Abstract:
A fluid delivery system, for e.g. a vehicle, includes a tank for holding fluid product, such as propane, a pump for pumping the fluid product from the tank, the pump being driven by hydraulic fluid, and a heat exchanger for using the fluid product to cool the hydraulic fluid. The heat exchanger also causes the fluid product to increase in temperature. The heated fluid product is returned to the tank, in the form of a vapor, for example. Embodiments of the invention provide a number of advantages, including increased pump flow rates, reduced cavitation, increased pump life, and elimination of a heat-exchanger fan.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The subject matter of this application is related to the subject matter of U.S. provisional patent application No. 60/174,138, filed Dec. 31, 1999, priority to which is claimed under 35 U.S.C. 119(e) and which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the invention relate to improvements in pumping fluids from tanks or other supplying vessels. Specific aspects of the invention, for example, relate to pumping propane from a vehicle, such as a bobtail or tank truck, with improvements in e.g. thermal characteristics and pump operation. Other examples will be described as well. 
     2. Description of Related Art 
     Liquefied compressed gases such as propane are generally transported via truck primarily in two different ways. The first way is via a transport. A transport is a trailer that holds approximately 7,000-10,000 gallons of liquid propane. The transport is used to fill outlying storage tanks and large industrial tanks. The second way is via a straight truck, which the propane industry typically calls a bobtail. The bobtail typically holds less than 3,500 gallons of liquid propane and is used to fill residential and small business propane tanks. 
     When a transport unloads, the operator generally will connect two hoses between the transport and the storage tank. The first hose connected is called the vapor hose and the second is called the discharge hose. The purpose for the vapor hose is to allow the vapor pressures between the transport and the storage tank to equalize and to allow vapor pressure to be pushed back into the transport vapor space while they are pumping. This equalizes the pressures and allows the liquid product pump to pump at a higher rate and lower pressures, which minimizes noise and internal damage to the propane pump. 
     When a bobtail unloads, the operator typically uses only a discharge hose. Most bobtails do not have a second vapor hose. Not having the vapor hose causes two things to happen. First, as the propane pump on the bobtail pumps liquid propane from the bobtail into the storage tank, the pressure in the storage tank continues to rise and causes back pressure on the discharge line. This back pressure causes the discharge line pressure to continue to rise, causing the pump to work harder and thus reducing the flow rate and increasing the wear of the propane pump. Second, as the propane pump pulls product out of the bobtail tank it creates a vacuum inside the bobtail tank. This vacuum creates bubbles in the propane which are then pulled through the propane pump. As these bubbles are pulled through the propane pump they compress and then expand rapidly, potentially causing damage to the internal vanes and rotor of the propane pump. These bubbles reduce the flow rate of the pump and create a higher level of pump noise. 
     Liquid products that do not change state as readily, such as fuel oil and refined fuel, are transported via truck primarily in two different ways. The first way is via a transport, described earlier. The second way is via a straight truck. The straight truck carries 500-5,000 gallons of product. The straight truck typically delivers to residential customers and to small industrial customers. 
     With liquid products that do not change state, both the transport and the straight truck unload in approximately the same way. The operator connects a single discharge hose between the transport or straight truck to the storage tank. Once this has been accomplished, the operator then starts the pump and pumps the liquid product into the storage tank. Since this type of liquid is not pressurized to maintain it as a liquid, the transport, straight truck and storage tanks can all be vented to atmosphere. This eliminates the need for a vapor hose. 
     Thus, the propane bobtail delivery market and the fuel-oil and refined-fuels tank-truck delivery market, for example, are similar in that typically they both use a tandem-axle-style truck with a multi-thousand gallon tank mounted on the chassis. These vehicles are used to deliver typically small quantities of e.g. propane, fuel oil, diesel fuel and gasoline to e.g. homes, farms and small businesses. 
     Currently, there is a movement in these industries to change from driveline-driven product pumps to hydraulic drives. This change is coming from a number of areas, e.g. safety, maintenance and a need to either mount the product pump in a location that cannot be easily driven by a driveshaft or a need for two or more product pumps on a truck. The tank-truck market is shifting towards having larger and multicompartment tanks on their trucks. This shift allows more efficient use of their trucks and their employees. 
