Abstract:
A combination coolant filter and pressure regulator for an automotive engine&#39;s cooling system is configured to be spliced in line with the coolant supply line to the heater core. The filter has a housing and a filter element that is moveable within the housing between a first position opening up communication through the housing and a second position restricting communication through the housing. A spring biases the filter element toward its first position. Normal coolant flow through the housing passes through the filter for removal of entrained contaminants. Under conditions of high coolant flow and thus high pressures, the filter element moves against the bias of the spring toward its second position restricting coolant flow and protecting the heater core from damage due to coolant overpressure.

Description:
TECHNICAL FIELD 
     The present invention relates generally to automobile engines and more particularly to the filtering of coolant circulating through automobile engines to remove casting sand, rust particles, and other sludge entrained within the coolant flow. The invention further relates to regulating coolant pressure to the heater coils of an automobile during rapid acceleration to prevent heater coil blowout. 
     BACKGROUND OF THE INVENTION 
     Water cooled cast iron or cast aluminum engines are used throughout the automotive industry to power modern cars and trucks. During fabrication, the engine blocks of such engines are formed by pouring molten metal into a mold formed in casting sand. When the molten metal cools and solidifies to form the metal block, the casting sand is removed from around and through the block, which is further machined to form the finished part. The process of removing the casting sand, particularly from inside the engine coolant passageways of a cast engine block, is not trivial. Typically, the blocks are tumbled to dislodge the casting sand and their coolant passageways are thoroughly flushed with a cleaning solution. 
     While the cleaning and flushing process cleans most of the casting sand from the coolant passageways of an engine block, there nevertheless remains a small amount of sand that is not removed because it is trapped in crevices or partially imbedded in the walls of the passageways. This sand becomes a problem during normal operation of a vehicle in which the engine block is installed because the grains of casting sand are slowly dislodged by the circulating engine coolant and entrained in the flow of coolant through the water pump and coolant passageways of the engine. The abrasive effect of this sand tends to erode rotors and seals within the water pump and can collect at certain locations within the coolant passageways creating partial blockages and “hot spots” that can eventually destroy an engine. In addition to casting sand, other contaminates such as rust flakes and calcified minerals can become entrained in the coolant flow over time. 
     Another common problem related to vehicle coolant systems is the rupturing or blowout of a vehicle&#39;s heater core as a result of unusually high coolant pressures. Such pressures typically occur during extreme acceleration or other high engine revolution when the water pump is operating at high speeds. While the problem is more common in high performance high revolution engines, it nevertheless can also occur in common passenger vehicles. A heater core blowout is particularly expensive to repair because the heating system of the vehicle must be disassembled, which usually entails disassembly of the dash and other major components of the vehicle. In addition, a go heater core blowout can quickly drain a vehicle of its coolant, resulting in overheating and ruination of the vehicle&#39;s engine. 
     Some attempts to filter or remove casting sand and other sludge entrained within a vehicle&#39;s coolant flow have been made. For example, U.S. Pat. No. 3,773,107 of Bener discloses a sump trap located at the inlet of a vehicle&#39;s radiator to collect entrained sludge. U.S. Pat. No. 5,662,791 of Hurst et al. discloses an in-line filter connected in the return hose of the cooling system to filter entrained sludge particles from the flow. Other general purpose filters and valves are illustrated in U.S. Pat. No. 4,166,792 of Offer et al., U.S. Pat. No. 4,183,812 of Rosaen et al., U.S. Pat. No. 4,697,617 of Bourke et al., U.S. Pat. No. 4,743,365 of Noland, and U.S. Pat. No. 5,181,534 of Hashida et al. While the devices disclosed in these patents can be effective in removing or filtering entrained sludge particles from engine coolant, none of them addresses the problems caused by heater core overpressure. Furthermore, applicant is aware of no device that simultaneously removes entrained sediments from the coolant and provides pressure regulation for a heater coil under conditions of extreme coolant pressure to prevent heater core blowout. 
