CN118257494A - Air screw transmission assembly and air screw - Google Patents

Abstract

The invention provides an air screw transmission assembly and an air screw, wherein the air screw transmission assembly comprises: the hammer type impact device comprises a hammer body and a drill bit connector, the hammer type impact device is installed on the transmission shaft, the transmission shaft is provided with a central channel, the hammer type impact device is communicated with the central channel, the hammer body can longitudinally reciprocate relative to the transmission shaft under the driving of air flow in the central channel to hammer the drill bit connector, and the technical problems that an air screw drilling tool is easy to clamp in the drilling process and the drilling efficiency of a hard stratum is low are solved.

Description

Air screw transmission assembly and air screw

Technical Field

The invention relates to the field of petroleum and natural gas exploitation engineering machinery, in particular to an air screw transmission assembly and an air screw.

Background

The air drilling technology can be applied to directional well and horizontal well drilling operation, and the air screw drilling tool is important equipment applying the air drilling technology. The development difficulty of coal bed gas exploitation is great, and the air directional drilling technology restricts the effective development and utilization of coal bed gas. The drilling fluid medium of the air screw drilling tool is different from that of the conventional screw drilling tool. An air compressor is used to pump gas as the motive medium for the air screw drilling tool. Similar to the conventional screw drilling tool, in the process of the drilling tool advancing, the underground operation working condition has similar conditions, and the drilling speed is greatly reduced due to the fact that the whole drilling tool rubs with the well wall to generate underpressure, so that the conditions of drill holding, drill sticking and the like occur. Air screw drilling tools generally provide rotational torque only, and are not ideal for drilling hard formations, and present difficult problems in drilling highly abrasive formations and directional drilling of hard rock.

Disclosure of Invention

The invention aims to provide an air screw transmission assembly and an air screw, which are used for solving the technical problems that an air screw drilling tool is easy to clamp in the drilling process and the drilling efficiency of a hard stratum is low.

The above object of the present invention can be achieved by the following technical solutions:

The invention provides an air screw drive assembly, comprising: the hammer type impact device comprises a transmission shaft and a hammer type impact device, the hammer type impact device comprises a hammer body and a drill bit connector, the hammer type impact device is installed on the transmission shaft, the transmission shaft is provided with a central channel, the hammer type impact device is communicated with the central channel, and the hammer body can longitudinally reciprocate relative to the transmission shaft under the driving of air flow in the central channel so as to hammer the drill bit connector.

In a preferred embodiment, the hammer impact device comprises a docking cylinder provided with a first docking through hole and a second docking through hole, both communicating with the central channel; the transmission shaft is provided with first installation cavity, dock section of thick bamboo install in the first installation cavity, the inner wall of first installation cavity with be provided with the second installation cavity between the dock section of thick bamboo, first butt joint through-hole with the second butt joint through-hole all with the second installation cavity intercommunication, the hammer block install in the second installation cavity, and the hammer block can block when being located the lower extreme gas in the second installation cavity to the central passageway flows.

In a preferred embodiment, the drill bit connector is provided with a sealing step, and the sealing step can be in sealing fit with the hammer body when the hammer body is located at the lower position.

In a preferred embodiment, the drill bit connector is located at least partially in the first mounting cavity; the sealing step part is annular, and is at least partially sleeved outside the butt joint barrel.

In a preferred embodiment, the hammer impact device comprises a limiting cylinder, and the limiting cylinder is sleeved outside the butt joint cylinder and is positioned above the hammer body.

In a preferred embodiment, the limiting cylinder is provided with a first runner, and two ends of the first runner are respectively communicated with the first butt joint through hole and the second butt joint through hole.

In a preferred embodiment, the hammer impact device comprises a flow guiding end plug, the flow guiding end plug is sleeved outside the abutting cylinder and is located above the limiting cylinder, the flow guiding end plug comprises an end face portion, a cylinder body portion and a flow guiding annular cavity, the end face portion is in sealing fit with the outer wall of the abutting cylinder, the cylinder body portion is in sealing fit with the end face of the limiting cylinder, a flow guiding through hole is formed in the side wall of the cylinder body portion and is used for communicating the flow guiding annular cavity with an outer space of the flow guiding end plug, and the first flow channel and the first abutting through hole are communicated with the flow guiding annular cavity.

