EP0086480B1 - Procédé de fabrication de fourches de bicyclette d'une seule pièce à partir d'une ébauche tubulaire de fer refoulé au milieu - Google Patents

Procédé de fabrication de fourches de bicyclette d'une seule pièce à partir d'une ébauche tubulaire de fer refoulé au milieu Download PDF

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Publication number
EP0086480B1
EP0086480B1 EP19830101399 EP83101399A EP0086480B1 EP 0086480 B1 EP0086480 B1 EP 0086480B1 EP 19830101399 EP19830101399 EP 19830101399 EP 83101399 A EP83101399 A EP 83101399A EP 0086480 B1 EP0086480 B1 EP 0086480B1
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EP
European Patent Office
Prior art keywords
butted
tubular
center
fork
bulge
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Expired
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EP19830101399
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German (de)
English (en)
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EP0086480A2 (fr
EP0086480A3 (en
Inventor
Isao Kimura
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D35/00—Combined processes according to or processes combined with methods covered by groups B21D1/00 - B21D31/00
    • B21D35/002—Processes combined with methods covered by groups B21D1/00 - B21D31/00
    • B21D35/005—Processes combined with methods covered by groups B21D1/00 - B21D31/00 characterized by the material of the blank or the workpiece
    • B21D35/006—Blanks having varying thickness, e.g. tailored blanks
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D53/00—Making other particular articles
    • B21D53/86—Making other particular articles other parts for bicycles or motorcycles

