Title of Invention

"MANUFACTURING METHOD FOR RESIN SPRING"

Abstract

[Object] To provide a manufacturing method for a resin spring which can improve the close contact between a spring body and inner - pressure generating members to thereby reduce variations in load characteristics due to repeated deformation in use. [Constitution] A manufacturing method for a resin spring including the steps of forming an elastomer preform 1 having inner closed chambers, inserting inner - pressure generating members 12 and 13 into the inner closed chamber:1, of the preform, and compressing the preform 1 with the inner -pressure generating members 12 and 13 by applying an exteinal force to produce a permanently deformed portion whose molecular structure is oriented.

Full Text

[DETAILED DESCRIPTION OF THE INVENTI0N] -[Fieid of the Invention] The present invention relates to a manufacturing method for a resin spring capale of generating a compressive damping force. [Prior Art] Resin springs are used at various places where absorption of vibrations is required. For example, a compression spring formed of an elastomer described in Japanese Patent (PCT international application) Laid-open No. 7-502698 is produced by joining hollow noncircular bodies together to form a preform and compressing the preform to orient its molecular structure for the purpose of removing compressive setting. However, when reducing the wall thickness of the preform to allow a large displacement, there occurs a large creep to cause variations in characteristics, and no sufficient energy absorption can be obtained. To cope with this problem, the present applicant has proposed a method of inserting inner-pressure generating members into the hollow portions of the resin spring (Japanese Patent Application No. 9-64714). By inserting the inner -pressure generating members into the hollow portions of the resin spring, sufficient energy absorption can be obtained with a large displacement, and the creep generated can be reduced. [Problem to be Solved by the Invention]] In the above method, however, the preform is preliminarily compressed to be formed into a spring body having an anti-setting performance, and the inner-pressure generating members are next inserted into the hollow portions of the spring body, thereby obtaining the resin spring. Accordingly, there are variations in permanent deformation of the spring body produced by the anti-setting treatment, so that the inner-pressure generating members inserted in the hollow portions of the spring body are in poor close contact with the spring body. As a result, there is a possibility that the spring body and the inner-pressure generating members inserted therein may slip relatively because of repeated deformation in using the resin spring, causing variations in load-characteristics of the resin spring. It is accordingly an object of the present invention to provide a manufacturing method for a resin spring which can improve the close contact between the spring body and the inner-pressure generating members to thereby reduce variations in load characteristics due to repeated deformation in use. [Means of Solving the Problem, Operation, and Effect] According to the invention as defined in claim 1, there is provided a manufacturing method for a resin spring, comprising the steps of forming an elastomer preform having an inner closed chamber; inserting an inner-pressure generating member into the inner closed chamber of the elastomer preform; and compressing the elastomer preform with the inner-pressure generating member by applying an external force to produce a permanently deformed portion whose molecular structure is oriented . After inserting the inner-pressure generating member into the inner closed chamber of the elastomer preform/ an external force is applied to the elastomer preform and the inner-pressure generating member- in the compressing step to produce permanent deformation and orient the molecular structure of the permanently deformed portion, thus carrying out an anti -setting treatment. Accordingly, by preliminarily making close contact of the inner-pressure generating member with the preform in the inserting step, the inner-pressure generating member is also deformed by deformation of the inner closed chamber of the preform by the external force applied in the compressing step, thereby highly ensuring the close contact between the spring body and the inner-pressure generating member. As a result, the slip between the spring body and the inner-pressure generating member can be prevented regardless of repeated deformation in use, thereby obtaining stable load characteristics. According to the invention as defined in claim 2, the inserting step in the manufacturing method for the resin spring as defined in claim 1 comprises injecting an inner -pressure generating resin into the