In Horizontal Or Inclined Drilling Or Passage Patents (Class 340/853.4)
  • Patent number: 11499372
    Abstract: Downhole tractor control systems and methods to adjust a load of a downhole motor to drive one or more wheels of the downhole tractor are disclosed. A method to adjust a load of a downhole motor includes receiving a user input of a desired speed and torque for a plurality of motors, where the plurality of motors powering rotation of wheels of a downhole tractor. The method also includes determining a minimum actual motor speed of the plurality of motors. For at least one motor of the plurality of motors, the method includes determining a power controller output and determining a torque controller output. The method further includes adjusting a voltage source invertor based on a lesser of the power controller output and the torque controller output to modulate voltage provided to the at least one motor.
    Type: Grant
    Filed: October 28, 2019
    Date of Patent: November 15, 2022
    Assignee: Halliburton Energy Services, Inc.
    Inventors: Yuan Qi, Sudhir Kumar Gupta
  • Patent number: 11268335
    Abstract: Provided is a wellbore tractor and method for operating a well system. The wellbore tractor, in one aspect, includes a base member, a hydraulically powered drive section coupled to the base member, and one or more turbines coupled to the hydraulically powered drive section for powering the hydraulically powered drive section based upon fluid flow across the one or more turbines. The wellbore tractor, according to this aspect, further includes one or more wellbore engaging devices radially extending from the hydraulically powered drive section, the one or more wellbore engaging devices contactable with a surface of a wellbore for displacing the wellbore tractor axially downhole.
    Type: Grant
    Filed: May 29, 2019
    Date of Patent: March 8, 2022
    Assignee: Halliburton Energy Services, Inc.
    Inventors: James Dan Vick, Jr., Michael Linley Fripp, Xiaoguang Allan Zhong
  • Patent number: 11131160
    Abstract: Systems and methods for delivering a tubular string into a subterranean well include a tubular running machine. The tubular running machine has a machine housing that includes a tubular member with a central bore. A turbine is located within the central bore of the machine housing. A control module is operable to provide energy and a communication signal to the turbine. A downhole connection assembly is located at a downhole end of the machine housing and is operable to releasably secure the tubular running machine to the tubular string.
    Type: Grant
    Filed: August 6, 2019
    Date of Patent: September 28, 2021
    Assignee: SAUDI ARABIAN OIL COMPANY
    Inventors: Ossama Sehsah, Mahmoud Adnan Alqurashi
  • Patent number: 10830033
    Abstract: During slide drilling, certain transient variances in differential pressure may indicate that a subsequent and temporary variance in a toolface angle error does not indicate that drilling should be interrupted. The transient variances in the differential pressure may be within a range of particular threshold pressures.
    Type: Grant
    Filed: October 2, 2019
    Date of Patent: November 10, 2020
    Assignee: Motive Drilling Technologies, Inc.
    Inventors: William Edward Weideman, John Jeremy Cantwell, An Binh Ho
  • Patent number: 9476274
    Abstract: The present invention relates to a system for measuring data in a well extending below surface, said system comprising a body having a longitudinal axis and a front end and a rear end; locomotion means; control means adapted to control direction and/or speed of the locomotion means; said control means being controllable from the surface. Thereby is achieved that a body may be remotely controlled from the surface e.g. the entrance of an oil well.
    Type: Grant
    Filed: November 23, 2010
    Date of Patent: October 25, 2016
    Assignee: MAERSK OLIE OG GAS A/S
    Inventors: Graham Edmonstone, Pieter Karel Anton Kapteijn
  • Patent number: 9347277
    Abstract: A wireline configurable well logging instrument is connected to a drill pipe carrier and movable from a retracted position to an extended position. The drill pipe carrier is positioned on a pipe string that may comprise a portion of wired pipes communicatively coupled at each joint. Communication between the drill pipe carrier and the well logging instrument includes the use of inductive couplers, wires and combinations thereof.
    Type: Grant
    Filed: March 22, 2010
    Date of Patent: May 24, 2016
    Assignee: Schlumberger Technology Corporation
    Inventors: Reza Taherian, Harold Steven Bissonnette, Chris Del Campo, Laurent Villegas, Shardul Sarhad
  • Patent number: 9035788
    Abstract: A real time telemetry system is disclosed for use with a drilling system including a rotary valve 28 controlling the supply of drilling fluid or mud to a downhole tool. The system comprises receiving data to be transmitted, encoding the data as a duration, and controlling the rotation the rotary valve 28 such that the rotary valve 28 is rotated for the said duration at a predetermined rotary speed to cause the formation of pressure fluctuations or waves in the drilling fluid or mud.