Definitions

  • the present invention relates to a method for manufacturing a front fork of the single unit type according to the first part of claims 1 and 2 resp.
  • the method for manufacturing the front fork of the single unit type conforms to present requirements of the saving of material, energy and labor.
  • the front fork comprises, a stem, a crown, and a pair of blades.
  • the stem, crown, and blades are manufactured separately. Except for the stem, the front fork is assembled by joining two blades to the crown. The manufacture of the crown itself required a somewhat complicated step.
  • butted tube refers to a tube having a wall which is thicker at a certain part along its length than the remainder.
  • butted tubing There exist three different types of butted tubing: single, double, and differential (or triple) butted tubes.
  • Single butted tubes are thicker at one end only, double butted tubes are thicker at both ends, and differential butted tubes have ends of varying thickness.
  • the butted tubes are butted because the stress in a tubing frame is highest at the ends where the tubes are joined. By butting, the tube can be made thinner and lighter as steel is removed from the middle of the tube where the stress is relatively low.
  • a process for manufacturing such butted tubes is known from DE-C-129 875. It describes a process for drawing seamless metal pipes having different inner and outer diameters at different places. A further process is known from DE-A-3 021 481, which describes the manufacturing of pipes having a unique inner diameter and different outer diameters.
  • center butted tube used in the present invention refers to a tube wall thickness of which exceeds only in the middle that of its two end portions. In the bicycle tubing, however, the center butted tube has never been mentioned, because the center butted tube may be of no use for bicycles.
  • the butted portion of the tube is thicker than the other portion thereof, and is thus also stronger than the other portion. Accordingly, the present invention is directed to the application of the thick and strong portion of the center butted tube to a crown portion of the single unit front fork.
  • both end portions of a tubular ferrous blank are tapered, and its middle portion is shaped ellipsoidal; the tubular blank so shaped is bent at two positions of the middle portion at right angles to form a two-bladefork; the tubular fork formed is set in a sectional die of top and bottom molds, and is subjected to the oil hydraulic bulge-forrning step to bulge-form a protuberant socket in the middle.
  • the socket can receive a stem to form a front fork blank of the single unit type.
  • center butted tube is not applied as a starting material in the above U.S. and JP-prior art documents.
  • Fig. 1 shows the tubular ferrous stock 1 with the longitudinal welded seam 1a, which is specified in JIS (Japanese Industrial Standard) G 3445" Carbon Steel Tubes for Machine Structural Purposes" STKM 11A-13A.
  • the steel described therein contains less than 0.25% C, less than 0.35% Si, 0.30-0.90% Mn, less than 0.040% P, less than 0.040% S, the remainder being Fe; and has the following physical properties: its tensile strength is more than 380 N/cm 2 (38 kg/mm 2 ), and it elongation more than 35%.
  • a spirally welded seam is not suitable, because in charging the welded tubular blank into the sectional die described hereinafter, care should be taken that the welded seam 1a is located outside the area where a single component is to be bulge-formed.
  • a seamless tube may be used as a tubular blank, offering the advantage that no attention may be paid to the welded seam so that the seamless tube may be automatically charged into the die, though, on the other hand, the seamless tube is more expensive than the welded tube.
  • Fig. 2 shows one of the known machines for making a butted tube, the invention and development of which are quite old.
  • the "Bicycle Technical Information Bulletin” No. 13 of Japan reports that the "butted tube” (developed in 1890) was imported from British Reynolds Co. into Japan as a steel tube having a thick end wall.
  • Rauch et al.: “Fahrradtechnik” published in West Germany 1980 by Bielefelder Verlags GmbH KG describes that the "butting process” was invented in 1935 by Reynolds Co., and further developed (p. 48).
  • center butted tube whose wall is particularly thick in the middle of the tube length has never been applied for use in the bicycle tubing. If the center butted tube is conceived as a tube whose wall is only thick in the middle, three different types are proposed as follows:
  • the center butted tube 2 having the outer thick wall 2a can in principle be manufactured by a known mechanism consisting of a die 14 which surrounds the tube 2 and a mandrel 15 closely inserted into the inside of the tube 2.
  • the outside diameter of the mandrel 15 is almost equal to the inside diameter of the tube 2 so that the mandrel 15 can be inserted into the inside of the tube to be processed so as to support the external force of the die 14 imposed on the wall of the tube.
  • the tube 2 into which the mandrel 15 has been inserted is then subjected to the cold drawing or extruding process by the die 14 in order to reduce the wall thickness of the tube 2 except for the middle portion, namely the butted portion 2a, to about 60% of the original wall thickness, whereby the center butted tube 2 with the outer thick wall 2a is formed.
  • FIG. 2 shows the fundamental principle of the known metal processing mechanism for manufacturing a butted tube.
  • machines which may be used in the manufacture of any of the center butted tubes listed under (1 )-(3) above:
  • the length of a tubular starting material is about 60-65 cm. It is elongated to about 90 cm when being subjected to a series of cold rolling, drawing, swaging, and tapering steps, etc.
  • the length of the middle portion of the tubular blank is selected to be about 10-15 cm, and the length of each blade portion is equal to about half the balance, namely, about 34-40 cm, respectively.
  • the outside diameter of the tubular material is in the range of 23.8-25.4 mm and the wall thickness is 2-2.3 mm. This size and dimension is merely illustrative, and it is understood that the present invention should not be limited thereby.
  • the wall thickness of the butted portion of the center butted tube listed in (1) and (2) is in the range of 2-2.3 mm which is the original thickness of the tubular starting material, and while the thickness of the two end portions which are reduced by 40% is in the range of 1.2-1.38 mm, which is 60% of the original thickness.
  • the wall thickness of the butted portion of the center butted tube of (3) is almost the same as that of (1) and (2). The details are omitted.
  • both reduced or thin portions of the center butted tube are subjected to the tapering process by a known swaging machine and the like to form tapered blades.
  • the section of the butted portion may be shaped elliptically or ovally, as depicted.
  • the center butted tubes depicted in Figs. 3-4 are then subjected to the bending process producing about right angles in the same direction and in the same plane at two positions so as to form tubular fork blanks as shown in Figs. 6-8.
  • the butted portion of the tube includes both bent shoulders at two positions as illustrated in Figs. 6-8 in order to give the shoulders sufficient strength to support both blades.
  • the longitudinal welded seam of the tubular material should face downwardly, in other words, the seam of the butted portion faces downwardly so that the seams of both blade portions between the two blades face each other.
  • the bending operation wherein the straight center butted tube is bent at two places, producing nearly the right angle to form a tubular fork shape with two prongs or blades, is performed by a known method and machine.
  • the bending operation may be carried out either in two steps, bending one blade first and then the other or in a single step bending two blades simultaneously.
  • Fig. 9 is a simplified view showing a front fork blank 8 with two blades 8a and 8b of the single unit type.
  • a socket 8c is to be formed by the oil hydraulic bulge-forming process which is described in detail hereinbelow.
  • the front fork blank 8 of the single unit type as shown in Fig. 9 should be compared with a disassembled front fork of the prior art illustrated in Fig. 11.
  • the conventional front fork is manufactured by joining two blades to a crown member shown in Fig. 10 by brazing and the like.
  • the front fork of the single unit type of the present invention requires neither a crown nor a brazing step.
  • the manufacturing cost of this invention can be considerably reduced as compared with that of the prior art.
  • such a crown member is at present generally manufactured in two methods: (a) a molten metal is cast into a crown-shaped mold; and (b) a metal plate is subjected to the metal drawing process in a press machine, and the thus formed product is welded together to obtain a finished crown. Accordingly, the manufacturing cost of the crown should not be negligible.
