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HEAT RESISTANT PLASTIC LAMP COMPONENTS AND METHODS OF
FORMING
BACKGROUND OF THE INVENTION
This invention relates generally to plastic components for lamps, and more
particularly to plastic headlamp components formed from multiple resins having
different heat distortion temperatures.
A variety of thermoplastic materials are available in the marketplace for use in
automotive lighting systems. A basic criterion for material selection in lighting
systems is the heat distortion temperature of the material. In general, the higher the
heat distortion temperature, the higher the cost of the thermoplastic. The heat
distortion temperature is the temperature at which the components begin to soften and
distort under a specified force. If the component is a headlamp reflector, the
temperature experienced by the reflector can be affected by design considerations
such as reflector diameter, bulb diameter, bulb depth, lens depth, spacer depth and
reflector depth.
One problem that has been observed is that some metallized thermoplastic lamp
components, when heated to temperatures close to their heat distortion temperature
become hazy in appearance which affects the performance and/or aesthetics of the
lamp component. Also, some unmetallized thermoplastics can distorted unacceptably
when heated above their heat distortion temperature. Using thermoplastics having
higher heat distortion temperature characteristics to form the entire component can
sometimes alleviate the problem. However, higher heat distortion temperature
materials are generally more expensive and can exhibit undesirable flow
characteristics which can affect molding operations.
BRIEF DESCRIPTION OF THE INVENTION
In one aspect, a molded plastic lamp component is provided. The lamp component
includes a first portion formed from a first material having a first heat distortion
temperature, and a second portion formed from a second material having a second
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heat distortion temperature. The first heat distortion temperature is higher than the
second heat distortion temperature.
In another aspect, a method of fabricating a light component is provided. The method
includes forming a first portion of the component from a first material having a first
heat distortion temperature, and forming a second portion of the component from a
second material having a second heat distortion temperature. The first heat distortion
temperature is higher than the second heat distortion temperature.
In another aspect, a method of fabricating a composite lamp component is provided.
The method including forming a first portion from a.first material having a first heat
distortion temperature, and molding a second portion around the first portion from a
second material having a second heat distortion temperature to form a composite
material lamp component. The first heat distortion temperature is higher than the
second heat distortion temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an illustration of a automotive headlamp reflector in accordance with an
embodiment of the present invention.
Figure 2 is an illustration of a automotive headlamp reflector in accordance with
another embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Plastic automotive headlamp components formed from multiple plastic resins having
different heat distortion temperatures are described below in detail. The lamp
components include a portion formed from a material having a higher heat distortion
temperature (HDT) than the material used to form the remaining portions of the lamp
component. The areas of the lamp component that are exposed to high temperatures
caused by convection impingement of hot air from the lamp bulb and/or a surrounding
bulb shield, are formed from the higher HDT material. The remaining areas of the
lamp component are formed from materials with lower HDT materials to reduce costs
and to facilitate molding the component.
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The lamp components can be formed by an insert molding process where a two
component part is produced by a two step process. The first step is the production of
an insert from the higher HDT material. The second step includes placing the insert
in a mold and the lower HDT material is then molded on top of or adjacent to the
insert to produce a lamp component made of two different materials. The lamp
components can also be formed by a two-shot molding process where both the high
HDT and low HDT materials are both injected in the same molding cycle into one
mold having the capability to reconfigure from one mold cavity configuration to
another cavity configuration. Although automotive lamp components are described,
other types of lamp components, other than automotive type lamps, can by formed in
a similar manner.
Referring to the drawings, Figure 1 is an illustration of a automotive headlamp
reflector 10. In an exemplary embodiment, reflector 10 includes a first portion 12 and
a second portion 14. First portion 12 extends from a top side 16 of reflector 10 at
least partially to a bottom side 18 of reflector 10. A bulb opening 20 extends through
first portion 12. Second portion 14 makes up the remainder of reflector 10. First
portion 12 is formed from a first material and second portion 14 is formed from a
second different material. The HDT of the first material is higher than the HDT of the
second material. In one embodiment, the HDT of the first material is at least about
15°C higher than the HDT of the second material, in another embodiment, the HDT of
the first material is at least about 20°C higher than the HDT of the second material,
and in another embodiment, the HDT of the first material is at least about 25°C higher
than the HDT of the second material.
The majority of reflector 10, second portion 14, is formed from the lower HDT
material, for example, a thermoplastic material. Suitable thermoplastics include, but
are not limited to, polycarbonates, polyestercarbonates, polyetherimides, polyarylene
ethers, polyolefins, including polymethylene, polyethylene, and polypropylene,
polystyrene, acrylonitrylstyrene, butadiene, polyesters, including
polyethyleneterephthalate, polybutyleneterephthalate, and polypropyleneterephthalate,
polybutyleneterachlorate, and polyvinyl chloride, acrylics, including polymethyl
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methacrylate, acrylonitrile-butylacrylate-styrene polymers, amorphous nylon, and
blends of these materials with each other or other polymeric materials.
First portion 12 includes less than 50 percent of the surface area of reflector 10 and is
the minor portion of reflector 10. As explained above, first portion 12 is formed from
a material having a higher HDT than the material used to form second portion 14, for
example, thermoplastics, including polyether imides, polycarbonates, and
polyarylates, glass, thermosetting plastics, including acrylics ,epoxies and polyesters,
ceramics, and metals, including steel and aluminum alloys.
Reflector 10 can be formed by "two-component" molding methods, for example,
insert molding and two-shot molding. Using the insert molding process, first portion
12 is formed as an insert from the higher HDT material in a first mold. Specifically,
molten plastic is injected into the first mold under pressure, and then cooled to
solidify the plastic to form the insert. When metal is used to form the insert, the metal
insert is formed by any suitable method ,for example, stamping, casting, or the like.
