FEMALE FASTENER AND RESIN RING SPRING FOR FEMALE FASTENER

Abstract

A female fastener that holds a resin ring spring accommodated in an accommodation housing of the female fastener, wherein the resin ring spring accommodated in the accommodation housing locks a male fastener inserted therein. The resin ring spring includes a plurality of outwardly projecting convex portions provided at a predetermined interval, in such a manner that, when the resin ring spring is in a natural state accommodated in the accommodation housing, a diametrical gap between an inner circumferential wall of the accommodation housing and an outer circumference of the ring spring increases and decreases alternately. A difference between an outer diameter of the resin ring spring and an inner diameter of the accommodation housing is 0.2 mm or less.

Claims

1. A female fastener that holds a resin ring spring accommodated in an accommodation housing of the female fastener, wherein the resin ring spring accommodated in the accommodation housing locks a male fastener inserted therein, the resin ring spring comprises a plurality of outwardly projecting convex portions provided at a predetermined interval, in such a manner that, when the resin ring spring is in a natural state accommodated in the accommodation housing, a diametrical gap between an inner circumferential wall of the accommodation housing and an outer circumference of the ring spring increases and decreases alternately, and a difference between an outer diameter of the resin ring spring and an inner diameter of the accommodation housing is 0.2 mm or less.

2. The female fastener according to claim 1, wherein a clearance value is defined as one half of a value obtained by subtracting a thickness of a material for the accommodation housing2 and the outer diameter of the resin ring spring from an outer diameter of the accommodation housing, and the clearance value is 0.1 mm or less.

3. The female fastener according to claim 2, wherein the clearance value is 0.05 mm or less.

4. The female fastener according to claim 1, wherein the resin ring spring comprises one or more multibridge portions that protrude(s) in an up-down direction that is vertical to a flat ring surface.

5. The female fastener according to claim 4, wherein the resin ring spring has a continuous star-shaped polygonal shape, as viewed in plan view.

6. A resin ring spring that locks a male fastener inserted therein while the resin ring spring is accommodated in an accommodation housing of a female fastener, the resin ring spring comprising: a plurality of outwardly projecting convex portions provided at a predetermined interval, in such a manner that, when the resin ring spring is in a natural state accommodated in the accommodation housing, a diametrical gap between an inner circumferential wall of the accommodation housing and an outer circumference of the ring spring increases and decreases alternately, and one or more multibridge portions that protrude(s) in an up-down direction that is vertical to a flat ring surface.

7. The resin ring spring according to claim 6, wherein the resin ring spring has a continuous star-shaped polygonal shape, as viewed in plan view.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIGS. 1(a) to 1(e) are illustrations for describing a typical example of a shape of a resin ring spring to be provided in a female fastener, wherein the female fastener is a part of a male/female fastener (which may be hereinafter called snap fastener) for clothes as described in an embodiment in the present disclosure.

[0016] FIGS. 2(a) and 2(b) are conceptual illustrations for describing a mode of use when the resin ring spring according to the embodiment is accommodated in an accommodation housing of the female fastener.

[0017] FIGS. 3(a) to 3(f) are general illustrations for graphically describing a structure and a functional expression mode of the snap fastener.

[0018] FIGS. 4(a) and 4(b) are schematic cross sectional views, with the resin ring spring according to another embodiment in the present disclosure being accommodated in the accommodation housing (which is frequently made of metal, and which may be also called spring plate) of the female fastener.

[0019] FIGS. 5(a) and 5(b) illustrate a typical example of the metal accommodation housing (the metal spring plate) of the female fastener, wherein FIG. 5(a) shows the metal accommodation housing with the resin ring spring accommodated, and FIG. 5(b) shows a back side of the accommodation housing.

[0020] FIG. 6 is a table of test results representing a degree of loss of the elastic deformation function in the fail-safe resin ring spring according to the embodiment, by comparing the results before and after the ring spring is broken.

[0021] FIGS. 7(a) to 7(d) show a specific shape example 1 of the resin ring spring according to the embodiment, wherein the ring shape includes eight concave portions and eight convex portions that are arranged alternately. FIG. 7(b) is a cross sectional view taken along a line A-A in FIG. 7(a), and FIG. 7(d) is a cross sectional view taken along a line B-B in FIG. 7(c).

[0022] FIGS. 8(a) to 8(d) show a specific shape example 2 of the resin ring spring according to the embodiment, wherein the ring shape includes six concave portions and six convex portions that are arranged alternately. FIG. 8(b) is a cross sectional view taken along a line A-A in FIG. 8(a), and FIG. 8(d) is a cross sectional view taken along a line B-B in FIG. 8(c).

[0023] FIGS. 9(a) to 9(d) show a specific shape example 3 of the resin ring spring according to the embodiment, wherein the ring shape includes six convex portions spaced from each other at a predetermined interval. FIG. 9(b) is a cross sectional view taken along a line A-A in FIG. 9(a), and FIG. 9(d) is a cross sectional view taken along a line B-B in FIG. 9(c).

[0024] FIGS. 10(a) to 10(d) show a specific shape example 4 of the resin ring spring according to the embodiment, wherein the ring shape includes four concave portions and four convex portions that are arranged alternately. FIG. 10(b) is a cross sectional view taken along a line A-A in FIG. 10(a), and FIG. 10(d) is a cross sectional view taken along a line B-B in FIG. 10(c).

[0025] FIGS. 11(a) to 11(c) are photographic views of an actual product corresponding to FIGS. 7(a) to 7(d), wherein FIG. 11(a) is a plan view, FIG. 11(b) is a cross sectional view taken along the line A-A, and FIG. 11(c) is a sectional view taken along the line B-B. For cross sectional photography, a right end of the product is clamped by a clip in FIGS. 11(b) and 11(c).

[0026] FIGS. 12(a) to 12(c) are photographic views of an actual product corresponding to FIGS. 8(a) to 8(d), wherein FIG. 12(a) is a plan view, FIG. 12(b) is a cross sectional view taken along the line A-A, and FIG. 12(c) is a sectional view taken along the line B-B. For cross sectional photography, a right end of the product is clamped by a clip in FIGS. 12(b) and 12(c).

