BUMPER SHAFT

SUPPORT DE PARE-CHOCS

Description

CA 02489504 2004-11-25
Bumper Material Selection
The primary function of the bumper is energy dissipation. The bumper acts to
absorb and distribute the shock of an external impact in a direction
perpendicular
to the line of action of impact.
Cast or foamed elastomeric materials are best suited to this application,
there are a
variety of candidate materials and vendors to choose from:
Bum er Materials Vendors


Thermoplastic Polyurethane RTP, Dow, Bayer, 3M, BASF


Thennoset Polyurethane Cytec, Innovative, DuPont,
Bayer, Henkel,
BJB E-. nterprises, GE, NuSil


Silicone Rubber Dow Corning, Silicones Inc.,
Bayer


Polyisoprene (Natural Rubber)Lavelle


Polybutadiene Bayer


Polyisobutylene PRC DeSoto


Latex Dow, DuPont


All of these materials are classified as elastomers and good as dissipating
energy
from impact.
The range of hardness or Durometer of the bumper could be from 10 Shore A to
80 Shore D depending upon the desired balance between tactical feel and energy
dissipation.
Injection Process and Tooling
There are a variety of different methods for attachment of the bumper onto the
carbon fiber shaft, they include but are not limited to:
In'ection Process Toolin


Injection Molding - thermoplasticCNC tool steel or aluminum


Injection Over Molding - thermosetCNC tool steel or aluminum,
cast .
elastomeric silicone


Pressure Molding CNC tool steel or aluminum


Compression Molding CNC tool steel or aluminum


Gravity Casting CNC tool steel or aluminum


Vacuum Castin CNC tool steel or aluminum


Secondary Bonding - this meansAluminum or steel alignment
to pre- jigs and
cure the elastomeric bumper fixtures
and then bond
or glue the bumper in place
on the shaft




CA 02489504 2004-11-25
Elastomers can be cured out from room temperature to elevated temperatures up
to the limit of the glass transition temperature of the carbon fiber shaft
(290
degrees F).
Over molding can be cast horizontally, vertically or with the tooling oriented
at an
angle. The injection can take place from either the top or the bottom of the
shaft.
Extension of coverage to include the blade
A logical extension of the bumper patent is to include the blade. The external
periphery
(edge) of the blade could be protected with the addition of an elastomeric
material. This
elastomer would protect the blade not only from impacts with another
shaft/blade, but
also from contact with the ice.
Generalized Process Specification - Bumner Shaft Tniection:
1. Install injection over molding tooling into injection press
2. Mold release the injection over molding tooling
3. Heat tooling to injection temperature
4. Wipe carbon fiber shafts with solvent to remove residual oils and
contaminants.
5. Install shafts into injection over molding tooling
6. Apply compression/clamping pressure to shafts with press
7. Connect meter mix dispense equipment to injection port on injection over
molding tooling
8. Discharge a metered shot of elastomer into tooling
9. Allow elastomer to cure
10. Demold over molded shafts
11. Clean tool
12. Mold release tool
13. Post cure shaft
14. Repeat
Based upon the current process development, the preferred erribodiment should
detail the
following:
~ Material - Family of Thermoset Polyurethane
~ Durometer - 60-80 Shore A
~ Process = Injection Over Molding
~ Tooling - CNC Aluminum
~ Cure Temperature - 100-180F depending upon cycle time or volume requirements