Abstract:
A bypass valve for thermally regulating a fluid flow in two directions by opening and closing a bypass fluid flow between the two directions. An example of application of such a bypass valve is for regulating the flow of engine coolant fluid between a vehicle engine and a heat-exchange system for cooling down the engine coolant. The bypass valve includes a housing inside which a first port, a second port, a bypass port and a barrier assembly are arranged. The barrier assembly is movable with respect to the bypass port, so that it can open or close the port depending on fluid temperature. In addition, the barrier assembly is arranged external to the first and second ports, so that it does not interfere with fluid passing through them. The bypass valve therefore provides substantially constant fluid pressure in the first and second ports, avoiding pressure drops associated with conventional bypass valves.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/908,523, filed Nov. 25, 2013, which is incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a bypass valve of the kind that includes a first port and a second port for passage of fluid, and a bypass port communicating the first and second ports, wherein the bypass port is opened or closed by a barrier assembly that does not interfere with the first and second ports, thus minimizing pressure drops in fluid passing through the first and second ports and permitting a higher flow rate through the ports at a given pressure. 
     BACKGROUND OF THE INVENTION 
     The following background information may present examples of specific aspects of the prior art (e.g., without limitation, approaches, facts, or common wisdom) that, while expected to be helpful to further educate the reader as to additional aspects of the prior art, is not to be construed as limiting the present invention, or any embodiments thereof, to anything stated or implied therein or inferred thereupon. 
     A valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Many kinds of valves are known in the art, depending on the kind of flow control to be performed, the kind of fluid they are to control, and/or other diverse technical factors. 
     Bypass valves, in particular, are valves that allow fluid to normally pass through one or more ports, and that open to direct fluid in an alternate direction after a set temperature, pressure, or voltage limit is reached. When the predetermined unit is exceeded, bypass valves allow the fluid to flow through a bypass port in the alternate direction. In this manner, bypass valves allow regulating parameters of a fluid. 
     An example of use of bypass valves is found in internal combustion engine cooling systems, whose purpose is to cool down a coolant fluid after the fluid has been in turn used to cool down the internal combustion engine and has thus become heated. Generally, the coolant fluid is cooled in a heat exchange system in which the engine coolant flows through a radiator; the engine coolant exchanges heat with cooler air adjacent to the radiator, and thus becomes cooled. However, in the event that the coolant fluid is not hot enough, a bypass valve bypasses the coolant fluid flow coming from the engine so that it flows back to the engine instead of to the heat exchange system; when coolant fluid is heated over a predefined threshold temperature, the bypass valve switches so that the coolant fluid is directed towards the heat exchange system. Fluid flow switching inside the bypass valve is carried out by a movable barrier assembly that is capable of opening and closing a bypass port communicating the different ports through which fluid flows to and from the heat exchange system. Even though bypass valves are very useful for internal combustion engine cooling systems and other applicable systems, they are not free of certain drawbacks. For example, bypass valves are known to create pressure drops in the fluid flowing from the engine towards the heat exchange system, and/or in the opposite direction. 
     Accordingly, there remains a need in the art for a bypass valve that provides a constant pressure of the fluid entering and exiting the valve while maintaining reasonably compact external dimensions. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the deficiencies of the known art and the problems that remain unsolved by providing a bypass valve having two fluid passage ports, a bypass port communicating them, and a barrier assembly capable of opening and closing the bypass port, where the barrier assembly is arranged not to invade the fluid passage ports. In this configuration, the barrier assembly engages and regulates the fluid in the bypass port, while avoiding direct contact with the first port, the second port, or the fluid in either port. This novel configuration improves fluid flow through the first and second ports at a given pressure, and inhibits undesirable pressure drops and flow restrictions caused by viscous forces on the barrier assembly. 
     In accordance with one embodiment of the present invention, the invention consists of a bypass valve for thermally regulating a fluid flow, the bypass valve comprising:
         a first port, configured to at least partially enable a fluid to pass through the valve in a first direction,   a second port, configured to at least partially enable the fluid to pass through the valve in a second direction,   a bypass port, arranged to extend between the first port and the second port for providing fluid communication between the first port and the second port;   a barrier assembly, adapted to move between an open position and a closed position in response to a variance in the fluid temperature; wherein   in the open position, the barrier assembly allows fluid to flow through the bypass port, whereas in the closed position the barrier assembly at least partially inhibits fluid flow through the bypass port; and wherein   the barrier assembly is movably arranged externally to the first port and second port.       