[0027] FIGS. 13(a) to 13(c) are photographic views of an actual product corresponding to FIGS. 9(a) to 9(d), wherein FIG. 13(a) is a plan view, FIG. 13(b) is a cross sectional view taken along the line A-A, and FIG. 13(c) is a sectional view taken along the line B-B. For cross sectional photography, a right end of the product is clamped by a clip in FIGS. 13(b) and 13(c).

[0028] FIGS. 14(a) to 14(c) are photographic views of an actual product corresponding to FIGS. 10(a) to 10(d), wherein FIG. 14(a) is a plan view, FIG. 14(b) is a cross sectional view taken along the line A-A, and FIG. 14(c) is a sectional view taken along the line B-B. For cross sectional photography, a right end of the product is clamped by a clip in FIGS. 14(b) and 14(c).

[0029] FIG. 15 is an illustration for describing two types of clearance: a longitudinal clearance value (t2) and a lateral clearance value (t1).

[0030] FIG. 16 is an illustration for describing the resin ring spring as used in measurement shown in Table 2, wherein the resin ring spring is vertically squeezed and fixedly clamped by a flanged portion of the spring plate.

[0031] FIG. 17 illustrates dimensions of the resin ring spring as shown in FIGS. 12(a) to 12(c) and FIGS. 8(a) to 8(d) and as used in measurement compiled in Table 1.

[0032] FIG. 18 illustrates dimensions of the resin ring spring as shown in FIGS. 11(a) to 11(c) and FIGS. 7(a) to 7(d) and as used in measurement compiled in Table 2.

[0033] FIGS. 19(a) and 19(b) show a stud used in the experiment and measurement compiled in Table 1 and Table 2, wherein FIG. 19(a) is a plan view and FIG. 19(b) is a sectional view.

DESCRIPTION OF EMBODIMENTS

First Embodiment

[0034] A resin ring spring described in the present embodiment has, for example, following features:

[0035] 1) A structure in which an intended function is imparted by rupture-resistant bending deformation (a concave polygonal structure). Typically, a structure in which inward corners of a concave polygon can expand is subject to bending stress rather than tensile stress and develops resistance to rupture.

[0036] 2) A structure that does not lose a snap fastener function even in the case of a partial rupture (a multibridge structure). Typically, a plurality of protrusions (multibridge portions) is arranged on a circumference of the resin ring spring. When the ring spring is accommodated and crimped in a main body (an accommodation housing), displacement of the protruding portions is restricted or fixed. This resin ring spring, even if partially ruptured, keeps its snap fastener function (prevents disengagement of the snap fastener).

[0037] 3) Adoption of a production method that ensures excellent quality stability and productivity (an ultrasmall injection molding machine). For example, the number of cavity in a single shot is reduced to overwhelmingly facilitate conditional probability.

[0038] 4) Adoption of a production method that minimizes generation of waste resin (a runnerless method). For example, use of a runnerless mold (a hot runner method) reduces waste resin and eliminates a loss in a channel part that cannot be made into a product.

[0039] FIGS. 1(a) to 1(e) are illustrations for describing a typical example of a shape of a resin ring spring 1300 to be provided in a female fastener, wherein the female fastener is a part of a male/female fastener for clothes as described in the present embodiment. FIG. 1(a) is a plan view of the resin ring spring 1300 having a concave polygon shape. While a male fastener is fitted in, the resin ring spring 1300 is configured to increase its diameter under bending stress rather than under tensile stress, for example, as shown in a plan view of FIG. 1(b). The resin ring spring having such a shape is significantly different from conventional, widely known, annular metal ring springs, both in shape and in functional expression mode.

[0040] Specifically, regarding the shape example shown in FIGS. 1(a) and 1(b), an inner diameter of the resin ring spring 1300 increases by outwardly expanding displacement of concave portions 1300(b) that are displaced more greatly than convex portions 1300(a) that project in plan view (a change from the state of FIG. 1(a) to the state of FIG. 1(b)). After an extreme end of the stud passes the resin ring spring 1300, the inner diameter of the resin ring spring 1300 decreases at a constricted portion of the stud by inwardly shrinking displacement of the concave portions 1300(b) that are displaced more greatly than the convex portions 1300(a) that project in plan view (a change from the state of FIG. 1(b) to the state of FIG. 1(a)).

[0041] As shown in FIGS. 1(c) to 1(e), the resin ring spring 1300 has eight convex portions 1300(a), and every other one of them (a total of four convex portions 1300(a)) is provided with multibridge portions 1400(1) to 1400(4) that protrude vertically to surfaces of the resin ring spring 1300 by a predetermined height. The position and number of the multibridge portions 1400 are not limited to the example shown in FIGS. 1(c) to 1(e), and any number of multibridge portions 1400 may be provided at any position around the convex portions 1300(a). FIG. 1(c) describes a natural state, and FIG. 1(d) describes a state with an expanded inner diameter.

[0042] Note that FIGS. 1(a) to 1(d) are plan views of the resin ring spring 1300, whereas FIG. 1(e) is a side view of the resin ring spring 1300. For example, when the resin ring spring 1300 in FIG. 1(e) has a thickness h1 of about 0.7 mm to 1.0 mm, the multibridge portions 1400 may have a thickness h2 of 1.3 mm to 1.6 mm. Depending on the shape and size of the accommodation housing of the female fastener for accommodating the resin ring spring 1300, the thickness h2 of the multibridge portions 1400 may be 1.3 mm or less. Additionally, when the resin ring spring has a thickness of 0.7 mm or greater, the thickness h2 may be 1.0 mm or less. The accommodation housing may be also called spring plate.

[0043] In the course of test production and improvement of the resin ring spring, the present inventors detected following issues.

[0044] 1) Increase in the number of cavity in a single shot results in a runner weight of 90% or greater.

