Process for making a vehicle grille guard

The present invention provides a new and improved process of producing vehicle grille guards by gas-assisted injection molding and the grille guards produced thereby. The process includes injecting a plastic resin into a mold cavity in an amount less than the total volume of the mold cavity. An inert gas in then injected into a center portion of the cavity and a hollow gas channel extending throughout the center portion is formed, forcing the plastic resin to flow along an outer surface of the cavity.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to vehicle grille guards, and more 
particularly to a structural web automotive grille guard and a process for 
preparing the same. 
2. Discussion 
Current grille guards are typically made of a welded steel construction and 
are usually chrome plated to provide an attractive finish surface. 
However, such prior art steel grille guards are relatively heavy, which is 
highly undesirable. For example, heavy grille guards may cause the balance 
of the vehicle to be adversely affected which in turn can render steering 
more difficult. 
Further, such prior art steel grille guards tend to be relatively expensive 
as to material cost, in view of the steel and chrome coating materials. 
Additionally, the manufacturing and labor costs tend to be high, due for 
example, from the need for welding the grille to the vehicle frame or 
chassis. Yet another possible problem with chrome coated grille guards is 
the likelihood that the chrome will wear away over time leaving the steel 
exposed and subject to unsightly rust. 
In an apparent effort to address one or more of the perceived problems with 
steel grille guards, other prior art grille guards have been proposed 
which are formed from semi-rigid, self-skinning, foamed polyurethane with 
reinforcing metal strips, as in U.S. Pat. No. 5,215,343 or polycarbonate 
tubes as disclosed in U.S. Pat. No. 4,168,855. However, the use of 
self-skinning foaming material or certain thermoplastic resins presents 
problems with regard to strength and durability as compared to steel 
guards. 
Thus, there exists a need in the art to produce a vehicle grille guard that 
is lightweight, cost effective, and of high strength. The present 
invention provides a structural web injected plastic grille guard that can 
be produced cost effectively, is lightweight and non-corrosive but 
maintains an effective combination of rigidity and flexibility. 
SUMMARY OF THE INVENTION 
The present invention provides a new and improved process of producing 
vehicle grille guards by gas-assisted injection molding and the grille 
guards produced thereby. The process of producing the vehicle grille guard 
of the present invention includes injecting a plastic resin into a mold 
cavity in an amount less than the total volume of the mold cavity. An 
inert gas is then injected into a center portion of the cavity and a 
hollow gas channel extending throughout the center portion is formed, 
forcing the plastic resin to flow along an outer surface of the cavity. 
The vehicle grille guard obtains a substantially smooth exterior surface 
as the resin flows along the outer surface of the cavity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1 and 2, there is shown a vehicle grille guard 10 
mounted to a front end 12 of a vehicle 14. Grille guard 10 may be attached 
under the surface of bumper 16 of front end 12, or alternatively, attached 
to the chassis of the vehicle using conventional mounting components. In 
one embodiment, referring to FIGS. 1 and 2, the grille guard 10 generally 
includes a body 18 including a pair of spaced vertically disposed bars 20 
and 22, each having a first end 24 and a second end 26, wherein the second 
end includes a substantially flat portion 28. Grille guard 10 includes an 
elongated loop 30 connected to and extending transversely from bars 20 and 
22 at two different points, 32 and 34, respectively. Elongated loop 30 
further includes first portion 36 and second portion 38. Grille guard 10 
further includes a pair of horizontally extending bars 40 and 42. 
Elongated loop 30, horizontally extending bars 40 and 42, and vertically 
extending bars 20 and 22 may preferably be formed as an unitary structure 
as will be described in greater detail below. Optionally, first and second 
portions 36 and 38, respectively, of the elongated loop may be formed so 
as to curve slightly inward toward front end 12 of the vehicle. 
Referring now to FIG. 2a, a grille guard in accordance with another 
embodiment of the invention is identified generally as reference numeral 
10'. Grille guard 10' is the same as grille guard 10 described above but 
grille guard 10' does not include elongated loop 30. 
To produce the vehicle grille guard of the present invention, an extruded 
plastic resin is injected into a mold cavity having the geometry of the 
desired grille guard end product. 
