US3284668A - Electronic speed sensor - Google Patents

Electronic speed sensor Download PDF

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Publication number
US3284668A
US3284668A US319162A US31916263A US3284668A US 3284668 A US3284668 A US 3284668A US 319162 A US319162 A US 319162A US 31916263 A US31916263 A US 31916263A US 3284668 A US3284668 A US 3284668A
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electrical
silicon controlled
relay
controlled rectifier
load
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US319162A
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Donald B Heaslip
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Bendix Corp
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Bendix Corp
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Priority to US319162A priority Critical patent/US3284668A/en
Priority to GB43793/64A priority patent/GB1034949A/en
Priority to DE19641426319 priority patent/DE1426319B1/en
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D13/00—Control of linear speed; Control of angular speed; Control of acceleration or deceleration, e.g. of a prime mover
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D17/00—Regulating or controlling by varying flow
    • F01D17/02—Arrangement of sensing elements
    • F01D17/06—Arrangement of sensing elements responsive to speed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
    • F02C7/26—Starting; Ignition
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P1/00—Details of instruments
    • G01P1/07—Indicating devices, e.g. for remote indication
    • G01P1/08—Arrangements of scales, pointers, lamps or acoustic indicators, e.g. in automobile speedometers
    • G01P1/10—Arrangements of scales, pointers, lamps or acoustic indicators, e.g. in automobile speedometers for indicating predetermined speeds
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P1/00—Details of instruments
    • G01P1/07—Indicating devices, e.g. for remote indication
    • G01P1/08—Arrangements of scales, pointers, lamps or acoustic indicators, e.g. in automobile speedometers
    • G01P1/10—Arrangements of scales, pointers, lamps or acoustic indicators, e.g. in automobile speedometers for indicating predetermined speeds
    • G01P1/106—Arrangements of scales, pointers, lamps or acoustic indicators, e.g. in automobile speedometers for indicating predetermined speeds by comparing the time duration between two impulses with a reference time
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/02—Devices characterised by the use of mechanical means
    • G01P3/14—Devices characterised by the use of mechanical means by exciting one or more mechanical resonance systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/42—Devices characterised by the use of electric or magnetic means
    • G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
    • G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
    • G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
    • G01P3/484—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals delivered by contact-making switches