In a preferred embodiment, the hammer impact device comprises a piston sleeve, the piston sleeve is sleeved outside the butt joint cylinder, and the hammer body is at least partially positioned between the piston sleeve and the butt joint cylinder.

In a preferred embodiment, the outer wall of the piston sleeve is provided with at least one first air flow flat groove, and the outer wall of the hammer body is provided with at least one second air flow flat groove.

In a preferred embodiment, the side wall of the piston sleeve is provided with a convection through hole.

In a preferred embodiment, the hammer impact device comprises a limiting split cylinder, and the limiting split cylinder is sleeved outside the piston sleeve.

In a preferred embodiment, the drill bit connector is connected with a limit post matched with the transmission shaft.

The invention provides an air screw, which comprises the air screw transmission assembly.

The invention has the characteristics and advantages that:

The drill bit is installed in the lower extreme of drill bit connector, and air screw drilling tool is when the well drilling to gas is regarded as the power medium, and the air current flows to hammer impact device through central passageway for through gas, the reciprocating hammering drill bit connector of hammer body, impact force is transmitted to the drill bit through the drill bit connector, produces the impact to the stratum. Through the transmission assembly, axial impact force can be generated on the drill bit of the air screw drilling tool, and the transmission assembly is used for keeping continuous drilling after the drill bit is released during clamping and braking, so that the working efficiency of drilling is improved; the drilling machine has the advantages that extra impact force is provided for the drill bit, the rotary impact drilling function is realized, the drilling mechanical efficiency and the rock breaking efficiency are improved, the drill bit is protected, the service life of the drill bit can be prolonged, the rock breaking efficiency is improved, the well construction period is shortened, the drilling economic benefit is improved, and the drilling machine is beneficial to drilling high-grinding stratum and hard rock directional drilling.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIGS. 1-2 are schematic illustrations of the structure of an air screw drive assembly provided by the present invention;

FIG. 3 is a schematic view of a hammer impact device in an air screw drive assembly according to the present invention;

FIG. 4 is an enlarged view of a portion of FIG. 3;

FIG. 5 is a schematic view of the docking cylinder of the hammer impact device of FIG. 3;

FIG. 6 is a schematic view of a flow-guiding end plug of the hammer impact device shown in FIG. 3;

FIG. 7 is a schematic view of a limiting cylinder of the hammer impact device shown in FIG. 3;

FIG. 8 is a schematic view of the piston sleeve of the hammer impact device of FIG. 3;

FIG. 9 is a schematic view of the hammer block of the hammer impact device of FIG. 3;

FIG. 10 is a schematic view of a bit connector of the hammer impact device shown in FIG. 3;

fig. 11 is a schematic structural view of a limiting split cylinder in the hammer impact device shown in fig. 3.

Reference numerals illustrate:

100. A hammer impact device;

1. a hammer body; 11. a second air flow flat groove;

2. A drill bit connector; 21. sealing the step part;

3. a butt joint barrel; 31. a first docking through hole; 32. a second butt joint through hole; 33. a docking channel;

4. a diversion end plug; 41. an end face portion; 42. a cylinder body; 43. a deflector ring cavity; 44. a diversion through hole;

5. a limiting cylinder; 51. a first flow passage;

6. A piston sleeve; 61. a first air flow flat groove; 62. a convection hole;

63. Limiting split cylinders;

71. A limit column; 72. a plug;

8. A transmission shaft; 80. a central passage;

81. A TC bearing static ring is arranged; 82. a TC bearing moving coil is arranged; 83. a rolling bearing group; 84. a housing welding assembly; 85. a shaft pad; 86. a lower locking mechanism; 87. a lower TC bearing static ring; 88. a lower TC bearing moving coil;

200. A water cap.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Scheme one

The present invention provides an air screw drive assembly, as shown in fig. 1-4, comprising: the hammer type impact device 100 comprises a hammer body 1 and a drill bit connector 2, the hammer type impact device 100 is mounted on the transmission shaft 8, the transmission shaft 8 is provided with a central channel 80, the hammer type impact device 100 is communicated with the central channel 80, and the hammer body 1 can longitudinally reciprocate relative to the transmission shaft 8 under the driving of air flow in the central channel 80 to hammer the drill bit connector 2.

