And Axial Or Circumferential Expansion Patents (Class 415/138)
  • Patent number: 4573867
    Abstract: A housing for a rotor of a turbomachine comprising, radially spaced inner and outer casings. The inner casing comprises a plurality of segments 20(a) to 20(e) each of which comprises one or more stator vanes 23. A first of the casings 19 has two or more axially spaced locating members 21,22 which co-operate with locating means 25,29 on the second of the casings 18 to locate the first casing 19 relative to the second casing 18. A first of the locating means 25 comprising a first surface 27 inclined to a direction extending axially along the second casing 18 and a second surface 28 that constitutes a sealing face. A first of the locating members 21 having a third surface 32 that confronts the first surface 27. In use, axial gas loads on the stator vanes 23 cause the first and third surfaces 27,32 to engage each other and slide along the incline to bring a fourth surface 33 on the member 21 into sealing engagement with the said second surface 28.
    Type: Grant
    Filed: November 22, 1982
    Date of Patent: March 4, 1986
    Assignee: Rolls-Royce Limited
    Inventor: Derek G. Hand
  • Patent number: 4566851
    Abstract: The first stage turbine vanes in a gas turbine are supported both axially and for torque control in a ring located within the diffuser case such that it is free to expand to minimize thermal stresses. The support ring is modified to permit assembly of all the turbines within the ring.
    Type: Grant
    Filed: May 11, 1984
    Date of Patent: January 28, 1986
    Assignee: United Technologies Corporation
    Inventors: Roger J. Comeau, Walter J. Baran, Jr.
  • Patent number: 4565492
    Abstract: A sealing device is disclosed for maintaining a small positive clearance between packing segments and the turbine blade tips of a turbojet engine. The packing segments are connected to an inner ring which is, in turn, connected to an outer ring, all disposed within the turbojet casing. The coefficient of thermal expansion of the inner ring is greater than that of the outer ring such that, as air is directed onto the structure from the engine compressor, the differential expansion or contraction of the rings serves to move the packing segment in a radial direction to maintain the clearance between them and the turbine blade tips.
    Type: Grant
    Filed: July 6, 1984
    Date of Patent: January 21, 1986
    Assignee: Societe Nationale d'Etude et de Construction de Moteurs d'Aviation "S.N.E.C.M.A."
    Inventors: Jacques R. Bart, Gerard E. A. Jourdain, Daniel Rambach
  • Patent number: 4553901
    Abstract: A stator structure 88 for supporting a pair of outer air seals 62, 72 and an array of stator vanes 82 from two axial locations A.sub.1, A.sub.2 on a coolable outer case is disclosed. Various construction details which enable the structure to respond to the movement of coolable rails are disclosed. In one embodiment, a pair of support rings 96, 100 and a pair of support rings 122, 124 extend between the outer case and the outer air seal and array of stator vanes 82.
    Type: Grant
    Filed: December 21, 1983
    Date of Patent: November 19, 1985
    Assignee: United Technologies Corporation
    Inventor: Vincent P. Laurello
  • Patent number: 4541776
    Abstract: A single-stage or multi-stage centrifugal blower for hot fluids has a rotor whose housing is made of steel or carbon filaments and whose vanes are made of a ceramic material. The internal surface of the housing is shielded from hot fluids by a lining which is made of a heat-resistant and heat-insulating material and which shares the angular movements of the rotor. The housing can stand pronounced tensional and bending stresses, and the vanes and the lining are designed to stand the pressure of the conveyed and/or compressed fluid or fluids. The blower can be used as a turbine, a suction fan or a pump and can convey gases whose temperature is in excess of 1600.degree. C. and whose pressure is in the range or in excess of 2000 mm water column.
    Type: Grant
    Filed: August 26, 1983
    Date of Patent: September 17, 1985
    Inventor: Christian O. Schon
  • Patent number: 4527385
    Abstract: A sealing device is disclosed for maintaining a small positive clearance between the sealing sectors and the turbine blade tips of a turbojet engine. The sealing segments are connected to an internal ring structure and an external ring structure located within the casing of the jet engine. The two ring structures serve to expand and contract the diameter of the ring formed by the sealing segments in conjunction with the expansion and contraction of the turbine blades for stabilized and transient engine operating modes. The device utilizes ventilating air taken from a stage of the jet engine compressor to cause the radial expansion or contraction of the internal and external rings in direct conjunction with the conditions under which the engine is operating.