Definitions

  • Some motors such as air turbine starters, require a speed-sensing device for interrupting the supply of air to the motor at a predetermined speed which corresponds to the speed necessary for starting an engine.
  • mechanical-fiyweight, speed-sensmg devices have been frequently used. Such devices depend upon mechanical movement against springs and involve the wearing of rotating parts which necessarily affect the accuracy and reliability. These rotating mechanical speed-sensmg devices also are relatively bulky and expensive.
  • electro-magnetic means for generating a speed-responsive signal which is used to actuate a control device for the motor to be regulated.
  • a resonant'reed relay is actuated by the electro-magnetic means which generates an A.C. signal.
  • several closures of the resonant reed relay contacts were necessary in order to provide sufficient power for operation of the relay coil. This functionlng sometimes resulted in a delay and improper operation and hence has disadvantages.
  • An object of the present invention is to provide an improved electrical speed-sensing control which does not rely on a mechanical, speed-sensing device whereby a wearing of rotating mechanical parts is avoided and more accurate and reliable speed-sensing is realized.
  • Another object is to provide an improved electrical speed-sensing control which is inexpensive, compact, and more sensitive.
  • a further object is the provision of a speed-sensing control having a resonant reed relay and an electro-magnetic speed sensing device wherein more rapid functioning of the resonant reed relay is achieved so that a control device for a motor is more precisely operated at a predetermined speed.
  • the drawing is a schematic showing of a DC. source, a main control switch for circuitry including an electromagnetic pickup, a resonant reed relay, a silicon controlled rectifier, and a double-throw control relay.
  • a DC. source 11 is connected to a main control switch 13 having wire 15 connected to lead 17 of the resonant reed relay 19.
  • Resonant reed relay 19 has a first reed contact 21 with lead 17 and a second reed contact 23 having lead 25.
  • the resonant reed relay 19 also has a power coil 27 for causing the two reed contacts 21 and 23 to vibrate at a natural frequency for the closing at the contact tips thereof.
  • the resonant relay coil 27 is connected to the energizing coil 29 of the electro-magnetic pickup device 31.
  • the magnetic pickup device 31 will generate an A.C. signal when energized by exciter rotor 33, having projections 35 of magnetic material.
  • Rotor 33 is rotated by an air turbine starter (not shown). At a predetermined speed and frequency, the generated A.C. signal will correspond to the natural frequency required for closing the reed contacts 21 and 23, as is well known.
  • a wire 41 extends from the juncture of wire 15 and lead 17 to the anode lead 43 of the silicon controlled rectifier (SCR) 45.
  • the cathode lead 47 from SCR 45 is connected to double-throw relay 49 by means of wire 51 while the gate lead 53 of SCR 45 is connected to lead 25 of resonant reed 23.
  • the double-throw control relay 49 has an actuating coil 61 which has a predetermined inductance and is grounded and a load resistance 63 is connected in parallel with coil 61.
  • the relay 49 includes a first fixed contact 65 which is normally open (N/O), a center moveable common contact 67, and a second fixed contact 69 which is normally closed (N/C).
  • the common switch contact 67 is connected by wire 71 to wire 41 at a location between SCR 45 and the main control switch 13.
  • the lower or first fixed contact 65 is connected to the juncture of the coil 61, the resistance 63, and the wire 51.
  • the upper fixed contact 61 is connected by wire 73 to a load 75 which is grounded.
  • Load 75 can be a normally-closed, air supply, solenoid valve for the mentioned air turbine starter.
  • the SCR 45 is a high speed, sensitive gating silicon controlled rectifier, such as the 2N1595 made by the Texas Instruments Company, Dallas, Texas.
  • the load resistor 63 (used in parallel with the coil 63 of the relay 49) has a value which permits a holding current to flow immediately through the SCR 45 when first gated in spite of the inductance of coil 63 whereby the SCR locks in immediately and operates more proficiently under inductive load.
  • the switch 13 is closed and then the solenoid of the normally-closed air supply valve or the load 75 is energized, whereby air is supplied to an air turbine starter (not shown) and thus causing toothed rotor 33 to rotate.
  • the toothed rotor 33 is part of the starter gear box (not shown) or other similar device.
  • an A.C. signal is generated in the coil 29 of the magnetic pickup 31.
  • This power signal is fed to the coil 27 of a resonant reed relay 19. Below starting speed, the resonant reed relay 19 will remain open since the output from the magnetic pickup is below the required resonant frequency.
  • the reeds 21 and 23 vibrate and contact each other.
  • the silicon controlled rectifier 45 is gated and slightly thereafter, the actuating coil 61 of the relay 49 is energized, causing the relay switch to operate.
  • the common element 67 of the switch breaks from the second or N/C contact 69, the load 75 is de-energized.
  • the common element 69 of the switch makes with the first or N/O contact 67, an additional holding circuit to the relay coil 61 is completed.
  • Relay 49 will not be de-energized until switch 13 is opened.
  • the resistance 63 offsets the inductive load from coil 61 so that SCR 45 operates better.
  • the use of the self-holding, silicon controlled rectifier circuit allows the relay 49 to operate after the first closure of the reed relay contacts 21 and 23. Many closures of the reed relay contacts to prov1de the energy necessary for a relay of the type shown to switch to holding position do not result.
  • the inductance of the relay coil 61 does not delay immediate flow of the holding current for the SCR since the load resistor 63 permits flow of the required holding current.
  • the coil 63 operates a few milliseconds after the SCR is initially gated with the consequent self-holding by flow through resistor 63. The inductance would prevent a self-holding current during the brief current flow at the first closing of the contact reeds.
  • a control system for a mechanical source of power having an associated primary source of electrical power connected to a load comprising:
  • electrical signal generating means generating a signal proportional to the speed of a portion of the mechanical source of power
  • a resonant reed relay having a plurality of contacts electromagnetically linked to the electrical signal generating means
  • a silicon controlled rectifier having an anode, a cathode and a gate, one of said resonant relay contacts connected to the anode of the silicon controlled rectifier, another of said resonant relay contacts connected to the gate lead of the silicon controlled rectifier;
  • a switch means having a first electrical connection between the cathode of said silicon controlled rectifier and the primary source of electrical power and a second electrical connection for the load, the switch means controllingthe electrical energization of the load;
  • the anode of the silicon controlled rectifier having an electrical connection for the primary source of electrical power.
  • the switch means having a movable contactor, a coil and a plurality of contacts
  • the movable contactor having an electrical connection relative to the primary source of electrical power; one of the plurality of switch contacts having electrical connection to the load, another of the contacts having an electrical connection to the switch coil.
  • the control system as claimed in claim 2 including further: resistive means connected in parallel with the switch coil.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Automation & Control Theory (AREA)
  • Reciprocating, Oscillating Or Vibrating Motors (AREA)
  • Control Of Eletrric Generators (AREA)

