Power plants – Pressure fluid source and motor – Pulsator
Reexamination Certificate
2001-10-26
2004-12-21
Lopez, F. Daniel (Department: 3745)
Power plants
Pressure fluid source and motor
Pulsator
Reexamination Certificate
active
06832479
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resin piston for mounting in a master cylinder in a brake system used for a vehicle and the like, for transforming brake treading force into a fluid pressure to operate a brake mechanism formed in each wheel. The invention further relates to the master cylinder, a die for molding the resin piston for the master cylinder, and a method of the manufacturing resin piston for the master cylinder.
2. Description of the Related Art
As the prior art concerning such types of resin pistons for a master cylinder, a resin piston for a master cylinder can be cited that is disclosed in Japanese Utility Model Publication No. Hei. 2-28134 and Japanese Laid-Open Patent Publication No. 2000-159088. When such a resin piston for a master cylinder is molded by injection molding, as shown in
FIG. 7
of the present specification, an upper die
11
and a lower die
12
, and a core for molding a concavity
13
and a core
14
are combined, and then a resin material is injected through a resin material injection hole
21
formed in the core
14
. Then, after the resin material has been solidified, the core for molding a concavity
13
and the core
14
are pulled out, and the upper die
11
and the lower die
12
are removed. Thus, a resin piston for a master cylinder
1
is molded.
In the resin piston for a master cylinder
1
molded in such a way, as shown in
FIG. 2
, a valve mechanism
41
is fixed in a concavity
31
of the resin piston for a master cylinder
1
in a state such that a stem
42
, being a part of the valve mechanism
41
, is inserted into a communicating hole
32
. The valve mechanism
41
opens its valve in a state such that the stem
42
is touched to a stopper pin
43
disposed in the through-hole
33
of the resin piston for a master cylinder
1
, and closes the valve in a state such that the stem
42
is separated from the stopper pin
43
.
In the communicating hole
32
of the resin piston for a master cylinder
1
that is molded by injection molding using the dies
11
,
12
and the cores
13
,
14
shown in
FIG. 7
, burrs are formed at a communicating section
51
in a direction to cover the communicating hole
32
along a surface at which the upper die
11
and the lower die
12
are touched with the core for molding a concavity
13
. The burrs are formed because the resin material flows into small gaps between the surfaces at which the upper die
11
and the lower die
12
are touched to the core for molding a concavity
13
in the process of the molding of the resin piston for a master cylinder
1
. The generation of the burrs depends on the precision of the dies, but it is very difficult to eliminate the generation of the burrs completely. Moreover, also in the case where glass fibers are mixed with the resin material with the object of increasing the strength of the resin piston for a master cylinder
1
, it is difficult to eliminate generation of burrs because it is apprehended that, when the burrs are scraped off after injection molding, the resin surfaces at the places where the burrs have been scraped off become roughened and the stem
42
is caught by the roughened surfaces. Then, a problem is generated such that the stem
42
becomes unmovable because the stem
42
is caught by the burrs and then the valve mechanism
41
becomes impossible to work.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a resin piston for a master cylinder capable of preventing a valve mechanism from becoming impossible to work because the stem of the valve mechanism is caught by burrs generated in the communicating hole of the resin piston for a master cylinder in the process of the injection molding thereof.
For attaining the object, a first aspect of the present invention is a resin piston for a master cylinder including a through-hole through which a stopper pin, being a component of a valve mechanism of the master cylinder, is inserted, a concavity in which the valve mechanism is fixed by being inserted therein, and a communicating hole communicating with the through-hole from the concavity, the resin piston for a master cylinder being molded by the injection of a resin material, wherein a burr to be generated by a flow of the resin material into a gap between a combined molding die and a core in a process of molding of the resin piston for a master cylinder by injection molding projects out of the communicating hole into the through-hole.
As described above, because the burr to be generated in the resin piston for a master cylinder projects out of the communicating hole, the burr does not interfere with the movement of a stem inserted into the communicating hole. According to the first aspect of the invention, operation and an effect of the resin piston for a master cylinder can be obtained such that it is prevented that the stem of the valve mechanism is caught by a burr that can be generated in the communicating hole of a resin piston for a master cylinder in the process of the injection molding to disable the valve mechanism from working.
A second aspect of the invention is a resin piston for a master cylinder including a through-hole through which a stopper pin, being a component of a valve mechanism of the master cylinder, is inserted, a concavity in which the valve mechanism is fixed by being inserted therein, and a communicating hole communicating with the through-hole from the concavity, the resin piston for a master cylinder being molded by injection of a resin material, wherein: the through-hole is molded with a core for through-hole molding; the concavity and the communicating hole are molded with a core for molding a concavity; and a part where the through-hole communicates with the communicating hole is molded in a state such that an end of the core for molding a concavity is impacted in an impact hole formed on the core for through-hole molding.
As described above, because the communicating part is molded in the state such that the end of the core for molding a concavity is impacted in an impact hole formed on the core for through-hole molding, a burr formed at the part where the communicating hole communicates with the through-hole is formed by the flow of the resin material into a gap between the end of the core for molding a concavity and the impact part. As a result, because the burr formed at the part where the communicating hole communicates with the through-hole is formed in the shape of a protrusion into the through-hole along the inner wall surface of the communicating hole, the shape of the burr does not interfere with the movement of a stem inserted in the communicating hole. According to the second aspect of the invention, operation and an effect of the resin piston for a master cylinder can be obtained such that it is prevented that the stem of the valve mechanism is caught by a burr that can be generated in the communicating hole of a resin piston for a master cylinder in the process of the injection molding to disable the valve mechanism from working.
A third aspect of the invention is the resin piston for a master cylinder as in the second aspect, wherein: the resin piston for a master cylinder is molded with a die formed by a combination of a first die and a second die, the first die including a first core, the second die including a second core; and the core for through-hole molding is constructed by a combination of the first core and the second core, whereby the impact hole is formed.
By the construction of the die for molding the resin piston for a master cylinder in such a way, it becomes possible to form the first die and the second die in a symmetrical shape. Thereby, according to the third aspect of the invention, operation and an effect of the resin piston for a master cylinder can be obtained such that the manufacture of the die is made easy in addition to the operation and the effect of the resin piston for a master cylinder of the second aspect.
A fourth aspect of the invention is the resin piston for a master cylinder as i
Honda Yukihiro
Nakagawa Keiji
Bosch Braking Systems Co. Ltd.
Lopez F. Daniel
Priest & Goldstein PLLC
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