Abstract:
A pump primer for a pump on a fire truck uses a high-speed compressed air in a venturi in a compressed air chamber to generate a vacuum in a vacuum chamber to prime a pump, with an integral valve which separates the pump from the priming ejectors (venturis), the valve being opened by the compressed air when the primer is activated, the valve being closed by a spring return when the compressed air supply is removed, where water drawn in through the primer is freely drained by gravity to prevent freezing in cold weather.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This utility patent application claims priority of Provisional Patent Application No. 60/251,002 filed Dec. 4, 2000 by Michael Sulmone. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention relates to priming pumps, and more particularly, it relates to the priming of pumps on fire trucks which use centrifugal water pumps as the means to pressurize and propel the water that is used to extinguish fires. Centrifugal pumps of this type used in the fire trucks are not self-priming and rely on a primer to bring the water to the pump. Typically, this involves pumping from a positive pressure source, like a fire hydrant, or using a primer when drafting water from a pond which is located below the pump. 
     The most common type of priming device used is a separate positive displacement pump, which evacuates the fire pump and suction line until the air is displaced by water. The prior art in this industry uses a sliding vane type pump which is driven by an electric motor. Other devices used include water-ring primer pumps, piston pumps, gear pumps and exhaust gas-ejector pumps. Each of the priming means just mentioned has varying drawbacks in complexity, cost, reliability, speed, ease of use, freezing, electrical current draw, contamination, installation ease, safety, maximum attainable vacuum, or environmental concerns. The invention disclosed herein is an improvement over the current technology used in fire trucks because of its simplicity, high reliability and performance. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to overcome the disadvantages of the prior art and to provide a primer which uses high speed compressed air in a venturi to generate a vacuum to prime a centrifugal pump. It uses compressed air supplied by the air brake compressor of an air-brake fire truck. 
     This provides for a consistent, highly reliable source of high-pressure air. The high-pressure air flows through a series of venturi (also referred to as ejectors) and is controlled by a valve, which is controlled by either the pump operator or is controlled automatically as part of the entire pumping system. The system is designed with an integral valve that separates the pump from the priming ejectors, and is opened by the compressed air when the primer is activated. The valve closes by a spring return when the air supply is removed. Any water drawn into the primer freely drains by gravity to prevent freezing of the primer in cold weather. 
     The air valve used is an electric solenoid actuated valve that is tied to a series of switches and sensors that automatically activate the priming system when needed and disengage it when the pump is fully primed. This automatic system may be turned off at the operator&#39;s switch or over-ridden in the “manual” mode of that switch when needed for such operations as inspection and test purposes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic drawing showing the priming system at rest with no compressed air entering the primer and with no vacuum being drawn from the pump. 
     FIG. 2 is a schematic drawing that shows the primer during operation with compressed air being fed to a compressed air chamber in the primer and with the vacuum being drawn from the pump into the vacuum chamber of the primer. 
    
    
     Both figures display all the components of the primer system, as well as a cross-sectional view of the compressed air chamber showing the ejector venturis and showing the integral valve between the compressed air chamber and the vacuum inlet chamber. 
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a primer  40  in a relaxed position where the pump  43  has pressure, which opens the electrical circuit  46  and stops the flow of compressed air from compressed air source  45 . 
     The pump  43  of a fire truck is typically located inside a “pump box” that is mounted in the central part of the fire truck. 
     The primer  40  is connected to the pump  43  by a vacuum conduit  44 . The conduit  44  screws into an inlet adapter  26  of the primer  40 . For practical purposes, the conduit  44  may just be a short pipe nipple that also supports the weight of the primer, but the primer  40  may also be remotely mounted with a longer conduit. 
     Another part of the primer system that is mounted on the pump  43  is the pressure switch  5 . It is a normally closed pressure switch which opens the circuit when the pump pressure reaches a pre-set minimum value. 
     The pressure switch  5  is electrically connected to the pump shift switch  4  which is located on the transfer case that provides power from the vehicle drive shaft to the pump  43 . The transfer case is not part of the primer  40 , but does provide a place for the primer  40  to sense the position of the shifting mechanism in the transfer case. It is either in “pump” or “road” position. When the transfer case is in road position the pump  43  is disengaged and the drive train to the truck wheels is engaged to enable the truck to move. When the transfer case is in pump position, the road gearing is disengaged and the pump  43  is engaged. The shift switch  4  is closed in the pump position and open in the road position. 
