Title of Invention

A PROCESS FOR PRODUCING A BUMPER FOR A VEHICLE

Abstract (A PROCESS FOR PRODUCING A BUMPER FOR A VEHICLE) ABSTRACT OF THE DISCLOSURE (1932/MAS/96) A process for producing a bumper for a vehicle uses a first step of injecting an outer layer forming material into a bumper forming cavity through a gate in a mold, and a second step of injecting a core forming material, thereby allowing the core forming material to flow into the outer layer forming material existing in said gate and said cavity, while allowing the outer layer and core forming materials to flow within the cavity. In the mold, the volume of a mounting portion forming area of the bumper forming cavity is set so that the thickness ti of at least a mounting portion of the bumper for mounting to a vehicle body to extend laterally from a central portion of the vehicle body can be larger than the thickness tz of a bumper main portion excluding the mounting portion, and the gate opens into the mounting portion forming area. Thus, the outer layer forming material can be allowed to flow substantially uniformly over the entire cavity, thereby enhancing the filling rate of the core forming material. t9
Full Text

PR^CEGg FOR rRODUCING A UUIilitll FOR A VEllI-GM:
rBACKGRQimD OF THE IIJ^^TIINTIOM
'FIELD OF THE IiriTOJaJn]^
The present invention relates to a process for producing
a bumper for a vehicle and particularly, to an improvement in
a process for producing a bumper for a vehicle, which is made
of a synthetic resin and has a sandwich structure including a
core and an outer layer covering the core, the process including
a first step of injecting an outer layer forming material into
a bumper forming cavity through a gate in a mold, and a second
step of injecting a core forming material, thereby allowing the
core forming material to flow into the outer layer forming
material existing in the gate and cavity, while allowing the
outer layer and core forming materials to flow within the cavity.
DESCRIPTION OF THE RELATED ART
In such a conventional bumper, the thickness thereof is
set such that it is relatively thin and substantially uniform
in its entirety, and a mounting portion for mounting to a vehicle
body to extend laterally from a central portion of the vehicle
body forms a rear edge of a front and upper portion of the bumper.
In this case, a gate opens into a mounting portion forming area
of the bumper forming cavity in the mold.
In the a process for producing the bumper, while the outer
layer forming material is flowing within the cavity, the core
forming material is allowed to flow into the outer layer forming

material. However, after a front portion of the outer layer
forming material in a flowing direction has reached to a terminal
end of the cavity to stop its flowing, it is difficult to allow
the core forming material to flow into the front portion of the
outer layer forming material in the flowing direction.
In an attempt to produce a bumper using the mold under
such a situation, when the outer layer form.ing material is
injected into the cavity, the capability to distribute the
material into the mounting portion forming area in a lengthwise
direction of the cavity (in a lateral direction of the vehicle
body) is low due to a small volume (i.e., a narrowness) of the
mounting portion forming area. For this reason, as compared
with the time taken for the outer layer forming material to reach
a central end area of the cavity nearer to the mounting portion
forming area to stop its flowing, the time taken for the outer
layer forming material to reach lengthwise opposite end areas
remoter from the mounting portion forming area to stop its
flowing is remarkably long. As a result, in the central end
area, the core forming m.aterial fails to flow into the outer
layer forming material. Due to this, it is impossible to
produce the bumper having a sandwich structure in its entirety.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to
provide a producing process of the above-described type,
wherein the capability to distribute the material into the
mounting portion forming area of the cavity in the lengthwise
3

direction of the cavity can be enhanced, thereby producing a bumper having a
sandwich structure.
FR-A-2494185 discloses a process of producing a bumper for a vehicle, which
is made of a synthetic resin and has a sandwich structure comprised of a core and an
outer layer covering said core, said process comprising a first step of injecting an
outer layer forming material into a bumper forming cavity through a gate in a mold in
which mold the volume of a mounting portion forming area of the bumper forming
cavity is set such that a thickness of at least a mounting portion of the bumper which
is to be mounted to a vehicle body and which extents laterally from a central portion
of the vehicle body is larger than a thickness of a bumper main portion excluding said
mounting portion, and a second step of injecting a core forming material; thereby
allowing said core forming material to flow into said outer layer forming material
existing in said gate and said cavity, while allowing said outer layer and core forming
materials to flow into said cavity.
According to the present invention, there is provided a process for producing a
bumper for a vehicle, which is made of a synthetic resin and has a sandwich structure
comprised of a core and an outer layer covering the core, the process comprising: a
first step of injecting an outer layer forming material into a bumper forming cavity
through a gate in a metal mold, in which the volume of a mounting portion forming
area of the bumper forming cavity is set such that a thickness of at least a mounting
portion of the bumper which is to be mounted to a vehicle body and which extends
laterally from a central portion of the vehicle body is larger than a thickness of a
bumper main portion excluding said mounting portion, the gate opening into the
mounting portion forming area; and a second step of injecting a core forming material.
-4-

