JPS6128077B2 - - 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 less deep and fast than modern rotating lock bits. In other words, modern bits can dig in a few hours to a depth that took several days with the original fuse bit. 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 completely friction-type bearings and holding mechanisms, and fuse bits at the time 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 a U.S. patent no.
No. 2049581 discloses a cutter that is rotatably attached by a snap ring to a bearing pin that is detachably connected to the leg or head of a bit. 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 Giunia U.S. Patent No.
No. 3,844,363 discloses a lock ring that holds the cutter and shaft in a lock bit with friction bearings. US patent for EM gear
No. 3,361,494 discloses a friction bearing having a tapered cylindrical portion, along with a friction plug lock and a pin lock retention system. 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 appear to 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 creates stresses that can pull into the assembly groove during excavation operations, causing the cutter to unintentionally dislodge. If the cutter is subjected to an inward thrust load, as occurs, for example, when drilling holes, the stress caused by the load on the ring may force the ring into the assembly groove, resulting in the cutter falling 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 a thrust load is applied inward 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 securely.

Other objects of the present invention according to the accompanying drawings below:
It also identifies configuration requirements and benefits.

Rock drilling drill bit 11 of the present invention shown in FIG.
It includes a body 13 formed of three head portions 15, often joined by welding. A known drill (not shown) is installed on the top of the main body 13.
A thread 17 is formed for connection to the string. Each head portion 15 is a cantilevered shaft or bearing pin 19 with its free end facing inward and downward.
Equipped with. A substantially conical cutter 21 is rotatably attached to each bearing pin 19. 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 a lubricating oil passage 27 (for bearing surface treatment, see U.S. Patent No.
3397928 and 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). U.S. Application No. filed in the name of Milsatpus dijunia
687131 “Lubrication Hydraulic Compensator for Rock Drill Bits”). O-ring seals 31 located between each bearing pin 19 and cutter 21 at the base of the bearing pins prevent lubricating oil from flowing out and underground fluids from entering (U.S. Pat. No. 3,397,928 for O-ring seals and U.S. patent on oil
3935114).

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 located 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 here is the bearing pin 1.
The side wall 37 remote from the inner end or tip 43 of 9 is straight and perpendicular to the 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 respect to a plane orthogonal to the axis of the bearing pin 19 and is a conical thrust surface or an inclined wall that is non-orthogonal to the axis of the bearing pin 19. 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 a side wall remote from the tip 43 of the bearing pin 19.
In the cross-sectional view, the side wall 46 is located at the bottom 3 of the groove 33 mentioned above.
It has an arc shape corresponding to a quarter circle with a radius approximately equal to the radius of 5. 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 having a curved bottom. In this annular hole,
A snap ring 47 is provided having a curved profile and preferably a circular cross-sectional shape. Snap・
Ring 47 is formed of resilient metal, preferably piano wire, and includes a gap 49 to allow its 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. The cross-sectional diameter of the ring 47 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 1/
2 and smaller than the cross-sectional diameter. This depth is preferably greater than one-half the cross-sectional diameter of ring 47 by an amount referred to as an "offset" (indicated by S in the figure) of 0.127 mm to 0.508 mm (0.005 inch to 0.020 inch). Therefore, the cross-sectional center line 51 of the ring 47 is positioned outward by the same amount from the bearing pin cylindrical surface 34 and the retaining groove edge.

