FASTENER

Abstract: A fastener (1) comprises a fastener body (1a) made of a synthetic resin. The fastener body (1a) is formed on and fixed to a first member (7) to be fixed with a second member (6), by outsert molding. A cylindrical fastening extension (2, 2′) extends from the fastener body (1), which fastening exten­ sion (2, 2′) is engageable with a through opening (6a) formed through the second member (6). The fastening extension (2, 2′) has an axial recess (3, 3a). A cylindrical knock member (5, 5′, 5a) is formed integrally with the fastener body (1a) and extends opposite the recess (3, 3a) of the fastening extension (2, 2′). The knock member (5, 5′, 5a) is coaxial with the fastening extension (2, 2′) and designed to enter the recess (3, 3a) so as to radially deform the fastening extension (2, 2′) and so depress its periphery against the inner periphery of the through opening (6a) of the second member (6) so as to fix the second member (6) to the first member (7). Preferably, the knock member (5, 5′, 5a) is integrally formed with the fastener body (1a) and connected to the latter through a thin annular strip section (1d). The annular strip section (1d) is designed to be broken when the head of the knock member (5, 5′, 5a) is struck to force the knock member (5, 5′, 5a) into the recess (3, 3a).

Description: The present invention relates to a fastener according to the generic part of claim 1. US-A-3,385,157 describes such a fastener, the cylindrical extension of which has the same diameter throughout its length, thus allowing only members having through openings of the same diameter to be fixed. A further disadvantage is the complicated design of the outer periphery of the extension which is provided with ribs extending in axial direction of the extension and progressively decreasing in width towards the free end of said extension. In the fixed state the two members are held in contact with each other by the supporting means provided on the main body in form of a rather flexible sealing lip and a shoulder formed by those portions of the ribs at the free end of the extension which, protruding from the through opening, are expanded radially outwardly. Hence, the shoulder and the supporting means lack sufficient stiffness and are therefore not suitable for holding the members together with a sufficient rigidity and for obtaining a fastener featuring the required durability. It is an object of the present invention to provide a fastener of a simpler design having improved retaining ability and durability. This object is attained by the characterizing features of new claim 1. Instead of holding the members between the flexible supporting means of the main body and flexible shoulder being formed while driving the knock member into the axial opening, the fastener according to the present invention holds the members between circular ribs which are formed during manufacture of the fastener. The middle rib separates the two members. Using the three circular ribs for holding the members together, the fastener according to the present invention is a straightforward design which does not require the complicated rib structure of the extension of the prior art fastener. According to claim 2 the main body has two ribs defining therebetween one of the two annular grooves, and the extension has one rib defining together with the adjacent one of the two ribs of the main body the other of the two annular grooves. It is also possible that the fastener has two extensions one on each side of the main body, the main body having one rib and the extensions having two ribs defining together with the one rib of the main body the two annular grooves. Furthermore, each extension may have at least one slit allowing radial deformation of the deformable portion. The axial opening may be cylindrical and the knock member may be tapered such that its larger diameter end is placed within the deformable portion of the extension when driven into it. It is also possible that the knock member is cylindrical and the axial opening is tapered towards the radially deformable portion of the extension. Furthermore, the axial opening may be open at the free end of the extension or at the main body portion of the fastener. According to claim 10, the main body is initially fixed to the corresponding one of the two members by means of outsert moulding. The fastener according to the preceeding claims may be utilized together with an assembly of two board-like members. In this case it is advantageous that the rib formed at the extension of the fastener has a greater diameter than the inner diameter of the through opening of one of the members, whereby inserting the extension through the through opening causes radial inward deformation of the deformable portion of the extension. The present invention will be understood more fully from the detailed description given herebelow and from the accompanying drawings of the preferred embodiment of the present invention, which however, should not be taken to limit the invention to the specific embodiment but are for explanation and understanding only. In the drawings: Fig. 1 is a cross-section through the preferred embodiment of a fastener according to the present invention; Fig. 2 is a plan view of the fastener of Fig. 1; Fig. 3 is a cross-section similar to Fig. 1, but showing the state in which two members are fixed to each other; Fig. 4 is a perspective illustration showing application of the preferred embodiment of the fastener to an actual substrate assembly; Fig. 5 is a cross-section through a modified form of the fastener of Fig. 1; Fig. 6. is a cross-section through another modified fastener; and Fig. 7 is a cross-section through yet another modified fastener. Referring now to the drawings, particularly to Fig. 1, the preferred embodiment of a fastener 