[0045] 2) Multicavity molding of about 24 to 32 pieces is still far below a recommended shot weight for the injection molding machine. In this case, the resin material remains in a heating cylinder for a longer time. Eventual thermal degradation causes molecular cleavage and deteriorates the product quality.

[0046] 3) Increase in the number of cavity in a single shot results in greater variation in timing when molten resin for circular products is merging (welding). As a result, products with a small weld strength and products with voids are more likely to occur.

[0047] Presumably, such issues are partly because the resin ring spring is as light as about 0.05 g or less per piece, and is much lighter than the metal ring spring. Being faced with these issues, the present inventors reached a possible solution by molding small products with use of an ultrasmall molding machine.

[0048] The present inventors further conceived an innovative shape as exemplified in the present embodiment. The structure and material as disclosed herein can realize a fail-safe ring spring that is resistant to rupture and that can minimize a loss of its spring function even if ruptured.

[0049] FIGS. 2(a) and 2(b) are conceptual illustrations for describing a mode of use when the resin ring spring 1300 according to the present embodiment is accommodated in the accommodation housing of the female fastener. The resin ring spring 1300 according to the present embodiment has a fail-safe shape and does not lose its function even if its annular circumference ruptures partially. In order to avoid a functional loss in the case of rupture and to ensure production workability, the resin ring spring according to the present disclosure is accommodated in the same manner as the metal ring spring, by being inserted in the spring plate and crimped so as not to come out. If the resin ring spring had the same shape and other properties as the conventional all-metal snap fastener and were accommodated in the housing of the female fastener, the resin ring spring would not be fixed at all.

[0050] According to the present disclosure, the resin ring spring is equipped with a plurality of protrusions (multibridge portions) provided along its circumference and extending vertically to ring surfaces. The multibridge portions are semi-fixed or fixed in an up-down direction on the plane of FIG. 2(b) through the crimping process, and thereby restrict movement of the resin ring spring. Eventually, even if a part of the resin ring spring ruptures, the resin ring spring that is semi-fixed or fixed by the protrusions (the multibridge portions) retains the snap fastener function.

[0051] More preferably, while the resin ring spring is accommodated in the accommodation housing of the female fastener, the projecting portions on the outermost circumference of the resin ring spring (corresponding to the eight convex portions 1300(a) in FIGS. 1(a) to 1(d) and FIG. 2(a)) abut on an inner circumferential wall of the accommodation housing, and thereby restrict any further outward movement of the resin ring spring. This configuration ensures a stabler fail-safe function and minimizes a loss of the spring function due to rupture.

[0052] A preferable material for molding of the resin ring spring is polyacetal (POM). POM is a crystalline engineering plastic that shows excellent thermal resistance and that also shows excellent abrasion resistance, fatigue failure resistance, and chemical resistance. Where necessary, the material may be a polyamide resin or a PPS resin.

[0053] Injection molding of the resin ring spring having the above-mentioned fail-safe function requires more precise control than in the case of a simple ring spring. For this reason, the resin ring spring is produced not by large-scale simultaneous molding with use of a middle- or small-size molding machine but by small-scale molding with use of an ultrasmall molding machine. Use of the ultrasmall molding machine provides following advantages: [0054] 1) can suppress thermal degradation in the molding machine; [0055] 2) can reduce the runner to zero or a minimum and can cut a runner cooling time; and [0056] 3) with a fewer number of cavity in a single shot, significantly facilitates mold adjustment for synchronizing the timing of filling.

[0057] Multicavity molding is a method for producing a large number of products in a single shot, and requires as many cavities as the number of products. It is desirable to fill the material into all cavities at the same timing, the same temperature and the same pressure. Multicavity molding further requires a runner, as a channel for feeding the material to a plurality of cavities.

[0058] For production of the resin ring spring according to the present disclosure (a fail-safe ring spring or the like having a concave polygonal structure and a multibridge structure), a hot-runner type (runnerless) prototype mold may be manufactured with introduction of an ultrasmall injection molding machine (mold clamping force: 3 tons), so as to set shaping conditions and to perform technical verification and mass-productivity evaluation such as quality stability and productivity.

[0059] In FIG. 2(a), an upper illustration is a plan view of the resin ring spring 1300, and a lower illustration is a side view thereof. FIG. 2(b) shows an exemplary mode of use, with the resin ring spring 1300 being accommodated in the female fastener 1200. In FIG. 2(b), the convex portions 1300(a) of the resin ring spring 1300 abut on an inner circumferential wall 1200(c) of the accommodation housing of the female fastener 1200 or are slightly spaced therefrom (with a gap of 0.1 mm or less).

[0060] Specifically, the convex portions 1300(a) are configured such that, when the inner diameter of the resin ring spring 1300 (in use, the spring is accommodated in the accommodation housing of the female fastener 1200) is stretched by insertion of a male fastener (a stud) 1100, outward displacement of the convex portions 1300(a) is restricted by their abutment on the inner circumferential wall 1200(c) of the accommodation housing at least during the inner diameter expansion process. This preferable configuration can minimize a functional loss due to partial rupture or other trouble in the resin ring spring 1300.

[0061] In other words, typically, at least when the inner diameter of the resin ring spring 1300 is expanding or has been maximally expanded by the insertion of the stud 1100, all of the convex portions 1300(a) abut on the inner circumferential wall 1200(c) of the accommodation housing of the female fastener 1200, and have their further outward displacement restricted. Additionally, in a natural state where the stud is not inserted, all of the convex portions 1300(a) may abut on the inner circumferential wall 1200(c) of the accommodation housing of the female fastener 1200, and may have their further outward displacement restricted.

[0062] This configuration reduces a loss of the spring function due to rupture. In the accommodation housing of the female fastener 1200, the resin ring spring 1300 may be arranged to be constantly rotatable or constantly slidably rotatable relative to the accommodation housing of the female fastener 1200. Having said that, the slidable rotation may be limited when the convex portions 1300(a) are squeezed most strongly or more strongly against the inner circumferential wall of the accommodation housing, by a squeezing frictional force or the like.

