Выражение встречается в следующем контексте:
Pneumatical hammers, each unit consisting of a ,,Delrin" ball which is
impelled to an impact plate on the wall by compressed air. The barrel and air reservoir are made of stainless steel W.Nr. 1.4301. Each hammer is equipped with solenoid valve, diaphram valve and non-return valve and a 1.5m polyamid hose. The solenoid valve is 24 V DC IP67.
Adaptor for mounting of hammer on el-hammer bracket.

Заранее спасибо