JOINT MEANS HAVING FLANGES

Abstract: A joint means has a first flange (l3) rigidly secured to the outer peripheral surface of an end portion of a first pipe (ll) and a second flange (l4) rigidly secured to the outer peripheral surface of an end portion (l2a) of a second pipe (l2). The first and second flanges (l3, l4) are aligned with each other and joined together by means of nuts and bolts so that the first and second pipes (ll, l2) are connected together and maintained in a hermetically sealed state by means of a closed loop-shaped sealing member (l6) clamped between the first and second flanges (l3, l4). The sealing member (l6) is fitted on the end portion (l2a) of the second pipe (l2) which slightly projects from the second flange (l4). The sealing member (l6) is formed by wrapping a thin metal sheet (2l) around a heat resistant material (20) and has an inner diameter which is equal to or slightly larger than the outer diameter of the second pipe (l2). A conically tapered surface (l9) aligned with the sealing member (l6) is formed along the inner peripheral edge of the first flange (l3).

Description: The present invention relates to a joint means having flanges. More particularly, the present invention pertains to an improvement in a joint means in which a closed loop-­ shaped sealing member which is interposed between two flanges is formed by wrapping a thin metal sheet around a heat resistant material. In general, the exhaust gas which is discharged from various kinds of exhaust gas generating sources, for example, automotive engines, is emitted into the atmosphere through a relatively long exhaust pipe connected at one end thereof to the exhaust manifold of the engine. It is a general practice to provide a muffler and a catalytic converter at an intermediate portion of such an exhaust pipe in order to damp noise components included in the exhaust gas and to make harmless certain noxious compo­ nents contained therein. Associated parts such as the muffler and the cata­ lytic converter are produced separately from the exhaust pipe and are joined to the intermediate portion of the pipe afterward using a joint means. This joint means must be made airtight so that no exhaust gas leaks. Accordingly, two pipe end portions which constitute a joint means have respective flanges which extend outwardly. These flanges are fastened to each other by means of bolts with a sealing member interposed between the flanges. Since the tempera­ ture of exhaust gas is relatively high, it is a general practice to employ a sealing member having high heat resist­ ance and relatively high rigidity. Since a sealing member having a relatively high rigidity comes into contact with the surface of a flange in a state close to a line contact state, it is necessary in order to obtain satisfactory exhaust sealing performance to precisely machine the flange surface which is to be contacted by the sealing member so that said surface has a high degree of accuracy in terms of surface roughness and flatness. Thus, the conventional joint means involves a difficult process for machining the flanges. In addition, at least one of the two flanges needs a groove for positioning the sealing member, and it is particularly difficult to finish this groove with a high degree of accuracy. In view of the above-described circumstances, it is an object of the present invention to reduce the number of portion of the flanges of a joint means which need to be machined with a high degree of accuracy. It is another object of the present invention to provide a joint means which excels in sealing performance relative to the prior art. According to the present invention, one flange is joined to one pipe at such a position that the end portion of the pipe projects from the flange. A closed loop-shaped sealing member which is formed by wrapping a thin metal sheet around a heat resistant material is disposed around the end portion of this pipe. The inner diameter of this sealing member is equal to or slightly larger than the outer diameter of the pipe. The other flange which is joined to the other pipe has a tapered surface along its inner periph­ eral edge, so that, when these two flanges are fastened to each other, the tapered surface presses the sealing member against the first flange and the outer peripheral surface of the first pipe. In regard to the combination of the first pipe and the first flange, the sealing member is in contact with two portions, that is, the flat surface of the flange and the outer peripheral surface of the pipe. It is, therefore, possible to achieve effective sealing without the need to machine these surfaces with a high degree of accuracy. As to the second flange, machining of its inner peripheral edge to form the tapered surface is easier than machining of the