The drill bit is installed in the lower extreme of drill bit connector 2, and air screw drilling tool is when the well drilling, uses gas as the power medium, and the air current flows to hammer impact device 100 through central passageway 80 for through gas, the reciprocating hammering drill bit connector 2 of hammer 1, impact force is transmitted to the drill bit through drill bit connector 2, produces the impact to the stratum. Through the transmission assembly, axial impact force can be generated on the drill bit of the air screw drilling tool, and the transmission assembly is used for keeping continuous drilling after the drill bit is released during clamping and braking, so that the working efficiency of drilling is improved; the drilling machine has the advantages that extra impact force is provided for the drill bit, the rotary impact drilling function is realized, the drilling mechanical efficiency and the rock breaking efficiency are improved, the drill bit is protected, the service life of the drill bit can be prolonged, the rock breaking efficiency is improved, the well construction period is shortened, the drilling economic benefit is improved, and the drilling machine is beneficial to drilling high-grinding stratum and hard rock directional drilling.

In one embodiment, as shown in fig. 4 and 5, the hammer impact device 100 includes a docking cylinder 3, the docking cylinder 3 being provided with a first docking through hole 31 and a second docking through hole 32, the first docking through hole 31 and the second docking through hole 32 each communicating with the central passage 80; the transmission shaft 8 is provided with first installation cavity, and butt joint section of thick bamboo 3 installs in first installation cavity, is provided with the second installation cavity between the inner wall in first installation cavity and the butt joint section of thick bamboo 3, and first butt joint through-hole 31 and second butt joint through-hole 32 all communicate with the second installation cavity, and hammer block 1 installs in the second installation cavity to hammer block 1 can block the gas in the second installation cavity and flow to central passageway 80 when being located the lower extreme.

Compressed gas enters the butt-joint barrel 3 through a central channel 80 of the transmission shaft 8; the gas enters the channel at the tail end of the hammer body 1, and when the gas pressure is higher and higher, the hammer body 1 is pushed to move upwards; when the hammer body 1 moves for a certain distance, gas is discharged from the second butt joint through hole 32 of the butt joint barrel 3, so that the whole tail end of the hammer body 1 is in a low-pressure state; because the high-pressure pump group on the ground continuously presses into the stratum, the front and back of the hammer body 1 form pressure difference, the hammer body 1 is pushed to a low pressure position from the high pressure position, and the hammer body 1 moves downwards and hammers the drill bit connector 2; thereby, the hammer body 1 longitudinally reciprocates back and forth along the transmission shaft 8 and continuously impacts the drill bit connector 2 so as to unclamp the drill bit.

The high pressure gas passes through the central passage 80 of the drive shaft 8 and flows through the first docking through hole 31 into the second mounting cavity; when the hammer 1 moves upward, the gas in the second mounting chamber flows back to the center passage 80 through the second docking through hole 32 to discharge the gas pressure. As shown in fig. 5, the first docking through hole 31 is disposed above the second docking through hole 32.

Further, as shown in fig. 4 and 10, the bit connector 2 is provided with a seal step 21 at the head, and the seal step 21 can be in sealing engagement with the hammer 1 when the hammer 1 is in the lower position. When the end face of the hammer body 1 is abutted with the drill bit connector 2, the hammer body 1 and the sealing step part 21 are overlapped at the upper part in the longitudinal direction, so that the sealing effect is improved; after the hammer body 1 moves upwards in the longitudinal direction for a certain distance, the hammer body 1 and the sealing step part 21 are completely separated, and a gap is formed between the hammer body 1 and the sealing step part, so that gas in the second installation cavity can flow back to the central channel 80 of the transmission shaft 8 through the second butt joint through hole 32, the pressure of the second installation cavity is relieved, and the whole tail end of the hammer body 1 is in a low-pressure state, so that the hammer body 1 can move downwards again.

The docking cylinder 3 has a docking passage 33, and the first docking through hole 31 and the second docking through hole 32 are both communicated with the docking passage 33, and the air flow in the central passage 80 first flows into the docking passage 33. Preferably, the axis of the docking channel 33 coincides with the axis of the central channel 80. As shown in fig. 1-4, the drill bit connector 2 is at least partially located in the first mounting cavity; the sealing step part 21 is annular, and the sealing step part 21 is at least partially sleeved outside the abutting cylinder 3.