The insert is then positioned in the final part mold and the lower HDT material used
to form second portion 14 is molded on top of or adjacent to the insert creating
reflector 10. Specifically, molten plastic material is injected into the final part mold
under pressure, and then cooled to solidify the plastic to form reflector 10.
Using the two-shot molding process in one embodiment, both the high HDT and low
HDT materials are both injected in the same mold having the capability to reconfigure
from one mold cavity configuration to another cavity configuration. Particularly, first
portion 12 is formed by injecting the high HDT material into the first mold cavity
configuration under pressure, then cooling the material. The mold is then
reconfigured to a second mold cavity configuration and the low HDT material is
injected into the second mold cavity and then cooled to form second portion 14 and
reflector 10.
The above described reflector 10 is formed from a relatively small amount of high
HDT material (first portion 12) and a relatively large amount of the lower HDT
material (second portion 14) which is less expensive than the high HDT material. The
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above described reflector 10 provides an economical solution to heat distortion and
hazing problems associated with high temperature air currents or direct thermal
radiation caused by the lamp bulb.
In an alternate embodiment, illustrated in Figure 2, a reflector 30 includes a first
portion 32, a second portion 34, and a third portion 36. First portion 32 extends from
a top side 38 of reflector 30 to a bottom side 40 of reflector 30. A bulb opening 42
extends through first portion 32. Second and third portions 34 and 36 make up the
remainder of reflector 30. First portion 32 is formed from a first material and second
and third portions 34 and 36 are formed from a second different material. The HDT
of the first material is higher than the HDT of the second material. In further alternate
embodiments, there are at least one additional portion formed from the higher HDT
material.
While the invention has been described in terms of various specific embodiments,
those skilled in the art will recognize that the invention can be practiced with
modification within the spirit and scope of the claims.
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WHAT IS CLAIMED IS:
1. A molded lamp component comprising:
a first portion formed from a first material having a first heat distortion temperature;
and
a second portion formed from a second material having a second heat distortion
temperature, said first heat distortion temperature greater than said second heat
distortion temperature.
2. A molded lamp component in accordance with Claim 1 wherein said first
material comprises at least one of a thermoplastic material, a thermosetting plastic
material, a ceramic material, and a metal material.
3. A molded lamp component in accordance with Claim 1 wherein said second
material comprises a thermoplastic material,
4. A molded lamp component in accordance with Claim 1 wherein a difference
between said first heat distortion temperature and said second heat distortion
temperature comprises at least about 20°C.
5. A molded lamp component in accordance with Claim 1 further comprising at
least one additional portion formed from said second material.
6. A molded lamp component in accordance with Claim 1 further comprising at
least one additional portion formed from the first material.
7. A method of fabricating a lamp component, said method comprising:
forming a first portion of the component from a first material having a first heat
distortion temperature; and
forming a second portion of the component from a second material having a second
heat distortion temperature, the first heat distortion temperature higher than the
second heat distortion temperature.
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8. A method in accordance with Claim 7 wherein forming a first portion of the
component comprises molding the first portion from the first material.
9. A method in accordance with Claim 6 wherein molding the first portion of the
component comprises:
injecting the first material into a first mold under pressure; and
cooling the first material to form the first portion.
10. A method in accordance with Claim 7 wherein forming a second portion of the
component comprises molding the second portion from the second material.
11. A method in accordance with Claim 10 wherein molding the second portion of
the component comprises:
positioning the first portion in a second mold;
injecting the second material into the second mold under pressure; and
cooling the second material to form the lamp component.
12. A method in accordance with Claim 8 wherein molding the first portion
comprises:
injecting the first material under pressure into a first cavity area of a mold;
cooling the first material to form the first portion;
realigning the mold to form a second cavity area in the mold surrounding the first
portion;
injecting the second material under pressure into the second cavity area to over-mold
the first portion; and
cooling the second material to form the lamp component.
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13. A method in accordance with Claim 7 wherein the first material comprises at
least one of a thermoplastic material, a thermosetting plastic material, a ceramic
material, and a metal material.
14. A method in accordance with Claim 7 wherein the second material comprises
a thermoplastic material.
15. A method in accordance with Claim 7 wherein a difference between the first
heat distortion temperature and the second heat distortion temperature comprises at
least about 20°C.
16. A method of fabricating a composite lamp component comprising:
forming a first portion from a first material having a first heat distortion temperature,
and
molding a second portion around the first portion from a second material having a
second heat distortion temperature to form a composite material lamp component, the
first heat distortion temperature higher than the second heat distortion temperature.
17. A method in accordance with Claim 16 wherein forming a first portion
comprises molding the first portion in a first mold, and said molding a second portion
comprises:
positioning the first portion in a second mold;
injecting the second material into the second mold under pressure; and
cooling the second material to form the lamp component.
18. A method in accordance with Claim 16 wherein molding the first part
comprises:
molding the first material in a first cavity area of a mold to form the first portion;
realigning the mold to form a second cavity area in the mold surrounding the first
portion;
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molding the second material in the second cavity area to form the lamp component.
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19. A method in accordance with Claim 16 wherein the first material comprises at
least one of a thermoplastic material, a thermosetting plastic material, a ceramic
material, and a metal material.
20. A method in accordance with Claim 16 wherein the second material comprises
a thermoplastic material.
21. A method in accordance with Claim 16 wherein a difference between the first
heat distortion temperature and the second heat distortion temperature comprises at
least about 20°C.

A molded plastic lamp component includes, in an exemplary embodiment, a first
portion formed from a first material having a first heat distortion temperature, and a
second portion formed from a second material having a second heat distortion
temperature. The first heat distortion temperature is higher than the second heat
distortion temperature.