Description

Nov. 8, 1966 D. B. HEASLIP 3,234,668
ELECTRONIC SPEED SENSOR Filed Oct. 28, 1965 INVENTOR. DONALD B. HEASLlP ATTORNEY United States Patent Ofiice 3,284,568 Patented Nov. 8, 1966 3,284,668 ELECTRONIC SPEED SENSOR Donald B. Heaslip, Sauquoit, N.Y., assignor to The Bendix Corporation, Utica, N .Y., a corporation of Delaware Filed Oct. 28, 1963, Ser. No. 319,162 3 Claims. (Cl. 3175) This invention relates to speed-responsive, electrical controls and more particularly concerns such a control which is initiated by electro-magnetic means.
Some motors, such as air turbine starters, require a speed-sensing device for interrupting the supply of air to the motor at a predetermined speed which corresponds to the speed necessary for starting an engine. In the past, mechanical-fiyweight, speed-sensmg devices have been frequently used. Such devices depend upon mechanical movement against springs and involve the wearing of rotating parts which necessarily affect the accuracy and reliability. These rotating mechanical speed-sensmg devices also are relatively bulky and expensive. It has been proposed to use electro-magnetic means for generating a speed-responsive signal which is used to actuate a control device for the motor to be regulated. In one such proposal, a resonant'reed relay is actuated by the electro-magnetic means which generates an A.C. signal. In some instances, several closures of the resonant reed relay contacts were necessary in order to provide sufficient power for operation of the relay coil. This functionlng sometimes resulted in a delay and improper operation and hence has disadvantages.
An object of the present invention is to provide an improved electrical speed-sensing control which does not rely on a mechanical, speed-sensing device whereby a wearing of rotating mechanical parts is avoided and more accurate and reliable speed-sensing is realized.
Another object is to provide an improved electrical speed-sensing control which is inexpensive, compact, and more sensitive.
A further object is the provision of a speed-sensing control having a resonant reed relay and an electro-magnetic speed sensing device wherein more rapid functioning of the resonant reed relay is achieved so that a control device for a motor is more precisely operated at a predetermined speed.
The realization of the above objects, along with the features and advantages of the invention, will be apparent from the following description and the accompanying drawing.
The drawing is a schematic showing of a DC. source, a main control switch for circuitry including an electromagnetic pickup, a resonant reed relay, a silicon controlled rectifier, and a double-throw control relay.
Referring to the drawing, a DC. source 11 is connected to a main control switch 13 having wire 15 connected to lead 17 of the resonant reed relay 19. Resonant reed relay 19 has a first reed contact 21 with lead 17 and a second reed contact 23 having lead 25. The resonant reed relay 19 also has a power coil 27 for causing the two reed contacts 21 and 23 to vibrate at a natural frequency for the closing at the contact tips thereof. The resonant relay coil 27 is connected to the energizing coil 29 of the electro-magnetic pickup device 31. The magnetic pickup device 31 will generate an A.C. signal when energized by exciter rotor 33, having projections 35 of magnetic material. Rotor 33 is rotated by an air turbine starter (not shown). At a predetermined speed and frequency, the generated A.C. signal will correspond to the natural frequency required for closing the reed contacts 21 and 23, as is well known.
A wire 41 extends from the juncture of wire 15 and lead 17 to the anode lead 43 of the silicon controlled rectifier (SCR) 45. The cathode lead 47 from SCR 45 is connected to double-throw relay 49 by means of wire 51 while the gate lead 53 of SCR 45 is connected to lead 25 of resonant reed 23. The double-throw control relay 49 has an actuating coil 61 which has a predetermined inductance and is grounded and a load resistance 63 is connected in parallel with coil 61. The relay 49 includes a first fixed contact 65 which is normally open (N/O), a center moveable common contact 67, and a second fixed contact 69 which is normally closed (N/C). The common switch contact 67 is connected by wire 71 to wire 41 at a location between SCR 45 and the main control switch 13. The lower or first fixed contact 65 is connected to the juncture of the coil 61, the resistance 63, and the wire 51. The upper fixed contact 61 is connected by wire 73 to a load 75 which is grounded. Load 75 can be a normally-closed, air supply, solenoid valve for the mentioned air turbine starter.
The SCR 45 is a high speed, sensitive gating silicon controlled rectifier, such as the 2N1595 made by the Texas Instruments Company, Dallas, Texas. The load resistor 63 (used in parallel with the coil 63 of the relay 49) has a value which permits a holding current to flow immediately through the SCR 45 when first gated in spite of the inductance of coil 63 whereby the SCR locks in immediately and operates more proficiently under inductive load.