     In another aspect, the barrier assembly extends in a substantially perpendicular orientation with respect to the bypass port, moving between the open position and the closed position. 
     In another aspect, the first port and second port are substantially parallel. 
     In another aspect, the barrier assembly is movable in a direction that is substantially parallel to the first direction and the second direction. 
     In another aspect, the barrier assembly comprises a linear thermal actuator element, a barrier affixed to the thermal actuator element, and a spring bearing upon the thermal actuator element and biasing the thermal actuator element towards the open position, said thermal actuator element being responsive to the fluid temperature for regulating the flow through the bypass port. The linear thermal actuator element is capable of causing the barrier to move from the open position to the closed position in dependence to the temperature of the fluid. The spring is biased to push the barrier assembly outward of the bypass port and towards the open position. 
     In another aspect, the barrier assembly includes a barrier that is adapted to move from the open position to the closed position in direct relation to the temperature of the fluid, wherein the barrier is operated by an electric motor, a solenoid, a pneumatic system, a hydraulic system, a manual force, and/or other mechanical or electric actuator, in dependence of the change of fluid temperature. 
     In another aspect, the movable barrier assembly includes at least one conduit allowing fluid to pass through from the bypass port to a separate space, separated from the first port and the second port. 
     In another aspect, the barrier assembly is arranged at least partially in the separate space, the at least one conduit extending between a first end surface of the barrier assembly that faces the separate space, and a second end surface of the barrier assembly that is opposite to the first end surface, wherein the second end surface is arranged so that the second end surface is inside the bypass port when the valve is in an open position, and outside the bypass port when the valve is in the closed position. 
     In another aspect, the barrier assembly includes an end surface that is in contact with fluid passing through the bypass port when the bypass valve is in the open position, said end surface being capable of sensing fluid temperature changes. 
     In another aspect, the linear thermal actuator element is arranged extending through the barrier so that an end surface of the linear thermal actuator element is in contact with fluid passing through the bypass port when the bypass valve is in the open position, said end surface being capable of sensing fluid temperature changes. 
     In another aspect, the bypass valve includes a housing in which the first port, second port, and bypass port are comprised. The housing may be manufactured from metal, composite material and/or any other applicable material. 
     In another aspect, the separate space is also comprised inside the housing. 
     In a further aspect, the bypass port defines a bypass inlet at the first port and a bypass outlet at the second port wherein the bypass inlet has a cross-sectional area greater than the bypass outlet. 
     In still a further aspect, when the bypass valve is in a closed position the barrier blocks the bypass outlet to prevent fluid flow therethrough and only partially blocks the bypass inlet. 
     Introducing another embodiment of the invention, the present invention consists of a bypass valve for thermally regulating fluid flow, which includes a housing defining a first port for the passage of a fluid in a first direction, defining a second port laterally disposed from the first port for the passage of a fluid in a second direction, defining a bypass chamber isolated from the first port and the second port, and defining a bypass port extending from said first port, through said bypass chamber to said second port. A barrier assembly is disposed in the bypass chamber and includes a barrier affixed thereto and is operably configured to translate the barrier between an open position and a closed position in response to a temperature change of the fluid. When the barrier assembly is in an open position fluid flow is permitted between the first port and the second port through the bypass port, and when the barrier assembly is in a closed position the barrier assembly blocks fluid flow through the bypass port. 
     In a second aspect, the housing comprises a first housing affixed to a second housing and includes an O-ring disposed therebetween. 
     In another aspect, the barrier assembly further includes a spring biasing the barrier assembly in the open position. 
     In still a further aspect, the biasing spring is a compression spring. 
     In another aspect, the barrier assembly further comprises a linear thermal actuator element having a sensor surface and is responsive to a temperature change of a fluid in contact with the sensor surface for actuating the barrier assembly to a closed position, and further wherein the barrier is disposed about the linear thermal actuator element. 
