An Elastomeric Impact-Absorbing Bumper System

Abstract

Abstract An elastomeric impact absorber was selected from a variety of mechanical designs involving a mechanical strut (Torshok), a buckling-column flat spring and an involute spring, several hydraulic shock absorbers, and various concepts utilizing elastomeric polyurethane foam. Functional and economic criteria as well as manufacturing considerations dictated the choice. The following list outlines the functional attributes that favored a rubber shear spring in the elastomeric impact absorber: 1) Simple, rugged design—all parts except rubber blocks are conventional steel stampings. 2) The device is capable of accepting high angular impacts. Due to the rugged I-beam arm, comer impacts and large torsion loads are tolerated. 3) Mounting requirements are incorporated in the case of the unit. This eliminates the need for separate brackets which results in a cost savings as well as a stronger, more integrated attachment between device and structure. 4) The device has very high compliance in skewed loading. This refers to the bumper geometry resulting from an in-line impact on one unit causing it to stroke fully while the other unit remains unstroked. Since the I-beam arm is unrestricted in the lateral direction except by the rubber blocks, the arm of the unstroked unit can assume an angular position in the plan view and does not bind up the bumper system nor does it unnecessarily load absorber faceplate or bumper reinforcement. 5) A high degree of interchangeability could be achieved with this device. In 1973, four basic designs satisfy the front bumper requirements of fourteen (14) different car lines, including attachment requirements. In addition to the many functional attributes for which this unit was selected, there are also several non-functional factors that were of significance. Some of these are: 1 ) The unit, with the exception of the rubber blocks, requiring only stamping plant facilities and technologies to fabricate, can be contained within existing facilities at moderate investment costs. 2 ) Only limited training is required for the work force. The typical automotive worker can be easily trained to produce this unit. 3) The only critical part in the device, the rubber block, can be obtained from a sufficient number of rubber suppliers to ensure adequate supply protection and complete rubber technology support. In summary, high volume production of a bumper impact absorbing device makes necessary a design that is simple yet rugged and reliable.