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US3745549A - Proximity alarm - Google Patents

Proximity alarm Download PDF

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Publication number
US3745549A
US3745549A US00135347A US3745549DA US3745549A US 3745549 A US3745549 A US 3745549A US 00135347 A US00135347 A US 00135347A US 3745549D A US3745549D A US 3745549DA US 3745549 A US3745549 A US 3745549A
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US
United States
Prior art keywords
alarm
transistor
control circuit
signal control
signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00135347A
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English (en)
Inventor
R Jepperson
C Simmonds
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CRANE PROD Mfg CO Inc
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CRANE PROD Mfg CO Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by CRANE PROD Mfg CO Inc filed Critical CRANE PROD Mfg CO Inc
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Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/26—Electrical actuation by proximity of an intruder causing variation in capacitance or inductance of a circuit
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B21/00—Alarms responsive to a single specified undesired or abnormal condition and not otherwise provided for
    • G08B21/02—Alarms for ensuring the safety of persons
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B21/00—Alarms responsive to a single specified undesired or abnormal condition and not otherwise provided for
    • G08B21/18—Status alarms
    • G08B21/182—Level alarms, e.g. alarms responsive to variables exceeding a threshold

Definitions

  • the induced signal control circuit in cludes amplifier means, half-wave voltage doubling means, oscillating means, power supply voltage regulating means and frequency filtering means
  • the switching circuit and the induced sig nal control circuit are located in a casing composed of a non-magnetic material.
  • the induced signal control circuit is encapsulated in a resinous material and is removably mounted within the casing.
  • this invention relates to systems for signalling the close approach of an object to an energized electrical transmission line.
  • the proximity alarms disclosed in U.S. Pat. Nos. 3,125,751 and 3,168,729 are examples of prior art alarms which have been developed for such usage.
  • the alarm system is designed to operate off the vehicle power supply. It was discovered that the power supply to the alarm system tended to vary sharply over a period of time. It was found that this fact seriously affected the sensitivity and effectiveness of the total alarm system.
  • the primary object of this invention is to provide a proximity alarm system which may be used in the field over an extended period of time and may be mass produced with a high degree of repeatability in construction and response characteristics.
  • Another object of this invention is to produce a proximity alarm which is not adversely affected by an intense heat environment or a substantial vibration environment.
  • a further object of this invention is to provide a proximity alarm device which overcomes all of the problems found to exist in conjunction with known prior art devices.
  • This invention is directed to an alarm system including antenna means for sensing the presence of an electrostatic field which thereby induces an alternating current potential therein.
  • a switching circuit and an induced signal control circuit are electrically connected to each other.
  • the switching circuit has an antenna sensitivity control, test circuitry and an alarm circuitry.
  • the induced signal control circuit includes amplifying means, half-wave voltage doubling means, oscillating means, power supply voltage regulating means and frequency filtering means.
  • the induced signal control circuit is encapsulated in a resinous material and disposed in a casing composed of a non-magnetic material.
  • the switching circuit is also disposed in the casing adjacent the encapsulated signal control circuit.
  • variable resistance means electrically connected to transistor means for establishing and maintaining predetermined induced signal response characteristics in the transistor means. While some prior art devices simply distinguish among the types of dangers to which it responds, the present alarm system is designed to eliminate extraneous alternating current frequency from the induced signal control circuit. It is through the specific circuit means set forth herein and the manner in which the control device is constructed that provides a unique approach and substantially improved results in working characteristics under severe environmental conditions.
  • FIG. 1 is a front elevational view of a control device made in accordance with this invention
  • FIG. 2 is a side elevational view partially in section of the device shown in FIG. 1,
  • FIG. 3 is a back elevational view of the device of FIG. 1 with the cover removed
  • FIG. 4 is a bottom elevational view of the device of FIG. 1,
  • FIG. 5 is a circuitry diagram of the induced signal control circuit made in accordance with this invention.
