JPS6128076B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rock drilling drill bit, and more particularly to a bearing and retention mechanism for retaining a rotating cutter on the bit.

The success of rotary drilling made it possible to discover oil and gas wells under the sea, and the rotary lock bit was the key invention that made this success possible. While early drag bits could only be drilled commercially in soft formations, the two-cone locking bit invented by HR Hughes and disclosed in U.S. Pat. - The hard rock of the field was excavated relatively easily. This old invention from the 1910s was far inferior in depth and speed to modern rotary lock bites. In other words, modern bits can be excavated to depths that took several days with the original fuse bit in just a few hours. Today, drilling depths are measured in miles rather than feet. Various improvements have dramatically improved the performance of lock bits.

The fuse bit at the beginning of its development was equipped with a rotating cutter, a friction bearing surface, and a ring-type retaining device with a thread to be held within the cutter.
Due to the difficulty of providing long-life seals,
A relatively large lubricating oil tank was required. 1930
By the 1990s, drill bits with non-sealed roller bearings had become mainstream, replacing sealed and lubricated drill bits. Such drill bits are known from Lewis E. Garfield et al.
It is disclosed in No. 2030442.

GO Atkinson etc. have extremely low leakage.
Granted US Patent No. 3,075,781 for a seal that requires only a small lubricant tank. A pressure compensator is an improvement that increases the reliability of the seal by minimizing the pressure difference between the two sides of the seal, and the most recent version of this pressure compensator and pressure relief system is the U.S. patent of Stuart C. Millsaps Giunia. No. 3942596. EM Gear has also been awarded US Patent No. 3,397,928 for an O-ring seal that ultimately allows friction bearings to be reintroduced to drill bits.
The new bearing configuration is covered by SR Scales' U.S. patent.
It is disclosed in No. 3922038. The bit includes a cylindrical friction bearing and a cutter held in a ball bearing similar to that disclosed in the Lewis E. Garfield et al. patent cited above.

There are inherent disadvantages to using ball bearings in lubricated lock bit bearings. Damage to the balls themselves or to the raceway surfaces on which they are arranged allows metal particles to enter the friction bearing, almost invariably resulting in bearing failure. Metal particles often damage seal rings, leading to loss of lubricant and rapid failure of the bearing. The ball must be inserted into the bearing ring by drilling, and a plug must be welded to hold the ball in place.
As the bits become more complex, the possibility of manufacturing errors also increases. Lock bits are the focus of expensive excavation operations with low tolerance for damage.

Some well-known lock bits do not use ball bearings or roller bearings, but instead utilize a completely friction-type bearing and holding mechanism, and fuse bits at the beginning of development also only used friction bearings. Next, we will briefly introduce some bits that use only friction bearings.

FL Scotto, in U.S. Pat. No. 1,803,679, discloses an oil-lubricated tapered friction lock bit bearing configured to retain a cutter with a resilient snap ring. JC Wright et al. has U.S. Patent No.
No. 2049581 discloses a cutter rotatably attached to a bearing pin detachably connected to the leg or head of a bit with a snap ring.
Also, U.S. Pat. No. 2,814,465 to WG Green discloses an oil-lubricated friction bearing that includes tapered cylindrical sections joined by suitable means and secured to the cutter by a retaining ring. Edward B.
Williams Genia, U.S. Pat. No. 3,844,363, discloses a lock ring that holds a cutter and shaft in a lock bit with friction bearings. EM Gear's U.S. Patent No. 3,361,494 describes a friction bearing with a tapered cylindrical portion as a friction plug.
A lock and pin lock retention system is disclosed. An example of an earlier threaded ring retainer that has recently been revisited is Murdock et al., US Pat. No. 3,971,600. However, all of today's commercially successful lock bits utilize ball bearing retention mechanisms.

Threaded retaining rings have several drawbacks that may limit their practical use. The threads act as stress-generating structures and must secure the ring against rotation while in occlusion with the cutter. Therefore, it is common to have to drill a hole in the head of the bit.

