Claims
- 1. A method for boring through the taphole in a molten metal blast furnace, comprising the steps of:
- providing a rotary percussion drill adapted for reciprocal rectilinear motion;
- providing a drill shaft assembly having:
- a drill tool piece shaft having a first end and a second end and a passageway extending through at least a portion of its length,
- a drill shaft having a first end connected with the second end of said drill tool piece shaft and having means for holding a drill bit, said drill shaft having a solid cross-section along substantially its entire length,
- a drill bit held by the second end of said drill shaft,
- air channel means disposed along the length of the drill shaft assembly for directing air flow toward but from a point above the second end of said drill shaft, said air channel means being in flow communication with the passageway of said drill tool piece, and
- coupler means for connecting the second end of said drill tool shaft to the first end of said drill shaft;
- operatively connecting the first end of said drill tool piece shaft with the rotary percussion drill;
- applying pressurized air into the passageway at the first end of said drill tool piece shaft so that pressurized air is directed along the drill shaft assembly and toward said drill bit; and,
- engaging said rotary percussion drill causing said drill bit to bore into the taphole of a molten metal blast furnace.
- 2. The method for boring through the taphole in a molten metal blast furnace of claim 1 wherein said providing said drill shaft assembly includes said air channel means being a longitudinal groove along the length of said drill shaft and an air blast tube embedded within the groove.
- 3. The method for boring through the taphole in a molten metal blast furnace of claim 2 wherein the air blast tube has a first end in flow communication with the passageway of said drill tool piece shaft and has a second, opposite end extending substantially all the way to the second end of said drill shaft.
- 4. A combination comprising:
- a molten metal blast furnace having a taphole;
- a rotary percussion drill means for boring through said taphole, said drill means being mounted adjacent said taphole;
- a drill tool piece shaft having a first end and a second end and a passageway extending through at least a portion of its length;
- connecting means for connecting the first end of said drill tool piece shaft with the rotary percussion drill means;
- a drill shaft having a first end connected with the second end of said drill tool piece shaft and having a second end having means for holding a drill bit, said drill shaft having a solid cross-section along substantially its entire length;
- a drill bit held by the second end of said drill shaft;
- air channel means disposed along the length of the drill shaft assembly for directing air flow toward but from a point above the second end of said drill shaft, said air channel means being in flow communication with the passageway of said drill tool piece; and,
- coupler means for connecting the second end of said drill tool shaft to the first end of said drill shaft.
- 5. The combination of claim 4 wherein said air channel means includes at least one longitudinal groove defined in the exterior surface of said drill shaft and extending substantially the entire length of said shaft.
- 6. The combination of claim 5 wherein said air channel means further includes an air blast tube embedded within said longitudinal groove, said tube having a first end in flow communication with the passageway of said drill tool piece shaft and having a second, opposite end extending substantially all the way to the second end of said drill shaft.
- 7. The combination of claim 4 wherein said drill shaft defines a first face at the first end of said drill shaft, and wherein the air channel means includes a radial air flow groove defined in the first face, the air flow groove being in flow communication with the passageway, and wherein the air flow groove further extends from the first face of said drill shaft along the outside of said drill shaft toward the second end of said drill shaft.
- 8. The combination of claim 7 wherein said drill shaft has a longitudinal axis and wherein the radial air flow groove extends parallel to the axis from the first face toward the second end of said drill shaft.
- 9. The combination of claim 7 wherein the radial air flow groove diametrically spans the first face of said drill shaft.
- 10. The combination of claim 9 wherein said drill shaft has a longitudinal axis and wherein the radial air flow groove extends parallel to the axis from the first face, on opposite sides of said drill shaft and toward the second end of said drill shaft.
- 11. The combination of claim 7 wherein the passageway is an axial hollow bore which extends to the second end of said drill tool piece shaft.
- 12. The combination of claim 11 wherein said drill tool piece shaft defines a second face at the second end of said tool piece drill shaft, wherein the air channel means further includes a back air flow groove defined in the second face, the back air flow groove extending radially from and being in flow communication with the hollow bore, and wherein the back air flow groove further extends from the second face exteriorly of said drill tool piece shaft toward the first end of said drill tool piece shaft.
- 13. The combination of claim 12 wherein said drill tool piece shaft has a longitudinal axis and wherein the back air flow groove extends parallel to the axis of said drill tool piece shaft.
- 14. The combination of claim 4 wherein said drill shaft is externally threaded a first longitudinal length at the first end of said drill shaft, and wherein said drill tool piece shaft is externally threaded a second longitudinal length at the second end of said drill tool piece shaft, and wherein said coupler means is a hollow coupling having internal threading for meshing with and drawing together said drill shaft and said drill tool piece shaft.
- 15. The combination of claim 14 wherein the internal threading of said hollow coupling has a third longitudinal length which is less than the sum of the first and second longitudinal lengths.
- 16. The combination of claim 4 wherein said drill shaft defines a first face at the first end of said drill shaft, and wherein said air channel means includes:
- a central longitudinal bore extending from the first face and partway toward the second end of said drill shaft, the central bore being in flow communication with the passageway of said drill tool piece, and
- at least one exit bore radially extending from and being in communication with said central bore.
- 17. A combination comprising:
- a molten metal blast furnace having a taphole;
- a molten metal blast furnace drilling means for drilling through the taphole of said molten metal blast furnace;
- said drilling means including a drilling shaft means for holding a drill bit and for imparting rotational motion from said drilling means to said drill bit;
- said drilling shaft means including a drill tool piece shaft having a first end rotatably mounted to said drilling means, a second opposite end, and a central bore;
- said drilling shaft means further including a coupler means having first mounting side and a second opposite mounting side, said first mounting side being connected to said second end of said drill tool piece shaft;
- said drilling shaft means further including a drill shaft being substantially a solid bar, said drill shaft having a first end connected to said second mounting side of said coupler and said drill shaft having air channel grooves cut into the exterior surface of said solid bar;
- said drill bit being connected to the second end of said drill shaft;
- pressurized air means in flow communication with the first end of said axial bore of said drill tool piece shaft for providing pressurized air flowing through said bore and then through said coupler and then along said grooves in said drill shaft.
- 18. The combination of claim 17 wherein said drill shaft includes at least one longitudinal groove defined in the exterior surface of said drill shaft and extending substantially the entire length of said shaft.
- 19. The combination of claim 18 including an air blast tube embedded within said longitudinal groove, said tube having a first end in flow communication with the bore of said drill tool piece shaft and having a second, opposite end extending substantially all the way to the second end of said drill shaft.
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is a continuation in part of my co-pending U.S. patent application Ser. No. 122,023 filed 11-18-87, now abandoned.
The present invention relates to the field of metallurgical furnace taphole-opening apparatus and more specifically to a drill shaft assembly and method for use with a molten metal blast furnace tap hole percussion drill and related molten metal blast furnace taphole-opening tools.
Metallurgical furnaces, such as molten metal blast furnaces, are normally opened for tapping by drilling a hole through a clay refractory material disposed in the furnace taphole. Background on blast furnace operation may also be found in U.S. Pat. No. 4,475,720 entitled Cast House Emission Control System to which this inventor is a co-inventor.
Drilling the taphole is ordinarily performed by a percussion-type drill and drilling tools which normally include a long, hollow shaft of high alloy tool steel pipe with a rock bit secured to the end thereof. As the bit drills through the refractory material, a great deal of dust is deposited within the bore. As drilling is continued the dust often tends to bind the bit, impeding further drilling. Often the high build up of dust will make it difficult to extract the bit from the bore once the bit breaks through to the molten metal. This binding causes damage to the drill shaft since it cannot be easily removed. Sometimes the hole itself may plug up. On other occasions if the drill binds up due to dust buildup it can only be removed by the use of an oxygen lance to cut the shaft.
In order to continuously clear the dust the drill bit in prior art devices has been provided with multiple holes which communicate with the bore of the drill shaft. The bore in the drill shaft in prior art devices extends for the entire length of the shaft from its connection to the drill motor to its connection with the drill bit. Pressurized air is directed down the hollow drill shaft through the holes in the bit to provide a continuous stream of pressurized air exiting the front of the bit, then passing to the side and behind the bit out the newly bored hole and forcing with it the dust concentration.
Drilling is continued until the drill bit strikes a glowing "skull" which is formed by contact of the clay materials with the molten metal within the furnace. Continued drilling after reaching the skull will break through into the blast furnace at which point the molten metal surges back through the taphole and into a runner trough for eventual distribution into various pugh ladles. Often times the surge of molten metal melts the drill bit. It then overcomes the pressurized air in the larger drill shaft bore and surges up the bore until it reaches the drill motor resulting in the destruction or severe damage to the motor and drill shaft.
Another disadvantage of the prior art devices is the excessive cost involved with replacing the components which were melted by the molten metal backwash. In anY event, the lower portion of the drill shaft which extends during drilling into the molten metal (2800 degrees Fahrenheit) is damaged. The drill shaft of the prior art was commonly made from a long piece of high alloy tool steel pipe with typically a 3/16ths-inch bore through its entire length or by the welding together of two shorter such pipes. That length extended from the drill motor to the drill bit. For a typical one taphole blast furnace, the furnace is drilled anywhere from seven to twelve times per day seven days every week. Consequently, drilling a taphole is an expensive process since an entire new drill shaft has to be replaced after each drilling. Considering the frequency of drilling, any savings in materials due to improved design is significant.
One prior art effort at reducing the cost of drill shafts was to break the drill shaft pipe into two components. Consequently, if there was no backwash, only the lower portion, which extended into the molten metal needed to be replaced. These components were joined in the middle by a coupling. In the prior art the coupling was done by threading the ends of the two drill shaft pipes and then having a coupling with internal threads. However, the entire thread length of each pipe fit inside the coupling so that the coupling and pipe mating often froze and could not be disengaged. Consequently, most current designs use just a single pipe and avoid the expense of the coupling. In addition the above mentioned design still used an internal bore through the length of the drill shaft and consequently still suffered from the molten metal backwash problem and the expense of using pipe steel.
Another method for solving the backwash problem is as described in this inventor's previous U.S. Pat. No. 3,862,750. However, that method requires the drilling of a portion of the taphole with one drill shaft and then using a specialized chuck apparatus to replace the more expensive pipe shaft with a less expensive solid shaft in the middle of the drilling process. This procedure slows the drilling process, requires more than one shaft, and requires tool changing in the environment of a blast furnace.
The present invention recognized the need for a drill shaft assembly which is less expensive, which continues to remove or improves the removal of the dust produced by drilling through the clay refractory material and which inhibits molten metal backwash from destroying the drill motor and adjacent components.
Generally speaking there is provided an improved drill shaft assembly for a blast furnace taphole-opening apparatus which retards molten metal backwash, aids in the removal of dust produced from the taphole drilling operation and allows for the use of cheaper materials. In the preferred embodiment, a drill bit is connected to the forward end of a drill shaft and the forward end of the drill shaft is solid. The rearward end of a drill shaft is coupled to the forward end of a drill tool piece shaft which is secured at its rearward end to a drill motor. The drill tool piece shaft defines a central axial bore in communication with a high pressure air source. The forward end of the drill shaft is solid while the rearward end is provided with an air flow channel in communication with the central bore of the drill tool piece shaft. Air forced through the central bore and through the air flow channel provides a forced air path for the removal of dust from the taphole drilling operation.
In an alternative embodiment, the drill shaft defines a longitudinal groove extending the length thereof. An air blast tube is fixed within the groove to extend nearly the length of the drill shaft to direct the forced air to the forwardmost end of the drill shaft and to the drill bit.
It is an object of the present invention to provide an improved and less expensive drill shaft assembly for drilling tapholes in a molten metal blast furnace.
It is a further object of the present invention to provide an improved drill shaft assembly which provides for removal of dust while drilling, retards molten metal backwash following taphole drilling of a blast furnace and allows the use of less expensive materials.
Further objects and advantages of the present invention will become apparent from the following description of the preferred embodiment.
US Referenced Citations (5)
Continuation in Parts (1)
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122023 |
Nov 1987 |
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Patent Grant
4895349