    Type: Grant
    Filed: January 30, 1984
    Date of Patent: July 9, 1985
    Assignee: Societe Nationale d'Etude et Je Construction de Moteurs d'Aviation "S.N.E.C.M.A."
    Inventors: Louis F. Jumelle, Marcel R. Soligny
  • Patent number: 4525998
    Abstract: Insulation material lines the inner wall of the case of a gas turbine engine and controlled hot and/or cold air is selectively impinged on the outer wall of the case so as to maintain a minimum gap between the outer peripheral edge of the rotating blades relative to their tip seal means for increased thrust specific fuel consumption (TSFC).
    Type: Grant
    Filed: August 2, 1982
    Date of Patent: July 2, 1985
    Assignee: United Technologies Corporation
    Inventor: Frederick M. Schwarz
  • Patent number: 4522559
    Abstract: In a compressor section of a gas turbine engine, a double wall casing is provided wherein a nonstructural inner wall is removably attached to a thin, structural outer casing. The inner wall isolates the thin stator outer casing during transient turbine operations of throttle burst and throttle chop. During throttle burst and chop, the nonstructural inner wall delays rapid heating and cooling of the relatively thin-walled outer casing, and reduces radial misalignment between the stator casing and rotor due to uneven thermal expansion and contraction. The nonstructural inner wall evens-out thermal expansion and contraction of the stator casing with respect to the rotor. To fine tune the actual clearances between stator and rotor and prevent the casing outer wall from overheating, thermal insulation material is used between the nonstructural inner wall and outer casing.
    Type: Grant
    Filed: July 23, 1984
    Date of Patent: June 11, 1985
    Assignee: General Electric Company
    Inventors: Joseph C. Burge, Julius Bathori
  • Patent number: 4505872
    Abstract: The present invention pertains to a means of connecting a primary pump (intended for sodium or the like) and the delivery pipe within a breeder reactor of the swimming-pool type, permitting limited movement of the pump and the pipe in relation to one another to occur, while also maintaining adequate sealing between low pressure areas and high pressure areas within said pump. The connecting component consists of a cylindrical sleeve (11) which, in a resting position, is situated along the same axis (1) as the delivery pipe for the pump. A cylindrical guide (3) which is fastened to the pump is fitted into the aforementioned pipe, and a sealing joint (13) is situated between the sleeve (11) and the guide (3). There is also a horizontal annular collar (12) which is fastened to the aforementioned sleeve (11), resting upon an annular rim (5) situated upon the upper flange (7) of the pipe (4).
    Type: Grant
    Filed: February 8, 1982
    Date of Patent: March 19, 1985
    Assignee: Jeumont-Schneider
    Inventor: N. Delloye
  • Patent number: 4502276
    Abstract: A casing structure for a gas turbine engine comprises an outer load-bearing casing within which is supported an inner casing which forms the static structure of a compressor. Bearing panels carried from the outer casing carry the rotor of the compressor and its associated turbine. In order to mitigate the undesirable consequences of the bending under load of the outer casing, the inner casing is mounted at a forward section by forward mounting means which maintain it concentric with the rotor axis and at a rearward section by rearward mounting means which maintain it parallel with a section of the outer casing which retains its parallelism with the rotor axis even when the casing bends. The forward mounting illustrated is a dogged engagement while the rearward mounting utilizes a parallel series of links as a parallel motion linkage.
    Type: Grant
    Filed: March 9, 1984
    Date of Patent: March 5, 1985
    Assignee: Rolls-Royce Limited
    Inventor: George Pask
  • Patent number: 4492518
    Abstract: A gas turbine engine bearing support structure comprises a central hub which carries a bearing and which is supported by a plurality of spokes from a ring member. The majority of the spokes are radially extending so that each is perpendicular to an imaginary tangent at its point of intersection with the ring member. However, two of the spokes are not perpendicular but are inclined so that compressive loading on the spokes results in partial rotation of the central hub, thereby leading to compressive loads in the non-inclined spokes being partially relieved by localised bending.