     It would be desirable to take advantage of the movement to change from driveline-driven product pumps to hydraulic drives, to further capitalize on the attendant advantages. Additionally, a need exists to diminish the problems of back pressure and vacuum-induced bubbles in e.g. propane, which bubbles are then pulled through the propane pump. It would also be desirable to diminish the disadvantages caused by using a fan for cooling, e.g. noise, vibration/resonance, and maintenance/upkeep concerns. 
     SUMMARY OF THE INVENTION 
     To achieve the above and other goals, one embodiment of the invention uses the product that the customer is pumping, e.g. propane, to cool the hydraulic oil used to run the pump. A liquid-to-liquid heat exchanger receives the hydraulic oil line and a line containing the pumped product. Approximately two gpm of product can be pumped through the heat exchanger, according to one embodiment. The two liquids are separated by thin channels of e.g. stainless steel or another material. The heat exchanger cools the hydraulic oil and warms the customer&#39;s liquid product. Embodiments of the invention have particular advantages in e.g. the propane industry. Propane is heated, vaporized and then pumped back into the top of the supplying tank. This vaporized propane increases pump flow rates, reduces cavitation and increases pump life. These advantages are obtained, according to embodiments of the invention, with no fan motor, better product pump performance, longer product pump life, and smaller and lighter pump weights. 
     The theory behind embodiments of the invention is twofold for e.g. propane types of application. First, by using the liquid propane as the cooling agent inside the liquid-to-liquid heat exchanger, the hydraulic oil is kept at a safe operating temperature without the use of a cooling fan. Second, as the hydraulic oil passes through the heat exchanger it heats the liquid propane. 
     The heated liquid propane is boiled or vaporized and then pumped back into the vapor space, or liquid space, in the bobtail tank. By reintroducing this vapor back into the bobtail tank, the problems that were stated above are minimized. Embodiments of the invention decrease the length of time during which product can be unloaded, stabilize the vapor pressure in the bobtail tank, reduce pump wear and noise, and cool the hydraulic system without the need for any type of cooling fan. 
     Embodiments of the invention for liquid products that do not as readily change state regulate a small amount of the liquid product being pumped through the heat exchanger. As the liquid passes through the heat exchanger, it cools the hydraulic oil. The heated liquid product is the reintroduced back into e.g. either the transport or straight truck tank or back into the discharge line of the pump. 
     Embodiments of the invention provide significant advantages, in that they can cool the hydraulic oil without the need for a cooling fan and can aid in the pumping of liquids that become more difficult to pump in colder climates. 
     Embodiments of the invention can be described as a combination of a hydraulic oil cooler and a supplying vessel pressure stabilizer. Embodiments of the invention can be used in applications that require hydraulic oil to be cooled while it is operating a product pump that is pumping some type of liquid product. The hydraulic oil is cooled via a “liquid-to-liquid” heat exchanger, for example. This heat exchanger can have up to at least three channels allowing up to at least three different liquids to pass through it at any one time. 
     On one side of the heat exchanger is the hydraulic oil and on the other side(s) are one or more liquid products that are being pumped by the product pump(s). The liquid products absorb the heat of the hydraulic oil. In effect, embodiments of the invention are cooling the hydraulic oil and heating the amount of liquid product that is being pumped through the heat exchanger. This device will work when the temperature of the liquid product being pumped is less than the maximum desired hydraulic oil temperature. Different types of liquids at different flow rates affect the cooling capacity of the heat exchanger and the amount of heat being transferred into the liquid product being pumped. Hydraulic oil flow rates at varying pressures affect the amount of heat (BTU&#39;s) that are produced. 
     At least two different types of liquid products can be used with this device. The first is a “non-state-changing” liquid, as referenced above. This type of liquid does not change its state when the amount of heat (BTU&#39;s) that a hydraulic system creates is dissipated and absorbed by the liquid. For example, embodiments of the invention simply add a fixed amount of BTU&#39;s to diesel fuel. These added BTU&#39;s increase the temperature of the diesel fuel to a predetermined and controlled safe temperature. The second type of liquid, the “state-changing” liquid, begins to boil or vaporize as its temperature is changed. These types of liquids are typically referred to as liquefied compressed gases. For example, propane will boil or vaporize as heat is introduced to it. 
     According to embodiments of the invention, the liquid product being pumped through the heat exchanger is reintroduced back into the supplying vessel once it has circulated through the heat exchanger. Depending upon the product, it will enter back into the supplying vessel as a warmed-up liquid or as a boiling liquid or vapor. This vapor can be extremely beneficial to certain types of supplying vessels to aid in the pumping process. This benefit will be described in detail, further into this description. 