     The shift switch  4  is electronically connected to the operator&#39;s switch  3  which is a three-position switch in which the center position is open. Toggling the switch to one side completes the circuit to enable the primer  40 . Toggling the switch the opposite way provides for a momentary contact, which completes the circuit regardless of the position of the shift switch  4  or the pressure switch  5 . The switch means described here may also be comprised of several separate switches that serve the same purpose. 
     The operator&#39;s switch  3  is electrically connected to the solenoid valve  1 . The solenoid valve  1  is mounted between the compressed air source  45  and the outboard body  9  which forms part of the compressed air chamber  9   a  of the primer  40 . The solenoid valve  1  is a normally closed valve that opens when voltage is applied to it. The solenoid valve  1  is coupled to the outboard body  9  either directly or through a pipe nipple which supports the weight of solenoid valve  1  or through any type of conduit with the solenoid valve  1  having alternative mounting means. 
     The primer  40  also works in a manual mode with a manually operated air valve in place of the solenoid valve  1 . In manual mode, none of the electrical wiring is necessary. It is a simplified, lower cost manual priming system with all of the features and components of the entire system minus the automatic mode. 
     Compressed air from compressed air source  45  enters the compressed air inlet port  2  which is adjacent to the priming valve stem  19  that travels linearly inside the outboard body  9  and compressed air chamber. A series of four components (first stage nozzle  11 , second stage nozzle  13 , third stage nozzle  14 , and third stage venturi  15 ) are located inside the outboard body  9  in a linear manner. They are approximately sized for the airflow output of the compressed air system of the vehicle. The nozzles and venturi  11 ,  13 ,  14 ,  15  are radially located by a close fit by their outside diameters and the concentric bores in the outboard body  9 . They are located axially by close fitting pins  17  and  16  into grooves in the outside diameters of the nozzles and venturi  11 ,  13 ,  14 ,  15 . The pins  17  and  16  are located in holes that are in the outboard body  9 . The pins  17  and  16  are also captured between the nozzles and venturi  11 ,  13 ,  14 ,  15  and the gasket  24 . An O-ring seal  10  separates the high-pressure compressed air from the high vacuum of the first stage  11 . There is also another O-ring seal  12  which separates the high vacuum of the first stage  11  and the second stage  13 . O-rings were not used on stages other than the first stage  11  due to the lower vacuum and higher flow requirements of the second stage  13  and third stage  14 . 
     A gasket  24  separates the inboard body  18  from the outboard body  9  and seals the porting between them. Cap-screws  25  hold the two bodies together. The gasket  24  also has flaps  7 ,  29  &amp;  30  cut into it which serve as check valves to prevent air flow from reversing from the lower vacuum second stage  13  and third stage  14  to the higher vacuum first stage  11 . The check valve flaps  7  and  30  in the second stage  13  and third stage  14 , along with the flap  29  in the first stage  11  also serve to capture the vacuum generated by the priming system during the transition when the priming valve  41  is moving back to it&#39;s relaxed position after the compressed air flow is stopped. The plug  28  seals the porting in the inboard body  18  from atmosphere. 
     The priming valve  41  extends from the outboard body  9  through the inboard body  18  and into the inlet adapter  26 . The priming valve  41  is comprised of the valve stem  19 , O-ring seal  19   a , spring  20 , valve seal  21 , seal washer  22 , and nut  23 . The function of priming valve  41  is to open when compressed air is in the compressed air inlet port  2  and to close in the absence of compressed air to seal the vacuum of the inlet port  6  and hence the pump  43 . It is also designed to seal against high pressure (&gt;500 psi) in the inlet port  6  as well as vacuum. When the valve  41  is closed as shown in FIG. 1, the spring  20  provides the force which biases the valve seal  21  against the face of the inboard body  18  and closes the vacuum path between the inlet chamber  6  and the interior of the inboard body  18 . The inlet adapter  26  is attached to the inboard body  18  by cap-screws  25  and sealed from the atmosphere by an O-ring  27 . If the primer were integrated as part of the pump  43 , the inlet adapter  26  would not be necessary and the inboard body  18  could attach to the suction port of the pump in a similar fashion. 
