Injection molded vehicle lamp and method of making

A vehicle lamp includes an injection-molded lamp body having a wall surface portion of substantially uniform thickness, and a gate mark and a rib extending along the wall surface portion from the gate mark, each formed in the wall surface portion of the lamp body.

This application claims the benefit of Japanese patent Application No. Hei. 
9-61790, filed Feb. 28, 1997, which is hereby incorporated by reference. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a vehicle lamp having an injection-molded 
lamp body. 
2. Discussion of the Related Art 
A lamp body of a vehicle lamp is generally formed by injection molding. To 
reduce weight and cost, it is preferable to form the lamp body as thin as 
possible. Therefore, the lamp body is usually formed with a wall surface 
portion of the lamp body having a substantially uniform thickness. 
In a large vehicle lamp, however, the lamp body also becomes fairly large. 
In molds used for injection-molding the lamp body, molten resin cannot be 
spread to every corner in a cavity, so that failures in injection-molding, 
such as surface sinkage, nesting, etc., frequently occur. 
To prevent such failures, molds having a plurality of gates are usually 
employed. These molds, however, have complicated structures, and are 
expensive because of complex machining involved. Particularly when molds 
use a hot runner, a plurality of hot tips are required corresponding to 
each of the gates. Accordingly, the cost of the molds is very high. 
SUMMARY OF THE INVENTION 
Accordingly, the present invention is directed to a vehicle lamp that 
substantially obviates one or more of the problems and limitations of the 
related art. 
An object of the present invention is to provide a vehicle lamp having a 
lamp body in which failures in injection-molding can be reduced without 
increasing the cost of molds. 
Additional features and advantages of the present invention will be set 
forth in the description which follows, and will be apparent from the 
description, or may be learned by practice of the invention. The 
objectives and other advantages of the invention will be realized and 
attained by the structure and process particularly pointed out in the 
written description as well as in the appended claims. 
To achieve these and other advantages and in accordance with the purpose of 
the present invention, as embodied and broadly described, in accordance 
with a first aspect of the present invention there is provided a vehicle 
lamp, including an injection-molded lamp body having a wall surface 
portion of substantially uniform thickness, and a gate mark and a rib 
extending along the wall surface portion from the gate mark, each formed 
in the wall surface portion of the lamp body. 
In another aspect of the present invention, there is provided a vehicle 
lamp, including an injection-molded lamp body having a wall surface 
portion of substantially uniform thickness; and a gate mark and a rib 
extending along the wall surface portion from the gate mark, each formed 
in the wall surface portion of the lamp body, wherein an opening portion 
for attachment of a light bulb is formed in the wall surface portion, and 
wherein an end portion of the rib surrounds the opening portion. 
In another aspect of the present invention, there is provided a vehicle 
lamp, including an injection-molded lamp body having a wall surface 
portion of substantially uniform thickness, and a gate mark and a rib 
extending along the wall surface portion from the gate mark, each formed 
in the wall surface portion of the lamp body, wherein an opening portion 
for attachment of a light bulb is formed in the wall surface portion, 
wherein an end portion of the rib surrounds the opening portion, wherein a 
height of the rib is not smaller than a thickness of the wall surface 
portion, wherein the wall surface portion includes a first wall surface 
portion located on a front side relative to a direction of releasing of a 
mold, and a second wall surface portion located in a rear side relative to 
the direction of releasing of the mold, wherein the gate mark is formed in 
the first wall surface portion, and wherein the rib extends from the first 
wall surface portion to the second wall surface portion. 
It is to be understood that both the foregoing general description and the 
following detailed description are exemplary and explanatory and are 
intended to provide further explanation of the invention as claimed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Reference will now be made in detail to the preferred embodiments of the 
present invention, examples of which are illustrated in the accompanying 
drawings. 
FIG. 1 shows a perspective view of a vehicle lamp of the present invention; 
FIG. 2 is a perspective view showing a lamp body; and FIG. 3 is a 
sectional view along line III--III of FIG. 2. 
As shown in FIG. 1, a lamp 10 is a head lamp for a left front portion of a 
vehicle body. A first lamp chamber 10A and a second lamp chamber 10B are 
adjacent to each other and are defined by a lens 12 and a lamp body 14 
located behind the lens 12. 
