Abstract:
A mobile fill station for filling propane cylinders by weight and volume. There can be up to three cabinets in the system wherein any one of the cabinets can have a beam scale with a hydraulic automatic stop device to stop filling automatically as the total weight of the cylinder reaches a pre-set scale limit. Any one of the cabinets can also include a flow meter to stop filling when an operator monitors an amount on the meter and manually stops propane flow. The cabinets could also include an electronic scale with a digital indicator where filling stops automatically as the total weight of the cylinder reaches a pre-set computer limit.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
   This application claims priority from U.S. Provisional Application No. 60/317,066 filed Sep. 2, 2001, and Ser. No. 60/317,360 filed Sep. 4, 2001. 

   FIELD OF THE INVENTION 
   This invention relates to propane dispensing systems and more particularly to a mobile fill station designed for propane cylinders and LP gas cylinders. 
   BACKGROUND OF THE INVENTION 
   Propane is a liquified petroleum gas and aromatic hydrocarbon that may be utilized as a gaseous fuel. Unlike methane vapor that is lighter than air, propane vapor is heavier than air. Liquid propane will vaporize at any temperature above −44° F. Propane, and all other hydrocarbon-based fuels, must be kept away from open flames and ignition sources. Propane must be handled with care and safety, particularly when filling propane tanks. Propane is sold as a liquid by the pound or as a vapor by the cubic foot. As ambient temperature rises, propane vapor pressure rises. When ambient temperature drops, propane vapor pressure drops. 
   Propane is typically sold and stored in portable containers for home use. When a container is filled to its proper liquid level, it will be approximately 80% full. The remaining 20% of the container&#39;s volume contains propane vapor. Propane vapor is typically consumed by household appliances. The vapor space in the container also provides room for the expansion of liquid propane. Liquid propane has a moderate coefficient of expansion and, accordingly, expands greatly when subjected to temperature increases. If a container is filled beyond its maximum permitted liquid filling density, a situation may develop in which there will not be enough space available to accommodate the liquid propane&#39;s expansion. When an overfilled container is exposed to any temperature increase, hazardous conditions may occur. Consequently, a need exists for a propane tank filling system which is able to fill a propane tank to its appropriate level economically and safely. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a mobile fill station designed to be an economical filling station for propane cylinders and LP gas cylinders. The present invention economically and safely fills propane and LP gas containers through weight by scales and by volume through flow meters. In one embodiment there can be up three cabinets in the system for filling the gas containers. One of the cabinets can include a beam scale with hydraulic automatic stop devices wherein the container filling stops automatically by the hydraulic device as the total weight of the cylinder reaches a pre-set scale limit. For a cabinet including a flow meter, the filling of the container is stopped when the operator sees the amount on the meter and manually stops the flow. A cabinet could also include an electronic scale with a digital indicator wherein the filling stops automatically as the total weight of the cylinder reaches a pre-set computer limit. The mobile filling station of the present invention is compatible with all propane/LPG storage facilities, gas stations, and dispensing/filling centers. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic illustration of a first embodiment mobile filling station of the present invention; 
       FIGS. 2A and 2B  are a schematic illustration of a first alternative embodiment of the present invention; 
       FIG. 3  is a schematic illustration of a second alternative embodiment mobile filling station of the present invention; and 
       FIGS. 4A and 4B  are a schematic illustration of a third alternative embodiment mobile filling station of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A first embodiment mobile fill station  10  of the present invention is shown in  FIG. 1 . The mobile fill station  10  is connected to a propane storage tank  12  in order to fill a propane or LPG cylinder  14 . The mobile fill station  10  is connected to the storage tank  12  by a liquid in line  16 , a liquid out bypass return line  18  and a vapor out line  20 . The liquid in line  16  can be a 1.5″ diameter pipe connected to the storage tank with a 3″ or 2″ internal valve  22 . The assembly for connecting the liquid in line to the storage tank also includes a pneumatic actuator, ball valve, flexible steel connector, Y-strainer flexible hose connector, and a reducing bushing for connecting the line by a forged steel coupling, all generally referred to as reference numeral  24 . The liquid out bypass return line  18  is connected to the storage tank  12  by a 1″ diameter pipe connection having a 2″ internal valve  26  also having a connection assembly including a pneumatic actuator, ball valve, flexible steel connector and reducing bushing generally referred to as reference numeral  28 . The vapor outline  20  is typically a 1″ diameter pipe connected to the storage tank  12  with a 2″ internal valve  30  and is attached to the storage tank  12  by a connection assembly  32  comprising a pneumatic actuator, ball valve, flexible steel coupling and reducing bushing. 