     Accordingly, there exists a need for an effective and efficient method and apparatus for removing entrained casting sand and sludge from the coolant flow within a vehicle engine while at the same time automatically regulating coolant pressure to the coils of a vehicle&#39;s heater core. It is to the provision of such a method and apparatus that the present invention is primarily directed. 
     SUMMARY OF THE INVENTION 
     Briefly described, the present invention, in one preferred embodiment thereof, comprises a combination sludge filter and pressure regulator valve or filter valve for an automotive coolant system. The filter valve comprises a cylindrical outer sleeve that carries an elongated cylindrical filter element. The filter element is capped at its upstream end by an upstream filter cap provided with a central opening communicating with the interior of the filter element and is closed at its downstream end by a downstream filter cap. The cylindrical hollow body of the filter element between the filter caps is formed by a porous filter medium. With this configuration, coolant entering the opening in the upstream filter cap moves into the interior of the filter element and passes through the filter medium to the outside of the filter element. 
     The cylindrical outer sleeve of the filter valve is capped at its ends by an upstream and a downstream end cap respectively, which capture the filter element within the outer sleeve. The upstream and downstream end caps are provided with coupling nipples for coupling the filter valve in line with the coolant hose supplying coolant to the heater coils from the water pump. An annular seal is provided around the periphery of the upstream filter cap of the filter element and the seal is sized for sliding movement against the interior surface of the valve body. The downstream filter cap is not sealed but, instead, coolant is free to flow around the downstream filter cap and through the coupling nipple on the downstream end cap of the filter valve. In this way, coolant entering the filter valve through the upstream end cap is confined by the annular seal to enter the interior of the filter element through the opening in the upstream filter cap. Since the downstream filter cap is closed, the coolant is then forced through the filter medium to the outside of the filter element, from where it flows around the downstream filter cap and through the coupling nipple of the downstream end cap of the filter valve. Thus, the invention provides an in line filter for removing casting sand and other sludge entrained in the coolant flow to the heater coils. 
     The filter element is shorter than the cylindrical outer sleeve of the filter valve. A coiled compression spring is disposed between the downstream filter cap of the filter element and the downstream end cap of the filter valve. The compression spring yieldably biases the filter element toward the upstream end of the filter valve with a force determined by the spring constant. Under normal coolant flow pressures, the compression spring is not compressed or is compressed only slightly by the force of coolant on the filter element and coolant flows freely through the filter valve and is filtered as it passes through the filter element. Thus, most of the time, the filter valve functions as an efficient in line coolant filter. 
     However, when the coolant pressure rises under conditions of extreme acceleration or other high rev condition to levels that could damage the heater core, the increased force on the filter element moves the filter element in a downstream direction against the bias of the compression spring thereby compressing the spring. This, in turn, causes coolant flow through the filter valve to be substantially restricted or shut off for the duration of the high pressure condition. The heater coil is thus protected from damage resulting from coolant pressure surges. When coolant pressure returns to normal, the compression spring urges the filter element back toward the upstream end of the filter valve, thereby restoring normal coolant flow to the heater coils. 
     Thus it is seen that a simple, efficient, and effective filter valve is now provided that addresses and solves the shortcomings of the prior art and that simultaneously performs the dual functions of filtering entrained contaminants from the coolant of an automotive engine and providing automatic regulation of coolant pressure to the heating coils of a vehicle&#39;s heating system. These and other features, objects, and advantages of this invention will become more apparent upon review of the detailed description set forth below taken in conjunction with the accompanying drawing figures, which are briefly described as follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective exploded view of the filter valve of this invention illustrating the various components thereof. 
     FIG. 2 is a side elevational longitudinally sectioned view of the filter valve of FIG. 1 shown in its assembled and operating configuration. 