Snap rings often have a groove structure that generates stress, which can cause the cutter to unintentionally dislodge if pulled into the assembly groove during excavation operations. If an inward thrust load is applied to the cutter, as occurs, for example, when drilling holes, the stress caused by the load on the ring may force the ring into the assembly groove, with the result that the cutter may fall out.

It is an object of the present invention to provide an improved friction bearing and snap ring retention mechanism for a lock bit having a rotatable cutter with a sealed and lubricated bearing and pressure compensation system. A preferred snap ring is a snap ring having a circular cross section that can fit into both a snap ring retaining groove formed in the cutter and a groove aligned with the groove formed in a bearing pin supporting the cutter. The grooves preferably have a circular or semi-circular bottom wall, one groove being an assembly groove of at least the same depth as the cross-sectional thickness of the ring;
The other groove is a retaining groove that is shallower than the cross-sectional thickness of the ring. outward to the cutter (i.e. against the hole wall)
When a thrust load is applied, a gap is created between the ring and the assembly groove, but when an inward thrust load is applied to the cutter, the ring is trapped between the assembly groove and the holding groove. The ring is pressed outward into the retaining groove under the influence of a conical force distribution generated by the offset edges of the assembly groove or by the inclined walls formed on the edges of the assembly groove. That is, this conical force distribution presses the ring into the retaining groove and prevents the ring from moving unintentionally into the assembly groove and causing the associated cutter to fall out. When a thrust load is applied to the cutter, the distance from the edge of the assembly groove to the opposite edge of the holding groove is smaller than the cross-sectional thickness of the ring, so that the cutter can be held more reliably.

Other objects of the present invention according to the accompanying drawings below:
It also identifies configuration requirements and benefits. The rock drilling drill bit 11 of the present invention shown in FIG. 1 includes three head sections 15, often joined by welding.
It includes a main body 13 formed of. The top of the body 13 is provided with a thread 17 for connection to a conventional drill string (not shown). Each head portion 15 includes a cantilevered shaft or bearing pin 19 with its free end directed inwardly and downwardly. A substantially conical cutter 21 is rotatably attached to each bearing pin 19. The cutter 21 has rock crushing teeth 23 on the outside and a center hole or bearing hole 25 for mounting the bearing pin 19 on the inside. The friction bearing member formed in the bearing pin 19 and the cutter bearing hole 25 communicate with the lubricating oil passage 27 (for bearing surface treatment, see U.S. Pat. No. 3,397,928 and U.S. Pat.
4012238). The pressure compensator 29 and its associated passage constitute a lubricating oil tank which limits the pressure difference between the lubricating oil and the ambient fluid surrounding the bit after passing through the nozzle 32 (Stuart C., dated May 17, 1976). (See U.S. Application No. 687131, “Lubricating Hydraulic Compensator for Rock Drill Bits,” filed in the name of Millsaps Giunia). O-ring seal 31 placed between each bearing pin 19 and cutter 21 at the base of the bearing pin
prevents the escape of lubricating oil and the inflow of downhole fluids (see U.S. Pat. No. 3,397,928 for O-ring seals and U.S. Pat. No. 3,935,114 for lubricating oils).

As shown in FIGS. 3, 4 and 5, the bearing pin 19
An annular assembly groove 33 is formed in the cylindrical surface 34 of. Groove 3
3 has a semi-circular bottom portion 35 centered at a point on the centerline 41. An outer wall 37 and an inner wall 39 extend from the semicircular bottom portion 35 to the surface of the bearing pin 19 .
The outer wall 37 referred to herein refers to the side wall farther from the inner end or tip 43 of the bearing pin 19. The outer wall 37 is straight and perpendicular to a common axis (not shown) of the bearing pin 19 and cutter 21. The inner wall 39 forms an angle .alpha. of preferably 15 DEG with a plane perpendicular to the axis of the bearing pin and is a conical thrust surface or sloped wall non-orthogonal to the axis of the bearing pin. This inner wall 39 forms the entrance to the groove 33 which is larger than the diameter of the semi-circular bottom portion 35 and is an advantageous thrust surface, as discussed below.