    Type: Grant
    Filed: January 11, 1983
    Date of Patent: January 8, 1985
    Assignee: Rolls-Royce Limited
    Inventor: Peter F. Neal
  • Patent number: 4487016
    Abstract: A structure and method for providing cooling fluids from a compression section 10 to a turbine section 14 of an axially flow rotary machine is disclosed. Various construction details and steps of the method enable the machine to minimize the effect that unscheduled variations in the temperature of the cooling fluids have on operating clearances in the turbine section. These unscheduled variations may result from changes in ambient temperature and component deterioration. An internal cooling fluid from the discharge region 52 of the rearmost compressor 18 is used to modulate the flow of a second fluid impinged on the exterior of the outer case 24 for controlling the clearance between an array of rotor blades 26 and a coolable stator shroud 64 spaced radially outwardly of the rotor blades. In one embodiment, a valve 32 for modulating the flow of the second fluid has at least one thermostatic bimetallic spring 86 for transducing a change in temperature into a displacement.
    Type: Grant
    Filed: October 1, 1980
    Date of Patent: December 11, 1984
    Assignee: United Technologies Corporation
    Inventors: Frederick M. Schwarz, James G. Griffin
  • Patent number: 4477222
    Abstract: A turbine vane assembly of a gas turbine engine includes inner and outer shroud walls and a plurality of airfoil-shaped vanes extending between and connected at their opposite ends with the inner and outer shroud walls. The mounting construction of the vane ends to the respective shroud walls includes a plurality of recessed ledges defined in the shroud walls along respective ones of the ends of the vanes. Each ledge forms a gap between the respective wall and vane end extending from a trailing edge pressure side of the vane along the pressure side to a location approximately midway between the trailing and leading edges of the pressure side of the vane. The remainder of the vane end is rigidly connected to the respective shroud wall.
    Type: Grant
    Filed: September 30, 1982
    Date of Patent: October 16, 1984
    Assignee: The United States of America as represented by the Secretary of the Air Force
    Inventor: Daniel S. Wolf
  • Patent number: 4425078
    Abstract: An annular ring 22 for an axial flow gas turbine engine disposed inwardly of an array of stator vanes 14 and between an annular flow path 18 for hot working medium gases and an annular flow path 20 for cooling air is disclosed. The ring abuttingly engages the array of stator vanes in the radial direction to provide radial support and abuttingly engages the array of stator vanes and an outer air seal block the intermixing of gases from the working medium flow path and gases from the cooling air flow path. The annular ring includes a first annular section 28 and a second annular section 30. The first annular section has an axial width to radial height ratio greater than one and the second annular section has an axial width to radial height ratio less than one to adapt the ring for axial flexibility and radial stiffness and to enable the ring to accommodate growth and axial growth between the outer air seal and the array of stator vanes while remaining within the elastic limit.
    Type: Grant
    Filed: July 18, 1980
    Date of Patent: January 10, 1984
    Assignee: United Technologies Corporation
    Inventor: Donald A. Robbins
  • Patent number: 4412782
    Abstract: A compressor case structure capable of enhanced active clearance control within the structure is disclosed. Various construction details which enable the discharge of cooling air against the case and which minimize thermal distortion of the case are developed. The concepts are applied to a longitudinally split compressor case and include an external bleed manifold or circular cross section which extends across the longitudinal split in the case. Cooling air is dischargeable beneath the manifold to cool the case structure.
    Type: Grant
    Filed: March 28, 1979
    Date of Patent: November 1, 1983
    Assignee: United Technologies Corporation
    Inventor: William G. Monsarrat
  • Patent number: 4395195
    Abstract: A shroud ring (22) for a gas turbine engine having a stator structure (14) and an array of inwardly extending stator vanes (20) is disclosed. The shroud ring is circumferentially segmented to accommodate inward and outward movement of the vanes and the stator structure. The shroud ring has a segmented outer ring (28) and a segmented inner ring (30). The outer ring engages the vanes to support the vanes and to position the inner ring and an integral seal member (24) about a rotor structure. In one embodiment the vanes (20) are rotatable about a spanwise axis S. In a second embodiment, the vanes (120) are integrally attached to the shroud ring (122).
