Abstract:
An antenna enclosure and mounting arrangement for transmitting meter-related information from a remotely readable commodity meter positioned within a subterraneous pit to a remote reading station. The antenna arrangement includes an antenna housing having an outwardly tapered support portion that contacts an inwardly tapered support surface formed in the pit lid. When the antenna housing is mounted within the pit lid, the top surface of the antenna enclosure is flush with the top surface of the pit lid, while the antenna contained within the antenna housing is positioned slightly below the top surface of the pit lid.

Description:
REFERENCE TO CROSS-RELATED APPLICATIONS 
     This application is based on and claims priority from provisional application Ser. No. 60/184,820 filed Feb. 25, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to a transmission antenna for flow meters and, more particularly, to an antenna for an indicating meter positioned beneath the ground such as used by utilities and municipalities to meter consumption of natural gas, water and electricity. 
     Commodities such as natural gas, water and electricity are routinely delivered to commercial and industrial establishments and residences by piping networks or electrical lines (as the case may be) operated by utility companies and municipalities. For billing purposes, such commodities are “metered” at the point of consumption. That is, the network line or “lateral” extending to the establishment or the residence includes a meter indicating how much of the commodity has been consumed in a period of time and the commodity customer is billed accordingly. 
     It has been estimated that there are about 600 million utility meters installed worldwide. It has also been estimated that there are about 270 million utility meters in the United States and that about 150-160 million of those meters are used for gas and water. Only a very small percentage of utility meters are configured to be read remotely. 
     In fact, most such meters are read visually by a person walking on site to actually view and manually record the information displayed on the meter dial. There are a number of disadvantages to this form of meter reading. One is that it is enormously labor-intensive. The overhead costs to a utility or municipality for “walk-by” meter reading are very substantial. 
     Another disadvantage of such form of meter reading is that the person reading meters is subjected to various forms of hazard, e.g. deep snow, barking (and perhaps biting) dogs and the like. And it is not unheard of that a customer intentionally keeps a ferocious dog in the hope of preventing the meter from being read. 
     Still another disadvantage is that property owners, especially residential owners, prefer that meter readers not walk on the property. Sometimes, there is a risk that however careful, the meter reader will trample flowers or ornamental shrubs. 
     In recognition of the disadvantages of walk-by meter reading, meters have been developed which can be read remotely. Such meters are configured as transponders and include a radio transmitter. When the meter is “interrogated” by a radio signal from a remote location, the meter responds by transmitting a signal encoded with the meter reading. 
     In each of the remote meters, an antenna assembly is connected to the meter to transmit the measured commodity use to the remote reading device. Examples of such systems are shown in U.S. Pat. Nos. 5,298,894 and 5,659,300. In the systems shown in the above mentioned patents, the meter itself is positioned beneath ground in a pit that is covered by a metal pit lid. 
     In each of these remote meter reading systems, an antenna is shown as extending above the top surface of the pit lid such that the radio frequency signal generated by the antenna is transmitted from above the pit lid. Typically, the pit lid is formed from a metallic material, such as iron, that inhibits the transmission of a radio frequency signal therethrough. 
     A significant disadvantage of such systems is that the antenna enclosure extends above the pit lid. Since meter pits can be located in a sidewalk, street or yard of individual user, the protruding antenna enclosure can be contacted by either a vehicle or a pedestrian. If the antenna enclosure is contacted by a vehicle, the antenna enclosure can be damaged and must thus be replaced to ensure proper operation. 
     Therefore, a need exists for an antenna enclosure that is flush mounted with the top surface of the pit lid to prevent the antenna enclosure from being damaged by contact with a vehicle or other device. Further, another object of the present invention is to provide an antenna enclosure and pit lid such that the antenna enclosure can be positioned beneath the pit lid and transmit the radio frequency signals through the pit lid. Further, it is an object of the present invention to configure the pit lid to receive the antenna enclosure of the invention to allow the radio frequency signals generated by the antenna to be transmit to a remote reading device. 
     SUMMARY OF THE INVENTION 
     The present invention involves an antenna enclosure and mounting arrangement for mounting a radio frequency antenna on a pit lid. The pit lid covers a pit enclosing a commodity meter. 