  • FIG. 6 is a circuitry diagram of the switching circuit made in accordance with this invention.
  • an alarm device as shown in FIG. 1 includes a casing 100 on which is mounted a warning lamp 81 which lights intermittently when a voltage is induced in a sensor cable (not shown).
  • the sensor cable is attached to the casing 100 at the sensor connection 11a.
  • the system is turned on when the battery switch 52 is in the on position.
  • the sensor cable is mounted on an object such as the boom of a crane which might enter an electrostatic field.
  • the manner in which the sensor cable or antenna is mounted onto the moving object is well known in the prior art and does not form a part of this invention. When the sensor cable is moved sufficiently close to a high voltage power line, the electrostatic field surrounding the power line induces a voltage in the sensor cable.
  • the sensitivity of the system to the electrostatic field which induces the voltage is adjusted through the sensitivity switches 14 and 23.
  • the battery switch 52 is connected to the battery of the system and the alarm device is operable when the switch 52 is in the on position. It may be desirable to have an exterior alarm attached to the system. In this instance, the exterior alarm switch 82 is placed in the on position.
  • warning light 81 mounted in the casing 100 is a primary warning signal in this specific embodiment.
  • Audible sounding devices may be used for warning the driver and other ground personnel when the alarm device is activated.
  • Other exterior and remote lights may also be used in conjunction with the warning system.
  • the warning device of this invention can be adjusted to actuate the alarm at any desired distance from one foot to several hundred feet depending upon the voltage of the energized power line.
  • the alarm mechanism such as warning light 81 and an external light will blink or a horn will sound.
  • the rate of blinking will increase or the oscillating of the audible alarm will increase as the object such as a boom or extension moves close to the energized power line.
  • the alarm system will continue to warn until the object is withdrawn from the danger zone.
  • Test switch 12 is located in the casing 100 for the purpose of testing the switching circuitry or the signal control circuitry of the alarm system-A sensor test light 80 will be turned on when the test switch 12 is placed in the on condition, if the sensor cable (not shown) is in working order.
  • a bank of connectors 101 is disposed on the bottom portion of the device of this embodiment for attaching the various alarms and battery sources that are used to supply energy to the alarm system.
  • the control device made in accordance with this invention has two basic circuit portions mounted in the casing 100.
  • the control device circuitry includes a switching circuit portion and an encapsulated signal control circuit portion.
  • the switching circuit portion is shown in detail in FIG. 6 and the signal control circuit portion is shown in FIG. 5.
  • the switching circuit includes test circuitry, sensitivity circuitry and alarm circuitry disposed in the casing 100.
  • the coarse sensitivity control 14 includes a bank of capacitors.
  • the fine sensitivity control 23 is composed of a variable resistance. Toggle switches are used for the battery switch 52 and exterior alarm switch 82.
  • a pushbutton device is used to form the test circuitry switch 12.
  • the relay 41 is mounted in the casing and is in a normally de-energized state. The wires have been removed from the drawing as shown in FIG. 3 for clarity.
  • An encapsulated module 10 is removably mounted within the casing and includes the signal control circuitry which is shown in detail in FIG. 5.
  • the encapsulating process for the signal control circuit 10 is accomplished in a standard prior art manner.
  • the circuitry as shown in FIG. 5 is placed in a housing or box construction and filled with a resinous material.
  • the housing is made of a plastic material in this embodiment.
  • the module 10 is mounted on the support memher 103, as shown in FIG. 2. Any type of fastening means may be used.
  • the switching circuitry and the encapsulated signal control circuit 10 are disposed adjacent each other within the casing 100 and connected through the use of a plug means 24a and 24b.
  • the casing 100 should be constructed of a non-magnetic material in an effort to shield the highly sensitive circuitry used in conjunction with the construction of this alarm control device.
  • an aluminum alloy is used to shield against electrostatic pickup and possible electromagnetic effects.
  • the construction as described hereinabove provides a very rugged device heretofore unavailable in the prior art.
  • the use of the particular circuit in the encapsulated module 10 has overcome the problems associated with fatigue failure due to vibration.
  • the control device of this invention has become suited to use under very high temperature conditions.
  • the use of sealing means between the cover 102 and the casing 100 provides a dust barrier which is a further significant improvement over any of the prior art devices known and used heretofore.