  • the tubular fork blank of the single unit type shown in Figs. 6-8 is set into a sectional die 13 (Fig. 16) consisting of a top half 13b and a bottom half 13c, and is subjected to the oil hydraulic bulge-forming process to form a socket 8c (Fig. 9).
  • the oil hydraulic bulge-forming process to expand a component of a desired shape from the tubular stock by inserting it into the sectional die 13 (Fig. 16), and introducing a working oil under high pressure into the tubular blank in the die to expand the above component is disclosed in Japan Patent Nos. 417,728; 417,730; 418,055 (1963), and also in "Industrie achingr", 1966, pp. 770 and 1001.
  • Fig. 12 shows a schematic view of a bulge-forming press machine 21 comprising an arch frame 22, a vertically reciprocating ram 23 suspended from the top, and a pair of horizontally reciprocating opposed rams 24, 25 at either side.
  • the top half 13b of the die 13 is secured to the vertical ram 23 with its recess facing downwardly, and the bottom half 13c is bolted onto the bed 26 with its recess facing upwardly so that the tubular fork blank is set within the die 13 when the top half 13b is exactly put on the bottom half 13c.
  • Fig. 13 of the drawings of this invention is a modified plan view illustrated in Fig. 3 of US-A-4 051 704 entitled, "Method for the Manufacture of Ornamental Head Lug of Single Unit Type for Bicycles" invented by S. Kumura.
  • a straight tubular blank is set in the sectional die and subjected to the oil hydraulic bulge-forming process to expand two protuberant components with the hydraulic oil delivered from both end openings in the tubular blank.
  • the tubular fork blank 8 has two tubular blades 8a, 8b, with the result that there is a hollow void from one end opening of the one blade 8a to the other end of the other blade 8b as seen from the top.
  • the hydraulic oil which is not pressurized is introduced into one end opening of the blade in the direction of the arrow as shown in Fig. 14 with the other end opening being closed to fill the whole tubular fork 8 in the die 13 with the oil.
  • piston 16,16a are housed in cylinders 17, 17a, respectively, but the piston 16 is inoperative and a passage 20 - is closed as described hereinbefore.
  • the oil and pressure are delivered from a central bore shown as a dotted line and provided within the piston 16a. It is to be noted that the central bore of the piston 16a is divided into two parts, namely, tow end openings of two blades.
  • the sectional die 13 is provided with an opening 13a at its end, and a mandrel 12 shown in Fig. 15 is so designed that it can be inserted into the opening 13a.
  • the mandrel 12 has a flange 12b at its one end while a concave recess 19a is formed at other end.
  • the sectional die 13 is provided with a recess corresponding to a desired shape, and in the present invention the recess is formed as a socket 8c at the middle of the top or shoulder of the tubular fork blank 8.
  • the middle top 8c is bulge-formed into the socket- like recess 8c of the die 13 (shown as dotted line in Fig. 14).
  • the production of a bicycle part or similar product from a tubular material by the bulge-forming process was considered almost infeasible, but mass production of various bicycle parts by the bulge-forming process has been in full swing for the past twenty years.
  • the height of the bulge-formed socket 8c may be 5-10 mm, as desired.
  • the mandrel 12 with the recessed female die 12a is caused to impinge on the middle top of the tubular blank 8 in order to bulge-form the socket 8c.
  • the concave recess 12 of the mandrel 12 corresponds to the contour of the socket 8c to be bulge-formed, in other words, the socket 8c acts as a male die while the recess 12a acts as a female die.
  • the die 13 of Fig. 13 is provided with the recess 8c which corresponds to the contour of the socket 8c.
  • the socket 8c should not be opened simultaneously at the beginning of the high pressure oil bulge-forming step, but should be opened by severing its closed top after the bulge-forming step.
  • the tubular front fork blank thus manufactured by the bulge-forming process from the center butted tube is an unfinished front fork product, from which a finished front fork article consisting of stem (not shown), socket on the crown integral with two blades, and fork ends (not shown) is obtained by the known various working step.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Shaping Metal By Deep-Drawing, Or The Like (AREA)
  • Axle Suspensions And Sidecars For Cycles (AREA)