1 is made of a synthetic resin, such as polyacetal, polypropylene and so forth. In the shown embodiment, the fastener 1 is designed to fix a second substrate 6 of a metal plate to a first substrate 7 of a metal plate. The fastener 1 has a cylindrical fastening extension 2 with a top end with an annular fastening jaw 2a. The fastening jaw 2a has a tapered axial end 2b. The fastening extension 2 also has an axial central recess 3 open at its upper end. The fastener 1 also has an essentially disc-shaped main body 1a defining an annular groove 1b which firmly engages the inner periphery of a through opening 7a in the first substrate 7. The fastening jaw 2a defines another annular groove 1c which engages the inner periphery of a through opening 6a in the second substrate. A plurality of slits 4 through the fastening extension 2 extend radially from the central recess 3. The axial depth of the slits 4 essentially corresponds to the axial length of the fastening jaw 2a in order to provide the fastening jaw 2a with sufficient flexibility for radial deformation. A knock member 5 of generally conico-cylindrical form and integral with the main body 1a extends from the side of the main body 1a opposite from the fastening extension 2. The knock member 5 has one end having a larger diameter than the other end connected to the main body 1a. The diameter of the knock member 5 is, near the larger-diameter end at least, slightly greater than the internal diameter of the central recess 3 at least in the level of the through opening 6a of the second member. As will be apparent from Fig. 1, the knock member 5 is connected to the main body 1a via an annular connecting section 1d. The connecting section 1d is relatively thin and weak so as to be easily broken by an impact applied to the head of the knock member 5. The fastener 1 is initially fixed to the first substrate 7 by outsert molding. In practice, outsert molding of the fastener 1 is performed by injection molding and other appropriate molding processes. The techniques involved in outsert molding have been disclosed in the aforementioned United States Patent No. 4,158,450. In order to assemble the second substrate 6 to the first substrate 7, the fastening extension 2 is first passed through the through opening 6a of the second substrate 6. When passing through the opening 6a, the tapered axial end 2b of the fastening jaw 2a contacts the inner peripheral edge of the opening 6a. This causes radially inward elastic deformation of the fastening extension 2. This allows the fastening extension 2 to pass through the through opening 6a so that the fastening jaw 2a projects out through the second substrate 6. At this state, the inner periphery of the opening 6a engages the groove 1c. At this time, engagement between the outer periphery of the fastening extension 2 and the inner periphery of the through opening 6a is still loose enough to allow relative axial displacement of the first and second substrates 7 and 6. Then, the head of the knock member 5 is struck with an appropriate tool, such as a hammer, with an impact sufficient to break or sheer off the connecting section 1d. This impact forces the knock member 5 into the recess 3, which causes radially symmetric distension of the fastening extension 2. The magnitude of expansion of the diameter of the fastening extension 2 is sufficient to establish firm engagement between the outer periphery of the fastening extension 2 and the groove 1c, as shown in Fig. 3. Fig. 4 shows an example of application of the fastener 1 constructed as set forth above, for assembling a substrate 6 to a base 7. In the shown example, four fasteners 1 are used to firmly fix the second substrate to the first substrate. Although a specific embodiment has been illustrated to facilitate better understanding of the invention, it would be possible to embody the present invention in various ways and similarly the shown embodiment can be modified in various ways. For example, the fastener can be made of a flexible metal, such as aluminium or the like. In cases where an aluminium fastener is used and electrically conductive substrates are to be connected, an appropriate insulating member may be provided to ensure insulation between the substrates. Also, it would be possible to provide a plurality of fastening extensions and corresponding knock members on a common main body. Furthermore, as shown in Fig. 5, the knock member 5' can be inserted from the top of the fastening extension 2'. In this case, the diameter of the knock member at the end opposing the top of the fastening extension 2' can be slightly smaller than the inner diameter of the through opening 3 and the diameter of the end remote from the top of the fastening extension can be slightly but sufficiently greater than the inner diameter of the through opening 3. Also, as shown in Fig. 6, instead of tapering the knock member as set out with respect to the preferred embodiment, a similar effect can be expected by slightly tapering the inner periphery of the recess or opening 3. In the example shown in Fig. 6, the fastener 1 is made of aluminium and the inner diameter of the recess gradually decreases toward the top. Fig. 7 is a modification of the example shown in Fig. 5. In this modification, a pair of fastening extensions 2'' extend outwards from a plate-shaped main body 1a. The inner diameter of an opening or recess 3a gradually decreases toward the distal ends of the respective fastening extensions 2''. A knock member 5a has a length corresponding to or slightly shorter than the overall length of the opening 3a. With the construction of Fig. 7, the fastener 1' can be manufactured wholly independently of the members to be connected. Such fasteners may be useful for connecting a variety of members including substrates for electrical circuits.