     When the primer is mounted in a substantially vertical position as depicted in the FIGS. 1 and 2, the inboard and outboard bodies  18  and  9  will gravity drain any residual water. This precludes any freezing problems. 
     The materials of construction are all corrosion resistant because of the nature of the service, and are of adequate strength to handle the pressures of the application. 
     OPERATION 
     Both FIG.  1  and FIG. 2 are used in this description. FIG. 2 depicts the system during operation and the arrows illustrate the flow paths of the compressed air and the vacuum. FIG. 2 shows the system, as it would be during a priming cycle prior to water entering the pump  43  and building pressure in its discharge. In this position, the normally closed electrical pressure switch  5  is closed. This allows current to flow through it when the pump pressure is below the pre-set minimum value. The pump can only build pressure up to the pre-set value when an adequate prime is established and water is in the centrifugal pump  43 . The electrical current is also permitted to flow through the shift switch  4  as the transfer case is in “pump” position. The operator&#39;s switch  3  is in the automatic mode, or on position. This completes the circuit from the voltage source to the solenoid valve  1 . With the solenoid valve  1  open, compressed air flows into the compressed air inlet  2  where it forces the priming valve  41  to the open position by compressing the spring  20 . The compressed air then travels through the center first stage nozzle  11 , then through successive lower vacuum nozzles and finally exits at the outlet port  8 . 
     The high velocity of the compressed air causes a pressure depression in the interior porting of the inboard body  18  and outboard body  9 , which creates a vacuum flow of air out of the pump  43  to evacuate it. As the compressed air forces open the priming valve  41 , it relieves the seal  21  from the sealing surface of the inboard body  18  and opens up a flow path for the vacuum to the pump  43 . The evacuated air travels from the pump  43  through a conduit  44  and into the inlet port  6 . The evacuating air then travels past the priming valve seal  21  and down the interior porting of the inboard body  18 . It then passes through the check valve flaps  7 ,  29  and  30  and into the flow path of the compressed air where it is expelled to the atmosphere along with the compressed air through the outlet port  8 . 
     Due to the higher vacuum capabilities of the first stage  11  and second stage  13 , the vacuum in the interior porting of the inboard body  18  exceeds the maximum attainable vacuum of the third stage  14 . At this point, the check valve flap  30  of the third stage  14  closes and the first two stages  11 ,  13  do all of the further priming. In a similar fashion, the first stage  11  overtakes the second stage  13  and the second stage flap  7  closes, leaving the first stage  11  to continue the evacuation process. Under many circumstances, the pump  43  achieves a prime before the third stage  14  closes. This allows for a very rapid prime under most conditions, which are relatively low lift situations. This is due to the fact that the third stage  14  is designed for high flow and low vacuum, while the first stage  11  is designed for high vacuum and low flow. The second stage  13  is designed for medium vacuum and medium flow. 
     When the pump  43  is primed, pressure builds in the discharge side of the pump, which opens up the circuit in the pressure switch  5 . This removes the voltage from the solenoid-actuated valve  1 , which in turn closes the solenoid valve  1  and stops the flow of compressed air. The remaining compressed air in the compressed air inlet port  2  then travels through the nozzles  11 ,  13 ,  14  and exits the exit port  8  until atmospheric pressure is equalized in the compressed air inlet port  2 . This takes a fraction of a second to happen. As it occurs, the spring  20  returns the integral, air actuated priming valve  41  back to sealed position as shown in FIG.  1 . Any water that entered the inboard body  18  or the outboard body  9  runs out of the system due to gravity. 
     The compressed air-powered pump priming system of the invention used is ejector venturi technology that has an integral, automatically opening and closing priming valve  41 . 
     In this priming system, the priming valve  41  is actuated by compressed air that is used to prime the pump. 
     In this compressed air-powered pump priming system, when switched to an automatic (on) mode, automatically senses if the pump has a prime and begins to evacuate the pump, if necessary, and cease evacuation when a prime is established. 
     This pump priming system utilizes the compressed air from an air compressor that is driven by an engine or motor on a fire truck. 