     The antenna enclosure of the present invention includes an antenna housing having a tapered upper support portion. The tapered upper support portion angles outward away from the cylindrical main body of the antenna housing to define an upper surface having a greater diameter than the cylindrical body portion. The upper support portion of the antenna housing contacts a similarly tapered surface that defines an opening within the pit lid. 
     When the antenna enclosure is mounted within the pit lid, the top surface of the antenna enclosure is flush with the top surface of the pit lid. The actual antenna contained within the antenna enclosure is thus positioned slightly beneath the top surface of the pit lid. When the antenna enclosure is mounted on the pit lid, the tapered surface that defines the opening within the pit lid allows for an increased angle of transmission from the antenna, thereby increasing the effective range of the antenna. 
     The antenna housing of the invention is secured to the pit lid by a compression fitting that surrounds the cylindrical main body portion and contacts the bottom surface of the pit lid. In this manner, the antenna housing is securely held within the opening formed in the pit lid. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings illustrate the best mode presently contemplated of carrying out the invention. 
     In the drawings: 
     FIG. 1 is a perspective view of a pit lid antenna of the invention as illustrated in use with a conventional pit lid and a sealed commodity meter; 
     FIG. 2 is an exploded perspective view illustrating the mounting of the pit lid antenna within the pit lid and the inductive coupling between the antenna and the commodity meter; 
     FIG. 3 is a bottom plan view illustrating the positioning of the pit lid antenna with respect to the pit lid; 
     FIG. 4 is a magnified perspective view illustrating the pit lid antenna housing and mounting arrangement; 
     FIG. 5 is a section view illustrating the mounting of the pit lid antenna within the pit lid and the transmission of the radio signals from the antenna; and 
     FIG. 6 is a section view illustrating the removal of the pit lid antenna from the pit lid. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIG. 1, thereshown is the antenna arrangement  20  of the present invention. The antenna arrangement  20  is used to transmit information from a commodity meter  22  to a remote location, such as a meter reading vehicle or stationary mounted receiving gateway. In the preferred embodiment of the invention, the commodity meter  22  measures the flow of a commodity, such as water or natural gas. The measured amount of commodity flow is transferred out of the sealed meter enclosure  24  to an antenna receptor  26 . As can be seen in FIG. 2, the antenna receptor  26  is sealed within a plastic enclosure  27  and receives a transmitted signal from the commodity meter through the plastic outer wall of the meter enclosure  24 . Specifically, the antenna receptor  26  is either inductively coupled or capacitively coupled to a transducer contained within the sealed meter enclosure. The specifics of the coupling between the antenna receptor  26  and the transducer  24  are described in commonly owned U.S. Pat. No. 5,659,300, incorporated herein by reference. 
     The antenna receptor  26  is connected by a cable  28  to an antenna  30 , as best shown in FIGS. 2 and 5. The antenna  30  is formed along the top surface of a circular circuit board and is configured to transmit a radio frequency signal that can be received by a radio frequency receiving station. The antenna  30  is mounted within an antenna housing  32 , which in turn is seated within an opening  34  formed in the pit lid  36 . As described in the &#39;300 patent, the pit lid  36  can be formed from metal, plastic, nylon or other material and is positioned above a meter pit in which the commodity meter  22  is located, as shown by the broken lines in FIG.  1 . In the preferred embodiment of the invention, the antenna housing  32  is formed from molded plastic or nylon material such that the antenna  30  can transmit the radio frequency signals through a top surface  38  of the housing  32 . 
     Referring now to FIGS. 5 and 6, the antenna housing  32  includes an outwardly tapered upper support portion  40  that is joined to a cylindrical main body portion  42 . The support portion  40  is tapered outwardly at an angle of preferably 120°, such that the diameter of the top surface  38  is greater than the diameter of the main body portion  42 . 
     As can be seen in FIG. 5, the antenna  30  is positioned within the upper support portion  40  near the transition between the main body portion  42  and the upper support portion  40 . Referring now to FIG. 2, the antenna  30  is formed on a generally circular circuit board and is supported within the antenna housing  38  by a circuit board  43 . The cable  28  is soldered to the circuit board  43 . The circuit board  43  includes an upper tab  44  that is received within a mating opening  45  formed in the antenna  30 , as shown in FIG.  5 . Specifically, the circuit board  43  is soldered to the antenna  30  to complete the electrical connection between the cable  28  and the antenna  30 . 