To attach the cutter 21 to the bearing pin 19,
Using a tool (not shown), insert the ring 47 into the groove 3.
Press fit into 3. Next, only a portion of the cutter 21 is inserted into the bearing pin 19, and the tool is removed. Then the fourth
As shown in the figure, press the cutter 21 outward until the opposing surfaces of the tapered tip bearing 52 engage with each other, and press the bearing pin 1.
9. Groove 45 is aligned with groove 33 so that ring 47 can fit therein. In FIG. 4, ring 47 is in contact with side wall 46 of groove 45 and not in contact with side wall 50. In FIG. The side wall 39 of the groove 33 also has a ring 47
is spaced apart from the ring 47 by a gap C ₁ to allow movement into the retaining groove 45 . Center line 5 of ring 47
1 is offset outwardly from surface 34 of bearing pin 19, preferably by 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 In other words, in Figure 5, the snap
The cross-sectional diameter of the ring 47 is X+Y, and the distance from the edge of the wall 39 to the opposite corner of the groove 46 is a distance X that is shorter than said X+Y. Therefore, if the cutter 21 is inserted, the ring 47 will fit into the assembly groove 33.
The cutter 21 cannot be pulled into the holding groove 45 and is held as it is in the holding groove 45, thereby preventing 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. The tapered surfaces of the bearing 52 engage, resulting in a gap C ₃ between the ring 47 and the wall 37 of the groove 33.
occurs, so 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 the fifth
As shown in the figure, the thrust load is suppressed by a ring 47 that transmits the thrust load between the side wall 46 and the side wall 39. 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 F that expands the ring 47 outward and causes it to fit into the groove 45 of the cutter 21. This is because the ring 47 is compressed and the bearing pin 19
The cutter 21 is fitted into the groove 33 of the cutter 21 and acts to prevent 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. 6th
Since the tapered wall 39 is shown exerting a force component F perpendicular to the surface of the ring 47 to force the ring 47 into the retaining groove 45, the "offset" is relatively small and may be unnecessary.

FIG. 7 shows a third configuration in which both side walls 37 and 39 of the assembly groove 33 are formed parallel to each other and perpendicular to the center line of the bearing pin 19. Here groove 33
The edge or outer wall 39 engages the ring 47 at a distance from the centerline 51 of the ring 47 equal to the "offset" of the cylindrical bearing surface 34. When an inward thrust load is applied to the cutter, a force component F acts on the ring 47 from an oblique direction perpendicular to the surface of the ring 47, forcing it 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. A preferable range of the offset amount S is such that when the angle α is preferably 15°, the surface 39, rather than the sharp edge, comes into contact with the ring 47. This surface contact is advantageous in reducing wear since sharp edges cause rapid wear on the ring 47.

All three configurations shown in FIGS. 4-7 include the configuration to minimize cutter loss, as already described in connection with FIG. In other words, the cross-sectional thickness X+Y of the ring 47 is determined from the distance X from the edge of the wall 39 to the corner of the groove 46 facing it when an inward thrust load is applied to the cutter 21 inserted into the bearing pin 19. It's also 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 holding 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,
When an inward thrust load is applied to the cutter, the snap ring is pressed into the retaining groove. 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...Drill bit, 13...Main body, 15
... Head, 19 ... Bearing pin, 21 ... Cutter, 23 ... Rock crushing tooth, 29 ... Pressure compensator, 3
1... O-ring seal, 33... Assembly groove, 45
...Retaining 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 on one of the cutter and the pin, and a retaining groove aligned with the assembly groove is formed on the other, and a snap ring is disposed within the groove, and the retaining groove has a depth. smaller than the cross-sectional thickness of the ring, the depth of the assembly groove is at least equal to the cross-sectional thickness of the ring, and the assembly groove, the retaining groove, and the snap ring are formed when a thrust load is applied to the cutter;
The cutter holding mechanism features a shape that traps the ring in the holding groove. 2 By making the depth of the retaining groove smaller than the cross-sectional thickness of the ring but larger than 1/2 of the cross-sectional thickness, an offset is created that engages the ring and presses it into the retaining groove when the thrust load on the cutter is removed. The cutter holding mechanism according to claim 1, characterized in that the cutter holding mechanism has a limited edge. 3. When an inward thrust load is applied to the cutter, the ring is held by making the distance from the offset annular portion of the assembly groove to the opposite retaining groove edge smaller than the cross-sectional thickness of the ring. The cutter holding mechanism according to claim 1, wherein the cutter holding mechanism is held within a groove. 4. The cutter holding mechanism according to claim 3, wherein the bottom wall of the groove is curved so that the cross section of the ring has a curved circumference. 5. The cutter holding mechanism according to claim 4, wherein the ring and the groove bottom wall have substantially circular and semicircular cross sections, respectively.