flange so as to form a groove. The above and other objects, features and advantages of the present invention will become clear from the follow­ ing description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, in which: Fig. l is a sectional view of a conventional joint means; Fig. 2 is a sectional view of a joint means according to a first embodiment of the present invention; Fig. 3 is an enlarged view of a part indicated by the reference symbol A in Fig. 2; Fig. 4 shows a part of a sealing member employed in the present invention; Fig. 5 is a fragmentary sectional view corresponding to Fig. 3, which shows a joint means according to a second embodiment of the present invention; and Fig. 6 is a fragmentary sectional view corresponding to Fig. 3, which shows a joint means according to a third embodiment of the present invention. Referring first to Fig. l, which is a sectional view of a conventional joint means shown for comparative purposes in order to make clear the feature of the present invention, the joint means is arranged to connect first and second pipes l and 2. A first flange 3 is rigidly secured to the outer peripheral surface of the end portion of the first pipe l, and a second flange 4 is similarly secured to the outer peripheral surface of the end portion of the second pipe 2. A closed loop-shaped groove 5 is formed in the surface of the first flange 3 which faces the second flange 4, and a sealing member 6 is fitted into the groove 5 in such a manner that a part of the sealing member 6 projects from the groove 5. In this state, after the first and second flanges 3 and 4 have been properly aligned with each other, bolts (not shown) are received through circular bores 7 and 8 which are respectively provided in the first and second flanges 3 and 4. Nuts (not shown) are then screwed onto the bolts and tightened to join together the first and second flanges 3 and 4, thus connecting together the first and second pipes l and 2 in a hermetically sealed state. With this arrangement, the sealing member 6 is in contact with the surface of the flange 4 at one portion thereof. In the groove 5 the sealing member 6 is in contact with the side walls thereof in addition to the bottom wall. However, the function of the side walls of the groove 5 is to position the sealing member 6, and the effective contact of the sealing member 6 with the groove 5 is made at one portion of the member 6 which is in contact with the bottom surface of the groove 5. When the sealing member 6 is made from a material having a relatively high rigidity, it is necessary in order to prevent sealing failure to machine the surface of the flange which is in contact with the sealing member 6 so that the machined surface has considerably good surface roughness and flatness. It is difficult to effect machining with such a high precision (particularly difficult at the bottom surface of the groove 5), and this leads to an increase in the production cost of the joint means. Figs. 2 and 3 show in combination a joint means according to a first embodiment of the present invention. In this embodiment, as shown in Fig. 2, first and second flanges l3 and l4 are rigidly secured to the respective outer peripheral surfaces of the end portions of first and second pipes ll and l2 in a manner similar to that employed in the above-described conventional joint means. The first and second flanges l3 and l4 are disposed so that circular bores l7 and l8 which are respectively provided therein are aligned with each other and, in this state, they are connected together by means of nuts and bolts (not shown). Thus, the first and second pipes ll and l2 are connected together and maintained in a hermetically sealed state by means of a sealing member l6 which is clamped between the first and second flanges l3 and l4. In the joint means having flanges according to the present invention, the end portion l2a of the second pipe l2 projects slightly from the second flange l4 secured to the outer peripheral surface of the pipe l2. A loop-shaped sealing member l6 is fitted on this end portion l2a. The sealing member l6 is formed with a closed loop shape by wrapping a thin metal sheet 2l such as a stainless steel sheet around a heat resistant material 20, as partially shown in Fig. 4. In the illustrated embodiment, the heat resistant material 20 is expanded graphite. This material is not only heat-resistant but also elastically deformable and therefore suitable for being used as a constituent element of a sealing member. A sealing member formed by wrapping expanded graphite is per se known and does not constitute any part of the feature of the present invention. The sealing member l6 has an inner diameter which is equal to or slightly greater (e.g., about 0.5 mm at maximum) than the outer diameter of the