inner closed chamber of the elastomer preform. The inner -pressure generating resin is injected into the inner closed chamber of the elastomer preform to fill the inner closed chamber, so that the inneir-pressure generating member molded from the inner-pressure generating resin is kept in close contact with the preform. Accordingly, the close contact between the preform and the inner-pressure generating member is highly maintained also in the compressing step for carrying out the anti-setting treatment. As a result, the slip between the spring body and the inner-pressure generating member can be prevented regardless of repeated deformation in use, thereby obtaining stable load characteristics . According to the invention as defined in claim 3, there is provided a manufacturing method for a resin spring, comprising the steps of integrally forming an elastomer preform and an inner-pressure generating member; and compressing the elastomer preform with the inner-pressure generating member by applying an external force to produce a permanently deformed portion whose molecular structure is oriented. Because the elastomer preform and the inner-pressure generating member are integrally formed with each other, the inner -pressure generating member is in close contact with the elastomer preform prior to the compressing step. Accordingly, the close contact between the preform and the inner-pressure generating member is highly maintained also in the compressing step. As a result, the slip between the spring body and the inner-pressure generating member can be prevented regardless of repeated deformation in use, thereby obtaining stable load characteristics. According to the invention as defined in claim 4, the integrally forming step in the manufacturing method for the resin spring as defined in claim 3 comprises integrally forming the elastomer preform and the inner-pressure generating member so as to exhibit a slope function . The integral body of the preform and the inner-pressure generating member has a slope function, so that the resin spring obtained by compressing the integral body does not have an interface where the property rapidly changes, thereby suppressing the generation of cracks or the like in the resin spring due to stress concentration or the like. According to the invention as defined in -claim 5, there is provided a manufacturing method for a resin spring, comprising the steps of forming an elastomer preform having an inner closed chamber; compressing the elastomer preform by applying an external force to produce a permanently deformed portion whose molecular structure is oriented, thereby forming a spring body having the inner closed chamber deformed; and injecting an inner-pressure generating resin into the inner closed chamber of the spring body and molding the inner-pressure generating resin into an inner-pressure generating member by using the spring body as a part of a die. The inner-pressure generating resin is injected into the inner closed chamber of the spring body obtained by the compressing step and is molded in this chamber by using the spring body as a part of the die. Accordingly, the close contact between the spring body and the inner pressure generating member can be highly ensured. As a result, the slip between the spring body and the inner-pressure generating member can be prevented regardless of repeated deformation in use, thereby obtaining stable load characteristics. Accordingly, the present invention relates to a manufacturing method for PUL_ a resin spring, comprising the steps of forming an elastomer .perform having at least an inner chamber, inserting an inner-pressure generating member into p\c_ each of said atleast one inner chamber of said elastomer perform and compressing said elastomer -perform with said inner-pressure generating member by applying an external force to produce a permanently deformed portion whose molecular structure is oriented, said compressing step comprises the steps of placing a base portion of the elastomer perform against a surface, inserting a pressure plate through a through hole formed in a flattened projecting portion of said elastomer preform and turning the pressure plate toward the surface to compress the elastomer perform with the inner-pressure generating member therein. [BRIEF DESCRIPTION OF THE/DRAWINGS] [FIG. 1] FIG. 1 is a side view of a preform according to a preferred embodiment of the present invention. [ FIG. 2] FIG. 2 is a side view showing a condition where upper and lower dies are set on the preform after it is raised. [FIG. 3] FIG. 3 is a cross section taken along the line III III in FIG. 2 . [FIG. 4] FIG. 4 is a sectional view of the preform and the inner-pressure generating members inserted therein just prior to a compression step. [FIG. 5] FIG. 5 is a side view of a resin spring finally obtained after the