    Type: Grant
    Filed: May 16, 1980
    Date of Patent: July 26, 1983
    Assignee: United Technologies Corporation
    Inventors: Anthony R. De Cosmo, John H. Young
  • Patent number: 4384822
    Abstract: A turbine nozzle vane suspension arrangement of the type wherein the nozzle vanes are suspended by their outer shroud segments from the outer turbine casing and are suspended by their vane ring segments from an annular vane carrier. The vane carrier has axially spaced apart and radially-extending wall sections cooperating with root-ends projecting radially from the vane ring segments. The vane ring segments and their root-ends, and the vane carrier and its wall sections define between them an annular channel for receiving cooling air. The forward wall section of the vane carrier is axially resilient and bears resiliently against the forward vane root-end to provide a seal for the annular channel. The resilient forward wall section can be flexed axially rearwardly to permit the vane ring segments to be mounted on the vane carrier.
    Type: Grant
    Filed: January 26, 1981
    Date of Patent: May 24, 1983
    Assignee: Motoren- und Turbinen-Union Munchen GmbH
    Inventors: Ludwig Schweikl, Horst Weiss, Friedrich Sippel
  • Patent number: 4379677
    Abstract: A device for adjusting the clearance between moving blades and the ring of a turbine wherein the ring includes a cylindrical sleeve, a perforated partition, and a wall, which together form an enclosure. Boreholes receive tubular elements which fit together with coaxial boreholes provided in opposite walls of a distribution chamber. The chamber communicates with pipes which admit heat regulating air. Alternating tubular elements traverse the perforated wall and the chamber to evacuate exhaust gas through pipes.
    Type: Grant
    Filed: October 7, 1980
    Date of Patent: April 12, 1983
    Assignee: Societe Nationale d'Etude et de Construction de Moteurs d'Aviation, "S.N.E.C.M.A."
    Inventors: Claude C. Hallinger, Robert Kervistin
  • Patent number: 4354687
    Abstract: A gas turbine engine blade tip seal consists of a sealing ring which is controlled by means of two annular control members. The members are arranged such that one control member has a relatively rapid thermal response rate and the other control member has a relatively slow thermal response rate, the sealing ring being controlled such that a preferred tip clearance is maintained under varying engine operating conditions.
    Type: Grant
    Filed: August 25, 1981
    Date of Patent: October 19, 1982
    Assignee: Rolls-Royce Limited
    Inventors: Brian C. Holland, Roy T. Hirst, Roger J. M. Sills, Cyril G. Moore
  • Patent number: 4337016
    Abstract: Apparatus for confining cooling air to a flowpath between an outer case and adjacent structure is disclosed. Various construction details which enable the means to sealingly engage the adjacent structure to block the leakage of cooling air and to accommodate changes in diameter are discussed. The means has dual walls which are segmented.
    Type: Grant
    Filed: December 13, 1979
    Date of Patent: June 29, 1982
    Assignee: United Technologies Corporation
    Inventor: Gary F. Chaplin
  • Patent number: 4330234
    Abstract: A rotor tip clearance control apparatus for a gas turbine engine comprises an annular shroud member which forms part of the static structure of the apparatus. The shroud member has an internal frusto-conical surface which co-operates with the outer extremities of the rotor to define a small clearance. In order to control this clearance the shroud member is mounted from fixed structure by rotatable eccentrics which can move the member axially and thus affect the clearance in a predetermined manner.
    Type: Grant
    Filed: January 21, 1980
    Date of Patent: May 18, 1982
    Assignee: Rolls-Royce Limited
    Inventor: Rowan H. Colley
  • Patent number: 4274805
    Abstract: A structure for supporting an array of stator vanes in an axial flow rotary machine is disclosed. Various construction details related to machine efficiency and machine durability are developed. In one structure, both the concentricity of the ring with respect to the axis of the engine and the diameter of the ring are unaffected by thermal and mechanical distortions of the outer case. A spline-type connection is formed between the ring and the outer case.
    Type: Grant
    Filed: October 2, 1978
    Date of Patent: June 23, 1981
    Assignee: United Technologies Corporation
    Inventor: Trent H. Holmes
  • Patent number: 4248569
    Abstract: A turbine rotor shroud is mounted by means for rigidly supporting it on an internal bearing for turbine and shaft components of a gas turbine engine and a low rate flexible seal member extends between the outer case of the gas turbine engine and an outer gas flow path wall for maintaining continuity of gas and air stream pass through the gas turbine engine during different modes of engine operation thereby to maintain a closely controlled clearance between blade tips of a row of turbine blades on a rotor connected to the gas turbine engine drive shaft and the rotor shroud to maintain close clearance under mechanical (static or dynamic) loads wherein the deflected rotor or engine casing systems move but the motion is accommodated by the flexible seal member and prevented by a rigid nozzle to turbine bearing support structure.