thereby allowing said core forming material to flow into said outer layer forming
material existing in said gate and the cavity, while allowing the outer layer and core
forming materials to flow into said cavity; wherein the injection speed of said core
forming material in said second step is higher than the injection speed of said outer
layer forming material in said first step.
If the volume of the mounting portion forming area of the cavity is set in the
above-described manner, the resistance to the flowing of the outer layer forming
material in the mounting portion forming area is alleviated, leading to an enhanced
capability to distribute the material into such area in a lengthwise direction of the
cavity. This results in a decreased

difference between the time taken for the outer layer forming
material to reach a central end area of the cavity nearer to
the mounting portion forming area to stop its flowing and the
time taken for the outer layer forming material to reach a
lengthwise opposite end areas remoter from the mounting portion
forming area to stop its flowing. Thus, it is possible to allow
the core forming material to flow substantially uniformly into
the outer layer forming material in the central end area and
the lengthwise opposite end areas to produce a high quality
bumper having a sandwich structure in its entirety.
The above and other objects, features and advantages of
the invention will become apparent from the following
description of a preferred embodiment taken in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig.l is a perspective view of a bumper;
Fig.2 is a sectional view in Fig.l;
Fig. 3 is a vertical sectional view of an inj ection molding
apparatus;
Fig.4 is a view for illustrating a first step;
Fig.5 is a view for illustrating a second step;
Fig.6 is a view for illustrating a third step;
Fig. 7 is a graph illustrating the relationship between
the injection time and the injection speed in an embodiment
of the present invention; and

Fig, 8 is a sectional view taken along a line 8-8 in Fig. 3,
illustrating the flowing of an outer layer forming material.
DETAILED DESCIPTION OF THE PREFERRED EMBODIMENT
The present invention will now be described by way of
preferred embodiments with reference to the accompanying
drawings.
Referring to Fig.l, a bumper 3 made of a synthetic resin
and having a sandwich structure is mounted to a front portion
of a vehicle body 2 of a vehicle 1. The sandwich structure is
comprised of a core 4 and an outer layer 5 covering the core
4, as shown in Fig.2. The bumper 3 has a band-like portion 3a
for mounting to the vehicle body 2, and extending laterally from
a central portion of the vehicle body A. This mounting portion
3a forms a substantially one third of a rear edge of a front
upper portion of the bumper 3 and has a wall thickness ti which
is larger than a wall thickness t2 of a main bumper portion 3b
excluding the mounting portion 3a. For example, a relation,
ti > 1.5 t2 is established between both the wall thicknesses
ti and t2.
The mounting portion 3a is mounted at one end of a steel
beam a by a plurality of clips b, and the other end of the beam
a is mounted to the vehicle body 2. Therefore, it is effective
to increase the wall thickness ti of the mounting portion 3a
for enhancing the mounting strength of the bumper 3.
The core 4 is formed from a main material which is produced
by pulverizing a recovered bumper which is formed using a
7

polypropylene (PP) modified by an ethylene propylene rubber
(EPR) and which has a thermo-setting synthetic resin on a surface
thereof. The outer layer 5 is formed from a main material which
is a polypropylene modified by an ethylene-propylene rubber.
Referring to Fig. 3, an inj ection molding apparatus 6 used
for producing the bumper 3 includes a first injection unit 10
having a screw 7 to inject an outer layer forming material, a
second injection screw 10 having a screw to inject a core forming
material, a nozzle 11 which connects both the injection units
8 and 10 to each other, a hot runner block 12 connected to the
nozzle 11, and a split metal mold 13 detachably mounted to the
hot runner block 12. The metal mold 13 is comprised of a
stationary die 13i mounted on the hot runner block 12, and a
plurality of movable dies 132 and 133 which are movable toward
and from the stationary die 13i.
A supply passage 14 in the nozzle 14 communicates with
a plurality of gates 16 in the metal mold 13 through a hot runner
15. Each of the gates 16 communicates with a mounting portion
forming area 17a in a bumper forming cavity 17. The mounting
portion forming area 17a has a volume which is set so that the
thickness ti of the mounting portion 3a is larger than the
thickness t2 of the bumper main portion 3b. In Figures, Hi is
a bumper heater, and H2 is a cartridge heater.
A hollow outer needle 18 and a solid inner needle 19 are
disposed concentrically within the nozzle 11. In the outer
needle 18, a valve portion 20 at a tip end is opposed to the
9