Claims (7)

1. Procédé de fabrication d'une ébauche de fourche avant du type d'une seule pièce, destinée à être utilisée dans des bicyclettes, comprenant une série d'opérations consistant dans le pliage de deux parties d'extrémité minces d'un matériau tubulaire (2; 3; 4) dans la même direction et dans le même plan par rapport à la partie centrale constituant la partie supérieure pour former une fourche tubulaire (8) comportant deux branches parallèles (8a et 8b); la constitution d'une ouverture (13a) à une extrémité d'un matrice sectionnelle (13) consistant en une moitié supérieure (13b) et une moitié inférieure (13c) alors qu'il est prévu un mandrin (12) à évidement concave (12a) conçu pour coopérer avec une douille en saillie (8c) destinée à être formée par refoulement sur ladite partie centrale de ladite fourche tubulaire (8), ledit mandrin (12) étant capable d'être inséré dans ladite ouverture (13a) de ladite matrice (13); l'insertion de ladite fourche tubulaire (8) dans ladite matrice (13) qui est conçue pour former par refoulement ladite douille en saillie (8c) sur ladite partie centrale de ladite fourche tubulaire (8); la soumission de ladite fourche tubulaire (8) dans ladite matrice (13) à la charge combinée d'une charge de compression verticale, de charges de compression axiales et d'une pression d'huile élevée envoyée à l'intérieur de ladite fourche tubulaire (8) à partir des deux ouvertures d'extrémités desdits branches tubulaires (8a, 8b); et l'application du procédé hydraulique de formage par refoulement au moyen d'huile sous pression pour former par refoulement ladite douille en saillie (8c) au milieu dudit matériau (2; 3; 4) de la fourche tubulaire, caractérisé en ce que ladite fourche avant (8) est fabriquée à partir d'un matériau tubulaire ferreux refoulé au milieu (2; 3; 4) comprenant une partie refoulée centrale (2a; 3a; 4a) et deux parties d'extrémité amincies réalisées en soumettant un matériau tubulaire ferreux et rectiligne à un processus d'étirage de métal dans une machine munie d'un mandrin (15) inséré dans ledit matériau tubulaire rectiligne et une filière d'étirage (14).
2. Procédé de fabrication d'une ébauche de fourche avant du type d'une seule pièce, destinée à être utilisée dans des bicyclettes, comprenant une série d'opérations consistant dans le pliage de deux parties d'extrémité minces d'un matériau tubulaire (2; 3; 4) dans la même direction et dans le même plan par rapport à la partie centrale constituant la partie supérieure pour former une fourche tubulaire (8) comportant deux branches parallèles (8a et 8b); la fourniture d'une matrice sectionnelle (13) consistant en une moitié supérieure (13b) et une moitié inférieure (13c) à évidement concave (12a) à l'intérieur conçu pour coopérer avec une douille en saillie (8c) destinée à être formée par refoulement sur ladite partie centrale de ladite fourche tubulaire (8); l'insertion de ladite fourche tubulaire (8) dans ladite matrice (13) qui est conçue pour former par refoulement ladite douille en saillie (8c) sur ladite partie cen- traie de ladite fourche tubulaire (8); la soumission de ladite fourche tubulaire (8) dans ladite matrice (13) à la charge combinée d'un charge de compression verticale, de charges de compression axiales et d'une pression d'huile élevée envoyée à l'intérieur de ladite fourche tubulaire (8) à partir des deux ouvertures d'extrémités desdites branches tubulaires (8a, 8b); et l'application du procédé hydraulique de formage par refoulement au moyen d'huile sous pression pour former par refoulement ladite douille en saillie (8c) au milieu dudit matériau (2; 3; 4) de la fourche tubulaire, caractérisé en ce que la matrice sectionnelle (13) n'a pas d'ouverture à une extrémité, l'intérieur de ladite matrice sectionnelle (13) est munie d'un évidement concave conçu pour coopérer avec ladite douille en saillie qui doit être formée par refoulement sur ladite partie refoulée au milieu dudit matériau pour fourche tubulaire, alors qu'il n'est prévu aucun mandrin.
3. Procédé selon la revendication 1 ou 2, caractérisé en ce que ladite partie centrale refoulée dudit tube refoulé au milieu (2) comprend un paroi (2a) faisant saillie vers l'extérieur par rapport à ladite paroi mince et rectiligne dudit tube refoulé au milieu (2).
4. Procédé selon la revendication 1 ou 2, caractérisé en ce que ladite partie centrale refoulée dudit tube refoulé au milieu (3) comprend une paroi (3a) faisant saillie vers l'intérieur par rapport à ladite paroi mince et rectiligne dudit tube refoulé au milieu (3).
5. Procédé selon la revendication 1 ou 2, caractérisé en ce que ladite partie centrale refoulée dudit tube refoulé au milieu (4) comprend des parois (4a) faisant saillie à la fois vers l'extérieur et vers l'intérieur par rapport à la ligne longitudinale centrale dudit tube refoulé au milieu (4).
6. Procédé selon l'une quelconque des revendications 1 à 5, caractérisé en ce que ladite ébauche de fourche tubulaire en fer (8) destinée à une bicyclette a une longueur d'environ 90 cm, l'épaisseur de paroi de ladite partie centrale refoulée est dans la plage allant de 2 à 2,3 mm, la longueur de ladite partie centrale refoulée est dans la plage allant de 10 à 15 cm, le diamètre extérieur de ladite partie centrale refoulée est dans la plage allant de 23,8 à 25,4 mm, l'épaisseur de paroi des deux parties d'extrémité minces est dans la plage allant de 1,2 à 1,38 mm, et la longueur d'origine dudit matériau tubulaire ferreux et rectiligne est dans la plage allant de 60 à 65 cm; et sa composition chimique comprend moins de 0,12% de C, 0,35 de Cu, de 0,25 à 0,60% de Mn, 0,040% de P et 0,040% de S au maximum, respectivement, le rest étant du Fe; et ses propriétés physiques sont les suivantes: résistance à la traction de 320--420 N/cm2 (32-42 kg/cm2), allongement de 30 à 40%.
7. Procédé selon l'une quelconque des revendications 1 à 5, caractérisé en ce que ladite ébauche de fourche tubulaire en fer (8) destinée à une bicyclette a une longueur d'environ 90 cm, l'épaisseur de paroi de ladite partie centrale refoulée est dans la plage allant de 2 à 2,3 mm, la longueur de ladite partie centrale refoulée est dans la plage allant de 10 à 15 cm, le diamètre extérieur de ladite partie centrale refoulée est dans la plage allant de 23,8 à 25,4 mm, l'épaisseur de paroi des deux parties d'extrémité minces est dans la plage allant de 1,2 à 1,38 mm, et la longueur d'origine dudit matériau tubulaire en fer et rectiligne est dans la plage allant de 60 à 65 cm; et sa composition chimique est de moins 0,25% de C, moins de 0,35% de Si, de 0,30 à 0,90% de Mn, moins de 0,040% de P, et moins de 0,040% de S, le reste étant du Fe; et ses propriétés physiques sont les suivantes: résistance à la traction supérieure à 380 N/cm2 (38 kg/cm2) et allongement supérieur à 35%.
EP19830101399 1982-02-15 1983-02-14 Procédé de fabrication de fourches de bicyclette d'une seule pièce à partir d'une ébauche tubulaire de fer refoulé au milieu Expired EP0086480B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP21200/82 1982-02-15
JP2120082A JPS58138525A (ja) 1982-02-15 1982-02-15 中央バテツド素材管より一体式フロント・フオ−ク材を製作する方法