     In yet another aspect, the bypass port defines a bypass inlet at the first port and a bypass outlet at the second port wherein the bypass inlet has a cross sectional area greater than the bypass outlet. 
     In still another aspect, when the bypass valve is in the closed position the barrier blocks the bypass outlet to prevent fluid flow therethrough and only partially blocks the bypass inlet. 
     Introducing yet another embodiment of the invention, the present invention consists of a bypass valve for thermally regulating a fluid flow, including a housing defining a first port for the passage of a fluid in a first direction, defining a second port laterally disposed from the first port for the passage of a fluid in a second direction, defining a bypass chamber isolated from the first port and the second port, and defining a bypass port extending from said first port, through said bypass chamber to said second port. A barrier assembly is disposed in the bypass chamber and includes a linear thermal actuator element having a sensor surface and is responsive to a temperature change of a fluid in contact with the sensor surface for actuating the barrier assembly to a closed position. A biasing spring biases the barrier assembly to an open position, and a barrier is affixed to the linear thermal actuator element and is operably configured to translate between an open position and a closed position in response to a temperature change of the fluid. The barrier assembly when in the open position permits fluid flow between the first port and the second port through the bypass port, and when in the closed position blocks fluid flow through the bypass port. 
     In a second aspect, the bypass port defines a bypass inlet at the first port and a bypass outlet at the second port wherein the bypass inlet has a cross-sectional area greater than the bypass outlet and further wherein when the bypass valve is in the closed position the barrier blocks the bypass outlet to prevent fluid flow therethrough and only partially blocks the bypass inlet. 
     These and other aspects, features, and advantages of the present invention will become more readily apparent from the attached drawings and the detailed description of the preferred embodiments, which follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred embodiments of the invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the invention, in which: 
         FIG. 1  presents a detailed perspective view of an exemplary bypass valve according to the invention, viewed from a top angle; 
         FIG. 2  presents another detailed perspective view of the bypass valve of  FIG. 1 , viewed from a bottom angle; 
         FIG. 3  presents an exploded view of the bypass valve of  FIG. 1 , viewed from a top angle; 
         FIG. 4  presents an exploded view of the bypass valve of  FIG. 1 , viewed from a bottom angle; 
         FIG. 5  presents a top view of the bypass valve of  FIG. 1 ; 
         FIG. 6  presents a front view of the bypass valve of  FIG. 1 ; 
         FIG. 7  presents a cross-sectional view of the bypass valve of  FIG. 1 , according to sectional plane  7 - 7  indicated in  FIG. 5 , the bypass valve being shown in an open position; 
         FIG. 8  presents the bypass valve of  FIG. 7  in a closed position; 
         FIG. 9  presents a detailed perspective view of a second exemplary embodiment of a bypass valve according to the invention, shown from a top right angle; 
         FIG. 10  presents a detailed perspective view of the bypass valve of  FIG. 9 , shown from a top left angle; 
         FIG. 11  presents a top view of the bypass valve of  FIG. 9 ; 
         FIG. 12  presents a left side view of the bypass valve of  FIG. 9 ; 
         FIG. 13  presents a cross-sectional view of the bypass valve of  FIG. 9 , according to sectional plane  13 - 13  indicated in  FIG. 11 , the bypass valve being shown in an open position; 
         FIG. 14  presents the bypass valve of  FIG. 13  in a closed position; 
         FIG. 15  presents a top isometric view of an alternate embodiment bypass valve; 
         FIG. 16  presents a bottom isometric view of the bypass valve of  FIG. 15 ; 
         FIG. 17  presents a top inverted isometric exploded view of the alternate embodiment bypass valve; 
         FIG. 18  presents a bottom inverted isometric exploded view of the alternate embodiment bypass valve; 
         FIG. 19  presents a top plan view of the alternate embodiment bypass valve; 
         FIG. 20  presents a cross-sectional view of the alternate embodiment bypass valve taken along the line  20 - 20  of  FIG. 19  and illustrating the alternate embodiment bypass valve in an open position; and 
         FIG. 21  presents the cross-sectional view of  FIG. 20  wherein the alternate embodiment bypass valve is in a closed position. 