[0063] Referring to FIG. 2(b), upward displacement of the multibridge portions 1400 of the resin ring spring 1300 is restricted by a flanged portion 1200(a), 1200(b) of the female fastener 1200. Specifically, when the resin ring spring 1300 is arranged in the accommodation housing of the female fastener, its in-plane displacement vertical to the plane of FIG. 2(b) is restricted by the inner circumferential wall 1200(c) of the accommodation housing, and its up-down displacement on the plane of FIG. 2(b) is restricted by the flanged portion 1200(a), 1200(b).

[0064] When the resin ring spring 1300 is crimped by the flanged portion 1200(a), 1200(b), the multibridge portions 1400 may be fixed by the accommodation housing such that the multibridge portions 1400 are sandwiched and clamped by the flanged portion 1200(a), 1200(b) in an up-and-down direction of FIG. 2(b). This configuration can also restrict displacement of the multibridge portions 1400, can prevent outwardly expanding displacement of the multibridge portions 1400 (namely, a given number of convex portions 1300(a)) during the insertion (press fitting) and removal of the stud 1100, and can eventually reduce a loss of the spring function due to rupture.

[0065] To give a preferable example, the resin ring spring 1300 has a star-shaped polygonal (polygram) shape that is continuous without a break. When the resin ring spring 1300 is accommodated in the accommodation housing of the female fastener 1200, the above-described configuration can reduce a mobile region in the natural state where the male fastener 1100 is not inserted, namely, can reduce backlash in an area surrounded by the flanged portion 1200(a), 1200(b). Hence, the above-described configuration can also reduce a clattering contact sound or other noise due to vibrations, etc.

[0066] Regarding the resin ring spring and the female fastener according to the present disclosure, their material, shape, structure/method, etc. are not limited to those described above and shown in the drawings. Such material, shape, structure/method, etc. may be adopted, varied, arranged, combined or optionally modified, within a range of the scope of the present disclosure by any suitable method or the like publicly or widely known to those skilled in the art. More specifically, those skilled in the art can easily understand that, for example, First Embodiment according to the present disclosure and Second Embodiment to be described below may be applied together to implement and embody a snap fastener and a resin ring spring that include features of both embodiments, and that such implementation does not particularly cause any trouble.

Second Embodiment

[0067] FIGS. 4(a) and 4(b) are schematic lateral cross sectional views, with the resin ring spring according to the present embodiment (indicated as (2) in the drawing) being accommodated in the accommodation housing (which is frequently made of metal, and which may be also called spring plate) (indicated as (1) in the drawing) of the female fastener. A star mark in FIG. 4(a) indicates a gap between the inner circumferential wall of the accommodation housing and an outer circumferential end of the resin ring spring. The present embodiment provides a fail-safe effect by setting the star-marked gap to 0.05 mm or less. The term fail-safe as used herein means that the resin ring spring continues to function as the spring in the female fastener, even if the ring spring is broken due to abrasion or for some reason. For example, when the size of the female fastener is determined in advance, the resin ring spring to be accommodated therein is configured to have the shape and size as defined in the present disclosure and to keep a gap of 0.05 mm or less between the outer circumferential end of the resin ring spring and the inner circumferential wall of the accommodation housing. For example, when the size of the resin ring spring is determined in advance, the female fastener is configured to keep a gap of 0.05 mm or less between the accommodation housing for accommodating the resin ring spring and the outer circumferential end of the resin ring spring.

[0068] From a different point of view, a preferable relationship between the outer diameter (the diameter) of the resin ring spring and the inner diameter (the diameter) of the accommodation housing of the female fastener is such that the inner diameter of the accommodation housing of the female fastener is greater than the outer diameter of the resin ring spring by 0.1 mm or less.

[0069] The resin ring spring used herein has at least two or more alternating concave portions and convex portions in a radial direction, and hence does not have a shape of a perfectly exact circle. The resin ring spring is circumferentially continuous, but a distance from the circumference to the center of the ring spring may increase and decrease alternately, as described later. In other words, the resin ring spring as used herein can have such a shape and structure that the resin ring spring hardly loses its spring characteristics (elastic deformation characteristics) even if broken at any one point.

[0070] As shown in FIG. 4(b), the press fitting process of the male fastener (which may be also called stud, not shown) into the female fastener causes the inner diameter of the resin ring spring to stretch and expand outwardly (a thick left arrow on the plane of FIG. 4(b)). In this state, it is more preferable that at least the outer circumferential end of the maximally expanded resin ring spring abuts on the inner circumferential wall of the accommodation housing. The abutment area is not necessarily the entire outer circumference of the resin ring spring, but may be the outwardly projecting portions only (typically, extreme ends of the convex portions 1300(a) shown in FIGS. 1(a) to 1(d)). The configuration in which the diameter-expanded resin ring spring abuts on the inner circumferential wall of the spring plate serves to restrict positional variation and displacement (for example, expansion of the ring spring diameter) in at least a part of the resin ring spring positioned in the flanged portion of the spring plate. Even if the ring spring is broken or fails otherwise, a snap fastener having this configuration can continue to serve without losing its snap fastener function.

[0071] FIGS. 5(a) and 5(b) illustrate a typical example of the metal accommodation housing (the metal spring plate) of the female fastener, wherein FIG. 5(a) shows the metal accommodation housing with the resin ring spring accommodated, and FIG. 5(b) shows a back side of the accommodation housing. The view in FIG. 5(a) is taken while the female fastener provided with the ring spring is halfway through its production, undergoing an assembly processing. From the state shown in FIG. 5(a), the female fastener is further required to go through an additional assembly processing step of forming the flanged portion, wherein an edge of the circumferential wall of the female fastener is folded inwardly so as to enclose the resin ring spring in a square U-shaped manner. Note that an arrow in FIG. 5(a) indicates the inner diameter of the spring plate, and an arrow in FIG. 5(b) indicates the outer diameter of the spring plate.

