Abstract:
A fluid control thermostatic valve contains thermally responsive wax. As temperature rises, the wax expands thus pushing a deformable member up a confined path defined by guide  40  until the member contacts a fixed post  60 . An immobile retainer  72  is secured to the fixed post  60 . Force from the elastic member against the post causes actuator  30  to separate from retainer  72 , thus opening a flow passage. The control valve is unique because retainer  72  functions as both a valve seat for actuator  30  and a fixed support for spring  84.

Description:
TECHNICAL FIELD 
     The present disclosure relates to a temperature sensitive fluid flow control valve which also functions as a pressure relief valve. One use for the disclosed valve is to control the opening and closing of a bypass passage in a fluid cooling system to provide warm up and steady state (cooling) flow paths for the fluid. The integrated pressure relief functionality prevents excess pressure accumulation. 
     BACKGROUND 
     Fluid cooler bypass valves are used in conjunction with engines, transmissions, power steering systems, hydraulic systems and other systems that heat a working or lubricating fluid. They are designed to provide a flow path by which fluid delivered to the valve from the heat source is returned without passing through a fluid cooler such as a radiator or other heat exchanger during warm-up periods. 
     Typical fluid cooler bypass valves include an actuator which responds to temperatures above a set-point to move a valve member from a bypass position where fluid is permitted to flow from the source of heated fluid to the fluid cooler return path without passing through the fluid cooler. Prior art bypass valves move from a bypass position where a bypass passage is open and the flow path to or from a cooler is obstructed to a steady state (cooling) position where the bypass passage is closed and the flow path to and from the fluid cooler is open. The fluid flow path can be re-configured using a single valve member. 
     The use of wax-filled actuators, otherwise referred to as wax motors, as thermally responsive control devices in fluid circulation systems is well known. Wax motors have been used as temperature sensitive actuators for valves employed in fluid cooling systems to control flow paths for fluid during warm-up and steady state operating conditions. Such bypass valves are designed to open or close in response to a predetermined change in temperature. Wax motors require no external power source, are reliable, extremely compact and powerful for their size. 
     Wax motors typically include a housing having a chamber filled with thermally responsive wax contained beneath a flexible diaphragm. The wax expands as temperature increases, exerting an outward force on the diaphragm and on a reciprocating piston disposed on the other side of the diaphragm. Movement of the piston is controlled by a guide extending from the actuator housing. The wax motor is constructed such that known changes in temperature produce predetermined axial movement of the piston with respect to the housing. 
     Consequently, there exists a need for a thermally actuated flow control valve with pressure relief capability that employs a simplified mechanism to provide warm-up and steady state flow paths in a fluid cooling system. 
     SUMMARY 
     The disclosure relates to a thermally actuated fluid flow control valve of simple construction and enhanced functionality. The temperature sensitive fluid flow control valve is configured to be placed within a bypass passage defined by a valve body. The bypass passage is in communication with fluid supply and fluid return passages associated with a source of heated fluid and a fluid cooler, the bypass passage connects a flow path from the source of heated fluid with a flow path from the fluid cooler. The bypass passage also includes a valve seat. 
     The disclosed fluid flow control valve includes an actuator having an actuator body, a guide extending in a first axial direction from the actuator body to a first end of the actuator and an oppositely directed plunger extending from the actuator body to a second end of the actuator. The guide defines an axial bore open at the first end of the actuator and includes a first flange projecting radially outwardly from the first end of the actuator. The actuator body includes a metering surface extending radially outward of the guide and substantially perpendicular to the axial length of the actuator. 
     The disclosed fluid flow control valve is an assembly configured for installation through a valve body opening communicating with the bypass passage. A cap is configured to cover the opening in the valve body and support the fluid flow control valve within the bypass passage. The cap includes an axially disposed post which is received in the axial bore of the guide to control movement of the actuator. A retainer is secured to the cap to form a flange facing the closed end of the cap and an opposed valve seat facing the bypass passage. The ring-shaped retainer defines a central flow aperture through which the actuator guide is received with the post extending into the guide axial bore. 
     The disclosed fluid flow control valve includes a valve member movably secured to the plunger and surrounding a second end of the actuator. The valve member is axially movable with respect to the plunger and biased toward an extended position projecting away from the actuator body toward a valve seat in the bypass passage defined by the valve body. 
     A bias member is engaged between a flange on the guide and the retainer to bias the actuator toward a bypass position where the actuator blocks the flow aperture defined by the retainer to close a fluid return path from the fluid cooler. The valve member secured to the actuator plunger is separated from the valve seat in the bypass passage when the fluid flow control valve is in the bypass position, thereby permitting fluid flow through the bypass passage between the source of heated fluid and a return flow path from said fluid cooler without flowing through the fluid cooler. 
