Hot line mountable hotline indicator having liquid crystal display with resettable memory function

• US 5,274,324 A
• Filed: 01/16/1991
• Issued: 12/28/1993
• Est. Priority Date: 11/08/1989
• Status: Expired due to Term

• Current Assignee: Edmund O. Schweitzer III, Jean E. Schweitzer, Marilyn L. Schweitzer
• Original Assignee: Edmund O. Schweitzer Jr
• Inventors: Schweitzer, Edmund O. Jr.
• Primary Examiner(s): NGUYEN, VINH P
• Application Number:
  US07/641,815
• Time in Patent Office: 1,077 Days
• Field of Search: 324/96, 324/126, 324/127, 324/133, 324/111, 324/115, 324/72.5, 340/664, 340/663, 340/654
• US Class Current: 324/96
• CPC Class Codes: G01R 13/403 using passive display devices, e.g. liquid crystal display or Kerr effect display devices
• CPC Class Codes: G01R 19/155 Indicating the presence of voltage

Abstract

A hot line indicator for instantaneously indicating the presence of voltage on an electrical conductor in an AC power distribution system includes a unitary one-piece housing having a projecting metallic probe and a hookeye for engaging a conventional lineman'"'"'s hot stick. Within the housing, the display electrodes of a high impedance liquid crystal display component are coupled to the monitored conductor through the probe and a capacitive coupling to ground to provide an unambiguous "HL" display indicative of the presence of voltage on the conductor.

Claims

1. A hot line indicator for use in conjunction with a lineman'"'"'s hot stick for visually indicating the presence of voltage in a high voltage AC conductor when positioned in close proximity to the conductor by the hot stick, said indicator comprising:

a housing having a front surface and an oppositely facing rear surface;

an elongated electrically conductive probe member extending from said rear surface of said housing;

a metallic ground coupling member disposed entirely within said housing in spaced-apart relationship to said probe member;

engaging means projecting from said front surface of said housing for receiving the hot stick in locked engagement, whereby said probe member can be fixedly positioned relative to said hot stick;

status indicating means within said housing comprising a high impedance display device having at least a pair of display electrodes disposed in operative association with a layer of voltage-responsive light controlling material, the display device providing on said front surface of said housing a first display condition in the absence of an actuating signal applied to said signal electrodes, and a second display condition in the presence of an actuating signal applied to said display electrodes;

display circuit means for electrically coupling one of said display electrodes to said probe member and the other of said display electrodes to said ground coupling member whereby said display device is caused to display said second display condition in the presence of voltage on said probe member;

a pair of electrical test terminals accessible from the exterior of said housing, and test circuit means for electrically coupling said test terminals to respective ones of said display electrodes, whereby said display device is actuated to said second condition upon application of a test voltage to said test terminals.

2. A hot line indicator as defined in claim 1 wherein said high impedance display device comprises a liquid crystal display having a display segment electrode electrically coupled to said probe member and a backplane electrode electrically coupled to said ground coupling member.

3. A hot line indicator as defined in claim 1 wherein said test circuit means provide a high-impedance ohmic connection between said test terminals and said display electrodes.

4. A hot line indicator for use in conjunction with a lineman'"'"'s hot stick for visually indicating the presence of a voltage on a high voltage electrical conductor after the indicator has been momentarily positioned in close proximity to the conductor, said indicator comprising:

a housing;

an electrically conductive probe member projecting from said housing;

a display storage capacitor;

status indicating means within said housing comprising a high impedance display device having at least a pair of display electrodes disposed in operative association with a layer of voltage-responsive light controlling material, said display device providing on the exterior of said housing a first display condition in the absence of an actuating signal applied to said display electrodes, and a second display condition in the presence of an actuating signal applied to said display electrodes; and

display circuit means within said housing for electrically coupling one of said display electrodes to said probe member and the other of said display electrodes to electrical ground, and for electrically coupling said display electrodes across said display storage capacitor, whereby said display device is actuated to said second display condition following the momentary presence of voltage on said probe member and remains in said second condition pending discharge of said capacitor.

5. A hot line indicator as defined in claim 4 wherein said display circuit means further include switch means actuable from the exterior of said housing for discharging said display storage capacitor to return said display device to said first display condition.

