A Picture of Sumitomo Electric in Those Days

1958 Starting production of air springs for railcars

Product engineering capabilities refined through electric wire development

Sumitomo Electric has been developing various new products based on its engineering capabilities in manufacturing electric wires. One such product is an air spring that consists of suspensions, rubber parts and metallic parts to suppress railcar vibration. The Company has a long track record in the electric wire business. Its rubber and plastic materials for the insulation sleeves performed well even before WWII. Electric wires and cables are exposed to sunlight and weather for long periods of time. Thus, insulation sleeves that are used under severe conditions must meet extremely high characteristics requirements. The material engineering capabilities that have made it possible to meet such requirements are utilized to manufacture important rubber parts that take advantage of air compressibility as a spring.

After the research department started studying air springs in 1955, Sumitomo Electric worked on developing air springs mainly for railcars. In 1957, the Company developed Sumipress, a new type of air spring. In 1958, the Company started production for private railways, and in 1960, it expanded the production for the Japanese National Railways (JNR, today the Japan Railways [JR] Group). Subsequently, air springs started being used for Shinkansen bullet trains. Efforts were made to develop new advanced technologies to meet the need for higher railcar speeds. Today, the air springs are used for various railcars including the N700 series Shinkansen trains, Japan’s first High Speed Surface Transport (HSST) system, and the New York City Subway. By 2018, Sumitomo Electric had delivered more than 530,000 units to customers in and outside Japan.