| US 7,537,721 B2 | ||
| Method of manufacturing boot for constant-velocity universal joint and manufacturing apparatus for use in the method, and boot for constant velocity universal joint | ||
| Kazuhiko Sueoka, Ageo (Japan); and Yasuji Takada, Ageo (Japan) | ||
| Assigned to Fukoku Co., Ltd., Saitama-Ken (Japan) | ||
| Filed on Aug. 18, 2004, as Appl. No. 10/920,315. | ||
| Claims priority of application No. 2003-310523 (JP), filed on Sep. 02, 2003; and application No. 2004-131959 (JP), filed on Apr. 27, 2004. | ||
| Prior Publication US 2005/0046077 A1, Mar. 03, 2005 | ||
| Int. Cl. B29C 45/14 (2006.01) | ||
| U.S. Cl. 264—328.12 [264/255; 264/259; 264/250] | 6 Claims |
| 1. A method of manufacturing a boot for a constant-velocity universal joint, including a plurality of large thickness portions
disposed approximately in equal distance in a peripheral direction of an inner surface of a large diameter side end portion
and a plurality of small thickness portions disposed in-between the large thickness portions and the thickness thereof in
the peripheral direction is thinner than that of the large thickness portions, the method comprising the steps of:
preparing a primary molded member, including a bellow portion with approximately conical shaped and hollow inside, a small
diameter side end portion provided to one side of the bellow portion and the large diameter side end portion provided to another
side of the bellow portion; and
a secondary molding step of welding the large thickness portions and the small thickness portions integrally to the inner
surface of the large diameter side end portion of the primary molded member;
wherein the secondary molding step has:
a first step of forming a secondary molding space between an outer periphery surface of a core mold and the inner periphery
surface of the large diameter side end portion by holding a small diameter portion placed just in vicinity of the large diameter
side end portion of the primary molded member with the core mold disposed in an inner periphery side of the large diameter
side portion and a metal mold disposed in an outer periphery side of the large diameter side end portion; the secondary molding
space having a plurality of thick portion molding spaces for molding the large thickness portions and a plurality of thin
portion molding spaces for molding the small thickness portions;
a second step of filling a molten material into the secondary molding space by injecting the molten material to the secondary
molding space from a plurality of molten material injection points;
a third step of integrally molding the large thickness portions and the small thickness portions to the inner surface of the
large diameter side end portion as the molten material filled in the secondary molding space solidifies; and
a fourth step of separating the core mold and the large diameter side end portion by having a plurality of parts of the core
mold, which are disposed in the thick portion molding spaces and abut on end portions of the large diameter side end portions,
move to a central direction of the core mold,
wherein the thick portion molding spaces and the thin portion molding spaces communicate with each other along a peripheral
direction of the large diameter side portion and molten material injection points are provided according to each of the thin
portion molding spaces; and
wherein the second step has the steps of:
setting a direction θ of the injection gate to 0°≤θ≤90° with respect to the inner peripheral surface of the large-diameter
side end portion; and
setting a position of the injection gate to 0≤t≤2a/3 when a distance between the inner surface of the large-diameter side
end portion and an injection gate center is t and that a diametric direction distance of an injection-side end portion of
the secondary molding space is “a” and injecting the molten material so as to bring the molten material into sliding contact
with the inner peripheral surface of the large-diameter side end portion.
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