     Embodiments of the invention contain a “liquid-to-liquid” heat exchanger, a hydraulic reservoir, and a hydraulic oil filter. These parts are manufactured and assembled into a package that is compact, light-weight and easy to install for the customer. Embodiments of the invention also diminish many of the problems referenced above, e.g. back pressure, vacuum-induced bubbles, cavitation, noise, vibration/resonance, maintenance/upkeep concerns, and the like. 
     Additional features and advantages according to embodiments of the invention will become apparent from the remainder of this patent application. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention will be described with respect to the figures, in which like reference numerals denote like elements, and in which: 
     FIG. 1 is a schematic view of a cooler/stabilizer according to an embodiment of the invention; 
     FIG. 2 is a schematic view of a cooler/stabilizer having a temperature-sensing, heat-generating control block according to an embodiment of the invention; 
     FIG. 3 is a detailed view of the temperature-sensing, heat-generating control block of FIG. 2; 
     FIG. 4 is a schematic view of a cooler/stabilizer having a pressure-sensing, heat-generating control block according to an embodiment of the invention; 
     FIG. 5 is a detailed view of the pressure-sensing, heat-generating control block of FIG. 4; 
     FIG. 6 is a schematic view of a cooler/stabilizer having a pressure-sensing, shut-off valve control block according to an embodiment of the invention; 
     FIG. 7 is a detailed view of the pressure-sensing, shut-off valve control block of FIG. 6; and 
     FIG. 8 is a schematic view showing a cooler/stabilizer according to an embodiment of the invention. 
     FIG. 9 is a schematic view showing a vehicle and receiving vessels, according to an embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Turning first to FIG. 1, fluid handling system  10  according to an embodiment of the invention includes supplying vessel or tank  15  for holding first fluid  20 , e.g. propane, fuel oil, diesel fuel, gasoline, or other liquid. Both liquefied compressed gases and liquid products that do not change state as readily are contemplated for use as first fluid  20 . Supplying vessel  15  also defines vapor space  25  disposed above first fluid  20 . 
     Discharge flow path  30  is in fluid communication with supplying vessel  15 . Discharge flow path  30  is disposed to receive first fluid  20  from supplying vessel  15  for discharge from supplying vessel  15  and, according to embodiments of the invention, from fluid handling system  10  to e.g. receiving tanks/vessels or the like external to system  10  at homes, farms, small business, etc. According to embodiments of the invention, discharge flow path  30  is defined, at least in part, by suction inlet port or pump inlet port  35 , product pump  40  and pump outlet discharge line  45 . Product pump  40  is a pumping mechanism that is constructed and disposed to move first fluid  20  along discharge flow path  30 . 
     Return flow path  50  is in fluid communication with discharge flow path  30  and, ultimately, with supplying vessel  15 . Return flow path  50  is disposed to receive first fluid  20  from discharge flow path  30  for return to supplying vessel  15 . According to the illustrated embodiment, return flow path  50  is defined, at least in part, by product/coolant line  55 , which intersects pump discharge line  45  at intersection point  60 , heat exchanger  65 , and liquid/vapor return line  70 . Product/coolant line  55  is connected to heat exchanger  65  via flow control  63 . 
     Fluid handling system  10  also comprises heat-exchange flow path  75 , which is disposed to contain second fluid  78 , which is e.g. hydraulic fluid or oil for actuating pump  40 . Second fluid  78  is free of fluid communication with first fluid  20 , according to embodiments of the invention. 
     According to the illustrated embodiment, heat-exchange flow path  75  is defined, at least in part, by hydraulic return line  80 , which is connected via hydraulic filter  85  to hydraulic tank assembly  90 . Hydraulic tank assembly  90  includes hydraulic breather  95  and site/level oil gauge  100 , according to the illustrated embodiment. Hydraulic suction line  105  connects hydraulic tank assembly  90  to hydraulic pump  110 , which is connected to power take-off (PTO)  115 . Hydraulic pressure lines  120  and hydraulic flow and PSI block  125  connect hydraulic pump  110  to deliver second fluid  78  for actuating product pump  40  via hydraulic motor  130 , which is mounted by hydraulic motor mounting assembly  135 . Thus, pump  40  is in fluid communication with heat-exchange flow path  75 . 