Publications (3)

Publication Number Publication Date
EP0086480A2 EP0086480A2 (fr) 1983-08-24
EP0086480A3 EP0086480A3 (en) 1984-03-21
EP0086480B1 true EP0086480B1 (fr) 1986-09-17

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EP19830101399 Expired EP0086480B1 (fr) 1982-02-15 1983-02-14 Procédé de fabrication de fourches de bicyclette d'une seule pièce à partir d'une ébauche tubulaire de fer refoulé au milieu

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EP (1) EP0086480B1 (fr)
JP (1) JPS58138525A (fr)
DE (1) DE3366171D1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4103082A1 (de) * 1991-02-01 1992-08-27 Eichelberg & Co Gmbh H D Verfahren zum hydrostatischen umformen von hohlkoerpern aus kaltumformbarem metall und vorrichtung zur durchfuehrung des verfahrens

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9579709B2 (en) * 2015-03-20 2017-02-28 Alex Global Technology, Inc. Method for manufacturing bicycle front fork having wheel clamping base

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE129875C (fr) *
FR477835A (fr) * 1914-07-01 1915-11-03 Furan Atel Du Procédé de fabrication des tetes de fourches pour cycles et motocycles
JPS517153B2 (fr) * 1971-12-06 1976-03-05
US4051704A (en) * 1975-11-19 1977-10-04 Senkichiro Kimura Method for the manufacture of an ornamental head lug of the single unit type for use in bicycles
JPS6016855B2 (ja) * 1979-09-27 1985-04-27 勲 木村 自転車用一体型前ホ−ク材の油圧バルジ成形法
DE3021481C2 (de) * 1980-06-05 1983-04-21 Mannesmann AG, 4000 Düsseldorf Verfahren und Vorrichtung zur Herstellung von Rohren

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4103082A1 (de) * 1991-02-01 1992-08-27 Eichelberg & Co Gmbh H D Verfahren zum hydrostatischen umformen von hohlkoerpern aus kaltumformbarem metall und vorrichtung zur durchfuehrung des verfahrens

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JPS58138525A (ja) 1983-08-17
EP0086480A2 (fr) 1983-08-24
EP0086480A3 (en) 1984-03-21
DE3366171D1 (en) 1986-10-23

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