Abstract:
A hydraulic pressure accumulator has an interior chamber containing a fire-suppressing gas such as nitrogen. The fire-suppressing gas in the accumulator is fluidly connected to a thermal device, such as a valve with a thermal fuse or a controlled valve triggered by a thermal sensor. The thermal device is designed to open a fluid connection between the accumulator&#39;s interior chamber to ambient when the exterior temperature exceeds a determined safety threshold, thereby releasing the fire suppressing gas from the accumulator.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to fire suppression systems, particularly for motor vehicles. 
       DESCRIPTION OF THE RELATED ART 
       [0002]    U.S. Pat. Nos. 5,495,912 and 6,719,080, both to Gray, disclose hydraulic hybrid motor vehicles using hydraulic pressure accumulators as energy storage devices for the vehicles. U.S. Pat. Nos. 7,121,304 (Gray) and 7,108,016 (Moskalik and Gray), both incorporated by reference herein, disclose high and low pressure hydraulic accumulators suited for use in applications that include hydraulic hybrid motor vehicles. 
         [0003]    Motor vehicle accidents, and other circumstances such as mechanical or electrical failures, can lead to fires occurring in a motor vehicle. Fires in motor vehicles of all kinds, including hydraulic hybrid motor vehicles, may create severe safety risks. Currently, around 12% of fire deaths in the United States involve motor vehicle fires. 
         [0004]    Automatic sprinkler systems triggered by thermal fuses are known in the art of fire suppression systems. 
       SUMMARY OF THE INVENTION 
       [0005]    An object of the present invention is to provide a fast and effective fire suppression means for motor vehicle fires, and particularly for hydraulic hybrid vehicles. 
         [0006]    Another object of the present invention is to provide a fire suppression means for other industrial, civilian, or military applications where hydraulic pressure accumulators are needed or used for energy storage or other purposes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  presents a schematic view of a hydraulic hybrid motor vehicle with a fire suppression system according to one embodiment of the invention. 
           [0008]      FIG. 2  presents a low pressure hydraulic accumulator. 
           [0009]      FIG. 3  presents a fire suppression system with thermal fuses fluidly connected to a low pressure hydraulic accumulator, according to one embodiment of the invention. 
           [0010]      FIG. 4  presents a high pressure hydraulic accumulator with thermal fuse, according to another embodiment of the invention. 
           [0011]      FIG. 5  presents a fire suppression system for a hydraulic hybrid motor vehicle, according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]      FIG. 1  presents a series hybrid powertrain for a motor vehicle, using a hydraulic energy storage system. An embodiment of this powertrain is more fully described in commonly-assigned U.S. Pat. No. 6,719,080 to Gray, which description is incorporated herein by reference. For purposes of this application, the arrangement of the hydraulic hybrid powertrain is not critical, and could instead use, for example, a parallel hydraulic hybrid powertrain such as is more fully set forth in U.S. Pat. No. 5,495,912, also to Gray. 
         [0013]    Referring to  FIG. 1 , internal combustion engine  1  operates to drive a rotary engine pump/motor  2  as a hydraulic pump. Engine pump/motor  2  may be integrated onto the crankshaft (not shown) of engine  1 , or connected thereto and driven by a driveshaft  3 . In pump mode, pump/motor  2  receives low pressure hydraulic fluid from low pressure line  4  and pressurizes the fluid to a higher pressure. The higher pressure fluid then exits the pump through high pressure line  5 . This high pressure fluid in line  5  may then be sent (a) to hydraulic drive assembly  6  to drive one or more hydraulic motors  7  to provide motive power to the vehicle drive wheels  8 , or (b) to high pressure accumulator  9  for energy storage and later reuse, or (c) to both purposes. 
         [0014]    Low pressure accumulator  20  serves as a fluid reservoir for the hydraulic energy storage system in  FIG. 1 . A bladder-type low pressure hydraulic accumulator  20  of known art is presented in greater detail in  FIG. 2 . A flexible bladder  21  contains a compressed inert gas, such as nitrogen. Other inert gases such as carbon dioxide could also be used. The inert gas is charged into bladder  21  through bladder fixture  22 . Hydraulic fluid is contained in space  23 , between housing  25  and bladder  21 , and enters and exits accumulator  20  through fixture  24  to low pressure line  4 . 
         [0015]    Referring now to  FIG. 3 , gas port  22  of low pressure accumulator  20  is fluidly connected to gas line  26 . Low pressure gas line  26  contains one or more ports  27  which are capped or plugged by a thermal device  28 . Thermal device  28  comprises a thermal fuse. While thermal device  28  is shown in the  FIG. 3  as a meltable plug that fills orifice  27 , it could also be in the form of a meltable cap that covers orifice  27 , such as by screwing onto external threads around port  27 . Thermal fuse  28  may optionally be retained in place by a protector/retainer  29 . Thermal fuse  28  is preferably made of one of multiple possible metal alloys that abruptly melt at a particular temperature. Alternatively, thermal fuse  28  could be made of another material that melts or burns at a particular desired temperature. As another alternative for a thermal device, a non-melting cap or plug may be placed in proximity to a material that combusts and which is connected to a fuse to trigger combustion at a certain temperature, thus resulting in destruction of the cap/plug when the fuse is triggered. Any of these arrangements and their equivalents will be collectively termed a thermal device for purposes of this application. For a preferred embodiment in which the thermal fuse  28  melts, melting of the thermal fuse  28  at a determined temperature (e.g. a maximum safe level for the area, such as 300 or 400 degrees Fahrenheit) creates an orifice at port  27  that allows the inert gas within gas line  26  and bladder  21  to escape. 
