Rotary table drive

1. A rotary table drive comprising:

a top plate and a bottom plate cooperating to define a bore through both and an adjacent gear housing;

a bushing adapter within the bore and defining a bushing adapter passage for receiving a bushing configured to mate with a segment of drill pipe allowing rotational motion to be imparted thereto;

a ring bearing having an inner ring affixed rigidly to the bushing adapter and defining a plurality of teeth around a perimeter thereof, and an outer ring rigidly affixed to the bottom plate; and

a plurality of braking notches defined in the upper portion of the bushing adapter;

wherein the gear housing receives output from a motor for imparting rotary motion to the bushing adapter via the teeth on the ring bearing;

wherein the bearing is sealed against exposure to the elements by being surrounded on all sides by a combination of the top plate, bottom plate, and bushing adapter;

wherein the bushing adapter comprises an upper portion that rotates at least partially above the top plate and a lower portion that proceed from the upper portion downwardly through the bore; and

wherein the upper portion and lower portion are a monolithic whole.

2. The rotary drive of claim 1 , further comprising a motor having an output shaft affixed to a drive gear inside the gear housing.

3. The rotary drive of claim 2 , wherein the motor is sealed to the bottom plate.

4. The rotary drive of claim 2 , further comprising an idler gear sealed within the gear housing and interposing the drive gear and the teeth of the inner ring of the bearing for transferring rotary forces between the two.

5. A rotary table drive comprising:

a top plate and a bottom plate cooperating to define a bore through both and an adjacent gear housing;

a bushing adapter within the bore and defining a bushing adapter passage for receiving a bushing configured to mate with a segment of drill pipe allowing rotational motion to be imparted thereto;

a ring bearing having an inner ring affixed rigidly to the bushing adapter and defining a plurality of teeth around a perimeter thereof, and an outer ring rigidly affixed to the bottom plate;

an upper main seal interposing the bushing adapter and the top plate; and

a lower main seal interposing the inner ring of the bearing and the bottom plate

wherein the gear housing receives output from a motor for imparting rotary motion to the bushing adapter via the teeth on the ring bearing; and

wherein the bearing is sealed against exposure to the elements by being surrounded on all sides by a combination of the top plate, bottom plate, and bushing adapter.

6. A rotary table drive comprising:

a top plate and a bottom plate cooperating to define a bore and an adjacent sealed gear housing;

a bushing adapter passing through the bore and configured to receive a bushing to mate with a segment of polygonal drill pipe allowing rotational motion to be imparted thereto;

a ring bearing having an inner ring affixed rigidly to the bushing adapter and an outer ring rigidly affixed to the bottom plate; and

a drive gear within the sealed gear housing mated to the bushing adapter such that the bushing adapter is rotated in response to rotation of the drive gear;

a sealed motor sealed to the bottom plate and having an output shaft mated to the drive gear; and

an idler gear interposing the drive gear and the gear teeth of the inner ring;

wherein the bearing is sealed against exposure to the elements by being surrounded on all sides by a combination of the top plate, bottom plate, and bushing adapter; and

wherein the bearing defines a plurality of gear teeth on the inner ring through which rotary motion is imparted to the bushing adapter.

7. The rotary table drive of claim 6 , further comprising a plurality of braking notches defined in an upper portion of the bushing adapter, superior to the top plate.

8. The rotary table drive of claim 7 , further comprising an upper main seal interposing the upper portion of the bushing adapter and the top plate.

9. The rotary table drive of claim 8 , further comprising a lower main seal interposing the inner ring of the bearing and the lower plate.

10. A method comprising:

providing an upper and lower plate defining a gear housing and an adjacent bore;

providing a bushing adapter through the bore riding on a ring bearing sandwiched between the upper and lower plate; and

driving the bushing adapter in a rotating fashion via a drive gear contained in the gear housing and affixed to a sealed motor outside the gear housing; and

driving the bushing adapter via an idler gear interposing the drive gear and a plurality of teeth defined on an inner ring of the bearing, which is rigidly affixed to the bushing adapter.

11. The method of claim 10 , further comprising defining a plurality of braking notches in an upper portion of the bushing adapter that rotates through a plane superior to the upper plate.

12. The method of claim 11 , further comprising sealing the upper portion of the bushing adapter where it mates against the upper plate.