For Non-concentric Members Patents (Class 166/189)
  • Patent number: 11021925
    Abstract: A pressure control device for use in an oil well is described. The pressure control device comprises a support member configured to be located on a mandrel or a tubular, the support member defining at least one conduit throughbore configured to receive a conduit and a flexible cup member mounted to the support member. In use, a conduit can pass through the pressure control device intact.
    Type: Grant
    Filed: December 15, 2016
    Date of Patent: June 1, 2021
    Assignee: RUBBERATKINS LIMITED
    Inventors: Nicholas Atkins, Craig Spalding, Krishna Kankanalapalli, Vijay Amirtharaj Avanashiappan
  • Patent number: 10876382
    Abstract: Apparatuses and methods for extracting gas from a reservoir including a well bore having a large cross sectional area which may be determined by dividing a target flow rate of the reservoir by an actual sustained flow rate and multiplying a result by a flow path area for the actual sustained flow rate. A method of converting a well of a low pressure gas reservoir is further provided.
    Type: Grant
    Filed: March 30, 2018
    Date of Patent: December 29, 2020
    Inventor: Kurt Carleton
  • Patent number: 10605029
    Abstract: A shoulder includes a shoulder body having a plurality of J-slots disposed circumferentially about the shoulder body at a first axial end of the shoulder body, a retainer ring disposed about the shoulder body having an exterior threaded surface and an annular lip, a load ring having a threaded interior surface configured to interface with the threaded exterior surface of the retainer ring and a tapered bottom surface, and a lock ring having a tapered bottom surface configured to interface with the tapered bottom surface of the load ring such that when the load ring moves axially toward the lock ring, the lock ring radially expands and when the load ring moves axially away from the lock ring, the lock ring radially contracts.
    Type: Grant
    Filed: December 20, 2016
    Date of Patent: March 31, 2020
    Assignee: Cameron International Corporation
    Inventor: Dennis P. Nguyen
  • Patent number: 9988875
    Abstract: A flow control system is provided for a horizontal well production system having a casing, a tube having an intake opening and disposed within the casing, and a gap formed between the casing and the tube. The flow control system includes a valve having an orifice, coupled to the tube and disposed proximate to the intake opening. The flow control system further includes an actuator coupled to the valve and configured to open the valve in response to a presence of a liquid in the gap, proximate to the intake opening, to permit flow of the liquid into the tube via the intake opening, and to close the valve in response to a presence of a gas in the gap, proximate to the intake opening, to prevent flow of the gas into the tube via the intake opening.
    Type: Grant
    Filed: December 18, 2014
    Date of Patent: June 5, 2018
    Assignee: GENERAL ELECTRIC COMPANY
    Inventors: Jeremy Daniel Van Dam, Joseph John Zierer, Jr., Michael Franklin Hughes, Zhipeng Zhang
  • Patent number: 9863208
    Abstract: An assembly having a sleeve member located over a tubular body, there being a chamber between the two and by increased pressure in the chamber the sleeve member is morphed to secure it to a well bore wall and create a seal between the sleeve and well bore wall to form an isolation barrier. The tubular body is formed in one or more sections so that annular planar faces are created for abutment between the sleeve member and the tubular body so as to remove the requirement for complex fittings and reduce the time of construction.
    Type: Grant
    Filed: October 21, 2015
    Date of Patent: January 9, 2018
    Assignee: MORPHPACKERS LIMITED
    Inventors: David Glen Martin, Davidson Harman, Cameron Radtke, Peter Wood, William Luke McElligott
  • Patent number: 9416596
    Abstract: An annular restrictor for use in a well can include a body which extends circumferentially about a tubular mandrel, and a section which, in cooperation with the body, restricts fluid flow through an annulus, a line being secured between the body and the section. A method of completing a well can include installing a line in an annular restrictor, and restricting fluid flow through an annulus, with the restricting being performed by the annular restrictor interconnected between steam injection valves. A method of attaching a line to a tubular string for use in a well can include covering the line with a section of an annular restrictor, and securing the section to a body of the annular restrictor, each of the section and the body having a flow restricting surface formed thereon, and the covering and securing steps being performed without splicing or making a connection in the line.
    Type: Grant
    Filed: June 2, 2011
    Date of Patent: August 16, 2016
    Assignee: HALLIBURTON ENERGY SERVICES, INC.