[0072] A certain component balance is required between the resin ring spring and the spring plate in the present embodiment. In the pre-assembly processing state of FIG. 5(a), if a dimensional difference between the inner diameter of the spring plate and the outer diameter of the resin ring spring is greater than 0.1 mm, there will be an excessive backlash gap/space that allows the resin ring spring to move in the spring plate (for example, swinging movement in the arrow direction in FIG. 5(a)). In this state, breakage of the resin ring spring will result in a loss of the elastic deformation function, expansion of the inner diameter of the resin ring spring, a loss of the interface between the stud and the ring spring as well as a loss of application of the elastic force that would otherwise be applied on insertion of the stud (the male fastener). Such a resin ring spring no longer has the snap fastener function.

[0073] According to this embodiment, the resin ring spring, even if broken, does not lose its elastic force and retains its snap fastener function. To produce the female fastener in an actual production process, the outer diameter of the spring plate before the resin ring spring is mounted (the diameter indicated by the arrow in FIG. 5(b)) and the outer diameter of the spring plate after the assembly step for mounting the resin ring spring (after the above-mentioned step of forming the flanged portion for covering the spring in a square U-shaped manner) are controlled to satisfy a tolerance of +0.05 mm to 0.1 mm. It is known that the assembly step in which the flanged portion for covering the spring in a square U-shaped manner is formed along the circumferential wall of the spring plate generally causes a tolerance of about 0.2 mm to 0.25 mm in the outer diameter of the spring plate.

[0074] Generally speaking, in the assembly step, the flanged portion for covering the spring is formed by press processing of the edge of the circumferential wall of the spring plate. Through this assembly step, the spring plate is squeezed to expand its outer diameter, which often increases the tolerance. In practice, it is impossible to examine the cross section of all shipping products or to examine the loss of the elastic deformation function by experimentally cutting the resin ring springs. In view of the situation, the present inventors have found that the assembly step that meets the above-mentioned dimension range can provide products with a satisfactory fail-safe function.

[0075] FIG. 6 is a table of test results representing a degree of functional loss of the elastic deformation function in the fail-safe resin ring spring according to the embodiment, by comparing the results before and after the ring spring is broken (typically, the resin ring spring as illustrated in FIGS. 1(a) to 1(e), having a substantially annular frame as a whole and being circumferentially elastic enough to turn into a convex-concave frame in which a distance from the center increase and decrease alternately along the circumference). Using the female fasteners equipped with conventional standard resin ring springs and those equipped with the resin ring springs according to the embodiment, a stud was press fit into and detached from a female fastener under the conditions of unbroken ring springs (normal continuous annular ring springs) and broken ring springs (discontinuous ring springs). Eight samples were tested under each condition. FIG. 6 shows the results of the first stud press-fitting/detachment tests and the tenth stud press-fitting/detachment tests.

[0076] As shown in FIG. 6, in the first stud press-fitting test, an average in the standard unbroken ring springs was 2.96 kgf, and an average in the standard broken ring springs was 0.84 kgf. The standard ring springs suffered from a significant decrease in elastic function due to ring breakage. According to the present embodiment, an average in the fail-safe unbroken ring springs was 3.63 kgf, and an average in the fail-safe broken ring springs was 2.94 kgf. The fail-safe ring springs retained the elastic function necessary and sufficient for snap fastening. Similarly, in the tenth stud press-fitting test, an average in the standard unbroken ring springs was 2.78 kgf, and an average in the standard broken ring springs was 0.78 kgf. The standard ring springs suffered from a significant decrease in elastic function due to ring breakage. According to the present embodiment, an average in the fail-safe unbroken ring springs was 3.30 kgf, and an average in the fail-safe broken ring springs was 2.58 kgf. The fail-safe ring springs retained the elastic function necessary and sufficient for snap fastening.

[0077] Also as shown in FIG. 6, in the first stud detachment test, an average in the standard unbroken ring springs was 1.06 kgf, and an average in the standard broken ring springs was 0.32 kgf. The standard ring springs suffered from a significant decrease in elastic function due to ring breakage. According to the present embodiment, an average in the fail-safe unbroken ring springs was 1.37 kgf, and an average in the fail-safe broken ring springs was 0.95 kgf. The fail-safe ring springs retained the elastic function necessary and sufficient for snap fastening. Similarly, in the tenth stud detachment test, an average in the standard unbroken ring springs was 0.97 kgf, and an average in the standard broken ring springs was 0.25 kgf. The standard ring springs suffered from a significant decrease in elastic function due to ring breakage. According to the present embodiment, an average in the fail-safe unbroken ring springs was 1.22 kgf, and an average in the fail-safe broken ring springs was 0.85 kgf. The fail-safe ring springs retained the elastic function necessary and sufficient for snap fastening.

[0078] In general, when the detachment strength was 0.4 kgf or less, the ring spring no longer keeps a snap fastener function and, in practice, the ring spring will be easily disengaged by slight vibration/shake or under small pressure. The results shown in FIG. 6 indicate that the female fasteners according to this embodiment retained the snap fastener function despite the trouble of ring breakage.

[0079] FIGS. 7(a) to 7(d) show a specific shape example 1 of the resin ring spring according to the embodiment, wherein the ring shape includes eight concave portions and eight convex portions that are arranged alternately. FIG. 7(b) is a cross sectional view taken along a line A-A in FIG. 7(a), and FIG. 7(d) is a cross sectional view taken along a line B-B in FIG. 7(c). The specific shape example 1 shown in FIGS. 7(a) to 7(d) may be also described as a substantially octagonal shape with all corners thereof rounded and slightly smoothed. As understood from FIGS. 7(b) and 7(d), the resin ring spring in this embodiment further includes protruding portions that extend in a thickness direction relative to the flat surfaces of the ring spring, and thus is unlevel in the thickness direction. This ring spring includes multibridge portions that protrude in an up-down direction that is vertical to a flat ring surface, as described earlier in First Embodiment. FIGS. 11(a) to 11(c) are photographic views of an actual product corresponding to FIGS. 7(a) to 7(d), wherein FIG. 11(a) is a plan view, FIG. 11(b) is a cross sectional view taken along the line A-A, and FIG. 11(c) is a sectional view taken along the line B-B. For cross sectional photography, a right end of the product is clamped by a clip in FIGS. 11(b) and 11(c).

