Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Reexamination Certificate
1999-11-30
2003-11-18
Staicovici, Stefan (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
C264S322000, C264S324000, C264S325000, C293S120000
Reexamination Certificate
active
06649109
ABSTRACT:
TECHNICAL FIELD
This invention relates to methods for molding and impact resistant automotive parts such as bumper beams produced thereby.
BACKGROUND ART
There is a need for automotive parts which are impact resistant by remaining in one piece after high speed impact. Such an automotive part is a bumper beam.
There are numerous requirements for automotive bumper beams both in North America and Europe. These requirements differ depending on whether there are for low speed impacts, high speed impacts, insurance requirements, etc.
For example, for low speed impacts the following are detailed requirements:
US Federal regulations REG 581: bumper standard. 5 impacts are required:
2 longitudinal pendulum impacts at 2.5 mph (at two heights between 16 and 20 inches);
2 corner pendulum impact (one on each corner) at 1.5 mph; and
1 longitudinal barrier at 2.5 mph.
After the 5 impacts, the requirements on the vehicle are shown in 581.5 c of the regulation.
Canada Safety Standards: Bumper passenger car CMVSS 215. 4 impacts are required:
2 longitudinal pendulum impacts at 5 mph (at two heights between 16 and 20 inches;
1 corner pendulum impact (one on each corner) at 3 mph; and
1 longitudinal barrier at 5 mph.
After 4 impacts, the requirements are the same as FED REG 581 with the important exception of requirement of FED REG 581.5c8 (no separation of polymeric coatings and permanent deviations except on bumper).
European Requirements (ECE 42). Pendulum impact at 4 km/h. Consequently, for low speed impacts, the beam must absorb energy by elastic deformation (deflection). Its rigidity is tuned to limit the deflection to the vehicle requirements.
For insurance purposes, the following are detailed requirements.
Europe: Danner
Impact at 15 km/h against a wall with 40% overlap. The goal is to reduce repair costs by limiting the degradation to the bumper. Absorbers are added between the bumper beam and the rails to protect the rails during impact. For Danner requirements, the beam+ absorber must be crushed progressively to absorb the impact energy and protect the rails.
US Requirements IIHS: Four 5 mph Crash Tests to Assess Bumper Performance
Front into flat barrier
Front into angle barrier
Rear into flat barrier
Rear into pole (7 inch diameter)
For high speed impact, the following are detailed requirements.
US Requirements: FMVSS n
o
208
Full frontal crash against a perpendicular rigid barrier at 30 mph with unrestrained and belt restrained 50th percentile Hybrid III male dummy. The injury criteria include threshold criteria for the head, chest deceleration, chest deflection, and femur lower leg.
European: EU Directive 96/79 EC
Impact speed is 56 kph (35 mph);
Impact object is fixed deformable barrier;
Vehicle frontal overlap with barrier: 40% overlap of the vehicle width directly in line with the barrier face;
Dummy type: belt restrained, 50th percentile Hybrid III male;
Injury criteria: same threshold criteria and in addition, viscous criteria, the neck, the knee, lower leg bending (tibia index), foot/ankle, compression, and compartmental intrusion.
Consequently, for high speed impact it is important that the bumper beam distributes the load and is still in one piece attached to the rails after impact.
Other requirements are:
Pedestrian Impact: Lower leg impact at 40 kph. Three criteria are used: tibia deceleration should be less than 150 g, knee bending angle should be less than 15° and knee shear displacement should be less than 6 mm.
Airbag Deployment: The beam should be stiff enough to trigger the airbag at 30 kph.
French Patent No. 2,749,535 discloses a process to manufacture a part in which glass fibers are adequately wetted by thermoplastic material so that parts can be molded with a better strength, stiffness and impact resistance than GMT (Glass mat thermoplastics) parts, such as bumper beams, for a given weight.
French and European patent application 99400421.6 discloses a bumper beam designed for small parking impacts (4 km/h), insurance requirements (Danner impact at 15 km/h), low weight (as compared with metallic solutions) and reduced cost. The beam is made of a profile that contains at least one polymeric material in which the profile has “cones” in the direction of the vehicle to attach the beam to the car.
Referring now to
FIGS. 1-3
, there is schematically illustrated a process for molding a bumper beam, generally indicated at
10
(FIG.
3
), in accordance with the above-noted French Patent No. 2,749,535. As illustrated in
FIG. 1
, to mold the beam
10
six blanks are provided (FIG.
1
): two blanks
12
of EMIR (that contain Twintex, manufactured by Vetrotex France. Twintex includes woven mats made of tows that contain both glass and polypropylene fibers); and four blanks
14
of GMT. The EMIR blanks
12
include outer layers of Twintex. The inner layers of EMIR may include a central glass mat layer sandwiched between polypropylene layers.
Preferably, the EMIR blanks
12
are made on a double belt press starting with 7 layers of materials. From top to bottom: Twintex (woven 4/1, 60 wt % glass, 920 g/m2), PP film, glass mats, extruded PP layer, glass mats, PP film and Twintex. The GMT in the center (i.e., the layers other than the Twintex layers) contains 30 wt % glass. The resulting EMIR blank
12
that is obtained contains 42 wt % glass and is 5 mm thick. The tows of glass fibers,are in contact (comingled) with thermoplastic material, where the fibers in each tow are wetted by the thermoplastic material in the tow. The dimensions of the EMIR blanks
12
are 1000 mm×125 mm. The blanks
14
of GMT contain 30 wt % glass and their dimensions are 166×360 mm. Their thickness is 3.7 mm.
The six blanks are heated in an oven. A robot stacks two blanks
14
of GMT, two blanks
12
of EMIR and two blanks
14
of GMT. The two stacks of GMT are put on top of the EMIR stack (on each side) with 30% overlap as shown in FIG.
2
.
The assembly is transferred into a press or mold and stamped to form the bumper beam
10
illustrated in FIG.
3
. The welding between the GMT blanks
14
and the EMIR blanks
12
is adequate. The GMT at the center of the EMIR blanks
12
flows to fill attachment portions
16
of the bumper beam
10
. A central portion
19
of the beam
10
includes the resulting thermoplastic reinforced fiber structure
18
. The attachment portions
16
include apertures
20
formed through cone portions (as illustrated in French and European patent application 99400421.6) for attachment of the bumper beam
10
to an automotive vehicle.
The resulting bumper beam
10
, while satisfying parking and insurance requirements, does not satisfy high speed requirements because the cone portions by which the beam
10
is attached to rails of a vehicle are made of GMT and cannot survive such impact.
Consequently, it is desirable to have a bumper beam that can:
absorb low speed impact by elastic deflection;
absorb Danner impact (if required) by progressive crush of molded-in cone absorbers; and
insure a link between rails and load distribution during a high speed crash.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a method for molding and an impact resistant automotive part such as a bumper beam produced thereby wherein the resulting bumper beam addresses both U.S. and European requirements (including high speed requirements) for bumper beams.
Another object of the present invention is to provide a method for molding and an impact resistant automotive part such as a bumper beam produced thereby wherein the bumper beam contributes to energy absorption during high speed impacts. During high speed impact, it is important that the beam remains in one piece and attached to the rails in order to distribute the impact load on a maximum area.
In carrying out the above objects and other objects of the present invention, a method is provided for molding an impact resistant automotive part adapted to be attached to an automotive vehicle at a pair of attachment locations spaced a predetermined distance apart. The method includes providing a plurality of bla
Kushman Brooks
Patent Holding Company
Staicovici Stefan
LandOfFree
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