6. A hot line indicator as defined in claim 4 wherein said high impedance display device comprises a liquid crystal display having a display segment electrode coupled to said probe member and an associated backplane electrode coupled to electrical ground.

7. A hot line indicator as defined in claim 4 including a metallic ground coupling member disposed entirely within said housing in spaced-apart relationship to said probe member, and wherein said display circuit means electrically couple said other of said display electrodes to said ground coupling member.

8. A hot line indicator as defined in claim 4 including a pair of test terminals accessible from the exterior of said housing, and test circuit means for electrically coupling said test terminals to said display electrodes, whereby said display device is actuated to said second condition upon application of a test voltage to said test terminals.

9. A hot line indicator for use in conjunction with a lineman'"'"'s hot stick for visually indicating the presence of voltage in a high voltage AC conductor when positioned in close proximity to the conductor by the hot stick, said indicator comprising:

a housing having a front surface and an oppositely facing rear surface;

an electrically conductive probe member extending from said rear surface of said housing;

engaging means projecting from said front surface of said housing for receiving said hot stick in locked engagement, whereby said probe member is fixedly positioned relative to said hot stick;

status indicating means within said housing comprising a high impedance display device having at least a pair of display electrodes disposed in operative association with a layer of voltage-responsive light controlling material, the display device providing on said front surface of said housing a first display condition in the absence of an actuating signal applied to said display electrodes, and a second display condition in the presence of an actuating signal applied to said display electrodes;

display circuit means for electrically coupling one of said display electrodes to said probe member and the other of said display electrodes to electrical ground whereby said display device is caused to display said second display condition in the presence of voltage on said probe member;

a pair of electrical test terminals accessible from the exterior of said housing; and

test circuit means for electrically coupling said test terminals to respective ones of said display electrodes, whereby said display device is actuated to said second condition upon application of a test voltage to said test terminals.

10. A hot line indicator as defined in claim 9 including a metallic ground coupling member entirely disposed within said housing in spaced-apart relationship to said probe member, and wherein said display circuit means electrically couple said other of said display electrodes to said ground coupling member.

11. A hot line indicator as defined in claim 9 wherein said display circuit means further provide a high impedance ohmic connection between said display electrodes.

12. A hot line indicator as defined in claim 9 wherein said high impedance display device comprises a liquid crystal display having a display segment electrode electrically coupled to said probe member and a backplane electrode electrically coupled to electrical ground.

13. A hot line indicator for use in conjunction with a lineman'"'"'s hot stick for visually indicating the presence of a voltage on a high voltage electrical conductor after being momentarily positioned in close proximity to the conductor, said indicator comprising:

a housing;

an electrically conductive probe member projecting from said housing;

a display storage capacitor;

status indicating means within said housing comprising a high impedance display device having at least a pair of display electrodes disposed in operative association with a layer of voltage-responsive light controlling material, the display device providing on the exterior of said housing a first display condition in the absence of an actuating signal applied to said display electrodes, and a second display condition in the presence of an actuating signal applied to said display electrodes;

display circuit means within said housing for electrically coupling one of said display electrodes to said probe member and the other of said display electrodes to electrical ground, and for electrically coupling said display electrodes across said display storage capacitor, whereby said display device is actuated to said second display condition following the momentary presence of voltage on said probe member and remains in said second condition pending discharge of said capacitor;

a pair of electrical test terminals accessible from the exterior of said housing; and

test circuit means for electrically coupling said test terminals to said display electrodes, whereby said display device is actuated to said second condition upon application of a test voltage to said test terminals.

14. A hot line indicator as defined in claim 13 wherein said display circuit means further include switch means actuable from the exterior of said housing for discharging said display storage capacitor to return said display to said first display condition.

15. A hot line indicator as defined in claim 13 wherein said high impedance display device comprises a liquid crystal display having a display segment electrode coupled to said probe member and an associated backplane electrode coupled to electrical ground.

16. A hot line indicator as defined in claim 13 including a metallic ground coupling member disposed within said housing in spaced-apart relationship to said probe member, and wherein said display circuit means electrically couple said other of said display electrodes to said ground coupling member.