Abstract:
A U flow radiator  10  with a header tank  12  split into inlet and outlet sides I and O by a lengthwise divider wall  18  has a coolant inlet consisting of a cylindrical pipe  22 . A hollow cylindrical barrel  24  co extensive and coaxial with pipe  22  and extending across divider wall  18 , with cut outs  26  and  28  opening respectively into both sides I and O. A thin walled, hollow cylindrical sleeve  30  turns within barrel  24  with windows  36  and  38  that alternately block or open the cut outs  26  and  28 , or open both partially. A rotary actuator  40  turns sleeve  30  within barrel  24 . Coolant can be selectively routed all to the tank outlet side O, by passing the radiator  10  for quick warm up. After warm up, coolant can be routed to I or O in desired proportions to increase or decrease cooling capacity. With high engine cooling demand, all coolant is routed to the inlet side I and all coolant passes through radiator  10.

Description:
TECHNICAL FIELD 
     This invention relates to heat exchangers, such as vehicle engine cooling radiators, and to a flow control valves therefore control valve that is integrated into the inlet of a U flow type radiator in a simple and non flow restrictive fashion. 
     BACKGROUND OF THE INVENTION 
     Flow control in vehicle engine cooling radiators has historically consisted of just a passively acting thermostat which, reacting to coolant temperature, blocks flow into the radiator to a greater or lesser degree, by passing the remainder of the flow through an by pass path external to the radiator. When wide open at the highest coolant temperature, all flow goes through the radiator. This standard system does not offer a high degree of control, generally using a thermally expandable wax material. Other systems attempt to add an extra degree of control by deliberately and externally heating the wax material to expand it, generally electrically heating it. There has been a recent trend, at least in published patents, toward active, electronically controlled flow control valves. An example may be seen in U.S. Pat. No. 6,314,920. The system shown there requires an electronically controlled coolant pump, and the valve is also external to the radiator, requiring an external by pass circuit around the radiator. 
     Other patents show control valves internal to the header tanks of the radiator, either passively or actively operated. One example is U.S. Pat. No. 5,305,826 shows a plunger operated double valve, either actively or passively controlled, that simultaneously blocks or opens both the inlet into a radiator of the two pass type, as well as blocking or opening a by pass passage between the two passes. As disclosed, the valve, being just downstream of the inlet, would represent a severe flow restriction within the header tank, in addition to the pressure drop that inherently happens as flow enters a header tank inlet and makes a ninety degree turn. Likewise, U.S. Pat. No. 4,432,410 shows a passively acting by pass valve located within the header tank, just downstream of the inlet. This, also, would represent a significant additional flow restriction and pressure drop. Coolant flow induced pressure drop through the inlet, outlet and header tank of a radiator is a serious issue, and features that add significantly to it are not preferred, despite the desirability of having an internal flow control valve, as opposed to an external flow control valve. 
     SUMMARY OF THE INVENTION 
     The invention provides an actively controllable radiator flow control valve that is internal to the radiator header tank, but which is integrated therewith in such a way as to not add a large pressure drop. 
     In the embodiment disclosed, the radiator is a U flow design, with two rows of flow tubes, in which one header tank is split between inlet and outlet portions by a dividing wall, with the inlet on one side and the outlet/pump inlet on the other side. The other header tank would act only to return the flow from the inlet to outlet portion of the first header tank. The physical coolant inlet to the first header tank is a cylindrical barrel that extends not only outside of the tank, as a conventional inlet fitting would, but also through the dividing wall and across the whole width of the interior of the tank. The exterior, outer end of the barrel provides the coolant inlet to the tank, while the inner surface provides a stationary outer housing and guide for the movable inner member of the control valve. Windows in the barrel allow open into the inlet and outlet side of the first header tank, one on either side of the dividing wall. The movable portion of the valve is a hollow cylindrical sleeve, closely and rotatably mounted within the outer barrel. One end of the sleeve opposite the inlet end of the outer barrel, can be turned back and forth about its central axis by a motor or similar actuator. Cut outs in the inner sleeve register with the windows in outer barrel, either completely or partially, or not at all, depending on the relative turned position of the inner sleeve. 