compression step. [FIG. 6] FIG. 6 is a sectional view of an essential part of a front-wheel suspension applying the resin spring. [Preferred Embodiment] A preferred embodiment of the present invention will now be described with reference to FIGS. 1 to 6. Reference numeral 10 generally denotes a resin spring according to a preferred embodiment of the present invention. The resin spring 10 is applied to a wheel suspension for a scooter type motorcycle. The steps of a manufacturing method for the resin spring 10 will be described in sequence with reference to FIGS. 1 to 5 . In the first step, a polyester elastomer is used to perform injection molding to obtain a preform 1 as shown in FIG. 1, which is a side view of the preform 1. The preform 1 has two hollow cylindrical portions 2 and 3 formed adjacent to each other in their radial directions, a base portion 4 formed adjacent to the cylindrical portion 2 and having a flat bottom surface, and a flattened projecting portion 5 formed adjacent to the cylindrical portion 3 so as to obliquely project from its cylindrical surface. The base portion 4 is formed with a through hole 4a elongated along the thickness thereof and extending over the width thereof. The flattened projecting portion 5 is also formed with a through hole 5a elongated along the width thereof and extending in a direction of projection thereof . The base portion 4 and the cylindrical portion 2 are integrally joined at their lower side as viewed in FIG. 1 by a reinforcing wall 6, and the cylindrical portion 2 and the cylindrical portion 3 are integrally joined at their lower side as viewed in FIG. 1 by a reinforcing wall 7. In the second step, the preform 1 is raised so that the right and left side surfaces become upper and lower surfaces, and is sandwiched by a lower die 8 and an upper die 9 as shown in FIG. 2. The lower die 8 closes the lower circular openings of the cylindrical portions 2 and 3, and the upper die 9 closes the upper circular openings of the cylindrical portions 2 and 3, thereby defining inner closed chambers 2a and 3a. The upper die 9 is formed with injection holes 9a and 9b respectively communicating with the inner closed chambers 2a and 3a. An urethane resin and a foaming agent are injected from the injection holes 9a and 9b into the inner closed chambers 2a and 3a (see FIG. 3) . The urethane resin is foamed by the forming agent in the inner closed chambers 2a and 3a, thereby forming solid cylindrical inner-pressure generating members 12 and 13 respectively filling the inner closed chambers 2a and 3a. Thus, the inner-pressure generating members 12 and 13 are foamed members respectively kept in close contact with the inner circumferential surfaces of the cylindrical portions 2 and 3. In the third step, an external force is applied to the preform 1 having the inner-pressure generating members 12 and 13 respectively inserted in the inner closed chambers 2a and 3a, thereby compressing the preform 1 to carry out an anti -setting treatment in the following manner. As shown in FIG. 4, the bottom surface of the base portion 4 is put into contact with a wall surface W, and a pressure plate P is inserted through the elongated hole 5a of the projecting portion 5. In this condition, the pressure plate P is turned toward the wall surface W, thereby -compressing the preform 1 and the inner -pressure generating members 12 and 13 for a given period -of time. As a result, the preform 1 is compressively deformed and its molecular structure is oriented to produce permanent deformation. In this condition, the preform 1 is changed to a spring body 11 retaining the permanent deformation even after removing the external force as shown in FIG. 5. The inner-pressure generating members 12 and 13 enclosed in the spring body 11 are also deformed, thus manufacturing the resin spring 10. The cylindrical portions 2 and 3 each originally having a circular shape as viewed in side elevation are deformed in their radial directions to become an elliptical shape as shown in FIG. 5. Accordingly, the inner-pressure generating members 12 and 13 are also similarly deformed so as to keep the close contact with the inner circumferential surfaces of the cylindrical portions 2 and 3, respectively. In this manner, the preform 1 is preliminarily compressed to produce a permanently deformed portion whose molecular structure is oriented, thereby improving an anti -'setting performance of the resin spring 10. The resin spring 10 thus manufactured is -used in a front-wheel suspension for a scooter type motorcycle in this preferred embodiment. FIG. 6 is a sectional view showing a damping force generating mechanism using the resin spring 10 in the front-wheel suspension. Reference numeral 30 denotes a front fork of the scooter type motorcycle. A pivot arm 31 as a link mechanism is pivotably supported by a pivot arm