     
    
    
     Like reference numerals refer to like parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the described embodiments or the application and uses of the described embodiments. As used herein, the word “exemplary” or “illustrative” means “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” or “illustrative” is not necessarily to be construed as preferred or advantageous over other implementations. All of the implementations described below are exemplary implementations provided to enable persons skilled in the art to make or use the embodiments of the disclosure and are not intended to limit the scope of the disclosure, which is defined by the claims. For purposes of description herein, the terms “upper”, “lower”, “left”, “rear”, “right”, “front”, “vertical”, “horizontal”, and derivatives thereof shall relate to the invention as oriented in  FIG. 1 . Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. 
     The illustrations of  FIGS. 1 and 2  present a first embodiment of a bypass valve according to the invention, shown from a top angle and a bottom angle respectively. The bypass valve  100  comprises a housing  110 , in which a first port  120  and a second port  130  are formed, whose purpose is to provide passageways for fluid to flow through the bypass valve  100 . The fluid may include, without limitation, engine oil, a radiator coolant, a liquid, a gas, a vapor, a fluidized solid, and a slurry. The first port  120  can, for instance, allow engine coolant to pass from a vehicle engine towards a heat exchange cooling system, and the second port  130  can allow the engine coolant to return from the heat exchange cooling system towards the vehicle engine. In the embodiment shown in the figures, the first and second ports  120 ,  130  are parallel through-holes comprised in the housing  110 . The first port  120  is configured to at least partially enable a fluid to flow in a first direction  122 . The second port  130  is configured to at least partially enable the fluid to flow in a second direction  132 . A bypass port  140 , not shown in the figures, is arranged inside the housing  110  and extending between the first port  120  and the second port  130  for providing fluid communication between the first port  120  and the second port  130 . The housing  110  may be manufactured from metal, composite material and/or any other applicable material. The bypass valve  100  further comprises a closure  150  to close the lower area of the housing  110  so that internal components of the bypass valve  100 , which will be explained in further figures, are secured inside the housing  110 . The closure  150  is attached to the housing  110  by any applicable means such as a magnet, a mechanical fastener, adhesive, etc. In the depicted embodiment, for instance, several screws  152  are used to secure the closure  150  to the housing  110 . To prevent leakage of fluid from the mating surfaces of the housing  110  and the closure  150 , an O-ring  154  (shown in  FIGS. 3, 4, 7 and 8 ) is seated between the housing  110  and the closure  150 . 
     The drawings of  FIGS. 3 and 4  show exploded views of the bypass valve  100  of  FIG. 1 . As shown, the bypass valve  100  further comprises a barrier assembly  160 , which in the present embodiment comprises an actuator pin  164 , a linear thermal actuator element  168 , a barrier  172 , and a spring  176  that join together to regulate flow through the bypass port  140 , slightly shown in  FIG. 4 . The barrier  172  of the present embodiment is in shape of a sleeve, comprising a first end surface  173 , an opposed second end surface  174  and a through hole  175  inside which the linear thermal actuator element  168  is partially arranged. The linear actuator element  168  is adapted to cause the barrier  172  to move in response to a change in fluid temperature, as will be shown in further figures. Specifically, the linear actuator element  168  of the present embodiment contains a paraffin wax formulated to expand when it reaches a specific temperature; the expansion of the wax causes an internal diaphragm to expand, pushing the actuator pin  164  outward, and thus generating a relative linear motion between the actuator pin  164  and the linear thermal actuator element  168 ; as the wax cools, the diaphragm contracts, and the actuator pin  164  is allowed to retract towards the linear actuator element  168 . Alternatively, the linear thermal actuator element  168  may include, without limitation, a metal alloy or other a thermal element. The spring  176  is biased to create an opposite force to the linear thermal actuator element  168 , i.e., a vertically upward force according to the position of the bypass valve  100  in the figures. 