     The components of the actuator are selected so that the actuator exerts a force F on the post at temperatures above a predetermined temperature T. The actuator force F is sufficient to overcome the bias of the bias member engaged with the actuator guide and move the actuator away from the cap to a steady state position. In the steady state position, the actuator is moved away from the valve seat defined by the retainer to open a fluid flow path between the cooler outlet and the heat source inlet. The same movement of the actuator moves the valve member secured to the plunger into contact with the valve seat defined by the valve body to close the bypass passage. In the disclosed fluid flow control valve embodiment, the actuator body provides a first valve, while the second end of the actuator carries a valve member with spring biased axial movement relative to the actuator. Movement of the actuator between the bypass and steady state positions first opens the flow path between the fluid cooler and the heat source and then closes the bypass passage. The cooler flow path and bypass passage cannot be open at the same time in the absence of excess pressure on the valve member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view through an embodiment of the disclosed fluid flow control valve installed in a valve body and shown in the bypass position; 
         FIG. 2  shows the fluid flow control valve and valve body of  FIG. 1  in the steady state (cooling) position; 
         FIG. 3  is a sectional view through an embodiment of the disclosed fluid flow control valve; 
         FIG. 4  is a sectional exploded view of the fluid flow control valve of  FIG. 3 ; 
         FIG. 5  is a sectional view of an embodiment of an actuator compatible with the disclosed fluid flow control valve; 
         FIG. 6  is an exploded sectional view of the actuator of  FIGS. 5 ; and 
         FIG. 7  is a perspective view of a cap component compatible with the disclosed embodiment of a fluid flow control valve. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosed fluid flow control valve  10  is configured for installation in a valve body  12  arranged between a source of heated fluid (not shown) and a fluid cooler such as a radiator or heat exchanger (not shown). Sources of heated fluid include internal combustion engines, vehicle transmissions, hydraulic pumps, or the like. A valve body  12  defines fluid flow passages for receiving heated fluid from a heat source, delivering the heated fluid to the fluid cooler and returning cooled fluid to the heat source. As shown in  FIGS. 1 and 2 , there are four fluid flow openings  14 ,  16 ,  18 ,  20  in the valve body  12 . Opening  14  receives fluid from the heat source. Opening  16  communicates with the fluid cooler input. Opening  18  receives cooled fluid from the fluid cooler. Opening  20  returns cooled fluid back to the heat source. The valve body  12  defines a bypass passage  22  in fluid communication with each of openings  14 ,  16 ,  18  and  20 . The bypass passage  22  includes a valve seat  15  and an opening  24  through the side of the valve body  12 , permitting installation of the disclosed fluid flow control valve  10 . 
     The disclosed fluid flow control valve  10  includes an actuator  30  which defines an internal cavity  32  containing thermally responsive wax material  46 . As best seen in  FIGS. 5 and 6 , the illustrated actuator  30  includes two primary structural components—a guide  34  and a cup  36 . In the illustrated embodiment, the guide  34  and cup  36  are constructed of half-hard  360  brass. The guide  34  defines an axial bore  38  and includes a radially projecting flange  40  at a first end  41  of the actuator  30 . The guide  34  also includes a radially projecting metering surface  42  axially spaced from the flange  40 . A plunger  44  extends integrally from the cup  36  in a direction opposite the guide  34 . Thermally responsive wax material  46  fills the cavity  32  defined by the cup  36 . A diaphragm  48  is arranged to contain the wax material  46  in the cavity  32 . A plug  50  and disc  52  are forced up the bore  38  by expansion of the wax material  46  to deliver an axial force F from the actuator  30  in response to a temperature rise above a pre-determined set point.  FIG. 5  shows the components of the actuator in an assembled configuration. A lip  54  projecting from the guide  34  is mechanically formed around a radially projecting flange  56  at the end of the cup  36  to secure the guide  34  to the cup  36  as shown in  FIG. 5 . The illustrated construction permits the guide  34  to have an uninterrupted, radially projecting metering surface  42  which facilitates use of the actuator  30  as a valve member as discussed below. 
       FIGS. 3 and 4  illustrate an exemplary embodiment of the disclosed fluid flow control valve  10 . The exemplary actuator  30  illustrated in  FIGS. 5 and 6  ties the other components of the fluid flow control valve  10  together to form an assembly that is easily installed through valve body opening  24 . A cap  60  is configured to close the valve body opening  24  and support the fluid flow control valve  10  in the bypass passage  22 . The cap  60  is retained in the opening  24  by a snap ring  62  or other appropriate mechanical connection such as threads (not shown). The cap  60  includes a closed first end  64  and an inwardly directed axial post  66 . Two arms  68  extend from the cap  60  to support an annular shoulder  70  radially outward of said post  66 . A ring-shaped retainer  72  is secured against the shoulder  70  and in fixed relation to the cup. In the disclosed embodiment, the retainer  72  is secured to the cap  60  by mechanically forming a lip  74  of the cap  60  over an angled peripheral surface  76  of the retainer  72 . This forms a mechanical connection between the retainer  72  and the cap  60 . Other connection methods will occur to those skilled in the art. The retainer  72  provides a flange  78  facing the closed first end  64  of the cap  60  and provides a valve seat  80  on the opposite side. The retainer  60  also defines a central opening  82  which serves as a flow path for fluid when the fluid flow control valve  10  is in the steady state position shown in  FIG. 2 . 