A holding groove 45 aligned with the groove 33 is formed in the bearing hole 25 of the cutter 21. The groove 45 is located on the outer wall 4
6 and an inner wall 50. Note that the outer wall 46 is the side wall farther from the tip 43 of the bearing pin 19. In the cross-sectional view, the side wall 46 has an arc shape corresponding to a quadrant with a radius approximately equal to the radius of the bottom portion 35 of the groove 33 described above. The depth of the groove 45 is greater than the radius of the arc. In the cross-section of FIG. 4, the inner wall 50 consists of a straight line that connects at one end with a quarter arc of the side wall 46 through a small radius, and at the other end forms a tapered or conical friction tip bearing 52.

Grooves 33 and 45 are arranged in alignment with each other to define an irregularly shaped annular hole with a curved bottom. In this annular hole is placed a snap ring 47 having a curved rim and preferably a circular cross section. Snap ring 47 is formed of resilient metal, preferably piano wire, and includes a gap 49 to allow its ring diameter to be compressed or expanded (FIG. 2). The diameter of the ring 47 is set so that it expands and fits into the groove 45 when relaxed. ring 4
The cross-sectional diameter of 7 is approximately equal to the diameter of the semicircular portion 35 of the groove 33.

The depth of the assembly groove 33 is set to be at least equal to the cross-sectional diameter of the ring 47. If you set it like this,
The ring 47 can be completely retracted into the groove 33 in order to assemble the cutter 21 on the bearing pin 19. The depth of the retaining groove 45 is equal to the cross-sectional diameter of the ring 47.
It is larger than 1/2 but smaller than the cross-sectional diameter. This depth is preferably 0.127 mm to 0.508 mm, as shown by the arrow in FIG.
(0.005 inch to 0.020 inch) “offset”
(indicated by S in the figure). Therefore ring 4
The cross-sectional center line 51 of No. 7 is located outside the bearing pin cylindrical surface 34 and the retaining groove edge by the same amount.

To attach the cutter 21 to the bearing pin 19, use a tool (not shown) to insert the ring 47 into the groove 3.
Press fit into 3. Next, insert only a portion of the cutter 21 into the bearing pin 19, remove the tool, and then insert the cutter 21 into the bearing pin 19.
As shown in the figure, the cutter 21 is pressed outward until the opposing surfaces of the tapered tip bearing pin 52 engage with each other to press against the bearing pin 19. Groove 45 is aligned with groove 33 so that ring 47 can fit therein. In FIG. 4, the ring 47 abuts the side wall 46 of the groove 45, and the side wall 5
There is no contact with 0. The side wall 39 of the groove 33 is also provided with a gap C ₁ so that the ring 47 can move into the retaining groove 45.
The distance from ring 47 is only 1. The centerline 51 of the ring 47 is preferably 0.127 mm to 0.508 mm (0.005 inch to
0.020 inch).

The center lines 41 and 51 are not located on a common plane perpendicular to the bearing pin axis, and the center line 51 is located on the same plane as the center line 41.
It is closer to the tip 43 than the tip 43. Having set the gap _C1 , the cutter 21 can be moved inwardly along the bearing pin 19 to the position shown in FIG. Ring 47 is trapped between the sidewall 46 of groove 45 and the corner of sidewall 39 of groove 33. A gap C ₂ appears between the opposing surfaces of the conical or tapered thrust bearing 52 .

When the cutter 21 is inserted to the position shown in FIG. smaller than That is, in FIG. 5, the cross-sectional diameter of the snap ring 47 is X+Y, and the wall 3
The distance from the edge of groove 9 to the opposite corner of groove 46 is a distance X that is shorter than the above-mentioned X+Y. Therefore, when the cutter 21 is inserted, the ring 47 cannot be pulled into the assembly groove 33, but remains in the holding groove 45.
This prevents the cutter 21 from falling off.

Next, the mode of action will be explained. Under the most common excavation conditions, an outward thrust load acts on the cutter 21 inserted into the bearing pin 19, as shown in FIG. Since the tapered surfaces of the bearing 52 interlock, and as a result, a gap C ₃ is created between the ring 47 and the wall 37 of the groove 33, no external force acts on the ring 47. When drilling a small hole, an inward thrust load may act on the cutter 21, and this inward thrust load tends to push the cutter 21 inward from the bearing pin 19. However, this effect is suppressed by a ring 47 that transmits the thrust load between the side walls 46 and 39, as shown in FIG. The inner wall 39 acts as a thrust surface and provides a compressive reaction force.