second pipe l2 so that the sealing member l6 is readily fitted on the end portion l2a of the second pipe l2 and, at the same time, no excessively large gap is produced between the outer peripheral surface of the end portion l2a and the inner peripheral surface of the sealing member l6. One end edge portion of the thin metal sheet 2l which wrapped around the heat resistant material 20 is arranged to overlap the other to define an overlapping portion 22 (see Fig. 3), and when the sealing member l6 is fitted on the end portion l2a of the second pipe l2, the overlapping portion 22 is so disposed as to face the second flange l4, as shown in Fig. 3. The first flange l3 which is rigidly secured to the end portion of the first pipe ll has a portion which projects from the end edge of a pipe ll. A conically tapered surface l9 which is aligned with the sealing member l6 is formed along the inner peripheral edge of the first flange l3 on the side thereof which faces the second flange l4. The angle ϑ of inclination of the tapered surface l9 is set so as to fall within a range of from 30° to 60°, prefer­ ably from 45° to 60°. Bolts (not shown) are received through the circular bores l7 and l8 which are respectively provided in the first and second flanges l3 and l4 that are rigidly secured to the end portions of the first and second pipes ll and l2, and nuts (not shown) are screwed onto these bolts and tightened. In consequence, the sealing member l6 which is fitted on the end portion l2a of the second pipe l2 is pushed rightward as viewed in Figs. 2 and 3 by the tapered surface l9 of the first flange l3 and is thereby pressed against the second flange l4 and, at the same time, the outer diameter of the sealing member l6 is elastically reduced, thus enabling the inner peripheral surface of the sealing member l6 to be brought into intimate contact with the outer peripheral surface of the end portion l2a of the second pipe l2. As this time, the overlapping portion 22 of the thin metal sheet 2l constituting part of the sealing member l6 is pressed against the second flange l4 substantially normally and no force is applied to the overlapping portion 22 from any other direction. There is therefore no risk of the overlapping portion 22 opening to let the heat resistant material 20 come out. Accordingly, employment of expanded graphite as a heat resistant material involves no risk of the material escaping and being burnt. Fig. 5 is a fragmentary view corresponding to Fig. 3, which shows a part of a second embodiment of the present invention. This embodiment differs from the first embodi­ ment only in the arrangement of the sealing member 26. In the second embodiment, the sealing member 26 is fitted on the end portion l2a of the second pipe l2 in the state wherein the overlapping portion 32 defined by the overlap­ ping end edge portions of the thin metal sheet 2l wrapped around the heat resistant material 30 faces the tapered surface l9 of the first flange l3. In this case, the end edge portions of the thin metal sheet 2l overlap in such a manner that the seam 32a which appears on the outside of the overlapping portion 32 faces the flange l4. In the second embodiment, when the flanges l3 and l4 are fastened to each other by means of nuts and bolts which are received through the circular bores l7 and l8, the end edge portions of the thin metal sheet 2l of the sealing member 26 are strongly pressed against each other as well as being deformed in such a manner that the overlapping area is enlarged (i.e., the substantially circular cross section of the sealing member 26 is contracted). Accordingly, there is less possibility of the overlapping portion 32 opening to let the heat resistant material 30 come out. Fig. 6 is a fragmentary view corresponding to Fig. 3, which shows a part of a third embodiment of the present invention. In this embodiment, the end portion 42a of the second pipe 42 projects from the second flange 44 by an amount which is shorter than that in the first and second embodiments. However, the amount by which the end portion 42a projects is greater than half the height of the sealing member 46. The sealing member 46 has the same arrangement as those in the other embodiments and is schematically illustrated in Fig. 6 by a simple circular cross section. The first flange 43 which is rigidly secured to the first pipe 4l differs from the flanges l3 in the other embodiments in that a surface 50 which is parallel with the surface of the flange 44 is provided at the inner side of the tapered surface 49. The height h of the tapered surface 49 is set to be smaller than the outer diameter R of the sealing member 46 but larger than half the diameter R (i.e., R > h > R/2). The width w of a sealing member receiving opening which is defined by the lower edge of the