[0080] FIGS. 8(a) to 8(d) show a specific shape example 2 of the resin ring spring according to the embodiment, wherein the ring shape includes six concave portions and six convex portions that are arranged alternately. FIG. 8(b) is a cross sectional view taken along a line A-A in FIG. 8(a), and FIG. 8(d) is a cross sectional view taken along a line B-B in FIG. 8(c). The specific shape example 2 shown in FIGS. 8(a) to 8(d) may be also described as a substantially hexagonal shape with all corners thereof rounded and slightly smoothed. FIGS. 12(a) to 12(c) are photographic views of an actual product corresponding to FIGS. 8(a) to 8(d), wherein FIG. 12(a) is a plan view, FIG. 12(b) is a cross sectional view taken along the line A-A, and FIG. 12(c) is a sectional view taken along the line B-B. For cross sectional photography, a right end of the product is clamped by a clip in FIGS. 12(b) and 12(c).

[0081] FIGS. 9(a) to 9(d) show a specific shape example 3 of the resin ring spring according to the embodiment, wherein the ring shape includes six convex portions spaced from each other at a predetermined interval. FIG. 9(b) is a cross sectional view taken along a line A-A in FIG. 9(a), and FIG. 9(d) is a cross sectional view taken along a line B-B in FIG. 9(c). The specific shape example 3 shown in FIGS. 9(a) to 9(d) may be also described as a substantially hexagonal shape with all corners thereof rounded and slightly smoothed, and may be also described as being smoother and closer to a perfectly annular shape than the specific shape example 2 shown in FIGS. 8(a) to 8(d). FIGS. 13(a) to 13(c) are photographic views of an actual product corresponding to FIGS. 9(a) to 9(d), wherein FIG. 13(a) is a plan view, FIG. 13(b) is a cross sectional view taken along the line A-A, and FIG. 13(c) is a sectional view taken along the line B-B. For cross sectional photography, a right end of the product is clamped by a clip in FIGS. 13(b) and 13(c).

[0082] FIGS. 10(a) to 10(d) show a specific shape example 4 of the resin ring spring according to the embodiment, wherein the ring shape includes four concave portions and four convex portions that are arranged alternately. FIG. 10(b) is a cross sectional view taken along a line A-A in FIG. 10(a), and FIG. 10(d) is a cross sectional view taken along a line B-B in FIG. 10(c). The specific shape example 4 shown in FIGS. 10(a) to 10(d) may be also described as a substantially square shape with all corners thereof rounded and slightly smoothed. FIGS. 14(a) to 14(c) are photographic views of an actual product corresponding to FIGS. 10(a) to 10(d), wherein FIG. 14(a) is a plan view, FIG. 14(b) is a cross sectional view taken along the line A-A, and FIG. 14(c) is a sectional view taken along the line B-B. For cross sectional photography, a right end of the product is clamped by a clip in FIGS. 14(b) and 14(c).

[0083] Comprehensively considering the observations and results in the above embodiments, it is preferable for the resin ring spring according to the present disclosure to have at least a part of the outer circumference of the ring spring abutting on or adjacent to the inner circumferential wall of the spring plate, so as to prevent expansion of the ring spring diameter even if the ring spring is broken. A large backlash space between the inner circumferential wall of the spring plate and the outer circumference of the ring spring causes a ruptured or otherwise damaged ring spring to expand outwardly and to increase its diameter. The increase in the ring spring diameter leads to an increase in the inner diameter through which the stud passes, thus impairing the snap fastener function for holding the stud. In order to prevent such an increase in the inner diameter of the ring spring even in the case of rupture or the like, at least a part of the outer circumference of the ring spring is preferably positioned to abut on or be adjacent to the inner circumferential wall of the spring plate and thereby to utilize the inner circumferential wall of the spring plate as a stopper for preventing expansion of the ring spring diameter. It is hence preferable to design the ring spring to have the shape, structure, and size suitable for and corresponding to such positioning. It is noted, just for reference, those skilled in the art can easily understand that the conventional, exactly circular ring springs cannot achieve the above-mentioned configuration and function.

[0084] Regarding the typical suitable shape, structure, etc. for achieving the above-mentioned configuration and function, the ring spring needs to satisfy following conditions: in order to ensure and retain the snap fastener function even if the spring has ruptured, the inner diameter of the non-ruptured spring in a naturally positioned state in the spring plate and the inner diameter of the ruptured spring are nearly equal (this condition is achieved by the relative positioning and size in relation to the inner circumference of the spring plate as mentioned above); and whether ruptured or not, the ring spring needs to ensure the action for press fitting the stud, the action for the stud holding function at the constricted portion (the snap fastener function), and the action for detaching the stud. Accordingly, whether the spring is ruptured or not, and even without expansion of the outer diameter of the spring, the required structure should allow free expansion of the inner diameter of the spring to such an extent as to enable the press fitting and detachment of the stud, and the required structure should also provide a natural state in which the inner diameter of the spring is narrow enough to satisfy the stud holding function at the constricted portion of the stud (the snap fastener function).

[0085] In order to allow independent expansion of the inner diameter of the resin ring spring without expansion of its outer diameter, it is typically preferable to impart a radial elastic function to the resin ring spring. In the above embodiments, the radial convex-concave structure provided along the circumference of the ring spring is configured by arms. Since the arms are flexible owing to the resin characteristics, the radial convex-concave structure has a radial elastic function that enables expansion of the inner diameter. Incidentally, the arm configuring the concave portions and the convex portions in the resin ring frame can be decomposed into orthogonal vectors: one in a tangential direction to the circumference of the ring spring and the other in a radial direction of the ring spring. Then, in particular, the radial vector component yields and enables expansion of the inner diameter for press fitting and detachment of the stud. Even if the resin ring spring is broken in terms of the circumferential vector component, flexibility in terms of the radial vector component is hardly affected.