The plastic resin employed may, for example, be selected from 
acrylonitrile-butadiene-styrene (ABS) resins, 
acrylonitrile-butadiene-styrene/polycarbonate blends, polyesters, 
polyvinyls, polycarbonate/polyester blends, such as XENOY.RTM., 
manufactured by GE Plastics, and mixtures thereof, among others. 
Regardless of the plastic employed, it is preferred that the resin is 
thermoplastic, has a high impact resistance and a flexural modulus of at 
least about 270,000 psi, and may be employed at a low temperature. 
The use of plastic resin material as opposed to steel found in conventional 
grille guards results in a non-corrosive plastic grille guard that is 
approximately one-half the weight of steel guards. The low weight of a 
structural plastic grille guard also reduces the effect on air bags and 
other passive restraint systems in a vehicle. Moreover, plastic, as 
opposed to metal, has the ability to absorb energy without permanent 
deformation. 
The present process is conducted by structural web or plastic web molding, 
a gas-assisted injection molding process that allows for the production of 
unitary or one piece grille guards at a lower cost than prior art 
multi-component grille guards. In addition, plastic web molding requires 
low pressure, subsequently allowing for reduced tooling budgets. Injection 
molding techniques allow for the production of more complex parts having 
closed cross sections, as compared to other molding procedures such as 
compression molding. In addition, many standard finishing techniques may 
be utilized, including, but not limited to, molded-in color, body color 
paint, and chrome. Gas-assisted injection molding methods are well known 
in the art, as set forth in, for example, U.S. Pat. Nos. 5,098,637 and 
5,204,050, incorporated herein by reference, and need not be discussed in 
great detail here. 
Structural web molding provides the vehicle grille guard of the present 
invention with increased strength and rigidity necessary for large 
structural parts. Additionally, the use of the structural web design 
provides an improved combination of rigidity and flexibility for the 
vehicle grille guard, allowing the design to be modified in order to meet 
different customer and vehicle requirements by adjusting the selection and 
design of attachments for mounting the grille guard, selection of 
material, cross-sections of the material, and process parameters. 
The process of producing the vehicle grille guard of the present invention 
by gas-assist injection molding includes injecting a plastic resin into a 
mold cavity in an amount less than the total volume of the mold cavity. An 
inert gas is then injected into a center portion of the cavity and a 
hollow gas channel extending throughout the center portion is formed, 
forcing the plastic resin to flow along an outer surface of the cavity. A 
cross-sectional view of hollow bar 42 of grille guard 10 of a preferred 
embodiment grille guard enclosed within a mold cavity 44 is as shown in 
FIG. 3. The geometry of mold cavity 44 includes a hollow center portion 46 
and an outer surface 48. The inert gas may be injected into the mold 
cavity at the same location as the plastic is injected; or alternatively, 
at a separate location. The inert gas employed is selected from the group 
consisting of air, helium, neon, argon, carbon dioxide, nitrogen, and 
mixtures thereof. 
Additionally, the vehicle grille guard obtains a substantially smooth 
exterior surface as a result of the resin flowing along the outer surface 
of the cavity. The smooth exterior surface produced is preferably a Class 
A surface, known in the automotive industry as a finished surface with 
very few defects and utilized on high visibility structural parts, such as 
grille guards and doors. 
As set forth herein, the grille guard of the present invention may be 
formed as an unitary structure as shown in FIGS. 2 and 2a. In another 
exemplary embodiment of the present invention, the grille guard may be 
formed as a multiple component structure. For example, first and second 
portions 36 and 38, respectively, (see FIG. 2), which function as brush 
guards and essentially wrap around and protect the vehicle's headlights, 
may be formed as separate components and added to the body of the grille 
guard. The grille guard in accordance with the teachings of the present 
invention, however, is not limited to the shapes as shown in the figures 
and may be molded into various geometries using the structural web 
process. 
While the above description constitutes the preferred embodiment of the 
invention, it will be appreciated that the invention is susceptible to 
modification, variation, and change without departing from the proper 
scope or fair meaning of the accompanying claims.