     FIG. 3 is a longitudinal sectioned view of the downstream end portion of the filter valve illustrating compression of the spring and consequent restriction of fluid flow under conditions of high coolant pressures. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, in which like numerals refer to like parts throughout the several views, FIG. 1 is an exploded perspective illustration of a preferred embodiment of the filter valve of the present invention. The filter valve  11  comprises a cylindrical outer sleeve  12 , preferably fabricated of plastic and shown in phantom lines in FIG. 1 for clarity. The cylindrical outer sleeve  12  has an open upstream end  13  and an open downstream end  14 . An upstream end cap  16  is configured to fit into the upstream end  13  of the outer sleeve and is formed with a cylindrical insert  17  capped by a disc-shaped cover  18  forming a radially projecting peripheral rim  19 . The insert  17  has an outer diameter substantially the same as or slightly larger than the inner diameter of the cylindrical sleeve  12  so that the end cap  16  can be pressed into the upstream end  13  of the sleeve  12  until its peripheral rim  19  abuts the end of the sleeve. In this way, the end cap  16  forms and is held in place by a friction fit with the inner wall of the sleeve  12 . Ancillary securing means such as pins or adhesive can be applied if desired to enhance the friction fit and assure that the end cap  16  does not become dislodged by coolant pressure during operation. The upstream end cap  16  is provided with an appropriately sized coupling nipple  21  that communicates with the interior of the sleeve through the cover for splicing the filter valve into the coolant supply hose to the heater coils of a vehicle. 
     Similarly, a downstream end cap  22  is provided for closing the downstream end of the filter valve  11 . In the preferred embodiment, the downstream end cap  22  is identical to the upstream end cap  16  and is formed with a cylindrical insert  23 , a disc-shaped cover  24  forming a peripheral rim  26 , and a coupling nipple  27  for splicing the filter valve in a coolant supply line. While one of the end caps  16  and  22  can be permanently secured to a respective end of the sleeve  12 , at least one should be selectively removable and replaceable to provide access to the interior of the filter valve for replacing the filter element when necessary. 
     A generally cylindrical filter element  31  is disposed within the outer sleeve  12 , as best illustrated in FIG.  2 . The filter element  31  has a hollow main body  35  formed of an appropriate porous filter medium such as, for example, fine screen or filter paper. The main body  35  is capped at its upstream end by an upstream filter cap  32  having a central opening  33  formed therethrough. The filter cap  32  is formed with an annular rim  34 , which, in turn, is provided with a circumferentially extending annular groove  36 . 
     An annular rubberized seal  37  is sized to fit in the groove  36  (FIG. 2) and has an outer diameter that is the same as or slightly smaller than the inner diameter of the cylindrical insert  17  on the upstream end of the filter valve. The seal  37  preferably is formed of a rubberized material and is sized to form a substantial seal with the inner surface of the end cap  16  but nevertheless to be longitudinally slidable along the inner surface to allow for longitudinal movement of the filter element  31  within the filter valve, as described in more detail below. 
     The downstream end of the filter element is capped by a closed filter cap  38  having an outer diameter less than the inner diameter of the downstream end cap  24  to allow for fluid flow around the periphery of the filter cap and out through the coupling nipple  27  of the downstream end cap  22 . 
     A compression spring  39  is disposed in the filter valve between the downstream filter cap  38  and the downstream end cap  22 . The compression spring  39  biases the filter element  31  toward the upstream end of the filter valve with a force that is determined by the spring constant of the compression spring. While a compression spring is illustrated in the drawings as the preferred biasing means it will be understood by those of skill in the art that other appropriate biasing means such as, for example, a leaf spring could be substituted for the illustrated compression spring with comparable results. 