Since the inner wall 39 is formed to be inclined by the angle α, a force component F (FIG. 6) is generated which forms the same angle α obliquely with respect to the axis of rotation of the cutter 21. That is, the special shape of the groove 33 generates a three-dimensional conical force distribution that expands the ring 47 outward and causes it to fit into the groove 45 of the cutter 21.
This acts to prevent the ring 47 from being compressed and fitting into the groove 33 of the bearing pin 19, thereby preventing the cutter 21 from falling off.

FIG. 6 shows a second configuration that differs from the configurations in FIGS. 4 and 5 in that both side walls 37 and 39 of the assembly groove 33 are parallel to each other and inclined at an angle α. In FIG. 6, the tapered wall 39 exerts a force component F perpendicular to the surface of the ring 47 to force the ring into the retaining groove 45, so the "offset" is relatively small and may be unnecessary. .

FIG. 7 shows a third configuration in which both ends 37 and 38 of the assembly groove 33 are formed parallel to each other and perpendicular to the center line of the bearing pin. Here, the edge or outer wall 39 of the groove 33 engages the ring 47 at a distance from the centerline 51 of the ring 47 equal to the "offset" with the cylindrical bearing surface 34. When an inward thrust load is applied to the cutter 21, a force component F acts on the ring 47 from an oblique direction perpendicular to the surface of the ring 47, forcing the ring 47 into the holding groove 45.

The preferred configuration of FIGS. 4 and 5 combines the configuration features of FIGS. 6 and 7, with groove 3
Taper the wall 39 (instead of the wall 37) of 3;
An “offset” configuration is also adopted. As a preferable range of the offset amount, the angle α is preferably
It is sufficient to set the ring 47 so that the surface 39 contacts the ring 47 instead of the sharp edge when the angle is 15 degrees. Sharp edges cause ring 47 to wear rapidly, so this surface contact is beneficial in reducing wear.

The three configurations shown in FIGS. 4 through 7 all include the configuration requirements for minimizing cutter loss, as described in connection with FIG. 5. In other words, the cross-sectional thickness X+Y of the ring 47 is greater than the distance big.

As can be seen from the foregoing description, the present invention provides various improvements with significant advantages.
The use of a bearing structure consisting of an oil-lubricated friction bearing surface that includes a friction retention mechanism simplifies the configuration and increases reliability. Furthermore, since the above-described snap ring and groove structure are adopted, there is almost no possibility that the cutter will fall off. Since the above-mentioned offset is set between the center line of the ring and the bearing surface near the assembly groove, an oblique force component acts to press the ring into the retaining groove. When an inward thrust load is applied to the cutter, the thrust surface without corners engages with the ring, which is advantageous in terms of reducing wear. Furthermore, since the thrust surface is inclined, the snap ring is press-fitted into the holding groove when an inward thrust load is applied to the cutter. Since the outer shape and thickness of the ring are smaller than those of the groove, the cutter can be held securely.

Although the present invention has been described above according to one embodiment, as is obvious to those skilled in the art, the present invention is not limited to this embodiment, and various modifications can be made without departing from the spirit of the present invention. It is possible.

[Brief explanation of the drawing]

FIG. 1 is a partial front view, partially in section, of an embodiment of the lock bit of the present invention, and FIG. FIG. 3 is an enlarged vertical sectional view showing a part of the cutter and bearing pin shown in FIG. 1;
The figure is a partial vertical sectional view showing the cutter and bearing pin that surround the cross section of the snap ring in Figure 1, with an outward thrust load acting on the cutter inserted into the bearing pin. Fig. 5 is a partial vertical cross-sectional view similar to Fig. 4 showing an inward thrust load acting on the cutter inserted into the bearing pin, and Fig. 6 shows an inward thrust load acting on the cutter. FIG. 7 is a partial vertical cross-sectional view showing the second configuration under a load, and FIG. 7 is a partial vertical cross-sectional view showing the third configuration under an inward thrust load on the cutter. 11... Bit, 13... Main body, 15... Head, 19... Bearing pin, 21... Cutter, 23
... Rock crushing tooth, 29 ... Pressure compensator, 31 ... O
Ring seal, 33... Annular assembly groove, 45... Holding groove, 47... Snap ring, S... Offset amount.