     This pump priming system utilizes an air compressor that is the one that is used for the air brake system of the fire truck. 
     This pump priming system only operates in automatic mode when the pump transfer case is in the “pump” position. 
     This pump priming system has a manual over-ride switch to allow for pump evacuation regardless of pump pressure or transfer case shift position. 
     This pump priming system automatically gravity-drains any water in the primer after the priming cycle has ended. 
     This pump priming system automatically drains any water by gravity after the priming cycle has ended. 
     This pump priming system may be used to prime the main water pump in fire trucks. 
     This pump priming system for priming the main water pump in fire trucks uses an air-jet ejector. 
     This pump priming system for priming the main water pump in fire trucks uses an air-jet ejector with a plurality of nozzles or stages. 
     In this pump priming system, nozzles may be held accurately in their positions with dowel pins located in grooves in the outside diameter of each nozzle. 
     The compressed air-powered pump priming system comprises a pump  43 , a compressed air source  45 , a primer  40  having a compressed air chamber  9   a  and a vacuum chamber  18   a , a hose connecting the compressed air source  45  to the compressed air chamber  9   a , a connection between the pump  43  and the vacuum chamber  18   a , a primer valve  41  connected between the vacuum port chamber  26   a  and the vacuum chamber  18   a , said primer valve  41  has a valve stem  19  connected between the compressed air chamber  9   a  and the vacuum chamber  18   a . The compressed air in the compressed air chamber  9   a  acts on the valve stem  19  to open the valve  41  between the vacuum port chamber  26   a  and the vacuum chamber  18   a  to draw a vacuum from the pump  43 . A series of valves  29 ,  7 ,  30  are positioned between the vacuum chamber  18   a  and the compressed air chamber  9   a , and said series of valves are opened when the valve stem  19  is opened to draw the vacuum and water from the pump  43  into the compressed air chamber  9   a , and outlet port  8  exhausts the air and any water from the compressed air chamber  9   a.    
     The priming system in a fire truck includes a compressed air source  45  and a pump  43 , and comprises a primer  40  having a compressed air chamber  9   a  and a vacuum chamber  18   a , a hose for connecting the compressed air source  45  to the compressed air chamber  9   a , a hose for connecting the pump  43  to the vacuum chamber  18   a , a primer valve  41  with a valve stem  19  connected between the compressed air chamber  9   a  and the vacuum chamber  18   a , a port between the vacuum port chamber  26   a  and the vacuum chamber  18   a , wherein when said compressed air pushes the valve stem  19  open then the compressed air is accelerated to a high velocity to draw a vacuum from the pump  43  and prime the pump  43 , said evacuation air flow opens a series of valves to the compressed air chamber  9   a.    
     Said compressed air chamber  9   a  has a series of venturis  11 ,  13 ,  14 ,  15  leading to an outlet port  8  for ejecting the compressed air and any water which may have been drawn into the compressed air chamber  9   a.    
     The primer  40  for a pump  43  which is mounted on a fire truck and is adapted to be connected to a source of water like a pond which is below the level of the pump and is not pressurized comprises a pressurized air chamber  9   a  adapted to be connected to a pressurized air source  45 , a vacuum port chamber  26   a  adapted to be connected to the pump  43 , and a valve  41  which connects the vacuum port chamber  26   a  to the vacuum chamber  18   a . Outlet port  8  discharges the combined pressure air and vacuum air from the primer  40 . 
     The method of priming a pump  43  on a fire truck comprises the steps of connecting the pump  43  by hose or direct couple to a vacuum chamber  18   a  of a primer  40 , connecting a source  45  of compressed air to a compressed air chamber  9   a  of the primer  40 , forcing compressed air into the primer compressed air chamber  9   a  and through several venturis  11 ,  13 ,  14 ,  15  in the compressed air chamber, drawing vacuum air from the pump  43  into a vacuum chamber  18   a  in the primer  40 , connecting the vacuum in the primer  40  to the compressed air exiting the primer  40  to draw water into the pump  43 , sensing when the pump  43  has been primed, shutting off the compressed air to the primer  43 , and draining off any water in the primer  40  so as to avoid the water from freezing into ice and blocking the discharge of water from the primer  40  for the next time it is used.