Drive belts including foamed undercord layers and methods of manufacturing the same

Abstract

A drive belt includes an undercord layer having a first region proximate a backing layer surface of the undercord layer and a second region proximate the exterior surface of the undercord layer, the first region being foamed and the second region either being foamed to a lesser extent than the first region or not being foamed. The drive belt further includes a cover layer formed over the exterior surface of the undercord layer. Alternatively, the drive belt may be foamed throughout the undercord layer thickness, with a cover layer formed on the exterior surface of the undercord layer. The manufacturing process for making the foamed undercord layer can include incorporating a first quantity of foaming agent in a first sheet of undercord layer material and either a second quantity of foaming agent in a second sheet of undercord layer material, the second quantity being less than the first quantity, or including no foaming agent in the second sheet. The first sheet and second sheet are disposed in a mold, to which heat and pressure is applied to cure the sheets and foam the first sheet and the second sheet when the second sheet includes foaming agent. The mold includes an exterior portion that forms ridges in the exterior surface of the undercord layer and a cover layer disposed on the exterior surface of the undercord layer. The drive belt incorporating the undercord layer having a foamed first region may exhibit reduced bending stiffness and improved energy efficiency.