Abstract:
A power pack has an electrically controlled internal combustion engine which is provided with a turbo charger which is immersed in liquid coolant to reduce the risk of a spark therefrom igniting combustible gas in the ambient atmosphere.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT/CA2008/000597, filed on Mar. 31, 2008, which in turn claims the benefit of U.S. Patent Application Ser. No. 60/907,386, filed on Mar. 30, 2007, the disclosures of which Applications are incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Statement of the Technical Field 
     This invention relates to power packs which include an electrical system and which have to be flame proof so that they can be used safely in an environment where a spark from the power pack may cause an explosion if it is not flame proof. Such conditions may exist for example in a mine such as a coal mine where methane gas is sometimes present and can be ignited by a spark. 
     2. Description of the Related Art 
     Present day power packs used in coal mines frequently comprise an electrically controlled diesel engine and it is necessary to ensure that the electrical system is not capable of igniting methane with a spark. 
     It is therefore an object of the invention to provide a power pack of this kind which is flame proof so that methane in the environment will not be ignited by a spark therefrom. 
     SUMMARY 
     According to the invention, a power pack comprising an electrically controlled internal combustion engine is rendered flame proof by effecting one or more of the following features:
         (a) providing a liquid immersed turbo charger;   (b) providing a surface temperature controlled filter assembly in the exhaust system;   (c) providing improved cooling for the engine control module; and   (d) providing a cooling circuit to effect cooling of various components.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, of which: 
         FIG. 1  a flame proof power pack in accordance with one embodiment of the invention, 
         FIGS. 2(   a ),  2 ( b ) and  2 ( c ) are perspective views of the turbo charger, 
         FIGS. 3(   a ) and  3 ( b ) are perspective views of the exhaust filter, 
         FIGS. 4(   a ) and  4 ( b ) are perspective views of the engine control module, and 
         FIG. 5  is a perspective view of the cooling circuit. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Referring to the drawing,  FIG. 1  shows a perspective view of a flame proof power pack in accordance with one embodiment of the invention. The power pack includes a diesel engine  12 ,  14 ,  16  and  18 . 
     Referring now to  FIGS. 2(   a ),  2 ( b ) and  2 ( c ), the power pack has a turbo charger  22  located in a housing  24 , with sealed joints at all connections. The turbo charger  22  is immersed in engine cooling liquid which flows through the housing  24 , the housing  24  being secured to a liquid cooled exhaust manifold so as to receive coolant therefrom. The coolant then flows out of the housing  24  through an exhaust fan. 
       FIGS. 3(   a ) and  3 ( b ) show an exhaust filter assembly  30  with a housing  32  which is attached to the outlet of the turbo charger exhaust so as to receive the hottest possible gas.  FIG. 3(   b ) shows the filter media  34 . The filter assembly  30  is cooled by engine coolant which flows through an end flange into the housing  32 . The housing  32  has a double skin, with exhaust on the inside and a 6 to 12 mm film of coolant flowing around the outside to keep the surface temperature below 150° C. (302° F.). 
     As shown in  FIGS. 4(   a ) and  4 ( b ), the engine control module (ECM)  42  is located in a housing  44 , with fuel being routed through the rear of the housing  42 . Engine sensors are controlled by the ECM  42  via an electrical circuit namely comprising intrinsically safe (IS) barriers and a PLC with custom software to manipulate signals to correct distortion caused by the IS circuitry. Since starting the diesel engine  12  requires an electrical supply to trigger the fuel injection until the alternator begins to supply power, two small batteries are provided for this purpose. 
       FIG. 5  shows the cooling circuit  52  which effects single circuit water cooling of exhaust, surface temperature control of intake and exhaust systems and engine temperature control. The cooling circuit  52  has a single pump which forces engine coolant through the following components in the order listed:
         1) engine block/cylinder head;   2) exhaust manifold;   3) turbocharger cooling enclosure;   4) exhaust treatment device (filter or straight tube dependent on requirements);   5) exhaust gas heat exchanger;   6) thermostat housing/thermostat;   7) radiator.       

     The location of the regulator/thermostat adjacent the end of the system permits a fast engine warm up and also enables the circuit to cool the engine and hottest components with the coolest water available. The circuit uses no flow control devices (orifices) and is vented to permit filling at the engine manufacturer&#39;s prescribed rate. 
     The advantages of the invention and other embodiments thereof will now be readily available to a person skilled in the art from the foregoing description.