supply passage 14, and a piston 21 is provided at a base end
and slidably received in a cylinder 22. The piston 21 and the
cylinder 22 constitute a supply passage opening/closing
mechanism 23, In the inner needle 19, a valve portion 24 at
a tip end is opposed to a valve bore 25 defined in the valve
portion 20 of the outer needle 18, and a piston 26 is provided
at a base end and slidably received in a cylinder 27 defined
at the base end of the outer needle 18. The piston 26 and the
cylinder 27 constitute a valve bore opening/closing mechanism
28.
The outer needle 18 has a tapered outer peripheral surface
connected to the valve portion 20, and an outer passage 29 is
defined between the tapered outer peripheral surface and an
inner peripheral surface of the nozzle 11. The outer passage
29 is adapted to communicate at one end thereof with the supply
passage 14 and at the other end thereof with the first injection
unit 8 through a through-hole 30 in the nozzle 11. The outer
needle 18 has a straight outer peripheral surface at its base
end, so that the through-hole 30 can be closed by such outer
peripheral surface.
The inner needle 19 has a tapered outer peripheral surface
connected to the valve portion 24 thereof, and an inner passage
31 is defined between such tapered outer peripheral surface and
the inner peripheral surface of the outer needle 18. The inner
passage 31 is adapted to communicate at one end thereof with
the valve bore 25 and at the other end thereof with the second
^

injection unit 10 through through-holes 32 and 33 in the nozzle
11. The inner needle 19 has a straight outer peripheral surface
at its base end, so that the through-hole 32 can be closed by
such outer peripheral surface.
A specified example for producing the bumper 3 using the
injection molding apparatus 6 will be described below.
Referring to Figs.l and 2, the dimensions of portions of
the bumper 3 are as follows: On the basis of the vehicle body
2, the lateral length c = 1700 mm; the longitudinal length d
= 550 mm, the height ^ = 300 mm; the lateral length £ of the
mounting portion 3a = 1200 ram; the longitudinal length g; = 40
mm; the thickness ti = 6 mm; and the thickness ta = 4 mm. A
relation, ti = 1.5 ts is established between both the thicknesses
ti and t2.
The dimensions of portions of the cavity 17 are determined
depending upon the shape of the bumper 3. In this case, the
number of the gates 16 is three; the diameter h of the gate 16
=1.5 mm; the lateral length k of the hot runner 15 = 900 mm;
and the length m between a center line of the supply passage
14 and the left and right ends of the hot runner 15 = 450 mm.
A. Preparation of core forming material
A recovered bumper molded using a polypropylene modified
by an ethylene-propylene rubber and having a two-pack urethane
coating on a surface thereof was selected. The composition of
the recovered bumper is as follows:
|o

Polypropylene 64 % by weight
Ethylene-propylene rubber 28 % by weight
Talc 7 % by weight
Coating 1 % by weight
The recovered bumper was thrown into a pulverizer and
pulverized therein. Then, the pulverized material was thrown
into and molten and kneaded in a granulator. The resulting
molten/kneaded material was passed through a filter of 80 to
100 mesh, whereby large particles were removed. Thereafter,
the molten/kneaded material was passed through a capillary
having an inside diameter of 1 mm to form a linear material.
The linear material was cut into a length of 1 to several mm
to provide a pellet-like core forming material.
B. Preparation of outer layer forming material
A mixture including
Polypropylene 63 % by weight
Ethylene-propylene rubber 30 % by weight
Talc 7 % by weight
to provide the same composition as the recovered bumper (however,
the coating is excluded) was thrown into the granulator and
subjected to the same procedure as in the above-described item
A to produce a pellet-like outer later forming material.
C. Production of bumper
(i) In Fig. 3, the outer layer forming material was placed into
the first injection unit 8 and maintained in a molten state of
210°C. The core forming material was placed into the second
1/