     Coolant flow entering the exterior end of the outer barrel then flows inside the close fitting inner sleeve, essentially just as it would with a conventional radiator tank inlet, and with no significant additional pressure loss. Depending on the relative registration of the inner sleeve and outer barrel cut outs and widows, flow exits the inner sleeve, and flows into either just the outlet side of the header tank, for a complete by pass of the radiator, or just the inlet side of header tank, forcing all flow through the radiator, or a mixed flow. Mixed flow can constitute the normal radiator operation, as determined by sensed engine or coolant temperature and consequent cooling demand, rather than the conventional operation of total flow through the radiator at all times other than initial warm up. This is feasible since a U flow radiator is inherently more efficient and the valve adds little additional pressure drop. Operating the radiator normally with some degree of by pass saves pump work and energy, regardless of how the pump is driven. Total radiator flow can then be reserved for severe engine cooling requirements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is perspective view of a radiator incorporating the flow control valve of the invention; 
     FIG. 2 is a perspective view of the inside of just the inlet/outlet or first header tank; 
     FIG. 3 is a disassembled view of the control valve and its actuator; 
     FIG. 4 is a perspective view of the inside of the upper end of the inlet/outlet tank, showing the flow control valve in a full by pass mode; 
     FIG. 5 shows the flow control valve in a mixed flow mode; 
     FIG. 6 shows the flow control valve in a full radiator flow mode. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIGS. 1 and 2, a heat exchanger of the U flow type, in this case a vehicle engine cooling radiator, designated generally at  10 , is the U flow type, with a first, vertically oriented, inlet/outlet header tank, designated generally at  12 , a second or return tank  14 , and regularly spaced pairs of flow tubes, two of which are shown at  16 . The pairs of flow tubes are separated by conventional, corrugated, air cooling fins  17 , brazed in place. External air flow across the outside of the tubes  16  is in the direction shown by the wavy arrow, while the internal coolant flow that is not by passed, as described below, flows in a U pattern from tank  12 , to  14 , and back. As seen in FIG. 2, the coolant flow pattern is determined by a dividing wall  18  that runs the length of the inside of first tank  12 , mating in sealed fashion to the inside of a header plate  20  to divide tank  12  into a front, coolant inlet side I and a rear, coolant outlet side O. Thus, the rear “half” of radiator  10  (the rear set of tubes  16 ) sees the hottest coolant as well as the hottest air flow (air which has already flowed over the front “half” of radiator  10 ) while the front “half” of radiator  10  (the front set of tubes  16 ), in which the coolant flow has already been partially cooled sees the coolest air flow. This provides the most thermally efficient pattern of air-coolant temperature differentials, and is inherently more efficient than a single flow radiator. The invention works in conjunction with this internal structure of header tank  12  to provide an improved flow control valve, so as to take even more advantage of the inherent thermal efficiency advantage of the U flow pattern. 
     Still referring to FIGS. 2 and 3, the coolant inlet fitting for the first tank  12  is, to all external appearances, a conventional, hollow cylindrical stub pipe  22  to which a coolant hose would be clamped. Normally, such a stub pipe  22  would do nothing but open through the outer wall of tank  12 , at about ninety degrees thereto, and open only into the inlet side I of tank  12 . Given the ninety degree turn that the coolant flow makes at and through the tank wall, a significant pressure drop is inevitable. In the embodiment of the invention disclosed, however, the sub pipe  22  is, in effect, the exterior protrusion of a hollow cylindrical barrel, indicated generally at  24 , that extends through one side wall of tank  12 , across and through the entire width of the header tank  12 , protruding slightly at the opposed side wall (as best seen in FIG.  3 ), but which is open to the exterior of tank  12  only at the stub pipe portion  22 . Barrel  24 , in and of itself, being essentially just an extension of the hollow cylindrical stub pipe  22 , would not add any additional pressure drop, but, in the absence of other provisions, would also not allow any coolant inflow. However, additional structural features, described below, allow the barrel to provide both an inlet and part of a coolant flow control valve. Further down on first tank  12 , well below inlet  22 , is a pump housing  25 , which is open only to the outlet side O of tank  12 . As shown, housing  25  would contain a non illustrated electric pump, but the invention here is not limited to use of an electric pump only. The pump powers coolant flow so that, as coolant is pumped out of the outlet side I of first header tank  12  and into the non illustrated engine cooling jacket, coolant is pulled out of the cooling jacket and into pipe  22 , where its flow path within radiator  10 , prior to reaching the pump again is determined by additional structure described next. 
     Still referring to FIGS. 2 and 3, barrel  24  has two windows or cut outs  26  and  28 , each generally rectangular in a planar, projected view, and one located on either side of the dividing wall  18 , so as to open to the interior of the first header tank  12  in its inlet and outlet sides I and O respectively. Closely received inside of barrel  24  is a hollow cylindrical sleeve, indicated generally at  30 , with an open end  32 , a closed end  34 , and relatively thin wall through which a pair of axially spaced, diametrically opposed windows  36  and  38  are cut, also generally “rectangular”. The windows  36  and  38  are located near the open end  32  and closed end  34  respectively. Sleeve  30  is inserted into barrel  24  until its closed end  34  abuts with the protruding end of barrel  24  and its open end  32  faces and is concentric to inlet pipe  22 . Sleeve  30 &#39;s outer surface fits closely and turnably within the inner surface of barrel  24 , and would be maintained co extensive and co axial with barrel  24  if it were either rotated or moved axially back and forth. The thin wall of sleeve  30  reduces the inner diameter of barrel  24  only slightly, and it becomes, in effect, almost an extension of the inlet pipe  22  inserted within barrel  24 . At the opposed outer wall of tank  12 , a rotary type actuator  40  is mounted, which has an electric motor that turns a splined shaft  42 . Shaft  42  enters a through hole  44  in the back of barrel  24  and is inserted non turnably into a closed ended hole  46  in the closed end  34  of sleeve  30 . A suitable seal would surround shaft  42  so as to prevent any leakage out of barrel  24 . Sleeve  30 , turned within barrel  24  by actuator  40 , provides an improved coolant flow within radiator  10 , as described next. 