     Case drain line  138  connects hydraulic tank assembly  90  to hydraulic motor  130 . 
     In operation, pump  40  is activated to move first fluid  20  along discharge flow path  30  for discharge from supplying vessel  15  and/or fluid handling system  10 . First fluid  20  in discharge flow path  30  is in the form of a liquid at intersection point  60  according to embodiments of the invention, as is first fluid  20  in return flow path  50  at point  60 . 
     The temperature of first fluid  20  in return flow path  50  is cooler upon entering heat exchanger  65  than second fluid  78  in heat-exchange flow path  75 . In heat exchanger  65 , thermal transfer occurs between first fluid  20  and second fluid  78 . According to one embodiment, second fluid  78 , e.g. hydraulic oil, is cooled by first fluid  20 , e.g. propane, and first fluid  20  is heated by second fluid  78 . Thus, heat exchanger  65  is constructed and disposed to cause a temperature change in both first fluid  20  and second fluid  78 , and the temperature of first fluid  20  is generally less than the maximum desired temperature of second fluid  78 . 
     In summary, fluid handling system  10 , which can be disposed on a vehicle, such as a truck, comprises tank  15  for holding fluid product  20 , pump  40  for pumping fluid product  20  from tank  15 , pump  40  being driven by hydraulic fluid  78 , and heat exchanger  65  for using fluid product  20  to cool hydraulic fluid  78 . Fluid product  20  can be propane. Further, heat exchanger  65  heats propane or other first fluid  20  and causes it to vaporize. The vaporized propane in liquid/vapor return line  70  than is pumped and returned either to vapor space  25  or the liquid space of tank  15 . In other words, heat exchanger  65  heats fluid product  20  and returns it to tank  15 . 
     Three control blocks can be offered as options to the FIG. 1 embodiment, as will now be described with respect to FIGS. 2-7. 
     The first of the three control blocks is temperature-sensing, heat-generating block  140 , shown generally in FIG.  2  and in detail in FIG.  3 . Block  140  is disposed in heat-exchange flow path  75 , just before heat exchanger  65 , in the illustrated embodiment. Block  140  includes valve body  145 , temperature sensing cartridge  150 , heat-generating cartridge  155 , hydraulic oil inlet and outlet ports  160 ,  165 , hydraulic oil pressure port  168 , and hydraulic oil pressure gauge  170 . Block  140  senses the temperature of the hydraulic oil or other second fluid  78  by temperature sensing cartridge valve  150 . It then will internally either route the e.g. hydraulic oil over hydraulic heat generating cartridge valve  155  and then into heat exchanger  65 , or it will route the hydraulic oil directly to heat exchanger  65 , bypassing hydraulic heat-generating cartridge valve  155 . The temperature at which block  140  switches the routing from one to the other can be changed to meet the requirements for a particular environment or application. 
     Thus, temperature sensor  150  is in communication with heat-exchange flow path  75  for sensing the temperature of second fluid  78 . Heat generator  155  is also in communication with heat-exchange flow path  75 , and is constructed and disposed for heating second fluid  78  in response to an indication from temperature sensor  150 . 
     Block  140  presents significant advantages. A cold outside air temperature or other ambient environment produces a colder tank and therefore less vapor pressure within the tank. In other words, the fluid product within the tank is more condensed. This cooler temperature causes pump  40  to draw a vacuum within tank  15  more quickly, potentially starting cavitation in pump  40  at an earlier time. Heating second fluid  78  causes increased thermal transfer to first fluid  20 , increasing the reduced vapor pressure in tank  15  and tending to diminish the cavitation problem. Additionally, heated fluid  78  provides e.g. start-up advantages in fluid handling system  10 . 