injection unit 10 and maintained in a molten state of 200°C.
The preheating temperatures of the stationary die 13i and the
movable dies 132 and 133 are 40°C and 50°C, respectively.
(ii) At a first step, in a condition in which the outer passage
29 was in a connected state and the inner passage 31 was in a
disconnected state, the outer layer forming material Mi was
injected into the bumper forming cavity 17 through the supply
passage 14, the hot runner 15 and the gates 16 under operation
of the first injection unit 8, as shown in Fig.4.
(iii) At a second step, a portion of the outer passage 29
adjacent the supply passage 14 was throttled by the valve portion
20 under operation of the first injection unit 8, as shown in
Fig.5. In a condition in which the inner passage 31 was in a
connected state, the core forming material Ma was injected under
operation of the second injection unit 10, whereby the core
forming material M2 is allowed to flow into the outer layer
forming material Mi in the supply passage 14, the hot runner
15, the gates 16 and the cavity 17, and the outer layer and core
forming materials Mi and M2 are allowed to flow within the cavity
17. Then, the operation of the second injection unit 10 was
stopped.
(iv) At a third step, in the condition in which the outer
passage 29 was in the connected state and the inner passage 31
was in the disconnected state, the outer layer and core forming
materials Mi and M2 of a double structure existing in the supply
|2^

passage 14, the hot runner 15 and the gates 15 were pushed into
the cavity 8 by the outer layer forming material under operation
of the first injection unit 8, as shown in Fig. 6, thereby forming
a core 4 and an outer layer 5. Then, the operation of the first
injection unit 8 was stopped.
(v) The metal mold 13 was moved away from the hot runner block
12 and then, the mold opening was conducted to provide a bumper
3.
After the above-described producing process, the outer
layer forming material Mi is retained in a molten state within
the hot runner 15 and hence, the molding of the bumper 3 can
be carried out continuously.
Table 1 shows the injection time and the injection speed
for the outer layer forming material Mi and the core forming
material Ma relating to the first, second and third steps in
the production of the bumper 3.
Table 1

Outer layer forming material Core forming material

Injection
speed (mm/sec) Injection
time (sec) Injection speed
(mm/sec) Injection
time (sec)
First
step Va 46.0 5.3

Vb 24.7 0.24


Second
step Vb 24.7 1.78 Ve 48.4 4.3

Vc 15.1 1.79




Vd 9.7 0.79



Third
step Vc 9.7 1.6 "* "
Fig.7 is based on Table 1 and shows the relationship
between the injection time and the injection speed. In this
/^

case, the injection speed was controlled at two stages for the
outer layer forming material Mi at the first step; at one stage
for the core forming material M2 and at three stages for the
outer layer forming material Mi at the second step; and at one
stage for the outer layer forming material Mi at the third step.
If the volume of the mounting portion forming area 17a
of the cavity 17 is set so that it is increased in accordance
with the thickness ti of the mounting portion 3a, as described
above, the resistance to the flow of the outer layer forming
material in the mounting portion forming area 17a is decreased
and hence, the capability to distribute the material in a
lengthwise direction of the cavity in the area 17a is enhanced,
as shown in Fig.8. As a result, a difference is decreased
between the time taken for the outer layer forming material Mi
to reach a central end area 17b of the cavity 17 nearer the
mounting portion forming area l7a to become stopped in flow as
shown in the cavity in Figs . 1 and 2 and the time taken for the
outer layer forming material Mi to reach lengthwise opposite-end
areas 17c of the cavity 17 remoter from the mounting portion
forming area l7a to become stopped in flow as shown in the bumper
3 in Fig.l. Thus, the core forming material M2 can be allowed
to flow substantially equally into the outer layer forming
material Mi in the central end area 17b and in the lengthwise
opposite-end areas 17c.
The bumper 3 produced in the above manner was excellent
in quality and had a sandwich structure in its entirety. For
IH

the bumper 3, the filling rate of the core forming material
prepared from the recovered bumper is high, which is effective
for providing a reduction in production cost of the bumper 3
and a resources saving.
If the injection speed Ve of the core forming material
M2 at the second step is set higher than injection speeds Va
and Vb of the outer layer forming material Mi at the first step,
it is possible to allow the a front portion of the core forming
material as viewed in a flowing direction to flow into a front
portion of the outer layer forming material as viewed in a
flowing direction, thereby forming the bumper 3 into near a more
perfect sandwich structure. In this case, if the injection
speeds Vb, Vc and Vd of the outer layer forming material Mi are
set lower than the highest injection speed Va at the first step,
the different between the injection speeds of both the materials
Ml and M2 can be increased even if the injection speed Ve of
the core forming material M2 is less high.
If the injection speed Vd of the outer layer forming
material Mi at the third step is set at a value equal to or lower
than the final injection speed of the outer layer forming
material Mi at the second step, e.g., at Vd in the production
of this bumper 3, the outer layer forming material Mi cannot
flow into the core forming material M2 at the third step, whereby
the gate communication portion of the bumper 3 can be formed
from only the outer layer forming material Mi.
/3'