    Type: Grant
    Filed: November 13, 1978
    Date of Patent: February 3, 1981
    Assignee: General Motors Corporation
    Inventor: Glenn W. Thebert
  • Patent number: 4230436
    Abstract: Cooling airflow to the shroud support apparatus is varied in response to both rotor speed and elapsed time above a predetermined level by the selective use and mixture of two air sources at different temperatures. For steady-state operation, each of four different operating modes has its prescribed cooling air delivery mode such that, generally, as the engine speed and cycle temperatures increase, so does that of the cooling air. For transient operation, a timer is employed to sequence the desired cooling air delivery modes in such a manner as to maintain optimum rotor-to-shroud clearances during the transient period.
    Type: Grant
    Filed: July 17, 1978
    Date of Patent: October 28, 1980
    Assignee: General Electric Company
    Inventor: Samuel H. Davison
  • Patent number: 4230439
    Abstract: A timing valve is responsive to certain hydraulic rotor speed input signals so as to schedule increased temperatures of air to a turbine shroud support in accordance with the thermal time constants of the rotor. Clearance between the rotor and the shroud is thereby minimized during both transient and steady-state operating conditions. Temperatures are incrementally increased by selectively combining air from the compressor fifth and ninth stage bleed manifolds. Under certain operating conditions, the timing valve is pre-empted and air is provided at a predetermined temperature level as a function of rotor speed only.
    Type: Grant
    Filed: July 17, 1978
    Date of Patent: October 28, 1980
    Assignee: General Electric Company
    Inventors: Joseph P. Smith, Jr., Robert L. Mentzer, Dana D. Freberg
  • Patent number: 4218180
    Abstract: A novel turbo-machine of the axial type including a rotor assembly rotatably supported within a stator housing, wherein the stator housing includes a plurality of partition wall sections, with each section supported within a separate ring member along a limited contact surface, and with each of the ring members attached to each other and to the stator housing in a manner ensuring proper alignment of the turbine assembly.
    Type: Grant
    Filed: July 5, 1978
    Date of Patent: August 19, 1980
    Assignee: Stal-Laval Turbin AB
    Inventor: Rolf Wikstrom
  • Patent number: 4208165
    Abstract: A novel turbo-machine of the axial type including a rotor assembly supported within a stator housing which includes a plurality of partition wall sections positioned adjacent one another, with each pair of sections extending on opposite sides of a rotor blade attached to the rotor assembly. Each of the partition sections is formed of a pair of similarly-shaped members, with adjacent pairs of members being rotated a specific angle prior to joining all of the pairs of each other via fasteners extending therethrough, with the plurality of joined sections then attached to the stator housing in a manner which compensates for both axial and radial thermal expansion during operation.
    Type: Grant
    Filed: July 5, 1978
    Date of Patent: June 17, 1980
    Assignee: Stal-Laval Turbin AB
    Inventor: Rolf Wikstrom
  • Patent number: 4171614
    Abstract: A gas turbine engine which includes an essentially axial-flow compressor drive turbine having at least one turbine stator and at least one turbine rotor and a reverse-flow annular combustion chamber arranged coaxially with a longitudinal centerline of the gas turbine engine. The turbine stator and turbine rotor are arranged in the gas turbine engine and sized for heat retentivity such that thermal expansion rates of the turbine stator and turbine rotor are substantially equal.
    Type: Grant
    Filed: April 13, 1977
    Date of Patent: October 23, 1979
    Assignee: Motoren- und Turbinen-Union Munchen GmbH
    Inventor: Wolfgang Weiler
  • Patent number: 4131388
    Abstract: An outer air seal circumscribing the tips of the rotor blades of a rotary machine is disclosed. Techniques for limiting the radial clearance between the tips of the blades and the outer air seal at steady state conditions are developed. Structure independent of the machine case for isolating the thermal response of the outer air seal from the thermal response of the machine case is discussed and illustrated.