    Inventor: Gary Maier
  • Patent number: 9388671
    Abstract: Disclosed is a swellable screen assembly having inflow control capabilities. One swellable screen assembly includes a base pipe comprising a sidewall portion defining at least one opening therein, a rigid member disposed about a first portion of the base pipe and having a piston arranged therein. The piston has a telescoping portion movably arranged within a non-telescoping portion. An autonomous valve is arranged within the piston and provides fluid communication between a filter medium disposed about the base pipe and the opening in the base pipe, the filter medium being coupled to the telescoping portion of the piston. A swellable material is disposed about a second portion of the base pipe and the filter medium is disposed about the swellable material, wherein, as the swellable material expands, the filter medium is displaced toward an inner surface of the wellbore, thereby extending the telescoping portion.
    Type: Grant
    Filed: June 28, 2012
    Date of Patent: July 12, 2016
    Assignee: Halliburton Energy Services, Inc.
    Inventor: Luke Holderman
  • Publication number: 20150060077
    Abstract: A subassembly is provided which is designed so that two passageways in concentrically arranged tubing strings can be formed to provide a flow-path which in a first direction communicates with equipment at surface in an annular passageway then switches partway along the tubing strings' length in the well to the subassembly and is redirected to the core passageway, and back from the string's lower end up the annular space to the subassembly and is again redirected this time to the tubing's core passageway back to surface equipment; the two passageways being: the core passageway formed of the core tubing's inner volume; and the annular passageway formed of the annular space between the core tubing string and a concentrically surrounding second tubing string's inner surface; the subassembly forming a two-way cross-over between the two passageways at the same part of the string.
    Type: Application
    Filed: September 5, 2013
    Publication date: March 5, 2015
    Applicant: MVM MACHINING
    Inventors: STEPHEN VETTER, STEPHEN MAERZ
  • Patent number: 8863832
    Abstract: An assembly employing multiple eccentric devices about a mandrel. The assembly is configured such that at least one of the eccentric devices is adjustably orientable relative another. Thus, for example, where the devices are packers disposed about completions tubing, the adjustable orientation may be utilized to ensure enough clearance is available for downhole advancement of the assembly. As such, the assembly may remain eccentric in nature without concern over damage during positioning, particularly to a communication line running to actuatable implements of equipment coupled to the completions assembly.
    Type: Grant
    Filed: September 28, 2010
    Date of Patent: October 21, 2014
    Assignee: Schlumberger Technology Corporation
    Inventors: Michael Hui Du, Kevin Beveridge
  • Publication number: 20130008643
    Abstract: Disclosed herein is a downhole sealing device. The device includes a swellable member, and a passageway having a perimetrically continuous wall. The swellable member is configured to cause sealing between a downhole structure and a plurality of tubulars when in a swelled condition, the plurality of tubulars are routed through a plurality of voids extending longitudinally through the swellable member, each of the plurality of voids has perimetrically continuous walls surrounding each of the plurality of tubulars.
    Type: Application
    Filed: September 14, 2012
    Publication date: January 10, 2013
    Applicant: BAKER HUGHES INCORPORATED
    Inventors: Robert O. Castillo, Darwin D. Arline, Gregory C. Badke
  • Patent number: 7422058
    Abstract: A packer device and methods of use for a packer within uncased wellbore to form a complete fluid seal. The packer device includes a central mandrel body that retains a plurality of nested, telescopic expanding elements that are moveable outwardly from the mandrel body. The mandrel body and expanding elements are surrounded by a load-distributing structure as well as a sealing element, which is typically comprised of elastomer. The packer device is hydraulically actuated to urge the expansion members radially outwardly against the load-distributing structure and the sealing element. Because there are a number of discrete expansion elements, the packer device is better able to create a fluid seal within an uncased borehole with surface irregularities.
    Type: Grant
    Filed: July 22, 2005
    Date of Patent: September 9, 2008
    Assignee: Baker Hughes Incorporated
    Inventor: Edward J. O'Malley
  • Patent number: 7216720
    Abstract: A production packer comprising a packer body, a flat plate, a sealing element, production tubing, water overflow tubing, gas vent tubing, pump cable pack-off tubing, and an optional pressure transducer port. The flat plate is welded onto the top of the packer body. The sealing element is bonded to the outside of the packer body. In the preferred embodiment, the packer body is a steel pipe, and the flat plate is made of steel. The packer is placed inside a production casing, and the diameter of the sealing element is greater than the diameter of the production casing. The sealing element is made out of a material that is durable enough to withstand the pressures associated with a production packer, flexible enough to fit inside the production casing, and elastic enough to create a seal between the packer body and the production casing.