bolt 33 to the lower end of the front fork 30. The pivot arm 31 has a free end to which a front wheel is supported through an axle 34. The front fork 30 has a sectionally U-shaped configuration consisting of a front wall and right and left side walls. The right and left side walls are formed at their lower end portions with bolt holes aligned to each other. The pivot arm 31 has a base pivot portion 31a having a through hole in which a bushing 35 is engaged. The base pivot portion 31a of the pivot arm 31 is engaged between the right and left side walls of the front fork 30 so that the bushing 35 is aligned with the bolt holes of the right and left side walls. The pivot arm bolt 33 is inserted through the bolt holes of the right -and left side walls of the front fork 30 and the bushing 35 of the pivot arm 31, thus pivotably supporting the pivot arm 31. The base pivot portion 31a of the pivot arm 31 has a cylindrical shape with its radially opposite portions expanded in diameter, at one of which a flat lever 32 is integrally formed. The flat lever 32 extends from the outer circumferential surface of the base pivot portion 31a in its centrifugal direction. The pivot arm 31 and the flat lever 32 extend substantially rearward from the base pivot portion 31a so that an angle of about 60' is formed between the pivot arm 31 and the flat lever 32. Accordingly, the flat lever 32 is located between the front fork 30 and the pivot arm 31. A substantially sectorial case 36 is located above the base pivot portion 31a of the pivot arm 31 in the vicinity thereof, and is fixedly engaged within the front fork 30. The case 36 is a boxlike member opening only at its lower end, and the resin spring 10 is accommodated in the case 36 .- The lever 32 integral with the pivot arm 31 is inserted in the elongated hole 5a of the projecting portion 5 of the resin spring 10, and a screw 38 is threaded into the end of the lever 32 with a washer 37 interposed therebetween, thereby fixing the projecting portion 5 of the resin spring 10 to the lever 32. Then, the assembly of the resin spring 10 and the lever 32 is forced into the case 36 from its lower opening. The case 36 is formed with a pair of elongated holes aligned to each other. A stop bar 39 is inserted through the elongated hole 4a of the base portion 4 of the resin spring 10, and the opposite ends of the stop bar 39 are engaged with the pair of aligned elongated holes of the case 6, thereby fixing the base portion 4 of the resin spring 10 to the case 36. The projecting portion 5 of the resin spring 10 accommodated in the case 36 is normally kept in contact with a rear wall of the case 36. Thus, the resin spring 10 is accommodated in the case 36 so that the front end portion of the resin spring 10 is positioned by the stop bar 39 and the rear end portion of the resin spring 10 is displaceably interposed between the case 36 and the lever 32. In operation, when the front wheel passes over an uneven spot on the road or receives a load upon braking, the pivot arm 31 and the lever 32 integral therewith are swung from a solid line to a dashed line as shown in FIG. 6. Accordingly, the resin spring 10 is urged by the lever 32 toward the front wall of the front fork 30, so that the spring body 11 of the resin spring 10 is elastically deformed . The inner-pressure generating members 12 and 13 enclosed in the spring body 11 are also compressed to generate an inner pressure serving as a repulsive force. The elastic characteristics of the resin spring 10 are such that when a load is applied to the resin spring 10 in its permanently deformed condition obtained by the above-mentioned compression step, a sufficient displacement of the resin spring 10 is ensured, whereas when the load applied is removed, the resin spring 10 restores its original shape as exhibiting a hysteresis, thus obtaining sufficient energy absorption with a large displacement . The resin spring 10 can exhibit an anti-setting performance because the preform 1 is preliminarily compressed to orient the molecular structure of the deformed portion. In addition, the inner-pressure generating members 12 and 13 are inserted in the inner closed chambers 2a and 3a of the spring body 11 to thereby reduce a creep and greatly improve the anti-setting performance over the conventional resin spring with no inner-pressure generating members. [0037] Furthermore, the inner-pressure generating members 12 and 13 are kept in close contact with the inner circumferential surfaces of the cylindrical portions 2 and 3 of the spring body 11. Accordingly, even when the spring body 11 repeats elastic deformation in using the resin spring 10, there occurs no slip between the spring body 11 and the inner-pressure generating members 12 and 13, thus obtaining stable load characteristics and reducing aged deterioration. As another preferred