Reflectors 20A and 20B are provided in the lamp chambers 10A and 10B, 
respectively, and light bulbs 16A and 16B and shades 18A and 18B are 
attached to the reflectors 20A and 20B, respectively. The shades 18A and 
18B are in front of the light bulbs 16A and 16B, respectively. The 
reflectors 20A and 20B are tiltably supported by the lamp body 14. 
The lens 12 inclines backward and outward in a direction across the 
vehicle. The reflector 20B of the second lamp chamber 10B is wider and 
deeper compared to the reflector 20A of the first lamp chamber 10A. 
As shown in FIG. 2, the lamp body 14 is injection-molded out of resin and 
includes a wall surface portion 22 serving as a back wall of the first and 
second lamp chambers 10A and 10B, and an outer circumferential groove 
portion 24 for securing an outer circumferential edge portion of the lens 
12. The wall surface portion 22 and the outer circumferential groove 
portion 24 have substantially uniform thicknesses. 
The wall surface portion 22 has a rear wall surface portion 22B in the 
second lamp chamber 10B located generally backward compared to a rear wall 
surface portion 22A in the first lamp chamber 10A because of the lateral 
inclination of the lens 12 and the size proportions of the reflectors 20A 
and 20B. Further, the two rear wall surface portions 22A and 22B are 
connected to each other through an intermediate wall surface portion 22C 
extending forward and backward. 
An opening portion 22Aa, for attaching a relatively small bulb 16A, is 
formed in the rear wall surface portion 22A. An opening portion 22Ba, for 
attaching a relatively large bulb 18A, is formed in the rear wall surface 
portion 22B. A gate mark 26, formed of a resin remaining in a gate 110 
(described below) during injection-molding of the lamp body 14, is formed 
as a pin-shape in an inner surface of a corner portion in the rear wall 
surface portion 22A on the intermediate wall surface portion 22C. Further, 
a rib 28, extending from the gate mark 26 to the rear wall surface portion 
22B through the intermediate wall surface portion 22C, is formed in the 
wall surface portion 22, expanding on the inside of the wall surface 
portion 22. 
The rib 28 is formed as a columnar boss portion 28a in a connecting portion 
between the gate mark 26 and the inner surface of the corner portion of 
the rear wall surface portion 22A. The rib 28 also is formed as a 
sectionally semicircular rib body 28b on the respective inner surfaces of 
the intermediate wall surface portion 22C and the rear wall surface 
portion 22B, such that a part of the boss portion 28a extends forward. As 
shown in FIG. 3, the height X of the rib body 28b is larger than the 
thickness Y of the wall surface portion 22. 
As shown in FIG. 2 and FIG. 3, the rib body 28b extends straight backward 
in the inner surface of the intermediate wall surface portion 22C and 
extends straight outward in the direction of the vehicle width in the 
inner surface of the rear wall surface portion 22B. The end portion of the 
rib body 28b is formed annularly surrounding the bulb attachment opening 
portion 22Ba. 
FIG. 4 is a side sectional view showing a mold 100 for injection-molding 
the lamp body 14. The mold 100 has a hot runner. A cavity 106 
corresponding to a shape of the lamp body 14 is formed between a fixed 
mold 102 and a movable mold 104. A hot tip 108 for heat-retaining the 
molten resin to prevent its solidification before injection is provided in 
the fixed mold 102. The gate 110 is formed in the forward end portion of 
the hot tip 108 connecting with the cavity 106. 
A portion 106a of the cavity 106 is used for forming a general portion of 
the wall surface portion 22 and an outer circumferential groove portion 24 
in the lamp body 14 having a substantially constant thickness because the 
wall surface portion 22 and the outer circumferential groove portion 26 
have a substantially uniform thickness, whereas a portion 106b for forming 
the rib 28 has a partially widened thickness. 