For comparison, to produce a bumper 3 including amounting
portion 3a having a thickness ti equal to a thickness tz of a
bumper main portion 3b, an attempt was made to produce a bumper
as a comparative example under the same conditions as those
described above, using a metal mold 13 having a narrower mounting
portion forming area 17a. As a result, the following
disadvantage was encountered: the core forming material M2
failed to flow into the outer layer forming material Mi in the
central end area 17b, and the core forming m.aterial M2 broke
through the outer layer forming material Mi to emerge onto the
surface of the outer layer forming material Mi.
63 % by weight
30 % by weight
7 % by weight
1 g/100g
1 g/lOOg
3 g/lOOg
3 g/lOOg
The outer layer forming material Mi which may be used for
the production of the bumper 3 includes the following examples:
[Composition example 1]
Polypropylene
Ethylene-propylene rubber
Talc
Weather-resistant stabilizer
Ultraviolet light absorber
Carbon black (pigment)
Coatability enhancing modifier
[Composition example 2]
Polypropylene 60 % by weight
Ethylene-propylene rubber 30 % by weight
Talc 10 % by weight
/4

Weather-resistant stabilizer 1q/100f
Ultraviolet light absorber 1 g/toOg
Carbon black (pigment) 3 g/lOOg
Coatability enhancing modifier 39/1009
The core forming material M2 which may be used for the
production of the bumper 3 includes the following examples:
(1) A forming material consisting of 93 % by weight of a
combination of a polypropylene and 7 % by weight of talc. In
this case, the polypropylene contains 30 % by weight of a
ethylene-propylene based rubber simultaneously synthesized at
a step of polymerization of the polypropylene. The talc was
added to the polypropylene at a final step of the synthesis of
the polypropylene. This forming material is more inexpensive
than a forming material containing a polypropylene and an
ethylene-propylene rubber separately produced and blended.
(2) A forming material containing the following components:
Polypropylene 60 % by weight
Ethylene-propylene rubber 30 % by weight
Talc 10 % by weight
The entire upper edge of the bumper 3 including the
mounting portion 3a may be thickened to have a thickness ti.
/7


1. A process for producing a bumper for a vehicle, which is made
of a synthetic resin and has a sandwich structure comprised of
a core and an outer layer covering said core, said process
comprising:
a first step of injecting an outer layer forming material
into a bumper forming cavity through a gate in a metal mold,
in which the volume of a mounting portion forming area of the
bumper forming cavity is set such that a thickness of at least
a mounting portion of the bumper which is to be mounted to a
vehicle body and which extends laterally from a central portion
of the vehicle body can be larger than a thickness of a bumper
main portion excluding said mounting portion, said gate opening
into said mounting portion forming area; and
a second step of injecting a core forming material, thereby
allowing said core forming material to flow into said outer layer
forming material existing in said gate and said cavity, while
allowing said outer layer and core forming materials to flow
into said cavity.
2,The process for producing a bumper for a vehicle as claimed in
claim 1, wherein the injection speed of said core forming
material at said second step is higher than the injection speed
of said outer layer forming material at said first step.

A process for producing a bumper for a vehicle
substantially as hereinbefore described with reference to the
accompanying drawings.


Documents:

1932-mas-1996 abstract duplicate.pdf

1932-mas-1996 abstract.pdf

1932-mas-1996 claims duplicate.pdf

1932-mas-1996 claims.pdf

1932-mas-1996 correspondence - others.pdf

1932-mas-1996 correspondence - po.pdf

1932-mas-1996 description (compelet) duplicate.pdf

1932-mas-1996 description (compelet).pdf

1932-mas-1996 drawings.pdf

1932-mas-1996 from - 2.pdf

1932-mas-1996 from - 26.pdf

1932-mas-1996 from - 4.pdf

1932-mas-1996 from - 6.pdf

1932-mas-1996 petition.pdf


Patent Number 197977
Indian Patent Application Number 1932/MAS/1996
PG Journal Number 30/2009
Publication Date 24-Jul-2009
Grant Date
Date of Filing 01-Nov-1996
Name of Patentee HONDA GIKEN KOGYO KABUSHIKI KAISHA
Applicant Address 1-1, MINAMI AOYAMA 2-CHOME, MINATO-KU, TOKYO
Inventors:
# Inventor's Name Inventor's Address
1 ATSUSHI TAKEUCHI C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO, 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA,
2 HITOSHI OHGANE C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO, 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA,
3 MINORU MAKUTA C/O KABUSHIKI KAISHA HONDA GIJUTSU KENKYUSHO, 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA,
PCT International Classification Number B29C45/16
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA