Abstract:
A cooling system for an internal combustion engine of a marine propulsion system is provided with a poppet that is overmolded with a resilient sealing material to enhance its sealing capacity. As a result, the pressure within the internal combustion engine cooling passages can be maintained more accurately. Because undesirable leakage past the poppet is more successfully prevented by the overmolded poppet, the cooling system can more accurately regulate the temperature of the engine.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is generally related to a pressure controlling device for an internal combustion engine and, more particularly, to a poppet that is overmolded to provide an improved sealing surface so that cooling water within an internal combustion engine of a marine propulsion system can be more accurately controlled. 
     2. Description of the Prior Art 
     It is well known to those skilled in the art that it is beneficial to regulate the pressure within the cooling system of an internal combustion engine in addition to regulating the temperature. 
     U.S. Pat. No. 5,937,802, which issued to Bethel et al on Aug. 17, 1999, discloses an engine cooling system which is provided with coolant paths through the cylinder block and cylinder head which are connected in serial fluid communication with each other. In parallel with the cooling path through the cylinder head, a first drain is connected in serial fluid communication with a pressure responsive valve and the path through the cylinder block. A temperature responsive valve is connected in serial fluid communication with the cylinder head path and in parallel fluid communication with the first drain. A pump is provided to induce fluid flow through the first and second coolant conduits and the first and second drains, depending on the pressure responsive valve and the temperature responsive valve. 
     U.S. Pat. No. 6,481,418, which issued to Ristich et al on Nov. 19, 2002, describes a fuel pressure regulator. A fuel pressure regulator for supplying fuel to the intake of an internal combustion engine at a substantially constant pressure is provided. The fuel pressure regulator includes a housing defining a fuel chamber in fluid communication with a fluid inlet. The housing further includes a fuel outlet opening in fluid communication with the fuel chamber. The housing defines a seating surface around the outlet opening. A valve body is moveably disposed within the housing and moves between open and closed positions. The valve body contact and seals against the seating surface and prevents fuel flow through the outlet opening when the valve body is in the closed position. The valve body is biased into the closed position. The valve body includes an extension with at least a portion thereof disposed in the fuel outlet opening to guide the valve body. 
     U.S. Pat. No. 3,918,418, which issued to Horn on Nov. 11, 1975, discloses a marine engine cooling system employing a thermostatic valve means and a pressure relief valve means. A pressure relief valve for an engine of an outboard motor includes a valve plate connected to a stem and spring loaded water cooling passageway in closed spaced relation to a thermostatically controlled valved passageway. The stem extends outwardly through a water discharge chamber directly in communication with the discharge passageway to the lower unit of the motor. A diaphragm is connected to the out end of the valve stem and is sealed to form a wall of the water discharge chamber. The discharge chamber is normally under a slight water discharge pressure whenever the thermostatic valve is open and thus creates a very slight pressure on the diaphragm which is balanced by the closure spring until such time as the pump pressure within the cooling system is sufficient to overcome the force of the spring. As the relief valve opens, the internal passageway pressure is transmitted to the discharge chamber. This results in the diaphragm rapidly moving outwardly and establishing the full open position of the relief valve. This, in turn, results in a reduction of the internal passageway pressure. 
     The technique of overmolding an object with either plastic or an elastomeric material is well known to those skilled in the art. Various techniques and processes have been developed to perform this overmolding procedure. In addition, many different objects have been manufactured through the use of an overmolding process. 
     U.S. Pat. No. 6,537,853, which issued to Johnson et al on Mar. 25, 2003, describes an overmolding encapsulation process. A method of encapsulating an article having first and second surfaces, including positioning the articles on a carrier such that at least a portion of the first surface contacts the carrier is described. A portion of the carrier carrying the article is then positioned within a mold and a seal is formed between the mold and the carrier. The mold is then filled with an encapsulating material to form a seal between the article and the carrier. 
     U.S. Pat. No. 5,588,202, which issued to Ehlers et al on Dec. 31, 1996, discloses a method for manufacturing an overmolded sensor. A method is described for manufacturing a plurality of proximity sensors which are attached to a printed circuit board during the manufacturing steps and subsequently severed from the printed circuit board by shearing. Each of the proximity sensors comprises a core and coil assembly, a plurality of electronic components and an electrical connector. These components of each of the proximity sensors is encapsulated during an overmolding process and the encapsulations are removed from the printed circuit board by a shearing step. Each of the encapsulations can be inserted into a cylindrical housing. 
     U.S. Pat. No. 6,523,380, which issued to McGuire et al on Feb. 25, 2003, describes an overmolded key including an ornamental element and method of making same. A vehicle ignition key having an ornamental element molded onto the key is described. The key includes a key blank and an undermold which is formed by molding a first plastic material over a portion of the key blank, defining a mounting surface for the element. The ornamental element is located on the mounting surface and secured to the heel portion of the key blank by an overmold which is formed by molding a second plastic material over the heel portion of the key blank, the undermold, and at least a portion of the element. In one embodiment, the overmold material covers substantially the entire peripheral edge of the element. 
     U.S. Pat. No. 6,116,884, which issued to Rowley et al on Sep. 12, 2000, describes a mold core for overmolded flexible valves. A mold core is provided for producing an overmolded flexible valve. The mold core comprises a mold body, a piston assembly, a piston retaining means, a collet bit positioning means and at least two collet bits. The mold core has a cylindrical void in a distal end and has a pressure means communicated with the cylindrical void. The piston assembly has a piston head sized and adapted for axial movement in the cylindrical void, with a piston shaft extending axially from the head. The shaft is tapered from a larger first diameter at one end to a smaller second diameter at the other end. The piston retaining means has a bore through it to allow insertion of the piston shaft. Each of the at least two collet bits has an inner cylindrical tapered surface segment, the taper of the surface segment being essentially the same as the taper of the piston shaft, and an out cylindrical surface segment, sized and adapted to be inserted inside the flexible valve. The at least two collet bits are positioned adjacent to the tapered portion of the shaft. The collet bits are positioned by the collet bit positioning means. 
     The patents described above are hereby expressly incorporated by reference in the description of the present invention. 
     If the poppet does not successfully prevent the flow of coolant from the cooling passage to the drain passage when the pressure within the cooling passage is less than a predetermined threshold magnitude, cooling liquid will flow out of the cooling passage and be replaced by colder cooling fluid. In a marine propulsion system, the replacement liquid is water from a body of water in which a marine vessel is operating. Typically, this water is much colder than the water within the cooling passage as the internal combustion engine operates. 
     In cases where the poppet does not properly seal to block the conduit, the engine operates at a temperature which is less than the optimal, or desired, temperature. Therefore, it is important to make sure that the poppet properly seals the conduit when the coolant in the cooling passage is at a pressure less than the preselected pressure for which the pressure regulating device was chosen. It would therefore be significantly beneficial to the operation of a marine engine if a poppet could be provided which assures proper sealing of the conduit when the coolant pressure is less than the predetermined pressure. 
     SUMMARY OF THE INVENTION 
     An engine cooling system, made in accordance with the preferred embodiment of the present invention, comprises a cooling passage formed within an internal combustion engine. It also comprises a drain passage and a conduit disposed in fluid communication between the cooling passage and the drain passage. A poppet, which is moveable relative to the conduit between a first position and a second position, is also provided. A liquid coolant is generally prevented from flowing through the conduit when the poppet is in the first position. The liquid coolant is generally permitted to flow through the conduit when the poppet is in the second position. A pressure regulating device is associated with the poppet to urge the poppet into the first position. A resilient sealing surface is overmolded on a sealing portion of the poppet. 
     The pressure regulating device can be a metal spring and the poppet can comprise the sealing portion and an insertion portion, wherein the insertion portion is disposed within the conduit to assist in aligning the poppet during its movement between the first and second positions. The sealing portion of the poppet can be a flange extending from a body of the poppet. 
     The resilient sealing surface can be formed on two surfaces of the flange of the poppet but, in a preferred embodiment, it is formed on three surface of the flange. The conduit is generally circular in cross-section and the sealing portion of the poppet is generally circular in cross-section. The sealing portion has a greater radius than the conduit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more fully and completely understood from a reading of the description of the preferred embodiment in conjunction with the drawings, in which: 
         FIG. 1  is an isometric exploded view of a portion of an internal combustion engine for a marine propulsion device; 
         FIG. 2  is an isometric view of a poppet made in accordance with the present invention; 
         FIG. 3  is a section view of a portion of the poppet shown in  FIG. 2 ; 
         FIG. 4  is a section view of a portion of an engine in combination with the present invention; and 
         FIG. 5  is an exploded view of the portion shown in FIG.  4 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Throughout the description of the preferred embodiment of the present invention, like components will be identified by like reference numerals. 
       FIG. 1  is an exploded isometric view of an internal combustion engine  10  with its poppet structure exploded away from their mounting location. A cover  12  is shaped to contain the poppet  16  of the present invention. A gasket  20  is used to provide a seal between the cover  12  and its associated mounting surface  24 . 
     With continued reference to  FIG. 1 , a diaphragm  30  is used in conjunction with a washer  32 , a screw  34 , and a spring  35 . The spring  35  maintains a force against the poppet  16  which urges it into its first position or sealing position. 
       FIG. 2  is an isometric view of the poppet  16  made in accordance with the preferred embodiment of the present invention. The poppet has a sealing portion  50  and an insertion portion  52 . The sealing portion  50  comprises a flange  56  that extends radially from the body of the poppet  16 . A resilient sealing material  58  is overmolded around the flange  56  that extends from the body of the poppet  16 . It is resilient and, in a preferred embodiment of the present invention, is made of Santoprene 101-73 which is available in commercial quantities. It should be understood that the sealing material  58  is overmolded and attached to three surfaces. This can be seen in the section view illustrated in FIG.  3 . 