The gate mark 26 created at the time of injection molding and the rib 28 
extending from the gate mark 26 are formed in the substantially uniform 
thick wall surface portion 22. That is, a large part of the molten resin 
injected from the gate 110 into the cavity 106 flows in the portion 106b 
to form the rib 28, which has a relatively large sectional area, before 
the remainder of the molten resin flows in the portion 106a to form the 
general portion of the wall surface portion 22. As described above, the 
mold 100 and portion 106b that functions as a path for the molten resin 
are designed so that the length of flow of the molten resin is long 
compared to the conventional mold 100' in which the rib 28 is not formed, 
as shown in FIG. 5. Accordingly, the molten resin can easily spread to 
every corner in the cavity 106. As a result, the lamp body 14 can be 
formed with no defects due to molding even if the number of gates 110 is 
reduced compared with the conventional mold 100'. 
Accordingly, occurrences of failures in molding can be reduced without 
increasing the cost of the molds. 
Further, the presence of the rib 28 improves the fluidity of the molten 
resin during injection molding. Accordingly, the thickness of the wall 
surface portion 22 can be reduced. Furthermore, improvement in the 
strength of the lamp body 14 can be attained by forming the rib 28 in the 
wall surface portion 22. 
Also, the wall surface portion 22 includes two stages (front and rear) so 
that the gate mark 26 is formed in the rear wall surface portion 22A 
located in front relative to the direction of releasing of the molds, 
whereas the opening portion 22Ba for attaching a relatively large bulb is 
formed in the rear wall surface portion 22B, which is located in the rear 
side. Accordingly, it is generally difficult to spread high-temperature 
molten resin to the rear portion of the bulb-attachment opening portion 
22Ba located far from the gate 110 in the cavity 106 when the molten resin 
is injected into the cavity 106. 
Therefore, the conventional mold 100' shown in FIG. 5 is designed so that a 
gate 110' is formed in a portion used for forming the rear wall surface 
portion 22B located in the rear side. In this case, not only is it 
necessary to machine the gate 110', but an additional hot tip 108' is 
required with the addition of the gate 110', and the cost of the mold 100' 
becomes very high. 
The rib 28 extending from the gate mark 26 to the rear wall surface portion 
22B through the intermediate wall surface portion 22C has an end portion 
formed annularly to surround the bulb-attachment opening portion 22Ba and 
is formed in the wall surface portion 22. Accordingly, the 
high-temperature molten resin can be spread to the rear portion of the 
bulb-attachment opening portion 22Ba in the cavity 106. As a result, 
occurrences of failures in molding can be effectively reduced. 
Furthermore, because the rib 28 is expanding toward the inner surface of 
the wall surface portion 22, the formation of the rib 28 does not hinder 
provision of items, such as structures for attachment of the lamp 10 to 
the vehicle body, aiming mechanisms, etc., in the outer surface side of 
the lamp body 14. 
Further, because the rib body 28b of the rib 28 has a substantially 
circular arc-like sectional shape and because the height X of the rib body 
28b is larger than the thickness Y of the wall surface portion 22, a path 
for the molten resin to easily flow through exists in the cavity 106. 
Furthermore, because the gate mark 26 is formed in the corner portion in 
the wall surface portion 22A on the intermediate wall surface portion 22C 
side, the mold 100 can have the molten resin injected straight from the 
gate 110 into the rib-forming portion 106b. As a result, there is a path 
for the molten resin to flow through more easily. Furthermore, because the 
connection portion of the rib 28 with the gate mark 26 is formed as the 
columnar boss portion 28a, the injection of the molten resin from the gate 
110 into the rib-forming portion 106b can occur more smoothly. 
In the vehicle lamp 10 of the present invention, a gate mark 26 generated 
at the time of injection molding and a rib 28 extending from the gate mark 
26 along a substantially uniform thick wall surface portion 22 of a lamp 
body 14 are formed in the wall surface portion 22. 
That is, with respect to the fluidity of molten resin in the cavity 106 in 
the molds, a large sectional area is generally better than a small 
sectional area. Accordingly, a large part of molten resin injected from 
the gate into the cavity 106 flows in the rib-forming portion of the wall 
surface portion 22 in the cavity 106 before the remaining part of the 
molten resin flows in the general portion-forming portion of the wall 
surface portion 22. In the molds where the rib-forming portion functions 
as a path of molten resin, the length of flow of molten resin can be large 
compared with conventional molds, where the rib 28 is not formed, so that 
the molten resin can be easily spread to every corner in the cavity 106. 