     FIG. 2 shows the filter valve of this invention as it appears during operation and under conditions normal or nominal coolant flow to the heater coils. While the coolant supply hose is not shown in the figures for the sake of clarity, it will be understood that the filter valve is spiced in line with the coolant supply hose with the coupling nipple  21  on the upstream end of the filter valve receiving coolant from the vehicle&#39;s water pump and the coupling valve  27  on the downstream end of the filter valve delivering filtered coolant to the heater coil of the vehicle. Coolant inflow is indicated by arrows  41  in FIG. 2 while coolant outflow is indicated by arrows  42 . Coolant flow through the filter element itself is illustrated by arrows  43 . 
     Coolant flow  41  is supplied from the vehicle&#39;s water pump through the coupling nipple  21 . As the flow enters the upstream end of the filter valve, it cannot pass around the outside of the filter cap  32  because this path is sealed by the annular seal  37 . Thus, the coolant is constrained to enter the interior of the filter element  31  through the opening  33  formed in the upstream filter cap  32 . From inside the filter element  31 , the coolant flows through the filter medium  35  and into the space between the filter element and the inner wall of the cylindrical sleeve  12  as indicated by arrows  43 . The coolant is forced through the filter medium because the downstream end of the filter element is closed off by the downstream filter cap  38 . As the coolant passes through the filter medium, entrained contaminants such as, for example, casting sand residue, rust chips, sludge, and the like are filtered out and remain trapped within the filter element. 
     From the space between the filter element and the cylindrical sleeve, the coolant flows around the downstream filter cap  38  and out the coupling nipple, as illustrated by arrows  42 , to be delivered through the attached heater hose to the heater coil of the vehicle&#39;s heating system. Thus, under normal coolant flow conditions, the filter valve of this inventions functions as an efficient in line coolant filter. 
     The pressure of the coolant within the filter element causes a proportional net force to be exerted on the filter element in the downstream direction. This force, in turn, bears against the compression spring  39 , which opposes the force. The spring constant of the compression spring is selected such that the force generated by coolant pressures under normal operation of the engine compresses the spring  39  only slightly, as illustrated in FIG.  2 . Under these conditions, the invention functions as a filter as described above. However, as illustrated in FIG. 3, when coolant pressure increases to dangerous levels under, for example, extreme acceleration or high rev conditions, the compression spring  39  is completely or substantially completely compressed by the resulting force. The compressed spring  39  and the proximity of the filter cap  38  to the end cap  22  forms a barrier that functions to restrict the flow of coolant around the downstream filter cap as indicated by arrows  44 . Coolant flow is therefore shut off or significantly restricted for so long as the coolant pressure remains critically high. When coolant pressure returns to a normal operating level, the compression spring again urges the filter element toward the upstream end of the filter valve so that coolant flow and filtering can resume. 
     Thus, the filter valve of this invention simultaneously functions as a coolant filter and as a check valve or regulator valve to prevent heater core damage as a result of extreme coolant pressures. Further, as the filter element becomes clogged over time, force resulting from fluid flow through the filter medium increases and gradually restricts the flow of coolant to the heater coils. This manifests itself in noticeably reduced heating capacity within the passenger compartment. Accordingly, reduced heating capacity serves as an automatic signal to the vehicle owner or a mechanic that the filter element within the filter valve needs replacing. 
     The invention has been described herein in terms of preferred embodiments and methodologies. However, various changes to the illustrated and described embodiments might well be implemented by those of skill in the art within the scope of the invention. For example, the filter valve has been illustrated as being cylindrical in shape. It might just as well be another shape such as, for example, square or hexagonal, although cylindrical is believed to be most efficient. Biasing means other than a compression spring might also be used and the end caps need not fit into the outer sleeve but could just as well fit on the outside of the sleeve or be threaded to the sleeve. Finally, plastic has been described as the preferred material from which to fabricate the filter valve and represents the best mode known to the inventor of carrying out the invention. However, other materials such as aluminum might be substituted according to the needs of a particular application. plastic construction therefore should not be considered a limitation of the invention. These and other additions, deletions, and modifications might well be made by those of skill in the art without departing from the spirit and scope of the invention as set forth in the claims.