    Type: Grant
    Filed: October 2, 2007
    Date of Patent: May 19, 2015
    Assignee: Schlumberger Technology Corporation
    Inventors: Geoff Downton, Luke Kuwertz
  • Patent number: 9013957
    Abstract: An apparatus, method, and system described for generating pressure pulses in a drilling fluid utilizing a flow throttling device longitudinally and axially positioned within the center of a main valve actuator assembly is described. The main valve actuator assembly includes a main valve pressure chamber, a magnetic cup encompassing a rotary magnetic coupling, and a pilot actuator assembly.
    Type: Grant
    Filed: February 7, 2012
    Date of Patent: April 21, 2015
    Assignee: Teledrill, Inc.
    Inventors: Gabor Vecseri, Benjamin Jennings
  • Patent number: 8997890
    Abstract: A drilling system performs underground boring using a drill rig and a boring tool which is configured for moving through the ground under control of the drill rig to form an underground bore. A monitoring arrangement, forming part of the system, includes a detection arrangement at the drill rig for monitoring at least one operational parameter to produce a data signal relating to at least one of a utility to be installed in the underground bore, the drill rig and the boring tool. A portable device forms another part of the system for receiving the data signal relating to the operational parameter for use by the portable device. A communication arrangement, for example using telemetry, transfers the data signal from the drill rig to the portable device. The operational parameter may be monitored for the purpose of preventing equipment failure.
    Type: Grant
    Filed: January 3, 2013
    Date of Patent: April 7, 2015
    Assignee: Merlin Technology Inc.
    Inventor: John E. Mercer
  • Patent number: 8655104
    Abstract: A method for removing cyclic noise from a borehole image includes transforming the image into the frequency domain using a two-dimensional (2-D) Fourier Transform, removing cyclic noise components from the transformed image, and inverse transforming the image back into the spatial domain using an inverse 2-D Fourier Transform. The cyclic noise component may also be isolated by subtracting the corrected image from the original image or by removing all non-cyclic noise components from the transformed image prior to inverse transforming. Removal of the cyclic noise from a borehole image tends to enable the identification of borehole features and provide for improved accuracy in formation parameter evaluation. Evaluation of the cyclic noise component may also enable the source of the noise to be identified and mitigated.
    Type: Grant
    Filed: June 18, 2009
    Date of Patent: February 18, 2014
    Assignee: Schlumberger Technology Corporation
    Inventors: Jun Zhang, Zhipeng Liu, Paul Boonen
  • Patent number: 8457917
    Abstract: A device, a method and a guiding device for setting out contours, points or works, including a computer-controlled measuring device provided with a movable measuring probe and a portable base unit provided with a rotatably supported elongate arm. The measuring probe is connected to the measuring device by means of a cord or a wire via the elongate arm, and the measuring device is provided with sensors for measuring a length or a change in the length of the cord or the wire and rotation of the arm in at least one degree of freedom for providing position data of the measuring probe.
    Type: Grant
    Filed: February 5, 2010
    Date of Patent: June 4, 2013
    Assignee: Holding Prodim Systems B.V.
    Inventor: Dick Teune
  • Patent number: 8353365
    Abstract: A drilling system performs underground boring using a drill rig and a boring tool which is configured for moving through the ground under control of the drill rig to form an underground bore. A monitoring arrangement, forming part of the system, includes a detection arrangement at the drill rig for monitoring at least one operational parameter to produce a data signal relating to at least one of a utility to be installed in the underground bore, the drill rig and the boring tool. A portable device forms another part of the system for receiving the data signal relating to the operational parameter for use by the portable device. A communication arrangement, for example using telemetry, transfers the data signal from the drill rig to the portable device. The operational parameter may be monitored for the purpose of preventing equipment failure.
    Type: Grant
    Filed: March 14, 2011
    Date of Patent: January 15, 2013
    Assignee: Merlin Technology Inc.