     The illustrations of  FIGS. 5 and 6  present further top and front views of the bypass valve  100  of  FIG. 1 , allowing to observe the valve from different angles to those provided by the previous figures. Again, the parallel and spaced-apart arrangement of the first and second ports  120 ,  130  of the present embodiment is observed, as well as the housing  110  of the bypass valve  100  being substantially rectangular in shape and arranged perpendicularly to the first and second ports  120 ,  130 . Such a perpendicular arrangement provides a compact solution where the components of the valve according to the invention are most integrated. 
     The drawing of  FIG. 7  shows a cross-sectional view of the bypass valve  100  of  FIG. 1 , where the cross section has been performed according to sectional plane  7 - 7  shown in  FIG. 5 . The cross-sectional view makes it possible to fully observe the bypass port  140  according to the invention, arranged to extend between the first port  120  and the second port  130  for providing fluid communication between the first port  120  and the second port  130 . In the embodiment shown, the bypass port  140  is perpendicular to the parallel first and second ports  120 ,  130 , to minimize the length of the bypass port  140  and the size of the bypass valve  100 . In the present illustration, the bypass valve  100  is shown in an open position in which the barrier assembly  160  allows the fluid to flow through the bypass port  140  as indicated by arrow  180 . This open position has been reached because the fluid temperature is not high enough for the linear thermal actuator element  168  to actuate, and the barrier  172  is thus biased by the spring  176  in a vertically upward direction according to the position in the figure and kept from closing the bypass port  140 . In the event that fluid temperature begins to increase, the linear thermal actuator element  168  starts applying an expansion force on the actuator pin  164  in a vertically upward direction according to the position of the figure. Because the actuator pin  164  is longitudinally fixed against an inner wall of the housing  110 , the reaction force pushes the linear thermal actuator element  168  downwards, towards the bypass port  140 , said reaction force counteracting the vertically upward force exerted by the spring  176 . If temperature continues increasing, the reaction force eventually overcomes the spring force and causes the barrier  172  to move towards the bypass port  140 . The illustration of  FIG. 8  shows the bypass valve  100  in a closed position, in which fluid temperature has increased enough for the barrier  172  to fully block the bypass port  140  and thus inhibit fluid flow through the bypass port  140 . As shown in the figures, the closure  150  provides an end stop to the barrier assembly  160  so that the spring  176  and linear thermal actuator element  168  can correctly exert their opposite forces. 
     According to the invention, the barrier assembly  160  is movably arranged externally to the first port  120  and the second port  130 . In other words, as can be observed in  FIGS. 7 and 8 , the barrier assembly  160  engages the fluid solely in the bypass port  140  while avoiding direct contact with the fluid in the first port  120  and the second port  130 , whether it be in the open position or in the closed position. Thus, the first and second ports  120 ,  130  are unaffected by the operation of the bypass valve  100  according to the invention. This novel positioning of the barrier assembly  160  outside of the first and second ports  120 ,  130  minimizes the surface area in contact with the fluid flowing through the first and second ports  120 ,  130 , and thus results in a reduction of viscous forces opposing fluid flow. In addition, having the barrier assembly  160  outside of the first and second ports  120 ,  130  reduces debris accumulation, turbulences or other undesired effects inside the first and/or second ports  120 ,  130  during operation of the valve. Fluid can permanently and cleanly flow through the first and second ports  120 ,  130  unaffected, showing minimal pressure drops caused by the bypass valve  100 . 
     Preferably, as shown, the barrier assembly  160  arranges perpendicularly in relation to the bypass port  140 , movable between the open position and the closed position, allowing for an optimum placement of the barrier assembly  160  and to increase the compactness of the bypass valve  100 , especially in the event that the first and second ports  120 ,  130  are parallel, as is the case of the present embodiment. 
     As shown in  FIGS. 7 and 8 , the movable barrier assembly  160  may further include at least one conduit  190 —two, in the present embodiment—for allowing fluid to pass through from the bypass port  140  to a separate space  194 , separated from the first port  120  and the second port  130 . The barrier assembly  160  is movably arranged between the bypass port  140  and the separate space  194 , and the conduits  190  allow relieving pressure differentials between the bypass port  140  and the separate space  194  that could affect operation of the valve. 
     In the depicted embodiment, the conduits  190  are comprised in the barrier  172 , and the linear thermal actuator element  168  is arranged partially in the separate space  194 . The first end surface  173  of the barrier  172  faces the separate space  194 . In turn, the second end surface  174  is arranged so that it is inside the bypass port  140  when the valve is in an open position, as shown in  FIG. 7 , and outside the bypass port  140  when the valve is in the closed position, as shown in  FIG. 8 . Such an arrangement allows fluid to pass between the bypass port  140  and the separate space  194  when the barrier assembly  160  is moving, so that pressures in both spaces  140 ,  194  can equalize. In turn, having the second end surface  174  arranged outside the bypass port  140  when the valve is in the closed position guarantees that fluid does not pass from the first port  120  to the second port  130  or vice versa. Also, in the embodiment shown, when the valve is in the closed position, the barrier assembly  160  delimits an enclosed spring space  196 , and the second end surface  174  is arranged facing said spring space  196  so that the conduits  190  communicate the spring space  196  with the separate space  194  and again relieve pressure differentials between the spaces  194 ,  196  so that the barrier assembly  160  can better operate back to the open position. 
     In the embodiment shown, the linear thermal actuator element  168  is arranged inside the sleeve-shaped barrier  172  so that an end surface  169  of the linear actuator element  168  is in contact with the fluid passing through the bypass port  140  when the bypass valve  100  is in the open position, as shown in  FIG. 7 . The linear actuator element  168  is adapted to actuate depending on the fluid temperature sensed on this end surface  169 . Thus, the linear thermal actuator element  168  is capable of responding to fluid temperature changes when the bypass valve  100  is in the open position. Further, once the valve is closed as shown in  FIG. 8 , the linear thermal actuator element  168  is kept at near the temperature of the fluid flowing through first and second ports  120 ,  130  because the barrier  172  arranged around the linear thermal actuator element  168  is in contact with that fluid and thus conducts heat to the linear thermal actuator element  168 . Once the fluid flowing through the first and second ports  120 ,  130  is substantially cooled, the temperature of the barrier  172  is cooled as well, and thus the linear thermal actuator element  168  begins to contract and the spring  176  forces the barrier  172  open again. 
     The illustrations of  FIGS. 9 and 10  present two detailed perspectives views of a second embodiment of the bypass valve according to the invention, shown from a from a top right angle and a top left angle respectively. The bypass valve  200  is again formed mainly inside a housing  210 . In the present embodiment, however, the housing  210  is divided into a first portion  212  and a second portion  214 . To prevent leakage of fluid from the mating surfaces of the first portion  212  and the second portion  214 , an O-ring  215  (shown in  FIGS. 13 and 14 ) is seated between the first portion  212  and the second portion  214 . The bypass valve  200  according to the present embodiment also includes a first port  220  and a second port  230 , similar to the previous embodiment of  FIGS. 1 through 8 . The drawings of  FIGS. 11 and 12 , in turn, respectively present a top view and an elevated side view of the bypass valve  200  of  FIG. 9 . As shown, this second embodiment does not include a cover for concealing and securing internal components of the valve; instead, internal components are inserted and secured inside the housing  210  by separating and joining the first and second portions  212 ,  214  of the housing  210 . In addition, the bypass valve  200  according to this second embodiment includes two side mounts  216  that attach to the sides of the housing  210  by means of applicable fasteners such as screws  218  (as shown in the figures), bolts, magnets, etc. 
     The bypass valve  200  of the present embodiment is shown in the open position and closed position in  FIGS. 13 and 14 , respectively. This second embodiment works essentially in the same way as the previous embodiment of  FIGS. 7 and 8 , by having a barrier assembly  260  movably arranged inside the housing and capable of allowing or preventing fluid flow through a bypass port  240  that communicates the first and second ports  220 ,  230 . As in the previous embodiment, the barrier assembly  260  is movably arranged externally to the first port  220  and second port  230 . This second embodiment is different in that, as shown, the barrier assembly  260  is secured between the first and second portions  212 ,  214  of the housing  210 . 
