in FIG. 8 is basically identical to the device illustrated in FIG. 1, and similar numerical references are there

  used to indicate the common elements of it.

  The lower die member 12 of the device shown in Fig. 8, however, is provided with a recessed groove 12d in certain regions of the lower flat surface 12a thereof, which groove 12d is not included in the lower die member 12 shown in FIG. 1. The upper die member 11 illustrated in FIG. 8 is also provided with a recessed bore (not shown) which is of the same extent as the bottom groove 12d. The device illustrated in Figure 8 may be used as described above to form a modified seal blank 25, illustrated in detail in Figures 9 to 11, having

  several regions of different densities and thicknesses.

  As illustrated therein, the seal blank 25 generally has flat top and bottom faces 25a and 25b, respectively, having respective upper and lower projecting surfaces 25c and 25d formed thereon. The flat faces 25a and 25b of the seal blank 25 correspond to those portions of the leaflets 15 and 16 which were engaged on the flat surfaces 11a and 12a of the die members 11 and 12, respectively, during the pressing. The projecting surfaces 25c and 25d of the seal blank 25 correspond to those portions of the leaflets 16 which were engaged on the grooves 12d during the pressing operation. Thus, the grooves 12d are provided to generate regions of different thicknesses within the seal blank 25. Apertures 25e correspond to the openings 17c described above. Similar to gasket tee 20

  illustrated in Figures 4 to 7, the draft

  seal 25 comprises a first density region f, a second density region 25g, a third density region 25h, and a fourth density region i. The first density region 25f extends from one end to the other of this part of the seal blank 25 where the first leaflets 15 were not covered by the second leaflets 16 during the pressing and o the first leaflets 15 were engaged on the flat surfaces 11a and 12a of the upper and lower die elements 11 and 12, respectively. Thus, the first density region 25f is made up of only the first layers 15compressed to the relatively smallest thickness defined by the upper and lower flat faces 25a and 25b, respectively, of the gasket blank 25. of second density 25g extends from one end to the other of this part of the seal blank 25 o the first leaflets 15 were not covered by the second leaflets 16 during the pressing operation o the first sheets 15 were engaged by the grooves 12d. Thus, the second density region 25g consists only of the first relatively thickest compressed sheets defined by the upper and lower projecting surfaces 25c and 25d, respectively, of the gasket blank 25. of the third density 25h extends from one end to the other of this part of the seal blank 25 o the first sheets 15 were covered by the second sheets 16 during the pressing operation and o the first and second sheets 15 and 16, respectively, were engaged on the upper and lower flat faces 11a and 12a of the elements.

  upper and lower die 11 and 12, respectively.

  Thus, the third density region 25h consists of the first and second two sheets 15 and 16, respectively, compressed to the relatively smallest thickness defined by the upper and lower flat faces 25a and 25b, respectively, of the blank. 25. Finally, the fourth density region 25i extends from one end to the other of this part of the seal blank 25 where the first sheets 15 were covered by the second sheets 16 during the pressing operation and where the first and second sheets were engaged on the grooves 12d. Thus, the fourth density region 25i consists of the first and second two sheets 15 and 16, respectively, compressed to the relatively largest thickness defined by the upper and lower projecting surfaces 25c and 25d,

  respectively, of the gasket blank 25.

  Of course, the invention is not limited to the embodiments described and illustrated and

  which have been given only as an example.

  On the contrary, the invention comprises all the technical equivalents of the means described and their combinations if they are carried out according to its spirit.

Claims (3)

  An improved seal having a plurality of regions of different densities, characterized in that it comprises a unitary layer of sealant material having end-to-end uniform thickness, said layer of sealant material seal having a first density region (17d) and a second density region (17e) different   of said first density region.   2. A method of forming a seal having several regions of different densities, characterized in that it consists of: a) providing a first sheet (15) of a seal material; b) providing a second sheet (16) of a seal material; c) arranging the first and second sheets (15, 16) in a partial overlap between opposed die elements (11, 12); and d) moving the opposed die members (11, 12) toward each other so as to exert a predetermined force level compressing the first and second sheets (15, 16) together, whereby a seal of seal is formed having a region of first density (17d) defined by that portion of the first sheet which has been covered by the second sheet during said compression and a region of second density (17e) defined by that portion of the first sheet which has not not been covered by the second   sheet during said compression.   3. A method of forming a seal having a plurality of regions of different densities, characterized in that it comprises: a) providing a first sheet of a seal material having a first form; b) providing a second sheet of seal material having a second shape different from said first form; c) arranging the first and second sheets in a lap ratio between opposed matrix elements; and d) moving the opposed die members toward each other so as to exert a predetermined force level compressing the first and second sheets together, whereby a unitary seal is formed comprising a first density region defined by that part of the first sheet which has been covered by the second sheet during said compression and a region of second density defined by that part of the first sheet which has not been covered by the   second month during the said nnession.   intervals, a second rigid screen which can be mounted on the other of these members and fixedly support a sensor disposed in a position such that it is   in service in front of said reference element, and one   b) providing a second sheet of a seal material having a second shape different from said first form; c) arranging the first and second sheets in a lap ratio between opposed die members having corresponding generally flat portions (11a, 12a) and corresponding profiled bosses (12c) formed on the flat portions; and d) moving the opposed die members toward each other so as to exert a predetermined force level compressing the first and second sheets together, whereby a unitary formed gasket having a first density region defined by that part of the first sheet which has been covered by the second sheet and which has been engaged on the boss portions of the matrix elements during said compression, a region of second density defined by that part of the first sheet which has been covered by the second sheet which has not been engaged on the boss parts of the matrix elements during said compression, a region of third density defined by that part of the first sheet which has not been covered by the second sheet and which has engaged on the boss portions of the matrix elements during said compression, and a fourth density region defined by that part of the first sheet that was not covered by the second sheet and that was not engaged on the boss parts of the elements of matrix during said compression.