    Type: Grant
    Filed: August 5, 2004
    Date of Patent: May 15, 2007
    Inventor: C. Duane Zimmerman
  • Patent number: 6892820
    Abstract: A packer that is usable with a subterranean well includes an assembly to circumscribe one out of multiple tubular arrays that are inserted through the packer. The packer also includes a member that is separable from the assembly to configure the assembly for connection to the tubular array. The member includes a first seal between the member and the tubular array and a second seal that is located between the member and the shell. The first seal is separate from the second seal. The assembly includes a slip to engage a casing of the well and a sealing element to seal an annulus of the well.
    Type: Grant
    Filed: August 9, 2002
    Date of Patent: May 17, 2005
    Assignee: Schlumberger Technology Corporation
    Inventors: Robert Divis, Jason Bigelow, Mark Mulligan, David Wolfe
  • Patent number: 6814144
    Abstract: A method for the treatment of a subterranean formation penetrated by a well in which, first and second flow paths are established from the wellhead into the vicinity of the formation. A plugging fluid comprising a suspension of a particulate plugging agent in a carrier liquid is circulated into the first flow path and into contact with the wall of the well within the subterranean formation. The carrier liquid is separated from the particulate plugging agent by circulating the carrier liquid through a set of openings leading to the second flow path, which are dimensioned to allow the passage of the carrier liquid while retaining the particulate plugging agent in contact with the set of openings. The circulation of the plugging fluid continues until the particulate plugging agent accumulates to form a bridge packing within the well.
    Type: Grant
    Filed: November 18, 2002
    Date of Patent: November 9, 2004
    Assignee: ExxonMobil Upstream Research Company
    Inventor: Lloyd G. Jones
  • Patent number: 6220351
    Abstract: A sliding link or connection apparatus for use in lowering an auxiliary conduit or other equipment into a well casing alongside a production pipe is of predetermined shape and dimensions different from, and smaller than, the shape and dimensions of the well casing. The link has a first through bore for sliding engagement over the production pipe, and a second through bore for securing over a conduit or equipment casing to be lowered.
    Type: Grant
    Filed: June 18, 1999
    Date of Patent: April 24, 2001
    Inventor: Juan José Tovar De Pablos
  • Patent number: 5425418
    Abstract: The invention relates to a multi-bore packer that has an annularly shaped sealing element. The assembly has a series of strings that run continuously so that they can be supported from the surface. At least one hub segment straddles the strings and is sealed in between. The entire assembly features one of the hubs with a sealing element. The outer sealing element, when compressed, seals against a casing or wellbore as well as against one of the hubs through which the strings extend. A greater effective piston area allows setting with surface pressures below 2500 psig. A provision is made in the assembly of hubs to provide for an operating mechanism to compress the outer seal between the casing and the hub, by increasing the applied sealing forces on the outer seal, should well conditions apply greater differential pressures, in either direction, to the outer seal than the original setting pressure used.
    Type: Grant
    Filed: April 26, 1994
    Date of Patent: June 20, 1995
    Assignee: Baker Hughes Incorporated
    Inventors: Napoleon Arizmendi, Jeffrey J. Lembcke
  • Patent number: 5129454
    Abstract: A multi-string packer for anchoring two or more non-concentric through tubes inside a larger pipe or casing (e.g. in an oil well). The packer can be deployed downhole, set, unset, and reset at least once without being withdrawn to the surface, despite the shearing of shear elements on each such operation. A lost-motion mechanism isolates the shear elements for the first packer resetting (the second setting) from packer-setting shear forces applied to the shear elements for the first packer setting, to preserve the second setting shear elements until the packer is actually required to be set for a second time. Similarly, another lost-motion mechanism isolates to shear elements for the second packer unsetting from the packer-unsetting shear forces applied to the shear elements for the first packet unsetting, to preserve the second unsetting shear elements until the packer is actually required to be unset for a second time.