  • a sensor 11 consisting of some type of antenna means is mounted along the portion of the object which might come into contact with electrostatic field around a power line.
  • the antenna means would be mounted on the boom of a crane, on the fork portion of a fork lift truck, or on the ladder portion of a ladder truck.
  • the electrostatic field which surrounds the power line induces a voltage in the antenna means or sensor 11.
  • the induced voltage is applied to the capacitor voltage divider network generally designated 14.
  • the induced voltage is applied to contact 13b of the test switch 12.
  • the voltage divider network 14 is also referred to as the coarse sensitivity control.
  • the capacitor divider network 14 includes a capacitor 15 and a bank of capacitors 16 through 21.
  • a 5 Megohm variable resistor 23 is placed across the capacitor bank thereby constituting the fine sensitivity control.
  • the fine adjustment of the sensitivity is accomplished by selecting any desired percentage of induced input voltage across the capacitor bank and connecting it into the input of the field effect transistor 25.
  • the switching circuit as shown in FIG. 6 is electrically connected to the encapsulated signal control circuit as shown in FIG. 5 through the use of pins 1 through 8 located in the plug means 24a and 24b.
  • One of the plug means portions 24a and 24b is male and the other is female.
  • the input of the induced voltage is accomplished through pins 1 and 2 into the field effect transistor 25.
  • variable resistance 60 connected to the source 25a.
  • the transistor 25 used in this specific embodiment is very sensitive to any contamination around its leads. A breakdown will occur in the input impedence by virtue of any building up of a conducting surface such as oxidation layers or moisture.
  • a primary problem associated with prior art devices has been the collecting of tial for the transistor 25 thereby improving the repeatability with respect to sensitivity established in each alarm control device being produced.
  • the transistors 25 and 26 constitute a two stage direct coupled amplifier.
  • the input voltage which is induced in the sensor 11 is amplified by the transistors 25 and 26 and subsequently applied to the emitterfollower transistor 27.
  • One of the basic problems associated with the prior art devices has been the difficulties associated with extraneous alternating current frequencies.
  • the inclusion of capacitor 62 has solved this basic problem by limiting the range frequencies to which the control device will respond. It is essential that the alarm is not triggered when regular transmitters are used at the work site or when the work is being done in the vicinity of a radio transmitter of any sort.
  • the capacitor 62 acts as a very low impedance shunt or bypass. The impedance is effective to pass frequencies of about 60 cycles per second up to about 450 cycles per second.
  • the amplified input voltage is taken from the emitter-follower 27 and applied to a half-wave voltage doubler means and a filter.
  • the half-wave voltage doubler means consists of the diodes 28 and 29.
  • the amplified input signal is coupled across the capacitor 70 to the junction of the diodes 28 and 29.
  • the diode 29 will be conductive and diode 28 will be open.
  • the capacitor 70 will charge to the full peak value of that positive wave form.
  • the diode 29 will be in the off condition and diode 28 will be biased forwardly.
  • the negative half cycle will cause current flow to diode 28 and the voltage that was charged previously in capacitor will also be applied through diode 28 thereby applying twice the voltage across the diode 28.
  • This diode configuration thereby produces a doubled half-wave pulse which is subsequently sent through the filter consisting of resistor 30 and capacitor 31.
  • the filter means establishes the doubled half-wave to a DC level proportional to the amplitude of the input voltage.
  • the capacitor 31 substantially eliminates any ripple that may be apparent in the half-wave rectified signal.
  • the capacitor 31 charges upon the half-cycle and then discharges so that only a DC voltage potential that is fully filtered is supplied to the transistor 32.
  • the voltage at this point in the circuit varies from about 0 to about 3 volts.
  • the proportional DC voltage is applied to a normally conducting transistor 32.
  • the voltage comes to the base 320 in a negative direction and will eventually cause the transistor 32 to turn off.
  • the transistor 32 turns off, the capacitor 36 starts to charge up to a higher level and the unijunction transistor 37 begins to fire.
  • the negative halfwave is used to cut off the normally conducting transistor 32 thereby allowing the uni-junction transistor 37 to begin oscillation.
  • the oscillation of the uni-junction transistor 37 is established at a frequency determined by the conductive state of transistor 32. In this specific embodiment, the maximum frequency of oscillation is 5 pulses per second. In this way, the oscillating means is completely compatible with the audible alarms that are used.