[0086] As another typical example, the resin ring spring may have a thin disc shape (like the shape of a CD or an old record). Such a disc ring spring may be made of a flexible material and/or a thin sheet-like material. The flexible material needs such a flexibility that, when the stud is press fit or detached, the disc yields to a pressing force and bends in a pressed/urged direction along its center hole, thereby expands the center hole, and eventually enables the stud to pass through the hole. The strength and like properties for the snap fastener function can be designed, adjusted, or otherwise controlled by adjustment of the sheet thickness and the characteristics of the flexible material. The sheet-like disc-shaped resin ring spring may include a cleaved slit in a sheet surface, with its position, size, area, and shape being freely selected. For example, radial slits having an optional width may be formed in the sheet-like disc-shaped resin ring spring at given intervals, which looks, at first sight, as if a plurality of strip-shaped (or elongated trapezoidal) resin sheets was arranged radially and annularly.

[0087] For example, a resin ring spring having a shape of the Saturn's ring will be unlikely to allow self-expansion of its inner diameter even if the ring spring is partially broken. In this case, it is not essential that a part of the outer circumference of the ring spring abuts on or is adjacent to the inner circumferential wall of the spring plate. In the expanding action following ring breakage, a resin ring spring having its length/width in a radial direction self-restricts the expanding action significantly, compared with a wire-like resin ring spring. This is because the length of expansion (flexure distance) is different between the resin on the inner side (closer to the center) and the resin on the outer side (farther from the center) (which may be taken as a difference between the inner ring and the outer ring). It is therefore assumed that there is no increase in the diameter of the hole for insertion and passing of the stud, and that there is no loss of the stud holding function (the snap fastener function).

Third Embodiment

[0088] Table 1, given below, shows experiment results that explain how a difference between the outer diameter of the spring plate and the outer diameter of the resin ring spring (clearance: twice the value of t1 in FIG. 15, i.e. t1 x 2) is related to the strength for press fitting/detaching the stud (i.e. retainability of the spring function).

TABLE-US-00001 TABLE 1 change in press fitting strength and detachment strength, in relation to the outer diameter and the ring clearance Comparative Example 1 Example 2 Example 3 Example 4 outer diameter (mm) 10.68 10.65 10.62 10.58 clearance (mm) 0.18 0.15 0.12 0.08 ring condition broken unbroken broken unbroken broken unbroken broken unbroken press fitting 0.80 3.00 2.90 4.15 2.80 3.40 2.84 3.63 strength (1st) kgf detachment 0.32 1.06 0.36 0.91 0.63 1.38 0.90 1.37 strength (1st) kgf press fitting 0.80 2.80 2.20 3.80 2.10 3.15 3.00 3.00 strength (10th) kgf detachment 0.30 0.97 0.34 0.83 0.54 1.21 0.85 1.22 strength (10th) kgf

[0089] The resin ring springs as shown in FIGS. 12(a) to 12(c) and FIGS. 8(a) to 8(d) were used in this experiment, with the dimensions given in FIG. 17. Note that, however, the resin ring springs are not limited thereto. In Table 1, clearance represents a value obtained by subtracting the thickness of a spring plate material x 2 and the outer diameter of a resin ring spring 2300 from the outer diameter of a spring plate 2210. More specifically, in this experiment, the thickness of the spring plate material was 0.35 mm, and the outer diameter of the resin ring spring was 9.80 mm. FIG. 15 graphically describes a lateral clearance value (t1), which is one half of a difference between the outer diameter of the spring plate 2210the thickness of the spring plate material2 and the outer diameter of the resin ring spring 2300, and a longitudinal clearance value (t2) between the inner wall of the flanged portion of the spring plate and the upper end of the resin ring spring 2300 at a flange-covered area (typically, the upper ends of the multibridge portions 1400(1) to 1400(4)).

[0090] As illustrated in FIG. 15, the clearance includes the longitudinal clearance value (t2) and the lateral clearance value (t1). Each clearance is considered to be effective and important as an element for restricting the mobile region and the degree of freedom at the flange-covered area of the resin ring spring.

[0091] As indicated in Table 1, when the outer diameter of the resin ring spring was set to 10.68 mm (Comparative Example 1), 10.65 mm (Example 2), 10.62 mm (Example 3), and 10.58 mm (Example 4), the lateral clearance value (t1)2 was 0.18 mm, 0.15 mm, 0.12 mm, and 0.08 mm, respectively. For each case, retainability of the spring function was evaluated by the values of press fitting strength/detachment strength (first test) kgf and press fitting strength/detachment strength (tenth test) kgf measured with and without a break (a broken part). Differences in strength with and without a break (a broken part) in the resin ring springs are derived from Table 1. In Comparative Example 1, the differences were 2.2 kgf in the first press fitting strength test, 0.74 kgf in the first detachment strength test, 2 kgf in the tenth press fitting strength test, and 0.67 kgf in the tenth detachment strength test. In Example 2, the differences were 1.25 kgf in the first press fitting strength test, 0.55 kgf in the first detachment strength test, 1.6 kgf in the tenth press fitting strength test, and 0.49 kgf in the tenth detachment strength test. In Example 3, the differences were 0.6 kgf in the first press fitting strength test, 0.75 kgf in the first detachment strength test, 1.05 kgf in the tenth press fitting strength test, and 0.67 kgf in the tenth detachment strength test. In Example 4, the differences were 0.69 kgf in the first press fitting strength test, 0.47 kgf in the first detachment strength test, 0 kgf in the tenth press fitting strength test, and 0.37 kgf in the tenth detachment strength test. By observing how a dimensional change in the lateral clearance value (t1) affects the strength with and without a break (a broken part) in the resin ring springs, it turned out that Example 4 showed the best result. Namely, the case where the lateral clearance value (t1)2 was 0.08 mm was least affected by ring breakage and was able to retain the strength.