Accordingly, the lamp body 14 can be molded without occurrence of a 
failure in molding even if the number of gates is reduced compared with 
the conventional molds. 
Further, the fluidity of the molten resin at the time of injection molding 
is improved by the presence of the rib 28. Accordingly, the thickness of 
the wall surface portion 22 of the lamp body 14 can be reduced. 
Furthermore, improvement in the strength of the lamp body results from the 
rib 28 being formed in the wall surface portion 22. 
In the lamp body 14, a bulb-attachment opening portion 22Ba having a 
relatively large size is generally formed in the wall surface portion 22, 
but a weld line caused by a confluence of molten resin at the time of 
injection molding is formed in the surroundings of the bulb-attachment 
opening portion 22Ba, so that the strength of the lamp body is likely to 
be lowered. If the bulb-attachment opening portion 22Ba is located far 
from the gate mark 26, a failure in molding, such as nesting, is likely to 
occur in the weld line portion. This failure occurs because the 
temperature of molten resin has already been lowered in the rear portion 
of the bulb-attachment opening portion 22Ba in the cavity 106 and the 
fluidity of the molten resin is low. 
In this case, therefore, if the end portion of the rib 28 is formed so as 
to surround the bulb-attachment opening portion 22Ba, high-temperature 
molten resin can be spread to the rear portion of the bulb-attachment 
opening portion 22Ba in the cavity 106. Accordingly, occurrences of 
failures in molding in the weld line-forming portion can be reduced. 
The word "rib" is not limited to any specific shape. The rib 28 may expand 
toward the inner surface side of the wall surface portion 22 or it may 
expand toward the outer surface of the wall surface portion 22 or toward 
both the inner and outer surfaces of the wall surface portion 22. The word 
"rib" is not limited specifically so long as the rib extends over a 
predetermined length along the wall surface portion 22 from the gate mark 
26 of the wall surface portion 22. Since structures for attaching the lamp 
10 to the vehicle body, such as aiming mechanisms, are usually provided in 
the outer surface side of the lamp body 14, the rib 28 is preferably 
formed expanding toward the inner surface of the wall surface portion 22. 
Further, the sectional shape of the rib 28 may be a number of sectional 
shapes, such as rectangular or wedge-like. The sectional shape is 
preferably a circular arc. The purpose of forming the rib 28 is to provide 
a path for the molten resin to flow easily. It is therefore preferable 
that the path is as thick as possible without increasing the contact area 
between the path and the molten resin. The substantially circular arc-like 
shape is therefore preferred. 
Furthermore, the words "height of the rib" is not limited specifically. It 
is preferable, from the point of view of providing the path in which the 
molten resin flows easily, that the height of the rib 28 is not smaller 
than the thickness of the wall surface portion 22. 
In a vehicle lamp 10 having two lamp chamber portions offsetting in the 
front and rear, the wall surface portion of the lamp body is usually 
formed to have first and second wall surface portions located in the front 
and rear sides with respect to the direction of releasing of the molds, 
respectively. Further, in the mold 100 for forming the lamp body 14, the 
gate 110 position is usually in the first-wall-surface forming portion in 
the mold 100 (of course, the gate mark 26 is formed in the first wall 
surface portion). In this case, the path in which molten resin flows 
easily can be secured if the rib 28 is formed extending from the first 
wall surface portion to the second wall surface portion. 
In this case, when the bulb-attachment opening portion 22Ba is formed in 
the second wall surface portion, it is particularly effective that the end 
portion of the rib 28 is formed surrounding the bulb-attachment opening 
portion 22Ba because the bulb-attachment opening portion 22Ba is located 
so as to be far from the gate mark 26. 
Further, if the gate mark 26 is formed in the second wall surface portion 
side corner portion of the first wall surface portion, molten resin can be 
injected straight from the gate to the rib-forming portion. Accordingly, a 
path for the molten resin to flow through more easily exists. 
While the invention has been described in detail and with reference to 
specific embodiments thereof, it will be apparent to one skilled in the 
art that various changes and modifications can be made therein without 
departing from the spirit and scope thereof. Thus, it is intended that the 
present invention cover the modifications and variations of this invention 
provided they came within the scope of the appended claims and their 
equivalents.