         [0016]    Thermal devices using metal alloys as discussed herein are commercially available, such as the T-Fuse™ pressure relief device available from Specialty &amp; Ball Valve Engineering, Inc. 
         [0017]    As shown in  FIG. 1 , orientation of the ports  27  may be such that when the thermal fuse  28  melts and allows the nitrogen gas to escape, the gas is directed to the most likely places where the fire-suppressing gas would be needed. In a motor vehicle, this would likely be the engine compartment, fuel tank and high pressure accumulator chamber. A sample arrangement is shown in  FIG. 1 . In other applications, the nitrogen or other fire-suppressing gas would preferably be directed to similar likely locations for fire, such as where hot machinery is found in close connection to leaks or other sources of flammable liquids or gases (such as gasoline, engine oil, transmission oil, or hydraulic oil). Preferably the fire-suppressing gases are not directed to enclosed occupied areas such as the passenger compartment of a car where it could potentially harm individuals by reducing oxygen concentrations below necessary breathing levels in such areas. 
         [0018]    The fire suppression methods and devices herein apply to piston-in-sleeve, diaphragm, metal bellows, or other types of hydro-pneumatic hydraulic pressure accumulators in addition to bladder accumulators. 
         [0019]    The fire suppression system could also be employed with a high pressure hydraulic accumulator. For example, with reference to  FIG. 4 , a thermal fuse could be located near, or incorporated into, a gas charge port/valve for a high pressure (or, alternatively, low pressure) hydraulic accumulator  50 . One sample mechanism for the thermal fuse in this additional embodiment would be to position melting metal alloy restraints  53  to retain the gas port valve  57  in a closed position, with the restraints  53  serving to prevent spring  54  from pushing valve stem  52  and unseating/opening the valve  57 . The restraints  53  further serve as a thermal fuse, with the restraints made from a selected metal alloy to melt at a desired activation temperature. When the thermal fuse restraints  53  melt, spring  54  pushes valve stem  52  to the right, thereby unseating valve  57  from surface  58 , and thereby allowing discharge of gas from the accumulator through the annulus  51  between the valve stem  52  and gas port stem  59 . One or more ports  62  may be positioned in shoulder  63  to allow discharge of the gas past the shoulder  63 ; alternatively, shoulder  63  does not need to extend all the way around the circumference of valve stem  52 . The flow of gas allowed to escape the accumulator may be allowed to fill the accumulator compartment, or alternately be directed to previously selected and ported locations by means of discharge fitting/hose  60 . 
         [0020]    Retainer  56  is threaded into metal boss  55  and prevents spring  54  movement to the left in the drawing. A high pressure accumulator with a fire suppression system of this type could be used in conjunction with a low pressure accumulator with a fire suppression system (such as in  FIGS. 1-3 ). For example, the high pressure accumulator and fire suppression system of  FIG. 4  could be configured with a thermal fuse that melts at a higher temperature than the thermal fuse for the low pressure accumulator so as to only be triggered in the event that the low pressure accumulator fire suppression system is insufficient to stop a fire, or to only be triggered if fire threatens the high pressure accumulator compartment itself. 
         [0021]    In another embodiment, referring now to  FIG. 5 , the thermal device includes a temperature sensor  64  which may be located, for example, in the engine compartment. Upon sensing a predefined maximum temperature depending on the particular location of the sensor (e.g. 300 to 400 degrees Fahrenheit-near fuel devices) and receiving a signal (through electrical line  65 , or wirelessly) generated by the temperature sensor, a small incendiary or other heating device  66  is configured to quickly heat and melt the fuse/plug in the accumulator. Appropriate incendiary or heating devices  66  could include a small combustion device such as are commercially used for airbag ignition and inflation; alternatively, a resistive heating wire could be used to melt the thermal fuse or plug. As another alternative, heating device  66  may be an electrically controlled valve that is triggered open based on temperature sensor  64  exceeding a predetermined threshold, e.g., 400 degrees Fahrenheit. 
         [0022]    A controlled gas vent valve, orifice, or a pressure regulator may also be used to help control the release of the gas, if desired. 
         [0023]    While particularly useful for hydraulic hybrid motor vehicle applications, it will also be understood that the device of the present invention may be used for other purposes as well, including, for example, industrial, military, and aviation applications that may use hydraulic pressure accumulators in the vicinity of heat-generating machines and flammable liquids such as oil. 
         [0024]    From the foregoing it will also be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.