Patent Publication Number: US-2003230858-A1

Title: Sealing bead

Description:
BACKGROUNG OF THE INVENTION  
       [0001] The present invention relates to sealing beads formed on metal sheets such as metal gaskets used for the cylinder head of internal combustion engines.  
       [0002] As known, while the opposing flange surfaces of machine parts are sealed by means of applying metal sheets like gaskets, their sealing ability essentially depends on sealing beads formed thereon. Sealing beads vary in shape depending upon the place on which to be disposed, the number of which to be required, and the condition of the flange surfaces under which to be applied.  
       [0003] However, shape of the sealing beads is generally divided into two forms. For convenience of explanation, the conventional sealing beads will be described by referring to FIGS. 1A and 1B and FIGS. 2A and 2B. FIG. 1A is a schematic cross section view of a conventional half sealing bead, illustrating the sealing bead not compressed. FIG. 1B is a schematic cross section view of a conventional half sealing bead, illustrating the compressed sealing bead. FIG. 2A is a schematic cross section view of a conventional full sealing bead, illustrating the sealing bead not compressed. FIG. 2B is a schematic cross section view of a conventional full sealing bead, illustrating the compressed sealing bead.  
       [0004] One is, as shown in FIG. 1A, the half sealing beads having one upward-bent position A and one downward-bent position B. The other is, as shown in FIGS.  2 A, full sealing beads having two upward-bent positions A 1 , A 2  and two downward-bent positions B 1 , B 2 . Referring to FIGS. 1B and 2B, while a sealing bead is mounted between opposing flange surfaces C 1 , C 2 , a linearly acting surface pressure is generated at the respective upward-bent positions A, A 1 , A 2  and the respective downward-bent positions B, B 1 , B 2 , thereby sealing an opening D against fluid which passes through the opening D.  
       [0005] As the half sealing beads have a relatively low spring constant due to its shape, a large height-displacement amount is required to generate effective linearly acting surface pressure required for enough sealing. Thereby, it is difficult for the half sealing beads to generate linearly acting surface pressure efficiently with respect to the height-displacement amount of the sealing bead. On the other hand, as the full sealing beads have a relatively high spring constant, the effective linearly acting surface pressure required for enough sealing are obtained with relatively small height-displacement amount. However, as rigidity of the flange surfaces, fastening forces of the bolts, and the like is required to increase, efficiency for generating linearly acting surface pressure with respect to the height-displacement amount of the sealing bead is not always enhanced.  
       SUMMARY OF THE INVENTION  
       [0006] An object of the present invention is to provide a sealing bead that generates linearly acting surface pressure at its positions whose corresponding positions of the conventional beads does not directly contribute to generating the linearly acting surface pressure, thereby enhancing efficiency for the generating with respect to the height-displacement amount the sealing bead.  
       [0007] First feature of the present invention is a sealing bead surrounding an opening formed on a metal sheet comprises a peripheral portion located between the opening edge of said opening and a bent position surrounding said opening edge. And the peripheral portion is bent up or down at a pre-determined degree of angle with respect to a corresponding flange surface.  
       [0008] Second feature of the present invention is a sealing bead according to the first feature, wherein the degree of the angle is determined so that a pre-determined amount of linearly acting surface pressure is generated at the opening edge while the sealing bead is mounted between opposing flange surfaces.  
       [0009] In the conventional sealing bead, the peripheral portion between the opening edge of the opening and the bent position surrounding the opening edge works only to support the bent position where linearly acting surface pressure is generated. In the present invention, however, as the peripheral portion is bent up or down at a pre-determined degree of angle with respect to a corresponding flange surface, the opening edge is press-contact with an opposing flange surface, to generate linearly acting surface pressure. Therefore, the sealing bead according to the present invention not only generates linearly acting surface pressure at the upward- or downward-bent position as in the conventional one, but also generates them at the opening edge, which does not directly contribute to generating linearly acting surface pressure in the conventional one. Thereby, its sealing effect improves.  
       [0010] The degree of the angle between the bent-up or bent-down peripheral portion of the sealing bead and the corresponding flange surface is preferably determined so that a pre-determined amount of linearly acting surface pressure is generated at the opening edge when the sealing bead is mounted between the opposing flange surfaces. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011] The foregoing and other features of the present invention will become apparent to one skilled in the art to which the present invention relates upon consideration of the invention with reference to the accompanying drawings, wherein:  
     [0012]FIG. 1A is a schematic cross section view of a conventional half sealing bead, illustrating the sealing bead not compressed;  
     [0013]FIG. 1B is a schematic cross section view of a conventional half sealing bead, illustrating the compressed sealing bead;  
     [0014]FIG. 2A is a schematic cross section view of a conventional full sealing bead, illustrating the sealing bead not compressed;  
     [0015]FIG. 2B is a schematic cross section view of a conventional full sealing bead, illustrating the compressed sealing bead;  
     [0016]FIG. 3A is a schematic cross section view of an embodiment of the present invention in the form of a full sealing bead, illustrating the full sealing bead not compressed;  
     [0017]FIG. 3B is a schematic cross section view of an embodiment of the present invention in the form of a full sealing bead, illustrating the compressed full sealing bead;  
     [0018]FIG. 4A is a schematic cross section view of the same embodiment as FIG. 3A in the form of a half sealing bead, illustrating the half sealing bead not compressed;  
     [0019]FIG. 4B is a schematic cross section view of the same embodiment as FIG. 3B in the form of the compressed half sealing bead, illustrating the compressed half sealing bead;  
     [0020]FIG. 5A is a schematic cross section view of another embodiment of the present invention in the form of a full sealing bead, illustrating the full sealing bead not compressed;  
     [0021]FIG. 5B is a schematic cross section view of another embodiment of the present invention in the form of the full sealing bead, illustrating the compressed full sealing bead;  
     [0022]FIG. 6A is a schematic cross section view of the same embodiment in FIG. 5A in the form of a half sealing bead, illustrating the half sealing bead not compressed;  
     [0023]FIG. 6B is a schematic cross section view of the same embodiment in FIG. 5B in the form of the half sealing bead, illustrating the compressed half sealing bead;  
     [0024]FIG. 7 is an explanatory view of test pieces used for test of restoration characteristics against compression of the sealing bead;  
     [0025]FIG. 8 shows test results of restoration characteristics against compression of the sealing bead of the embodiment of the invention; and  
     [0026]FIG. 9 shows test results of restoration characteristics against compression of the sealing bead of the embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0027] Referring to FIGS. 3A and 3B, at least one sealing bead  2  is formed on a metal sheet to surround an opening  1  formed therein, through which fluid flow. As in the conventional sealing bead, the sealing bead  2  has two upward-bent positions  3   a ,  3   b  and two downward-bent positions  4   a ,  4   b . However, the sealing bead  2  differs in having a peripheral portion  5   a  bent up at the upward-bent position  3   b  at a pre-determined angle α with respect to a flange surface  6 B.  