tapered surface 49 is set to be slightly larger than the width of the sealing member 46 in its free state so that the sealing member 46 is readily received in the opening. Bolts (not shown) are received through circular bores which are respectively provided in the first and second flanges 43 and 44 in the same way as in the other embodi­ ments, and nuts (not shown) are screwed onto the bolt and tightened. In consequence, the sealing member 46 which is fitted on the end portion 42a of the second pipe 42 is elastically compressed within the space surrounded by the tapered surface 49 and parallel surface 50 of the first flange 43, the end portion 42a of the second pipe 42 and the second flange 44 and the width of the sealing member 46 is thereby enlarged, so that the outer surface of the sealing member 46 is brought into intimate contact with the tapered surface 49 and parallel surface 50 of the first flange 43, the outer peripheral surface of the end portion 42a of the second pipe 42 and the second flange 44. Accordingly, when exhaust gas flowing through the first and second pipes 4l and 42 leaks to the outside, the gas must pass through two sealed areas to reach the atmos­ phere no matter which side of the sealing member 46 the gas passes. The sealing member 46 may have a circular cross-­ sectional configuration; if it has an oval cross section which the elongation being in the direction in which the sealing member 46 is compressed (i.e., the vertical direc­ tion as viewed in Fig. 4), there is an increase in the degree to which the width of the sealing member 46 enlarges when compressed, so that it is possible to increase the contact pressure between the outer peripheral surface of the sealing member 46 and the tapered surface 49 and that between the inner peripheral surface of the sealing member 46 and the outer peripheral surface of the end portion 42a of the second pipe 42. Thus, it is possible to improve the sealing performance of the joint means. In the case of the embodiment shown in Fig. 6, the angle of inclination of the tapered surface 49 with respect to the central axis of the two pipes 4l and 42 is set at 45° or less (preferably from l0° to 30°).

Claims: 1. A joint means having a first flange (l3, 43) rigidly secured to the outer peripheral surface of an end portion of a first pipe (ll, 4l) and a second flange (l4, 44) rigidly secured to the outer peripheral surface of an end portion (l2a, 42a) of a second pipe (l2, 42), said first and second flanges (l3, l4; 43, 44) being aligned with each other and joined together by means of a nut and a bolt so that said first and second pipes (ll, l2; 4l, 42) are connected together and maintained in a hermetically sealed state by means of a sealing member (l6, 26, 46) clamped between said first and second flanges (l3, l4; 43, 44), characterized in that said second flange (l4, 44) is secured to the second pipe (l2, 42) so that the end portion (l2a, 42a) of the second pipe (l2, 42) slightly projects from the second flange (l4, 44); said sealing member (l6, 26, 46) is comprised of a closed loop-shaped sealing member fitted on the end portion (l2a, 42a) of said second pipe (l2, 42), the sealing member (l6, 26, 46) being formed by wrapping a thin metal sheet (2l) around a heat resistant material (20, 30) and having an inner diameter which is equal to or slightly larger than the outer diameter of said second pipe (l2, 42); and said first flange (l3, 43) is secured to the first pipe (ll, 4l) so that a part of the first flange (l3, 43) projects from the end edge of the first pipe (ll, 4l), a conically tapered surface (l9, 49) aligned with said sealing member (l6, 26, 46) being formed along the inner peripheral edge of said first flange (l3, 43). 2. A joint means according to claim l, wherein said first flange (l3, 43) has a surface parallel with said second flange (l4, 44) at the inner side of said tapered surface (l9, 49). 3. A joint means according to claim l or 2, wherein an overlapping portion (22, 32) defined by overlapping end edge portions of the thin metal sheet (2l) of said sealing member (l6, 26, 46) is positioned so as to face said second flange (l4, 44). 4. A joint means according to claim l or 2, wherein an overlapping portion (22, 32) defined by overlapping end edge portions of the thin metal sheet (2l) is positioned so as to face the tapered surface (l9, 49) of said first flange (l3, 43), and the seam (32a) of said overlapping portion which is present on the outer peripheral surface of said sealing member (l6, 26, 46) faces said second flange (l4, 44).

Inventors: BUSEKI, HIROO, FUJISAWA, KATSUHIDE, TAKAHASHI, MASAKATSU, TAKANAKA, TOSHIMASA MITSUBISHIDENSENKOGYO K.K.
Applicants: NIPPON REINZ CO.,LTD.
Application year: 1987
Main classification: F16L23
IPC codes: F16J15, F16L23, F01N13