Metal deforming – By extruding through orifice – Expressing non-uniform cross-section or non-linear product
Reexamination Certificate
2002-01-31
2004-01-27
Tolan, Ed (Department: 3725)
Metal deforming
By extruding through orifice
Expressing non-uniform cross-section or non-linear product
C072S264000, C072S269000, C072S468000
Reexamination Certificate
active
06681610
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 USC 119 to Japanese Patent Application No.
2001-024920
filed on Jan. 31, 2001, the entire contents thereof is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for extruding a tube having different sections in its longitudinal direction, and a die for tube extrusion molding used when the tube is extruded. The tube is used for a vehicle for example, particularly for the body frame of a motorcycle.
2. Description of Background Art
A process for extruding a tube used for a member forming the body of a vehicle such as a motorcycle and having variable sections in its longitudinal direction and a die for extrusion used for extrusion molding, respectively, are disclosed in Japanese published unexamined patent application No. Hei 10-286619 (see FIG. 11). This die for extrusion is provided with a fixed female die having a fixed die hole and a slide die which has a slide die hole in the same shape as the fixed die hole and which can be slid on the lower surface of the fixed female die. Two or three fixed cores are arranged in parallel in the fixed die hole via clearance, and two or three slide cores integrated with the slide die are also arranged in parallel in the slide die hole via clearance. The slide core is laminated on the fixed core and can be slid on the fixed core. A tube-like member is formed (hereinafter merely called a tube) in the shape of a letter E or in the shape of the letter E having one more bar in the center of the inside of which a rib for reinforcement. The tube has a sectional form which changes in the longitudinal direction, and is formed by moving the slide die in a direction perpendicular to the direction of extrusion, extruding the material from a communicating part between the slide core and the fixed core, and between the fixed die hole and the slide die hole by the die for extrusion.
Since the width of the reinforcement rib of the above-mentioned conventional type changes, and extends in a longitudinal direction, the enhancement of the rigidity afforded by the rib may not be enough. One example of this is when a tube having a width that changes in the longitudinal direction is used for a part requiring high rigidity against a load that acts from a direction in which the width of the tube changes, such as when it is used as a main pipe of a motorcycle. In this case, the enhancement of the rigidity by the rib may not be sufficient.
In a situation in which a tube is connected to another member and a large load acts on a connection of the tube, in order to keep the tube as light in weight as possible, it is desirable to not to reinforce the whole tube, but only to reinforce the tube in the vicinity of the connection of the tube. However, in the conventional type tube described above, the rib for reinforcement is formed over the entire longitudinal direction of the tube. As such, the rib is formed in a part not requiring the enhancement of the rigidity, increasing the weight of a product using the tube, for example a vehicle. In addition, the amount of the material used for the tube becomes more than the required amount, and the cost of the material is increased. As a result, there is a problem in that the cost of the product using the tube is increased.
Ways to add rigidity selectively to only the part of the tube requiring rigidity have been considered. For example, a reinforcing member could be added by welding to only that part of the tube requiring the rigidity. However, this approach is problematic, in that an increase of manufacturing man hours and the increase of the cost by welding are caused.
Also, it is desirable that rigidity be enhanced only at the end of main pipe that connects to the head pipe. By maintaining a lesser rigidity at the other end of the pipe, ride quality is enhanced due to the spring action of the end of the pipe having less rigidity. However, there is no known conventional die or extrusion method capable of producing a pipe with these requirements.
SUMMARY AND OBJECTS OF THE INVENTION
The present invention is made in view of the above situation. The common object of the present invention is to provide an extrusion molding process wherein a tube having an intermediate wall extended in a direction crossing a direction in which the width of the tube changes can be easily and cost effectively formed. Further, the object of the invention is to provide an extrusion molding process wherein a tube the rigidity of only a required part of which is enhanced by an intermediate wall can be easily formed. An additional object of the invention is to provide a die for tube extrusion molding suitable for embodying the invention.
One aspect of the invention is a process for extruding a tube having different sections wherein a tube is formed by extruding the material via an opening formed by the superposition in the direction of extrusion of a first die hole formed in the first die, and a second die hole formed in the second die. The process uses a die for tube extrusion molding provided with the first die and the second die which are superposed in the direction of extrusion, and which can be relatively moved in a set direction along the superposed surface. The sectional form of the tube is varied in the direction of extrusion by relatively moving the first die and the second die in the set direction. Further, the process is characterized by extruding a tube having different sections through an outflow passage having an opening for a tube wall and an opening for at least one intermediate wall which continues to the opening for the tube wall inside the opening for the tube wall. The opening for the tube wall has a predetermined width extending in a first direction, which is a direction when the set direction is projected on a plane perpendicular to the direction of extrusion, and extends in a second direction crossing the first direction on the perpendicular plane and by relatively moving the first die and the second die in the set direction. Material is then extruded from the outflow passage, forming the wall of the tube, the width in the first direction varying in the longitudinal direction by means of the opening for the tube wall, and simultaneously forming the intermediate wall in the inside space of the tube by means of the opening for the intermediate wall, the intermediate wall having a fixed thickness of the predetermined width in the first direction, and extending in the longitudinal direction and continuing to the tube wall.
Additionally, according to the invention, one or more intermediate walls extended in the second direction crossing the first direction can be easily formed by the opening for the intermediate wall in the inside space of the tube in which the width of the wall formed by the opening for the tube wall varies in the first direction by relatively moving the first and second dies in the set direction. Material is then extruded from the outflow passage, causing the rigidity of the tube to be further enhanced by having one or more intermediate walls formed in the direction crossing the direction in which the width of the tube varies. Cost can also be reduced. In addition, since the intermediate wall can have a fixed thickness corresponding to the predetermined width in the longitudinal direction in situations when the width of the tube varies, the weight of the tube by forming the intermediate wall can be kept to a minimum.
The invention further includes the process for extruding the tube having different sections, whereby the intermediate wall is a connecting wall connecting two tube wall parts opposite in the second direction of the tube wall. This process partitions the inside space into a plurality of independent partial spaces on the section of the tube and a number of the connecting walls in the longitudinal direction of the tube. These spaces are changed by opening or blocking at least one of the openings for the intermediate walls according to the am
Hoshi Konomu
Yanagibashi Yoshitaka
Birch & Stewart Kolasch & Birch, LLP
Honda Giken Kogyo Kabushiki Kaisha
Tolan Ed
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