In one embodiment, the hammer impact device 100 includes a limiting cylinder 5, where the limiting cylinder 5 is sleeved outside the docking cylinder 3 and is located above the hammer body 1. As shown in fig. 4 and 7, the stopper cylinder 5 is provided with a first flow passage 51, and both ends of the first flow passage 51 communicate with the first docking through hole 31 and the second docking through hole 32, respectively. When gas enters the butt joint barrel 3, a part of pressure can be removed through the first flow passage 51, so that the situation that the pressure in the cavity is blocked and braking is caused due to the fact that the inlet pressure is too high is prevented.

Further, the hammer impact device 100 includes a guide end plug 4, as shown in fig. 4 and 6, the guide end plug 4 is sleeved outside the docking cylinder 3 and above the limiting cylinder 5, the guide end plug 4 includes an end surface portion 41, a cylinder portion 42 and a guide ring cavity 43, the end surface portion 41 is in sealing fit with the outer wall of the docking cylinder 3, the end surface of the cylinder portion 42 is in sealing fit with the end surface of the limiting cylinder 5, a guide through hole 44 is disposed on a side wall of the cylinder portion 42, the guide through hole 44 is used for communicating the guide ring cavity 43 and an external space of the guide end plug 4, and the first flow channel 51 and the first docking through hole 31 are both communicated with the guide ring cavity 43.

The gas enters the guide ring cavity 43 in the guide end plug 4 through the first butt joint through hole 31 in the butt joint cylinder 3, and the guide through hole 44 enters the outer space of the guide end plug 4. When the gas enters the guide end plug 4, a part of the gas may cause the guide end plug 4 to be blocked due to impurities in the gas, so as to suppress pressure, and a part of the gas can be leaked from the first flow passage 51 of the limiting cylinder 5 to avoid suppressing pressure.

As shown in fig. 4 and 8, the hammer impact device 100 includes a piston sleeve 6, the piston sleeve 6 is sleeved outside the docking cylinder 3, and the hammer block 1 is at least partially located between the piston sleeve 6 and the docking cylinder 3.

Further, as shown in fig. 4, 8 and 9, the outer wall of the piston sleeve 6 is provided with at least one first air flow flat groove 61, and the outer wall of the hammer body 1 is provided with at least one second air flow flat groove 11. The first air flow flat groove 61 transmits the air at the top of the piston sleeve 6 downwards, the air flows to the second air flow flat groove 11 of the hammer body 1 through the first air flow flat groove 61, and the hammer body 1 is pushed to move downwards along with the increasing pressure of the air, so that the drill bit connector 2 is knocked, and the drilling tool is released. Preferably, the outer wall of the piston sleeve 6 is provided with 8 first air flow flat grooves 61, and the outer wall of the hammer body 1 is correspondingly provided with 8 second air flow flat grooves 11, so that air can completely flow through the first air flow flat grooves 61 to push the hammer body 1 to move.

In an embodiment, the sidewall of the piston sleeve 6 is provided with a convection hole 62, so that the gas in the flow passage can not be suppressed after the drill bit connector 2 moves down, and the pressure can be released from the convection hole 62 to the middle flow passage, so that the whole annular gas is smooth.

As shown in fig. 1-4, gas is transferred from the central through hole of the drive shaft 8 into the docking channel 33 of the docking cylinder 3; through the first butt joint through hole 31, the vehicle walks outwards through the diversion end plug 4; the gas walks towards the direction approaching the drill bit through the air passage at the upper end of the limit cylinder 5 and finally enters the air passage at the upper part of the hammer body 1; when gas flows into the air passage at the lower side of the hammer body 1, the hammer body 1 is pushed to move upwards, and the gas is discharged from the second gas passage in the butt joint barrel 3; thereby generating high-low pressure difference in front and back of the hammer body 1, and the newly-entered high-pressure gas continuously pushes the hammer body 1 to move to a low-pressure position to form effective impact, thereby forming a reciprocating impact action.