  • variable resistance 34 is used in conjunction with the oscillating transistor 37.
  • a basic production problem occurs when uni-junction transistors such as those used in the circuitry of this control device are purchased in bulk. All of these uni-junction transistors have different firing points. They vary considerably with regard to their sensitivity. The transistors having sensitive firing points will oscillate at a much higher frequency. In that instance, a larger amount of resistance must be inserted in combination therewith to slow the oscillation down. It has been found that the combination of using a variable resistance 34 to standardize the oscillating frequency of the transistor 37 together with encapsulation of the entire circuit provides, a totally standardized, highly efficient and workable device in the field. This result has heretofore been unknown with respect to alarm devices used to give warning when an object approaches an electrostatic field around an energized power line.
  • Another feature of this invention is directed to the use of a pulse stretcher means to insure a solid signal for driving the alarms used with the control device of this invention.
  • a pulse stretcher means to insure a solid signal for driving the alarms used with the control device of this invention.
  • the amplified output of transistor 43 is applied to a high current transistor switch 45 and pin of the plug means 24b.
  • This circuitry connection allows current to flow through the alarm relay 46 across pins 5 and 6 from pin 7 through resistance 47 to pin 6 of plug 24b. Current continues through alarm relay 46 to pin 5 through high current transistor 45 and then to pin 4.
  • Diode 48 serves to dampen high voltage spikes which may be produced by the coil relay 46.
  • the alarm relay 46 When the alarm relay 46 is energized, contacts 49, S0 and 51 are closed. Contact 49 connects the ungrounded vehicle battery terminal to the external terminal of the boom light and the alarm spares. The contact 51 connects the alarm light 81 across the crane battery supply at pins 4 and 7 of plug 24a. The flow of current is effected only when the switch 52 is in the on or closed position.
  • the relay 46 is a 6 volt relay. When this relay is used in conjunction with resistor 47, a louder clicking sound will result than if a 12 volt relay is used.
  • a very important feature of this invention is directed to the problem which was discovered to exist only after prior art devices were used in the field. It was found that the output voltage from the generator and battery systems of vehicles such as cranes varies drastically. It is determined that such output voltage variation in the power supply of the vehicle itself adversely affected the frequency of oscillation for the oscillating means 37. It is necessary to hold this voltage constant and thereby effectuate a highly efficient and standardized circuitry which would operate properly in the field.
  • the voltage regulating means accepts voltages from about 10 volts to about 16 volts and regulates it down to about 8 to 8 volts.
  • the zener diode 54 used in combination with the transistor 53 constitutes the voltage regulating means across the supply voltage of the vehicle which includes the voltage across the generator and battery system thereof. It was the discovery of this particular problem that led to the solution proposed by the inventors and resulted in a sound alarm control device which is extremely efficient and highly reproducible. None of these advantages were available in the known prior art devices.
  • the capacitor 56 acts as a filter to prevent noise from the vehicle battery power supply from entering the circuitry of the control device.
  • the resistors 71 and 72 and capacitor 68 provide additional filtering against such noise.
  • the testing circuitry includes the test button 12 and contacts 13a, 13b and 13c.
  • the contacts 13a, 13b and 130 are moved from their lower positions as shown in FIG. 6 to their upper closed positions when the button 12 is pressed.
  • Contact 13a connects the base terminal of the shunt transistor 32 to ground. This manually cuts off conduction in the transistor 32 and causes the oscillator 37 to oscillate at its maximum rate of 5 pulses per second.
  • the oscillation of transistor 37 checks the relay alarm light 81 and the external outputs which may be connected to audible alarms.
  • contacts 13b and 130 make a path to allow battery current to flow from the on-off switch 52 through the sensor 11 from terminal A to B, through 13b to the sensor power test lamp 80.
  • the closing of this circuitry tests the continuity of the sensor cable. If there is a break in the sensor cable somewhere along the vehicle, the lamp 80 will not be turned on.
  • Another basic advantage of the alarm system made in accordance with this invention is that it is massproducible due to its use of very simple and straightforward components made in an encapsulated module unit.