In operation, the switch 13 is closed and then the solenoid of the normally-closed air supply valve or the load 75 is energized, whereby air is supplied to an air turbine starter (not shown) and thus causing toothed rotor 33 to rotate. The toothed rotor 33 is part of the starter gear box (not shown) or other similar device. As toothed rotor 33 rotates, an A.C. signal is generated in the coil 29 of the magnetic pickup 31. This power signal is fed to the coil 27 of a resonant reed relay 19. Below starting speed, the resonant reed relay 19 will remain open since the output from the magnetic pickup is below the required resonant frequency. When a predetermined speed of rotor 33 is reached and the frequency of the generated signal is the same as the natural frequency of the reeds 21 and 23 of the resonant reed relay 19, the reeds 21 and 23 vibrate and contact each other. At the first closure of the contacts on the tips of the reeds 21 and 23, the silicon controlled rectifier 45 is gated and slightly thereafter, the actuating coil 61 of the relay 49 is energized, causing the relay switch to operate. As the common element 67 of the switch breaks from the second or N/C contact 69, the load 75 is de-energized. As the common element 69 of the switch makes with the first or N/O contact 67, an additional holding circuit to the relay coil 61 is completed. Relay 49 will not be de-energized until switch 13 is opened. The resistance 63 offsets the inductive load from coil 61 so that SCR 45 operates better.
It is to be noted that the use of the self-holding, silicon controlled rectifier circuit allows the relay 49 to operate after the first closure of the reed relay contacts 21 and 23. Many closures of the reed relay contacts to prov1de the energy necessary for a relay of the type shown to switch to holding position do not result. As mentioned, the inductance of the relay coil 61 does not delay immediate flow of the holding current for the SCR since the load resistor 63 permits flow of the required holding current. The coil 63 operates a few milliseconds after the SCR is initially gated with the consequent self-holding by flow through resistor 63. The inductance would prevent a self-holding current during the brief current flow at the first closing of the contact reeds.
It is to be understood that changes can be made in the disclosed embodiment of the invention by persons skilled in the art without departing from the invention as set forth in the following claims.
What is claimed is:
1. A control system for a mechanical source of power having an associated primary source of electrical power connected to a load comprising:
electrical signal generating means generating a signal proportional to the speed of a portion of the mechanical source of power;
a resonant reed relay having a plurality of contacts electromagnetically linked to the electrical signal generating means;
a silicon controlled rectifier having an anode, a cathode and a gate, one of said resonant relay contacts connected to the anode of the silicon controlled rectifier, another of said resonant relay contacts connected to the gate lead of the silicon controlled rectifier;
a switch means having a first electrical connection between the cathode of said silicon controlled rectifier and the primary source of electrical power and a second electrical connection for the load, the switch means controllingthe electrical energization of the load; and
the anode of the silicon controlled rectifier having an electrical connection for the primary source of electrical power.
2. The control system as claimed in claim 1 wherein:
the switch means having a movable contactor, a coil and a plurality of contacts;
4 the movable contactor having an electrical connection relative to the primary source of electrical power; one of the plurality of switch contacts having electrical connection to the load, another of the contacts having an electrical connection to the switch coil. 3. The control system as claimed in claim 2 including further: resistive means connected in parallel with the switch coil.
References Cited by the Examiner UNITED STATES PATENTS 2,941,120 6/1960 Harman et al 317--5 3,213,323 10/1965 Circle 317148.5X
OTHER REFERENCES Silicon Controlled Rectifier Manual, second edition (General Electric), Dec. 29, 1961, pages 89-90 relied on.
New Design Ideas From Solid State Products, Inc., Bulletin #6, Controlling Relays with Microsecond Pulses, June 29, 1961.
1955 AIEE-IRE Electronic Components Conference at Los Angeles, California, A New Transistor with Thyratron-Like Characteristics, by Richard F. Rutz and Arvid W. Berger, May 26, 1955.
MILTON O. HIRSHFIELD, Primary Examiner.
J. A. SILVERMAN, Assistant Examiner.

