Drill bit direct drive for deep well drilling tools

A drill bit direct drive for deep well drilling tools includes a tubular casing, a rotary machine provided inside the casing and driven by oil well fluid flowing through it, a radially mounted shaft connected to a rotary drill bit and at least one friction bearing exposed to the oil well fluid for axial bearing of the shaft and having at least one trace ring supported on the shaft plus at least one bearing ring supported on the housing and working together with one trace ring. This bearing ring has a number of bearing segments distributed regularly around its periphery including a bearing body supported with respect to the bearing ring so it can be shifted axially and tilted to a limited extent against the action of a spring force. The bearing body is designed as a circular disk that has a holding pin on its lower side that engages an axial hole in the bearing ring with some tolerance and is supported with respect to the bearing ring by a spring assembly that has at least two disk springs stacked in the same direction.

BACKGROUND OF THE INVENTION 
This invention concerns a drill bit direct drive for deep well drilling 
tools. 
With a known drill bit direct drive of this type (German Patent No. 
3,513,124), the bearing segments are each arranged at the free end of a 
bending bar that is a shaped component of the bearing ring. Such an axial 
bearing design is especially low in wear, because it permits formation of 
a gap that converges relative to the bearing segments in the direction of 
rotation of the bearing ring and the oil well fluid can form a lubricant 
film in this gap. The bending bars are also suitable for absorbing very 
high loads, but they have a very small spring range in operation and 
therefore impart only a very small equalization of tolerance to the axial 
bearing per trace ring/bearing ring pair. In cases when a relatively great 
equalization of tolerance by the axial bearing is necessary, the axial 
bearing must have a number of trace ring/bearing ring pairs which is in 
turn associated with high costs and also a substantial structure size of 
the axial bearing. 
This invention is based on the problem of creating a drill bit direct drive 
with an axial bearing that is suitable especially for low axial loads, is 
inexpensive and yields a greater equalization of tolerance per trace 
ring/bearing ring pair. 
The tiltability achieved with the axial bearing of the drill bit direct 
drive according to his invention makes it possible to form a lubricant gap 
in operation and thus permits operation under favorable wear conditions. 
The spring assembly supporting the bearing body permits axial shifting of 
the bearing body with a far greater spring range, so the bearing yields a 
great equalization of tolerance. The disk springs made of special spring 
steel are especially insensitive to temperatures, they resist wear despite 
the abrasive effect of the drilling fluid and they present especially 
favorable static and dynamic friction values. The load bearing capacity of 
a trace ring/bearing ring pair is lower in comparison with the known 
bearing with bending bar support of the bearing segment but can be adapted 
more easily to the given load requirements, because the spring 
characteristics can be varied more easily and inexpensively by changing 
the spring assembly than those of a bending bar shaped in the bearing ring 
.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
The drill bit direct drive illustrated in FIG. 1 includes a tubular casing 
1 that can be connected by a thread 2 to casing pipe 3. Inside casing 1, 
there is a rotary machine in the form of a turbine that can be driven by 
oil well fluid flowing through it and its shaft 5 passes axially out of 
casing 1 and has a thread 7 for joining it to a rotary drill bit 6. In the 
example shown in FIG. 1, an axial bearing with two trace ring/bearing ring 
pairs 8 is provided to receive the axial forces acting on shaft 5, and in 
the version shown in FIG. 3, there are three trace ring/bearing ring pairs 
8 which are preferably identical to each other and each has one trace ring 
9 and one bearing ring 10. The number of trace ring/bearing ring pairs 8 
depends on the given load conditions under which the deep well drilling 
tool must operate. 
As shown in FIG. 3, the trace rings 9 are each supported on shaft 5 with 
the assistance of spacers 11 while the bearing rings 10 are each supported 
on casing 1, likewise with the help of spacers 12. 
Bearing rings 10 have several bearing segments 13 distributed regularly 
around the periphery, each including a bearing body 14 that has limited 
tilting and axial movement against the action of a spring force in 
comparison with bearing body 14 supported on the bearing ring. Bearing 
body 14 is designed as a circular plate that has a holding pin 15 on its 
lower side. These holding pins 15 which are designed preferably with a 
polygonal cross section to prevent sedimentation phenomena mesh with axial 
boreholes 16 in bearing ring 10 with enough tolerance remaining between 
the holding pin 15 and the preferably circular axial boreholes 16 that the 
bearing bodies 14 can be tilted as a whole to a limited extent. 
Bearing bodies 14 are supported with respect to bearing ring 10 by a spring 
assembly 17 or 18, where spring assembly 17 has two disk springs 19, 20 
stacked in opposite directions and spring assembly 18 includes four disk 
springs 19, 19', 20, 20', where disk springs 19, 19' on the one hand and 
20, 20' on the other hand are paired up and in contact in the same 
direction and then are arranged in pairs facing in opposite directions. 
Bearing bodies 14 may be designed as steel bodies having a bearing layer 21 
of a hard wear resistant bearing material, e.g., a sintered metal powder 
ceramic material or preferably a polycrystalline diamond material on the 
top side. Trace rings 9 in turn consist of a bearing body, preferably made 
of steel, with a support made of bearing material of the above-mentioned 
type. 
Bearing ring 10 has slits 22 for the oil well fluid to pass through 
radially outside bearing body 14 and is also provided with recesses 23 
that improve the passage of oil well fluid in the area of the internal 
edge. At the same time slits 22 to 23 reduce the weight of the bearing 
rings. 
The axial bores 16 in bearing ring 10 are interconnected at the upper ends 
by sections 24 of a ring groove cut in the top side of bearing ring 10 
(and interrupted in the area of the axial bores 16) where the average 
diameter corresponds to the diameter of the midpoint circle 25 of the 
axial bores 16. This groove also serves to prevent deposits in the area of 
bearing body 14, especially in the axial bores 16, which might interfere 
with the spring action shifting movements of bearing bodies 14.