  • the various uses of voltage regulating means, filtering means and variable resistance means allow the units to be more repeatable in the field. That is, the best that could be accomplished with prior art devices was to effect a 50 percent variation from one control device to the next with respect to the sensitivity to the electrostatic field. In other words, it would be necessary to adjust the unit as much as 50 percent before the appropriate sensitivity would be attained.
  • the control device of the present invention it is possible to obtain an adjustment down within the 10 percent range and there is a substantial reduction of the variations between units.
  • the basic use of a switching circuit portion in combination with encapsulated signal control circuitry portion has overcome many of the failures which have been caused by fatigue due to vibration environment.
  • the basic mechanical integrity of the control device has been improved substantially and in a manner that allows the device to be commercially acceptable as compared to the prior art devices which were not commercially acceptable.
  • said signal control circuit portion being encapsulated and disposed adjacent the switching circuit and being removably mounted in said casing, and
  • plug means for electrically connecting the switching circuit portion to the signal control circuit portion.
  • the signal control circuit portion includes variable resistance means electrically connected to transistor means for establishing and maintaining predetermined induced response characteristics within said transistor means.
  • the signal control circuit portion includes amplifier means having transistor means for receiving any induced signal emanating from the electrostatic field and a variable resistance means electrically connected to the transistor means for establishing a predetermined biasing potential within said transistor means.
  • said transistor means is a field effect transistor and said induced signal is received at the gate of the transistor and said variable resistance means is electrically connected to the source of the transistor.
  • the signal control circuit portion includes filtering means having means electrically connected to the output of the transistor means for filtering extraneous alternating current frequency from the system.
  • said filtering means includes means for applying the filtered extraneous alternating current frequency to the casing thereby effecting grounding thereof.
  • the signal control circuit portion includes oscillating means having a uni-junction transistor and a variable resistance means electrically connected to the uni-junction transistor for establishing a predetermined firing point in said transistor.
  • the signal control circuit portion includes oscillating means and power supply voltage regulating means which controls varying voltage supply to the alarm system thereby maintaining the frequency of the oscillating means at a predetermined level.
  • the signal control circuit portion is responsive to an induced voltage signal and includes means for amplifying the induced voltage signal, means for converting the amplified induced signal to a doubled half-wave form, oscillating means for producing short duration pulses in response to said double half-wave form, and means for stretching the width of the short duration pulses from the oscillating means to provide satisfactory energizing of the alarm circuitry.
  • a. alarm means electrically connected to a normally de-energized relay
  • oscillating means for producing short duration pulses in response to said doubled half-wave form
  • a. antenna means for sensing the presence of said field which thereby induces an alternating current potential therein
  • a switching circuit including means for controlling the sensitivity of the antenna, circuit means for testing the alarm system, and alarm circuit means,
  • a signal control circuit responsive to any induced signal received from the electrostatic field to form an oscillating response signal effective to operate the alarm circuit means
  • a proximity alarm control device comprising:
  • a a casing composed of a non-magnetic material
  • b means for receiving an induced input voltage from an electrostatic field around energized power lines
  • said switching circuit including circuit means for testing the device, alarm circuit means and means for providing a power supply voltage to the control device,
  • said signal control circuit being encapsulated and disposed adjacent the switching circuit and being removably mounted in said casing, and
  • plug means for electrically connecting the switching circuit to the signal control circuit.
  • the signal control circuit includes variable resistance means connected to transistor means for establishing and maintaining predetermined induced signal response characteristics in said transistor means.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Emergency Alarm Devices (AREA)
  • Measurement Of Current Or Voltage (AREA)
  • Control And Safety Of Cranes (AREA)
  • Burglar Alarm Systems (AREA)
  • Jib Cranes (AREA)
US00135347A 1971-04-19 1971-04-19 Proximity alarm Expired - Lifetime US3745549A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US13534771A 1971-04-19 1971-04-19