    Inventor: John E. Mercer
  • Patent number: 8354939
    Abstract: A logging system and method for measuring propped fractures and down-hole subterranean formation conditions including: a radar source; an optical source; an optical modulator for modulating an optical signal from the optical source according to a signal from the radar source; a photodiode for converting the modulated optical signal output from the optical modulator to the source radar signal. A transmitter and receiver unit receives the source radar signal from the photodiode and transmits the source radar signal via at least one antenna attached to the casing and in communication with at least one photodiode into the formation and receives a reflected radar signal. A mixer mixes the reflected radar signal with the source radar signal to provide an output. This can describe fractures connected to the wellbore and differentiate between the dimensions of the two vertical wings of a propped fracture.
    Type: Grant
    Filed: September 12, 2007
    Date of Patent: January 15, 2013
    Assignee: Momentive Specialty Chemicals Inc.
    Inventors: Robert R. McDaniel, Michael L. Sheriff, Eric E. Funk, Ethan A. Funk
  • Patent number: 8350715
    Abstract: Mud pulse telemetry systems and methods that employ some combination of modulated pulse positions, modulated pulse widths, and modulated pulse amplitudes to increase telemetry data rates. In at least some of the employed coding techniques, information is conveyed by the positions of both the upward and downward transitions. In some embodiments, fixed symbol intervals are used to convey combinatorial coded waveforms. In other embodiments, variable length symbol intervals include both a pulse position interval and a pulse width interval. The two intervals can be independently varied to convey telemetry data. Subject to specific system constraints, optimal coding efficiencies may be expected at data rates of between four and seven bits per symbol interval.
    Type: Grant
    Filed: July 11, 2007
    Date of Patent: January 8, 2013
    Assignee: Halliburton Energy Services, Inc.
    Inventor: Eric S. Shearer
  • Patent number: 8044819
    Abstract: A method to detect the relative position of a drill bit with respect to a coal seam boundary using an electric-field borehole telemetry apparatus, that includes the steps: providing a measure-while-drilling apparatus that includes inclination sensors, directional sensors, logging sensors of choice and an electric-field borehole telemetry apparatus, within the electric-field borehole telemetry apparatus, in addition to monitoring the inclination, direction and logging parameters, monitoring one or more parameters of the electrical output of the telemetry apparatus, transmitting to the surface the inclination, direction and logging parameters as well as the one or more parameters of the electrical output by means of the telemetry apparatus, computing the usual drilling parameters needed to guide the drill string along the intended path, determining from the one or more transmitted parameters of the electrical output from the downhole apparatus parameters indicative of approaching or penetrating the coal boundar
    Type: Grant
    Filed: October 23, 2006
    Date of Patent: October 25, 2011
    Assignee: Scientific Drilling International
    Inventors: Pierre C. Bessiere, James C. Liu, Matthew A. White
  • Patent number: 7994932
    Abstract: An acoustic telemetry apparatus and method for communicating encoded digital data from a down-hole location through a borehole to the surface is described including an acoustic channel terminated at a down-hole end by a reflecting terminal (133, 134), an acoustic wave generator (140) located at the surface and providing an acoustic wave carrier signal through said acoustic, channel, a modulator (162, 163) located down-hole to modulate amplitude and/or phase of said carrier wave in response to an encoded digital signal and one or more sensors (150) located at the surface adapted to detect amplitude and/or phase related information of acoustic waves traveling within said acoustic channel to determine the encoded digital data.
    Type: Grant
    Filed: March 24, 2004
    Date of Patent: August 9, 2011
    Assignee: Schlumberger Technology Corporation
    Inventors: Songming Huang, Franck Monmont, Robert Tennent
  • Patent number: 7926589
    Abstract: A drilling system performs underground boring using a drill rig and a boring tool which is configured for moving through the ground under control of the drill rig to form an underground bore. A monitoring arrangement, forming part of the system, includes a detection arrangement at the drill rig for monitoring at least one operational parameter to produce a data signal relating to at least one of a utility to be installed in the underground bore, the drill rig and the boring tool. A portable device forms another part of the system for receiving the data signal relating to the operational parameter for use by the portable device. A communication arrangement, for example using telemetry, transfers the data signal from the drill rig to the portable device. The operational parameter may be monitored for the purpose of preventing equipment failure.
    Type: Grant
    Filed: May 1, 2007
    Date of Patent: April 19, 2011
    Assignee: Merlin Technology, Inc.