     Referring next to FIG. 4, during engine warm up, actuator  40 , based on a temperature signal or other indication of the warm up condition, would turn sleeve  30  within barrel  24  to the point shown, where the barrel cut out  26  is completely blocked by the wall of sleeve  30 , while the sleeve window  38  and barrel cut out  28  are fully registered and aligned. As a consequence, all coolant entering stub pipe  22  flows directly within sleeve  30 , with very little restriction or pressure drop, due to the coaxial orientation of sleeve  30  to both pipe  22  and barrel  24 , and its relatively thin wall. Coolant flows out of sleeve  30  only through window  38  into the outlet side O of first header tank  12 . From there, it would be pulled down and out of pump housing  25 , without ever flowing through the radiator tubes  16 . As such, the engine would be able to warm up quickly, with no need for a by pass flow path external to radiator  10 . Coolant flowing inside of sleeve  30 , and then turning 90 degrees to enter the tank outlet side O, would not undergo significantly more pressure drop than it would by just flowing through stub pipe  22  and into the interior of a regular tank. Thus, the sleeve  30  uniquely cooperates with barrel  24  (which is effectively an extension of pipe  22 ) to create the valving action at essentially no cost to performance. Benefits not only include the more rapid engine warm-up, but also a pre warming of the header tank  12  to reduce thermal stress later. As disclosed, the inlet side I becomes fully blocked only as the outlet side O becomes fully opened. However, the shape and orientation of window  38  could be changed so that cut out  24  remained blocked by sleeve  30  as window  38  registered progressively more or less with cutout  28 , so as to meter and regulate the degree of by pass flow. 
     Referring next to FIG. 5, as the engine warms up and some external heat rejection becomes necessary, actuator  40  turns sleeve  30  within barrel  24  until each sleeve window  36  and  38  is registered partially with a respective barrel cut out  26  and  38 . This allows some coolant flow into tank inlet side I, and some directly into outlet side O. That coolant flowing into inlet side I will flow through one row of tubes  16 , into return tank  14  and back through the other row of tubes  16  and into tank outlet side O, rejecting heat to the air flow in the process. During normal operation, post engine warm up, but not under extreme conditions, it is contemplated that there would always be some by pass flow directly into the tank inlet side O. As such, relatively more of the sleeve window  38 , and relatively less of the sleeve widow  36 , would be open than is shown in FIG.  5 . Again, this could be provided by how far actuator  40  turned sleeve  30  within barrel  24 , as based on coolant temperature or other sensed parameters. The inherent efficiency of the U flow radiator design shown is such that some radiator cooling capacity could normally be held “in reserve” for extreme conditions. This, as opposed to the normal radiator flow pattern where all coolant flow fully through the radiator once engine warm up is completed. 
     Referring finally to FIG. 6, in the case of extreme conditions where more than normal cooling capacity was needed, then sleeve  30  would be turned so as to fully block the barrel cut out  28  in the tank outlet side O, and to fully register the sleeve window  36  with the barrel cut out  26  in the tank inlet side I. Now, all flow runs through the radiator tubes  16  and back, and none is by passed, for maximum cooling capacity. Again, it is not contemplated that this would be the normal radiator flow path, as in a conventional radiator. 
     Variations in the disclosed embodiment could be made within the spirit of the invention. A downflow design with top and bottom tanks, rather than vertical tanks, could be used. The radiator could be divided up into a U flow pattern in a side to side, rather than the back to front, design shown. That is, the divider wall  18  could run across the center width of the tank  12 , rather than lengthwise. A similar sleeve turning within a similar barrel that opened into both the inlet and outlet sides of the tank would provide the same controlled flow advantages. Other shapes could be provided for the barrel cut outs and sleeve windows, other than the rectangular (in projection) shape disclosed, such as triangular, trapezoidal, etc, which would provide even more control of the flow rates as the sleeve turned to progressively register and align the two. Since one of the main advantages is the close fit of the sleeve within the barrel, coaxial to both the barrel and the inlet pipe, with the attendant low pressure drop, it would be theoretically possible to move a similarly close fitting sleeve axially back and forth within the barrel so as to align and misalign, block and un block, matching windows and cut outs. This could create a similar flow pattern. However, the rotary action shown is convenient and compact, and there are existing rotary actuators that would serve that purpose well. Potentially, a combination of both axial plunging and rotary turning could be used, since both motions would be well guided by the close fit of hollow cylindrical sleeve within cylindrical barrel.