Claims (1)

1. A CONTROL SYSTEM FOR A MECHANICAL SOURCE OF POWER HAVING AN ASSOCIATED PRIMARY SOURCE OF ELECTRICAL A SIGNAL CONNECTED TO A LOAD COMPRISING: ELECTRICAL SIGNAL GENERATING MEANS GENERATING A SIGNAL PROPORTIONAL TO THE SPEED OF A PORTION OF THE MECHANICAL SOURCE OF POWER; A RESONANT REED RELAY HAVING A PLURALITY OF CONTACTS ELECTROMAGNETICALLY LINKED TO THE ELECTRICAL SIGNAL GENERATING MEANS; A SILICON CONTROLLED RECTIFIER HAVING AN ANODE, A CATHODE AND A GATE, ONE OF SAID RESONANT RELAY CONTACTS CONNECTED TO THE ANODE OF THE SILICON CONTROLLED RECTIFIER, ANOTHER OF SAID RESONANT RELAY CONTACTS CONNECTED TO THE GATE LEAD OF THE SILICON CONTROLLED RECTIFIER; A SWITCH MEANS HAVING A FIRST ELECTRICAL CONNECTION BETWEEN THE CATHODE OF SAID SILICON CONTROLLED RECTIFIER AND THE PRIMARY SOURCE OF ELECTRICAL POWER AND A SECOND ELECTRICAL CONNECTION FOR THE LOAD, THE SWITCH MEANS CONTROLLING THE ELECTRICAL ENERGIZATION OF THE LOAD; AND THE ANODE OF THE SILICON CONTROLLED RECIFIER HAVING AN ELECTRICAL CONNECTION FOR THE PRIMARY SOURCE OF ELECTRICAL POWER.
US319162A 1963-10-28 1963-10-28 Electronic speed sensor Expired - Lifetime US3284668A (en)

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Application Number Priority Date Filing Date Title
US319162A US3284668A (en) 1963-10-28 1963-10-28 Electronic speed sensor
GB43793/64A GB1034949A (en) 1963-10-28 1964-10-27 Electronic speed sensor
DE19641426319 DE1426319B1 (en) 1963-10-28 1964-10-27 Speed-dependent electrical control for gas turbine starter

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3417289A (en) * 1966-08-26 1968-12-17 Ametek Inc Speed sensing switch for rotary drums and the like
US3440433A (en) * 1966-05-19 1969-04-22 Bendix Corp Aircraft starter control
US3573782A (en) * 1968-05-23 1971-04-06 United Aircraft Corp Current monitor
US3751719A (en) * 1972-05-24 1973-08-07 Trw Inc Heavy current relay circuit
US4259567A (en) * 1976-12-23 1981-03-31 The Frymaster Corporation Positive reset safety control circuit for frying apparatus
US4739435A (en) * 1985-06-05 1988-04-19 C. & E. Fein Gmbh & Co. Safety device for an electric power tool
US4847721A (en) * 1985-02-07 1989-07-11 C. & E. Fein Gmbh & Co. Safety device for a tool powered by an electric motor
US20120266606A1 (en) * 2011-04-20 2012-10-25 Honeywell International Inc. Air turbine start system with monopole starter air valve position

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2941120A (en) * 1956-05-14 1960-06-14 Napier & Son Ltd Speed control of rotary bladed machines
US3213323A (en) * 1962-10-16 1965-10-19 Westinghouse Electric Corp Breaker tripping signal circuit

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2991395A (en) * 1956-10-04 1961-07-04 Stewart Warner Corp Speed responsive control device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2941120A (en) * 1956-05-14 1960-06-14 Napier & Son Ltd Speed control of rotary bladed machines
US3213323A (en) * 1962-10-16 1965-10-19 Westinghouse Electric Corp Breaker tripping signal circuit

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3440433A (en) * 1966-05-19 1969-04-22 Bendix Corp Aircraft starter control
US3417289A (en) * 1966-08-26 1968-12-17 Ametek Inc Speed sensing switch for rotary drums and the like
US3573782A (en) * 1968-05-23 1971-04-06 United Aircraft Corp Current monitor
US3751719A (en) * 1972-05-24 1973-08-07 Trw Inc Heavy current relay circuit
US4259567A (en) * 1976-12-23 1981-03-31 The Frymaster Corporation Positive reset safety control circuit for frying apparatus
US4847721A (en) * 1985-02-07 1989-07-11 C. & E. Fein Gmbh & Co. Safety device for a tool powered by an electric motor
US4739435A (en) * 1985-06-05 1988-04-19 C. & E. Fein Gmbh & Co. Safety device for an electric power tool
US20120266606A1 (en) * 2011-04-20 2012-10-25 Honeywell International Inc. Air turbine start system with monopole starter air valve position
US9845734B2 (en) * 2011-04-20 2017-12-19 Honeywell International Inc. Air turbine start system with monopole starter air valve position
EP2514949A3 (en) * 2011-04-20 2018-01-24 Honeywell International Inc. Air turbine start system with monopole speed sensor

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DE1426319B1 (en) 1969-09-04
GB1034949A (en) 1966-07-06

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