   Propane is drawn through the liquid in line by a pump  34  and into a flow meter  36  and ultimately into the propane cylinder  14  through dispenser  38 . Pump  34  can be a Smith Pump having a maximum pumping capacity of 35 gallons per minute to 43 gallons per minute (132 liters per minute to 165 liters per minute) Pump  34  is driven by a motor  36  which can be a Baldor Explosion-Proof 3HP motor. The flow meter  36  can be a Liqua-Tech LPG Flow Meter having a maximum 18 gallon per minute flow rate (68 liters per minute). The pump  34  and the flow meter  36  are connected by pipe  40  which preferably is Bell Pipe Extra Heavy Schedule  80  Pipe (material A 150FS). Pipe fittings for the Bell Pipe are heavy forged steel, 2,000 lbs. and/or 3,000 lbs. of the same material. A bypass valve  42  is positioned in pipe  40  for the return of propane gas to the storage tank by liquid out bypass return line  18 . The bypass valve can be a Fisher, Apollo, Rego or Smith valve of the ball, by-pass, back-check or hydro-relief variety. The propane gas flows through the flow meter to the dispenser through pipe  44  similar to pipe  40 . Flow meter  36  also has a vapor eliminator  46  for the return of propane vapor to the storage tank via vapor out line  20 . 
   The dispenser  38  can be a hydraulic automatic stop filling system or a quick acting adapter. The mobile fill station has an electrical connection  48  typically a Killark Explosive Proof Electrical Control Switch Box. The entire mobile fill station  10  is contained within a cabinet  50 . 
     FIGS. 2A and 2B  illustrate a first alternative embodiment mobile fill station  60  in accordance with the present invention. Mobile fill station  60  is a multiple cabinet station having a first cabinet including mobile fill station  10  of  FIG. 1  as shown in  FIG. 2A  and a second cabinet  62  shown in  FIG. 2B . Cabinets  50  and  62  are connected by liquid in line  64  and liquid return line  66 . Liquid in line  64  is connected to line  40  below bypass valve  42 . Liquid return line  66  connects to liquid out bypass return line  18  to return liquid to the storage tank  12 . Liquid in and liquid return lines  64  and  66  are pipes similar to pipes  40  and  44  and are attached to pipes  44  and liquid return line  18  by conventional connections. 
   In cabinet  62  propane cylinders  14  are filled by dispensers  68 . Dispensers  68  include hydraulic automatic stops  70  and also includes a propane control valve, master cylinder, quick setting shutoff and a soft nosed cylinder coupling. The propane enters the dispenser from liquid in line  64  through a set of valves  72  including an excess flow valve  74 , a ball valve  76  and a hydrostatic relief valve  78 . The valve means  72  are connected by pipes  80  extending between in line  64  and hydraulic automatic stop  70 . Liquid in line  64  can extend out of cabinet  62  and into a third cabinet  82  if mobile fill station  60  requires a third cabinet or the line can be capped off  84 . Propane cylinders  14  located in cabinet  62  are positioned on beam scales  86  which work in conjunction with the hydraulic automatic stop to automatically stop filling the cylinders as the total weight of the cylinder reaches a pre-set scale limit. The scale can be a Fairbanks scale with a 360 lb. maximum (163 kg). 
     FIG. 3  illustrates a second alternative embodiment for the second cabinet  90  of the mobile fill station  60  shown in  FIGS. 2A and 2B . In this embodiment, cabinet  90  includes a digital weight indicator  92  comprising an electronic scale  94  and a computer control  96 . The computer control  96  is a part of the dispensing assembly  98  which includes a digital ultra low power indicator intrinsically safe instrument, battery pack and safe area data interface box and analog I/O board, trickle charge and barrier set and intrinsically safe interface cable, and internal pilot operated solenoid valves connected to two LPG hose and quick acting adapter filler. The digital scale  94  has a digital readout  100 . In this embodiment, the filling of the propane cylinders  14  stops automatically as the total weight of the cylinder reaches the pre-set computer limit. The scale is a Fairbanks Electronics Scale equipped with a load cell of 200 lbs. (90 kg). 
     FIGS. 4A and 4B  illustrate a third alternative embodiment mobile filling station  100  in accordance with the present invention.  FIG. 4A  illustrates a first cabinet  102  (although shown in a simplified form) is identical to cabinet  50  of  FIG. 2A  with the exception of having an additional vapor return line  104  attached to vapor return line  20  and extending to a second cabinet  106  shown in  FIG. 4B . In this embodiment the propane cylinders  14  are filled in cabinet  106  by propane entering from in line  64  through flow meter  108  and through valve means  110  and into dispenser  112 . The valve means  110  includes excess flow valve  114 , back valve  116 , hydrostatic relief valve  118  and ball valve  120 . The valve means is connected by pipe  122 . Vapor return line  104  vents the propane vapor from the flow meter  108  back to the storage tank  12 . The filling stops in this version when the operator sees the amount of propane on the flow meter and then stops the flow. In cabinet  106  the valve means is utilized to prevent excess speed of the gas flow and to control the gas if it exceeds the predetermined flow rate to shut off the gas flow when pressure drops below a preset limit. In line  64  extends through cabinet  106  to a third cabinet  108  if desired or can be capped off. 
   Although the present invention has been described and illustrated with respect to four embodiments thereof, it is to be understood that many variations can be achieved without departing from the scope of the invention. For example, any number of cabinets containing any one of the various methods for filling the cylinder can be incorporated. The cabinets can contain the flow meter, scales, or digital scales in any combination depending upon the intended end use of the system.