     In the assembled fluid flow control valve  10  as shown in  FIG. 3 , the guide  34  passes through the central opening  82  of the retainer  72  and receives the post  66  extending from the cap  60  into the axial bore  38  of the guide  34 . A bias member  84  is engaged between the flange  40  of the guide  34  and the flange  78  of the retainer  72  to bias the actuator  30  toward the bypass position illustrated in  FIG. 1 . Expansion of the thermal wax material  46  in response to an increase in temperature above a predetermined set point produces a force F through the plug  50  and disc  52  against the post  66  to overcome the bias of the bias member  84 . The disclosed bias member  84  is a conical coil spring with end faces that are ground within 3° of normal to the spring axis. Other forms of bias member will occur to those skilled in the art. 
     The opposite end  43  of the actuator  30  includes a plunger  44  extending from the cup  36 . The plunger  44  includes a circumferential groove  86  which receives a retaining clip  88 . A valve member  90  is axially slidably movable relative to the plunger  44  and is retained to the plunger by the clip  88 . The clip  88  and valve member  90  are configured so that the valve member  90  is permitted limited axial movement with respect to the plunger  44 . A bias member  92  is arranged to bias the valve member  90  toward the extended position shown in  FIGS. 1-3 . Mounting the valve member  90  to the end of the actuator plunger  44  with biased axial movement serves two functions. First, temperatures in the valve body  12  may exceed the normal operating temperature for which the actuator  30  was designed. At such elevated temperatures, the wax  46  in the actuator  30  will continue to expand and continue to exert force on the post  66 , moving the actuator  30  further away from the valve seat  80  illustrated in  FIG. 2 . The spring-biased valve member  90  accommodates excess movement of the actuator  30  and prevents possible damage to valve components that may otherwise occur. Second, the spring-biased slidably movable valve member  90  allows the disclosed fluid flow control valve  10  to relieve excess pressure on the “hot” side of the valve body  12  (openings  14 ,  16 ). Under certain circumstances, the fluid flowing through the valve body  12  may become overly pressurized. Such excess pressure can damage the fluid cooler (not shown). In the illustrated embodiment, excess fluid pressure in the fluid passageways  14  or  16  will overcome the spring bias on the valve member  90  and move it away from its valve seat  15 , allowing fluid to flow back to the fluid source. 
     The disclosed fluid flow control valve  10  includes two alternatively operating valves. The first valve is formed by the actuator  30  closing the flow aperture  82  defined by the retainer  72 . The valve interface is formed by the actuator radially projecting metering surface  42  and the valve seat  80  defined by the retainer  72 . The second valve is formed by the valve member  90  mounted to the actuator plunger  44  and the valve seat  15  defined by the valve body  12 . As shown in  FIG. 1 , when the fluid flow control valve  10  is in the bypass position, the metering surface  42  is seated against the retainer valve seat  80 , closing the fluid flow aperture  82  defined by the retainer  72 . This valve prevents fluid flow between the cool side (return  18 ) of the fluid cooler (not shown) and the fluid return  20  to the heat source. When the disclosed fluid flow control valve  10  is in the bypass position illustrated in  FIG. 1 , the valve member  90  is separated from the valve seat  15  defined by the valve body  12 . Fluid flow through the fluid cooler (not shown) is obstructed, while fluid flow through the bypass passage  22  between the heat source outlet  14  and the fluid return  20  is permitted. 
       FIG. 2  illustrates the disclosed fluid flow control valve  10  in its steady state, or cooling position. When the heat source has warmed the fluid circulating in the valve body  12  to a predetermined set-point, the wax  46  contained in the actuator cup  36  expands, exerting force F on the post  66  and moving the actuator  30  away from its bypass position to the position shown in  FIG. 2 . In the steady state position, the valve member  90  is now in contact with the valve seat  15  defined by the valve body  12 , closing the bypass passage  22 . Meanwhile, the actuator  30  has moved away from its bypass position, separating the metering surface  42  from the valve seat  80  defined by the retainer  72  and opening a fluid flow path between the cool side  18  of the cooler and the cool fluid input  20  to the heat source (not shown). 
     The pressure relief functionality of the disclosed fluid flow control valve is adjustable by selecting the bias member  92 . The illustrated bias member  92  is a coil spring, though other appropriate bias members are suitable. By selecting an appropriate bias member, the pressure at which the valve member  90  is moved away from the valve seat  15  can be adjusted. For example, the pressure relief set point may be selected at 20 psi less than the burst pressure of the fluid cooler or heat exchanger. Similarly, the actuator  30  can be configured to change position from bypass to steady state at a predetermined temperature by selection of actuator wax and bias member  84 . For example, the actuator  30  may be selected so the fluid flow control valve  10  is fully opened at a temperature of approximately 230° and fully closed at a temperature of 220°. Those skilled in the art will understand that these pressure and temperature set points are merely exemplary and a range of temperature and pressure set points are available through appropriate component selection and design. 
     While a preferred embodiment of the disclosed fluid flow control valve has been set forth for purposes of illustration, the foregoing description should not be deemed a limitation of the invention herein. Accordingly, various modifications, adaptations and alternatives may occur to one skilled in the art without departing from the spirit and the scope of the present invention.