    Inventor: John E. Mercer
  • Patent number: 7737863
    Abstract: A system and method of interfacing a drilling machine with one of a number of different walk-over guidance systems involves receiving an ID signal from a particular walk-over guidance system selected for use with the drilling machine. A protocol library associated with the particular walk-over guidance system is accessed in response to the ID signal. The protocol library is used to effect communication between the particular walk-over guidance system and a control system of the drilling machine during cooperative use of the particular walk-over guidance system and drilling machine. Using the protocol library involves converting, as prescribed by the protocol library, locator signals received from the particular walk-over guidance system from a locator protocol to a common protocol used by the control system of the drilling machine. Locator and drilling machine data of various types can be presented to a drilling machine operator via an on-board display.
    Type: Grant
    Filed: May 15, 2007
    Date of Patent: June 15, 2010
    Assignee: Vermeer Manufacturing Company
    Inventors: Jeremy Jin, Scott Rempe
  • Patent number: 7729895
    Abstract: Methods and systems may be provided for simulating forming a wide variety of directional wellbores including wellbores with variable tilt rates and/or relatively constant tilt rates. The methods and systems may also be used to simulate forming a wellbore in subterranean formations having a combination of soft, medium and hard formation materials, multiple layers of formation materials and relatively hard stringers disposed throughout one or more layers of formation material. Values of bit steerability and controllability calculated from such simulations may be used to design and/or select drilling equipment for use in forming a directional wellbore.
    Type: Grant
    Filed: August 7, 2006
    Date of Patent: June 1, 2010
    Assignee: Halliburton Energy Services, Inc.
    Inventor: Shilin Chen
  • Patent number: 7546209
    Abstract: A method of drilling a well. The method includes calculating an estimated formation dip angle, wherein said estimated formation dip angle being based on offset well data, seismic data, core data, pressure data. Next, the method includes drilling a well with a logging while drilling means so that real time logging data is generated along with drilling data and calculating an instantaneous formation dip angle. Next, real time logging data is obtained and a target formation window is projected ahead of the well path that includes a top of formation and a bottom formation. The method includes monitoring the real time logging and drilling data and drilling the well through the target formation window. The method further includes changing the estimated instantaneous formation dip based on the obtained data and adjusting the target formation top and bottom window.
    Type: Grant
    Filed: February 14, 2007
    Date of Patent: June 9, 2009
    Inventor: Danny T. Williams
  • Patent number: 7283060
    Abstract: A method and apparatus for a computer controlled apparatus for use in wellbore completions. A touch-screen is provided that facilitates commands and information that is entered by an operator ordering movement of a downhole tool. In another embodiment, real-time information about the status of the downhole tools is transmitted to the apparatus based upon operating variables within the system, like pressure, flow rate, total flow, and time.
    Type: Grant
    Filed: January 22, 2004
    Date of Patent: October 16, 2007
    Assignee: Weatherford/Lamb, Inc.
    Inventors: Clark Robison, Scott Weatherill
  • Patent number: 7225885
    Abstract: A drilling system performs underground boring using a drill rig and a boring tool which is configured for moving through the ground under control of the drill rig to form an underground bore. A monitoring arrangement, forming part of the system, includes a detection arrangement at the drill rig for monitoring at least one operational parameter to produce a data signal relating to at least one of a utility to be installed in the underground bore, the drill rig and the boring tool. A portable device forms another part of the system for receiving the data signal relating to the operational parameter for use by the portable device. A communication arrangement, for example using telemetry, transfers the data signal from the drill rig to the portable device. The operational parameter may be monitored for the purpose of preventing equipment failure.
    Type: Grant
    Filed: June 28, 2005
    Date of Patent: June 5, 2007
    Assignee: Merlin Technology, Inc.
    Inventor: John E. Mercer
  • Patent number: 7218244
    Abstract: A system and method of interfacing a drilling machine with one of a number of different walk-over guidance systems involves receiving an ID signal from a particular walk-over guidance system selected for use with the drilling machine. A protocol library associated with the particular walk-over guidance system is accessed in response to the ID signal. The protocol library is used to effect communication between the particular walk-over guidance system and a control system of the drilling machine during cooperative use of the particular walk-over guidance system and drilling machine. Using the protocol library involves converting, as prescribed by the protocol library, locator signals received from the particular walk-over guidance system from a locator protocol to a common protocol used by the control system of the drilling machine. Locator and drilling machine data of various types can be presented to a drilling machine operator via an on-board display.