Publications (1)

Publication Number Publication Date
US3745549A true US3745549A (en) 1973-07-10

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ID=22467692

Family Applications (1)

Application Number Title Priority Date Filing Date
US00135347A Expired - Lifetime US3745549A (en) 1971-04-19 1971-04-19 Proximity alarm

Country Status (8)

Country Link
US (1) US3745549A (xx)
JP (1) JPS53152587U (xx)
AU (1) AU474202B2 (xx)
CA (1) CA963553A (xx)
DE (1) DE2137893C3 (xx)
FR (1) FR2134977A5 (xx)
GB (2) GB1367641A (xx)
NL (1) NL7111829A (xx)

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4362992A (en) * 1978-01-30 1982-12-07 Sperry Limited System and method of detecting the proximity of an alternating magnetic field
US4649375A (en) * 1985-10-31 1987-03-10 Fmc Corporation Apparatus for detecting power lines
US4683464A (en) * 1983-06-30 1987-07-28 Texaco Inc. Safety monitor means and method
US4727447A (en) * 1982-12-20 1988-02-23 Texaco Inc. Safety system and method
US4845476A (en) * 1986-12-17 1989-07-04 Societe D'assistance Technique Aux Industries Electroniques, Pneumatiques, Hydrauliqes Proximity detector between a metallic mass and an element to which is applied an electric voltage
USD383076S (en) * 1995-07-24 1997-09-02 Cripe Rodney J Emergency vehicle proximity alarm system
US5910775A (en) * 1996-08-29 1999-06-08 S&C Electric Company Phasing and indicator arrangements for switchgear or the like
US6002348A (en) * 1998-05-13 1999-12-14 Safe Flight Instrument Corporation Pilot's aid for detecting power lines
US6124798A (en) * 1998-12-09 2000-09-26 Institute Of Occupational Safety And Health, Council Of Labor Affairs, Executive Yuan Alarm device designed to warn of danger of hitting high voltage power line by crane in motion
US6600426B1 (en) 1999-10-04 2003-07-29 The United States Of America As Represented By The Department Of Health And Human Services Alarm system for detecting hazards due to power transmission lines
US20030174061A1 (en) * 2002-03-14 2003-09-18 Nickerson Irvin H. High voltage proximity warning system and method
US20070018841A1 (en) * 2004-11-22 2007-01-25 Nickerson Irvin H High voltage proximity warning system utilizing wireless sensors and method
US20090108840A1 (en) * 2007-10-24 2009-04-30 Givens Gerald E Power Line Sensor
US20100214094A1 (en) * 2007-10-24 2010-08-26 Givens Gerald E Wireless Sensor System
US8786447B1 (en) 2012-02-26 2014-07-22 Bryan C. Wise High voltage detection assembly

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993003403A1 (en) * 1991-08-01 1993-02-18 Gabriel Fortin Method and device for electrostatically investigating surface and sub-surface structures

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4362992A (en) * 1978-01-30 1982-12-07 Sperry Limited System and method of detecting the proximity of an alternating magnetic field
US4727447A (en) * 1982-12-20 1988-02-23 Texaco Inc. Safety system and method
US4683464A (en) * 1983-06-30 1987-07-28 Texaco Inc. Safety monitor means and method
US4649375A (en) * 1985-10-31 1987-03-10 Fmc Corporation Apparatus for detecting power lines
US4845476A (en) * 1986-12-17 1989-07-04 Societe D'assistance Technique Aux Industries Electroniques, Pneumatiques, Hydrauliqes Proximity detector between a metallic mass and an element to which is applied an electric voltage
USD383076S (en) * 1995-07-24 1997-09-02 Cripe Rodney J Emergency vehicle proximity alarm system
US6426616B1 (en) * 1996-08-29 2002-07-30 S&C Electric Co. Phasing and indicator arrangements for switchgear or the like
US5910775A (en) * 1996-08-29 1999-06-08 S&C Electric Company Phasing and indicator arrangements for switchgear or the like
US6002348A (en) * 1998-05-13 1999-12-14 Safe Flight Instrument Corporation Pilot's aid for detecting power lines
US6124798A (en) * 1998-12-09 2000-09-26 Institute Of Occupational Safety And Health, Council Of Labor Affairs, Executive Yuan Alarm device designed to warn of danger of hitting high voltage power line by crane in motion
US6600426B1 (en) 1999-10-04 2003-07-29 The United States Of America As Represented By The Department Of Health And Human Services Alarm system for detecting hazards due to power transmission lines
US20030174061A1 (en) * 2002-03-14 2003-09-18 Nickerson Irvin H. High voltage proximity warning system and method
US6853307B2 (en) * 2002-03-14 2005-02-08 Irvin H. Nickerson High voltage proximity warning system and method
US20070018841A1 (en) * 2004-11-22 2007-01-25 Nickerson Irvin H High voltage proximity warning system utilizing wireless sensors and method
US20090108840A1 (en) * 2007-10-24 2009-04-30 Givens Gerald E Power Line Sensor
US20100214094A1 (en) * 2007-10-24 2010-08-26 Givens Gerald E Wireless Sensor System
US8477027B2 (en) 2007-10-24 2013-07-02 Gerald E. Givens Wireless sensor system
US8786447B1 (en) 2012-02-26 2014-07-22 Bryan C. Wise High voltage detection assembly

Also Published As

Publication number Publication date
CA963553A (en) 1975-02-25
DE2137893C3 (de) 1979-12-06
AU3135971A (en) 1973-01-25
FR2134977A5 (xx) 1972-12-08
GB1367641A (en) 1974-09-18
NL7111829A (xx) 1972-10-23
JPS53152587U (xx) 1978-12-01
AU474202B2 (en) 1976-07-15
DE2137893B2 (de) 1979-04-19
DE2137893A1 (de) 1972-11-09
GB1367642A (en) 1974-09-18

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