    Type: Grant
    Filed: November 13, 1990
    Date of Patent: July 14, 1992
    Assignee: Nodeco Limited
    Inventor: George Telfer
  • Patent number: 4930573
    Abstract: A dual string packer for releasable, hydraulic setting within a wall casing is disclosed. The packing seal elements and hydraulic actuator assembly are mounted for sliding movement along primary and secondary packer mandrels. Setting forces are applied to the packing seal elements by a setting cylinder which is mounted for slideable, sealing engagement against the primary and secondary packer mandrels, and setting forces are applied to the anchor slips by a piston which is sealed against the primary and secondary packer mandrels. The set condition is maintained by a pair of locking rods and segmented ratchet slips. The locking rods are carried by the setting cylinder head and are retracted axially out of piston pockets as a variable volume pressure chamber is pressurized. Upon achieving set engagement of the anchor slips and seal elements, the locking rods are trapped in compression between the head of the setting cylinder and the segmented ratchet slips.
    Type: Grant
    Filed: April 6, 1989
    Date of Patent: June 5, 1990
    Assignee: Otis Engineering Corporation
    Inventors: Andrew R. Lane, Richard M. Sproul
  • Patent number: 4852649
    Abstract: An improved seal element especially for well packers having multiple mandrels, the improvement providing slits therein of various configurations which allow the seal element to be expanded to sealing condition in response to longitudinal compression such that the resultant stresses created within the element body are minimized in that they are substantially evenly distributed therethrough, thus enabling the multiple packer to seal more readily and to withstand greater pressure differentials.
    Type: Grant
    Filed: September 20, 1988
    Date of Patent: August 1, 1989
    Assignee: Otis Engineering Corporation
    Inventor: Carter R. Young
  • Patent number: 4749036
    Abstract: A dual bore well treating tool having a pressure operated valve therein that is useful in conjunction with a dual bore packer and with a dual bore on and off or connection tool. One of the bores through the on/off tool, the treating tool and the packer is utilized for producing oil and/or gas from the well bore, and a second bore is utilized for opening the valve and for simultaneously injecting a treating material into the fluid being produced.
    Type: Grant
    Filed: October 6, 1986
    Date of Patent: June 7, 1988
    Assignee: Dresser Industries, Inc.
    Inventor: Norman W. Read
  • Patent number: 4726422
    Abstract: An annular safety assembly comprising, between an upper cylindrical body and a lower cylindrical body, through which connecting tubes of production tubes pass, a packer and a low-bulk anchorage system consisting of a radial spacing ring, a resilient anchorage ring split along a generatrix and provided with peripheral anchorage teeth and a thrust ring which can be moved upwardly by thruster-plungers extending from the lower cylindrical body to apply the anchorage ring to the casing, and a safety valve arranged separately from the connecting tubes, which extend between the said cylindrical bodies, and below the lower cylindrical body.
    Type: Grant
    Filed: January 27, 1986
    Date of Patent: February 23, 1988
    Assignee: Total Compagnie Francaise des Petroles
    Inventors: Paul M. Helderle, Jean A. Lescoeur
  • Patent number: 4637460
    Abstract: A parallel flow tube assembly for producing or treating formations in a well bore wherein the formations are isolated by upper and lower spaced packers. The parallel flow tube assembly includes a coupling member having parallel bores therein. A seal sleeve extends downwardly therefrom for sealingly engaging the interior of the upper packer. A tube extends downwardly through and in sealing engagement with the lower packer and said coupling member is connected to a primary tubing string that is in fluid communication with the formation below the lower packer and a secondary tubing string that is connected in communication with the formation located between the packers.
    Type: Grant
    Filed: March 21, 1985
    Date of Patent: January 20, 1987
    Assignee: Dresser Industries, Inc.
    Inventors: Jody R. McGlothen, Damon P. Little
  • Patent number: 4508166
    Abstract: Disclosed are a subsurface safety system and a method of inserting into or removing from an offset bore of a mandrel a tubular valve. The system includes an entry mandrel having a full bore outlet, a full bore primary inlet and a laterally offset full bore secondary inlet. A full bore primary tubing extends downwardly from the primary inlet to a formation. A full bore secondary vent tubing is connected to the secondary inlet and extends down the hole generally parallel to the primary tubing and includes an open lower end positioned in the annulus above the formation. A dual packer is provided in the system between the entry mandrel and the lower end of the secondary tubing. The secondary tubing includes a vent above the packer and the upper end of the secondary tubing is normally closed by a removable plug. Subsurface safety valves are provided in both the primary and secondary tubings. The subsurface safety valve in the secondary tubing is positioned between the open lower end and the vent.