     Referring back to FIGS. 2 and 5, the lower end of the circuit board  43  is supported on a threaded nipple  46 . The threaded nipple  46  passes through a central opening formed within an outer can  47  that encloses the antenna housing  32 . The outer can  47  is preferably formed from a metallic material and provides a consistent ground for the antenna  30  of the invention. The outer, threaded portion of the nipple  46  receives a nut  48  that securely mounts the can to the housing  42 . 
     The can  47  includes a tapered upper edge  49  that is received within groove  50  formed along the support portion  40  of the antenna housing  32 , as shown in FIG.  5 . Thus, tightening of the nut  48  along the threaded portion of the nipple  47  causes the tapered upper edge  49  of the can  37  to be tightly received within the groove  50 . In addition to acting as a consistent ground for the antenna, the can  47  provides a waterproof enclosure for the circuit board  43  and antenna  30  contained within the antenna housing  32 . 
     Referring now to FIG. 6, the outwardly tapered upper support portion  40  of the antenna housing  32  contacts and engages a mating tapered surface  51  formed in the pit lid  36 . As can be seen in FIG. 6, the tapered surface  51  increases in diameter from the bottom surface  58  to the top surface  52  of the pit lid  36 . Preferably, the taper of the surface  51  is identical to the taper of the support portion  40  to create a smooth fit. 
     As can be understood in FIG. 6, the mating tapered surfaces  40  and  51  increase in diameter as they extend away from the antenna  30  such that the antenna  30  can radiate a signal outwardly, as illustrated by the phantom lines  53  in FIG.  5 . Since radio frequency signals are unable to pass through metal, the tapered surface  48  of the pit lid  36  allows the antenna  30  to transmit the signals over a much wider broadcast area, specifically when the antenna  30  is used in a metallic pit lid. The tapered surfaces also allow top surface  38  of the antenna housing  32  to be flush with the top surface  52  of the pit lid  36 . 
     As can be seen in FIG. 5, when the antenna housing  32  is mounted within the opening formed in the pit lid  36 , the antenna  30  is actually positioned below the top surface  52  of the pit lid. The tapered surface  51  that defines the opening in the pit lid  36  allows the angle of possible broadcast radio frequency waves from the antenna  30  to be increased, as compared to an opening having vertical walls. 
     Referring now to FIGS. 1 and 5, the mounting arrangement between the pit lid  36  and the antenna housing  32  allows the top surface  38  of the antenna housing  32  to be flush with the top surface  52  of the pit lid  36 . In addition to allowing the radio frequency signals to be transmit from the antenna  30 , the mating tapered surfaces of the upper support portion  40  and the opening formed in the pit lid  36  allow the top surface  38  of the antenna housing  32  to flush mount with the top surface  52  of the pit lid  36 . This feature is unlike the prior art pit lid antenna mounting systems in which the antenna enclosure extended above the top surface  52  of the pit lid. In the prior art systems, the antenna was mounted above the top surface  52  of the pit lid to increase the effective broadcast range for the antenna. In the present system, the tapered portion of the opening formed in the pit lid  36  allows the antenna to transmit signals over the required range. 
     Referring now to FIGS. 2 and 4, the antenna housing  32  is secured within the opening  34  formed in the pit lid  36  by the combination of a convoluted washer  54  and a compression fitting  56 . As can best be seen in FIG. 3, the convoluted washer  54  is positioned between the bottom surface  58  of the pit lid  36  and the compression fitting  56 . The compression fitting  56  is a spring element that compresses around the cylindrical outer surface of the can  47  positioned around the antenna housing  32 . Although the preferred embodiment of the invention is shown as including the compression fitting  56 , it is contemplated by the inventors that any type of device that engages the bottom surface  58  of the pit lid  36  to prevent the antenna housing  32  from moving through the opening  34  formed in the pit lid  36  would be an equivalent to the structure illustrated. 
     As can be understood in the Figures, the antenna arrangement  10  of the present invention is flush mounted with the top surface  52  of a metallic pit lid  36 . The mounting arrangement includes mating tapered surfaces on the antenna housing and the pit lid to allow the antenna to transmit a radio frequency signal over a required broadcast area. In accordance with the invention, the flush-mounted top surface of the antenna housing prevents both contact and damage to the antenna housing when the antenna housing is contained with in a pit lid  36  positioned in an area that receives both foot traffic and vehicle traffic. 
     Various alternatives and embodiments are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.