    Type: Grant
    Filed: September 24, 2002
    Date of Patent: May 15, 2007
    Assignee: Vermeer Manufacturing Company
    Inventors: Jeremy Jin, Scott Rempe
  • Patent number: 7000710
    Abstract: A method for generating a new or corrected horizontal underground bore path from a point below ground for use with a horizontal boring machine. In the preferred embodiment, orientation and depth measurements for a boring tool located below ground are recorded. The current position of the boring tool is determined using a previously determined position, measured orientation of the boring tool, and calculating for pipe bend characteristics. Previous measurements and determined positions are recorded to provide a map of the bore. A new path is calculated using the current position as a starting point and through predetermined critical points for the bore. Instructions for drilling the next segment of the bore are made available to an operator or to a control system for a boring machine.
    Type: Grant
    Filed: April 1, 2003
    Date of Patent: February 21, 2006
    Assignee: The Charles Machine Works, Inc.
    Inventor: Daniel T. Umbach
  • Patent number: 6935439
    Abstract: A drilling system performs underground boring using a drill rig and a boring tool which is configured for moving through the ground under control of the drill rig to form an underground bore. A monitoring arrangement, forming part of the system, includes a detection arrangement at the drill rig for monitoring at least one operational parameter to produce a data signal relating to at least one of a utility to be installed in the underground bore, the drill rig and the boring tool. A portable device forms another of the system for receiving the data signal relating to the operational parameter for use by the portable device. A communication arrangement, for example using telemetry, transfers the data signal from the drill rig to the portable device. The operational parameter may be monitored for the purpose of preventing equipment failure.
    Type: Grant
    Filed: July 3, 2001
    Date of Patent: August 30, 2005
    Assignee: Merlin Technology, Inc.
    Inventor: John E. Mercer
  • Patent number: 6886644
    Abstract: An apparatus and method for horizontally drilling provides for detecting subsurface features and avoiding such features during closed-loop control of an underground drilling machine. A horizontal drilling system includes a base machine capable of propelling a drill pipe rotationally and longitudinally underground. A cutting tool system is coupled to the drill pipe, and a control system controls the base machine. A detector is employed to detect a subsurface feature. A communication link is utilized for transferring data between the detector and the control system. The control system uses the data generated by the detector to modify control of the base machine in response to detection of the subsurface feature.
    Type: Grant
    Filed: August 20, 2002
    Date of Patent: May 3, 2005
    Assignee: Vermeer Manufacturing Company
    Inventors: Gregory S Stump, Christopher T. Allen
  • Patent number: 6854535
    Abstract: A method for calibrating a pitch measurement of a horizontal underground bore location system includes providing a probe having a pitch sensor that measures deviation between a predetermined orientation and a measurement axis. A receiver has an antenna that detects a signal radiated by the probe and has receiver circuitry that detects the deviation from the received signal. A bore head is aligned with the predetermined orientation. The probe is placed in the bore head. The receiver detects the deviation when the bore head is aligned with the predetermined orientation. The receiver offsets deviation measurements thereafter detected from the probe by the measured deviation.
    Type: Grant
    Filed: December 3, 2002
    Date of Patent: February 15, 2005
    Assignee: Merlin Technology, Inc.
    Inventor: Morio Mizuno
  • Patent number: 6766869
    Abstract: A remote lock-out system and method are employed with a drilling machine. The remote lock-out system includes a remote lock-out override controller capable of interrupting a drilling operation of the drilling machine. The remote lock-out override controller includes a transmitter and a receiver. A remote lock-out controller is capable of issuing a lock-out signal and a run signal, wherein the lock-out signal, when received by the HDD machine, initiates suspension of the HDD machine drilling operation, and the run signal initiates enablement of the HDD machine drilling operation. The remote lock-out controller includes a transmitter and a receiver. The HDD machine drilling operation generally includes displacing and rotating the drill string, and can further include supplying a drilling fluid through the drill string.