In one embodiment, as shown in fig. 3 and 11, the hammer impact device 100 includes a limiting split cylinder 63, and the limiting split cylinder 63 is sleeved outside the piston sleeve 6. After entering the guide end plug 4, the gas enters a channel between the limiting split and the hammer body 1 along a gas channel outside the piston sleeve 6, and when the gas pressure in the channel is higher and higher, the hammer body 1 is pushed to move upwards.

The drill bit is connected to the screw drilling tool through the drill bit connector 2, when the hammer body 1 continuously impacts the drill bit connector 2 for a long time, a gap is formed between the drill bit connector 2 and the transmission shaft 8, and when the drill bit meets a hard stratum, the gap returns.

Compressed gas enters the butt joint cylinder through the transmission shaft; when the gas enters the guide end plug through the butt joint cylinder, a part of the gas possibly causes the guide end plug to be blocked due to impurities in the gas, so that the pressure is suppressed, and a part of the gas is leaked from the limit cylinder; after entering the guide end plug, the gas enters a channel between the limiting split and the hammer body along a gas channel above the piston sleeve, and when the gas pressure in the channel is higher and higher, the hammer body is pushed to move forwards; when the hammer body moves for a certain distance, namely, leaves the step surface, the gas in the channel is discharged from the hole of the butt joint barrel, so that the whole tail end of the hammer body is in a low-pressure state; because the high-pressure pump group on the ground continuously presses into the stratum, the front and the back of the hammer body form pressure difference, and the hammer body is pushed to a low pressure position from a high pressure position; therefore, the hammer body reciprocates back and forth, and the drill bit connector is continuously impacted to release the drill bit.

In one embodiment, as shown in fig. 1-3, the drill bit connector 2 is connected with a limit post 71 that mates with the drive shaft 8. In one embodiment, the air screw drive assembly further includes a plug 72.

As shown in fig. 2, the air screw transmission assembly further includes a water cap 200, an upper TC bearing static ring 81, an upper TC bearing moving ring 82, a rolling bearing set 83, a casing welding assembly 84, a shaft pad 85, a lower locking mechanism 86, a lower TC bearing static ring 87 and a lower TC bearing moving ring 88, and the control of the air passage is realized through the transmission shaft 8, so that the air enters the hammer impact device 100, and a power source is provided for realizing the reciprocating motion of the hammer body 1.

The central passage 80 of the drive shaft 8 is connected to the water cap 200 and gas is transferred from the motor assembly to the cardan shaft assembly and thence to the central passage 80 of the drive shaft 8 via the water cap 200. The upper end of the water cap 200 is connected with a bypass valve assembly, a motor assembly and a universal shaft assembly, and a drill bit is connected with the drill bit connector 2. The compressed gas flows through the bypass valve assembly, the motor assembly and the cardan shaft assembly and then into the water cap 200, through the transmission shaft 8 and into the docking cylinder 3. The water cap 200 assembly is a component for transferring air medium transferred from the cardan shaft assembly, and its functions mainly include: the ground air compressor pumps air into the motor assembly through the bypass valve assembly and then through the cardan shaft assembly to the water cap 200.

In one embodiment, the downhole operating conditions are: the gas enters the bypass valve assembly through the drill string and then enters the motor assembly to drive the rotor to conduct planetary rotation, the universal shaft assembly converts the planetary rotation of the rotor into fixed shaft motion, and finally power is transmitted to the transmission assembly. After the gas enters the transmission assembly, the gas can be split at the position of the limiting cylinder 5, and a small part of the gas passes through the first flow passage 51 and enters the second butt joint flow passage of the butt joint cylinder 3 to be discharged, so that the gas entering the high-pressure cavity of the hammer body 1 is prevented from being suppressed due to accidental factors. The rotary motion of the transmission shaft 8 and the reciprocating motion of the hammer body 1 form rotation and high-frequency impact in the drilling process to act on the drill bit connector 2, so that the drill bit has the clamping and releasing functions and is axially impacted and rotated, the mechanical rotation speed of the drill bit is improved, the drilling rate of drilling by rotary impact can be improved, under the action of axial impact force with a certain frequency, the cutting teeth of the drill bit are not easy to form mud and stick-slip caused by mud, and meanwhile, the formation cutting force is ensured to be uniform, thus the drilling rate of drilling by mechanical drilling can be improved to be more than 30%.