     The invention contemplates the use of alternative barrier assemblies to the barrier assemblies  160 ,  260  shown in the figures. For instance, the barrier assembly can be an electric barrier assembly, a solenoid, a hydraulic barrier assembly, a pneumatic barrier assembly, a manually-operated barrier assembly, etc. In some embodiments, it could be that a spring were not necessary, for instance in the event that the barrier assembly is electrically-operated by a reversible motor. 
     Referring now to  FIGS. 15 through 21 , an alternate embodiment bypass valve  300  is illustrated showing its various elements and components. As is illustrated in  FIGS. 15 through 18 , the bypass valve  300  includes a two-part housing  310  comprising a first portion  312  and a second portion  314 . The housing  310  defines a first port  320  extending vertically therethrough for accommodating fluid flow in a first direction  322  and a second port  330  laterally separated from first port  320  and also extending vertically therethrough for accommodating fluid flow in a second direction  332 . To prevent leakage of fluid from the mating surfaces of the first portion  312  and the second portion  314 , an O-ring  315  (best shown in  FIGS. 17, 18, 20 and 21 ) is seated between the first portion  312  and the second portion  314 . As shown in  FIGS. 20 and 21 , the housing  310  further defines a bypass chamber  394  between the first port  320  and the second port  330 . A bypass port  340  extends from the first port  320  to the second port  330  such that the first port  320  is fluidly communicable with the second port  330 . The bypass port  340  has a bypass inlet  342  at the first port  320  and a bypass outlet  344  at the second port  330 . The bypass inlet  342  has a cross-sectional area which is greater than the bypass outlet  344 . 
     A barrier assembly  360  is operably disposed in the bypass chamber  394  defined by housing  310 . The barrier assembly  360  includes a linear thermal actuator element  368  having an actuator pin  364  having one end bearing upon the second portion  314 , and wherein the thermal actuator element  368  is responsive to a temperature change of the fluid communicated through bypass port  340  for actuating the barrier assembly between an open and closed position. A barrier  372  is disposed about the periphery of the thermal actuator element  368  and has a cross-sectional geometry only slightly smaller than that of the cross-sectional geometry of the bypass chamber  394 , in order for the barrier assembly  360  to be able to slide through the bypass chamber  394  guided by the walls of the bypass chamber  394 . The barrier  372  of the present embodiment is generally rectangular, comprising a first end surface  373 , an opposed second end surface  374  and a through hole  375 , through which the thermal actuator element  368  extends. The barrier  372  can also include one or more conduits  390  extending therethrough to permit the flow of fluid therethrough when the barrier  372  is translated between its open and closed position. The barrier  372  is operable in conjunction with the thermal actuator element  368  to block the bypass outlet  344  of the bypass port  340  when the barrier assembly  360  is in a closed position. A biasing spring  376  is disposed between the barrier  372  and the first portion  312  for biasing the barrier assembly  360  to an open position. 
     Referring now to  FIGS. 19 through 21 , the bypass valve  300  works essentially identical to the bypass valves  100 ,  200  described above. However, as best shown in  FIGS. 20 through 21 , the bypass inlet  342  is larger than the bypass outlet  344 . When the bypass valve  300  is in the open position, as illustrated in  FIG. 20 , the larger bypass inlet  342  does not restrict fluid flow to the extent that the smaller bypass outlet  344  restricts fluid flow. Thus, there is less of a pressure drop across the bypass port  340 . Further, when the bypass valve  300  is in the closed position, as illustrated in  FIG. 21 , the barrier  372  only seals the outlet port  344  to prevent fluid passage through bypass port  340 . However, when the barrier assembly  360  is in its closed position the barrier  372 , as a result of the larger bypass inlet  342 , fluid from the first port  320  will still remain in contact with the sensing surface  369  of the thermal actuator element  368 , ensuring the thermal actuator element  368  is not insulated from the fluid flowing through first port  320  and thus will have a more timely response to a temperature change of the fluid. 
     The above-described embodiments are merely exemplary illustrations of implementations set forth for a clear understanding of the principles of the invention. Many variations, combinations, modifications or equivalents may be substituted for elements thereof without departing from the scope of the invention. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all the embodiments falling within the scope of the appended claims.