天井钻机最早的产品是美国罗宾斯(Ro-bbjns)公司生产的41R型,后发展到61R和81R型以及最近的83R和85R型。该公司已生产130多台41R至85R型的天井钻机。罗宾斯的85R型坑内天井钻机是世界上最大的型号,在南非的斯顿·迪普·利维斯金矿使用。钻机的推力100万磅,断裂转矩55万呎·磅,连续扩孔转矩36.5万呎·磅。这台钻机可钻直径8～12呎(2.4～3.66米)的天井,可在抗压强度4万磅/吋~2的石英岩钻进。钻机系液压传动,允许以较高的转矩值通过12(7/8)吋直 The earliest product for a patio rig was Type 41R manufactured by the Ro-bbjns Company of America and later developed into Types 61R and 81R and more recently models 83R and 85R. The company has produced more than 130 41T to 85R wellhead drilling rigs. Robbins’ Model 85R pit drill is the largest model in the world and is used at the Stumpdown Levis Gold mine in South Africa. The drilling rig has a thrust of 1 million pounds, a breaking torque of 550,000 pounds per pound, and a continuous counterbore torque of 365,000 pounds per pound. The rig drills a patio of 8 to 12 feet (2.4 to 3.66 meters) in diameter and can drill into quartzite at compressive strength of 40,000 pounds per square inch. The rig is hydraulically driven to allow straight through 12 (7/8) inches with higher torque