     [0028] Still referring to FIGS. 3A and 3B, the degree of the angle α is determined so as to generate a pre-determined amount of linearly acting-surface pressure at the opening edge  1   a  while the sealing bead  2  is mounted between the opposing flange surfaces  6   a ,  6   b . The degree of the angle α also varies depending upon factors such as material and thickness of the metal gasket, size and shape of the flange surface to which the sealing bead is applied, and size and shape of the sealing bead. While not limiting the scope of the present invention, the degree of the angle α is generally equal to or larger than that of the angle β, which is formed at the upward-bent position  3   a  between a slanting surface  7  of the sealing bead  2  and the flange surface  6   b.    
     [0029] Further referring to FIGS. 3A and 3B, the sealing bead  2  is mounted between the opposing flange surfaces  6   a ,  6   b  and fastened by a fastening bolt (not shown). Thereby, while generating linearly acting surface pressures at the upward-bent positions  3   a ,  3   b  and the downward-bent positions  4   a ,  4   b  as in the conventional sealing bead, the sealing bead  2  simultaneously generates linearly acting surface pressure at the opening edge  1   a  due to the peripheral portion  5   a  bent up at the angle α with respect to the flange surface  6   b.    
     [0030] Referring to FIGS. 4A and 4B, showing the present invention in the form of a half sealing bead, a sealing bead  2  has a peripheral portion  5   b  bent up at an upward-bent position  4   c , to generate linearly acting surface pressure at an opening edge  1   b  of the opening as well as at the upward-bent position  3   c  and the downward-bent position  4   c.    
     [0031]FIGS. 5A to  5 B show another embodiment of the present invention applied to a flange surface, which is relatively narrow in area such as a cylinder head/block where plurality of bores are closely disposed with each other.  
     [0032] Referring to FIGS. 5A and 5B, which show still another embodiment in the form of a full sealing bead, a sealing bead  2  has peripheral portions  5   c,    5   d,  equivalent to the peripheral portion  5   a  in FIG. 3. As the peripheral portions  5   c,    5   d  are bent up at upward-bent positions  3   a ,  3   b  respectively, the sealing bead  2  generates linear loads not only at downward-bent positions  4   a ,  4   b  but also at inner edges  1   c,    1   d  of respective openings  1 ,  1 .  
     [0033] Referring to FIGS. 6A and 6B, which show another embodiment in the form of a half sealing bead, the sealing bead  2  has peripheral portions  5   e,    5   f  equivalent to the peripheral portion  5   b  in FIGS. 4A and 4B. As the peripheral portion  5   e  is bent up at a upward-bent position  3   c , and as the peripheral portion  5   f  is bent down at a downward-bent position  4   c , a sealing bead  2  generates linearly acting surface pressure at opening edges  1   e,    1   f  of respective openings  1 ,  1  as well as either at the upward-bent position  3   c  or at the downward-bent position  4   c.    
     [0034] A comparative test is conducted to examine the sealing effect of the present invention. As shown in FIG. 7, ring-like test pieces are arranged, which are made of SUS sheet metal with either 0.20 mm or 0.25 mm in thickness and are formed with the outer diameter of 90 mm and the inner diameter of 74 mm. Some of the test pieces are provided with a sealing bead of the present invention either in the form of full sealing bead in FIG. 5 or in the form of half sealing bead in FIG. 6. For comparative purposes, others are provided with a conventional sealing bead either in FIGS. 1A and 1B or FIGS. 2A and 2B.  
     [0035] Each of the test pieces is repeatedly compressed so as to generate a linearly acting surface pressure of 2.94 kN/cm. Thereby, compression/recovery characteristics both at the first compression and at n-th compression are evaluated on each test piece, and the result is shown in FIG. 8.  
     [0036] Generating amount of the linearly acting surface pressure with respect to the compression amount thereof and compression resistance coefficient of the sealing bead are calculated as shown in FIG. 9.  
     [0037] The results clearly indicates that the sealing bead of the present invention is smaller than the conventional bead both in compression resistance and in variation of the linearly acting surface pressure with respect to the variation of the sealing bead compression amount. It means that pre-determined linearly acting surface pressures are maintained, thereby required sealing effect are maintained even if fastening forces of the bolts by which the sealing bead is mounted between the flange surfaces vary or change due to the passing of time.  
     [0038] From the above description of the invention, one skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.  
     [0039] The entire disclosure of Japanese Patent Application No. 2002-170903 filed on Jun. 12, 2002 including the specification, claims, drawings and summary is incorporated herein by reference in its entirety.