    Type: Grant
    Filed: May 26, 1977
    Date of Patent: December 26, 1978
    Assignee: United Technologies Corporation
    Inventor: Robert F. Brodell
  • Patent number: 4127357
    Abstract: A turbine shroud segment is supported by a pair of eccentric shafts which are rotated in response to the engine operating temperatures to selectively vary the radial position of the shroud segment so as to minimize the radial clearance between the shroud segment and the rotatable blades circumscribed therein during variable operating conditions. The bimetal actuator moves in response to changes in the temperature of the cooling air to rotate a ring gear which in turn rotates the eccentric shafts to modulate the radial position of the shroud segment. By proper selection of component design specification and operating parameters, the radial clearance can be minimized during steady-state operating conditions without attendant rubbing during transient operating conditions.
    Type: Grant
    Filed: June 24, 1977
    Date of Patent: November 28, 1978
    Assignee: General Electric Company
    Inventor: William R. Patterson
  • Patent number: 4069662
    Abstract: The clearance between the outer air seal of a gas turbine engine and the tip of the turbine rotor is controlled by selectively turning on and off or modulating the cool air supply which is directed in proximity to the air seal supporting structure so as to control its thermal growth. The cooling causes shrinkage thereby holding the clearance low and effectively reducing fuel consumption.
    Type: Grant
    Filed: December 5, 1975
    Date of Patent: January 24, 1978
    Assignee: United Technologies Corporation
    Inventors: Ira H. Redinger, Jr., David Sadowsky, Philip S. Stripinis
  • Patent number: 4019320
    Abstract: A reduction of the opening of the clearance between the outer air seal secured to the case of a turbo-fan engine and the tip of the turbine buckets is obtained by selectively turning on and off or modulating the cool air supply. The cool air is bled from the fan discharge duct and is directed externally of the engine case adjacent the seal. Circumferentially mounted spray bars are axially spaced to fit juxtaposed to the annular flanges extending from the engine case and carry a plurality of holes judiciously located to direct the flow of cool air to impinge on the side walls of the flanges to effectuate shrinkage of the case.
    Type: Grant
    Filed: December 5, 1975
    Date of Patent: April 26, 1977
    Assignee: United Technologies Corporation
    Inventors: Ira H. Redinger, Jr., David Sadowsky, Philip S. Stripinis
  • Patent number: 3975114
    Abstract: An arrangement for sealing the joints formed between the facing ends of turbine stator segments arranged in an annular array to form a turbine diaphragm is disclosed, the arrangement basically consisting of seal strips formed by at least two bimetal ribbons fastened along their longitudinal centerlines and adapted to deflect away from each other with increasing temperatures, the opposite edges of the strips being disposed in grooves in the facing ends of the stator segments.
    Type: Grant
    Filed: September 23, 1975
    Date of Patent: August 17, 1976
    Assignee: Westinghouse Electric Corporation
    Inventor: Ralph W. Kalkbrenner
  • Patent number: 3965066
    Abstract: A seal for use between an annular combustor and a turbine nozzle, disposed downstream of the combustor, is provided with means for effectively innerconnecting the combustor with a sidewall surrounding the nozzle. The sidewall includes an upstream extending radially projecting flange and the combustor includes an axially projecting downstream extending flange. The seal includes means for frictionally engaging each of these flanges and retaining them in a sealing relationship while permitting axial and radial frictional sliding motion therebetween. In addition, the present invention provides means for passing cooling air from a surrounding plenum through the seal in a cooling fashion to a pocket formed between the combustor-associated flange and a film-promoting lip which comprises a portion of the combustor liner.
    Type: Grant
    Filed: March 15, 1974
    Date of Patent: June 22, 1976
    Assignee: General Electric Company
    Inventors: Albert P. Sterman, Henry J. Brands, Frederick W. Weissborn, Jr.
  • Patent number: 3947145
    Abstract: A seal is provided between adjacent stationary annular shroud members in a gas turbine. The shroud members have an axially directed gap disposed between their adjoining ends. Each adjoining end of each stationary shroud has a shoulder arrangement which provides support for a seal disposed across the gap. The shoulders on the ends of the shrouds provide restraint against radially inwardly directed dislocation, and a blade ring which supports the shroud members themselves, provides restraint against axial and radially outwardly directed dislocation. The seal prevents escape of hot motive fluid from the generally axially directed working fluid flow path.
    Type: Grant
    Filed: October 7, 1974
    Date of Patent: March 30, 1976
    Assignee: Westinghouse Electric Corporation
    Inventors: Frank Michel, Egidio J. Ruffini