Medium frequency mine communication system

• US 5,093,929 A
• Filed: 04/16/1991
• Issued: 03/03/1992
• Est. Priority Date: 05/29/1987
• Status: Expired due to Fees

• Current Assignee: Stolar Incorporated
• Original Assignee: Stolar Incorporated
• Inventors: Stolarczyk, Larry G., Mondt, William E., Smoker, Kurt A., Zappanti, James L., Smith, Seth A., Moore, Edward D., Hasenack, Marvin L. Jr., Boese, Gerald J.
• Primary Examiner(s): KUNTZ, CURTIS A
• Application Number:
  US07/686,874
• Time in Patent Office: 322 Days
• Field of Search: 455/40, 455/14-16, 455/41, 455/3, 455/89, 455/95, 455/100, 455/90, 455/121, 455/11, 455/344, 455/351, 340/347 R, 340/347 AD, 340/825.44, 367/81
• US Class Current: 455/40
• CPC Class Codes: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/28 using the near field of leaky cables, e.g. of leaky coaxial cables

Abstract

A method for using an underground mine communication system to effect minewide communication and an intrinsically safe current limiter circuit for insuring that electrical equipment in the system will not cause incendiary conditions. The underground mine communication system comprises a plurality of repeaters and medium frequency radios, including mobile, portable and personal-carried radios, coupled to electrical conductors and natural waveguides existing in the earth by tuned loop antennas. Messages transmitted by the radios are carried to the repeaters by the conductors or coal seam waves. The repeaters amplify, replicate and retransmit the message at two different frequencies for transmission of the message to a surface base station and to other radios in the system. A paging system, which has a separate set of repeaters, is also coupled to the network of electrical conductors and natural waveguides by tuned loop antennas. The paging system alerts miners to contact the surface base station. Radios, pagers and repeaters in the system are equipped with the intrinsically safe current limiter circuit to preclude the development of incendiary conditions. The current limiter circuit comprises a series arrangement of a current trip circuit, a redundant current trip circuit and a current limiting field effect transistor controlled by a feedback control amplifier.

Claims

1. A personal-carried magnetic dipole formed by a vertical plane loop antenna assembly for an underground communication system including a transmission line electrical conductor extending longitudinally within a mine, the antenna assembly comprising:

a one-piece harness for mounting on a person located within a mine, the harness including a pair of flexible shoulder straps which loop over a person'"'"'s shoulders, means for attaching the shoulder straps to a belt worn about the person'"'"'s waist and a pair of cross straps which run perpendicular to the shoulder straps, along a back face of the harness, with each of the cross straps being connected to each of the shoulder straps and a space "w" being left between the two cross straps such that the two cross straps and shoulder straps form a constant rectangular area when the harness is mounted on a person;

a tuned resonant continuous wire loop antenna attached to the outer face of the constant rectangular area formed by the cross straps and the shoulder straps to establish a magnetic dipole loop antenna in a plane substantially vertical relative to said transmission line electrical conductor within said mine such that the loop area establishes a horizontal electric field for coupling to said conductor when the harness is mounted on a person within said mine and proximate to said mine transmission line; and

a magnetic dipole loop antenna tuning box electrically connected to the wire loop antenna and attached to one of the shoulder straps, the box being tunable to frequencies lying in the medium frequency range.

2. The personal-carried vertical tuned loop antenna of claim 1, wherein,

the pair of cross straps run perpendicular to the shoulder straps along a front face of the harness.

3. The personal-carried vertical tuned loop antenna of claim 1, wherein,

the loop antenna tuning box contains a series tuned circuit for switching the continuous wire loop between a receiving mode and a transmitting mode.

4. The personal-carried vertical tuned loop antenna of claim 1 further including :

a pager electrically connected to the loop antenna tuning box, said pager including a receiver and a means for alerting the person that a signal is being received by the receiver.

b. adjusting the loop bandwidth to the smallest value possible that will still accommodate the bandwidth of the frequency modulated carrier signal.