Boring or penetrating the earth – Automatic control – Of advance or applied tool weight
Reexamination Certificate
1998-11-24
2001-04-17
Johnson, Brian L. (Department: 3671)
Boring or penetrating the earth
Automatic control
Of advance or applied tool weight
C175S213000, C175S048000, C175S066000, C173S003000, C173S004000
Reexamination Certificate
active
06216800
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an improved system for in-situ drilling, and more particularly, to such a system where the rate of drilling is regulated by monitoring one or more parameters of the fluid flow for disposing of the cuttings and dust.
BACKGROUND OF THE INVENTION
Most earth drilling systems employ some form of rotary or percussion powered drills. There have been many advances in recent years to make the drilling operation more efficient, and thus provide better and faster drilling speeds, especially in rock layers. Typically, a drilling machine, such as for forming a hole for an explosive charge, or for anchoring a roof bolt, includes a drill stem with a drill bit on the distal down hole section thereof. The stem/bit on a rotary drill machine is rotated by a spinner mounted on a drill head to form the drill hole. The rotary driving motion of the spinner is usually hydraulically or pneumatically driven and manually regulated by the operator of the drill machine. Due in part to the advances in the technology, such as in regard to the drill bit and/or components of the drilling machine, providing attendant easier and faster drilling, operators have become accustomed to set the controls to try to drill the hole in the least amount of time. In doing so, the spinner head is rotated and the feed of the drill head is engaged to move the drill stem into the hole as rapidly as possible. The operator typically changes these settings only in the event that a problem develops.
As a part of the more efficient drilling, the cuttings and dust must be collected and removed from adjacent the drill bit so that clean cutting edges are provided at the bottom of the hole to allow the most efficient contact with the rock, or other strata. Typically, a pneumatic or hydraulic cuttings/dust collection/suppression and removal system is employed. Pressurized air, or a suitable hydraulic fluid such as water, or an air/water mixture, is forced down a center passage through the drill stem to bail or pick up the cuttings and dust for disposal. It is also known to impose a vacuum on the center passage of the drill stem drawing air into the hole around the periphery of the drill stem, whereupon the cuttings and the dust particles are entrained and removed through the center passage. In either system, this withdrawn debris is pneumatically or hydraulically conveyed away from the drill hole. When using air, the cuttings and dust are then filtered out at a remote location and disposed of. In systems where water is used, either exclusively or in a mixture with other fluids, an option is to simply allow the dust to be suppressed and then deposited outside the drill hole. In either case, airborne contamination is advantageously substantially eliminated.
A typical drilling arrangement and cuttings/dust collecting system is shown in the prior art; Howeth, U.S. Pat. No. 4,434,861. In this patent, the bailing air is supplied through the center passage of the drill stem and the cuttings/dust is removed from the hole by a vacuum head. Insofar as the '861 disclosure is concerned, the advancement of the drill stem into the hole, and the rotation of the drill bit, are manually controlled by the operator. Other functions of the drilling system are however automatically controlled, such as the extending or retracting the drill stem with respect to the deck plate. In other words, the drill stem extends to the drilling position only when the drill stem is supplied with sufficient bailing air to be operative, and the drill stem is automatically retracted from the hole when the bailing air supply is terminated (see column 14, lines 14-37).
Another feature of the prior art Howeth '861 patent is to provide an improved vacuum skirt around the hole and the drill stem so as to attempt to improve the sealing, and thus enhance the efficiency of the bailing operation by reducing the tendency of the bailing system to choke or overload. This patent also teaches the fundamental premise of making certain that the passageways are proportioned sufficiently larger than the drill hole to also help alleviate choking of the bailing air carrying the cuttings/dust (see column 14, lines 38-66). While this overall system is an improvement over prior art drilling machines, problems still arise with regard to choking or overloading the vacuum system, especially where the drill speed is increased beyond normal levels and when strata containing soft minerals, coal, shale, mud stone or the like debris are encountered in the drilling operation.
Other patents, such as the patent to Ek, U.S. Pat. No. 3,946,818, have disclosed other efforts of inventors to improve the sealing of the skirt in a different manner to try to improve the flow so that choking does not occur as readily. Heretofore, approaches other than these stop gap methods to solve the same problem have simply not been successful, insofar as we are aware. In theory, the operator of the drilling machine is simply depended upon to try to anticipate any approaching choking or flow overload situation and then shut the machine down. Unfortunately, in an overwhelming percentage of times, this is not possible because of the response time factor, and the collecting system becomes overloaded. The entire drilling operation must then be shut down for an extended period, the drill stem and bit removed from the drill hole and all passageways cleared of the debris. Alternatively, drilling must be performed at a continuously reduced rate to compensate and thus prevent these intermittent overload conditions.
Other inventors have concentrated on improving other aspects of the drilling machines, such as with respect to an improved cyclone filter, as set forth in the England U.S. Pat. No. 5,320,188. Indeed, there have even been attempts to control the flow of pneumatic fluid to the drilling tool in an automatic fashion. In the McDonald et al. U.S. Pat. No. 4,936,397, the pneumatically controlled valve is operable to transmit an initial, extra strong pulse of air to initiate operation of the down hole drilling motor. Once the motor is operating, the valve is kept open at a lower pressure than is required to open it so that the drilling can continue at a lower energy level.
Similarly, energy saving is the impetus in the Enlund et al. U.S. Pat. No. 5,409,072, wherein the pneumatic air supply is provided by a compressor driven by a hydraulic drive motor with adjustable displacement. The pneumatic pressure supplied by the compressor is adjusted inversely proportional to the pressure primarily used to drive the percussion drill along its linear path, and/or the input pressure of the drive motor itself. In this manner, it is proposed that the energy required to operate the entire system is maintained substantially constant during all phases of the operation.
Thus, while many refinements have been made in drilling machines and their method of operation, there is a marked absence of more responsive control systems, and more particularly with regard to regulating the drill feed and rotation in response to one or more parameters occurring in the cuttings/dust collecting or suppression system. Such a concept would have specific usefulness in improving the drilling efficiency especially for forming small (20-50 mm) diameter holes using rotary cutting tools and high tool feed forces. In such an arrangement, we have discovered that it would be especially advantageous to keep the drill penetration rate as rapid as possible, while at the same time control the rate of tool advance and/or rotation using feedback from the cuttings/dust collection or suppression system. In this manner, it is believed that clogging or overload, and its deleterious side effects, can be avoided. What we envision as a need in the underground mining industry, and particularly for drilling small diameter holes for installation of roof bolts, explosive charges or the like, is such an automatic control, but through a system that is simple in design and operation.
Accordingly, it is a primary object of the present invention
Hinshaw Gregory E.
McIntyre, Jr. William S.
Wilson Henry E.
J. H. Fletcher & Co., Inc.
Johnson Brian L.
King and Schickli PLLC
Sliteris Joselynn Y.
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