    Type: Grant
    Filed: April 6, 1983
    Date of Patent: April 2, 1985
    Assignee: BST Lift Systems, Inc.
    Inventors: Billy G. Becker, Charles V. Swafford
  • Patent number: 4420044
    Abstract: A control valve for a passageway in which the valve is reciprocated toward and away from its seat by pressure within a pressure dome and pressure exteriorly of the valve housing and in which reciprocation is controlled by a J-slot capable of latching the valve in open position while being run and releasing the valve for reciprocation after being landed in the well together with a frangible disc which may be ruptured to permit flow past the valve member; said valve being used to control flow through a H mandrel in a pumpdown system.
    Type: Grant
    Filed: August 19, 1982
    Date of Patent: December 13, 1983
    Assignee: Otis Engineering Corporation
    Inventors: William H. Pullin, Olen R. Long
  • Patent number: 4373584
    Abstract: An apparatus is provided for producing a well from at least one productive zone penetrated by the well bore in which casing is set below the top of the well. Tubing hanger means support at least one production tubing string extending downwardly in the well bore and communicating with a production zone. Anchor means on the tubing hanger means are actuatable into anchoring engagement with the casing. The tubing hanger means receives at least one upper production tubing string section typically carrying safety valve means thereon extending to the top of the well and sealingly engageable with the tubing hanger means before, during and after the anchoring engagement of the tubing hanger means with the casing, whereby the upper production tubing string section is respectively communicable with the downwardly extending production tubing string when the tubing hanger is set.
    Type: Grant
    Filed: May 7, 1979
    Date of Patent: February 15, 1983
    Assignee: Baker International Corporation
    Inventors: Raphael J. Silberman, Frederick T. Tilton, Everett H. Smith, Dennis A. Wichkoski
  • Patent number: 4345647
    Abstract: A method of improving the rate of extraction of oil bearing liquid from an oil well comprising the steps of providing a sump in the well casing below the openings through the casing communicating with the oil bearing formation so that the oil bearing liquid flowing into the casing flows into the sump; removing the oil bearing liquid collected in the sump through an oil lift pipe whose intake is submerged in the oil bearing liquid so that the intake of the oil lift pipe remains submerged in the oil bearing liquid; and imposing a vacuum in the casing at the openings through the casing to the oil bearing formation and above the oil bearing liquid in the sump to increase the flow of oil bearing liquid from the oil bearing formation into the casing through the openings. The application also discloses the apparatus for carrying out the method.
    Type: Grant
    Filed: July 18, 1980
    Date of Patent: August 24, 1982
    Inventor: William C. Carmichael
  • Patent number: 4248307
    Abstract: The present invention provides a latch assembly carriable on a tubing string extendible into a subterranean well, the latch assembly being selectively engageable between upper and lower sections of the tubing string. The latch assembly comprises an outer housing and an inner body, with latching means carried on one of the housing and the body for selectively securing the latch apparatus to the lower section. Latch engaging means are carried on the other of the housing and the body and the lower tubing section for selective co-engagement between the latching means, the lower tubing section, and one of the housing and the body. Piston means are on one of the housing and the body and have a piston head with first and second piston chambers between the piston head.
    Type: Grant
    Filed: May 7, 1979
    Date of Patent: February 3, 1981
    Assignee: Baker International Corporation
    Inventors: Raphael J. Silberman, Frederick T. Tilton, Everett H. Smith, Dennis A. Wichkoski
  • Patent number: 4236734
    Abstract: A well bore tubing system for releasably coupling upper tubing strings with lower tubing strings. The system includes an orienting body connectible on the upper end of a well packer and having a pair of separate laterally spaced longitudinal bores, each having a locking recess and a seal surface, a longitudinal side orienting surface along the body, an upper end male guide surface leading to the orienting surface, an orienting head assembly to releasably couple with the orienting body comprising an orienting head having two longitudinal bores alignable with the bores in the orienting body and a lower end female guide surface engageable with the male surface on the orienting body, a longitudinal orienting arm secured on the guide head having a longitudinal orienting surface engageable with the orienting surface on the orienting body, and a tubular seal and latch assembly secured at one end in each of the bores of the orienting head.
