Sequential co-extrusion of carrier reinforcements for automotive seals.

Flexible automotive seals which are clamped on the car body are manufactured today by using a metal carrier. These metal carriers are usually endless and have either stamped out holes or slots. Before the extrusion process, these carriers are pre-bent, and at the end of the extrusion line finally bent to their intended shape.

The project, replacing metal carriers, is intended to develop an automotive seal which has better functionality/properties, as well as lower weight, and can be manufactured easier and at lower cost.

Technical solution

To achieve an automotive seal with high clamping forces, however, without a metal carrier, u-shaped sections of alternating hard and soft material will be extruded in a continuous strand. Similar to a human spine, the hard sections are responsible for the stiffness of the profile, and the soft sections assure the flexibility.

Advantages of metal carrier replacements

Metal carrier replacements offer the following advantages:

* Savings in material cost--In relation to a clamp profile with a volume of 120 [cm.sup.3]/m, the weight and cost relations in table 1 apply for 1 km of product. The material cost for 1,000 meters of a sequentially co-extruded clamp profile total up to 336 Euros compared to 569 Euros for a conventionally manufactured profile (metal carrier covered with EPDM). This results in material savings alone of 233 Euros per 1,000 meters of profile.

* Weight reduction--A sequentially co-extruded carrier profile weighs approximately 97 kg less per 1,000 meters than a conventional clamp profile (metal carrier covered with EPDM). At a total profile weight of approximately 280 kg/km for the EPDM/metal carrier profile, this results in a weight reduction of approximately 35%.

* Improved profile surface--Using a sequentially co-extruded carrier eliminates the visible pattern of stamped/ slotted metal carriers on the surface (the so called hungry-horse effect).

* Better recycling--Through the use of TPE and PP-T instead of metal and rubber for the clamp component, the recycling/recyclability is being improved.

* Lower capital equipment cost--The use of a sequentially co-extruded carrier reduces the capital equipment cost for a production line, since letoffs, accumulators, pre-profiler, carrier pre-heater and final profiler will no longer be required.

[FIGURES 1-3 OMITTED]

* Reduced die wear--Accelerated wear in the metal carrier guiding area inside the extrusion dies is eliminated. The use of a sequentially co-extruded carrier does not require any guiding.

* Production reliability--Line shutdowns, and therefore lost production due to metal carrier breakage, are eliminated when using a co-extruded carrier.

* Process control--An easier process control (as part of the quality management) can be achieved while co-extruding the carrier by monitoring temperature, pressure and screw speed.

* Assembly handling--Straight sections of a seal with a co-extruded carrier can consist only of the hard component, allowing it to safely snap in place on the car body.

Frank Reineke Troester GmbH & Co. KG

Table 1

Material   Density      Price/kg     Weight ratio   Cost ratio

TPE        0.97 g/      3.30 Euros   58.2 kg/km     192 Euro/km
           [cm.sup.3]                (50%)
PP-T       1.20 g/      2.00 Euros   72.0 kg/km     144 Euro/km
           [cm.sup.3]                (50%)
EPDM       1.23 g/      1.65 Euros   132.8 kg/km    219 Euro/km
           [cm.sup.3]                (90%)
Metal      7.85 g/      --           94.2 kg/km     350 Euro/km
carrier    [cm.sup.3]                (10%)