embodiment, the elastomer preform and the inner -pressure generating members may be integrally formed in the first step. Accordingly, the inner -pressure generating members can be kept in—close contact with the preform, and the close contact therebetween can be maintained after the subsequent compression step. As a result, even when the spring body repeats elastic deformation in using the resin spring, there occurs no slip between the spring body and the inner-pressure generating members, thereby stabilizing the load characteristics. In the above integral forming step, the preform and the inner-pressure generating members are integrally formed so as to exhibit a slope function. In this case, the resin spring finally produced after the compression step does not have an interface where the property rapidly changes. Accordingly, the resin spring in this preferred embodiment can be made less prone to cracks or the like due to stress concentration or the like. [0040] As still another preferred embodiment, the elastomer preform having inner closed chambers is first formed. In the next step, only the preform is compressed without inserting the inner-pressure generating members into the inner closed chambers, thereby orienting the molecular structure of the permanently deformed -portion to carry out an anti-setting treatment. Finally, an inner -pressure generating resin to be molded into the inner-pressure generating members is injected into the inner closed chambers of the spring body obtained by the above anti-setting treatment, then forming the inner-pressure generating members by use of the spring body as a part of the die. According to this preferred embodiment, the inner-pressure generating resin is injected into the inner closed chambers of the spring body and then molded into the inner-pressure generating members. Accordingly, the spring body and the inner-pressure generating members can be highly maintained in close contact with each other, thereby eliminating the occurrence of slip between the spring body and the inner - pressure generating members due to repeated elastic deformation of the resin spring and accordingly obtaining stable load characteristics. [Explanation of Reference Numerals] 1: preform 2, 3: cylindrical portion 4 : base portion 5: projecting portion 6, 7: reinforcing wall 8: lower die 9: upper die 10: resin spring 11: spring body 12, 13: inner-pressure generating member 30: front fork 31: pivot arm 32: lever 33: pivot arm bolt 34: axle 35: bushing 36: case 37: washer 38 : screw 39: stop bar We claim: 1. A manufacturing method for a resin spring, comprising the steps of: forming an elastomer preform having an inner closed chamber; inserting an inner-pressure generating member into each of said atleast one inner chamber of said elastomer preform; and compressing said elastomer preform with said inner-pressure generating member by applying an external force to produce a permanently deformed portion whose molecular structure is oriented, said compressing step comprises the steps of: placing a base portion of the elastomer preform against a surface; inserting a pressure plate through a through hole formed in a flattened projecting portion of said elastomer preform; and turning the pressure plate toward the surface to compress the elastomer preform with the inner-pressure generating member therein. 2. A manufacturing method for a resin spring as claimed in claim 1, wherein said step of inserting an inner pressure generating member comprises injecting an inner-pressure generating resin into said inner closed chamber of said elastomer preform to form the inner- pressure generating member. 3. A method of manufacturing a resin spring as claimed in claim 1, wherein said step of inserting an inner pressure generating member comprises the steps of: providing a lower die and an upper die for covering lower and upper openings in said at least one inner chamber, at least one of said lower and upper dies includes at least one injection hole formed therein; and injecting an inner-pressure generating resin through said at least one injection hole and into said at least one inner chamber of said elastomer preform to form the inner-pressure generating member. 4. A manufacturing method for a resin spring substantially as hereinbefore described with reference to the accompanying drawings.

Documents:

339-del-1999-abstract.pdf

339-del-1999-claims.pdf

339-del-1999-correspondence-others.pdf

339-del-1999-correspondence-po.pdf

339-del-1999-description (complete).pdf

339-del-1999-drawings.pdf

339-del-1999-form-1.pdf

339-del-1999-form-13.pdf

339-del-1999-form-19.pdf

339-del-1999-form-2.pdf

339-del-1999-form-3.pdf

339-del-1999-form-4.pdf

339-del-1999-form-6.pdf

339-del-1999-gpa.pdf

339-del-1999-petition-137.pdf

339-del-1999-petition-138.pdf

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