[0092] Typically, the strength of about 1 kgf or greater can be judged that a spring function durable in practical use has been retained. As seen in Table 1, when the outer diameter of the resin ring spring was 10.58 mm (Example 4), the detachment strength was 0.90 kgf in the first test and was 0.85 kgf in the tenth test. It is therefore understood that this resin ring spring, even if broken or partially damaged, retained the spring function to the highest degree among the test samples. In consideration of this result, the lateral clearance value (t1)2 is preferably 0.2 mm or less, and more preferably 0.1 mm or less (t10.05 mm) to retain the spring function. Note that the studs as shown in FIGS. 19(a) and 19(b) were used in the above experiment and measurement, but the configuration and dimensions of the studs are not limited to those shown in FIGS. 19(a) and 19(b).

[0093] Table 2 shows measurement results about retainability of the spring function with and without a break in the resin ring spring, where the multibridge portions of the resin ring spring were sandwiched and fixedly clamped by the flanged portion of the spring plate. While the ring spring is fixedly clamped from above and below by the flanged portion of the spring plate, the multibridge portions of the resin ring spring are held in a sandwiched manner and serve to fix the ring spring.

TABLE-US-00002 TABLE 2 change in press fitting strength and detachment strength, in relation to the multibridge structure Comparative Example 1 Example 1 (not fixed) (fixed) outer diameter (mm) 10.8 10.80 lateral clearance (mm) 0.30 0.30 longitudinal 0.20 0.05 clearance (mm) ring condition broken unbroken broken unbroken press fitting 1.80 4.80 5.00 6.10 strength (1st) kgf detachment 0.22 1.12 1.04 1.53 strength (1st) kgf press fitting 1.45 4.10 4.20 4.70 strength (10th) kgf detachment 0.21 1.04 0.91 1.39 strength (10th) kgf

[0094] For the measurement shown in Table 2, the resin ring spring 2300 was squeezed and fixedly clamped from above and below by the flanged portion of the spring plate 2210, as shown in FIG. 16. The resin ring springs as shown in FIGS. 11(a) to 11(c) and FIGS. 7(a) to 7(d) were used in this experiment, with the dimensions given in FIG. 18. Note that, however, the resin ring springs are not limited thereto. Similar to the measurement for Table 1, the studs as shown in FIGS. 19(a) and 19(b) were used in the experiment and measurement shown in Table 2, but the configuration and dimensions of the studs are not limited to those shown in FIGS. 19(a) and 19(b).

[0095] Table 2, given above, shows experiment results that explain how the clearance value (t2 in FIG. 15) between the inner circumferential wall of the flanged portion of the spring plate and a top surface of the resin ring spring (i.e. the multibridge portions) is related to the strength for press fitting/detaching the stud (i.e. retainability of the spring function).

[0096] In Table 2, the longitudinal clearance value (t2) represents the value obtained by subtracting the thickness of the spring plate material (hw1)2 and the wire diameter of the resin ring spring 2300 (spring height=spring thickness) from the enclosing height of the spring plate 2210 (hk), as shown in FIG. 16. More specifically, in the experiment compiled in Table 2, the thickness of the spring plate material was 0.35 mm, the outer diameter of the resin ring spring was 9.80 mm, and the thickness of the resin ring spring (measured at the thickest part, i.e. the thickness of the multibridge portions, typically the thickness h2 of the multibridge portions 1400 shown in FIGS. 1(c) to 1(e)) was 1.70 mm.

[0097] As shown in Table 2, the outer diameter of the resin ring spring was 10.80 mm, and the lateral clearance value (t1)2 was 0.30 mm. The longitudinal clearance value (t2)2 was set to 0.20 mm (when the resin ring spring was not fixedly clamped) and 0.05 mm (when the resin ring spring was fixedly clamped). For each case, retainability of the spring function was evaluated by the values of press fitting strength/detachment strength (first test) kgf and press fitting strength/detachment strength (tenth test) kgf measured with and without a break (a broken part). Note that the longitudinal clearance value (t2)2 was a negative value of 0.05 mm (when the resin ring spring was fixedly clamped). This is because (the multibridge portions of) the resin ring spring was slightly squished after being squeezed and fixedly clamped by the flanged portion, and consequently its thickness (height) in the squished state became smaller than the thickness in the natural state before the resin ring spring was squeezed and fixedly clamped.

[0098] Typically, the strength of about 1 kgf or greater can be judged that a spring function durable in practical use has been retained. As seen in Table 2, when the longitudinal clearance value (t2)2 was 0.05 mm (Example 1), the detachment strength was 1.04 kgf in the first test and was 0.91 kgf in the tenth test. It is therefore understood that this resin ring spring, even if broken or partially damaged, retained the spring function to the highest degree among the samples. In consideration of this result, the longitudinal clearance value (t2)2 is preferably about 0 mm, and more preferably a negative value (i.e. the resin ring spring was squished slightly, squeezed and fixedly clamped) to retain the spring function.

[0099] Regarding the resin ring spring, the female fastener, etc. described herein, their shapes and structures, combinations of such shapes and structures, their materials, production methods, etc., are not limited to those specifically described in the above embodiments. Those skilled in the art can easily understand that these elements can be optionally adjusted, changed, or arranged within the technical thoughts of the present disclosure by suitably incorporating the common technical knowledge of those skilled in the art, generally known/commonly used art, and the like.

[0100] The present application claims priority to Japanese Patent Application No. 2022-202290, filed Dec. 19, 2022. The contents of this application are incorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

[0101] The present disclosure can be widely developed in the field of, and can be applied to, a variety of fasteners (closures), snap fasteners and the like, to be used in garments, bags, shoes, various types of leather goods, fabric goods, etc.

REFERENCE SIGNS LIST

[0102] 100 male fastener [0103] 200 female fastener [0104] 300 ring spring