    Type: Grant
    Filed: June 25, 2002
    Date of Patent: July 27, 2004
    Assignee: Vermeer Manufacturing Company
    Inventors: Ivan R. Brand, Scott Kilborn, Hans Kelpe, Gregg A. Austin
  • Patent number: 6688408
    Abstract: An auger drill directional control system includes a positional transmitter mounted on a drillhead at the front of a pipe, the positional transmitter transmitting directional and pitch signals to a positional receiver disposed above the grade at the desired terminal location of the drillhead; the positional receiver transfers the signal information to the positional processor that detects deviations by the drillhead from the desired course of travel and produces a correction signal to compensate for the deviation; the correction signal is transmitted by a control transmitter and is received by a control receiver disposed on the underground boring machine; the control receiver passes the correction signal to the control processor which converts the correction signal into a correction command that is delivered to an adjustment apparatus operatively connected with the drillhead.
    Type: Grant
    Filed: May 15, 2001
    Date of Patent: February 10, 2004
    Inventors: James S. Barbera, Russell J. Miller
  • Patent number: 6435286
    Abstract: An apparatus and method for determining a location and an orientation of an underground boring tool by employment of a radar-like probe and detection technique. The boring tool is provided with a device which generates a specific signature signal in response to a probe signal transmitted from above the ground. Cooperation between the probe signal transmitter at ground level and the signature signal generating device provided at the underground boring tool results in accurate detection of the boring tool location and, if desired, orientation, despite the presence of a large background signal. Precision detection of the boring tool location and orientation enables the operator to accurately locate the boring tool during operation and, if provided with a directional capacity, avoid buried obstacles such as utilities and other hazards. The signature signal produced by the boring tool may be generated either passively or actively, and may be a microwave or an acoustic signal.
    Type: Grant
    Filed: September 29, 2000
    Date of Patent: August 20, 2002
    Assignee: Vermeer Manufacturing Company, Inc.
    Inventors: Gregory S Stump, Christopher T. Allen
  • Patent number: 6427784
    Abstract: A method for mapping a bore below a ground surface is provided. A boring rod head configured to transmit a signal indicating the pitch angle of the boring rod head with respect to a horizontal plane is disposed within a bore. The boring rod head is advanced within the bore in predetermined linear increments. The pitch angle is measured at each increment. The change in depth is determined at each increment from a prior increment based on the length of the increment and the measured pitch angle at the increment. For each increment, the changes of depth determined in the prior step are added, including the change of depth for the most recent increment. Thus, the depth of the bore at each increment with respect to a predetermined horizontal plane is determined.
    Type: Grant
    Filed: August 1, 2000
    Date of Patent: August 6, 2002
    Assignee: McLaughlin Manufacturing Company, Inc.
    Inventors: John T. Archambeault, David J. Gasmovic, Morio Mizuno
  • Patent number: 6408952
    Abstract: Systems and methods for remotely altering operation of a horizontal directional drilling machine provide for remotely disabling movement of a drill string coupled to a cutting head or reamer and, in addition, disabling dispensing of fluid, foam and/or air communicated through the drill string. A lockout signal is transmitted from a portable or hand-manipulatable remote unit operated by an operator remotely situated with respect to the drilling machine. The lockout signal is received at the drilling machine. In response to the received lockout signal, a controller of the drilling machine prevents movement of the drill string and thus the cutting head or reamer. The controller also disables dispensing of fluid, foam and/or air through the drill string in response to the received lockout signal. The controller effects transmission of a verification signal from the drilling machine to the remote location.
    Type: Grant
    Filed: December 17, 1999
    Date of Patent: June 25, 2002
    Assignee: Vermeer Manufacturing Company
    Inventors: Ivan R. Brand, Gregg A. Austin, Fred G. Delonti
  • Patent number: 6279668
    Abstract: A locating and control arrangement forms part of a drilling apparatus which also includes a boring tool that emits a locating signal. The locating and control arrangement is used for locating and controlling underground movement of a boring tool which is operated from a drill rig. The locating and control arrangement includes a portable device for generating certain information about the position of the boring tool in response to the locating signal. The portable device includes a command arrangement forming one portion of the locating and control arrangement for generating at least one movement command such that maintaining the movement command requires a continuous interaction between the portable device and a user, and for transmitting the movement command to the drill rig. A receiving arrangement forms another portion of the locating and control arrangement, located at the drill rig, for receiving the movement command for use in controlling the boring tool responsive to the movement command.
    Type: Grant
    Filed: May 1, 2000
    Date of Patent: August 28, 2001
    Assignee: Digital Control Corporation
    Inventor: John E. Mercer