    Type: Grant
    Filed: July 20, 1978
    Date of Patent: December 2, 1980
    Assignee: Otis Engineering Corporation
    Inventor: Mansour Ahangarzadeh
  • Patent number: 4098334
    Abstract: A hanger for supporting dual tubing strings in a well casing from hanger mandrels which can swivel to facilitate threadedly connecting each mandrel to its associated tubing string. The hanger includes an orienting sleeve for receiving safety shut-off valves, the sleeve being adapted to swivel with respect to the rest of the hanger, making it easier to assemble the hanger onto the running and setting tool used for setting the hanger in the casing.
    Type: Grant
    Filed: February 24, 1977
    Date of Patent: July 4, 1978
    Assignee: Baker International Corp.
    Inventor: Talmadge L. Crowe
  • Patent number: 4098335
    Abstract: A hanger for supporting dual tubing strings in a well casing from hanger mandrels which can swivel to facilitate threadedly connecting each mandrel to its associated tubing string. The hanger includes an orienting sleeve for receiving safety shut-off valves, the sleeve being adapted to swivel with respect to the rest of the hanger, making it easier to assemble the hanger onto the running and setting tool used for setting the hanger in the casing. The running and setting tool is releasably secured to the hanger. By imposing fluid pressure on the setting tool, the tubing hanger slips are expanded against the casing.
    Type: Grant
    Filed: March 24, 1977
    Date of Patent: July 4, 1978
    Assignee: Baker International Corp.
    Inventor: Bobby F. Goad
  • Patent number: 4067385
    Abstract: Apparatus is disclosed for tieing at least one tubing string suspended in a well pipe from a subsea non-rotatable christmas tree located on the sea floor to a downhole hanger affixed to the well pipe. The tubing string has a tie-back tool arranged on its lower end which contains first orienting means. The hanger contains second orienting means which is engageable with the first orienting means to position the tie-back tool in a desired angular position. Means arranged on the tubing string permit the tie-back tool to rotate to such angular position without placing torsional load on the tubing string. The method in which the tubing string is tied to the hanger is also disclosed.
    Type: Grant
    Filed: September 29, 1976
    Date of Patent: January 10, 1978
    Assignee: Exxon Production Research Company
    Inventors: Thomas E. Schwager, Joseph A. Burkhardt
  • Patent number: 4056145
    Abstract: Hydraulic locking means is provided in a dual stinger latching mechanism which hydraulic locking means secures tubular conduit within the packer latching mechanism against pressure below the packer tending to pump the conduit out. The hydraulic locking means utilizes the pressure below the packer to activate a gripping means on the conduit which is subject to the upward pressure force.
    Type: Grant
    Filed: October 28, 1975
    Date of Patent: November 1, 1977
    Assignee: Dresser Industries, Inc.
    Inventors: Marion Barney Jett, Dennis Mitchel Spriggs
  • Patent number: 4022274
    Abstract: A versatile multistring mechanically actuated well packer featuring compression or tension set utilizes unitary tubular anchor means and compressible elastomeric packer elements, with a tension-shearable emergency release.
    Type: Grant
    Filed: June 15, 1976
    Date of Patent: May 10, 1977
    Assignee: Dresser Industries, Inc.
    Inventor: Marion Barney Jett
  • Patent number: 3934648
    Abstract: A well tubing system for releasably coupling lower tubing strings with upper tubing strings in a well bore without rotation from the surface including a well packer on a plurality of lower tubing strings, a first flow coupling and guide sleeve on the upper end of the packer, and a second flow coupling and guide head on the lower ends of the upper tubing strings. The upper tubing strings and guide head are connected with and disconnected from the guide sleeve on the packer by longitudinal motion only. The guide head has spiral guide surfaces leading to a vertical orienting slot. The guide sleeve includes a guide lug which engages the guide head guide surfaces and slot to rotate the head and upper tubing strings to the desired orientation. In alternate forms of the invention means are provided for the running and retrieving of either one or both of the upper tubing strings independently of the other of the strings after the initial connection of the guide head into the guide sleeve in the well bore.
    Type: Grant
    Filed: December 18, 1974
    Date of Patent: January 27, 1976
    Assignee: Otis Engineering Corporation
    Inventors: Amareswar Amancharla, Carter R. Young