     The undersurface  60 , shown in  FIG. 3 , is the actual sealing surface in a preferred embodiment of the present invention. However, in order to make the overmolded poppet  16  more robust, the resilient sealing material  58  is also formed on the edge  62  of the flange  56  and the top surface  64  of the flange. This places the resilient sealing material  58  on three surfaces of the flange  56 . 
       FIG. 4  is a section view showing the cover  12  and the poppet  16 . A spring  35  which serves as the pressure regulating device which urges the poppet  16  into its first position, as illustrated in  FIG. 4 , which blocks the flow of liquid coolant and prevents it from flowing upwardly through the conduit  70  which is disposed in fluid communication between a cooling passage  72  of the engine  10  and a drain passage  74  which directs the coolant to a discharge opening through which the coolant is returned to the body of water in which the marine vessel is operating. The resilient sealing material  58  is shown in its position where it is overmolded around the flange  56 . When the poppet  16  moves downwardly into its first position, as shown in  FIG. 4 , the force of the spring  35  causes the undersurface  60 , as described above in conjunction with  FIG. 3 , to seal against the sealing surface  80  formed at the downstream end of the conduit  70 . 
       FIG. 5  is an exploded view of the arrangement shown in FIG.  4 . The insertion portion  52  of the poppet  16  is shaped to be received in the conduit  70  to guide the movement of the poppet  16 , in a vertical direction in  FIG. 5 , between its first position and second position. The first position is illustrated in  FIG. 4 and , when in the second position, the poppet  16  is raised upwardly above surface  80  to allow liquid coolant to flow from the cooling passage  72 , through the conduit  70 , between the undersurface  60  of the flange  56  and surface  80  of the engine, and upwardly through the cover  12  to pass through the drain passage  74 . This flow occurs when the pressure within the cooling passage  72  exceeds a preselected pressure that is sufficient to raise the poppet  16  against the downward force provided by the spring  35  which operates as a pressure regulating device. 
     With continued reference to  FIGS. 1-5 , it can be seen that an engine cooling system made in accordance with the preferred embodiment of the present invention, comprises a cooling passage  72  formed within an internal combustion engine  10 . It also comprises a drain passage  74  and a conduit  70  that is disposed in fluid communication between the cooling passage  72  and the drain passage  74 . A poppet  16  is moveable relative to the conduit  70  between a first position, shown in  FIG. 4 , and a second position in which the undersurface  60  of the poppet  16  is raised above surface  80  of the engine to allow coolant to pass between surface  80  and the underside  60  of the flange  56 . A liquid coolant is generally prevented from flowing through the conduit  70  when the poppet  16  is in the first position, as shown in  FIG. 4 , and is generally permitted to flow through the conduit  70  when the poppet is in its second position. A pressure regulating device  35 , such as the spring shown in  FIGS. 1 ,  4 , and  5 , is associated with the poppet  16  to urge the poppet into the first position shown in  FIG. 4. A  resilient sealing material  58  is overmolded on a sealing portion  50  of the poppet  16 . The poppet comprises the sealing portion  50  and an insertion portion  52 , wherein the insertion portion  52  is shaped to be disposed within the conduit  70 . The sealing portion of the poppet is a flange  56  that extends radially from a body of the poppet  16 . A resilient sealing material  58  can be formed on two surfaces of the flange  56 , but in a preferred embodiment of the present invention, it is formed on three surfaces. 
     With continued reference to  FIGS. 1-5 , it can be seen that the conduit  70  is generally circular in cross-section and has a radius which is measured in a generally horizontal direction in FIG.  4 . The sealing portion  50  of the poppet  16  is also generally circular in cross-section. The sealing portion  50  has a greater radius than the conduit  70  to allow the underside  60  of the flange  56  to form a seal with surface  80  to prevent flow of coolant upwardly through the conduit  70  from the cooling passage  72  to the drain passage  74 . 
     By overmolding the flange  56 , an improved seal is provided between the sealing portion  50  and surface  80 . In known types of cooling systems, a plastic poppet  16  is expected to seal, with its relatively hard plastic underside  60  against the sealing surface  80 . Because of potential irregularities in manufacturing and as a result of the relative hardnesses of both the sealing surface  80  and the underside  60  of the poppet  16 , cooling water often leaks through the conduit  70  even when the pressure within the cooling passage  72  is less than the preselected pressure that is expected to be maintained by the force of the spring  35 . This allows warmed water to flow from the cooling passage  72  to the drain  74  after which it is discharged back into the body water from which it was drawn. Because of the removal of this warmed water from the cooling system of engine  10 , colder water is pumped into the engine to replace the water that leaked passed the poppet  16 . This creates significant difficulty in maintaining the temperature of the engine  10  at desired levels. By overmolding the flange  56  with the resilient sealing material  58 , this leakage past the flange  56  is prevented and the cooling system can more accurately regulate the temperature of the cooling water within the cooling passage  72 . This allows the engine to run more efficiently. 
     Although the present invention has been described in particular detail and illustrated to show a preferred embodiment, it should be understood that alternative embodiments are also within its scope.