Claims (1)

Claims: 1. A rock drilling bit comprising at least one cantilevered bearing pin rotatably supporting a sealed and lubricated cutter, the friction comprising the inward thrust surface of said pin; a bearing member is provided between the cutter and the pin; an assembly groove is formed in one of the cutter and the pin, and a holding groove aligned with the assembly groove is formed in the other; a snap ring is disposed in the grooves that are aligned with each other; the depth of the retaining groove is less than the cross-sectional thickness of the ring; and the assembly groove is at least equal to the cross-sectional thickness of the ring. a depth, an outer wall and an inner wall, the inner wall having a truncated conical surface, the conical surface being inclined at a selected angle α with respect to a plane perpendicular to the axis of the pin to engage the snap ring. When the cone is engaged and the cone is thrust inwardly and away from the thrust surface, a force component is generated oblique to the shaft to press the snap ring into the retaining groove. Retention mechanism. 2. A rock drilling bit comprising at least one cantilever bearing pin rotatably supporting a sealed and lubricated cutter, wherein a friction bearing member including an inward thrust surface of the pin is connected to the cutter. an assembly groove is formed on the pin, and a holding groove is formed on the cutter that is aligned with the assembly groove, and a snap ring is provided in both grooves that are aligned with each other. the depth of the retaining groove is less than the cross-sectional thickness of the ring; the assembly groove has a depth and inner and outer walls at least equal to the cross-sectional thickness of the ring; the surface and the inner wall of the assembly groove intersect at a corner, said inner wall having a truncated conical surface inclined at a selected angle α with respect to a plane perpendicular to the axis of the pin; A cutter retention mechanism comprising: engaging a ring and press-fitting the snap ring into a retention groove as the cone thrusts inwardly away from the thrust surface. 3. A rock drilling bit having at least one cantilever bearing pin rotatably supporting a sealed and lubricated cutter, wherein a friction bearing member including an inward thrust surface of the pin is connected to the cutter. provided exclusively between the pins; a pressure regulator for controlling the pressure difference on both sides across the seal is provided within the lubrication system; and the cutter and the pin. an assembly groove having a curved bottom wall on one side, and a retaining groove aligned with the assembly groove and having a curved bottom wall on the other side; and a snap having a curved cross-sectional profile in both grooves.・
a ring is disposed; the retaining groove has a depth equal to at least one-half the cross-sectional thickness of the ring and a curved outer wall for engaging the snap ring; and the assembly groove has a depth equal to at least one-half the cross-sectional thickness of the ring; and having inner and outer walls equal to the depth of A cutter holding mechanism characterized by: press-fitting a snap ring into a curved outer wall of a holding groove when the cutter is thrust and separated from the thrust surface. 4. A rock drilling bit comprising at least one cantilever bearing pin rotatably supporting a sealed and lubricated cutter, wherein a friction bearing member including an inward thrust surface of the pin is connected to the cutter. a pressure regulating device for controlling the pressure difference on both sides across the seal is provided within the lubrication system; and substantially between the pin and the pin; an assembly groove having a circular bottom in the cutter, and a retaining groove formed in the cutter that is aligned with the assembly groove and having substantially circular side walls; a ring is disposed; the retaining feature has a depth equal to at least half the cross-sectional thickness of the ring; and the assembly groove has a depth at least equal to the cross-sectional thickness of the ring and inner and outer walls. the face of the pin and the inner wall of the assembly groove intersect at a corner; the inner wall has a frusto-conical surface inclined at a selected angle α with respect to a plane perpendicular to the axis of the pin;
A cutter holding mechanism that makes surface contact with the ring rather than edge contact, and is characterized by the following.