Concentric Shaft Drive

This invention pertains to a drive shaft arrangement and, more particularly, to a drive shaft arrangement having an inner shaft, an outer shaft concentric about the inner shaft, a clutch means, and a first and second transmission means.

In power transmitting applications, such as in the case of drilling rig applications, it is desired to have drive shaft arrangements which are as compact as possible. In the case of drill rigs, there is limited room on the rig, and the rig must be transported from place to place putting size requirements on the shaft size.

This invention pertains to a shaft drive arrangement having an inner shaft wherein the inner shaft has a first end and a second end. An outer shaft concentric about the inner shaft is also provided. The outer shaft has a first, a middle and a second end. A clutch means for transmitting rotary power between the inner shaft and the outer shaft is cantileverly mounted on the second end of the shaft. A first transmission means for transmitting torque is mounted on the second end of inner shaft and a second transmission means for transmitting torque is mounted about the middle of the outer shaft.

The FIGURE is a cross section, schematic illustration of a shaft drive arrangement.

In the FIGURE, a shaft drive arrangement 10 is shown. Shaft drive arrangement 10 is comprised of an inner shaft 12 which has a first end 14 and a second end 16. An outer shaft 18 is positioned concentric about the inner shaft 12. Outer shaft 18 has a first end 20, a middle 22, and a second end 24. A first transmission means for transmitting torque is mounted on first end 14 of inner shaft 12. First transmission means include conventional transmission means such as sheave 26 which is connected to inner shaft 12 by means of member 28. In this embodiment of the invention, sheave 26 drives inner shaft 12. Inner shaft 12 then becomes the driver shaft. The invention, however, is not limited to this embodiement, and inner shaft 12 may be the driven shaft. Mounted on second end 16 and second end 24 of the shafts is a clutch means for transmitting rotary power between inner shaft 12 and outer 18. The clutch means is cantileverly mounted on the second end of the shafts. The clutch means includes conventional clutch means such as the embodiment shown in the figure. In this embodiment there is a member 30 mounted on the second end of shaft 12. Attached to member 30 is an inflatable ring 32. Inflatable ring 32 may be inflated with pneumatic pressure. Attached to inflatable ring 32 is a contact ring 34 which has a contact surface 36. When ring 32 is inflated, contact surface 36 presses against a contact surface 38. Contact surface 38 is part of member 40 which is affixed to second end 24 of outer shaft 18. When the clutch is engaged, the outer shaft 18 rotates as does the inner shaft 12. Connected to middle section 22 of outer shaft 18 is a second transmission means for transmitting torque. Second transmission means includes conventional transmission means such as sprocket 42 shown in the drawing. In this embodiment of the invention, sprocket 42 is driven by outer shaft 18. This invention, however, includes means wherein outer shaft 18 is driven by second transmission means 42. Bearings 44 are mounted on journals 46 to permit rotation of outer shaft 18.

It has been found when the present invention is employed a very compact space-conserving design is used. The design allows for relatively small diameter shafts for long spans. Large diameter bearings can be used without increase of shaft size. The clutch driven members are cantilevered and open for easy service. The inner shaft is placed in pure torsion. All bending moments are on the outer shaft. Bearings are mounted on journals external to the outer shaft eliminatinng any bearings on the inner shaft.