Claims: A fastener (1) for fixing at least two members (6, 7) having through openings (6a, 7a) and being placed in opposition to each other, said fastener comprising a main body (1a), at least one cylindrical extension (2, 2') thereof, and a knock member (5, 5', 5a), said extension (2, 2') and said main body (1a) having an axial opening (3, 3a) open at least at one end thereof, said extension (2, 2') being radially deformable at least at a portion near its free end so as to engage with its outer periphery the periphery of the through opening (6a, 7a) of at least one of said two members (6, 7), said main body (1a) having a supporting means engageable with at least one of said two members, and said knock member (5, 5', 5a) being formed integrally with said fastener (1) and opposing said axial opening (3, 3a), said knock member (5, 5', 5a) being connected to the peripheral portion of said open end of said axial opening (3, 3a) through a sheer section (1d) which is sufficiently thin to be sheered off by an impact applied to said knock member (5, 5', 5a) so as to allow entry of said knock member into said axial opening (3, 3a) with resulting outward deformation of said deformable portion of said extension (2, 2'), characterized by said supporting means having the form of three circular ribs formed on said main body (1a) and said extension (2, 2') and defining two annular grooves (1b, 1c) therebetween for holding said two members (6, 7) therein. A fastener as claimed in Claim 1, characterized by said main body (1a) having two ribs defining therebetween one (7a) of said two annular grooves, and said extension (2, 2') having one rib (2a) defining together with the adjacent one of said two ribs of said main body (1a) the other (6a) of said two annular grooves. A fastener as claimed in Claim 1, characterized by two extensions (2a, 2b), one on each side of said main body (1a), said main body having one rib and said extensions (2a, 2b) having two ribs defining together with said one rib of said main body (1a) said two annular grooves. A fastener as claimed in any of Claims 1 to 3, characterized in that said extension (2, 2') has at least one slit (4) allowing radial deformation of said deformable portion. A fastener as claimed in any of Claims 1 to 4, characterized by said axial opening (3) being cylindrical and said knock member (5) being tapered such that its larger diameter end is placed within the deformable portion of said extension (2) when driven into it. A fastener as claimed in any of Claims 1 to 4, characterized by said knock member (5', 5a) being cylindrical and said axial opening (3, 3a) being tapered towards the radially deformable portion of said extension (2, 2a, 2b). A fastener as claimed in any of Claims 1 to 6, characterized by said axial opening (3, 3a) being open at the free end of said extension (2, 2a, 2b). A fastener as claimed in any of Claims 1 to 6, characterized by said axial opening being open at the main body portion of said fastener. A fastener as claimed in any of Claims 1 to 8, characterized in that said fastener (1) is made of a synthetic resin. A fastener as claimed in any of Claims 1 to 9, characterized in that said main body (1a) is initially fixed to the corresponding one (7) of the two members by means of outsert moulding. An assembly of two board-like members (6,7) and the fastener (1) of the preceding claims. The assembly as claimed in claim 11, characterized in that said rib (2a) formed at said extension (2,2',2'') of said fastener (1), has a greater diameter than the inner diameter of said through opening (6a) of one (6) of said members (6,7), whereby inserting said extension (2,2',2'') through said through opening (6a) causes radial inward deformation of said deformable portion of said extension (2,2',2'').

Inventors: YAMADA, HIDETAKA C/O SONY KOHDA CORPORATION
Applicants: SONY CORPORATION
Application year: 1985
Main classification: F16B19
IPC codes: F16B19, F16B5, F16B21