When the air drives the screw motor to perform directional drilling of coal bed methane, frequent stall braking of the screw motor occurs due to the compression performance of the air. The air screw drill adopting the air screw transmission assembly enables the drill bit to continuously impact the stratum, and can well solve the problem of braking. The air screw transmission assembly can be used in directional deflecting, so that the mechanical drilling speed of the directional deflecting is improved; can also be used in composite drilling, and can improve the mechanical drilling speed of the composite drilling.

Scheme II

The invention provides an air screw, which comprises the air screw transmission assembly.

The air screw has the structure and beneficial effects of the air screw transmission assembly, and the detailed description is omitted herein

The foregoing is merely a few embodiments of the present invention and those skilled in the art may make various modifications or alterations to the embodiments of the present invention in light of the disclosure herein without departing from the spirit and scope of the invention.

Claims (13)

1. An air screw drive assembly, comprising: the hammer type impact device comprises a transmission shaft and a hammer type impact device, the hammer type impact device comprises a hammer body and a drill bit connector, the hammer type impact device is installed on the transmission shaft, the transmission shaft is provided with a central channel, the hammer type impact device is communicated with the central channel, and the hammer body can longitudinally reciprocate relative to the transmission shaft under the driving of air flow in the central channel so as to hammer the drill bit connector.

2. The air screw drive assembly according to claim 1, wherein the hammer impact device comprises a docking barrel provided with a first docking through hole and a second docking through hole, both in communication with the central channel;

The transmission shaft is provided with first installation cavity, dock section of thick bamboo install in the first installation cavity, the inner wall of first installation cavity with be provided with the second installation cavity between the dock section of thick bamboo, first butt joint through-hole with the second butt joint through-hole all with the second installation cavity intercommunication, the hammer block install in the second installation cavity, and the hammer block can block when being located the lower extreme gas in the second installation cavity to the central passageway flows.

3. The air screw drive assembly according to claim 2, wherein the bit connector nose is provided with a sealing step portion, the sealing step portion being capable of sealing engagement with the ram when the ram is in the down position.

4. An air screw drive assembly according to claim 3 wherein said bit connector is at least partially located in said first mounting cavity; the sealing step part is annular, and is at least partially sleeved outside the butt joint barrel.

5. The air screw drive assembly according to claim 2, wherein the hammer impact device comprises a limiting cylinder sleeved outside the docking cylinder and above the hammer body.

6. The air screw drive assembly according to claim 5, wherein the limiting cylinder is provided with a first flow passage, and two ends of the first flow passage are respectively communicated with the first butt joint through hole and the second butt joint through hole.

7. The air screw drive assembly according to claim 6, wherein the hammer impact device comprises a flow guiding end plug, the flow guiding end plug is sleeved outside the abutting cylinder and located above the limiting cylinder, the flow guiding end plug comprises an end face portion, a cylinder body and a flow guiding annular cavity, the end face portion is in sealing fit with the outer wall of the abutting cylinder, the end face of the cylinder body is in sealing fit with the end face of the limiting cylinder, a flow guiding through hole is formed in the side wall of the cylinder body and used for communicating the flow guiding annular cavity and an outer space of the flow guiding end plug, and the first flow channel and the first abutting through hole are communicated with the flow guiding annular cavity.

8. The air screw drive assembly according to claim 2 wherein said hammer impact device comprises a piston sleeve, said piston sleeve being disposed externally of said docking barrel and said hammer body being at least partially disposed between said piston sleeve and said docking barrel.

9. The air screw drive assembly according to claim 8, wherein the outer wall of the piston sleeve is provided with at least one first air flow flat groove and the outer wall of the hammer body is provided with at least one second air flow flat groove.

10. The air screw drive assembly according to claim 8 wherein the sidewall of the piston sleeve is provided with a convection opening.

11. The air screw drive assembly according to claim 8 wherein said hammer impact device comprises a limiting split barrel, said limiting split barrel being sleeved outside said piston sleeve.

12. The air screw drive assembly according to claim 1, wherein the drill bit connector is connected with a limit post that mates with the drive shaft.

13. An air screw comprising the air screw drive assembly of any one of claims 1-12.