     The second unique, optional control block for fluid handling system  10  is pressure-sensing, heat-generating control block  175 , shown in FIG. 4 in heat-exchange flow path  75  and shown in more detail in FIG.  5 . Block  175  senses vapor pressure in supplying vessel  15  via sensing line  180  routed between vessel  15  and control block  175 . Via product sensing port  185  and end cap  187 , which includes a filter, the vapor pressure in supplying vessel  15  pushes on piston  190 . Piston  190 , in turn, moves against bias spring  195  disposed within piston chamber  200 . This movement determines a pass-through orifice size, by moving orifice spool  205 , anchored in spool block  210 . Hydraulic oil or other second fluid  78  enters block  175  at inlet port  215 , passes through the orifice whose size is determined in the manner described above, and then out through outlet port  220  enroute to heat exchanger  65 . The size of the orifice determines the amount of hydraulic heat transferred in heat exchanger  65 . The lower the product vapor pressure, the smaller the orifice size, which in turn equals a higher hydraulic oil temperature. The maximum pressure limitations of supplying vessel  15  will determine the maximum amount of hydraulic heat that can be generated through control block  175 . Thus, control block  175  includes a pressure sensor constructed and disposed to indicate vapor pressure in supplying vessel  15 , and a temperature regulator in communication with heat-exchange flow path  75 , the heat generator being constructed and disposed for heating second fluid  78  in response to an indication from the pressure sensor. According to one embodiment, the pressure sensor and temperature regulator are disposed as an integral unit  175  in fluid communication with both return flow path  50  (via sensing line  180 ) and heat-exchange flow path  75 . 
     The third unique, optional control block is pressure-sensing, shut-off control block  260 , illustrated in FIG. 6 in return flow path  50  and illustrated in more detail in FIG.  7 . Block  260  is designed to mechanically shut off the flow of cooling liquid (e.g. first fluid)  20  if and when the pressure in supplying vessel  15  reaches a predetermined pressure. This shut-off protects supplying vessel  15  from over-pressurization. 
     Block  260  senses vapor pressure in supplying vessel  15  via sensing line  265 , which is in fluid communication with return flow path  50  and thus is in fluid communication with supplying vessel  15 . The vapor pressure in supplying vessel  15  pushes against piston  290 , via product sensing port  285  and end cap  287  (which includes a filter). Piston  290  in turn moves against bias spring  295  disposed within piston chamber  300 . This movement determines whether or not spool  305  moves within spool block  310  to a position that does or does not allow first fluid  20  (product/coolant) to flow from inlet port  315  to outlet port  320  and on to heat exchanger  65 . Thus, according to this embodiment, fluid handling system  10  includes a pressure sensor constructed and disposed to indicate vapor pressure in supplying vessel  15 , and a flow regulator in fluid communication with return flow path  50 , the flow regulator being constructed and arranged to decrease flow of first fluid  20  in return flow path  50  in response to a high-pressure indication from the pressure sensor. The pressure sensor and flow regulator are disposed as an integral unit  260  in fluid communication with return flow path  50 . 
     Returning to FIG. 6, according to this embodiment heat exchanger  65  is in fluid communication with engine  330  via engine coolant return lines  335 ,  340 . Engine coolant bypass valve  345 , preferably a ball valve, allows bypass of heat exchanger  65  via engine coolant bypass line  348  if desired. Power take-off  350  draws power off engine  330  for activating pump  40  via driveline  355 . Thus, fluid handling system  10  according to this embodiment uses engine coolant as an equivalent to the previously described second fluid  78 . Alternatively, hydraulic oil or other fluids can also be used in this embodiment in the manner described previously. 
     FIG. 8 shows additional aspects of fluid handling system  10 , including system casing  360 , fittings  365  for connection with pump  110 , and fittings  370  for connection with hydraulic motor  135  and pump  40 . Pump  110 , according to this embodiment, can have a pump speed of 1,500 rpm, producing 16 gpm at 1,500 PSI. PTO  115  can accommodate 1,300 engine rpm, according to one embodiment. Hydraulic motor  135  optionally can be attached to pump  40  by hydraulic adapter  375 , and pump  40 , according to one embodiment, is a 10 HP pump at 640 rpm. Of course, other sizes, speeds and related parameters are contemplated according to embodiments of the invention. 
     FIG. 9 is a schematic illustration of vehicle  380  with engine  382 . System  10  is supported on vehicle  380  and discharges first fluid, e.g. propane, to receiving vessels  384  external to system  10 . 
     While embodiments of the invention have been described with reference to particular preferred embodiments, the invention is not limited to the specific examples given. Use with a wide variety of tractors, trailers, and other vehicles and devices and with a wide variety of liquids is contemplated. Various materials can be used according to the invention, e.g. stainless-steel componentry, or any material having strength and durability sufficient to withstand severe operational conditions. Various modifications and changes will occur to those of ordinary skill upon reading this disclosure, and other embodiments and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention.